纳米二氧化硅填充辐射硫化三元乙丙橡胶

用辐射硫化法替代传统硫化法,并以纳米二氧化硅为填料成功制备了纳米填充型三元乙丙橡胶密封材料。研究结果表明,纳米二氧化硅对辐射硫化三元乙丙橡胶有明显的补强效果,其最佳用量为40phr;吸收剂量超过20kGy后,橡胶总体性能下降;硫化胶的凝胶含量随填料含量的增加而增加,且凝胶含量的增大有利于提高辐射硫化胶的性能。对所得辐射硫化胶的透气透水性进行测试,数据显示与传统硫化法相比,辐射硫化法制备的橡胶其透气率和透水率均明显下降,表明材料的密封性较好。     

载药EVA/二氧化硅复合物薄膜的制备及体外缓释性能

采用溶胶-凝胶法制备了乙烯-醋酸乙烯酯共聚物(EVA)/二氧化硅的缓释复合材料.研究了复合材料的结构、亲-疏水性,并以阿司匹林为药物模型,考察二氧化硅添加量对聚合物缓释性能的影响.结果表明:采用溶胶-凝胶法能使二氧化硅微粒均匀分散在聚合物中;二氧化硅的加入能提高EVA载药膜的缓释性能;当二氧化硅质量分数为10%时,二氧化硅粒径为2～4 μm,复合膜缓释性能最好,缓释时间超过72 h;并且复合膜的药物释放过程符合Fickian扩散定律.     

PEO/LiClO_4纳米SiO_2复合聚合物电解质的电化学研究

将实验室制备的纳米二氧化硅和市售纳米二氧化硅粉末与PEO LiClO4复合 ,制得了复合PEO电解质 .它们的室温离子电导率可比未复合的PEO电解质提高 1～ 2个数量级 ,最高可以达到 1 2 4× 10 - 5S cm .离子电导率的提高有两方面的原因 :一是无机二氧化硅粉末的加入抑制了PEO的结晶 ,是二氧化硅粉末和聚合物电解质之间形成的界面对电导率的提高也有一定的作用 .在进一步加入PC EC(碳酸丙烯酯 碳酸乙烯酯 )混合增塑剂后制得的复合凝胶PEO电解质 ,可使室温离子电导率再提高 2个数量 ,达到 2× 10 - 3 S cm .用这种复合凝胶PEO电解质组装了Li|compositegelelectrolyte|Li半电池 ,并测量了该半电池的交流阻抗谱图随组装后保持时间的变化 ,实验观察到在保持时间为 144h以内钝化膜的交流阻抗迅速增大 ,但在随后的时间内逐渐趋于平稳 ,表明二氧化硅粉末的加入可以有效地抑制钝化膜的生长     

常压干燥制备二氧化硅气凝胶*

二氧化硅气凝胶是典型的纳米多孔轻质材料,由于具有独特的性能并在许多领域存在潜在的应用价值而受到广泛关注。二氧化硅气凝胶的制备传统上采用超临界干燥工艺,但此工艺成本高、工艺复杂而且具有一定的危险性。为了实现二氧化硅气凝胶的大批量生产和商品化应用,研究低成本常压干燥制备技术非常必要。目前常压干燥制备工艺已取得了较大进展,本文主要介绍了二氧化硅气凝胶的常压干燥制备方法及其特点,并概述了二氧化硅气凝胶复合材料制备的最新研究进展。以纤维和聚和物为增强体的二氧化硅气凝胶复合材料改善了气凝胶的力学性能,进一步扩宽了其应用范围。     

多重环境刺激响应性聚苄醚型树状分子凝胶制备及性能研究

环境刺激响应性超分子凝胶材料在传感器、光开关、人工触角、药物缓释等领域表现出潜在的应用前景。本文设计合成了一种新型的核心含偶氮苯官能团聚苄醚型树枝状分子凝胶因子CA-G2。成胶性能测试表明,该凝胶因子在23种有机溶剂和混合溶剂中均可以形成稳定的淡黄色凝胶,其中在苯中表现出最优的成凝胶性能,临界成胶浓度(CGC)可达2.0mg/mL(0.23(wt)%),相当于一个树枝状分子可以固定1.5×10⁴个溶剂分子,表明该凝胶因子具有非常优异的成凝胶性能。并且,该类凝胶材料能够同时对热、超声和触变等外界环境刺激产生响应,并伴随着宏观上凝胶-溶胶的相互转变。此外,该类凝胶对罗丹明B染料分子具有优异的吸附性能,吸附效率高达96.7%。     

一步可控合成二氧化硅纳米管和空心球

通过简单的溶胶凝胶法在相同体系中可控合成了新颖有序的二氧化硅纳米管和空心球,对制备二氧化硅纳米管的多种反应条件进行了系统研究。发现反应时间、溶液中水和乙醇比例、搅拌和滴加速度对形成管状结构都有着重要影响。同时,纳米管的形成机理研究表明,在醇水混合溶液中柠檬酸三铵晶体为细柱状形貌,其作为重要的结构导向剂为二氧化硅胶晶附着提供模板,从而形成管状结构,二氧化硅空心球也显示了相似的形成过程。     

勃姆石纤维增强二氧化硅气凝胶的制备及性能

以六水合氯化铝为铝源, 通过水热法制备勃姆石纤维; 以甲基三甲氧基硅烷和正硅酸乙酯为硅源共前驱体, 采用溶胶-凝胶法进而常压干燥制备了勃姆石纤维掺杂的二氧化硅复合气凝胶; 探究了勃姆石纤维的掺杂量对复合气凝胶性能的影响. 当勃姆石纤维的掺杂量(质量分数)为1%时, 气凝胶的机械性能最好, 能够承受17.1%的压缩应变, 最大压缩强度为1.12 MPa, 压缩模量高达2.57 MPa, 复合气凝胶在150 ℃仍然具有较低的导热系数(0.0670 W·m^?1·K^?1). 勃姆石纤维能够一定程度地抑制二氧化硅颗粒在高温下的烧结和相转变, 对二氧化硅气凝胶的耐高温性能有显著的提升作用, 复合气凝胶在1100 ℃高温热处理后, 仍能保持良好的隔热性能和较高的机械强度.     

结冷胶与聚乙二醇丙烯酸酯双网络凝胶的制备及生物相容性评价

针对结冷胶脆性较大的问题,将聚乙二醇丙烯酸酯(PEGDA)引入结冷胶,通过紫外交联制备了结冷胶/PEGDA双网络凝胶,并对单组分凝胶和双网络凝胶的溶胀性能、微观形貌、拉伸力学性能、动态压缩性能和流变性能等进行比较.结果表明,双网络凝胶在类生理环境中具有较小的溶胀率和较好的尺寸稳定性,PEGDA的引入能够大幅度提高结冷胶的韧性,双网络凝胶的拉断伸长率可达340%,断裂能达1.01×103J/m2,与天然关节软骨相当.将成纤维细胞种植在凝胶内部进行体外三维立体培养,结果显示,细胞在凝胶内部生存状态良好,双网络凝胶的细胞负载率高于单网络结冷胶,说明该体系在生物医用领域具有良好的应用前景.     

二氧化硅气凝胶对挥发性有机污染物的吸附性能研究（英文）

以TEOS为前驱体、乙醇为溶剂、氢氟酸为催化剂,一步法合成了常规二氧化硅气凝胶。经乙醇超临界干燥后,通过SEM、FTIR和N_2吸脱附分析仪等仪器对二氧化硅气凝胶样品进行表征,以更好地了解吸附机理与样品性质的关系。结果表明,样品的比表面积高达519m~2/g,孔体积为1.9cm~3/g,平均孔径为15.15nm,是一种优良的吸附材料。考察了样品对甲苯、对二甲苯和苯的吸附效果。结果表明,二氧化硅气凝胶对三种污染物都具有很高的吸附量,其高吸附能力归因于气凝胶的三维纳米网络结构。综上所述,二氧化硅气凝胶具有优异的吸附性能,是一种很有前景的处理挥发性有机化合物的吸附剂。     

不同功能基团的有机盐作为低相对分子质量凝胶因子对原油的成胶性能

低相对分子质量凝胶作为治理原油泄漏的材料具有一些优异的性能,但其在水油相中的成胶规律仍不明确,本文以有机酸及有机胺为原料设计合成了一系列有机盐。 通过核磁共振波谱仪(NMR)、傅里叶红外光谱仪(FTIR)、扫描电子显微镜(SEM)和倒挂实验等技术手段表征了有机盐的结构和成胶性能。 结果表明,有机盐A3C3(A3:肉桂酸;C3:月桂胺)在室温下能使原油形成稳定凝胶,成胶溶度为质量分数6%,该分子在溶剂中自组装形成树枝状三维网状结构。 凝胶的形成需要分子间π-π堆积作用、氢键、静电作用和范德华力等多种作用力协同作用,分子间的π-π堆积作用有利于凝胶的形成,含有多个苯环的凝胶因子更易在芳香族溶剂中形成凝胶。 这些成胶规律对处理原油泄漏的低相对分子质量凝胶因子的设计合成具有实际的指导意义。     

Effects of the degree of surface modification on the rheological responses of precipitated silica suspensions in benzyl alcohol

Two types of precipitated silica powders modified by poly (dimethylsiloxane) (PDMS) were suspended in benzyl alcohol and their rheological properties were investigated as a function of silica volume fraction, φ. The suspensions were classified into sol, pre-gel, and gel states based on the increase in φ. An increase in the degree of surface modification by PDMS caused gelation at higher φ. Plots of apparent shear viscosity against shear rate in the sol and pre-gel states of highly modified silica suspensions showed weak shear thickening behavior, while the same plots for silica suspensions with a low modification level exhibited shear thinning behavior. The dynamic moduli of hydrophobic suspensions in the pre-gel and gel states were dependent on the surface modification: the storage modulus G′ was larger than the loss modulus G″ in the linear region and these moduli increased with increasing φ, irrespective of the silica powder. The linear region of the φ range for the precipitated silica suspensions was wider than that for the fumed silica powders modified by PDMS suspended in benzyl alcohol, while the G′ value in the linear region for the precipitated silica suspensions was less than those for the fumed silica suspensions.     

Synthesis of TiO2/ZrO2/SiO2 powders and their structural,optical and photocatalytic properties

Research on Chemical Intermediates - Ternary oxide powders based on titania, zirconia and silica have been synthesized by the sol–gel method. The characterization of the powders was performed...     

Sol–gel synthesis and crystallization behaviour of β-spodumene

Lithium aluminum silicate powders in the form of β-spodumene were synthesized through sol–gel technique by mixing boehmite sol, silica sol and lithium salt. The gel and oxide powders were characterized by thermogravimetry, differential thermal analysis (DTA), X-ray diffraction (XRD), Fourier transformed infrared (FTIR) spectroscopy and scanning electron microscopy. DTA, XRD and FTIR results confirmed that crystallization of β-spodumene took place at about 800 °C. The tiny crystallites with average size less than 1 μm appeared when the gel powders were sintered at 800 °C. A substantial increase of the crystal grain size was observed with increasing sintering temperatures.     

Dispersion stabilities and rheological properties of fumed silica suspensions

Herein, we have reviewed fumed silica suspensions in dispersing fluids, polymer melts, and polymer solutions, focusing on their dispersion stability and rheological properties as a function of the surface character of fumed silica powders and the silica volume fraction, ?. Hydrophilic fumed silica powders are well dispersed at ? < 0.01 in polar dispersing fluids or polar polymer melts, and their phase states change from sol to gel with increasing ?. Such changes should also be strongly related to the rheological responses of the hydrophilic fumed silica suspensions, which change from Newtonian flow behavior to gel-like elasticity with increasing ?. On the other hand, hydrophobic fumed silica powders are stabilized in both polar and nonpolar dispersing fluids, depending on the interactions between the surface hydrophobic moieties and the dispersing fluids, in addition to those between the residual surface silanol groups and dispersing fluid, except for the particle–particle interactions. Moreover, the effects of the adsorption and desorption of polymers, as well as of non-adsorbing polymers on the dispersion stability and rheological behavior of fumed silica suspensions are discussed, by taking account of their optical microscopic observation and SANS curves.     

Alkyl-glycoside surfactants in the synthesis of mesoporous silica films

Alkyl glycosides were used as templating surfactants in the sol–gel processing of thin silica films. The sols were made from a prehydrolyzed silicate solution with the addition of a glucoside or a maltoside surfactant. The sol–gel–xerogel transitions and the silica–sugar interactions were studied by IR ATR spectroscopy. The siloxane condensation rate in the silica/glycoside sol was considerably reduced compared to a pure silica system due to hydrogen bonding interactions between the silanols and the sugar head groups. Thin films were deposited on silicon wafers and characterized by IR transmission, X-ray diffraction and TEM analysis. The size of the sugar head group had a large influence on the type of the mesophases formed. The use of the glucoside surfactant only resulted in temperature unstable lamellar phases, whereas the maltosides at low concentrations assembled in curved mesophases that were stable to template removal by extraction or calcination.     

二氧化硅溶胶的形成与硅胶膜性能

采取溶胶-凝胶成膜技术,以正硅酸乙酯(TEOS)为原料,分别以水为溶剂NH3催化、乙醇为溶剂HCl催化和冰醋酸为溶剂各自制备出粒状结构、簇状结构和网状结构的二氧化硅溶胶,丙三醇作为添加剂与TEOS水解中间体以氢键结合控制二氧化硅溶胶形态,聚乙烯醇(PVA)与二氧化硅溶胶形成有机/无机互穿网络结构,易于成膜。热处理能使二氧化硅凝胶薄膜中的添加剂逸出并形成疏松结构,塑性形变使硅胶薄膜形成多孔、疏松、致密结构二氧化硅薄膜。实验表明,催化剂和溶剂效应直接影响着二氧化硅溶胶微观结构,从而影响着所形成的硅胶薄膜的微结构。多孔硅胶膜的平衡吸湿量是致密硅胶薄膜的3倍;而疏松结构的硅胶薄膜的吸湿量高于多孔硅胶薄膜的吸湿量,且其吸附速率明显大于多孔硅胶薄膜的吸附速率。     

Direct Electrochemistry of Cytochrome c on a Silica Sol‐Gel Film Modified Electrode

Dilute silica sol‐gel was simply dropped on the surface of a basal plane graphite electrode (BPGE) to form a silica sol‐gel film modified electrode. Direct electrochemical response of cytochrome c (Cyt c) on the modified electrode was observed by cyclic voltammetry (CV). The results suggested that Cyt c could be tightly adsorbed on the surface of the silica sol‐gel film modified electrode. A couple of well‐defined and nearly reversible redox peaks can be observed in a phosphate buffer solution (pH 7.0), which anodic and cathodic peak potentials were at ?0.243 and ?0.306 V (vs. Ag/AgCl), respectively. Cyt c adsorbed on the surface of silica sol‐gel film shows a remarkable electrocatalytic activity for the reduction of oxygen. Based on these, a third‐generation biosensor could be constructed to detect the concentration of oxygen in aqueous solution.     

Highly Efficient and Stable Palladium Nanoparticles Supported on an Ionic Liquid Silica Sol?Gel Modified Electrode

A carbon ionic liquid electrode modified with a thin layer of silica sol? gel containing phosphinite ionic liquid was prepared for deposition of palladium nanoparticles. Palladium nanoparticles were formed easily by simple contact of the modified electrode with palladium chloride solution. The novel material overcomes the shortcomings of conventionally modified electrodes with a thin layer of silica sol? gel, due to the existence of ionic liquid in silica matrix. A crack‐free sol? gel matrix was obtained and also, the uniform porous structure of the ionic liquid‐sol? gel matrix resulted in a fast mass transport and increased ionic conductivity. The electrode exhibits high electrocatalytic effects towards hydrazine and ascorbic acid. It is very stable against repetitive cycling in the applied potential window.     

硅源对MCM-22分子筛合成及物化性质的影响

在动态水热条件下,研究了硅溶胶、白炭黑、硅酸及硅胶为硅源时对MCM-22分子筛合成及物化性质的影响。以硅溶胶、白炭黑、硅酸三种硅源均可合成出高结晶度且无杂晶的片状MCM-22分子筛,其平均粒径分别为190、220和750 nm。硅源影响分子筛的聚集形态,三种硅源分别形成晶粒分散、晶粒半分散及晶粒聚集形态。三组样品的酸强度分布基本一致,都具有较多的中强酸分布,由硅溶胶和硅酸所得MCM-22分子筛在中强酸范围具有更高的B/L酸比值,以白炭黑合成的分子筛总酸量最高。NMR结果表明,样品中的铝以骨架铝为主,不存在明显的非骨架铝。由于硅胶对合成体系中游离水的吸附作用,水热反应难以发生,不能得到MCM-22分子筛,硅胶作为分子筛合成硅源时需要选择合适的反应条件。     

Effect of sepiolite fiber on the structure and properties of the sepiolite/silica aerogel composite

Sepiolite fiber-reinforced silica aerogel composites for thermal insulators were prepared by dispersing sepiolite fiber in silica sol, aging, solvent exchanging, and drying in supercritical fluid. The surface treated sepiolite fiber and sepiolite/silica aerogel composite were characterized by scanning electron microscope; transmission electron microscope and Fourier transform infrared spectroscopy. The influence of surface treated sepiolite fiber on the mechanical and thermal properties of the aerogel composite was studied. The results indicate the hydroxyl groups on silica sol particles surface able to condense with the hydroxyls of sepiolite fibers with forming Si–O–Si between sepiolite fibers and aerogel matrix in the sol–gel process, which achieves excellent interfacial interaction in the sepiolite/silica aerogel composite, so the mechanical properties of the aerogel composite have been improved effectively without sacrificing much thermal insulating performance.