Ultra-long SiC nanowires synthesized by a simple method

Abstract

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.

Facile synthesis of silicon nitride nanowires with flexible mechanical properties and with diameters controlled by flow rate

“…Fe 2 O 3 from the crucible would also be reduced to active Fe nanoclusters under the reductive gas from the reaction system to promote the growth of the NWs39. Meanwhile, alumina from the crucible could also be an effective mediator, playing an important role in controlling the concentration of reactants containing Si16. According to the results in the previous literature, alumina could react with silica to form mullite, which might be in a metastable phase when the temperature and the mole fractions of SiO 2 and Al 2 O 3 are within a certain range16414243.…”

“…Meanwhile, alumina from the crucible could also be an effective mediator, playing an important role in controlling the concentration of reactants containing Si16. According to the results in the previous literature, alumina could react with silica to form mullite, which might be in a metastable phase when the temperature and the mole fractions of SiO 2 and Al 2 O 3 are within a certain range16414243. It is noteworthy that mullite could occur in the liquid phase separation process and generate liquid SiO 2 , which could react with other gases containing Si and then dissolve into the Fe nanoclusters to promote the growth of the Si 3 N 4 NWs.…”

“…Meanwhile, the liquid phase formation temperature of Al 2 O 3 -SiO 2 would obviously be decreased if a small amount of oxide impurity was contained in the system of the Al 2 O 3 -SiO 2 . For example, the liquid phase formation temperature of the Al 2 O 3 -SiO 2 system with a low content of alumina is 1595 °C, a value that decreases as low as 985 °C with the incorporation of 1% K 2 O164243. It is noteworthy that there is approximately 4.5% Na 2 O in alumina, indicating that the liquid phase separation process would occur more easily, which would further promote the reaction between SiO 2 and other gaseous products containing Si and would lead to continuous growth of the Si 3 N 4 NWs.…”

“…Moreover, several techniques have been applied to prepare 1D Si 3 N 4 nanomaterials, including the pyrolysis of polymeric precursors, carbothermal reduction, and chemical vapor deposition (CVD)131415. Meanwhile, Si 3 N 4 nanomaterials with lengths on the order of millimeters or even centimeters could be more valuable in some fields (e.g., connections for devices and reinforcements for composites) compared with shorter versions161718. Thus, great efforts have been made to prepare ultralong Si 3 N 4 nanomaterials with high yields.…”

Synthesis of several millimeters long SiC–SiO2 nanowires by a catalyst-free technique

“…7III. In the view of crystallographic, the growth direction of SiC nanowires is preferentially normal to the (111) plane of β-SiC [37,38], and SiC nanowires would grow subsequently along the fixed direction as long as the gases reactant continuously produced, and then large-scale and several millimeters long SiC nanowires would be formed. It is also worth being pointed out that reactions of 7and 8…”