Preparation of Metal Films Containing Nano-Size Channels

由超细颗粒固结而成的金属薄膜可能沿晶界含有纳米尺寸的孔和沟道，有望应用于金属纳米过滤器或催化材料。为了制备含纳米沟道的金属薄膜，采用气相沉积法制备了低密度纳米金薄膜。制备的n-Au薄膜的密度约为体Au密度的93~98%，平均晶粒尺寸约为10~20 nm。一些n-Au薄膜在室温下对氦气体的气体渗透率约为10^&lt；-11；molm/(Pam^2 S)，比天然橡胶等塑料薄膜的渗透率大两个数量级以上。在高透气性的n-Au薄膜的STM表面图像中发现了直径约为20 nm的孔状韧窝。N-Au薄膜的气体渗透率与气体分子量的平方根成正比。这些观察表明，目前n-Au薄膜的气体渗透性是由于直径为~20 nm、面积分数为~1%的沟道所致，其中气体原子以分子流的形式渗透到n-Au薄膜中。此外，相对密度约为95%的n-Au薄膜具有较高的热稳定性，即在1200K下经1.8K的热处理后，平均晶粒尺寸保持在40 nm左右。这表明样品中的纳米通道或孔洞对目前n-Au薄膜的高热稳定性起着重要作用。

Metallic films prepared by consolidation of ultra-fine particles may contain nano-size pores and channels along the grain boundaries, and they are expected for the application to metallic nano-filters or catalytic materials. In order to prepare the metallic films containing nano-size channels, low-density nanocrysatlline (n-) Au films were prepared by applying the gas-deposition method. The density of n-Au films prepared was about 93 〜 98 % of the bulk Au density and the mean grain size about 10 〜 20 nm. Some of the n-Au films showed gas-permeability of about 10^<-11> mol m/(Pa m^2 s) for helium gas at room temperature, that is larger by mare than two order than those of the plastic films such as the natural rubber. Pore-like dimples with the diameter of 〜 20 nm were found in the STM surface images of n-Au films with the high gas-permeability. The gas-permeability of the n-Au films was decreased in proportional to the square root of the molecular weight of gas. These observations suggest that the gas-permeability of the present n-Au films is due to the channels with the diameter of 〜 20 nm and the area fraction of 〜 1%, where the gas atoms are assumed to permeate the n-Au films as a molecular flow. Further, the n-Au films with the relative density of 〜 95 % showed a high thermal stability, i.e. the mean grain size remained to be about 40 nm after the annealing at 1200 K for 1.8 ks. It suggests that the nano-channels or pores in the specimens play an important role on the high-thermal stability of the present n-Au films