Pyrolytic synthesis of nanopowders ( English pyrolytic synthesis of nanopowders or nanopowder synthesis by pyrolysis ) is a method of producing nanopowders of metals, alloys or chemical compounds ( oxides , borides , nitrides , carbides ) by thermal decomposition of element and organometallic compounds, hydroxides , carbonyls , formates , nitrates , oxalates , amides , imides and other compounds that decompose at a certain temperature with the formation of a synthesized substance and the evolution of a gas phase.
Content
Description
A common method of pyrolytic production of nanopowders is aerosol pyrolysis.
Another option for pyrolysis is the decomposition of organometallic compounds in a shock tube, followed by the condensation of free metal atoms from supersaturated steam. The long steel pipe closed on both sides is partitioned into two unequal parts by a thin diaphragm made of film or foil. The longer part of the pipe is filled with argon under a pressure of 1000–2500 Pa with an admixture of 0.1–2.0 mol.% Organometallic compounds. The other part of the pipe is filled with helium or a mixture of helium with nitrogen until the membrane breaks. When the membrane ruptures, a shock wave arises at the front of which the temperature reaches 1000–2000 K. Shock heating of the gas leads to decomposition of the organometallic compound in a few microseconds and the formation of a highly supersaturated vapor capable of rapid condensation.
The main disadvantage of thermal decomposition is the low selectivity of the process, since the reaction product is usually a mixture of the target product and other compounds. The average particle size of the powders obtained by pyrolysis depends on the nature of the starting reagents and ranges from 50 to 300 nm .
See also
- Aerosol Pyrolysis
Sources
- Gusev A.I. Nanomaterials, nanostructures, nanotechnology. - M .: Fizmatlit, 2007 .-- 416 p.
- Gusev AI, Rempel AA Nanocrystalline Materials. - Cambridge: Cambridge International Science Publishing, 2004 .-- 351 p.