The anodization of aluminum is an electro-chemical process that changes the surface chemistry of the metal, via oxidation, to produce an anodic oxide layer. During this process a self organized, highly ordered array of cylindrical shaped pores can be produced with controllable pore diameters, periodicity and density distribution. This enables anodic aluminum oxide (AAO) membranes to be used as templates in a variety of nanotechnology applications without the need for expensive lithographical techniques. This review article is an overview of the current state of research on AAO membranes and the various applications of nanotechnology that use them in the manufacture of nano-materials and devices or incorporate them into specific applications such as biological/chemical sensors, nano-electronic devices, filter membranes and medical scaffolds for tissue engineering.

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Progress in Nano-Engineered Anodic Aluminum Oxide Membrane Development

Super-hydrophobic film fabricated on aluminium surface as a barrier to atmospheric corrosion in a marine environment

Effect of anodizing pretreatment on laser joining CFRP to aluminum alloy A6061

Hollow nanoarchitectured materials with straight channels play a crucial role in the fields of renewable energy, environment and biotechnology due to their one-dimensional morphology and extraordinary properties. The current challenge is the difficulty on tailoring hollow nanoarchitectures with well-controlled morphology at a relatively low cost. As a conventional technique, electrochemistry exhibits its unique advantage on machining nanostructures. In this review, we present the progress of electrochemistry as a valuable tool in construction of novel hollow nanoarchitectures through pulse/step anodization, such as surface pre-texturing, modulated, branched and multilayered pore architectures, and free-standing membranes. Basic principles for electrochemical engineering of mono- or multi-ordered nanostructures as well as free-standing membranes are extracted from specific examples (i.e. porous silicon, aluminum and titanium oxide). The potential of such nanoarchitectures are further demonstrated for the applications of photovoltaics, water splitting, organic degradation, nanostructure templates, biosensors and drug release. The electrochemical techniques provide a powerful approach to produce nanostructures with morphological complexity, which could have far-reaching implications in the design of future nanoscale systems.

Electrochemical engineering of hollow nanoarchitectures: pulse/step anodization (Si, Al, Ti) and their applications

Daytime passive radiative cooler using porous alumina

Effect of Processing Parameters on Pore Structure and Thickness of Anodic Aluminum Oxide (AAO) Tubular Membranes.

Several homogenisation treatments were applied to direct chill (DC) cast ingots of aluminium alloy 6063, in order to analyse the resulting microstructures developed from these diverse conditions and their effects on the hot ductility of this alloy. Imaging was performed using scanning electron microscopy (SEM) and a focused ion beam (FIB) instrument. These techniques identified variations in distribution and morphology of second phase particles (AlFeSi and Mg2Si). FIB results for the various AlFeSi particles correctly identify their shapes in three dimensions (3D). The particles were identified by energy dispersive spectroscopy (EDS) in the SEM, and by X-ray diffraction (XRD) for bulk samples. Hot tensile testing (HTT) was conducted between 470 and 600°C to asses the hot ductility for each condition. The inferior ductility of as cast samples was due to the poor bond strength of the β AlFeSi phase at the grain boundaries. Homogenised samples, which contain α AlFeSi, exhibited improved ductility. Sa...

Effects of homogenisation treatment on microstructure and hot ductility of aluminium alloy 6063

Electron backscattered diffraction (EBSD) is performed with the scanning electron microscope (SEM) to provide a wide range of analytical data; e.g., crystallographic orientation studies, phase identification and grain size measurements. A diffraction pattern can be obtained in less than a second, but pattern quality is improved by utilizing a longer scan time. Grain mapping requires development of diffraction patterns at each pixel in the field and is a slower process. The quality of the diffraction pattern, which influences the confidence of the indexing of the diffraction pattern, depends upon removal of damage in the lattice due to specimen preparation. It has been claimed that removal of this damage can only be obtained using electrolytic polishing or ion-beam polishing. However, the use of modern mechanical preparation methods, equipment and consumables does yield excellent quality diffraction patterns without use of dangerous electrolytes and the problems and limitations associated with electropolishing and ion-beam polishing. Basically, if mechanical preparation results in quality polarized light images of non-cubic crystal structure elements and alloys (e.g., Sb, Be, Hf, α-Ti, Zn, Zr), or color tint etching of cubic, or non-cubic crystal structure elements or alloys produces high-quality color images, then the surface is free of harmful residual preparation damage and EBSD patterns with high pattern quality indexes will be obtained. Because of the acute angle between the specimen and the electron beam (70 – 74°), exceptional surface flatness is also necessary for best results.

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W. H. Van Geertruyden

Papers

Effect of Processing Parameters on Pore Structure and Thickness of Anodic Aluminum Oxide (AAO) Tubular Membranes.

Effects of homogenisation treatment on microstructure and hot ductility of aluminium alloy 6063

Metallographic Preparation for Electron Backscattered Diffraction

Surface grain structure development during indirect extrusion of 6xxx aluminum alloys