cryochemical synthesis otherwise cryochemical processing; cryoprocessing (rus. синтез, криохимический) — A set of methods to synthesise substances and materials based on low-temperature chemical processes.

Description

The most widespread of such methods are cryochemical synthesis techniques with the use of aqueous solutions. In this case, solutions, suspensions or products of chemical co-precipitation of initial solution components containing cathions of the synthesised material in a stoichiometric proportion are rapidly frozen and freeze dried in vacuum, after which thermal decomposition follows. The products of this synthesis are generally oxide powders with crystallite sizes of 40-300 nm whose degree of agglomeration depends on the choice of substances frozen in the process (solution/suspension/sludge). It is also possible to remove ice by low-temperature extraction in polar organic solvents (cryoextraction) and coprecipitation of frozen components in low temperature precipitant solution (cryoprecipitation).

When applying catalysts on porous supports it is advisable to use the cryoimpregnation method, where substrates soaked with a solution of catalytically active components undergo rapid freezing and freeze-drying. The use of low temperatures can significantly increase the homogeneity of the micro component distribution on the substrate's surface.

According to some authors, cryochemical methods also include low-temperature mechanochemical techniques, in particular, cryomilling.

Deposition of metal vapors on very cold surfaces in the presence of inert gases or organic substances is an efficient method to produce nanoparticles of metals ranging from 1 to 10 nm in size (see cryocondensation, cryochemistry).

Illustrations

Basic processes of cryochemical synthesis involving frozen aqueous solutions.
Basic processes of cryochemical synthesis involving frozen aqueous solutions.

Author

  • Shlyakhtin Oleg A.

Sources

  1. Tretyakov Yu.D., Oleynikov N.N., Shlyakhtin O. A. Cryochemical technology of advanced materials. — London: Chapman & Hall, 1997. — 319 p.
  2. Tretyakov Yu.D., Shlyakhtin O. A. Recent progress in the cryochemical synthesis of oxide materials // J. Mater. Chem. 1999. V. 9. P. 19–24.
  3. Tretyakov Yu.D. Low temperature processes in chemistry and technology (in Russian). // Sorosovskijj obrazovatel'nyjj zhurnal. 1996. №4. 45–51 pp. — www.pereplet.ru/nauka/Soros/pdf/9604_045.pdf (reference date 12.12.2011).
  4. Shabatina T. I., Sergeev G. B. Low-temperature reactions in the chemistry of nanosystems (in Russian). // Uspekhi khimii. 2003. V. 72, №7. 643–663 pp.

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