Nanocomposites - a new material design concept
Nanocomposites - a new material design concept
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DOI：
10.1016/j.stam.2004.07.001
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发表时间：
2005-01-01
影响因子：
5.5
通讯作者：
Awaji, H
中科院分区：
文献类型：
--
作者：
Choi, SM;Awaji, H
综述了陶瓷基纳米复合材料的研究进展，着重介绍了陶瓷材料设计的新概念。首先，由以前的研究人员观察到的纳米复合材料的特点进行了总结，显着或适度的提高强度，断裂模式的急剧变化，从整体陶瓷的沿晶断裂的纳米复合材料的穿晶断裂，断裂韧性的适度增强，改善其他机械性能，和观察位错。其次，以前提出的几种机制来解释这些特点进行了审查。第三，解释了我们基于位错活动的纳米复合材料的强韧化机理。在纳米复合材料中，由于基体与分散颗粒之间的热膨胀系数不匹配，在基体晶粒中产生高度局部化的残余应力，并且在烧结后的冷却过程中产生位错。这些位错释放了烧结陶瓷基体晶粒中固有的拉伸残余应力，提高了材料的强度。此外，由于这些位错不能在室温下移动，当扩展裂纹的尖端接近该区域时，基质中的固着位错在裂纹尖端前方的前沿过程区（FPZ）中作为纳米裂纹核操作。因此，FPZ的尺寸扩大，结果断裂韧性提高。最后，为了阐明其在纳米复合材料中的增韧机理，对临界FPZ尺寸的估算进行了解释。(c)2004 Elsevier Ltd.保留所有权利。
Ceramic-based nanocomposites were reviewed, emphasizing the newly developed concept of material design for ceramics. First, characteristics of the nanocomposites observed by previous researchers were summarized as, significant or moderate improvement in strength, drastic change of the fracture mode from intergranular fracture of monolithic ceramics to transgranular fracture of nanocomposites, moderate enhancement of fracture toughness, improvement of other mechanical properties, and observations of dislocations. Second, several mechanisms proposed previously to explain these characteristics were reviewed. Third, our strengthening and toughening mechanisms of nanocomposites on the basis of dislocation activities were explained. In nanocomposites, the highly localized residual stresses in the matrix grains are generated by the mismatch of thermal expansion coefficients between the matrix and the dispersed particles, and the dislocations are yielded during the cooling process after sintering. These dislocations then release the tensile residual stresses intrinsically existing in the matrix grains of sintered ceramics and improve the strength of the materials. In addition, as these dislocations cannot move at room temperature the sessile dislocations in the matrix operate as nano-crack nuclei in a frontal process zone (FPZ) ahead of the crack tip when the tip of a propagating crack approaches this area. Therefore, the size of the FPZ is expanded and as a result the fracture toughness is improved. Finally, estimation of the critical FPZ size was explained in order to clarify its toughening mechanism in nanocomposites. (c) 2004 Elsevier Ltd. All rights reserved.