Synthesis of tough nanoporous metals by controlled electrolytic dealloying
Synthesis of tough nanoporous metals by controlled electrolytic dealloying
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DOI：
10.1088/0957-4484/17/9/040
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发表时间：
2006-05
期刊：
影响因子：
3.5
通讯作者：
N. Senior;R. Newman
中科院分区：
文献类型：
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作者：
N. Senior;R. Newman
均相金属合金（如Ag-Au）的脱合金（选择性溶解）产生具有有趣性质的纳米多孔金属。到目前为止，还不可能常规地制备这种材料，使其能够抵抗机械应变，例如在膜、传感器或致动器等应用中可能遇到的机械应变。现在已经确定了一个阈值电位，用于在水溶液HClO4中对Ag-Au进行脱合金处理，在此阈值电位之上，由于单层氢氧化金的形成，会发生自发穿晶断裂。断裂机制涉及到表面扩散系数的降低，防止了多孔材料中诱导张力的松弛，以及可能的更奇特的影响。通过优化合金中Au的含量，保持在阈值电位以下，提高电解液的温度，可以制备出机械完整性高的合金膜。在这种制备方法下，纳米多孔材料表现出特殊的性能，如退火时晶界烧结，在空气中干燥时可逆硬化和脆化。
Dealloying (selective dissolution) of homogeneous metallic alloys such as Ag–Au generates nanoporous metals with intriguing properties. Until now, it has not been possible routinely to prepare such materials in a form in which they would resist mechanical strains, such as might be encountered in applications as membranes, sensors or actuators. Now a threshold potential has been identified, for dealloying of Ag–Au in aqueous HClO4, above which spontaneous transgranular fracture occurs due to the formation of a monolayer of gold hydroxide. The fracture mechanism involves a reduction in surface diffusivity, preventing relaxation of induced tension in the porous material, and possible more exotic effects. By optimizing the Au content of the alloy, staying below the threshold potential and increasing the temperature of the electrolyte, dealloyed membranes with a high degree of mechanical integrity have been prepared. When prepared in this way, the nanoporous material shows peculiar behaviours, such as grain-boundary sintering under annealing, and reversible stiffening and embrittlement when dried in air.