Abstracts

Novosibirsk participants

FOR THE MEETING ON THE TRANSFER OF HI-TECH KNOW-HOW:

A new high-efficiency method for producing fine particles of silica [1-4] and oxides of other elements by evaporation of solids followed by condensation has been developed and realized since 1991. Power density necessary for evaporation (up to 5000 kW/cm2) is provided by conventional ELV accelerator of the power up to 100 kW and energy 1.4 MeV with electron beam emitted to air under the atmospheric pressure used as a heat source. Fine particle production is a continuous process with the efficiency of tens of kilograms an hour. Essentially, it is as follows: evaporation of a solid by electron beam, fast cooling of vapor-air mixture with the subsequent condensation of the substance as nanoparticles, extraction of nanoparticles produced. The raw material is oxide of large-sized fractions (powder, sand, crushed stone) obtained by standard techniques, or cheap naturally occurring material, primarily, of crystalline structure. The developed method has a number of advantages. We specify the most important of them: - chemical purity, only electron beam and raw material are involved in the process, no other chemical reagents are needed; - bulk energy delivery directly to irradiation object ensures high efficiency of electric-to-heat energy conversion; - the possibility of affecting the size of the particles by varying the degree of initial vapor dilution by air, controlling electron beam power and vapor cooling rate; - under fast cooling the particles become structurally amorphous; - fine particle production by this technology is ecologically safe. With the method developed, fine particles of silica, alumina, magnesia and zirconia of the size of 50-200 nm with the specific surface of more than 100 m2/g have already been produced. Various physical-chemical studies of nanoparticles have been carried out in different scientific institutions. The investigations reveal that the particles obtained are constituents of secondary conglomerates, have certain porosity, and are structurally amorphous. The obtained fine particles can find application in many of branches of industry as fillers of composite materials, white and coloured rubbers, the principal component of unique ceramics, fillers of tooth pastes, dispersers in the production of consolidating products, thixotropy of liquids, etc. For example, nanoparticles produced by our method exhibit higher activity on sintering, and sintering temperatures are 150 K degrees lower than those of common particles; ceramics grains are of submicron size. Marketing investigations show that obtaining of nanoparticles by the method advanced can be a highly profitable production with fast recoupment of capital investments. In future the process could be realized in controlled medium (the use of vacuum, inert and other gases). This will make it possible to obtain fine particles of different chemical elements and their compounds (carbides, nitrides, etc.), as well as to produce activated fine particles by delivering hydrogen-containing compounds to evaporation zone.

REFERENCES

1. Bardakhanov, S.P.; Dandaron, G.-N.B.; Ivanchenko, A.I.; et al. (12 authors); 1992 "Amorphous silica"; Report of Sc.-Tech. Com. Center "North of Russia", Novosibirsk, 125 pp. (in Russian).
2. Lucashov, V.P.; Bardakhanov, S.P.; Salimov, R.A.; Korchagin, A.I.; Fadeev, S.N.; Lavrukhin, A.V.; 1996 "A way to obtain the ultrafine silica powder, device for its realization and ultrafine silica powder"; Russia Patent No. 2067077.
3. Bardakhanov, S.P.; 1996 "The formation of amorphous silica powder in quartz vaporization"; In: Abstracts of Conference on "Chemical and Mechanical Processes in Composite Materials and Structures", pp. 178-180, Moscow (in Russian).
4. Bardakhanov, S.P.; 1997 "The formation of fine silica powder after vaporization of quartz"; In: Abstracts of V International Conference on "Computer-Aided Design of Advanced Materials and Technologies (CADAMT-97)", pp. 88-89, Baikal Lake, Russia.

Note. Abstracts are published in author's edition

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