Relationship between microstructure and mechanical properties of silicon nitride ceramics

Abstract

Abstract; The microstructure of silicon nitride ceramics is related to the mechanical properties. It is demonstrated that the room temperature strength and toughness is determined by size and morphology of the Si3N4 grains and the grain boundary phase. The high temperature properties are mainly controlled by the composition and properties of the grain boundary. The grain boundary crystallization, as one strategy for the development of high-temperature resistant materials, is analysed with respect to the phase relationships between Si3N4 and the additives and the impossibility of a complete devitrification. It is shown that small amounts of impurities in the starting powder can be enriched in thin grain boundary films and degrade the high-temperature properties.

Pore morphology designs of porous Si3N4-based ceramics using Si3N4 and Al2O3 poly-hollow microspheres as pore-forming agents

“…3(c)). Nevertheless, large amount of Al 2 O 3 PHMs in SN-AO would play as the sintering additives in the sintering process, which could further promote the formation of liquid phase, and it is beneficial for the replacement of Si 4þ by Al 3þ and N 3À by O 2À [14]. Therefore, the Al 2 O 3 PHMs disappear and the pores are more obvious in SN-AO (see Fig.…”

Processing and Characterization of Silicon Nitride Bioceramics

“…While quantitative analyses of grain size and distribution were not performed, differences in mechanical properties between the Ube SN-E10 and Starck M-11 compositions were self-evident from their respective microstructures (cf., Figures 3a and 3b). The estimated average grain size for the Starck M-11 composition was approximately 2x that of the comparable Ube SN-E10 composition, which is the principal reason for its lower strength [11]. It is believed that the agglomerated nature of the Starck M-11 powder was the reason for the larger observed grain size (cf., Table 1).…”

“…Synthesized in 1859, it was first manufactured into useful refractory shapes in the 1950s-60s, but was not extensively developed as an engineered ceramic until the 1980s [1][2][3][4]. Since then, it has garnered considerable attention because of its unique combination of excellent room-and high-temperature mechanical strength, toughness, oxidation, and thermal shock resistance [1,[5][6][7][8][9][10][11][12][13][14][15]. Si 3 N 4 is currently used in demanding mechanical applications involving high loads, wear, and corrosion [16].…”

CaO–SiO2–Al2O3–Y2O3 glasses as model grain boundary phases for Si3N4 ceramics

“…Firstly, the presence of crystalline phases in grain boundary junctions increases the creep resistance by increasing the energy required to initiate deformation by grain boundary sliding. 9 Secondly, a significant volume change can be observed during crystallisation, as a consequence of the formation of crystalline phases with specific volume smaller than the specific volume of original glass. The creep resistance (and also room temperature strength) is then impaired by the formation of cavities, and microcracks in triple pockets, and by debonding of crystals from the adjoining silicon nitride grains.…”