The Ins and Outs of Materials Science

The Ins and Outs of Materials Science

By Teaming With a Variety of Fields, Rice Scientists Can Make Design a Reality

BY LIA UNRAU

Rice News Staff

Jan. 21, 1999

From filters used in environmental engineering to polymers used in bioengineering bone tissue, materials science provides the foundation of our technological age and acts as a springboard for future progress.

Metals and alloys, ceramics and glasses, cements and concrete, polymers and plastics, composites, semiconductors, superconductors, graphite, diamond and carbon nanotubes, all are within the materials scientist’s realm.

“A materials scientist acts as a bridge between basic physics and chemistry research and engineering,” says Rex McLellan, professor of materials science. By its very nature, the field is highly interdisciplinary.

“Materials science is almost like mathematics in the sense that it is the foundation of a large number of other disciplines,” says Sidney Burrus, dean of the George R. Brown School of Engineering.

Some of the more traditional areas of materials science include applications in the energy industry, electronics, semiconductor materials, ceramics and polymers.

“We have very good capabilities in traditional materials science,” Burrus says, “and now we’re moving more into the nanoscale materials science and looking at the interplay between materials science and mechanical engineering, electrical engineering and chemical engineering. There are important applications of materials science that appear in all three of these traditional engineering areas. And there is now much greater interplay with activities in the natural sciences.”

For example, a lot of nanoscale science research that comes out of chemistry and physics is being folded into the engineering applications; where before these were somewhat isolated and separate, now they are much more integrated.

“As exciting innovations and progress are made in basic science, these developments must be constantly incorporated into the arsenal of the materials scientist in the quest to continue the generation of new materials and appropriate fabrication techniques,” McLellan says.

Materials scientists work to create and optimize diverse materials, and the work shares a common theme. Scientists want to understand and control the structure of materials, so that their properties, either alone or in combination, may be understood, and their performance can be optimized.

In other words, a materials scientist helps design become reality.

The mechanics of launching men to the moon and rocket propulsion systems were ready for liftoff long before NASA scientists developed materials that could withstand the extreme temperatures of atmospheric re-entry.

Just as manned space flight became possible after the development of nose cone materials, modern materials also have catapulted the field of bioengineering to a new level of performance. The mechanical heart valve, developed decades ago and made of metals, has been greatly improved by the creation of pyrolitic carbon. This material improves over the old in many ways; it will not be corroded by body fluids such as blood, and the valves can be formed without welding and the inherent defects that welding introduces.

Clearly, the application of materials science has an impact on a variety of industries, and local industry has long shown an interest in Rice research.

Franz Brotzen, the Stanley C. Moore Professor Emeritus of Materials Science and founder of materials science at Rice in 1954, says the connection between the materials science group at Rice and local industry has been strong for many years. He points out that one of the reasons for this is that Houston’s lifeline has been the oil and gas industry, which traditionally uses the most advanced materials for exploration. The electronics industry also has supported a variety of research projects at Rice in the development and study of

materials for microchips.

Andrew Barron, professor of chemistry and materials science, and Enrique Barrera, associate professor of mechanical engineering and materials science, both have numerous collaborations with Texas companies, from consulting to research.

Barrera recently organized the Materials Technology Consortium with local industries. He collaborates on a variety of projects with NASA. He is currently on sabbatical at the Johnson Space Center acting in part as a liaison between Rice and NASA in nanotechnology. He is also developing nanotube materials for space applications.

“Materials science is an area that in current technology is a critical area for development,” Barrera says. “You don’t go to market unless you have the material.”

The future is likely to bring even smaller and more powerful computers, electronic paper and stronger, lighter and safer materials for all types of vehicles. Scientists are working fast and furiously to develop materials to make these technologies possible.

An area which is greatly impacting future development is nano-structured materials. The development of buckyballs, discovered at Rice in 1985, and particularly carbon nanotubes, is one facet of nanotechnology that clearly represents enormous potential for the development of materials and the micro-engineering of new devices. Much of Barrera’s research utilizes nanotubes and nanoscale science, and Barron’s research makes use of nanotechnology as well (see related story).

Another burgeoning area is computational materials science. The use of sophisticated computational techniques can be used to solve problems in materials engineering just as they are used in other branches of engineering and the pure sciences. Among the many potential applications, McLellan points out, is the modeling of crack behavior. How cracks spread through brittle solids is not well understood even from a macroscopic viewpoint.

“Yet brittle crack propagation is a severe limitation to the engineering utilization of many metallic, ceramic and composite materials exhibiting otherwise superlative mechanical behavior and corrosion resistance,” he says.

Barrera also sees computational materials science as an important area for the future.

“As fields become more expensive and complex, computational materials science will provide a means for exploring and testing concepts,” Barrera says. “The idea is great because you can first experiment on paper.” For example, the ability to model nanotubes in the design of new materials systems requires a lot of number-crunching capability. Using theory and coupling it with parallel computing and analytical computation will afford scientists the ability to do more selective testing of properties and performance.

Another area that McLellan feels is significant and will expand in the future is materials in bioengineering. Not only will bioengineering materials require stringent mechanical and electrical properties, but also the demands of biocompatibility are always present.

Barrera also names some specialty areas that are picking up speed in the materials field: metastable phase materials and micro-electrical mechanical systems, or MEMS.

In addition to these newer areas of research, there are old problems in more traditional materials science that are yet to be solved. These old problems are still with us because they beg to be solved and because their solution would bring a technological boon. One such case is the hydrogen problem. Hydrogen atoms can easily enter most metallic solids and even at very small concentrations–as little as one proton per million metal atoms–they make the metal too brittle for engineering use. McLellan has been working to understand the basic nature of hydrogen embrittlement, and his recent work shows promise (see related story).

For materials science at Rice, a strong core of researchers with good collaborations across campus and in industry is the key to success, Barrera says.

“An advantage is that this group can be the mainstay for interaction between groups and experiments,” he says. “We have the facilities, the spectroscopy, microscopy, and we have a nice working arena and a good core of people to connect with others.”

“It is our plan and expectation that the materials science program will evolve to a point of more strength and more interactions with other programs in the Department of Mechanical Engineering and Materials Science and at Rice,” says Tayfun Tezduyar, the James Barbour Professor in Engineering and chair of mechanical engineering and materials science. “We have every reason to believe that the future will bring exciting times for the materials science program.”