Note: Descriptions are shown in the official language in which they were submitted.
32
COMBINED THERMAL ANALYZER POD
WRY DIFFRACTOMETER
This invention relates to a scientific apparatus
and a method for observing thermodynamic and structural
properties of materials. It particularly relates to an
instrument for simultaneous calorimetric and X-ray
diffraction analysis.
In characterizing the physical and chemical
behavior of substances, it is customary to separately
investigate both their thermodynamic (e.g., calorimetric)
and their structural (e.g. crystallographic) properties.
Thermodynamic properties are commonly deter-
mined by differential scanning calorimetry (DISC) and by
differential thermal analysis (DATA). Modern DISC and
DATA instruments are highly advanced, affording sensitive
temperature regulatLoll end measurement, of-ten to a
fraction of a Centigrade degree. A sample may be
heated rapidly through a wide temperature range, and
calorimetric output measured with precision, over a
period of a very few minutes.
32,131-F -1-
-2- ~2~858~
Crystallogl-apllic properties are often studied
by X-ray diffraction ~XRD) spec-trormetry. To achieve
high revolution, dilf-action data have been collected
on photographic film, or wow scintillation counters.
Such procedures are slow, requiring data collection
times of thirty minutes or more for each pattern at
each temperature. A single scan over a range of them-
portrays may consume most of a day or longer. Because
of the slow data collection times for X-ray diffraction
scans, structural and calorimetric data could not be
correlated for fast processes. In industrial processes,
heat and/or chemical treatments often occur on a matter
of a few minutes or seconds (i.e. the extrusion of a
polymer or the oxidation of a catalyst). In addition,
-the equipment for heating samples in X-ray diffraction
analysis has been comparatively crude, e.g., uniform
sample temperature control within five degrees has been
attainable only rarely east near room temperature.
For both reasons, rapid scanning, i.e., dynamic reading
of a series of X-ray diffraction patterns correlated
accurately and simultaneously with temperature rise as
a sample is heated, has not been previously practiced.
Instead, the usual approach has been to
analyze a sample first by one of the foregoing techniques
and then by the other. Data from the two de-terminations
were correlated as best might be, -to elucidate as far
as possible the -thermostruc-tural bellaviol- of the sample.
However, due to the differences in sample heating
conditions and sample size, and in -the data collection
times between DISC and conventional XRD, the diffraction
and calorimetric data did no-t correlate well when
trying to assign an observed structural change to a
particular calorimetric event. In applying this method
32,131-F -2-
I 58~
to multi-cGmpoIlent samples, separate physicocl~emica]
pnenolneila occur-lns at closely spaced -'temperatures were
often missed or misinterpreted as were indi~Gtions of
transitory species and irreversible phase changes
occurring over a period of a minute or two.
More recently, one aspect of this situation
has been improved. Position sensitive detectors have
been developed as X-ray detectors, dramatically increasing
the speed of acquiring diffraction data. With them,
the time scale for X-ray diffraction analysis can be
shortened to be compatible with that of differential
thermal analysis and differential scanning calorimetry.
The present invention takes advantage of this
improvement and provides a workable instrument and
method for simultaneous dynamic observation of thermos
dynamic and structural properties of a sample undergoing
temperature and/or environmental change.
The instrument of the invention includes in
combination both an X-ray diffractometer and a thermal
analyzer (either a differential scanning calorimeter or
a differential thermal analyzer) mounted to cooperate
and simultaneously cocci on the same sample undergoing
analysis. The diffractometer includes a source of an
X-ray beam directed -to impinge on a sample also being
acted upon and observed for de-termination of certain
thermodynamic properties, and a rapid position sensitive
detector to receive radiation diffracted from the
sample to determine structural properties. The thermal
analyzer includes within a sample holder assembly, a
32,131-F -3-
I
sample holder on or by which means the sample is post-
toned and retained for the join-t analysis. The sample
holder assembly has an inlet port or Zoo transparent
window positioned to allow the diffractometer X-ray
beam to strike the sample in the holder and an outlet
slit or window to allow passage of diffracted radiation
to the X-ray detector. The analyzer also includes
control means for changing the temperature of the
sample in the holder and means for observing the
I thermodynamic behavior of the sample during such
change.
The X-ray source preferably provides a
focused monochromatic beam. Advantageously, it is a
line source equipped with a Gunner diffraction system
and a curved focusing monochromator. The source and
the sample holder (and the surrounding enclosure) are
arranged geometrically so that a sample in the holder
lies at a point along the focusing circle of the
diffractometer.
The X-ray detector is preferably a position-
sensitive proportional counter mounted for movement
about the focusing circle of the diffractometer with
the sensitive element placed along the arc of the
circle. The detector is connected to electronic
readout circuitry. This may include a multi channel
analyzer with a display terminal or recorder to
indicate numerically and graphically the positions and
intensities of the lines forming the X-ray diffraction
pattern.
The thermal analyzer is preferably a differ-
entlal scanning calorimeter provided with electronic
32,131-F -4-
I ~28~82
readout circuitry to display and record bottle the temper--
lure of tile sample ~h?;ougilout analysis and the existence
and m2gni_ude of calori.net-ic events occur in in the
sample. The circuitry also contains means for controlling
the temperature of the sample in the holder. Beneficially,
this means is programmable to increase, decrease or
hold the temperature.
As a non limiting example, the sample holder
assembly (sometimes referred to as the specimen holder
assembly or cell) may comprises a protective enclosure,
conveniently a metal block with a cover to seal the
interior tightly. The block contains two chambers (or
alternatively a single common chamber) for the sample
and reference holders.
More broadly, various different sample holder
assembly designs than -that specifically described are
known and may be alternatively employed, e.g., as
illustrated by the literature and DISC and DATA commercial
instruments made reference to herein. Similarly, the
sample holder may -take numerous forms, modified where
required -to permit the simultaneous analysis of sample
contemplated by the invention.
For sealed operation, -the X-ray -transmitting
inlet port and outlet silt of -the sample holder assembly
are remade in-to windows by caviling -them with a thin
sheet of X-ray transmitting material. If the in.,trumell-t
is to be used to study -the effect of a particular
gaseous medium on a test sample undergoing analysis,
the sample holder assembly may also be provided with
inlet and outlet means for controllable passing gas
through it and into contact with the sample.
32,131-F -5-
1~8~8~:
Besides p ovidiIlg a novel instrument, the
invention also resides in a method of simultarleously
analyzlllg -the theri-nodynamic and structural piopeLtieS
of materials. In this method, a sample of the material
is subjected to a program of temperature and/or
environment change. During the program, e.g., in the
DISC mode, the differential heat flow into and out of
the sample indicative of calorimetric behavior is
observed throughout. At the same time, the sample is
exposed to a focused X-ray beam and diffraction data
from the sample are also observed throughout. The
calorimetric data and X-ray data are then compared as
functions of temperature and environment. This
comparison affords great insight into the fundamental
physicochemical behavior of the sample, and, in the
case of a multi-component sample, also of the substances
composing it and how -these materials may interact with
equal other.
The instrument and method may be operated
over a very wide range of temperatures and with a
variety of atmospheres. They can scan and record
calorimetric and X-ray diffraction data simultaneously
while the sample is heated through an interval of
several hundred degrees, and do it all in a few minutes.
Roy data are recollected dynamically as thermal analysis
proceeds, providing direct correlation of struct~lrcll
change with brief transient calorimetric events. The
kinetics of -thermally and atmospllericcllly induced
strut tubal transformations can be investigated with
precision, making possible interpretation of complex
DISC curves. In samples contailling several components,
phases can be readily distinguished and calorimetric
events assigned with assurance to individual components
32,131-F -6-
I
or to equines between two or more components. Results
of this character have not heretofore been achieved.
The invention Moe he explained with ruffians
to the accoll~panying drawings, in which
FIG. 1 is a schematic overhead view of a combined
X-ray diffractometer and differential scanning calorie
meter according to the invention, omitting the electronic
control and recording systems. The view shows the
instrument in the geometry of the Huber-Guinier system.
FIG. 2 is a side view, partly schematic, of
the central part of the instrument of FIG. 1, enlarged
to show the sample enclosure and its mounting.
FIG. 3 is a cutaway perspective view of the
sample enclosure of FIG. 2.
FIG. 4 is a schematic sectional elevation of
the sample enclosure, taken along the line 4-4 in FIG.
3, showing the sample holder with associated heating
and temperature sensing elements. The figure also
shows the gas port inlets and outlet.
FIG. 5 is a schematic sectional view of a
linear position sensitive proportional counter used as
an X-ray detector as shown in FIG. 1.
FIGS. pa and 6b are schematic sectional views
of a curved position sensitive proportional counter
which may be used as an alternative to the counter of
FIG. 5. The figures also show the common errors associated
with these types of detectors.
32,131-F -7-
~2~8~82
LUG. 7 is a block diagram showing schematically
the detector Conrail arid recording systems OX tile X-ray
diffLactol,leter pro lion o f -the instrument_ according to
the invention.
FIG. 8 is a schematic plan vie of an alternative
X-ray diffractome-ter using the geometry of the Bragg-
~rentano system.
FIG. 9 is a block diagram of the electronic
sensing and control systems of the differential scanning
calorimeter forming another portion of the instrument
of the invention.
FIG. 10 is a schematic elevation Al section of
an alternative apparatus configuration in which the
X-ray beam is directed vertically upward.
FIG. 11 is a schematic block diagram showing
the relation of the control and recording systems of
the entire apparatus according to the invention, and
including a system for supplying gas -to the sample
enclosure and for analyzing effluent gas from the
enclosure.
FIGS. AYE and 12B illustrate typical recordings
of Y-ray diffraction patterns (FIG. 12B) and corresponding
DISC scans (FIG. AYE) made to -the apparatus of the
invention during a heating cycle.
FIGS. AYE and 13B are similar to the recording
of FIGS. AYE and 12B, respectively, except made during
a cooling cycle.
32,131-F -3-
I ~2~82
FIGS. AWOKE illustrate SKYE scans of a
polymorphic organic compound before, during and after,
respectively, a DSC/XP3 experiment
FIG. 15 - X-ray diffraction patterns made
with the apparatus of the invention showing the
interconversion of the lower melting to the higher
melting polymorph.
The basic elements of the invention, in a
preferred form, are shown schematically in FIGS. 1 and
2. They include an X-ray diffractometer, indicated
generally as 17, and a differential scanning calorie
meter, the sample holder assembly of which is indicated
generally at 18. They are grouped together closely and
are mounted on a common base 19 for alignment and
positioning purposes as will be described further
below.
A sample 20 of material to be studied is held
in a small pan 22 or crucible, e.g., of aluminum foil,
and placed in a sample holder 96, FIG. 3, within the sample
holder assembly 18. Only milligrams of the material,
usually as powder or film, are required. The sample
holder assembly of the block design mentioned previously
is made from a protective enclosure block 24 taken from
a commercial instrument. However, it is modified and
placed so that it also serves as -the sample support of
the X-ray diffractometer. In this way, tile diffractometer
17 and calorimeter 18 share the sample in common and
study it simultaneously.
32,131-F -9-
-10- ~2~Ç;8;~
In the diffractometer 17, source 26 produces
a team 23 of Zeus which impinges on a monochromator
30. This fattier disperses and redirects the X-rays,
providing a monoenergetic beam 32 which converges on
5 the sample 20. The X-radiation passes through the
sample, and a part is diffracted away from the main
beam at various fixed angles. Two are shown in FIG 1
as 34 and 34'. The diffraction or "scattering" angles,
conventionally called I (two theta), and the cores-
pounding intensities of the diffracted X-rays, are
characteristic of the crystal structure(s) of the
sample. The diffracted X-rays are collected by a
position sensitive detector 36. Detector 36 registers
the arrival of diffraction radiation and also provides
information about where along its length (one-dimensional
detector) or over its area (two-dimensional detector)
the radiation was absorbed. See also the transactions
of The American Crystallographic Association, Vol. 18,
1982, page 9, R. C. Himalayan, Ed.
This detector is of known design and includes
a 25 micron diameter wire 38 for sensing the angular
pOSitiOIlS and frequency (i.e., counts/sec) at which
incident X-ray photons enter. The detector, which
covers an angular range of about 20 two theta, is
connected to a multi channel analyzer 40 (FIG. 7). This
latter stores the output data indicating angular position
and intensity of the diffraction data. The detector
and analyzer are further described below.
Both the test sample 20 and the detector 36
are positioned so that they lie in a horizontal plane
on the circumference of -the focusing circle 41 of the
32,131-F -10-
2~368~
Yore diffractometer (dashed circle in FIG. 1). At 211
points along -the circle, -the Alas are at their best
focus and resolution of the deflection data is at to
highest. The position of the sample 20 stays fixed,
but the detector 36 is mounted on a bracket 42 pivoted
about a post 44. The post is screwed in-to a mounting
block 46 held adjustable on the base 19 by means not
shown. The mounting block 46 is positioned so that the
post 44 is at the center of the focusing circle 41. In
this arrangement, the detector may be revolved to success
size positions along the focusing circle when it is
desired to observe data over an angular range greater
than that subtended by the detector in a single location.
The enclosure block 24, which supports the
sample 20 in the path of the X-ray beam 32, is closed
by a cover 48. To allow passage of the Years, the
wall of -the block 24 and the cover 48 are machined out
to form an inlet port 50 for incoming X-radiation and
an exit slit 52 for the X-radiation (FIGS. 2 to 4).
The port 50 is -tapered conically, narrowing down
inwardly to minimize intensity loss of -the converging
X-ray beam 32 toward the sample. A small hole 51 is
machined in the side of sample holder 96 near the
location of the sample pan 22 to allow X-rays to
impinge directly upon the sample 20. The sample holder
cover (not shown) which is normally placed on -top of
the sample holder 96 must be modified or removed, as ill
this case, to permit -the diffracted Years -to exit the
sample holder 96 and enclosure block 24. For optimum
DISC heat measurement sensitivity, the X-ray inlet port
51 and the sample holder top may be covered with an
X-ray transmitting material which will help to minimize
unwanted radiative and convective heat transfer from
32,131-F -11-
-12- ~2~8~8~
the sample. Additionally, Wylie the chamber in the
block is tug be kept ys-.ight, the inner and outer ens
of the inlet port Cindy of the ox t slot are covered with
I. -thin films I and 55 of X-ray transmitting material,
I such as a sheet of beryllium or of Mylar (polyethylene
terephthalate plastic). Mylar windows have the advantage
that the sample can be visually observed at any time
during an experiment if the sample pan is not covered.
For positioning the sample 20 in the X-ray
beam, the sample holder assembly 18 is adjustable
mounted in all directions by securing it to a mounting
assembly 58 (FIG. 2) which rests on the base 19. The
block 24 of the sample holder assembly is mounted on a
plate 60 which is tilted so that the X-ray beam 32 can
impinge at an angle on the sample 20. The tilted block
also provides a good thermal contact between the sample
pan 22 and the sample holder 96. The plate is adjustable
secured to a pillar 62 which is socketed and pinned at
72 to a threaded post 64. The post 64 is seated at its
other end in a mounting block 66. A nut 68 allows for
vertical adjustment of the sample holder assembly. For
lateral adjustment, the mounting block 66 is slide ably
adjustable relative to -the base 19, -to which it is held
by screws. The sample holder assembly may be pivoted
to a desired position and locked in place by a locking
screw 71.
In a preferred embodiment of the invention,
the X-ray detector 36 is a linear position sensitive
proportional counter, a commercially available unit.
It is shown schematically in FIG. 5. This detector has
an elongated shallow box-like housing 74. Terminals 76
are insulated from the housing and support a single
straight anode counter wire 38, a carbon-coated
ok J rye
32,131-F -12-
-13~ ~%~8~82
quartz Burr of high resistance. joy voltage is
applied between this wire and one or more cathode
elements 75 paralleling it. Diffracted Ray photon.
34 enter the counter through a beryllium window 80 and
initiate gas ionizations which characterize their
entrance positions along the counter wire. External
circuitry supplies the required voltage and records the
angular positions and the intensities of the diffracted
X-rays. A gas mixture, such as argon-methane or xenon-
methane, may be passed under pressure through the housing by way of an inlet 82 and an outlet 82' (FIG.
7) to maintain, in a known manner, the levels of sense-
tivity and efficiency of the detector.
Instead of the linear detector just described,
an alternative, is a curved detector as shown in FIGS.
PA and 6B. Here the housing aye is of arcuate shape
and supports a curved counter wire aye. One suck
curved counter is described in US. Patent No. 4,076,981.
Various position sensitive detectors optimize either
speed, detection area or resolution. Depending on the
particular experiment, one type of detector may be
preferred over another (e.g., for a detailed discussion
of common errors associated with these detectors, see
Reference (1), below). The following references describe
these detectors:
(1) R. A. Newman, T. G. Foist, P. lo rchhoff,
Advances in X ray Analysis, Vol. 27, 1984 (in
press).
(2) H. E. Nobel, Advances in X-ray Analysis, Vol.
30 22, 1979, p. 255-265.
32,131-F-13-
-14- ~2~8~
(3) I. E. Gob, Advances in Zoo Analysis, Vol.
25, (198~), p. 315-324.
(4) C. O. Bud Industrial Research and development,
January, 1983, p. 84-87.
(~) Proceedings of the Symposium on New Crystal-
graphic Detectors, Transactions of the American
Crystallographic Association, Vol. 18, 1982,
Pi. C. Himalayan, Ed.
The control and display apparatus associated
with the detector 36 is shown diagrammatically in FIG. 7.
The gaseous atmosphere in the detector is provided from a
supply 84 which regulates flow and pressure. The high
voltage of the sensing wire 38 is delivered by a source
86. The X-ray output data from the detector are stored
in a digital analyzer 40 in about 1500 discrete channels,
each corresponding to a location along the wire 38.
Thus, the detector and analyzer together observe incident
X-ray photons and record the diffraction data as angular
positions or addresses at which the diffracted photons
enter the detector chamber and -the number of such
incidents at each location. With a detector covering
an angular range of 20 (two theta) an analyzer recording
1500 channels can discriminate between angles of incidence
with a selectivity of about 0.8 minute of arc.
For ins-tantaneolls observation, -the analyzer
is connected to a video terminal 88 which displays
graphically -the data accumulating in the analyzer. The
raw data also go to a computer 90. This latter may be
programmed with peak-fitting and data-reduction routines,
smoothing and background suppressing algorithms, etc.,
to record and output parameters such as angular positions
32,131-F -14-
~2~8~
aloud magnitudes c1- peak intensities, peak areas and
hall-wid-tl~s, and other-- desired parameters. The computer
output i. displayed on a video terminal 92 and recorded
on a plotter I OX printed on a printer 95. The resulting
diffraction data, in which the intensities of X-ray
diffraction lines are plotted as a function of diffraction
angles, as in FIG. 15, constitutes the ultimate data
output of the diffractometer part of the instrument of
the invention.
The detector and the control and read-out
equipment are available commercially. The method of
using this detector and of interpreting results are
known. For more description of detector-counters and
appropriate circuitry, see N. Broil, M. Henna, and W.
Krantz, Simmons Corporation Application Note No. 57,
Sept. 1980, Cherry Hill, NO and Analytical Application
Notes No. 271 from [lmovative Technology, Inc., South
Hamilton, MA.
As shown in FIGS. 2 to 4, the sample 20 and
pan 22 are placed inside the sample holder 96 which is
mounted inside a chamber in the enclosure block 24
which is preferably made of a metal such as, for example,
alumillum. This block forms a protective chamber and
temperature controlled environment of -the calorimetry.
The block may include an attachment, not shown, for
circulating fluid -to cool or heat i-t. The chamber may
be made gas-tight by its cover 48.
Within the block 24, the sample pan 22 rests
on a -thermally conducting sample holder 96 (FIG. 4).
32,131-F -15-
-15~ I
eye holder, supported by a center post 98 mounted an a
holder support disc 99, includes a resistance ligating
element 100 and a resistance -~emperatu-e-sensing element
in close proximity. These elements are convected
by leads to electronic control and sensing circuits
shown diagrammatically in FIG. 9. Also within the
block 24 is a reference or matching holder assembly
(shown generally as 96') supporting an optional
calorimetric reference specimen (not shim) in a
matching pan 22'.
In a known mode of operating the differential
scanning calorimeter of the general type shown, the
same "average" power is supplied to both the heating
elements 100 and 100' to control continuously the
temperatures of the sample and reference material
gradually through -the range of temperatures over which
the thermal behavior of the sample is to be analyzed.
The temperatures indicated by the two thermometric
elements 102, 102' are observed throughout the scan by
the control system, which also acts to maintain -them in
equilibrium by applying the necessary amount of power
to the heating elements. When an endothermic event
occurs in the sample, the control system supplies more
differential power to the sample -to keep -the sample and
reference temperatures in equilibrium. When an
exothermic reaction occurs, essay differential power is
applied -to the sample. Tile magnitude of this differential
power is a measure of -the magnitude of the physical or
chemical process. Its value, shown by the instrumentation
described, is one of the major parameters or outputs of
the apparatus of the invention.
32,131-F -16-
358~
In the control system (FIG. 9), thy programrller
104 (I h its assQciaLed temperature recorder 136) may
be prose by Intel Al circuitry (nut Slyly ) to dictate
the temperature conditions of the experiment whether
they be heating, cooling, isothermal or a ccmbinatio.
of these operating modes. The programmer, together
with a computer 108, which manages the temperature
averaging network, controls an amplifier 110 which
supplies the main (or average) power to the sample and
specimen. The differential power is supplied by a
second amplifier 112 and is measure by a recorder 114.
As shown, the circuitry includes control loops for the
average temperature and for the differential power.
This control system, which is solid-state digital
throughout, is available commercially. The methods for
operating it and for interpreting the results are known
in the art. For a further description, see E. S. Watson
et at., Analytical Chemistry, 36, 1233-8 (1964). See
also US. Patent Nos. 3,263,484 and 3,732,722.
Tile recorders 106 and 114 (FIG. 9) may be
connected together at a terminal and plotted at 115
(FIG 11) to produce a chart in which the variations in
differential power are shown as a function of temperature.
Such a DISC curve (as in FIG. aye) constitutes the
ultimate data output of the calorimeter por-tiorl of the
instrument of the invention. A major Advent of -the
invention is that these calorimetric data may be correlated
accurately with the X-ray diffraction data produced
simultaneously by the diffractometer. Detailed insight
into both structural and thermodynamic properties of
the sample is thus possible.
32,131-F -17-
1228~i8~
The X-rav diffraction unit, as described and
shim in FIG. l, employs the geometry of the Gunner
diffraction system and is equipped with a Huger curved
focusing crystal monochromator. In the Gunner system,
the sample 20 is located at one point along the focusing
circle 41 of the diffractometer, while the detector 36
is at a different point along the circle. The X-ray
beam 32 is converging as it passes through the sample
but is not sharply focused on it. The focus is at a
10 third point 116 along the circle 41. For practical
reasons, the main beam may be terminated short of focus
by an X-ray stop. The X-rays 34 diffracted by the
sample reach true focus at points along the circle 41,
within the detector 36. This Gunner geometry and its
consequences have been considered at length by H. E.
Nobel, Advances in X-Ray Analysis, 25, p. 315-324
(1982), and by T. G. Foist et at., foe. cit., 26 p.
171-180 (1982).
The Gunner geometry, while preferred, is not
an essential requirement of the present invention. An
alternative system is the Bragg-~rentano system, shown
in FIG. 8. In this system, the X-rays 28 are generated by
the source 26 at a point which is itself along the focusing
circle 41. The sample instead of being placed along
the circle, is at its center 120. The sample may be in
either a reflection 21 or transmission 23 position.
X-rays diffracted from -the sample are observed by the
detector 36 at points along the circumference of the
focusing circle 41. This system has also been discussed
by H. E. Nobel, Advances in X-Ray Analysis, 22, p.255-265
(1979)-
32,131-F -18-
- 1 9 8g~8X
Still another geometry satisfactory in the
invention is that of a Debye-Scherrer camera, as oescrlbed
in Us Patent No. ~,076,~
The X-ray geometry may be either wide angle
or low angle, i.e. Station, geometry. A line source,
monochromatic and focused, is preferred. High resolution
systems are helpful.
An alternative diffractometer and DISC con-
figuration is shown in FIG. 10 where the X-ray beam is
passed vertically through the bottom of the sample
holder. Such a configuration should provide better DISC
sensitivity by an improved thermal contact; and an
improved X-ray sensitivity by placing more sample
specimen directly in the X-ray beam. In the FIG. 10
I arrangement, simultaneous X-ray and calorimetric
measuremell-ts are made using an enclosure block 24 which
rests horizon-tally on a table. The X-ray beam 32 is
directed vertically upward, entering through an inlet
window in the bottom of the block and leaving through
an exit window in the top of the block. Diffracted
X-rays 34 pass through the exit window to the detector
36. The sample holder and holder support post have,
e.g., hollow centers in order to allow for the trays-
mission of X-rays. The sample rests in a pan (not
shown) made of an X-ray -transmi-t-tillg material. Besides
allowing for a number of geol-lletric arraIlgemellts of -the
diffractome-ter, -the invent Loll also admits of various
ways of mounting the sample and sample enclosure relative
to the X-ray beam. For example, an alternative arrangement
to FIG. 10 may utilize the ~ragg-~rentano geometry
(FIG. 8) for the diffractometer portion of the instrument
in place of -the Gunner trallsmission geometry (see FIG. 1).
32,131-F -19-
o I
The Debye-Scherrer geometry is also feasible. Generally,
any arrangement my be us Ed which allows for impinging
an X-ray by m on a sample and for observing the dill raced
Eras with a position sensitive detector.
The simultaneous observation of X-ray diffract
lion patterns and thermal data according to the invention
may be used with advantage in studying phase transitions
in solid or semi-solid samples while they are undergoing
chemical reaction with a gas. Such studies are par-
titularly valuable in investigating oxidation and
reduction changes in complex metal oxide compositions
used as heterogeneous catalysts. For this purpose, the
arrangement shown in FIG. 11 may be employed.
The sample is placed in the sample block 24
which is fitted with inlet ports 144 for admitting gas
and an outlet port 146 for outflow. With the sample
block cover in place, the only gas communication with
the enclosure interior is through these ports.
The enclosure block 24 is positioned so that
the X-rays 32 impinge on the sample. Diffracted rays
34, 34' are received by the detector I and the resulting
X-ray data are stored by the SPOOK electronic module 39
(data is stored ill multi-channel analyzer described in
detail with respect -to FIG. 7) and displayed a-t -the
tenninal 88, as previously described. Calorimetric
signals from -the enclosure as the -temperature of the
sample is scanned through a range to be studied are
received by the DISC electronic control unit 113
(described in detail with respect to FIG. 9) and
displayed at recorder 115. A reactive gas, such as
hydrogen or compressed air from a cylinder 130,
32,131-F -20-
-21~ I
or oxygen from a cylinder 131, aloud a carrier gas, such
as n.tl-ogen, from another- cylinder 132, are used in 'ore
study. The gases flow through purifying and pressure
Regulating units 134. The flows merge at Maxine chamber
142 and are then routed -through the inlet ports 144
into the sample block 24 and into contact with the
sample being studied. Gaseous reaction products leave
through the outlet port 146 to a flow meter 138 or to a
gas analyzer 140 by means of a switching valve 139. my
comparing X-ray diffraction patterns with calorimetric
signals, and with the indications of a gas analyzer
141, structural and chemical changes occurring in the
sample during a scan can be identified and measured
quantitatively.
The thermoanalytical equipment forming a part
of the apparatus of the invention has been illustrated
as a differential scanning calorimeter (DISC) of the
power compensation type. This DISC is available come
Marshall and known as the Perkin-Elmer Model DSC-2
(cf. US. Patents Nos. 3,263,484 and 3,732,722). While
this is well suited for the purpose, other -types of
differential scanning calorimeters known in the art may
be employed, e.g., the commercially available Dupont
DISC, Mottler DISC 20, and Setaram Model DISC 111. Also
useful are other -thermoanalytical units which are not
strictly calorimeters, such as differential thernlal
analyzers (DTA's), e.g., the Mottler Model TO 10 and
the Dupont DATA.
As may be appreciated, the present invention
is not restricted to any particular DISC or DATA. It is
essential only that the analyzer have means for con-
trolling the temperature of the sample being studied,
32,131-F -21-
I ~22~
and detector means fur observing and recording a pane-
meter indicative of the thermodynamic behavior of the
sample during such change. "I`herm~dynamic Properties"
refers broadly to calorimetric measurements of samples
which can be determined or observed using a DISC or DATA
instrument. This generally means for DISC, observing or
measuring enthalpy change or specific heat capacity.
For DATA experiments, it generally means or refers to
observing or measuring qualitatively or semi-quantitatively
exothermic and endothermic events of the samples under
study as some function of temperature.
While the manner of operating the apparatus of the
invention is believed largely apparent from the fore-
going description, it will, for added clarity, now be
summarized.
The apparatus and method are useful for
investigating simultaneously the thermodynamic and
structural properties of materials. Single crystals
and multi crystalline solids, inorganic, pharmaceuticals,
and organic, as well as mixtures of materials, solid
and semi-solid plastics en masse or as powder or film,
and even liquids, may be studied to advantage.
In making a run, a sample 20 is placed on
the sample holder 96. At the same time, a thermal
reference specimen may also be placed in the reference
pan 22' on the reference sample holder 96'. The sample
holder assembly 18 serves simultaneously to hold the
sample in place relative to the X-ray diffractometer
and to constitute the calorimetric chamber of the
thermal analyzer.
32,131-F -22-
-23- ~2~82
With the sample and reference specimen in
place, the sample holder assembly is positioned, by
careful adjustment ox its mount, so that the sample is
in the path of the X-ray beam at a point on the focusing
circle of the X-ray diffraction unit. The control end
readout circuitry of both the diffractometer and calorimeter
are then readied. If a gas atmosphere is to be circulated
through the sample chamber, this too is readied. The
controls are programmed to heat the sample and rev-
erroneous materials through the temperature range to restudied, and the rate of heating is also preset.
When everything is ready, the X-ray diffractro-
meter and calorimeter are energized. Scanning then
proceeds automatically. The diffractome-ter readout
observes and records the angles and intensities of the
X-rays diffracted from the sample. (These are measures
of the angular positions of the diffraction peaks.)
The record is presented by the plotter 94 on which the
intensity is shown as a function of diffraction angle.
The plot is repeated at frequent intervals which are
time marked. The same data appear visually on the video
terminal 88 for instant attention by the operator.
Simultaneously, the scanning calorimeter
observes and records both the temperature of the sample
at each instant throughout the scan and -the differential
power, if any, required to hold -the sample and reference
temperatures in equilibrillm. This record is also pro-
sensed as a strip chart by the recorder 115, with the
differential power shown as a function of temperature.
The temperature line is also time-marked. If desired,
the data may also be read visually on a terminal. The
scan continues until the final preset temperature is
reached, at which the run terminates.
32,131-F -23-
-24-
I
To Interpret -the results, the analyst operator
compares the diffraction data and calorimetric printouts.
The telltale matings on the printouts make possible the
identification of simultaneous events. thus, if the
calorimeter printout shows a thermal even-t when some
particular temperature was reached in the scan, the
corresponding diffraction data will show what changes,
if any, took place in the diffraction pattern at the
same moment. The analyst studies the diffraction
patterns and compares them with standard reference
patterns known in the art as identifying various crystal
species. The comparison allows identification of the
phases involved in the change and the nature of the
change.
In the apparatus of the invention, diffraction
spectra and thermal events are detected and recorded so
rapidly that entire scans over several hundred degrees
Centigrade may be completed in a fez minutes. The
analyst can detect rapid crystallographic events, such
as the appearance and disappearance of transitory
phases having a brief life span, which would hove
escaped notice in the methods of the prior art. The
analyst can also examine complex mixtures and detect
and identify successive phase changes in individual
components which take place over a temperature interval
of only a few degrees. Chemical interactions of components
of a multi-component mixture can be identified. Complex
thermograms can be analyzed. In a single experiment,
thermally induced structural changes, molecular orientation,
crystallinity, s-tress, and strain as a function of
temperature can all be studied, due to the precise
temperature control and rapid speed of analysis of the
instrument and method of the invention. Observations
32,131-F -24-
-25~ ~2~82
of these kinds have been impossible or the indications
have been missed or misunderstood in prior art methods.
A further advantage of the invention may be
brought into play when a thermal event or phase change
has been observed in a first scan as occurring at a
particular temperature, but the full details of the
event are not clear. Another scan can be started, on
the same or a fresh sample, but with the temperature
rise stopped, or its rate slowed dramatically, when the
temperature range in question is approached. Since
only simple adjustment of the control circuitry is
required, these temperature stops or rate changes can
be made midway through a scan, whenever the need for
change becomes evident. With the temperature steady or
rising only slowly, extensive X-ray or thermal observe-
lions can be made to pick up critical details that may
have been masked in the original rapid scan. This
capability of interactive analysis, dynamic in that
experimental parameters can be adjusted during an
experiment, has made possible identification and
characterization of structural and thermal correlations
which have long been puzzling or even unknown.
The -techniques of the invention are especially
helpful when a reactive gas is being passed over a
sample undergoing analysis. The scan can be stopped at
any point, and the thermal and structural changes
caused by reaction with the gas examined a-t length,
while they are occurring.
Although the foregoing discussion has assumed
that the temperature scans involve heating the sample,
32,13l-F -25-
-26~ I
it is equally possible, in the invention, to scan down-
wardlv in tempQratu~-e. Obse-va'_ions car be started at
an elevated 'cempe~ature and cooling allowed to occur
naturally or at a specified Nate. To investigate
ranges below room temperature, artificial cooling may
be applied. The apparatus can be operated from temperatures
as low as those of liquid nitrogen up to as high as
600C or more.
Example 1
Use or operation of the invention may be
further explained by the following example.
In the X-ray diffractometer (XRD) 17 (FIGS. 1
and 7), a Phillips X-ray generator providing a Cut X-ray
line source delivered the incident X-ray beam 28. A
Gunner diffraction system with a Huger curved focusing
germanium crystal monochromator was used to separate
Quickly from Quick and Quick radiation. The resulting
incident beam 32 converging on the sample was moo-
chromatic (wave length = 1.5406 A).
The detector 36 was a Brawn curved position-
sensitive proportional counter (SPOOK). This detector,
with its voltage supply 86 and mutational analyzer 40
allowed simultaneous collection of diffracted X-rays
over a range of about 20 I Ageist moving -the
detector Abbott -the post 44 -to various positions allowed
coverage of an accessible range of scattering angles,
I of 0 to 70~.
The differential scanning calorimeter (DISC)
used was a Per~in-Elmer DSC-2. The sample holder
32,131-F -26-
-27~ 82
assemhl~l 13 was constructed from the oven of the DSC-2.
A -ray inlet and an outlet were machined in the
aluminum bloat; and were covered with a Owl mm Mylar
film for sealed operation. The sample 20, usually
about 20 my of material, was encapsulated in a 0.02 mm
aluminum foil and placed in the sample holder 96. When
Y,-rav intensity was not otherwise adequate, holes were
punched in the foil to admit the full beam.
Operating parameters of the X-ray equipment
10 were:
X-ray source Cut line source, long fine
focus
Current 20 ma
Voltage 40 TV
SPOOK gas 90% argon, 10% methane
Gas pressure 11 - 12 bar
Gas flow rate lo cc/hr
SPOOK voltage 4.0 - 4.4 TV
The multi channel analyzer 40 collected the
diffraction data with continuous observation made via a
video terminal. After collection, X-ray diffraction
data files were transferred via a commercial computer
interface 87 to a hard disk on a PDP-11/34 computer for
storage and analysis. At the end of an experiment, the
patterns were processed in known mantel- by inputting to
a peak-fi-ttirlg lid data reduction Routine to obtain as
parameters -the peak positron area, hal:E-width, etc.
(cf. J. I. Edmorlds e-t at., Advances in X-Ray Analysis,
22, p. 143 (1979).) Transfer time was about 30 seconds
for a 1200 point data file.
32,131-F -27-
I
In operating this equipment, the DISC was
scanned at a east speed, usually between 20C/min and
1.25C~min. Ray diffraction patterns were Turin at
desired temperatures along the scan using collection
times of less than five minutes per pattern.
Example 2
In a demonstration run, a sample of polyp
ethylene was heated to melting (FIGS. AYE and 12B) and
then cooled back to room temperature (FIGS. AYE and
13B). The cycle was run at Mooney and X-ray diffract
lion data was taken at two minute intervals. Correlation
of the calorimetric and structural data shows the
cr~stallinity of the sample as a function of temperatures
and thermal (calorimetric) behavior.
Example 3
In another example, the DSC/XRD just described
was used to investigate the interconversion of two
organic polymorphs. A typical fast DISC scan of this
compound is shown in FIG. AYE. This compound was known
to exhibit two polymorphs with melting points differing
by only 3 to 4C (FIGS. 14B and C). Previous analyses
conducted in separate X-ray diffraction and differential
scanning calorimetry laboratories showed that quanta-
station of the polymorphs by these techniques gave
similar but not identical results. A DSC/~RD Somali-
Tunis experiment was conducted to study the dip-
furnaces in measurements. Previous work by hot stage
microscopy had indicated that the lower melting form
(II) might convert slowly to the higher melting form
(I) upon heating, but there had been no clear
understanding of the phenomenon, since microscopy could
not differentiate between the two structures.
32,131-F -28-
I I
To evaluate the transformation, a sample of
the pure lower melting form II was placed in the apparatus
and an I'm scan made. The ec~uipmcnt was prog-rar,mlcd LO
heat the sample slowly (1.25~C/min) until a meltillg
endotherm was first observed on the DISC output at 145C
( FIG . 14B ) . The temperature was then held constant at
this value for three minutes while another OR scan was
taken ( FIG. 15). The sample was then subjected to
cycles, in each of which the temperature was raised
slightly and then held level while another XRD scan was
acquired, until the DISC showed the peak of the endotherm
to have been reached. A-t this point, the temperature
of the sample was held constant while more XRD scans
were made. Finally, the temperature was lowered to
100C at a rate of 10C/min, with an additional XRD
scan being made. The entire run took no more than 25
minutes.
The data from this run are shown in FIG. 15.
Comparison of the peaks in the diffraction spectrum of
the initial scan at room temperature and the final one
at Luke clearly shows that form II has been transformed
to form I. It can also be seen -that -the two scans
taken a-t -the peak of the melt endotherm reveal small
form I crystalline peaks remaining superimposed on the
background. Analysis of -these peaks using computerized
peak fitting routines showed -that -the final conversion
of one phase -to the other over -the -time of -the export-
mint was about percent compute.
The apparatus of the invention allowed precise
temperature control which enabled the X-ray diffraction
detector to observe the polymorphic interconversion.
If the temperature was too high, both polymorphs would
32, 1 3 l - F - 2 9 -
I
Wright lath no interconversion. If the temperature was
too low, both materials would remain solid and no
convert. Only if the temperatl1Le was within 1~5-1~L~C,
would interconversion take place. The interactive DISC
data indicated to the experimenter the precise point of
the endothermic melt and potential interconversion.
The X-ray data were used to identify not only the
interconversion, but the rate and completeness of the
conversion. In summary, the DISC provided accurate
temperature control and indicated the start of the
endotherms, while the X-ray data identified a polymorphic
interconversion and measured its rate. This was done
on a single sample in a single experiment.
These results showed that previous quantitation
of the polyrnorphs by DISC had been misinterpreted since
not only did the polymorphs melt but they also inter-
converted during the experiment enabling a reconciliation
of the previous DISC and XRD data.
The apparatus and method of the invention may
2G be applied to study the interrelation of simultaneously
occurring structural (e.g., crystallographic) and
thermodynamic changes in materials in order to elucidate
a wide variety of phenomena. In the plastics industry,
the release of strains in the crystalline lattice of
-thermoplastics, such as molded polyethylene durillg
annealing has been examined; crystallite size, structure,
and crystallinity all were measured and identified.
The combined DSC/XRD experiments described
below were performed on the apparatus of the invention.
Examples are given in which the simultaneous DSC/XRD
32,131-F -30-
I
experimellt provided information which could not be
obtained by either instrument alone.
Example 4
-
In the analysis of a polymer, the DISC data
were characterized by a single endothermic peak at
185C. However, the Ray data taken simultaneously
showed two structural events at the same temperature.
One of the events us a crystallization (exothermic) of
a portion of the sample. Therefore, the apparatus of
the invention (DSC/X~D) showed that the observed DISC
endotherm was in reality a combination of a larger
endotherm with a smaller exotherm (i.e. two thermal
events instead of one). The precise temperature control
of the apparatus allowed for the X-ray detection and
observation of the two events at the same temperature
and elucidated the phenomena that the thermal transition
at 185C was associated with two events of opposite
heat flow (i.e., ego- and endotherm).
Example 5
A multi component product containing a blend
of inorganic, organic and polymers was analyzed by
the apparatus of the invention. In addition, the
experiment was run so that the temperatures, atmospheric
environment and heating times and rates simulated those
of the commercial process. The sample was heated
rapidly and cooled rapidly in a cycle from 23-300C.
The entire experiment took 90 minutes. The DISC data
show 3 events. Prior art comparisons of the multi-
component product to standards of the individual
materials comprising the product could only identify
the glass transition of the polymer. The other two
events, an exotherm and an endotherm, could not be
32,131-F -31-
~2~8~
identified LOWE comparisoll to standards. The DSC/XP~
experiment Swede that_ the exotherm was a crystallization
of an organic in the polymer matrix. The e~dothermic
transition was shown by the X-ray diffraction data to
be the dissolution of the organic in the sample matrix.
The dissolution of the organic in the product occurred
70C below the melting point of the pure organic. When
the experiment was conducted at either a different
heating rate or under a different atmosphere, the
exothermic and endothermic transitions were shifted by
as much as 40C. Therefore, to identify the structural
nature of the thermal transition, both X-ray diffraction
and calorimetric data had to be acquired simultaneously.
Prior art instruments could not simulate either the
speed or the temperature control of the apparatus of
the invention. The experiments also showed how complex
mixtures could be analyzed and how the chemical inter-
actions among the components of the mixture (i.e., the
in situ crystallization and dissolution 70C melting
point) can be elucidated by the apparatus of the invention.
Once again this analysis was critical since other
experiments have shown that the impact strength of the
product is affected Brie how the components blend in the
mixture.
Example 6
Several copper compounds and copper compounds
blended with additives were analyzed by -eye DSC/X~D
apparatus of the invention for potential catalytic
uses. The experiments usually consist of three parts:
first, a careful preheating of the material in a con-
trolled atmosphere (sometimes No, sometimes oxidative
gas mixtures), second, reduction in a mixed H2/N2
atmosphere and finally, a catalyst regeneration program
which involves both oxidation and reduction.
32,131-F -32-
P~28~8~
-33-
The DSC/XR3 instrument provides careful them-
portray control -n all phases of the experiment. In
catalytic studies, this control can prevent unwalled
runaway exotllermic reaction (as in the reduction of
metal catalysts). In the preheating stage, the DSC/XP~
instrument provides precise measurement of thermal
decomposition by correlating the DISC data with the
observed X-ray diffraction patterns. On a multi component
mixture, the correlated data identifies which material
is being thermally changed and the magnitude and rate
of that transition. Catalysts are commonly composed of
the active material, a multi component substrate and
other materials such as binders and poulticing lubricants.
In the reduction experiments, which may be
run isothermally, the DISC data indicate the start and
the completion of the reductive exo-therm. This is
important since the X-ray diffraction data are a result
of bulk transitions and are not sensitive to small
changes which can be seen in the DISC data (i.e., the
initiation of the reduction and the very last steps of
the completion of the reduction). In general, X-ray
diffraction methods are sensitive to crystalline changes
of one percent by total weight. The DISC data can
detect noncrystalline changes in the material and some
changes below one percent. The ROD data are used to
determine which material or materials are being reduced.
As in Example 3, experiments have been run whole the
reductive exotherm a-t an elevated temperature has been
a combination of the simultaneous reduction of Cut,
Queue and a copper salt to Cut (metal) all in one step.
Experiments have been run where ~50 percent of the
total reducible (or oxidizable) materials have keen
32,131-F -33-
I 2 6 82
reduced (or oxidized) in less than 5 seconds. There-
fore, the speed of tune apparatus of the invention
results in measured reaction rates with the~mal-sl_ructural
material identifications which have not been previously
identified or measured.
In all phases of the catalytic cycles (oxidation,
reduction, regeneration), times and temperatures can be
optimized by the use of the invention. For example, if
a high surface area catalyst is desired, the apparatus
of the invention can be used to optimize the aforementioned
cycles to get the desired physical properties in the
shortest preparation twirl or in the best cost effective
manner.
32,131-F -34-
