Preparation of Alumina Aerogel Films by Low Temperature CO2 Supercritical Drying Process

Alumina aerogel thin films were formed by a new synthesis route. Sols were prepared by the Yoldas process. Gels were formed by sol evaporation in a few hours. Films were prepared by dip coating glass or alumina substrates into both the sols and the gels. Aerogel films with special morphology were produced for the first time by exchanging the film solvent with acetone after the dip coating, followed by supercritical drying. The morphology of the films, studied by SEM and TEM, consists of fiber-like network of round chains (≈0.1 μm thick), and pores (0.1–0.5 μm in diameter). It is shown that the fibers contain a homogeneous arrangement of sol particles, 2–4 nm in size. Formation of this microstructure can be attributed to phase separation in the alumina-water-acetone system in a 2D film geometry. A conceptual model for the film development is proposed.     

Effects of Ti Addition on Alumina/Titania Composite Aerogels Synthesized by Sol–Gel Process and Supercritical Ethanol Drying

Alumina/titania composite aerogels with different titania contents were synthesized by the sol–gel process and supercritical ethanol drying. The structures and morphologies of synthesized aerogels were analyzed by X‐ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, thermogravimetry, and N₂ adsorption–desorption tests. Supercritical ethanol drying induced the crystallization of titania, which prompted the transformation of the structure from pseudoboehmite to γ‐Al₂O₃ . Reversely, alumina retarded the anatase‐to‐rutile transformation of titania. The content of titania significantly affected the structure and morphology of alumina/titania composite aerogels. A high content of titania (≥40%) resulted in the phase separation of titania particles, which grew to form the anatase phase octahedral particles with well‐developed facets. When the titania content was low, titania particles could be homogeneously dispersed in alumina particles to form spherical clusters with the poor crystallinity. Titania particles were in the anatase phase, and no rutile phase was formed until the temperature rose to 1000°C. In addition, titania addition resulted in a decrease in the specific surface area (SSA) of alumina aerogels because the SSA of titania was lower than that of alumina aerogels.     

块状石英纤维/Al_2O_3气凝胶复合材料的非超临界干燥法制备及表征

采用溶胶-凝胶法和常压干燥法以N,N′-二甲基甲酰胺(DMF)作为干燥控制化学添加剂制备了低密度石英纤维增强Al2O3气凝胶复合材料.通过氮气吸附-脱附实验比较研究了石英纤维对氧化铝气凝胶孔结构参数的影响;采用X射线衍射技术表征了在升温过程中石英纤维/Al2O3气凝胶复合材料的相结构变化;利用扫描电子显微镜和透射电子显微镜观察了Al2O3气凝胶基体及其石英纤维复合材料的微观形貌;初步探讨了DMF对Al2O3气凝胶形貌和密度的影响.研究结果表明石英纤维/Al2O3气凝胶复合材料成块性好,纤维与气凝胶基体结合紧密,石英纤维提高了Al2O3相转变温度,适量的DMF有利于形成均匀凝胶网络结构,减小干燥收缩压力.     

碳纳米管负载氧化铝材料的制备及其吸附水中氟离子的研究

采用碳纳米管和硝酸铝制备了碳纳米管负载氧化铝新型除氟材料.X射线衍射检测发现,当焙烧温度低于850℃时,氧化铝为无定形态,当焙烧温度为1050℃时,氧化铝为α形态,扫描电子显微镜观察到碳纳米管与氧化铝均匀掺杂.同时用碳纳米管负载氧化铝复合材料进行水中氟离子的吸附研究,结果表明,该复合材料具有优良的除氟效能.氧化铝负载量为30%、焙烧温度为450℃条件下制备的碳纳米管负载氧化铝复合材料的吸附除氟能力是γ-氧化铝的2.0～3.5倍,与IRA-410聚合树脂的吸附除氟能力相当,适宜pH范围为5.0～9.0,吸附等温线符合Freundlich方程.     

Synthesis of New Hybrid Organic-Inorganic Alumina Gels by the Sol-Gel Method

New hybrid organic-inorganic alumina gels have been prepared by reacting aluminum sec-butoxide and propane-1,2-diol, in CCl₄ as solvent. This reaction occurred without water addition and without the use of any catalyst, leading to the formation of transparent and monolithic gels. IR,²⁷Al and¹³CNMR show that an interchange reaction between OBu ^s alkoxide groups and diol groups occurred, leading to the hybrid gels. Samples heat treated at different temperatures under argon are weakly porous and have a small specific surface area. XRD indicates the presence of pure α-alumina at 1450°C.     

异丁醇-水-硝基乙烷体系中的双因素自耦合界面不稳定现象

指导了发生在异丁醇、硝基乙烷和水三组分两相体系中的多因素复合界面不稳定现象，文中通过对一个滴加在异丁醇水溶液表面的硝基乙烷液滴的运动特征的分析，揭示了该现象的规律，在体系趋于热力学平衡的过程中，硝基乙烷液滴先表现出周期性的振荡运动，然后转变为螺旋线和圆周运动，提出了一个溶质迁移和相间溶解的双因素自耦合机理，认为该现象的根本起因是表面活性剂溶质相间迁移所导致的溶质Ｍａｒａｎｇｎｉ效应，但由于丁醇的相     

有机模板剂辅助喷雾干燥法制备LiFePO4/C正极材料及其电化学性能研究

分别使用3种有机物辅助模板剂,由喷雾干燥制得LiFePO4/C复合正极材料,X射线衍射（XRD）、扫描电镜（SEM）表征、考察了不同模板剂对样品的形貌和性能的影响.交流阻抗（EIS）、循环伏安（CV）和恒电流充放电测试电极性能.结果表明：样品的形貌和结构因添加不同的有机模板剂而改变.无模板剂时,得到的样品是光滑实心球;...     

Pd／硫酸化氧化铝一种新型甲烷选择还原NO催化剂

 中译文： 最近，以甲烷为还原剂选择性还原NO引起人们的极大关注[ ，2]. 已有的结果表明：钯基催化剂对该反应有较高的活性[3-6]. 然而，在该反应中，钯基催化剂的活性对载体的性质有很强的依赖性[3，4]. 迄今为止，只有酸性的沸石[3，4]和酸性的氧化锆[4-6]被证明是钯基选择性还原NO催化剂的有效载体. 相反，Pd/g-Al2O3作为目前最被广泛应用的一种三效催化剂[7]，对于甲烷选择性还原NO反应只有很低的活性[3]. 在本工作中，我们首次研究了一系列担载Pd的硫酸化氧化铝（SA）催化剂上甲烷选择性还原NO反应并考察了Pd含量对催化剂活性的影响。 硫酸化氧化铝（SA）按照Hamada等人[8]的方法, 将g-Al2O3（分析纯，上海试剂公司，中国）用2.5 mol/L硫酸溶液按照15 ml/g 比例浸渍, 得到产物缓慢搅拌半小时, 然后不洗涤直接过滤并在110 ℃下干燥过夜. 通过用氯化钯的水溶液等体积浸渍的方法实现Pd的担载. 所有样品先在110 ℃下干燥8小时，然后在600℃下空气氛中焙烧6小时. 反应在固定床反应器中进行，混合气 (组成为：0.2 % NO, 0.2 % CH4, 2.0 % O2, He为底气) 以60毫升/分钟的流速流过1毫升催化剂（GHSV=3600 h-1）. 气体产物用气相色谱在线分析. NO转化率以N2的产率计算，甲烷的转化率由其消耗量来计算. 图1给出了四种不同催化剂上NO和CH4转化率与反应温度的关系. 由图1可见，g-Al2O3对甲烷选择性还原NO只有微弱活性. 硫酸化后，NO和CH4的转化率都明显下降. 这种活性下降可以归因为硫酸化后在g-Al2O3表面上生成了活性更低的硫酸铝的缘故[8]. 当我们将0.1 wt.% Pd担载到g-Al2O3 和 SA上时，两种载体的催化活性发生了明显的变化. 与Misono等人[3]一样，我们发现担载 0.1 wt.% Pd后，g-Al2O3上甲烷转化率增加，但NO的转化率仍然很低. 这一结果表明，在g-Al2O3上担载Pd后，只促进了燃烧反应. 另一方面，担载Pd后，SA上的NO和CH4转化率都明显提高. 在Pd/SA上，NO转化率于500℃达到最大值75 %. 显而易见，SA是一种用于甲烷选择性还原NO反应的Pd催化剂的新型载体，载体的硫酸化对提高甲烷还原NO的选择性是必要的. SA可以通过硫酸溶液浸渍商业化的g-Al2O3获得，这就使其比酸性的沸石或酸性的氧化锆更便宜和更容易获得. 因此我们认为SA有希望成为一种用于甲烷选择性还原NO的Pd催化剂的商业化载体. Pd含量对Pd/SA催化剂催化活性的影响如图2所示. 可以看出Pd/SA催化剂的活性随Pd含量的增加而增加，当Pd的含量为0.1 wt.%左右时达到最大值，然后下降. 这一结果表明对于Pd/SA催化剂，Pd的最佳含量大约为0.1 wt.%.     

Characterization of Fumed Alumina/Silica/Titania in the Gas Phase and in Aqueous Suspension

Fumed oxide alumina/silica/titania was studied in comparison with fumed alumina, silica, titania, alumina/silica, and titania/silica by means of XRD, ¹H NMR, IR, optical, dielectric relaxation, and photon correlation spectroscopies, electrophoresis, and quantum chemical methods. The explored Al₂O₃/SiO₂/TiO₂ consists of amorphous alumina (22 wt%), amorphous silica (28 wt%), and crystalline titania (50 wt%, with a blend of anatase (88%) and rutile (12%)) and has a wide assortment of Brønsted and Lewis acid sites, which provide a greater acidity than that of individual fumed alumina, silica, or titania and an acidity close to that of fumed alumina/silica or titania/silica. The changes in the Gibbs free energy (ΔG) of interfacial water in an aqueous suspension of Al₂O₃/SiO₂/TiO₂ are close to the ΔG values of the dispersions of pure rutile but markedly lower than those of alumina, anatase, or rutile covered by alumina and silica. The zeta potential of Al₂O₃/SiO₂/TiO₂ (pH of the isoelectric point (IEP) equals ≈3.3) is akin to that of fumed titania (pH(IEP_TiO2) ≈ 6) at pH > 6, but it significantly differs from the ζ of fumed alumina (pH(IEP_Al2O3) ≈ 9.8) at any pH value as well as those of fumed silica, titania/silica, and alumina/silica at pH < 6. The particle size distribution in the diluted aqueous suspensions of Al₂O₃/SiO₂/TiO₂ studied by means of photon correlation spectroscopy depends relatively slightly on pH in contrast to the titania/silica or alumina/silica dispersions. Theoretical calculations of oxide cluster interaction with water show a high probability of hydrolysis of Al–O–Ti and Si–O–Ti bonds strained at the interface of alumina/titania or silica/titania due to structural differences in the lattices of the corresponding individual oxides. Ab initio calculated chemical shift δ_H values of H atoms in different hydroxyl groups at the oxide clusters and in bound water molecules are in agreement with the ¹H NMR data and show a significant impact of charged particles (H₃O⁺ or OH⁻) on the average δ_H values of water droplets with (H₂O)_n at n between 2 and 48.     

负载型钼系超细催化剂的合成,结构与反应性能研究

负载型钼系催化剂广泛用于加氢脱硫、抗硫甲烷化及部分氧化等,其加氢脱硫活性与低温氧的表面吸附量成正比,活性组分受载体性质的影响。超细粒子是近年来兴起的新型催化材料,由于其表面及体积效应,导致其特殊的表面吸附性能。以超临界法合成NiO/Al_2O_3、Fe_2O_3/SiO_2等超细催化剂已有报道,但该法对MoO_3/Al_2O_3的合成尚未见报道。本文以MoO_3/Al_2O_3超临界法合成超细粒子催化剂,根据超细催化剂分散性与粒径的关系选择了活性与钼表面分散性有依赖关系的临氢重整反应为探针,研究了超细MoO_3/Al_2O_3催化剂的性质。     

Comparison of Different Clean-Up Procedures for the Analysis of Deoxynivalenol in Cereal-Based Food and Validation of a Reliable HPLC Method

Three different clean-up methods for the analysis of deoxynivalenol in cereals and cereal-based foods are described and compared. DON was extracted with water or acetonitrile/water (84/16, v/v) and the extracts were cleaned-up by passing either through two different immunoaffinity columns (DONtest, Vicam; DONPrep, Rhone) or a charcoal/alumina column (MycoSep, Romer Labs). Determinative analysis was performed by high performance liquid chromatography (HPLC) with diode array detection (DAD) and fluorescenic detection (FLD) after post-column derivatisation. Different parameters were optimised and possible reasons for diverse results are discussed. The final method was validated and adopted to different matrices. Best results were obtained using immunoaffinity columns for clean-up in combination with HPLC-FLD detection of the DON-derivative.     

Preconcentration and Spectrophotometric Determination of Chromium (VI) and Total Chromium in Drinking Water by the Sorption of Chromium Diphenylcarbazone with Surfactant Coated Alumina

Abstract

A simple and inexpensive method for determining chromium (VI) in drinking water by spectrophotometry after preconcentration with sodium dodecyl sulphate (SDS) coated alumina column is described. Chromium(VI) is reacted with diphenylcarbazide (DPC) and the Cr-DPC complex is quantitatively adsorbed onto a SDS coated alumina column from 800 ml of sample solution. The complex is then eluted with a 8 ml mixture of methanol, acetone and hydrochloric acid and determined by spectrophotometry. Total chromium can be determined after oxidation of chromium (III) to chromium (VI) by KMnO₄. The relative standard deviation (10 replicate analyses) at the 10 μg l^?1 of chromium (VI) and 10 μg l^?1 of total chromium were 3.5% and 3.4% and corresponding limits of detection (based on 3 σ) were 0.040 μg l^?1 and 0.033 μg l^?1, respectively.     

定向Monte Carlo格点搜索算法用于氧化铝团簇(Al2O3)n (n=1~50)的结构搜索

氧化铝纳米团簇在众多技术应用中日益受到重视, 找到其最优结构对进一步的研究非常重要. 本工作提出了一种定向Monte Carlo格点搜索算法用于搜索不同氧化铝晶体(α, θ和δ)内的不同尺寸的氧化铝纳米团簇的结构, 并对结构进行了分析比较. 通过定向移动策略, 定向Monte Carlo格点搜索中每一步都是“有效”移动, 极大地增加了搜索效率. 研究结果发现α氧化铝团簇形成一种多层结构, θ和δ氧化铝团簇形成一种单层薄膜结构. θ和δ氧化铝团簇的二阶能量差分存在奇偶震荡, 偶数尺寸的氧化铝团簇具有相对更高的稳定性. 通过相对能量比较发现相同尺寸下θ和δ氧化铝团簇薄膜结构比α氧化铝团簇结构更稳定, 在对这种薄膜进行第一性原理计算后进一步验证这种薄膜具有良好的稳定性和抗氧化性.     

Effect of Precursor Drying Process on the Properties of LiFePO4/C Composite with Low Carbon Content

<正>Properties of two LiFePO_4/C composites with low carbon content synthesized from precursors dried by spray drying and blast drying are investigated by scanning electron microscopy, X-ray diffraction, Raman spectroscopy and electrochemical measurements. The two samples have a different morphology and particle size, while the structure of LiFePO_4 is unaffected. The LiFePO_4/C composite prepared from the precursor dried by blast drying has a much lower surface resistance and a much better rate capability because the deposited carbon is more graphite-like and more conductive. The cycling performance is also much better for the LiFePO_4/C composite prepared from the precursor dried by blast drying because only a slight impedance growth is involved upon cycling. These results suggest that the precursor drying process has a significant impact on the properties of LiFePO_4/C composite, and its effect is highly dependent on the carbon content.     

Multidimensional anharmonic calculation of the vibrational frequencies and intensities for the trans and cis isomers of HONO with the use of normal coordinates

The equilibrium geometry and the potential energy and dipole moment surfaces have been determined for the cis and trans isomers of the HONO molecule by an ab initio Moller–Plesset (MP2) calculation with a wide set of atomic orbitals. The multidimensional anharmonic vibrational Schrodinger equations are solved using the variational method with the Hamiltonian and wave functions written in the normal coordinates of cis and trans isomers. All one- and two-dimensional and a number of three-dimensional vibrational problems are solved to obtain the energy levels and vibrational eigenfunctions. The frequencies and intensities for the fundamental, overtone and some combination bands are determined in good agreement with the available experimental results. The calculation shows the strength of coupling between different vibrational modes and reveals the presence of strong resonances between the (v₁, v₃, v₆) and (v₁, v₃−1, v₆+2) states of cis-HONO. This fact may be important for understanding the energy redistribution between the intermolecular degrees of freedom. The magnitude and direction of vibrationally averaged ground-state dipole moment of both isomers, as well as the direction of transition dipole moments, are in good agreement with the experimental findings. The changes in the values of dipole moment and some geometrical parameters of cis- and trans-HONO on vibrational excitation are also computed.     

Use of the diffusive gradients in thin films technique (DGT) with various diffusive gels for characterization of sewage sludge-contaminated soils

The diffusive gradients in thin film technique (DGT) was used for characterization of South Moravian arable soils (sampling sites Zlín, Tuřany, and Chrlice) amended by sewage sludge in the 1980s. Two types of polyacrylamide diffusive gel with different pore size (APA gels—cross-linked with agarose and RG gels—cross-linked with bis-acrylamide) were employed. The (bio)available parts of Cd, Cu, and Ni and the proportions of inorganically and organically complexed species of these metals were assessed. The degree of metal resupply from the soil solid phase to the soil solution was also determined. Metal concentrations obtained by the DGT technique were lower by almost 4 to 5 orders of magnitude in comparison with those obtained by extraction with aqua regia. DGT concentrations of metals were also lower by approximately 1 to 2 orders of magnitude in comparison with those obtained by extraction with sodium nitrate (commonly used for assessment of the (bio)available part of metals). Results obtained by DGT measurement were expected to be closer to the actual content of available metal species than results obtained by extraction with sodium nitrate. Using RG gels together with APA gels provided resolution of inorganically and organically complexed metal species and their proportional representation. Inorganic metal species (particles smaller than 1 nm) formed a predominant part of assessed metal content in all studied soil samples and horizons. However, there was the exception of the cadmium content in the middle profile of Chrlice sandy soil sample. Ratio R values indicated that resupply of Cd, Cu, and Ni from the solid phase to the soil solution varied for individual soil samples and individual depth profiles. Mobile and labile species of Cd, Cu, and Ni were much more closely related to upper rather than deeper horizons. This observation correlates very well with the mechanical treatment and amendment of the studied soils.     

高载量、高活性Ni/Al2O3催化剂的制备及其芳环加氢催化反应

使用共沉淀法制备了担载量很高的Ni/Al2O3催化剂,通过正丁醇干燥处理,提高了催化剂的表面积和担载镍的分散度.实验发现,镍的担载量和干燥过程刘催化剂的表面积、孔结构及金属镍的还原度和分散度影响很大.经过正丁醇处理的80%Ni/Al2O3-B催化剂具有较高的表面积,而担载镍的还原度和分散度也显著提高,使得催化剂具有很高...     

Preparation of the Monolith of Hierarchical Macro‐/Mesoporous Calcium Silicate Ultrathin Nanosheets with Low Thermal Conductivity by Means of Ambient‐Pressure Drying

Calcium silicate monolith was prepared by the hydrothermal reaction of a slurry of SiO₂, calcium hydroxide, and surfactant (OP‐10) obtained by high‐energy ball milling, followed by drying at ambient pressure. By using this strategy, the shrinkage due to the collapse of pores during the drying of porous materials, which is a commonly observed phenomena, was successfully avoided. It has a unique microstructure of hierarchical macro‐/mesoporous ultrathin calcium silicate nanosheets with a layered gyrolite crystalline structure. Very interestingly, the calcium silicate nanosheets can be peeled off to give a single‐layer nanosheet (1.23 nm) of gyrolite by ultrasonication. The monolith has a low apparent density (0.073 g cm^?3) and low thermal conductivity (0.0399 W K^?1 m^?1). The reasons behind why the formation of the unique hierarchical macro‐/mesoporous ultrathin nanosheets avoids shrinkage during the hydrothermal reaction and drying, and considerably decreases the thermal conductivity, is discussed.     

壳壁上具有介孔的Si/Al复合氧化物中空微球的制备

近年来,由于中空的球形材料具有良好的表面渗透性、低密度和高比表面积等性质而受到人们的普遍关注,在无机中空球的制备过程中,所采用的方法大多为模板法,合成的无机中空球主要以SiO2、金属氧化物(如TiO2和SnO2等)及金属(金、银、钯和镍等)为主,而有关二元复合氧化物中空球合成的研究报道较少,制备球壳上具有介孔的中空球已有报道,但是,其得到的介孔常常不均一,因此,将中空球形材料、复合氧化物和均一介孔有效地结合起来将是非常有意义一项工作。     

微波辐射法制备NiW/TiO2-Al2O3加氢脱硫催化剂

 利用微波技术和常规等体积浸渍法制备了一系列NiW/TiO2-Al2O3加氢脱硫催化剂样品,并采用BET,XRD,XPS和TPS(程序升温硫化)方法对催化剂样品进行了表征. 结果表明,微波处理改变了催化剂的孔径分布,提高了WO3,NiO和TiO2在Al2O3表面的的分散性,削弱了WO3和NiO同载体的强相互作用,改善了催化剂的硫化性能. 噻吩脱硫活性考察结果表明,经微波处理的催化剂上噻吩转化率比常规催化剂上提高约5%.