WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan.
Nat Commun. 2012;3:1052. doi: 10.1038/ncomms2047.
Ceramics typically have very high hardness, but low toughness and plasticity. Besides intrinsic brittleness associated with rigid covalent or ionic bonds, porosity and interface phases are the foremost characteristics that lead to their failure at low stress levels in a brittle manner. Here we show that, in contrast to the conventional wisdom that these features are adverse factors in mechanical properties of ceramics, the compression strength, plasticity and toughness of nanocrystalline boron carbide can be noticeably improved by introducing nanoporosity and weak amorphous carbon at grain boundaries. Transmission electron microscopy reveals that the unusual nanosize effect arises from the deformation-induced elimination of nanoporosity mediated by grain boundary sliding with the assistance of the soft grain boundary phases. This study has important implications in developing high-performance ceramics with ultrahigh strength and enhanced plasticity and toughness.
陶瓷通常具有很高的硬度，但韧性和塑性较低。除了与刚性共价或离子键相关的固有脆性外，多孔性和界面相是导致其在低应力水平下以脆性方式失效的首要特征。在这里，我们表明，与传统观点相反，即这些特征是陶瓷机械性能的不利因素，通过在晶界处引入纳米多孔性和弱非晶碳，可以显著提高纳米晶碳化硼的抗压强度、塑性和韧性。透射电子显微镜揭示了这种不寻常的纳米尺寸效应是由晶界滑动引起的纳米多孔性的变形消除引起的，而晶界滑动是在软晶界相的辅助下进行的。这项研究对于开发具有超高强度和增强的塑性和韧性的高性能陶瓷具有重要意义。
