Doped Tungsten Doping Process

Because blue tungsten oxide powder particles pores and cracks many large surface area , strong adsorption capacity , permeability , chemical activity is good, and in contact with an aqueous solution of a compound having an ion exchange capacity , so the use of blue tungsten oxide doped than doped tungsten oxide doped with better results. Production of tungsten oxide equipment are rotary tube furnace and two kinds. Doped tungsten oxide is tungsten or tungsten oxide doped blue trace hydroxide, alumina. Since the 1960s , many countries have adopted doping process instead of blue tungsten oxide doped tungsten trioxide , thereby increasing the doping effect . In order to make the dopant can be uniformly distributed in the tungsten oxide , the actual production are not used directly , potassium hydroxide, aluminum oxides such insoluble , but with which the decomposition of soluble salts and easy , usually formulated as a potassium silicate and aluminum nitrate ( or aluminum chloride ) was added. Dopant formulations typically within the following ranges ( based on tungsten ) : potassium : 0.3% -0.45 % ; alumina : 0.02% -0.03 % . Doping methods are wet method and the spray French. Wet method in the pot with a steam jacket for evaporation . First, the evaporation pot adding deionized water, was added under constant stirring yellow blue tungsten or tungsten , into a paste, and with stirring , adding potassium silicate solution side , stirred for a while , then add the aluminum nitrate solution , evaporated to dryness moved after drying oven , and finally mixed and sieved .

Spray method is potassium silicate solution was sprayed into the tungsten oxide fine mist ( 80 to 90C) , and continue stirring until basic evaporated to dryness , then a solution of aluminum nitrate was added to the same manner , the final drying , mixing, sieving . Studies have shown that the addition of silicon in the tungsten oxide , potassium aluminum nitrate solution , is not a simple mechanical mixing , but to partially react and generate a multi- tungsten oxide complex tungstate , which generates the same number of characteristics of the substrate , doped miscellaneous agents of the various components and the doping conditions. Tungsten powder and acid preparation is usually used in industrial production hydrogen reduction of tungsten oxide ( blue tungsten oxide or tungsten oxide ) tungsten powder preparation methods . Reduction process, the system depends on the particle size of tungsten powder , particle size composition and oxygen content , potassium content requirements. Often used in a production stage and two-stage reduction to restore two processes . A phase of tungsten oxide reduction is a direct reduction of tungsten powder (D powder ) . Two-stage reduction in two steps : first in the 550-800C will tungsten trioxide or tungsten dioxide reduction of blue tungsten ; Then make tungsten dioxide at 750-900 ℃ reduced to tungsten powder (B powder ) . Reduction is usually in a tubular furnace or rotary furnace . Practice has proved that the particle size of tungsten powder and tungsten trioxide or tungsten blue size is not a simple relationship , with the reduction of different specifications , either coarse or fine tungsten trioxide or blue tungsten powder, tungsten can get crude fine powder or tungsten powder, tungsten powder particle size depends largely on the particle size of tungsten dioxide .


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