低温下溶胶凝胶法制备TiO2纳米晶

从含过量水的溶胶出发,在室温下得到了TiO₂纳米晶。通过红外光谱,透射电子显微镜法和X射线粉末衍射法对含有过量水的溶胶体系中TiO₂纳米晶的室温形成机理进行了研究。与传统的溶胶凝胶法相比,在改良的溶胶凝胶体系中,在缩聚反应之前由于水过量使得钛的先驱体快速且充分的水解,从而生成[TiO₆]基团,随之形成TiO₂纳米晶。晶粒的尺寸为约3.5 nm,该法得到的TiO₂纳米晶比传统溶胶凝胶法得到的TiO₂纳米晶和商用光催化剂德固赛P25具有更好的光催化活性。     

Production of nanodisperse particles of doped yttrium-aluminum garnet by a sol-gel process

Method for synthesis of nanodisperse yttrium-aluminum garnet powders activated with cerium and silicon ions was developed. The method is based on a combination of sol-gel synthesis and coprecipitation of hydroxides of the corresponding metals. The process modes were optimized and the structural, physicochemical, and spectral-luminescent characteristics of the samples obtained were studied.     

硼酸对Sr2CeO4荧光粉的物相组成和发光性质的影响

采用正交试验确立了高温固相法合成Sr₂CeO₄的主要影响因素。研究了H₃BO₃和n_Sr/n_Ce(物质的量的比)对Sr₂CeO₄物相组成和发光强度的影响。XRD结果表明保持n_Sr/n_Ce为5.5和添加6.5wt%的H₃BO₃，有利于形成良好的Sr₂CeO₄晶体结构和大幅度提高Sr₂CeO₄的发光强度。荧光光谱测试表明助熔剂法合成样品的发光强度分别比传统固相法合成和溶胶-凝胶法提高了201.2%和15.7%。     

三种化学方法合成K0.5Bi0.5TiO3粉体的机理比较

采用溶胶-凝胶法、水热法和溶胶-凝胶-水热法三种化学方法合成K_0.5Bi_0.5TiO₃ (KBT)无铅压电陶瓷粉体. 用X射线衍射(XRD)分析产物的结构, 用扫描电镜(SEM)和透射电镜(TEM)观察产物的形貌. 实验结果表明, 三种化学方法均可获得纯钙钛矿相KBT粉体, 但不同工艺获得的粉体在形貌和生成机制上有很大的不同. 溶胶-凝胶法属高温固相扩散机制, 需要700 ℃以上温度煅烧才可获得KBT纯相, 且粉体颗粒度大、团聚严重. 水热法符合溶解-结晶机制, 生长出四方形的KBT纳米片. 溶胶-凝胶-水热法利用了凝胶团聚体空间链状结构的模板作用, 通过原位结晶机制生长出KBT纳米线.     

A Sol-Gel Precursor as a Powder Binder for PZT Ceramic Fabrication

A lead zirconate titanate (PZT) precursor sol was prepared by a diol sol-gel route and used as a binder for assisting the uniaxial die pressing of PZT powders. The powders, of composition Pb(Zr_0.52Ti_0.48) O₃, were prepared by a two step mixed oxide route using lead carbonate, zirconia and titania starting powders. The densification characteristics of the powders, which were not milled after the final calcination step, were compared to samples prepared using PVA as a conventional binder. Improved sintering behaviour was observed for the novel sol-gel binder system. For example, using a sol concentration, equivalent to 7 wt% of PZT derived from the binder, pellets of 95% theoretical density were obtained after firing at 1150°C for 4 h, whereas for the same firing conditions, samples blended with PVA resulted in a density of only 78% theoretical.     

不同方法制备CaMoO4∶0.05Eu3+红色荧光粉的对比研究

分别以高温固相法、溶胶-凝胶法、水热法和共沉淀法合成Eu3+掺杂的CaMoO4红色荧光粉,通过X-射线衍射(XRD)、场发射扫描电镜(FESEM)、傅立叶变换红外光谱(FTIR)、光致荧光光谱(PL)进行表征,考察荧光粉晶相、形貌及发光性能对制备方法的依赖性。实验表明,由于Ca2+的半径(0.099 nm)与Eu3+半径(0.094 7 nm)大小相差不大,Eu3+容易取代Ca2+的位置进入晶格,Eu3+掺杂的CaMoO4在晶体结构上保持白钨矿结构。FESEM结果表明:未经后处理的水热法所得样品为片状、多孔结构;高温固相法所得样品尺寸大、团聚严重;溶胶-凝胶法所得样品分散度好、呈条形结构;共沉淀法所得样品形貌、尺寸比较均一。荧光光谱显示,四种样品发光强度差异很大,共沉淀法制得样品的发光强度为未经后处理的水热法制得样品的6-7倍,该现象主要是由样品形貌及表面缺陷的差异引起的。     

Preparation and Characterization of CeO2 Nanoparticles

The preparation and characterization of cerium oxide nano-powder has attracted much attention over the past few years due to their great potential in many fields. It is commonly used in glass, ceramics, fluorescence powder and catalyst etc.1. Cerium oxide was produced by oxalic acid decomposition in industry. Take this way, the products are pure but the size of powder is large ( ＞3 μ m )2. Up to now,various methods have been reported to synthesize ultra fine cerium oxide powders, such as homogeneous deposition method, hydrothermal method, sol-gel method and spray deposition method etc. 3-6. However, these methods are not convenient for synthesis of large amounts of powders because of the difficulty of technique and expensive equipment involved. Although sol-gel method is well suited to synthesize ultrafine powders, this reaction is always in high temperature.     

Synthesis and characterization of alumina- and zirconia-based powders obtained by the ultrasonic spray pyrolysis

The ultrasonic spray pyrolysis (USP) technique was used for synthesis of alumina- and zirconia-based powders. The starting agents were aqueous solutions, atomized by the ultrasonic spray generator and pyrolized in the furnace under the open-air conditions. The powders prepared by USP were in the form of solid and hollow aggregates (spheres) consisted of nanosize amorphous grains as determined by the microscopy and the X-ray diffraction techniques. The alumina-based powders were consolidated by the pulse plasma sintering resulting in single-phase materials. Different behavior of solid and hollow particles during the isostatic sintering is found; a higher degree of deformation of spheres is observed in the second case.     

Synthesis of high surface area potassium hexatitanate powders by sol-gel method

Potassium hexatitanate (K₂Ti₆O₁₃) powders were synthesized by sol-gel method using supercritical drying to produce ion-exchangeable fine powders with high surface area. The effects of titanium alkoxides and mole ratios of K/Ti were investigated. By using sol-gel method, potassium hexatitanate powders were obtained at 630°C which is 350°C lower than that by melting method. The surface area of this sample was about 30–40 m²/g which was higher than that of melting method sample. Addition of H₂O and decrease in mole ratios of K/Ti increased surface area of powders.This work was partially supported by the IAEA (Research Program on Waste Treatment Immobilization Technologies Involving Inorganic Sorbent) contract. Many thanks to the IAEA's support.     

Synthesis of titanium silicalite-1 (TS-1) zeolite with high content of Ti by a dry gel conversion method using amorphous TiO2–SiO2 composite with highly dispersed Ti species

In this study, we have developed a new method to synthesize mesoporous titanium silicalite-1 (TS-1) with a higher content of active titanium in the framework (more than 5%) than that obtained from the conventional hydrothermal synthesis. The new method combines two methods as follows: (1) a sol-gel method in tetrahydrofuran for the synthesis of TiO₂–SiO₂ composite with highly dispersed Ti species and (2) a dry gel conversion method for the crystallization to TS-1. This investigation revealed that the dispersion of Ti in the starting materials was quite important to synthesize mesoporous TS-1 with high content of Ti besides dry conversion method. The obtained mesoporous TS-1 with a high content of titanium showed higher catalytic activity in 1-hexene epoxidation than conventional TS-1. This high activity is likely to originate from the high content of titanium in the framework.     

Novel Siloxane-Silica Nanocomposite Aerogels and Xerogels

Novel covalently bonded silicone-silica nanocomposite network materials have been synthesized from a single component molecular precursor. A novel polymeric sol-gel precursor was prepared by hydrosilation of oligo(methylvinylsiloxane) with triethoxysilane and it was applied in sol-gel processing for the synthesis of silicone-silica based gel networks. Acid/base catalyzed hydrolysis and condensation reactions were performed from solutions of the pure macro precursor as well as from mixtures of this precursor with tetraalkoxysilanes followed by either supercritical drying with liquid carbon dioxide or drying at ambient conditions. In both cases monolithic gels as well as powders were obtained and properties such as porosity, surface area and thermal stability have been investigated. Solid state (CP MAS) ²⁹Si-NMR were used to evaluate the chemical composition and extent of condensation of the gels.     

Effect of alumina incorporation on restricting grain growth of nanocrystalline tin(IV) oxide

In this project, nanocrystalline SnO₂ powders were successfully prepared by (a) citrate sol-gel and (b) direct precipitation methods. Powders were characterized using thermal analysis techniques (DTA-TG-DSC), X-ray powder Diffraction (XRD), surface area (BET) and electrical conductivity measurements. XRD patterns showed the presence of the cassiterite structure. SnO₂ particles, prepared through sol-gel method exhibit crystallite sizes in the range from 3.1 to 22.3 nm when the gel is heat treated at different temperatures up to 900°C. SnO₂ nanocrystallites prepared by the precipitation method are comparatively larger in size. The higher specific surface area was obtained for the powder prepared using sol-gel method and the obtained average grain size (d) is relatively large compared with that of the average crystallite size. The powders show a semiconducting behavior with increasing temperature. The higher conductivity obtained for SnO₂ prepared by sol-gel method can be attributed to their smaller average crystallite size. XRD of alumina doped powder exhibits finer particles than pure SnO₂. TEM images showed that the particles are spherical in shape and consist of a core of SnO₂ surrounded by a coating of alumina. The calculated surface area was found to decrease with temperature increases. Due to the effective role of Al₂O₃ additive as a grain growth inhibitor for the matrix grains, the observed surface area for the coated materials are predominantly higher than for the uncoated materials.      

锂离子电池正极材料LiMn2O4的合成与晶体结构（英）

Spinel LiMn₂O₄ powders were prepared using two-step synthesis method consisting of solid-state reaction method and citrate modified sol-gel method. The effects of the calcination temperature and the Li/Mn ratio of raw materials were studied on the physicochemical and electrochemical properties of the spinel LiMn₂O₄ powders, such as crystallinity, lattice constant and density. The title compound was characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Polycrystalline LiMn₂O₄ powers calcined at 750 ℃ were found to be composed of very uniformly-sized microcrystal with an average particle size of 300 nm. The improvement in electrochemical properties was mainly attributed to the process of re-grinding by absolute alcohol.     

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.     

Pt-ZnO/C复合材料的合成及对醇类催化活性的研究

采用溶胶-凝胶法制备了ZnO微米颗粒,电沉积Pt合成了Pt-ZnO/C复合材料。利用X射线衍射仪（XRD）和扫描电子显微镜（SEM）对产物的晶型和形貌进行了表征,并利用循环伏安法（CV）研究了所得复合材料对甲醇和乙醇的电催化活性。实验结果表明,该催化剂在ZnO的质量分数为50%时对甲醇和乙醇氧化的电催化活性最好。
     

Composite SiO2—Iron Oxide Materials for Magnetically Intensified Adsorption

Composite SiO₂—iron oxide materials were prepared by three experimental procedures. In the first case, the iron oxides were precipitated during a sol-gel process. In the second case, a SiO₂ matrix was initially obtained, and the iron oxides were formed by thermal treatment after impregnation of a soluble Fe²⁺ salt in the previously processed matrix. In the third method, ferrite powders, prepared by wet chemical method, were embedded into a SiO₂ based sol-gel matrix. Materials with convenient porosity and nano-sized iron oxide content could be prepared using the mentioned methods. The prepared composite has been tested for arsenic(V) removal.     

腐蚀法制备工艺对SiC量子点光学性质的影响

通过可控的化学腐蚀法制备碳化硅量子点,以氢氟酸和硝酸的混合液为腐蚀剂腐蚀自蔓延燃烧合成的原始碳化硅粉体,而后经超声空化作用及高速离心层析裁剪获得水相的碳化硅量子点,研究了制备工艺参数对量子点光致发光强度、发射波长等光谱特性及粒子尺寸的影响,结果表明,腐蚀剂组分及其配比是影响量子点光致发光强度的主要因素,而超声振动时间和...     

Synthesis and characterization of organofunctionalized MCM-41 by the original stepped templated sol-gel technology

Four types of organofunctionalized (by phenyl, 3-aminopropyl, 3-chloropropyl, and N-aminoethylaminopropyl, respectively) mesoporous silicates MCM-41 (hereafter R-MCM-41) have been successfully synthesized via the grafting method, the conventional templated sol-gel technology, and the original stepped templated sol-gel technology. The prepared inorganic-organic hybrid materials were characterized in detail by powder X-ray diffraction (XRD), 29Si and 13C MAS NMR spectrometry, isothermal nitrogen adsorption-desorption analysis, FT-IR spectrometry including in situ drift technique, and thermogravimetric analysis (TGA). Through a series of investigations and comparisons, the advantageous stepped templated sol-gel technology introduced in this paper is demonstrated to be a remarkable approach that gathers the superior properties of the current grafting method and the conventional hydrothermal co-condensation synthesis, yielding as a consequence both thermodynamically firm fixation and relatively large content of organic functional species on the MCM-41 support. The novel synthetic strategy also evidently shortens the crystallization time for the organofunctionalized MCM-41 with regular specific structure.     

Effect of synthesis duration on the morphological and structural modification of the sea urchin-nanostructured γ-MnO2 and study of its electrochemical reactivity in alkaline medium

Single-crystalline nanorods and sea urchin-like morphology of the γ-MnO₂ nanostructures were successfully synthesized by hydrothermal method at different synthesis durations. The as-synthesized products were characterized by the techniques X-ray powder diffraction (XRD), field emission gun-scanning electron microscope (FEG-SEM) coupled with energy-dispersive X-ray elemental analysis (EDX), transmission electron microscope (TEM), isotherms of N₂ adsorption/desorption and BET-BJH models. The effect of synthesis duration on the morphology, porous structure, and crystallographic form of MnO₂ powders was studied. The electrochemical reactivity of as-prepared powders was investigated in 1 mol L^?1 KOH by both cyclic voltammetry and impedance spectroscopy by using a micro-cavity electrode. The results show that the best electrochemical reactivity of the MnO₂ powder was obtained with synthesis duration of 24 h.     

Preparation and evaluation of nano-hydroxyapatite/poly(styrene-divinylbenzene) porous microsphere for aspirin carrier

A novel vehicle for the delivery of aspirin (ASA) was prepared from porous nano-hydroxyapatite/poly(styrene-divinylbenzene) [nano-HAP/P(St-DVB)] composite microspheres by grafting nano-HAP [Ca10(PO4)6(OH)2] onto porous P(St-DVB) microspheres. Four types of porous composite microspheres were prepared, each with different nano-HAP contents. The ASA-loaded composite microspheres prepared with 10% and 15% nano-HAP (mass ratio) exhibited excellent buoyancy with relatively short instantaneous floating time (within 10 min) and a long sustained floating time (12 h) in simulated gastric juice. They also offered good sustained release of ASA (up to 8 h). Furthermore, these composite microspheres displayed good buffering capacity that prevented the buildup of acidity caused by hydrolysis of ASA, keeping the pH of gastric juice within the normal range (pH 0.9 to 1.5). The results showed that porous nano-HAP/P(St-DVB) composite microspheres prepared with 10% and 15% nano-HAP could be used as a novel drug carrier for ASA, providing a sustained release dose without leading to stomach irritation, a side effect that is often associated with ASA medication.