Nano-Science & Technology Center, LINTEC OF AMERICA, Inc. , 990 North Bowser Road, Suite 840, Richardson, Texas 75081, United States.
Nano Lett. 2018 Jan 10;18(1):208-214. doi: 10.1021/acs.nanolett.7b03930. Epub 2017 Dec 22.
Nanotwinned-metals (nt-metals) offer superior mechanical (high ductility and strength) and electrical (low electromigration) properties compared to their nanocrystalline (nc) counterparts. These properties are advantageous in particular for applications in nanoscale devices. However, fabrication of nt-metals has been limited to films (two-dimensional) or template-based (one-dimensional) geometries, using various chemical and physical processes. In this Letter, we demonstrate the ambient environment localized pulsed electrodeposition process for direct printing of three-dimensional (3D) freestanding nanotwinned-Copper (nt-Cu) nanostructures. 3D nt-Cu structures were additively manufactured using pulsed electrodeposition at the tip of an electrolyte-containing nozzle. Focused ion beam (FIB) and transmission electron microscopy (TEM) analysis revealed that the printed metal was fully dense, and was mostly devoid of impurities and microstructural defects. FIB and TEM images also revealed nanocrystalline-nanotwinned-microstructure (nc-nt-microstructure), and confirmed the formation of coherent twin boundaries in the 3D-printed Cu. Mechanical properties of the 3D-printed nc-nt-Cu were characterized by direct printing (FIB-less) of micropillars for in situ SEM microcompression experiments. The 3D-printed nc-nt-Cu exhibited a flow stress of over 960 MPa, among the highest ever reported, which is remarkable for a 3D-printed material. The microstructure and mechanical properties of the nc-nt-Cu were compared to those of nc-Cu printed using the same process under direct current (DC) voltage.
纳米孪晶金属（nt-metals）相较于其纳米晶（nc）对应物具有更优异的机械（高延展性和高强度）和电学（低电迁移）性能。这些特性在纳米尺度器件的应用中尤其具有优势。然而，nt-metals 的制造一直局限于薄膜（二维）或基于模板（一维）的几何形状，使用各种化学和物理过程。在这篇快报中，我们展示了在环境气氛中局部施加脉冲电流的电沉积工艺，用于直接打印三维（3D）独立式纳米孪晶铜（nt-Cu）纳米结构。通过在含有电解质的喷嘴尖端施加脉冲电流进行了 3D nt-Cu 结构的增材制造。聚焦离子束（FIB）和透射电子显微镜（TEM）分析表明，打印的金属完全致密，并且基本上没有杂质和微观结构缺陷。FIB 和 TEM 图像还揭示了纳米晶-纳米孪晶-微观结构（nc-nt-microstructure），并证实了在 3D 打印的 Cu 中形成了相干孪晶界。通过直接打印（无 FIB）微柱进行原位 SEM 微压缩实验，对 3D 打印 nc-nt-Cu 的力学性能进行了表征。3D 打印的 nc-nt-Cu 表现出超过 960 MPa 的流动应力，这是迄今为止报道的最高值之一，对于 3D 打印材料来说非常显著。将 nc-nt-Cu 的微观结构和力学性能与使用相同工艺在直流（DC）电压下打印的 nc-Cu 进行了比较。
