NEWS OF THE WEEK What CMA and other trade associations supporting the treaty are concerned about is the price their industries will pay if the U.S. does not ratify the treaty. As Burgess explains, 'The [treaty] specifically restricts trade in regulated chemicals." Countries that have ratified the treaty will not be able to trade in some chemicals with countries that have not ratified the accord. CMA's senior assistant general counsel, Michael P. Walls, warns, "If we can't trade in a particular chemical and our customers have to go elsewhere, it will make it easier for them to go elsewhere for other chemicals as well." Also, he says, there is "the potential for some countries to look at the [treaty] as a way of imposing other trade barriers" by refusing to sell to U.S. companies chemicals whose trade is not restricted by the treaty. At press time, 60 nations had ratified the treaty. Sixty-five ratifications are needed to start the 180-day clock ticking until entry into force. There are no consequences for the U.S. if it ratifies before entry into force, even if it is not among the first 65 nations to do so. Until recently, U.S. ratification was considered a near certainty. But a Senate staffer tells C&EN that "as many as 28 senators" are now likely to vote
against approval. "We're probably lacking six to eight votes to defeat ratification," he claims. An Administration official, pegging the nay votes at 10 to 15, says 28 "is highly inaccurate. There are only five votes on record against the treaty." The Senate is expected to consider ratification around Sept. 14. If the treaty is ratified, Congress is expected to take up implementing legislation early next year. Such legislation is needed to bring U.S. law and regulations in line with treaty obligations. Graydon R. Powers, president of the Synthetic Organic Chemical Manufacturers Association, which is a supporter of treaty ratification, is calling for implementing legislation "that produces the least burdensome reporting requirements that do not exceed the objectives of the treaty, contains adequate protection for proprietary information, and does not damage the domestic chemical industry's competitive position." The executive branch is now trying to figure out a way to compel industry to declare treaty-required data and accept on-site inspections—an executive order, perhaps—before implementing legislation is in place. Lois Ember
Carbon onion cores converted to diamonds Researchers in Germany have found a way of synthesizing diamond crystals from graphitic carbon. The discovery could lead to a deeper understanding of the way graphite transforms into diamond. Research scientist Florian Banhart and visiting research fellow Pulickel M. Ajayan at the Max Planck Institute for Metal Research in Stuttgart nucleated nanometer-sized diamond crystals in the cores of carbon "onions" [Nature, 382, 433 (1996)]. Carbon onions are spherical particles of carbon consisting of concentric shells of graphitic carbon, like layers of an onion. They are formed by intense electron-beam irradiation of carbon nanoparticles produced in a carbon arc. They were discovered in 1992 by physicist Daniel Ugarte of the Institute of Experimental Physics at Federal Polytechnic College in Lausanne, Switzerland. 6
AUGUST 5,1996 C&EN
Diamond crystal forms at center of graphitic onionlike shells. Reprinted with permission from Nature, 382, 433 (1996). Copyright 1996 Macmillan Magazines Limitea
Banhart and Ajayan transformed the graphitic shells at the onion cores into diamond crystals by subjecting the particles to electron irradiation at about 700 °C in a high-resolution transmission electron microscope. "This experiment enables us, for the first time, to monitor the graphite-
diamond transformation in situ on an atomic scale," Banhart tells C&EN. "It is still very uncertain, however, that this will lead to a new way of producing macroscopic amounts of diamond. "The onions are up to 100 to 200 nm in diameter. We find that at high temperatures, the particles are even more perfect than at room temperature. They have perfect spherical symmetry and perfectly closed shells." The carbon onions act as "nanoscopic pressure cells" for diamond formation, Banhart explains. When the particles are irradiated at high temperatures, they contract, compressing the core. The interlayer spacing between the shells decreases from about 3.1 Ao between the outer shells to about 2.2 A at the core. Spacing between layers of graphite is normally about 3.4 A, he notes. "The high pressure in the cores aids the nucleation of diamond crystals," he says. "No external pressure is applied, nor are catalysts used." "The results are fundamentally interesting," comments Harry Kroto, professor of chemistry at Sussex University, England, and leader of the fullerene research group there. The metamorphosis from graphite to diamond appears to occur at about 700 °C but not at room temperature, he observes. "That is important for graphite nanotechnology," he says. "It means that you can rearrange the bonds in pure carbon at that temperature but not at lower temperatures." Formation of carbon onions at high temperature is a prerequisite for coherent shells, self-contraction, and diamond formation, according to Banhart. Other methods of transforming graphite into diamond require much higher temperatures and also high pressures, he notes. He points out that diamonds can be grown from vapor (not from graphite) at low pressure by chemical vapor deposition, but the presence of hydrogen is necessary. Catalysts can aid the graphite-diamond transformation at high temperatures and pressures. Banhart and Ajayan predict that "carbon onions with compressed shells might show interesting properties such as modified electrical conductivity or a localization of electrical charge." They add that "foreign materials inside hollow graphitic particles could be subjected to extreme pressures by applying irradiation at high temperature." Michael Freemantle
