Sintese de materiais nanoestruturados MS IND. 2 (M = Mo, W) com alta pureza de fase e morfologia / Synthesis of MS IND. 2 (M = Mo, W) nanostructured materials with high purity of phase and morphology

AUTOR(ES)

Luciana Lima Vieira

DATA DE PUBLICAÇÃO

2008

RESUMO

The main of this Dissertation is the preparation of nanostructured WS2 and MoS2 from a template reaction with the respective nanorods oxides. Molybdenum oxide nanorods with diameters around 100 nm and microscale lengths were prepared from MoO3·2H2O via a one step solvothermal reaction. The formation of MoO3 rods proceeds in acidic media at 180 °C. The oxide was converted in quantitative yield to MoS2 nanorods by H2S in a reducing atmosphere. TEM and SEM analysis reveals that the rod-like morphology of the oxide precursor is preserved during the H2S treatment. Monoclinic W18O49 nanorods of 5–15 nm in diameter have been synthesised by a low temperature hydrothermal route using sodium sulfate as structural and morphological modifier. The important role of Na2SO4 salt in the synthesis has been demonstrated. These nanorods were found suitable as a precursor for the synthesis of nanostructured WS2 by reducing them with H2S at 800 °C for 30 min. This reaction can work out without a reducing atmosphere. The morphological and structural features of WS2 nanotubes, generated from WO3 nanorods, by an in situ heating process, have been studied. The nanorods were prepared by a simple annealing method of a low-crystalline tungsten oxide (from a sol-gel reaction between WCl6 and methanol) at 600-1000 °C. Finally, an alternative route to molybdenum and tungsten sulfide by solution chemical reactions was also explored. The reaction was carried out from the respective oxides and sulfurization reagents such as S, CH3CSNH2 and CSN2H4 through hydrothermal method. MoS2 nanostructures including flower-like particles have been synthesized. The hydrothermal reaction with tungsten has not produced WS2 but W18O49 nanorods after thermal annealing. These oxides were converted in nanostructured WS2 by solid-gas reaction in H2S atmosphere at 800°C.

ASSUNTO(S)

sulfeto de molibdenio nanotubos inorganicos molybdenum sulphide sulfeto de tungstenio tungstenio sulphide inorganic nanotubes nanorods nanobastões

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