Abstract Silicon nitride ceramics were prepared by pressureless sintering, with Al2O3-Y2O3 as sintering aids, after dry pressing and cold isostatic pressing. The shrinkage and densification of Si3N4 ceramics was observed in real time with TOM-AC high temperature sintering equipment. Meanwhile, the densification process of Si3N4 ceramics was studied by analyzing the structure and morphology of ceramics sintered at different temperatures. The results show that α-Si3N4 begins to transform into β-Si3N4 at 1 400 ℃. The density increases rapidly in the range of 1 400-1 600 ℃, and the higher the density of compact, the faster the densification rate. When the sintering temperature is higher than 1 600 ℃, α-Si3N4 transforms into β-Si3N4 columnar crystal completely, and the crystal grain grows obviously, while the densification rate decreases. The compacts density has little effect on the final sintering density. The optimal sintering process is sintering at 1 650 ℃ and 1 800 ℃ for 2 h respectively. The density of Si3N4 ceramics is 98.4%, and the hardness (HV10) is 15.7±0.5 GPa. The bending strength and fracture toughness are 1037.3±48.9 MPa and 5.8±0.2 MPa∙m1/2, respectively.
LIU Wenyong,LI Jianbin,SUN Zhenfei, et al. Densification process of pressureless sintered silicon nitride ceramics[J]. Materials Science and Engineering of Powder Metallurgy, 2020, 25(3): 191-196.
[1] 谢志鹏. 结构陶瓷[M]. 北京: 清华大学出版社, 2011: 418-439. XIE Zhipeng.Structural Ceramics[M]. Beijing: Tsinghua University Press, 2011: 418-439. [2] SOUZA J V C, SILVA O M M, ANDRADE N M D C, et al. Si3N4 ceramic cutting tool sintered with CeO2 and Al2O3 additives with AlCrN coating[J]. Materials Research, 2011, 14(4): 514-518. [3] BOCANEGRA B M H, MATOVIC B. Mechanical properties of silicon nitride-based ceramics and its use in structural applications at high temperatures[J]. Materials Science & Engineering A, 2010, 527(6): 1314-1338. [4] ZHOU Y, HYUGA H, KUSANO D, et al.Development of high-thermal-conductivity silicon nitride ceramics[J]. Journal of Asian Ceramic Societies, 2015, 3(3): 221-229. [5] RILEY F L.Silicon nitride and related materials[J]. Journal of the American Ceramic Society, 2000, 83(2): 245-265. [6] ZIEGLER A, Interface structure and atomic bonding characteristics in silicon nitride ceramics[J]. Science, 2004, 306(5702): 1768-1770. [7] NAOTO H, AKIRA O, MATOBA K.Sintering of Si3N4 with the addition of rare-earth oxides[J]. Journal of the American Ceramic Society, 1988, 71(3): C144-C147. [8] KRSTIC Z, KRSTIC V D.Silicon nitride: the engineering material of the future[J]. Journal of Materials Science, 2012, 47(2): 535-552. [9] STUART HAMPSHIRE.Silicon nitride ceramics[J]. Materials Science Forum, 2009, 606:27-41. [10] YANG L L, DITTA A, FENG B, et al.Study of the comparative effect of sintering methods and sintering additives on the microstructure and performance of Si3N4 ceramic[J]. Journal of Materials Science, 2019, 12(13): 2142. [11] HAN W, LI Y, CHEN G, et al.Effect of sintering additive composition on microstructure and mechanical properties of silicon nitride[J]. Materials Science and Engineering A, 2017, 700: 19-24. [12] LI W J, WU Y L, HUANG R X, et al.Effect of Si addition on the mechanical and thermal properties of sintered reaction bonded silicon nitride[J]. Journal of the European Ceramic Society, 2017, 37(15): 4491-4496. [13] ZHOU Y, HYUGA H, KUSANO D, et al.A tough silicon nitride ceramic with high thermal conductivity[J]. Advanced Materials, 2011, 23(39): 4563-4567. [14] CECILIA C G S, FLAVIO M S C, JOSE C. Effect of rare-earth oxides on properties of silicon nitride obtained by normal sintering and sinter-HIP[J]. Journal of Rare Earths 2012, 30(11): 1177-1183. [15] WANG L, QI Q, CAI P, et al.New route to improve the fracture toughness and flexural strength of Si3N4 ceramics by adding FeSi2[J]. Scripta Materialia, 2017, 126: 11-14. [16] GUO W M, WU L X, MA T, et al.Rapid fabrication of Si3N4 ceramics by reaction-bonding and pressureless sintering[J]. Journal of the European Ceramic Society, 2016, 36(16): 3919-3924. [17] 豆高雅. 自增韧氮化硅陶瓷的制备与性能研究[J]. 陶瓷, 2019(9): 53-62. DOU Gaoya.Preparation and properties of self toughened silicon nitride ceramics[J]. Journal of Ceramics, 2019(9): 53-62. [18] 梁汉琴, 姚秀敏, 黄政仁, 等. 碳化硅陶瓷液相烧结时的液相生成过程[J]. 机械工程材料, 2015, 39(2): 34-37. LIANG Hanqin, YAO Xiumin, HUANG Zhengren, et al.Liquid phase formation process during liquid phase sintering of silicon carbide ceramics[J]. Mechanical Engineering Materials, 2015, 39(2): 34-37. [19] KINGERY W D.Densification during sintering in the presence of a liquid phase. I. theory[J]. Journal of Applied Physics, 1959, 30(3): 301. [20] SCITI D, BELLOSI A.Effects of additives on densification, microstructure and properties of liquid-phase sintered silicon carbide[J]. Journal of Materials Science, 2000, 35(15): 3849-3855. [21] RAJ P M, ODULENA A, CANNON W R.Anisotropic shrinkage during sintering of particle-oriented systems— numerical simulation and experimental studies[J]. Acta Materialia, 2002, 50(10): 2559-2570. [22] RAHAMAN M N.Ceramic processing and sintering[J]. International Materials Reviews, 2003, 41(1): 36-37. [23] HAMPSHIRE S, JACK K H.Progress in Nitrogen Ceramics[M]. Netherlands: Springer, 1983. [24] 谢娇娇, 艾江. 烧结助剂(Y2O3、Al2O3、La2O3)对β-Si3N4自增韧陶瓷的性能研究[J]. 陶瓷, 2017, 1(9): 37-43. XIE Jiaojiao, AI Jiang.Study on properties of β-Si3N4 self-toughened ceramics with sintering aids (Y2O3, Al2O3, La2O3)[J]. Ceramics, 2017, 1(9): 37-43. [25] 詹创添, 吴利翔, 牛文彬, 等. 以ZrO2-MgO-Y2O3为添加剂的气压反应重烧结Si3N4陶瓷的制备与性能研究[J]. 功能材料, 2019, 50(12): 12108-12112. ZHAN Chuangtian, WU Lixiang, NIU Wenbin, et al.Preparation and properties of Si3N4 ceramics using ZrO2-MgO-Y2O3 as an additive under atmospheric pressure reaction[J]. Journal of Functional Materials, 2019, 50(12): 12108-12112.
2020, Vol. 25 
