Development of rectangular column structured titanium oxide photocatalysts anchored on silica sheets by a wet process

Commercially available powdered photocatalysts such as P-25 are known to show high photocatalytic performance. However, in practical use, their anchoring onto a substrate without any binders is still very difficult. The purpose of this study is to design and develop high-performance photocatalysts that can be anchored onto a substrate, and to this end we have prepared a titanium oxide photocatalyst using a wet process. The results of this study led to the successful development of rectangular column structured titanium oxide crystals which could be anchored onto silica sheets. The rectangular columnar crystal was 100- 500 nm wide and 1000- 5000 nm long. Moreover, investigations on the complete oxidation reaction of acetaldehyde into CO₂ and H₂O showed a high performance equivalent to that of the most efficient marketed powdered photocatalysts.     

催化量的氧化钙-硅胶对Sharpless烯丙醇不对称环氧化的影响

当在Sharpless试剂中加入催化量的金属氢化物和硅胶后, 烯丙醇的不对称环氧化反应时间大为缩短, 而化学和光学产率不受影响。着重讨论了氢化钙和硅胶对Sharpless烯丙醇不对称环氧化的作用。     

Modified nanofiller epichlorohydrin elastomer composite

A Zn-ion coated nanosilica filler has been developed and tested as vulcanizing activator and reinforcing filler for poly(epichlorohydrin-co-ethylene oxide-co-allyl glycidyl ether); Hydrin 400. In this study ZnO has been replaced by the Zn-ion coated nanosilica filler with the aim of studying the dual role of this nanofiller. The Zn-ion coated nanosilica filler proved to be a better reinforcing and curing agent than the ZnO added from outside. Poly(epichlorohydrin-co-ethylene oxide-co-allyl glycidyl ether) and ethylene thiourea (NA22) was more reinforcing with high state of cure when Zn-ion coated nanosilica filler was used in presence of mercaptobenzoimidazole, in comparison to the peroxide curative system. However, the peroxide cure system offers better thermal stability. ZnO, when added from outside, is less reinforcing than Zn-ion coated nanosilica filler because of improved elastomer–filler surface interaction.     

Microstructure and interfacial interaction of polyimide/silica hybrid nanocomposites prepared with 3-aminopropyltriethoxysilane

A series of polyimide (PI)-silica hybrid nanocomposites are prepared from 3,3′,4,4′biphenyltetracarboxylic dianhydride (BPDA)-4,4′-oxydianiline (ODA) polyamic acid (PAA) and tetraethoxysilane (TEOS) or tetramethoxysilane (TMOS) by the sol-gel process. 3-Aminopropyltriethoxysilane (3-APS) is used to enhance the interfacial interaction between polyimide and silica. The morphology, interfacial interaction, and properties of the hybrids are investigated using scanning electron microscope (SEM), UV-vis spectroscopy, atomic force microscope (AFM), Fourier transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA). SEM and AFM images indicate that silica particles of ca. 45-55 nm size are uniformly distributed in polyimide matrices and that the interfacial interaction between PI and TEOS is better than that between PI and TMOS. The optical transparencies of the PI/TEOS hybrids are better than that of the PI/TMOS hybrids. FTIR spectra confirm the Si O Si bond as well as the conversion of PAA to polyimide and PI/silica hybrid films. The thermal stability is increased after incorporation of the silicas in the polyimide matrix.     

Effect of Abrasives on Three-Body Abrasive Wear Behaviour of Particulate-Filled Polyamide66/Polypropylene Nanocomposites

Polyamide66/polypropylene (PA66/PP) blend, graphite (Gr)-filled PA66/PP composite and nanoclay (NC)-filled PA66/PP nanocomposites were prepared by twin screw extrusion and injection molding. Three-body abrasive wear behaviour of the injection moulded composites was carried out using a rubber wheel abrasion wear tester. In this study, angular silica sand and quartz particles of size ranging from 200 to 250 μm were used as dry and loose abrasives. The tests were carried out for 150, 300, 450 and 600 m abrading distances at a constant load of 36 N. It was observed that inclusion of particulate fillers in PA66/PP have significant influence on wear under varied abrading distances for different abrasive particles. Further, it was found that NC-filled PA66/PP nanocomposite exhibited lower wear rate compared to Gr filled ones for different abrasive particles. In addition, the worn surfaces of the samples were examined by scanning electron microscopy (SEM) and the morphology was also discussed.     

Formation of Composites in the System of Organic Europium Complexes–Silica

Lanthanide doped sol–gel glasses are an attractive type of luminescent material which can be processed at ambient temperatures. However, it is very difficult to obtain a uniform distribution of the complexes in glass materials because of their strong tendency to cluster formation. This problem can be solved by covalently linking of lanthanide complexes to silica matrix. In our work such materials were obtained by the sol–gel method of hydrolysis and polycondensation of tetramethoxysilane with europium complexes containing trimethoxysilyl groups. For this purpose we synthesized a novel ligand — (N-3-trimethoxysilylpropyl)-N′-1,10-phenanthroline-5-yl-thiocarbamide — and corresponding complexes [Eu(tta)₃phen′]Cl₃ and [Eu(pta)₃phen′]Cl₃. Our approach enabled us to simplify the synthetic procedure. A number of uniform samples showing intense luminescence have been obtained and the concentration dependence of their luminescence has been studied.     

Interfacial modification for controlling silica–polysiloxane interactions and bonding in some elastomeric composites

Silica reinforcing fillers were generated using the sol-gel approach and their surfaces were modified using either a vinyl alkoxysilane (to provide permanent bonding to a host poly(dimethylsiloxane) elastomer), or a hemiacetal ester (to provide bonding that could be thermally ruptured). The surface areas of the fillers were measured by nitrogen absorption, and their morphologies, interfacial structures, and crosslinking to the elastomer were characterized by ultra small angle and small angle X-ray scattering, scanning electron microcopy, and Fourier-transform infrared spectroscopy. Increasing the amount of the silane coupling agent decreased silica domain sizes, with corresponding increases in surface area and stronger filler-polymer interactions. Vinyltrimethoxysilane had a larger effect than vinylmethyldimethoxysilane. The tensile moduli, tensile strengths, and degrees of toughness of the composites were determined using stress-strain measurements in elongation, both under near-equilibrium conditions and under continuous extension. The permanently bonded modifications gave composites with improved mechanical properties. Rupturing the hemiacetal ester bonding at 120-150°C gave some increase in ultimate stress, maximum elongation, and toughness, thus underscoring the importance of interactions or 'networking' between filler particles.     

Preparation of well-structured organosilane layers on silica

An efficient grafting process of monofunctional alkylchlorosilanes (general formula: CH₃-(CH₂) _n-1-Si(CH₃)₂Cl with n varying from 4 to 30) onto silica nanoparticules was developed by varying the surface preparation and the solvent used for the deposition process. A vapor phase deposition method was considered as reference and silicon wafers with a native SiO₂ layer were used as a model surface of the silica particles. The grafting method was evaluated by studying the wettability and the grafting densities of the resulting monolayers. The chain conformation of the monolayers was determined by comparing the thickness measured by SE ellipsometry and AFM. By comparing the solvent and vapor phase deposition methods, it was demonstrated that the deposition process had a large influence on the structure of the grafted monolayers. The same structure as from a vapor phase method can be obtained from a solvent deposition process by a suitable choice of the solvent and by a strict cleaning of the surface before deposition. The grafting of much longer chains of such silane-terminated polyethylenes with different molar mass on the silica surface was also investigated in order to study the effects of the chain length on the grafting density and the layer structure. For both the short alkylchlorosilanes and polymeric grafted chains, the proposed organization of the grafted chains at the silica surface is found to be strongly dependent on the length of the alkyl chains.     

流变学法研究部分水解聚丙烯酰胺/Cr(III)交联反应I.浓度的影响

采用流变学法系统地考察了部分水解聚丙烯酰胺（HPAM）/Cr(III)交联体系的 反应动力学。HPAM溶液的粘性模量G”大于弹性模量G’,且其数值随时间不发生变 化,体系为粘性溶液。而HPAM/Cr(III)体系的G’和G”的数值都随时间变化,G” 在反应开始阶段大于G’,当反应进行一段时间后,G’超过G”占据主要地位,体 系成为弹性体系。交联过程可分为三个阶段：第一上升阶段,平缓上升阶段和第二 上升阶段。利用G’～ t曲线可以推测反应机理。实验发现成胶速率随反应物HPAM 和Cr(III)的浓度的增加而增加,而成胶时间缩短。在羧基浓度过量的情况下,交 联反应对Cr(III)浓度的反应级数是1。凝胶的有效弹性交联密度随聚合物浓度的增 加而增,且随凝胶反应的进行而增加。凝胶的交联点间的平均分子量随Cr(III)浓 度的增加和交联反应的进行而下降。     

直接由SiO2低温合成含硅环氧化合物及其结构表征

研究了直接由SiO2(沉淀白炭黑)、乙二醇、KOH为原料低温合成高活性的五配位有机硅络合物[KSi-(OCH2CH2O)2OCH2CH2OH]然后与环氧氯丙烷反应,生成含硅环氧化合物,并借助于红外、核磁共振、热分析、能谱元素分析等现代测试手段,对合成的产物进行了结构表征。