パラタングステン酸アンモニウムの熱分解における超微粒タングステン酸化物の生成機構

概要

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The determing factor of tungsten oxide particle size during thermal decomposition of monoclinic ammonium paratungstate (APT) has been studied. APT was decomposed by thermobalance in nitrogen, oxygen, air and mixture of ammonia and nitrogen atmosphere. Formation mechanism of ultrafine tungsten oxide particle was investigated using X-ray diffraction analysis, scanning electron microscopy and specific surface area measurement. The relationship of particle size between hexagonal ammonium tungsten bronze (ATB) and tungsten oxide was discussed. Formation of ATB was controlled by parameters such as heating rate, sample mass and kind of atomosphere. Particle size of tungsten oxide was affected with amount of ATB formed in the intermediate, that is, particle size was very fine when ATB was formed in large quantities. Ultarfine individual particle of tungsten oxide was formed by a decomposing reaction from ATB to W0<SUB>3</SUB> or WO<SUB>2.9</SUB>, and grain growth of its particle took place at temperatures above 873 K.
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