以氣相去合金法合成奈米多孔銅銀之動力學與機械性質分析

Abstract

氣相去合金法是一種已經被證實可回收的去合金方法，用於合成奈米多孔金屬而不產生化學廢物，例如先前研究透過銅-鋅前驅合金合成奈米多孔銅。然而目前仍然缺乏透過氣相去合金法從三元前驅合金中合成奈米多孔雙金/合金的相關研究。本研究使用了銅-銀-鋅當作前驅合金，並透過氣相去合金法製作奈米多孔銅-銀結構，並且探討貴金屬銀的添加對生長動力學與機械性質的影響。實驗結果顯示銀在氣相去合金過程中抑制了銅-銀原子之間的擴散和重組，因此有效減小了多孔結構的支架尺寸。此外，在機械性質表現上，擁有相似相對密度的奈米孔洞銅-銀的能量吸收達75.4 MJ/cm³，比起奈米孔洞銅的42.5 MJ/cm³能量吸收要來的高出許多，也超過了透過其他方法合成的多孔銅或銅複合材料的能量吸收表現，這是由於支架連接性、銅-銀雙金屬強化機制與奈米尺寸效應的協同效應讓其機械性質得到大幅的提升，提供了航太材料或是汽車產業等需要高強度輕量化需求的材料選擇。此外，實驗中也觀察到銅-銀支架的生長會有中間相的形成，且在特定比例的前驅合金經過氣相去合金後會有明顯的前驅合金母相相邊界的保留，這是由於銀的偏析現象以及不同合金相會有不同的支架形貌與尺寸。最後再藉由支架生長活化能預測確定了奈米多孔銅-銀的活化能約為1.3 eV與1.57 eV，這意味著銅-銀支架的形成可能是一種晶界擴散或是相界面擴散的過程。

The vapor phase dealloying (VPD) has been demonstrated as a recyclable dealloying technique for synthesizing nanoporous metals without chemical waste, such as nanoporous Cu (NPC) from Cu-Zn precursor alloys. However, there was still a lack of utilizing the VPD method to synthesize nanoporous bimetallic/alloy structures from ternary precursor alloys. In this study, copper-silver-zinc was utilized as the precursor alloy, and nanoporous copper-silver structures (NPCS) were synthesized via the VPD process, investigating the influence of noble metal Ag addition on ligament growth kinetics and mechanical properties. Experimental results revealed that silver suppressed the diffusion and rearrangement of the remaining atoms Cu-Ag during the VPD process, effectively reducing the ligament size and increasing mechanical properties. However, in terms of the mechanical properties, the energy absorption capacity of NPCSs is up to 75.4 MJ/cm³, which is considerably higher than the 42.5 MJ/cm³ energy absorption of NPC via VPD at a similar relative density. It also exceeds the energy absorption performance of porous copper or copper composites synthesized by other methods. This significant enhancement in mechanical properties is attributed to the synergistic effects of ligament connectivity, Cu-Ag strengthening mechanisms and nano size effects, providing materials choices for industries such as aerospace or automotive, which demand high-strength lightweight materials. Moreover, it was observed that the morphology of the precursor phase boundary can be preserved after VPD, due to the segregation of silver and the different ligament morphologies and sizes of different alloy phases. Through varying VPD times and temperatures, the calculated activation energy for ligament growth was determined to be approximately 1.3eV and 1.57eV, suggesting that the formation of the Cu-Ag ligaments was dominated by grain boundary diffusion or interphase boundary diffusion.