College of Engineering 1996 Annual Report: Progress By Design Materials Science and Engineering
3D plot and its 2D projection of the magnetic field distribution at the surface of a new class of high-temperature superconductor tape. The tape is made by a new Ion Beam Assisted Deposition (IBAD) technique which creates a very high critical current density tape (~0.5 MA/cm2) of YBa2Cu3Ox. (21K JPG) Surface magnetic field of superconductor tape

Clearing the way for new glass-ceramics

A process of floating molten silicates over molten tin results in smooth, clear architectural and automotive glass. Professor Reid F. Cooper is investigating how to make substitutions to the float process that could result in high-value glass and glass-ceramic products such as optical panels for notebook computers or heat-resistant automotive glass. These applications require additions of iron and/or titanium oxides to the glass. The glass additions require, in turn, additions to the molten tin, so as to avoid adverse chemical reactions between glass and metal melts, or at least to slow any reactions down. "We understand the chemical reactions between reactive gasses and complex glass melts," Cooper said. "We know, too, which atoms move in the melt to make these reactions go. The reactions with a molten metal are more complex, however, and these reactions can make it difficult to control glass chemistry enough to make crystals grow uniformly in the glass."

Strength of steels with about half the density

Professor John H. Perepezko is developing new design strategies for solidification of metals based on rapid-solidification processing methods where liquids are quenched at high rates (greater than 105 °C/Sec) and freeze at high undercoolings. These methods often result in novel, non-equilibrium structures with unique properties. For example, amorphous aluminum alloys processed through partial devitrification yielded material with the strength of steels, but with about half the density. In other studies of heterogeneous nucleation during solidification, new basic understandings led to a patent for evaluating grain refinement in castings. He is also examining phase stability in new high-temperature intermetallic alloys and composite synthesis designs based on multiphase architectures in collaboration with industry and national labs.

Putting atoms in the right places

Semiconductors will soon shrink to the point where the behavior of an individual atom or electron will affect the performance of electronic devices. Putting atoms in the right places and fabricating very small, carefully controlled and precisely arranged crystals of semi-conductors is paramount for creating successful new technologies. Erwin W. Mueller Professor Max G. Lagally and his colleagues are growing and characterizing small "quantum dot" structures using both chemical vapor deposition and molecular beam epitaxy. Focusing on Group IV semiconductors (silicon and germanium) they are leading the development of methodology for "self-organized growth" of well-organized arrays of quantum dot structures. Such arrays in silicon have potential for a wide range of technologies, from tiny, powerful computers to sensors and data storage.

Understanding stabilities at interfaces

Composite materials, whether used in electronic devices or as structural components, are emerging as an important class of engineered materials. Wisconsin Distinguished Professor Y. Austin Chang continues his investigation of stabilities at composite interfaces and the integration of thermodynamic modeling/phase diagram calculations with kinetic models to study microsegregation of alloys during their solidification. Interfacial stability is a generic phenomenon common to the design, processing and development of this class of engineered materials systems (e.g., metal-semiconductor contacts for electronic devices, fiber-matrix interfaces in structural composites, liquid metals/substrate interfaces in solder joints, etc.) The ultimate performance of these composite materials systems depends primarily on the stabilities of the interfaces between component phases. Chang's research has led to an understanding such that researchers are now in a position to design, a priori, composite structures in a variety of fields for technological applications.


Copyright 1996 University System Board of Regents

Content by perspective@engr.wisc.edu
Date last modified: 25-Sep-1996
Date created: 25-Sep-1996

1996 Annual Report Contents