Synthesis of High Surface Area Silica Gels Using Porous Carbon Matrices

Porous silica was prepared using the sol-gel synthesis with porous carbon matrices as a pore-forming support. Tetraethoxysilane (TEOS) was hydrolyzed in an acid medium in the presence of a substoichiometric amount of water. Various carbon materials were used, among them Sibunit and catalytic filamentous carbon. Carbon matrices were impregnated with hydrolyzed TEOS and dried, then carbon was removed by burning out in air at 873 K. The obtained porous silica samples were studied by adsorption and electron microscopic methods. The specific surface area as high as 1267 m²g and pore volume as high as 5.7 cm³/g were determined for some silica samples. Thus deposited SiO₂ was found to cover the carbon surface copying its surface. With CFC used as carbon matrix, silica nanotubes were obtained. Thermostability of such silica is significantly greater as compared to silica gels reported earlier.     

Bioactivity and Mechanical Properties of Poly(dimethylsiloxane)-Modified Calcia–Silica Hybrids with Added Titania

Hydrolysis and polycondensation of poly(dimethylsiloxane) (PDMS), tetraethoxysilane (TEOS), and calcium nitrate, added with tetraisopropyltitanate (TiPT) at a TiPT/(TiPT + TEOS) molar ratio of 0.15, gave a pore- and crack-free transparent monolithic organic-inorganic hybrid material. It was speculated to be composed of a Si–O–Ti–O⁻ network modified with methyl groups, and a Ca²⁺ ion ionically bonded to the network. The hybrid obtained showed a high apatite-forming ability on its surface in a simulated body fluid that is indicative of high bioactivity, as well as mechanical properties such as bending strength, Young's modulus, and strain at failure, analogous to those of the human cancellous bone. This hybrid material is expected to be useful as a new type of bioactive bone-repairing material.     

仿生物矿化制备硅纳米材料

利用正硅酸乙酯和人工合成的多肽,在比较温和的条件下快速合成了硅纳米材料,并研究了制备过程中的多种因素对产物形貌的影响,研究发现:在pH值=8.0的磷酸盐缓冲液中,当R5肽的浓度为10 mg/mL,正硅酸乙酯的浓度0.1mol/L,反应15min时,可得到规则的球状颗粒。X射线能谱分析证明产物为硅和多肽的复合物。     

以硅凝胶网络结构为模板制备多孔炭材料的研究

分别以蔗糖和正硅酸乙酯(TEOS)作为炭和硅凝胶的前驱体,通过溶胶凝胶过程形成蔗糖聚合物和硅凝胶的复合物,经高温炭化后将硅模板刻蚀去除制备了一种多孔炭材料。研究发现,影响多孔炭孔结构的主要因素是原料的摩尔比,另外还与胶凝温度、炭化温度、刻蚀方式有关。     

SiO_2气凝胶的常温法合成研究及表征

以正硅酸乙酯（TEOS）为硅源,采用酸、碱两步催化的溶胶-凝胶法,通过L9（34）四因素三水平正交试验,研究了无水乙醇（ETOH）、草酸（H2C2O4）和氨水（NH3 H2O）之间的摩尔比以及酸碱间隔时间对气凝胶性能的影响,并对所得产品结构和性能进行了比表面（BET）、傅立叶转换、红外线光谱（FTIR）和扫描电镜（SEM）表征,从而首次实现了SiO2气凝胶的常温合成。实验结果表明：原料最佳摩尔比为TEOS∶ETOH∶H2C2O4∶NH3.H2O=1∶7∶3.5∶2.5,酸碱最佳间隔时间为18 h,SiO2气凝胶的平均粒径为6.58 nm,密度为100 kg/m3,孔径分布为2～30 nm,比表面达到938.17 m2/g,室温条件下合成的SiO2气凝胶,不亚于高温合成法的产品性能。     

铽-N-苯基邻氨基苯甲酸的合成及荧光性质

采用共沉淀法制备了稀土铽的N-苯基邻氨基苯甲酸二元配合物.同时,采用溶胶-凝胶法制备了掺杂稀土铽的N-苯基邻氨基苯甲酸二元配合物的SiO2凝胶玻璃复合发光体,研究了合成的2种配合物的热稳定性及荧光性质.结果表明,在凝胶玻璃中合成的稀土二元配合物,其热稳定性明显提高,而其特征荧光基本保持不变.     

Synthesis and Photoluminescence Property of Silicon Carbide Nanowires Via Carbothermic Reduction of Silica

Silicon carbide nanowires have been synthesized at 1400 °C by carbothermic reduction of silica with bamboo carbon under normal atmosphere pressure without metallic catalyst. X-ray diffraction, scanning electron microscopy, energy-dispersive spectroscopy, transmission electron microscopy and Fourier transformed infrared spectroscopy were used to characterize the silicon carbide nanowires. The results show that the silicon carbide nanowires have a core–shell structure and grow along <111> direction. The diameter of silicon carbide nanowires is about 50–200 nm and the length from tens to hundreds of micrometers. The vapor–solid mechanism is proposed to elucidate the growth process. The photoluminescence of the synthesized silicon carbide nanowires shows significant blueshifts, which is resulted from the existence of oxygen defects in amorphous layer and the special rough core–shell interface.     

合成条件对气相法白炭黑性能的影响

以甲基三氯硅烷、氢气、空气为原料,制备气相法白炭黑。考察了原料配比、骤冷介质温度、合成炉温度、原料气速对白炭黑的比表面积、平均粒径的影响。结果表明：甲基三氯硅烷、氢气的量之比与白炭黑的比表面积成反比;合成炉温、骤冷介质温度与白炭黑的比表面积、平均粒径成反比;原料气速与白炭黑的比表面积成正比,与平均粒径成反比。较佳工艺为：甲基三氯硅烷、氢气与空气的量之比为0.33∶0.47∶1,冷却介质温度80～90℃,炉温800～850℃,气体流速5～6 m/s。     

环己基三乙氧基硅烷的合成

以正硅酸乙酯(TEOS)、金属镁、氯代环己烷(C6H11Cl)为原料，少量碘为引发荆，采用格氏试剂法一步合成了环己基三乙氧基硅烷(CTEOS)。讨论了影响合成反应的主要因素，得到了最佳合成工艺：反应温度150℃，反应物的量之比n(Mg)：n(TEOS)：n(C6H11Cl)为1．2：1：1．05，反应时间2h，在此条件下，产品收率为80．5％；并借助红外光谱仪、色质联用仪等对产物结构进行了表征。     

Sol–Gel Synthesis of Cadmium Telluride-Microcrystal-Doped Silica Glasses

The sol–gel process has been applied to the preparation of small-sized CdTe-doped silica glasses. Gels synthesized by the hydrolysis of a complex solution of Si(OC₂H₅)₄, Cd(CH₃COO)₂· 2H₂O, and Te were heated from 350° to 600°C in a H₂─N₂ atmosphere to form fine cubic CdTe crystals. The size of CdTe crystals, determined from the line broadening of X-ray diffraction pattern, increases from 4 to 9 nm in diameter with increasing heat-treatment temperature. The optical absorption edge shifts to the higher-energy side as the size of the CdTe crystals decreases. This phenomenon is interpreted in terms of a quantum confinement effect of electron and hole in the CdTe microcrystals.     

Field Emission Characteristics of Amorphous Diamond

Amorphous diamond is diamond-like carbon (DLC) that contains no other impurities. It can be conveniently deposited by bombarding a substrate with a cathodic arc. The arc contains a flux of ionized carbon atoms that are driven by a negative bias. In this research, this bias is set at 20 V. Various forms of amorphous diamond were deposited on silicon substrate of n-type (100) by varying the arc current set at 30, 50, 80, and 100 A. The sp³/(sp³+ sp²) ratios of these deposited coatings were measured by electron spectroscopy for chemical analysis and Raman spectroscopy, and the asperity height these films were imaged by an atomic force microscope. It was found that the sp³/(sp³+ sp²) ratio peaked at a value of about 50% when the current was set at 80 A. The average roughness increased linearly with the increasing current from ∼0.5 nm at 30 A to about 1.1 nm at 100 A. The maximum asperity height was approximately 10 times that of the above average roughness figures in all cases. The minimum effective work function (Φ_e) calculated by a Fowler–Nordheim plot was about 0.063 14 eV. By controlling the asperity height of amorphous diamond, high-emitting efficiencies could be achieved with good reproducibility.     

大颗粒超高纯度硅溶胶的制备及其表征(英文)

采用新工艺路线制备四乙氧基硅烷（tetraethoxysilane,TEOS）,以TEOS为原料制备超纯度大颗粒硅溶胶。TEOS是烷氧基硅烷法制备甲硅烷的副产物,经过精馏提纯以后,加入盐酸或氨水催化剂,采用溶胶-凝胶法制备硅溶胶。结果表明：TEOS和硅溶胶金属杂质离子总含量都低于0.3mg/L。用盐酸催化TEOS水解制备溶胶,胶粒直径达到129nm;用氨水催化,胶粒直径达272nm。当物质的量比n（C2H5OH）/n（TEOS）=6,n（H2O）/n（TEOS）=5,搅拌速度为250 r/min,制备的硅溶胶胶粒均匀度最好。加水不搅拌,胶粒很容易发生团聚,但是,当搅拌速率高于500 r/min时,胶粒出现团聚现象。     

Synthesis of Mesoporous Silica Materials via Nonsurfactant Urea-Templated Sol-Gel Reactions

Mesoporous silica materials with pore diameters of 2 to 6 nm have been prepared using urea as a nonsurfactant template or pore-forming agent in HCl-catalyzed sol-gel reactions of tetraethyl orthosilicate, followed by removing the urea molecules by extraction with methanol or water. Characterization results from nitrogen sorption isotherm, powder X-ray diffraction, and transmission electron microscopy indicate that the materials have large specific surface areas (e.g., 600 m²/g) and pore volumes (e.g., 0.8 cm³/g) as well as narrow pore size distributions. The mesoporosity is arisen from interconnecting wormlike channels and pores of regular diameters. As the urea concentration is increased, the nitrogen sorption isotherms of the silica matrices transform from the reversible type I to the type IV form with type H2 hysteresis, along with increases in the diameter and volume of the pores.     

Synthesis of multiwalled carbon nanotubes supported manganese and cobalt zinc oxides nanoparticles for the photodegradation of malachite green

Multiwalled carbon nanotubes (MWNTs) supported and unsupported bimetallic zinc and manganese oxides nanoparticles (Zn–Mn NPs) were synthesized by wet chemical precipitation method. Zn–Mn and MWNTs/Zn–Mn oxides NPs were used as photocatalysts for the photodegradation of malachite green in aqueous medium under UV irradiation. The photodegradation study of malachite green was carried out by UV/vis spectrophotometer. The Mn–Zn and MWNTs/Mn–Zn oxides NPs degraded about 93% and 96% of dye, respectively, within 2 h of irradiation time. Effect of several parameters like time, pH, catalyst dosage and concentration of dye on the photocatalytic degradation was studied. The optimum conditions were obtained at pH 9 (93% dye degraded in 1.5 h), at 0.0435 g of catalyst (76.04% of dye degraded in 1 h), at 12.5 ppm dye concentration (88.41% dye degraded in 45 min). The activity of recovered catalyst was also examined.     

超疏水/超亲油SiO2薄膜的制备和表征

采用溶胶-凝胶法以正硅酸乙酯和甲基三乙氧基硅烷为共前驱体制备纳米疏水SiO2溶胶,经十二烷基三甲氧基硅烷(dodecyltrimethoxysilane,DTMS)改性后,制备出SiO2粒子薄膜,用红外光谱分析SiO2粒子的化学组成,用透射电镜观察凝胶时间对SiO2粒子形貌的影响,用扫描电镜和接触角表征SiO2涂膜的表...     

二氧化硅无机薄膜的制备及性能研究

采用溶胶-凝胶法,以正硅酸乙酯为原料,不同浓度氨水溶液做催化剂制备了SiO2薄膜,用可见分光光度计,综合热分析仪、X射线粉末衍射等分析手段对薄膜进行表征。研究发现,随氨水浓度的提高,所制备的SiO2薄膜的透光率提高,薄膜与基底的附着力也相应提高。XRD分析结果表明二氧化硅薄膜具有非晶态的无序结构。     

Synthesis of Platinum/Silica Nanocomposite Particles by Reverse Micelle and Sol–Gel Processing

Pt/SiO₂ nanosized particles have been synthesized using a reverse micelle technique combined with metal alkoxide hydrolysis and condensation. The size of the particles and the thickness of the coating can be controlled by manipulating the relative rates of the hydrolysis and condensation reactions of tetraethoxysilane (TEOS) within the microemulsion. The average size of synthesized particles was in the size range of 21–42 nm. The effects of synthesis parameters, such as the molar ratio of water to TEOS and the molar ratio of water to surfactant, are discussed.     

New hybrid materials incorporating tetrabutyl titanate and tetraethoxysilane with functional SEBS elastomer via the sol-gel process: Synthesis and characterization

New flexible hybrid materials were prepared by incorporating amino-functionalized styrene-ethylene-butylene-styrene block copolymer (SEBS elastomer) with tetrabutyl titanate and tetraethoxysilane. SEBS was modified via nitration and subsequent reduction, giving the product SEBS II bearing amino groups in the hard segments. The trimethoxylsilane functionalization was then achieved by the addition of coupling agent, 3-glycidyloxypropyl trimethoxysilane (GOTMS) in the sol-gel processing. The hydrolytic condensation of these trimethoxylsilane groups on SEBS II with metal alkoxide led to the formation of covalent bonds between the organic polymer chains and the inorganic networks produced in situ to prevent macrophase separation, resulting in better optical properties. Electron micrographs clearly show that the size of dispersed inorganic phase can be reduced by the use of trimethoxyl silane functionalization. The results of dynamic mechanical analysis are also discussed. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 853–860, 1997     

由稻壳炭合成介孔二氧化硅

以稻壳发电残渣稻壳炭的碱提取液为硅源,十六烷基三甲基溴化铵(CTAB)为模板剂,在碱性条件下通过溶胶-凝胶方法合成多孔二氧化硅前驱体。获得的前驱体采用萃取的方式脱除模板剂,合成产品采用低温氮气吸脱附、XRD、TEM、白度仪等手段进行了表征,确证得到的产品为高比表面、有序介孔二氧化硅。讨论了前处理和脱模方式对合成产物结构和性质的影响。     

Hydroxylated Cyclophosphazene/Silica Hybrid Materials: Synthesis and Characterization

The synthesis of new hybrid materials that are prepared by the sol-gel technique is presented. The synthesis involves the reaction of a free hydroxylic group-containing cyclophosphazene, hexakis(4-hydroxyphenoxy)cyclophosphazene, and a hydrolyzed tetraethoxysilane under acid catalysis. Evidence for the formation of genuine chemical bonds between the hydroxylated cyclophosphazene and the three-dimensional silica network is presented. The formation of these bonds was confirmed by spectroscopic techniques (FTIR, ³¹P, ²⁹Si, and ¹³C NMR both in solution and in the solid state and X-Ray Diffraction analysis). The results are supported by thermal characterization of the materials based on Differential Thermal Analysis (DTA) and Thermogravimetric Analysis (TGA) determinations.