TiO2纳米管的合成机理研究

采用水热合成方法制备出外径约8nm,壁厚为1nm的纳米管,以TEM、XRD和TG等分析手段对不同工艺条件下获得的产物进行了表征,对它们的热稳定性进行了测试.研究结果表明,纳米管是在NaOH水热处理过程中形成的,而不是在清洗过程中形成的.其形成机理可能是纳米氧化钛颗粒在强碱作用下形成的Na2Ti3O7片状物经过卷曲而成短纳米管,通过溶解-吸收机理,逐渐长成长纳米管.但清洗溶液的pH值对生成的纳米管的成分和结构有影响,通过控制清洗产物时的溶液的pH值和热处理温度,可以获得组成分别以Na2Ti3O7、H2Ti3O7和TiO2为主晶向的纳米管,且纳米管具有较好的热稳定性.     

氧化钛纳米管阵列阳极氧化法的制备及形成机理研究

采用阳极氧化法在氢氟酸、冰醋酸、聚乙二醇水溶液恒压处理钛箔,制备了结构规整有序的高密度TiO2纳米管阵列.利用电子扫描电镜(SEM)对纳米管的形貌进行了表征,详细考察了氧化时间对纳米管阵列形貌和尺寸的影响,绘制并分析了电流-时间曲线.对纳米管阵列的形成机理进行了研究,认为纳米管的形成经历了4个关键阶段,分别是致密膜的生成、微孔的出现、纳米管的融合和管长稳定生长至最长.     

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.     

水热法制备钛酸盐纳米管的研究进展

作为一种有诱人前景的新材料,钛酸盐纳米管的研制开发正在国内外展开.介绍了钛酸盐纳米管的微观结构和形成机理;综述了目前最为常见的钛酸盐纳米管的合成方法--水热法以及水热法制备钛酸盐纳米管的诸多影响因素:NaOH的浓度、反应时间和反应温度等;简要介绍了钛酸盐纳米管的应用.     

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.     

KOH碱性环境中TiO_2纳米管的水热制备及机理探讨

以锐钛矿型纳米TiO2粉体为前驱体,KOH溶液为水热介质,采用水热法成功地制备出TiO2纳米管.研究了水热条件及后处理过程对TiO2纳米管形貌、晶型结构的影响,并对TiO2纳米管的形成机理进行了初步探讨.结果表明,经140℃水处理24h、酸洗干燥、400℃恒温煅烧2h后,可得到多层中空、两端开口的锐钛矿型TiO2纳米管.     

TiO_2/MnTiO_3复合纳米管的光谱学性能研究

采用水热法制备了TiO2/MnTiO3复合纳米管,研究了TiO2纳米管经三元半导体MnTiO3复合后光谱性能的变化。用X射线衍射(XRD)、紫外-可见光谱(UV-Vis DRSs)、拉曼光谱等对制得的样品进行表征。MnTiO3的复合改变了TiO2纳米管的表面缺陷态,增强了TiO2纳米管在可见光区的吸收。     

超声波-水热法合成Bi2Te3纳米管

以水为反应介质，NaBH4为还原剂，合成了BizTe3纳米管及纳米微粒。溶液首先在超声波发生器中预处理1h，然后置于150℃，水热反应釜中继续反应48h。XRD分析表明：合成产物主要物相为Bi2Te3；SEM观察可见产物中有纳米管生成，纳米管直径约为50-100nm，管壁厚约8-10nm，长度在500nm以上。EDS分析表明：纳米管成份为Bi2Te3。Bi2Te3纳米管可能的生长机制为纳米薄片-卷曲-闭合-纳米管。     

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.     

稀土Ce3+离子置换钛酸盐纳米管的制备及表征

采用水热法制备了钛酸盐纳米管,随后以硝酸铈溶液与钛酸盐纳米菅进行了离子交换反应,并利用TEM、XRD、FT-IR、UV-Vis、zeta电位等对试样进行了测试表征.结果表明:该方法得到的钛酸盐纳米管管径约为8～10nm,钛酸盐纳米管的物相可以近似表示为NaxH2-xTi3O7(x≈0.70).离子交换后,XRD分析显示纳米管的骨架结构基本保持不变;禁带宽度由3.26eV减少到2.70eV,扩展了其光谱吸收范围;且经离子交换后的样品的zeta电位绝对值较起始钛酸盐纳米管的电位值有所提升,水相体系更加稳定.     

Understanding Formation Mechanism of Titanate Nanowires through Hydrothermal Treatment of Various Ti-Containing Precursors in Basic Solutions

Titanate nanowires prepared by hydrothermal treatment of TiO₂ in NaOH solution have attracted intensive attentions,but the formation mechanism is still under debate.Herein,we report an in-depth study on the formation mechanism through investigating the hydrothermal behavior of various Ti-containing precursors in basic solutions,including Ti,TiN,TiO₂,Ti₂SnC and Ti₂AlN.Based on the results by means of X-ray diffraction（XRD）,transmission electron microscopy（TEM） and Raman spectroscopy,it is demonstrated that the crystal structure of the hydrothermal products is irrespective to the structure of the precursors or the types of basic solution（NaOH or KOH） in use.Alkali ions play an important role in the formation of titanate nanowires.The formation mechanism of the resultant titanate nanowires was proposed to be dissolution-crystallization mechanism.     

负载Ti02NBs太阳能电池材料的制备及表征

本文主要是采用水热法制备一维的二氧化钛纳米带（TiO2NBs）,在Ti02NBs上分别负载硒化镉（GdSe）硫化镉（CdS）,再对比负载后的Ti02NBs的光吸收特性,运用X-射线衍射（XRD）、扫描电子显微镜（SEM）、紫外-可见（UV—vis）漫反射吸收光谱等表征。     

水热合成勃姆石纳米棒及其改性复合膜

商用锂离子电池隔膜遭受高温时,会发生热收缩现象,通过涂覆无机颗粒对隔膜进行改性,可以有效地提高隔膜的热稳定性能,从而提高锂离子电池的安全性能,而勃姆石纳米棒具有耐热性好和弹性模量大等特点,适用于涂覆改性隔膜.本研究利用AlCl3和NaOH与NH4 OH混合沉淀剂,通过水热法制备了勃姆石纳米棒,并使用线棒涂布工艺制备了涂...     

Effect of Ni+2-substituted Fe2TiO5 on the H2-reduction and CO2 Catalytic Decomposition Reactions at 500℃

CO2 is a major component of the greenhouse gases, which causes the global warming. To reduce CO2 gas,high activity nanosized Ni 2 substituted Fe2TiO5 samples were synthesized by conventional ceramic method.The effect of the composition of the synthesized ferrite on the H2-reduction and CO2-catalytic decomposition was investigated. Fe2TiO5 (iron titanate) phase that has a nanocrystallite size of ～80 nm is formed as a result of heating Fe2O3 and TiO2 while the addition of NiO leads to the formation of new phases (～80 nm)NiTiO3 and NiFe2O4, but the mixed solid of NiO and Fe2O3 results in the formation of NiFe2O4 only.Samples with Ni 2=0 shows the lowest reduction extent (20%); as the extent of Ni 2 increases, the extent of reduction increases. The increase in the reduction percent is attributed to the presence of NiTiO3 and NiFe2O4 phases, which are more reducible phases than Fe2TiO5. The CO2 decomposition reactions were monitored by thermogravimetric analysis (TGA) experiments. The oxidation of the H2-reduced Ni 2 substituted Fe2TiO5 at 500℃ was investigated. As Ni 2 increases, the rate of reoxidation increases. Samples with the highest reduction extents gave the highest reoxidation extent, which is attributed to the highly porous nature and deficiency in oxygen due to the presence of metallic Fe, Ni and/or FeNi alloy. X-ray diffraction (XRD) and transmission electron microscopy (TEM) of oxidized samples show also the presence of carbon in the sample containing Ni 2＞0, which appears in the form of nanotubes (25 nm).     

Effect of Ni+2-substituted Fe2TiO5 on the H2-reduction and CO2 Catalytic Decomposition Reactions at 500℃

CO2 is a major component of the greenhouse gases, which causes the global warming. To reduce CO2 gas, high activity nanosized Ni＋2 substituted Fe2TiO5 samples were synthesized by conventional ceramic method. The effect of the composition of the synthesized ferrite on the H2-reduction and CO2-catalytic decomposition was investigated. Fe2TiO5 （iron titanate） phase that has a nanocrystallite size of -80 nm is formed as a result of heating Fe2O3 and TiO2 while the addition of NiO leads to the formation of new phases （-80 nm） NiTiO3 and NiFe2O4, but the mixed solid of NiO and Fe2O3 results in the formation of NiFe2O4 only. Samples with Ni^＋2=0 shows the lowest reduction extent （20%）; as the extent of Ni＋2 increases, the extent of reduction increases. The increase in the reduction percent is attributed to the presence of NiTiO3 and NiFe2O4 phases, which are more reducible phases than Fe2TiO5. The CO2 decomposition reactions were monitored by thermogravimetric analysis （TGA） experiments. The oxidation of the H2-reduced Ni＋2 substituted Fe2TiO5 at 500℃ was investigated. As Ni^＋2 increases, the rate of reoxidation increases. Samples with the highest reduction extents gave the highest reoxidation extent, which is attributed to the highly porous nature and deficiency in oxygen due to the presence of metallic Fe, Ni and/or FeNi alloy. X-ray diffraction （XRD） and transmission electron microscopy （TEM） of oxidized samples show also the presence of carbon in the sample containing Ni＋2〉0, which appears in the form of nanotubes （25 nm）.     

Photoelectrochemical Performance of Nb-doped TiO2 Nanoparticles Fabricated by Hydrothermal Treatment of Titanate Nanotubes in Niobium Oxalate Aqueous Solution

Nb-doped TiO2 nanoparticles were prepared by hydrothermal treatment of titanate nanotubes in niobium oxalate aqueous solution.The effect of Nb doping and rutile content on the photoelectrochemical performance based on TiO2 powder electrodes was investigated.The results show that Nb-doped TiO2 with a small amount of rutile exhibits the enhanced photoelectric conversion efficiency for dye-sensitized solar cell.The highest photoelectric conversion efficiency of 8.53%is obtained for 1%Nb—TiO2 containing a small amount of rutile.When a small amount of rutile contained in 2%Nb—TiO2,a higher photoelectric conversion efficiency of8.77%is achieved.     

水热法制备二氧化钛纳米管:形成机理、影响因素及应用

TiO2纳米管由于具有较大的比表面积、优异的光催化活性以及结构可控的特性,使其在电学、光学、催化剂以及传感器、锂离子电池、染料敏化太阳能电池、能源转换等方面具有非常大的应用潜力。目前采用简单的水热法就能够在较低的温度和压力下制备出二氧化钛纳米管,这使得水热法合成TiO2纳米管受到广泛关注。文章主要综述了水热法制备TiO2纳米管的形成机理以及温度、原料、酸洗、干燥、填充度等因素对纳米管形成的影响。     

工业硫酸氧钛合成有序介孔TiO2及其机理研究

采用复合表面活性剂CTAB和P123形成的超分子模板为结构导向剂,以工业硫酸氧钛液为钛源,控制溶液pH值及水解条件调控TiOSO₄的水解缩聚及与模板剂的自组装速率,钛水解胶粒通过界面作用形成介孔前驱体,脱模后制得二维六方,比表面积为205.7m²/g,平均孔径为3.28nm的锐钛型有序介孔TiO2. 用XRD、HRTEM、SAED及等温N2吸附等对样品进行了表征,初步探讨了介孔的形成过程. 钛水解胶粒和复合模板剂通过界面处的静电和氢键等相互作用,协同形成介孔结构,属协同作用机理.     

Investigation on the film-coating mechanism of alumina-coated rutile TiO2 and its dispersion stability

The alumina and alumina-coated rutile TiO₂ samples were synthesized by the chemical liquid deposition method under various pH values and aging temperature. The prepared samples were characterized by X-ray diffraction (XRD), Transmission electron microscopy (TEM), ζ-potential as well as X-ray photoelectron spectroscopy (XPS). The relationship between pH values, the dispersion stability, crystalline types and microstructure of alumina-coated rutile TiO₂ samples were studied. It is indicated that the coating film exhibited amorphous hydrous alumina (at pH 3–7), boehmite (at pH 7–9) and bayerite (pH > 11), respectively. And the higher aging temperature was in favor of the elevation of boehmite content of coating film. As the boehmite content increased, the dispersion stability was gradually enhanced and the prepared sample exhibited optimum dispersion stability at pH 9 and aging temperature 200 °C, respectively. The increase of steric hindrance and electrostatic repulsion led to the promotion of dispersion stability via coating hydrous alumina film on the surface of rutile TiO₂. The detection of AlO and the significantly enhancement of AlOTi intensity confirmed that the film coating process should be main attributed to both chemical bonding and physical adsorption.     

纳米TiO2粉体的制备及其表征

采用溶胶-凝胶技术制备了纳米TiO2粉体,并对其热性能、相结构、颗粒大小和分布进行了表征,结果表明,TiO2干凝胶粉经300℃煅烧后已有锐钛矿相出现,经550℃煅烧后有金红石相出现,完全相转变的温度约为600℃,纳米TiO2粉体的颗粒尺寸随煅烧温度的升高而增大,采用溶胶,凝胶技术制备的干凝胶粉经400℃煅烧后可获得团聚轻、颗粒大小分布比较均匀、颗粒尺寸约为15nm的球状TiO2粉体,