TiO2/SiO2复合气凝胶的制备与传热特性

针对SiO2气凝胶红外遮光性能差的问题,以纳米二氧化钛作为掺杂剂,以正硅酸乙酯(TEOS)为原料,采用溶胶-凝胶工艺和非超临界干燥方法制备了不同TiO2掺杂量的纳米孔改性SiO2气凝胶复合材料,研究了pH值和乙醇含量对凝胶时间的影响,并采用SEM、TEM和BET方法分别对凝胶的表面形貌和孔结构进行了分析表征.结果表明,当pH为6时,乙醇/TEOS为8∶1(摩尔比)时,可得到掺杂均匀、完整的TiO2/SiO2凝胶;热处理后的复合气凝胶具有网状纳米孔结构;当掺杂量小于5％时,干凝胶平均孔径为20～50 nm,比表面积均大于1 000 m2/g.通过红外透过率及消光性能比较,TiO2掺杂SiO2干凝胶复合材料的红外光屏蔽功能较纯SiO2气凝胶提高了50％.     

溶胶-凝胶法制备聚氨酯/二氧化硅杂化材料

为了获取一种新型的聚氨酯／二氧化硅杂化材料，采用溶胶-凝胶法制备了不同二氧化硅含量的聚氨酯／二氧化硅杂化材料，详细研究了加水量、催化剂HCl用量、温度对溶胶-凝胶过程的影响以及偶联剂的加入对杂化材料性能的影响；确定了实验最佳条件为：n(H2O)：n(TEOS)=4：1，n(HCl)：n(TEOS)=0．5：1，通过红外光谱、扫描电镜和光电子能谱等手段考察了杂化材料的结构与性能。结果表明：通过溶胶-凝胶法制备的PU／SiO2杂化材料中PU和SiO2形成了较强的化学作用，而不是简单的共混，同时随着SiO2含量的增加材料的脆性逐渐增大，但加入偶联剂后，材料的韧性又有所提高。     

复合硅源制备SiO_2气凝胶及改性研究

以正硅酸乙酯(Tetraethyl orthosilicate,TEOS)为主要硅源,以三甲基氯硅烷(trimethyl chlorosilane,TMCS)和r-缩水甘油基丙基三甲氧基硅烷(3-Glycidyloxypropyltrimethoxysilane,KH560)作为改性硅源,采用溶胶-凝胶法制备了二氧化硅(SiO_2)气凝胶。研究结果表明,改性后SiO_2气凝胶的接触角由27°提升至130°;在H_2O/TEOS摩尔比为5时,凝胶时间为3min;改性的SiO_2气凝胶为多孔结构,密度为0.22g/cm~3,孔隙率为89.9%,比表面积为870.42m~2/g,孔体积为1.38cm~3/g,平均孔径为48.6nm。     

二氧化硅溶胶稳定性的研究

二氧化硅溶胶是二氧化硅微粒分散于水中或有机溶剂中的胶体溶液, 在陶瓷、纺织、造纸、涂料、水处理、半导体等行业中有着广泛的应用。以正硅酸乙酯(TEOS)为原料, 乙醇为溶剂, 盐酸为催化剂, 用溶胶-凝胶工艺制备二氧化硅溶胶, 初步研究了溶剂、pH 值以及添加剂对二氧化硅溶胶稳定性的影响, 从而可以利用这些因素来实现对二氧化硅溶胶稳定性的控制。结果表明, 随着乙醇含量的增加, 溶胶的稳定性增加;无添加剂时, 随着pH 值的升高, 溶胶的稳定性也随之增加;在添加剂存在下, 随着pH 值增加, 溶胶的稳定性先增加后降低;加入添加剂DMF, 能使溶胶的凝胶时间延长;n (TEABr)/ n (TEOS)大于0 .05 时, TEABr 能使溶胶的凝胶时间延长。     

羧化纤维素气凝胶的制备及其对亚甲基蓝染料的吸附性能

为研究羧化纤维素气凝胶对亚甲基蓝的吸附性能,以微晶纤维素为原料,利用2,2,4,6-四甲基哌啶氧化物(TEMPO)介导氧化制备羧化纤维素,并通过冷冻干燥制备羧化纤维素气凝胶.通过电导率仪、红外光谱仪、热重分析仪和扫描电子显微镜对制备所得羧化纤维素气凝胶的羧基含量、形貌和结构进行表征,探究pH值、溶液初始质量浓度、温度等...     

离子液体[HMIM]Br和[HMIM]BF4对SiO2气凝胶制备的影响

利用离子液体[HMIM]Br、[HMIM]BF4作催化剂,TEOS作前驱体在常压下制备出了高孔隙率块状SiO2气凝胶,并研究了离子液体对气凝胶制备的影响.离子液体[HMIM]BF4比[HMIM]Br拥有更好的催化性能,可以大大缩短凝胶时间,且两种离子液体制备凝胶过程中,凝胶时间都随n(IL)/n(Si)的增加而逐渐延长.在n(IL)/n(Si)=1.5时,制得密度最小、孔隙率最大的气凝胶;n(IL)/n(Si)>1.5时,随离子液体的摩尔比率的增加,气凝胶的密度增大,孔隙率、成块性和透明性逐渐降低.     

离子液体[HMIM]Br和[HMIM]BF_4对SiO_2气凝胶制备的影响

利用离子液体[HMIM]Br、[HMIM]BF4作催化剂,TEOS作前驱体在常压下制备出了高孔隙率块状SiO2气凝胶,并研究了离子液体对气凝胶制备的影响。离子液体[HMIM]BF4比[HMIM]Br拥有更好的催化性能,可以大大缩短凝胶时间,且两种离子液体制备凝胶过程中,凝胶时间都随n(IL)/n(Si)的增加而逐渐延长。在n(IL)/n(Si)=1.5时,制得密度最小、孔隙率最大的气凝胶;n(IL)/n(Si)>1.5时,随离子液体的摩尔比率的增加,气凝胶的密度增大,孔隙率、成块性和透明性逐渐降低。     

纳米级SiO2玻璃粉的合成与表征

采用正硅酸乙酯为前驱物.用溶胶-凝肢法制备纳米级SiO2粉,分别用X射线衍射仪、透射电镜进行了表征,并探讨了水、乙醇用量及催化剂对凝胶时间和凝胶效果的影响.结果发现:在水解度为4,Elthanol/TEOS=3时,用HCl做催化剂,控制pH值为2-3,凝胶时间短且凝胶效果好.     

环氧树脂增强SiO2气凝胶复合材料的制备

以正硅酸乙酯（TEOS）为硅源,环氧树脂为增强相,采用溶胶一凝胶法常压制备了环氧树脂增强Si02气凝胶复合材料,研究了pH值、EtoH和环氧树脂含量与复合材料结构、密度的关系;采用SEM检测手段对复合材料断面的微观形貌进行了测试;采用TG-DSC进行了试样热分析,并采用阿基米德法测定了其密度．结果表明,加入环氧树脂后,气凝胶结构变化较大,而且乙醇、环氧树脂用量以及pH值对TEos的水解缩聚反应有较大影响;材料在600℃以下具有良好的稳定性．     

二氧化硅含量对形状记忆聚氨酯杂化材料性能的影响

以形状记忆聚氨酯(SMPU)为基体,正硅酸乙酯(TEOS)为前躯体,固体酸对甲基苯磺酸(PTSA)为催化剂,通过溶胶-凝胶法制备SMPU/SiO2有机-无机杂化材料。通过SEM、TGA和万能试验机等对材料的形貌结构、热力学和形状记忆性能进行测试和分析。结果表明:随着二氧化硅(SiO2)质量分数的增加,杂化材料的耐热温度有所提高;二氧化硅的加入,对杂化材料的力学性能和形状记忆性能具有较大的影响,在二氧化硅质量分数为2.7%时,杂化材料在具有良好的拉伸强度和模量的同时,仍然能保持较好的形状回复性能。     

硅气凝胶的研究进展

目前硅气凝胶是世界上最轻、隔热性最好、孔隙率较高且声传播速率较低的固体材料,由于其特殊的网络结构使其具有很多独特的性能。本文从其研究历史及现状出发,对其性能以及在不同方面的应用和制备原理进行了综述,并对其广阔的发展前景进行了展望。     

SiO2 Aerogels Prepared with Ambient Pressure Drying and Its Properties

SiO₂ aerogels were produced from tetraethyl orthosilicate (TEOS) as silicon resources, ethanol as solvent and watery HCl or ammonia by sol-gel method and surface modification at ambient pressure. Scanning electronic microscopy,Fourier transform infrared spectrometer (FT-IR),pore size distribution measurement, packing density and some other experiment methods were used to characterize the morphology and pore structure and other properties of the silica aerogels. The results show that the silica aerogels have a typical nano-porous microstructure with hydrophobic property. It was discovered that SiO₂ aerogels have better properties when the preparation condition is as following: the watery HCl concentration is 1%, the aging reagent is CH₃CHOHC₄H₉, the aging time is 20d, the volume concentration of trimethylchlorosilane (TMCS) in hexane is 6% and the surface modification time is 24h.     

纤维素/氧化硅有机-无机杂化复合气凝胶的研究进展

依据纤维素与SiO_2的复合工艺特点,综述了采用溶液浸渍法、直接混合法和逐层沉积法制备纤维素/SiO_2有机—无机杂化复合气凝胶材料的研究现状.探讨了纤维素的不同溶解或分散状态和SiO_2引入方式对形成纤维素/SiO_2复合气凝胶的影响,分析了纤维素与SiO_2之间具有的组织结构特征和结合机理,并对比了不同工艺方法获得的纤维素/SiO_2复合气凝胶材料在力学、隔热、光学、疏水性、生物等方面所呈现的性能特点.基于有机纤维素与无机SiO_2的物理化学特性,指出了两者复合时面临的问题,并对潜在的应用前景进行了展望.     

Preparation and adsorption property of hydrophobic SiO<Subscript>2</Subscript> aerogels modified by methyl triethoxysilane

The hydrophobic SiO2 aerogels were prepared by in-situ polymerization sol-gel method and supercritical drying of ethanol method with tetraethylorthosilicate(TEOS) as silica source, methyl triethoxysilane (MTMS) as modifier, ethanol as solvent. Moreover, the structure and adsorption property of SiO2 aerogels were also studied. As results, the surface area of SiO2 aerogels was 863.59 m2/g, the pore volume was 3.57 cm3/g, and the contact angle was 150 °. Adsorption intensity of silica aerogels for organic liquid (alkanes, benzene compounds, and nitro-compounds) is bigger than that of activated carbon. The mass of the liquid absorbed increased linearly with the surface tension of the liquid. The lower surface tension and boiling point are, the shorter desorption time is. After regenerating 10 times, nitromethane regeneration rate remain the same, and almost more than 94%. So SiO2 aerogels have good absorption and regeneration property.     

Mechanical properties of silica aerogels prepared from a mixture of TEOS and organo-alkoxysilanes of type R1SiX3

Silica aerogels were prepared from a mixture of tetraethylorthosilicate and organo- alkoxysilanes. The effects of organo-alkoxysilanes on the mechanical properties of the silica aerogels were studied. The flexibility of silica aerogels was significantly improved by incorporation of organo-alkoxysilanes. When MTES and TEOS were combined as precursors of silica areogels, with the increased amount of MTES, the apparent elastic modulus and apparent compressive strength monotonously rose. At the same organo- alkoxysilanes to TEOS ratio, the size of alkyl groups of the organo-alkoxysilanes had little effect on the mechanical properties. In series of MTES and TEOS, the lowest elastic modulus of silica skeleton and the highest compressive strength of silica skeleton were observed at MTES to TEOS ratio of around 50：50. At a certain organo-alkoxysilanes to TEOS ratio, the elastic modulus of silica skeleton increased and the compressive strength of silica skeleton decreased with the size increase of the alkvl grouns.     

氨水浓度对常压制备硅气凝胶片性能的影响

以甲基三甲氧基硅烷(MTMS)为前驱体,通过溶胶一凝胶法在常压下制备出密度在0.16～0.33 g/cm3问的白色疏水型硅气凝胶片.通过傅立叶变换红外光谱(FT-IR)、扫描电镜(SEM)、接触角(OCA)＼比表面分析仪(BET)、热重(TG)等对硅气凝胶片的性能和结构进行表征和初步研究.结果表明:在保持MTMS、甲醇与水的物质的量之比一定的情况下,氨水浓度变化对凝胶时间、所得硅气凝胶密度、收缩率和硅气凝胶片的完整性等影响较大.     

Synthesis and characteristics of mesoporous silica aerogels with one-step solvent exchange/surface modification

The synthesis procedures and physical properties of the ambient dried hydrophobic silica aerogels by using different contents of ethanol (EtOH)/trimethylchlorosilane (TMCS)/n-Hexane as surface modification agent were investigated. One-step solvent exchange and surface modification were simultaneously progressed by immersing silica hydrogels in EtOH/TMCS/n-Hexane solution. It is found that microstructures as well as properties of silica aerogels like porosity, specific density and specific surface area are affected by the contents of surface modification agent in the sol from the results of SEM, TEM morphology, FT-IR chemical structure, BET surface area and BJH pore size analyses. The volume of TMCS is of 10% and 20% of hydrogels, and the final product is hydrophilic xerogels. When TMCS’s percent (v/v) is elevated to 75%–100%, hydrophobic silica aerogels with good performance are synthesized, the porosities of aerogels are in the range of 93.5%–95.8% and the average pore size diameter is less than 20 nm. Funded by the National Mega-Project of Scientific & Technical Supporting Programs, Ministry of Science & Technology of China (No.2006BAJ04A 04), and the Science Foundation of Liaoning Province, China (No.20062147)     

植物多糖气凝胶材料应用的研究进展

植物多糖气凝胶是一种轻质多孔状材料,具有高孔隙率、高比表面积、低密度、环境友好等优异的性能. 本文系统介绍了植物多糖气凝胶材料制备方法、结构性能及其发展历程,并总结了其在不同领域的应用研究. 因其具有导热系数低、吸附能力强、释放药物量可控和具有一定的组织再生能力等特点,植物多糖气凝胶可作为隔热材料、吸附材料、药物包载材料和组织再生、创伤护理材料. 植物多糖气凝胶材料作为一种绿色环保型材料,在不同应用领域将有更广阔的应用前景.     

纤维素纳米纤维气凝胶的制备方法及应用进展

纤维素气凝胶作为继无机气凝胶和聚合物气凝胶之后的第三代气凝胶,在兼具第一、二代气凝胶共性的同时融入自身优异的特性,如绿色可再生性、生物相容性和降解性。纤维素气凝胶中的天然纳米纤维素气凝胶由于其优良的柔韧性和抗压缩性而备受研究者的青睐。本文综述了近年来纤维素纳米纤维(NFC)气凝胶的制备方法及其在隔热、储能和吸附等领域的功能化应用进展。最后,本文对NFC气凝胶的未来发展趋势进行了展望。