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NBS SPECIAL PUBLICATION 260-65
NATIONAL BUREAU OF STANDARDS

The National Bureau of Standards' was established by an act ot Congress on March 3, 1901. The Bureau's overall goal is to strengthen and advance the Nation's science and technology

and facilitate their effective application for public benefit. To this end, the Bureau conducts

research and provides: (1) a basis for the Nation's physical measurement system, (2) scientific and technological services for industry and government, (3) a technical basis for equity in trade, and (4) technical services to promote public safety. The Bureau's technical work is per- formed by the National Measurement Laboratory, the National Engineering Laboratory, and

the Institute for Computer Sciences and Technology.

THE NATIONAL MEASUREMENT LABORATORY provides the national system of

physical and chemical and materials measurement; coordinates the system with measurement

systems of other nations and furnishes essential services leading to accurate and uniform

physical and chemical measurement throughout the Nation's scientific community, industry,

and commerce; conducts materials research leading to improved methods of measurement,

standards, and data on the properties of materials needed by industry, commerce, educational

institutions, and Government; provides advisory and research services to other Government

agencies; develops, produces, and distributes Standard Reference Materials; and provides

calibration services. The Laboratory consists of the following centers:

Absolute Physical Quantities-' — Radiation Research — Thermodynamics and

Molecular Science — Analytical Chemistry — Materials Science. THE NATIONAL ENGINEERING LABORATORY provides technology and technical ser- vices to the public and private sectors to address national needs and to solve national problems; conducts research in engineering and applied science in support of these efforts; builds and maintains competence in the necessary disciplines required to carry out this research and technical service; develops engineering data and measurement capabilities;

provides engineering measurement traceability services; develops test methods and proposes

engineering standards and code changes; develops and proposes new engineering practices;

and develops and improves mechanisms to transfer results of its research to the ultimate user. The Laboratory consists of the following centers:

Applied Mathematics — Electronics and Electrical Engineering 2 — Mechanical

Engineering and Process Technology2 — Building Technology — Fire Research —

Consumer Product Technology — Field Methods.

THE INSTITUTE FOR COMPUTER SCIENCES AND TECHNOLOGY conducts

research and provides scientific and technical services to aid Federal agencies in the selection, acquisition, application, and use of computer technology to improve effectiveness and

economy in Government operations in accordance with Public Law 89-306 (40 U.S.C. 759), relevant Executive Orders, and other directives; carries out this mission by managing the Federal Information Processing Standards Program, developing Federal ADP standards

guidelines, and managing Federal participation in ADP voluntary standardization activities; provides scientific and technological advisory services and assistance to Federal agencies; and

provides the technical foundation for computer-related policies of the Federal Government.

The Institute consists of the following centers:

Programming Science and Technology — Computer Systems Engineering.

'Headquarters and Laboratories at Gaithersburg, MD, unless otherwise noted; mailing address Washington, DC 20234. 'Some divisions within the center are located at Boulder, CO 80303.
Standard Reference Materials:

Micro-Homogeneity Studies of NBS Standard tio.&C-u

Reference Materials, NBS Research

Materials, and Other Related Samples

R.B. Marinenko, K.F.J. Heinrich,

and F.C. Ruegg

National Measurement Laboratory

National Bureau of Standards

Washington, DC 20234

bl

U.S. DEPARTMENT OF COMMERCE, Juanita M. Kreps, Secretary

Luther H. Hodges, Jr., Under Secretary

Jordan J. Baruch, Assistant Secretary for Science and Technology

NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Director

Issued September 1979
Library of Congress Catalog Card Number: 79-6001 21

National Bureau of Standards Special Publication 260-65

Nat. Bur. Stand. (U.S.), Spec. Publ. 260-65, 84 pages (Sept. 1979) CODEN: XNBSAV

U.S. GOVERNMENT PRINTING OFFICE

WASHINGTON: 1979

For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402 Stock No. 003-003-021 14-1 Price $3.50

(Add 25 percent additional for other than U.S. mailing)

U.S. GOVERNMENT PRINTING OFFICE : 1 979—O-300-303
PREFACE

Standard Reference Materials (SRM's) as defined by the

National Bureau of Standards are well-characterized materials,

produced in quantity and certified for one or more physical

or chemical properties. They are used to assure the accuracy

and compatibility of measurements throughout the nation.

SRM's are widely used as primary standards in many diverse

fields in science, industry, and technology, both within the

United States and throughout the world. They are also used

extensively in the fields of environmental and clinical analysis. In many applications, traceability of quality control

and measurement processes to the national measurement system

are carried out through the mechanism and use of SRM's. For

many of the nation's scientists and technologists it is

therefore of more than passing interest to know the details

of the measurements made at NBS in arriving at the certified

values of the SRM's produced. An NBS series of papers, of

which this publication is a member, called the NBS Special

Publication - 260 Series is reserved for this purpose.

This 260 Series is dedicated to the dissemination of

information on different phases of the preparation, measurement, certification and use of NBS-SRM's. In general, much

more detail will be found in these papers than is generally

allowed, or desirable, in scientific journal articles. This

enables the user to assess the validity and accuracy of the

measurement processes employed, to judge the statistical

analysis, and to learn details of techniques and methods

utilized for work entailing the greatest care and accuracy.

These papers also should provide sufficient additional information not found on the certificate so that new applications

in diverse fields not foreseen at the time the SRM was originally issued will be sought and found.

Inquiries concerning the technical content of this paper

should be directed to the author(s). Other questions concerned with the availability, delivery, price, and so forth

will receive prompt attention from:

Office of Standard Reference Materials

National Bureau of Standards

Washington, D.C. 20234

George A. Uriano, Chief

Office of Standard Reference Materials

iii
OTHER NBS PUBLICATIONS IN THIS SERIES

Catalog of NBS Standard Reference Materials

(1979-80 edition), R. W. Seward, ed., NBS

Spec. Publ. 260 (April 1979) $3.00* SN003-003-

02048-6

Michaelis, R. E., and Wyman, L. L., Standard

Reference Materials: Preparation of White Cast

Iron Spectrochemical Standards, NBS Misc.

Publ. 260-1 (June 1964). COM74-1 1061**

Michaelis, R. E., Wyman, L. L., and Flitsch, R., Standard Reference Materials: Preparation of

NBS Copper-Base Spectrochemical Standards,

NBS Misc. Publ. 260-2 (October 1964). COM74-

11063**

Michaelis, R. E., Yakowitz, H., and Moore, G. A.,

Standard Reference Materials: Metallographic

Characterization of an NBS Spectrometric LowAlloy Steel Standard, NBS Misc. Publ. 260-3

(October 1964). COM74-1 1060**

Hague, J. L., Mears, T. W., and Michaelis, R. E., Standard Reference Materials: Sources of

Information, NBS Misc. Publ. 260-4 (February

1965). COM74-11059

Alvarez, R., and Flitsch, R., Standard Reference

Materials: Accuracy of Solution X-Ray Spectrometric Analysis of Copper-Base Alloys, NBS

Misc. Publ. 260-5 (March 1965). PB 168068**

Shultz, J. I., Standard Reference Materials:

Methods for the Chemical Analysis of White

Cast Iron Standards, NBS Misc. Publ. 260-6

(July 1975). COM74-11068**

Bell, R. K., Standard Reference Materials:

Methods for the Chemical Analysis of NBS

Copper-Base Spectrochemical Standards, NBS

Misc. Publ. 260-7 (October 1965). COM74-

11067**

Richmond, M. S., Standard Reference Materials:

Analysis of Uranium Concentrates at the

National Bureau of Standards, NBS Misc. Publ.

260-8 (December 1965). COM74-1 1066**

Anspach, S. C, Cavallo, L. M., Garfinkel, S. B., Hutchinson, J. M. R., and Smith, C. N., Standard Reference Materials: Half Lives of Materials

Used in the Preparation of Standard Reference

Materials of Nineteen Radioactive Nuclides

Issued by the National Bureau of Standards,

NBS Misc. Publ. 260-9 (November 1965).

COM74-1 1065**

Yakowitz, H., Vieth, D. L., Heinrich, K. F. J., and

Michaelis, R. E., Standard Reference Materials:

Homogeneity Characterization on NBS Spectrometric Standards II: Cartridge Brass and LowAlloy Steel, NBS Misc. Publ. 260-10 (December

1965). COM74-11064**

Napolitano, A., and Hawkins, E. G., Standard

Reference Materials: Viscosity of Standard

Lead-Silica Glass, NBS Misc. Publ. 260-11

(November 1966). NBS Misc. Publ. 260-11**

Yakowitz, H., Vieth, D. L., and Michaelis, R. E., Standard Reference Materials: Homogeneity

Characterization of NBS Spectrometric Standards III: White Cast Iron and Stainless Steel Powder Compact, NBS Misc. Publ. 260-12

(September 1966). NBS Misc. Publ. 260-12**

Spijkerman, J. L., Snediker, D. K., Ruegg, F. C,

and DeVoe, J. R., Standard Reference Materials: Mossbauer Spectroscopy Standard for the Chemical Shift of Iron Compounds, NBS Misc.

Publ. 260-13 (July 1967). NBS Misc. Publ.

260-13**

Menis, O., and Sterling, J. T., Standard Reference

Materials: Determination of Oxygen in Ferrous

Materials - SRM 1090, 1091, and 1092, NBS

Misc. Publ. 260-14 (September 1966). NBS Misc.

Publ. 260-14**

Passaglia, E., and Shouse, P. J. Standard Refer- ence Materials: Recommended Method of Use

of Standard Light-Sensitive Paper for Calibrating Carbon Arcs Used in Testing Textiles for Colorfastness to Light, NBS Misc. Publ. 260-15

(June 1967). (Replaced by NBS Spec. Publ.

260^1.)

Yakowitz, H., Michaelis, R. E., and Vieth, D. L., Standard Reference Materials: Homogeneity

Characterization of NBS Spectrometric Standards IV: Preparation and Microprobe Characterization of W-20% MO Alloy Fabricated by

Powder Metallurgical Methods, NBS Spec.

Publ. 260-16 (January 1969). COM74-1 1062**

Catanzaro, E. J., Champion, C. E., Garner, E. L., Marinenko, G., Sappenfield, K. M., and Shields,

W. R. Standard Reference Materials: Boric

Acid; Isotopic and Assay Standard Reference

Materials, NBS Spec. Publ. 260-17 (February

1970). Out of Print

iv
Geller, S. B., Mantek, P.A., and Cleveland, N.

G., Standard Reference Materials: Calibration of NBS Secondary Standard Magnetic Tape

(Computer Amplitude Reference) Using the

Reference Tape Amplitude Measurement

"Process A, "NBS Spec. Publ. 260-18 (November

1969). (See NBS Spec. Publ. 260-29.)

Paule, R. C, and Mandel, J., Standard Reference

Materials: Analysis of Interlaboratory Measurements on the Vapor Pressure of Gold (Certification of Standard Reference Material 745). NBS

Spec. Publ. 260-19 (January 1970). PB190071**

Paule, R. C, and Mandel, J., Standard Reference

Materials: Analysis of Interlaboratory Measurements on the Vapor Pressures of Cadmium and

Silver, NBS Spec. Publ. 260-21 (January 1971).

COM74-11359**

Yakowitz, H., Fiori, C. E., and Michaelis, R. E., Standard Reference Materials: Homogeneity

Characterization of Fe-3 Si Alloy, NBS Spec.

Publ. 260-22 (February 1971). COM74-1 1357**

Napolitano, A., and Hawkins, E. G., Standard

Reference Materials: Viscosity of a Standard

Borosilicate Glass, NBS Spec. Publ. 260-23

(December 1970). COM71-00157**

Sappenfield, K. M., Marineko, G., and Hague, J. L., Standard Reference Materials: Comparison

of Redox Standards, NBS Spec. Publ. 260-24

(January 1972). COM72-50058**

Hicho, G. E., Yakowitz, H., Rasberry, S. D., and

Michaelis, R. E., Standard Reference Materials:

A Standard Reference Material Containing

Nominally Four Percent Austenite, NBS Spec.

Publ. 260-25 (February 1971). COM74-1 1356**

Martin, J. F., Standard Reference Materials:

National Bureau of Standards-US Steel Corportion Joint Program for Determining Oxygen and

Nitrogen in Steel, NBS Spec. Publ. 260-26

(February 1971). 85 cents* SN003-003-00786-2

Garner, E. L., Machlan, L. A., and Shields, W. R.,

Standard Reference Materials: Uranium

Isotopic Standard Reference materials, NBS

Spec. Publ. 260-27 (April 1971). COM74-

11358**

Heinrich, K. F. J., Myklebust, R. L., Rasberry, S. D., and Michaelis, R. E., Standard Reference

Materials: Preparation and Evaluation of

SRM's 481 and 482 Gold-Silver and GoldCopper Alloys for Microanalysis, NBS Spec.

Publ. 260-28 (August 1971). COM7 1-50365**

Geller, S. B., Standard Reference Materials: Calibration of NBS Secondary Standard Magnetic

Tape (Computer Amplitude Reference) Using

the Reference Tape Amplitude Measurement

"Process A-Model 2," NBS Spec. Publ. 260-29

(June 1971). COM7 1-50282

Gorozhanina, R. S., Freedman, A. Y., and

Shaievitch, A. B. (translated by M. C. Selby),

Standard Reference Materials: Standard

Samples Issued in the USSR (A Translation

from the Russian). NBS Spec. Publ. 260-30 (June

1971). COM71-50283**

Hust, J. G., and Sparks, L. L., Standard Reference

Materials: Thermal Conductivity of Electrolytic Iron SRM 734 from 4 to 300 K, NBS Spec. Publ.

260-31 (November 1971). COM7 1-50563**

Mavrodineanu, R., and Lazar, J. W., Standard

Reference Materials: Standard Quartz Cuvettes,

for High Accuracy Spectrophotometry, NBS

Spec. Publ. 260-32 (December 1973). 55 cents* SN003-003-01213-1

Wagner, H. L., Standard Reference Materials:

Comparison of Original and Supplemental

SRM 705, Narrow Molecular Weight Distri- bution Polystyrene, NBS Spec. Publ. 260-33

(May 1972). COM72-50526**

Sparks, L. L., and Hust, J. G., Standard Reference

Materials: Thermoelectric Voltage, NBS Spec.

Publ. 260-34, (April 1972). COM72-50371**

Sparks, L. L., and Hust, J. G., Standard Refer- ence Materials: Thermal Conductivity of

Austenitic Stainless Steel, SRM 735 from 5

to 280 K, NBS Spec. Publ. 260-35 (April 1972.)

35 cents* COM72-50368**

Cali, J. P., Mandel, J., Moore, L. J., and Young, D.

S., Standard Reference Materials: A Referee

Method for the Determination of Calcium in Serum, NBS SRM 915, NBS Spec. Publ. 260-36

(May 1972). COM72-50527**

Shultz, J. I. Bell., R. K. Rains, T. C, and Menis,

O., Standard Reference Materials: Methods of

Analysis of NBS Clay Standards, NBS Spec.

Publ. 260-37 (June 1972). COM72-50692**

Richmond, J. C, and Hsia, J. J., Standard Refer- ence Materials: Preparation and Calibration of

Standards of Spectral Specular Reflectance,

NBS Spec. Publ. 260-38 (May 1972). COM72-

50528**

Clark, A. F., Denson, V.A., Hust, J. G., and

Powell, R. L., Standard Reference Materials

The Eddy Current Decay Method for Resistivity

Characterization of High-Purity Metals, NBS

Spec. Publ. 260-39 (May 1972). COM72-50529**
McAdie, H. G., Garn, P.D., and Menis, O., Standard Reference Materials: Selection of Thermal

Analysis Temperature Standards Through a Cooperative Study (SRM 758, 759, 760), NBS

Spec. Publ. 260-40 (August 1972.) COM72-

50776**

Wood, L. A., and Shouse, P. J., Standard

Reference Materials: Use of Standard LightSensitive Paper for Calibrating Carbon Arcs

Used in Testing Textiles for Colorfastness to Light, NBS Spec. Publ. 260-41 (August 1972)

COM72-50775**

Wagner, H. L. and Verdier, P. H., eds., Standard

Reference Materials: The Characterization of

Linear Polyethylene, SRM 1475, NBS Spec.

Publ. 260-42 (September 1972). COM72-

50944**

Yakowitz, H., Ruff, A. W., and Michaelis, R. E., Standard Reference Materials: Preparation and

Homogeneity Characterization of an Austenitic

Iron-Chromium-Nickel Alloy, NBS Spec. Publ.

260-43 (November 1972). COM73-50760**

Schooley, J. F., Soulen, R. J., Jr., and Evans, G. A.,

Jr., Standard Reference Materials: Preparation

and Use of Superconductive Fixed Point

Devices, SRM 767, NBS Spec. Publ. 260^4

(December 1972). COM73-50037**

Greifer, B., Maienthal, E. J. Rains, T. C, and

Rasberry, S. D., Standard Reference Materials:

Powdered Lead-Based Paint, SRM 1579, NBS

Spec. Publ. 260-45 (March 1973). COM73-

50226**

Hust, J. G., and Giarratano, P. J., Standard Refer- ence Materials: Thermal Conductivity and

Electrical Resistivity Standard Reference Materials: Austenitic Stainless Steel, SRM's 735 and

798, from 4 to 1200 k, NBS Spec. Publ. 260-46

(March 1975). SN003-003-0 1278-5

Hust, J. G., Standard Reference Materials: Electrical Resistivity of Electrolytic Iron, SRM 797,

and Austenitic Stainless Steel, SRM 798, from 5 to 280 K, NBS Spec. Publ. 260-47 (February

1974). COM74-50176**

Mangum, B. W., and Wise, J. A., Standard Refer- ence Materials: Description and Use of Precision

Thermometers for the Clinical Laboratory,

SRM 933 and SRM 934, NBS Spec. Publ. 260^8

(May 1974). 60 cents* SN003-003-0 1278-5

Carpenter, B. S., and Reimer, G. M., Standard

Reference Materials Calibrated Glass Standards for Fission Track Use, NBS Spec. Publ.

260^9 (November 1974). SN003-O03-0 1344-7

Hust, J. G., and Giarratano, P. J., Standard Refer- ence Materials: Thermal Conductivity and Electrical Resistivity Standard Reference Materials:

Electrolytic Iron, SRM's 734 and 797 from 4 to 1000 K, NBS Spec. Publ. 260-50 (June 1975).

$1.00* SN003-003-0 1425-7

Mavrodineanu, R., and Baldwin, J. R., Standard

Reference Materials: Glass Filters As a Standard

Reference Material for Spectrophotometry;

Selection; Preparation; Certification; Use-SRM

930, NBS Spec. Publ. 260-51 (November 1975).

$1.90* SN003-003-01481-8

Hust, J. G., and Giarratano, P. J., Standard Refer- ence Materials: Thermal Conductivity and Electrical Resistivity Standard Reference Materials

730 and 799, from 4 to 3000 K, NBS Spec. Publ.

260-52 (September 1975). $1.05* SN003-003-

01464-8

Durst, R. A., Standard Reference Materials:

Standardization of pH Measurements, NBS

Spec. Publ. 260-53 (Under Revision).

Burke, R. W., and Mavrondineanu, R. Standard

Reference Materials: Certification and Use of

Acidic Potassium Dichromate Solutions as an

Ultraviolet Absorbance Standard, NBS Spec.

Publ. 260-54 (August 1977). $3.00* SN003-003-

01828-7

Ditmars, D. A., Cezairliyan, A., Ishihara, S., and

Douglas, T. B., Standard Reference Materials:

Enthalpy and Heat Capacity; Molybdenum

SRM 781, from 273 to 2800 K, NBS Spec. Publ.

260-55 (September 1977). $2.20* SN003-003-

01836-8

Powell, R. L., Sparks, L. L., and Hust, J. G.,

Standard Reference Materials: Standard

Thermocouple Materials, Pt.67: SRM 1967, NBS

Spec. Publ. 260-56 (February 1978). $2.20*

SN003-003-0 18864

Cali, J. P. and Plebanski, T., Guide to United

States Reference Materials, NBS Spec. Publ.

260-57 (February 1978). $2.20* SN003-003-

01883-0

Barnes, J. D., and Martin, G. M., Standard Refer- ence Materials: Polyester Film for Oxygen Gas

Transmission Measurements SRM 1470, NBS

Spec. Publ. 260-58 (June 1979) $2.00* SN003-

003-02077

Chang, T., and Kahn, A. H., Standard Reference

Materials: Electron Paramagentic Resonance

Intensity Standard: SRM 2601, NBS Spec.

PubJ. 260-59 (August 1978) $2.30* SN003-

003-01975-5

vi
Velapoldi, R. A., Paule, R. C, Schaffer, R.,

Mandel, J., and Moody, J. R., Standard Refer- ence Materials: A Reference Method for the Determination of Sodium in Serum, NBS Spec.

Publ. 260-60 (August 1978). $3.00* SN003-003-

01978-0

Verdier, P. H., and Wagner, H. L., Standard Refer- ence Materials: The Characterization of Linear

Polyethylene (SRM 1482, 1483, 1484), NBS

Spec. Publ. 260-61 (December 1978). $1.70*

SN003-003-02006-1

Soulen, R. J., and Dove, R. B., Standard Reference

Materials: Temperature Reference Standard

for Use Below 0.5 K (SRM 768), NBS Spec.

Publ. 260-62 (April 1979). $2.30* SN003-003-

02047-8

Velapoldi, R. A., Paule, R. C, Schaffer, R.,

Mandel, J., Machlan, J. L., and Gramlich, J. W.,

Standard Reference Materials: A Reference

Method for the Determination of Potassium in Serum, NBS Spec. Publ. 260-63 (May 1979).

$3.75* SN003-003-02068

Velapoldi, R. A., and Mielenz, K. D., Standard

Reference Materials: A Fluorescence Standard

Reference Material Quinine Sulfate Dihydrate

(SRM 936), NBS Spec. Publ. 260-64 (in press).

Marinenko, R. B., Heinrich, K. F. J., and Ruegg,

F. C, Standard Reference Materials: MicroHomogeneity Studies of NBS Standard Reference

Materials, NBS Research Materials, and Other

Related Samples, NBS Spec. Publ. 260-65 (in

press).

Venable, W. H., Jr. and Eckerle, K. L., Standard

Reference Materials: Didymium Glass Filters for Calibrating the Wavelength Scale of Spectrophotometers (SRM 2009, 2010, 2013), NBS Spec.

Publ. 260-66 (in press).

Velapoldi, R. A., Paule, R. C, Schaffer, R., Mandel,

J., Murphy, T. J., and Gramlich, J. W., Standard

Reference Materials: A Reference Method for the

Determination of Chloride in Serum, NBS Spec.

Publ. 260-67 (in press).

* Send order with remittance to: Superintendent

of Documents, US Government Printing

Office, Washington, DC 20402. Remittance

from foreign countries should include an

additional one-fourth of the purchase price for postage. ** May be ordered from: National Technical

Information Services (NTIS), Springfield,

Virginia 22151.

vii
List of Tables

Table No. Page

I. Standard Reference Materials and Research

Materials which are Tested for Microscopic

Homogeneity 3

II. Specifications for Periodic Integrator Assembly. 12

III. Homogeneity Study of SRM 661 25

IV. Homogeneity Study of SRM 662 . . 26

V. Homogeneity Study of SRM 663 27

VI. Homogeneity Study of SRM 664 28

VII. Comparison of Random Sampling with Homogeneity

Traces for Iron and Steel SRMs 30

VIII. Homogeneity Study of Low-Alloy Steel SRMs 461

and 463 32

XI. Homogeneity Study of Gold-Copper Alloy SRM 482 . 34

X. Homogeneity Testing of Cartridge Brass SRM 478 . 36

List of Figures

Figure No.

1. Conventional ratemeter trace of molybdenum,

chromium, and manganese in the steel SRM 663. . 5

2. Periodic integrator homogeneity traces of

manganese, chromium, and molybdenum

simultaneously recorded from NBS SRM 663 steel. 7 3. Periodic integrator homogeneity traces of

manganese and chromium simultaneously recorded

from NBS SRM 663 steel 8

4. Periodic integrator homogeneity traces of

aluminum and barium simultaneously recorded

from NBS Glass K-489 10

5. Periodic integrator including scalers, ratemeter,

and recorder 11

viii
List of Figures (continued)

Figure No. Page

6. Interfacing of the periodic integrator with the

electron microprobe and the recorder 13

7. Cross-section of SRM 664 20$

21

8. Cross-section of SRM 663 22

9. Longitudinal cros s - sect ion of SRM 662 23

10. Periodic integrator homogeneity trace of tungsten

and molybdenum simultaneously recorded from

SRM 480 35

11. Periodic integrator homogeneity trace of zinc and

copper simultaneously recorded from NBS SRM 478

Cartridge Brass 38

12. Periodic integrator homogeneity trace of lead and

silicon simultaneously recorded form NBS RM

Glass K-493 40

13. Periodic integrator homogeneity trace of

germanium and lead simultaneously recorded from

NBS RM Glass K-491 42

14. Periodic integrator homogeneity trace of

silicon, barium, and zinc simultaneously

recorded from NBS RM Glass K-489 42

15. Periodic integrator homogeneity trace of

aluminum, phosphorus, and mangesium

simultaneously recorded from NBS RM

Glass K-497 43

ix
Table of Contents

Page

I. Introduction 2 New Homogeneity Testing 4

General Description 4

Instrumentation 9

Statistical Evaluation of Data 12

II. Results 15

Iron and Steel SRMs 661 , 662 , 663, 664 17

Low-alloy Steel SRMs 461 and 463 31

Gold-Silver and Gold-Copper Wires, SRMs 481 and

482 31

Tungsten - 20 Molybdenum Alloy, SRM 480 33

Cartridge Brass, SRM 478 36

Iron-Three Percent Silicon, SRM 483 37

Glasses for Microanalysis, RM-30 39

Austenitic Iron- Chromium-Nickel Alloy, SRM 479a. . . 39

References 45

Appendices 46

x
Abstract

A simple routine technique for studying homogeneity in

the micrometer range with the electron microprobe has been

developed. For graphic display, a digital periodic integrator is used. In conjunction with scalers and a stepping

motor on the sample stage, traces similar to industrial

control charts based on a comparison of the experiment with

the expected (Poisson) counting statistics are quickly

obtained. A computer program has been developed to numerically evaluate sample homogeneity.

Several Standard Reference Materials (SRMs) have been

tested. These include the iron and steels (SRMs 661-664,

461, and 463), the gold-copper and gold-silver alloys (SRMs

481 and 482), the tungsten- 20 percent molybdenum alloy (SRM

480), cartridge brass (SRM 478), the iron-3 percent silicon

alloy (SRM 483), and the new iron- chromium-nickel alloy (SRM

479a). A Research Material, Glasses for Microanalysis (RM30), has also been tested.

Key Words: Digital periodic integrator; electron microprobe;

homogeneity; Standard Reference Materials;

steel

.

1
I. Introduction

The development and refinement, since the 1960's, of

sophisticated instrumental techniques for determining the

elemental composition of microscopically small areas have

imposed stringent requirements upon reference materials to

be used for this purpose. The analyst often requires that

the composition assigned to the bulk material should apply

as well on the micrometer (urn) scale. This occurs in the

testing of samples by techniques such as spark source mass

spectrometry which can sample an area as small as 25 ym in

diameter, electron probe microanalysis (EPMA) in which

typically a sphere about 1-3 ym in diameter is analyzed, and

secondary ion mass spectrometry (SIMS) which may sample a cylindrical volume as small as 1 ym in diameter and 10 nm

deep. Those NBS Standard Reference Materials (SRMs) and

Research Materials (RMs) that have been found useful for

microanalyt ical techniques are listed in Table I.

In earlier homogeneity studies conducted in our laboratory with the EPMA [1,2]*, existing metal Standard Reference

Materials which had been certified in bulk were examined.

These materials included low-alloy steels (SRMs 461 and 463)

and cartridge brasses (SRMs C1102 and 1102) . Ratemeter line

scans were used for graphic display of linear traces across

the samples, and the extent of homogeneity was defined

statistically from many random samplings with a 1-4 ym

electron beam.

Some SRMs were specifically prepared with microhomogeneity in mind. The first of these was SRM 480, a tungsten20 percent molybdenum alloy [3,4]. Ratemeter line scans were

used as a preliminary homogeneity check. A point -by -point

analysis was then made with a quantitative raster scanning

(QRS) technique which electronically displaced the electron

beam. The raster size in these analyses was 48 ym on an

edge with ten different points along each, giving a total of

100 points in each raster.

The gold-silver (SRM 481) and the gold-copper (SRM 482)

alloys were also carefully prepared to be microscopically

homogeneous. For the studies of these SRMs [5] a computercontrolled sampling procedure was developed. Again, the

electron beam was electronically moved in a one- or twodimensional raster with preselected distances between points.

The data were automatically recorded on magnetic tape and

statistically evaluated by TOPO, a data reduction computer

program for homogeneity studies [5].

figures in brackets indicate the literature references at

the end of this paper.

2
Table 1. Standard Reference Materials and Research Materials

which are Tested for Microscopic Homogeneity3

No.

SRM 4 78

SRM 479

SRM 480

SRM 481

SRM 4 82

SRM 4 83

RM 30

RM 31

Cartridge Brass

Fe-Cr-Ni Alloy

Tungsten- 20 % Molybdenum

Gold-Silver

Gold-Copper

Iron-3% Silicon

Glasses for

Microanalysis

Glass Fibers for

Microanalysis

Form

Cube and

Cylinder

Wafer

Wafer

Six Wires

Six Wires

Platelet

SI ices

Fibers

El ement s (nominal wt %)

Cu-73; Zn-2 7

Fe-71 ;Cr-18;Ni-ll

W-78;Mo-22

Au-100; 80; 60; 40;

20; 0

Ag-0; 20; 40;60;

80 ; 100

Au-100; 80; 60; 40;

20 ; 0

Cu-0; 20; 40; 60;

80 ; 100

Fe-97 ;Si-3

10 Compositions

of Various Oxides

10 Compositions

of Various Oxides

Taken from "NBS Standard Reference Materials for Electron

Probe Microanalysis and Scanning Electron Microscopy," 1976,

an advertising brochure published by NBS.

There were several disadvantages in using this testing

procedure. Firstly, it was dependent on a computer external

to the laboratory. If the computer was inoperative or if

on-line interruptions occurred, no information was obtained,

or the stored information was erratic. Secondly, the program

TOPO can handle only two elements simultaneously although as

many as four elements could be studied simultaneously. Both

of our electron probe instruments have three crystal spectrometers and a lithium-drifted silicon detector for analyses of

more complex samples. Thirdly, the defocusing of the crystal

spectrometers becomes a problem limiting the maximum length

of the electron beam scan in either dimension on the specimen

3
to 40-50 ym. Fourthly, random sampling is not quite adequate

because the dimension of uniform regions within the inhomogeneous sample cannot be estimated and conventional analog

ratemeter traces cannot be relied upon to reveal such

information.

We therefore sought a less complicated and less limiting

procedure for studying microhomogeneity . This is described

below

.

New Homogeneity Testing Procedure

General Description

We required a simple procedure which could be performed

quickly with our equipment and independently of external

systems. A ratemeter scan is a good solution because it can

provide a quick visual interpretation of the level of homogeneity. (With TOPO, which relied on two external computer

manipulations, no visual data were available until the

statistics had been computed.) But the conventional analog

ratemeter scan is unsatisfactory because of the difficulty in

assigning Poissonian confidence limits to ratemeter excursions

and thus in separating real composition changes from statistical fluctuations. This can be seen in figure 1 which is a conventional analog ratemeter trace of molybdenum, chromium,

and manganese in SRM 663 which is moving continuously under

a 1 ym beam. The average concentrations of these elements

are 0.30, 1.31, and 1.50 weight percent respectively. There

is a distinct difference between the fluctuations of the

signal from the sample when moving and when still, yet limits

due only to counting statistics cannot be accurately assigned.

The molybdenum concentration is so low here that there is no

perceptible signal above the background.

A periodic integrator, such as previously described by

Heinrich [6] but based on digital operations (i.e., on a microcomputer), was constructed at NBS . The total number of

counts acquired by the scalers in a preselected time period

(e.g., 10 s.) is output simultaneously to a teletype (digitally) and to a fast strip chart recorder. The analog signal

on the recorder is related linearly to the number of counts

in the preceding signal collection period, and remains

unchanged until the next time period is completed. A stepping

motor on the specimen stage of the electron probe is also

controlled by the periodic ratemeter. Between counting periods

the stage can be advanced from 1 ym up to 10 ym and the data

collection at each spot on the specimen can be repeatedly

sampled from 1 to 15 times. In addition, the signal can be

digitally multiplied by any appropriate factor and a bias

can be applied to digitally subtract any desired count rate

4
NBS STEEL SRM 665

Manganese 1.50 vt

A

Sample

not moving

Chromium 1.51 wt. «

2 0 ym beam 1 ym beam

Molvbdenum .05 0 wt

.

%

Figure 1. Conventional ratemeter trace of molybdenum,

chromium, and manganese in the steel SRM 663. On

the right side of the trace, the sample was moving

under a 1 ym electron beam. To the left, the

sample was stationary under a 20 ym beam.

5
from the signal display. This enhances the excursions of

the signal on the chart to any desired level.

An example of the graphic display is shown in figure 2 of SRM 663. The homogeneity trace was prepared with a 1 ym

electron beam moving in steps of 1 ym across the sample

(visible inclusions were avoided) . The operating voltage was

chosen so that the effective diameter of the excited area did

not exceed 2 ym. Counts were accumulated once on each step

for ten-second counting periods. The shaded area through the

center of each trace represents a rang_e of ±3/N around the

average number of counts per period, N. According to Poisson

counting statistics, the square root of the mean number of

counts collected in a counting period is an unbiased estimate

of its standard deviation; /N ~ a . Hence, a 99.7 percent

confidence limit for Poisson counting statistics applies to

the range in the shaded area; deviations outside this region

represent specimen inhomogeneity or instrumental variations

at the 99.7 percent confidence level. With the traces presented here, it can be easily observed that the graphic

representation of step scans provides information on the

spatial distribution of elements along the line of scan, and,

if several elements are observed, of the degree of correlation

between changes in the concentrations of these elements.

The degree of homogeneity required depends upon the

intended use of the sample; measurement conditions can be

chosen so that the Poisson limits are within the desired

level of homogeneity. For example, the beam intensity,

operating potential, and time period of signal collection can

be adjusted to render these confidence limits congruent with

the required accuracy of the measurement. Note that in

figure 2 chromium and manganese show large deviations which

coincide spatially for these two elements. The molybdenum

signal falls within the shaded region because of poor counting

statistics. Only the background level is being observed here.

To the left of the figure is a trace recorded from

repeatedly counting for ten-second intervals on a stationary

20x20 ym 2 area. The signal from an area this size should be

close to the average concentration value for this sample and

such repetitions should lie within Poisson counting statistics

which they do here. This test verifies that excursions outside the ±3-sigma range in the right trace are in truth due

to the sample variability and not to instrumental factors

such as drift and instability.

Figure 3 shows another ratemeter trace of the chromium

and manganese distributions across a specimen of the same

standard (SRM 663) . Instrumental conditions here were nearly

the same as in figure 2 except that an electron beam of 2 ym

diameter was used here, and for each 2 ym step across the

6
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sample duplicate 10-s. readings were recorded. Movement of

the specimen from one location to the next is indicated in

the figure by the dots between the two traces. Differences

between steps which are not attributable to counting statistics alone are clearly observable, but repetitive measurements

on the same step are in quite good agreement, i.e., within

counting statistics. Such a mode of operation permits a statistical comparison of the counting variations within a spot and from spot to spot. This figure again proves that

the large variations from one position across the sample to

another are indeed due to inhomogenei ty

.

We have also been using the periodic integrator to characterize glasses prepared specifically for microanaly tical

work and to test homogeneity in the micrometer dimensional

range. Traces for the aluminum Ka and barium Lai signals in

NE° Glass K-489 are shown in figure 4. In both cases - the

moving 1 ym beam and the stationary 20 ym beam - deviations

are within Poisson counting statistics. These two elements

thus are homogeneously distributed in this glass, within the

statistical limits indicated on the graph. The above observation of homogeneity can be made in only one stepping direction

at a given time. This is a limitation of the procedure. At

least one other trace perpendicular to the one above or preferably several more are required to guarantee homogeneity.

One must be careful, though, not to assume that homogeneity is within desirable limits simply because the signal

excursions from a traverse across a specimen fall within the

Poisson limits for a given set of operating conditions. Where

the average number of counts collected per point is low, such

as for molybdenum in the SRM steel 663 and aluminum in glass

K-489, the ±3-sigma limit imposed by Poisson counting

statistics alone is quite large relative to the average number

of counts per point. Where possible, therefore, the total

number of counts in such a case should be increased by adjusting experimental conditions. Also, a statistical comparison

between the moving and the stationary specimen is helpful

in separating the effect of inhomogeneity from instrumental

instabi lity

.

Instrumentation

The periodic integrator shown in figure 5 consists of

the following components: (1) a single-board microcomputer,

(.2) a multichannel digital sealer/timer, (3) four digitalto-analog converters with four-digit resolution, and (4) a four-channel fast-pen-response recorder. Specifications for

the periodic integrator are listed in Table II.

9
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10

Table II. Specifications for Periodic Integrator Assembly.

Scalers

:

Input Level: TTL 0 to +5 volts

Scaler Capacity: 7 digits

Maximum Count Frequency: 10 MHz

Time Base: Crystal controlled, accurate to 1 part in 10

Scaler Accuracy: ±1 count

Data Output: 8 bit parallel ASCII byte serial

Microcomputer Section:

Data Input: 8 bit parallel ASCII byte serial

Calculation Accuracy: Log mode, ±.31

Linear mode, 4 digits

Data Output: 0 to +5.000 volts

The microcomputer is programmed to receive data from

four seven-digit scalers and to operate on any selected

group of four adjacent digits out of the field of seven.

The folloi/ing operations are performed by the microcomputer:

(1) subtract a four-digit baseline, (2) multiply the result

by a two-digit multiplier and (3) compute the logio of the

result if a log display is desired.

The computed results are transferred by the microcomputer

to the four digital-to-analog converters, and the analog outputs are connected to a multi-pen strip chart recorder for

display. The microcomputer can also advance the stage of the

electron microprobe to a new position after one to sixteen

scaler read-outs. A block diagram of the interfacing components is shown in figure 6.

Statistical Evaluation of Data

The periodic ratemeter traces described above can be

acquired rapidly. If desired, the data can at the same time

be recorded numerically on a teletype and stored in an

appropriate recording device such as magnetic tape for later

statistical analyses.

12

The computer program we have been using was written by

Dr. Robert Paule of the National Measurement Laboratory,

NBS. It takes into account three types of signal fluctuations

that can occur. These are: (1) those due to concentration

differences from point to point, (2) the signal variation on

a single point due only to Poisson counting statistics, and

(3) the signal drift due to contamination build-up and instrumental instability. To account for the latter two types of

signal fluctuations, the Paule program can handle as many as

20 duplicate measurements on a single point (though we are

ins trumentally limited to 16) for as many as 50 independent

points. For each group of duplicate measurements on a single point, an average and a standard deviation are calculated, and also an overall mean and standard deviation are

ob tained

.

By a simple analysis of variance we obtain an estimate

of the standard deviation for one point as well as an estimate

of the standard deviation between points. These estimates

are called the "within" and "between" components of the

standard deviation.

The "within" component reflects the variation found in

duplicate measurements caused by fluctuations in counting and

from instrument drift if present. The "between" component

reflects only the variation observed from point to point,

excluding the previously mentioned sources of fluctuations.

If the "within" and "between" components are quite different,

i.e., if the latter is several times larger than the former,

a high degree of inhomogenei ty of the element or elements in

the sample is assumed. The equations used for these calculations are in Appendix 10.

A second computer program is sometimes used. This is

an OMNITAB statistics program which was developed at NBS for

general usage [7]. We use it to plot the average of the

counts for each point, calculated in the previous program,

vs. sequence. In addition, OMNITAB calculates many statistical parameters such as the mean, range, standard deviation,

variance, etc. of the total number of counts.

14
II. Results

The homogeneity test procedure described above was used

to study several SRMs . These include the iron and steel

SRMs 661, 662, 663, 664, 461, and 463, which had not been

certified for microanalysis. Some SRMs that had been certified

for microanalysis, such as the gold-silver alloys (SRM 481),

the gold-copper alloys (SRM 482), the W-20Mo alloy (SRM 480),

cartridge brass (SRM 478), and iron-3 percent silicon (SRM

483) were reevaluated with the new procedure. The homogeneity

of RM 30, a set of glasses manufactured specifically for

microhomogeneity , was also evaluated, as was a new issue of

the iron- chromium-nickel alloys (SRM 479a)

.

Several of the samples above had been previously tested

for homogeneity by the best methods available at that time.

Rigorous evaluations were employed and gross inhomogeneities

were readily detected by conventional ratemeter scans, TOPO,

QRS, or random sampling. However, the extent of homogeneity,

or inhomogeneity , is dependent upon the spatial definition

of homogeneity and hence upon the method of measurement used

in the testing procedure which should be chosen according to

the purpose for which the material has been prepared. Microanalytical techniques vary considerably in the amount of

material sampled. EPMA was chosen to determine microhomogeneity because one can quantitate with the method and because a large number of micro samplings can be taken with reasonable

ease. While such a refined determination of microhomogeneity

would not be necessary when the material is used as a standard

in spark source mass spectrometry (or optical emission spectroscopy) , the information obtained is of considerable benefit

to the understanding of material variability and how such

variability could affect the measurement process.

We have now extended our ability to learn about these

materials by using the new homogeneity testing procedure.

With little trouble a material can be observed from micrometer to micrometer under complete automation. But just

because we may now know more about this material does not mean

that its quality as a microhomogeneity standard has changed.

The new information should be helpful to the experimentalist

in determining its usefulness in micro techniques.

Much of the following discussion is devoted to the steel

standards (SRM 661-664). This is not because these materials

are of any greater importance than the other materials that

were tested; in fact, SRMs 661-664 were not specifically prepared for use as standards with EPMA. However, this is the

first publication to include studies on the characterization

of these standards while the other materials listed above

were described in detail in previous publications [1-5,9,10].

Also, these steels are good examples for demonstrating the

15
microhomogeneity test procedure that we have developed. They

have several added elements distributed between two phases

and several types of inclusions. The discussion below shows

how these materials can be used as standards even though a minor degree of inhomogenei ty can be demonstrated.

Unless otherwise stated, experimental homogeneity scans

were performed by moving the sample in 1 ym steps under a

1 ym-diameter electron beam. The computer program used in

the statistical evaluation allowed for 50 steps per scan;

therefore, each scan was 50 ym long. Counts were accumulated

for ten seconds per reading. Two readings were taken on each

step. The counts from, each 10-s counting period were printed

on a teletype. As many as three elements were simultaneously

investigated. The specimen current was also recorded for each

10-s interval; this allowed easy observation of instrument

drift. Unless otherwise stated, all homogeneity tests were

made according to the above conditions.

For comparison, after each homogeneity test scan was

prepared, data were collected with the sample stationary.

To simulate a scan of a homogeneous target, 100 10-s

readings were recorded for the same area. Usually a 20 ym

diameter electron beam was employed to avoid sample contamination and to approach the value corresponding to the

average composition.

As long as there is no significant drift, the statistics

from the stationary scan reflect only the counting statistics

and small random instrumental errors. The results should be

equivalent to what one would observe for a truly homogeneous

sample. The comparison of the statistics on the moving sample

to those of the stationary sample can therefore reveal the

homogeneity or inhomogeneity of the specimen. For all stationary scans both the "within" and "between" components of

the standard deviation were small and in agreement with that

predicted from counting statistics only. The results of

stationary scans are not included in the following tables of

results as they were primarily used to verify that the larger

standard deviations observed in the test scans of the moving

sample were indeed due to inhomogeneity and not to large

instrumental errors.

For samples that were homogeneous, i.e., within the

±3-sigma limits predicted from Poisson statistics, a periodic

ratemeter scan was all that was needed to define the homogeneity. In the few cases where the statistical evaluation

was also done on apparently homogeneous materials, the standard

deviations, including the "between" component, were very small.

But in the cases which appeared to be inhomogeneous in the

ratemeter scans, a large "between" component of the standard

16
deviation was obtained in the analysis of variance. The

magnitude of this component depended upon the degree of

inhomogeneity in the scanned region.

In the following discussions of the results there are

several tables of statistical results. The standard deviations cited therein are not certified values because we have

no proof at present that the micro- inhomogeneity is sufficiently uniform within each batch of specimens that its

numerical expression can be guaranteed for the entire batch.

The numbers given are only an approximate estimate of the

inhomogeneity one can expect from a particular element in a given SRM. The estimates were calculated from only one 50 ym

scan on only one sample. Although the homogeneity procedure

has been considerably simplified, it would be an onerous task

to provide a certified value defining the extent of inhomogeneity even if the batches were of uniform homogeneity. To do

this for each element, several 50 ym scans on several samples

of the same standard would be needed.

We therefore provide only a rough estimate of inhomogeneity to the users of these SRMs . If the user finds it

necessary to apply any of these materials which were found

to be inhomogeneous as standards, we advise that he determine

the "within" and "between" components of variance of his

measurements from his own SRM samples. This can be easily

done by taking many random readings from the sample and

calculating the components from the equations in Appendix 10.

Iron and Steel SRMs 661, 662, 663, 664

The certificates for these SRMs are shown in Appendix 1.

The concentrations were obtained by analysis of the bulk sample

Although these standards have numerous inclusions, they can

be used in microanalyses for those elements which are not

preferentially concentrated in the inclusions, and are

fairly homogeneously distributed throughout the metal matrix.

These steel SRMs had been previously studied in this

laboratory [8] to determine the chemical compositions and

distribution densities of the inclusions. The SRMs are in

the form of rods 3.2 mm in diameter and 51 mm long. Polished

mounts were prepared of cross sections (normal to the long

axis) and of longitudinal sections (parallel to the axis)

.

In these early studies, a large number of inclusions in each

steel were qualitatively analyzed with the lithium-drifted

silicon detector [Si(Li)] on the EPMA. To confirm the

17
results from the Si (Li) detector, wavelength scans of several

inclusions in SRM 661 were recorded.

In the earlier studies, at least two types of inclusions

were found in all steels - those with elements of average

atomic number higher (high-Z) than the matrix and those with

elements of average atomic number lower (low-Z) than the

matrix. These classifications were made on the basis of the

target current images, i.e., on whether the inclusions were

lighter or darker than the matrix. The major constituents

found in the high-Z inclusions in all steels were titanium,

niobium, zirconium, and tantalum. This type of inclusion is

probably what the metallurgist refers to as a refractory

carbide. Some silicon was observed in the wavelength scans

of such inclusions in SRM 661. If silicon were present in

the high-Z inclusions in the other steels, it was obscured

in the energy-dispersive spectra by the Ta Ma peak and the

Nb and Zr La peaks. A small amount of silver was also found

in the high-Z inclusions of SRM 664.

In SRMs 661, 662, and 663 most of the low-Z inclusions

contained sulfur, manganese, and selenium. Oxygen, magnesium,

aluminum, silicon, zirconium, niobium, and cerium were also

found in the wavelength scans of such inclusions in SRM 661.

These probably are another common type of inclusion generally

referred to as "glassy", which contain oxides of silicon,

aluminum, magnesium, and cerium and some sulphides, mainly

manganese sulphide.

In all the steels some of the low-Z inclusions contained

the same elements as the high-Z inclusions. It was concluded

that these were probably holes which formed when part of the

high-Z inclusion had been chipped out in the polishing procedure. Such holes would appear to be low-Z inclusions in the

target current image.

The low-Z inclusions in SRM 664 were varied in composition. Some contained mostly iron with small amounts of

molybdenum. Others were quite similar in composition to the

matrix and contained also small amounts of sulfur, vanadium,

and manganese.

Figures 7 to 9 show target current images and x-ray

area scans of cross- sections of SRM 663 and SRM 664 and of a longitudinal section of SRM 662. In figure 7 the two types

of inclusions are present in the target current image (a) of

SRM 664. The low-Z inclusions appear as white spots and

the high-Z inclusions are dark. X-ray area scans b, c, and

d show that titanium, tantalum, and niobium are considerably

more concentrated in the inclusions than in the matrix.

Manganese and nickel (scans e and f respectively) show no

18
preferential enrichment in the inclusions; yet the manganese

distribution appears to be spotty while that of nickel seems

to be more evenly distributed.

In figure 8 the x-ray area scan of titanium (b) in

SRM 663 shows that this element again is preferentially

located in the low-Z inclusions. The x-ray area scan for

vanadium (c) is spotty indicating inhomogenei ty of this

element

.

Several of the inclusions in the longitudinal section

(figure 9) form stringers (a) . Zirconium (b) and again

titanium (c) are present primarily in the inclusions.

Regions of the main phase in SRMs 661-664 were tested

for homogeneity. All scans were made at 30 KV with a beam

current of approximately 1.5x10 7 A. The results of the

statistical evaluations of these homogeneity scans are shown

in Tables III thru VI. Two different samples of each steel

were analyzed — a cross - section and a longitudinal section.

All elements that exhibited a discernible signal above the

baseline were tested in the cros s - s ec t ion scans. Only

nickel and copper were tested in the longitudinal section.

In these tables the postulated mean concentrations are

those taken from the SRM certificate (Appendix 1) . X is

the average (in counts) of the 100 x-ray measurements (50

steps, each repeated once), and the background, B, is an

average of five readings taken from pure iron (rounded to

the nearest 100)

.

The estimated standard deviations (in counts) , and

6g are the "within" and "between" components respectively.

The numbers in parentheses are the coefficients of variation

100 e w

100 3

B (in percent) , ——XXand —— , respectively. The equations

used to calculate 6 1lT and are numbers 2 thru 6 in

W B

Appendix 10. A comparison of 3g with (in either counts or

percent) gives a good indication of how inhomogeneous the

element is in the sample.

The "between" standard deviation d^, in weight percent,

represents the inhomogeneity component of the standard deviation in terms of concentration for a single measurement. It

is a rough estimate calculated on the basis of a linear relationship between the number of counts and the concentration.

The equation used is

19
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23
a -ft concentration (wt. %) , ,

.

°B(in wt. %) aB(in counts) X = = UJ

This value is strictly valid for the measured standard specimen

only. It is not intended to be used for accurate work with

another piece of the same SRM; rather, it is meant to provide

a rough estimate of the affect of inhomogenei ty when the SRMs

tested here are used as standards in other laboratories and

where the necessary accuracy does not warrant that the experimentalist redetermine the inhomogenei ty of his particular

standard material specimen. r Once awr . is obtained (from W(m wt%) v several duplicate readings), it can be combined with 6^ , . ^ d (_ m wt -g J and with the uncertainty in the mean concentration from the

certificate (Ui , in wt%) to obtain a fair estimate of the

total uncertainty, U, in terms of concentration as derived

from the intensity measurements. See equation 10 in

Appendix 10.

In Tables III thru VI, the uncertainty of the electron

probe measurement CU 2 , combines the "within" and "between"

components of variance with the contribution from the background measurement. U is the total uncertainty (99.7%

confidence level) in the estimate of concentration obtained

by combining CU2 and Ui. The equations used for estimating

these uncertainties are in Appendix 10.

The elements tested in the four steels were those which

are primarily located in the main phase. Exceptions to this

were manganese and titanium. Manganese appears to be located

throughout both the main phase and the inclusions with apparently no strong preference for either. This can be observed

in the area scans (see figure 7e) . But titanium, though

present in both phases, shows a strong preference for the

inclusions (see figures 7b, 8b, and 9c). This preference

alone precludes the use of these SRMs as micro standards for

titanium in steel. The results of titanium measurements

were included here only to show how the magnitude of the d-g

reveals that the element is grossly inhomogeneous

.

In a few cases the signal above the background is not

large (only a few hundred counts) . Such is the case for

copper in SRMs 661 and 663, vanadium in SRM 662, and tungsten

in SRM 664. The relative values for 6^ could, in these situations, be largely due to poor counting statistics only.

Therefore, one cannot draw any conclusions regarding homogeneity when counting statistics are poor.

24
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28
Only nickel and copper were tested in the longitudinal

sections. These two elements appeared to be reasonably

homogeneous in the cross - sect ion scans. Also, nickel is

expected to be homogeneous as in principle it is completely

soluble in the iron matrix. Scan I of the longitudinal

section was parallel to the length of the rod from which the

standard pieces were sectioned, while scan II was perpendicular to it. Scan II is essentially a cross section scan.

The results of the measurements for nickel and copper in

both samples are comparable.

As previously discussed, other laboratories wishing to

use these SRMs for micro standards may wish to evaluate the

homogeneity of their specimen of the standard reference

material. The easiest and least time-consuming way to do

this is by random sampling. To check the validity of such

a procedure, we determined the error due to inhomogenei ty

obtained to random sampling for three elements in our four

specimens and compared this error to the "between" component

of the standard deviation.

Nickel, chromium, and manganese were measured in the

four SRMs. A 1 ym beam was used at 30KV and a beam current

of slightly less than 1.5x10 7 A. Counting periods were 10s.

Data were taken from ten randomly chosen points on the specimen

avoiding all visible inclusions. Each specimen was used twice

in the experiment; therefore, two independent standard deviations were calculated for each element and SRM. Equation (1)

was used to calculate these standard deviations in weight

percent (o^ ^

n wt ^)- ^ n Table VII they are compared to

-t-o^ obtained from the homogeneity traces (Tables V

d { m w L ~6 ) through VII). In most cases . to J 0 calculated from B(m wt%)

random sampling agrees quite well with that calculated from

the homogeneity traces.

Generally, a particular level of precision for the

measurement process is desired. This generally can be met by

taking the appropriate number of random samples, n. The

standard deviation of a single point, as determined alone,

multiplied by n is an estimate of the standard deviation of

the average of n measurements. One, therefore, can predetermine how many measurements must be made to meet the

desired precision. Such a procedure should, however, be

interpreted with caution. It implies, among other things,

that the subsample (specimen) used by the analyst does not

differ significantly in composition from the portions which

were used in chemical analysis.

29
Table VII. Comparison of Random Sampling with Homogeneity

Traces for Iron and Steel SRMs

.

Element

Sample Ni Cr Mn

661 Cnnr fwt %

~\ a B(wt 0O

RS a RS,

HT

1 QQ

0.046

0.041

0.034

n f> q

0.120

0.093

0.110

U . O D 0.089

0.067

u.083

662 Cone fwt?H

a B(wt%) RS

RS

HT

0 5Q

0.021

0.018

0.017

0.045

0.040

0.048

i n a 0.087

0.089

0.086

663 Cone (wt'%) a B(wt%) RS

RS

HT

0.32

0.014

0.011

0.009

1.31

0.110

0.198

0.250

1 . 50

0.075

0.155

0. 180

664 Cone C.wt%) a B(wtl) RS

RS

HT

0.14

0. 024

0.020

0.018

0.07

0.021

0.028

0.011

0.26

0.101

0 .064

0.058

RS = Random Sampling.

HT = Homogeneity Trace.

In conclusion, there are few elements in these samples

which are close to being homogeneously distributed on the

micrometer scale. Any use of these SRMs as micro standards

in quantitative analyses must be done with great caution.

Our estimates of inhomogenei ty should only be applied to

other specimens of the standards when high accuracy is not

needed. To improve the accuracy of analysis, one shoulcl

redetermine the inhomogenei ty of one's own piece by taking

many random samplings and applying the equations in Appendix

10. The larger the number of samplings taken, the more

accurate will be the estimate of inhomogenei ty , and of the

x-ray intensity which corresponds to the nominal average

composition of the standard.

30
Low-Alloy Steel SRMs 461 and 463

These SRMs were previously tested for homogeneity [1,2].

The overall compositions of these samples appear in the

Provisional Certificate of Analysis in Appendix 2.

In the first homogeneity study of SRM 461, chromium,

silicon, and manganese were found at high levels in the

inclusions. Nickel and iron were reported to be homogeneous

throughout the matrix. This was determined from numerous

random samplings with a 2-4 ym diameter electron beam.

Sulphur, zirconium, niobium, and tantalum were found in

the inclusions of SRM 463. Manganese was determined to be

inhomogeneously distributed throughout the matrix while iron,

copper, nickel, and silicon were found to be homogeneous at

the 3 ym level

.

In the present work, homogeneity test scans were prepared

for nickel, copper, molybdenum, and cobalt in SRM 461 and for

silicon, nickel, copper, and vanadium in SRM 463. The results

appear in Table VIII. Only the nickel in SRM 461 shows a high signal above the background level. Since is more

than three times 8-^, nickel is probably somewhat inhomogeneously distributed throughout this sample. The homogeneity

of the other three elements could not be determined since the

signals are low in these cases. In SRM 463, nickel again

appears to be inhomogeneous , as does vanadium. But silicon

and copper appear to be more homogeneous.

Gold-Silver and Gold-Copper Wires, SRMs 481 and 482

The certificates for the gold-silver (SRM 481) and the

gold-copper alloys (SRM 482) are shown in Appendices 3 and

4. The original criterion for acceptable homogeneity of

these samples was that the maximum composition variations

should not exceed .01 (mass - fraction) . The data quoted in

the certificate indicate that this criterion was met.

The original homogeneity test was made with TOPO (5)

.

We retested these samples for homogeneity with the new

procedure. Two scans perpendicular to each other were made

for each of two samples of each wire. The sample was moved

in 1 ym steps under a 1 ym diameter electron beam for a length of 100 ym. The periodic ratemeter traces of these

scans were within the limits of ±3-sigma calculated from

Poisson counting statistics and within 1 percent. Therefore,

these samples are considered satisfactorily homogeneous.

31
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32
Statistical evaluations with the computer programs were

not done for most of these samples. Experience has shown

that if a ratemeter trace looks satisfactory, i.e., all or

most readings fall within the ±3-sigma limits, the calculated

standard deviations will be small.

One homogeneity scan was statistically evaluated for a Au80-Cu20 sample. This was a 50 ym scan with a 1 ym

diameter beam stepping across the sample in 1 ym steps, each

repeated once. The statistical results which appear in

Table IX show no evidence of inhomogeneity

.

Tungsten- 20 Molybdenum Alloy, SRM 480

This SRM was previously tested for homogeneity in 1968

by the QRS procedure [3], A total of 100 points were tested

in a 10 x 10 point matrix 48 ym along each edge. Four to

five rasters in each of three samples were tested. The

overall coefficient of variation was determined to be 2.5

percent for molybdenum and 1.5 percent for tungsten. The

certificate for this SRM is in Appendix 5.

The usual homogeneity scan of one specimen using 1 ym

steps across 50 ym in the sample interior showed a portion

of a wavy, continuous signal. While the counts for one

component increased, the counts for the other decreased. The

deviations from the average number of counts were outside

the Poisson ±3-sigma limits. The first few scans of this type

indicated that these "waves" extended well beyond 50 ym. Thus,

scans over longer distances were needed. In the QRS procedure

used previously this type of trend could have been missed.

Subsequent scans of 1 ym steps across 250 ym confirmed

the above results and showed that the fluctuations or waves

are not periodic. Finally three scans were made across the

same specimen in 10 ym steps from edge to edge. Each scan

was approximately 60° from the previous. Figure 10 illustrates

one of these scans. The ±3-sigma limits about the average

are indicated by double-headed arrows. The regions beyond

the dashed lines at the beginning and end of the scan correspond to the extreme edges of the sample which, as previously

suggested [3], should be avoided when using this standard.

In figure 10 the concentration change represented by a signal fluctuation from a maximum to a minimum is approximately 3 weight percent. If the statistics found previously

[3] are applied to this trace, most points fall within the

±3-sigma limits. The 2.5 percent coefficient of variation

for molybdenum is equivalent to ±0.53 weight percent or a ±3-sigma of ±1.59 weight percent. And for tungsten the 1.5

percent coefficient of variation is equivalent to a ±3-sigma

of ±3.6 weight percent.
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Statistical evaluations with the Paule program were not

made of these scans. The equations used in this program are

based on random distribution models and they do not apply to

the type of trends that we are observing here.

The other two scans of this specimen are similar to

figure 10. One scan shows only one maximum and minimum near

the beginning of the trace with very little change across the

second half of the scan. Such anomalies and lack of consistency reinforces the need for taking many randomly selected

samples when using this specimen as a standard.

Cartridge Brass, SRM 478

The certificate for SRM 478 is in Appendix 6. This SRM

consists of two forms - wrought (NBS-1102) and cast (NBSC1102) . SRM 478 was one of the first NBS reference materials

tested for microhomogenei ty [2]. The random sampling technique

with a 1 pm electron beam was used to observe the major components, copper and zinc. Twenty- four random analytical

points were used to test the wrought form; forty-two were

used to test the cast form. To check reproducibility, a duplicate reading was taken at each test point.

The results of this early work are in Table X. The wrought

form of the brass was found to be less homogeneous than the

cast form, but none of the errors were so prohibitively large

as to prevent the use of this SRM as a micros tandard

.

Table X. Homogeneity Testing of Cartridge Brass SRM 478. a

Sample Element

Standard Deviation

(%) Computed from

Experiment

Analytical Range

(two standard

deviations in wt%)

NBS-C1102 Cu 0.72 71.8 to 73.8

Zn 0. 79 26.7 to 27.5

NBS-1102 Cu 1.0 71.1 to 74.6

(wrought)

Zn 2. 2 25.9 to 28.3

Data taken from reference (2)

.

36
In our present work, two pieces of the wrought form and

two pieces of the cast form were studied. For each piece,

two periodic ratemeter traces normal to one another were

prepared. The sample was moved in 5 ym steps under a 1 urn electron beam. The probe was operated at 30 KV with a 1.5x10 7 A beam current.

A periodic integrator trace of copper and zinc in one of

the wrought samples is in figure 11. This homogeneity trace

is typical of those observed for all samples. The composition

of these elements changes in a wave-like manner across the

samples. The waves are not periodic; those in close proximity

are about 125 ym from peak to valley but most waves stretch

out over longer distances. Of the four traces prepared from

the wrought sample, the largest concentration difference

between a minimum and maximum was equivalent to 1.7 weight

percent. For the cast samples the largest concentration

fluctuation was 1.4 weight percent. These variations are

within the deviations found previously (Table X)

.

Iron-Three Percent Silicon, SRM 483

This SRM was previously certified for microhomogenei ty

(see Appendix 7) . The original testing was done on six different samples of the material [9]. Quantitative area scanning

was used with a square matrix of 20x20 points covering an area

of about one square millimeter. The use of the lithium-drifted

silicon detector made it possible to study such a large area

without defocusing problems. Statistical and spacial analysis

was done with TOPO. From a total of 3700 individual analytical

points, a conservative estimate of the coefficient of variation

was determined to be one percent for the entire group of

samples

.

In the present work, homogeneity traces of iron and

silicon were prepared at 20 KV with a 1.5x10 7 A beam current.

The sample was moved in 5 ym steps under a 1 ym electron beam.

Counting periods were 10s. These traces were made both along

the longest dimension and normal to the longest dimension of

two different pieces of this SRM.

The traces along the sample length covered a distance of

about 1.5 mm. Some upward drift in the iron and silicon

signals occurred which could only be attributed to a positive

beam current drift. For both samples, most of the signal

fluctuations fell within the ±3-sigma limits. One sample

showed a short wave-like fluctuation for iron over about

50 ym where the peaks and valleys fell slightly outside the

±3-sigma limits. Such a fluctuation is still within the 1

percent coefficient of variation quoted in the certificate

for microhomogeneity . The iron signal showed greater random

37
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dimension than in those run along the longest dimension.

The signal often falls outside the ±3-sigma limits, but again

not so far as to exceed the 1 percent certificate limits. In

all homogeneity traces, the silicon signal is within the

±3-sigma limits.

Glasses for Microanalysis, RM-30

A list of ten glasses that make up this NBS Research

Material Set appears in Appendix 8. The nominal compositions

are listed; they were calculated from the weight of material

added to the melt. These Research Materials were prepared to

fulfill a need for standards containing low concentrations of

many different elements. Glasses were selected as the matrix

material because they can easily meet the microhomogenei ty

requirement and because most metal oxides can easily be added

to glasses in small quantities.

Except for the AI2O3-B2O3 glasses, homogeneity traces

were prepared for the major constituents of the glasses.

Scans were run on two different pieces of each glass at 15 KV

with a beam current of about 7.5x10 8 A. A 1 ym electron beam

was used while moving the sample in 1 ym steps under the beam

for 10-s counting periods. The traces are in figures 12

through 15, where the scan across the moving sample is to

the right and the trace with the stationary 20 ym beam is to

the left. Deviations are within the ±3-sigma limits. The

traces contain no evidence of inhomogenei ty

.

Austenitic Iron-Chromium-Nickel Alloy, SRM 479a

The certificate for SRM 479 is in Appendix 9 where the

coefficient of variation for 160 points on each of five

samples is stated to be not greater than 1.5 percent. The

homogeneity characterization is described in detail in

reference [10] . The five specimens came from the extreme

ends and the 1/4, 1/2, and 3/4 positions of the alloy rod.

On each specimen six manual traces were made of the three

elements. Two traces were along diameters normal to one

another and the remaining four were chords of the specimen.

Points were 200 ym apart.

SRM 479 was no longer available when this homogeneity

work was being done but testing on the proposed renewal,

479a, was requested. Three traces were prepared for each of

the five specimens (samples taken as described previously for

SRM 479) using a 1 ym beam and 5 ym steps. Two traces normal

to one another and at the center of the specimen covered a distance of about 500 ym. The third trace was used for statistical analyses. In all traces no serious inhomogeneit ies

were observed. The signals for all three elements fell

39
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41
20vim beam

Stationary

7.8 wt .

I

Glass K-489

lym beam i Mm steps

2000

0.0 wt.% Zinc Kcx 3.0 wt

.

%

•0 -

53 .9 wt.% 13,000

Barium La, 3 9.3 wt . % n

o

c

3

33 . 0 wt -8000

2 6.8 wt.%- -23, 000

Silicon Ka 21.9 wt

21.0 wt.V =18,000

Figure 14. Periodic integrator homogeneity traces of silicon,

barium, and zinc simultaneously recorded from NBS

RM Glass K-489 (voltage = 15 kV, beam current = 7.5xlO" 8 A). In the trace on the right, the sample

was advanced 1 ym under a 1 ym electron beam after

each ten-second counting period. To the left, the

sample was not moved during repeated ten-second

counting periods with a 20 ym electron beam. The

double-headed arrows to the right represent a range of ±3/N around the average number of counts

per 10 seconds, N, for the entire trace.

42
Glass K-497

20um beam

Stat ionary

6.09 wt

lum beam lym steps

Magnesium Kot 5 . 2 wt . %

-12,000

5.51 wt.% -7000

42 .8 wt . % •8000

n

o

c

3

r+

in

Phosphorus Ka 55.2 wt.%

o

16.1 wt.% 5000

10.9 wt . % 5200

Aluminum Ka 5 . 8 wt

.

%

2.1 wt.% 700

Figure 15. Periodic integrator homogeneity traces of aluminum,

phosphorus, and magnesium simultaneously recorded

from NES RM Glass K-497 (voltage = 15 kV , beam

current - 7.5xlO~ 8 A). In the trace on the right,

the sample was advanced 1 um under a 1 urn electron

beam after each ten- second counting period. To the

left, the sample was not moved during repeated tensecond counting periods with a 20 ym electron beam.

Double-headed arrows to the right represents a range of ±3/N around the average number of counts

per 10 seconds, N, for the entire trace.

43
within the ±3-sigma limits and the "between" component of

the standard deviation, was in all cases the same or smaller

than 8^ t the "within" component.

The five specimens were intercompar ed by two operators

using random sampling. One end sample did appear to be

somewhat different from the remaining four. This end will

probably be eliminated when the SRM is issued. Complete

details of this homogeneity study will appear soon in a new

publication on the preparation and analysis of SRM 479a.

We extend our thanks to Dr. J. Mandel and Dr. R. C. Paule

for preparing the computer program used in the statistical

treatment of the homogeneity scans, to Mrs. M. C. Croarkin

and Dr. H. H. Ku for assisting in the statistical handling

of the results including the preparation of the equations

that appear in Appendix 10, and to Mr . R. L. Myklebust and

Ms. B. B. Thorne for adapting the Paule program to our

facilities and for preparing the data from the homogeneity

scans for the computer. Our thanks also to Mr. J. A. Norris

and Mr. R. E. Michaelis for their useful suggestions during

the preparation of this manuscript.

44
References

Michaelis, R. E., Yakowitz, H. , and Moore, G. A., J. Res

Nat. Bur. Stand. -A. Phys. and Chem. 6_8A, No. 4, 1 (1964)

Yakowitz, H. , Vieth, D. L., Heinrich, K. F. J., and

Michaelis, R. E . , Nat. Bur. Stand. U.S. Misc. p ub

.

260-10 (1965).

Yakowitz, H. , Michaelis, R. E. , and Vieth, D. L., Nat.

Bur. Stand. U.S. Spec. Pub. 260-16 (1969).

Ibid, Adv. in X-ray Anal., 12 (1969).

Heinrich, K. F. J., Myklebust, R. L . , Rasberry, S. D.,

and Michaelis, R. E., Nat. Bur. Stand. U.S. Spec. Pub.

260-28 (1971).

Heinrich, K. F. J., Adv. in X-ray Anal. 7_, 382 (1963).

Hogben, D., Peavy, S. T., Varner, R. N., NBS Tech. Note

552, (1971).

Myklebust, R. L., Fiori, C. E., and Heinrich, K. F. J.,

"Report of Analysis by Electron Probe Microanalysis on

Inclusions in SRM Steels 661-665", 1971.

Yakowitz, H., Fiori, C. E., and Michaelis, R. E., Nat.

Bur. Stand. U. S. Spec. Pub. 260-22 (1971).

Yakowitz, H., Ruff, A. W. , and Michaelis , R. E . , Nat.

Bur. Stand. U. S. Spec. Pub. 260-43 (1972).

45
U.S. Department;*! Commerce

Rogers C3Bi Morton.

Secretory

National Bureau of Standards

Ernest Ambler, Acting Director

Appendix 1 Rational ^mmxx of Standards

Certificate of JVnalgsig

Standard Reference Material 1261

AISI 4340 Steel

This standard is in the form of disks 31 mm (1 1/4 in) in diameter and 19 mm (3/4 in) thick,

generally for use in optical emission and x-ray spectrometric analysis.3

Element Percent, by weight Element. Percent, bv weight

Carbon 0.38 9 Aluminum (total) 0.02i

Manganese .66 Niobium .022

Phosphorus .015 Tantalum .020

Sulfur .017 Boron .0005

Silicon .223 Lead .00002 5

Copper .042 Zirconium .009

Nickel 1.99 Antimony .0042

Chromium 0.690 Bismuth .0004

Vanadium .011 Silver .0004

Molybdenum .19 Calcium .00002 8

Tungsten .017 Magnesium .00018

Cobalt .030 Selenium .004

Titanium .020 Tellurium .0006

Arsenic .017 Cerium .0014

Tin .010 Lanthanum .0004

Neodymium .0002 9

This material also is available in the form of chips, SRM 361, for use in chemical methods of analysis; rods, SRM 1095, 6.4 mm

(1/4 in) in diameter and 102 mm (4 in) long for the determination of gases in metals by vacuum fusion and neutron activation methods of analysis; and rods, SRM 661, 3.2 mm (1/8 in) in diameter and 51 mm (2 in) long for application in microchemical methods of analysis such as electron probe microanalysis, spark source mass spectrometric analysis, and laser probe analysis.

CERTIFICATION : The value listed for a certified element is the present best estimate of the "true"

value based on the results of the analytical program The value listed is not expected to deviate from

the "true" value by more than ±1 in the last significant figure reported; for a subscript figure, the

deviation is not expected to be more than ±5. Based on the results of homogeneity testing, maximum variations within and among samples are estimated to be less than the uncertainty figures

given above.

The overall direction and coordination of the technical measurements at NBS leading to certifi- cation were performed under the direction of K. F. J. Heinrich, 0. Menis, B. F. Scribner, J. I. Shultz, and J. L. Weber, Jr.

The technical and support aspects involved in the preparation, certification, and issuance of this Standard Reference Material were coordinated through the Office of Standard Reference Materials

by R. E. Michaelis.

Washington, D.C. 20234 J. Paul Cali, Chief

January 8, 1976 Office of Standard Reference Materials

(Originally issued July 26, 1970

with revisions August 16, 1972, and

attachment February 24, 1975) (over) 46
PLANNING, PREPARATION, TESTING, ANALYSIS: This standard is one of five replacements

for the original eight 1100 series iron and steel SRM's. Material from the same melt is availahle in a

variety of forms to serve in checking methods of analysis and in calibrating instrumental techniques.

The material for this standard was vacuum melted and cast at the Carpenter Technology Corporation, Reading, Pennsylvania, under a contract with the National Bureau of Standards. The eontract was made possible by a grant from the American Iron and Steel Institute.

The ingots were processed by Carpenter Technology Corporation to provide material of the

highest possible homogeneity. Following acceptance of the composition based on NBS analyses,

selected portions of the ingot material were extensively tested for homogeneity at NBS by J. R. Baldwin, D. M. Bouchette, S. D. Rasberry, and J. L. Weber, Jr. Onlv that material meeting a critical evaluation was processed to the final sizes.

Chemical analyses for certification were made on composite samples representative of the ac- cepted lot of material.

Cooperative analyses for certification were performed in the analytical laboratories of Bethlehem

Steel Corporation, Sparrows Point Plant, Maryland, R. H. Rouse; Carpenter Technology Corporation, Research and Development Center, Reading, Pennsylvania, E. J. Cramer; The Timken Roller Bearing Company, Steel & Tube Division, Canton, Ohio, R. G. Cover; United States Steel Corporation, Applied Research Laboratory, Monroeville, Pennsylvania, L. Melnick; and Gary Steel Works,

Gary, Indiana, E. H. Shipley.

Analyses were performed in the Analytical Chemistry Division of the National Bureau of Standards by the following: R. Alvarez, J. R. Baldwin, D. A. Becker, R. K. Bell, R. W. Burke, B. S. Carpenter, E. L. Garner, T. E. Gills, G. J. Lutz, L. A. Machlan, E. J. Maienthal, J. McKay, L. J. Moore, C. W. Mueller, T. J. Murphy, P. J. Paulsen, T. C. Rains, S. D. Rasberry, T. A. Rush, K. M.

Sappenfield, B. A. Thompson, S. A. Wicks, and J. Wing.

ADDITIONAL INFORMATION ON THE COMPOSITION: Certification is made only for the ele- ments indicated. The five replacements, however, contain a graded series for 40 elements and

information on the elements not certified mav be of importance in the use of the material. Al- though these are not certified, values are presented in the following table for the remaining ele- ments.

Value from a single method of analysis:

Element

Gold

Zinc

Praseodymium

Hafnium

Nitrogen

Percent, by weight

(<0.00005)

(.0001)

(.00014)

(.0002)

(.0037)

Element

Oxygen

Hyd rogen Strontium

Iron (by difference)

Percent, by weight

(0.0009)

(<.0005)

a-(<0005)

(95.6)

Dash indicates "not detected." Value in parenthesis following the dash is the conservative "upper limit" of detection.

Approximate value from heat analysis:

Germanium [0.006]

47
U.S. Department -of Commerce

Rogers; C.jjjL Morton,

Secretary

National Bureau of Standards

Ernest Ambler, Acting Director National ^mtnn of Standards

Certificate of (Attaint*

Standard Reference Material 1262

AISI 94B17 Steel (Modified)

This standard is in the form of disks 31 mm (1 1/4 in) in diameter and 19 mm (3/4 in) thick,

generally for use in optical emission and x-ray spectrometric analysis.8

Element Percent, by weight Element Percent, by wei

Carbon 0.16 0 Aluminum (total) 0.09 5 Manganese 1.04 Niobium .29 Phosphorus 0.042 Tantalum .20 Sulfur .038 Boron .0025

Silicon .39 Lead .0004 3

Copper .50 Zirconium .19 Nickel .59 Antimony .012o

Chromium .30 Silver .0011

Vanadium .04i Calcium .00014

Molybdenum .06» Magnesium .00062

Tungsten .20 Tellurium .0011 Cobalt .30 Cerium .0015

Titanium .084 Lanthanum .0004

Arsenic .09 2 Neodymium .0006 4 Tin .016

This material also is available in the form of chips, SRM 362, for use in chemical methods of analysis; rods, SRM 1096, 6.4 mm

(1/4 in) in diameter and 102 mm (4 in) long for the determination of gases in metals by vacuum fusion and neutron activation methods of analysis; and rods, SRM 662, 3.2 mm (1/8 in) in diameter and 51 mm (2 in) long for application in microchemical methods of analysis such as electron probe microanalysis, spark source mass spectrometric analysis, and laser probe analysis.

CERTIFICATION: The value listed for a certified element is the present best estimate of the "true"

value based on the results of the analytical program. The value listed is not expected to deviate from

the "true" value by more than ±1 in the last significant figure reported; for a subscript figure, the

deviation is not expected to be more than ±5. Based on the results of homogeneity testing, maximum variations within and among samples are estimated to be less than the uncertainly figures

given above.

The overall direction and coordination of the technical measurements at NBS leading to certifi- cation were performed under the direction of K. F. J. Heinrich, O. Menis, B. F. Scribner, J. I. Shultz, and J. L. Weber, Jr.

The technical and support aspects involved in the preparation, certification, and issuance of this Standard Reference Material were coordinated through the Office of Standard Reference Materials by R. F. Michaelis.

Washington, D.C. 20234 J. Paul Cali, Chief

January 8, 1976 Office of Standard Reference Materials

(Originally issued July 27, 1970

with revisions August 16, 1972,

and attachment February 24, 1975) 48

(over)
PLANNING, PREPARATION, TESTING, ANALYSIS: This standard is one of five replacements

for the original eight 1100 series iron and steel SRM's. Material from the same melt is available in a variety of forms to serve in checking methods of analysis and in calibrating instrumental techniques.

The material for this standard was vacuum melted and cast at the Carpenter Technology Corporation, Reading, Pennsylvania, under a contract with the National Bureau of Standards. The contract was made possible by a grant from the American Iron and Steel Institute.

The ingots were processed by Carpenter Technology Corporation to provide material of the

highest possible homogeneity. Following acceptance of the composition based on NBS analyses, selected portions of the ingot material were extensively tested for homogeneity at NBS by J. R.

Baldwin, D. M. Bouchette, S. D. Rasberry, and J. L. Weber, Jr. Only that material meeting a critical evaluation was processed to the final sizes.

Chemical analyses for certification were made on composite samples representative of the ac- cepted lot of material.

Cooperative analyses for certification were performed in the analytical laboratories of Allegheny

Ludlum Steel Corporation, Research Center, Brackenridge, Pennsylvania, R. B. Fricioni; Inland

Steel Company, East Chicago, Indiana, R. W. Bley and J. E. Joyce; Republic Steel Corporation,

Canton, Ohio, R. W. Jones; and the Youngstown Sheet and Tube Company, Youngstown, Ohio, L.

E. Chalker.

Analyses were performed in the Analytical Chemistry Division of the National Bureau of Standards by the following: J. R. Baldwin, R. K. Bell, R. W. Burke, D. M. Bouchette, B. S. Carpenter, T.

E. Gills, G. J. Lutz, L. A. Machlan, E. J. Maienthal, L. T. McClendon, J. McKay, L. J. Moore, T. J. Murphy, P. J. Paulsen. T. C. Rains, S. D. Rasberrv, B. A. Thompson, J. L. Weber, Jr., and S. A.

Wicks.

ADDITIONAL INFORMATION ON THE COMPOSITION : Certification is made only for the ele- ments indicated. The five replacements, however, contain a graded series for 40 elements and

information on the elements not certified may be of importance in the use of the material. Al- though these are not certified, values are presented in the following table for the remaining ele- ments.

Value from a single method of analysis:

Elftmflnt Percent, by weight Element Percent by weight

Bismuth (0.002) Hafnium (0.0003)

Gold (<00005) Nitrogen (.00404)

Selenium (.0012) Oxygen (.00107)

Zinc (.0005) Hydrogen (<.0005)

Praseodymium (.00012) Strontium a-(<.0005)

Iron (by difference) (95.3)

Dash indicates "not detected." Value in parenthesis following the dash is the conservative "upper limit" of detection. Approximate value from heat analysis:

Germanium [0.002]

49
l.S. Departingnt .-of Com mo no

Rogers V.M....Morton,

tfcere tarj

National Bureau of Standards

Ernest Ambler, Acting Director Rational ^mmn of Standards

Certificate of JVnalgsi*

Standard Reference Material 1263

Cr-V Steel (Modified)

This standard is in the form of disks 31 mm (1 1/4 in) in diameter and 19 mm (3/4 iri) thick,

generally for use in optical emission and x-ray spectrometric analysis.3

Element Percent, by weight Element Percent, by wei

Carhon 0.62 Aluminum (total) 0.24 Manganese 1.50 Niobium .049 Phosphorus 0.02 9 Boron .0009

1

Sulfur .008 Lead .0022

Silicon .74 Zirconium .049

Copper •09 8 Antimony .002

Nickel .32 Silver .0037

Chromium 1.31 Gold .0005

Vanadium 0.31 Calcium .00013

Molyhdenum .030 Magnesium .00049

Tungsten .046 Tellurium .0009

Cohalt .048 Cerium .0014 Titanium .050 Lanthanum .0006

Arsenic .010 Neodymium .0006o

Tin • 104

This material also is available in the form of chips, SRM 363, for use in chemical methods of analysis; rods, SRM 1097, 6.4 mm

(1/4 in) in diameter and 102 mm (4 in) long for the determination of gases in metals by vacuum fusion and neutron activation methods of analysis; and rods, SRM 663, 3.2 mm (1/8 in) in diameter and 51 mm (2 in) long for application in microchemical methods of analysis such as electron probe microanalysis, spark source mass spectrometric analysis, and laser probe analysis. CERTIFICATION: The value listed for a certified element is the present best estimate of the "true"

value based on the results of the analytical program. The value listed is not expected to deviate from

the "true'

1 value by more than ±1 in thedast significant figure reported; for a subscript figure, the deviation is not expected to be more than ±5. Based on the results of homogeneity testing, maximum variations within and among samples are estimated to be less than the uncertainty figures

given above.

The overall direction and coordination of the technical measurements at NBS leading to certifi- cation were performed under the direction of K. F. J. Heinrich, O. Menis, B. F. Scribner, J. I. Shultz, and J. L. Weber, Jr.

The technical and support aspects involved in the preparation, certification, and issuance of this Standard Reference Material were coordinated through the Office of Standard Reference Materials by R. E. Michaelis.

Washington, D.C. 20234 J. Paul Cali, Chief

January 8, 1976 Office of Standard Reference Materials

(Originally issued October 2, 1970,

with revisions August 16, 1972,

and attachment February 24, 1975) _»

(over)
PLANNING, PREPARATION, TESTING, ANALYSIS: This standard is one of five replacements

for the original eight 1100 series iron and steel SRM's. Material from the same melt is available in a variety of forms to serve in checking methods of analysis and in calibrating instrumental techniques.

The material for this standard was vacuum melted and cast at the Carpenter Technology Corporation, Reading, Pennsylvania, under a contract with the National Bureau of Standards. The contract was made possible by a grant from the American Iron and Steel Institute.

The ingots were processed by Carpenter Technology Corporation to provide material of the

highest possible homogeneity. Following acceptance of the composition based on NBS analyses,

selected portions of the ingot material were extensively tested for homogeneity at NBS by D. M.

Bouchette, S. D. Rasberry, and J. L. Weber, Jr. Only that material meeting a critical evaluation was

processed to the final sizes.

Chemical analyses for certification were made on composite samples representative of the ac- cepted lot of material.

Cooperative analyses for certification were performed in the analytical laboratories of Climax

Molybdenum Company of Michigan, Ann Arbor, Michigan, J. W. Mann and H. E. Trapp; MidvaleHeppenstall Co., Nicetown, Philadelphia, Pennsylvania, W. L. MacBride; Standard Steel Co.,

Burnham, Pennsylvania, J. Metzger; and The Steel Company of Canada, Hamilton, Ontario, Canada,

0. P. Bhargava.

Analyses were performed in the Analytical Chemistry Division of the National Bureau of Standards by the following: J. R. Baldwin, R. K. Bell, R. W. Burke, D. M. Bouchette, B. S. Carpenter, T.

E. Gills, G. J. Lutz, L. A. Machlan, E. J. Maienthal, L. T. McClendon, J. McKay, L. J. Moore, T. J. Murphy, P. J. Paulsen, T. C. Rains, S. D. Rasberry, B. A. Thompson, J. L. Weber, Jr., and S. A.

Wicks.

ADDITIONAL INFORMATION ON THE COMPOSITION: Certification is made only for the ele- ments indicated. The five replacements, however, contain a graded series for 40 elements and

information on the elements not certified may be of importance in the use of the material. Al- though these are not certified, values are presented in the following table for the remaining ele- ments.

Value from a single method of analysis:

Element Percent, of weight

Tantalum

Bismuth

Selenium

Zinc

Praseodymium

Iron ( bv difference)

(0.053)

(.0008)

(.00016)

(.0004)

(.00018)

(94.4)

Element

Hafnium

Nitrogen

Oxygen

Hydrogen

Strontium

Percent, by weight

(0.0005)

(.0041)

(.00066)

(<.0005)

a-(<.0005)

a Dash indicates "not cei-tified'.'Value in parenthesis following the dash is the conservative "upper limit" of detection.

Approximate value from heat analysis : Germanium [0.010]

51
I .S. Department <»! Commerce

Movers C.-B. Morton,

Secretary

National Kureau of Standards

Krnest Ambler. Acting Director Rational bureau of j^tandartte

(Hertiftcate of ^nalgsts

Standard Reference Material 1264

High-Carbon Steel (Modified)

This standard is in the form of disk s 31 mm (1 1/4 in) in diameter and 19 mm (3/4 in) thicl generally lor use in o|il ical emission and vray speclromelrie analysis."

Mement

• Percent, by weight K lenient Percent, by weight

Carbon fiyi. 87,, o /o Niobium 0. 1 5 7 Manganese .255 Tantalum .11 Phosphorus .01 Moron .011

Sulfur .028 Lead .024

Silicon .067 Zirconium .068

Copper .24, Antimony .034

Nickel .14, Col.l .0001

Chromium .06

5 Calcium .00004

V anadinm •105 Magnesium .00015

Molybdenum .49 Tellurium .00018

Tungsten .10 , Cerium .0002 2 Cobalt .15" Lanthanum .00007

Titanium .24 Neod\ mium .00007

Arsenic .()>> Tin .008

a This material also is available in the form of chips. SUM .'104. lor use in eliemieal methods of analysis; rods, SRM 664, 3.2 mm

(l/lt in) m diameter and 51 mm (2 in) long for application in microclicinical mel hods of anal) sis such as electron probe microanalysis, spark source mass speetrometric analysis, and laser proU' analysis; rods. SRM 1098. 6.4 mm (1/4 in) in diameter and 102 mm (4

in) long for the determination of gases in metals h> vacuum fusion and neutron activation methods of analysis.

CKIITIF1 CATION; The value listed for a certified element is the present best estimate of the "true"

value based on the results of the analytical program. The value listed is not expected to deviate from

the "true" value by more than ±1 in the last significant figure reported; for a subscript figure, the

deviation is not expected to be more than ±5. Based on the results of homogeneity testing, maximum variations within and among samples are estimated to be less than the uncertainty figures

given above. (See CAUTION below.)

CA UTION: This standard has beenfound satisfactory for application in x-ray speetrometric methods ofanalysis, however, in application testingfor optical emission speetrometric analysis some biases were observed • particularly for the carbide-forming elements (Ti, Nb, Zr). This is due to metallurgical structure differences in this particular standard. Reference: Michaelis, R. E., "Homogeneity ofSRM's", NBS Spec. Publ. 408, pp 557-571

(U. S. Government Printing Office, 1975). This SRM does not pose a problem for the determination of the elements normally specified in a steel when optical emission methods ofanalysis are used. However, the user is cautioned that inaccuracies and imprecisions may occur in the determination of the carbide-forming elements,

the magnitude of which will depend on the excitation source parameters employed.

Washington, D.C. 20234 J. Paul Cali, Chief

January 8. 1976 Office of Standard Reference Materials with revisions August 16, 1 972, February 12, 1973.

and attachment I'Yhruarv 24, 1975)

52

(over)
(MANNING, PREPARATION, TESTI NC . ANALYSIS: This standard is one of five replacements

lor the original eight I 100 series iron anil steel SRM"s. Material from tin: saint; melt i.s available in a variety of forms lo serve in cheeking methods of analysis and in calibrating instrumental techniques.

The material for this standard was vacuum melted and easl at the Carpenter Technology Corporation, Reading, Pennsylvania, under a eon tract with the National Bureau of Standards. The contract was made possible by a grant from the American Iron and Steel Institute.

The ingots were processed by Carpenter Technology Corporation to provide material of the

highest possible homogeneity. Following acceptance of the composition based on NBS analyses,

selected portions of the ingot material were extensively tested for homogeneity at NBS by I). M.

Bouchette, S. I). Rashcrry, and J. I.. Weber. Jr. Only that material meeting a critical evaluation was

processed to the final sizes.

Chemical analyses for certification were made on composite samples representative of the accepted lot of material.

Cooperative analyses for certification were performed in the analytical laboratories of Ford

Motor Co., Dearborn, Michigan, C. A. Nahsloll; kaweeki Berylco Industries, Inc., Boyerlown,

Pennsylvania, F. T. Covle: and Lukens Steel Co.. Coatesville. Pennsylvania, .). 11. Morris and J. Scott."

Analyses were performed in the Vnalvlical Chemistry Division of the National Bureau of Standards by the following: J. R. Baldwin, R. k. Bell, R. W. Burke. I). M. Bouchette, B. S. Carpenter, T.

E. Gills, 0. J. Lutz. L. A. Machlan. E. J. Maienthab L. T. McClendon, J. McKay, L, J. Moore, T. J. Murphy, P. J. Paulsen, T. C. Rains. S. D. Rashcrry, B. \. Thompson, |. L. Wclier, |r., and S. A.

Wicks.

The overall direction and coordination of the technical measurements at NBS leading to the

certification were performed under the direction of k. K. |. Ileinrich, O. Menis, B. F Seribncr I I Shultz, and J. L. Weber, Jr.

The technical and support aspects involved in the preparation, certification, and issuance of this Standard Reference Material were coordinated through the Office of Standard Reference Materials

by R. E. Michaclis. ADDITIONAL INFORMATION ON THE COMPOSITION: Certification is made only for the ele- ments indicated. The five replacements, however, contain a graded series for 40 elements and

information on the elements not certified may In: of importance in the use of the material. Al- though these arc not certified, values are presented in the following table for the remaining ele- ments.

Value, from a single method of analysis:

Eje men

t

Percent, by weight

Aluminum (total)

Bismuth

Silver Selenium

Praseodymiu m

Iron (by difference)

(0.00B0)

(.0009)

(.00002)

(.00021)

(.00003)

(%.7)

A pproximate value from heat analysis:

Zinc

Germanium

10.001

1

| .003

1

53

Element

Hafnium

Nitrogen

Oxygen

ll\ drogen

Strontium

Percent, by weight

(0.0013)

(.0032)

(.0010)

(<.0005)

(.0005)
U. S. Department of Commerce

John T. Connor, Secretary

National Bu>»eii«f Standards

A. V. AsShJ^ Director

Appendix 2

Certificate of &nalpste

SPECTROGRAPH IC INGOT IRON AND LOW-ALLOY STEEL STANDARDS

(Revised—May 5, 1965)

NBS No. 1

Designation

461 1161

Low- Alloy

Steel A

462 1162

Low-AUov

Steel B

'

463 1163

Low- Alloy

Steel C

464

1164

Low-Alloy

Steel D

465

1165

Ingot

Iron L

466 1166

h Ingot

Iron F

K>7

1 167

Low- Alios stcei <;

Element

CMn

PS

SiCu

NiCr

VMo

Sn

TiB

AsW

ZrNb

Ta

Al Co

PbAgGe0

N

Percent Percent

0.15 0.40

.36 .94 .053 .045

(.02)2 (.02) .047 .28

.34 .20 1.73 .70 0.13 .74 .024 .058

.30 .080

.022 .066

(.01) .037

.000 2 .000 s .028 .046

.012 .053

(.003)

(.001 s ) (.001 5 ) (•02 0) (•00 6 )

.006 (<0002)

(.003 0) (.006)

( 008 )

Percent

0.19

1.15

0.031

(-02)

.41

Percent

0.54

1.32 0.017

(.02)

.48

^ .022 010

.057

.15 .069

.02 7 .005

.01 3 02 8 .012 .020 (<0002) (.003 0 ) (.002 5 ) (.001 5 ) (.007) (.006)

( 006 ) (.00 7 )

Percent Percent

01

.20 .000, .010

(.001)

(.002) (.001)

.001

.19 .008 (<.0005)

(.0002 5 ) (.003,)

(.003)

(.00 s )

.005 .057 (0002 ) .014

(.006) (<005)

.005 .002

.01 5 046 (.001,)

(. 0004 s )

( .0030 ) (.005)

(•00 h )

Percent

0.11 0.26

•2~s 17 .033 .023

(.01) (.02)

.26 .075

.067 .26 .088 1.03 .036 0.54

.041 .17

.021 .20

.10 .009

.26 .01 1 <.(I00 2

) .009

.14 .008

.20 .077

.001 (<.005)

.29 .006

.23 .005

.16 .0t2 .074

.Id"

.000,, (<. OOOo

(.004n) (<.0002

(.003 0) (.001(1 (0(H) ( .0041

(.00 4 ) ( 00„)

1 Sizes: 400 series, rods % inch in diameter and 4 inches long. 1100 series, disks \ \i inches in diameter and % inch thick.

2 Values in parenthesis are not certified, but are given for information on the composition.

OVER

54
Caution: Because these standards contain a graded composition for more than 20 elements, care must be observed in their use to make certain that element lines and internal standard lines are free from interference. All of the analytical points certified have been made to fit a smooth analytical curve at the National Bureau of Standards.

Material for each standard was melted in a one-ton induction furnace at the Naval Research Laboratory and cast into a single ingot. The base material was furnished by Armco Steel Corp. and U. S. Steel Corp. Each ingot was processed by Republic Steel Corp. by forging to a slab having one dimension of the cross

section four times that of the other dimension. After cropping top and bottom, the slab was cut lengthwise and the center section corresponding to one-fourth of the original ingot was discarded. The two slab portions were hot rolled to oversize rods and centerless ground to size. About 900 pounds of finished rods were ob- tained for each standard as follows: 100 pounds of rods 7/32 in. in diameter from the outer sections near the bottom of the original ingot; 400 pounds of rods 1% in. in diameter from the outer sections near the middle

of the original ingot that is currently certified; and 400 additional pounds of rods \

xk in. in diameter which

will be issued later as a renewal standard for the 1100 series.

Homogeneity testing was performed by spectrochemical and chemical analyses at the National Bureau

of Standards both in slab form and in finished sample form and was found satisfactory for the elements

certified.

Chemical analyses and chemical-spectrographic analyses were made on millings cut from the cross section of the 400 and 1100 series rods by the National Bureau of Standards, and on the 1100 series rods by chemical laboratories of the following: American Cast Iron Pipe Co., Armco Steel Corp., Bethlehem Steel Co., Crucible Steel Co. of America, Electro Metallurgical Co., General Motors Corp., Timken Roller Bearing Co., and

the U. S. Steel Corp. The values for silver and germanium are the results of spectroscopic determinations

only at the National Bureau of Standards. Oxygen and nitrogen values are the result of vacuum fusion determinations at the National Bureau of Standards and at the Research Laboratory of the Jones & Laughlin

Steel Corp.

Washington, D. C. 20234

May 5, 1965.

W. Wayne Meinke, Chief,

Office of Standard Reference Materials.

55
U. S. Depart*^ of Commerce Appendix 3

Maurice ;Ji. Stans

Secretary

National Bar^Sfc of Standards

A. V. A«y^-Director

Certificate of Attaints

Standard Reference Material 481

Gold-Silver Wires for Microprobe Analysis

These standard reference materials are designed for use in quantitative elemental

microprobe analysis. Although the selection of this particular system was circumscribed by

the requirements of standard reference materials for electron probe microanalysis, the

materials will be equally useful for other micro techniques. Accurate chemical characterization and the achievement of homogeneity on a microscopic scale was given special emphasis.

SRM 481 Color Nominal Cominco U.S. Bureau Average

wire code comp American'1 of the Mint b NBS C Value H Au Au Ag Au Ag Au Ag

Percent by weight

A Gold AulOO 100.00 B Gray Au80- Ag20 80.00 80.02 20.00 80.13 19.93 80.0

5 19.96 C Yellow Au60- Ag40 60.01 60.11 39.85 60.04 39.98 60.0

5 39.

9

2 D Blue Au40- Ag60 39.99 40.03 59.90 40.06 59.96 40.03 59.93 E Red Au20- Ag80 22.42 22.42 77.59 22.46 77.56 22.43 77.58 F Silver AglOO ioo.o

0

a The fire assay method was employed for the determination of Au by Cominco American.

b At the U.S. Bureau of the Mint, Au was determined by fire assay and Ag was determined

by titration as AgCl.

c At NBS, Au was determined from the residue after treatment of the alloys with HN03

. The Au residue was dissolved in aqua regia, filtered, the Au precipitated by sulfurous acid,

and weighed. Ag was determined gravimetrically as AgCl in all four alloys, and also coulometrically in the 80 percent Ag alloy.

d The results of individual laboratories agree within a range of ±0.1 percent absolute from

the average values. The agreement between results by the different methods and analysts,

and the summation of results close to 100 percent for each binary alloy, indicate that the averages are free from significant bias.

The set of standard reference materials, SRM 481, consists of six wires each having a diameter of approximately 0.5 mm and a length of approximately 5 cm. For identification, the four alloy wires were covered with an easily removable colored coating.

The overall direction and coordination of technical measurements leading to certifica- tion were performed under the chairmanship of B. F. Scribner.

The technical and support aspects involved in the preparation, certification, and

issuance of these standards were coordinated through the Office of Standard Reference

Materials by R. E. Michaclis. 56

Washington, D. C. 20234 W. Wayne Mcinke, Chief

February 14, 1969 (over) Office of Standard Reference Materials
PREPARATION AND PlRITY: The standards were prepared by Comineo American Inc. in the form of wires approximately 150 meters long. The end members of the series, as well as the

starting materials for the alloys, were of the highest purity grade and precautions were taken

to minimize contamination. Two of the alloy standards were heat-treated at NBS to improve

niicrohomogeneity . The pure metal standards were examined by the residual resistivity ratio technique atid the total of electrically active impurities in each was estimated to be about

0.001 percent. The gold-silver wires were examined speetrographieally for metallic

impurities; no significant impurities were found at detection limits ranging from 0.0001 to 0.010 percent.

LONGITUDINAL HOMOGENEITY: Variation in composition along the full length of each alloy

wire was investigated by electron probe microanalysis for areas 25 jiim diameter on cross sections at three to five positions along the wire including the two ends. The observed

differences in composition for the positions, expressed as the range between the highest and

lowest values for each alloy, were as follows:

Nominal Composition Au80 Au60 Au40 Au20

Observed rangel 0.3% 0.6% 0.3% 0.5%

Homogeneity along the wires was also tested by measurement of the residual resistivity

ratio. These measurements indicated I hat the variation (macroscopic) of composition along

all standard wires was less than 0.1 percent absolute. Further information on longitudinal

homogeneity of the wires was obtained by determinations of Au at the extreme ends of the

alloy wires by the Bureau of the Mint; the dala also indicate that the extreme variation along the wires is less than 0. 1 percent absolute.

Transverse and Micro Homogeneity: Variation in composition within the above mentioned cross sections of the wires was investigated by electron probe microanalysis. For each

cross section, measurements were made along two diagonals at right angles. On each

diagonal, determinations were made at 25 points, 1 |im or less in diameter, starting and

ending at approximately 25 pun from the edge. For each alloy, the element which could be

determined with the hetter precision was used in the evaluation. The variation was

calculated in terms of the standard deviation for an individual determination for each

traverse. In the table below, the variation is presented as the range between the lowest and

highest observed standard deviations for the six to eight traverses performed on each alloy.

Range of Standard

Nominal Composition Element Determined Deviation for Traverses3 Au80 Ag 0.08-0.11%

Au60 Au .08- .16 Au40 Au .08- .13 Au20 Au .12- .37

57
The homogeneity on a microscopic scale was further investigated by performing

quantitative measurements in two arrays of 10 x 10 points (1 fim diameter) on each of the

cross sections. The distance between adjacent points was 3.5 nm. This was repeated on

several cross sections so that 6 to 8 arrays were obtained on each alloy. For the element

which could be measured with better precision, the range is given between the lowest and

highest observed standard deviation for an individual determination for the 6 to 8 arrays for each alloy .

Nominal Composition

Au80

Au60

Au40

Au20

Element Evaluated

Ag

Au

Au

Au

Range of Standard

Deviations for Arravs3

0.09 - 0.15%

.18- .57 .19- .25,

.11- .66

(Note: This range and the two ranges in the following tables are close to the precision of

the method and should be considered upper limits of estimates of inhomogeneity.)

Extensive homogeneity studies were performed with the electron probe microanaly zer

at NBS by M. A. Giles, R. L. Myklebust, C. E. Fiori. and K. F. J. Heinrich. Measurements of

residual resistivity ratio were made at NBS. Boulder,Colorado, by R. L. Rutter. J. G. Hust,

and R. L. Powell. Heat treatment of the alloys at NBS was performed by G. E. Hicho and

M. R. Meverson. Spectrograph^ survey analyses were made at NBS by V. C. Stewart. Determinations of composition were made at Cominco American, Inc.. Spokane, Washington, by T. A. Rice: at the U.S. Bureau of the Mint, Washington. D. C.. by

II. G. Hanson. Jr.: and at NBS by R. A. Durst. G. Marinenko, and C. E. Champion.

58
U. S. Department? of Commerce

Maurices;JJ. Stans

Secretary

Appendix 4

National Bpre

A. V. :a«$& of Standards /JT i*t* i t *K 1 *

STANDARD REFERENCE MATERIAL 482

Gold-Copper Wires for Microprobe Analysis

These standard reference materials are designed for use in quantitative elemental microprobe

analysis. Although the selection of this particular system was circumscribed by the requirements

of standard reference materials for electron probe microanalysis, the materials will be equally

useful for other micro techniques. Accurate chemical characterization and the achievement of

homogeneity on a microscopic scale were given special emphasis.

SRM 482 Color Nominal Cominco U.S. Bureau Average

wire code composition American 3 of the Mint b NBSC value d

Aii Au Cu Au Cu Au Cu

Percent by weight

A Gold AulOO 100.

0

0 B Gray Au80 - Cu20 80.10 80.13 19.81 80.21 19.85 80.

1

5 19.8 3 C Blue Au60 - Cu40 60.30 60.37 39.66 60.41 39.62 60.

3

6 39.64 D Yellow Au40 - Cu60 40.12 40.06 59.88 40.11 59.97 40.

1

0 59.9 2 E Red Au20 - Cu80 20.04 20.12 79.84 20.21 79.86 20.

1

2 79.85 F Copper CulOO 100.

0

0

a The fire assay method was employed for the determination of Au by Cominco American.

b At the U. S. Bureau of the Mint, Au was determined by fire assay and Cu was determined by

electrodeposition.

c At NBS, Au was determined by precipitation from solution; Cu was determined by electro- deposition.

d The results of individual laboratories agree within a range of ± 0.1% absolute from the average

values. The agreement between results by the different methods and analysts, and the summation

of results close to 100% for each binary alloy, indicate that the averages are free from significant

bias.The set of standard reference materials, SRM 482, consists of six wires each having a diameter

of approximately 0.5 mm and a length of approximately 5 cm. For identification, the four alloy

wires were covered with an easily removable colored coating.

The overall direction and coordination of technical measurements leading to certification were performed under the chairmanship of B. F. Scribner.

The technical and support aspects involved in the preparation, certification, and issuance of

these standards were coordinated through the Office of Standard Reference Materials by

R. E. Michaelis.

Washington, D. C. 20234

June 6, 1969

59

(over)

W. Wayne Meinke, Chief

Office of Standard Reference Materials
PREPARATION AND PURITY: The standards were prepared by Cominco American, Inc. in the form of

wires approximately 150 meters long. The end members of the series, as well as the starting materials for the alloys, were of the highest purity grade and precautions were taken to minimize

contamination. Two of the alloy standards were heat-treated at NBS to improve microhomogeneity.

The pure metal standards were examined by the residual resistivity ratio technique and the total of

electrically active impurities in each was estimated to be about 0.001%. The gold-copper wires were examined spectrographically for metallic impurities; no significant impurities were found at detection limits ranging from 0.0001 to 0.010%.

Longitudinal Homogeneity: Variation in composition along the full length of each alloy wire was

investigated by electron probe microanalysis for areas 25 /Ltm diameter on cross sections at three

positions along the wire including the two ends. The observed differences in composition for the

positions, expressed as the range between the highest and lowest values for each alloy, were as follows:

Nominal Composition Au80 Au60 Au40 Au20

Observed range* 0.3% 0.7% 0.9% 0.9%

Homogeneity along the wires was also tested by measurement of the residual resistivity ratio. These measurements indicated that the variation (macroscopic) of composition along all standard

wires was less than 0.1% absolute. Further information on longitudinal homogeneity of the wires was obtained by determinations of Au at the extreme ends of the alloy wires by the Bureau of the Mint; the data also indicate that the extreme variation along the wires is less than 0.1% absolute.

Transverse and Micro Homogeneity: Variation in composition within the above mentioned cross sections of the wires was investigated by electron probe microanalysis. For each cross section,

measurements were made along two diagonals at right angles. On each diagonal, determinations were made at 25 points, 1 /um or less in diameter, starting and ending at approximately 25 nm from

the edge. For each alloy, the element which could be determined with the better precision was used

in the evaluation. The variation was calculated in terms of the standard deviation for an individual determination for each traverse. In the table below, the variation is presented as the range between

the lowest and highest observed standard deviations for the six traverses performed on each alloy.

Nominal Element Range of Standard

Composition Determined Deviations for Traverses* Au80 Cu 0.09 - 0.24%

Au60 Cu .16- .27 Au40 Au .13- .23 Au20 Au .13- .20

60
The homogeneity on a microscopic scale was further investigated by performing quantitative

measurements in two arrays of 10 x 10 points (1 nm diameter) on each of the cross sections. The

distance between adjacent points was 3.5 jum. This was repeated on several cross sections so that 6

arrays were obtained on each alloy. For the element which could be measured with better precision,

the range is given between the lowest and highest observed standard deviation for an individual determination for the 6 arrays for each alloy.

Nominal Element Range of Standard

Composition Determined Deviations for Arrays*

Au80 Cu 0.19 - 0.28%

Au60 Cu .28- .37 Au40 Au .25- .31 Au20 Au .12- .20

*The ranges indicated are close to the precision of the method and should be considered upper

limits of estimates of inhomogeneity.

Extensive homogeneity studies were performed with the electron probe microanalyzer at NBS

by M. A. Giles, D L. Vieth, R. L. Myklebust, C. E. Fiori, and K. F. J. Heinrich. Measurements of

residual resistivity ratio were made at NBS, Boulder, Colorado, by R. L. Rutter and R. L. Powell. Heat treatment of the alloys at NBS was performed by G. E. Hicho and M. R. Meyerson.

Spectrographs survey analyses were made at NBS by V. C. Stewart. Determinations of composition were made at Cominco American, Inc., Spokane, Washington, by T. A. Rice; at the U. S. Bureau of

the Mint, Washington, D. C, by H. G. Hanson, Jr.; and at NBS by J. R. Baldwin and R. A. Durst.

61
U. S. Depart^^o^Commerce Appendix 5

National

A. V Certificate of &nalpsrts»

Standard Reference Material 480

Tungsten—20% Molybdenum Alloy

Electron Microprobe Standard

SRM No. Tungsten Molybdenum

weight percent 480 78.5 21.5

This standard is a composite consisting of a core of W—20 wt % Mo alloy wire (1 mm diameter), embedded in pure Mo rod (5 mm diameter) onto which has been electroplated a layer of pure W (1 mm thick). Each standard is 1 mm thick. Chemical analyses were performed by the Analytical Chemistry Division, NBS. Two

independent methods were employed the first of which utilized an ion exchange separation, followed by gravimetric determination of the ignited oxides. An average value of 78.5 wt % was

obtained for W with a standard deviation for a single determination of ± 0.3 wt % (n = 4). For Mo

the average value obtained was 21.5 wt % with a standard deviation of ±0.2 wt % (n =4). Analyst — R. K. Bell. A spectrophotometric thiocyanate method was used for the determination of Mo

only. In this method, Mo was reduced with Sri*" 2 and the color system stabilized with butyl

cellosolve. An average value of 21.7 wt % was obtained with a standard deviation for the single determination of ± 0.2 wt % (n = 6). Analyst - E. R. Deardorff. Homogeneity testing by means of the NBS electron microprobe was performed on four

selected samples of the composite rod using an operating voltage of 20 kV, a monitor current (proportional to beam current) of 2 microamperes corresponding to a specimen current of 0.22 microamperes. The LCK lines of the W and Mo were monitored by means of LiF(W) and EDDT(Mo)

monochromator — proportional counter channels. The dead time in each channel was 2.3 microseconds. The x—ray emergence angle was was 52.5 . A quantitative raster scanning procedure was employed to obtain the homogeneity data which is summarized in the following table for three of the four samples. Analyst — H. \ akowitz. Homogeneity Characterization Results Specimen Condition CV — Moa CV — W

a Determinations

(each element)

EMS-72 Lightly etched 2.47 1.24 400

EMS-73 Unetched 2.37 1.55 400

EMS-74 Lightly etched 2.54 1.34 500

*cv =

( 1Q°) ( Std- Dev-) Mean number of counts Approximate mean number of counts accumulated for W = 500,000

Approximate mean number of counts accumulated for Mo = 45,000

The material for the standard was prepared in the Lamp Metals and Components Department,

General Electric Company, Cleveland, Ohio, through the use of a powder metallurgy process

involving high—purity metal powders.

Details of the preparation, testing, and intended use of this standard can be found in NBS

Spec. Publ. 260—16, Standard Reference Materials: Homogeneity Characterization of NBS

Spectrometric Standards IV: W—20% Mo Alloy Prepared by Powder Metallurgical Methods,

H. Yakowitz, R. E. Michaelis, and D. V. Vieth, (in press). The overall direction and coordination of technical measurements leading to the certification were performed under the chairmanship of J. R. DeVoe.

The technical and support aspects involved in the preparation, certification and issuance of this Standard Reference Material were coordinated through the Office of Standard Reference Materials bv R. E. Michaelis.

Washington, D.C. 20234

November 22, 1968 W. Wayne Meinke, ChiefOffice of Standard Reference Materials
U. S. Department of Commerce . Frederick B. Dent Appendix 6

Secretary

National Burma of Standards

Richard W. Roberta, Director ^National T&nttmx of jltantlartta

Certificate of ^nal^is

Standard Reference Material 478

Microprobe Standard - Cartridge Brass

This Standard Reference Material consists of one specimen

each of chill cast material (SRM C1102) and wrought material

(SRM 1102). The cast material is supplied as a cube 6 mm on

an edge; the chill cast face is polished. The wrought material

is supplied as a right circular cylinder 6 mm diameter by 6 mm

high. Some sixteen elements are certified for their chemical

composition in SRM's C1102 and 1102. However, at the micrometer

level of spatial resolution these brasses comprising SRM 478, are certified to be homogeneous with resDect to copper and

zinc only.

CERTIFIED CHEMICAL CHARACTERIZATION

SRM COPPER ZINC

478 (both specimens) 72.

8

5 27.1

The material for each component of the standard was melted and

cast at the Naval Research Laboratory, Washington, D. C. Highpurity metals were used either directly or in the preparation of

master alloys. Approximately 325-kg heats were melted under a charcoal cover in a high-frequency induction furnace and the

molten metal cast on a massive water-cooled plate to provide

rapid unidirectional solidification. The casting for each

standard was about 68.5 cm (27 in) in diameter and 8.9 cm

(3 1/2 in) thick.

The material for the chill -cast samples was obtained from the

area of the casting nearest the chill-cast face. Samples were

originally finished to a size 31 mm (1 1/4 in) square, 19 mm

(3/4 in) thick.

The material for the wrought samples was obtained after removal

of the chill-cast material and discard of about 19 mm (3/4 in)

thickness from the slab ton. Strips of this material were forged,

fully annealed, and finished to samples 31 mm (1 1/4 in) in

diameter, 19 mm (3/4 in) thick.

The micronrobe specimens were cut by e lectrical -discharge

machining into the form provided as SRM 478. The chill-cast

face was me tallogranhically polished by mechanical means

prior to the electrical -discharge machining.

Samples for chemical analysis were prepared in the form of

millings taken from the cross section of the finished samples

of both the chill-cast and wrought material.

Washington, D. C. 20234 J. Paul Cali, Chief

February 28, 1974 Office of Standard Reference Materials

(over) 63
Chemical analyses were oerformed in the NBS Analytical Chemistry

Division by R. Alvarez, R. K. Bell, P. W. Burke, A. P. T.andgrebe , E. E. Maczkowske, E. J. Maienthal , C. W. Smith, and P. K. Wolford.

(See NBS Miscellaneous Publ. 260-7 99PP (1965) for details.)

Coooerative analyses for certification were oerformed in the

analytical laboratories of Anaconda American Brass Co. , Waterbury, Conn., O. P. Case and K. M. O'Brien; Denartment of Mines

and Technical Surveys, Mines Branch, Ottawa, Ontario, Canada,

A. E. LaRochelle, E. M. Penner, C. H. McMaster, and W. R. Inman;

Mueller Brass Co., Port Huron, Mich., S. C. Richards, P. Stevens,

and A. Stuever.

Technical and suoport aspects involved in the n reparation , certi- . fication, and issuance of this Standard Reference Material

were coordinated through the Office of Standard Reference

Materials by R. E. Michaelis.

The homogeneity of Cu and Zn in SRM 478 was investigated bv

means of the electron probe microanalvzer. Two seoarate channels

with LiF analyzing crystals and sealed orooortional detectors

were emoloyed. The instrument was onerated at 30 keV with orobe

currents of 100 na. The probe diameter was aooroximate lv one micrometer. The count rate for Cu was on the order of 13,500

c/s, whereas the count rate for Zn was on the order of 4,000 c/s.

Signal-to-background ratios for Zn were greater than 100 to 1. Results of homogeneity testing follow:

CERTIFIED HOMOGENEITY CHARACTERIZATION

Element

Coe f f i cient

of variation

for counting

Standard

deviation (%)

comDuted from

exner iment

Analytical range

(two standard deviation

limits o f comoosition

at the three micrometer level

of snatial resolution)

0 .0036

.0036

.0019

.0027

2.2

0 . 79

1 .0

. 72

71.1 to 74.6

71.8 to 73.8

2 5.9 to 2 8.3

26.7 to 27.5

aCas t

Wrought

64
SRM-478 contains inclusions that are extremelv small and appear

to be essentially round indicating that thev are soheres in

three dimensions. The size of the inclusions ranqes f rom submicrometer to about two micrometers in diameter. Thev are dull grey in color. In the cast form, they are randomly distributed while in the wrought form thev are usual lv found at

grain boundaries. There are about 800 inclusions oer cubic

millimeter of brass.

Wavelength scans were taken of manv inclusions in both forms

of the brass to identify the elements present. The presence

of reasonably large amounts of Pb and S was noted. Some

variable amounts of Zn, Si, and Al were found. Excent for Zn

,

these elements are not exoected to be uniformly distributed

within the brass; the concentration of these elements

varied considerably from inclusion to inclusion.

Details of the homogeneity testing are contained in NBS

Misc. Publ. 260-10, 28PP (1965).

Electron probe microanalysis of SRM 478 was performed at

NBS and at seven other laboratories. [See ASTM Spec. Tech.

Publ. 430, 343 (1968) for details.] The results confirm the

homogeneity levels and analysis limits stated above. SPM

478 should be especially useful for establishing correct

relative intensity ratios between specimen and standard.

Caution should be observed in the use of the chill -cast

samples. Determinations made on other than the chill-cast,

or test surface, are not recommended because of the unidirectional solidification.

65
U. S. Department' of Commerce

Mauriceifi. Stans . . . _ se^p* Appendix 7

National Bjureiif v£ Standards _

L. M. Brimscomb; Director /^T . + . f

*k 1/ ^ Qkritttcate of ^ttaltjgt*

Standard Reference Material 483

Fe-3Si Alloy Microprobe Standard

0

This standard is characterized for chemical homogeneity of iron and silicon at the micrometer

level of spatial resolution and is satisfactory for use as a homogeneous material for electron probe

microanalysis.

Silicon Iron (by difference)

SRM Weight, percent

483 3.22b ± 0.02c 96.7 - 96.8

a

Size: 3 mm X 3 mm X 0.28 mm thick. The material is from coarse-grained sheet stock having the so-called Goss orientation in which a [110] grain is parallel to the surface and [001 ] is the rolling direction. Each sample is supplied HF etched and ready for metallographic mounting and polishing. ^Determination of silicon involved 49 samples of SRM 483. SRM 125b, certified at 2.89 wt. % Si, was used as a control standard and

2.90 wt % Si was found. Method: One gram samples were dissolved in hydrochloric and nitric acids. A double dehydration of the silicon with perchloric acid was made with an intervening filtration. The weight of silicon present was determined from the loss resulting from treatment with

hydrofluoric acid. Analyst — R. A. Paulson, NBS Analytical Chemistry Division.

c Standard deviation of a single determination based on results obtained on SRM's 483 and 125b, but also including similar method

error estimations from previous determinations.

HOMOGENEITY TESTING AND QUANTITATIVE ANALYSIS BY

ELECTRON PROBE MICROANALYSIS

Homogeneity was checked by means of quantitative raster scanning in which a square matrix

(1.1 mm X 1.1 mm) of individual points is analyzed by the microprobe. Each matrix represents 400

separate analyses. Six selected matrices were run for iron and silicon with three of these rerun. The

coefficient of variation for both the iron and silicon is less than one percent. Analysts — H. Yakowitz, NBS Metallurgy Division, and C. E. Fiori, NBS Analytical Chemistry Division.

Quantitative microprobe analysis of this alloy gave a silicon content of 3.14 wt. % and an iron content of 96.9%. Analyst — H. Yakowitz, NBS Metallurgy Division.

Details of the microprobe testing and analyses, as well as the sample preparation, are given in NBS Special Publication 260-22, Standard Reference Materials: Homogeneity Characterization of

Fe-3Si Alloy, H. Yakowitz, C. E. Fiori, and R. E. Michaelis, Feb. 1971.

The technical and support aspects involved in the preparation, certification, and issuance of this standard were coordinated through the Office of Standard Reference Materials by R. E. Michaelis.

Washington, D. C. 20234 J. Paul Cali, Chief June 11, 1971 Office of Standard Reference Materials 66
U.S. Department of Commerce

Elliot L. Richardson,

Secretary Appendix 8

National Bureau of Standards

Krnest Ambler, Acting Director Rational ^ureau of jltandartte

Report of Investigation

Glasses for Microanalysis RM 30

Glass Fibers for Microanalysis RM 31

K. F. J. Heinrich, D. H. Blackburn, M. M. Darr, C. E. Fiori, R. B. Marinenko, D. E. Newbury, and J. A. Small

Five types of glasses are available as research materials (RM) in the form of bulk samples, 2x2x20 mm, and as

fibers ranging from 10-100 /um in diameter and 50-60 mm long.

The major constituents of the glasses were selected so that a variety of matrices of differing average atomic

numbers would be represented. For each of the five matrices, there are two glasses - one with and one without

the low-concentration additives.

Applications

These Reference Materials were developed for use in microanalysis techniques such as electron probe microanalysis (EPMA) and secondary ion mass spectrometry (SIMS). These homogeneous vitreous solids containing

known low-concentration additions of several elements should be useful in the analysis of complicated un- knowns. The fibers were drawn for use in particulate analyses for which there presently are no well-characterized standards of complex composition and simple shape.

Preparation of the Glasses The compounds employed in the manufacture of the glasses were reagent-grade materials or compounds of equal or greater purity. Usually the oxides were used, but where this was not possible, the carbonates, nitrates, or phosphates were used. After weighing, the batch materials were mixed thoroughly as dry powders prior to melting.

The glass components were melted in 300 ml platinum crucibles in electrically heated furnaces in an oxidizing

atmosphere (air). To ensure homogeneity, the glasses were stirred from four to six hours with a motor-driven,

double-bladed, propeller-type stirrer made of a platinum-rhodium-alloy. Melting and stirring temperatures

ranged from 900-1400 °C depending upon the glass being prepared. After completion of the melting and

stirring operations, the glass was cast into a rectangular block and annealed to remove residual strain. Composition

The compositions in weight percent of the oxides in the glasses are listed in the attached table. These are nominal

values calculated from the weight of the component added to the melt during the manufacture of the glass. Pre- liminary analyses with the electron probe indicate that these nominal values are accurate to five percent relative or better for the major constituents, and to 20 percent relative for the low-concentration additions. A thorough analysis and homogeneity study of these glasses by the electron probe is now in progress. Other

analytical methods are also being used when necessary. This report will be revised when the analytical results are available.

67

(over)
Preparation of Bulk Samples

The bulk samples, approximately 2x2x20 mm, were cut from the large annealed rectangular glass block. A

precision wafering saw was used with a 0.071x15.2 cm, (0.028 x 6") 100 grit diamond wheel and a petroleum- based coolant. An acetone-soluble adhesive was used to mount the glass block and slices onto the cutting plate. Several 2 mm slices were cut from near the middle of the glass block. These slices were in turn cut at 2 mm

intervals. The glass slices were removed from the cutting plate and rinsed with acetone several times to remove

all traces of adhesive.

Preparation of Fibers Preliminary to drawing fibers, a glass fragment was melted in a platinum boat that was heated directly by an

electric current. The fiber was formed by drawing a thread of molten glass through an orifice in the bottom of

the platinum boat. The continuous glass fiber was wound onto a 25.4 cm (10 inch) diameter metal drum driven by a variable speed electric motor ( 1000-4000 rpm). Different orifice sizes and drum speeds were used in drawing

the fibers, depending upon the viscosity and surface tension of each glass. This procedure requires a minimum

amount of working time and low temperatures, therefore minimizing compositional changes due to vaproization.

1. Fiori, C. E.; Heinrich, K. F. J.; Marinenko, R. B.; Darr, M. M.; Blackburn, D. H.; Newbury, D. E.; and

Small, J. A., "An Overview of the Glass Standards Program for Microanalysis at the National Bureau of Standards," paper to be presented at the Joint Meeting of Electron Microscopy Society of America and

Microbeam Analysis Society, Miami Beach, Fla., August 1976.

2. Marinenko, R. B.; Heinrich, K. F. J.; Fiori, C. E.; Darr, M. M., Blackburn, D. H.; Newbury, D. E.; and

Small, J. A., "Glass Standards for Microanalysis of Particles," paper to be presented at Federation of

the Analytical Chemistry and Spectroscopy Societies 3rd Annual Meeting, Philadelphia, Pa., November,

1976.

68
Glasses for Microanalysis

Melt No. K-456 K-493 K-453 K-491 K-458 K-489 K-495 K-490 K-496 K-497

Composition in Weight Percent

SiO: 28.77 27.89 0.19 49.38 46.76 0.42 0.27 PbO 71.23 69.08 58.72 59.35 1.28 1.55 .99 Ge02 41.28 37.98 BaO 46.80 43.88 ZnO 3.82 3.72

79.54 76.03 MgO 9.03 8.64 AhO, 0.20 0.16 0.29 20.00 18.68 11.43 10.92 B: 0, .14 .11 .20 75.00 70.00 0.15 ZrO: .49 .40 .70 0.85 .54 TiO: .32 .26 .46 .55 .35 CeO: .68 .56 .98 1.19 .76 Ta: Ch .88 .72 1.26 1.53 .98 Fe: 0, .32 .26 0.46 0.55 .35

Li: 0 .001 .001 .002 5.00 4.67 .001

69
U. S. Department* of Commerce Mau^rfar|

tans Appendix 9 Secretary

National Bure'afl of Standards

L. M. Branscomb, Director Rational ^ttram of j^tanrtanfe

d^rttftcat^ of (Analysts

Standard Reference Material 479

Fe-Cr-Ni Alloy Microprobe Standard

This Standard Reference Material is characterized for chemical homogeneity of iron, chromium,

and nickel at the micrometer level of spatial resolution and is satisfactory for use as a homogeneous

material for electron probe microanalysis. It is issued in wafer form, 4.6 mm in diameter and 1 mm

thick, in the as-cut condition after electrical discharge machining.

CERTIFIED CHEMICAL CHARACTERIZATION

SRM Nickel3 Chromium3 Iron (by difference) b Weight, percent

479 10.7 18.3 71.0

a Nickel was determined gravimetrically by the nickel dimethylglyoxime method; chromium was oxidized to chromate and titrated with a standard ferrous ammonium sulfate solution. Analyst - R. A. Paulson

Pure chromium, nickel, and iron were used in the preparation of this alloy (99.9% minimum purity for each element). (For

information only, carbon was determined to be 0.012%.) CERTIFIED HOMOGENEITY CHARACTERIZATION

Homogeneity testing for iron, chromium, and nickel was carried out by means of the NBS

electron microprobe with an operating voltage of 20kV and spectrometers equipped with LiF

crystals and sealed proportional detectors. Approximately 160 analyses were made on each of five samples taken from the original alloy rod ends, and the 1/4, 1/2, and 3/4 positions, respectively.

The observed coefficient of variation was not greater than 1.5% for any of the three elements. For

sixteen determinations made for each element, the observed 99% confidence intervals about the means were (Wt.%):

Iron ± 0.80

Chromium ± 0.20

Nickel ±0.12

Analyst - H. Yakowitz

The preparation of the original alloy ingot and subsequent thermal and mechanical processing

steps to improve chemical homogeneity were conducted by D. P. Fickle and A. W. Ruff.

The technical and support requirements associated with the issuance of the Standard Reference

Material were coordinated through the Office of Standard Reference Materials by R. E. Michaelis.

Technical details concerning the preparation and characterization of this SRM are given in NBS

Special Publication 260-43, Preparation and Homogeneity Characterization of an Austenitic Iron- Chromium-Nickel Alloy.

Washington, D.C. 20234

October 16, 1972 70

(over)

J.Paul Cali, Chief

Office of Standard Reference Materials
SUPPLEMENTARY INFORMATION

The original alloy ingot was produced by the arc fusion method in an inert gas atmosphere of

argon, gettered by titanium. The ingot was repeatedly swaged, and annealed in a sealed quartz tube

until the final diameter of 4.6 mm was reached. A diffusion annealing step was included for 5 days

atll20°C.

The rod was cut into wafers approximately 1 mm thick by electro-discharge machining in an

organic solvent. The specimens selected for homogeneity characterization were ground on a series of

SiC papers, followed by 6jum diamond and then 1/4/im diamond particle polishing. Final polishing was done using 0.05/um A12 03 particles on Gamal cloth.

Electron probe microanalysis was performed on the 1/4, 1/2, 3/4 specimens using pure element

standards (M. M. Darr, H. Yakowitz, C. E. Fiori, and R. L. Myklebust). Results are as follows:

Element Voltage (kV) Concentration (Wt. %)

Fe 15 70.8

Fe 20 70.1 Fe 25 71.7

Fe 30 71.1 Cr 15 18.4

Cr 20 19.2 Cr 25 19.2

Cr 30 19.3

Ni 15 10.9 Ni 20 10.7

Ni 25 10.7

Ni 30 10.7

Prior to the production of SRM 479, a portion of the original ingot was used to produce foil specimens for subsequent determination of the stacking fault energy of the alloy over the temperature range 25 to 325 °C using transmission electron microscope methods (R. M. Latanision and

A. W. Ruff, Met. Trans. 2, 505 (1971)). Those results indicated that satisfactory solute homogeneity should be obtained by a suitable thermal and mechanical processing program.

71
Appendix 10

The equations used in the computer program for the determination of standard inhomogeneity are as follows. A mean

intensity, y^ > is calculated from each group of replicate

measurements on a single point. This is,

y.

j = i

y 13

where

y 13

s =

the number of counts observed at the 1 th

. th

(2)

step

and the j

L11 replicate reading on this point,

the total number of readings on the same point.

For the entire homogeneity scan a "grand" mean intensity,

y.., is calculated according to

y = \ I y ± (3)

1 i=l ' where

,

r = the total number of points sampled.

The estimates of the components of variance of y-jj are then

calculated according to the equations below. The total

variance is

The "within" component is

2

l ^ij-y±y aw r(s-l) (5)

And the "between" component is

ft 2

a

2 ft 2 QW (6) 8

B

= d

T ~ —

These components of variance are calculated from the

total number of counts, including the background. But the

expression of uncertainty in terms of concentration is more

useful. The background intensity is subtracted from the

line intensity in concentration calculations. The variance

for the number of net counts above the background is

estimated by

72
2 2

Var (X-B) = rg

+ £

(7)

where

X = y..

B = average of the background counts

and

L = the number of times the background is read. The

uncertainty in the number of counts at the 99.7 percent

confidence level, assuming no systematic error, is it^,

U

2 - 3

2 2 a

iV +s8B

r s L (8)

Assuming a linear relationship between the number of counts

above the background and the concentration, where

%conc

(X-B)

= c (9)

the uncertainty, ±Ui , in terms of concentration and including the

uncertainty in the chemical analysis is given by

U = 9c

where

,

2 2 d W

+ s8

B rs

+ i

+ u

i (10)

= the uncertainty in the concentration given in the

certificate.

73
NBS-114A (REV. 9-76)

U.S. DEPT. OF COMM. BIBLIOGRAPHIC DATA

SHEET

1. PUBLICATION OR REPORT NO. SP 260-65

2.Gov't Accession No. 3. Recipient's Accession No.

4. TITLE AND SUBTITLE Standard Reference Materials: Micro-Homogeneity

Studies of NBS Standard Reference Materials, NBS

Research Materials, and Other Related Samples

5. Publication Date September 1979

6. Performing Organization Code

7. AUTHOR(S)

Marinenko, R. B. , Heinrich, K. F. J., and

Ruegg, F, C.

8. Performing Organ. Report No.

9. PERFORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, DC 20234

10. Project/Task/Work Unit No.

11. Contract/Grant No.

12. SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS fS(ree<, City, state, ZIP) Same as sbove

13. Type of Report & Period Covered Final

14. Sponsoring Agency Code

15. SUPPLEMENTARY NOTES Library of Congress Number 79-600121

|

| Document describes a computer program; SF-185, FIPS Software Summary, is attached.

16. ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a significant bibliography or

literature survey, mention it here.) A simple routine technique for studying homogeneity in the micrometer

range with the electron microprobe has been developed. For graphic

display, a digital periodic integrator is used. In conjunction with

scalers and a stepping motor on the sample stage, traces similar to

industrial control charts based on a comparison of the experiment with

the expected (Poisson) counting statistics are quickly obtained. A

computer program has been developed to numerically evaluate sample

homogeneity

.

Several Standard Reference Materials (SRMs) have been tested. These

include the iron and steels (SRMs 661-664, 461, and 463), the gold-copper and gold-silver alloys (SRMs 481 and 482), the tungsten-20 percent

molybdenum alloy (SRM 480), cartridge brass (SRM 478), the iron-chromium

nickel alloy (SRM 479a). A Research Material, Glasses for Microanalysis

(RM-30), has also been tested.

17. KEY WORDS (six to twelve entries; alphabetical order; capitalize only the first letter of the first key word unless a proper name;

separated by semicolons) Digital periodic integrator; electron microprobe; homogeneity; Standard

Reference Materials; steel.

18. AVAILABILITY [X} Unlimited

| | For Official Distribution. Do Not Release to NTIS

|

| Order From Sup. of Doc, U.S. Government Printing Office, Washington, DC

20402, SD Stock No. SN003-003-02114-1

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JOURNAL OF RESEARCH—The Journal of Research

of the National Bureau of Standards reports NBS research and development in those disciplines of the physical and

i engineering sciences in which the Bureau is active. These

' include physics, chemistry, engineering, mathematics, and

computer sciences. Papers cover a broad range of subjects,

I with major emphasis on measurement methodology, and

the basic technology underlying standardization. Also inj eluded from time to time are survey articles on topics closely

I related to the Bureau's technical and scientific programs. As

a special service to subscribers each issue contains complete

1 citations to all recent NBS publications in NBS and non- NBS media. Issued six times a year. Annual subscription:

j domestic $17.00; foreign $21.25. Single copy, $3.00 domestic;

!| $3.75 foreign.

j Note: The Journal was formerly published in two sections:

I Section A "Physics and Chemistry" and Section B "Mathematical Sciences." DIMENSIONS/NBS

This monthly magazine is published to inform scientists, engineers, businessmen, industry, teachers, students, and

consumers of the latest advances in science and technology,

with primary emphasis on the work at NBS. The magazine

I highlights and reviews such issues as energy research, fire

j protection, building technology, metric conversion, pollution

abatement, health and safety, and consumer product perI formance. In addition, it reports the results of Bureau pro- grams in measurement standards and techniques, properties

of matter and materials, engineering standards and services, instrumentation, and automatic data processing.

Annual subscription: Domestic, $1 1. 00; Foreign $13.75

NONPERIODICALS

! Monographs—Major contributions to the technical liter-

; ature on various subjects related to the Bureau's scientific and technical activities. Handbooks—Recommended codes of engineering and industrial practice (including safety codes) developed in cooperation with interested industries, professional organizations, and regulatory bodies.

Special Publications—Include proceedings of conferences

sponsored by NBS, NBS annual reports, and other special

publications appropriate to this grouping such as wall charts, pocket cards, and bibliographies.

Applied Mathematics Series—Mathematical tables, manuals, and studies of special interest to physicists, engineers,

chemists, biologists, mathematicians, computer programmers,

and others engaged in scientific and technical work.

National Standard Reference Data Series—Provides quantitative data on the physical and chemical properties of

materials, compiled from the world's literature and critically evaluated. Developed under a world-wide program co- ordinated by NBS. Program under authority of National

Standard Data Act (Public Law 90-396).

NOTE: At present the principal publication outlet for these data is the Journal of Physical and Chemical Reference Data (JPCPvD) published quarterly for NBS by the American Chemical Society (ACS) and the American Institute of Phvsics (AIP). Subscriptions, reprints, and supplements

available from ACS, 1155 Sixteenth St. N.W., Wash., D.C.

20056.

Building Science Series—Disseminates technical information developed at the Bureau on building materials, components,

systems, and whole structures. The series presents research

results, test methods, and performance criteria related to the

structural and environmental functions and the durability

and safety characteristics of building elements and systems. Technical Notes—Studies or reports which are complete in themselves but restrictive in their treatment of a subject.

Analogous to monographs but not so comprehensive in scope or definitive in treatment of the subject area. Often

serve as a vehicle for final reports of work performed at NBS under the sponsorship of other government agencies.

Voluntary Product Standards—Developed under procedures

published by the Department of Commerce in Part 10, Title 15, of the Code of Federal Regulations. The purpose

of the standards is to establish nationally recognized require- ments for products, and to provide all concerned interests with a basis for common understanding of the characteristics of the products. NBS administers this program as a supple- ment to the activities of the private sector standardizing

organizations.

Consumer Information Series—Practical information, based on NBS research and experience, covering areas of interest to the consumer. Easily understandable language and

illustrations provide useful background knowledge for shopping in today's technological marketplace.

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pursuant to the Federal Property and Administrative Services Act of 1949 as amended, Public Law 89-306 (79 Stat. 1127), and as implemented by Executive Order 11717

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BIBLIOGRAPHIC SUBSCRIPTION SERVICES

The following current-awareness and literature-survey bibli- ographies are issued periodically by the Bureau:

Cryogenic Data Center Current Awareness Service. A litera- ture survey issued biweekly. Annual subscription: Domestic, $25.00; Foreign, $30.00.

Liquefied Natural Gas. A literature survey issued quarterly.

Annual subscription: $20.00.

Superconducting Devices and Materials. A literature survey

issued quarterly. Annual subscription: $30.00. Send subscription orders and remittances for the preceding bibliographic

services to National Bureau of Standards, Cryogenic Data

Center (736.00) Boulder, Colorado 80303.
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