Synthesis and characterization of NiWO4 crystals

Nickel tungstate (NiWO4) catalyst has been synthesized by reacting ammonium metatungstate and nickel nitrate as a function of temperature from 673 to 1073 K and of 1-h reaction time. It was found that NiWO4 is formed from 823 to 1073 K. The yield of 99% was obtained from 903 K to higher temperatures . The average crystal sizes have been determined by the Scherrer analysis a nd the surface area was measured by the Brunauer-Emmett-Teller (BET) method . The former increase from 55 to 112 nm, while the second decrease from 16 to 3 m(2) g(-1) in both cases, as the reaction temperature increases from 8 23 to 1073 K. Elemental composition and morphological structure were studie d by energy dispersive spectroscopy (EDS) and scanning electron microscopy (SEM). The structural characterization has been performed using X-ray diffr action (XRD). (C) 2001 Elsevier Science B.V. All rights reserved.