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Monoclinic ammonium paratungstate with different particle size can be obtained by different heating stages. The changes of particle size and surface area at each stage in rapid thermal decomposition of monoclinic APT can be concluded by differential thermal analyzer (DTA) and laser particle size analyzer, which can guide the preparation of tungsten oxide with desired particle size. Rapid Thermal Decomposition of Monoclinic Ammonium Paratungstate 1. Monoclinic APT was heated to 600°C at a rate of 9°C/min in argon (Ar) for…

Single crystal ammonium paratungstate is a key material for producing high quality tungsten wire, which is always applying in cars. That is because the single crystal APT has the characteristics of good tensile property and fracture resistance. And the tungsten wire using the single crystal APT as raw material has yield of 90%, which is higher than that of adopting polycrystalline paratungstate ammonium as raw material with yield of 70%. Single crystal APT also has many other excellent physical properties…

Ultra-fine ammonium paratungstate has received widespread attention around the world since the 1990s as it can be used to prepare ultrafine tungsten (W) powders, which a hot tungsten product to produce tungsten carbide powder and other down-stream products on tungsten. Compared with tungsten powder of conventional particle size, the sintering temperature of ultrafine W powder can be greatly reduced. And therefore, the preparation of ultrafine grain size APT has been researched a lot both in China and abroad. The particle…

Crystalline ammonium paratungstate may be prepared by evaporative crystallization, which has been favored in industrial production as this method has the characteristics of simple operation, low cost, uniform particle size and stable quality. The purity of ammonium paratungstate can be guaranteed by controlling the evaporative crystallization rate. To obtain high purity APT, the crystallization rate must be controlled to be low as the evaporative crystallization process requires long production cycle and consumes a lot of energy. Certainly, there are a…

Coarse grain size ammonium paratungstate may be prepared by using ammonium tungstate solution (produced by ion exchange method) as raw material, controlling certain process conditions and adopting specific operating systems. The coarse APT produced by this method has average particle size of 40μm or above. The purity of ammonium tungstate (abbreviated as AT) solution is one of the factors affecting the particle size of APT. The AT solution prepared by ion exchange method contains a large amount of impurity -…

Medium grain size ammonium paratungstate means the ammonium paratungstate that has apparent density under the range of medium particle size, such as at the range from 1.65g/cm3 to 1.90g/cm3. It is necessary to control the particle size of ammonium paratungstate in the process of powder metallurgy to ensure the uniformity of tungsten powder. At present, ammonium paratungstate is often prepared by evaporative crystallization method at home and abroad. However, the APT produced by conventional evaporative crystallization process has relatively coarse…

Fine grain size ammonium paratungstate may be prepared by microwave-ultrasonic cooperative evaporation crystallization at higher temperature and without addition of surfactant. A fine single crystal APT-4 with average particle size of 7.6μm, uniform particle size distribution and complete crystal form can be obtained under the following conditions: Not stirred by machinery or under magnetism; No addition of surfactants; Under better APT preparation conditions – ultrasonic frequency of 25kHz, power of 1000W, microwave power of 700W, temperature of 80°C, ammonium tungstate…

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…

High purity ammonium paratungstate is prepared to meet higher requirements of high-end tungsten carbide materials (APT). With the development of the process technology of follow-up product, customers who have demand in high-end tungsten carbide products not only makes certain requirements on the content of impurities and physical properties of APT, but also strict requirements on the content of K, Na in APT. Why the K, Na content in APT should be well controlled? During producing tungsten oxide and tungsten powder,…

Ammonium paratungstate powder (APT) may be produced by secondary reduction process. In other words, APT is reduced to blue tungsten oxide (BTO) in first stage, and BTO is reduced to tungsten powder (W powder) in the second stage. There are two methods for reducing APT to BTO – hydrogen reduction and self-reduction. And there are also two types of blue tungsten oxide – doped blue tungsten oxide and undoped blue tungsten oxide. The W powder using undoped blue tungsten oxide…