| 介孔空心球状WC微球结构与晶相形成机理 | |
| Structure and Crystal Phase Formation Mechanisms of Hollow Global Tungsten Carbide (WC) Microsphere with Mesoporosity | |
| 摘要: 采用喷雾干燥微球化处理-气固反应法制备了介孔空心球状WC微球，应用扫描电子显微镜(SEM)对微球的形貌变化进行了表征。结果表明，介孔空心球状结构是逐步形成的。其中，空心球状结构形成于前驱体微球化处理过程中，介孔结构形成于空心微球还原碳化过程中。在与样品制备工艺条件相同的情况下，采用原位X射线衍射技术(in situ XRD)对样品的晶相演变规律进行了监测。结果表明，样品在CO/CO2气氛中进行还原碳化时，当温度缓慢而连续上升到750 ℃时，其晶相变化遵循AMT → WO3 → WO2 → W2C → WC规律;当采用“阶跃式”升温，即温度缓慢而连续上升到400 ℃，然后再快速上升到750 ℃，并在750 ℃下进行还原碳化时，其晶相变化规律为AMT → WO3 → WO2 → WC。这说明，样品的晶相演变不仅与还原碳化温度和时间有关，而且与升温方式和升温速率有关。 | |
| 关键词: 介孔 空心球状 碳化钨 微球 形成机理 | |
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| Abstract: Hollow global tungsten carbides with meso-porosity were prepared by Spray Dryer Sphere Miniaturation-Gas-Solid Reaction， using ammonium metatungstate (AMT) as raw material， carbon monoxide as source of carbon and reducing gas. The samples were characterized by SEM. The results show that the hollow structure of the microsphere is formed during Spray Dryer Sphere Miniaturation， and mesoporosity is produced during the reduction and carbonization. The samples were characterized by in situ XRD reactor， under the same conditions as in the preparation course. The results show that during the reduction and carbonization of the sample in CO/CO2 atmosphere， when the temperature of the reduction and carbonization is raised slowly and continuously， the phase transition of the sample follows AMT → WO3 → WO2 → WC; when the temperature is raised in a manner of “step-jumping” to 673 K slowly and continuously， and then to 1 023 K quickly， the phase transition of the sample follows AMT → WO3 → WO2 → W2C → WC. These results indicate that the phase transition from ammonium metatungstate to tungsten carbide (WC) depends on the temperature and the time of the reduction and carbonization， and the manner and the rate of the temperature ramp during the reduction and carbonization. | |
| Keywords: mesoporosity hollow globe tungsten carbide microsphere formation mechanism | |
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| 李国华,竺金涛,田 伟,楼颖伟,马淳安.介孔空心球状WC微球结构与晶相形成机理[J].无机化学学报,2007,23(12):2044-2048. | |
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