Mixed oxide films on tin

Towards efficient photocatalytic degradation of organic pollutants in hierarchical TiO2/SnO p-n heterojunction under visible-light irradiation

Preparation of a p-n heterojunction with hierarchical structure is of great significance for photocatalysis due to its large specific surface area, abundant active sites and increased charge separation rate. Herein, we designed the novel p-n heterojunction photocatalyst TiO₂/SnO microflower (TiO₂/F-SnO) with hierarchical architecture by decorating TiO₂ nanoparticles on the surface of the SnO microflower via a simple hydrothermal route. Compared to pure TiO₂ and TiO₂/SnO with a microplate structure (TiO₂/P-SnO), TiO₂/F-SnO heterojunctions exhibited significantly enhanced photocatalytic performances for organics removal such as toluidine blue O (TBO) and methylene blue (MB) under daylight fluorescent lamp irradiation (350-800 nm). The improved performance was not only ascribed to the promoted charge transfer and separation efficiency induced by the formation of p-n junction, but also attributed to the larger specific surface area, sufficient active sites and stronger redox ability provided by the hierarchical microflowers. Moreover, after three photocatalytic cycles (24 h), the TiO₂/SnO heterojunction still exhibited a stable photocatalytic activity. Finally, the photocatalytic enhancement mechanism for the TiO₂/SnO heterojunction was proposed based on band alignments calculation and the active species trapping experiments.

Internal corrosion and shelf-life of food cans and methods of evaluation

Internal corrosion in food cans is characterized by metallic dissolution which is an electrochemical reaction. In lacquered cans, corrosion may also cause disruption in the continuity of the lacquer film. These reactions may cause organoleptic changes in the product, loss of vacuum, swelling, and leaking in extreme cases. In some instances the metal dissolution (i.e., lead) may give rise to toxicological problems. Therefore, these phenomena are often the limiting factor in the shelf life of canned products. Changes in color, texture, and sensoric properties of the foods, which take place simultaneously, affect the aesthetic and nutritional value of the product and thus its shelf life. These changes are often related to interactions with the container. For example, tin dissolution prevents browning and loss of ascorbic acid. Shelf life of canned foods is governed by the quality of the raw materials, the processing technology, quality of the container and storage conditions which will be reviewed in this paper. Can manufacturing technologies, mechanisms of electrochemical corrosion, methods of their measurement and prediction of shelf life will be discussed.