Sealing Pores By Atomic Layer Deposition

Aluminum has small density, excellent corrosion resistance, high ductility, and suitable for various processing technology. It has a wide range of applications in the field of architecture, daily supplies, transportation and so on. Aluminum is chemically active substances, usually the natural oxide film does not has enough protection performance. So it should be treated to get better protection. The anodic aluminum oxide can protect the aluminum substrate and can be easily modified. High porosity of the porous having a strong adsorption capacity can adsorb pollutants and corrosive substances, and effect the appearance and durability of aluminum. The porous must be seal. Traditional sealing techniques mainly include high-temperature sealing, middle-temperature sealing, cold sealing technology. High temperature sealing has the properties of high energy consumption, limited protection performance, easy to crack and so on. Chromium and nickel in the middle-temperature sealing can pollute the environment. The cold sealing based on the Fluorine-Nickel system also has environmental pollution. Thus, in the aspect of energy saving and environmental protection, a new model sealing process technology will be the main technology in the future.Atomic layer deposition (atomic layer deposition, ALD) technology is a new and green technology, deriving from CVD technology, with a wide range of applications. In the1990s, ALD technique has been used with different thicknesses of170nm500nm to prepare Al2O3, TiO2, and Ta2O5single layer and Al2O3-TiO2nano-laminated layer as corrosion protection layer. ALD technique has also been used to prepare Al2O3and TiO2films to protect microporous materials and other defects in the surface of PVD materials, steel and so on. ALD technology has high uniformity and shape retention, and the thickness of the film can have precise control in angstrom level. ALD technology to control the film thickness by the number of cycles, and gradually reduce the membrane surface pore size, lower the surface pore density, and thus has a great advantage in terms of sealing porous materials. ALD technology’s features make it become a ideal sealing technology, it will have broad application prospects in green sealing process technology.Research work and the results are as follows:1.Anodization experiments:At the voltage of16.5V, in sulfuric acid electrolyte, at the temperature of18℃anodized25～30min, to prepare a large pore size of about16nm porous anodic alumina as ALD sealing test substrate. The aluminum with the chemical polishing can obtain better anodized porous structure.2.ALD deposition:The deposition process was used in pulsed deposition model. The high purity N2(99.99%) was used as a carrier gas and the cleaning gas. The trimethyl aluminum (TMA,99.7%), titanium tetraisopropoxide (C12H2sO4Ti) and deionized H2O were used as the Al source, Ti source (65℃) and O source, at0.15torr to prepare the film in different cycles, different temperatures, the time series and different sealing laminate.3.Film Analysis:Al2O3thin film is amorphous film, TiO2films are polycrystalline film. The deposition rate of Al2O3thin film is1.21A/cycle, and the deposition rate of TiO2film is0.3A/cycle XPS results show Al2O3and TiO2films has high purity. The surface structure is constitute of～25nm particle and the surface has uniform and dense structure.4.Porous size changing analysis:near the surface of the porous film, the process of sealing of the high aspect ratio porous structure can easily form of the type of CVD The sealed sample has cavity in the internal structure.5.Dyeing test:with the increases number of cycles in the ALD process the ability of anti-dyeing gradually increased, and after sealed the sample has excellent anti-dyeing properties.6.Acid corrosion research:under the temperature of200℃the corrosion resistance of the single Al2O3film sealed samples increased with the increasing temperature, and then decreased as the temperature increased higher than200℃. At the temperature of200℃the sample has the best corrosion resistance. The corrosion resistance of the single TiO2film sealed samples decreased with the increasing temperature the temperature increased higher than200℃. Corrosion resistance at a film temperature of200℃best. At the temperature of200℃the sample has the best corrosion resistance. The Al2O3/TiO2film laminated with25cycles per material has the best corrosion resistance. With the growth of the deposition temperature the corrosion performance decreased.