Tungsten trioxide (WO3) has excellent electrochromic, photochromic, gasochromic and catalytic nature, in the flat panel display, smart windows, write - read - rub optical devices, gas sensors and fields have great potential catalyst application. Producing a specific composition and morphology of tungsten trioxide nanostructures to obtain a special performance, its application is important. In this work, hydrothermal synthesis method, were synthesized WO3·1 / 3H2O and hexagonal WO3 (h-WO3) nanorods, quadrature phase WO3 (o-WO3) and monoclinic WO3 (m-WO3) rectangular plate, and m-WO3 brick stack and WO3·1 / 3H2O star assembly, and to explore its mechanism. In addition, the synthesis of monodisperse acid nanoparticles will make by UV irradiation. Use the following UV irradiation generated acid nanoparticles in the hydrothermal environment successfully assembled into m-WO3 brick stack such nanostructures. In the study we found, WO3 and hydrates lower nanoparticles (particles, rods, sheets) has a clear self-assembled habits in the hydrothermal environment.

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Tungsten powder is the raw materials of hard tungsten alloy and tungsten processing materials, so the particle size and particle size distribution of tungsten powder, there are stringent requirements. In the production the tungsten powder controlling the particle size becomes crucial. Many factors affecting tungsten powder, first in terms of reduction of the production process temperature, temperature gradient, pushing the boat speed and boat loading amount of hydrogen and hydrogen flow humidity. Second, the original size of the material and size of the impurities also will influent the tungsten powder quality. In terms of reduction temperature is high, the production process for the production of coarse particles of tungsten powder. Production of fine particles of tungsten powder are mostly two-stage reduction, first restore at the lower temperature, the second at the high-temperature reduction. And in terms of the flow of hydrogen, hydrogen flow increase in favor of timely discharge of water vapor to accelerate the reduction reaction rate, easy access to fine particles of tungsten powder. Boat loading capacity is also an important factor, as much as the amount of hydrogen loaded boat difficult to penetrate deep inside the material layer, is not conducive to obtain fine particles of tungsten powder. Raw materials and impact of impurities tungsten powder is also larger, WO3 large specific surface area and impurities may get coarser tungsten powder.

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Atomistic simulations focusing on sintering of crystalline tungsten powders at the submicroscopic level are played to shed light on the processing of the nanoscale powders. When the sintering simulations performed, the neck growth and shrinkage were calculated at the same time. That lead to the possibility of extend these results to the global physical property evolution through sintering. With variations in temperature, pressure, particle configuration, additives, and crystalline misalignment between particles during sintering, the densification and grain growth were calculated. The findings were of great importance for a virtual method to creating the processing and materials design to nanoscale powders. Maybe in near future, there will be a better sintering mechanism of nanoscale tungsten powder comes out.

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Producing tungsten trioxide can use ammonium tungsten or tungsten acid by dried and calcined. First it will be at 100 ℃ removed moisture from tungsten acid or ammonium paratungstate. Then removed water and ammonium compounds by calcination . Tungsten acid at a temperature of 773 ~ 873 ℃ calcined product is still less than 0.5% of water, and at a temperature of 973 ~ 1023 ℃ calcined only less than 0.1% water. Tungsten acid reaction formula is: H2WO4 = WO3 +H2O; however ammonium paratungstic (APT) can be reacted at temperatures higher than 523 ℃, ammonium tungsten reaction formula is: 5 (NH4) 2O · 12WO3 · NH2O = 12WO3 + 10NH3 ↑ + (n + 5) H2O ↑. Calcination temperature and speed which has a significant impact on the product, the higher the calcination temperature, the coarser granularity WO3 are. And a sharp rise in the temperature of the system the specific surface area of WO3 is large. On the contrary, slowly heated then WO3’crystal morphology will more complete so that the small specific surface area WO3 has. China will divided WO3 into three levels, first level was 99.95%, secondary 99.9% purity, the third levels of 99.5%. Particle size is generally used for the production of bulk density of WO3 tungsten products or specific surface area, said the finer the particle size, the smaller the bulk density, the greater specific surface area. Ammonium paratungstate or tungsten acid job is usually calcined in a rotary tube furnace for firing, furnace tube made of stainless steel pipe external resistance wire heating, calcining furnace tube when constant rotation speed of approximately 2.5r/min. Tungsten acid calcination temperature is 1023 ~ 1123K, ammonium paratungstate calcination temperature is 873 ~ 973K, the specific choice of the calcination temperature depends on the product requirements.

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