Coiled whisker

Figure 2.2. (a) Coiled whisker of rutile in cabochon-cut quartz (courtesy of E. A. Jobbins). (b) Crysotile crystals resembling stacked ice cream cones. (Transmission electron microphotograph taken by K. Yada.) (c) Pyrolusite polycrystalline dendritic pattern formed along a bedding plane of sedimentary rock. 

The modified diimide decomposition process uses gas mixtures of Si2Cl2, NH3, and H2. Amorphous whiskers are deposited on quartz or graphite substrates coated with a metal catalyst. The uniqueness of this method is the ability to form whiskers of a special shape, e.g., a coil. Whiskers with the best coil regularity have been obtained at 1200°C on a graphite substrate with Fe as the catalyst. All whiskers have a very smooth surface,... 

H. Iwanaga, M. Kawaguchi and S. Motojima. Growth mechanisms and properties of coiled whiskers of silicon nitride and carbon. J. J. Appl. Phys., 32 [1], 105-115 (1993). 

Crystals formed under small driving force conditions (see Section 3.2) in a dilute ambient phase, such as the vapor phase or solution phase, will generally exhibit polyhedral forms, irrespective of their size. Even crystals of micrometer size, such as clay minerals, show polyhedral forms. However, there are crystals that show elongated needle forms that resemble whiskers, coils, hollow tubes, and even ice cream cones (see Figs. 2.2 (a), (b)) others exhibit tree-like polycrystalline aggregates of dendrites (see Fig. 2.2 (c)). 

Whiskers/Platelets/Nano-Belts/Nano-Tubes/Coiled Fibres... 

Preformed nanofillers (and impact modifiers, as well) will be offered in masterbatch forms and diluted with suitable resins upon request. Further on, great efforts will be devoted to generate novel nanofillers, like graphite sheets, CNT-clay hybrids, coiled CNTs. The potential of nanofillers of natural origin, like cellulose whiskers, will be checked in various polymers, including rubbers. In respect of nanofillers, the RfeD work will focus on their possible functional properties ( smart nanoparticles). 

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