结构均匀的超低密度纳米多孔金块体制备与表征及其体积收缩的控制

Fabrication, characterization of ultra-low-density bulk nanoporous gold with uniform structure and volume shrinkage control during drying

摘要:

超低密度纳米多孔金块材是惯性约束聚变(ICF)的目标材料。由于结构的不均匀性和有机模板分解造成的碳元素残留等原因,现有的多孔金在ICF应用中有一定的局限性。因此,结合去合金化方法以二氧化硅为模板制备出了具有亚微米级大孔和纳米级小孔的双级孔结构的纳米多孔金块体。然而,模板尺寸的急剧减小使得金含量用量极低而引起样品在干燥过程中严重收缩。因此研究了干燥方式对多孔金体积收缩的影响。结果表明,样品在普通干燥过程中体积收缩高达86.41%,而采用超临界干燥体积收缩被控制到4%以下,密度被控制到0.35g/cm₃(孔隙率98.19%)以下。制备的超低密度多孔金明显地缩小了模板留下的大孔(500 nm)和去合金产生的小孔(2-70nm)之间的尺寸差距,有效地提高了结构的均匀性。

Abstract:

Ultra-low-density bulk nanoporous gold (NPG) is required in inertial confined fusion (ICF) experiments. Existing bulk NPG has some limitations in ICF application due to non-uniformity structure or residues of C elements originated from organic template. Here, combined with dealloying, NPG with submicron cavities and nanopores was prepared by nano-SiO₂ templates. However, the smaller templates bring greater challenges for the volume shrinkage control during drying as gold content on each shell is extremely low for ultra-low density. Therefore, the influence of drying method on volume shrinkage was investigated. The results show that volume shrinkage was up to 86.41% during conventional drying, but it was controlled below 4% by supercritical CO₂ drying. Finally, NPG with ultra-low-density of 0.35g/cm₃ was successfully fabricated. Compared to NPG prepared by micro templates, the NPG with 500nm spherical cavities and 2-70nm nanopores reduces the size difference between large cavities and nanopores and significantly improves the uniformity of its structure.