New materials with photocatalytic properties
Photocatalytic titanium oxide can be produced using an industrial depositing process (PVD). The coating is up to 28 times higher than the activity of commercially available ‘self-cleaning’ glass. The result has been obtained through control of the atomic composition, the crystalline composition and the micro structure of the material.
A new material consisting of titanium oxide nanotubes has been developed. The nanotubes are formed around a thin coating on e.g. glass or stainless steel. The coating is transparent and has higher photocatalytic activity than coatings of commercially available titanium oxide. At present, a patent application has been submitted for this method.
Self-cleaning particles are manufactured by means of so-called sol-gel solutions. The material is intended to be used to make metals, glass and plastic self-cleaning.
Photocatalytic coatings
The coating thickness of photocatalytically active titanium dioxide is between 50 and 3000 nanometre. The coatings can be deposited on materials of e.g. aluminium, steel, silicon, glass, powder-lacquered aluminium and various types of plastic (e.g. polycarbonate).
Transparent photocatalytically active TiO2 films have been manufactured on the basis of a so-called sol-gel method. In order to avoid degradation of underlying material a barrier layer has been developed, which makes it possible to coat plastic or painted surfaced with photocatalytic coating.
Characterization methods
Determination of self-cleaning property: A test setup of the water treating properties of the photocatalytic materials has been established. The water treating properties are determined by measuring degradation of the colouring agent methylene blue in aqueous solution. The method follows the German standard DIN 52980.
Determination of fat-cleaning property: The ability of self-cleaning surfaces to degrade fat can now be determined. Stearic acid is used as model compound. The method is based on the German standard Degradation of stearicacid (DIN pre draft).
Determination of air-cleaning property: Equipment for measurement of the air-cleaning properties of photocatalytic materials has been developed. Acetone is used as model gas. The acetone is degraded to CO2 during the photocatalytic exposure. The air-cleaning properties of materials can be determined within few hours.
Degradation of gasses: Photocatalytic oxidation of e.g. carbon monoxide and NOx’s can be determined by means of new developed micro reactor.
Determination of degradation: Organic substances, which are in physical contact with photocatalytic materials, are degraded to e.g. gaseous products. Analysis method for determination of these degradation products has been established.
Products and fields of application
At present, work is carried out regarding use of self-cleaning surfaces for outdoor products.
At present, work is carried out regarding use of photocatalysis in connection with air cleaning and degradation of undesirable gasses in equipment where ultra-violet light is present.
At present, work is carried out regarding development of self-cleaning paints and coatings with commercial aim.
How efficient is photocatalysis?
Our measurements show that photocatalytic surfaces can degrade up to 5 ml fatty substance per square metre per hour in ordinary sunlight.