Application of microwave discharge for the synthesis of TiB 2 and BN nano- and microcrystals in a mixture of Ti-B powder
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Application of Microwave Discharge for the Synthesis of TiB2 and BN Nano and Microcrystals in a Mixture of Ti–B Powders in a Nitrogen Atmosphere G. M. Batanova, N. K. Berezhetskayaa, V. D. Borzosekova, L. D. Iskhakovab, L. V. Kolika, E. M. Konchekova, A. A. Letunova, D. V. Malakhova, F. O. Milovichb, E. A. Obraztsovaa, E. D. Obraztsovaa, A. E. Petrova, K. A. Sarksyana, N. N. Skvortsovaa, V. D. Stepakhina, and N. K. Kharcheva a
Prokhorov General Physics Institute, Russian Academy of Sciences, ul. Vavilova 38, Moscow, 119991 Russia b Fiber Optics Research Center, Russian Academy of Sciences, ul. Vavilova 38, Moscow, 119333 Russia email: [email protected] Received April 8, 2013; in final form, May 16, 2013
Abstract—Synthesis of titanium diboride and boron nitride nano and microcrystals by means of a pulsed microwave discharge in a mixture of Ti–B powders in a nitrogen atmosphere is considered. For this purpose, a new type of reactor with a free surface of the powder mixture was used. The reactor design permits free expansion of the reaction products into the reactor volume and their deposition on the reactor walls. Condi tions for the synthesis of TiB2 and BN compounds were studied as functions of the energy input in the dis charge, the powder component ratio, the rate of the nitrogen flow through the reactor, and the structure and phase composition of the compounds deposited on the reactor walls. The synthesis of boron nitride and tita nium diboride in crystal structures is proven. An important role in the process of synthesis is played by the heating of the mixture due to the titanium diboride synthesis reaction, its behavior in the bulk of the reactor, and the titanium concentration in the powder mixture. It is also found that, as the number of discharges in the bulk of the reactor increases, a dust cloud forms. The luminescence of this cloud indicates that the initi ated discharge proceeds not only on the powder surface and in the powder bulk, but also in the reactor vol ume. DOI: 10.1134/S1063780X13100024
1. INTRODUCTION At present, plasmachemical technologies make it possible to synthesize new materials with unusual properties and earlier unknown structures (see, e.g., [1]). Much attention in such studies was paid to tech nologies for the formation of highly rigid TiB2 coatings and nanostructures consisting of BN hightempera ture semiconductor (see reviews [2, 3]). Interest in these technologies is motivated, first of all, by possible applications of such materials. The range of such applications is very wide: from elements of integrated circuits to the strengthening coatings of machines, instruments, and bone tissues [1]. New possibilities of the synthesis of such hightem perature compounds are offered by pulsed microwave discharges in mixtures of dielectric and metal powders [4, 5]. Microwave discharge on the surface and in the bulk of a mixture of dielectric and metal powders is characterized by a high density of charged particles (~1017 cm–3), high degree of excitation of e
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