高分子纤维增韧SiO_2气凝胶复合材料的制备

以正硅酸乙酯为硅源,乙醇和水为溶剂,芳纶纤维为增强相,通过溶胶凝胶及常压干燥等步骤,实现了芳纶增韧SiO_2气凝胶复合材料的非超临界制备.采用扫描电镜、吸附-脱附等分析手段及热导率测试对所得气凝胶样品进行结构分析和性质表征.结果表明,调节反应体系的各反应参数可以获得具有不同外形、密度及热导率的复合材料;所得气凝胶平均孔径约为10～20 nm,比表面积可达1000 m~2/g,可望在隔热材料等领域得到应用.     

常压制备低密度高比表面积SiO_2气凝胶的工艺研究

以正硅酸乙酯、乙醇、去离子水、盐酸和氨水为原料制备出SiO_2凝胶后,经老化、表面改性、溶剂置换工艺,再通过常压干燥制备出SiO_2气凝胶,研究了表面改性及溶剂置换工艺对SiO_2气凝胶性能的影响.结果表明,随着表面改性次数和改性剂浓度的增加,气凝胶的密度和比表面积降低;溶剂置换对气凝胶的密度和比表面积影响不大.通过优化的工艺制备出的SiO_2气凝胶具有疏水性,与水的接触角约为118°,密度为0.124 g/cm~3,孔隙率94.3%,平均孔径为23.3 nm,比表面积712 m~2/g.     

稻壳灰制备掺杂TiO2硅气凝胶研究

以稻壳为硅源制备SiO2气凝胶，在溶胶凝胶过程中加入TiO2纳米粉末，可制得掺杂TiO2硅气凝胶。通过SEM、BET吸附．脱附测试等手段，与同种方法制得的纯SiO2气凝胶在结构和物性特征方面等进行了比较。结果显示，掺杂TiO2气凝胶的平均颗粒直径为50nm左右，而纯SiO2气凝胶的粒径约为20nm，且孔洞直径明显减小、孔径分布更为均匀；此外，TiO2纳米粉末的加入可以使气凝胶的弹性模量提高约23％，并且通过TiO2对气凝胶溶胶-凝胶过程的影响研究了其影响机理。     

低成本制备孔容和孔径可控的介孔二氧化硅

通过可控的溶胶凝胶过程,使用廉价的水玻璃为硅源、氨水为助剂制备了孔容和孔径可控的介孔二氧化硅.研究了溶胶凝胶过程中的影响因素.结果表明,控制氨水/二氧化硅的比例、水玻璃的浓度、凝胶温度和终点的pH值可以制备出介孔二氧化硅.制备的介孔二氧化硅的主要特点包括孔容高和孔径可调.     

常压干燥条件下基于甲基三甲氧基硅烷的二氧化硅气凝胶膜制备（英文）

硅源作为制备二氧化硅气凝胶前驱体的重要组成部分,对获得结构完整、性能优良的二氧化硅气凝胶至关重要。常压干燥条件下,采用溶胶-凝胶法,选择具有有机基团的硅源前驱体甲基三甲氧基硅烷(MTMS)成功制备了SiO_2气凝胶膜,并简化了常压制备SiO_2气凝胶膜的操作步骤。对样品的微观结构、折射率、孔隙率、透过率等进行了表征,研究了热处理温度对SiO_2气凝胶膜结构和性能的影响。结果表明:随着热处理温度升高,气凝胶膜的孔隙率增加、透过率升高。     

热处理温度对硅石气凝胶结构的影响

以水玻璃为硅源、甲酰胺为催化剂、乙二醇为干燥控制化学添加剂(DCCA),结合溶胶-凝胶法常压下干燥制备了硅石气凝胶粉体.采用BET,TG-DSC,XRD,SEM,FT-IR的方法研究了硅石气凝胶在热处理过程中的组成、结构及其组织形貌的变化特点.研究发现随着热处理温度的升高,气凝胶的堆积密度略有增加而比表面积却降低显著.在升温过程中,气凝胶中的-OH基团逐渐减少,到700℃时,气凝胶开始由无定型的SiO2转变为晶态SiO2.     

氧化硅气凝胶的高温性能

以正硅酸乙酯为硅源,在酸碱催化作用下通过溶胶-凝胶工艺得到SiO_2溶胶,经凝胶老化,超临界干燥得到SiO_2气凝胶。采用FT-IR、XRD、TG-DSC、SEM、BET等手段对SiO_2气凝胶在高温下的结构和性能进行了分析和表征。结果表明:SiO_2气凝胶经过600~900℃的热处理后,-OH数量减少,气凝胶仍然保持了非晶结构。经过1500s的热处理过后,气凝胶内部出现了微孔,导致材料比表面积增大。经900℃热处理9000s后,比表面积降为514.299m2/g,气凝胶团聚严重。     

溶胶-凝胶法制备硅石多孔材料

在酸性条件下,以水玻璃为硅源,通过溶胶-凝胶法制备了硅石气凝胶,然后用去离子水洗去钠离子,老化72 h后进行溶剂交换,经三甲基氯硅烷表面修饰后在常压下干燥,获得了孔径约20～50 nm的多孔材料.     

聚甲基硅倍半氧烷气凝胶的制备及相分离控制研究

以甲基三甲氧基硅烷(methyltrimethoxysilane, MTMS)为先驱体、二甲基亚砜(dimethylsulfoxide, DMSO)为溶剂,采用溶胶—凝胶法和超临界干燥技术制备了聚甲基硅倍半氧烷(polymethylsilsesquioxane, PMSQ)气凝胶。通过改变碱性催化剂氨水和DMSO的相对含量用量,获得了PMSQ凝胶时间的变化规律。PMSQ气凝胶具有典型的纳米多孔结构。凝胶时间随氨水用量的增加而缩短,随DMSO用量的增加而延长。DMSO含量越多,溶胶粘度变化越缓慢;氨水含量越多,粘度变化越快。不可水解基团–CH₃的存在将引起短链或环状Si–O–Si结构,造成颗粒团聚,产生沉淀,引起相分离。控制凝胶时间与相分离时间的关系,可获得均匀凝胶。     

碳纳米管掺杂SiO2气凝胶隔热材料的制备与性能表征

以正硅酸乙酯（TEOS）和碳纳米管（CNTs）为原料，采用溶胶-凝胶法和常压干燥法制备不同碳纳米管（CNTs）含量的SiO2气凝胶隔热材料。采用DET、SEM、XRD等测试方法考察了添加CNTs对SiO2气凝胶比表面积、孔结构特征和密度的影响。结果表明：添加CNTs不仅能够增强SiO2气凝胶的强度，而且能够在很大程度上提高气凝胶的比表面积，使孔结构分布更加均匀。     

Modified aging process for silica aerogel

To increase the porosity and monolithic performance of silica aerogel, two methods were used to age the silica gels derived from tetraethoxysilane (TEOS) by two-step sol–gel process: aging in 100 °C-autoclave with TEOS/ethanol mixed solution and in pure ethanol at room temperature. The structural characteristics and physical properties of the resultant two kinds of aerogels after supercritical CO₂ drying were investigated and compared with the help of infrared spectra (IR), N₂ absorption, differential scanning calorimetry (DSC)/thermogravimetry (TG) and high-resolution ²⁹Si nuclear magnetic resonance (NMR) techniques. Aging in 100 °C-autoclave yields silica aerogel with high pore size and pore volume, twice of that aged in ethanol at room temperature. High aging temperature and pressure can promote the dissolution and reprecipitation process of silica and the esterification process of silanols, which will enhance the backbone strength of silica gel, and hence produce silica aerogel with low bulk density, good monolithic performance and hydrophobic features. While the latter aging method produces silica aerogel with high bulk density and cracking appearance.     

Porous silica aerogel/honeycomb ceramic composites fabricated by an ultrasound stimulation process

The synthesis behavior of nanoporous hydrophobic silica aerogel in honeycomb-type ceramics was observed using TEOS and MTES. Silica aerogel in the honeycomb ceramic structure was synthesized under ultrasound stimulation. The synthesized aerogel/honeycomb ceramic composites were dried under supercritical CO₂ drying conditions. The values for the line shrinkage of the wet gels during supercritical CO₂ drying declined from 19% to 4% with an increase in the H₂O/TEOS molar ratio from 8 to 24. Low shrinkage was a key factor in increasing the interface compatibility with the aerogel/honeycomb ceramic composites. The optimum condition of silica aerogel in the honeycomb-type ceramic structure had a TEOS:MTES: H₂O:glycerol ratio equal to 1:1.2:24:0.05 (mol%).     

Preparation and characterization of CuO-CoO-MnO/SiO2 nanocomposite aerogels as catalyst carriers

CuO-CoO-MnO/SiO₂ nanocomposite aerogels were prepared by using tetraethyl orthosilicate (TEOS) as Si source, and aqueous solution of Cu, Co and Mn acetates as the precursors via sol-gel process and ethanol supercritical drying technique. The gelatination mechanism was investigated by nuclear magnetic resonance (NMR) and X-ray photoelectron spectroscopy (XPS). The microstructure and composition of the CuO-CoO-MnO/SiO₂ nanocomposite aerogels were characterized by field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), electron dispersive spectroscopy (EDS) and XPS. The specific surface area, pore size and pore size distribution of the nanocomposite aerogels were determined by the Brunauer-Emmett-Teller (BET) method. The products were analyzed by gas chromatography (GC). The results show that the CuO-CoO-MnO/SiO₂ nanocomposite aerogels are porous, with a particle size distribution of 10–150 nm, a pore size distribution of 2–16 nm, an average pore size of 7.68 nm, and a specific surface area of 664.4–695.8 m²/g. The molar fraction of transition metals in the nanocomposite aerogels is 0.71%-13.77%. This kind of structure is favorable not only to increase the loading of catalysts, but also to make full use of the effect of transition metal oxides as cocatalysts; CuO-CoO-MnO/SiO₂ nanocomposite aerogels can be used as a novel catalyst carrier in the safer and environment-friendly synthesis of diphenyl carbonate and other fields of catalysis.     

SiO2气凝胶及纤维复合SiO2气凝胶隔热材料表征方法

SiO₂气凝胶及纤维复合SiO₂气凝胶材料因轻质、高效、导热系数低等优点在保温隔热领域备受关注,应用前景广阔。其隔热性能、力学性能与微观结构、化学组成密切相关。本文对现阶段常见的微观结构、隔热性能、力学性能的表征方法做了介绍,常见的有密度、疏水角、晶态结构、微观形貌、比表面积及孔径分布、导热系数、化学组成、热稳定性、抗弯抗压等。综述了以上各种表征方法存在的优缺点及表征参数变化说明的问题。各种表征方法得到的表征参数之间存在紧密联系,需要从多角度理解和分析。     

溶胶-凝胶法有序介孔氧化硅薄膜的蒸发诱导自组装制备

以表面活性剂CTAB为模板,将TEOS与APTES以一定的比例混合,自组装共聚合成出有序介孔氧化硅薄膜,并采用XRD、FTIR、TEM、TGA及N2吸附等手段对PMO薄膜进行了表征,结果表明,当APTES/(TEOS APTES)比例为0.10时,介孔薄膜有序性最好,平均孔径为2.16 nm,比表面积达到1060 m2/g,孔容积达到0.76 cm3/g.     

可加工疏水SiO2气凝胶的制备及表征

介绍了一种基于正硅酸乙酯(TEOS)的疏水SiO2气凝胶的制备及其表征方法.结果表明,最后制备的气凝胶具有一定塑性,可进行机械加工.     

二氧化硅气凝胶及其复合材料吸声性能的研究进展

制备出良好的具有高孔隙率的吸声材料对于噪声的控制至关重要。二氧化硅气凝胶凭借其高孔隙率和高声阻抗近年来越来越受关注,将其与传统吸声材料相复合可显著结合两者的吸声优势,对于噪声的消除具有很重要的意义。介绍了吸声性能的概念、吸声结构、机理以及测量表征方法,深入探究了空气流阻、密度、厚度、孔隙率、孔径、杨氏模量以及颗粒大小对气凝胶吸声性能的影响规律,详细综述了二氧化硅气凝胶与有机物、有机物/无机矿物以及非织造布复合材料吸声性能的研究进展,最后展望了目前面临的挑战和未来的发展方向。