纳米银-二氧化硅粒子的制备及其在抗静电PET中的应用

以正硅酸乙酯(TEOS)、硝酸银、硼氢化钠等为原料,通过溶胶凝胶法制备了纳米银-二氧化硅粒子,用扫描电子显微镜(SEM)、X射线能谱(EDS)对纳米银-二氧化硅粒子进行了表征.将所制得的纳米银-二氧化硅粒子应用于聚对苯二甲酸乙二醇酯(PET)中,制得到了抗静电的聚对苯二甲酸乙二醇酯,对其电阻率的测试表明聚酯/纳米银-二氧化硅粒子复合材料有较好的抗静电性能.     

常压制备疏水型二氧化硅气凝胶及透光率分析

采用溶胶-凝胶法,通过常压干燥制备了疏水型二氧化硅气凝胶。研究了pH、水解时间等因素对二氧化硅气凝胶透光率的影响。以正硅酸乙酯为原料,通过酸（草酸）-碱（氨水）两步催化,采用溶胶-凝胶法常压干燥制备了疏水型介孔二氧化硅气凝胶。正硅酸四乙酯、乙醇、草酸、氨水物质的量比为1∶4∶5∶0.2,草酸和氨水的浓度分别为0.008、0.05 mol/L时,采用二甲基二氯硅烷为改性剂常压制备了二氧化硅气凝胶。透射电镜、扫描电镜测试表明：二氧化硅气凝胶具有纳米介孔结构。接触角测定表明：二氧化硅气凝胶与水的接触角为148°,表现出疏水性。     

纳米二氧化锡的多种方法制备、表征及其对比

本文采用共沸蒸馏法、水热法、溶胶-凝胶法分别制备纳米SnO2粉体,所制得的SnO2粉体利用X-射线衍射(XRD)和扫描电子显微镜(SEM)表征。结果表明,3种方法制备得的粉体均为四方金红石结构,共沸蒸馏法所得粉体平均颗粒约为20nm。水热法所得粉体的平均颗粒约为10nm。溶胶-凝胶法所得粉体的平均颗粒约为70nm。研究不同制备方法合成纳米SnO2粉体在合成工艺,生产周期,产物颗粒大小等方面的优缺点。     

毛竹NFC/SiO_2气凝胶的制备和疏水改性

以毛竹为原料,高压均质法制备纳米纤丝化纤维素(NFC),再采用溶胶―凝胶法制备NFC/二氧化硅(SiO_2)气凝胶。采用傅里叶变换红外光谱(FTIR)、X射线衍射(XRD)、扫描电子显微镜(SEM)、能谱(EDS)等对其进行表征,通过改变正硅酸乙酯/无水乙醇的体积比获得样品微观形貌较佳的反应工艺条件,并采用十八烷基三氯硅烷的正己烷溶液对NFC/SiO_2气凝胶进行疏水改性,用接触角测量仪测试改性NFC/SiO_2气凝胶的疏水性能。研究结果表明NFC/SiO_2气凝胶在正硅酸乙酯/无水乙醇体积比为1.25%时,二氧化硅复合效率高,且所获得的气凝胶形貌较好,二氧化硅以颗粒的形式附着在纳米纤丝化纤维素表面。改性NFC/SiO_2气凝胶接触角为132°,达到疏水状态。     

二氧化硅气凝胶/玻纤棉复合材料 导热性的研究

设计制备了二氧化硅气凝胶粉体材料,使用KH550将其表面改性后与粘结剂醋酸乙烯-乙烯共聚乳液搅拌为混合液,在超声波清洗器中将厚度为9mm的玻璃纤维针刺棉浸入混合液中之后,干燥制备得二氧化硅气凝胶/玻纤棉复合材料。结果表明采用KH550表面改性的二氧化硅气凝胶材料在水性粘结剂中的溶解性良好,超声波处理有助于二氧化硅气凝胶材料均匀分散于玻璃纤维棉中;含二氧化硅气凝胶材料的玻璃纤维棉导热系数明显下降,且随温度升高,其隔热性能比普通玻璃纤维棉更好。对二氧化硅气凝胶/玻纤棉复合材料的导热机理进行了研究,结果表明二氧化硅气凝胶材料的存在有效削弱了玻璃纤维棉的热桥效应及其气相导热效果。     

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。     

疏水性二氧化硅气凝胶的合成及表征

本文以正硅酸乙酯为原料,经溶胶-凝胶过程制备二氧化硅醇凝胶,再利用二甲基二氯硅烷对醇凝胶进行化学表面修饰,最后用超临界干燥方法制备了疏水性二氧化硅气凝胶.运用红外光谱、BET、扫描电镜、X射线衍射等测试方法对制得样品的结构、形貌及化学组成进行了分析.结果表明该样品是表面存在疏水基团-CH3 的疏水性SiO2 气凝胶,是呈连续网络结构的球状纳米粒子,孔径分布主要集中在2～10 nm,是热稳定性较高的非晶、多孔、轻质介孔材料.     

溶胶凝胶法制备SiO2气凝胶/纤维复合材料及其性能的表征

以正硅酸乙酯（TEOS）为前躯体,采用溶胶-凝胶工艺制备氧化硅溶胶,将其与无机陶瓷纤维预置体在常温下复合干燥后得到SiO2气凝胶隔热复合材料。利用扫描电子显微镜（SEM）对样品微观结构进行分析,利用热平板法对材料的热学性能进行表征,分析了氧化硅气凝胶隔热复合材料隔热机理。研究表明：采用溶胶凝胶工艺和真空技术,气凝胶充分填充在纤维预置体的空隙中,可以制得低导热系数、低热扩散系数和低比热容的SiO2气凝胶/纤维复合材料,导热系数为0.06815W/mK,热扩散系数为0.2677mm^2/s,比热容为0.2919MJ/m3K。     

超声波辅助溶胶-凝胶法制备SnO2纳米晶的研究

以SnCl4·5H2O和氨水为主原料,采用超声波辅助溶胶-凝胶法成功合成出了SnO2纳米晶,并讨论了制备过程中超声波作用时间、超声波的有无、烧结温度和表面活性剂等因素对纳米晶性能的影响。样品采用XRD,TEM进行了表征。结果表明,超声波辅助溶胶-凝胶法合成的SnO2微粒呈圆球形,粒径在20 nm左右,其中阴离子表面活性剂-柠檬酸对SnO2纳米晶的团聚能够起到很好的分散作用。     

二氧化硅气凝胶的制备工艺与应用

三维纳米孔隙结构的二氧化硅气凝胶具有孔隙率高、密度低、比表面积大等基本特征,这些优异的特性使二氧化硅气凝胶在许多领域得到广泛研究和应用。二氧化硅气凝胶一般通过溶胶-凝胶过程、老化、干燥处理得到。主要总结了二氧化硅气凝胶的制备过程及机理,介绍二氧化硅气凝胶的相关领域的应用,并对二氧化硅气凝胶材料的发展前景进行了展望。     

Zirconia aerogels: Effect of acid used in the sol-gel process on morphological properties

Zirconia aerogels have been prepared from butanolic zirconium(IV) tetra-n-butoxide diluted in ethanol via stoichiometric hydrolysis with water in ethanol. Nitric acid or acetic acid were used to modify the sol-gel process. After calcination in air at 573 K, the aerogel prepared with nitric acid possesses a specific surface area of 240 m² · g^–1 and a unimodal pore size distribution with a maximum at ca. 24 nm, whereas the use of acetic acid results in an aerogel with specific surface area of 228 m² · g^–1 and bimodal pore size distribution with maxima at 3 and 65 nm. The crystalline fractions of both aerogels are predominantly tetragonal with a small contribution of monoclinic ZrO₂.     

Acetic Acid Catalyzed Carbon Aerogels

We prepared carbon aerogels with a wide range of structural properties and densities using the weak acetic acid as a catalyst. Two series of acetic acid catalyzed carbon aerogels with different dilution of the catalyst and the monomers were investigated accurately. Structural investigation was performed via (U)SAXS, gas sorption and SEM. The pore and particle size can be tailored according to the used amount of monomers and catalyst, respectively. The connectivity of the primary particles turned out to be exceptionally high, as was found from SEM photographs and is reflected in a large elastic modulus and a high electrical conductivity. IR transmission spectra of the acetic acid catalyzed resorcinol-formaldehyde aerogels indicate the existence of a carbonyl group within the aerogel network, which may be important for the structural development of the this gel. As no metal containing catalyst was employed, the resulting carbon aerogels are extremely pure.     

以水玻璃为硅源制备纳米孔超级绝热材料

采用廉价的水玻璃为硅源，通过溶胶凝胶法，用离子交换树脂除去钠离子，并进行溶刑替换，用三甲基氯硅烷进行表面修饰，采用常压干燥，制备出具有纳米多孔结构的SiO2超级绝热材料，并用扫描电镜、孔径分布测试仪等对其结构进行表征。     

SiO_2气凝胶超临界干燥工艺参数的优化

用溶胶-凝胶两步催化法和乙醇超临界干燥法制备了S iO2气凝胶。以密度为评价标准,设计了四因素、三水平的正交实验研究乙醇超临界干燥工艺(乙醇的用量、预加压力、超临界温度和超临界压力)。结果表明,最佳工艺条件为:乙醇400 mL,预加压8 MPa,超临界温度270℃,超临界压力12 MPa,得到样品的密度为0.091 1 g/cm3,并通过SEM、TEM、FTIR对其微观结构进行了研究。     

酸碱催化剂浓度对柔性硅气凝胶性能和结构的影响

以甲基三甲氧基硅烷(MTMS)和正硅酸乙酯(TEOS)作为混合硅源,甲醇为溶剂,十六烷基三甲基溴化铵(CTAB)为表面活性剂,通过酸碱两步催化溶胶凝胶法制备醇凝胶,经超临界干燥可以制备高弹性疏水块状硅气凝胶。分别采用0.1 mol·L^-1 和0.01 mol·L^-1 的草酸作为酸催化剂,5 mol·L^-1 和10 mol·L^-1 的氨水作为碱催化剂,研究不同酸碱催化剂浓度对其网络结构的影响。发现高浓度酸和高浓度碱以及低浓度酸和低浓度碱作为催化剂合成的硅气凝胶的网络结构更加均匀,孔径分布更窄。其中,在草酸浓度为0.01 mol·L^-1、氨水浓度为5mol·L^-1 时,所得硅气凝胶密度为0.135 g·cm^-3、比表面积为807 m²·g^-1、孔隙率约为93%,凝胶最大可压缩至其起始长度的60%,压缩回弹率为100%。     

Preparation and characterization of zirconia-phosphate aerogels

Zirconia-phosphate aerogels were prepared by two methods: a one-step sol-gel synthesis followed by supercritical drying and an incipient wetness impregnation synthesis of a calcined zirconia aerogel. These samples were characterized by nitrogen adsorption, X-ray diffraction, infrared spectroscopy, and 1-butene isomerization. We identified both the conditions when zirconia-phosphate aerogels possess Bronsted acid sites, and the phosphate species responsible for their generation.     

乙醇胺为碱性催化剂对硅气凝胶性能的影响

以正硅酸乙酯为硅源,盐酸为酸性催化剂,乙醇胺(一乙醇胺、二乙醇胺、三乙醇胺)、氨水为碱性催化剂,采用酸碱两步催化溶胶-凝胶法制备二氧化硅湿凝胶,凝胶不经过表面改性,采用真空干燥制得二氧化硅气凝胶。通过对二氧化硅气凝胶样品进行比表面积测定和扫描电镜观察,表明添加不同的乙醇胺所得二氧化硅气凝胶的性能不同。采用乙醇胺作催化剂与氨水作比较所得二氧化硅气凝胶平均孔径较大。采用一乙醇胺作催化剂与氨水作比较,在添加量为（5.1～8.5）×10^-2  mol时,所得二氧化硅气凝胶的吸附能力提高,内表面粗糙度减小,孔隙率提高,减轻了孔壁的坍塌。采用二乙醇胺作催化剂与其他碱性催化剂作比较,随着其添加量的增加所得二氧化硅气凝胶平均孔径增加幅度较大。采用三乙醇胺作催化剂与其他碱催化剂相比,所得二氧化硅气凝胶的内部表面最粗糙。     

Fabrication and microstructure evolution of monolithic bridged polysilsesquioxane-derived SiC ceramic aerogels

SiC aerogels are representative high-temperature ceramic aerogels that have demonstrated extensive potential utility in the thermal insulation field under extreme conditions. Although the efficient fabrication of monolithic and highly crystalline SiC aerogels is crucial, it remains highly challenging. Herein, a one-step pyrolysis strategy of a bridged polysilsesquioxane (BPSi) aerogel precursor is reported. The preceramic BP aerogel was prepared via a sol-gel method followed by vacuum drying, and the subsequent pyrolysis process conveniently converted the BPSi aerogel precursor into a SiC aerogel. This circumvents the need for harsh synthetic conditions, high-cost noble metal catalysts, special drying, and additional calcination processes. Furthermore, a competitive mechanism between the “gas-escape” caused by the volatilization of low molecular compounds and carbothermal reduction reaction, and the “volume-shrinkage” resulting from high-temperature sintering was proposed to explain the evolution of phase composition and pore hierarchy of BPSi-derived ceramic aerogels.     

超临界C02干燥法工艺条件对氧化锆气凝胶结构性质的影响

以无机盐ZrOCl2·8H2O为原料,采用溶胶-凝胶过程结合超临界CO2干燥法制备了ZrO2气凝胶.采用BET、TG/DTA、XRD、TEM以及SEM等手段对样品进行了表征分析.考察了超临界CO2干燥过程中,操作压力、操作温度、CO2流率及干燥时间等工艺条件对样品比表面积、孔性质等的影响.结果表明利用本方法制备的ZrO...     

Adsorption of Ce(IV) Ions from Aqueous Solution by Silica Aerogels

The adsorption process of Ce(IV) ions from aqueous solution by the silica aerogels was studied. The silica aerogels with hydrophobicity were prepared by the sol-gel process, supercritical drying, and heat treatment. The SEM image and nitrogen adsorption-desorption isotherm show that the heat-treated silica aerogel was a co-continuous porous structure with high BET surface area and narrow pore size distribution. The adsorption of Ce(IV) ions onto the silica aerogels was found to be fitted well by pseudo-second-order kinetics and Langmuir isotherm model. The activation energy for Ce(IV) adsorption onto silica aerogels could be calculated to be about 17.88 kJ/mol, which implied that the attractive forces of adsorption were weak electrostatic forces accompanying most ion-exchange reactions. The thermodynamic parameters showed that the adsorption process was spontaneous and endothermic.