Impurity and preparation dependent properties of titania thin films
Date
2014-07-07
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Abstract
TiO2 on laialt kasutatav nii tööstuslikult kui ka igapäevaelus, seda kasutatakse palju valge pigmendina ja paakumisvastase ainena värvides, plastikutes, paberis ja teistes toodetes. Samuti kasutatakse TiO2-te päikesekreemides UV-kiirgust blokeeriva ainena, samuti on TiO2 kasutusel toiduvärvina (E171).
Lisaks on TiO2 juba leidnud või alles leidmas rakendust fotokatalüütilise materjalina, pooljuhtmaterjalina päikesepatareides, bioloogiliselt ühilduva materjalina ja isepuhastuvate katete baasmaterjalina. Nanostruktuursus, kristallstruktuur, puhtus ja paljud teised omadused mõjutavad TiO2 kasutamist erinevates rakendustes.
Käesolevas töös uuriti põhjalikult nii erinevate lisandite kui ka aluse eeltöötluse mõju TiO2 õhukeste sool-geel meetodil valmistatud kilede struktuurile ja kristallilisele koostisele. Näidati, et kilede kristalliline koostis ja faasisiirde temperatuur anataasist rutiiliks sõltub tugevalt konkreetsest lisandist ja ka aluse eeltöötlusest. Samuti näidati, et lisandiaatomid segregeeruvad kilede kuumutamise käigus TiO2 kiledest välja ja nii tekivad lisandirikkad piirkonnad kile pinnal.
Näidati, et kilede fotokatalüütiline aktiivsus sõltub nii nende nanostruktuursusest kui ka lisandite valikust ja mõjust. Lisaks õhukestele sool-geel metoodikaga valmistatud kiledele valmistati eelnevalt sünteesitud nanoosakestes koosnevaid TiO2 kilesid ning uuriti nende fotokatalüütilisi omadusi. Näidati, et nanoosakestest koosnevad TiO2 kiled lagundavad väga efektiivselt orgaanilisi ühendeid ja omavad tugevat antibakteriaalset toimet. Nanoosakestest koosnevaid kilesid on lihtne valmistada, mistõttu on nad potentsiaalselt kasutatavad ka tööstuslikes rakenduste.
Titania (TiO2) is widely used in industry and our everyday life. It finds use as white pigment and anticaking agent in paints, plastic, paper and other consumer products. It also finds application in sunscreens as UV blocker and in foodstuff as colouring agent (E171). Titania has been considered also as a perspective material for many advanced applications. It has been studied extensively as a promising photocatalyst, solar cell material, biocompatible material, material for anti-fogging and self-cleaning coatings. Nanostructure, crystal structure, purity and other qualities all play important roles in many of titania applications. Influence of the different dopants and the substrate pretreatment to the sol-gel film structure and crystal phase composition was thoroughly investigated. It was demonstrated that exact crystal phase transition temperature and extent from anatase to rutile are highly dependent on the doping element and the substrate pre-treatment. Also during annealing the impurity element tends to segregate out of the titania matrix and form dopant rich regions on the surface of the film. It was shown that the photoactivity of the TiO2 film depends on the choice of the impurity element and the nanostructure of the films. Beside titania sol-gel thin films also titania thin films consisting of premade nanoparticles were prepared and their photoactive properties were investigated. It was shown that thin titania films consisting of small premade nanoparticles exhibited enhanced photocatalytic and antibacterial properties. The films consisting of premade nanoparticles are simple to prepare and they are also efficient photocatalysts which means that they are potentially scalable to industrial level.
Titania (TiO2) is widely used in industry and our everyday life. It finds use as white pigment and anticaking agent in paints, plastic, paper and other consumer products. It also finds application in sunscreens as UV blocker and in foodstuff as colouring agent (E171). Titania has been considered also as a perspective material for many advanced applications. It has been studied extensively as a promising photocatalyst, solar cell material, biocompatible material, material for anti-fogging and self-cleaning coatings. Nanostructure, crystal structure, purity and other qualities all play important roles in many of titania applications. Influence of the different dopants and the substrate pretreatment to the sol-gel film structure and crystal phase composition was thoroughly investigated. It was demonstrated that exact crystal phase transition temperature and extent from anatase to rutile are highly dependent on the doping element and the substrate pre-treatment. Also during annealing the impurity element tends to segregate out of the titania matrix and form dopant rich regions on the surface of the film. It was shown that the photoactivity of the TiO2 film depends on the choice of the impurity element and the nanostructure of the films. Beside titania sol-gel thin films also titania thin films consisting of premade nanoparticles were prepared and their photoactive properties were investigated. It was shown that thin titania films consisting of small premade nanoparticles exhibited enhanced photocatalytic and antibacterial properties. The films consisting of premade nanoparticles are simple to prepare and they are also efficient photocatalysts which means that they are potentially scalable to industrial level.
Description
Väitekirja elektrooniline versioon ei sisalda publikatsioone.
Keywords
titaandioksiid, oksiidkiled, õhukesed kiled, keemilised omadused, füüsikalised omadused, titanium dioxide, oxide films, thin films, chemical properties, physical properties