Tungsten Powder made by Waste Tungsten Bar- Chemical Vapor Migration

With the rapid development of industry, although it has high economic benefits, but the damage of the environment is on the increase every year. Due to ecological environment worsening and water resource shortage, the human living environment will face the serious challenge. The ecological environment is fragile, and the task of ecological construction and environmental protection is still heavy. And therefore countries pay more and more attention to the recovery of metals. Japan set up a special committee for tungsten recovery in 1975, which is called WR for short. The commission estimates that 31.3 tons of tungsten can be recycled while producing 100 tons of carbide. Or we can say that is the 31.3 percent recovery, the actual recovery rate in Japan is 10% and the United States is 20%. The equipment for chlorination pulping process is relatively simple, and it has a wide adaptability of raw materials, at present, this method is considered as one of the most promising methods. In recent years, ultrafine tungsten powder extracted from the waste tungsten bar through the chemical vapor migration has aroused general concern. Chemical vapor migration is a chemical process used to produce high quality, high-performance, solid materials. The process is often used in the semiconductor industry to produce thin films. Microfabrication processes widely use this way to deposit materials in various forms, including monocrystalline, polycrystalline, amorphous, and epitaxial.

The first is to use chloridize the cutting of both ends of the clamping head of tungsten bar while vertical sintering at environment of 950 ℃. Chloride will be supplied to reduction tubes with argon, and then being deoxidized by hydrogen. Chlorine is loaded in industrial bottle, and mixed with argon after dehydrating by concentrated sulfuric acid. Deoxidizing hydrogen with palladium asbestos at the temperature of 350 ℃, then drying it by silica gel and molecular sieve. Finally, gathering the ultrafine tungsten powder obtained by the reaction in powder collecting pipe. After purifying and absorbing hydrogen chloride, exhaust gas which contains hydrogen would be emitted and combustion. The final wolfram powder would have 0.64% oxygen, 0.075% chlorine, and 0.033% chlorinated residue.

Adopting chemical vapor migration methods can also produce the same quality of wolfram powder. Although the aluminum content is higher, all other metal impurities are mostly below or equal to the ultrafine wolfram powder. On the one hand, it can greatly reduce industrial costs. On the other hand, it helps to promote the application of wolfram powder.

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