氧化钒纳米管的自组装合成机理

以V₂O₅和十六胺为原料在水热条件下合成了氧化钒纳米管, 采用XRD、SEM、TEM、FTIR、ESR等手段分析研究了氧化钒纳米管的形成机理. 结果表明, 氧化钒纳米管的形成主要基于“卷曲机理”, 其形成过程包括: 表面活性剂分子嵌入到钒氧化物层间, 形成新层状化合物前驱体; 水热驱动下层状化合物边缘松动, 并开始卷曲, 降低体系能量; 合适的水热反应时间下最终形成钒氧化物纳米管. 模板剂嵌入到钒氧化物层间形成一定大小的层间距以及V⁴⁺的存在对从层状化合物卷曲成纳米管起到了积极的作用.     

水热温度和酸洗浓度对水热法合成钛酸盐纳米管的影响

以P25纳米粉体和NaOH为原料,采用水热合成法制备出钛酸盐纳米管。通过TEM和XRD表征手段,研究了水热温度和酸洗浓度对钛酸盐纳米管微观形貌和晶型组成的影响。结果表明,用去离子水或低浓度的酸处理反应产物时,纳米管的结构清晰完整,其成分主要是H2Ti2O5.H2O;用高浓度的酸处理反应产物时会破坏纳米管结构,其成分主要是锐钛矿型TiO2。反应温度对产物的微观结构和晶型组成也有显著影响:水热温度90℃时的产物只能得到膜状物和少量纳米管,而水热温度从110℃升至190℃时,纳米管的长度逐渐增长,而管径基本不变;低温反应得到的产物晶型与原料类似,较高反应温度的产物为锐钛矿。     

钛纳米管的水热合成研究及应用进展

钛纳米管是一种新型一维管状纳米材料,合成方法中研究得最深入的是水热法。钛纳米管具有的特殊性质使其在催化、负载、光电化学、吸附和离子交换等领域有着潜在的应用前景。本文综述了近5年来研究者们对钛纳米管组成成分、形成机理、及水热条件对产物形貌影响的研究进展,介绍了其应用研究现状。     

阳极氧化时间对二氧化钛纳米管阵列形貌的影响

采用电化学阳极氧化法,以乙二醇体系作为电解液,在60V的直流电压下,在纯钛基底表面制备高度有序的TiO2纳米管阵列,通过改变氧化时间来探究其对TiO2纳米管阵列形貌的影响。运用XRD、SEM分别对TiO2纳米管阵列的结构、形貌特征进行表征。结果表明,氧化时间对TiO2纳米管的管壁厚度、管径以及管长均有影响;氧化时间为2...     

阳极氧化时间对二氧化钛纳米管阵列形貌的影响

采用电化学阳极氧化法,以乙二醇体系作为电解液,在60V的直流电压下,在纯钛基底表面制备高度有序的TiO2纳米管阵列,通过改变氧化时间来探究其对TiO2纳米管阵列形貌的影响。运用XRD、SEM分别对TiO2纳米管阵列的结构、形貌特征进行表征。结果表明,氧化时间对TiO2纳米管的管壁厚度、管径以及管长均有影响;氧化时间为2～2.5h时,所得到的二氧化钛纳米管管壁约为10nm、管径约为200nm、管长为2～3μm。     

氧化法热处理温度对氧化钒薄膜热敏特性的影响

采用直流磁控溅射法制备氧化钒薄膜,并采用不同的温度对其进行氧化法热处理,通过XRD、SEM、四探针薄膜电阻测试,分析了不同热处理温度对氧化钒薄膜的晶相特性与热敏特性的影响。实验分析证明热处理温度升高后(400℃)得到的薄膜热敏特性良好,其室温电阻为160KΩ·cm,室温电阻温度变化系数为-2.4%/℃,变温过程中(20~98℃)其平均值约-1.98%/℃,表明温度升高有利于改善薄膜热敏特性,在非制冷红外探测器应用方面具有发展潜力。     

CeO2纳米管的水热合成、表征及性能研究

以P123为表面活性剂,采用水热法合成CeO2纳米管.研究反应时间、反应温度、表面活性剂浓度对CeO2纳米管形成的影响规律.采用TEM、XRD、N2吸脱附仪对样品的微观结构进行表征.并考察CeO2纳米管对亚甲基蓝溶液的催化性能.结果表明,当反应时间为72 h、反应温度为160℃、n(P123):n(CeCl3.7H2O)=1:5时,可制备出单晶结构的CeO2纳米管.所制备的CeO2纳米管外径为40~60nm,内径为20 nm左右,长度为500~1000nm.CeO2纳米管是由Ce(OH)3晶种的溶解再结晶-异向生长-自我卷曲形成的.相对于CeO2纳米颗粒和CeO2纳米棒,CeO2纳米管对亚甲基蓝染料的脱色率有明显提高.这与CeO2纳米管孔道的吸附作用,暴露的高反应活性面(110)和表面有大量缺陷有关.     

聚吡咯/钒氧纳米管复合阴极材料的制备及其电化学行为研究

以V2O5粉末和过氧化氢为原料,十六烷基胺为模板剂,利用水热合成法制备钒氧纳米管,然后结合阳离子交换技术,用导电聚合物聚吡咯修饰替换钒氧纳米管中的有机模板剂,成功制备了聚吡咯/钒氧纳米管复合材料。借助透射电子显微镜和傅里叶红外光谱观察和分析了修饰前后纳米管的形貌和结构变化,实验结果证实聚吡咯不但成功修饰替换了钒氧纳米管中的有机模板剂,而且还很好地保持了纳米管的管状结构。采用恒流充放电和循环伏安分别测试了修饰前后样品的电化学性能,测试结果表明导电聚合物聚吡咯的修饰替换极大地提高了电极材料的首次充放电比容量和循环稳定性,循环伏安结果和20次循环后的表面形貌分析也进一步证实了这一结论。由于聚吡咯具有高的电导率和良好的柔韧性,不仅提高了复合纳米管材料的电导率,而且还改善了复合纳米管材料的结构稳定性。     

合成温度对二氧化钛纳米管的影响

以P25纳米粉体和NaOH为原料,采用水热合成法,在不同的合成温度下制备TiO2纳米管.用XRD、TEM、BET、TG-DSC、Uv-vis等方法对TiO2纳米管的形貌、成分和性能进行了表征.结果表明,合成温度对产物有显著影响:随着反应温度的升高,纳米管的比表面积逐渐增大,长度逐渐增长,而管径基本不变,纳米管的产率也有增加的趋势.150℃反应制得粉体的比表面积为641.855m2/g,管外径为8nm.160℃反应制得的粉体经560℃处理后降解亚甲基蓝的能力要远优于市售的P25纳米粉体.鉴于以前水热处理温度对纳米管形成方面的影响研究报道较少,系统的研究了温度对纳米管形成的影响.     

钛盐纳米管的制备及光电性能研究

采用水热法制备了钛盐纳米管,并用TEM、XRD对其进行了表征.结果表明,纳米管是在洗涤过程中形成的,管径在5～30nm之间,管长约为0.1～1μm.纳米管具有不同于锐钛矿型的钛盐的结构;将其在450℃下热处理2h后,纳米管转变为锐钛矿型TiO2粒子.将钛盐纳米管制备成纳米管结构电极,并进行了光电化学研究.钛盐纳米管产生阳极光电流,为n型半导体.     

Optical properties of vanadium oxide nanotubes

The optical properties of vanadium oxide nanotube dispersions have been characterized using visible and near infrared absorption spectroscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, and nonlinear transmission of optical intensities in the visible and near infrared. Using transmission electron microscopy, optical properties have been correlated to the occurrence of two distinct nanoparticle morphologies: nanotubes and unrolled tubes or platelets. Raman spectroscopy indicates that color changes associated with tub unrolling can be attributed to V2O5 formation. The nanotube and platelet morphologies both show strong optical intensity limiting at 532 and 1064 nm. However, dependencies on repetition rate suggest that slightly different mechanisms dominate at the two wavelengths.     

Hydrothermal synthesis of vanadium oxide nanotubes from oxide precursors

Vanadium oxide nanotubes were synthesized as the main product by a direct hydrothermal treatment of oxide precursors and long chain amines as structure-directing templates. The morphology and structure of nanotubes was characterized by powder X-ray diffraction, electron microscopy, and thermal analysis. Nanotubes of high aspect ratio with layered structures were found to grow together in the form of bundles. The paper also discusses the chemistry issues involved in synthesizing nanostructured vanadium oxides.     

A one-step hydrothermal way for the synthesis of vanadium oxide nanotubes containing the phenylpropylamine as template obtained via non-alkoxide route

Vanadium oxide nanotubes (VO_x-NTs) with high crystallinity were synthesized by using the crystalline V₂O₅ as precursor for the first time with 3-phenylpropylamine as structure-directing template via one-step hydrothermal way. Structure and morphology of the nanotubes were investigated by Scanning Electron Microscopy, Transmission Electron Microscopy, X-ray powder diffraction, Thermal analysis and Infrared. The inner and the outer of the obtained nanotubes vary respectively between 15 to 25 nm and 70 to 100 nm with a length up to 4 μm.     

W doped vanadium oxide nanotubes: Synthesis and characterization

W doped vanadium oxide nanotubes (VONTs) were prepared via a rheological phase reaction followed by self-assembling process. The nanotubes were characterized by elemental analysis, IR, XRD, SEM, TEM, HRTEM, SAED and XPS. Elemental analysis, IR, XRD, SAED and XPS could confirm the crystalline characteristic of the W doped VONTs, while the SEM, TEM, and HRTEM confirmed their morphology and microstructure.     

Synthesis of vanadium oxide nanotubes from V2O5 sols

Vanadium oxide nanotubes (VO_x-NTs) were prepared by using V₂O₅ sols as precursor for the first time with hexadecylamine (HDA) as structure-directing template via a modified sol–gel method followed by hydrothermal treatment. Structure and morphology of the nanotubes were investigated by XRD, SEM, HRTEM, TGA, FT-IR and XPS. The obtained nanotubes were found having outer diameters from 30 to 100 nm and inner diameters from 10 to 30 nm with length up to several micrometers. It is also confirmed that water molecules enter vanadium oxide layers together with structure-directing template and the low valence vanadium occurs in the VO_x-NTs.     

Synthesis of Ag modified vanadium oxide nanotubes and their antibacterial properties

Vanadium oxide nanotubes (VO_x-NTs) modified by highly dispersed Ag nanoparticles have been synthesized via a facile silver-mirror reaction. The crucial factors that affected the preparation of the Ag modified vanadium oxide nanotubes (Ag/VO_x-NTs) have been also studied. The dispersion and structure of Ag nanoparticles in the obtained materials were characterized by transmission electron microscopy (TEM), electron diffraction (ED) and X-ray diffraction (XRD). The results showed the distribution and size of the formed Ag particles were greatly influenced by the concentration of AgNO₃ solution. Typically, Ag nanoparticles were well dispersed on the VO_x-NTs with the size range from 3 to 10 nm. The corresponding antibacterial tests demonstrated the as-synthesized Ag/VO_x-NTs exhibited strong antibacterial activity against Escherichia coli (E. coli).     

Influence of interstitial oxygen on the superconducting transition temperature of vanadium

The critical temperatureT _c and residual resistivity ₀ were measured in homogeneously oxidized thin vanadium foils. The per at % oxygen induced variations are respectively T _c =–1.2K and ₀=53 n-m. TheT _c data are used to calculate the electron-phonon coupling constant, which decreases 5% per at % of oxygen.