Fabrication of SiC and Si₃N₄Whiskers under Pressurized Ar and N₂Atmosphere through High-Energy Ball Milling

Abstract

SiO 2(activated or mesoporous silica) /Mg (magnesiothermic or metal sintering aid) /C (activated or polymeric carbon) / N 2(atmosphere) systems were used in the one-step synthesis of β-SiC and β-Si 3 N 4 whiskers. In this study, a mixture of the active precursors was allowed to react via a self-sustaining reaction (highenergy ball milling process). Scanning electron micrographs and X-ray diffraction (XRD) analysis showed that the rod-like SiC whiskers (~800 μm) were synthesized in situ by the direct carbothermal reduction of silicon nitride (or silicon) with activated carbon in N 2 (or Ar) atmosphere. The results show that β-Si 3 N 4 (without β-SiC) was fully formed after 5 h of milling with four different morphologies, namely whisker tip (droplet/no droplet) and nonuniform whiskers (short hexagonal/ rhombohedral/rod-like) with a length of 0.1-400 μm. By adding metal sintering aids, the liquid phase Mg-Si-O-N and the rate of carbothermal reduction increased (enhanced densification via particle rearrangement) and their hexagonal whiskers tended to assume a rod-like shape. The effect of the concentration of CO (reduction of α-Fe 2 O 3 to Fe by CO) on the whisker synthesis suggests that, in addition to the concentration of CO, the nature of the family of mesoporous silica/carbon template is an important factor in the synthesis of β-SiC and β-Si 3 N 4 whiskers. The possible chemical reactions were investigated by studying the unwanted phases (MgO

A New Route to High Yield Mesostructure Boron Carbide Powder from SiC/Si3N4 Whiskers

“…Mesoporous silica and mesoporous SiC have similar Brunauer–Emmett–Teller data, as previously reported (total pore volume, average pore diameter, and BET surface area of 0.7 or 0.5 cm 3 /g, 2.2 or 5.81 nm, and 1200 or 331 m 2 /g, respectively) . High‐energy ball milling was carried out in a planetary ball mill at 600 rpm using a ball/powder mass ratio of 55:1 (total powder mass = 2–4 g).…”

Clean synthesis of silicon carbide whiskers using recycled carbon black and waste silicon dioxide

“…After milling, the components were mixed thoroughly, and the number of chemically active defect sites increased, resulting in a significantly low silicon carbide nucleus formation energy. Saeedifar and Saeedifar [21] reported that, after milling for 5 h, β-SiC and β-Si3N4 whiskers were formed, with three different morphologies (short hexagonal, rhombic, and rod-like) at the front end of the whiskers.…”