NEWS OF THE WEEK
NANOTUBE OXIDE COMPOSITES New materials could have catalysis uses discharge technique to synA team of researchers thesize gram quantities of the / % working in France has Metal oxide coats, fills carbon nanotube nanotubes. X J L created metal oxide Ajayan and lijima subsefibers with nanometer-sized quently showed, in 1993, that diameters using carbon nanothe caps of hollow carbon tubes as removable templates, nanotubes can be opened and opening up the possibility for the nanotubes converted into new types of nanostructured nanocomposite fibers by heatmaterials. Metal oxides with ing the material in the presnanostructures may be useful ence of air and lead. Under in industrial applications such these conditions, molten lead as catalysis, where maximizis drawn into the tubes. Last ing the surface area of the acyear, Malcolm L. H. Green, a tive material is important. professor of inorganic chemisThe group, led by materials try, and coworkers at Oxford scientist Pulickel M. Ajayan, University, England, reported coated carbon nanotubes with the use of nitric acid to open thin films of vanadium pentthe carbon nanotubes, which oxide (V205). The carbon can they then filled with crystalbe partially removed by oxiline oxides of nickel, cobalt, dation, leaving behind vanaand iron. dium pentoxide fibers [NaOpen nanotube ture, 375, 564 (1995)]. In esThe ability to coat the unresence, says Ajayan, the carbon active graphite nanotube surnanotube acts as "a degradfaces with thin films of vanaable template" that could be dium pentoxide increases the used "to make new kinds of versatility of the nanotubes, t Coating nanocomposites and ceramic according to the French team. Lower magnification image (top) reveals uniform vanananostructures." "We believe this is a signifidium pentoxide coating on nanotube; higher magnificacant result for future R&D," The researchers prepare the tion image (middle) shows coating on upper and lower says Ajayan. "Vanadium oxnanotube-oxide composites parts of tube (red arrows) and filled core of tube (allwhite arrows); molten metal oxide fills and coats tube ides are catalytically active by annealing a mixture of by capillary action (bottom). substances. There is also a big partially oxidized nanotubes industrial effort to fabricate and vanadium pentoxide vanadium oxide thin films powder in air above the melting point of the oxide. Surface-tension films of vanadium pentoxide using cap- because they are functional ceramics effects induce the growth of uniformly illarity. This essentially exposes a new with uses in a range of areas—batteries thin films of the oxide on the outside of surface that is chemically active and that for example." the nanotubes. The oxide also fills the in- can be further used to build chemical The oxide film on the nanocomposites ternal cavities and the spaces between complexes by synthetic routes." is "sometimes only a monolayer thick," the concentric shells of the nanotubes. Carbon nanotubes are hollow, nano- according to Ajayan and his coworkers. The new composites were developed meter-wide tubes of concentric graphitic They observed the black annealed mixat the National Center for Scientific Re- carbon capped by fullerene-like hemi- ture by transmission electron microscosearch (CNRS), University of Paris- spheres. They were first reported in 1991 py and scanning transmission electron South, by Ajayan, doctoral students by Sumio lijima of NEC Corp. in Tsuku- microscopy. Resultant images reveal that Odile Stephan and Philipp Redlich, and ba, Japan. lijima prepared the nanotubes the coatings on isolated nanotubes are Christian Colliex, a professor at the uni- using an arc-discharge evaporation uniform in thickness and rarely thicker versity and director of research at CNRS. method similar to that used for fullerene than 1 nm. Continuous cylindrical films The result is unique, Ajayan tells synthesis. In 1992, Thomas W. Ebbesen extend for up to a few hundred nanoC&EN: "We have been able to coat the and Ajayan, working at the NEC lab, re- meters, although they do not always covnanotube surfaces with extremely thin ported the use of a variation of the arc- er the whole nanotube surface. 6
JUNE 19,1995 C&EN
Carbon nanotubes oxidize below the melting point of vanadium pentoxide. The French team was able to remove most of the graphite from the nanocomposite by heating it in air below this temperature. The researchers showed by electron energy loss spectroscopy that larger oxide structures left in the resulting "twice-oxidized" sample have hollow morphology with no trace of carbon. These structures initially covered unseparated nanotube bundles. "Our next step is to improve the efficiency of the oxide coating on the nanotubes," says Ajayan, using perhaps different temperatures or time scales, or chemical methods. "At the moment, we just melt the oxide and the tubes together. Using vanadium pentoxide precursors and some solution chemistry might be a much more efficient method of forming the films." Michael Freemantle
Monsanto ponders sale of styrenics business In the next few months, Monsanto will decide whether to put its long-time, multi-million-dollar styrenics plastics business on the block. Sale of the business would remove Monsanto, currently the third largest supplier of styrenics worldwide, from a market in which it has participated for nearly half a century. The sale would also remove the company almost entirely from the plastics field. The business accounts for an estimated 7% of Monsanto's $8.3 billion in annual sales. The top two styrenics suppliers are Taiwan's Chei-Mei Corp. and GE Plastics, a subsidiary of General Electric. "Although we are pleased with the progress the acrylonitrile-butadienestyrene (ABS) and styrene-acrylonitrile (SAN) business has made," says Robert G. Potter, Monsanto7s executive vice president, "this business may be more valuable from a strategic point of view to another company." Another company may find possible synergies with Monsanto 7 s styrenic polymers business in terms of raw materials, processes, end-use products, and technologies. "Our business includes expertise for a potential buyer in polymer structure understanding and
diverse polymerization processes, which enable us to tailor products to specific customer requirements," says Potter. Monsanto7s styrenics business has been at a competitive disadvantage because the company no longer produces styrène, a key raw material for the copolymers. Monsanto exited styrene production almost 10 years ago when it sold its business to Houston-based Sterling Chemicals. However, Monsanto does produce its own acrylonitrile in Chocolate Bayou, Texas; all of that capacity is consumed captively, mainly in the production of ABS and SAN resins and acrylic fiber. Monsanto says its interest in exploring a sale is consistent with the company's policy to regularly examine opportunities to grow and strengthen its global business portfolio. The sale would also fit with Monsanto's desire to sell assets that do not cover the cost of capital, says Paul K. Raman, a vice president with New York City-based investment banking firm SBC Warburg. And demand for ABS, the star of Monsanto's styrenics portfolio, has been dampened by competition from other, new, polymer grades. For instance, new modified grades of polystyrene have been making inroads into end-use markets, such as the appliance and floppy disk markets, traditionally dominated by ABS. And metallocene catalyst technology has enabled the production of new grades of polyolefins that are poised to attack the styrenic polymers market. Raman thinks Monsanto should be able to sell its business, which he estimates to have revenues of $550 million to $600 million and operating income of about $55 million to $60 million. He speculates that possible suitors may be the Huntsman Group, which recently bought Monsanto's linear alkylbenzene business and makes SAN in a joint venture with GE, or Germany's Bayer, a producer of ABS. Monsanto's major manufacturing sites include Antwerp, Belgium; LaSalle, Quebec; Addyston, Ohio; Muscatine, Iowa; and Map ta Phut, Thailand, a joint-venture location that will start up next year. Technology locations include Louvain-La-Neuve, Belgium; Detroit, Michigan; and Springfield, Mass. Monsanto's styrenics plastic unit employs about 1,200 people worldwide. Susan Ainsworth
Appeal hearings begin on misconduct charge The final scenes in a nine-year drama of scientific misconduct got under way last week in Washington, D.C., as federal government lawyers began presenting their case against Thereza Imanishi-Kari, the Tufts University immunologist accused of falsifying research she reported in a 1986 paper. Among the dozens of witnesses expected to be called in the hearing requested by Imanishi-Kari is Nobel Laureate David Baltimore, one of the coauthors of the controversial publication. Imanishi-Kari asserts she is innocent of any wrongdoing. She asked for the hearing after the Department of Health & Human Services7 Office of Research Integrity (ORI) concluded late last year that she was guilty of fabricating and falsifying critical results (C&EN, Dec. 5, 1994, page 8). If ORI's finding is upheld, Imanishi-Kari would be barred from receiving federal grant or contract money for 10 years. "The evidence will show that this is one of the more egregious cases of scientific misconduct ever encountered by ORI/ 7 said ORI attorney Marcus H. Christ Jr. in his opening statement. Not only did Imanishi-Kari misrepresent her research in the publication, he said, but "she then deliberately set out to fabricate and falsify additional data to support the claims in the paper/ 7
Imanishi-Καή: requested appeal heanngs JUNE 19,1995 C&EN
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