Surface/Interface Diffraction Using Synchrotron Radiation
H. H. Chen,* T. C. Chiang,* H. Hong, Z. Wu, T. Gungoren
State of Illinois; IBHE-HECA; U.S. Department of Energy, DE-FG02-96ER45439 (In cooperation with the Materials Research Laboratory)

The objective of this project is to use surface/interface sensitive x-ray diffraction/scattering techniques, e.g., grazing incidence diffraction/scattering/fluorescence, specular reflectivity, standing and evanescent wave experiments, and truncation-rod experiments (all of which require the use of the synchrotron radiation) to examine various materials systems of scientific and technological importance. Some specific areas of investigation are: studies of the reconstructed structure, stress fields, relaxations, roughness, and phase transitions of single-crystal surfaces and interfaces such as Ag/Si(111), Ge/Si, C60/Si, Cu/Al2O3, SnO2/Al2O3, GaN/Al2O3; the dynamical structural and compositional evolution associated with melting, solidification, passivation, and corrosion.

Atomistics of Growth and Transport at Metal and Semiconductor Surfaces
G. Ehrlich,* S. Koh, K. Kyuno, S. C. Wang
U.S. Department of Energy, DE-FG02-96ER45439 (In cooperation with the Materials Research Laboratory)

The individual atomic events contributing to the growth of crystals and films are being explored on the atomic level. Through the use of the field ion microscope, single atoms are visualized, and processes such as condensation, diffusion, nucleation, and incorporation into the lattice are examined quantitatively to reveal how structure and chemical composition affect growth processes.

Tensile/Compressive Fatigue Analysis of Mullite Fiber/Aluminum-Magnesium Alloy Metal Matrix Composites
J. K. Shang,* C. Huang
Chrysler Motors Corp.

The fatigue behavior of mullite fiber reinforced Al-Mg alloy matrix composites is examined as a function of Mg concentration and fiber volume fraction. The primary objective is to understand the role of the interface in the fatigue crack initiation and growth processes. Several reaction products are found at the fiber/matrix interface in the as-received composite. Research is in progress to evaluate the effect of the interfacial reaction on the fatigue properties of the composite.

Microstructure and Properties of Interfaces
J. K. Shang,* Z. Zhang, J. Ryan, C. Zhang, Z. Xing, L. Lei
U.S. Department of Energy; Ford Motor Co.; U.S. Air Force Office of Scientific Research, FAMI-15-81014; Federation of Advanced Materials Industries

Experimental and theoretical studies are carried out to understand the relationship between microstructure and mechanical properties of bi-materials interfaces. We have developed new experimental techniques to measure mechanical properties of interfaces and applied these techniques to metal-ceramic, metal-polymer, glass-ceramic, and bi-metals interfaces. We are developing model interfacial microstructures at graphite-epoxy, alumina-aluminum, polyimide-copper, epoxy-metal, and solder-copper interfaces by chemical, physical, electrochemical, and metallurgical surface-modification techniques. We are modeling several salient mechanisms of crack growth, such as crack sliding, crack interlocking, and crack tip plasticity, along model interfaces.