High-Throughput Surface Modification of Ordered Mesoporous Alumina Enables Structural Stabilization and Selective Chemical Control

TL;DR

This paper introduces post-processing methods to improve the stability and purity of porous alumina for energy storage applications.

Contribution

The study introduces optimized post-processing treatments to remove carbon and stabilize mesoporous alumina structures.

Findings

UV/Ozone and oxygen plasma effectively remove carbon residues from the films.

High-temperature nitrogen oven anneals stabilize the porous structure at elevated temperatures.

Nanoindentation reveals treatment-induced changes in mechanical stiffness.

Abstract

Porous ceramic oxides have gained significant interest as components in a wide variety of energy storage devices. Their use, however, is limited by long and high-temperature processing methods. We recently demonstrated Porogen-integrated Rapid Oxidation (PiRO) as a new method to manufacture porous aluminum oxide in significantly shorter times and with substantial manufacturing cost savings, but challenges remain with the resultant porous matrices. First, carbonaceous residue remains in the films after the combustion event, which is necessary to minimize for electronic applications. Second, the porous structure is not stable at elevated temperatures (>250 °C), which are often required for nanocomposite applications of the matrices where filling with a second phase is achieved through high-temperature annealing. Here, we address these challenges by using post-processing treatments, including UV/Ozone, high-temperature nitrogen oven anneals, and oxygen plasma. First, we characterize the treatments’ efficacy in carbon removal using FTIR and measure bulk carbon removal with XPS. Second, we characterize the matrices’ thickness collapse and porosity changes after treatments with ellipsometry. Finally, we use nanoindentation to understand changes in stiffness resulting from the various treatments. By understanding the treatments’ roles in removing carbon from the films and stabilizing the matrix structure, we are able to select optimal post-processing treatments for designing a stable platform for further applications of the mesoporous oxide.

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