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Published online by Cambridge University Press: 10 January 2013
Charles Barrett's work in phase transformation at the atomic level helped redefine the underpinnings of the science and practice of metallurgy. His work in low temperature physical chemistry has extended its range. And, perhaps more than anyone else, as a teacher and author, he has helped introduce the technique of X-ray diffraction to the present generations of practicing metallurgists.
The relevance of his contributions is demonstrated by the continuing utility of his widely translated metallurgical text, Structure of Metals, which, when it first appeared, made the understanding of metallurgy at the atomic level accessible to a wide audience. Today this book has become a compendium of first principles.
page 164 note * Private communication from Maurice Nellis, a schoolmate of Barrett's and co-worker at the radio station.
page 165 note * “Arthur Compton's brother who was at MIT had invented an electrometer … the one I used.”
page 165 note ** Private communication from R. H. Mehl to A. H. Taylor.
page 166 note * Mehl, R. F., “The Beginning of the Division of Physical Metallurgy”. 17, 18 Report of NRL Progress, July 1973Google Scholar.
page 166 note ** “Metals”, Chapter 5, Crystallography in North America eds. McLachlan, D. Jr, Glusker, J.. Am. Cryst. Assoc. 1983Google Scholar.
page 166 note * Guinier, A.X-Ray Diffraction Freeman, W. H., 1963.Google Scholar (The method, as described by Guinier: “Let us consider, for a crystal face illuminated by a linear source situated at a large distance — say, 30cm — the crystal being oriented so that the characteristic radiation K is reflected. If we place a photographic film parallel to the surface and as close as possible to the crystal, the rays reflected by a point in the crystal traverse die film over a very small area so that the film gives a true image of the surface of the crystal, with a resolving power of the order of a few microns. …
The regions which contain imperfections appear black, because the energy reflected at these points is larger than in good parts of the crystal. The contrast can be very great and the slightest scratch shows up clearly.” X-Ray Diffraction op. cit.
page 169 note * Blocking patterns, like Laue patterns, of course yield crystal symmetries, axial ratios and orientations of crystals. However, if treated as superpositions of many orders of diffraction, by important (hkl) planes, of many different wavelengths of scattered protons it is possible to determine some atom position parameters with an accuracy that approximates X-ray values — for the simple crystals in which this unconventional method was tried. (C. S. Barrett: Adv. in X-ray Analysis, 1969; Trans. TMS-AIME, 1969; Met. Trans. 1970; summarized by Barrett, C. S. in “Channeling: Theory, Observation and Application”, Morgan, D. V., Ed., Wiley and Sons, pps. 331.347, 1973.Google Scholar) He treated the intensity of a line as the sum of all orders of reflection from the corresponding plane. (Barrett, C.S., Met. Trans. Vol. 1, p. 171, 1970CrossRefGoogle Scholar; summarized in “Channeling Theory, Observation and Application.)
page 170 note * There were chapters on these subjects and, of course, on the powder method.
page 170 note * In Fifty Years of X-Ray Diffraction, ed. Ewald, P. P. 441 1962 International Union of CrystallographyCrossRefGoogle Scholar.
page 170 note ** When he was asked about the possibility of writing a text for use in teaching more elementary courses, Barrett refused. “This decision was a very correct one. What happened was that B. D. Cullity, who had been teaching such courses for years, wrote just the right book (following rather closely my outline for the X-ray methods).”
page 171 note * Later to be known as the James Franck Institute.
paeg 171 note ** Shortly after World War II, Cyril Stanley Smith, who, in 1926, had came to the Massachusetts Institute of Technology from the University of Birmingham in England to take his Ph.D. and had remained in the U.S., was asked to organize a group at Chicago. Smith, an extremely creative and far seeing metallurgist had been attracted to Los Alamos to head the metallurgical part of the Manhattan project. His success in that post lead to the realization that the engineering and design challenges were best resolved by an initial study of the structure of the metals with which they had to work — plutonium, uranium, special alloys, etc. X-ray diffraction had, of course, played an important role. With this immediate background Smith, when he came to Chicago sought to complete a team of people (physicists, metallurgists, crystallographers, physical chemists) who would be able to do advanced and interesting research, of which low temperature work was an important example. Barrett was a natural choice for this position, the challenge of research having always been an important one for him. His teaching responsibilities were limited to one graduate student (positions were available for postdocs) and Barrett's association with the distinguished staff assembled by Smith promised to be productive and pleasant.
page 171 note *** Hume-Rothery, W. “Applications of X-ray Diffraction to Metallurgical Science”, Ch. 12, p. 203Fifty Years of X-Ray Diffraction. ed. Ewald, P. P.. Pub. by the International Union of CrystallographyGoogle Scholar.
page 171 note * This early scene is recalled in a private communication by J. W. Stout, of the Department of Chemistry of the University of Chicago and a colleague of Barrett's, who notes: “When the Institute for the Study of Metals began operations in 1946 we were housed in the West Stands, a sturdy concret structure at the west end of Stag athletic field. At the top of the stand was the bleachers where spectators at football games had once sat but beneath these were two stories which were utilized for laboratories and offices for the Institute. The north end of the stands was the site where Fermi's first pile had operated and we were in the south end which was free from radioactive contamination. At one end of the basement corridor was the low temperature laboratory where three of us (Earl Long, Lester Gutman and I) were busy constructing liquefiers for hydrogen and helium and at the other end the X-ray laboratory where Chuck Barrett set up the equipment used by all in the Institute. In between were the Institute shop and metallographic and preparative laboratories. There was daily contact and strong scientific interaction among all of us.”
page 172 note * Stout again describes this early scene, referring first to Zener's ideas regarding the beta brass and the questions it raised in relation to the possibility of body-centered cubic metals becoming “unstable with respect to close packed structure at low temperature. Barrett found this transformation in lithium cold-worked at the boiling point of nitrogen and reported the result in a letter in the Physical Review in 1947. Shortly thereafter he found that the transition would occur spontaneously when the temperature was lowered by pumping on the liquid nitrogen. He delighted in having us listen to the audible dicks as regions undergoing this martensitic transition snapped over while the temperature was being lowered. Barrett's interest in transformations and his close interaction with the low temperature group naturally led to the design of cameras and diffractometers for X-ray measurements at low temperatures down to 1.2°. One of these, designed by Earl, BarrettLong, Lothar Meyer and Walker, Chris, is described in Acta Crystallographica 9, 621 (1956)Google Scholar and was used by Barrett in his work on the sodium transformation. A similar design was used by Barrett and Meyer in their extensive work on phase diagrams of condensed gases. … “
page 173 note * Barrett, C. S. “Metallurgy at Low Temperatures” (1957)Google Scholar (1956 Edward De Mille Campbell Memorial Lecture), Transactions of the American Society for Metals, Vol. 49, p 87Google Scholar.
page 173 note * At Chicago, Barrett and Massalski worked together on solid state transformations in beta-brass, induced by cooling or deformation. Beta-brass is BCC like Na and Li and the same ideas as Zener's for alkali metals should apply. Barrett's deformation rig and flexible bellows on the X-ray cryostat proved invaluable for this purpose. With this approach they were the first to demonstrate that ordered beta-brass would transform into a dose packed hexagonal structure if deformed (and therefore disordered mechanically) at temperatures near absolute zero. So there is no such thing as a completely stable beta-brass.
page 175 note * Charles and Dorothy Barrett's daughter, Marjorie A. Barrett-Gultepe, worked in England for a time on electron diffraction and ellipsometry after obtaining a degree at the University of Birmingham. She then did research on films on metals, using ellipsometry, at the Norges Tekniske Hogskole, Trondheim, Norway, and, following that, at the University of Bristol in England, where she obtained a PhD degree in Physical Chemistry. Upon returning to the U.S.A. in 1978 (to Case Western Reserve University) her research shifted mainly to computer programming in ultrasonic research projects.