Preparation and characterizations of SiO2/TiO2/γ-glycidoxypropyltrimethoxysilane composite materials for optical waveguides

SiO₂/TiO₂/γ-glycidoxypropyltrimethoxysilane composite materials processed by the sol-gel technique were studied for optical waveguide applications. Waveguide films with thickness more than 1.7 μm were prepared on a silicon substrate by a single-coating process and low-temperature heat treatment from these high-titanium-content composite materials. Scanning electron microscopy (SEM), atomic force microscopy (AFM), thermal gravimetric analysis (TGA), UV-visible spectroscopy (UV-VIS), Fourier-transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS) have been used to characterize the waveguide films. TGA curves showed that organic compounds in the composite materials would decompose in the temperature range from 200 °C to 480 °C. SEM, AFM and UV-VIS results showed that a dense, porous-free, and high transparency in the visible range waveguide film could be obtained at a low heat-treatment temperature. It was also noted that the carbon content in the film with higher titanium content heated at high temperature was evidenced by XPS. The waveguide propagation loss properties of the composite material films were also investigated and showed a dependence on the titanium molar fraction. Received: 13 June 2000 / Accepted: 21 June 2000 / Published online: 20 September 2000     

光催化剂SO2- 4/TiO2和TiO2 的光谱行为比较

用ＩＲ、Ｒａｍａｎ和ＤＲＳ光谱研究了ＳＯ＾２－４／ＴｉＯ２光催化剂和ＴｉＯ２光催化剂的光谱行为差别。结果表明,ＴｉＯ２光催化剂的表面只有Ｌ酸中心,而ＳＯ＾２－４／ＴｉＯ２光催化剂表面既有Ｌ酸中心也有Ｂ酸中心。ＴｉＯ２的硫酸化有效地抑制了晶相转变和晶粒度的增加。与ＴｉＯ２相比,ＳＯ＾２－４／ＴｉＯ２光催化剂的锐钛矿相含量较多、晶粒较小、光谱吸收边蓝移,从而增大了光吸收阈值,增强了光生空穴和电子的氧化     

Nanometric core-shell-shell γ-Fe2O3/SiO2/TiO2 particles

The preparation of core-shell-shell γ-Fe₂O₃/SiO₂/TiO₂ nanoparticles of few tens nanometers is performed by successively coating onto magnetic nanoparticles a SiO₂ layer and a TiO₂ layer, using sol–gel methods. The thickness of the two layers and the aggregation state of the particles can be controlled by the experimental conditions used for the two coatings. These composite nanoparticles may find application as magnetic photocatalysts, since they are characterized by their small diameters which allow a good accessibility to the TiO₂ shell. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Diffusion and point defects in TiO2−x

The self-diffusion of ⁴⁴Ti has been measured both parallel to and perpendicular to the c axis in rutile single crystals by a serial-sectioning technique as a function of temperature (1000–1500°C) and oxygen partial pressure (10^?14 ? 1 atm). The oxygen-partial-pressure dependence of. D¹_Ti indicates that cation selfdiffusion occurs by an interstitial-type mechanism and that both trivalent and tetravalent interstitial titanium ions may contribute to cation self-diffusion. At p_o2 = 1.50 × 10^?7 atm where impurity-induced defects are unimportant,

$\text{D}{}^1{}_{\mathrm{<mtext>Ti</mtext>}}\text{(∥c)=}\text{6.50}\text{+1.33}\text{?1.11}\text{exp}\text{?}\text{(66.11±0.56}\text{kcal}\text{mole}\text{RT}\text{cm}{}^2\text{S}$

and

$\text{D}{}^1{}_{\mathrm{<mtext>Ti</mtext>}}\text{(⊥c)=}\text{4.55}\text{+1.78}\text{?1.28}\text{exp}\text{?}\text{(64.08±0.99)}\text{kcal}\text{mole}\text{RT}\text{cm}{}^2\text{S}\text{.}$

In the intrinsic region, the ratio D¹_Ti (⊥c)/D¹_Ti(∥c) was found to increase from 1.2 to 1.6 as the temperature decreased from 1500 to 1000°C. Computations based upon the defect model of Kofstad (involving the atomic defects Ti^..._iTi^...._iand V^.._o), of Marucco etal. (Ti^...._i and V^.._o), and of Blumenthal etal. (Ti^..._i and Ti^...._i) are compared with the experimental data on deviation from stoichiometry, electrical conductivity, cation self-diffusion and chemical diffusion in TiO_2?x. These comparisons provide values of the defect concentrations, cation-defect diffusivities, electron mobility and reasonable values of the correlation factor for cation diffusion by the interstitialcy mechanism. Only the model of Kofstad is inconsistent with the data.     

C1催化剂MoS2/K2CO3/TiO2的制备

根据“盐类及氧化物等在高比表面载体上有自发分散倾向”的原理，制备了一种新型的用于由合成气（H2／CO）合成甲醇的催化剂MoS2/K2CO3/TiO2(DSA),该催化剂具有较好的耐硫性和对甲醇有较高的选择性。     

Shear Stress and Dielectric Characteristics of Polyaniline/TiO2 Composite‐Based Electrorheological Fluid

Adopting both conducting polyaniline (PANI) and organic titanium dioxide (TiO₂), which possesses a high dielectric constant, we synthesized PANI/TiO₂ hybrids via in situ oxidative polymerization to prepare an electrorheological (ER) materials. These were then characterized via thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). The ER responses and dielectric properties of the synthesized hybrids dispersed in silicone oil were measured as a function of different particle fractions of TiO₂ under an applied electric field. Series of analyses revealed that composite composition (the ratio of TiO₂ to PANI) plays a crucial role in affecting the ER performance, which exhibited interesting behaviors when the ratio of TiO₂ to PANI approaches a critical value. Interestingly, we found that our proposed constitutive equation fit the shear stress in the low shear rate region better than the Bingham fluid model. The dielectric spectra of the ER fluid, along with polarizability, were found to explain the flow behaviors of the PANI/TiO₂ under applied electric fields.     

TiO2/SiO2复合材料的制备及光催化性能

通过TiCl4水解与超细石英粉制备TiO2/SiO2复合材料,红外光谱表明TiO2与SiO2发生键合作用,形成了Si-O-Ti的网络结构,XRD结果表明TiO2/SiO2复合材料为锐钛矿晶型结构,透射电镜结果表明复合粒子之间有团聚现象.以TiO2/SiO2复合材料对甲基橙进行降解,光催化120min可达到69％的降解率...     

RuO2/TiO2/漂珠复合光催化剂的制备及性能

"利用RuO2/TiO2前驱体溶胶,采用溶胶-凝胶-浸渍法在漂珠(FP)表面沉积RuO2/TiO2膜,经120 ℃干燥、500 ℃焙烧制备复合光催化剂RuO2/TiO2/FP,并通过SEM、XRD以及FT-IR分别对其结构进行了表征． 结果表明,RuO2/TiO2膜的平均厚度(三层)约1 1m,膜材料中TiO2主要呈现锐钛矿型结构,而RuO2是以非晶态高度分散在粒子表面．以高效氯氰菊酯杀虫剂的光催化降解为模型反应,研究了RuO2/TiO2/FP的光催化性能,探讨了影响催化剂活性的因素及采用太阳光做光源处理     

Comparison of TiO2 and ZrO2 Films Deposited by Electron-Beam Evaporation and by Sol-Gel Process

TiO2 and ZrO2 films are deposited by electron-beam （EB） evaporation and by sol-gel process. The film properties are characterized by visible and Fourier-transform infrared spectrometry, x-ray diffraction analysis, surface roughness measure, absorption and laser-induced damage threshold （LIDT） test. It is found that the sol-gel films have lower refractive index, packing density and roughness than EB deposited films due to their amorphous structure and high OH group concentration in the film. The high LIDT of sol-gel films is mainly due to their amorphous and porous structure, and low absorption. LIDT of EB deposited film is considerably affected by defects in the film, and LIDT of sol-gel deposited film is mainly effected by residual organic impurities and solvent trapped in the film.     

Synthesis of TiO2 nanoparticles and spectroscopic upconversion luminescence of Nd3+-doped TiO2–SiO2 composite glass

Nd³⁺-doped TiO₂–SiO₂ composites were prepared by sol–gel method. Optical properties such as radiative life-time (τ), stimulated emission cross-section (σ_p) and branching ratio (β) were calculated using Judd–Ofelt theory. Violet to blue upconversion emissions at 380 nm (⁴D_3/2→⁴I_11/2), 399 nm (²P_3/2→⁴I_11/2), 420 nm (²D_5/2→⁴I_9/2) and 452 nm (²P_3/2→⁴I_13/2) were obtained under 578 nm xenon-lamp excitation. The choice of 578 nm is justified by the absorption spectra of the same samples, which shows a strong absorption peak at 578 nm. This 578 nm excitation pump produces upconversion in Nd³⁺ by a sequential two-photon absorption process.     

CO在MoS2/K2CO3/TiO2上的加H2反应

根据“盐类及氧化物等在高比表面载体上有自发分散倾向”的原理，制备了一种新型的用于由合成气（H2／CO）合成甲醇的催化剂MoS2/K2CO/TiO2(DSA),该催化剂具有较好的耐硫性和对甲醇有较高的选择性，通过对反应条件的教察得出结论：高压、低温、高空速有利于提高醇的选择性。     

ZnO/TiO2 core–shell heterojunction for CdS and PbS quantum dot-cosensitized solar cells

ZnO nanorods (NRs) with regular morphology were prepared through hydrothermal method, and the TiO₂ shell was assembled onto the surface of ZnO NRs by spin coating to the ZnO/TiO₂ core–shell heterojunction. CdS and PbS quantum dots (QDs) were used to cosensitize the ZnO/TiO₂ nanostructure by direct adsorption (DA) and successive ionic layer adsorption and reaction, respectively. SEM, TEM, and HRTEM images show that the samples possessed a rough surface and four lattice fringes indicating the successful synthesis of the ZnO/TiO₂/CdS/PbS composite structure. The ZnO/TiO₂(10T)/CdS/PbS sample showed a high absorption intensity at a broad range of wavelength to visible light region. The ZnO/TiO₂(10T)/CdS/PbS photoelectrode with QDSSCs showed the highest IPCE of 36.04% and photoelectric efficiency (η) of 1.59%; these values increased by approximately 550% and 150% compared with those of unsensitized ZnO (0.29%) and ZnO/TiO₂(10T) (1.04%) and about 146% and 120% compared with those of ZnO/TiO₂(10T)/CdS and ZnO/TiO₂(10T)/PbS, respectively. The fill factor was 0.36, and the photocurrent density (J_sc) and open circuit voltage (V_oc) reached the maximum values of 9.73 mA cm⁻² and 0.46 V, respectively.     

TiO2/SnO2复合氧化物的制备和光谱特性

为了研究TiO2/SnO2复合氧化物的光学特性,用胶体化学方法制备了以SnO2为内核的TiO2/SnO2复合氧化物,并且用紫外-可见光吸收光谱、X射线衍射和红外光谱对TiO2/SnO2复合氧化物的特性进行了分析.结果显示TiO2和TiO2/SnO2的能带宽度分别为4.13和3.86 eV,表现出量子尺寸效应;TiO2/SnO2在紫外区域具有宽的强吸收带.X射线衍射中TiO2的(110)衍射峰的位置移动了1.6°,强度也发生了变化;与TiO2红外光谱相比,TiO2/SnO2中Ti-O键的伸缩振动由500cm-1移到了656 cm-1,并有560 cm-1的肩峰,与吸附水相应的1650 cm-1附近的吸收峰和3420 cm-1的吸收峰均有所增加.     

RuO2/TiO2复合光催化剂的制备及性能研究

采用溶胶-凝胶-浸渍法制备了RuO2/TiO2复合光催化剂, 以紫外灯为光源, 直接耐晒黑G溶液的光催化降解为模型反应, 研究了RuO2/TiO2的光催化性能. 结果表明 掺杂量ω(RuO2)为0.16%、煅烧温度500 ℃、催化剂投加量为5.00 g·L-1时, RuO2/TiO2复合光催化剂催化活性最高. 直接耐晒黑G降解反应遵从Langmuir-Hinshelwood动力学模型, 测得反应速率常数为4.94×10-3 mmol(L·min)-1和吸附常数14.2 L·mmol-1.     

Decomposition of chlorinated volatile organic compounds (CVOCs) using NTP coupled with TiO2/GAC,ZnO/GAC,and TiO2–ZnO/GAC in a plasma-assisted catalysis system

No study was found in the literature on the catalytic effect of TiO₂/GAC (Granular activated carbon), ZnO/GAC, and TiO₂–ZnO/GAC combined with non-thermal plasma (NTP) for the decomposition of chlorinated volatile organic compounds (CVOCs) in gas streams. In the present study, this catalytic NTP process was investigated to examine the effect of specific input energy (SIE), initial concentration, as well as residence time on the removal efficiency (RE) of CVOCs in a corona discharge reactor energized by a high frequency pulsed power supply. A dip-coating sol–gel impregnation technique was used to coat TiO₂, ZnO, and mixture of TiO₂–ZnO nanoparticles on GAC, which were then combined with NTP in a two-stage configuration. The results revealed that the efficacy of the catalysts was in the order TiO₂–ZnO/GAC ≅ TiO₂/GAC > ZnO/GAC with chloroform feeding, while when chlorobenzene introduced, the order changed to TiO₂–ZnO/GAC > ZnO/GAC > TiO₂/GAC. A significant enhancement was observed with RE as catalysts coupled with NTP in all cases and a RE of 100% was achieved in the presence of both TiO₂/GAC and TiO₂–ZnO/GAC at SIE of ca. 400 J L⁻¹. Considerable improvement was also noticed for coupling TiO₂ and ZnO in both efficiency and catalyst life time.     

Optical and photocatalytic properties of novel heterogeneous PtSe2–graphene/TiO2 nanocomposites synthesized via ultrasonic assisted techniques

Novel material PtSe₂–graphene/TiO₂ nanocomposites were successfully synthesized through a facile ultrasonic assisted method. The prepared composites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) with an energy dispersive X-ray (EDX),transmission electron microscopy (TEM), Raman spectroscopic analysis, UV–vis absorbance spectra and UV–vis diffuse reflectance spectra (DRS) analysis were obtained. The catalytic behavior was investigated through the decomposition of rhodamine B (Rh.B) as a standard dye. Enhanced photocatalytic activities were observed by increasing the weight% of graphene in the PtSe₂–graphene/TiO₂ nanocomposites. We observed that the coupling of TiO₂ with PtSe₂–graphene alter the optical properties by observing a precise band gap in the visible range.     

Photocatalytic Properties of TiO2/Si-NPA Nano Composite Systems

A new composite system is fabricated by depositing the TiO2 film on a silicon nanoporous pillar array （Si-NPA） and annealing at 500℃ using the spin coating method. Such a composite system exhibits a uniform morphology with the micron-dimension pillar array. Photocatalytic properties are investigated based on the degradation of methyl orange dye solution, and the results show that the photocatalytic efficiency of such a nano-composite system is 1.7 times that of the TiO2/glass system. The enhancement of photocatalytic efficiency is attributed to the large surface area of the TiO2/Si-NPA system.     

TiO2/丝光沸石光催化降解甲醛特性研究

使用吸附材料丝光沸石与一种常用光催化材料TiO2(德国Degussa公司生产P25)的混和材料光催化降解空气中微量甲醛,探讨了空气流速、甲醛进口浓度、紫外光波长和强度以及水蒸气浓度对光催化效果的影响。发现:增大空气流速会减小甲醛的转化率但提高其降解速率;在实验浓度范围内甲醛的光催化反应可近似为零次反应;在相同光强下使用杀菌灯降解甲醛的效果优于黑光灯;当水蒸气浓度大于4000 mg/cm3时,甲醛的转化率不受水蒸气浓度影响,当水蒸气浓度为零时材料活性明显降低。这些结果为此类混和光催化材料的应用提供了科学指导。     

多孔TiO2/Al/SiO2纳米复合结构的紫外光吸收特性研究

在SiO2玻璃衬底上用脉冲激光沉积(PLD)技术,分别沉积Ti和Ti/Al膜,经电化学阳极氧化成功制备了多孔TiO2/SiO2和TiO2/Al/SiO2纳米复合结构.其中TiO2薄膜上的微孔阵列高度有序,分布均匀.实验研究了Al过渡层对多孔 TiO2薄膜光吸收特性的影响.结果表明:无Al过渡层的多孔 TiO2薄膜其紫外吸收峰在270 nm处.且峰强不随阳极氧化工艺参数调节;而有Al过渡层的多孔TiO2薄膜其紫外吸收峰红移至293 nm处,峰强和峰形不仅受阳极氧化电压调节而且受Al过渡层厚度的影响也很敏感.进一步分析了两种结构在吸收边附近的光跃迁特性.这些结果对基于多孔 TiO2的光伏电池和紫外光传感器的应用研究非常有益.     

V2O5/WO3/TiO2催化剂制备及其SCR性能研究

本文通过浸渍法制备了V2O5/TiO2系列筛选催化剂及V2O5/WO3/TiO2负载型催化剂,并在模拟评价装置上考察了上述催化剂在SCR反应巾的催化性能.结果表明,V2O5在涂材料中应该低于3wt.%;钒系催化剂对NOx的净化效率随反应温度的升高,先增加而后减小,存在一个适宜反应温度窗口;随反应温度升高, NH3泄漏量逐渐降低,在温度达到350°C之后,NH3泄漏世不再随温度的升高而变化;SCR反应温度较低时HC和CO浓度基本不变,但从450°C开始,HC浓度逐渐降低,而CO浓度则急剧升高;随NOx/NH3比例增加,NOx转化效率逐渐降低.