Silicon nitridation mechanism in reaction‐bonded Si₃N₄–SiC and Si₃N₄‐bonded ferrosilicon nitride

Abstract

Reaction‐bonded Si3N4–SiC and Si3N4‐bonded ferrosilicon nitride, with Si powder, SiC particles and Fe3Si–Si3N4 particles as raw materials, respectively, are prepared in flame‐isolation nitridation shuttle kiln with flowing N2 at 1723K. There is columnar β‐Si3N4 in both Si3N4–SiC and Si3N4‐bonded ferrosilicon nitride. However, fibrous α‐Si3N4 is only observed in Si3N4–SiC and Si3N4‐bonded ferrosilicon nitride contains much more Si2N2O than Si3N4–SiC. By analyzing the oxidation thermodynamics of Si and Si3N4, it is known that in the process of producing Si3N4–SiC, Si is oxidized first to gaseous SiO and fibrous α‐Si3N4 is generated with SiO and N2. The existence of SiO is the reason of low silicon nitridation rate. But in the process of producing Si3N4‐bonded ferrosilicon nitride, Si3N4 is easier to be oxidized than Si and Si2N2O is generated on the surface of Si3N4 hexagonal prisms in ferrosilicon nitride particles. Meanwhile, Si in raw materials forms new ferrosilicon alloys with Fe3Si, which decreases the temperature of liquid appearance and blocks some open pores in the samples, which stops the matter loss of nitridation. Liquid ferrosilicon alloys favors β‐Si3N4 generation from Si direct nitridation and fibrous α‐Si3N4 transformation, which used to exist in ferrosilicon nitride raw materials.

Anisotropic, Biomorphic Cellular Si3N4 Ceramics with Directional Well-aligned Nanowhisker Arrays Based on Wood-Mimetic Architectures

“…Each nal value was averaged over three measurements. liquid phase [22]. Except for the Si 3 N 4 , no other phase of silicon carbide (SiC), nor graphite, or other impurities were detected, indicating a high purity of the sintered products.…”

Improved water vapor corrosion resistance of SiC bricks via in situ formation of microporous Yb2Si2O7 bonding phase

“…In SiC‐based refractories, the bonding phases were filled between the SiC particles and connected the SiC particles, the stability of bonding phases greatly affected working life. However, the common bonding phases, including SiO 2 , clay, Si 3 N 4 , β‐SiC, Si 2 N 2 O, β‐Sialon, AlN polytype, and Ti 3 SiC 2 , in SiC‐based products could be corroded by hot water vapor 20–36 …”

“…However, the common bonding phases, including SiO 2 , clay, Si 3 N 4 , β-SiC, Si 2 N 2 O, β-Sialon, AlN polytype, and Ti 3 SiC 2 , in SiC-based products could be corroded by hot water vapor. [20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36] Yb 2 Si 2 O 7 not only had good chemical stability but also performed close coefficient of thermal expansion (CTE) with SiC substrate, 37,38…”

Boron nitride nanosheet @ quantum‐sized diamond nanocrystal complex/epoxy nanocomposites with enhancing thermal conductivity and sufficient dielectric breakdown strength

“…[6][7][8][9] In order to achieve high thermal conductivity, excellent electrical insulation, and good heat resistance properties, researchers have mainly studied the inorganicorganic polymer composites, allowing the simultaneous utilization of the distinctive benefits of both organic polymers and inorganic fillers to expectantly achieve complementary material properties. Currently, the most commonly used inorganic particles for thermal conductivity are boron nitride (BN), [10][11][12][13][14] alumina, [15][16][17][18][19][20] aluminum nitride, [21][22][23] silicon nitride, [24][25][26] silicon carbide, [27][28][29][30][31][32][33][34][35] and so forth. Among them, BN has been extensively studied due to its advantages such as light weight, high thermal conductivity, good electrical insulation, and exceptional heat resistance.…”