Fabrication and strengthening of porous Si3N4 ceramics by replacement of oxide phase with Si3N4 at grain boundary through carbothermal nitridation. Issue 17 (6th July 2017)

• Record Type: Journal Article
• Authors: Zhi, Qiang; Xu, Zhaoyun; Pan, Huan; Yang, Jianfeng; Deng, Yuchen; Wang, Bo
• Is Part Of: Journal of materials research. Volume 32:Issue 17(2017)
• Page Start: 3344
• Page End: 3352
• Publication Date: 2017-07-06
• Subjects: ceramic, -- strength, -- grain boundaries; Materials -- Research -- Periodicals; 620.1105
• DOI: 10.1557/jmr.2017.252
• Languages: English
• ISSNs: 0884-2914

Abstract

Abstract: Abstract : Porous silicon nitride ceramics are attracting extensive attention due to its high strength and low dielectric loss. However, further strength enhancement at elevated temperatures is hindered by its intergranular phase, forming from sintering additives. This paper describes the fabrication of porous silicon nitride ceramic materials, by using a replacement method of carbothermal nitridation. The initial samples which were obtained from the sintering of mixed powder consisted of 95 wt% Si3 N4 and 5 wt% Y2 O3 . After the removal of the oxide intergranular phase and the infiltration of mixtures of phenolic resins and silica sols, carbothermal nitridation process was carried out at 1550 °C for 2 h under nitrogen. X-ray diffraction and microstructural analysis revealed a complete replacement of oxide intergranular phases by the newly formed Si3 N4 intergranular phase. The unmodified ceramic exhibited lower flexural strength at 1400 °C, which was only 50% of the room-temperature strength. Although the modified ceramic attained a slightly lower flexural strength at room temperature after the replacement of intergranular phase, its strength measured at 1400 °C could attain 90% of room-temperature strength.