Nanopowder of xwt% SiO2+WO3(x=0,3,10,15,20) was prepared by means of solid state reaction and deposition method.The microstructure was characterized by XRD and TEM.It was observed that the nanosized monoclinic and...Nanopowder of xwt% SiO2+WO3(x=0,3,10,15,20) was prepared by means of solid state reaction and deposition method.The microstructure was characterized by XRD and TEM.It was observed that the nanosized monoclinic and triclinic crystal phase of WO3 formed together and the grain size decreased with the increasing adulterate quantity of SiO2.The average grain size of the solid power is about 5060nm,the deposition power is about 2030nm,and the granularity is uniform.With the increasing amount of SiO2,the proportion of the monoclinic phase decreased,and the proportion of the triclinic phase increased.展开更多
Hexagonal WO3 nanorods are fabricated by a facile hydrothermal process at 180 ℃ using sodium tungstate and sodium chloride as starting materials. The morphology, structure, and composition of the prepared nanorods ar...Hexagonal WO3 nanorods are fabricated by a facile hydrothermal process at 180 ℃ using sodium tungstate and sodium chloride as starting materials. The morphology, structure, and composition of the prepared nanorods are studied by scanning electron microscopy, X-ray diffraction spectroscopy, and energy dispersive spectroscopy. It is found that the agglomeration of the nanorods is strongly dependent on the PH value of the reaction solution. Uniform and isolated WO3 nanorods with diameters ranging from 100 nm-150 nm and lengths up to several micrometers are obtained at PH = 2.5 and the nanorods are identified as being hexagonal in phase structure. The sensing characteristics of the WO3 nanorod sensor are obtained by measuring the dynamic response to NO2 with concentrations in the range 0.5 ppm-5 ppm and at working temperatures in the range 25 ℃-250 ℃. The obtained WO3 nanorods sensors are found to exhibit opposite sensing behaviors, depending on the working temperature. When being exposed to oxidizing NO2 gas, the WO3 nanorod sensor behaves as an n-type semiconductor as expected when the working temperature is higher than 50 ℃, whereas, it behaves as a p-type semiconductor below 50 ℃. The origin of the n- to p-type transition is correlated with the formation of an inversion layer at the surface of the WO3 nanorod at room temperature. This finding is useful for making new room temperature NO2 sensors based on hexagonal WO3 nanorods.展开更多
文摘Nanopowder of xwt% SiO2+WO3(x=0,3,10,15,20) was prepared by means of solid state reaction and deposition method.The microstructure was characterized by XRD and TEM.It was observed that the nanosized monoclinic and triclinic crystal phase of WO3 formed together and the grain size decreased with the increasing adulterate quantity of SiO2.The average grain size of the solid power is about 5060nm,the deposition power is about 2030nm,and the granularity is uniform.With the increasing amount of SiO2,the proportion of the monoclinic phase decreased,and the proportion of the triclinic phase increased.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.60771019,61271070,and 61274074)the Tianjin Key Research Program of Application Foundation and Advanced Technology,China(Grant No.11JCZDJC15300)
文摘Hexagonal WO3 nanorods are fabricated by a facile hydrothermal process at 180 ℃ using sodium tungstate and sodium chloride as starting materials. The morphology, structure, and composition of the prepared nanorods are studied by scanning electron microscopy, X-ray diffraction spectroscopy, and energy dispersive spectroscopy. It is found that the agglomeration of the nanorods is strongly dependent on the PH value of the reaction solution. Uniform and isolated WO3 nanorods with diameters ranging from 100 nm-150 nm and lengths up to several micrometers are obtained at PH = 2.5 and the nanorods are identified as being hexagonal in phase structure. The sensing characteristics of the WO3 nanorod sensor are obtained by measuring the dynamic response to NO2 with concentrations in the range 0.5 ppm-5 ppm and at working temperatures in the range 25 ℃-250 ℃. The obtained WO3 nanorods sensors are found to exhibit opposite sensing behaviors, depending on the working temperature. When being exposed to oxidizing NO2 gas, the WO3 nanorod sensor behaves as an n-type semiconductor as expected when the working temperature is higher than 50 ℃, whereas, it behaves as a p-type semiconductor below 50 ℃. The origin of the n- to p-type transition is correlated with the formation of an inversion layer at the surface of the WO3 nanorod at room temperature. This finding is useful for making new room temperature NO2 sensors based on hexagonal WO3 nanorods.
