Publicação: Influence of the thermal treatment in the crystallization of NiWO4 and ZnWO4
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Springer
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Artigo
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Resumo
NiWO4 and ZnWO4 were synthesized by the polymeric precursor method at low temperatures with zinc or nickel carbonate as secondary phase. The materials were characterized by thermal analysis (TG/DTA), infrared spectroscopy, UV-Vis spectroscopy and X-ray diffraction. NiWO4 was crystalline after calcination at 350 A degrees C/12 h while ZnWO4 only crystallized after calcination at 400 A degrees C for 2 h. Thermal decomposition of the powder precursor of NiWO4 heat treated for 12 h had one exothermic transition, while the precursor heat treated for 24 h had one more step between 600 and 800 A degrees C with a small mass gain. Powder precursor of ZnWO4 presented three exothermic transitions, with peak temperatures and mass losses higher than NiWO4 has indicating that nickel made carbon elimination easier.
Descrição
Palavras-chave
Wolframite, ZnWO4, NiWO4, Thermal treatment, Order-disorder
Idioma
Inglês
Como citar
Journal of Thermal Analysis and Calorimetry. Dordrecht: Springer, v. 97, n. 1, p. 167-172, 2009.
