Abstract A C/SiO 2 /SiC ternary aerogel was prepared from a formaldehyde–catechol/silicon source via the sol−gel method, supercritical drying, and high-temperature carbothermal reduction. The effects of different carbon/silicon molar ratios on the microstructure, chemical composition, and mechanical and shielding properties of the C/SiO 2 /SiC aerogels were investigated. The fabricated aerogels exhibited low density of 0.118–0.271 g/cm 3 , low thermal conductivity of 0.044 to 0.089 W/(m∙K) and a high specific surface area of 774 m 2 /g. The aerogel exhibited electromagnetic interference shielding effectiveness (SE) properties; the maximum SE value was 24 dB over 12.4–18.0 GHz with an absorption-dominant shielding characteristic. To improve the mechanical properties of the ternary aerogel, novel SiC w -C/SiO 2 /SiC aerogel composites were prepared by adding different contents of SiC whiskers into precursor solutions. The mechanism affecting thermal and mechanical properties of aerogel composites was investigated. This composite having high strength and low thermal conductivity had potential applications in space shuttles and reusable carrier thermal protection materials.
The fabricated C/SiO 2 /SiC ternary aerogels exhibited low density of 0.118–0.271 g/cm 3 and low thermal conductivity of 0.044−0.089 W/(m∙K). The aerogel exhibited electromagnetic interference shielding effectiveness (SE) properties; the maximum SE value was 24 dB over 12.4–18.0 GHz with an absorption-dominant shielding characteristic.
Humidity sensing and water molecule monitoring have become hot research topics attributed to their potential applications in monitoring breathing/physiological conditions of humans, air conditioning in greenhouses, and soil moisture in agriculture. However, there is a huge challenge for highly sensitive and precision humidity detection with wireless and fast responsive capabilities. In this work, a hybrid/synergistic strategy was proposed using a LiNbO3/SiO2/SiC heterostructure to generate shear-horizontal (SH) surface acoustic waves (SAWs) and using a nanocomposite of polyethylenimine-silicon dioxide nanoparticles (PEI-SiO2 NPs) to form a sensitive layer, thus achieving an ultrahigh sensitivity of SAW humidity sensors. Ultrahigh frequencies (1∼15 GHz) of SAW devices were obtained on a high-velocity heterostructure of LiNbO3/SiO2/SiC. Among the multimodal wave modes, we selected SH waves for humidity sensing and achieved a high mass-sensitivity of 5383 MHz · mm2 · μg–1. With the PEI-SiO2 NP composite as the sensitive layer, an ultrahigh sensitivity of 2.02 MHz/% RH was obtained, which is two orders of magnitude higher than those of the conventional SAW humidity sensors (∼202.5 MHz frequency) within a humidity range of 20–80% RH.
Passive anti-icing and active deicing have been combined to improve the anti-icing performance of substrate surface in recent years. Some researchers have prepared active deicing coatings by inducing particles with photothermal or magnetic thermal properties. However, the thermogenesis of these coatings can weaken due to loss of particles. In this work, we first take advantage of the photothermal properties of iodine in deicing process, using polymer substrate doped with iodine by heating to endow the substrate with a photothermal property. Superhydrophobic SiO 2 /SiC coatings with passive anti-icing properties were fabricated on the iodine-doped substrate by a simple spray coating method. The prepared surface of samples can warm up to melt the ice under the irradiation of near infrared light and possesses excellent water repellency with a contact angle up to 162°. The results of 3D profile and microstructure observed via scanning electron microscopy demonstrate that the coatings combined with microscale SiC and nanoscale SiO 2 form voids that can capture air pockets. The photothermal effect of substrate-iodine was demonstrated as the surface temperature of the coatings rapidly increased to about 200 °C upon 10 s of irradiation. The concept of harnessing the iodine doping substrate to achieve superior photothermal performances in deicing might shed new light on the development of anti-icing materials for various applications.
Yan Liu,Qian Jiang,Ke Zhou,Qilin Gu,Zhaoxiang Zhong,Wenheng Jing,Yiqun Fan,Weihong Xing
The combustion efficiency of diesel can be significantly improved in the form of emulsion, contributing to the reduced emission of nitrogen oxides. It is thus worthwhile to develop an energy-efficient way to prepare stable diesel emulsions with uniform droplet size. Ceramic membranes with hydrophobic surface are highly desirable for high-efficient membrane emulsification process. We proposed a novel and straightforward approach of immersing silicon carbide (SiC) membrane into hydrophobic silica solutions obtained by co-hydrolysis to tailoring hydrophobic SiO 2 /SiC membranes. The effects of methyltriethoxysilane addition and aging days on the hydrophobicity of these silica particles were systematically investigated. Then, the deposition of silica particles on the SiC substrates was further controlled by regulating the dipping duration and dipping times. The membranes (M2-SiO 2 /SiC) prepared with 240 s and dipping 4 times showed an increased contact angle (136°), mean pore size of 0.4 μm, open porosity of 30 %, and pure water permeance of ∼ 1500 L·m −2 ·h −1 ·bar −1 . Moreover, the modified membranes were demonstrated to be mechanically stable. Furthermore, monodisperse diesel emulsions with an average droplet size of 2.1 μm and droplet size distribution of 0.61 can be generated by using the optimized M2-SiO 2 /SiC membranes at high emulsifying flux (1910 L·m −2 ·h −1 ). This work proposed an efficient strategy to simultaneously optimize the surface wettability and pore structure of ceramic membranes, satisfactorily for membrane emulsification applications with high efficiency.
危险品化学品经营许可证（带存储）