Advanced Materials

Cover image for Advanced Materials

October, 1998

Volume 10, Issue 15

Pages 1157–1280

    1. Novel Nanocarbons—Structure, Properties, and Potential Applications (pages 1157–1171)

      Shekhar Subramoney

      Version of Record online: 26 JAN 1999 | DOI: 10.1002/(SICI)1521-4095(199810)10:15<1157::AID-ADMA1157>3.0.CO;2-N

      The discovery of novel carbon-based nanoparticles was spurred by the discovery of the buckminsterfullerene molecule in 1985. In this review multi- and single-walled nanotubes (see Figure for a comical representation of nanotube connectors and tripods), carbon onions, and carbon-encapsulated nanoparticles are covered. The interrelationships between the various nanostructures the traditional forms of carbon are also explored.

    2. Nanoparticles: Uses and Relationships to Molecular Cluster Compounds (pages 1173–1184)

      Norman Herron and David L. Thorn

      Version of Record online: 26 JAN 1999 | DOI: 10.1002/(SICI)1521-4095(199810)10:15<1173::AID-ADMA1173>3.0.CO;2-6

      The relationship between nanometer-sized particles and inorganic molecular cluster compounds is examined and some implications for the synthesis and chemistry of nanoclusters are considered in this review. The authors also present examples of applications of nanoparticles: Semiconductor nanoparticles and their polymer composites as well as other polymer/inorganic nanocomposites are covered in addition to a survey on nanophase materials as catalysts. Zeolites and the MCM-41 family are also reviewed with respect to their ability to form new materials with fascinating optical and electronic properties.

    3. Nylons from Nature: Synthetic Analogs to Spider Silk (pages 1185–1195)

      John P. O'Brien, Stephen R. Fahnestock, Yves Termonia and KennCorwin H. Gardner

      Version of Record online: 26 JAN 1999 | DOI: 10.1002/(SICI)1521-4095(199810)10:15<1185::AID-ADMA1185>3.0.CO;2-T

      The biosynthesis of structural materials in the form of fibers and biocomposites is unsurpassed—complex multicomponent composite structures can be made through seamless integration of polymer synthesis, mineralization, and self-assembly. The results of multidisciplinary research to understand structure/property relationships in natural silk and to prepare synthetic analogs to spider draglines (see Figure for a schematic representation) are reviewed.

    4. Surface-Fluorinated Coatings (pages 1197–1205)

      Doug Anton

      Version of Record online: 26 JAN 1999 | DOI: 10.1002/(SICI)1521-4095(199810)10:15<1197::AID-ADMA1197>3.0.CO;2-F

      Teflon (PTFE) and other fluoropolymers have many properties that are desirable in coatings. However, due to their poor solubility it can be very difficult to formulate coatings containing fluoropolymers, especially if low total fluorine levels are desired. Here the author reviews several methods to modify existing coatings by surface fluorination to create systems with the bulk properties of the existing coating, but with a very low energy, repellant surface and low total fluorine levels. This is mainly achieved by designing fluorinated molecules that stratify to the surface in the wet coating.

    5. Toughened Nylons: A Fracture Mechanics Investigation (pages 1207–1211)

      Donald D. Huang, Barbara A. Wood and Edmund A. Flexman

      Version of Record online: 26 JAN 1999 | DOI: 10.1002/(SICI)1521-4095(199810)10:15<1207::AID-ADMA1207>3.0.CO;2-R

      The application of fracture mechanics to polymer systems is an emerging field. Here the authors report the investigation of a ductile/brittle temperature transition—based on Izod tests—in toughened nylon blends by characterizing both fracture toughness and yield strength. The Figure shows a transmission electron microscopy (TEM) image of a deformed region of toughened amorphous nylon taken from a fracture toughness test.

    6. Soluble Perfluoropolymers (pages 1211–1214)

      Colin Anolick, Jeffrey A. Hrivnak and Robert C. Wheland

      Version of Record online: 26 JAN 1999 | DOI: 10.1002/(SICI)1521-4095(199810)10:15<1211::AID-ADMA1211>3.0.CO;2-O

      Soluble perfluoropolymers, readily coatable as thin films, have recently appeared on the market for premium applications such as for pellicles and fiber optic coatings. These polymers (e.g., Teflon AF and Cytop) are inherently expensive because of multistep monomer preparations, for example, of perfluorodimethyldioxole in the case of Teflon AF. Here the authors report how less expensive monomers can be used to achieve similar solubility, coatability, and optical properties. These novel polymers also have a significantly lower glass transition temperature as compared to Teflon AF and Cytop.

    7. Polymeric Dispersants in Ink Jet Technology (pages 1215–1218)

      Harry J. Spinelli

      Version of Record online: 26 JAN 1999 | DOI: 10.1002/(SICI)1521-4095(199810)10:15<1215::AID-ADMA1215>3.0.CO;2-0

      The introduction of pigmented inks is one reason for the rapid growth of ink jet technology over the last 15 years. Essential for the success of these pigmented inks has been the development of polymeric dispersants to provide a balance of dispersion quality, stability, and pen performance in ink jet devices. The Figure illustrates the ionic and steric stabilization of an aqueous pigment dispersion by a structured dispersant.

    8. Optical Photopolymers: Design and Applications (pages 1219–1224)

      T. John Trout, John J. Schmieg, William J. Gambogi and Andrew M. Weber

      Version of Record online: 26 JAN 1999 | DOI: 10.1002/(SICI)1521-4095(199810)10:15<1219::AID-ADMA1219>3.0.CO;2-D

      The combination of precise optically recorded patterns and changes in the physical properties upon light-induced polymerization leads to the unique function and utility of photopolymers in enabling improvements in the display of information or data storage. The authors focus on the newest photopolymers under development at DuPont—optical photopolymers—and their commercialization. A description of the materials is followed by a discussion of several applications under development, e.g., laser eye protection filters, liquid crystal display systems, optical interconnection, and holographic data storage.

    9. Tailored Fiber Cross Sections (pages 1225–1227)

      Barry Rubin

      Version of Record online: 26 JAN 1999 | DOI: 10.1002/(SICI)1521-4095(199810)10:15<1225::AID-ADMA1225>3.0.CO;2-Z

      The cross-sectional shape and size of individual fibers have a major impact on the appearance of carpets or fabrics. A mathematical model for the interaction of light with fiber cross-sectional geometry has been developed and applied for the development of new products. The Figure represents the cross section of a new nylon carpet. The selection of this shape was based in part on model predictions.

    10. Polyimide Films (pages 1229–1232)

      John A. Kreuz and James R. Edman

      Version of Record online: 26 JAN 1999 | DOI: 10.1002/(SICI)1521-4095(199810)10:15<1229::AID-ADMA1229>3.0.CO;2-B

      Tailored surface and bulk properties of polyimide films have resulted from new technology demands, e.g., the request for stronger, more dimensionally stable films with lower moisture content. The technology trends parallel the demands of the marketplace as well as the demands of manufacturing. The authors present the changes both in the processing methods and in the backbone of the polyimides—for example, higher molecular weight, new substituents, and new ring formations—that led to improvements to the electrical, optical, and chemical properties of the polyimide films.

    11. Non-woven Aramid Reinforcement for Printed Wiring Boards (pages 1233–1237)

      Gary L. Hendren, Birol Kirayoglu, David J. Powell and Michael Weinhold

      Version of Record online: 26 JAN 1999 | DOI: 10.1002/(SICI)1521-4095(199810)10:15<1233::AID-ADMA1233>3.0.CO;2-8

      Modern integrated circuit packaging demands new technologies for printed wiring boards (PWBs). Non-woven aramid reinforcement is used for PWBs with a low coefficient of thermal expansion (see Figure for a representation of a non-woven aramid part). Their selection should be based on an understanding of the physical, mechanical, and electrical properties of non-woven aramid laminates and the fabrication techniques of PWBs.

    12. Fluorocarbon Process Gases in Microelectronics (pages 1239–1242)

      Charles C. Allgood

      Version of Record online: 26 JAN 1999 | DOI: 10.1002/(SICI)1521-4095(199810)10:15<1239::AID-ADMA1239>3.0.CO;2-9

      New gases for new chips—only one result of the drive toward higher performance and lower costs in the highly competitive semiconductor industry. New multistep thin-film manufacturing processes have been developed that critically depend on ultrahigh-purity fluorocarbon gases to deliver the highest levels of process performance and end-product reliability. The author concentrates on the discussion of the development of such new high-purity process gases, which are expected to play an important role in future generations of thin-film manufacturing technology.

    13. Inorganic/Organic Hybrid Materials (pages 1243–1248)

      Kenneth G. Sharp

      Version of Record online: 26 JAN 1999 | DOI: 10.1002/(SICI)1521-4095(199810)10:15<1243::AID-ADMA1243>3.0.CO;2-6

      Hybrid inorganic/organic materials show a remarkable range of materials behaviors. Here the author describes new chemistry for forming silicate networks with formic acid and in completely fluorinated solvents. The results of the surprising combination of grossly dissimilar materials such as fluoropolymers and polysilicates and the substantial toughness of glassy star gels (the Figure shows a star gel molecular precursor) are also discussed.

    14. Thin-Film High-Temperature Superconductors for Advanced Communications and Electronics (pages 1249–1254)

      Alan Lauder, Kirsten E. Myers and Dean W. Face

      Version of Record online: 26 JAN 1999 | DOI: 10.1002/(SICI)1521-4095(199810)10:15<1249::AID-ADMA1249>3.0.CO;2-7

      High-quality films of several superconducting materials are finding increasing applications. Thin films of materials such as YBa2Cu3O7 (YBCO), Tl2Ba2CaCu2O8 (TBCCO), and (Tl,Pb)Sr2CaCu2O7 (TPSCCO) can be made by a variety of methods, including sputtering and pulsed laser deposition. Magnetron sputtering is now used exclusively by the authors, because it is reproducible, robust, amenable to scale-up, and practised throughout the semiconductor industry. Additionally, sputtered films have proven to have desirable properties in terms of microstructure, surface resistance, and power handling.

    15. Towards the Sulfuric Acid of Solids (pages 1255–1257)

      Mark A. Harmer, William E. Farneth and Qun Sun

      Version of Record online: 26 JAN 1999 | DOI: 10.1002/(SICI)1521-4095(199810)10:15<1255::AID-ADMA1255>3.0.CO;2-T

      Solid acids offer a simple and more benign alternative to traditional acid-catalyzed chemical processes. Ways in which this opportunity is being addressed through the synthesis and characterization of new solid acids incorporating perfluorosulfonic acid groups as proton donors are described. The Figure represents a perfluorosulfonic acid, which is covalently linked to a porous silica surface at a density of ca. 0.05–0.5 nm–2.

    16. Direct Probing of Gas Molecule–Solid Catalyst Interactions on the Atomic Scale (pages 1259–1263)

      Pratibha L. Gai

      Version of Record online: 26 JAN 1999 | DOI: 10.1002/(SICI)1521-4095(199810)10:15<1259::AID-ADMA1259>3.0.CO;2-5

      Direct imaging of catalysts in action is possible using the in situ environmental cell high-resolution electron microscope described here. In contrast to traditional techniques, it allows gas molecule–solid catalyst surface interactions to be probed directly at the atomic level. It is demonstrated that such studies, coupled with reaction chemistry, provide a unique route to access the dynamic atomic structural geometry and catalyst mechanisms—essential for a definitive understanding of technological processes and rational approaches to catalyst development.

    17. Engineered Particle Surfaces (pages 1264–1270)

      Reg Davies, George A. Schurr, Paul Meenan, Ralph D. Nelson, Horacio E. Bergna, Carol A. S. Brevett and Richard H. Goldbaum

      Version of Record online: 26 JAN 1999 | DOI: 10.1002/(SICI)1521-4095(199810)10:15<1264::AID-ADMA1264>3.0.CO;2-X

      Particle surface engineering is the term used to describe the technology that allows the design and manufacture of particles with the desired surface properties. Here the power of this technology is discussed and illustrated. The Figure shows MicroFree powder, a DuPont product containing antimicrobial ingredients that prevent the growth of the bacteria and molds responsible for unpleasant odors and discoloration.

    18. Computation of Light Scattering by Anisotropic Spheres of Rutile Titania (pages 1271–1276)

      Erik S. Thiele and Roger H. French

      Version of Record online: 26 JAN 1999 | DOI: 10.1002/(SICI)1521-4095(199810)10:15<1271::AID-ADMA1271>3.0.CO;2-C

      Rutile titania is the most widely used white pigment in the worldwide marketplace for coatings, plastics, and paper. A fundamental goal, both of consumers and manufacturers, is to maximize the light scattering efficiency of the pigment. This requires identifying and subsequently controlling the factors that affect the light scattering. In the study described here, a finite element method that produces rigorous full-field solutions to Maxwell's equations is applied to the problem of light scattering by anisotropic spheres of rutile titania.

    19. High-Resolution and Low-Voltage SEM Imaging and Chemical Microanalysis (pages 1277–1280)

      Edward D. Boyes

      Version of Record online: 26 JAN 1999 | DOI: 10.1002/(SICI)1521-4095(199810)10:15<1277::AID-ADMA1277>3.0.CO;2-D

      Simple direct surface imaging of bulk samples at a resolution of 0.5 nm or better is possible in the scanning electron microscope (SEM) described here, which integrates a high-brightness field emission gun and a high-resolution condenser-objective immersion lens. The Figure shows high-resolution surface details of a carbon fiber, which could only be visualized accurately at very low voltages (<1 kV).