Ammonium Metatungstate Decomposition Temperature
Ammonium metatungstate decomposition temperature is the temperature of AMT coming out decomposition reaction; while in the actual production environment, ammonium metatungstate will have several different decomposition temperatures according to complete reaction or not. Decomposition temperature of a substance means the temperature at which the substance chemically decomposes, which the chemical decomposition caused by heat. The reaction is usually endothermic as heat is required to break chemical bonds in the compound undergoing decomposition. If decomposition is sufficiently exothermic, a positive feedback loop is created producing thermal runaway and possibly an explosion.
Ammonium metatungstate will produce different products at different decomposition temperatures. When the heat treatment temperature is 200~300°C, AMT will be removed of all crystal water and most of the ammonium ions; then phase transformation will occur at 300-350°C to generate metastable tungsten oxide species; when the heat treatment temperature rise to 500~550°C, a small amount of ammonium and bound water is still not broken down; and when the temperature rises to 600°C and above, ammonium metatungstate will completely decomposed into tungsten trioxide (WO3); when the temperature raised to 700°C and held for 2 hours, mesoporous tungsten trioxide hollow balls will be obtained.
About ammonium metatungstate:
Ammonium metatungstate (AMT) is an important intermediate compound in tungsten wet smelting process, with the appearance of white or slightly yellow crystalline, the biggest solubility in all the tungsten compound, wherein the solubility will bigger than 300g WO3/100ml H2O at 25℃. The preparation methods of ammonium metatungstate are mainly Acid neutralization, Thermal separation, electrodialysis, solvent extraction and ion exchange method and the method depends on ammonium paratungstate (APT). AMT is the important raw material of tungsten compound (such as tungsten trioxide, blue tungsten oxide, tungsten hexachloride ect.); at the same time, it is usually used in industries of petroleum, chemical, ceramic, lubrication and so on; in addition, since the continually developing of electronics industry and the constantly mining of new material, AMT is also used in film substrate, capacitor and shielding ect. of semiconductor devices.
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