Understanding the thermal conductivity variations in nanoporous anodic aluminum oxide

An important variation in the thermal conductivity of porous alumina membranes has been observed from RT up to 1300 °C. This is due to the water loss at low temperatures or phase transitions at higher temperatures.

The Incorporation of Carbon Element into Nanoporous Anodic Alumina by Pulse Anodization

The incorporation of carbon element into nanoporous anodic aluminum oxides from oxalic acid electrolyte was studied. The carbon element content in nanoporous anodic alumina by pulse anodization reaches up to ∼20 at.%, while it remains ∼7 at.% under constant anodization. It was proposed that the ionic dynamics in nanopores governs the carbon-containing anions incorporation into nanoporous anodic oxides. For the same 20 V resting voltage, the content of carbon element remains unchanged in a broad range of working voltages: 40–150 V. X-ray photoelectron analysis further revealed that the sp2/sp3 and C–O/C═O ratios increased significantly as the working voltage increased. The color exhibited by the nanoporous anodic alumina was related to the chemical states of the carbon present in the alumina, and not the carbon content.