Ultra-long SiC nanowires with the lengths ranging from several millimeters to one centimeter were successfully prepared by the raw materials of graphite, silicon, silica and alumina via a simple carbon thermal reduction method in a tube furnace at 1300 o C. Scanning electron microscopy (SEM), electron energy scattering (EDX), Xray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) and Fourier transform infrared spectroscopy (FTIR) were employed to characterize the morphology and microstructure of the obtained products. The results showed that the nanowires mostly consisted of 3C-SiC and exhibited mainly a straight-line shape with diameters in the range of 30-150 nm. Alumina may be as a novel and highly effective mediator playing an important role in controlling the concentration of SiO during the growth of ultra-long SiC nanowires and an alumina-assisted growth of vapor-solid (VS)mechanism was proposed for the growth mode of the ultra-long SiC nanowires.
As one of the most promising photocatalysts, graphitic carbon nitride (g-CN) shows a visible light response and great chemical stability. However, its relatively low photocatalytic efficiency is a major obstacle to actual applications. Here an effective and feasible method to dramatically increase the visible light photocatalytic efficiency by forming CN/BiFeO ferroelectric heterojunctions is reported, wherein the band alignment and piezo-/ferroelectricity have synergistic positive effects in accelerating the separation of the photogenerated carriers. At the optimum composition of 10 wt% BiFeO, the heterojunction shows 1.4 times improved photocatalytic efficiency than that of the pure CN. Most importantly, mechanical pressing and electrical poling can also improve the photocatalytic efficiencies by 1.3 times and 1.8 times, respectively. The optimized photocatalytic efficiency is even comparable with that of some noble metal based compounds. These results not only prove the improved photocatalytic activity of the CN-ferroelectric heterojunctions, but also provide a new approach for designing high-performance photocatalysts by taking advantage of ferroelectricity.
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