Robust and Density Tunable Kevlar/Hexagonal Boron Nitride Microribbon Aerogels with Excellent Thermal, Mechanical, and Oil-Absorption Properties.

With rapid advancements in aerospace and supersonic aircraft technology, there is a growing demand for multifunctional thermal protective materials. Aerogels, known for their low density and high porosity, have garnered significant attention in this regard. However, developing a lightweight multifunctional aerogel that combines exceptional thermal and mechanical properties through a straightforward and time-efficient method remains a significant challenge. Herein, a facile and universal approach is developed for the preparation of Kevlar/hexagonal boron nitride (h-BN) aerogels, in which a spin-assisted method is applied to create robust microribbons and further accelerate solvent displacement. The resulting microribbon scaffold, with its entangled nanofiber-nanosheet morphologies, exhibits sufficient strength to prevent volume shrinkage during drying, thereby allowing precise control over aerogel density. The porous hybrid aerogels, featuring controllable geometric characteristics and tailored densities ranging from 6.9 to 100 mg cm-3, can be successfully fabricated. These aerogels exhibit excellent thermal insulation properties, and the thermal conductivities of the as-prepared KBX aerogels have a wide distribution in the range of 0.0269-0.0450 W m-1 k-1. The thermal stability of the hybrid aerogels is enhanced to 566 °C. Moreover, the resulting hybrid aerogels exhibit an ultrahigh bearing ratio, supporting more than 2000 times their own weight while maintaining stable structural integrity. These aerogels also demonstrate high compressive strength, hydrophobicity, and excellent sorption performance for various oils and solvents. Additionally, the oil-saturated aerogels can be easily recovered through heat treatment or combustion in air. The features endow hybrid Kevlar/h-BN aerogels with significant potential for applications in thermal management, environmental protection, and neutron protection.

Facile and scalable fabrication of Ni cantilever nanoprobes using silicon template and micro-electroforming techniques for nano-tip focused electrohydrodynamic jet printing.

Electrohydrodynamic jet (E-Jet) printing is a powerful technique for micro/nanostructure fabrication with high resolution and efficiency. However, conventional E-Jet printing are still limited in printing accuracy and ink adaptability due to the nozzle clogging effect. In this paper, we develop a nano-tip focused electrohydrodynamic jet (NFEJ) method to print high-resolution structures. The Ni cantilever nanoprobes with nanoscale radius of curvature (ROC) on their tips were manufactured by a facile and scalable method using silicon template and micro-electroforming technique. Scanning electron microscope was used to analyse the micromorphology of the silicon template with inverted pyramid pits, which was obtained from anisotropic wet etching of silicon. Electroforming mold was obtained by photolithography and plasma etching which divide the top side of Ni film into isolated cantilever pits. Ni cantilever nanoprobes with an average tip ROC of about 48 nm were achieved by the subsequent micro electroforming process. High-resolution droplets array with an average diameter of about 890 ± 93 nm were printed by the NFEJ printing head equipped with these Ni nanoprobes, which verified the practicality of the developed Ni nanoprobes for NFEJ printing.