Because of the information it provides concerning the sub microscopic structure
of any kind of material from x-ray diffraction analysis, information usually
obtainable only by inference from other methods of examination, this method of
crystal analysis has become very important to modern industry. The large number
of industrial applications already made prove the value of these crystal structure
studies, and provide a firm foundation for this branch of technology. Hence the
chemist, the physicist, the metallurgist, and the engineer now have in x-ray
diffraction a powerful scientific instrument for use in the quest for better
methods and improved materials, and for the maintenance of required quality
throughout the manufacturing processes.
APPLICATIONS TO
METALLURGY AND METALLOGRAPHY
1. The
Composition and Structure of Alloys.
- Identification of alloy components and compounds.This is a special case of the general problem of chemical analysis by
x-ray diffraction, and is used very frequently in many laboratories
as a check on the results of other methods of examination.
- Differentiation between compound formation and solid solution.This is also a special case of chemical analysis
in which a compound formed between two or more elements will give rise to a new
x-ray pattern which is different from that of any of the constituents, while
the solid solution will in general give the pattern of one of the elements, but
with a shift in line positions which depends upon the relative amounts of the
other elements present in the solution.
- Routine determination of percentage composition of solid solution
phases, on the basis of measurement of line shift with varying amounts of
solute present.
- Determination of the mechanism of alloy formation. This involves study
of reflection and back reflection patterns of a series of alloys with
various thermal treatments, and the correlation of the conclusions with
chemical and microscopic data.
- Determination of miscibility limits and solid-phase boundaries of
many-component alloy systems, by correlating lattice parameters with increasing
percentage of alloying constituents.
- Working out and checking the details of the solidus phases of the
equilibrium diagrams of binary and many-component alloy systems. X-ray
diffraction analysis is the most convenient and dependable of the accepted
modern methods for this purpose.
- The most rational classification of alloy types and systems has been
made on the basis of x-ray crystal analysis.
- Study of the "order-disorder" phenomena in alloy systems.
2. The
Effects of Rolling and Working on Metals and Alloys.
- Determination of structural changes accompanying successive reductions
of sheet and wire, as a comparison of methods of reduction .by different
techniques.
- Study of the effect of initial grain size, carbon content, initial
strip thickness, and of rolling variables on the final structure of rolled
strip steel in determining the proper scientific methods of working and
forming.
- Determination of the effects of twisting and bending strip and wire.
- Measurement of the extent of deformation and distortion by rolling,
drawing, shaping, etc., as a routine check on the efficacy of the manufacturing
process.
- Determination of slip planes, "fiber" structure, etc., of
rolled sheet and drawn wires.
- Differentiation between surface and interior structures, or study of
"zonal" structural characteristics.
- Determination of the most desirable structure of a sheet or wire to be
subjected to a forming operation, and a rational method of classifying metals as
to workability. This method is used in many laboratories to "grade"
every production lot. In this way the sheet mill can guarantee delivery of
metal best suited to the manufacturer's shaping processes,
- Furnishes an explanation of structural failures in spinning, cupping,
and stamping operations. "Trouble shooting" in regard to these
operations is one of the best paying uses of x-ray crystal analysis in the
metallographic laboratory.
- Measurement of the depth of cold work caused by machining, drilling,
punching, grinding, etc.
- Study of the mechanism of "fatigue" and other types-of metal
failures, and in many cases a determination of the cause for premature or
unexpected failures.
3. The
Effects of Annealing and Other Thermal Treatments on Metals.
- Establishment and routine maintenance of scientifically correct
annealing techniques, and in many eases also for heat treating techniques.
- Study of recrystallization mechanism, and exact determination of recrystallization
temperature.
- Study of precipitation and age hardening phenomena.
- Study of the relation of carbon content to annealing, and the
relations between amount of reduction, time and temperature of anneal, and the
final structure.
- Determination of quench and temper structures of spring steels, and a
continuous check on hardening and tempering operations.
- Study of growth of texture in castings.
- Measurement of strain relief upon annealing.
- Determination of surface effects, such as decarburization, oxidation,
excessive crystal growth, etc., as differentiated from interior structure.
4.
Miscellaneous Applications to Metals.
- Determination of true "crystal size" as distinguished from
microscopic 'grain size". This is a common and much used procedure in many
factories.
- Determination of the structure
of welds and the presence of strain or distortion in the neighbourhood of the
weld.
- Determination of the reason for and indication of the cure for
"embrittlement" of malleable iron.
- Measurement of crystal size, crystal orientation, and absence of
distortion (or degree of crystal perfection) in relation to electrical and
magnetic properties of transformer steels.
- Determination of the effects of thermal treatments on the
"spoilage" and recovery of permanent magnet alloys.
- Determination of uniformity, depth, and mechanism of surface
hardening.
- Measurement of crystal size, preferred orientation, and thickness of
electrodeposited films, a routine check on the plating process.
- Determination of the chemical composition of protective films, and
study of mirrors and sputtered films.
- Study of the effects of included and absorbed or adsorbed gases on the
structure of metals.
- Determination of optimum crystal size and best structure for
electrical contact points, and a continuous check on these during manufacture.
- Study of the effects of crystal size and crystal orientation on
electrical properties.
- Aid in the study of corrosion and corrosion or thermal
"fatigue" and chemical embrittlement, and determination of the
chemical composition of boiler scales.
- Furnishes a scientific approach to the preparation of new alloys, and
a prediction of the properties of new or untried alloys.
- Study of the transition zone between base and covering of plated or
enameled metals.
- Rational determination of the effects of minute impurities upon the
structure of metals.
- Identification of inclusions in metals. This is a special case of
chemical analysis by x-ray diffraction.
- An absolute and non-destructive measure of residual elastic surface
stresses in metals. This is used quite extensively in several countries in the
study of steel structures such as bridges and building frameworks.
- Determination of particle size in the colloidal region.
APPLICATIONS IN
CHEMISTRY
1. General
and Physical Chemistry
- Determination of ultimate crystal structure, including lattice types,
unit cell dimensions, atomic positions, ionic groupings, and crystallographic
systems of substances.
- Furnishes a unique and unquestionable characterization of individual
chemical compounds. This is the basis of the wide-spread use of x-ray
diffraction for chemical analysis. The analysis is, of course, made in terms of
chemical compounds rather than in terms of elements and ionic groupings.
- Differentiation between a mixture, solid solution or complex compound
formation.
- Supplies a quantitative estimate of the relative amounts of the
various compounds in a mixture. The estimate can be refined by the proper use
of a recording microphotometer.
- Furnishes a certain test for the crystallinity or non-crystallinity of
a material, either in the solid state or in solution.
- Determination of crystal sizes in the microscopic and sub-microscopic
(colloidal) ranges.
- Study of allotropic modifications and transitions of an element or
compound, and the effects of impurities on these.
- Determination of the ideal or theoretical density of a substance,
giving a basis for the estimation of porosity.
- Differentiation between true and false hydrates.(Chemical analysis.)
- Discovery of unsuspected chemical reactions.
- Recognition of colloidally dispersed phases, and differentiation
between true solutions and suspensions.
- Determination of crystal size and structure of colloidal so is and
gels.
- Identification of adsorbed films and chemical changes involved in
adsorption.
- Determination of optimum crystal sizes and orientations for maximum
catalytic activity, and study of the mechanism of catalysis and
"poisoning" of catalysts. This is used not only to find the best processes
for preparing a catalyst but also as a routine test of production.
- Determination of molecular sizes in liquid solutions, and molecular
weights of liquids.
- Determination of the mechanism and course of dry reactions and
allotropic transformations in the solid state, even at extremely high or
extremely low temperatures.
2. Organic
Chemistry
The list given above for General and Physical Chemistry, and in addition
furnishes:
- A sure test for the identity or non-identity of synthetic and
naturally occurring materials.
- Estimation of molecular weights of hydrocarbons, etc.
- Measurement of atomic sizes, interatomic distance and diameters of
molecules.
- A method of following chemical reactions, as for example addition to
or oxidation of a multiple bond.
- Estimation of the purity of soaps, acids, etc.
- Estimation of the positions of side chains and functional groups.
- Measurement of the thickness of oriented films.
- Determination of molecular orientation in fibers, and molecular structure of naturally occurring
fibers and membranes.
- A method of following polymerization and condensation reactions, and
decomposition in breaking up long chain compounds.
- Study of lubrication and lubricants, including a routine method of
quantitatively comparing efficiency of lubricants.
- Study of changes taking place in the ripening of cheese, and during
other processing of dairy products.
- A rational classification of synthetic and natural plastics, and a
qualitative scheme for identification of these.
3.
Analytical Chemistry.
In addition to the applications listed above, x-ray diffraction provides
for:
- Identification of the chemical composition of precipitates.
- Tests for purity and identification of impurities in precipitates.
- Measurement of particle (crystal) sizes of precipitates in relation to
treatment and reagent concentrations.
- Determination of the state of perfection of the crystal lattice in
precipitates, particularly in regard to aging effects, etc.
APPLICATIONS IN
THE PROCESS INDUSTRIES
Since the process industries are engaged in chemical manufacture, the general
applications listed under "chemistry" could be repeated here. To avoid
duplication, however, only those applications of x-ray crystal analysis to some
particular problems will be given.
1. Paints
and Pigments.
- Structure and crystal sizes as functions of color, spreading, wetting
and obscuring power, stability, gloss, and method of preparation.
- Study of the drying and setting of oils, the mechanisms of the
reactions involved, etc., and their relationships to the structure and
composition of pigments.
- Tests for solution of driers, and study of the mechanisms of their
action.
- Routine analysis for purity of pigments. This is an important
production test, particularly for those pigments which can exist in more than
one crystal form, as for example titanium dioxide.
2. Ceramics
and Glass.
- Routine qualitative and quantitative analysis of materials and clay
mixtures, in terms of compounds present.
- Determination of the structural and chemical changes occurring during
sintering, fusing, and other thermal treatments and the mechanisms of these
reactions.
- Furnishes the best and fastest method for determining and checking the
solidus phases of many component systems, and for determining miscibility
limits.
- Gives a definite test for incipient devitrification of glass.
- Identification of substances imparting color or opacity to glasses or
enamels.
- Determination of crystal size with relation to color of pigment.
- Study of transition zones between base metal and vitreous enamel.
- Measurement of chemical reaction rates in melt or during sintering.
3. Cement
and Plaster.
- Study of reaction rates and mechanisms taking place during manufacture
and use of cement.
- Routine chemical analysis of raw materials and clinker.
- Differentiation between particle size of aggregates and true crystal
size.
- Method of determining and checking complex phase diagrams with
certainty.
- Investigation of setting accelerators and their effects on the final
structure of concrete.
- Control analysis of lime for crystal size, etc., to ensure proper
plastic properties of plaster.
- Study of structure of limestone and its kiln behaviour in relation to
the properties of the final product.
- Study of the dehydration of gypsum and the structural changes involved
in the use and reuse of plaster of Paris molds.
4. Storage
Batteries.
- Study of physical and chemical structure of plates as related to
performance.
- Study of chemical reactions occurring during charge and discharge.
- Study of the influence of the structure of grid and composition and
aging of the paste upon the physical properties of the plates, and control
analysis for the manufacturing process.
- Identification of deposits and sediments on plates, separators, and in
cell.
5. Rubber
and Allied Products.
- Study of chemical reactions taking place during vulcanization and
other processing.
- Determination of crystallinity, state of dispersions, crystal sizes of
fillers, etc., and their relation to the physical characteristics of the
finished products.
- Study of the basic structure of rubber and rubber-like materials.
X-ray diffraction furnishes the only sure test of the fundamental relationships
between natural and synthetic rubber.
- Study of fabrics and other binding materials used in the manufacture
of rubber products, and routine grading of fibers as explained below.
6. Textiles
and Fibers.
- Determination of the degree'of fiberingn . A quantitative relationship
between the degree of fibering and tensile strength of cotton fibers has been
developed and is being used as a routine method of grading cotton.
- Furnishes a scientific method of classifying cotton, silk, wool, and
other natural and synthetic fibers.
- Determination of the rate, mechanism, and completeness of
mercerization, nitration, and other chemical reactions, and use in control
analysis.
- Determination of the mechanism of fire-proofing fibers, and of exact
amount of reagent required.
- Identification of adsorbed films and the chemical changes involved in
adsorption, particularly as applied to dyeing of fibers.
- Great improvements in quality, tensile strength, and non-wrinkling
properties of rayon and other synthetic fibers has been made through x-ray
studies. The development of artificial wool from skim milk, peanuts, beans,
etc., can be traced directly to x-ray diffraction studies of the structures of
the various proteins. The development of "nylon", the new synthetic
silk, has depended to a great degree on x-ray studies of its fiber
characteristics by x-ray diffraction.
- X-ray diffraction studies on collagen fibers (side walls of animal
intestines, tendons, etc.) have resulted in enormous improvement in the quality
and wearing properties of tennis racket strings, and in the strength and
controlled digestibility of surgical ligatures and sutures.
APPLICATIONS IN MINERALOGY
1. General
Mineralogy.
- Complete and unambiguous mineralogical analysis of ores, clays, and
other mineral mixtures.
- Analysis of industrial dusts, and correlation with the occurrence of
industrial diseases.
- Classification and evaluation of certain commercial ores.
- Identification and classification of the clay minerals and complexes
making up the so-called soil-colloid.
- A scientific method of studying the changes produced in natural
minerals by weathering, accelerated weathering tests, and other chemical and
physical degradations.
- Specifications for asbestos, mica, and other natural insulating
materials for special purposes.
- Classification of coal, charcoal, etc.
2. Precious
Stones and Gems.
- Identification, classification, and differentiation of genuine, both
natural and synthetic, and imitation gems by a non-destructive test.
- Differentiation between natural and synthetic gems, nondestructively.
- Differentiation between natural and cultured pearls, non-destructively.
This is a routine procedure with some of the leading jewelry manufacturers
throughout the world.
- Determination of the proper orientation for a "jeweled" bearing
(in watches, electric meters, etc.) to give maximum service and wearing
qualities.
- Selection and classification of "black" diamonds for drills
and dies, determination of causes for undue wear, and proper crystallographic
orientations for optimum service.
- Determination of the proper direction of cutting quartz crystals for
crystal oscillators in radio broadcasting and telephone equipment.
APPLICATIONS IN
PHYSIOLOGY, PATHOLOGY, AND BIOLOGY
1. The
applications under this heading are quite recent developments and are not yet
generally used. Listing of some, however, will serve to show the general trend
and possibilities of x-ray diffraction research in these complex and difficult,
but extremely important fields,
- Differentiation between some normal and pathological tissues.
- Study of the effects of diseases on the structures of tissues, as on
bone structure changes in rickets, cancer of the bone, and other bone diseases.
- Study of structure of living tissue, as nerve and muscle, in relation
to body functions.
- Identification and classification of mineral deposits in organs, such
as calcifications, gall stones, siliceous deposits, etc.Much interest is
evident at present in the study of the action of free quartz on lung tissue in
silicosis, and of other industrial diseases and their occurrence, and many
papers have been published in medicinal journals on x-ray diffractipn studies of
silicotic lung tissue.
- Structure and classification of tooth enamel, dentyne, etc., and
structures of the teeth in relation to diet.
2. Papers of
interest to pharmacists have appeared recently on the following subjects:
- Identification of minerals in rhubarb.
- Differentiation between natural and synthetic camphor.
- Study of the reactions between menthol and the mercuric oxides.
