Nano rods for coloured glasses obtained by hybrid sol-gel coating

Many new materials are now allowing new properties thanks to nanotechnology because this domain of physics gives possibilities to optimize targeted properties even if these materials react in very various influential parameters. Architectural, automotive, bone pathologies, environment, display applications are some concerned domains. The sol-gel process is a method allowing the realisation of coats at ambiant temperature, thus it is possible to realize Liquid Crystal Display (LCD), water-repellent coatings on privacy glass, antireflective coatings, hydrophobic or hydrophilic surfaces, bone tissue regeneration. In this study, the purpose is to show the thermal influence on a covered glass with a complex hybrid sol-gel solution. This coated glass is going to change color from red to orange under the heat influence. This color change effect comes from the evolution of various compounds organizations then/or from their loss during the degassing sequence. We show in spite of the complexity of the process that the responsible is mainly the organic dye. Thus the structure of the heated glass at 250 degrees C looks radically different than the heated one at 350 degrees C. SEM measurement allows to identify the surface compositions and to determine the elementary composition along the sample's cross section. TGA is used to justify a mass loss when samples are annealed. UV/Visible measurement is realized by two methods: in-line transmission to evaluate luminous flux and thus give colorimetric dot in the normalized CIE diagram and diffuse transmission to observe the size influence of the pigments. Infrared Reflectivity allows to evaluate the influence of species on the structure and to better target the nature of the lost compounds during annealing. TEM measurement proves that the obtained iron particles are nano rods for both samples.     

Pechini溶胶-凝胶法制备SiO2/TiO2复合微粒

采用超声St(o)ber法制备了单分散性的纳米载体SiO2,再采用Pechini溶胶-凝胶制备法制备出SiO2/TiO2复合微球.通过X射线衍射仪、场发射扫描电子显微镜(FESEM)对粉体的晶型和显微形貌进行测试分析.结果表明:纳米载体SiO2球形颗粒为无定形态,Ti02粉体为形貌多样的块状颗粒,大颗粒粒径大于10μm...     

溶胶-凝胶法制备纳米TiO2

用溶胶 -凝胶法制备纳米TiO2 粉晶。用X射线粉末衍射 (XRD)对不同温度热处理的系列粉末进行了研究 ,结果表明用溶胶 -凝胶法制备的TiO2 纳米晶其晶型转变温度与凝胶时间有关     

溶胶-凝胶法制备聚醚砜/TiO2杂化膜

采用溶胶-凝胶法制备聚醚砜-二氧化钛杂化膜,用TEM对铸膜液中二氧化钛分散程度进行表征,并用SEM及接触角仪对膜材料的表面及断面形态、膜材料的亲水性能进行表征.结果表明,当TiO2凝胶添加量(质量分数)达到4%时,表面明显分布有大量分布均匀的TiO2纳米粒子,其断面结构则表现为皮层变厚,亚孔层消失,只存在指状大孔结构,表现为水通量随之增大,改善了聚醚砜材料的疏水性,提高了膜的抗污染性.随着二氧化钛纳米粒子浓度的提高,由于纳米粒子的团聚现象导致其在聚合物基上不能分散均匀,当膜受到外力作用时引起膜内部应力集中,使膜力学性能下降.     

TiO2 coating on silica particles by deposition of sol-gel-derived nanoparticles

TiO₂ was coated on nonporous transparent silica particles of 3.2 μm diameter by deposition of sol-gel-derived TiO₂ nanoparticles. Effects of water concentration, feed rate of titanium tetraisopropoxide (TTIP) solution and amount of supplied TTIP solution on the amount of TiO₂ coated on the silica particles were examined. Scanning electron microscopy observation confirmed that TiO₂ was coated on the silica particles in the form of ‘nanoparticles’ by using this method. Because of that, even though the TiO₂ surface area decreased due to sintering after calcination at high temperature to change the crystalline phase of TiO₂ to the anatase phase, the final surface area was still much larger than that of the original silica particles. The results also showed that as the water concentration increased, the amount of coated TiO₂ decreased. On the other hand, when the amount of supplied TTIP solution increased, the amount of coated TiO₂ increased. It was also confirmed that the feed rate of TTIP solution had little effect on the amount of coated TiO₂. The photocatalytic activities of the resulting TiO₂-coated silica particles were also evaluated by the photocatalytic decomposition of 2,4-dinitrophenol as a model substance. The results showed that the photocatalytic activity of the particles is not a function of the total surface area, but of the surface area in which anatase phase TiO₂ is exposed to the reaction space. The sedimentation velocity of the TiO₂-coated silica particles becomes about 5 orders of magnitude faster than that of the primary particles of the TiO₂. This indicates that the handling of the TiO₂ was also improved considerably by coating on the silica particles.     

表面TiO2包膜对制备CaCO3／TiO2复合材料颜料性能的影响

采用机械力化学方法，通过对碳酸钙进行表面TiO2包膜制备了CaCO3／TiO2复合材料，对CaCO3／TiO2复合材料的颜料性能、CaCO3和TiO2的结合形态与反应机理进行了研究。结果表明：CaCO3／TiO2复合材料形成了具有类似钛白粉的颜料性质，遮盖力为钛白粉的90％，吸油量和紫外线吸收功能与钛白粉相同；CaCO3／TiO2复合材料中TiO2在CaCO3颗粒表面形成均匀包覆和二者通过各自表面羟基形成化学结合是导致其呈现钛白粉颜料性质的内在机制。     

采用溶胶-凝胶法在刀具表面制备MoS2软涂层的研究

在成功地采用柠檬酸溶胶-凝胶法在硬质合金试样表面制备出MoS2软涂层的基础上,采用扫描电镜形貌观察和摩擦系数测定等实验方法研究了MoS2加入量对涂层表面微观形貌及其摩擦性能的影响规律。结果表明,采用溶胶-凝胶法在1.6mol/L柠檬酸水溶液中分别添加13、20和27g/L MoS2粉末条件下,应用刷涂法均可以在硬质合金试样表面得到与基体结合牢固、表面质量较高的MoS2软涂层。所获得的MoS2软涂层的表面形貌呈片状。MoS2软涂层的存在明显地降低了硬质合金试样的摩擦系数,由硬质合金试样的0.58～0.86降低到软涂层的0.18～0.23。而具有不同MoS2加入量的软涂层间的摩擦系数相差不大。软涂层试样的摩擦系数明显低于硬质合金试样的原因与涂层中存在有摩擦系数低、承载力大等优良性能的MoS2以及软涂层的存在改变了原摩擦副材料间的性质等因素有关。     

Nitridation of TiO2 fibres prepared by the sol-gel method

Preparation of TiN fibres by ammonolysis of the sol-gel derived TiO₂ fibres has been performed in the present study. TiO₂ gel fibres were prepared from Ti(O-i-C₃H₇)₄ by hydrolysis and polycondensation. As a result, TiN is found to form above 900°C. A thermodynamic interpretation of the nitridation reaction of TiO₂ was considered. Moreover, from the kinetic treatment, it is found that the nitridation reaction of TiO₂ is controlled by diffusion of either reactant (NH₃) or one of the products (H₂O) through the reaction layer.     

High surface area neodymium phosphate nano particles by modified aqueous sol-gel method

Synthesis of nano rod shaped neodymium phosphate (NdPO₄) particles with specific surface area as high as 107 m²g⁻¹ and an average length of 50 nm with aspect ratio 5 was achieved using modified sol gel method. Crystallite size calculated from the X-ray diffraction data by applying Scherer equation was 5 nm for the precursor gel after calcination at 400 °C. NdPO₄ was first precipitated from neodymium nitrate solution using phosphoric acid followed by peptization using dilute nitric acid and further gelation in ammonia atmosphere. The calcined gel powders were further characterized by surface area (Brunauer-Emmet-Teller nitrogen adsorption analysis), Transmission electron microscopy, scanning electron microscopy, UV-vis and FT-IR analysis. Transmission electron microscopy confirms the formation of rod like morphology from the sol, gel and the calcined particles in nano size range. These particles could be compacted and sintered at as low as 1300 °C to a density of 98.5% (theoretical) with an average grain size of ∼1 μm.     

Photocatalytic activity of La, Y Co-doped TiO2 nanoparticles synthesized by ultrasonic assisted sol-gel method

Bare TiO2 (T), La-doped TiO2 (LT), Y-doped TiO2 (YT), La, Y co-doped TiO2 (LYT) were successfully prepared by facile ultrasonic assisted sol-gel synthesis using Ti(OC4H9)4 as the precursor. The products were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), UV-visible diffuse reflectance spectra (DRS), and X-ray photoelectron spectroscopy (XPS), respectively. The photocatalytic activities of anatase samples, with the average particle diameters ranging from 14 nm to 21 nm, were evaluated for photodegradation of methyl orange (MO). The XPS results indicated that Y atoms were incorporated into titania lattice, while La atoms existed on the crystal surface. Due to doping, the optical absorption edges of LT, YT, and LYT shifted to the visible light region by 21 nm, 29 nm and 35 nm, respectively. The photocatalytic performances of the doped samples, such as LT, YT and LYT, were much higher than that of bare TiO2 under UV-visible light irradiation. And the photoreactivity efficiency of the LYT was the highest. It indicated that a strong La-Y synergistic interaction appeared to play a decisive role in driving the excellent photocatalytic performance of titania.     

Preparation of mesoporous TiO2 by the sol-gel method assisted by surfactants

Mesoporous titania was obtained by gelation of tetraisopropyl orthotitanate in aqueous or alcoholic solutions with addition of a cationic or anionic surfactant. The gels were dried and calcined to obtain the oxides. The dried samples and the oxides were characterized by thermal analysis, N₂- adsorption measurements, infrared spectroscopy, X-ray diffraction and titration with n-butylamine. The effect of the type of surfactant, the chain length of the surfactant and the synthesis method on the textural and surface characteristics of the oxides obtained has been investigated. Cationic surfactants such as dodecyltrimethylammoniumbromide and cetyltrimethylammoniumbromide are effective in controlling the pore size and in increasing the pore volume and the surface area. On the contrary, the sodium dodecylsulphate employed as an anionic surfactant is not incorporated to the hydrous titanium oxide network. The use of a surfactant in the preparation enhances the acid strength of the surface sites of the titanium oxide formed.     

Photoelectric properties of TiO2-ZrO2 thin films prepared by sol-gel method

Acidic sols of TiO2, ZrO2 and Ti-Zr mixed oxide precursors were prepared. The sols were then smeared on quartz substrate and annealed at 650 degrees C for 2 hour to form polycrystalline oxide films. XRD, SEM, UV-visible absorption spectra and XPS were carried out to characterize the films. It was found that the crystalline phase of pure titania is an anatase and pure zirconia is a tetragonal. The binary oxides show the anatase phase at the molar ratio of Ti:Zr = 2.73:1, which means that solid solution was formed. The absorption edge of the TiO2-ZrO2 binary oxides showed obvious blue shift as the Zr ratio increased. The results obtained indicate that the band gap of the binary oxides could be adjusted from 3.2 eV (TiO2) to 7.8 eV (ZrO2) by varying the molar ratio of Ti and Zr. Au interdigitated electrodes were produced by planar technology and MSM (metal-semiconductor-metal) structure UV detector based on TiO2-ZrO2 binary oxides was fabricated. Obvious photoelectric response was observed.     

Structural and optical properties of TiO2 thin films grown by sol-gel dip coating process

The mono and bi-layer TiO₂ thin films have been prepared by sol-gel method on glass. X-Ray diffraction, Raman spectroscopy, atomic force microscopy, spectroscopic ellipsometry and m-lines spectroscopy techniques have been used to characterize the TiO₂ films. The mono-layer film is found to be amorphous, while the bi-layer film shows the presence of anatase phase. The bi-layer film exhibits more homogeneous surface with less roughness. The thickness effect on the refractive index, extinction ceofficient, packing density and optical band gap is analysed. The waveguiding measurements of the bi-layer film exhibit single-guided TE₀ and TM₀ polarized modes from which we can measure the refractive index and the film thickness.     

溶胶-凝胶法制备TiO_2及其光催化性能研究

采用溶胶-凝胶法制备TiO2,以甲基橙为模型污染物,考察了影响TiO2光催化活性的主要因素,并采用SEM和XRD等方法对样品进行了表征.结果表明:在450℃下煅烧2h后,可以制得具有较高光催化活性的TiO2粉末.当甲基橙溶液中TiO2的质量浓度为1.0g/L时,光催化效果最佳;TiO2粉末主要具有锐钛矿型晶体结构.     

溶胶凝胶法制备TiO2薄膜的微观结构和光学性能研究

以乙二醇甲醚为溶剂,羟基纤维素（HPC）为添加剂,用溶胶-凝胶法制备了多孔TiO2薄膜。扫描电镜（SEM）观察发现多孔TiO2薄膜孔径随HPC含量增加而变大。X射线衍射（XRD）表明得到的TiO2薄膜均为锐钛矿相,对XRD点阵参量进行计算,发现随HPC含量的增大,薄膜晶粒尺寸先减小后增大。表面轮廓仪膜厚测试表明随HPC含量的增大,薄膜厚度逐渐减小。UV—vis光谱分析表明随HPC含量增大,薄膜透射性能有所下降。     

TiO2 supported on SiO2 photocatalysts prepared using ultrasonic-assisted sol-gel method

TiO₂-SiO₂ (TiO₂ supported on SiO₂) photocatalysts were prepared using an ultrasonic-assisted sol-gel method. These photocatalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR) and photoluminescence spectra (PL). Their photocatalytic activities were investigated by the method of methyl orange oxidation. It was found that the photocatalytic activity of TiO₂-SiO₂ was optimal when the molar ratio of hexadecyl trimethyl ammonium bromide to titanium butoxide was 1:10. The average crystallite size of TiO₂-SiO₂ was smaller than that prepared by the stirring method. Furthermore, for pure anatase phase samples, it was shown that the lower the photoluminescence intensity, the higher the photocatalytic activity.