july04_researchers.qxp RESEARCH/RESEARCHERS MRS BULLETIN/JULY 2004 433 As reported in the May 21 issue of Science (p. 1129), the researchers placed solutions of nanotubes inside a chamber containing very strong magnetic fields. Lasers illuminated the samples, and con- clusions were drawn based upon analysis of the light absorbed and emitted by the samples during polarization-dependent magneto-absorption spectroscopy. Kono said, “Our data show…that the so-called Aharonov-Bohm phase can directly affect the band structure of a solid. The Aharonov-Bohm effect has been observed in other physical systems, but this is the first case where the effect inter- feres with another fundamental solid-state theorem, that is, the Bloch theorem. This arises from the fact that nanotubes are crystals with well-defined lattice periodici- ty. I wouldn’t be surprised to see a corre- sponding effect in other tubular crystals like boron nitride nanotubes.” According to the researchers, the band- gap behavior of the nanotubes in a strong magnetic field derives from their quantum properties. Because of the material’s tubu- lar, crystalline structure, electrons are limit- ed to moving around the surface of the tube rather than in the hollow center. Kono said that this discovery may lead to experiments on one-dimensional magneto- excitons, quantum pairings that are inter- esting to researchers studying quantum computing, nonlinear optics, and quan- tum optics. αα-SiAlON Ceramics with High Transparency Obtained After Lu2O3 Addition The most widely studied SiAlON ceramics, for which the two major phases are α and β, are those stabilized with Y2O3. Oxide additions help to stabilize the α phase of the Si3N4-based solution by substituting some of the silicon and nitro- gen in the Si3N4 lattice. Further addition of a stabilizing element, usually a rare earth, equilibrates the valence difference of the α phase. The smaller the size of the ion added, the larger the temperature Figure 1. The peaks represent the amount of light emitted by semiconduct- ing carbon nanotubes through interband photoluminescence. The bottom graph depicts light-emission activity in the absence of a magnetic field. The top graph shows a significant shift of light emission peaks to lower energies taken from nanotubes inside a 45-T field. (Figure courtesy of Sasa Zaric, Rice University.) https://doi.org/10.1557/mrs2004.133 Downloaded from https://www.cambridge.org/core. Carnegie Mellon University, on 06 Apr 2021 at 02:04:52, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1557/mrs2004.133 https://www.cambridge.org/core https://www.cambridge.org/core/terms RESEARCH/RESEARCHERS MRS BULLETIN/JULY 2004 435 and composition ranges where the α phase is stable. In compositions with 100% α phase, the grain-boundary phase is reduced as all of the additives can enter into the structure. Now, by using a novel stabilizing material, Lu2O3, a team of sci- entists from the Agency of Industrial Science and Technology (AIST) and the Fine Ceramics Research Association in Nagoya, Japan, have obtained a highly dense, transparent Lu-α-SiAlON ceramic. As reported in the April issue of the Journal of the American Ceramic Society (p. 714), M.I. Jones and K. Hirao of AIST, H. Hyuga of the Fine Ceramics Research Association, and colleagues hot-pressed a mixture of Si3N4, Al2O3, AlN, and Lu2O3 at 1950°C and 40 MPa for 2 h in a 0.9 MPa nitrogen atmosphere. X-ray diffraction patterns of this material showed that only α-SiAlON was present. Both scanning and transmission electron microscopy observa- tions revealed a fully dense, uniform microstructure of equiaxed grains, with a grain size of ~1 µm and with little or no grain-boundary phase present at triple points. Vickers hardness measurements using 98 N load gave results above 19 GPa, and indentation fracture using 98 N load gave a fracture toughness of ~2.5 MPa m1/2. Four-point bend tests with inner and outer spans of 10 mm and 30 mm, respectively, and a crosshead speed of 0.5 mm/min gave a bending strength of 400 MPa. Optical transmission measurements using spectrophotometry in the wave- length range of 350–800 nm were per- formed on 0.5-mm-thick samples. At 350 nm, transmission was ~35%, increasing with increasing wavelength. At ~500 nm, transmission was more than 60%, and for wavelengths larger than 600 nm, trans- mission was ~70%. Similar measurements reported in the literature on β-SiAlON ceramics gave ~40% transmission maximum at ~4.5 µm wavelength, with low transmission in the visible region. The investigators attribute the high transparency of Lu-α-SiAlON to the lack of grain-boundary phases, lack of porosity, and the small uniform grain size. The investigators said that they will now study the mechanical properties of this material, which are expected to be better than the more commonly studied Y-stabilized SiAlON, at high temperatures. SIARI SOSA Nanostructured Biosensors Produced by Nanosphere Lithography Biosensors rely on the principle of spe- cific interactions between the sensor sup- port and the biomolecule targeted. Thus, high control over the sensor-surface shape and functionality at the nanoscale is needed. Optical lithography can be used to generate patterned surfaces, but becomes complicated for feature sizes below 200 nm because of diffraction lim- its. Nanosphere lithography is an alterna- tive method capable of producing nano- topography over large surface areas, as explained by A. Valsesia and a team of researchers at the Institute for Health and Consumer Protection, Ispra, Italy. As reported in Nano Letters (Web release date, May 8), the researchers produced polymeric nanoislands with biospecific chemical functionalities, combining plas- ma deposition and etching techniques with colloidal particle masking. A polymer film of acrylic acid (PAA) was deposited on silicon wafers by plasma- enhanced chemical vapor deposition. The substrate was later covered by a mono- layer of polystyrene particles, with an For more information, see http://advertisers.mrs.org https://doi.org/10.1557/mrs2004.133 Downloaded from https://www.cambridge.org/core. Carnegie Mellon University, on 06 Apr 2021 at 02:04:52, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1557/mrs2004.133 https://www.cambridge.org/core https://www.cambridge.org/core/terms For more information, see http://advertisers.mrs.org https://doi.org/10.1557/mrs2004.133 Downloaded from https://www.cambridge.org/core. Carnegie Mellon University, on 06 Apr 2021 at 02:04:52, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1557/mrs2004.133 https://www.cambridge.org/core https://www.cambridge.org/core/terms RESEARCH/RESEARCHERS 438 MRS BULLETIN/JULY 2004 The Franklin Institute has announced award recipients for 2004, including: Roger Bacon, Amoco Corporation and Union Carbide, retired, who received the Benjamin Franklin Medal in Mechanical Engineering for his fun- damental research on the production of graphite whiskers and the determination of their microstructure and properties, for his pioneering development efforts in the production of the world’s first con- tinuously processed carbon fibers and the world’s first high modulus, high- strength carbon fibers using rayon pre- cursors, and for his contributions to the development of carbon fibers from alter- native starting materials; Robert B. Meyer, Brandeis University, who received the Benjamin Franklin Medal in Physics for his creative synthe- sis of theory and experiment demon- strating that tilted, layered liquid-crystal phases of chiral molecules are ferroelec- tric, thus launching both fundamental scientific advancement in the field of soft condensed matter physics and in the development of liquid-crystal displays that meet the demands of current tech- nology; and Robert E. Newnham, The Pennsyl- vania State University, who received the Benjamin Franklin Medal in Electrical Engineering for his invention of multi- phase piezoelectric transducers and their spatial architecture, which has revolu- tionized the field of acoustic imaging. The Presidential Early Career Awards for Scientists and Engineers have been given to 57 researchers, including the following MRS members: Susmita Bose (Washington State University); Christine Orme (Lawrence Liver- more National Laboratory); Michelle L. Pantoya (Texas Tech University); Bridget Rogers (Vanderbilt Uni- versity); and Gregory Neil Tew (University of Massachusetts). The Institute for Scientific Information (Philadelphia, Pa.) has identified the top 10 most cited materials scientists for the period of January 1993–October 2003, including MRS members: Anthony G. Evans (University of California—Santa Barbara); Akihisa Inoue (Tohoku University, Japan); Terry Langdon (University of Southern California); Galen D. Stucky (University of California—Santa Barbara); and Ruslan Z. Valiev (Ufa State Aviation Technical University—Russia). The International Centre for Diffraction Data has selected six recipients for the 2004 Ludo Frevel Crystallography Scholarship Program: Geoffrey Kwai-Wai Kong, University of Melbourne/St.Vincent’s Institute of Medical Research, Australia, for explo- ration into “Crystallographic Studies of the Amyloid Precursor Protein (AAP)”; Chong Lim, University of Illinois at Urbana-Champaign, Urbana for re- search concerning “Reaction Path and Crystallography of CoSi2 Formation on Si(001) by Reactive Deposition Epitaxy”; Andrew Locock, University of Notre Dame, for “Crystal Structure and Synchrotron Radiation Study of Uranyl Oxysalts of Phosphate and Arsenate— Implications for Remediation”; Robin T. Macaluso, Louisiana State University, for research involving “X-ray and Neutron Diffraction Studies for Understanding Geometrically Frustrated Systems”; Petra Simoncic, University of Bern, Switzerland, for studies focusing on “Defect Structure of the Natural and Synthetic Zeolites Mordenite—Structure Characterization of Dye Modified, Synthetic Mordenite”; and Kimberly Tait, University of Arizona, for “Investigations into the Stability, Morphology and the Crystal Structure of the Coexistence of Structure I and Structure II Methane-ethane Clathrate Hydrates—Occurrence and Geological Implications.” tion in recognition of his invention of the practical light-emitting diode in 1962. Charles Lieber, Mark Hyman Jr. Professor of Chemistry at Harvard University, has been elected into the National Academy of Sciences. Paras Prasad, SUNY Distinguished Professor in the Department of Chem- istry in the University at Buffalo’s College of Arts and Sciences and Samuel P. Capen Chair, has been awarded the 2004 Morley Medal by the Cleveland section of the American Chemical Society. Gary L. Smith, a staff scientist at the Department of Energy’s Pacific Northwest National Laboratory, has been appointed chair of the ASTM International Com- mittee C26 on Nuclear Fuel Cycle. This prominent and influential committee develops standards important to work done on the nuclear fuel cycle, including spent nuclear fuel, waste materials, and repository waste packaging and storage. Smith also was honored with the Harlan J. Anderson Award, which is presented annually to a member of C26 who has made outstanding contributions toward the successful operation of the committee. Robert L. Snyder has been named Distinguished Fellow of the International Centre for Diffraction Data (ICDD). For more information, contact: Anita B. Miller Materials Research Society 506 Keystone Drive, Warrendale, PA 15086 Tel: 724-779-3004, X 551; Fax: 724-779-8313; amiller@mrs.org www.mrs.org/publications/bulletin https://doi.org/10.1557/mrs2004.133 Downloaded from https://www.cambridge.org/core. Carnegie Mellon University, on 06 Apr 2021 at 02:04:52, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1557/mrs2004.133 https://www.cambridge.org/core https://www.cambridge.org/core/terms