振动流化床制备疏水纳米二氧化硅

本文以纳米二氧化硅为原料,六甲基二硅氮烷为改性剂,甲醇为改性助剂,利用振动流化床对疏水纳米二氧化硅进行了改性研究,分别探讨了改性剂用量、反应温度、反应时间、改性助剂用量、振幅和频率等因素对纳米二氧化硅表面改性效果的影响,获得了较佳工艺条件:改性助剂用量为6%,反应时间15 min,反应温度300℃,氮气流量1.5 m3/h,振动频率18 Hz,振幅0.5 mm.通过透射电镜测定了纳米二氧化硅的团聚性,并以乙醇和水对纳米二氧化硅的疏水性进行了测定.     

改性纳米二氧化硅制备及FTIR分析初探

以正硅酸乙酯为硅源,乙醇为溶剂．氨水为催化剂,Stober溶胶．凝胶法合成纳米二氧化硅。KH－550硅烷偶联荆改性纳米二氧化硅。改性轴米二氧化硅的宏观形貌呈白色粉末状。傅里叶交换红外（FTlR）分析结果表明改性纳米二氧化硅并未政变纳米二氧化硅的体相成分和晶体结构,只是使其表面的部分羟基与硅烷偶联剂作用生成Si－0键,疏水性增强。     

疏水型气相二氧化硅技术获专利

广州吉必盛科技实业有限公司开发的连续表面处理制备疏水型纳米级二氧化硅的方法已获国家发明专利授权,标志着我国在气相法二氧化硅的连续表面处理改性方面取得了自主知识产权。该专利技术实施有望打破国外公司对我国疏水型气相二氧化硅市场的垄断局面。目前吉必盛公司有能力生产与国外公司对应的所有牌号疏水型气相二氧化硅产品。计划在其子公司连云港吉必盛新材料有限公司筹建气相二氧化硅在线表面处理生产线,最终形成5000t/a疏水型气相二氧化硅生产线。     

武汉合成纳米SiO2 复合材料

武汉现代工业技术研究院选用某大型企业副产品成功合成纳米二氧化硅材料 ,并进行了表面疏水改性。这种具有疏水性的纳米二氧化硅微粒能均匀地分散到塑料用增塑剂中或橡胶用操作油中而制得纳米复合塑料或纳米复合橡胶。纳米二氧化硅材料表面能高 ,为热力学不稳定系统 ,该系统表面吉布斯函数导致纳米粒子易二次集聚成微米粒子。该研究院打破常规将具有疏水 (亲油 )性的纳米粒子分散在烃及其衍生物中 ,有效防止了纳米二氧化硅的二次集聚 ,为纳米复合材料提供了一种新的制作方法 ,并为有机高分子材料升级换代创造了条件。武汉合成纳米SiO_2复合…     

二氧化硅颗粒表面硅烷化对其润湿性能的影响

采用3-氨丙基三乙氧基硅烷(APTES)接枝改性二氧化硅颗粒表面,通过调节APTES的接枝密度(颗粒表面每平方纳米接枝硅烷偶联剂分子的个数)定量控制二氧化硅颗粒在石蜡/水界面上的接触角。结果表明:随着APTES在二氧化硅颗粒表面接枝密度的增加,颗粒由超亲水转变为疏水,在油水界面的接触角从15°增加到116°;改性颗粒在石蜡/水界面形成固态膜,当石蜡低温固化后,改性颗粒在石蜡相中的部分被掩盖;相比于未改性颗粒,改性后的颗粒在石蜡表面形成的包裹层更加紧密有序。     

单分散纳米二氧化硅微球表面化学修饰与表征

通过溶胶-凝胶法制备纳米二氧化硅微球,以乙醇作为分散介质,用硅烷偶联剂采用一步法对纳米二氧化硅进行了表面化学修饰。通过X-射线光电子能谱（XPS）、透射电子显微镜（TEM）和傅立叶红外光谱仪（FT-IR）等手段对其改性前后效果进行了分析。研究发现修饰后的纳米二氧化硅微球的疏水性增强;硅烷偶联剂与纳米二氧化硅表面羟基发生了化学反应。     

纳米二氧化硅增强硅橡胶膜

<正>北京防化研究院的秦墨林等人以六甲基二硅氮烷为改性剂,采用湿法工艺对纳米二氧化硅进行表面疏水改性,制得用于离子迁移谱仪进样的纳米二氧化硅增强硅橡胶膜。结果表明,在疏水化改性反应中,随着加热温度的升高或反应时间的延长,纳米二氧化硅的表面羟基数量下降,比表面积减小,最佳加热温度120℃,反应时间4 h;     

沉积温度对气凝胶表面制备氮化硼薄膜微观结构及其疏水性能的影响

为研究氮化硼纳米薄层在气凝胶疏水改性领域的应用前景,采用气相沉积法在二氧化硅气凝胶基底上制备了氮化硼纳米片薄层,研究了制备参数(制备温度、保温时间)对氮化硼纳米薄层的表面形貌及其疏水性能的影响.结果表明:生长涂层的最佳制备参数为生长温度1200℃,保温时间60 min.同时,生长涂层的表面形貌与参数关系不大,但是涂层的润湿性能与涂层的制备温度密切相关,在1100～1200℃之间实现了亲水到疏水的奇异转变,这归因于涂层表面化学组分的改变.本研究表明,氮化硼纳米涂层可实现二氧化硅气凝胶的疏水改性,表面化学组分起关键性作用.     

鞣酸改性纳米二氧化硅对UV固化涂料性能的影响

通过在纳米二氧化硅-乙醇悬浮液中加入一定量鞣酸的方法,在纳米二氧化硅表面引入羟基等活性基团对纳米二氧化硅进行表面改性,并用SEM、FTIR和TG等手段对鞣酸表面改性纳米二氧化硅的改性机理进行研究。利用交流阻抗图谱(EIS)研究包覆后二氧化硅对UV固化涂料的防腐蚀性能。结果表明:鞣酸是以化学键合的方式接枝到纳米二氧化硅表面,改性后的纳米二氧化硅分散良好,鞣酸改性纳米SiO2能极大提高UV固化涂层防腐蚀效果。     

合成纳米SiO_2及其复合材料

武汉现代工业技术研究院选用某大型企业副产品成功合成了纳米二氧化硅(SiO_2),并对其进行了表面疏水改性。这种具有疏水性的纳米SiO_2微粒能均匀地分散到塑料用增塑剂或橡胶用操作油中,从而可制得纳米复合塑料或纳米复     

Viscoelastic Behavior of Alkyl Ether Sulfate Systems Containing Nanosized Colloidal Silica

Surfactant systems incorporating wormlike micelles (WLM) are utilized in both industrial and consumer products. While the viscoelastic behavior of such systems provides for many desired end-use properties, there is often a need to further modify the rheological properties of such systems. These WLM systems behave much like polymer systems. Furthermore, incorporation of nanosized particles results in interaction of nanoparticles with the large WLM structures altering the rheological behavior. While there are a number of studies that have focused on the effect of particles on the rheological behavior in cationic surfactant systems, fewer studies have been done on systems containing anionic surfactants. In this study, relaxation behaviors in systems containing sodium alkyl ether sulfate and sodium carbonate were studied. The anionic surfactant was an alkyl ether sulfate with an average chain length of 12 carbons and one ethoxy group. WLM behavior was achieved through the addition of sodium carbonate. Ludox TMA, a nanosized colloidal silica, was employed at different concentrations in the WLM systems. Temperature was varied between 5 and 45°C. While characterization of relaxation in terms of the Maxwell model adequately described data below the threshold of ωτ ~1, the model failed to adequately describe behavior at higher frequencies. A modified expression with an additional relaxation mode adequately described relaxation throughout the frequency range studied. It was also found that zero-shear viscosities generally increased with an increase in silica concentration, and relaxation times decreased. Measurements of relaxation due to a compressive stress via ultrasonic attenuation measurements in the surfactant/particle systems are also discussed.     

Effect of Silica Nanoparticle Size on the Stability of Alumina/Silica Suspensions

The influence of the addition of silica particles (5, 15, 25, and 300 nm) on the zeta potential and viscosity of aqueous alumina slurries (250 nm particles) was investigated in a pH range where the surface charge was positive for alumina and negative for silica. For slurries formulated with the smaller silica particles, the isoelectric point shifted from pH 9.0 to pH ∼3 (depending on the particle size of the silica) with increasing volume fraction of silica particles. At pH 9, the original isoelectric point for the alumina alone, these mixed slurries had a shear-rate-independent, low viscosity (Newtonian behavior). Both of these results show that the smaller (≤25 nm) silica particles adsorb to the surface of alumina. The fraction of silica adsorbed to the alumina surface was dependent on the size of the silica particles, and was consistent with surface coverage calculations based on the effect of surface curvature on the limits of dense random parking. The larger silica particles (300 nm) could not physically cover the surface of the alumina particles, and simply formed a mixed, attractive particle network that exhibited a much higher viscosity with non-Newtonian (viz., shear rate thinning) behavior.     

Silica Nanoparticles with Proton Donor and Proton Acceptor Groups: Synthesis and Aggregation

The effects of precursor structure and polycondensation conditions on the properties of hybrid nanoparticles synthesized from organo-trimethoxysilanes were studied. Hybrid nanoparticles containing groups capable of forming hydrogen bonds were synthesized from functional derivatives of 3-aminopropyltrimethoxysilane. For the synthesis of phenylurea-functionalized organosilica nanoparticles different approaches to nanoparticle preparation were used. It was shown that the nature of the functional groups (proton-donor or proton-acceptor) affects the aggregation of silica nanoparticles. Also, the difference in behavior of nanoparticles prepared using surface modification and polycondensation was demonstrated for different pH, ionic strength and solvent polarity. As a result, by changing the pH of the solutions, it is possible to shift the aggregation pattern of these nanoparticles, such as the size of the initially formed aggregates.     

Facile Fabrication of Ultrafine Hollow Silica and Magnetic Hollow Silica Nanoparticles by a Dual-Templating Approach

The development of synthetic process for hollow silica materials is an issue of considerable topical interest. While a number of chemical routes are available and are extensively used, the diameter of hollow silica often large than 50 nm. Here, we report on a facial route to synthesis ultrafine hollow silica nanoparticles (the diameter of ca. 24 nm) with high surface area by using cetyltrimethylammmonium bromide (CTAB) and sodium bis(2-ethylhexyl) sulfosuccinate (AOT) as co-templates and subsequent annealing treatment. When the hollow magnetite nanoparticles were introduced into the reaction, the ultrafine magnetic hollow silica nanoparticles with the diameter of ca. 32 nm were obtained correspondingly. Transmission electron microscopy studies confirm that the nanoparticles are composed of amorphous silica and that the majority of them are hollow.     

SiO_2复合磁性纳米粒子的合成及表面性质的研究

采用溶胶凝胶法合成具有快速磁场响应能力的SiO2复合磁性纳米粒子。用表面电位仪研究了不同包覆层厚度对粒子表面性质的影响。用AFM对粒子的表面形貌进行了表征。并考察了不同SiO2包覆层厚度粒子的抗酸性。结果表明生长3层SiO2后复合粒子的表面完全被SiO2所包覆,粒子具有高的磁含量和快速的磁场响应能力,并具有高的抗酸性。     

氟化SiO2纳米颗粒双疏涂层的制备及性能研究

采用氟化硅烷偶联剂对合成的单分散SiO2纳米颗粒进行表面接枝改性,并通过旋涂法将制备的氟化SiO2颗粒沉积在硅晶基板上.采用粒径分析仪、傅里叶变换红外光谱仪(FTIR)、热重分析仪(TG-DTA)、扫描电镜(SEM)和接触角测量仪对氟化SiO2纳米颗粒涂层的表面形貌、化学组成、接枝密度和润湿性能进行分析表征.结果表明:氟化硅烷偶联剂在SiO2纳米颗粒表面的接枝密度为5.94 nm-2;制备的氟化SiO2纳米颗粒薄膜具备微纳米双重复合网络结构,增加了涂层表面的粗糙程度;氟化SiO2纳米颗粒涂层展现出超疏水和强疏油性能,水和柴油在氟化SiO2纳米颗粒薄膜上的接触角分别为158.4°和125.7°.     

Silica nanoparticles functionalized via click chemistry and ATRP for enrichment of Pb(II) ion

ABSTRACT: Silica nanoparticles have been functionalized by click chemistry and atom transfer radical polymerization (ATRP) simultaneously. First, the silanized silica nanoparticles were modified with bromine end group, and then the azide group was grafted onto the surface via covalent coupling. 3-Bromopropyl propiolate was synthesized, and then the synthesized materials were used to react with azide-modified silica nanoparticles via copper-mediated click chemistry and bromine surface-initiated ATRP. Transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and thermogravimetric analysis were performed to characterize the functionalized silica nanoparticles. We investigated the enrichment efficiency of bare silica and poly(ethylene glycol) methacrylate (PEGMA)-functionalized silica nanoparticles in Pb(II) aqueous solution. The results demonstrated that PEGMA-functionalized silica nanoparticles can enrich Pb(II) more quickly than pristine silica nanoparticles within 1 h.     

A New Insight into the Pressure-Decreasing Mechanism of Hydrophobic Silica Nanoparticles Modified by <Emphasis Type="Italic">n</Emphasis>-Propyltrichlorosilane

Hydrophobic silica nanoparticles were prepared for pressure decreasing in water injection through modification of hydrophilic silica nanoparticles by n-propyltrichlorosilane. Fourier transform infrared spectroscopy analysis and surface hydroxyl number measurement results certified that the modification was very successful. The core flowing experiment showed that the modified hydrophobic silica nanoparticles have an excellent pressure-decreasing ability. The contact angles measurement results showed that the core chip changed from strong water wet to neutral wet after treated by the modified silica nanoparticles. In this work, a roughness decreasing mechanism is proposed to explain the pressure-decreasing mechanism of modified silica nanoparticles. After injection into the core, the modified silica nanoparticles occupied the spaces between the sand grains, forming a discontinuous hydrophobic film on the flowing channel surface. This can not only partially change the wettability of the sand surface, but also decrease the roughness of the core flowing channel, decreasing the critical layer thickness and flowing pressure accordingly.     

Silica nanoparticles as a tool for fluorescence collection efficiency enhancement

In this work we demonstrate enhancement of the fluorescence collection efficiency for chlorophyll-containing photosynthetic complexes deposited on SiO₂ spherical nanoparticles. Microscopic images of fluorescence emission reveal ring-like emission patterns associated with chlorophyll-containing complexes coupled to electromagnetic modes within the silica nanoparticles. The interaction leaves no effect upon the emission spectra of the complexes, and the transient behavior of the fluorescence also remains unchanged, which indicates no influence of the silica nanoparticles on the radiative properties of the fluorophores. We interpret this enhancement as a result of efficient scattering of electromagnetic field by the dielectric nanoparticles that increases collection efficiency of fluorescence emission.     

Effects of Silica Nanoparticles Content on the Properties and Corrosion Behavior of Electroless Ni-Ba-B Alloy Coatings

The beneficial role of silica nanoparticles addition as reinforcing agent on the various properties of the novel developed Ni-Ba-B coating was highlighted. Barium was considered as third element to act as an inhibiting alloying element for anodic passivation purposes. The ternary Ni-Ba-B coatings in three different concentrations of silica nanoparticles (0.5, 1.0 and 2.0 g/L) were coated on St 37 steel substrate in the presence of sodium dodecyl sulfate (SDS). The effect of nanoparticles on morphology and structure was investigated by FE-SEM, XRD and AFM tests. The nodularity and surface roughness of the coating increased by the presence of SiO2 nanoparticles in the electroless bath. The nanocomposite coating has amorphous and crystalline phases and its XRD peak at 44.50 is slightly sharper than the composite coating. DSC thermogram showed two exothermic peaks demonstrating its phase transformations. The WCA value of coating was confirmed its hydrophilicity property. Results also confirmed that the existence of silica nanoparticles results in an increase in the microhardness and corrosion resistance which may be attributed to the distribution of silica nanoparticles into Ni-Ba-B matrix.