The organizers of the Dr. John J. Stephens, Jr. Memorial Symposium: Deformation and Interfacial Phenomena in Advanced High-Temperature Materials are honoring the memory of Dr. Stephens and his many technical contributions that were accomplished over a relatively brief twenty year career. His research spanned the areas of creep and deformation of metals, dispersion-strengthened alloys and their properties, metal matrix composite materials, processing and properties of refractory metals, joining of ceramic-ceramic and metal-ceramic systems, active braze alloy development, and mechanical modeling of soldered and brazed assemblies. The purpose of this presentation is to highlight his research and engineering accomplishments, particularly during his professional career at Sandia National Laboratories in Albuquerque, NM.
The purpose of the report is to summarize discussions from a Ceramic/Metal Brazing: From Fundamentals to Applications Workshop that was held at Sandia National Laboratories in Albuquerque, NM on April 4, 2001. Brazing experts and users who bridge common areas of research, design, and manufacturing participated in the exercise. External perspectives on the general state of the science and technology for ceramics and metal brazing were given. Other discussions highlighted and critiqued Sandia's brazing research and engineering programs, including the latest advances in braze modeling and materials characterization. The workshop concluded with a facilitated dialogue that identified critical brazing research needs and opportunities.
The main objective of this project was to develop reliable, low-cost techniques for joining silicon nitride (Si{sub 3}N{sub 4}) to itself and to metals. For Si{sub 3}N{sub 4} to be widely used in advanced turbomachinery applications, joining techniques must be developed that are reliable, cost-effective, and manufacturable. This project addressed those needs by developing and testing two Si{sub 3}N{sub 4} joining systems; oxynitride glass joining materials and high temperature braze alloys. Extensive measurements were also made of the mechanical properties and oxidation resistance of the braze materials. Finite element models were used to predict the magnitudes and positions of the stresses in the ceramic regions of ceramic-to-metal joints sleeve and butt joints, similar to the geometries used for stator assemblies.
The objective of this study was to investigate the technology used by Spectrolab Inc. to manufacture photovoltaic modules that have provided twenty years of reliable service at Natural Bridges National Monument in southeastern Utah. A field survey, system performance tests, and a series of module and materials tests have confirmed the durability of the modules in the array. The combination of manufacturing processes, materials, and quality controls used by Spectrolab resulted in modules that have maintained a performance level close to the original specifications for twenty years. Specific contributors to the durability of the modules included polyinyl-butyral (PVB) encapsulant, expanded metal interconnects, silicon oxide anti-reflective coating, and excellent solder/substrate solderability.