Silicon carbide (SiC) aerogels, which possess unique porous structure and high ablation resistance, show great potential as thermal insulation materials, but their wide application is limited by expensive and cumbersome synthetic procedures. Therefore, it is pivotal to develop a facile, versatile, and cost-effective method for producing SiC aerogels. Herein, we have successfully prepared ultra-light SiC nanowire aerogels (SNWAs) boasting remarkably low thermal conductivity, using biomass-derived carbon templates (BCTs) through a direct carbothermal reduction method. The BCTs obtained by simply carbonizing freeze-dried eggplants can serve not only as the carbon sources but also as the templates for the in situ growth of SiC nanowires. The resultant three-dimensional (3D) SNWAs possess various porous structures, incorporating the original micro-sized pores inherited from the eggplant and nano-sized pores constructed from interconnected SiC nanowires. These multi-scale pore structures bestow SNWAs with lower gas-phase heat conduction characteristics. Besides, the numerous stacking faults and heterojunctions present in the SiC nanowires play a key role in obstructing the solid-phase heat transfer and reinforcing the SiC skeleton. As a result, the SNWAs show an exceptionally low thermal conductivity, measuring 0.0149 W m⁻¹ K⁻¹ at room temperature, and maintain this low value (0.0256 W m⁻¹ K⁻¹) even at 500 °C. Remarkably, even after being exposed to air at 1200 °C for 2 h, the SNWAs maintain a low thermal conductivity of 0.0226 W m⁻¹ K⁻¹. Such low-cost and effective preparation of biomass-derived SiC aerogels is anticipated to pave a new avenue for the development of advanced thermal insulators.

Cubic gauche nitrogen (cg-N) has received wide attention for its exceptionally high energy density and environmental friendliness. However, traditional synthesis methods for cg-N predominantly rely on high-pressure techniques or the utilization of nanoconfined effects using highly toxic and sensitive sodium azide as precursor, which substantially restrict its practical application. On the basis of the first-principles simulations, we found that adsorption of potassium on the cg-N surface exhibits superior stabilization compared to sodium. Then, we chose safer potassium azide as precursor for synthesizing cg-N. Through plasma-enhanced chemical vapor deposition treatment, the free-standing cg-N was successfully synthesized without the need for high-pressure and nanoconfined effects. It demonstrated excellent thermal stability up to 760 K, and then rapid and intense thermal decomposition occurred, exhibiting typical thermal decomposition behaviors of high-energy-density materials. The explosion parameters were also measured using laser-induced plasma spectroscopy. Our work has substantially promoted the practical application of cg-N as HEDMs.

Ultrafine VOOH nanoparticles were prepared using the Kirkendall effect, and the VOOH can be transformed to VO ₂ with advanced thermochromic properties.