In industry, yellow tungsten oxide or blue tungsten oxide is generally used as raw material, and hydrogen reduction method is used to produce tungsten powder and tungsten carbide powder. The tungsten powder and tungsten carbide powder obtained in this way have large particle size and wide distribution, which seriously affects the quality of cemented carbide. the quality of. Therefore, on the premise of ensuring the purity of the powder, the key to the technical quality of tungsten powder and tungsten carbide powder for ultra-fine-grained cemented carbide is the ultra-fine and uniform particle size. The pure phase blue tungsten oxide with a large specific surface area is obtained by the intrinsic reduction method, and its intrinsic reducing tungstate (IRT) is hydrazine tungstate.
Hydrazine and oxalic acid were used as additives to prepare hydrazine tungstate oxalate complex salt, which was used as a precursor to prepare black tungsten oxide.
The results of thermogravimetric analysis show that the thermal decomposition has been completed at 500°C, and the black tungsten oxide was prepared by thermal decomposition of the compound salt under the protection of nitrogen. The effect of the addition amount of hydrazine and oxalic acid on the product properties, determine the optimal ratio (mass ratio) of tungstic acid, hydrazine, and oxalic acid to be 1.0:4.0:0.5. The research found that thermal decomposition temperature and thermal decomposition time have certain influence on product properties.
When the optimal proportion of the precursor is thermally decomposed, the temperature is 650°C and the time is 30 minutes, the typical product obtained is black; when the temperature is higher, the product is slightly dark brown, indicating that the product mainly contains WO2 relative to NH in black tungsten oxide. +4 quality score. Under the chosen conditions, the ammoniacal tungsten bronze phase is negligible. The powder X-ray diffraction (XRD) pattern of a typical black oxide product shows that. Black oxide mainly contains W18O49, which is less than WO2. The specific surface area (BET method) of a typical black oxide is 12m2•g-1, and the particle size (d50) of the black oxide aggregate is 3.68μm.
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