硅-二氧化硅超晶格——探索硅基发光材料的一条新途径

理论上认为，由于Ｓｉ／ＳｉＯ２超晶格中硅层（阱层）的电子和空穴都受到极强的量子限制效应，硅层能带有可能从体硅的间接带隙转变为直接带隙，从而发光效率大大提高．实验上，在非晶Ｓｉ／ＳｉＯ２超晶格中观察到在可见光波段的室温光致发光和明显的量子限制效应现象．晶体Ｓｉ／ＳｉＯ２超晶格研究也取得了初步的结果．

乙烯直接氧化制乙酸工艺研究

采用Pd-SiW12 /SiO2 系列催化剂 ,对乙烯直接氧化制乙酸工艺进行了研究。考察了原料气配比、反应温度、反应压力、空速、催化剂颗粒度等因素对反应的影响 :在原料气体积比为 φ(C2 H4 )∶φ(O2 )∶φ(N2 )∶φ(H2 O) =5 0∶7∶1 3∶30 ,反应温度为 1 6 0℃ ,反应压力 0 .7MPa ,空速 30 0 0h-1的条件下 ,乙酸的选择率达到 88.1 % ,时空产率为 4 1 7.6g/h·L ;在催化剂粒径为 0 .2 8～ 2 .0mm时 ,该反应在表面反应动力学区进行。

富Si-SiO_2薄膜的制备、结构及光致发光特性的研究

利用双离子束溅射沉积共溅射方法制备了富Si SiO2 薄膜 ,研究了沉积参数、时间、工作气压PAr、基片温度等对沉积速率的影响 ,用TEM和XRD分析了样品的结构 ,当基片温度Ts <4 50℃时 ,所制备一系列样品均为非晶结构 ,当沉积基片温度较高时 (Ts ≥4 50℃ ) ,薄膜样品中才出现Si的颗粒 我们还分析了样品的室温光致发光现象 ,从PL谱中可以看出 ,样品有～ 32 0nm、～ 4 10nm、～ 560nm和～ 630nm四个PL峰 。

硅光电器件抗反射系统设计研究

根据ＳｉＯ２Ｓｉ系统在空气中的反射率公式，讨论了ＳｉＯ２层厚度和入射光波长对反射率的影响，提出了在两种情况下确定ＳｉＯ２层厚度的方法：（１）实现在某一波长范围抗反射效果最佳；（２）实现在某一光照条件下光电流最大。

Polarization-Insensitive Silica on Silicon Arrayed Waveguide Grating Design

A new technology for fabrication of silica on silicon arrayed waveguide grating (AWG) based on deep etching and thermal oxidation is presented.Using this method,a silicon layer is remained at the side of waveguide.The stress distribution and effective refractive index of waveguide fabricated by this approach are calculated using finite element and finite difference beam propagation method,respectively.The results of these studies indicate that the stress of silica on silicon optical waveguide can be matched in parallel and vertical direction and AWG polarization dependent wavelength (PDλ) can be reduced effectively due to side-silicon layer.

H_4SiW_(12)O_(40)/SiO_2催化合成丁酮1,2-丙二醇缩酮

以二氧化硅负载硅钨酸为催化剂,以丁酮和12,-丙二醇为原料催化合成丁酮1,2-丙二醇缩酮。探讨了丁酮与1,2-丙二醇摩尔比、催化剂用量、带水剂用量及反应时间对收率的影响。试验表明,在n(丁酮)∶n(1,2-丙二醇)=1∶1.5,催化剂用量占反应物料总质量的0.8%,环己烷作带水剂用量12 mL,反应时间45 min的优化条件下,丁酮1,2-丙二醇缩酮的收率可达98.3%。

Effect of inorganic salt impurities on seeded precipitation of silica hydrate from sodium silicate solution

To clarify the precipitation of silica hydrate from the real desilication solutions of aluminosilicate solid wastes by adding seeds and improve integrated waste utilization,the seeded precipitation was studied using synthesized sodium silicate solution containing different inorganic salt impurities.The results show that sodium chloride,sodium sulfate,sodium carbonate,or calcium chloride can change the siloxy group structure.The number of high-polymeric siloxy groups decreases with increasing sodium chloride or sodium sulfate concentration,which is detrimental to seeded precipitation.Calcium chloride favors the polymerization of silicate ions,and even the chain groups precipitate with the precipitation of high-polymeric sheet and cage-like siloxy groups.The introduced sodium cations in sodium carbonate render a more open network structure of high-polymeric siloxy groups,although the carbonate ions favor the polymerization of siloxy groups.No matter how the four impurities affect the siloxy group structure,the precipitates are always amorphous opal-A silica hydrate.

硅基光电子材料的研究

综述了硅基发光材料的研究新进展 ,分别以发光多孔硅、多孔碳化硅、纳米硅薄膜和发光硅基超晶格为例 ,分析讨论了其制备。

Effects of nano-SiO_2 on reinforcing and toughening polypropylene

SiO2 nano particle, through surface modification by silicane coupling agent KH-570, was successfully applied to make nano SiO2/PP composite material by the melt-out blending process with twin-screw extruder. Effects of nano SiO2on the reinforcing and toughening of PP were studied by analyzing the material impact broken fracture, the crystal structure and the diameter of SiO2nano particle using SEM, XRD and TEM, respectively. Results showed that the impact strength and the tensile strength of nano SiO2/PP composite material were improved apparently; the impact strength of PP was fracture was increased to 67% when the nano SiO2 content was 4%; while the nano SiO2 particle upon surface treatment will impose obvious heterogeneous nucleation function over PP crystal.

Al-modified mesocellular silica foam as a superior catalyst support for dibenzothiophene hydrodesulfurization

A series of Al‐containing mesostructured cellular silica foams(Al‐MCFs)with different Si/Al molar ratios(x;x=10,20,30,40,or50)were prepared by a post synthetic method using aluminum isopropoxide as an alumina source.The corresponding NiMo catalysts supported on Al‐MCFs were prepared and evaluated using dibenzothiophene(DBT)as the probe reactant.All the synthesized samples were characterized by small‐angle X‐ray scattering,scanning electron microscopy,nitrogen adsorption‐desorption,UV‐Vis diffuse reflectance spectroscopy,H2temperature‐programmed reduction,27Al MAS NMR,temperature‐programmed desorption of ammonia,pyridine‐FTIR,Raman spectroscopy,HRTEM,and X‐ray photoelectron spectroscopy to analyze their physicochemical properties and to gain a deeper insight of the interrelationship between the structures and the catalytic performance.The synthesis mechanism was proposed to involve the formation of Br?nsted acid and Lewis acid sites through the replacement of Si4+with Al3+.Aluminum introduced into MCFs by the post synthetic method has a negligible influence on the mesostructure of the parent MCFs but can form silicoaluminate materials with moderate Br?nsted acidity.For Al‐MCFs(x)materials,the detection of tetrahedrally coordinated Al3+cations demonstrated that the Al species had been successfully incorporated into the silicon frameworks.Furthermore,the DBT hydrodesulfurization(HDS)catalytic activity of the NiMo/Al‐MCFs(x)catalysts increased with increasing Si/Al molar ratio,and reached a maximum at a Si/Al molar ratio of20.The interaction of Ni and Mo species with the support became stronger when Al was incorporated into the MCFs supports.The high activities of the NiMo/Al‐MCFs catalysts for the DBT HDS were attributed to the suitable acidity properties and good dispersions of the Ni and Mo active phases.

Synthesis of Waterborne Polyurethane Modified by Nano-SiO_2 Silicone and Properties of the WPU Coated RDX

A series of nano silica/silicone modified waterborne polyurethane(WPU) have been synthesized from polytetramethylene glycol and isophorone diisocyanate, dihydroxymethyl propionic acid and triethylamine, ethylenediamine, trimethylolpropane, nano-SiO2 and the silane coupling agent KH550. The effect of the dosage of nano-SiO2 on the WPU-Si membrane and the coated RDX(cyclotrimethylenetrinitramine) particles have been studied in terms of their surface properties, mechanical properties, and thermal stability. The results showed that with the increase of Si content, the stability of the emulsion reduced gradually. The material with more Si content displayed an increased thermodynamic stability, an increased high temperature resistance, an increased tensile strength and a decreased elongation at break. With the increase of Si content, the surface tension of the material decreased, the bibulous rate reduced, and the contact angle increased gradually, so that the surface tension of the polyurethane and RDX are close to each other which could improve the performance of coating.

Preparation and Characterization of Nanosized Al-MCM-41 Using Different Silica Sources

Silica sources influence different aspects of Al-MCM-41 product. The crystallinity of nanosized Al-MCM-41 zeolites prepared crystallization and lead to change in the properties of the final from precursors mixtures containing different silica sources, e.g. tetraethylorthosilicate （TEOS）, colloidal silica （CS）, silicic acid （SA） and fumed silica （FS） have been studied. The produced samples are investigated using XRD, SEM, FT-IR, pyridine adsorption and N2 physisorption. XRD results show that the products obtained from different silica sources are in Al-MCM-41 phase. SEM results show that silica sources influence the produced Al-MCM-41 shape. Using silicic acid leads to formation of spherical crystals, TEOS gives cubical crystals, colloidal silica forms spherical crystals with smaller aggregated, and fumed silica gives rounded crystals. N2 physisorption results show that silica sources influence pore-diameter and pore-volume of the produced Al-MCM-41 ; the pore diameter of the produced Al-MCM-41 in case of colloidal silica, TEOS, fumed silica, and silicic acid are 12, 20, 15, and 17A respectively. Also, the pore volume of the produced AI-MCM-41 in case of colloidal silica, TEOS, fumed silica and silicic acid are 0.78, 0.71, 0.76, and 0.8 cm^3/gm, respectively.

Fabrication of low-loss SiO2/Si channel waveguides by roughness reduction

An experimental study of the dependence of SiO2 waveguide side wall roughness on the etch condi- tions and etch masks in CHF3/O2 based reactive ion etching plasma was reported. When working under standard low-pressure （20mtorr） etching conditions, a novel etch roughening phenomenon has been observed in the plasma, that is, the roughness of the etched front surface increases with the amount of material etched, independent of etch rate, RF power, and gas composition. Besides, the etched underlying side wall will be tapered as the upper SU-8 resist pattern degradation transfers downward. A process using double-layered mask, consisting of SU-8 resist and thin Chromium film, was developed for improving the side wall smoothness. Based on the studies, SiO2/Si channel waveguides with the propagation loss less than 0. 07dB/cm were fabricated at last.

Influence of silicate anions structure on desilication in silicate-bearing sodium aluminate solution

The structural changes of silicate anions in the desilication process with the addition of calcium hydrate alumino-carbonate were studied by measuring Raman spectra, infrared spectra and corresponding second derivative spectra. The results show that the desilication ratio in the solution prepared by the addition of sodium silicate(solution-SS) is much greater than that in the solution by the addition of green liquor(solution-GL), and low alumina concentration in the sodium aluminate solutions facilitates the desilication process. It is also shown that alumino-silicate anions in the solution-GL, and Q^3 polymeric silicate anions in solution-SS are predominant, respectively. In addition, increasing the concentration of silica favors respectively the formation of the alumino-silicate or the Q^3 silicate anions in the solution-GL or the solution-SS. Therefore, it can be inferred that the low desilication ratio in the silicate-bearing aluminate solution is mainly attributed to the existence of alumino-silicate anions.

Dip-coating of SiO2 onto ZnO-SiC Composite Membrane

SiC composite membrane was fabricated by mixing with SiC and ZnO powder. This mixture was pressed and sintered at 1,300 ℃ under air condition. This sintered ZnO-SiC membrane was dip-coated by silica sol and followed by heat-treatment. This membrane was characterized by XRD （X-ray diffraction）, FE-SEM （field emission scanning electron microscopy） and BET （Brunauer-Emmett-Teller） instruments. Hydrogen permeation test was conducted at 0.1 MPa pressure and also variation of temperatures. The obtained value of heat-treated membrane after dip-coating at 298 K was obtained as 1.61 × 10-6 mol/（m2·s·Pa）.

Electron-Irradiation Induced Nanocrystallization of Pb（ll） in Silica Gels Prepared in High Magnetic Field

In a previous study, structure of silica gels prepared in a high magnetic field was investigated. While a direct application of such anisotropic silica gels is for an optical anisotropic medium possessing chemical resistance, we show here their possibility of medium in materials processing. In this direction, for example, silica hydrogels have so far been used as media of crystal growth. In this paper, as opposed to the soft-wet state, dried silica gels have been investigated. We have found that lead （II） nanocrystallites were formed induced by electron irradiation to lead （ll）-doped dried Hydrogels made from a sodium metasilicate solution doped with silica gels prepared in a high magnetic field such as B = 10 T. lead （II） acetate were prepared. The dried specimens were irradiated by electrons in a transmission electron microscope environment. Electron diffraction patterns indicated the crystallinity of lead （II） nanocrystallites depending on B. An advantage of this processing technique is that the crystallinity can be controlled through the strength of magnetic field B applied during gel preparation. Specific skills are not required to control the strength of magnetic field.

Synthesis and Characterization of Modified Epoxy Resins by Silicic Acid Tetraethyl Ester and Nano-SiO_2

A kind of modified epoxy resins was obtained by condensation of epoxy resin with silicic acid tetraethyl ester（TEOS） and nano-SiO2. The reactions were performed with hydrochloric acid as a catalyst at 63 ℃. The structure, thermal stability and morphological characteristics of the modified epoxy resins were studied through infrared spectra（FT-IR） analysis, thermogravimetric（TG） analysis and scanning electron microscopy respectively. It has been found from the IR and TG study that modified epoxy resins have greater thermal stability than epoxy resins, and its thermal stability has been improved by the formation of inter-crosslinked network structure. The modified epoxy resins exhibit heterogeneous morphology and heterogeneity increases with more TEOS feeding, which in turn confirms the formation of inter-crosslinked network structure in modified epoxy resins.

Synthesis of Thiol-functionalized Mesoporous Materials for Hg2. Trapping

Mesoporous silica materials with uniform channels containing functionalized organic monolayers have been synthesized by grafting a thiol functional group, （3-Mercaptopropyl） trimethoxysilane （MPTMS）. A new approach to heavy metal ion adsorbents based on the covalent grafting of MPTMS groups to the framework pore walls of mesoporous silica molecular sieves has been developed and investigated with regard to hydroxyl group densities, channel dimensions, morphologies and reaction conditions. Results show that the ordered mesostructures of functionalized samples were retained after modification and the thiol functional group was immobilized mainly inside the mesopore channel. The relative surface coverage of the monolayer can be systematically varied up to 95%. The functionalized hybrid materials show exceptional selectivity and capacity for removing mercury from aqueous waste stream with distribution coefficients up to 435,000. The regenerated material show high mercury ion uptake capacity of 2.87 mmol/g （86.5%）.

MEMS陀螺芯片的晶圆级真空封装

微机电系统(MEMS)陀螺需要真空封装以确保其检测精度,晶圆级真空封装可以使MEMS微结构避免芯片切割过程中的粘连以及颗粒污染,提高芯片的成品率。为实现MEMS陀螺芯片的晶圆级真空封装,提出了一种全硅MEMS陀螺芯片的晶圆级真空封装结构方案,并突破了Si-SiO_(2)直接键合、吸气剂制备、金-硅(Au-Si)键合等关键技术,实现了MEMS芯片的晶圆级真空封装。Si-SiO_(2)直接键合和Au-Si共晶键合的剪切强度分别达到了56.5 MPa和35.5 MPa,表明晶圆级封装中晶圆键合强度满足晶圆级真空封装的需要。晶圆级真空封装实现陀螺仪谐振最大Q值为103879,对应的真空压力为2 Pa左右,陀螺仪芯片已达到MEMS陀螺工程化的需要。

Optimization of Plasma Etching Parameters and Mask for Silica Optical Waveguides

Optical waveguides in silica-on-silicon are one of the key elements in optical communications.The processes of deep etching silica waveguides using resist and metal masks in RIE plasma are investigated.The etching responses,including etching rate and selectivity as functions of variation of parameters,are modeled with a 3D neural network.A novel resist/metal combined mask that can overcome the single-layer masks’ limitations is developed for enhancing the waveguides deep etching and low-loss optical waveguides are fabricated at last.