Preparation of Metal Films Containing Nano-Size Channels

通过超细颗粒的固结制备的金属薄膜可能含有纳米尺寸的孔和沿沿着的通道，并且它们有望用于金属纳米过滤器或催化材料。为了制备具有纳米孔道的金属薄膜，采用气相沉积法制备了低密度的纳米晶（n-）Au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。某些n-Au薄膜在室温下对氦气的透气性约为10 μ <-11>mol·m/（Pa·m^2·s），比天然橡胶等塑料薄膜的透气性大两个数量级以上。在具有高透气性的n-Au薄膜的STM表面图像中发现了直径约为20 nm的孔状凹坑。的n-Au膜的气体渗透性的下降成正比的气体的分子量的平方根。这些观察结果表明，目前的n-Au膜的气体渗透性是由于通道的直径为1.20 nm，面积分数为1.1%，其中气体原子被假定为渗透的n-Au膜的分子流。此外，相对密度为1.95%的n-Au薄膜具有很高的热稳定性，即在1200 K下退火1.8 ks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隙对本发明的n-Au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