MATERIALS SCIENCE AND ENGINEERING

SUPERCONDUCTING ADVANCES

Collaborating with researchers at the Princeton Materials Institute and Iowa State University's Ames Laboratory, scientists at the college's Applied Superconductivity Center (ASC) have made significant discoveries that may boost the potential of newly discovered high-temperature superconducting metal magnesium diboride.

Superconducting materials can conduct electricity with almost no loss of energy. In January 2001, Japanese scientists reported that magnesium diboride superconducts up to 39 degrees Kelvin (minus 390 degrees Fahrenheit), almost twice the temperature of any other metallic superconductor. Then Professors David Larbalestier, Eric Hellstrom, Susan Babcock and Chang-Beom Eom found evidence that the material can transport high electrical currents because its grain boundaries do not obstruct current flow, as did previous high-temperature superconductors.

Recently, Eom made the first textured thin films of magnesium diboride and discovered that alloying enables magnesium diboride to carry 100,000 amps of current per square centimeter in very strong magnetic fields (10 tesla) and withstand twice as high a magnetic field as the current commercially used superconducting material, niobium-titanium. To describe their discoveries, the groups published papers in the journal Nature in March and May 2001, and in several specialized journals.

TECHNOLOGY FOR AN IMPROVED VIEW

Pictured from left: Chang-Beom Eom, graduate students Jung-Hoon Choi and Land Belenky, and undergraduate student Peter Titus. The group recently grew magnesium diboride thin films in the vacuum chamber. (42K JPG)

Current medical ultrasound imaging technology isn't powerful enough to detect a few-millimeter tumor deep within the breast. But a group of five researchers led by Professor Chang-Beom Eom hopes to push that technology's limits and fabricate materials to make new, ultrasensitive high-frequency medical ultrasound transducers that doctors can use to find tiny, early-stage tumors.

To make the transducers small enough — one-quarter the width of a hair — and fabricate the materials to take advantage of their electro-mechanical properties, the group is making epitaxial single-crystalline forms of lead- magnesium-niobium-lead-titanate. The compound has a much higher electromechanical coupling coefficient than conventional transducer materials; its higher sensitivity and broader bandwidth translate to improved imaging resolution and depth of penetration.

Researchers in the group are testing the transducers' resolution and measurement capabilities by imaging an artificial tumor cell. Eventually, they hope to fabricate multilayer stacks, which operate at low voltage, and transducer linear arrays. Among their applications, doctors also could use the high-frequency transducers for intracardiac and intravascular imaging for minimally invasive surgery, and ultrasound microscopy for imaging skin, excised blood vessels and cell suspensions.

Left: One of the first wires made from the new super-conducting material, this is a cross-section of an unreacted magnesium diboride wire. The center is magnesium diboride, the middle layer is niobium and the outer ring is copper. (15K JPG)

INTEGRATING OPPOSITES

Cellular telephones have become indispensable communications tools — all-in-one organizers that include such features as E-mail and Web access. And collaborative research between Professor Max Lagally, Chemical Engineering Professor Thomas Kuech, electrical engineers from Georgia Tech and a SUNY-Albany structural-analysis expert, may make the devices even more powerful.

The group hopes to integrate compound semiconductor devices made from fast, optically sensitive materials such as gallium arsenide with silicon, which offers increased computational power. One of the group's goals, which researchers have yet to accomplish, is to integrate the materials as a system. The results could have an immediate impact in defense applications where battlefield communication increasingly relies on wireless technologies. But the research also could translate into computers that quickly send mountains of data using optics instead of cables, or chemical and biological sensors in which one component integrates the optical emitters, detectors, micropumps and processors. The Defense Advanced Research Projects Agency is funding the project through a three-year, $1.8 million grant.