The preparation method of nanometer tungsten trioxide
As is known to all, tungsten trioxide is tungsten oxide (WO3), from preparing tungsten elemental important intermediates of tungsten industry. The smelting process involves two steps: first step with alkali treatment tungsten, WO3, was then used carbon and hydrogen reduction of tungsten trioxide, get metal tungsten: WO3 + 3 h2 - W + 3 h2o £¬Wo3 2 + 3 + 3 c - 2 w co2
So the question comes, how ultrafine tungsten trioxide preparing?
Method is as follows:
1 solid instead should method: solid instead should method is the basic means of ceramic materials preparation, often is the product of the final synthesis needed raw materials, mixing ratio, with a high temperature solid instead superfine powder system, combustion occurs again or by crushing superfine powder, including a certain amount of tungsten acid by them in muffle furnace with high temperature calcined 3 hours under 500 degrees Celsius, agate mortar after natural cooling grinding to get the average particle size of wo3 powders in 50 to 60 mm.
2 liquid phase method, liquid phase of nanoparticles prepared by the common characteristic of the law in homogeneous solution is as a starting point, through various channels. Make the solute separated from solution, form a certain shape and size of particles, are required for the former body of powder, resulting from the pyrolysis of nano particles. Liquid phase method can precisely control the product composition and particle size, mainly include: precipitation method, hydrothermal method, microemulsion method, sol - gel method, etc.
2.1 precipitations, precipitation has a co precipitation method and chemical precipitation method. According to certain proportion Na2WO4 solution and Na2SnO4 solution, after mixing thin - H2SO4 slowly drops to a boil, stirring constantly generate precipitation, then through aging, washing. Filtration, drying and calcining the SnO2 - WO3 material.
2.2 hydrothermal synthesis methods, hydrothermal synthesis method is point to some hydroxide under high temperature and high pressure in water solubility is greater than the corresponding oxide in water solubility, and the separation oxide hydroxide dissolved in the water at the same time.
2.3 microemulsion methods, microemulsion method are usually composed of surface active agent, surfactant, oil and aqueous solution of transparent, isotropic thermodynamic stability of the system. In microemulsion system, containing the body of water before nuclear surface active agent and the help of surfactant monolayer interface, this special micro environment can be regarded as a ¡°micro reactor¡± and its size can be controlled in a few to tens of nanometers.
2.4 Sol - gel method: making sol-gel is a product by controlling the gel temperature, phase and particle size of the product, for example small particle size, narrow distribution, high purity of the powder.
3. gas phase method, gas phase method is direct use or through various means to material into a gas, make it in gas state change physical or chemical change, the last of the nanoparticles in condensed grew up in the process of cooling method.
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