二氧化硅气凝胶的研究进展

探究了二氧化硅气凝胶的成型机理和制备方法的差异对气凝胶性能的影响,阐明现阶段二氧化硅气凝胶高温条件下结构坍塌、性能衰减的原因及其在吸附、建筑保温等领域的应用效果。     

SiO_2气凝胶的制备及在保温隔热领域中的应用

由于SiO_2气凝胶拥有极高的比表面积、低密度、低导热系数,因而引起科学界的兴趣。气凝胶通过溶胶-凝胶法合成,为了维持气凝胶的多孔结构通常气凝胶需要进行疏水改性,并通过特殊的干燥方法进行干燥。考虑到气凝胶的优异性能,主要讨论气凝胶的干燥技术以及在保温隔热领域中的应用。     

二氧化硅气凝胶在反射隔热涂料中的应用

为了提高SiO₂气凝胶在反射隔热涂料中的分散性,减少其用量从而降低涂料的成本,促进其在未来的推广与应用,以Zeta电位和透光率为评价指标,研究了几种助剂的用量、分散方法与时间和pH对SiO₂气凝胶分散效果的影响。在分散剂用量为1.50%,SiO₂气凝胶用量为1.00%,润湿剂用量为0.75%,稳定剂用量为1.50%,pH为7.5,10 000 r/min分散10 min的条件下可以制得均匀的SiO₂气凝胶浆料。含1.00%SiO₂气凝胶的反射隔热涂层的导热系数低至0.065W/(m·K),太阳光反射率达91.0%,隔热温差为15.8°C,表现出良好的保温隔热效果。     

二氧化硅气凝胶用纤维研究进展

介绍了纤维/SiO₂气凝胶复合材料的制备方法,综述了纤维种类、纤维有关参数对复合材料最终性能影响的研究进展。指出与纤维相关的一些参数有着明显的交叉影响关系,在嵌入纤维过程中需重点处理好纤维相关参数之间的关系,还需着重关注任何可以导致SiO₂气凝胶孔径增大的网络结构的因子,为SiO₂气凝胶复合材料在隔热领域中的研究和应用提供了参考。     

气凝胶在建筑保温隔热涂料中的应用研究

在满足保温隔热涂料导热系数和力学性能要求时,单独使用气凝胶会导致体系收缩率较高,且大量使用气凝胶成本过高,并无实用价值。本研究主要利用气凝胶的热学性能,并配合使用膨胀玻化微珠、膨胀珍珠岩作为保温隔热骨料,制得具有实用性的保温隔热涂料。试验结果表明,随着保温隔热骨料配比的增加,保温隔热涂料的干密度、抗拉强度降低;保温隔热涂料的黏结强度和抗拉强度都随着S-400弹性建筑乳液配比的提高而显著增大;随着气凝胶配比的增加,涂层的干密度、导热系数和抗拉强度降低。     

二氧化硅气凝胶的研究进展

介绍了二氧化硅(SiO_2)气凝胶的发展历程,总结了SiO_2气凝胶的制备方法和应用,从疏水化、增强改性、掺杂改性等几个方面介绍了SiO_2气凝胶的研究进展。     

二氧化硅气凝胶隔热涂料的性能评价

通过控制合适的条件,将SiO2气凝胶微球加入到纯丙乳液中,混合其它助剂,制成SiO2气凝胶隔热涂料;并运用相关国家标准提供的方法对其进行性能检测。实验结果表明,它具有较好的液态性能、颜色和外观、硬度和附着力、耐水耐热性和隔热性;在实验探索中,还建立了一套针对于SiO2气凝胶隔热涂料的性能评价体系。     

二氧化硅气凝胶及复合体的应用研究进展

二氧化硅气凝胶具有低密度、高孔隙率、高比表面积、低导热率、物化性能稳定等特点,广泛应用于隔热、隔音、催化传输、吸附过滤、光电子等领域。介绍了以稻壳灰、粉煤灰和多晶硅副产四氯化硅等固废资源为硅源,采用喷雾冷冻干燥和燃烧干燥等技术制备二氧化硅气凝胶及复合体作为吸附材料和催化材料应用的研究进展。     

SiO2气凝胶保温隔热材料及其在建筑节能中的应用

建筑节能是全球关注的课题,新材料是影响建筑节能的关键之一。SiO₂气凝胶超低导热系数、A级不燃、吸湿率低、轻质等特点,被誉为“改变世界的神奇材料”,在建筑保温隔热领域有着广阔的应用前景,是未来建筑节能领域中理想的新型建筑材料。以建筑节能减碳为目标,重点阐述了SiO₂气凝胶保温隔热材料的种类及其在建筑领域应用现状。     

二氧化硅气凝胶复合隔热材料研究进展

二氧化硅气凝胶具有高孔隙率、低热导率等特点,使其成为新型超级隔热材料。然而,二氧化硅气凝胶的柔韧性、整体性差,并且常温干燥制备的气凝胶在高温时热导率迅速上升,这些都大大限制了二氧化硅气凝胶的应用。近些年,通过原位溶胶-凝胶法和模压成型法制备得到的二氧化硅气凝胶复合隔热材料,在一定程度上提高了其韧性、整体性和高温隔热性能,使得二氧化硅气凝胶作为单独块体隔热材料成为可能。本文阐述了二氧化硅气凝胶隔热材料的隔热机理,综述了近年来抗辐射型、纤维增强型和聚合物增强型二氧化硅气凝胶复合隔热材料的研究现状,最后讨论了该领域今后研究趋势。     

氧化硅气凝胶绝热材料及其建筑减碳应用

无机氧化硅气凝胶因具有超低导热系数、A级不燃、吸湿率低、轻质等特点,在航天航空、工业及建筑领域的节能减碳方面具有广泛的应用潜力。然而氧化硅气凝胶力学性能差、制备成本高等缺点限制了其发展应用。介绍了氧化硅气凝胶绝热材料制备工艺的研究进展,对氧化硅气凝胶在建筑领域的应用形式（如超轻气凝胶泡沫混凝土、超高性能气凝胶保温隔热板、超低传热系数气凝胶节能玻璃等）进行了综述,并对氧化硅气凝胶在建筑节能领域的发展方向进行了展望。响应碳中和发展目标,随着气凝胶制备技术的发展与成本降低,氧化硅气凝胶绝热材料将在建筑墙体保温隔热方面广泛应用,同时对其性能提出了更多功能性要求,对氧化硅气凝胶材料还需开展更系统的基础研究以及工程应用技术研发,推动建筑领域的节能减碳与可持续发展。     

A novel strategy for the construction of silk fibroin–SiO2 composite aerogel with enhanced mechanical property and thermal insulation performance

The practical application of silica aerogels is an enormous challenge due to the difficulties in improving both mechanical property and thermal insulation performance. In this work, silk fibroin was used as scaffold to improve the mechanical property and thermal insulation performance of silica aerogels. The ungelled SiO₂ precursor solution was impregnated into silk fibroin to prepare silk fibroin–SiO₂ composite aerogels via sol−gel method followed by freeze-drying. By virtue of the interfacial hydrogen-bonding interactions and chemical reactions between silk fibroin and silica nanoparticles, SiO₂ was well-dispersed in the silk fibroin aerogel and composite aerogels exhibited enhanced mechanical property. By increasing the loading of silk fibroin from 15 wt % to 21 wt %, the maximum compressive stress was enhanced from 0.266 to 0.508 MPa when the strain reached 50%. The thermal insulation performance of the composite aerogels was improved compared with pure silica aerogel, as evidenced that the thermal conductivity was decreased from 0.0668 to 0.0341 W∙m^‒1∙K^‒1. Moreover, the composite aerogels exhibited better hydrophobicity and fire retardancy compared to pure silica aerogel. Our work provides a novel approach to preparing silk fibroin–SiO₂ composite aerogels with enhanced mechanical property and thermal insulation performance, which has potential application as thermal insulation material.     

影响二氧化硅气凝胶隔热涂料热导率的因素

采用溶胶凝胶法及雾化技术制备了二氧化硅气凝胶微球,同时制备了二氧化硅气凝胶隔热涂料。利用扫描电镜（SEM）对涂料的微结构进行观测,采用激光粒度检测仪对二氧化硅气凝胶微球的尺寸进行检测,采用Hot Disk热导率仪测量了二氧化硅气凝胶隔热涂料的热导率。结果显示：根据SEM 图像,气凝胶微球在涂料中形成明显团聚,且在气凝胶体积分数较高时,涂料中气孔增多。此外,小粒径气凝胶微球更容易形成团聚。由于气凝胶微球热阻极大,气凝胶隔热涂料的热导率随气凝胶微球含量的增加而下降。气凝胶微球的团聚相比均匀分散不利于热导率的降低,而孔隙的增多则有利于涂料热导率下降,因为空气的热阻高。小粒径微球的界面热阻比大粒径微球更大,导致小粒径微球制备的隔热涂料热导率低,混合粒径使气凝胶微球堆积密度增大,有利于降低涂料的热导率。     

Opacifier embedded and fiber reinforced alumina-based aerogel composites for ultra-high temperature thermal insulation

A novel method was developed to uniformly disperse sub-micron TiO₂ opacifier into fiber reinforcements using agar and silica as binders via freeze drying. TiO₂ opacifier/ fiber/ alumina-based aerogel ternary (TFA) composites with high strength and excellent high-temperature thermal insulation were successfully prepared by sol-gel route, impregnation process and supercritical fluid drying. The microstructure, mechanical and thermal insulation properties of TFA composites were investigated comprehensively. The results show that the mechanical property of TFA composites can be significantly enhanced by mullite fiber felt and the incorporation of SiO₂ binder. The effect of TiO₂ opacifier on the high-temperature thermal conductivity was studied by adjusting the content of TiO₂ from 0 to 15 wt%. The obtained TFA composites exhibit high Young's modulus of up to 3.58 MPa and low high-temperature thermal conductivities of 0.129 W/m·K at 800 °C and 0.168 W/m·K at 1000 °C, respectively. The mechanism of heat transfer in TFA composites at high-temperature was also analyzed.     

二氧化硅气凝胶高温稳定性研究

二氧化硅气凝胶具有极高的孔隙率和非常低的热导率,在保温隔热领域应用前景十分广阔。探究了二氧化硅气凝胶在不同温度热处理条件下热导率的变化情况,并从微观结构角度解释了其变化机理。随着热处理温度升高,气凝胶热导率先降低后升高。当热处理温度低于400 ℃时,气凝胶的热导率随热处理温度的升高而降低,这是因为较低温度的热处理去除了气凝胶内部的大部分杂质,并且使气凝胶的内部孔隙结构更加均匀;当热处理温度处于400~700 ℃时,更高温度的热处理使得气凝胶内部的孔径明显增大,气凝胶颗粒增大,使得热导率随热处理温度的升高而增加;当热处理温度高于700 ℃时,气凝胶颗粒开始烧结,骨架结构坍塌,密度显著增大,热导率也急剧上升,此时已不具备气凝胶轻质多孔的典型特征,可以认为已经失效。实验结果对亲水型气凝胶的应用给出了一定的指导:为保证气凝胶绝热能力的最优化,可以对气凝胶在400 ℃的温度下进行一段时间的保温;工作温度应在700 ℃以下,温度的升高会轻微降低气凝胶的隔热能力;气凝胶在700 ℃以上时会失去其绝热能力,因此不宜用于温度高于700 ℃的环境。     

Elytra-mimetic ceramic fiber aerogel with excellent mechanical,anti-oxidation,and thermal insulation properties

High-performance thermally insulating aerogel with low density, high porosity, and low thermal conductivity characteristics was widely used in heat insulation. However, the large-scale application of aerogel was still limited by its brittleness and infrared radiation transparency at high-temperature. Fiber composite aerogel had achieved significant progress, but its anti-oxidation ability was poor, and its thermal insulation required further improvement at ultra-high temperatures. Herein, inspired by the structure of elytra, nanoparticle fiber (NF) was prepared by electrospinning of coaxial fiber loaded with opacifier and antioxidant nanoparticles. The NF was incorporated into the SiBCN aerogel to prepare NF/SiBCN ceramic fiber aerogel. The mechanical properties were improved by fiber networks. The shell structure increased the antioxidant properties. Heat conduction and heat convection were suppressed by the aerogel, while heat radiation was reduced by the coaxial fiber. The results showed that the ceramic fiber aerogel exhibited superior mechanical, antioxidant, and ultra-low thermal conductivity properties.     

Flexible Electrospun strawberry-like structure SiO2 aerogel nanofibers for thermal insulation

Herein, a novel flexible SiO₂ aerogel composite nanofiber membrane with strawberry-like structure and excellent thermal insulation properties, in which SiO₂ aerogel particles act as thermal insulation filler, was prepared by electrospinning technology. With the addition of nano-pore structure SiO₂ aerogel particles, the heat transfer path of the fibers inside the membrane became discontinuous, endowing the as-prepared membrane an ultra-low thermal conductivity of 30.3 mW/(m?K) and large surface area of 240 m²/g. Moreover, the nanofibers membrane also possesses the combined merits of excellent fire resistance, high-temperature stability, and temperature-invariant flexibility, rendering it a promising in the application of insulation and gas adsorption. The successful preparation of this flexible nanofiber membrane paves a new way to design materials with excellent thermal insulation and adsorption properties.     

Mechanical and thermal insulation properties of isocyanate crosslinked resorcinol formaldehyde aerogel: Effect of isocyanate structure

In this article, the mechanical and thermal properties of resorcinol formaldehyde (RF) aerogels were improved using two different crosslinkers including hexamethylene diisocyanate (HDI) and methylene diphenyl diisocyanate (MDI). The crosslinking was performed after the aerogel drying process, with two concentrations of crosslinking agent. The formation of urethane linkages was investigated by Fourier transform infrared spectroscopy. The effect of crosslinking process and crosslinking agent type on the mechanical properties was analyzed by compression, bending, and impact tests. The improvement of mechanical strength was attributed to the neck thickness, which was studied by atomic force microscopic test. The results revealed that a higher improvement was obtained by increasing the crosslinking agent value. HDI crosslinked aerogel represented the highest strain-at-break and MDI-reinforced sample showed the highest strength. By crosslinking, the samples density was increased <59% and the reduced compressive strength was enhanced upto eight times. The effect of crosslinking on the thermal conductivity was explored. The increment of neck size and density enhanced the solid conductivity and, consequently, raised the thermal conductivity. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48196.     

Novel high-temperature-resistant Y2SiO5 aerogel with ultralow thermal conductivity

A novel Y₂SiO₅ ternary aerogel was prepared from tetraethoxysilane and yttrium chloride hexahydrate via the sol-gel method followed by high-temperature calcination. The effects of different calcination temperatures on the microstructure, mechanical and thermal stability of the Y₂SiO₅ aerogels were investigated. The aerogels exhibited low densities of 0.33-0.62 g/cm³, low thermal conductivities of 0.029-0.05 W/(m·K), and a relatively high strength of 0.16-56.47 MPa. Moreover, compared with the Al₂O₃–SiO₂ aerogel, the Y₂SiO₅ aerogel has higher thermal stability and more excellent high-temperature insulation, which has potential applications as a thermal protection material in hypersonic vehicles.