Carbothermal Reduction and Nitridation of Quartz Mineral for the Production of Alpha Silicon Nitride Powders

Abstract

In this study, α-Si3N4 powder was produced by carbothermal reduction and nitridation (CRN) of quartz from Can-Canakkale. Carbon with a specific surface area of 110 m2g−1 and quartz powders were mixed then the powder mix was placed in an alumina tube furnace and reacted in between 1300-1500°C for 4 hours under nitrogen flow. The quartz powder was carbothermally reduced and nitrided to form silicon nitride powders. XRD results showed that the reaction product was mainly α-Si3N4 and contained some β-Si3N4 and residual quartz. In order to reduce amount of unreacted quartz, the raw materials mixture was grinded either with carbon black or with no carbon. After CRN reactions of separate grinded quartz powders with carbon, residual quartz was disappeared, reaction temperature was decreased and α-Si3N4 rate was increased. Hence, a better mixing of carbon and fine silica enhanced the α phase formation. SEM images and XRD pattern showed that sub micron particles (0.6–0.87m), high α-phase content Si3N4 powders can be produced at 1450°C for 4 h in flowing nitrogen gas during the CRN process.

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

“…Table shows the increased Si 3 N 4 and SiC crystallite sizes with increasing the graphite content, suggesting that the increased graphite content has enhanced the diffusion rate and thus growth rate of the crystals. This result is consistent with the previous study . Nevertheless, this observation alone does not rule out the effect of graphite acting as the nucleation site for Si 3 N 4 and SiC.…”

“…This result is consistent with the previous study. 35 Nevertheless, this observation alone does not rule out the effect of graphite acting as the nucleation site for Si 3 N 4 and SiC. The consistence of the present investigation with previous studies, 35 however, does provide an additional new insight, that is, the crystal growth rates for both Si 3 N 4 and SiC increase with the graphite content regardless of the status of SiO 2 .…”

“…The consistence of the present investigation with previous studies, however, does provide an additional new insight, that is, the crystal growth rates for both Si 3 N 4 and SiC increase with the graphite content regardless of the status of SiO 2 . The crystalline SiO 2 used in the previous study and the amorphous SiO 2 used in the present work, all exhibit the same trend regarding how the Si 3 N 4 and SiC contents vary with the graphite content.…”

“…Assuming that reactions (4) and (6) are dominant for the formation of Si 3 N 4 particles, the overall reaction of carbothermal reduction of SiO 2 in the presence of nitrogen for the formation of Si 3 N 4 will be 15,35,36 3SiO 2ðsÞ þ 6C ðsÞ þ 2N 2ðgÞ $ Si 3 N 4ðsÞ þ 6CO ðgÞ ð8Þ…”

“…It should be pointed out that the formation of 79% a-Si 3 N 4 at 1465°C in a nitrogen atmosphere for 2 h obtained in this study is the highest amount of a-Si 3 N 4 formed under 2 h of holding time during the carbothermal nitridation and reduction. Previous studies 35 require up to 14 h at 1400°C to achieve a-Si 3 N 4 contents of 82%. Similarly, the formation of a-SiC at 1415°C is among the lowest temperatures to form SiC using the solid-state synthesis reaction reported in the open literature.…”