Ultrafine BTO powder may be prepared by APT calcination method.
APT Calcination Method to Produce Blue Tungsten Oxide
The principle is during heating process, keep positive pressure in furnace to prevent air goes in, and the ammonia generated by APT decomposition can split out hydrogen and nitrogen to keep the mild reducing atmosphere in furnace to obtain the final product - blue tungsten oxide. Besides that, in order to adjust phase composition of product, ammonia gas can be injected in furnace. The phase composition of blue tungsten oxide is depended on the chosen non-oxidative system. It means if some kind of phase composition of blue tungsten oxide is needed, the product can be easily obtained by controlling temperature and non-oxidative atmosphere.
The production parameters are 550°C in one zone, 600°C in two zones, and the gas pressure in the furnace tube is controlled 5~10mm water column above atmospheric pressure. Supplement ammonia to maintain the reducing atmosphere.
More details, please visit:
http://www.tungsten-powder.com/Blue-Tungsten-Oxide.html
