柠檬酸溶胶凝胶法制备LiCoO_2电极材料及其表征

目前研究较多的锂离子电池正极材料主要有LiCoO2、LiNiO2和LiMn2O4犤1犦,虽然LiCoO2的成本相对较高,但LiCoO2具有最为优良的电化学性能,如高且平稳的充放电平台、高比容量以及良好的循环性能犤2犦,是目前应用最广泛的商品化电极材料。LiCoO2材料主要采用高温固相法犤3～5犦制备,该方法工艺简单,容易实现大规模生产,但缺点是需要较高的焙烧温度和较长的焙烧时间,且反应原料混合均匀程度有限,易导致非化学计量、非均相以及不规则的颗粒形貌等,因此材料的比容量、循环寿命等电化学性能以及反应的可控性还不甚理想。研究表明犤6犦电极材…     

Ferricyanide Confined in a Protonated Amine-Functionalized Silica Film on Gold: Application to Electrocatalytic Sensing of Nitrite Ions

An amine-functionalized porous sol–gel silica film was shown to be an effective platform to immobilize small anionic redox mediators of high solubility on solid electrodes by electrostatic interaction. The highly soluble mediator hexacyanoferrate was used as a model. The film was grown and firmly anchored on a gold electrode surface via thiol groups of a self-assembled monolayer of (3-mercaptopropyl)trimethoxysilane. Film growth and thickness were controlled by electrochemical modulation of pH at the electrode/solution interface in a sol of a hydrolyzed solution of tetraethoxysilane and 3-[2-(2-aminoethylamino)ethylamino]propyltrimethoxysilane by the application of a negative potential to the electrode. Protonation of the amine groups made the amine-functionalized surface useful to immobilize hexacyanoferrate on gold. Thus, the immobilization is pH dependent, being highly effective in strongly acidic medium. Cyclic voltammetry and scanning electron microscopy were used to characterize the film and to optimize the experimental conditions. The stability of the film was demonstrated by applying the catalytic properties of the hexacyanoferrate containing surface for nitrite sensing using a flow injection analysis (FIA) system. Under the optimized conditions, the sensor exhibited high sensitivity, low detection limit, easy handling, and stability with a linear range from 1.0 to 40.0?µmol?L^?1 and a detection limit of 0.53?µmol?L^?1 based on a signal-to-noise ratio of 3. The sensor was successfully applied to nitrite determination in water samples using FIA with excellent recoveries.     

Hydrophobic Silica Sol Coatings on Textiles—the Influence of Solvent and Sol Concentration

Hydrophobic silica sol coatings on textiles were investigated with respect to the influence of the solvents and the concentration of the sol. For this purpose, two silica sols, prepared with the hydrophobic additives octyltriethoxysilane and perfluoroctyltriethoxysilane were diluted by different solvents: water, ethanol and aceton.In case of using pure water for dilution, the hydrophobicity of coated textiles decreases drastically with increasing dilution of the applied sol. For coatings on polyester fabrics or mixed fabrics made from polyester and cotton, the use of the organic solvents ethanol or aceton leads to significant hydrophobicity even in case of strong dilution down to a sol concentration < 1%. The hydrophobic effect of coated polyamide textile is less. The reason for different hydrophobicity of coated textiles resulting from the use of water instead of organic solvents is explained by different surface morphologies of the coatings deposited on the textile fibres, as observed by REM. In case of using organic solvents the coatings contain a more flat morphology which covers the fibres completely. In contrast, sols with higher water content lead to less adhesive coatings with crack formation.The use of a combination of water with less inflammable organic solvents such as di(propylene glycol) n-propyl ether (Dowanol^TM DPnP) in hydrophobic silica sols yields textile coatings with good hydrophobicity, even in case of low sol concentration. For practical application of textile coatings, especially silica sols with high water content are of interest, due to less risk of inflammation and lower ecological impact. Therefore, the use of water diluted hydrophobic silica sols with small amounts of DPnP offers a chance for textile refinement by the sol–gel technique.     

LaCo0.9Cu0.1O3的蔗糖溶胶-凝胶法合成及二甲苯催化氧化性能研究

蔗糖溶胶 凝胶法合成了稀土钙钛矿型复合氧化物LaCo0 .9Cu0 .1 O3,并对其进行了XRD ,BET ,TPR表征和二甲苯催化氧化性能测试 ,并与柠檬酸溶胶 凝胶法作了比较。结果表明 ,蔗糖作为络合剂成胶和干胶容易 ,粒径较小 ,具有进一步降低LaCo0 .9Cu0 .1 O3形成温度的作用 ,以蔗糖作为络合剂在 70 0℃所制备的催化剂LaCo0 .9Cu0 .1 O3低温活性较好。     

用无机硅剂水热法合成纳米NiO/SiO2及其催化乙炔分解制备纳米碳管

以硅溶胶为硅源．水热法制备NiO／SiO2催化剂，用于化学气相沉积法(Chemical Vapor Deposition，CVD法)制备碳纳米管通过SEM表征，研究了催化剂原料及其配比，水热制备工艺条件对催化效果的影响．结果表明：用硅溶胶可替代正硅酸乙酯作为硅源；制备的最佳条件为：MSiO2：MNi（NO3）2=1：12～1：14，水热温度为180～200℃，压力为1．2～1．5MPa．保温时间为0．5～2h．     

氟掺杂锐钛矿型TiO2溶胶的制备、表征及催化性能

以四氯化钛为前驱物, 采用改性的沉淀-溶胶-水热晶化法制备了一种具有锐钛矿型结构的氟掺杂的二氧化钛(F-TiO₂)溶胶. 研究了氟掺杂、水热晶化的温度、时间及介质pH值对溶胶粒子的晶型和晶化度的影响. 采用XRD, TG-DTA, TEM, UV-Vis-DRS, FTIR, XPS技术及吸附、表面酸度测定手段对溶胶粒子的结构进行了表征. XRD分析结果表明: 氟的掺入可以降低水热晶化反应的温度或减少反应时间、提高粒子的晶化度, 溶胶粒子具有锐钛矿型结构; TEM分析显示: 粒子呈圆球型, 平均粒径大约为6.5 nm. XPS测定结果表明; 氟在溶胶粒子中以吸附态和结合态两种形式存在; 吸附、表面酸度及光催化活性测定表明: 与P25型TiO₂及纯TiO₂溶胶粒子相比, F-TiO₂溶胶粒子具有更大的吸附能力、更强的表面酸度及更高的光催化活性. 还从光生载流子分离效率等方面探讨了掺杂对催化剂活性影响的机理.     

XPS characterisation of core-shell silica-polymer composite particles synthesised by atom transfer radical polymerisation in aqueous media

Near-monodisperse, siloxane-functionalised silica particles are used as a colloidal substrate for the surface-initiated polymerisation of various hydrophilic methacrylates: oligo(ethylene glycol) methacrylate (OEGMA), 2-(N-morpholino)ethyl methacrylate (MEMA), and ammonium 2-sulfatoethyl methacrylate (SEM) by atom transfer radical polymerisation in aqueous media at room temperature. The bulk and surface compositions of the resulting composite particles were assessed using various techniques. Thermogravimetric analysis of the resulting silica-polymer composites indicated polymer loadings of 5.4-8.6%, depending on the nature, structure and target degree of polymerisation (D_p). Dynamic light scattering studies indicate increases in hydrodynamic diameter of 14-87 nm compared to the reference silica particles. FT-IR spectroscopy confirmed additional features characteristic of the carbonyl group and pendant end-chain functionalities of the methacrylic polymer chains. The elemental and chemical surface compositions of the initial silica particles and final polymer-grafted composite particles were extensively investigated by X-ray photoelectron spectroscopy (XPS). The composite particles had appreciably higher C/Si atomic ratios, compared to the original initiator-functionalised silica particles, and these ratios increased with increasing target D_p. In addition, close inspection revealed that the relative intensities of the various components of the peak-fitted C1s envelopes varied significantly, depending on the target degree of polymerisation and the chemical structure of the methacrylic monomer. Moreover, in the case of the MEMA and SEM polymerisations, new nitrogen (MEMA) and sulfur (SEM) XPS signals were detected. This XPS study confirmed the presence of a thin outer layer of grafted polymer chains surrounding the silica particles.     

溶胶-凝胶固定化多酶催化二氧化碳转化为甲醇反应初探

 为了探索温室气体CO2的固定和利用的新途径，以正硅酸乙酯为\r\n前驱体，用改进的溶胶－凝胶法对甲酸脱氢酶、甲醛脱氢酶和乙醇脱氢\r\n酶进行了包埋共固定化，并以包埋的三种酶为催化剂，以还原型烟酰胺\r\n腺嘌呤二核苷酸（NADH）为电子供体，在低温低压下将CO2转化为甲醇\r\n．初步研究了反应温度、pH值、酶含量及NADH用量对甲醇收率的影响．\r\n实验结果表明，在37℃和pH7．0的条件下，甲醇的收率可达92．4％．\r\n由于酶空间构型的微小变化和空间位阻效应的存在，与液相酶反应结果\r\n相比，包埋后的酶活性略有降低．     

Research on successive preparation of nano-FeNi alloy and its ethanol sol by pulsed laser ablation

Since Ogale et al.[1,2] firstly prepared metastable matter by pulsed laser ablation at the solid target sub-merged in liquid, there has been a great interest in it. Tokura et al.[3] prepared carbon films in the water by pulsed laser ablation. Zheng et al.[4—6] prepared nano and cluster matters with different shapes through pulsed laser ablation at interface of liquid and solid target. Yang et al.[7,8] prepared cube nano-nitride boron crystalloid and nano-diamond crystalloid with the same meth…     

Characterisation of nanocrystalline magnesium oxide by X-ray absorption spectroscopy.

There are numerous methods of preparing nanocrystalline materials. Magnesium oxide is an ideal model system on which to probe the relation of the preparative route and the microstructure. Using X-ray absorption spectroscopy (XAS) we show that the sol-gel route can be used to prepare highly crystalline material provided there is careful control of the calcination conditions. In the present work this is achieved by calcining at high temperatures (at least 800 degrees C). However, this results in grain growth that can be prevented by the addition of a pinning agent, SiO(2), during the preparation of the sol. The pinned samples maintain a particle size of 11 nm even after calcining at 1000 degrees C. Ball-milling is a common method of preparing nanocrystalline oxides, however the present work shows that this produces a significant fraction of amorphous material, the fraction increasing with decreasing grain size (e.g. approximately 30 % for a grain size of 23 nm).