Formation Efficiency of Anodic Porous Alumina in Sulfuric Acid Containing Alcohol: Comparison of the Effects of Monohydric and Polyhydric Alcohols as Additives

Abstract

Focusing on the coulombic efficiency of film formation, we systematically investigated the effects of polyhydric alcohols added to a sulfuric-acid-based electrolyte on the anodization behavior of aluminum, the coating ratio, the porosity, and the maximum attainable film thickness of the anodic oxide film by comparison with the effects of monohydric alcohols. Anodization was conducted in sulfuric acid containing various alcohols with different physical properties at a constant current density of 100 A·m−2 and at 20 °C. The viscosity and conductivity of the mixed electrolyte were affected by the addition of alcohol, resulting in an increase of the steady-state voltage with increasing alcohol concentration because of the high viscosity and low conductivity of the mixed electrolyte. Although the coating ratio, which is an index value used to evaluate the efficiency of the film formation, and the maximum attainable film thickness also increased with the addition of any of the alcohols, the addition of a polyhydric alcohol was more effective than that of a monohydric alcohol. When sulfuric acid with 50 vol% ethylene glycol was used as an electrolyte, an alumina film with less than 10% porosity was formed with high coulombic efficiency of film formation.

Porous Alumina Films Fabricated by Reduced Temperature Sulfuric Acid Anodizing: Morphology, Composition and Volumetric Growth

“…Secondly, the investigation was carried out in a pure SA solution containing no additives, as in refs. [41,43]. Thirdly, the study is methodologically comparable with the previously conducted studies for solutions of oxalic and orthophosphoric acids [54][55][56][57].…”

“…A currently rapidly developing field is the creation of nanoscale structures and composite materials using porous anodic aluminum oxide as a highly ordered nanostructured matrix for the formation of various kinds of functional materials and devices [17][18][19][20][21][22][23][24][25][26], including nanostructures such as carbon nanotubes, nanodiamonds, and graphene [27][28][29]. The above-described PAFs implementations require research results on the effect of the electrolyte nature, electrical anodizing modes, and other factors on the cellular-porous structure parameters and the PAF properties both in traditional electrolytes [30][31][32][33][34][35][36][37][38][39][40] in various compositions [41][42][43] and unconventional acidic solutions [44][45][46][47][48][49][50][51]. It is known, for example, that galvanostatic anodizing of aluminum in acidic electrolyte can occur at different rates, depending on the electrolyte nature and concentration, and on the anodic current density [26,30].…”

Recent Advances in Nanoporous Anodic Alumina: Principles, Engineering, and Applications

“…Additionally, the growth rate had decreased as compared to the anodization without ethylene glycol [ 101 ]. When different alcohols are compared, effects are more pronounced for polyhydric alcohols [ 102 ]. However, not every aspect of electrolyte additives has been revealed so far.…”

Enhancing Forbidden Light Propagation in Nanoporous Anodic Alumina Gradient-Index Filters by Alcohol Additives

“…38−43 Studies using alcohol additives to produce NAA films under steady mild anodization conditions focused on assessing their impact on the geometric features of nanopores and the Coulombic efficiency of anodization under these conditions. 44,45 Herein, the effect of alcohol additives on the structural, chemical, and optical properties of NAA-GIFs produced by sinusoidal pulse anodization under mild conditions is elucidated (Figure 1a). Comprehensive analysis of key physical and chemical features of NAA-GIFs and output electrochemical signals allows us to determine the interplay between type [methanol, ethanol, isopropanol, and ethylene glycol] and concentration (10−70 vol %) of alcohol additives in engineering the structure of these NAA-based PCs (Figure 1b,c).…”