Transactions of the INDIAN CERAMIC SOCIETY Vol. 66 2007
Leaching Kinetics of Tungstic Acid and in situ Synthesis of Tungsten Carbide in Silica Gel Matrix
Debashis Chaira**, Mahua Ghosh Chaudhuri**, G. C. Das*, S. Mukherjee,
M. K. Mitra and A. Bhattachariya***
Pages : 167-170
Leaching of tungstic acid is carried out in ammonium hydroxide solution at two different pH (8 and 10.5), at three different temperatures of 40o, 50o and 60oC. It is observed that initially the dissolution rate is very fast followed by decrease in rate with time. It also increases with increase of temperature and pH. The mechanism of isothermal leaching kinetics of tungstic acid in ammonium hydroxide is mainly of contracting geometry type. Ammonium tungstate has been used as a precursor to synthesize nano tungsten carbide in the silica gel matrix by in situ generation of hydrogen and extremely fine carbon. The size of tungsten carbide is found to be in the nm range.