Reference LPI-ARTICLE-1999-017View record in Web of Science Record created on 2006-02-21, modified on 2017-05-12

/pdf/metal-oxide-surfaces-and-their-interactions-with-aqueous-22jt31pax0.pdf

Metal Oxide Surfaces and Their Interactions with Aqueous Solutions and Microbial Organisms.

Nanostructured oxides in chemistry: characterization and properties.

Use of DFT to achieve a rational understanding of acid–basic properties of γ-alumina surfaces

Corundum, α-Al 2 O 3 , is the thermodynamically stable phase of coarsely crystalline aluminum oxide, but syntheses of nanocrystalline Al 2 O 3 usually result in γ-Al 2 O 3 . Adsorption microcalorimetry, thermogravimetric analyses, and Brunauer-Emmett-Teller adsorption experiments, coupled with recently reported high-temperature solution calorimetry data, prove that γ-Al 2 O 3 has a lower surface energy than α-Al 2 O 3 and becomes energetically stable at surface areas greater than 125 square meters per gram and thermodynamically stable at even smaller surface areas (for example, 75 square meters per gram at 800 kelvin). The results are in agreement with recent molecular dynamics simulations and provide conclusive experimental evidence that differences in surface energy can favor the formation of a particular polymorph.

https://science.sciencemag.org/content/sci/277/5327/788.full.pdf

Surface Energies and Thermodynamic Phase Stability in Nanocrystalline Aluminas

It has been expected that superhydrophobic (SHP) surfaces could have potential anti-icing applications due to their excellent water-repellence properties. However, a thorough understanding on the anti-icing performance of such surfaces has never been reported; even systematic characterizations on icing behavior of various surfaces are still rare because of the lack of powerful instrumentations. In this study, we employed the electrochemical anodic oxidation and chemical etching methods to simplify the fabrication procedures for SHP surfaces on the aluminum alloy substrates, aiming at the anti-icing properties of SHP surfaces of various engineering materials. We found that the one-step chemical etching with FeCl3 and HCl as the etchants was the most effective for ideal SHP surfaces with a large contact angle (CA, 159.1°) and a small contact angle hysteresis (CAH, 4.0°). To systematically investigate the anti-icing behavior of the prepared SHP surfaces, we designed a robust apparatus with a real-time control system based on the two stage refrigerating method. This system can monitor the humidity, pressure, and temperature during the icing process on the surfaces. We demonstrated that the SHP surfaces exhibited excellent anti-icing properties, i.e., from the room temperature of 16.0 °C, the icing time on SHP surfaces can be postponed from 406s to 676s compared to the normal aluminum alloy surface if the surfaces were put horizontally, and the icing temperature can be decreased from -2.2 °C to -6.1 °C. If such surfaces were tilted, the sprayed water droplets on the normal surfaces iced up at the temperature of -3.9 °C, but bounced off the SHP surface even as the temperature reached as low as -8.0 °C. The present study therefore suggests a general, simple, and low-cost methodology for the promising anti-icing applications in various engineering materials and different fields (e.g., power lines and aircrafts).

Preparation and Anti-icing Behavior of Superhydrophobic Surfaces on Aluminum Alloy Substrates

Corundum, α-Al2O3, appears to be the thermodynamically stable phase of aluminum oxide at all common pressure and temperature conditions, but attempted syntheses of nanocrystalline Al2O3 usually res...

A. J. Perrotta

Papers

Effects of increased surface area and chemisorbed H2O on the relative stability of nanocrystalline γ-Al2O3 and α-Al2O3