On the 2H- to 3C-Type Transformation and Growth Mechanism of SiC Nanowires upon Carbothermal Reduction of Rice Straws

SiC nanowires (NWs) and nanoparticles (NPs) fabricated by carbothermal reduction of rice straws with/without FeSi catalysts were characterized by transmission electron microscopy to study the catalyst-facilitated vapor-liquid-solid (VLS) growth against the oriented attachment of the crystals, which underwent 2H- to 3C-type transformation. The cotectic melt of the FeSi catalyst in the Fe-Si-C-O system turned out to promote the VLS growth to form straight and occasionally tapered NWs in contrast to the zigzag ones via the (hkl)-specific coalescence of the faceted NPs. The SiC NWs showed [0001]_2H-directed growth more or less stacked with {111}_3C interlayers following the optimum crystallographic relationship (0001)_2H//{111̅}_3C; [21̅1̅0]_2H//⟨101⟩_3C with zigzag {111}_3C lateral steps and polysynthetic twins/faults near the (0001)_2H/(111)_3C interface. The FeSi-assisted VLS growth and twinning/stacking fault-coupled 2H to 3C phase change may be extended to novel green manufacturing and design of sustainable resources for other semiconductor NWs.