水热-凝胶法ZrO2 气凝胶的制备与表征

以硝酸氧锆为锆源,尿素为凝胶促进剂,通过水热凝胶法结合超临界乙醇干燥,可成功制备出具
有良好纳米三维网络结构的ZrO2 气凝胶。采用透射电镜(TEM)、比表面积及孔隙度分析仪(BET),X 射线衍
射仪等测试手段对其结构进行了表征与测试。结果表明,ZrO2 气凝胶主要由无定型和四方晶相组成,其比表
面积为445 m2 / g,孔径主要分布在5 ~7 nm 和30 ~40 nm 两处。     

柔性二氧化硅气凝胶综述

二氧化硅气凝胶具有低密度、高孔隙率、高比表面积、低导热性等特点,但存在强度低、韧性差等缺陷.在此基础上,柔性二氧化硅气凝胶通过改进传统二氧化硅气凝胶的制备工艺表现出了更优的力学性能与适用性.本文综述了国内外柔性二氧化硅气凝胶的最新研究进展,分析对比了不同类型气凝胶的性能参数;重点介绍了柔性二氧化硅气凝胶常用的制备方法,...     

氧化铝气凝胶复合高温隔热瓦的制备及性能

以陶瓷纤维制成的高温隔热瓦为骨架,真空浸渍氧化铝溶胶,再经过凝胶、老化和超临界干燥制备出氧化铝气凝胶复合高温隔热瓦,研究了其在不同温度处理后(最高温度1 400℃)的微观结构、隔热和力学性能。结果表明:气凝胶复合高温隔热瓦在1 400℃保温30 min后线收缩率仅为2%;随着热处理温度升高,气凝胶颗粒发生熔并、长大,气凝胶从填充纤维空隙到不断收缩,但对纤维骨架没有明显影响;隔热瓦的室温、高温热导率均显著降低;在热面1 400℃的背温测试中,复合后材料的背温从945℃降到870℃;复合后隔热瓦的力学性能略有增加;但是1 200~1 400℃的压缩强度下降较大。可见,气凝胶复合高温隔热瓦可改善其隔热性能,但在高温下力学性能下降。     

Spectroscopic evaluation of polyurea crosslinked aerogels,as a substitute for RTV-based chromatic calibration targets for spacecraft

Room temperature vulcanizing (RTV)-based components have been used on Mars Pathfinder, the Mars rovers, Spirit and Opportunity, as well as the Phoenix Lander as a support matrix for pigmented panoramic camera calibration targets. RTV 655 has demonstrated superiority to other polymers due to its unique range of material properties namely mechanical stability between −115 and 204 °C and UV radiation tolerance. As a result, it has been the number one choice for many space-related missions. However, due to the high mass density and the natural tendency for electrostatic charging RTV materials have caused complications by attracting and retaining dust particles (Sabri et al., 2008). In the current project we have investigated the relevant properties of polymer-reinforced (crosslinked) silica aerogels with the objective of substituting RTV-based calibration targets with an aerogel based design. The lightweight, mechanical strength, ability to accept color pigments, and extremely low dust capture makes polyurea crosslinked aerogels a strong candidate as a chromatic standard for extraterrestrial missions. For this purpose, the reflection spectra, gravimetric analysis, and low temperature response of metal oxide pigmented, polyurea crosslinked silica aerogels have been investigated and reported here.     

气凝胶中遮光剂的辐射特性计算及优化设计

以TiO2 微米颗粒为例,计算了不同形状遮光剂颗粒的光学特性,表征形状、尺寸对颗粒光学特性
的影响,并考虑实际遮光剂颗粒的粒径分布,计算了不同形状颗粒的平均光学特性。为满足工程需要,针对球
形遮光剂,给出了粒径服从对数正态分布律时使材料高温下辐射热导率最小的遮光剂参数优化设计,由此可使
1 300 K 下遮光气凝胶的辐射热导率降低至纯气凝胶的1/10 左右。     

SiO2气凝胶制备及疏水改性研究

采用六甲基二硅氮烷(HMDZ)和六甲基二硅氧烷(HMDSO)为表面改性剂,对正硅酸乙酯(TEOS)经溶胶-凝胶过程制备的凝胶进行表面改性,大幅度简化了洗涤过程,常压干燥制备了疏水SiO2气凝胶,并研究了表面改性剂对SiO2气凝胶结构和性能的影响.结果表明,所制备的疏水SiO2气凝胶有良好的疏水性能,吸附水量低于3%,与水的接触角大于130°;疏水SiO2气凝胶的密度、比表面积和孔隙率分别为150～225 kg/m3、750～900 m2/g和88%～93%,其颗粒尺寸为1～100 nm.     

Thermal conductivity studies of a polyurea cross-linked silica aerogel-RTV 655 compound for cryogenic propellant tank applications in space

Silica-based aerogel is an ideal thermal insulator with a makeup of up to 99% air associated with the highly porous nature of this material. Polyurea cross-linked silica aerogel (PCSA) has superior mechanical properties compared to the native aerogels yet retains the highly porous open pore network and functions as an ideal thermal insulator with added load-bearing capability necessary for some applications. Room temperature vulcanizing rubber-RTV 655—is a space qualified elastomeric thermal insulator and encapsulant with high radiation and temperature tolerance as well as chemical resistance. Storage and transport of cryogenic propellant liquids is an integral part of the success of future space exploratory missions and is an area under constant development. Limitations and shortcomings of current cryogenic tank materials and insulation techniques such as non-uniform insulation layers, self-pressurization, weight and durability issues of the materials used, has motivated the quest for alternative materials. Both RTV 655 and PCSA are promising space qualified materials with unique and tunable microscopic and macroscopic properties making them attractive candidates for this study. In this work, the effect of PCSA geometry and volume concentration on the thermal behavior of RTV 655—PCSA compound material has been investigated at room temperature and at a cryogenic temperature. Macroscopic and microscopic PCSA material was encapsulated at increasing concentrations in an RTV 655 elastomeric matrix. The effect of pulverization on the nanopores of PCSA as a method for creating large quantities of homogeneous PCSA microparticles has also been investigated and is reported. The PCSA volume concentrations ranged between 22% and 75% for both geometries. Thermal conductivity measurements were performed based on the steady state transient plane source method.     

气凝胶隔热材料在空间探测领域研究与应用进展

气凝胶材料具有纳米颗粒组成的骨架结构,形成独特的纳米尺度孔洞,密度和热导率极低,可以节省航天器空间和质量资源,是空间探测领域极端低温和高温温度环境（-230～1 800℃）下优选的隔热保温材料。本文详细综述了气凝胶材料在国内外航天器中装置隔热、空间电源保温、低温储箱保温以及星际宇航服等领域应用进展,并对气凝胶在空间探测中的未来发展进行了展望。     

刚性隔热材料的力学性能

采用纤维烧结法制备了刚性隔热材料,研究了材料密度、纤维取向、测试温度、与气凝胶复合等因素对材料力学强度的影响规律.结果表明:隔热材料力学强度随着密度的提高而增加;隔热材料平面方向拉伸和压缩强度均达到厚度方向的4倍以上;800和1 000℃下,材料的压缩强度保持率分别达到90%和50%;与气凝胶复合后隔热材料在拉伸强度维持不变的情况下,压缩强度增加35%以上.     

SiO2气凝胶骨架增强改性研究进展

分析SiO_2气凝胶骨架增强改性的特点,阐述了共前驱体、化学添加剂、老化、表面改性和热处理工艺在SiO_2气凝胶骨架增强方面的国内外研究动态和未来发展趋势,以期为设计并优化SiO_2气凝胶的微结构及性能提供理论依据和方法。