Research On Preparation Of Tungsten Based Materials By Solution Combustion Synthesis And Their Applications

Tungsten and tungsten compounds are widely used in the fields of catalysis, electron, aerospace, national defense and military industry et al., due to their unique physicochemical properties. Solution combustion synthesis ?SCS? is a fast-growing wet-chemical method to prepare nano materials and has lots of superiorities, such as convenience, time-saving, energy efficiency, high activity of reaction products et al. On this basis, the main research contents are listed as follows:?1?The influences of fuel types and fuel ration on the reaction process, mechanism and structure, morphology, phase composition of the products were investigated. Pure WO 3 and W₁₈O₄₉ were obtained through one-step combustion process. In the case of using glycine and glycine/citric acid as fuel, W₁₈O₄₉ nanoneedle with the size of ?100 nm in diameter and ?5 ?m in length was prepared; in the case of using urea as fuel, the as-prepared WO 3 had the average size of less than 100 nm. The products in all systems could degrade the MB ?40ppm? in 50 min completely.?2?By introducing doping elements, the photocatalysis property of doped tungsten oxide prepared by SCS can be improved. The Fe-doped W₁₈O₄₉ nanopowder was prepared through SCS for the fist time, using water-soluble iron nitrate as Fe source. When doped with 0.5 wt% Fe³⁺, the powder had a better catalytic effect and could finish the degradation of MB ?40 ppm? in 30 min. The amorphous C-coated WOx nanopoder was obtained by SCS using glucose as carbon source, which could degrade the MB ?80 ppm? in 40 min and had excellent cycling stability.?3?By introducing lanthanum nitrate as lanthanum source in SCS, the tungsten oxide/lanthanum oxide composite precursor with narrow size distribution and superior mixing uniformity were fabricated by solution combustion synthesis. The tungsten nanopowders with good dispensability and excellent homogeneity, consisted of 20?30 nm particles, were obtained by reduction of the composite precursor.?4?The as-prepared W-La₂O₃ composite powders possessed high sintering activity which could be sintered via a pressureless process to more than 95% relative density at 1500 ?. Under the same sintering conditions, with the increase of the content of rare earth oxides ?0-1 wt.%?, the grain size gradually decreased. With the increase of temperature, the microhardness of La2P3-doped W alloy increased first and then decreased. When the temperature was 1500?. the microhardness reached the maximum. When the content of La₂O₃ reached 1.0% and sintering temperature was 1500?, the microhardness of W- La₂O₃ was 703 Hv_0.2.