Growth of porous type anodic oxide films at micro-areas on aluminum exposed by laser irradiation

Abstract

Aluminum covered with pore-sealed anodic oxide films was irradiated with a pulsed Nd-YAG laser to remove the oxide film at micro-areas. The specimen was re-anodized for long periods to examine the growth of porous anodic oxide films at the area where substrate had been exposed by measuring current variations and morphological changes in the oxide during the re-anodizing. The chemical dissolution resistance of the pore-sealed anodic oxide films in an oxalic acid solution was also examined by measuring time-variations in rest potentials during immersion.The resistance to chemical dissolution of the oxide film became higher with increasing pore-sealing time and showed higher values at lower solution temperatures. During potentiostatic re-anodizing at five 35-µm wide and 4-mm long lines for 72 h after the film was removed the measured current was found to increase linearly with time. Semicircular columnar shaped porous type anodic oxide was found to form during the re-anodizing at the laser-irradiated area, and was found to grow radially, thus resulting in an increase in the diameter. After long re-anodizing, the central and top parts of the oxide protruded along the longitudinal direction of the laser-irradiated area. The volume expansion during re-anodizing resulted in the formation of cracks, parallel to the lines, in the oxide film formed during the first anodizing.

Fabrication of anodic porous alumina via anodizing in cyclic oxocarbon acids

“…Thin porous oxides measuring approximately 1 µm in thickness were also formed in the region between the burned oxides (i.e., except for the burned region). This local thickening of the anodic oxide is typically observed when anodizing under the burning conditions [43,62], and similar structures have also been observed during the selective growth of anodic porous alumina films in micro-sized areas of aluminum substrates exposed by imperfections and laser irradiation [65][66][67]. In addition, it was observed that the burned oxides possessed several cracks measuring a few micrometers in width from the surface and throughout their thickness.…”

Aluminum bulk micromachining through an anodic oxide mask by electrochemical etching in an acetic acid/perchloric acid solution

“…2c). The applied voltage during electrochemical etching was chosen in reference to previous investigations [8,14], and the voltage is a typical value for electrochemical polishing of aluminum. A platinum plate was used as the counter electrode, and the specimens were set in parallel 15 mm from the counter electrode during electrochemical etching.…”

“…1). After the laser irradiation, subsequently electro-and electro-less plating caused a selective metal and organic compound deposition on the exposed aluminum substrate, and microstructure fabrication such as micro-coils [8][9][10][11], printed circuit boards [12][13][14], plastic injection molds [15], three-dimensional (3D) complicated micromachine components [16,17], 3D micro-actuators [18,19], and electrochemical micro-reactors [20], was successfully achieved.…”

Fabrication of Anodic Porous Alumina by Squaric Acid Anodizing

“…Porous anodic oxide films of aluminum (anodic porous alumina) have been widely investigated as nanotemplates and resist films with good insulating properties for various micro-and nano-technology applications, such as magnetic recording media [1,2], electronic devices [3], biosensors [4], photonic crystals [5][6][7], microlens arrays [8,9], plasmonic devices [10][11][12], three-dimensional microstructures [13][14][15] and other basic nanodevices [16]. When aluminum is anodized in appropriate acidic electrolytes, porous alumina develops, which exhibits a uniform array of hexagonal cells, each containing a uniform cylindrical nanopore at the center [17][18][19][20][21][22] (lower right in Fig.…”