Role of Oxalate Anions on the Evolution of Widened Pore Diameter and Characteristics of Room-Temperature Anodic Aluminum Oxide

Abstract

Anodic Aluminum Oxide (AAO) has a variety of applications depending on its pore diameter, uniformity and porosity. Here, we investigate a new finding of the widened pore diameter of AAO greatly linked to the oxalic acid anions contaminated in the AAO. As AAO was prepared by hybrid-pulse anodization in oxalic acid at low-to-high concentrations (0.3∼0.9 M) and room temperature (25 • C) instead of conventional low temperature (0∼10 • C) and low concentration (0.3 M), the average pore diameter roughly increased with concentration from 42.8 nm to 46.5 nm; while it inversely decreased with concentration from 85.6 nm to 80.0 nm after widening to enhance all pore diameters. High oxalic acid concentration resulted in AAO walls containing more anions that further decreased etching rate during widening. This new phenomenon became more pronounced by direct-current anodization than by the hybrid-pulse anodization. The possible mechanism of evolution of AAO pore diameter during pore widening in the phosphoric acid was proposed and supported by the plane-view and cross-section SEM results and photoluminescence spectra.

ppb‐Level ethanol gas sensor of porous anodic aluminum oxide at room temperature

“…The Al 2 O 3 , C = O, and PO 3 − are observed at 530.8, 531.6, and 532.9 Ev, respectively 31 . Al 2 O 3 and C=O were produced during anodization, and PO 3 − (phosphoric) ions were produced during pore expansion 32 . At the anodizing temperature of 20°C, C=O, and PO 4 3− peaks are the most pronounced.…”

“…31 Al 2 O 3 and C=O were produced during anodization, and PO 3 − (phosphoric) ions were produced during pore expansion. 32 At the anodizing temperature of 20 • C, C=O, and PO 4 3− peaks are the most pronounced. That is, the hydroxyl and oxalate anion contamination is the strongest at the anodizing temperature of 20 • C. As shown in Figure 3d, the FTIR spectrum was also confirmed to contain the most C=C and C=O functional groups at 20 • C.…”

Mechanically Robust and Thermally Conductive Nano-Porous Anodic Aluminum Oxide Templates via Thermal Stress Minimization and Alpha Phase Transformation for Interposer

“…The Al 2 O 3 , CO, and PO 3 – are observed at 530.8, 531.6, and 532.9 eV, respectively . Al 2 O 3 and CO are produced during anodization, and PO 3 – (phosphoric) ions are produced in the pore-widening process . In the alpha-AAO template, CO peak is not confirmed, and the fraction of Al 2 O 3 is increased.…”

“…34 Al 2 O 3 and C�O are produced during anodization, and PO 3 − (phosphoric) ions are produced in the pore-widening process. 35 In the alpha-AAO template, C�O peak is not confirmed, and the fraction of Al 2 O 3 is increased. An increase in the amount of Al 2 O 3 and a decrease in carbon impurities through annealing are confirmed.…”

Self‐Charging Dual‐Modal Sensor for Glucose Monitoring Based on Piezoelectric Nanowire/Microgel Hybrid Film

“…In this work, we used an AAO template because of the high breakdown strength of aluminum oxide and because of the conductive Al substrate which allows voltage application during EHD without an additional electrode material. [54][55][56] The vertically-aligned nanowires fabricated through the EHD pulling method [48,49] offer higher energy conversion efficiency compared to randomly-structured electrospun nanofibers. [57][58][59] Moreover, during the EHD pulling, poling was performed simultaneously during the growth of nanowires, and thus no additional step of dipole alignment is required.…”