研究了MgO-Y2O3-Al2O3体系(相应的层状复合陶瓷试样记为A)、Y2O3-Al2O3体系(相应的层状复合陶瓷试样记为B)及La2O3-Y2O3-Al2O3体系(相应的层状复合陶瓷试样记为C)烧结助剂对Si3N4/BN层状复合陶瓷结构与性能的影响.研究表明:在相同的烧结工艺下,试样A、B、C的抗弯强度分别为700、630、610MPa,断裂功分别为2100、1600、3100J/m2.试样A、B以脆性断裂为主,裂纹偏转现象不明显,而试样C的载荷-位移曲线显示了明显的“伪塑性”特征,裂纹的偏转与扩展现象明显.试样A中Si3N4晶粒大小不均且长径比较小,而试样C中长柱状Si3N4晶粒发育完善,有较大的长径比.
The effects of additives to Si3N4 matrix layers on microstructure and properties of laminated
Si3N4/BN ceramics were studied. Laminated Si3N4/BN ceramics with La2O3-Y2O3-Al2O3 (denoted as C), Y2O3-Al2O3 (denoted as B), MgO-Y2O3-Al2O3
(denoted as A) added as sintering aids to the Si3N4 matrix layers were prepared and tested separately. The results obtained show that WOF
(work of fracture) of sample C is 3100J/m2, which is higher than that of 2100 and 1600J/m^2 of sample A and B. Bending strength of sample C is 610MPa, which is lower than
that of 700 and 620MPa of sample A and B. In sample C, crack deflection and propagation occur, which result in high-energy absorption and high
toughness. And in sample C, elongated β-Si3N4 grains grow very well, which is caused by the addition of La2O3.
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