定向凝固规则微-纳双尺度复合银基多孔材料的结构控制机理

The study on fabrication, structural controlling and property of nanoporous metal has become a hot research topic of material science, chemistry and surface science etc. The traditional dealloying precursor metal has the shortcomings of thin thickness (<100 μm) and high brittleness. So with the aim to eliminate these disadvantages, this project will make an attempt to fabricate regular porous metal by the metal-gas eutectic directional solidification (GASAR process). The main research objects of the project are the Mg-Ag-(Pd) alloys. The researches begin with the structural control of GASAR precursor alloys: analyzing the effect of crystal growth model on the pore structure; building the relationship between crystal orientation and pore regularity; exploring the control method for symplastic growth of primary phases, eutectic phases, the second phase particles and the pores. Then, the research will be expanded to control the nanoporous structure of dealloying: studying the influence of precursor characteristic parameters and dealloying process parameters on nanoporous structure; building the relationship between characteristic parameters and threshold composition; analyzing the pore formation mechanism about the vacancy; and accomplishing the fine-grained control for nano-porous structure. Based on the above investigations, realize the effective control of the micro-nanoporous structure at finally. The research of this project has important theoretical and practical significance to enrich the solidification theory of solid-gas eutectic, and to promote the application of nanoporous material.

纳米多孔金属的脱合金法制备及其结构和性能的研究，已成为材料科学、化学及表面科学等学科的研究热点。针对传统脱合金前驱体材料厚度极薄（<100 μm）且脆性极高的缺点，本项目提出利用金属-气体共晶定向凝固（GASAR工艺）制备的微孔材料作为前驱体合金，以突破传统工艺在尺寸及性能方面技术瓶颈的新思路。项目以共晶系的Mg-Ag-(Pd)合金为对象，研究从前驱体合金的结构控制入手：分析晶体生长方式对气孔结构的影响规律，建立晶体取向与气孔规则性间的关系，探明初生相-共晶体-第二相粒子-气孔协同生长的控制方法；然后拓展到脱合金纳米多孔结构的控制：分析前驱体特征参数及脱合金参数对多孔结构的影响规律；建立合金特征参数与成分阈值间的关系，探讨与空位有关的脱合金孔隙形成机理；最终实现对微-纳复合结构的有效控制。本项目的研究对于丰富固-气共晶定向凝固理论，推进纳米多孔材料的产业应用具有重要的理论和现实意义。

利用脱合金法制备纳米多孔金属材料，是近十几年来材料科学、化学及表面科学等领域的新兴研究方向。针对传统脱合金前驱体材料尺寸极薄且力学性能极脆的缺点，本项目提出利用金属-气体共晶定向凝固（GASAR）工艺制备的微孔材料作为前驱体合金，以突破传统工艺在尺寸及性能方面技术瓶颈的新思路。以共晶系Mg-Ag合金为研究对象，本项目研究内容分为两大部分：首先分析了固/液界面凝固模式、晶体取向和“糊状区”凝固等对气孔定向生长的影响机理，获得了GASAR前驱体合金气孔结构的控制方法及理论依据；然后基于脱合金实验，掌握了前驱体特征参数及脱合金工艺参数对微-纳复合多孔结构的影响规律，探明了微-纳复合多孔结构的有效控制方法以及与空位有关的脱合金孔隙形成机理，最终实现了对定向凝固规则微-纳复合多孔金属孔结构的精细控制，为其在催化剂等领域的应用奠定基础。本项目的完成对丰富和完善传统共晶定向凝固理论，促进生物、化工、材料等领域的产业发展，提升云南乃至全国镁资源利用水平，具有重要的科学价值和现实意义。