硅灰石合成高比表面积二氧化硅的工艺研究

一系列硅灰石酸处理实验表明,产物物理性质与反应速度、反应时间、中和最终ｐＨ值等工艺条件有关。同时发现,如果工艺条件恰当,可以制得４００～６００ｍ＾２／ｇ的高比表面积二氧化硅。     

含钛介孔SiO2 催化剂的合成及其催化性能

分别以廉价硅酸钠与正硅酸乙酯为硅源,通过复合模板剂制备了介孔二氧化硅,并利用吸附相反应技术合成了TiO2/SiO2复合催化剂。用X射线衍射(XRD)、红外谱图分析(FT-IR)等手段对其结构进行了表征,通过苯酚的羟基化反应考察了催化剂的催化性能。     

Synthesis and characterization of porous media produced by a sol-gel method

Mesoporous silica materials were synthesized by sol-gel method using tetraethoxysilane (TEOS) as precursors and surfactants i.e., cetyltrimethyl ammonium bromide (CTAB), sodium dodecyl sulfate (SDS), and polyoxyethylene cetyl ether (Brij 56) as templates. Surfactant templates were completely removed by calcination to form mesoporous structure. The effects of type and amount of surfactants on the characteristics of samples were studied. The textural characteristics such as surface area, pore volume, pore size, and pore size distribution were determined by nitrogen sorption isotherms. Fourier transform infrared (FTIR) spectroscopy was employed to qualitatively identify the chemical functionality and to confirm the removal of surfactant template. Scanning electron microscope (SEM) and transmission electron microscope (TEM) were used to directly observe surface morphology and mesoporous structure, respectively. The adsorption capacity of the synthesized adsorbent for toluene vapor was examined. We found that the pore volume and pore size of mesoporous materials affected the adsorption capacity. The sample prepared with high content of CTAB under basic condition (pH ∼7) yielded large pore volumes and pore sizes and subsequently possessed the high adsorption capacity for toluene vapor.     

Nanosized silica‐supported metallocene/MAO catalyst for propylene polymerization

A nanosized silica particle was used as the support to prepare an Et[Ind]₂ZrCl₂/MAO catalyst for propylene polymerization of polypropylene. The catalyst and the polymer produced were characterized with nitrogen adsorption, ICP, DSC, SEM, TEM, XRD, solution viscometer, ¹³C NMR and optical microscopy. The effects of polymerization temperature and [Al]/[Zr] ratio on catalyst activity and polymer melting point were investigated. Under identical reaction conditions, nanosized catalyst exhibited better polymerization activity than the microsized catalyst (e.g., the former had 64% higher activity than the latter at the optimum polymerization temperature (50°C) and [Al]/[Zr] = 570). DSC results indicated that polymer melting point increased with the increase of [Al]/[Zr] ratio and with the decrease of polymerization temperature. XRD results showed that the percentage of γ crystals increased with decreasing [Al]/[Zr] ratio. Electron microscopic results showed that the polymer particle size increased with increasing polymerization temperature. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2573–2580, 2006     

Chemical control of colloidal fouling of reverse osmosis systems

Fouling of membranes by colloidal organic and inorganic particles continues to be documented as the most common and challenging obstacle in attaining stable continuous operation of reverse osmosis (RO) and ultrafiltration (UF) systems. Much current research is being conducted on physical parameters to mitigate such fouling. The focus has been on membrane synthesis and element design; microfiltration and ultrafiltration pretreatment; electromagnetic devices; correlation with physical factors such as Silt Density Index, zeta potential and critical flux; technique of direct observation of fouling process through a membrane; and classification of macromolecular organics for correlation with fouling characteristics. We report initial successes with chemical control of colloidal fouling. Through screening with a large number of observable coagulations of natural colloids, we have developed a group of proprietary anticoagulants and dispersants that would, at less than 10 ppm dosage to the RO feedwater, control various classes of colloidal foulants. Case studies of the control of humic matter, elemental sulfur and colloidal silicate in problematic RO systems that became stabilized are briefly presented. We conclude that a great need and potential exists in economically controlling the myriads of fouling interactions of colloidal particles during concentration within the brine channels of RO membrane elements. Low dosages of antifoulants can in many cases obviate the need for installation and maintenance of pretreatment unit or operations designed to remove such colloidal foulants from the process stream.     

填料对双组分缩合型室温硫化硅橡胶性能的影响

考察了多种补强填料和半补强(或增量)填料如硅藻土、碳酸钙和氧化铝等对室温硫化(RTV)硅橡胶的机械性能和介电性能的影响。结果表明,采用经六甲基二硅氮烷处理的气相法白炭黑或沉淀法白炭黑作填料时,RTV硅橡胶多方面的性能都有所提高;采用补强填料和半补强填料并用的RTV硅橡胶的性能优于使用单一补强填料的RTV硅橡胶;随着填料用量的增加,RTV硅橡胶的机械性能、相对介电常数和介质损耗因数都有一定程度的提高,但体积电阻率有所降低。     

Preparation and properties of T300 carbon fiber‐reinforced thermoplastic polyimide composites

In this study, a series of T300 carbon fiber‐reinforced polyimide (CFRPI) composites were prepared by laminating premolding polyimide (PI) films with unidirectional carbon fiber (CF) layers. On the basis of PI systems design, the effect of CF volume fraction, processing conditions, and PI molecular structure on the properties of CFRPI composites was studied in detail. In addition, two kinds of nano‐particles, including carbon nano‐tube (CNT) and SiO₂ were filled into the premolding PI films with different concentrations. And the effect of nano‐particles on the properties of CFRPI composites was also investigated. The surface characteristic of T300 CF was measured by X‐ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). The properties of premolding PI film and CFRPI composites were measured by dynamic mechanical analysis (DMTA), SANS testing machine, scanning electron microscopy (SEM), and so forth. These experimental results showed that the properties of CFRPI composites were mainly affected by the premolding PI film and molding condition. The change of CF volume fraction from 55% to 65% took little effect on the mechanical properties of CFRPI composites. In addition, the incorporation of nano‐particle SiO₂ could further improve the properties of CFRPI composites, but CNT hardly improved the properties of CFRPI composites. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 646–654, 2006     

Synthesis and characterization of organic-inorganic hybrid thin films from poly(acrylic) and monodispersed colloidal silica

Hybrid thin films containing nano-sized inorganic domain were synthesized from poly(acrylic) and monodispersed colloidal silica with coupling agent. The 3-(trimethoxysilyl)propyl methacrylate (MSMA) was bonded with colloidal silica first, and then polymerized with acrylic monomer to form a precursor solution. Then, the precursor was spin coated and cured to form the hybrid films. The silica content in the hybrid thin films was varied from 0 to 50 wt%. The experimental results showed that the coverage area of silica particle by the MSMA decreased with increasing silica content and resulted in the aggregation of silica particle in the hybrid films. Thus, the silica domain in the hybrid films was varied from 20 to 35 nm by the different mole ratios of MSMA to silica. The results of scanning electron microscope, transmission electron microscope, and elemental analysis support the above results. The prepared hybrid films from the crosslinked acrylic polymer moiety showed much better film uniformity, thermal stability and mechanical properties than the poly(methyl methacrylate) (PMMA) based hybrid materials. Large pin-holes were found in the PMMA-silica hybrid films probably due to the significant difference on thermal properties between the two moieties or the evaporation of solvent. The refractive index decreased linearly with increasing the silica fraction in the hybrid films. Excellent optical transparence was obtained in the prepared hybrid films. These results show that the hybrid thin films have potential applications as passive films for optical devices.     

界面光催化剂对罗丹明B的吸附及其光催化性能研究

以中空粒子TiO2@@SiO2为载体,通过表面烷基化改性,制备出一种能漂浮于水面的界面光催化剂TiO2@@SiO2-O,并用IR,TG,接触角对其进行表征。结果表明:在无搅拌状态下,与中空粒子TiO2@@SiO2相比,界面光催化剂TiO2@@SiO2-O对罗丹明B的吸附性大大增加,其光催化效率提高了30%。     

纳米电路交叉冗余容错技术研究

提出了一种针对纳米电路的数字电路容错设计新方法．该方法基于交叉冗余原理,利用两种二进制错误的不对称性,采用模块化方法对纳米电路进行容错设计．以阵列乘法器为例,采用新方法对电路进行设计和仿真,并结合实验结果与传统的可重构和三模冗余容错方法进行比较．交叉冗余方法无需检测模块及表决器,不会增加系统延时,并且在资源消耗方面远低于传统方法,对纳米电路尤其适用．