Electron Microscopic Study on the Progress of Reduction of WO<SUB>3</SUB> Single Crystal (Electron Microscopic Studies on the Progress of Reduction of Metal Oxides by Hydrogen. (3))

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  • 酸化タングステン単結晶の還元過程の電子顕微鏡による研究
  • サンカ タングステンタンケッショウ ノ カンゲン カテイ ノ デンシ ケンビキョウ ニ ヨル ケンキュウ

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Abstract

WO3 single crystals were mounted on the sharply pointed end of a platinum wire and exposed to heated hydrogen gas at one atmospheric pressure in the specimen-treating adaptor for the electronmicroscope, previously devised by the author and others, and the morphological and chemical changes at a certain chosen region of the specimen were followed by taking micrographs and selected-area-diffraction patterns. In the earier stages of reduction, WO2 particles and β-W particles were formed in the oxide crystal, the latter being completely transformed into α-W particles when heated above 700°. The pattern of a arangement of these tungsten particles can differ markedly as one passes from one oxide crystal to another. α-W particles sufficiently grown always gave rise to elongation of diffraction spots, and also often to extinction contours, though diffuse, in the micrograph. Based on these observations, an attempt was made to picture the way of formation and growth of W-particles.

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