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Title: Pulsed microwave discharges in powder mixtures: Status, problems, and prospects

Results of experiments on the excitation of pulsed microwave discharges by gyrotron radiation (λ = 4 mm, P{sub 0} = 100–500 kW, τ = 1–10 ms) in the volumes and on the surfaces of metal-dielectric powder mixtures are presented. It is shown that there are two phases of discharge development: the spark phase, accompanied by a partial evaporation of the powder material, and the phase of a developed discharge, characterized by a plasma density of ∼10{sup 17} cm{sup –3}, high absorption, and high temperatures (∼5–10 kK) in a thin layer (∼0.1–0.2 mm) of plasma and vapor. It is demonstrated that the conductivity induced in the targets by UV radiation play an important role in the microwave absorption by powder grains. It is found that, in the course of the discharge, a conductive metal mesh forms in the powder volume as a result of metal evaporation. Reactions of high-temperature synthesis were initiated in various powder mixtures (Ti + B, Al + Fe{sub 2}O{sub 3}, Mo + B, etc.). It is shown that the reactions of high-temperature synthesis last for up to 0.1 s and are accompanied by the evaporation of powder grains and the formation of an aerosol cloud due tomore » free expansion of reactants from the sample surface. The possibility of experimentally studying the kinetics of reactions of high-temperature synthesis is demonstrated. It is noticed that microwave discharges can be used to initiate plasmachemical reactions on the surfaces of radioparent materials in active gaseous media.« less
Authors:
;  [1]
  1. Russian Academy of Sciences, Prokhorov General Physics Institute (Russian Federation)
Publication Date:
OSTI Identifier:
22472098
Resource Type:
Journal Article
Resource Relation:
Journal Name: Plasma Physics Reports; Journal Volume: 41; Journal Issue: 10; Other Information: Copyright (c) 2015 Pleiades Publishing, Ltd.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ABSORPTION; AEROSOLS; DIELECTRIC MATERIALS; ELECTRIC CONDUCTIVITY; ELECTRIC DISCHARGES; EVAPORATION; EXCITATION; FERRITES; HIGH-FREQUENCY DISCHARGES; IRON OXIDES; MICROWAVE RADIATION; PLASMA DENSITY; POWDERS; SURFACES; SYNTHESIS; THIN FILMS; ULTRAVIOLET RADIATION