Infrared spectrophotometer accelerated corrosion-erosion analysis system

A preferred embedment of the system and a method are provided utilizing Fourier Transform Infrared Spectrophotometer (FITR) for examination and analysis of materials on a real-time basis in a chamber at elevated temperatures with corrosive-erosive gaseous environments that cause accelerated material deterioration. The apparatus is capable on a real-time basis of examining and analyzing a wide variety of materials subjected to accelerated deterioration events missed by prior art systems and methods. Empirical data of accelerated corrosion-erosion events are also acquired and stored for subsequent computer analysis of recorded absorbed and reflected vibrational frequencies detected. The system utilizes preselected adjustable grazing angles of an incident beam of the infrared beam impinging upon a material sample during the observation and analysis processes to enhance the data to be collected. The system provides feed back laser signals for alignment adjustment for the selectable grazing angles.

FIELD OF INVENTION 
The present invention relates to apparatus and processes for measurement, 
life assessment and analysis of the accelerated real-time deterioration 
effects of corrosion/erosion of materials, devices and structures while 
exposed to elevated temperature and hostile gaseous environmental. 
BACKGROUND OF THE INVENTION 
In the prior art Fourier Transform Infrared (FTIR) spectrophotometery 
techniques are well known techniques to improve the signal-to-noise ratio 
by multiple interactions with a sample's surfaces to provide a real-time 
surface monitoring capability at mono-layer levels. 
Steven G. Barbee, et al, in U.S. patent Ser. No. 5,386,121, entitled "In 
Situ, Non-Destructive CVD Surface Monitor", issued Jan. 31, 1995, 
discloses an in-situ monitoring and process control technique using 
Fourier Transform Infrared spectrophotometery with Multiple Internal 
Reflections (FTIR-MIR) which looks at the Si--H bond vibrations. The 
technique disclosed is reputed to be useful in monitoring UHV Chemical 
Vapor Deposition (CVD), Low Pressure CVD (LPCVD), mid-pressure and 
atomiospheric Chemical Vapor Deposition (CVD) systems. In the system a 
substrate under analysis is configured, i.e., bevelled ends at 45.degree., 
so that output signal has a predetermined angle on exiting the substrate 
after Multiple Internal Reflections (MIR) which can look at the Si--H bond 
vibrations on a silicon sample's surfaces. The technique is used to 
monitor a critical passivating hydrogen layer on the surface necessary for 
successful epitaxial growth, and it is the integrity of this critical 
passivating layer that is monitored so as to readily detect surface 
changes when destructive species are introduced to the substrate surfaces. 
In the prior art the principal underlying infrared spectrophotometery have 
been appreciated for more than a century. It is understood to be one of 
the few techniques that can provide information about chemical bonding in 
materials. It is useful for the nondestructive analysis of solids and thin 
films. Chemical bonding tests vary widely in their sensitivity to probing 
by infrared techniques. For example, carbon-sulfur bonds often give no 
infrared signal and so cannot be detected at any concentration, while 
silicon-oxygen bonds can produce signal intense enough to be detected when 
probing sub-mono-layer quantities. Thus, the utility of infrared 
spectrophotometery is a function of the chemical bond of interest, rather 
than being applicable as a generic probe. 
The goal of most basic infrared experiment is to determine changes in the 
intensity of a beam of radiation as a function of wavelength or frequency, 
after it interacts with a material sample. The function of the infrared 
spectrophotometer is to disperse the light from a broadband infrared 
source so that its intensity at each frequency can be measured and 
analyzed. The ratio of the intensity before and after the light interacts 
with the sample is determined and a plot of this ratio versus frequency is 
known as the infrared spectrum. 
Further in the prior art, it has been concerned with utilizing infrared 
spectrophotometery technology as a tool for nondestructive test and 
analysis on materials and products at ambient temperatures and in 
non-hostile environments. No techniques are known wherein infrared 
technology is used for test and analysis of materials and products on a 
real-time basis or as simulated accelerated life-test basis, at elevated 
temperatures and in hostile environments. 
However, accelerated testing and life assessment of materials, components 
and products have been used in the prior art in several industries to 
ascertain changes to them over time. Notably in such industries, for 
example, as the paint, electronics component, metal fabrication and 
chemical industries. In each of these industries the products and 
materials thereof may be subjected to elevated temperatures and 
non-ambient environments. The evaluation of such exposure is usually 
conducted at specified time intervals during the tests or at the 
conclusion thereof. Such evaluation processes frequently include 
examination of the materials and products after testing by means of the 
naked human eye; examination for changes in the physical, chemical or 
electrical properties with the aid of various devices; and examination for 
changes in color, texture or physical appearance also with the aid of 
other devices. These types of examination and analysis after the fact of 
testing have proven wholly inadequate for predicting what changes have 
occurred in the materials or products on a real-time basis. More, 
specifically, it is difficult, if not impossible to ascertain, for 
example, whether the changes are as a result of processes such as chemical 
oxidation and reduction, formation of new or and different surfaces or 
structural changes; and more importantly, it is also difficult, if not 
impossible to determine when, time-wise, such undesirable changes have 
occurred. Thus, there exist in the prior art a long standing and 
significant need for test and analysis systems to provide real-time 
information and data that is useful in determining what changes have 
occurred and when these changes have occurred. Such information and data 
on a real-time bases would be useful in understanding the nature of the 
occurrences and when they occurred, and therefore, would be useful in 
predicting useful life of materials and products, what changes may occur 
during its useful life, and as an aid in the design and manufacture of 
more reliable and longer life materials and products. For example, its has 
been recognized in metal fabrication industry that the lack of such 
real-time information and data during the life or accelerated life test of 
various fabricated materials has had a significant impact in reducing the 
gross national economy of the United States because of materials corrosion 
and failure. 
The present invention utilizes infrared spectrophotometery technology to 
provide apparatus and processes for addressing and solving the foregoing 
long standing problem in the prior art by providing real-time information 
and data of tests made on materials and products while they are 
selectively subjected to various conditions of elevated temperatures and 
hostile environments simulating and accelerating real life time 
conditions. 
BRIEF SUMMARY OF THE INVENTION 
The present invention provides apparatus and a method utilizing Fourier 
Transform Infrared Spectrometer (FTIR) for non-destructive and destructive 
examination and analysis of solids and thin films, at elevated 
temperatures and corrosive-erosive gaseous.backslash.vapor environments to 
provide real-time empirical data of accelerated corrosive-erosive events 
in a contained chamber. Such real-time data is acquired and stored for 
subsequent computer analysis. In accordance with the present invention, 
the apparatus utilizes a pair of adjustable infrared transmission mirrors 
to provide preselectable grazing angles of the infrared incident impinging 
and reflective beams during observations and analysis, while utilizing 
various testing methods. These adjustable mirrors enable the apparatus to 
be adjusted to provide a wide range of grazing angles (0-85 degrees from 
the normal to the sample substrate), especially certain angles that have 
been determined critical in some applications of the inventive concept. 
The FTIR spectrometer also measures the concentration and change in 
concentration of the gaseous species which initiate corrosion in the same 
spectra. The gaseous species frequency band is distinct and separate from 
the frequency band for the metal oxides and surface corrosion salt 
species. 
The apparatus of the present invention, also includes a companion laser 
system which is used to provide feed-back signals to the apparatus for 
continuous adjustment of the adjustable infrared transmission mirrors, so 
that the impinging infrared beam strikes a sample target at the desired 
grazing angle. As an alternate means the grazing angle for the impinging 
infrared beam may be controlled by a laser using a feedback signal derived 
from the target platform upon which a target is located during test. 
Feedback signals to the laser enable the laser to move an adjustable 
target platform so as to maintain the desirable grazing angle(s). 
In addition to the foregoing features of the present invention, the 
apparatus includes a chamber into which a target or sample platform is 
provided, upon which test samples are placed during test and analysis. The 
platform may also elevate the temperature of the chamber and sample when 
an electrical heating element, such as a laser synthesized silicon carbide 
resistance proximity heater, that is preferred because it is corrosion 
resistance at high temperatures, thereof is energized. The chamber has 
input and output transmission windows, such as highly pure silicon carbide 
which has a use temperature of 925.degree. C., silicon is corrosion 
resistant but has a use temperature of only 300.degree. C. and has a 
frequency gap 360 to 660 cm.sup.-1, diamond has a use temperature of 
730.degree. C., but is ten times more expensive, Cadmium Telluride and 
Zinc Selenide are both brittle and have a maximum use temperature of 
300.degree. C., while polyethylene transmits down to 250 cm.sup.-1 at room 
temperature but must be isolated from high temperatures to accommodate the 
incoming and exiting infrared and laser beams. Diamond rich surface layers 
created by chemical deposition, ion implantation and similar methods and 
fluoride such as MgF.sub.2 may also prove useful. It also has accessible 
ports to accommodate the injection of selected gases and the removal 
thereof; and another port is provided to provide support for the target 
platform, to provide electrical input power and to receive feedback 
electrical signals from the target platform useful to the laser for 
angular adjustment of the target platform. 
The apparatus utilizes two moveable mirrors and two fixed mirrors. The 
moveable mirrors are adjusted mechanically or by feedback signals used by 
the laser for such adjustments. One moveable mirror intercepts the 
incident infrared and laser beams before they enter the chamber through an 
input window and a second moveable mirror intercepts and transmits the 
infrared and laser beams exiting the chamber through an exit or output 
window. A first and second fixed mirror are disposed along the output 
beams path. The second or last mirror communicates infrared and laser 
signals to a detector which subsequently transmits such signal via an 
interfacing device to the FTIR control system for processing and 
transmission to data acquisition and storage device. Liquid nitrogen 
cooled mercury cadmium telluride (MCT) detectors are typically used and 
are protected by the same window material used in the chamber. 
Systematized collection and recorded data may be monitored on a real-time 
basis by a monitor device or may be analyzed later from the stored data. 
In another embodiment of the present invention, apparatus and methods are 
provided that enable the examination and analysis at a field site or at an 
in-plant site to ascertain the scope and nature of the internal material 
surface deterioration or failure in chemical processing containers, 
storage tanks and the like, when such material surfaces have been or being 
exposed to corrosive/erosive gaseous/vapor and elevated temperatures 
during their normal uses. Such tests and analysis may be done as an 
interim or after-the-fact occurrence, and therefore, may be useful for 
future container or storage tank material selection and design. In this 
embodiment the apparatus, in accordance with the teachings of the present 
invention, is viewed as portable for field or on-site use. Thus, the 
apparatus may be used to examine and analyze the interior surface of a 
container or tank in an after-the-fact use mode or during an active 
manufacturing processing mode where these enclosures are subjected to 
corrosive/erosive and elevated temperatures on a real-time basis. 
As used herein the terms "systematized", "systematizing" and 
"systematization" means to analyze and the arrangement of data in 
accordance with a plan or scheme derived from data collected from the 
interferogram which are processed by the Fourier integral using a fast 
Fourier transform (FFT) algorithms.

DETAIL DESCRIPTION OF THE INVENTION 
A brief discussion of the theory of operation of the Fourier Transform 
Infrared (FTIR) spectroscopy may be helpful in understanding its relation 
and use in connection with the present invention. One of the primary 
objects of the present invention is to use specular reflectance from the 
surface of a sample in a hostile environment of elevated temperatures and 
corrosive gases, as a way of analyzing the sample while simulating the 
accelerated life thereof and further monitoring such analysis on a 
real-time basis. 
The infrared spectroscope's main purpose is to determine an optical 
intensity versus frequency or wavelength. It needs a light source, a means 
to set or measure wavelength, a detector and a device to record the 
spectrum. In theory, a standard technique for visible light spectroscopy 
uses a black-body source with a dispersive grating spectrometer as the 
wavelength selector. The forbearer spectroscopy uses a black-body source, 
but replaces the dispersive grating spectrometer with a Michelson 
interferometer. This gives the Fourier transforms of the desired spectrum, 
known as the interferogram. The interferogram requires extensive computer 
manipulation to yield the desired intensity versus wavenumber spectrum. 
The basic process in FTIR spectroscopy is light wave interference. The 
data collected from the interferogram are processed by the Fourier 
integral using fast Fourier transform (FFT) algorithms. Most commercially 
available FTIR instruments come with pre-written software, for example, a 
Spectra Cal package for Galactic Industries Corporation, 395 Main Street, 
Salem, N. H. 03079, ready to deal with the integral equation. There are 
several known suppliers of FTIR spectroscopy systems, however, the present 
invention uses the MIDAC M Series FTIR spectrometer, which is designed to 
rapidly acquire complete high resolution spectra and is compatible with 
IBM compatible PC computers, and a data system with pre-installed software 
for printer and plotters. Data reduction capabilities include peak marking 
and identification, plotting multiple spectra overlay for comparison and 
advance smoothing functions. The FTIR spectrometer provides an 
interferogram that is a composite of all wavelengths in the entire 
spectrum, i.e. 4000-250 cm.sup.-1 wavenumber using conventional 
connotations. Use of the Michelson interferometer as the grating means, 
i.e. for dispersion of the infrared beam across the spectrum in a matter 
of seconds, enables about 10 scans to be made in about 15 seconds. 
Referring now, to the drawings, there is shown in FIG. 1, a Fourier 
Transform Infrared (FTIR) control system 10, which is a modified version 
of the MIDAC M Series FTIR spectrometer, which for purpose of this 
disclosure, contains an infrared and laser light source for generating 
light beams of each, a Michelson-type interferometer for dispersion of the 
infrared beam, i.e. spreading or splitting up the beam across its entire 
spectra from 4000-250 cm.sup.-1 wavenumbers. This spreading of the light 
beam is commonly termed "grating" the beam. An infrared and laser output 
beam port 12 is connected to a waveguide assembly 14 along which the 
infrared and laser beams travel where they intersect a first adjustable 
light transmission mirror 16 disposed along the beam path, where it is 
held in place by a fixture 18 connected to waveguide assembly 14 at its 
input end. The output end of fixture 18 is connected to a chamber 20 in 
which material samples may be examined. Chamber 20 of the present 
invention may be readily incorporated into a complementary analytical 
instrumentation arrangement selected from the group consisting of Auger 
electron spectroscopy, X-ray photo-electron spectroscopy, secondary ion 
mass spectroscopy, scanning electron, FTIR and optical microscopes. In 
such incorporated arrangements the results obtained from such 
complementary analytical instrumentation occur simultaneously as the FTIR 
results of the present invention are obtained, such that the various 
results can be monitored and compared on a real-time basis during the 
evaluation and analysis process of a sample material test. 
Chamber 20 has an input window 22 and an output window 24 for entering and 
exiting beams, respectively. As shown, a test sample support platform and 
a sample material 26 are disposed within the chamber however, it should be 
noted that the sample could be a selected area of the interior of a 
chamber wall. Such an arrangement will be discussed hereinbelow in greater 
detail. Chamber 20 has a receiving port 28 that is used to access the 
inner chamber space. The output window end of chamber 20 is connected to 
an input end of a holding fixture 30 that contains a second adjustable 
mirror 32. During operation of the apparatus the infrared and laser beams 
are transmitted through mirror 16 and input window 20 to imping upon the 
sample of component 26, and thence through the chamber 20 and through its 
output window 24 so as to intersect second adjustable mirror 32. It should 
be noted that input and output transmission infrared beam windows 22 and 
24, may be of materials from the group consisting of Potassium Bromine 
(KBr), Silicon (Si), Diamond, Cadmium Telluride (CdTe), Zinc Selenide 
(ZnSe), Magnesium Fluorine (MgF.sub.2) and diamon coating of the foregoing 
materials. An output end 34 of mirror holding fixture 30 is connected to 
the input end of a third fixture 36, that holds a first fixed mirror 38 
that is disposed along the beam path after passing through second 
adjustable mirror 32. It should be noted that mirror 38 is provided as an 
attenuation medium along the beam path, to reduce the signal level of the 
laser beam in some applications where the signal may be too high such that 
it may cause damage to detector 48. An output end 40 of fixture 36 is 
connected to an input end 42 of a fourth holding fixture 44, wherein a 
second fixed mirror 46 is disposed along the beam path, intercepting it 
and deflecting it to an infrared and laser detector device 48. Also shown 
in fourth fixture 44 is depicted a cooling device 50 for cooling detector 
device 48. A signal is outputted from detector 48 through an electrical 
conductor 51 to a preamplifier circuit 52, and the output thereof is fed 
to FTIR control system 10 along electrical conductor 53. 
An output signal from FTIR control system 10 is fed along an electrical 
conductor 54 to a connected data acquisition system 56 that in turn feeds 
the collected data through electrical conductor 58 to a connected data 
storage device 60. The primary functions of the data acquisition system 56 
and storage device 60 is to collect, store, transform, display and 
manipulate data collected by the FTIR control system 10 so that such data 
may be used on a real-time basis or later analyzed. The data acquisition 
system 56 has software necessary to manipulate Fourier transform (FFT) 
algorithms for proper data storage, display or plots of real-time FTIR 
surface chemistry as spectra graphs of absorbance versus wavenumbers of 
samples, both during and after test sample examination in chamber 20. 
To continue with the disclosure of the present invention, reference is made 
to FIG. 2, wherein a simplified schematic of FIG. 1 is depicted for 
clarity of description. As shown FTIR control system 10 contains a laser 
source 66 which may be a HeNe type, and an infrared source, which may be 
silicon carbide, so as to create a dual light beam 69, a combination of a 
laser beam 102 and an infrared beam 100, that are transmitted through 
output beam port 12. Associated with these beam sources is a collector 
circuit 94 and a spectrophotometer 98 which are functional for 
systematization of collected data from detector 48 via preamplifier 52, 
and for transmitting such data to a data acquisition system 56 and thence 
to a data storage device 60. 
Also included in FTIR control system 10 is an alignment controller circuit 
96 which may receive feedback signals from moveable mirrors 16 and 32, and 
platform/material combination 26. These signals are fed to the controller 
circuit 96 through electrical conductor 92 so as to actuate one or more of 
a first electrically driven alignment device 104 connected to adjustable 
mirror 16, a second electrically driven alignment device 74 connected to 
support platform arrangement 26. It should be noted that each of the 
aforementioned components of the apparatus may in the alternative, be 
manually adjusted instead of electrically adjustment. In either event, 
information fed to the FTIR control system along 10 conductor 53 also 
provides information for manually adjusting the alignment of mirrors or 
platform to provide the desired alignment for the beam paths. 
Continuing with the disclosure, it can be seen that the adjustable mirrors 
16 and 32, material sample and support platform 26, the two fixed mirrors 
38 and 46, and detector 48 are all disposed in the of a beam 90, and 
further terminates at detector 48. Also shown are electrical conductors 
106, 110 and 112, each connected to electrical conductor 92, from their 
respective components, 104, 74 and 108, to transmit signals to the FTIR 
control system 10 useful for beam alignment. 
The detector 48 may be a photoluminescence diode, made of materials 
selected from the group consisting of Lithium Tantalum Oxide (LiTa 
O.sub.3) mercury cadmium telluride (MCT) or deuterated tri-glycene sulfate 
(DTGS) which affords good linearity and signal-to-noise ratio but must be 
operated at room temperature. 
Referring now to FIG. 3, there is shown an enlarged view of a material 
sample 70 disposed on a support platform 71. As shown an incoming infrared 
beam 82 strikes sample 70 at a grazing angle 78 to an x-axis and exits as 
exiting beam 84, the angle on exiting is equal to the incoming beam angle 
78. Also shown is electrically driven alignment device 74 connected to 
sample support platform 71, which may be adjusted manually or electrically 
to change the angles of the incoming and exiting beams. It can be seen 
that a conventional heating element 72 is provided within the body of 
platform 71 to provide heat to the sample and to elevate the temperature 
of chamber 20 and all the contents contained therein to selected 
temperatures. In the alternative, however, an electrical conducting 
heating element or pattern (not show in this figure) may be formed on a 
surface of platform 71 by means of laser conversion when platform 71 is a 
substrate of silicon carbide or aluminum nitride, in accordance with the 
teachings of U.S. patent Ser. No. 5,391,841, dated Feb. 21, 1995, and U.S. 
patent Ser. No. 5,145,741, dated Sep. 8, 1992, both issued to applicant. 
The latter technique for providing a heater element may be considered 
preferred because such heating elements have been found and proven to be 
excellent for elevated temperature operation in adverse gaseous 
environments, such as corrosive hydrogen chloride, as an example. 
EXAMPLE 
The following example with reference to FIGS. 4 and 5, will serve to 
illustrate how the present invention operates to determine on a real-time 
basis what is measured and an analysis of a sample in accordance with the 
teaching thereof. 
The spectrophotometer determines the changes in the intensity of a beam of 
infrared radiation as a function of frequency (wavenumber) after it 
interacts with the sample under observation. The spectrophotometer 
disperses the light from a broadband infrared source, such as that of FTIR 
control system 10, using a Michelson interferometer as the dispersing 
element, and it measures the intensity at each frequency from 4000-250 
wavenumbers (cm.sup.-1). The ratio of the intensity before and after the 
light interacts with the sample is determined. A typical plot of this 
ratio versus frequency is the infrared spectrum (reference: J. Neal Cox, 
Vibrational Spectroscopies, page 416). 
In the present example a mercury cadmium telluride (MCT) detector 48 is 
used having a Potassium Bromine (KBr) detector window and is liquid 
nitrogen cooled by system device 50. The chamber windows 22 and 24 used 
were of KBr, which limited the chamber from operating at maximum 
temperatures. 
In accordance with the teachings of the present invention, the change in 
infrared beam intensity results from the absorbance of specific 
frequencies by chemicals, particularly transition metal spinel oxides and 
metal halides (salts) formed during corrosion, existing or formed on the 
sample surface during exposure to high temperatures (200.degree. C.) of 
the chamber and gases such as hydrogen chloride (37%) and water (63%) 
injected into the chamber 20. In this example, a sample used was an alloy 
HR-160 (37.7 wt % nickel, 28 wt % chromium, 29 wt % cobalt, 2.75 wt % 
silicon, 2 wt % iron 0.5 wt % manganese and 0.05 wt % carbon) forms oxides 
in air at room temperature form these elements to protect the base metal 
from chemical attack. Referring to FIG. 4 there is shown an absorption 
peak at 600 cm.sup.-1 before exposure to the infrared beam. Data provided 
by Geoffrey C. Allen and Michael Paul, "Chemical Characterization of 
Transition Metal Spinel Oxides by Infrared Spectroscopy", APPLIED 
SPECTROSCOPY, Volume 49, Number 4, 1995, shows the highest absorption 
frequency band to range from 560 to 630 cm.sup.-1 for transition metal 
spinel type oxides comprised of iron, cobalt, nickel, manganese and 
oxygen. Thus, an observation of an HR-160 oxide peak in this frequency 
band is plausible. It should be noted that the Allen and Paul data is 
obtained using transmission IR Spectral analysis through fine oxide 
powdered mixed with KBr, polyethylene or adamantine as the medium. In 
accordance with the teachings of the present invention, the oxide 
condition of the oxide, and resultant chlorides which indicates the onset 
of oxide destruction, and consequently corrosion, are examined in-situ as 
a solid or film on the alloy's surface using reflectance/absorbance. The 
y-axis is relative absorption intensity and the x-axis is frequency 
(wavenumbers in units of cm.sup.-1). The y-axis relates to the 
concentration of an oxide and the x-axis identifies the oxide peak. 
Referring now to FIG. 5, it can be seen that after the introduction of the 
HCl and water, the height of the peak at about 600 cm.sup.-1 is decreased; 
the chemical concentration or amount of this oxide is decreased indicating 
a loss in the thickness or amount of protective oxide to resist corrosion. 
The 37% HCl+63% H.sub.2 O mixture is chemically reducing the oxide. It 
should be noted that other reducing or oxidizing gaseous/vapor 
environments may be used such as SO.sub.2, SO.sub.3, NH.sub.4, and 
NO.sub.X. The importance is that the FTIR measurement is sensitive to the 
initiation of the corrosion process. It is actually sensitive to the 
"latent" corrosion process which is not monitored by other known 
technologies. Deterioration of the passive protective oxide is detected 
before the underlying alloy, metal etc. surface is attacked. The 
spectrophotometer is actually measuring the intensity of the remaining 
light (reflected light) after absorption by the sample's surface at each 
frequency. Absorption spectra are preferred for quantitative results 
because to the first order it is a linear function of concentration. The 
grazing angle relection-absorption depicted in FIGS. 1, 2 and 3, are more 
sensitive than normal (perpendicular) incident measurements of very thin 
oxides and surface chemical layers because the electromagnetic field 
strength in the plane containing the incident and reflected radiation is 
greatly increased. In other words, the incident light intensity is higher 
and after interaction with the surface chemicals the absorbed intensity 
and reflected intensities are stronger. 
The output intensity (I) from the sample interaction is eventually measured 
by the detector 48. The output intensity information is sent back to the 
spectrophotometer to determine the intensity ratio(I/I.sub.o) where 
I.sub.o is the incident or original beam intensity before interaction with 
the sample's surface at each frequency. This data is sent back to the PC 
computer where the data is analyzed using the MIDAC/Galactic software. The 
data is displayed, wavenumbers are identified and labeled, and a chemical 
library assigns chemical names to peaks (note that some chemicals may have 
two or more peaks or frequency bands). 
It should be noted that the primary purpose of the laser 66 in the present 
spectrophotometer system is to monitor the direction and velocity of the 
moving mirrors which are measured by a pair of quadrature phase detectors 
in the FTIR control system 10, and for system alignment. Monitoring the 
moveable mirrors enables the control of the Michelson interferometer or 
"interferogram signal" and allows rapid data accumulation in only 10-15 
seconds. Remember this is the dispersing or "light grating" element for 
infrared light: it forms the "channels" in the incident beam. 
Referring now to FIG. 6, an alternative embodiment of the present 
invention, in which the incoming and exiting beams enter and exit through 
the single chamber window. As shown in FIG. 6, a FTIR control system 110 
is disposed adjacent to a chamber 120, which may be of a cylindrical or 
spherical configuration, is shown in part by cross-section and a dotted 
line, and a window 122 for transmission of an incident infrared beam 182 
and reflected beam 184. It should be noted that window 122 is 
enviornmentally resistant to heat and corrosive gases, such as Potassium 
Bromine (KBr). In addition, the input/output transmission infrared beam 
window 122 may be of materials from the group consisting of Potassium 
Bromine (KBr), Silicon (Si), Diamond, Cadmium Telluride (CdTe), Zinc 
Selenide (ZnSe), Magnesium Fluorine (MgF.sub.2) and diamond coating of the 
foregoing materials. A test sample 170 is supported within chamber 120 by 
a sample support platform 172, so as to receive incident beam 182 platform 
172 also includes an electrical heating element of one of the types 
discussed in connection with FIG. 3 and is connected to an electrical 
conductor 174 to provide electrical current thereto so as to provide an 
elevated temperature within chamber 122 and to sample 170. The electrical 
heater source for the heater is not shown, but conductor 174 and and means 
for supporting the heater and sample have access through a port 178 in the 
wall of chamber 120. There is also provided an inlet port 176 through the 
wall of chamber 120 for admitting selected gaseous mixtures into chamber, 
and a second port 180 provides access to chamber 120 for removal of gases 
therefrom. Neither the gas source or a gas removal device are depicted, 
since they may be conventional devices known in the prior art. 
The angle between incident and exiting beam from a contact point 186 at the 
surface of sample 170 depicted in FIG. 6, has a preferred range of 
5.degree. to 45.degree., about a y-axis of the chamber arrangement. The 
exiting beam is detected by detector 148 through a receiving arrangement 
140 which is in turn fed to a preamplifier circuit 152 by means of 
electrical conductor 192. The output of pre-amp 152 is fed back to FTIR 
110 by means of electrical conductor 153. After systemization of the 
signal from pre-amp 152, it is fed to a data acquisition system 156, and 
is split into to two output signals, one to a real-time monitor system 162 
and a data storage device 160, in a similar manner as that shown in FIG. 
2. 
Referring now to FIG. 7, there is shown an apparatus that is useful as a 
field diagnostic system for examination, analysis and determinating the 
nature and scope of surface deterioriation or failure of selected areas of 
the interior surface of a chemical processing container or chamber that 
was subjected to a HCL+H.sub.2 O corrosive/erosive gaseous/vapor 
environment during the chemical process. As shown in FIG. 7, there is a 
FTIR control system (FTIR) 200, an infrared detector 210 disposed in 
spaced apart relationship to one another and in spaced apart relationship 
to a flexible bundle of infrared transmission fiber optics 220, comprising 
two parallel sections 230 and 240 divided by a parallel non-transmission 
divider member 294. Fiber optics section 230 has an infrared beam input 
surface 290 and an infrared beam output surface 250. In a similar manner 
fiber optics section 240 has a reflected infrared beam input surface 260 
and an reflected infrared beam output surface 280. As shown surfaces 250 
and 260 intersect at a point 252 along parallel member 294 forming equal 
angles with an y-axis designated 370. 
The angular arrangement between these two surfaces 250 and 260, may be 
formed so as to provide a selected angular separation 360 between an 
incident and reflected infrared beam. By enlarging an angle 254, the beam 
separation increases and by decreasing angle 254, the beam separation is 
reduced. This simple arrangement provides a means for a wide range of 
control for varying the separation between the incident and reflected 
infrared beams. Continuing with the description of FIG. 7, an incident 
infrared beam 270 is transmitted to fiber optics bundle surface 290 to 
fiber optics bundle 230 exiting from surface 250 impinging upon an 
interior surface 310 of a container 300 in an surface area designated 320 
at an intersection point 340. The surface area 320 is analogous to the 
test samples discussed hereinabove with respect to FIGS. 1,2 and 6. 
As shown in FIG. 7, incident infrared beam 270 is reflected as a beam 280, 
intercepting reflected input angular surface 260 at an angle equal to 
and/or complementary to, that of beam 270, with respect to y-axis 370. 
Beam 280 is transmitted to infrared detector 210, by a conductor 212, 
where it is subsequently fed to FTIR control system 200 for processing in 
accordance with the teachings of the present invention. As discussed 
hereinabove with respect to FIGS. 1, 2 and 6, a signal 400 is fed from 
FTIR control system 200, to a data acquisition system (D.A.S.) 410 and 
subsequently to a real time monitor (R.T.M.) 420 and data storage device 
(D.S.) 430, respectively, for use in accordance with the teachings of the 
present invention. 
For purposes of discussing FIG. 7, it should be noted that container 300 is 
of an alloy HR-160, as discussed hereinabove and it was used with a 
chemical process where the internal environment was equal and/or 
equivalent to the HCl+H.sub.2 O corrosive/erosive gaseous/vapor and 
elevated temperature environment as that from which FIG. 5 was derived. 
Consequently, the results derived by using the arrangement of FIG. 7, were 
comparable, since the starting spectrum profile for container 300, shown 
as a portion thereof in cross-section, before its exposure to the hostile 
chemical processing environment was of the same material as the sample 
material whose characteristics are depicted in FIG. 4, i.e. before 
exposure to gaseous/vapor and elevated temperatures. Thus, it can readily 
be appreciated by those knowledgeable in the prior art of the present 
invention, that the arrangement shown in FIG. 7, is a highly useful and 
advantageous tool for providing corresponding results as with arrangements 
of FIGS. 2 or 3, by use of a portable field tool or apparatus of the type 
depicted in FIG. 7. 
The apparatus depicted in FIG. 7, consisting of flexible bundle light 
transmission fiber optics 220, FTIR control system 200, infrared detector 
210, data acquisition system 410, real-time monitor 420, and data storage 
device 430 may be utilized to examine and analyze the interior surface of 
an enclosure similar to the enclosure 120 shown in FIG. 6, which does not 
have ports 176, 178 and 180, while it is operating in an active processing 
mode with the corrosive/erosive gaseous/vapor and elevated temperature 
environment as part of the operation mode. In such mode of operation 
selected areas of the interior surface walls of the enclosures may be 
considered as a sample of material of interest and observation by use of 
the enumerated apparatus from FIG. 7. Access to the interior of an 
enclosure is accomplished through an input/output infrared beam window of 
the type disclosed in reference to FIG. 6, i.e. window 122 of FIG. 6. 
The foregoing embodiment operates in accordance with teachings of the 
present invention and is intended to be used as a portable field system 
than that shown in FIGS. 2 and 3 and therefore, is not as precision a 
device as that depicted in FIGS. 2 and 3. However, it should be noted that 
the reflection-absorption signal received by infrared detector 200 may be 
less than optimum when a grazing angle of near 10.degree. with respect to 
the x-axis of test sample surface area is used, and therefore, is not 
considered to be the preferred mode of operation when use for deriving a 
standard characteristic profile of a material. 
The foregoing disclosure and teachings of the present invention readily and 
adequately demonstrated that real-time life assessment and analysis of the 
accelerated deterioration effects of corrosion/erosion of materials, 
devices and structures while exposed to elevated temperature and hostile 
gaseous environment, can be used thereby solving long standing problems in 
the prior art with regard to corrosion/erosion of materials. The teachings 
of the present invention are clearly applicable for extensive use to 
determine and monitor deterioration effects caused by corrosion/erosion of 
materials in such industries as paint, electronics, metal fabrication and 
chemical industries on a real-time and accelerated basis or in the 
alternative as an after the fact technique of surface analysis of possible 
failure evaluation and/or determination for on-site field situations. It 
should be understood that the above described embodiments are only 
illustrative of the principles applicable to the invention. Various other 
arrangements and modifications may be defined or devised by those skilled 
in the art without departing from the spirit and scope of the invention. 
Consequently, is it understood that the present invention is limited only 
by the disclosure and appended claims.