Photoreduction of Europium (III) in Sol-Gel Derived Inorganic-Organic Hybrid Materials

Eu²⁺-doped inorganic-organic hybrid materials, which are potentially suitable for a tunable laser in the near ultra violet and blue region, were prepared through the photoreduction of Eu³⁺ ions in the materials under the irradiation of the fourth harmonic wave light (266 nm) of the Nd:YAG laser. The hybrid materials doped with Eu³⁺ ions were prepared from Si(OCH₃)₄, CH₃Si(OCH₃)₃, EuCl₃ and chloropropyltrimethoxysilane (CPTM). After the prehydrolized silica sol was added to the Eu³⁺-containing solution, Eu³⁺-doped transparent inorganic-organic hybrid material was obtained by drying at 50°C. The emission peak around 450–475 nm due to the charge transfer transition (5d-4f) of Eu²⁺ ions increased with the laser irradiation time. Eu³⁺ ions were effectively photoreduced to Eu²⁺ ions in pore-free materials prepared at high CPTM to Eu³⁺ ratios. Eu²⁺ ions were generated by the photodecomposition of the bond between Eu³⁺ and Cl (Cl^– or Cl(CH₂)₃ in CPTM).     

Synthesis of Polysiloxane Having Methacryloyloxy Group from Tributylstannyl Ester of Silicic Acid and Silane Coupling Agent

Polysiloxane derivative (MPS), obtained from the reaction of polymeric tributylstannyl ester of silicic acid (PTBS) and (3-methacryloyloxypropyl)dimethylchlorosilane (1a), was shown to be a useful inorganic component for the preparation of organic-inorganic hybrid resin as a nanocomposite. Copolymerization of MPS containing methacryloyloxypropyl groups with the common monomer such as styrene, acrylonitrile, or methyl methacrylate proceeded readily at room temperature under UV irradiation to give the corresponding resins (HR). The resins obtained from MPS and methyl methacrylate showed a good transparency and resistance in scratch test, but a poor flexibility. The gels consisted of analogous structure to HR were obtained from PTBS, 1a, and the monomer by one-pot procedure, in which substitution and polymerization proceeded simultaneously.     

Optical and Electrical Properties of Ferroelectric SBN Thin Films Prepared by Sol-Gel Process

Strontium barium niobate thin films were prepared by sol-gel method on various substrates using an improved process, two-step heating process. The two-step heating process applies an additive heat-treatment before crystallization for enhancement of the densification and the nucleation of films. Also, highly c-axis oriented SBN thin films with various compositions were obtained on MgO(100) and Pt(100)/MgO(100) substrates. Their optical and electrical properties such as optical propagation loss, refractive index, P-E hysteresis, and dielectric constant, were characterized as a function of the film composition.     

A chitosan-templated monolithic siliceous mesoporous-macroporous material

 We synthesised a porous siliceous material via hydrothermal hydrolysis of sodium silicate, using chitosan as a template. As far as we know, this is the first synthesis of siliceous porous material using chitosan as a template in a hydrothermal way. A fibrous material was obtained, whose macroscopic fibres were formed by a spongelike siliceous network with pores having a radius of 0.57 μm. The siliceous walls of the pores were, in turn, of the form of a microporous–mesoporous material; the pore radius distribution was polymodal with maxima at 0.84, 1.0, 1.2 and 1.5 nm and a broad band between 3 and 10 nm. This structure may be due to the aggregation of the hydrated chitosan helices in bundles of parallel fibres with different size and the gelation of the system. The aggregation process might be induced by the addition of silicate. Received: 12 January 2000/Accepted: 7 March 2000     

低噪音摩阻复台材料影响因素的探讨

采用动态粘弹谱仪（ＤＤＶ）、电子扫描显微镜（ＳＥＭ）和摩擦试验机等对影响摩阻复合材料制动噪音的因素进行了探讨。结果表明，摩阻材料基体的合理改性以提高其损耗角正切ｔａｎδ对减少振动、降低噪音行之有效。同时对传统解决噪音的方法，如添加固体润滑剂、橡胶共混等进行了分析比较。     

对杂散光测试材料要求的探讨

从分光光度计杂散光测试原理出发,对我国目前在用的几种杂散光测试材料特性进行了分析。通过实验验证,指出了其中的不合理处,并提出了对杂散光测试材料特性的基本要求。 ,     

稀土复合弹性材料的制备和力学性能

利用稀土醇盐与季铵盐化的吡啶改性丁苯橡胶乳液反应,制备含稀土ＰＳＢＲ胶片,然后与天然橡胶并用,获得含稀土复合材料弹性材料发现其物理力学性能有明显提高。通过红外光谱、差示扫描热量计以及交联密度分析,讨论了其结构与性能的关系。     

Mercury species immobilized on sulphydryl cotton: A new candidate reference material for mercury speciation

A batch of sulphydryl cotton microcolumns was prepared and charged with a mixed Hg standard solution (methyl-, ethyl- and inorganic Hg, 10 g l^–1 as Hg, 3 ml) and stored at 4 °C in a light-tight box. At regular time intervals over a 4 month period microcolumns were removed and Hg species were quantified by gas chromatography microwave-induced plasma atomic emission spectrometry (after elution, extraction and derivatization steps). It was found that analyte recoveries for methyl- and inorganic Hg were quantitative over the 4 month period while ethyl-Hg species appeared to be stable for up to 2 months.