Cobalt doped ammonium paratungstate (Co-doped APT) precursors for the fabrication of cemented carbides were synthesized by co-precipitation, where W and Co are mixed on the atomic scale. The effect of cobalt content on the reduction of W–Co precursor was studied. W–Co precursors with different ratios of tungsten to cobalt were prepared and calcined at 220 °C for 5 h in air, followed by a reduction in hydrogen gas at 600 and 650 °C for different times. The resulting powders were characterized with respect to phase constituent, specific surface area, particle size, density, and morphology of the reduced powders.

It has been found that the addition of cobalt results in a higher reduction rate toward the metallic phases. However, the particle size of the reduced powders increases with increasing cobalt content, while its relative density decreases. The specific surface area of reduced powders at 650 °C increases for short reduction times, due to reduction of oxides to metal powder, and decreases for long reduction time due to agglomeration of metal powder. Cobalt plays the role as a catalyst during the reduction processing. On the other hand, it promotes the agglomeration of small particles. However, the completely reduced powders were well nanostructured with an average particle size between 20–50 nm.




Tungsten Manufacturer & Supplier: Chinatungsten Online -http://www.tungsten-powder.com
Tel.: 86 592 5129696; Fax: 86 592 5129797
Email: sales@chinatungsten.com
Tungsten & Molybdenum Information Bank: http://i.chinatungsten.com
Tungsten News & Tungsten Prices, 3G Version: http://3g.chinatungsten.com
Molybdenum News & Molybdenum Price: http://news.molybdenum.com.cn

Non-isothermal kinetic (k, A and ΔE) and thermodynamic (ΔH, C_p and ΔS) parameters of ammonium paratungstate decomposition to the onset of formation of WO₃, were determined by analysing thermogravimetry (TG), differential thermal analysis (DTA) and differential scanning calorimetry (DSC) curves recorded at various heating rates (1–30°C min⁻¹). Thermal events encountered throughout the decomposition course were due to three endothermic (at 120 ° C (I), 195 ° C (II) and 359 ° C (IV)) and two exothermic (at 265 ° C (III) and 386 °C (V)) processes. The events I–IV were accompanied by weight losses resulting from the elimination of volatile components [(NH₄)₂O, NH₃ and H₂O] leading to the formation of intermediate solid products (metatungstate and polytungstate), whereas event V was due to the crystallization of WO₃ in the immediate vicinity of its formation (at 370 ° C).


Tungsten Manufacturer & Supplier: Chinatungsten Online -http://www.tungsten-powder.com
Tel.: 86 592 5129696; Fax: 86 592 5129797
Email: sales@chinatungsten.com
Tungsten & Molybdenum Information Bank: http://i.chinatungsten.com
Tungsten News & Tungsten Prices, 3G Version: http://3g.chinatungsten.com
Molybdenum News & Molybdenum Price: http://news.molybdenum.com.cn

In order to improve the quality of tungsten products and the export need of tungsten wire, the method for producing high purity ammonium paratungstate is under research. In order to reduce producing cost, improve producing efficiency of tungsten, ammonium paratungstate prepared by tungsten concentrate is studied.

Tungsten concentrate preparing ammonium paratungstate mainly uses soda lye under alkaline leaching tungsten concentrate. During the processing procedure, the alkaline using amount is 2-3.5 times more than the theoretically amount. The first step is evaporation and crystalline of sodium tungstate. Firstly evaporate sodium tungstate in the reaction tower, coarse sodium tungstate crystal is produced. Then add water and hydrochloric acid into it and then acid decomposition happens. After acid decomposition, tungstic acid is produced and was mixed up with ammonium. It is then being processed under 80-95 degree Celsius for 4-6 hours, evaporation amount is between 60-70. The final process is crystalline, filtering, washing and dry. Then the finished ammonium paratungstate is made. 




Tungsten Manufacturer & Supplier: Chinatungsten Online -http://www.tungsten-powder.com
Tel.: 86 592 5129696; Fax: 86 592 5129797
Email: sales@chinatungsten.com
Tungsten & Molybdenum Information Bank: http://i.chinatungsten.com
Tungsten News & Tungsten Prices, 3G Version: http://3g.chinatungsten.com
Molybdenum News & Molybdenum Price: http://news.molybdenum.com.cn

Due to tungsten alloy has high density, excellent radiation attenuation properties, and environmetal frendly, it is widely used to produce into tungsten syringe shield. Tungsten syringe shields, also called injection shields, are designed to reduce hand exposure to radioactive injections. With a great ability of radiation shielding, the barrel of the tungsten syringe shield can reach 0.06''-0.08''. And it is able to reduce radiation exposure from Tc-99m by more than 99%.
            
Detials of Tungsten Syringe Shield:

  Tungsten Alloy Manufacturer & Supplier: Chinatungsten Online- http://www.tungsten-alloy.com
  Tel.: 86 592 5129696; Fax: 86 592 5129797
  Email:  sales@chinatungsten.com
  Tungsten & Molybdenum Information Bank: http://i.chinatungsten.com
  Tungsten News & Tungsten Prices, 3G Version: http://3g.chinatungsten.com
  Molybdenum News & Molybdenum Price: http://news.molybdenum.com.cn