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

The alpha-Si3N4 membrane was prepared by tape casting of silicon slurry, followed by calcination at 1300 degrees C in flowing NH3 gas. It comprised of alpha-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 similar to 160 degrees, by coating with a vesicular SiNCO nano-layer. The experimental results showed that nanowire structure also favored super-hydrophobicity. 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 degrees C, which was maintained for more than 500 h.