Structure and thermal decomposition of ammonium metatungstate

Abstract

The structure, morphology of ammonium metatungstate (AMT), (NH 4 formed between 380-500 °C, (iv) which then transformed into the more stable m-WO 3 between 500-600 °C. As a difference in air, the as-formed NH 3 ignited with an exothermic heat effect, and nitrous oxides formed as combustion products. The thermal behavior of AMT was similar to ammonium paratungstate (APT), (NH 4 ) 10 [H 2 W 12 O 42 ]•4H 2 O, the only main difference being the lack of dry NH 3 evolution between 170-240 °C in the case of AMT.)

Influences of Temperature on the Conversion of Ammonium Tungstate Pentahydrate to Tungsten Oxide Particles with Controllable Sizes, Crystallinities, and Physical Properties

“…Several scientific papers have reported the thermal behavior of tungsten-related material [2][3][4][5][6][7][8][9][10]. For example, Hunyadi et al [6] reported the thermal behavior of "ammonium metatungstate", and Van put [10] reported "ammonium paratungstate."…”

“…For example, Hunyadi et al [6] reported the thermal behavior of "ammonium metatungstate", and Van put [10] reported "ammonium paratungstate." Although current papers describe well information about experimental results and analysis, fundamental reason behind the change of physicochemical properties (including size, crystallinity, and physical properties) during the thermal decomposition process is still lacking.…”

“…In addition, ATP is selected as a model of tungsten-related material because ATP is one of the prospective tungsten raw materials for producing tungsten oxides, tungsten carbides, and tungsten metal in the industry [6]. Further, ATP possesses reactivity on temperature, and its physicochemical properties changing can be observed easily.…”

Synthesis of Fe8V10W16O85 by a solution method

“…Both processes are accompanied by endothermic effects. Mass loss recorded in this stage of decomposition of WP (5.0 mass %) is considerably greater than the mass loss (2.4 mass %) recorded in analogous stage of decomposition by Hunyadi et al [10]. The third stage of investigated process commences at 220°C, runs with 4.5 % mass loss and is also accompanied by endothermic effect.…”

“…Hunyadi and coworkers [10] In order to know WO 3 content in WP, sample of tungsten precursor was subjected to DTA-TG investigations. Figure 2 shows DTA and TG curves of WP.…”