乙醇辅助低温水热法生长TiO2纳米棒阵列

本文采用乙醇作为添加剂，通过低温水热法在透明导电玻璃衬底上制备晶化良好的金红石相TiO₂纳米棒阵列。对样品进行了X射线衍射(XRD)、扫描电子显微镜(SEM)等结构形貌表征和光电化学性能测试。实验发现乙醇加入有利于前驱物水解缩聚反应，同时提高水热反应压力，促进TiO₂晶粒低温成核和生长，从而实现70℃直接在基底表面生长出TiO₂纳米棒阵列。通过调控水热反应温度、时间以及乙醇添加量等参数可有效调控TiO₂纳米棒阵列的形貌，改善其光电化学性能。同时低温水热制备工艺也降低了对衬底材料的限制，拓展了TiO₂纳米棒阵列的应用领域，表现出良好的应用前景。     

改性纳米TiO2/水性丙烯酸酯耐老化涂料的制备及性能研究

利用自制具有强烈紫外吸收的改性纳米TiO₂粒子,对水性羟丙二级分散体进行共混改性,搭配氨基树脂制成高温烘烤涂料。研究了改性纳米TiO₂粒子对涂层性能尤其是耐老化行为的影响规律。研究结果表明：二氧化硅包膜改性的纳米TiO₂粒子能有效提高材料的紫外吸收性能;当改性纳米TiO₂粒子在涂料中占比为0.4%时,涂层具有优异的硬度、附着力、柔韧性等机械性能;改性纳米TiO₂粒子可明显提高涂层耐老化性能。     

PFSA-PES-纳米颗粒复合纳米纤维的制备及催化性能

利用静电纺丝法制备了全氟磺酸(PFSA)-聚醚砜(PES)-纳米颗粒(SiO₂、TiO₂和Al₂O₃)复合纳米纤维,比较了SiO₂、TiO₂和Al₂O₃等不同纳米颗粒对磺酸基团在纤维表面分布的影响,并利用乙酸乙酯合成反应考察了纤维结构对表面磺酸基团活性的关系。结果表明:静电纺复合纳米纤维的比表面积可达85.6 m²·g^-1,纳米颗粒均匀分布在纤维表面,表面酸性中心占PFSA酸性基团总量最高达71.2%。酯化反应实验表明,复合纳米纤维具有很好的催化性能,纳米颗粒的存在可以提高酸中心的活性;同时,所得复合纳米纤维膜表现出很好的回收与可再生性能,有望作为一种对环境友好的固体酸催化剂。     

TiO2-SiO2复合材料应用研究进展

无机材料TiO₂和SiO₂因稳定性好、无毒害等性能得到广泛关注和应用,TiO₂-SiO₂复合材料因TiO₂和SiO₂组分的协同作用,表现出更加优异的性能。综述TiO₂-SiO₂复合材料在药物缓释、光催化、吸附、抗菌等相关应用领域中的研究进展,以期为其后续研究提供参考。     

多级孔ZrO2/TiO2/ZSM-5分子筛的合成及吸附-光催化协同性能

以碱酸改后的凹凸棒土为硅源,利用溶胶-凝胶法将 TiO₂和 ZrO₂负载于一步水热合成的多级孔 ZSM-5 分子筛表面,形成多级孔 ZrO₂/TiO₂/ZSM-5 分子筛。通过 XRD、SEM 和 N₂吸附-脱附仪等手段对样品进行表征,研究 TiO₂和 ZrO₂掺杂对多级孔 ZSM-5骨架结构、形貌及孔道的影响,并对亚甲基蓝溶液进行实验,探究其吸附-光催化协同性能。结果表明：ZrO₂负载促进了锐钛矿 TiO₂的形成,同时利用分子筛的多级孔道和比表面积提高了底物富集能力。当反应进行 20 min时,TiO₂掺杂量为 10% 的 TiO₂/ZSM-5 分子筛光催化降解效率达 73%;进一步掺杂 ZrO₂,ZrO₂/TiO₂/ZSM-5 分子筛光催化反应效率提高至 96.2%,说明 ZrO...     

以硅氧烷溶胶为介质制备纳米TiO2光致超亲水涂层

简单、经济、规模化制备二氧化钛（TiO₂）光致超亲水表面备受重视。本研究利用硅氧烷溶胶为介质,将TiO₂纳米颗粒浸涂到玻璃表面。考查了颗粒在表面的分散状况和TiO₂含量对涂层光致超亲水性能、透明性以及涂层牢固度和表面硬度的影响。结果发现:浸涂并经紫外辐照1h或120℃烘干3h后,TiO₂纳米颗粒能均匀、牢固地负载到玻璃表面;10min UV辐照后,表面变得超亲水;涂层附着力达0级,表面硬度达到5H。硅氧烷溶胶对玻璃表面的良好浸润性和对含羟基纳米颗粒的良好"粘结"性能是纳米颗粒在玻璃表面能均匀、牢固负载的主要原因。研究结果为大规模、低成本制备透明自清洁表面提供了理论和实验基础。     

WC/TiO2纳米复合材料晶相形成机理及电催化性能

以金红石相纳米TiO₂为载体,偏钨酸铵为钨源,采用表面修饰技术制备了纳米复合材料的前体,将前体在甲烷/氢气气氛下还原碳化并采用XRD对其进行表征,研究了还原碳化温度、时间对纳米复合材料晶相组成的影响,并探讨了WC/TiO₂纳米复合材料的形成机理。通过扫描电子显微镜、热重-差热分析等手段对WC/TiO₂纳米复合材料的形态结构和热稳定性进行了表征。采用循环伏安法研究了纳米复合材料物相组成与电催化性能之间的关系,结果表明由WC和TiO₂两相组成的WC/TiO₂纳米复合材料对对硝基苯酚电还原反应的电催化性能最佳。     

壳聚糖/纳米纤维素/石墨烯改性纳米TiO2复合膜光催化降解性能

以氧化石墨烯改性纳米二氧化钛为光催化活性成分,通过流延成型法制备了壳聚糖/纳米纤维素/石墨烯改性纳米TiO₂光催化复合膜。利用热重分析仪(TG)、傅里叶红外光谱仪(FTIR)和扫描电子显微镜(SEM)对复合膜的结构进行表征。研究了壳聚糖/纳米纤维素/改性纳米TiO₂复合膜的力学性能,对比了复合膜对亚甲基蓝及甲基橙的光催化降解性能。结果表明,改性纳米TiO₂的添加提高了壳聚糖复合膜的力学性能及耐热性能。改性纳米TiO₂质量分数为4%的复合膜抗拉强度最大,达到43 MPa。改性纳米TiO₂质量分数为2%的复合膜断裂伸长率最大为13.6%。在模拟溶液质量浓度为20 mg/L时,改性纳米TiO₂质量分数为2%的复合膜对亚甲基蓝降解率最大,为51.7%。改性纳米TiO₂质量分数为4%的复合膜对甲基橙降解率最大,为42.2%。模拟溶液初始浓度愈高,则复合膜对亚甲基蓝及甲基橙降解率均降低。     

有机改性金红石型纳米TiO2对聚乙醇酸抗光老化性能的研究

用硅烷偶联剂（A-172）对金红石型纳米TiO₂进行有机表面改性,采用红外光谱（FTIR）、透射电镜（TEM）对改性结果进行了表征。红外光谱表明,A-172以化学键的方式结合在纳米TiO₂表面;透射电镜照片表明,改性后的纳米TiO₂表现出较强疏水性。将改性后的纳米TiO₂作为紫外线屏蔽剂添加到聚乙醇酸（PGA）中,分别制备了TiO₂质量分数为0.5%、1%、1.5%和2%的复合材料,并采用氙灯气候试验机对纯PGA和PGA/纳米TiO₂复合材料进行加速老化对比试验。实验结果表明,改性后的纳米TiO₂在PGA材料中具有良好的分散性,使PGA具有更宽的紫外吸收范围和更强的紫外吸收峰,其中,当添加质量分数为1.5%时改性效果最佳,经过800h加速老化后,复合材料黄色指数只增加4.1,拉伸强度和缺口冲击强度保持率为56.34%和65.15%,分别比纯PGA提高了42.29%和37.21%,重均分子量和数均分子量保持率也分别提高了33.64%和33.99%。     

甘油中水合TiO2及不同晶型纳米TiO2光致变色现象

系统地研究了甘油中水合TiO₂及不同晶型纳米TiO₂的光致变色现象。实验结果显示无定型水合TiO₂具有最明显的变色行为,锐钛型纳米TiO₂变色程度次之,金红石型纳米TiO2没有明显变色现象发生,混晶型(金红石和锐钛)纳米TiO₂的变色程度介于金红石型和锐钛型之间。XPS结果表明TiO₂的光致变色是由Ti³⁺引起的。从电子-空穴对复合率影响Ti ³⁺形成的角度对实验现象作出了详细解释,电子-空穴对复合率越高,Ti³⁺形成率越低,从而变色程度越浅;并运用双注入机制和小极子模型阐述了不同晶型TiO₂的光致变色机理。分析了甘油环境对TiO₂光致变色现象的影响,得出甘油对TiO₂的光致变色行为有促进作用。     

Effect of carbon dioxide and nitrogen on the diffusivity of methane confined in nano-porous carbon aerogel

The microscopic diffusivity of methane (CH₄) confined in nano-porous carbon aerogel was investigated as a function of added carbon dioxide (CO₂) and nitrogen (N₂) pressure using quasi-elastic neutron scattering (QENS). In the range of the external pressure of 1-2.5 MPa, the self-diffusivity of methane was found to increase with CO₂ pressure and remain practically unchanged in the N₂ environment. Increasing mobility of methane with CO₂ pressure suggests that the adsorbed CH₄ molecules become gradually replaced by CO₂ on the surface of carbon aerogel pores, whereas the presence of N₂ does not induce the replacement. The molecular mobility of the methane, with or without added carbon dioxide and nitrogen, is described by the unrestricted diffusion model, which is characteristic of methane compressed in small pores. On the other hand, both nitrogen and carbon dioxide molecules in carbon aerogel, when studied alone, with no methane present, follow a jump diffusion process, characteristic of the molecular mobility in the densified adsorbed layers on the surface of the aerogel pores.     

Mesoporous silica supports for improved thermal stability in supported Au catalysts

In this work, we present a comprehensive review of our research on the role of mesoporous silica pore architecture, composition of the pore walls (addition of Co or Al), and silica surface chemistry (surface modification by TiO₂) to improve the hydrothermal stability of Au particles. We have found that mesoporous silica architecture plays an important role in improving Au stability, with three dimensional mesoporous architectures being less effective than one dimensional (1-D) pores. The tortuous 1-D pores in aerosol silica were found to be most effective at controlling Au particle size. Since Au particles continue to grow larger than the pore diameter, we conclude that Ostwald ripening must be the dominant sintering pathway for these Au catalysts. These catalysts are active for CO oxidation even after the Au particles have grown large enough to block the pores, suggesting that the thin walls of mesoporous silica provide easy access to gas phase molecules. Further improvements in Au stability and reactivity were obtained by surface modification of the aerosol and MCM-41 silica with TiO₂. After TiO₂ modification of the silica, the Au particles remained smaller than the pore size (< 3 nm) even after three cycles of CO oxidation at temperatures up to 400 °C.     

Photocatalytic water splitting performance of TiO2 sensitized by metal chalcogenides: A review

Titanium dioxide (TiO₂) has been extensively studied for photocatalytic water splitting applications for more than 50 years because of its advantages, such as its low cost, abundance, good chemical stability, nontoxicity, and sufficient energy potential to oxidize and reduce water molecules. On the other hand, TiO₂ has its own set of limitations, namely its wide bandgap (Eg = ～3.2 eV), which makes it less effective in sunlight. A few methods have been reported to overcome these problems, one of which is to make a heterojunction composite with other materials. The added material can inject electrons directly into the conduction band of TiO₂ and provide a tiered band structure, which can reduce the occurrence of photogenerated electron and hole recombination. Currently, the research and development of heterojunctions consisting of TiO₂ with chalcogenide materials has attracted the attention of many researchers. Metal chalcogenides offer a number of advantages, including absorption onset tuning, a size-dependent bandgap that can lead to high theoretical quantum efficiencies, effective charge transfer to the conduction band when TiO₂ is exposed to visible light, and high photochemical stability. In this review, the performance of various TiO₂/metal chalcogenide heterojunctions for photoelectrochemical water splitting is presented. The role of most common metal chalcogenides in TiO₂ will be exposed. Finally, the review concludes with a summary and recommendations for further research on this hot issue.     

Effect of Ti combined with Si and C on mechanical performance and oxidation resistance of SiC castables for plasma gasifier

Gaseous products released during the oxidation of SiC at 1700?°C lead to serious degradation of SiC castables. Ti combined with Si and carbon black are added to improve the mechanical behavior and oxidation resistance of SiC castables in this study. The mechanical behavior, isothermal oxidation, microstructure, and thermodynamic analysis are used to evaluate the properties of SiC castables. The result shows that SiC castables with more Ti exhibit better degradation resistance at high temperature oxidation atmosphere. The preferential oxidation of metal Ti to TiO₂ reduces the oxidizing gases and increases the content of SiO (g) in the matrix, which is beneficial for the generation of SiC fibers; in turn, this reinforces the mechanical behavior. In addition, a certain amount of TiO₂ dissolves into SiO₂ glass following the decrease in viscosity. TiO₂ is not only more difficult to volatilize than SiO₂, but also can decrease the viscosity of SiO₂ glass to improve the mobility of the liquid, which is good for healing the pores on the surface and protecting the inner SiC from being oxidized; this improves the mechanical properties and oxidation resistance.     

Synthesis and properties of epoxy/TiO2 composite materials

Epoxy/TiO₂ composites were prepared by solution mixture method, in which epoxy resin and nano‐TiO₂ liquid were mixed in the presence of methyl isobutylketone. According to the experimental results, hydrogen bonds can be formed by mixing TiO₂ particles and epoxy resin. The SEM analysis suggests that TiO₂ particles are uniformly distributed within the material, while some silver streaks occur at the surface of materials. Besides, thermo‐resistance and mechanical property of materials are found to improve with the addition of TiO₂, but degrades if the nano‐TiO₂ is the excess of 3%. Furthermore, these properties can be improved with the increasing concentration of methyl isobutylketone. POLYM. COMPOS., 27:195–200, 2006. © 2006 Society of Plastics Engineers.     

Developments in photocatalytic antibacterial activity of nano TiO<Subscript>2</Subscript>: A review

TiO₂, which is one of the most explored materials, has emerged as an excellent photocatalyst material for environmental and energy fields, including air and water purification, self-cleaning surfaces, antibacterial and water splitting. This review summarizes recent research developments of TiO₂-based photocatalyst used for photocatalytic antibacterial applications. Several strategies to enhance the efficiency of TiO₂ photocatalyst are discussed, including doping with metal ions, noble metals, non-metals, and coupling with other materials. The mechanism of photocatalytic antibacterial activity in the presence of nano-sized TiO₂ is also discussed. The modified TiO₂ photocatalyst significantly inhibits the growth of bacterial cells in response to visible light illumination. TiO₂ photocatalysis appears to be promising as a route of advanced oxidation process for environmental remediation.     

Characterisation and spectral properties of surface adsorbed phenosafranine dye in zeolite-Y and ZSM-5: Photosensitisation of embedded nanoparticles of titanium dioxide

Synthesis, characterisation and photosensitisation of titanium dioxide nanoparticles by phenosafranine dye adsorbed on the external surfaces of microporous materials were carried out. Titanium dioxide nanoparticles were anchored on the external surface as well as encapsulated in the cavities of porous zeolites. The composite materials are characterized using powder XRD and UV–visible diffuse reflectance spectroscopy. The organic dye phenosafranine is used as visible light absorbing sensitiser. Photosensitisation of the titanium dioxide nanoparticles deposited on the external surface of the microporous silicates are effected by the singlet excited states of phenosafranine and the mechanism of photosensitization is suggested to be static in nature. Photosensitisation of the TiO₂ nanoparticles encapsulated in the cavities of the host is more efficient. In the case of the sensitisation of the TiO₂ nanoparticles encapsulated inside the zeolite framework, the process is facilitated by the interaction between the host lattice with adsorbed water molecules and the excited state of the dye molecules at the outer surface of the host. The present investigation for the first time reports on the sensitization of TiO₂ nanoparticles by the organic dye separated in space by the insulator host material.     

Photocatalytic TiO2 films and membranes for the development of efficient wastewater treatment and reuse systems

In order to develop efficient photocatalytic TiO₂ films and membranes for application in water and wastewater treatment and reuse systems, there is a great need to tailor-design the structural properties of TiO₂ material and enhance its photocatalytic activity. Through a simple sol–gel route, employing self-assembled surfactant molecules as pore directing agents along with acetic acid-based sol–gel route, we have fabricated nanostructured crystalline TiO₂ thin films and TiO₂/Al₂O₃ composite membranes with simultaneous photocatalytic, disinfection, separation, and anti-biofouling properties. The highly porous TiO₂ material exhibited high specific surface area and porosity, narrow pore size distribution, homogeneity without cracks and pinholes, active anatase crystal phase, and small crystallite size. These TiO₂ materials were highly efficient in the decomposition of methylene blue dye and creatinine, destruction of biological toxins (microcystin-LR), and inactivation of pathogenic microorganisms (Escherichia coli). Moreover, the photocatalytic TiO₂ membranes exhibited not only high water permeability and sharp polyethylene glycol retention but also less adsorption fouling tendency. Here, we report results on the synthesis, characterization, and environmental application and implication of photocatalytic TiO₂ films and membranes.     

木质素磺酸钠在TiO2/水界面的吸附特性

木质素磺酸钠在固体表面的吸附特性决定了其应用性能,利用红外和紫外分光光度仪,采用剩余质量分数法研究了温度、pH值、无机盐和氢键破坏剂脲对木质素磺酸钠在TiO₂/水界面吸附动力学和等温吸附性能的影响,初步探讨了其在固液界面的吸附作用机理。结果表明,该吸附为单层多点式吸附,随着温度升高和pH值减小,木质素磺酸钠在TiO₂/水界面的吸附速率常数和饱和吸附量均增大,而离子强度的增大和脲的加入却使吸附速率常数减小;木质素磺酸钠在TiO₂/水界面的吸附驱动力为静电、疏水和氢键作用,疏水作用力可显著增加其吸附量。     

Effect of Pore Structure on Proton Conductivity and Water Uptake in Nanoporous TiO<Subscript>2</Subscript>

This paper reports on an investigation involving water content, water properties and proton conductivity in nanoporous TiO₂ materials fabricated through sol-gel processing techniques. TiO₂ nanoparticles having a primary particle diameter of less than 5 nm are packed into xerogels at room temperature and at 50^∘C. The resulting xerogels are fired at temperatures of 200, 300 and 400^∘C to alter the structural properties of these materials. Further alteration in the surface chemistry of the pore walls of these materials are made by equilibrating these porous wafers at pH 1.5 and 4.0 using nitric acid. Porosity, pore size, and surface area are evaluated with nitrogen adsorption techniques. Water content is calculated using data from thermogravimetric methods and water adsorption isotherms. Proton conductivity is measured using impedance spectroscopy. Of all variables affecting water content, water structure, and proton conductivity, the pH of pre-equilibrating the fired xerogels is the most important. However, porous structures of TiO₂ arising from the open packing of nanoparticles, that have less tortuosity, are substantially different in the uptake of water with relative humidity than samples obtained from the close-packing of these same particles regardless of firing temperature. Also, the material with the smallest pore size (a close-packed structure fired at 200^∘C) has the highest proton conductivity when measured between 20–60% relative humidity making this system the most favorable in terms of proton exchange membrane systems. Lastly, it is interesting to note that the density of water in these pores can vary between 1.2 and 1.6 g/l which is different than the 1.0 g/l of bulk water. This result likely comes from a combination of surface charge and surface roughness that affects the structure of interfacial water. These findings have importance not only for proton exchange membrane systems but also for other membrane technologies, cements, sensors, fabrication of wetting surfaces and in other areas that might benefit from the use of nanoporous materials.