Synthesis of Gels in the System Na2O-ZrO2-SiO2

Gels have been synthesized in the SiO₂-Na₂O-ZrO₂ system and calcined at various temperatures up to 700°C. They have been studied by infrared absorption spectroscopy. The position of the asymmetric stretching frequency of the SiO₄ unit is used as a tracer of the homogeneity. It is shown that sodium increases the solubility of zirconium in the silica matrix as already observed in fused glasses.     

Hybrid Inorganic-Organic Sol–Gel Coatings in the SiO2-TiO2 System

In the present work, the influence of substituted Si-alkoxides on the structural and optical properties of films obtained in the SiO₂-TiO₂ system was studied. Methyltriethoxysilane (MTEOS) and 3-(tri-methoxysilyl)propyl methacrylate (TSPM) were used as SiO₂ sources and Ti(OBu)₄ was used as TiO₂ source. Acetylacetone was added to the Ti(OBu)₄ as chelating agent and the synthesis was carried out in acid medium. The films were deposited on oxidized Si-wafers by spin-coating. The films were characterized by XRD, spectro-ellipsometry (SE), and atomic force microscopy (AFM). The results obtained have shown that in the case of hybrid films the desired thickness could be obtained in a single deposition step. The thickness of the films and the optical properties are controlled by the bulkiness of the organic substitute bounded to Si. Among other optical applications, the potential use of such films as optical waveguides is proposed.     

Preparation of Al2TiO5-ZrO2 mixed powders via sol-gel process

Sol-gel routes in the ternary system Al₂O₃-TiO₅-ZrO₂ were investigated to prepare Al₂TiO₅-ZrO₂ mixed powders. The preparation of ZrTiO₄ and Al₂TiO₅ was studied before going on with the ternary system. Zirconium titanate precursor gels were prepared from Ti(OPrⁱ)₄ and Zr(OPrⁿ)₄ mixtures. The crystallization of ZrTiO₄ develops at T<700°C. Al₂TiO₅ was prepared by different ways, using mixtures of Al(OBu^s)₂(C₆H₉O₃) with Ti(OPr ⁱ )₄ (i), or with acetic acid addition (ii). Route (i) leads to a separate crystallization of TiO₂ and -Al₂O₃, with subsequent formation of -Al₂TiO₅ at T1360°C. Although the pseudobrookite -Al₂TiO₅ is thermodynamically unstable below 1280°C, route (ii) leads to the crystallization of metastable -Al₂TiO₅ at T800°C. At increasing temperature, -Al₂TiO₅ decomposes into TiO₂ and -Al₂O₃, then the two compounds react to form stable -Al₂TiO₅. For the ternary system, all the preparation routes which were studied lead to ZrTiO₄ and -Al₂O₃ with subsequent reaction (at T1500°C) to give -Al₂TiO₅ and ZrO₂.     

SiO2-TiO2 membranes by the sol-gel process

The use of membranes for gas separation represents an important alternative from the viewpoint of energy conservation in industrial separation processes. Polymeric Si-Ti sols prepared from titanium isopropoxide (Ti(OPrⁱ)₄) and tetraethoxysilane (TEOS) were used to deposit membranes on α-Al₂O₃ supports. Acetylacetone (2,4 pentanedione, acacH) and isoeugenol (2-methoxy-4-propenylphenol, isoH) were employed separately to chelate the Ti precursor in order to slow down the chemical reactivity, avoiding precipitation. The radial distribution functions (RDF) of the gels aging at room temperature were obtained. The xerogels were studied by Thermal Gravimetric (TGA) and Differential Thermal (DTA) Analysis in air. The Microporosity of the solids calcined at 773 K was determined by N₂-adsorption at 77 K. The membrane thickness was determined from SEM photographs. Preliminary permeance results of the supported membranes on commercial alumina support were obtained for He, N₂ and CO₂ in a single gas equipment. At 773 K the separation factors α(He/CO₂) and α(N₂/CO₂) for both membranes exceeds the theoretical Knudsen limit.     

Thermally effected structural and surface transformations of sulfated TiO2, ZrO2 and TiO2-ZrO2 catalysts

Preparations were characterized by specific surface area, thermogravimetry, and X-ray diffractometry. Thermal effects observed were (a) sulfur loss, (b) sintering, (c) crystallization and transformation of the crystalline phase(s). Thermoanalytical curves indicate that decomposition of the sulfate occurs in two distinct steps. Decrease of surface area due to (b) and (c) is concomitant to decomposition of sulfate. Sulfate was found to hinder sintering, crystallization and phase transformations of ZrO₂ and TiO₂. In low-titania and -zirconia sulfated TiO₂-ZrO₂ the minor component enhances the effect of sulfate. In equimolar TiO₂-ZrO₂ sulfate decomposition is accompanied by rapid formation of crystalline TiZrO₄.This work was supported by the MOL Rt., Hungary, which is gratefully acknowledged.     

具有双孔径分布的介孔C-Al2O3-TiO2纳米复合材料的合成及其红外发射率

以嵌段共聚物F127 (PEO₁₀₆PPO₇₀PEO₁₀₆, M_W=12600)为模板剂, 异丙醇铝和钛酸四丁酯为金属源, 低分子量的酚醛树脂为碳源, 通过溶胶-凝胶三元共组装法合成了具有双孔径分布的C-Al₂O₃-TiO₂纳米复合材料.用X射线衍射(XRD)、透射电子显微镜(TEM)、扫描电子显微镜(SEM)及N₂吸附-脱附对该复合材料进行结构表征. 结果显示, 当铝钛原子的摩尔比为1:10 时, 对应的纳米复合材料具有较好的有序介孔结构, 其双孔径分别为3.9和6.5 nm, 比表面积可达259 m²·g^-1, 孔容0.37 cm³·g^-1. 以三元乙丙橡胶(EPDM)为粘结剂, 与介孔纳米复合材料混合制备涂层. 通过调节复合材料中铝钛摩尔比和涂层厚度, 红外发射率在0.450-0.617之间可调.     

Synthesis of SiO2-TiO2 xerogels by sol-gel process

A new method to synthesize SiO₂-TiO₂ gels by sol-gel process has been developed. This technique uses tetraisopropylorthotitanate [Ti(O ⁱ Pr)₄] and tetraethylorthosilicate [TEOS]: they are mixed in the same solvent and then directly hydrolysed. This one-step reaction is possible because of the use of 2-methoxyethanol, a protic polar solvent. This alcohol plays two different specific roles: it acts as a solvent as well as a stabilizer of titanium alkoxide towards the hydrolysis-precipitation reaction. So, by an accurate adjustment of the quantity of methoxyethanol in the mixture, we can control the reactivity of the titanium precursor.Monolithic and transparent xerogels were obtained whatever the composition. Three monolithic SiO₂-TiO₂ gels containing 20, 50 and 75 mol% of TiO₂ were prepared and studied in details.By using the TG-DSC analysis, we can follow the evolution of the loss of water and organic residues.The structural evolution of gels during calcination is characterized by IR spectroscopy and X-Ray diffraction.     

Application of Hot Press Sintering to Na2O-B2O3-SiO2 Gels Containing Quantum Dots for Lowering of Densification Temperature

Na₂O-B₂O₃-SiO₂ (NBS) gels containing a large amount of CdS quantum-dots (10 wt%) were densified using the hot press (HP) sintering method. By HP treatment, full-densification temperature could be lowered by about 40°C than that of the normal non-pressing (NP) heat treatment. Exciton absorption of CdS quantum-dots in HP-sample showed a large blue shift compared with that in the NP sample, and the size-distribution of CdS dots remained very sharp, with a mean particle diameter d = 3.66 nm and a standard deviation of = 0.72. HP pressure had a large effect on the reduction of sintering temperature and time, resulting in the suppression of the aggregation and growth of CdS quantum-dots in NBS glasses.     

Thin and Thick RuO2-TiO2 Coatings on Titanium Substrates by the Sol-Gel Process

Thin and thick 20 mol% RuO₂–80 mol% TiO₂ coatings have been obtained through a combination of different preparation parameters, including catalyst and oxide concentrations, using ruthenium trichloride trihydrate and titanium n-butoxide. Acid catalysed solutions produced uniform, crack-free coatings that were too thin for use on electrocatalysis electrodes. On the other hand, base catalysed solutions produced thicker, cracked coatings. Electrodes prepared with base catalysed solutions performed well in electrocatalysis lifetime testing for corrosion stability.     

Proton Affinity at the Porous Surface of SiO2-TiO2 Binary Oxides

SiO₂-TiO₂ binary oxides are typically used as solid supports for different applications, from catalysts to optics. Tailoring the pore diameter, pore size distribution, and surface area is of great importance for any of those applications. Tailoring the chemical properties of the porous surface, e.g. in terms of polarity or acidity, is of capital importance as well. Thus, in catalytic applications or in sensing devices, where diffusion of a solute through the matrix is required, the affinity/compatibility of the solute with the matrix porous surface will determine the proper work of the device. Moreover, when the sensor is based on the adsorption of an active organic molecule or biomolecule on the porous surface matrix, the proton concentration at the surface may also modify the behavior of the active molecule. In this work, the proton affinity of the porous surface is tailored by the preparation of number of SiO₂-TiO₂ binary oxides with different SiO₂/TiO₂ weight ratios. Proton affinity is studied through the incorporation of a pH indicator as bromocresol green.     

制备方法对CuO/CeO_2-ZrO_2催化CO低温氧化活性的影响

采用微波加热分解法(一步法)和微波加热处理共沉淀+浸渍法(两步法)制备了CuO/CeO2-ZrO2催化剂,并对其进行了X射线衍射、低温氮气吸附/脱附和程序升温还原等表征,采用色谱流动法考察了催化剂的催化CO低温氧化性能.结果表明,一步法比两步法更有利于使催化剂表面CuO高度分散,CuO与CeO2-ZrO2间的相互作用更强,CuO更容易被还原,从而具有更高的催化CO氧化活性.与CeO2-ZrO2有相互作用的高分散和小颗粒CuO有利于催化剂活性的提高,与CeO2-ZrO2无相互作用的大颗粒CuO对催化剂的活性有抑制作用.     

B2O3/TiO2-ZrO2的结构表征及其与酸性和催化性能间的关系

采用XRD、N₂吸附、 ¹¹B MAS NMR、NH₃-TPD和催化性能评价等方法研究了B₂O₃/TiO₂-ZrO₂催化剂的结构、酸性及催化环己酮肟气相Beckmann重排反应性能间的关系。结果表明,催化剂中的B₂O₃同时以三配位的BO₃和四配位的BO₄结构单元存在;     

Preparation,Characterization of CeO2-ZrO2 Composite Hollow Microspheres and Their Application as Electrocatalysis Materials for Hemoglobin in Biosensor

Composite hollow microspheres of CeO₂-ZrO₂ were prepared by using anionic PSA latex particles as template and then calcining the PSA core particles at 600°C. The samples were characterized by XRD, TEM, TG, SEM, EDS, and FT-IR spectra. The effects of the proportion of CeO₂ on the structure of the microspheres were also studied. Electrochemical assay showed that the CeO₂-ZrO₂ composite hollow spheres hydrided with chitosan could be used as a novel biosensing material to detect the direct electron transfer of hemoglobin.     

Characterization of an all Sol-Gel Electrochromic Device WO3/Ormolyte/CeO2-TiO2

Electrochemical lithium intercalation in thin films of CeO₂-TiO₂ and WO₃, prepared by the sol-gel technique was investigated with cyclic voltammetry and spectroelectrochemical techniques in propylene carbonate solutions. A solid state system having the configuration WO₃/Ormolyte/CeO₂-TiO₂ has been assembled. The solid electrolyte, an organically modified electrolyte (ormolyte), was prepared with different [O]/[Li] ratios. The transmittance variation of this system during a potentiostatic step from –0.7 V to 0.8 V was about 35% at 550 nm.     

Crystallization Behavior of SiO2-TiO2 Ceramics Derived from Titanosiloxanes on Pyrolysis

The crystallization behavior of SiO2-TiO2 ceramics derived from titanosiloxanes was investigated in relation to the structure of the precursor and the pyrolysis temperature. The titanosiloxanes, [Si(OBut)2OTi(acac) 2O]2, [(ButO)3SiO] 2Ti (OPri)2, and [(ButO)3SiO] 3Ti(OPri), were pyrolyzed in an air atmosphere to form SiO2-TiO2 ceramics which crystallized to anatase at 600–650°C, 700–750°C, and 800–850°C, respectively. The crystallization temperature decreased with increased titanium content of the precursor. The average crystallite size of anatase increased with increased pyrolysis temperature and the titanium content. The crystallization temperature and the crystallite size for SiO2-TiO2 ceramics is controlled by the precursor structure, which may enable control of the physical properties of the ceramic materials.     

Anomalies in Heat Capacity Measurements of RuO2-TiO2 System

DSC was used for heat capacity measurements of pure RuO₂ in the temperature range from 300 to 1170 K of solid solutions corresponding to the compositions of (Ti_1−x Ru_x )O₂ (x ≤0.15 and x ≥0.85) and in the temperature range from 300 to 1550 K of pure TiO2. The analysis of experimental data obtained within ±2% of accuracy has shown that the characteristic temperatures representing the harmonic lattice vibrations do not strongly depend on the chemical composition x . It was demonstrated that non-harmonic heat capacity is strongly correlated to x. The existence of additional excess heat capacity was observed with the mixed oxide solid solution samples of low Ru content and explained by the defect formation model. This revised version was published online in August 2006 with corrections to the Cover Date.     

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.     

Synthesis and thermal investigation of Na2Cd(SO4)2·2H2O

The synthesis and thermal decomposition of Na₂(SO₄)₂·2H₂O in both air and nitrogen are described. The synthesis was performed by two different procedures, but in both cases the same product was obtained, corresponding to the general formula given above. The crystals obtained were investigated by methods of X-ray powder diffraction, and chemical and thermal analysis. The differences in thermal decomposition in air and nitrogen are discussed.     

Facile one-pot synthesis of 2-arylbenzothiazoles catalyzed by H3PO4/TiO2-ZrO2 (1/1) under solvent-free conditions

A highly efficient and simple protocol for the preparation of 2-arylbenzothiazoles through condensation of 2-aminothiophenol and different aldehydes in the presence of H₃PO₄/TiO₂-ZrO₂(1/1)-cetyl pyridinium bromide (CPB) is described. The reaction proceeded under mild and solvent-free conditions to afford 2-arylbenzothiazole derivatives. In this method, the title compounds were obtained in good to excellent yields and short reaction times. The structures of synthesized products were identified by infrared, ¹H NMR, ¹³C NMR, and mass spectroscopy.     

Catalytic methanol decomposition to carbon monoxide and hydrogen over Pd/CeO2-ZrO2-La2O3 with different Ce/Zr molar ratios

The catalytic behaviors of Pd (1.4 wt%) catalysts supported on CeO₂-ZrO₂-La₂O₃ mixed oxides with different Ce/Zr molar ratios were investigated for methanol decomposition. Nitrogen adsorption-desorption (BET), X-ray photoelectron spectroscopy (XPS), H₂ temperature-programmed reduction (H₂-TPR), X-ray diffraction (XRD) and Pd dispersion analysis were used for their characterization. Pd/Ce_0.76Zr_0.18 La_0.06O_1.97 catalyst showed the highest BET surface area, best Pd dispersion capability and strongest metal-support interaction. Moreover, XPS showed that there was lattice defect oxygen or mobile oxygen. According to the result of O 1s measurements the lattice defect oxygen or mobile oxygen helped to maintain Pd in a partly oxidized state and increased the activity for methanol decomposition. The Pd/Ce_0.76Zr_0.18La_0.06O_1.97 catalyst exhibited the best activity. A 100% conversion of methanol was achieved at around 260 °C, which was about 20-40 °C lower than other catalysts