Ultrafine ammonium paratungstate is the key raw material for preparing fine grain size tungsten products with superior performance such as ultrafine tungsten powder, ultrafine tungsten carbide powder, etc. That is because the properties of tungsten products such as grain size and crystal morphology have great “inheritance” relationship with their raw material - APT.
At present, APT is mainly produced by crystallization process in industry with the particle size of 25-60μm, which is difficult to meet the requirements for producing fine grain size tungsten products. Although the grain size of APT can be effectively controlled by reducing crystallization temperature and adding surfactants, the addition of surfactants will inevitably affect the purity of APT and the performance of subsequent tungsten products with the reduction of crystallization temperature, extension of crystallization cycle and decrease of productivity.
Studies have shown that, compared with traditional crystallization method, microwave-ultrasonic combination method has obvious advantages in terms of accelerating crystallization rate, refining product gain size, and improving product purity.
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