plasma chemical technique (rus. синтез нанопорошков, плазмохимический) — a chemical method to produce highly dispersed powders of nitrides, carbides, borides and oxides which consists in initiating a reaction in low temperature plasma away from equilibrium at a high rate of nucleation and a low rate of growth of nucleation centres.

Description

Plasma chemical synthesis uses a low-temperature (4000-8000 K) nitrogen, ammonia or hydrocarbon plasma, or argon arc, glow, high- or microwave discharge plasma; as a feedstock, chemical elements, their halides and other compounds are used. The characteristics of powders produced by this method depend on the feedstock used, the synthesis technology, and the type of reactor. Particles of plasma chemical powders range in size from 10 to 100-200 nm, and more. Plasma chemical synthesis provides a high rate of formation and condensation of compounds and has a fairly high performance. The main downsides of plasma chemical synthesis are a broad distribution of particle sizes at a low process selectivity, and a high content of impurities in the powder. To produce powders with low impurity contents electrodeless high-frequency and microwave plasma reactors are used.

In the first phase of plasma chemical synthesis, active reagent particles are formed, following which, as a result of quenching, the products of the reaction are separated out. By selection of quenching location and rate, powders with the desired composition, shape and size (from 10 to 100 nm) of particles can be produced. Intensive cooling inhibits the growth of particles and increases the rate of nucleation of the condensed phase.

The plasma chemical method is used to produce metal powders by means of hydrogen reduction of metal chlorides in argon arc plasma.

Author

  • Gusev Alexander I.

Sources

  1. Gusev A. I. Nanomaterials, Nanostructures, and Nanotechnologies (in Russian) // Fizmatlit, Moscow (2007) - 416 pp.
  2. Gusev A.I. Rempel A.A. Nanocrystalline Materials. - Cambridge: Cambridge International Science Publishing, 2004. - 351 p.
  3. Cvetkov Yu.V. Thermal plasma in nanotechnology. (in Russian) http://www.den-za-dnem.ru/page.php?article=208 (reference date: 31.07.2010).

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