# Presentation: 656490

## Controlled Atmospheres at High Temperature for Neutron Scattering Experiments

***K. J. Volin and J. S. Fieramosca***
***I****ntense ****P****ulsed ****N****eutron ****S****ource Division*
*Workshop on Sample Environment at*
*Neutron Scattering Facilities*
*Abingdon, UK*
*June 23-25, 2004*

**Notes:**
Controlled Atmospheres at High Temperature for Neutron Scattering Experiments
K. J. Volin and J. S. Fieramosca
Intense Pulsed Neutron Source
Argonne National Laboratory, Argonne, IL

Increased scientific and engineering interest in the characterization of materials 
in extreme environments has led to the development of high temperature, 
controlled atmosphere sample environments for neutron scattering experiments.  
In the case of high temperature studies, furnaces operating up to ~2000C are 
widely used at neutron scattering facilities.  However, they are predominately 
used in a vacuum environment for diffraction experiments.  Consequently, high-
temperature properties, particularly atomic dynamics of ceramics under ambient 
or oxidizing atmospheres, cannot be properly characterized.  In-situ investigations 
of chemical reactions, corrosive behavior or densification processes further demand 
accurate control and monitoring of molecular streams or application of pressure in 
conjunction with very high temperature.  Sample environment equipment at the 
Intense Pulsed Neutron Source (IPNS) has matured to meet these needs.  The 
structure of materials can be studied in a controlled oxidizing, reducing, or inert 
atmosphere, or under vacuum at temperatures up to 1450C.  Using the 
Experimental Physics and Industrial Control System (EPICS) to monitor and 
control both the temperature and atmosphere through a graphical user interface 
(GUI) helps tie the sample environment control to the execution of a particular 
experiment data set.

## Science Drivers for Controlled Atmospheres

**Functional high strength materials at high temperatures**
**Catalytic materials**
**Ionic conductors**
**High T****c**** superconductors**

**Notes:**

Functional high strength materials at high temperatures
Nitride- and carbide-based ceramics, e.g. Si3N4, SiC
Transition-metal based alloys, e.g. Ni- or Ti-based alloys
Sintering Behavior of Nanostructured Titania Studied by In-Situ Powder Diffraction and Molecular Dynamics
Catalytic materials
Zeolites
Ionic conductors 
In –Situ Neutron Diffraction Study of Oxygen Ion Conductor Sr(F30.8Ga0.2))3-d
A High Temperature Structural Study of Strontium Substituted Lanthanum Iron Oxide
In-Situ Neutron Diffraction Study of Sr(CO0.87Fe0.1Cr0.03)O3-d Phase Transformations at Variable Temperature and Oxygen Partial Pressure
High Tc superconductors
Oxygen-content dependence of crystal structure and Tc of (Nd0.675Ce0.325)2(Ba0.664Nd0.336)2Cu3.00Oy

## The Miller Furnace

**RT to 1450****°C(1723K)**
**Atmospheres**
- Oxidizing
- Reducing*
- Inert
- Vacuum
**Type S thermocouples**
- furnace control
- sample temperature monitor
**Mass flow controllers**
- adjustable concentration of several gas mixtures
- adjustable total flow rate
**Oxygen sensor**
- % to ppm range
**BN collimation ********90 Degrees**

**Notes:**
The Miller furnaces are tantalum ribbon resistive-element type furnaces used for
 heating samples to 1300°C. Alumina is the primary material used in construction
 of these furnaces. The sample volume is separate from the instrument volume, so 
the samples can be used with a static air, purge gas, or vacuum, and sample 
changes can be done without breaking instrument vacuum. Typically, powder 
samples are pressed into pellets for use in the Millers, but other sample container 
type arrangements can also be used upon request. The instrument vacuum protects 
the tantalum ribbon and heat shields from oxidation, and is interlocked using a 
Teledyne Hastings analog vacuum gauge. The furnaces are controlled using 
Eurotherm controllers and have remote computer interface capabilities. A Newport 
temperature alarm unit provides an independent temperature interlock. Electronic 
Measurements 250V, 20A DC power supplies are used to heat the furnaces. All 
control and interlock equipment are supplied in mobile cabinet racks. Each 
furnace uses tow sheathed type S thermocouples for control and police 
interlocking. The sample temperature is monitored using a bare-wire type S 
thermocouple located inside the sample volume and typically in contact with the 
sample. Due to the scattering geometry, only 90( scattering angles are available 
with the Miller furnaces; therefore, the only compatible instruments are the SEPD 
and GPPD. 

## The Miller Furnace - Construction

**Aluminum oxide sample space**
**Aluminum oxide double threaded shell**
- Incident and exit beam windows
- 90° scattered beam windows
**Tantalum ribbon windings**
**Tantalum foil heat shields (2 ea)**
**Dual type S thermocouples for furnace control (2 ea)**
**Exposed furnace materials to atmosphere**
- Aluminum oxide
- Platinum
- Stainless steel

## The Miller Furnace – Sample Insert

**Notes:**
Samples are typically a stack of pressed pellets 1/2” diameter x 1/8” height – 
10 to 12 discs comprising a sample.  These are held in the sample insert by a 
ceramic rod along with a type S thermocouple to monitor the sample 
temperature (A).  Other variations are to suspend the sample with a platinum 
wire (B) or support a flat plate with a platinum stand (C).

## The Miller Furnace

**Structural Behaviors of Oxygen Permeable Ceramic Membranes**

**Notes:**
Yaping Li - Structure Characterization and Oxygen Permeability of 
(La0.2Sr0.8)3Fe1.5Co0.5Ox Ruddlesden-Popper Phase Ceramic Membrane 
for Syngas Production

## The Miller Furnace

**Structural Behaviors of Oxygen Permeable Ceramic Membranes**

## The Miller Furnace

## The Miller Furnace – Atmosphere Control

**Brooks Instruments Model 5850 Mass Flow Controllers**

**Notes:**
Constant temperature thermal mass flowmeters, such as those produced by 
EPI & Brooks Instrument, require two active sensors (typically platinum RTDs)
 that are operated in a balanced state. One acts as a temperature sensor reference; 
the other is the active heated sensor. Heat loss produced by the flowing fluid tends
 to unbalance the heated flow sensor and it is forced back into balance by the 
electronics. With this method of operating the constant temperature sensor, only 
the skin temperature is affected by the fluid flow heat loss. This allows the sensor 
core temperature to be maintained and produces a very fast response to fluid 
velocity and temperature changes. Additionally, because the power is applied as 
needed, the system has a wide operating range of flow and temperature. The 
heated sensor maintains an index of overheat above the environmental temperature 
sensed by the unheated element. The effects of variations in density are virtually
 eliminated by molecular heat transfer and sensor temperature corrections.
 These meters typically have a turn down ratio of 1000:1 when properly sized. 
Brooks Instrument5850 Series MFC

## The Miller Furnace – EPICS Interface

**The Experimental Physics and Industrial Control System (EPICS) graphical user interface (GUI) for the Brooks Instruments mass flow controllers.  This allows run file control of the concentration of individual gases and the total flow rate of the gaseous atmosphere.**

**Notes:**
EPICS is a set of software tools and applications which provide a software 
infrastructure for use in building distributed control systems to operate devices 
such as Particle Accelerators, Large Experiments and major Telescopes. Such 
distributed control systems typically comprise tens or even hundreds of computers,
 networked together to allow communication between them and to provide control 
and feedback of the various parts of the device from a central control room, or 
even remotely over the internet.
EPICS uses Client/Server and Publish/Subscribe techniques to communicate 
between the various computers. Most servers (called Input/Output Controllers or
 IOCs) perform real-world I/O and local control tasks, and publish this information
 to clients using the Channel Access (CA) network protocol. CA is specially 
designed for the kind of high bandwidth, soft real-time networking applications 
that EPICS is used for, and is one reason why it can be used to build a control 
system comprising hundreds of computers.

## The Miller Furnace – Data

***The Miller Furnace ******– Data***

## The Howe Furnace

**The Howe furnace, on semi-permanent loan from Leicester University, is a vanadium foil vacuum furnace capable of 1100****°C.  It has been modified with a vanadium sample well separating the sample and furnace vacuum spaces.  Samples are typically held in an open vanadium can suspended on the end of a sheathed thermocouple.**

**vanadium **
**element**

**vanadium **
**heat shields**

**vanadium **
**sample well**

**pedestal and **
**thermocouple**

**Notes:**
The Howe is a vanadium resistive-element type furnace used for sample heating 
to 1000°. Incident and scattered neutrons pass through two vanadium heat shields, 
a vanadium heating element, an inner vanadium sample housing, and a sample 
container during experimentation. The sample environment is kept separate from 
the instrument chamber by a sample housing which enables sample exchange-gas 
purging and quick sample changes without the need to remove the entire furnace 
from the instrument. The furnace utilizes the instrument vacuum to protect the 
vanadium heating element from oxidation. A Balzers dual vacuum controller 
provides vacuum interlocks for the sample volume and the instrument chamber. 
The furnace is controlled using a Eurotherm controller and has remote computer 
interface capabilities. A Newport temperature alarm unit provides an independent 
temperature interlock. An Electronic Measurements 20V, 250A DC power supply 
is used to heat the furnace. A portable Edwards roughing pump and Balzers turbo 
pump are used to evacuate the sample volume. All control and interlock equipment 
are supplied in a mobile cabinet rack. The furnace uses one sheathed type K 
thermocouple positioned within the instrument vacuum in the center of the heating 
element for furnace control. A dual probe type K thermocouple is used for sample 
temperature monitoring and police interlocking, and is used as the sample container 
mount within the sample vacuum volume. This furnace is used primarily in the GLAD, SEPD , 
and GPPD instruments, but could be used in the following instruments as well but with a smaller 
sample than normally used: LRMECS. The Howe furnace can also be outfitted with a tantalum 
element and heat shields for use on QENS. 

## The Howe Furnace – Modified for Atmospheres

***The Howe Furnace – ******Modified for Atmospheres***

**To accommodate a user requiring a flow of reactive gas through the sample, the Howe furnace was modified with a fused silica tube outfitted with a coarse quartz frit to hold the powder sample.  The gas, along with sheathed thermometry, are attached to the fused silica tube with stainless Swagelok fittings.**

**fused silica wool**

**coarse quartz frit**

**type K thermocouple**

**type K thermocouple**

**sample**

**stainless steel Swagelok feedthroughs**

**A professional scientific glassblower installed the quartz frit into the fused silica tubes while the rest of the modifications were done by IPNS staff.**

## The Howe Furnace – Modified for Atmospheres

## The Howe Furnace – Data

## Convection Cryofurnace - Requirements

**Extended temperature range****	****	****10K < T < 800K**
**Rapid temperature equilibrium****	****	****order of minutes**
**Measurement of gas temperature before and after sample**
**Use of oxidizing, reducing, or reactive gases**
**Simple changing of samples**
**Capable of isolating samples during sample change**
**Robust design – user friendly to even unfriendly users**

**Notes:**
Extended temperature range		10K < T < 800K	
Minimum and maximum temperature is negotiable but it is important to go smoothly through room temperature
Rapid temperature equilibrium		order of minutes
 In addition to high ramp rate ~100°C/min
Measurement of gas temperature before and after sample
Monitor how much heat is going into or out of the sample.
Use of oxidizing, reducing, or reactive gases
 X%GAS:BAL-He
Simple changing of samples
Capable of isolating samples during sample change
 Turner valve
Robust design – user friendly to even unfriendly users

## Convection Cryofurnace

**Notes:**
C. Hillier and P. WigginsAS Scientific LtdAbingdon, Oxfordshire, UK
M. JurmanisJanis Research CompanyWilmington, MA USA
T. RuferAdvanced Research Systems, IncAllentown, PA USA
I. Bailey and R. DoneISIS FacilityRutherford Appleton LaboratoryDidcot, Oxfordshire, UK

## Convection Cryofurnace 

**American Conference on Neutron Scattering****College Park, MD, June 6-10, 2004**
- Breakout Session on *Sample Environment for Neutron Scattering Experiments* (Volin, Dender, Fieramosca, & Santodonato)
**Common interest in a flow through cryofurnace among facilities****ANL/IPNS, NIST/NCNR, ORNL/SNS, and ORNL/HFIR**
**Common interest among elastic and inelastic instruments**
**Sharing of effort, expertise, and equipment among neutron facilities**
- Common specifications as requirements
*Temperature range*
*Performance specs*
- Individual specifications as options
*Vacuum tails*
*Sample mounting*
- Open bid process through DOE and/or DOC

**Notes:**
American Conference on Neutron ScatteringCollege Park, MD, June 6-10, 2004
Breakout Session on Sample Environment for Neutron Scattering Experiments (Volin, Dender, Fieramosca, & Santodonato)
Common interest in flow through cryofurnace among facilitiesANL/IPNS, NIST/NCNR, ORNL/SNS, and ORNL/HFIR
Common interest among elastic and inelastic instruments
	J. Copley (NIST/NCNR) and J. Jorgensen (ANL/IPNS)
Sharing of effort, expertise, and equipment among neutron facilities
Common specifications as requirements
Temperature range (probably most negotiable)
Performance specs (cooling rates, gas flow, chemical compatibility)
Individual specifications as options
Vacuum tails including instrument mounting (pulsed vs. reactor)
Sample mounting (inelastic vs. elastic, flange vs. stud)
Open bid process through DOC (NIST) and/or DOE (everyone else) 

## Summary

**Controlled atmospheres at high temperatures have afforded the neutron scatterer the opportunity to explore previously uncharted phase space, investigate engineering problems involving harsh environments, and follow chemical reactions in-situ.**** **
**Neutron scattering facility users will not only continue make use of available controlled atmosphere sample environments but will continue to ask for more – higher temperatures, bigger (or smaller) sample sizes, more reactive atmospheres.**** **
**It’s just a matter of money, manpower, and ingenuity.**

## Acknowledgements

**Many in the IPNS Division have contributed to the material presented but in particular the following have participated with the authors in the modifications of the furnaces**
**Evan Maxey, Ashfia Hug, and Yaping Li****General Purpose Powder Diffractometer (GPPD)**
**Simine Short****Special Environment Powder Diffractometer (SEPD)**
**Rich Como****Sample Environment and Ancillary Equipment Group **
**John Hammonds and Rodney Porter****Computer DAS Group**
**Dave Leach****Neutron Operations Group**
- The work reported in this presentation is supported by the
- U.S. Department of Energy, BES Materials Sciences,
- under contract **W-31-109-ENG-38**