19 June 2018

"МЕЗОПОРИСТЫЙ" - ЗНАЧИТ ЛУЧШИЙ

Titanium dioxide TiO2, in tons used in titanium white, is actually a more "smart", useful, simply unique material with amazing physical and chemical characteristics that have not been thoroughly investigated until now.


The most interesting from the point of view of practical application of titanium dioxide are its sensory and catalytic properties. So, almost any organic compounds can be oxidized to the surface of TiO2, practically any organic compounds can be oxidized to the surface of TiO2, therefore creation of titanophotocatalysts on the basis of dioxide to purify water and air from toxic organic substances is the most important and very real applied task.


Microphotographs of porous titanium dioxide:

a) Surface of the film oxidized at 20V;

b) The surface of the metal after separation of the TiO2 film;

c) Surface of the film oxidized at 30 V;

d) The surface of the metal after the separation of this TiO2 film.

Studies on this topic have been actively conducted during the last 10-15 years. Between 1993 and 2001, six international conferences were held on the photocatalytic treatment method, which gave examples of its pilot industrial applications for air purification at an explosives plant, in microelectronics workshops, in Boeing airliners , in residential urban areas and tunnels, in hospitals to suppress pathogenic microflora in the air, in the treatment of allergic diseases and asthma, in pharmaceutical industries, as well as in the destruction of military offenses substances. Photocatalysts based on titanium dioxide can also be used to create self-cleaning coatings.


The surface of a film of porous titanium dioxide (top view).

Titanium dioxide is transparent to visible light, so thin TiO2 films deposited on the glass will be invisible to the eye. The glass itself, coated with a TiO2 film, can be cleaned from organic impurities by the action of sunlight. In addition, glass coated with a TiO2 film will not fog. Fogging is usually associated with poor wettability of the glass surface, on which small drops of water, scattering light, form. If you cover the surface of the glass with a thin film of titanium oxide, the organic impurities adsorbed on the surface of the glass will be oxidized by the action of light, and therefore the dew that has settled on such a glass is not collected in droplets, but spreads over the surface and then evaporates. In addition, titanium oxide with gold nanoparticles deposited on it can be used as a catalyst that oxidizes carbon monoxide from car exhausts, in mines, in gas masks - and all this happens already at room temperature!

Now one of the most popular objects of research are nanotubes based on titanium dioxide and titanium bronzes. It turns out, however, that not less, but even more interesting objects are mesoporous titanium dioxide films, which are formed as a result of self-organization processes during anodic oxidation of the titanium surface in the media of various liquid electrolytes. Their advantage lies in the fact that they are "immobilized" (fixed) on the surface (although they can be separated from it by chemical means and thereby transformed into a thin porous membrane). In addition, such films have a high surface area, since they consist of cylindrical pores. This openwork architecture results in the fact that the films fulfill all the functions that have been known so far for other forms of titanium dioxide, but they often do much more efficiently and do not contaminate the reaction zone with their material. An additional advantage of the films is that by varying the production conditions, not only the desired pore diameter, but also the homogeneous pore size distribution, and also their local ordering can be achieved.


A photomicrograph of the cleavage of a titanium dioxide film oxidized at 60V in an electrolyte containing ethylene glycol (99.99% pure titanium).