Novel α-Si3N4 planar nanowire superhydrophobic membrane prepared through in-situ nitridation of silicon for membrane distillation

The α-Si3N4 membrane was prepared by tape casting of silicon slurry, followed by calcination at 1300 °C in flowing NH3 gas. It comprised of α-Si3N4 nanowire of diameter 70 nm which were converted from silicon powder via the vapor–liquid–solid (VLS) growth mechanism. The surface of the obtained membrane was transformed from hydrophilic to superhydrophobic, with a high water contact angle of ~ 160°, by coating with a vesicular SiNCO nano-layer. The experimental results showed that nanowire structure also favored superhydrophobicity. Water desalination performance of the membrane was tested with a sweeping gas membrane distillation (SGMD) device. High water flux of 8.09 l m−2 h−1 was achieved for 20 wt% NaCl aqueous solution in the feed at 90 °C, which was maintained for more than 500 h.