金屬材料NT和HNT諸結(jié)構(gòu)的實驗、原子和理論研究成果

納米孿晶（NT）和分層納米孿晶（HNT）面心立方（FCC）金屬最近在實驗、計算和理論模型方面均取得了較大的研究進展。

來自香港城市大學(xué)的呂堅教授（法國技術(shù)科學(xué)院院士，本刊編委，曾在本刊發(fā)表研究論文“Super square carbon nanotube network: a new promising water desalination membrane”） 對此作了全面綜述。HNT結(jié)構(gòu)是一種新穎的結(jié)構(gòu)，與NT結(jié)構(gòu)材料相比具有更高的強度/延展性。

綜述主要關(guān)注金屬材料中NT和HNT諸結(jié)構(gòu)的實驗、原子和理論方面的最新研究成果：

1）闡述了用于制造NT和HNT結(jié)構(gòu)的幾種自下而上和自上而下的先進技術(shù)。

2）采用塑性形變技術(shù)可成功誘導(dǎo)HNT結(jié)構(gòu)的形成，而采用晶體生長的模式則幾乎不能成功合成HNT結(jié)構(gòu)。對NT和HNT FCC金屬的分子動力學(xué)（MD）研究揭示了諸如雙晶間距、晶粒尺寸和塑性取向等納米尺度效應(yīng)極大地改變了NT和HNT金屬的性能。因而與NT結(jié)構(gòu)相比，HNT結(jié)構(gòu)有可能開啟材料學(xué)的一些獨特現(xiàn)象；

3）人們基于實驗和MD模擬觀測揭示的現(xiàn)象和機制而提出了一系列理論模型，可有效描述NT和HNT兩類金屬的力學(xué)行為；

4）目前HNT結(jié)構(gòu)的制造技術(shù)及其對金屬性能的影響研究，均處于起步階段，迫切需要進一步的探索來推動先進材料的設(shè)計。

The recent studies on nanotwinned (NT) and hierarchical nanotwinned (HNT) face-centered cubic (FCC) metals are presented in this review. The HNT structures have been supposed as a kind of novel structure to bring about higher strength /ductility than NT counterparts in crystalline materials. We primarily focus on the recent developments of the experimental, atomistic and theoretical studies on the NT and HNT structures in the metallic materials. Some advanced bottom-up and top-down techniques for the fabrication of NT and HNT structures are introduced. The deformation induced HNT structures are available by virtue of severe plastic deformation (SPD) based techniques while the synthesis of growth HNT structures is so far almost unavailable. In addition, some representative molecular dynamics (MD) studies on the NT and HNT FCC metals unveil that the nanoscale effects such as twin spacing, grain size and plastic anisotropy greatly alter the performance of NT and HNT metals. The HNT structures may initiate unique phenomena in comparison with the NT ones. Furthermore, based on the phenomena and mechanisms revealed by experimental and MD simulation observations, a series of theoretical models have been proposed. They are effective to describe the mechanical behaviors of NT and HNT metals within the applicable scope. So far the development of manufacturing technologies of HNT structures, as well as the studies on the effects of HNT structures on the properties of metals are still in its infancy. Further exploration is required to promote the design of advanced materials.