Ultra-Light and Ultra-Low Thermal Conductivity of Elastic Silica Nanofibrous Aerogel with TiO2 Opacifier Particles as Filler.

The thermal radiation phenomenon is more crucial than other thermal transportation phenomena at elevated temperatures (>300 °C). Therefore, infrared radiation resistance and its performance on thermal conduction of nanofibrous aerogel with Titanium oxide (TiO2) filler have been investigated compared to control groups (silica nanofibrous aerogels with and without filler). Nanofibrous aerogel has been produced by electrospun silica nanofibers. Later, TiO2 opacifier and a non-opacifier filled materials were prepared by a solution homogenization method and then freeze-dried to obtain particle-filled nanofibrous aerogel. Moreover, the thermal radiation conductivity of the composite was calculated by numerical simulation, and the effect of the anti-infrared radiation of the TiO2 opacifier was obtained. The fascinating inhibited infrared radiation transmission performance (infrared transmittance ~67% at 3 µm) and excellent thermal insulation effect (thermal conductivity of 0.019 Wm−1K−1 at room temperature) and maximum compressive strengths (3.22 kPa) of silica nanofibrous aerogel with TiO2 opacifier were verified. Excellent thermal insulation, compression and thermal stability properties show its potential for practical application in industrial production. The successful synthesis of this material may shed light on the development of other insulative ceramic aerogels.

High ZT Value of Pure SnSe Polycrystalline Materials Prepared by High-Energy Ball Milling plus Hot Pressing Sintering.

The research of thermoelectric materials is of great significance to solve the energy crisis and environmental problems. In this work, a series of pure SnSe bulk crystals were prepared by melting, high-energy ball milling, and hot pressing processes. The results show that the ZT value of the prepared pure SnSe polycrystalline material is up to 2.1 at 873 K. On the one hand, due to the reduction of grain size and lattice distortion caused by long-time high-energy ball milling, the lattice thermal conductivity is significantly reduced, which is only 0.18 W K-1 m-1 at 873 K. On the other hand, high-energy ball milling leads to the increase of Sn vacancies, which improves the conductivity of SnSe polycrystalline materials. Since the whole process of ball milling was carried out in a closed ball milling tank filled with high-purity argon, no oxidation of the SnSe powder is also a guarantee to obtain pure SnSe polycrystalline materials with high ZT value.