The discovery of superconductors transformed the life of a young materials scientist. Now, R&D Magazine’s Innovator of the Year hopes his work will do the same for the rest of us.
Amit Goyal, R&D Magazine's 2010 Innovator of the Year, has helped bring high-temperature superconductors to market as a result of numerous innovations. Image: Oak Ridge National Laboratory.
In 1987, engineering student Amit Goyal was completing a materials science degree at the Univ. of Rochester in New York when he read about the latest recipients of the Nobel Prize for Physics. Georg Bednorz and Alex Müller of IBM were the honorees of the annual prize, in recognition of their discovery of a material that scientists had theoretically ruled out two decades before.
The world’s first high-temperature superconductor (HTS) was the technology; the award was made one year after the discovery.
Nobel Prizes are typically given 10 to 15 years after a discovery, but the excitement over HTS was immediate and profound. In a few short years, superconductors that vastly outperformed the one Bednorz and Müller discovered were introduced. Researchers everywhere abandoned traditional metallic elements in favor of new combinations of oxides and metals. Hundreds of laboratories devoted projects to tap the limits of these new materials. If superconductors could be constructed to operate at ever-higher temperatures, a host of technologies we use everyday, from trains to magnetic resonance imaging machines, would be revolutionized.
The discovery struck a chord with Goyal, who was ready to pursue an MBA. But when he read about high-temperature superconductors, he switched gears. Ever since, the key focus of his research work has been unlocking practical applications for these materials. This has led to Dr. Amit Goyal’s selection as R&D Magazine’s 10th Innovator of the Year.
The last three years, in particular, have highlighted his major impact on HTS research. Goyal, a Corporate Fellow and Battelle Distinguished Inventor at the University of Tennessee-Battelle, Knoxville, and Oak Ridge National Laboratory (ORNL), Oak Ridge, Tenn., has received three recent R&D 100 Awards related to the fabrication of HTS wires, making valuable improvements to both performance and the process technology involved in making next-generation ultra-high performance wires. These innovations include the use of self-assembly techniques for introducing defects that aid overall wire performance. His invention of the process for manufacturing second-generation HTS wires is now being used globally.
And in his nearly 20-year career at ORNL, Goyal has also invented new materials for flexible electronic devices, such as solar cells and complex 3D structures through self-assembly. The inclination toward business he showed in college has never disappeared, and his endeavors in the commercial marketplace have been successful even as he pursues R&D at ORNL. He has brought innovations to market through successful collaborations with SuperPower Inc., Schenectady, N.Y. and by way of his own startup, TexMat, Knoxville, Tenn., which is commercializing semiconductor substrate materials.
“I have always been interested in materials engineering and being able to make materials do what you would like them to do. Materials by design has always fascinated and intrigued me,” says Goyal, who earned his doctorate in materials science and engineering from the Univ. of Rochester.
A career moment
While working on his master’s degree, Goyal believed that his career would follow the intersection of engineering with business, with an emphasis on management. But he also appreciated the importance of a thorough knowledge of materials, and with the arrival of HTS materials he felt he had a unique opportunity to become an expert in an emerging field of study.
“Every newspaper and magazine carried articles of how these novel materials would change the world we live in,” he recalls.
Goyal understood that his best option in studying HTS materials would be to find ways to make it work in the commercial marketplace. In his mind, he saw large-scale uses for a technology that would introduce the world to resistance-free conductivity. He could return to business school later.
He is certainly not alone in this field of R&D. More than 100,000 papers have been published about HTS in the last 20 years. Most researchers are concerned with fundamental physics in HTS, but many others are also looking for practical ways to apply the phenomenon. Goyal got a head start in this new field of technology by joining ORNL, a U.S. Dept. of Energy (DOE) laboratory already known for its superconductor research.
In 1990, while working toward his doctorate in materials science and engineering at the Univ. of Rochester, Goyal met Tony Schaffhouser, the program director of the DOE superconductivity pilot center, at a conference. Their conversation about the HTS work being performed at ORNL suggested opportunities for people with materials science backgrounds.
“Tony was undoubtedly an excellent ambassador for ORNL. The laboratory is an exciting place with top-notch tools and people,” says Goyal.
He soon became an expert in examining materials by way of electron-beam diffraction techniques that set the stage for several materials science advances later his career. The need to characterize the misorientation of hundreds of grain boundaries in polycrystalline superconductors to understand the barriers to supercurrent flow led him to develop strong skills in electron backscatter Kikuchi diffraction, which was a fledgling field in the early 1990s. Later, Goyal used this knowledge to build a single-crystal-like substrate for HTS applications.
“That is indeed the beauty of being a materials scientist. You can mold yourself into a metallurgist for some years, and a physicist or a ceramist or a film deposition person in other years. Materials science gives one the basics for a broad scientific background,” he says.
A mystery with promise
The discovery in 1986 of the first true HTS marked a major shift in the fortunes of superconductivity. There are two reasons for the excitement. First, materials that are capable of producing HTS can sometimes operate at or higher than 77 K, which is the boiling point of liquid hydrogen, a readily available and relatively inexpensive coolant. The other reason may have even more to do with the success of HTS. The higher the operating temperature, the higher the magnetic field a superconductor can withstand before superconductivity is destroyed.
“The physics of why high-temperature superconductors tick and enabling practical devices from these novel materials are two completely different and disconnected areas,” says Goyal. “The community trying to develop the theory which could explain high-temperature superconductivity is a different community and, as we know, it is still not fully clear what makes these materials superconduct.”
In one of his first big breakthroughs in HTS, Goyal invented a process called RABiTS (1999 R&D 100 Award) that lets manufacturers fabricate long lengths of single-crystal-like, flexible, superconducting wire using scalable processes. RABiTS, which stands for “rolling-assisted biaxially textured substrates”, builds on a class of HTS materials made from yttrium, barium, and copper oxides. The RABiTS process and subsequent papers based on this research have led to a portfolio of about 50 issued patents, all of which relate to the fabrication of HTS wire. These papers are among Goyal’s most highly cited works and have removed many of the roadblocks hindering HTS.
He later invented a third generation, “round” wire technology called “SSIFFS”, which received a 2009 R&D100 Award. The low-aspect ratio wire, which can operate at up to 77 K, was the result of research for applications for which low AC losses are a requirement. It is formed by epitaxial deposition of the superconductor on long flexible single-crystal aluminum oxide fibers (Structural, Single-Crystal, Faceted, Fibers, or SSIFFS) with well-defined crystallographic facets that help the growth of the superconductor.
Second-generation HTS wires have also been further developed by Goyal. By design, a single-crystal HTS wire has a high current, especially in the absence of applied magnetic fields. However, magnetic fields tend to suppress these currents. Self-assembly of non-superconducting, nanoscale columnar defects at nanoscale spacing within the superconducting wire is an elegant way, according to Goyal, to create the much-needed defects or “pinning centers” to allow the wire to sustain high “supercurrents” in the presence of high applied magnetic fields. The wires also benefit from biaxially textured superconducting layers. The dual axis texture means that few, if any, high-angle, weakly conducting grain boundaries are present that could inhibit current flow. This technology is the basis for one of Goyal’s 2010 R&D 100 Awards: High-Performance, High-Tc Superconducting Wires enabled via Self-assembly of Nonsuperconducting Columnar Defects.
The future of HTS
Goyal believes the field of HTS is nearly ready for prime time. In the realm of electric power applications, these include underground transmission lines, fault current limiters, generators and transformers. Other large-scale applications include high-field magnets, magnetic billet heaters, and high-field nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI).
Most of the impact on HTS applications, says Goyal, is due to the support of DOE funding through national laboratories and universities.
“Electronic devices based on semiconductors such as diodes, transistors, and integrated circuits can be found everywhere. For many of these applications, if the cost of the device is significantly reduced without significantly reducing the performance, many more applications can be envisaged,” he says.
Already, HTS is making an impact on commercial power distribution. The world’s largest high temperature superconductor wire order for superconductor power cables was recently announced by LS Cable Ltd. in South Korea. The company is the world’s third-largest power cable manufacturer, and has placed an order for 3 million meters of Amperium wire, American Superconductor Corp.’s proprietary second generation (2G) HTS wire based on the RABiTS process.
Large-scale applications can benefit from new substrate materials as well, which has led Goyal to capitalize on his earlier work in created textured materials. After developing a proprietary process for constructing a new flexible substrate material that would be suitable for use in the semiconductor industry, he formed Texmat, which now makes thin, single-crystal semiconductor layers up to 100 m long by 1 m wide. Suitable for building epitaxial devices, these substrates can be wrapped around mandrels for high-throughput manufacturing, and according to Texmat, the cost is orders of magnitude less than silicon, germanium, and gallium arsenide.
Goyal holds more than 50 patents and has published more than 240 papers. He is now among the most highly cited HTS researchers in the world, and his work now will depend on his success in 3D self-assembly processes. He and his team are now working on controlled synthesis of nanoarrays using self-assembly and epitaxial techniques developed for superconductors. He expects the performance of HTS wire to improve significantly while cost drops. His accomplishments so far, he says, always have root in fundamental understanding of the basic nature of materials.
“My approach to research has always been to ask the question: what is the ideal microstructure of the material needed to meet the performance goals for the application?” says Goyal. And then he goes to the lab and builds it.
Published in R & D magazine: Vol. 52, No. 7, December, 2010.