Synthesis of SiC nanowires on biochar surfaces by a simple direct method

Demand for air filters is crucially required due to PM 2.5. So, SiC nanowire networks are directly grown on biochar surfaces that serve strength and filtering purposes. The nanowires were prepared by spraying silicon powder on Lesser bulrush and Grey sedge biochars which acted as carbon sources and heating up to 1300℃ to 1500℃ for 1 h in Ar atmosphere. As a result, silicon powder evaporated and diffused on biochar surfaces. Meanwhile, CO vapor was generated from biochar reacted with O2 in the chamber. The evaporated silicon reacted with both C(s) and CO(g) to form cubic SiC nanowires. At the early stage of the reaction, large nuclei of SiC nanowires were formed at 1300℃. Those nuclei became smaller to promote nanowires when a higher temperature was applied before being disappeared at 1500℃. At such temperature, the obtained network structure SiC nanowires with 10 nm to 30 nm diameters on the outer and inner surfaces of biochars were completed, facilitating superior strength and filtering purposes. Comparatively, the Lesser bulrush provided higher strength than those of the Grey sedge ones, thus it was selected for the filtering efficiency test. The results showed that particulate filter efficiency was up to 97% but it was still over the range of pressure drop at 30 in H2O.