Technology for Producing Fine Tungsten Carbide Powders

The article shows the advantage of electric arc synthesis and subsequent centrifugal spraying of tungsten carbide to obtain a high-quality highly dispersed powder. A tungsten electrode (anode) is fed to the surface of a rotating graphite electrode (cathode) until an electric arc occurs between the electrodes, and the cathode is made in the form of a ring. The angular speed of rotation of the annular graphite electrode is set in accordance with the calculated ratio, which provides fine-dispersed centrifugal atomization of the molten product particles. To prevent intense evaporation of tungsten and the formation of an excessive amount of fine particles, the power of the electric arc for melting the anode is limited to a set value.As a result, the uniformity of the powder increases and the dispersion of the particles of the main fraction decreases.

Recovery of Ultra-Fine Tungsten and Tin from Slimes Using Large-Scale SLon-2400 Centrifugal Separator

China is very rich in tungsten and tin resources, but most of them are finely disseminated with gangues, and thus, fine grinding is required for effective separation, which results in the abundant production of ultra-fine tungsten and tin values into slimes and tailings. The SLon centrifugal separator is highly effective in recovering ultra-fine heavy particles, because it operates on the centrifugal acceleration of particles in the flowing film of a few millimeters thick. The recovery of ultra-fine tungsten minerals from a slime assaying 0.22% WO3, in which 81.85% distributed in −40 µm fraction, was investigated using large-scale SLon-2400 centrifugal separator. Under optimized operating conditions, it produced a primary tungsten concentrate assaying 1.65% WO3 at a high recovery of 77.83%. Moreover, it produced a primary tin concentrate assaying 1.56% Sn at a high recovery of 79.85% from a tin slime assaying 0.27% Sn, in which 74.78% Sn was distributed in −40 µm fraction; then, followed by the flotation cleaning process, a final tin concentrate assaying 16.23% Sn with 66.7% recovery was produced. It was particularly noted that in this large-scale centrifugal separator, the three-conical separation drum stuck with abrasion-resistant ceramic slices on its inner surface played a key role for achieving high constant separation performance. It was concluded that the SLon centrifugal separator has important application prospects for high-efficient recovery of ultra-fine heavy minerals from slimes and tailings.

Investigation of X-ray radiation effect on the structure and microhardness of tungsten powder filled composite

The study focuses on the radiation resistance of a composite filled with fine tungsten powder having the 200–500 nm particle size. The studied composite is designed to provide radiation protection of electronic equipment. A sample with the test material was exposed to continuous spectrum X-ray radiation to an absorbed dose of 3 MGy. A characteristic of radiation resistance was sample microhardness measured before and after X-ray irradiation. Scanning electron microscopy was used to study the microstructure of a sample transverse cleavage after irradiation, and it was found that the sample had no visible defects in its structure. This result can be explained by uniform energy dispersion from local stresses due to high degree of composite filling with tungsten powder having a high thermal conductivity coefficient. The study of sample microhardness showed its 10 % increase attributable to the radiation hardening effect where increasing strength results in a simultaneous increase in microhardness. Experiments proved that this effect is manifested with an increase in the absorbed radiation dose.

Fine Tungsten Powder Obtained with Blue Tungsten Oxide through the Hydrogen Reduction

Fine tungsten powder is prepared with blue tungsten oxide (BTO) through the hydrogen reduction. The samples were characterized with the scanning electron microscope (SEM), fisher sub-sieve sizer (FSSS) and the particulate size description analyzer (PSDA). Fine tungsten powder is easily obtained when the reduction temperature is low. With the increasement of the reduction temperature, the grain size of tungsten powder becomes coarse. The increase of the weight of BTO in the ceramic boat leads to the increasement of the thickness of its bed. Therefore, the weight of BTO in the ceramic boat ought to reduce if fine tungsten powder is prepared. Fine tungsten powder can be obtained when the hydrogen flow increases.