Role of Temperature and Nitrogen Flow Rate During the Carbothermic Synthesis of SiC/Si₃N₄ Nanocomposite Powder from Gel

Abstract

This research article explores the synthesis of SiC/Si 3 N 4 nanocomposite powder via a carbothermic reaction of silica xerogel under nitrogen atmosphere. The influence of both reaction temperature and nitrogen flow rate on the properties of the produced sample was thoroughly investigated. The results revealed that both reaction temperature and nitrogen flow rate played a very important role not only on the composition ratio of SiC/Si 3 N 4 in the finally produced sample but also on the morphology of both phases. At 13001C, spherical particles of 40 nm grain size for both phases (SiC and Si 3 N 4 ) were produced, while silicon nitride is the predominant phase. With increasing the reaction temperature, the amount of SiC increased at the expense of the amount of Si 3 N 4 till SiC becomes the predominant phase at 15001C. At 15001C, almost both phases have the shape of nanorods with different grain sizes. At low nitrogen flow rate and reaction temperature of 15001C, SiC predominates while with increasing nitrogen flow rate the Si 3 N 4 becomes the predominant phase. The photoluminescence spectra revealed that a strong emission was observed at 354 and 389 nm for the sample produced at low and high N 2 flow rate, respectively. On the other hand, a high surface area of 578 and 471 m 2 /g were produced for samples prepared under low and high nitrogen flow rate, respectively. Also, the mechanism of formation of the SiC/Si 3 N 4 nanocomposite powder was postulated.N. Padture-contributing editor

Tailoring the Relative Si3N4 and SiC Contents in Si3N4/SiC Nanopowders through Carbothermic Reduction and Nitridation of Silica Fume

“…This may not be a surprise if one graphite particle can serve as nucleation sites for multiple SiC and Si 3 N 4 crystals. The present observation is consistent with the previous studies showing that Si 3 N 4 and SiC nucleate on the surface of carbon.…”

“…The formation of α‐Si 3 N 4 by carbothermal reduction and nitridation of silica has been reported to occur in two principal reaction steps. The first step consists of reduction of silicon dioxide to gaseous silicon monoxide species following either reactions or . Once the gaseous SiO species is formed, the silicon nitride particle nucleates on the surface of carbon and grows following reactions and .…”

“…Based on the mechanisms discussed above, the results shown in Table can be explained as follows. When the graphite concentration increases, more sites are available for nucleation of both Si 3 N 4 and SiC . Furthermore, both Si 3 N 4 and SiC crystals grow faster (to be discussed later).…”

Metalorganic chemical vapor deposition of mesoporous SiTiOC nanostructured thin films

“…All produced films are obviously show very interesting features of ultraviolet (UV) PL emission with high intensity bands centered at 331, 390, 420 and 480 nm when the samples are excited by a 354 nm light from Xe lamp at room temperature. The positions of these emission lines are consistent with that found in the early reported literatures for SiO 2 , SiOC, SiC, TiO 2 and TiOC phases, respectively [4,28,[32][33][34][35][36][37]. This observation is rather confirmed that these films are most probably a nanocomposite film of the Si\Ti\O\C system.…”

“…They are far above the band gap energy of bulk SiC and SiOC and they suffering from structure defects [3,37]. Song et al reported that the introduction of carbon impurities in the -O\Si\O-network, in the form of -O\C\O-or -Si\C-bonds, can also cause blue emission.…”