高性能硫/碳凝胶复合正极材料的制备及应用

以碳凝胶作导电骨架,合成硫/碳凝胶复合物.XRD、SEM等表征显示,该复合材料完全保持了碳凝胶的形貌,颗粒大小在10μm以下,硫吸附在碳凝胶内部空隙中呈无定形态,表现出良好的电化学性能.以0.1C放电,该材料首圈放电容量达到1311mAh/g.0.2C循环充放,首圈放电容量为1107.1mAh/g,30周充放电后,放电容量仍不低于800mAh/g.     

小角x射线散射方法研究甲基改性氧化硅干凝胶的孔结构

以正硅酸乙酯［Si(OC2H5)4，TEOS］为前驱体制备SiO2悬浮液，分别以甲基三乙氧基硅烷［CH3Si(OC2H5)3，MTES］和二甲基二乙氧基硅烷［(CH3)2Si(OC2H5)2，DDS］为前驱体制备硅氧烷聚合物溶液，通过混合法得到两种不同的甲基改性氧化硅凝胶-测量了凝胶的散射强度，计算了凝胶的孔径分布、平均孔径DSAXS、界面层厚度E等参数，结合氮气吸附实验，分析了凝胶的孔结构-发现SiO2一次簇团被MTES聚合物或DDS聚合物连接为二次簇团时产生微孔，同时甲基随聚合物连接于凝胶骨架上形成与 关键词： 小角x射线散射 甲基改性氧化硅 干凝胶 孔结构     

Nucleation Phenomenon in Silica Xerogels and Pd/SiO2, Ag/SiO2, Cu/SiO2 Cogelled Catalysts

Pd/SiO₂, Ag/SiO₂ and Cu/SiO₂ xerogel catalysts have been synthesized by cogelation of tetraethoxysilane (TEOS) and chelates of Pd, Ag and Cu with 3-(2-aminoethylamino)propyltrimethoxysilane (EDAS). It appears that, in cogelled samples, the metal complex acts as a nucleation agent in the formation of silica particles. The resulting catalysts are then composed of completely accessible metallic crystallites with a diameter of about 3 nm located inside silica porous particles with a monodisperse microporous distribution. Xerogels without metal synthesized with EDAS and TEOS (C. Alié, R. Pirard, A.J. Lecloux, and J.-P. Pirard, J. Non-Cryst. Solids 289, 88 (2001)) verify this hypothesis of nucleation by EDAS.     

Congo Red Immobilized on a Silica/Aniline Xerogel: Preparation and Application as an Amperometric Sensor for Ascorbic Acid

Congo red (CR) was immobilized on a silica/aniline xerogel through electrostatic interaction. The dye is strongly retained and is not easily leached from the xerogel matrix. The material containing the adsorbed dye was used to prepare a carbon paste electrode and the electrochemical properties of the hybrid material were investigated using cyclic voltammetry and amperometry. The modified electrode was used to study the electrochemical oxidation of ascorbic acid. The adsorbed dye mediates ascorbic acid oxidation at the solid electrode surface‐solution interface at an anodic potential of 0.18 V at pH 7, in a 0.5 mol L^?1 KCl solution. This novel modified carbon paste electrode shows good analytical performance for the determination of ascorbic acid in commercial Vitamin C tablets.     

Silica xerogels as a delivery system for the controlled release of different molecular weight heparins

In this work, we investigated a sol–gel derived silica matrix as a delivery system for the prolonged release of different molecular weight heparins, which allows the glycosaminoglicons to retain their whole biological activity. Several xerogels were obtained by embedding different molecular weight heparins into matrices prepared by using different amount of NH₄OH as a catalyst during gel formation. Gel synthesis parameters, drug release properties, and xerogels surface area were evaluated. Unfractionated, low and oligo-molecular weight heparins were embedded into xerogels and the effect of the molecular weight on the release kinetics and the retained biological activity has been investigated. The results show that the surface area of the matrix is a determinant parameter affecting drug release kinetics. This structural feature can be modified by varying the catalyst tetraethoxysilane molar ratio used during the matrix synthesis. In most cases release kinetics fitted the Higuchi diffusive model and a lower diffusion rate was observed from silica matrices characterized by a smaller surface area. In the case of matrices with lower surface area, loaded with unfractionated heparin, zero order kinetics was observed. In this paper, we have defined a heparin release silica xerogel system and we have pointed out how modulation of its synthesis parameters allows adjusting the release of heparin according to therapeutic needs.     

镍基气凝胶催化CH4-CO2重整制取合成气反应的研究Ⅱ.制备方法对Ni/CeO2-Al2O3催化剂反应性能的影响

采用浸渍法、溶胶 凝胶过程与普通干燥、超临界干燥过程相结合的方法制备了三种 82 3K焙烧的NiO CeO2 Al2 O3 体系催化剂 ,分别为浸渍型催化剂 (iNCA5 5 0 )、干凝胶催化剂 (xNCA5 5 0 )和气凝胶催化剂 (aNCA5 5 0 ) ,考察了它们在CH4 CO2 重整反应中的催化性能及反应的稳定性 ,采用TG、TEM、XPS等手段研究了反应前后催化剂的结构性质。研究结果表明 ,在 10 73K、CH4 CO2 =1∶1、180 0 0mL h·g的反应条件下 ,三种催化剂中aNCA5 5 0在CH4 CO2 重整反应过程中的积碳量较大 ,但却具有最好的反应稳定性 ;aNCA5 5 0具有较大积碳量与其表面酸量较大、酸性较强及较大镍分散度有关 ,然而由于它具有较大的积碳容量和很强的金属抗烧结能力 ,因此保持了较好的反应稳定性。催化剂积碳和金属镍烧结导致催化剂表面活性中心数目减少是催化剂失活的主要原因。     

V2O5 xerogel-poly(ethylene oxide) hybrid material: Synthesis, characterization, and electrochemical properties

In this work, we report the synthesis, characterization, and electrochemical properties of vanadium pentoxide xerogel-poly(ethylene oxide) (PEO) hybrid materials obtained by varying the average molecular weight of the organic component as well as the components’ ratios. The materials were characterized by X-ray diffraction, ultraviolet/visible and infrared spectroscopies, thermogravimetric analysis, scanning electron microscopy, electron paramagnetic resonance, and cyclic voltammetry. Despite the presence of broad and low intensity peaks, the X-ray diffractograms indicate that the lamellar structure of the vanadium pentoxide xerogel is preserved, with increase in the interplanar spacing, giving evidence of a low-crystalline structure. We found that the electrochemical behaviour of the hybrid materials is quite similar to that found for the V₂O₅ xerogel alone, and we verified that PEO leads to stabilization and reproducibility of the Li⁺ electrochemical insertion/de-insertion into the V₂O₅ xerogel structure, which makes these materials potential components of lithium ion batteries.     

51V NMR of inclusion compounds H2V12O31-y ·n H2O

The parameters of hyperfine interactions on⁵¹V nuclei were determined on films of the inclusion compound H₂V₁₂O_31-y ·n H₂O at different stages of hydration. It was established that the axial symmetry plane of the magnetic interaction tensor coincides with the film plane. The most probable direction (40° of the film plane) and the magnitude of the electric field gradient (EFG) on⁵¹V nuclei (egQ/h = 0.233 MHz) were found for a completely dehydrated sample. An analysis of the line width angular dependences of satellites has shown the existence of a disorientation of the main EFG direction with a distribution width of about 50° in the film plane. The absence of satellites and the presence of an angular dependence of the⁵¹V NMR central signal of hydrated samples allowed the conclusion that the interaction of the V-O layer with molecules of water led to an increase in the disorientation of the film plane.     

Adjustably Bioresorbable Sol-Gel Derived SiO<Subscript>2</Subscript> Matrices for Release of Large Biologically Active Molecules

Amorphous, sol-gel derived SiO₂ are known to biocompatible and bioresorbable materials. Bioresorbable materials have potential applications as implants or injectable matrices in the controlled delivery of biologically active agents in the living tissue. Bioresorbable matrices provide desirable properties, e.g., extra removal operations that have to be done with biostable matrices are avoided and the release of large therapeutic molecules can be controlled by matrix degradation rather than by diffusion. New important groups of drugs, such as biotechnically-produced peptides and proteins, are potential to be encapsulated in bioresorbable SiO₂, because they are typically larger in size and their direct oral administration without protecting matrix is difficult due to digestion. The methods to achieve a wide range of SiO₂ bioresorption rates (from days to months) are introduced in this study. This is done by a “conventional” alkoxy-based sol-gel method at protein-friendly conditions by adjusting the precursor ratios, aging of the sol and by using different preparation methods (casting, spray-drying and freeze-drying). The prepared morphologies include implantable monolithic sticks and injectable microspheres. The importance of chemical structure is shown in comparison with the specific surface area and pore volume.     

Preparation and characterization of novel bi-functionalized xerogel for removal of methylene blue and lead ions from aqueous solution in batch and fixed-bed modes: RSM optimization,kinetic and equilibrium studies

A new bi-functionalized xerogel is fabricated and then was identified by ²⁹Si CP MAS NMR, SEM, FTIR, and nitrogen adsorption–desorption approaches. As-prepared xerogel efficiency for simultaneous uptake of methylene blue (MB) and Pb²⁺ ions from aqueous solution is investigated. Individual and combination effects of operating variables (xerogel mass, contact time and initial MB and Pb²⁺ ion concentration) on the retention performance is achieved with central composite design (CCD) and upgraded through response surface method (RSM). Batch equilibrium outcomes uncovered that MB and Pb²⁺ ions adsorption onto hybrid composite could be all around depicted by Langmuir isotherm model contrasted with Freundlich equation. Howbeit, the column trials reported that the breakthrough capacities of MB and Pb(II) are observed to be 512 mg.g⁻¹ and 400 mg.g⁻¹ respectively. XPS and FTIR investigations uncovered that the main mechanism of lead uptake ought to be credited to the chelation with –NH₂ and ion exchange with –SH groups in the xerogel frameworks. While the MB adsorption system is proposed to be electrostatic attractions, π-π stacking interactions and hydrogen bonds. The work undertaken in this research highlights the major role of the as-synthesized xerogel for treatment of industrial wastewater.