Pressureless solid-state sintering of SiC ceramics with BN and C additives

Abstract

This study proposes BN as a new sintering aid for pressureless solid-state sintering of SiC ceramics. The full densification of SiC ceramics for 0.5-2.7 wt% BN addition showed the composition tolerance of the newly developed ceramics. The electrical resistivity decreased by an order of magnitude (10 7 →10 6 Ω•cm) as BN content increased from ~0.5 to ~0.9 wt% because of the increased BN-derived B doping in the SiC lattice. A further increase in BN content had no significant effect on the electrical resistivity, which is attributed to the limited solubility of B in the SiC lattice. The thermal conductivity decreased with increasing BN content owing to increased phonon scattering at B-doped sites and the thermally insulating BN phase located at the grain boundaries. The fracture toughness increased with increasing BN content owing to interfacial debonding at the weak SiC-BN interfaces. However, intrinsically weak BN grains with low hardness were responsible for reduced flexural strength and hardness with increasing BN content.

Possibility of using boric acid and glutinous rice flour as additive for producing silicon carbide ceramic via pressureless solid-state sintering

“…Prochazka produced 96% relative density of SiC ceramic with additions of 0.5 wt% boron and 1 wt% carbon after sintering at 2050℃ to 2150℃ in an argon atmosphere [8]. The SiC ceramics were fabricated via pressureless solid-state sintering at 2100℃ for 2 h in argon atmosphere with additives, boron nitride as boron source in range of 0.45 wt% to 2.65 wt% and phenolic resin as carbon source [9]. The fabrication of SiC ceramic via pressureless solid-state sintering with boron carbide (B4C) and carbon additives at temperatures between 1950℃ and 2180℃ for 1 h in a vacuum sintering furnace was studied by D. C., et al [10].…”

The influence of carbon source and content on structure and mechanical properties of sic processed via spark plasma sintering method

“…However, addition of B 4 C to SiC without C causes glassy phase formation [25]. Therefore, these two additives should be added together to SiC since studies have shown that SiC produced by solid state sintering has a wide range of uses since SiC sintered by the solid-state method can be produced without losing its superior properties [7,13,17,25,34,35]. Even if SiC is produced using these two additives, the additive ratios must be adjusted well, otherwise SiC with large grain size will be obtained and the elastic modulus and hardness of these SiC will be low [35].…”

Silicon Carbide/Polysilazane Composite: Effect of Temperature on the Densification, Phase, and Microstructure Evolution

“…However, the sintering of SiC is complex, requiring a high temperature and pressure to obtain a dense microstructure. For instance, the sintering of SiC through solid-state requires temperatures ≥ 1900 °C [1][2][3][4][5][6][7][8][9][10][11][12][13], whereas liquid-phase sintering requires a temperature range of 1750-1900 °C [14][15][16][17][18][19][20]. Although a dense SiC body can be achieved under such sintering conditions, the microstructure of SiC undergoes coarsening.…”