"Titanium dioxide - a compound out of this world" "Preparation and characteristics of porous structures of titanium dioxide prepared with physical methods" Anna Maria Białous1, Arkadiusz Sobczyk2 1The Szewalski Institute of Fluid - Flow Machinery PASci Photophysics Department,, ul. Fiszera 14, 80-231 Gdańsk e-mail: anna.bialous@imp.gda.pl 2 The Szewalski Institute of Fluid - Flow Machinery PASci Electrohydrodynamics Department, ul. Fiszera 14, 80-231 Gdańsk e-mail: arkadiusz.sobczyk@imp.gda.pl SEM image of a layer of Ti obtained on the surfaces of titanium plate (60 minutes, in nitrogen)

Description popularizing the research project

According to a well known saying a Jack of all trades is a master of none. Yet it does not seem to be true as far as titanium dioxide is concerned. The compound has been heralded as a compound of the future. The compound fused with the surface of roads is reported to neutralise a significant portion of exhaust pollution. Added to the exterior paint would make it resistant to dirt and capable of self-cleaning. Paper products and ceramics also benefit from the addition as their shine and durability increase. The same titanium dioxide is used in production of pharmaceuticals and food as dyes, lightening the palette of the products. Another worth-mentioning long-known use of titanium dioxide is the one as an admixture to cosmetics to protect users against UV rays.
Extraordinary properties of titanium dioxide give it a plethora of potential uses. Today's technology goes not a step but a whole quest ahead, applying TiO2 in numerous ultramodern products and technologies. Its ability to participate in light-dependent reactions makes it possible to use it in solar cells and solar thermal collectors. With light energy it works as a catalyst of many reactions, including the ones which clean air, water and soils of pollution. It is successfully applied in car engines, anti-bacterial filters and optical fibres. No wonder that all around the world there are large scale research projects on the compound, aimed at its production and constant perfecting its application, as it meets the criteria to enter the elite world of nanotechnologies. Although the fascination with the TiO2 compound is offset with the voices of concern over the side effects to the human health and the environment, getting to know it better may verify at least some of them. All the more so titanium dioxide, as a mineral, occurs in nature. Also in Poland e.g. in the Sudetes.

Abstract

1. Research project objectives. The project aims at investigating the dependence of structural and optical properties of mesoporous titanium dioxide layer on the conditions of preparing it with the physical method based on laser76 77 assisted vapor deposition. It is expected that understanding and describing the relationship between the process parameters and properties of the structures will make it possible to develop a new, effective preparation method.
2. Research methodology. Phenomena description will be performed and verified step by step (Cartesian Method), based on experimental results. In the project, the mesoporous semiconductor layers (TiO2) will be prepared by means of physical deposition. Methods based on the ablation of material with a pulsed laser beam will be used. These are known as PLVD (Pulsed Laser Vapor Deposition) in the literature, and are particularly useful for research purposes, because of the possibility of practically unlimited choice of experimental conditions and process parameters, e.g. the reactive gas (gas mixture composition) and its pressure, type of material used to produce vapor (solid or pressed powder/nanopowder), the intensity of vapor flux (system geometry, distance vapor source-substrate, the evaporation rate), the vapor energy flux (depending on the pulse fluency and rate, and wavelength of the laser), the temperature of the material and substrate. In the first stage of the project we will answer the question whether the reproducible preparation of mesoporous TiO2 structures can be obtained with proper selection of the PLVD process parameters. Our study and a few literature reports indicate a strong dependence of the morphology and the degree of porosity of the deposited layers on the pressure of the reactive gas (oxygen) and the system geometry. Our results obtained for oxygen show, that in a narrow pressure range the layers of desired crystalline structure can be prepared, however, the degree of porosity is insufficient. That is why we plan studying preparation of the layers at elevated pressure. In the next step the contribution of the variable geometry system will be investigated. Here, the new cognitive results can be expected from the application of the ablation-based method with GLAD (glancing angle deposition) configuration. In the PLVD+GLAD, angle ? measured between the normal to the substrate and the direction of the vapor flux is greater than 80, in contrast to the classical PLVD, where ? = 0. Literature indicates, that during deposition the screening of precipitates on substrate and the columnar structure growth depends strongly on ?. Moreover, simultaneous rotation of the substrate and a variation of angle results in columns of different slopes and shapes (e.g. the regular spirals, zigzags, or trees). In the second project stage, after obtaining a positive preparation results of porous structures, the degree of surface porosity and optical properties will be investigated systematically in dependence on the preparation conditions. Reproducibility of experimental results will be examined. The final stage of the project will be devoted to elaborating a consistent description of the experimentally verified results. The obtained model of the phenomena will be related to the new method of controlling preparation of porous thin films of titanium dioxide. The results will be prepared for publication. 3. Expected impact of the research project on the development of science, civilization and society. The results of the project will have a measurable impact on the recent, intensive research on effective methods of preparing mesoporous semiconductor materials. In particular, a new, efficient preparation method characterized by flexibility and low complexity will be proposed. The project outcomes summarized in publications in renowned scientific journals (e.g. Thin Solid Films, N) will contribute to the recent state of the arts.

Komitet Organizacyjny

Sponsorzy

Patronat medialny