Passivation of TiO2 by ultra thin Al oxide

The passivation of sol gel TiO2 by ultra thin layers of alumina has been investigated using transient and spectral photovoltage techniques. The ultra thin layers of alumina were prepared by the Ion Layer Gas Reaction ILGAR technique and modified by thermal treatments in air, vacuum or Ar H2S atmosphere. The samples where characterized by Elastic Recoil Detection Analysis ERDA , x ray photoelectron spectroscopy, and contact potential difference technique. Without an alumina surface layer, electronic states in the forbidden gap of TiO2 are formed during thermal treatment in vacuum and Ar H2S atmosphere as well. The trap density is strongly reduced at the TiO2 alumina interface. The formation of electronic defects is prevented by a closed ultra thin layer of alumina which stabilizes the chemical potential of oxygen at the TiO2 surfac

Seaweed biopolymers as additives for unfired clay bricks

Unfired clay bricks are an environmentally friendly alternative to conventional masonry materials such as fired bricks and concrete blocks but their use is currently limited by their relatively poor mechanical and durability properties. While products like cement and lime are commonly added to earthen materials in an effort to improve their physical performance, these additives can also have a negative influence on the overall environmental impact. The purpose of this research is to investigate the use of alginate, a natural and renewable biopolymer obtained from brown seaweeds, as an admixture for unfired clay blocks. A total of 5 different alginates have been investigated and combined with 3 soil compositions to create prototype specimens which have then been characterised and compared in relation to flexural and compressive strength, microstructure, abrasive strength and hygroscopic behaviour. The results demonstrate that improvements in mechanical strength are dependent on the type of alginate used and the composition of the soil. The greatest increase in compressive strength is achieved using an alginate sourced from the Laminaria Hyperborea seaweed and offers a value more than double that of the equivalent control specimen. Increases in the alginate dosage do not necessarily lead to an increase in strength suggesting that there is an optimum concentration at which strength improvement is most effective