Nanoporous Anodic Aluminum Oxide Layers Research Articles

Intermediate-temperature sensors based on La0.5Ba0.5MnO3/nanoporous anodic aluminum oxide multilayered film thermistors

Perovskite La0.5Ba0.5MnO3 (LBMO) film thermistors for temperature monitoring over a wide range of intermediate temperatures (200–450 °C) were fabricated on thin Al-foil substrates with a nanoporous anodic aluminum oxide layer at the Al surface (AAO-Al).

Oil‐Impregnated Nanoporous Oxide Layer for Corrosion Protection with Self‐Healing

The major drawback of current passivation techniques for preventing corrosion is the lack of ability to withstand any external damages or local defects. In this study, oil‐impregnated nanoporous anodic aluminum oxide (AAO) layers are investigated to overcome such limitations and thus advance corrosion protection. By completely filling hydrophobized nanopores with oil via a solvent exchange method, a highly water‐repellent surface that prevents the penetration of corrosive media into the AAO layer and hence the corrosion of aluminum is achieved. The impregnation of oil into the hydrophobic nanoporous AAO layer enhances the corrosion resistance of an AAO layer by two and four orders of magnitude compared to that of a hydrophobic (i.e., air‐entrained) and a bare (hydrophilic) AAO, respectively. In the presence of local defects, the oil impregnated within the hydrophobic nanoporous AAO layer naturally permeates into the defects and ultimately inhibits the exposure of the aluminum surface to corrosive media. Whereas the corrosion current density of the air‐entrained hydrophobic AAO layer increases by more than 30 times after cracks, that of the oil‐impregnated AAO layer increases by no more than 4 times, showing superior anticorrosion property even after there are cracks, owing to the effective self‐healing capability.

Nanoporous anodic alumina oxide layer and its sealing for the enhancement of radiative heat dissipation of aluminum alloy

Various types of nanoporous anodic aluminum oxide layers and their sealings were studied to enhance the thermal emissivity and hence improve the heat dissipation of aluminum alloy for energy application. Dissipating heat fluxes from the anodized aluminum surfaces were measured using a modified steady-state method and investigated with respect to the various nanoporous morphologies obtained with different anodizing conditions and sealing methods. Results show that the anodized nanoporous oxide layers significantly enhance the thermal emissivity and heat dissipation of aluminum alloy, compared to bare aluminum alloy, and such enhancement is further improved with sealings. A thicker nanoporous oxide layer anodized in oxalic acid results in higher thermal emissivity and better heat dissipation than that in sulfuric acid, showing a darker color which is attributed to the more irregular and disordered pore size and pattern of the nanoporous oxide layer. The nanoporous oxide layer with cold NiF2 or black sealing shows further enhancement in thermal emissivity and heat dissipation, demonstrating the highest enhancement in emissivity up to 0.906 in case of the nanoporous oxide layer anodized in oxalic acid with black sealing, which is seven times greater than that of bare aluminum. The nanoporous oxide layer with black sealing also results in the significant improvement of the cooling efficiency of a heat exchanger system of aluminum alloy by 36.4%, suggesting great energy saving for real energy application.

Air-Impregnated Nanoporous Anodic Aluminum Oxide Layers for Enhancing the Corrosion Resistance of Aluminum.

Nanoporous anodic aluminum oxide layers were fabricated on aluminum substrates with systematically varied pore diameters (20-80 nm) and oxide thicknesses (150-500 nm) by controlling the anodizing voltage and time and subsequent pore-widening process conditions. The porous nanostructures were then coated with a thin (only a couple of nanometers thick) Teflon film to make the surface hydrophobic and trap air in the pores. The corrosion resistance of the aluminum substrate was evaluated by a potentiodynamic polarization measurement in 3.5 wt % NaCl solution (saltwater). Results showed that the hydrophobic nanoporous anodic aluminum oxide layer significantly enhanced the corrosion resistance of the aluminum substrate compared to a hydrophilic oxide layer of the same nanostructures, to bare (nonanodized) aluminum with only a natural oxide layer on top, and to the latter coated with a thin Teflon film. The hydrophobic nanoporous anodic aluminum oxide layer with the largest pore diameter and the thickest oxide layer (i.e., the maximized air fraction) resulted in the best corrosion resistance with a corrosion inhibition efficiency of up to 99% for up to 7 days. The results demonstrate that the air impregnating the hydrophobic nanopores can effectively inhibit the penetration of corrosive media into the pores, leading to a significant improvement in corrosion resistance.

Self-patterned localized metal contacts for silicon solar cells

Abstract

Liquid crystal alignment in nanoporous anodic aluminum oxide layer for LCD panelapplications

This paper reports the implementation and integration of a self-assembled nanoporousanodic aluminum oxide (np-AAO) film and liquid crystal (LC) on an ITO–glass substratefor liquid crystal display (LCD) panel applications. An np-AAO layer with a nanoporearray acts as the vertical alignment layer to easily and uniformly align the LCmolecules. Moreover, the np-AAO nanoalignment layer provides outstanding materialproperties, such as being inorganic with good transmittance, and colorless onITO–glass substrates. In this application, an LCD panel, with the LC on the np-AAOnanoalignment layer, is successfully implemented on an ITO–glass substrate, and itsperformance is demonstrated. The measurements show that the LCD panel, consisting ofan ITO–glass substrate and an np-AAO layer, has a transmittance of 60–80%.In addition, the LCD panel switches from a black state to a bright state at 3 Vrms, with a response time of 62.5 ms. In summary, this paper demonstrates the alignment of LCon an np-AAO layer for LCD applications.