nanowhisker (rus. нановискер) — a type of filamentary crystal (whisker) with cross sectional diameter ranging from 1 to 100 nm and length to diameter ratio >100.

Description

Whiskers are crystalline materials with distinct crystal anisotropy of properties and an almost dislocation-free structure, which makes conventional plastic strain mechanisms almost inapplicable to them and brings their strength close to the theoretical ultimate strength value of a given material. As a result, whiskers can be several dozen times stronger than regular crystals and can demonstrate considerable flexibility and corrosion resistance. Whiskers of micron scale are heavily used as reinforcing fibres to impart structural composite materials with enhanced mechanical properties. On the other hand, spontaneous formation of whiskers, for example, on surfaces of metals like zinc or tin may lead to short circuits and malfunctioning of electrical equipment.

Today we are aware of several processes that result in the development of whiskers from different materials and under various conditions. For example, silicon whiskers are usually grown using gold particles that interact with silicon at a temperature of 950ºС to form the supernatant liquid Au–Si. This is known as the vapour-liquid-solid growth mechanism. Semiconductor silicon and gallium arsenide (GaAs) whiskers with lengths as small as several nanometres are grown using molecular beam epitaxy and electron-beam evaporation techniques.

Development of oxide and hydroxide whiskers is often observed during anodic oxidation of metals in aqueous solutions. So, organised masses of ZnO-based nanowhiskers and similar one-dimensional structures may develop, in the presence of seeding agents, on substrates both in the process of hydrothermal synthesis and during hydrothermolysis of precursors in hot aqueous solutions (90–100°C) in atmospheric pressure conditions. Admittedly, the quality of the crystalline structure of whiskers grown to these techniques may be considerably inferior to the quality of products of conventional growth methods.

Fullerene-based nanowhiskers may be grown on the interface of rich fullerene solution in toluene and in some other organic solvents even in the conditions of atmospheric pressure and room temperature. This growth mechanism was named LLIP (liquid-liquid interfacial precipitation).

Nanoscale filamentary systems are often produced in the process of acid hydrolysis of some natural polymers, for example, cellulose pulp. Still, crystals grown to this technique qualify to the above definition of “nanowhisker” only provisionally, notwithstanding the fact that some authors identify them as belonging to this class.

Illustrations

Tin dioxide nanowhiskers. Authors: Alexander G. Veresov, Daniil M. Itkis, P. B. Kocherginskaya, L

Tin dioxide nanowhiskers. Authors: Alexander G. Veresov, Daniil M. Itkis, P. B. Kocherginskaya, Lomonosov Moscow State University. Quoted from Nanometer Nanotechnology Community portal, www.nanometer.ru


Authors

  • Shlyakhtin Oleg A.
  • Goldt Anastasia E.

Sources

  1. Whisker (metallurgy) // Wikipedia, the free Encyclopedia. — http://en.wikipedia.org/wiki/Whisker_(metallurgy) (reference date: 12.12.2011).
  2. Fang F., Markwitz A. Controlled fabrication of Si nanostructures by high vacuum electron beam annealing // Physica E- 41(10), 2009. P. 1853–1858.
  3. Hu X., Masuda Y., Ohji T., Kato K. Fabrication of Blanket-Like Assembled ZnO Nanowhiskers Using an Aqueous Solution // J. Am. Ceram. Soc. 2009. V. 92, №4. P. 922–926.
  4. Braun B., Dorgan J. R. Single-Step Method for the Isolation and Surface Functionalization of Cellulosic Nanowhiskers // Biomacromolecules. 2009. V. 10. P. 334–341.
  5. Miyazawa K. Synthesis and Properties of Fullerene Nanowhiskers and Fullerene Nanotubes // J. Nanosci. Nanotechnol. 2009. V. 9, №1. P. 41–50.

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