Spherical Ammonium Para Tungstate by Ball Milling Method

Ammonium para tungstate (APT) is composed of ammonium tungstate solution prepared by crystallization unit operation. The main methods of evaporation and crystallization, crystallization and freezing crystallization. APT morphology, particle size and particle size distribution on the performance of the subsequent oxidation of tungsten, tungsten powder, tungsten carbide powder has a great influence.

At present, the technology of refining and spheroidizing tungsten powder mainly includes plasma rapid condensation process. In the plasma flame of 10000K temperature, the raw coarse tungsten powder is carried by argon gas, which is melted, evaporated and ionized. By rapid condensation and reducing the contact between space particles, the tungsten powder particles are spheroidizing and making. It is difficult to achieve industrialization because of its complex equipment, high preparation cost and low production capacity, and it is only in the experimental stage.

In the process of evaporation and crystallization of the (NH4) 2WO4 solution, some researchers have proposed a process to create the process conditions by strengthening the rolling friction between the particles of para tungstate to produce a spherical parotungstate. The main steps are as follows:

The crystallization process is evaporated and crystallized at 95~100°C and evaporated to 40% of the initial solution volume. The time of filling liquid is 3-4h.

Ammonium paratungstate by cube ballof relies mainly on rolling contact and friction between APT particles and the crystallization process of forming. Into spherical conditions: stirring speed fast (friction force), the solid solution of high concentration, friction time enough.

In order to improve the concentration of solid phase in the solution (to ensure the full contact of APT particles), the technological measures for reducing the pressure of vapor and slowing the growth of the crystal must be taken in the later period of crystallization to prolong the friction time. By controlling the speed of adding the solution, maintaining the balance between the added amount and the evaporation, the friction between the APT particles and the friction time can be increased.

The preparation of spherical ammonium para tungstate by ball milling has the characteristics of low cost and stable effect. It is not necessary to increase production process and cost, save the cost of preparing spherical tungsten powder, and has good prospects.

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