engleski

Synthesis of tungsten trioxides hydrates and their chemical behavior

Tungsten trioxide hydrates were synthesized by (a) cation exchange reaction from sodium tungstate solution, and (b) precipitation from sodium tungstate solution by the addition of HCl solution. The sample were analyzed by XRD, DTA/TGA, Raman and FT-IR spectroscopies. XRD showed formation of WO3H2O by cation exchange reaction, whereas WO3 0.33H2O was identified by XRD as a product of the acidification of sodium tungstate solution with HCl solution. After heating at 320 oC, WO3 H2= transformed into WO3, Whereas the WO3 0.33H2O crystal structure remained unchanged. These results were in agreement with DTA/TGA results. The phase transformation WO3H2O - WO3 was also monitored by Raman and FT-IR spectroscopies. In the case of WO3 0.33H2O samples, the basic features of Raman and FT-IR spectra did not change on heating up to 320 oC, thus indicating that heating of WO3 0.33H2O up to this temperature did not destroy the original crystal structure. Heating of WO3 0.33 H2o up to 800 oC favoried formation of monoclinic WO3.

tungsten trioxide. cation exchange. synthesis. XRD. DTA. FT-IR. laser Raman

nije evidentirano