Preparation and properties of SiO2-TiO2 thin films from silicic acid and titanium tetrachloride

The preparation of SiO₂-TiO₂ thin films by the sol-gel method using silicic acid and titanium tetrachloride as starting materials was studied. The homogeneous sols were obtained by the condensation reaction of silicic acid with titanium tetrachloride in methanol-tetrahydrofuran. The dipcoating of slide glasses and silicon wafers followed by heat treatment gave oxide thin films of 88–93% transmittance, 3000–4500 Å thickness, and 1.45–1.80 refractive index, depending on heat-treatment temperature and TiO₂ content. FT-IR measurement showed that the Si-O-Ti bond is formed even in the sol and films. The variations of film thickness and refractive index on transformation from the gels into the oxides were found to be quite low.     

Sol-Gel Processing of Zirconia Coating for HR Mirrors with High Laser Damage Threshold

High laser-damage resistant coatings are very important in high power laser systems. In this study ZrO₂ thin films are prepared by sol-gel spin-coating technology from suitable zirconia aqueous colloidal suspensions containing nano-crystalline ZrO₂ at room temperature synthesized by a hydrothermal process from an inorganic precursor (ZrOCl₂·8H₂O). By adding a soluble organic binder PVP to the suspension prior to application, it is possible to substantially increase the coating refractive index and the abrasion-resistance as well as the laser damage threshold. The features of the coatings and the colloidal suspensions are investigated. Multilayer highly reflective dielectric coatings are also elaborated by applying quarterwave-thick alternating coatings of the binder-aided zirconia and silica, which is prepared with the sol-gel process from TEOS. To achieve 99% reflectivity, 19–21 layers are required. Single shot laser damage tests are carried out using a high power laser at 1064 nm wavelength with a pulse duration of 2.5 ns. The laser damage thresholds of 18 and 15 J/cm² are achieved for single ZrO₂-PVP coating and ZrO₂-PVP/SiO₂ multilayers respectively.     

Functionality of Aerosol-Gel Deposited TiO2 Thin Films Processed at Low Temperature

TiO₂ thin films have been deposited using the Aerosol-gel process and heat-treated at low temperature. Functional coatings necessitate reasonably good abrasion resistance in order to support possible damages related to a targeted application. Besides, specific applications of TiO₂ films require additional criteria, e.g. a tailored refractive index, a controlled chemical composition or a suitable crystallization degree. In this paper, we present several low temperature preparation procedures that answer the different criteria and allow to envisage applications on thermally sensitive substrates.     

CNTs表面改性与TiO2-CNTs异质结光催化性能

碳纳米管(CNTs)混酸(H₂SO₄/HNO₃, 体积比为3:1)超声辅助纯化及氧化植入活性基团－COOH, 进一步借助其转化为酰氯基团, 分别于CNTs 表面共价嫁接亲水性赖氨酸及亲脂性正十八胺基团, 赋予赖氨酸表面改性CNTs 显著水溶(6.85 mg·mL-1)和十八胺表面改性CNTs 显著醇溶(10.15 mg·mL^-1)性能. 运用低温水热法以亲水性CNTs 复合TiO₂, 溶胶-凝胶法以亲脂性CNTs 复合TiO₂, 观察到复合催化剂光催化性能随CNTs 溶剂分散性能增加而明显提升. 运用傅里叶变换红外(FTIR)、激光拉曼、X射线衍射(XRD)、Brunauer-Emmett-Teller 低温氮气吸附、透射电镜(TEM)及X光电子能谱(XPS)等手段表征, 系统探讨CNTs 的表面改性机制及CNTs 溶解分散性能与复合催化剂的光活性的关联. 认为表面改性CNTs 借助Ti－O－C键合促进其与纳米TiO₂的异质结合, 从而充分利用CNTs的大比表面积及电荷传输性能促进催化剂的污染物光催化降解.     

Sol-gel coatings of BaO-TiO2-SiO2 compositions

New alkali resistant BaO-TiO₂-SiO₂ coatings have been developed via the sol-gel process. In the solutions and in the gels (T<300°C) an infrared absorption band at 930 cm^–1 gives the possible evidence of mixed Si-O-Ti bonds, which have not been found in the system SiO₂-TiO₂-ZrO₂. Baking the films at about 500°C for less than 1 h leads to stable layers with negligible residual carbon contents. Compositions near 20 BaO-40 TiO₂-40 SiO₂ showed the best performance.     

Extended Cauchy Model for Tunable Refractive Index of Titania Nanoparticles at Visible Region

The extended Cauchy model is derived based on the experimental data for describing the mass fraction-, crystallite size-, and calcination-dependent refractive index of anatase and rutile TiO₂ nanoparticles. This model fits the experimental data of TiO₂ nanoparticles well in the visible spectral region. There is a tunable correlation between the refractive index of TiO₂ nanoparticle and the anatase nanoparticle size at visible region. Moreover, there is a near correlation between experimental and calculated Abbe number at 588 nm.     

Electrochromism in Materials Prepared by the Sol-Gel Process

Electrochromism is defined as the persistent but reversible optical change (usually transmission) produced electrochemically. The preparation by the sol-gel process of thin films made of amorphous or crystalline nanoparticles of WO₃, V₂O₅, Nb₂O₅, TiO₂, CeO₂, Fe₂O₃ and mixed compounds such as WO₃−TiO₂, CeO₂−TiO₂, CeO₂−SnO₂, have opened remarkable new opportunities for obtaining electrochromic layers exhibiting large optical transmission variation in the UV, visible or infrared range and acceptable kinetics under H⁺ or Li⁺ insertion. In this paper we give an overview of what has been recently achieved in this field, with emphasis for cathodic electrochromic coatings of Nb₂O₅ and TiO₂ composition. Finally we stress the future developments in this fast growing field.     

不同基底对TiO2和SiO2薄膜的光学性能的影响

采用溶胶-凝胶法分别在K9玻璃、单晶硅和石英玻璃基底上制备了纳米TiO₂和SiO₂薄膜。利用SEM、UV-Vis及反射式椭圆偏振光谱仪对薄膜的微观结构及光学特性进行了表征和分析。结果表明:3种基底中, 单晶硅基底上TiO₂和SiO₂薄膜折射率最大;在非晶态K9玻璃和石英玻璃基底上TiO₂薄膜折射率和透光率差异较大;SiO₂薄膜在非晶态基底上折射率、透光率相近;3种基底上薄膜的折射率和消光系数都有随波长增大而减小的趋势, 同时Cauchy模型能较好的描述单晶硅基底上两种薄膜在400~800 nm波段的光学性能。     

不同基底对TiO2和SiO2薄膜的光学性能的影响

采用溶胶-凝胶法分别在K9玻璃、单晶硅和石英玻璃基底上制备了纳米TiO₂和SiO₂薄膜。利用SEM、UV-Vis及反射式椭圆偏振光谱仪对薄膜的微观结构及光学特性进行了表征和分析。结果表明：3种基底中, 单晶硅基底上TiO₂和SiO₂薄膜折射率最大;在非晶态K9玻璃和石英玻璃基底上TiO₂薄膜折射率和透光率差异较大;SiO₂薄膜在非晶态基底上折射率、透光率相近;3种基底上薄膜的折射率和消光系数都有随波长增大而减小的趋势, 同时Cauchy模型能较好的描述单晶硅基底上两种薄膜在400~800 nm波段的光学性能。     

CuO Catalysts Supported on Porous TiO2 Microspheres for Low-Temperature CO Oxidation

The porous TiO₂ microspheres were prepared by the reversed-phase suspension polymerization and sol-gel method using reversed-phase suspension droplets as the templates. The CO oxidation catalytic properties of the CuO/TiO₂ catalysts prepared by hydrothermal method and impregnation method were extensively investigated. The structure of CuO/TiO₂ catalysts was determined by TG-DTA, XRD, TEM, and XPS. The results indicated that the redox capacity of CuO/TiO₂ was greatly depended on the aqueous solution concentration of Cu(NO₃)₂ used in the preparation of CuO/TiO₂ and the calcination temperature of the CuO/TiO₂ catalysts.     

Structure of TiO2 in TiO2-SiO2 prepared by a complexing agent-assisted sol-gel procedure

Many types of TiO₂-SiO₂ (Ti:Si=50:50 mol%) were prepared by the sol-gel procedure with and without 2-methyl-2, 4-pentanediol (MPD) as an organic ligand. The effect of MPD on the gel structure and the properties of the TiO₂ crystals were studied by XRD and raman spectroscopy, and the effect of the sol standing time on the properties of the TiO₂ crystals were also studied by XRD spectroscopy. In the gels with MPD, anatase of TiO₂ appeared at approximately 580°C, and the crystal structures were similar despite the difference in the gel preparation procedure. The titania gels with MPD were presumed to be dispersed in the silica gel matrix without any Ti-O-Si bond. In the presence of MPD, the formation of titania gels is controlled and the specified TiO₂ crystal is produced.     

TiO2-石墨烯光催化剂：制备及引入石墨烯的方法对光催化性能的影响

利用溶胶-凝胶法原位制备了二氧化钛/石墨烯(TiO2-GE)复合光催化剂,研究了纯TiO2以及不同方法制备的TiO2-GE复合光催化剂对亚甲基蓝及罗丹明B光催化降解性能。结果表明:石墨烯的引入提高了TiO2的光催活性,这主要是得益于石墨烯优异的电子传输性能及较好吸附特性。不同方法制备TiO2-GE复合催化剂的光催化活性也存在较大差别。原位制备的TiO2-GE复合光催化剂表现出最佳的光催化活性。     

Photo-Induced Hydrophilicity of TiO<Subscript>2</Subscript> Films Deposited on Stainless Steel via Sol-Gel Technique

The photo-induced hydrophilicity of TiO₂ films deposited on stainless steel substrates and silicon wafers using two different sol-gel routes has been investigated. The results indicate that crystalline titanium oxide films with excellent hydrophilic properties can be obtained on silicon wafer with both routes. XPS and XRD data reveal that films deposited on stainless steel exhibit crystallization features similar to those of films deposited on silicon wafers, and only differ by their oxidation degree owing to a TiO₂ reduction process associated to a diffusion of iron ions during deposition of the acidic sol and/or high temperature post-treatment. Consequently, hydrophilic properties of films deposited on stainless steel are inhibited. The deposition of a SiO_x barrier layer at the film/substrate interface allows preventing such a detrimental substrate influence. A low temperature deposition route of the TiO₂ film associated to the presence of a barrier layer yields best results in preventing iron contamination of the films.     

TiO2掺杂调控聚苯乙烯微球折射率及胶体光子晶体结构色

胶体光子晶体由于其可调变的结构色在绿色印刷、印染等领域备受关注,而其光子带隙的宽度和位置由光子晶体的晶格参数(晶面间距,通常受胶体微球尺寸影响)和介质的折射率决定。现有人工胶体光子晶体主要基于SiO_2和高分子(如聚苯乙烯(PS)等)微球的组装制备,由于胶体微球材质种类有限,折射率调控受限,因而目前调控胶体光子晶体结构色主要靠改变胶体微球的尺寸来实现。本文首先制备高折射率(2.6)的TiO_2纳米晶,在乳液聚合制备单分散的PS(折射率1.6)微球过程中,将所制备的TiO_2纳米晶掺杂于PS微球中,通过TiO_2的掺杂量有效调控胶体微球的折射率,进而实现胶体光子晶体的结构色调控。以多色胶体光子晶体微球的水溶液为墨水,采用彩色喷墨打印技术打印了电脑设计的光子晶体彩画。本文发展的光子晶体结构色调控新技术拓展了胶体光子晶体的应用。     

改进型溶胶-凝胶法制备粒径可调高染料吸附量TiO2微球及其在染敏电池光散射层中的应用

利用改进型的溶胶-凝胶法, 制得了由锐钛矿相纳米颗粒组成的TiO₂多孔微纳小球。通过调节前驱物浓度, 合成出粒径可控的尺寸分别为100, 175, 225, 475 nm的TiO₂微纳小球, 并通过电泳沉积法将合成出的小球作为光散射层引入到染料敏化太阳电池(DSSC)中。由于这种微纳小球在具备良好的光散射性能的同时也具备较高的染料吸附量, 因此相较于基于纳米颗粒的单层结构的DSSC拥有更高的光电转换效率。通过比较分析, 粒径尺寸为475 nm的微球作为光散射层的DSSC光电转换效率可以达到6.3%, 较之于基于纳米颗粒的DSSC提高了30%。     

改进型溶胶-凝胶法制备粒径可调高染料吸附量TiO2微球及其在染敏电池光散射层中的应用

利用改进型的溶胶-凝胶法,制得了由锐钛矿相纳米颗粒组成的TiO2多孔微纳小球。通过调节前驱物浓度,合成出粒径可控的尺寸分别为100,175,225,475 nm的TiO2微纳小球,并通过电泳沉积法将合成出的小球作为光散射层引入到染料敏化太阳电池(DSSC)中。由于这种微纳小球在具备良好的光散射性能的同时也具备较高的染料吸附量,因此相较于基于纳米颗粒的单层结构的DSSC拥有更高的光电转换效率。通过比较分析,粒径尺寸为475 nm的微球作为光散射层的DSSC光电转换效率可以达到6.3%,较之于基于纳米颗粒的DSSC提高了30%。     

Synthesis of high surface area nanocrystalline anatase-TiO2 powders derived from particulate sol-gel route by tailoring processing parameters

Stabilised titania sols were prepared using an additive free particulate sol-gel route, via electrostatic stabilisation mechanism, with various processing parameters. Peptisation temperature, 50°C and 70°C, and TiO₂ concentration, 0.1, 0.2 and 0.4 molar, were chosen as processing parameters during sol preparation. Results from TiO₂ particle size and zeta potential of sols revealed that the smallest titania hydrodynamic diameter (13 nm) and the highest zeta potential (47.7 mV) were obtained for the sol produced at the lower peptisation temperature of 50°C and lower TiO₂ concentration of 0.1 M. On the other hand, between the sols prepared at 70°C, smaller titania particles (20 nm) and higher zeta potential (46.3 mV) were achieved with increasing TiO₂ concentration up to 0.4 M. X-ray diffraction (XRD) and Brunauer-Emmett-Teller (BET) results of produced powders annealed at different temperatures showed that the 300°C annealed powder made from 0.1 M sol prepared at 50°C was a mixture of anatase and brookite, corresponding to a major phase of anatase (∼95% estimated), with the smallest average crystallite size of 1.3 nm and the highest specific surface area (SSA) of 193 m²/g. Furthermore, increasing TiO₂ concentration up to 0.4 molar for the sols prepared at 70°C resulted in decreasing the average crystallite size (1.9 nm at 300°C) and increasing SSA (116 m²/g at 300°C) of the powders annealed at different temperatures. Anatase-to-rutile phase transformation temperature was increased with decreasing peptisation temperature down to 50°C, whereas TiO₂ concentration had no effect on this transition. Anatase percentage increased with decreasing both peptisation temperature and TiO₂ concentration. Such prepared powders can be used in many applications in areas from photo catalysts to gas sensors.     

Low temperature CO oxidation on Au/TiO2 sol-gel catalysts

A comparative study on Au/TiO₂catalysts prepared by impregnation with HAuCl₄of commercial TiO₂ or by impregnation of sol-gel derived TiO₂has been carried out during CO oxidation. Specific surface areas and mean Au particle of 49 and 74 m²/g and 35 and 25 Å were obtained for impregnated commercial TiO₂ and sol-gel preparations, respectively. XRD patterns shown that in sol-gel derived TiO₂ only anatase phase was identified, while in commercial TiO₂ anatase and rutile phases co-exist. Titania support effect on Au activity for the oxidation of CO has been observed. The light-off during the reaction on Au/TiO₂initiates at 50°C, whereas for commercial impregnated TiO₂ catalyst the light-off initiates at 200°C.     

Sol-Gel Poly-Component Nano-Sized Oxide Powders

Nano-sized, amorphous and monodispersed poly-component powders in the Al₂O₃–TiO₂–MgO and Al₂O₃–TiO₂–SiO₂ systems have been obtained by the sol-gel method. These powders have been characterized by XRD, IR spectroscopy, DTA/TGA and EDAX spectrometry. This last method confirmed the composition of the ternary powders, which are formed during the gelation process.The powders were tested as precursors for obtaining advanced ceramics, as tialite, Al₂TiO₅. The samples prepared with powders obtained by sol-gel method have shown a high reactivity, and the formation of tialite was improved.     

Two-Dimensional Sol-Gel Synthesis of Ultrathin Zirconia and Hetero-Layered Titania/Zirconia Films

Synthesis of ZrO₂ and hetero-layered TiO₂/ZrO₂ ultrathin films was investigated by two-dimensional sol-gel process assisted by n-octadecylacetoacetate (C₁₈AA). When a hexane solution of tetrabutoxyzirconium (TBZ) and C₁₈AA was spread on the water surface, Zr-based gel films stabilized with C₁₈AA were formed at the air/water interface. After deposition on substrates, the gel films were successfully transformed into ZrO₂ ultrathin films by heating at 773 K for 0.5 h, the thickness of which was controllable on the order of sub-nanometer level by the number of gel-layer deposition and the molar ratio of [TBZ]/[C₁₈AA]. Well-organized hetero-multilayers composed of ultrathin TiO₂ and ZrO₂ layers could be fabricated by the alternate deposition of C₁₈AA-stabilized Ti- and Zr-gel films.