T. Weston (Wes) Capehart, a physicist at the General Motors Research and Development Center in Warren, Michigan, passed away at his home on October 26, 2007, following a brief, intense battle with pancreatic cancer.
Wes was born October 18, 1948 in Norfolk County, Virginia, and grew up in Chesapeake. Following graduation from Carnegie Mellon, Wes earned a Ph.D. degree from Cornell and immediately began his 28-year career at GM R&D, where he engaged in a variety of projects, unusually wide, even for industry. Bringing his customary enthusiasm and drive for results, he made notable contributions to each of these. Most of these projects were team efforts that benefited greatly from Wes' affable, collegial personality and his natural ease in working with others. The range of projects reflected Wes' considerable experimental and theoretical expertise, which included a host of x-ray absorption and electron emission spectroscopies, mass spectrometry, measurement and analysis of mechanical properties, modeling hysteresis in both magnetic and mechanical systems, and electronic structure calculations for molecular and polymeric materials. The diversity of Wes' scientific activities and accomplishments is illustrated by the following research themes, a list that is by no means exhaustive:
Characterization of surfaces and highly disordered solids. Wes employed uv and x-ray photoemission, x-ray absorption near edge structure (XANES), and extended x-ray absorption fine structure to investigate systems such as films of tin oxide, nickel hydroxide, and CVD diamond; Ag:Pd (100); noble metal overlayers on Al (100); Rh-Ce/alumina catalysts, and chemisorbed molecules on Rh (100). With colleagues at the University of Michigan he conducted pioneering work on the use of positrons to probe surface defects and surface magnetism.
Magnetic materials. Considerable opportunity for the investigation of properties such as rare earth valence and substitutional effects was presented by the discovery of the permanent magnet compound Nd2Fe14B and its many relatives, and Wes systematically exploited it. His studies included the determination of the Pr valence in Pr2(Fe1-xCox)14B, the behavior of the Ce valence in (La1-xCex)2Fe14B, and determination of the Zr site in Zr-substituted Nd2Fe14B. He also ventured into the realm of magnetostrictive materials, conducting strain and other measurements on a variety of steels and composites such as highly magnetostrictive SmFe2 in Al and Fe matrices that were of interest for sensor applications.
Tribology and wear. Wes was involved in many different projects of a tribological nature. One body of work focused on the design and characterization of novel candidate traction fluids for continuously variable transmissions. With colleagues at both GM R&D and the University of Western Ontario he investigated the properties of antiwear films on cylinder bore materials with XANES, nanoindentation, and nanorheological techniques; the inquiries elucidated technologically significant effects.
Fuel cell-related research. Over the past couple of years Wes became fascinated with scientific issues connected with the development of fuel cell technology. This was not surprising in view of the fact that he was a strong supporter of environmental stewardship and responsibility. Much of this effort was centered on the behavior and properties of proton exchange membrane materials such as perfluorosulfonic acids (PFSAs). On the experimental side he measured proton transport in membranes at low temperatures using dc conductivity and calorimetry. Theoretical work included calculation of the interaction of model acids with water clusters; modeling the Flory-Huggins mixing parameter of PFSA Nafion and water, studies done in collaboration with researchers at the University of Sherbrooke in Quebec; and mesoscale simulation of membrane morphology. One study which certainly must have engendered great parental pride was on the phase diagram for the melting of water in Nafion conducted with his son, Jason.
Overall, Wes' contributions also reflect his unique combination of natural curiosity, ever-positive outlook, and ability to easily enter new fields. Beyond the pursuit of his own activities, Wes freely provided insight and inspiration to those around him who were working in other areas. His generosity in this regard is evidenced by the fact that his name often appears in the acknowledgment section of friends' and colleagues' publications.
Wes was a member of the APS, ACS, AAAS, the CHESS, NSLS, and APS User Groups, and an affiliate member of SAE. He was an active proponent of science education and appreciation in the community, frequently judging at Science and Engineering Fairs of Metro Detroit and performing demonstrations at the Cranbrook Institute in Bloomfield Hills, for example. In addition to his professional activities, Wes enjoyed hiking and camping with his family (especially in Rocky Mountain National Park), running, tennis, and fishing (especially in the Outer Banks of North Carolina).
Wes is survived by two older sisters, Anne L. Walker and Bettie C. Starr, his wife, Gail, and their three children, Jason, Kevin, and Stacy.
George Graham
Jan Herbst
