Preparation and colloidal dispersion behaviors of silica sol doped with organic pigment

Silica sol doped with organic pigment was prepared by hydrolyzing tetraethoxysilane with a basic catalyst via dispersing pigment in silica sol. The colloidal properties of SiO₂/pigment hybrid sol and its deposited film were investigated. The presence of pigment in SiO₂/pigment hybrid sol affects the Zeta potential, particle size and surface tension compared to the silica sol without pigment. The SiO₂/pigment hybrid sol exhibited good dispersion stability in the centrifuge process. The maximum absorption wavelength was consistent with that of the pigment disperse solution, indicating that the pigment in SiO₂/pigment hybrid sol remained unchanged. Thermogravimetric analysis of the contents of organic component in silica sol and SiO₂/pigment hybrid sol were conducted, and the differential value was ascribed to the weight of the pigment and the condensate of polyoxyethylene octylphenol ether (OP-10) and γ-Glycidoxypropyltrimethoxysilane (KH-560). The surface topography of SiO₂/pigment hybrid silica film was characterized by AFM. The analysis of silica sol doped with organic pigment provides useful information for an effective pathway to disperse pigment on fiber and other substrates.     

二氧化硅修饰纳米氧化锆陶瓷材料的制备及性能

以二甲基二乙氧基硅烷为硅源,在水溶液中成功制备了SiO2修饰纳米ZrO2颗粒;利用透射电子显微镜、热重分析仪、X射线衍射仪、红外光谱仪分析了样品的形貌和结构;将SiO2/ZrO2与α-Al2O3制成陶瓷材料,考察了其机械性能.结果表明,所制备的SiO2/ZrO2晶粒均一,直径约为10nm,硅原子在SiO2/ZrO2中以Si―O―Zr键合形式存在,SiO2不影响ZrO2的晶型.引入SiO2使得ZrO2晶粒细化、尺寸均匀性提高;SiO2/ZrO2/Al2O3陶瓷气孔率小,具有致密的显微结构和优异的机械性能.     

Antiwetting silica–gelatin nanohybrid and transparent nano coatings synthesised through an aqueous sol–gel process

Hydrophobic silica-biopolymer hybrid has been synthesised using colloidal silica as the precursor for silica, gelatin as the biopolymer counterpart and vinyltrimethoxysilane as the surface modifier through a sol–gel method. The precursor sol was coated on glass substrates and further investigated for the extent of chemical modification, thermal degradation, hydrophobicity, particle size and transparency in the UV-Visible region. Stereomicrographs clearly indicate the water repellent nature of the hybrid coatings with respect to a water drop. FTIR was used to follow the presence of vinyl groups that impart hydrophobicity to the resultant hybrids. By varying the concentration of functionalizing agent, the extent of hydrophobic property could been tailored. The optimum concentration for effective surface modification of the silica–gelatin hybrid is about 50 wt%. Nearly 100% optical transmittance was obtained for silica–VTMS–gelatin hybrid coatings on glass substrates and this may have potential applications in optical devices and also for transparent biocompatible hydrophobic coatings on biological substrates such as leather.     

Preparation and characteristics of NiO-coated nano-fibriform silica

NiO-coated nano-fibriform silica (NFS) was prepared by an excessive soakage method and was characterized using transmission electron microscopy, X-ray diffraction, and physical N₂ adsorption techniques under different conditions. The results demonstrate that the coated NiO is of a cubic crystal form. The best preparation conditions are incubation in a water bath at 95 °C for 2 h and drying at 45 °C for 17 h, which lead to a higher NFS utilization ratio and thus lower cost, and a well-distributed NiO coating on the carrier NFS. Nitrogen adsorption isotherms for NiO-coated NFS are similar to a type IV curve, with a specific surface area of 292.7 m²/g, adsorptive capacity of 379.2 cm³/g, and pore volume of 0.59 cm³/g. The average pore diameter of NiO-coated NFS is 8.01 nm, but most pore diameters are in the range 2.1–3.9 nm. Comparison of NiO-coated NFS and NiO(Ni)-coated sol–gel silica as catalysts reveals that NiO-coated NFS may be an effective catalyst and that NFS may be a good catalyst carrier.     

Preparation of dendritic and network PANI/silica composite fibers

Dendritic and network PANI fibers with controlled diameters from nanosize to sub-micrometer-size were prepared at room temperature. Conducting polyaniline (PANI)/silica composite fibers were synthesized via a sol-gel progress thereafter. Structural characterization was performed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). FT-IR and UV-vis were used to verify the incorporation of the silica.     

Abrasive properties of nano silica particles prepared by a sol–gel method for polishing silicon wafers

Abrasive properties of cocoon shaped silica particles fabricated by a sol–gel method have been studied. Since silicon wafers are polished with slurry by the mechanism of Chemical Mechanical Polishing, polishing rates may depend on various chemical and mechanical factors, such as particle concentration in slurry, slurry pH and kinds of basic compounds for controlling the slurry pH. The silicon wafer was polished by slurry continuously fed on a pad, and the polishing rate was estimated as a weight loss of the wafer. For studying the effects of the various factors on the rate, the slurries were prepared by adding the silica particles, basic compounds or salts, and the polishing rates of the slurry were measured. The effects of the various factors were made clear as follows: For the effect of particle concentration, the rates increased with increasing of the concentrations up to 1.0 wt.%. And for the effect of the slurry pH, slurries added basic compounds, such as KOH, NaOH, ammonia, were tested, and it was found that increasing of the slurry pH brought increases of the polishing rates. KOH-containing slurry of pH 13.2 had the fastest rate, 3.6 times as fast as the standard slurry with pH 9.4. For the effect of the adding of salts, it was indicated that the salts, such as KCl, NaCl, NH₄Cl, NaNO₃ and K₂SO₄ increased the polishing rates, and that KCl-containing slurry of 0.36 mol/l had the highest polishing rate, 3.4 times as fast as that of the standard slurry containing no salts.     

Properties of optical coatings formed on silicate glass from silica sol with alumina sol additive

The addition of 0.1—0.5 mol.% of alumina sol causes the increase in hardness of single-layer optical coatings, produced on silicate glass from silica sol at gel setting temperatures of 60—80 °C, from F—H to 7H—9H. Small concentrations of the additive do not affect the light transmission of the coated glasses. Atomic force microscopy has shown the coating surface to be homogeneous, the surface roughness not exceeding 4.0 nm.     

Combination of silica sol and dyes on textiles

The embedding in sol-gel coatings can improve the fastness properties of dyes on textiles. The aim of this study is to investigate, whether it is necessary to apply dye and sol together in one step or the application of dye and sol can be performed in separate steps. For practical applications, it can be of high interest to apply sol and dye separately, because by this the fastness properties of once coloured textiles can be improved by sol-gel coatings or an uncolored sol-gel treated fabric can be dyed afterwards with higher fastness properties. For this, modified silica sols and dye molecules were applied in combination on textiles. The investigations were performed with the two triphenylmethane dyes Malachite Green and Guinea Green. These dyes were applied using four different methods – without sol, applied before or after sol treatment and together with the sol. The silica sols were applied in different concentration. It was demonstrated that the application together with the silica sol or the aftertreatment of dyed textile with silica sol lead to significant improvement of leaching fastness. Also the low bleaching fastness of the triphenylmethane dyes can be enhanced significantly.     

Synthesis of acrylic-modified sol–gel silica

Silica was obtained by sol–gel process through hydrolysis and condensation of tetraethyl orthosilicate (TEOS) using molar fraction of H₂O/TEOS=9 under alkaline catalysis, at different reaction times (5 min to 24 h). At the end of each time, the reaction medium appeared as a suspended microparticle system. After solvent evaporation, the yield was calculated to be around 100% and practically independent of the time of reaction. The silica had its surface modified through the condensation reaction with acryloyl chloride forming organically modified silica. The unmodified and modified silica were characterized by thermogravimetry and derivative thermogravimetry (TG/DTG), infrared spectrometry (FT-IR), size particle and optical microscopy (OM). The acrylic content was independent of the reaction time. The methodology represents an alternative route to obtain silica with an unsaturated organic group, able to polymerize and stabilize up to 300–400°C. The modified material has a potential application as compatibilizing filler in dental composite.     

Preparation of highly active heteropolyacid - silica composite catalysts using the sol - gel method

It is shown that HPA/silica composite catalysts are much more active than HPA/Polyaniline composites in the reaction of isopropanol decomposition. The catalysts prepared using ethyl silicate 40 as a silica precursor showed better texture properties than those prepared using tetraethoxysilane but activities of the two families appeared to be similar. The use of 3-aminopropyltriethoxysilane, as an additive promoted the formation of a porous texture but this had no positive effect on the catalysts activity.     

Preparation of polypropylene/silica composites by in-situ sol–gel processing using hyperbranched polyethoxysiloxane

Based on a volatile-free silica liquid precursor polymer—hyperbranched polyethoxysiloxane (PEOS), an industrial compatible in situ sol–gel process for the preparation of polymer/silica nanocomposites has been developed. It has been shown that in the presence of a catalyst water vapor induced a fast conversion of liquid PEOS to solid silica in polypropylene (PP) melt in a twin-screw microcompounder. Solid state NMR showed that the in situ conversion of PEOS proceeded to a large extent. With small amounts of PEOS this procedure yielded PP/silica composites with particle size less than 100 nm. The particle size increased with the PEOS amount blended with PP. Nevertheless, the particles were observed to be homogeneously dispersed within the polymer matrix. PP/silica composites prepared by in situ sol–gel technology showed improved thermal properties, but almost not affected mechanical properties in comparison with pure PP.     

硅溶胶改性及其应用研究进展

二氧化硅在自然界中通常为晶态,而以溶胶-凝胶、水热、模板剂等方法人工合成的二氧化硅纳米颗粒(SiO₂ NPs)通常为无定形态。无定形SiO₂ NPs广泛应用于航空航天、催化剂载体、靶向送药等众多高端领域。生产SiO₂ NPs的方法有很多,但制备结构、形貌简单的SiO₂ NPs的主要方式为离子交换法、硅醇盐水解法、单质硅粉水解法,这些方法可制备粒径在10～800 nm的单分散SiO₂ NPs,同时可根据生产条件控制粒子的单分散性与粒径大小。寻找一种成本低廉且成品单分散性好、粒径可控的生产方法成为目前研究的热点。本文简介了SiO₂ NPs的结构形貌、基础性质、生产方法和最佳合成条件,总结了各方法的优缺点与适用领域。随后介绍了近年来SiO₂ NPs的改性研究与应用,最后在此基础上展望了合成硅溶胶存在的挑战与未来需解决的问题。     

苯基修饰二氧化硅纳米片纤维的制备及其对多环芳烃的固相微萃取

采用水热处理和溶胶-凝胶法在镍钛合金（NiTi）纤维表面组装了二氧化硅纳米片（SiO₂NFs）,成功制备了新型SiO₂纤维涂层,并用苯基三氯硅烷进行了自组装表面修饰,得到了可用于固相微萃取（SPME）的NiO/TiO₂@SiO₂NFs-Ph纤维。将制备的SPME纤维与高效液相色谱联用,通过对典型芳香化合物的分析评价了所制备纤维的萃取性能。该纤维对多环芳烃（PAHs）具有较高的萃取率和良好的萃取选择性。实验优化了pH值、搅拌速率、萃取温度、萃取时间和离子强度对PAHs萃取率的影响。在优化条件下,5种PAHs在各自的范围内呈良好的线性关系,相关系数（r）大于0.999,检出限为0.013~0.108 μg/L。使用单根纤维对含有50 μg/L PAHs的加标水样进行萃取,其含量的日内及日间RSD分别为4.1%~5.9%和4.8%~6.8%。实际环境水样中5种PAHs在10 μg/L和30 μg/L加标水平下的加标回收率分别为90.8%~105.7%和93.6%~103.1%。该法制备的NiO/TiO₂@SiO₂NFs-Ph纤维稳定性高、制备重现性好,适用于环境水样中目标PAHs的富集和测定。     

Optimum sol viscosity for stable electrospinning of silica nanofibres

Silica nanofibres have, due to their excellent properties, promising characteristics for multiple applications such as filtration, composites, catalysis, etc. Silica nanofibres can be obtained by combining electrospinning and the sol–gel process. To produce silica nanofibres most of the time organic solutions are applied containing a carrying polymer, which is afterwards removed by a thermal treatment to form pure ceramic nanofibres. Although electrospinning of the pure silica precursors without carrying polymer is preferred, the parameters influencing the stability of the electrospinning process are however largely unknown. In addition, this knowledge is essential for potential upscaling of the process. In this study, the optimum viscosity to electrospin in a stable manner is determined and the way to obtain this viscosity is evaluated. Sols with a viscosity between 120 and 200 mPa.s could be electrospun in a stable way, resulting in uniform and beadless nanofibres. Furthermore, this viscosity region corresponded with nanofibres having the lowest mean nanofibre diameters. Electrospinning with diluted sols was possible as well, but electrospinning of the fresh sols was more stable. These results illustrate the importance of the viscosity and degree of crosslinking of the sol for the stable electrospinning of silica nanofibres and demonstrate that upscaling of the electrospinning process of silica nanofibres is feasible.     

树脂交换法制备白炭黑溶胶

用白炭黑溶胶作造纸工业的添加剂,可以改进纸的滞留性和脱水性,将带有阴离子的白炭黑溶胶与一些阳离子聚合物一起使用,效果更佳。在造纸工业中添加的白炭黑溶胶粒径应在4～7nm,比表面为700～300m^2／g,稳定性好,传统方法制备的白炭黑溶胶难于达到此要求。本文对用树脂交换法制备白炭黑溶胶的条件、影响因素、最佳工艺进行了探讨。     

硅胶表面铜离子印迹聚合物的制备和性能研究

以Cu2+为模板,1,4-二羟基蒽醌为单体,硅胶为载体,γ-(甲基丙烯酰氧)丙基三甲氧基硅烷(KH-570)为偶联剂,利用表面离子印迹技术制备了Cu2+印迹聚合物。采用紫外光谱法、傅里叶变换红外光谱法(FT-IR)、扫描电镜对Cu2+印迹聚合物进行结构和表面形貌表征,并用原子吸收光谱法考察了吸附时间、吸附酸度、吸附温度、吸附浓度等对聚合物吸附性能的影响,研究了印迹聚合物在混合溶液中对Cu2+的选择性,将该聚合物重复利用6次,吸附量达到第一次的82%,并将该印迹聚合物应用到河水和自来水中,能够有效地测出水中铜离子的浓度,回收率分别为95.5%和107.2%。     

Preparation and stability of silica sol/TPGDA dispersions and its application in the UV-curable hybrid coatings for fire protection

A series of silica sols modified by γ-methacryloxypropyltrimethoxysilane (MPS) were synthesized by the acid-catalyzed sol–gel method, and then the solvent in these sols were extracted under several vacuum distillation conditions. The stability of the sol after the distillation can be improved by means of increasing the dosage of MPS and incorporating reactive diluent TPGDA into the sol as new dispersion medium. Optimized samples have maintained stable for over 180 days. The sol dispersions and UV-curable organic compounds were mixed to form the hybrid coatings for fire protection. Effects of the distillation treatment and the cosolvent anhydrous ethanol added into the reaction solution on thermal and combustion performances and physical properties of the hybrid coatings were studied by thermogravimetric analysis, microscale combustion calorimeter, limit oxygen index test and UL-94 horizontal test, etc. The results showed that the distillation treatment for the sol was necessary to improve thermal performance and physical properties of the hybrid coatings. In addition, in the flammability experiment, hybrid coatings showed a quick and efficient protection of the substrate.     

十八烷基键合硅胶整体柱的制备及其色谱性能评价

选用十八烷基二甲基氯硅烷作为硅烷化试剂,制备十八烷基反相键合硅胶整体柱,并用元素分析进行了表征。以苯、甲苯、联苯、萘、菲混合物作为测试溶质,在以甲醇和水为二元流动相的反相色谱条件下评价了该键合整体柱的色谱性能,考察了该整体柱适用的pH范围,以及柱压降、柱效与流速的关系。结果表明,该硅胶整体柱键合效果良好,具有较好的反相色谱性能,且在pH 2~8之间稳定性好,柱压降、柱效受流速影响较小,对5种心血管系统用药可以达到快速、有效的分离。     

Preparation of core-shell and hollow fibers using layer by layer (LbL) self-assembly of polyelectrolytes on electrospun submicrometer-scale silica fibers

Herein, fabrication of hollow fibers made of polyelectrolyte multilayers is reported. Silica submicrometer-scale fibers were fabricated by electrospinning and layer by layer deposition of polyelectrolytes were performed to coat silica fibers with polyelectrolyte multilayers, which were prepared by consecutive deposition of poly(ethyleneimine) and poly(styrene sulfonate sodium salt)/sodium dodecyl sulfate onto the surface of the silica fibers. In order to obtain hollow fibers, the core removal was carried out by introducing the core-shell fibers to a hydrofluoric acid solution. The hollow fibers were stable in hydrofluoric acid solution and displayed pH-dependent structural changes. SEM microscopy indicated the formation of the glass fibers and the fibers coated with polyelectrolyte multilayers (Silica—polyelectrolyte multilayers (PEM) fibers). The diameter of the core-shell fibers was increased after layer-by-layer coating. ATR-FTIR was performed for characterization of the glass fibers before and after layer-by-layer coating as well as after selective core removal. IR spectrum of the Silica-PEM fibers indicates C-H stretching modes of saturated hydrocarbons, confirming multilayers formation. Core removal was also confirmed by IR spectroscopy as Si-O-Si band disappears for the IR spectrum of the fibers after core-removal.