Different shapes of ZnO nanobelts were synthesized at 550 ℃ by zinc acetate[Zn(CH3COO)2] and polyvinyl alcohol（PVA） as row material,under controlling the temperature rise rate.The analytical results of SEM and TEM ...Different shapes of ZnO nanobelts were synthesized at 550 ℃ by zinc acetate[Zn(CH3COO)2] and polyvinyl alcohol（PVA） as row material,under controlling the temperature rise rate.The analytical results of SEM and TEM indicate that the ZnO nanobelts possess a hexagonal wurtzite structure with preferred orientation along the direction of ZnO.For different experimental parameters,ZnO nanobelts have different widths and scales. The effect on zinc oxide nanobelts dimension and shape of proportion of mixture of raw material and mixing condition were discussed.Preliminary growth mechanics of ZnO nanobelts was proposed.展开更多
碳纳米管是一种性能优良的场发射冷阴极材料,具有低的阈值电场和高的发射电流密度,在平板显示领域具有广阔的应用前景。本文从Fow ler-Nordhe im s场发射理论出发,阐述了CNT的场发射机制,详细论述了包括CNT的结构、方向性、阵列密度、...碳纳米管是一种性能优良的场发射冷阴极材料,具有低的阈值电场和高的发射电流密度,在平板显示领域具有广阔的应用前景。本文从Fow ler-Nordhe im s场发射理论出发,阐述了CNT的场发射机制,详细论述了包括CNT的结构、方向性、阵列密度、吸附气体、工作环境等诸多因素对其场发射特性的影响。研究表明,垂直取向,长径比高,密度适中,表面洁净的CNT场增强因子较大,场发射性能较好。展开更多
Ultrathin VO_2 nanobelts with rough alignment features are prepared on the induction layer-coated substrates by an ethylenediaminetetraacetic acid（EDTA）-mediated hydrothermal process. EDTA acts as a chelating reagen...Ultrathin VO_2 nanobelts with rough alignment features are prepared on the induction layer-coated substrates by an ethylenediaminetetraacetic acid（EDTA）-mediated hydrothermal process. EDTA acts as a chelating reagent and capping agent to facilitate the one-dimensional（1D） preferential growth of ultrathin VO_2 nanobelts with high crystallinities and good uniformities. The annealed induction layer and concentration of EDTA are found to play crucial roles in the formation of aligned and ultrathin nanobelts. Variation in EDTA concentration can change the VO_2 morphology of ultrathin nanobelts into that of thick nanoplates. Mild annealing of ultrathin VO_2 nanobelts at 350℃ in air results in the formation of V_2O_5 nanobelts with a nearly unchanged ultrathin structure. The nucleation and growth mechanism involved in the formations of nanobelts and nanoplates are proposed. The ethanol gas sensing properties of the V_2O_5 nanobelt networks-based sensor are investigated in a temperature range from 100℃ to 300℃ over ethanol concentrations ranging from 3 ppm to 500 ppm.The results indicate that the V_2O_5 nanobelt network sensor exhibits high sensitivity, good reversibility, and fast responserecovery characteristics with an optimal working temperature of 250℃.展开更多
A novel three-dimensional（3D） hierarchical structure and a roughly oriented one-dimensional（1D） nanowire of WO3 are selectively prepared on an alumina substrate by an induced hydrothermal growth method.Each hierar...A novel three-dimensional（3D） hierarchical structure and a roughly oriented one-dimensional（1D） nanowire of WO3 are selectively prepared on an alumina substrate by an induced hydrothermal growth method.Each hierarchical structure is constructed hydrothermally through bilateral inductive growth of WO3 nanowire arrays from a nanosheet preformed on the substrate.Only roughly oriented 1D WO3 nanowire can be obtained from a spherical induction layer.The analyses show that as-prepared 1D nanowire and 3D hierarchical structures exhibit monoclinic and hexagonal phases of WO3,respectively.The gas-sensing properties of the nanowires and the hierarchical structure of WO_3,which include the variations of their resistances and response times when exposed to NO2,are investigated at temperatures ranging from room temperature（20 ℃） to 250 ℃ over 0.015 ppm-5 ppm NO2.The hierarchical WO3 behaves as a p-type semiconductor at room temperature,and shows p-to-n response characteristic reversal with the increase of temperature.Meanwhile,unlike the1 D nanowire,the hierarchical WO3 exhibits an excellent response characteristic and very good reversibility and selectivity to NO2 gas at room temperature due to its unique microstructure.Especially,it is found that the hierarchical VO3-based sensor is capable of detecting NO2 at a ppb level with ultrashort response time shorter than 5 s,indicating the potential of this material in developing a highly sensitive gas sensor with a low power consumption.展开更多
文摘Different shapes of ZnO nanobelts were synthesized at 550 ℃ by zinc acetate[Zn(CH3COO)2] and polyvinyl alcohol（PVA） as row material,under controlling the temperature rise rate.The analytical results of SEM and TEM indicate that the ZnO nanobelts possess a hexagonal wurtzite structure with preferred orientation along the direction of ZnO.For different experimental parameters,ZnO nanobelts have different widths and scales. The effect on zinc oxide nanobelts dimension and shape of proportion of mixture of raw material and mixing condition were discussed.Preliminary growth mechanics of ZnO nanobelts was proposed.
文摘碳纳米管是一种性能优良的场发射冷阴极材料,具有低的阈值电场和高的发射电流密度,在平板显示领域具有广阔的应用前景。本文从Fow ler-Nordhe im s场发射理论出发,阐述了CNT的场发射机制,详细论述了包括CNT的结构、方向性、阵列密度、吸附气体、工作环境等诸多因素对其场发射特性的影响。研究表明,垂直取向,长径比高,密度适中,表面洁净的CNT场增强因子较大,场发射性能较好。
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61274074,61271070,and 61574100)
文摘Ultrathin VO_2 nanobelts with rough alignment features are prepared on the induction layer-coated substrates by an ethylenediaminetetraacetic acid（EDTA）-mediated hydrothermal process. EDTA acts as a chelating reagent and capping agent to facilitate the one-dimensional（1D） preferential growth of ultrathin VO_2 nanobelts with high crystallinities and good uniformities. The annealed induction layer and concentration of EDTA are found to play crucial roles in the formation of aligned and ultrathin nanobelts. Variation in EDTA concentration can change the VO_2 morphology of ultrathin nanobelts into that of thick nanoplates. Mild annealing of ultrathin VO_2 nanobelts at 350℃ in air results in the formation of V_2O_5 nanobelts with a nearly unchanged ultrathin structure. The nucleation and growth mechanism involved in the formations of nanobelts and nanoplates are proposed. The ethanol gas sensing properties of the V_2O_5 nanobelt networks-based sensor are investigated in a temperature range from 100℃ to 300℃ over ethanol concentrations ranging from 3 ppm to 500 ppm.The results indicate that the V_2O_5 nanobelt network sensor exhibits high sensitivity, good reversibility, and fast responserecovery characteristics with an optimal working temperature of 250℃.
基金supported by the National Natural Science Foundation of China(Grant Nos.61274074 and 61271070)the Natural Science Foundation of Tianjin,China(Grant No.11JCZDJC15300)
文摘A novel three-dimensional（3D） hierarchical structure and a roughly oriented one-dimensional（1D） nanowire of WO3 are selectively prepared on an alumina substrate by an induced hydrothermal growth method.Each hierarchical structure is constructed hydrothermally through bilateral inductive growth of WO3 nanowire arrays from a nanosheet preformed on the substrate.Only roughly oriented 1D WO3 nanowire can be obtained from a spherical induction layer.The analyses show that as-prepared 1D nanowire and 3D hierarchical structures exhibit monoclinic and hexagonal phases of WO3,respectively.The gas-sensing properties of the nanowires and the hierarchical structure of WO_3,which include the variations of their resistances and response times when exposed to NO2,are investigated at temperatures ranging from room temperature（20 ℃） to 250 ℃ over 0.015 ppm-5 ppm NO2.The hierarchical WO3 behaves as a p-type semiconductor at room temperature,and shows p-to-n response characteristic reversal with the increase of temperature.Meanwhile,unlike the1 D nanowire,the hierarchical WO3 exhibits an excellent response characteristic and very good reversibility and selectivity to NO2 gas at room temperature due to its unique microstructure.Especially,it is found that the hierarchical VO3-based sensor is capable of detecting NO2 at a ppb level with ultrashort response time shorter than 5 s,indicating the potential of this material in developing a highly sensitive gas sensor with a low power consumption.
