APT煅烧工艺对WO2.72晶体生长机制的影响

利用工业回转炉,在不同温度和保温时间下煅烧仲钨酸铵(APT)粉末制备WO_2.72粉末。结果表明,在煅烧温度高于800℃时可获得单相WO_2.72粉末。煅烧温度强烈影响WO_2.72晶粒的形貌和尺寸,随温度升高至大约770~800℃,其形貌由细长针状晶粒向短粗棒状晶粒转变。对于细长针状晶粒,随温度升高,其直径微量增大,长度急剧增大,生长机制为单晶晶粒形核,向APT颗粒内部生长,伴随有APT颗粒表面微量的WOx·nH₂O气相沉积,然后还原长大;对于短粗棒状晶粒,随温度升高,结果相反,其生长机制是通过多个晶粒成束形核,共同向APT颗粒内部生长成棒状晶粒。随保温时间延长,WO_2.72棒晶的形貌无明显变化,其直径和长度微量增大。

Effect of calcining process of APT on growth mechanisms of WO2.72 crystals

WO_2.72 powder was prepared by calcining APT powder at various temperatures and holding time in an industrial rotary furnace.The results indicate that the single-phase WO_2.72 powder can be obtained above 800℃.The morphology and size of WO_2.72 grains are strongly affected by calcining temperature,and the morphology changes from long-needle-like to short coarse rod-like at about 770?800℃with increasing temperature.For long needle-like grains,with increasing temperature,their diameters increase slightly,but their lengths increase sharply.The growth mechanism is that monocrystalline grains nucleate grow into APT particles,accompanying by a small amount of WOx·nH₂O vapor deposition-re-reduction on the surface of APT particles.For short coarse rod-like grains,with increasing temperature,an opposite result is obtained.The growth mechanism is that the multiple grains clustery nucleate and grow into APT particles to form rod-like grains.With increasing holding time,there is no obvious change in the morphology of WO_2.72 grains,and their diameter and length increase slightly.