NEWS OF THE WEEK
SUPERCONDUCTIVITY: Current-carrying capacity soars Researchers at IBM's Thom as J. Watson Research Cen ter in Yorktown Heights, N.Y., have increased 100fold the current-carrying capacity measured in the new relatively-high-tem perature superconducting ceramics. In a specially pre pared single-crystal thin film, the researchers mea sured a critical current den sity of more than 100,000 amp per sq cm at the boil ing point of liquid nitro gen, 77 K. Such a value is "in the ballpark for most practical applications," says IBM s p o k e s m a n Gerald Present. The measurement marks IBM researchers Laibowitz (left) and Koch measure yet another milestone in resistance of superconducting thin film the fast-paced research ef fort that has surrounded these ma a coolant. But practical applications terials for the past six months. Last also require materials that can carry November, researchers at the Uni a large amount of current and can versity of Tokyo and at the Univer do so in the presence of a strong sity of Houston confirmed an earli magnetic field. Recent work at er report by IBM researchers in AT&T Bell Laboratories has shown Zurich, Switzerland, that certain that the new superconducting ma copper oxide ceramics could con terials retain their superconductivi duct electricity with virtually no re ty in magnetic fields much stronger sistance at temperatures well above than those that destroy this proper absolute zero. Since then, materials ty in present-day commercial super scientists in laboratories all over the conductors, which work only at world have been joining the race to lower, liquid helium temperatures. understand these materials and to Now IBM's Praveen Chaudhari, see if they will really prove practi Robert Laibowitz, Roger Koch, cal for hundreds of electrical appli Thomas McGuire, and Richard Gamcations (C&EN, May 11, page 7). bino find that the inherent ability Much of the work so far has fo of the new materials to carry high cused on raising the temperature at currents is also good enough for which the materials lose most of commercial use. Not unexpectedly, their electrical resistance and become they find the amount of current the superconducting—the so-called crit material can carry increases as the ical temperature, or Tc. Many labo temperature declines, so that at 4 K, ratories now have materials with Tcs liquid helium's boiling point, the in the range of 90 to 100 K, temper critical current density for their sam atures that can be reached fairly eco ple is greater than 5 million amp nomically using liquid nitrogen as p e r s q c m . 4
May 18, 1987 C&EN
The IBM measurements were made in a singlecrystal thin film of yttri um-barium-copper oxide measuring about an inch in diameter and 1 μπι in thickness. The film was made using electron beam vapor deposition, and the crystal itself was epitaxially g r o w n on a s t r o n t i u m titanate substrate. As the individual atoms of the film are deposited on the substrate, they align them selves so as to match the crystal structure of the sub strate as closely as possi ble, thereby producing a single-crystal film. That the IBM sample is a single crystal accounts for the great jump in its cur rent-carrying capacity, the research ers believe. "The reason that peo ple in the past have not been able to get such high values is that the measurements were being done in polycrystalline materials," Present says. "Essentially what was happen ing was that you had this collection of crystals that each independently could sustain very high currents, but they couldn't pass these high currents from one crystal to the next. Material scientists feel confident they can overcome that problem now knowing that the material is indeed capable of sustaining such currents." That a single-crystal film conducts a current better than a polycrystal line one is just one more difference between the new superconductors and the ones currently in use, such as niobium-titanium and niobiumtin alloys, points out Gilbert Y. Chin, director of the materials re search laboratory at Bell Labs. In conventional superconductors, he
explains, "the idea usually is that the more grain b o u n d a r i e s you have—the more defects you put into the material—the h i g h e r is the current-carrying capacity/' Although for some applications, such as microcircuitry, single-crystal films may be a suitable form for superconducting materials, many potential applications will require polycrystalline materials. "You can't make a single crystal hundreds of miles long for use in a cable," Present says. "The next challenge is to see how you can make polycrystalline materials exhibit that kind of current density." The new materials also have problems with inherent strength and brittleness that will need to be overcome before they will be practical for many uses. D
Montedison, EniChem continue merger talks Officials at Montedison were busy seeking corrections last week to press reports that implied the big Italian chemical company was close to merging with another large firm, EniChem, the chemicals arm of the Italian-state-owned oil company Ente Nazionale Idrocarburi (ENI). A Montedison official confirmed that talks are going on. "We are talking, but we are not elaborating," he says. "It is a fake to say Montedison has announced anything." According to Albert Alonzo, securities analyst with London firm Barclays de Zoete Wedd, "The talks have been going on for some time, particularly since autumn of last year." Those talks arose following the breakdown of negotiations for Montedison to sell one of its plants to EniChem; talks broke down when the price could not be agreed upon. After that, the two began talking about a possible joint venture. But Alonzo questions whether the talks will lead to anything, at least in the near future. One reason is Montedison's climb back to profitability after years of losses. He attributes Montedison's success to, among other things, the restructuring of the Italian chemical industry in 1982, when the industry
was essentially polarized. EniChem took over commodity chemicals, M o n t e d i s o n the more specialty products. Montedison and EniChem exchanged assets, Alonzo says, "and EniChem got the duds. I don't see a great deal of enthusiasm on the part of Montedison for going through with this—it is doing quite well on its own." EniChem would be the beneficiary of any combination, he believes. Montedison, on the other hand, would want to look outside Italy to improve its international strength. One factor that could inhibit an agreement would be the Italian state involvement in EniChem. Montedison previously was partly owned by the state, but in 1981 the state's share was purchased by private individuals. Moreover, earlier this year, some 40% of Montedison— effectively, a controlling share—was acquired by Feruzzi Group, an agricultural commodities firm run by an aggressively individualistic owner. The significance of a linkup between Montedison and EniChem is important enough that, when the talks first began, they were discussed at the Italian Cabinet level. But the government would not be in a position to order the venture or impose an agreement. D
Carbide, India tighten Bhopal liability cases By the middle of next month, the tempo will be quickening in the bitter legal wrangle between Union Carbide and the government of India over liability in the Bhopal methyl isocyanate gas disaster of December 1984. Last week an Indian legal team flew into Washington, D.C., and met with its government's U.S. attorneys to review strategies to be taken over the next several weeks. The case is currently in the discovery process. Some observers believed at first that a major purpose of the visit was to discuss a settlement with Carbide. But both sides quickly quashed that idea. Both agreed that a settlement will be reached, perhaps before fall, but that the time is not yet ripe. Hopes for settlement ride on the scheduling of legal events in the Indian district court in Bhopal where the litigation is taking place. In about three weeks the Indian government will submit its brief to Judge M. W. Deo outlining why Carbide cannot escape legal blame for the disaster. Deo was appointed judge to succeed G. S. Patel, who reportedly was found to have secretly
Drickamer wins Welch Award in Chemistry Harry G. Drickamer, professor of chemical engineering, chemistry, and physics at the University of Illinois, UrbanaChampaign, and a dominant figure in high-pressure research, has won the 1987 Robert A. Welch Award in Chemistry. The award totals $225,000 and is given annually for outstanding career contributions in chemical research. This year it recognizes especially Drickamer's discovery of pressure tuning spectroscopy at very high pressures, work that has led to major advances in the detailed understanding of molecular, atomic, and electronic properties of matter. Author of more than 350 scientific papers, Drickamer, 68, has won a number of major scientific awards. He will receive the Welch award during ceremonies in Houston next Nov. 2.
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