Synthesis of vanadium dioxide films by a modified sol-gel process

Vanadium dioxide films have been grown on silicon substrates and on SiO₂ layers on silicon by a modified sol-gel process using methyl cellosolve as a solvent. We have failed to obtain vanadium dioxide layers on Pt/TiO _x /SiO₂/Si substrates. For all of the substrates studied, we have examined the effect of synthesis conditions (initial solution concentration, deposition procedure, and oxidation and reduction anneals) on the phase composition, thickness, and surface morphology of the films.     

Thin films of calcium phosphate and titanium dioxide by a sol-gel route: a new method for coating medical implants

Titanium is a commonly used biomaterial for dental and orthopaedic applications. To increase its ability to bond with bone, some attempts were made to coat its surface with calcium phosphate (CaP). This paper describes a new type of coating. Instead of a pure CaP layer, a mixing of titanium dioxide (TiO₂) and CaP is fabricated and deposited as a coating. These layers are deposited by a sol-gel route on pure titanium substrates using various pre-treatments. The method consists of mixing a solution of tetrabutyl ortho-titanate or a sol of titanium dioxide with a solution of calcium nitrate and phosphorous esters. This composite is deposited on to commercially pure titanium plates, mechanically polished or blasted with pure crystalline aluminum oxide, using the spin-coating technique. These coatings are then fired at 650 or 850°C for various times. The samples are characterized by X-ray diffraction for their crystallinity, X-ray photoelectron spectroscopy for their surface chemical composition and scanning electron microscopy for their topography. Samples treated at 850°C present a well-pronounced crystallinity, and a high chemical purity at the surface. The topography is strongly related to the viscosity of the precursor and the substrate pre-treatment. Possibilities to structure the outermost layer are presented. © 1999 Kluwer Academic Publishers     

Synthesis of functional diamond-like carbon nanocomposite films containing titanium dioxide nanoparticles

Synthesis of diamond-like carbon (DLC) films with UV-induced-hydrophilicity function was studied by inductively-coupled plasma (ICP) chemical vapor deposition. Titanium tetraisopropoxide (TTIP) and oxygen gases were employed as the precursors to deposit diamond-like nanocomposite films containing titanium dioxide (TiO₂) nanoparticles. X-ray diffraction and high-resolution transmission electron microscopy revealed that TiO₂ nanocrystallites were formed in the DLC films when oxygen concentration was higher than TTIP concentration during deposition. The DLC nanocomposite film was hydrophobic without ultraviolet (UV) irradiation, and became highly hydrophilic under UV irradiation, exhibiting the self-cleaning effect. A very broad peak centered at 1580 cm^− 1 was observed in the Raman spectra confirming the formation of DLC films. The hardness of the film was about 8 GPa with a stress of 3 GPa. ICP was essential in forming the photocatalytic TiO₂ nanoparticles in the DLC matrix.     

溶胶-凝胶法制备纳米复合透明保护薄膜

以正硅酸乙酯、钛酸丁酯、异丙醇铝和γ-缩水甘油醚氧丙基三甲氧基硅烷为先驱体,通过分步水解法制得SiO2-TiO2-Al2O3复合溶胶,利用提拉法在普通玻面镀制无机-有机复合透明保护薄膜,通过各种测试方法,对SiO2-TiO2-Al2O3复合薄膜的结构和性质进行了分析。结果表明该薄膜具有致密、透明、耐磨擦等性能。由于铝、钛纳米氧化物颗粒的存在,使得硬度及耐磨擦性能比纯SiO2薄膜均有较大的提高。     

Photocatalytic oxidation of nitric oxide with immobilized titanium dioxide films synthesized by hydrothermal method

Gas-phase photocatalytic oxidation (PCO) of nitric oxide (NO) with immobilized TiO2 films was studied in this paper. The immobilized TiO2 films were synthesized by hydrothermal method. The characterization for the physicochemical properties of catalysts prepared under different hydrothermal conditions were carried out by X-ray diffraction analysis (XRD), transmission electron microscopy (TEM), high resolution-transmission electron microscopy (HR-TEM), Brunauer-Emmett-Teller measurements (BET) and scanning electron micrograph (SEM). It was found that the PCO efficiency of the catalyst was mainly depended on the hydrothermal conditions. The optimal values of hydrothermal temperature and hydrothermal time were 200 degrees C and 24 h, respectively. Furthermore, it was also known that the photocatalytic efficiency would decrease remarkably when the calcination temperature was over than 450 degrees C. Under the optimal conditions (hydrothermal condition: 200 degrees C for 24 h; calcination temperature: 450 degrees C), the photocatalytic efficiency of catalyst could reach 60% higher than that of Degussa P25.     

Synthesis of single-crystalline perovskite barium titanate nanorods by a combined route based on sol-gel and surfactant-templated methods

The single-crystalline perovskite barium titanate nanorods were successfully synthesized by a combined route based on sol-gel and surfactant-templated methods at low temperature. The synthesis was accomplished by using barium acetate (Ba(CH₃COO)₂) and tetrabutyl titanate (Ti[O(CH₂)₃CH₃]₄) as the starting materials and laurylamine as the surfactant, respectively. Well-isolated single-crystalline cubic perovskite BaTiO₃ nanorods with diameters ranging from 20 to 80 nm and lengths reaching up to > 10 μm can be easily fabricated by this route. The crystal form and morphology of the nanorods were characterized by X-ray diffraction, TEM and HRTEM. The mechanism of the formation of the single-crystalline cubic perovskite BaTiO₃ nanorods was discussed based on the theory of oriented attachment.     

Preparation of alumina films by the sol-gel method

This review describes our study on preparation of alumina films by a sol-gel process and their several applications that have been investigated since 1986. Alumina films were prepared from alkoxide or inorganic salt. Both as-prepared alumina films were transparent in ultraviolet, visible and near infrared regions. The alumina from inorganic salt (inorganic alumina) was structureless even after annealed at 300–700°C in air, while the alumina from alkoxide (alkoxide alumina) was in pseudo-boehmite at an annealing temperature lower than 400°C and was in - or -type at 400–700°C. Both alumina films became opaque after annealed at temperatures above 1000°C. The inorganic alumina film annealed at 800°C showed a gas permeability that was influenced by physico-chemical properties of penetrant and alumina. Composite films of alumina and poly(vinyl alcohol) (PVA) were hydrophilic but insoluble in water, and removal of PVA from the composite films by annealing at 600°C led to formation of transparent alumina films. Such properties enabled us to use a counter diffusion method for fabricating -Fe₂O₃-doped alumina films. Alumina films doped with organic dyes such as laser dyes, hole-burning dyes and non-linear optical dyes, which were fabricated by gelation of dye-added alumina sol, exhibited laser emission, hole-spectra and second- or third-harmonic generation properties, respectively. Hydrogenation of alkene was catalyzed by Ni nanoparticles doped alumina films that were prepared by gelation of Ni²⁺ solution-added alumina sol and annealing the Ni²⁺-doped alumina gel in hydrogen gas. Nonlinear optical properties were observed for alumina films doped with CdS, Au and Ag nanoparticles, which were fabricated by gelation of Cd²⁺, HAuCl₄ and AgNO₃ solution-added alumina sols and annealing the Cd²⁺-doped alumina gel in H₂S gas and the Ag⁺- and Au³⁺-doped alumina gels in H₂ gas. Rare earth metal ion-doped alumina films, which were prepared by gelation of rare earth metal ion solution-added alumina sol and annealed the ion-doped alumina gel, exhibited not only normal luminescence but also up-conversion emission, energy transfer type luminescence and long lasting luminescence.     

Synthesis of nanocrystalline titanium nitride by reacting titanium dioxide with sodium amide

A new method for synthesis of nanocrystalline titanium nitride was developed through the reaction of titanium oxide and sodium amide at 500–600 °C for 12 h in an autoclave. X-ray diffraction (XRD) and electron diffraction (SAED) results indicated the product had a cubic phase with lattice parameter a = 4.242 Å. Transmission electron microscopy (TEM) and field emission scanning electron microscopy (FESEM) revealed that the particle sizes were 10 to 40 nm. Quantitative analysis using X-ray photoelectron spectrum (XPS) showed the atomic ratio Ti:N was 1.03:1.     

Synthesis of ordered mesostructured polymer-organosilica composites by the triconstituent co-assembly method

Ordered mesoporous polymer-organosilica composites have been synthesized through a triconstituent co-assembly strategy. These composites have ordered 2-D hexagonal mesostructures (space group p6m) with uniform pore size (6.2-7.3 nm), suitable surface areas (619-794 m² g⁻¹) and pore volumes (0.61-0.88 cm³ g⁻¹). With increasing BTSE (1,2-bis(triethoxysilyl)ethane) content, the surface area and pore volume reduce. The composites have homogeneous interpenetrating frameworks, in which both polymer and organosilica synergistically support the ordered mesostructure. The hybrid materials exhibit good adsorption capacities of benzene (up to 2.0 mmol g⁻¹), suggesting their use as a potential adsorbent for removal of volatile organic compounds.     

Preparation of cobalt–titanium dioxide nanocomposite films by combining inverse micelle method and plasma treatment

We investigated the processing of a metal nanogranular thin film of Co–Ti–O system by combining a colloidal wet process (inverse micelle method) and a dry process (plasma treatment). Both TEM and EDS analyses revealed that the film was prepared along with suppression of metal cobalt nanoparticles' oxidization. Results showed that plasma processing provides new possibilities for processing of materials that are difficult to prepare under equilibrium conditions.     

Synthesis and characterization of cadmium titanium oxide powders by sol-gel technique

Uniform crystals of CdTiO₃ orthorhombic phase have been preapred by Sol-Gel method using titanium butoxide and cadmium acetate. For the first time the sample has been characterised detailedly to confirm the formation of pure single phase of CdTiO₃. It is observed that the sample sintered at 500°C for 5 h showed complete formation of the single phase of CdTiO₃ by X-ray diffraction technique. X-ray photoelectron spectroscopy measurement has been carried out for the bulk CdTiO₃ sintered at 500 °C for 5 h, which showed 20% of Cd, 20% of Ti and 60% of O indicating stoichiometric CdTiO₃. Surface morphology studies by scanning electron microscopy showed uniform crystals of CdTiO₃. The purity of the compound has also been checked by Energy Dispersive X-ray method indicating the absence of foreign ions apart from that, the ratio of Cd : Ti has been calculated and found to be 1 : 1 indicating the stoichiometric CdTiO₃.     

Photoinduced hydrophilicity of titanium dioxide thin films prepared by cathodic electrodeposition

Crystal structure and microstructural properties of titanium dioxide thin films prepared by cathodic electrodeposition on indium-tin-oxide coated glass substrates from aqueous peroxo-titanium complex solutions have been investigated as a function of sintering temperature (25-500 °C) for the first time. We have noticed pronounced photoinduced hydrophilicity for such thin films on exposure to ultraviolet (UV) light illumination. It was observed that all the films, irrespective of their crystalline nature (amorphous and crystalline), display transformation from hydrophobic to super-hydrophilic behavior upon UV illumination. This observation can be correlated with typical nanoporous morphology of electrodeposited TiO₂ films.     

Synthesis of aluminium borate nanowires by sol-gel method

A sol-gel process followed by annealing was employed to fabricate single crystal aluminium borate (Al₄B₂O₉ and Al₁₈B₄O₃₃) nanowires. The diameter of Al₄B₂O₉ nanowires synthesized at 750 °C annealing is ranging from 7 to 17 nm, and that of Al₁₈B₄O₃₃ nanowires synthesized at 1050 °C annealing is about 38 nm. Instead of the well-known vapor-liquid-solid (VLS) mechanism, self-catalytic mechanism was used to explain the growth of the nanowires.     

Kinetics of internal photoeffect in titanium dioxide films

The internal photoeffect in X-ray-amorphous titanium dioxide (TiO₂) films deposited by reactive magnetron sputtering onto silica glass substrates has been studied. It is established that cyclic illumination of samples leads to a change in the photoinduced current kinetics, whereby the kinetic curves initially exhibit an extremum that subsequently decreases and eventually disappears. Using a system of equations that describes the kinetics of free electrons with allowance for their trapping on deep monoenergetic traps, it is shown that the observed behavior is related to a significant increase in the coefficient of interband recombination and a decrease in the concentration of vacant traps.     

PEG辅助的溶胶凝胶法制备多孔ZnO薄膜

以醋酸锌为前驱体,乙醇为溶剂,二乙醇胺为络合剂,通过聚乙二醇(PEG)辅助的溶胶--凝胶法在玻璃基片上制备了ZnO多孔薄膜.利用IR、TG-DTA、XRD及SEM等测试方法对薄膜的结构和特性进行了分析.探讨了样品在溶胶-凝胶及煅烧过程中的物理化学变化.研究了前驱体浓度、PEG2000加入量对薄膜结构和性能的影响.结果表明,当Zn2 的浓度为0.6mol/L的溶胶在70℃水浴时,加入PEG2000后,有利于ZnO多孔结构的形成,而且孔尺寸及密度也随PEG加入量的增大而增大.     

Synthesis of hexatitanate and titanium dioxide fibers by ion-exchange approach

Hexatitanate (K₂Ti₆O₁₃) and titanium dioxide (TiO₂) fibers were synthesized by ion-exchange method using fibrous potassium titanate (K₄Ti₃O₈) as initial material. Fibrous K₄Ti₃O₈ was prepared by treating TiO₂ with 80 wt.% concentrated KOH solution at 220 °C for 2 h under atmospheric pressure. Then, high qualities of K₂Ti₆O₁₃ and TiO₂ fibers were formed by a thermal treatment of the hydrolytic intermediates K_4−bH_bTi₃O₈ (1.2 ≤ b ≤ 3.0) and H₄Ti₃O₈, which were quantitatively obtained by controlling the pH value ranging from 10.9 to 12.0 and from 2.0 to 5.0 in the hydrolytic process of K₄Ti₃O₈, respectively. Based on the experimental results, the possible ion-exchange and phase transformation mechanisms in the reaction process were discussed.     

Synthesis of titanium dioxide nanoparticles by reactive DC magnetron sputtering

Nanometer-sized titanium dioxide (TiO₂) particles were prepared on carbon substrates by reactive direct-current magnetron sputtering. By performing measurements with high resolution electron microscopes, the mean nanoparticle diameter and the coverage fraction of the substrate by the nanoparticles (NPs) were measured at 19 nm and 30%, respectively. Moreover, electron diffraction analysis showed that the TiO₂ NPs' crystalline structure on the carbon substrate was a mixture of anatase and rutile. Finally, we provided information on the TiO₂ initial growth stage: crystalline NPs were formed after deposition of amorphous nanoparticles on the substrate and heating.