2020年10月28日星期三

How to Prepare Ultrafine Tungsten Powder by Ultrasonic Spray Drying

 With the development of high and new technology, the requirement of pure tungsten and its alloy material is higher and higher.

There are many methods to prepare tungsten powder, and spray drying is one of the most important methods. The spray drying method or chemical synthesis method, it is a method of physical and chemical solution atomization obtain ultrafine particles through physical means of combining the process, including the original solution was prepared with solution blending, mixing, spray drying and subsequent processing. 

In recent years, the influence of nozzle structure, spray drying speed and temperature on particle size has attracted extensive attention. It is found that the concentration of precursor solution plays an important role in the morphology and particle size of ultrafine tungsten powder during ultrasonic spray drying. In order to prove this theory, some scholars have used 2 different concentrations of ammonium tungstate solution to spray drying respectively. The concentration of ammonium tungstate in solution 1 was 25% (mass ratio), and the concentration of solution 2 was 10%. The air pressure was 3 MPa and the drying temperature was 130 ~ 200 °C. Two kinds of different precursor powders were obtained, and the ultrafine tungsten powder was prepared by hydrogen reduction method.


After comparison test, it is concluded that when the concentration is 10%, the ammonium tungstate solution is low and the crystal grows slowly, so that the crystal powder has been dried when the crystal is not sufficiently crystallized, and the ultrafine tungsten powder precursor powder is obtained. When the concentration is 25%, the concentration of ammonium tungstate solution is high, the nucleation rate is high, so the crystal growth rate is very fast, and the crystallization process has been crystallized during drying, so the precursor powder of crystalline tungsten flake powder is obtained, and the particle size is coarser.

In conclusion, the concentration of ammonium acid solution is the main factor of the morphology and particle size of ultrafine tungsten powder, and the finer spherical tungsten powder precursor can be obtained in the range of 5% - 10%, which can be easily reduced to prepare ultrafine tungsten powder.

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