<p>   Contamination of surface and ground water from industrial wastes and anthropogenic activities represents one of the greatest challenges to the sustainable development of human society. Heterogeneous photocatalysis, a kind of advanced oxidation process characterized by the production of highly oxidative hydroxyl radicals, is a relatively novel subject with tremendous potential in water treatment applications.</p><p>    The purpose of this research was first to develop feasible hydroxyl radical detection methods, which can be used to evaluate efficiency of photocatalytic process, and second to prepare immobilized TiO2 films with high photocatalytic activities by the sol gel method.</p><p>    The feasibility of Indigo carmine and phthalic hydrazide as OH-radical probes was investigated. The organic dye Indigo carmine absorbs visual light strongly at 610 nm and its destruction can be monitored conveniently in a spectrophotometer. Results showed that both ^·OH and HO₂^·can bleach Indigo carmine, and the bleaching yield of ^·OH was pH independent. The photocatalytic dye bleaching in black light UV illuminated Degussa P25 TiO2 aerated suspensions was then investigated. A strong pH dependency of the bleaching yield was found.  This implies that the quantum yield of OH radical at pH 3 is one fourth compared to that at pH 10. The reaction of the OH radical with phthalic hydrazide will form strongly chemiluminescent 3-hydroxyphthalic hydrazide. Using the more specific phthalic hydrazide as OH radical probe, an even stronger pH dependent quantum yield of OH radical was found. At pH 10 the quantum yield reached the same magnitude as that obtained by using Indigo carmine, whereas the quantum yields at acidic pH were close to zero. However it was found that the addition of phosphate and fluoride anions can substantially enhance the OH radical yield at acidic pH by blocking the adsorption of phthalic hydrazide onto the TiO2 surfaces. Hence the adsorption of phthalic hydrazide to TiO2 is an important factor to consider when this method is used. <em></em></p><p>    Photocatalytic TiO2 films coated on metal plates were prepared by a sol gel method using titanium isopropoxide as TiO2 precursor and isopropanol as solvent. The photocatalytic activity of the obtained films was evaluated by bleaching of indigo carmine at pH 9 under black light UV irradiation. The effect of the molar ratio of isopropanol, water and hydrochloric acid to titanium isopropoxide was studied. It was also shown that the activities of TiO2 films are considerably influenced by calcination temperature, coating cycles and the supporting materials.</p> / <p>    Förorening av yt- och grundvatten från industrier och humana aktiviteter utgör en av de största utmaningarna för en hållbar utveckling av det mänskliga samhället. Heterogen fotokatalys, en slags avancerad oxidations process som kännetecknas av att starkt oxidativa hydroxylradikaler produceras, är en relativt ny teknik med stor potential för vattenrening.</p><p>    Ett syfte med detta licentiatarbete var först att utveckla och genomföra olika metoder för att detektera bildningen av hydroxylradikaler såväl i laboratoriet som i tekniska miljöer. Det andra syftet med arbetet var att syntetisera immobiliserade TiO2 filmer med hög fotokatalytisk effektivitet med en sol-gel metod.</p><p>    Möjligheten att använda indigokarmin och ftalhydrazid som OH-radikalprob undersöktes. Det organiska färgämnet indigokarmin absorberar synligt ljus starkt vid 610 nm vilket gör att dess nedbrytning lätt kan följas i en spektrofotometer. Resultaten av gammaradiolys visade att båda ^•OH och HO₂^• kan bleka indigokarmin och att den blekning som härrör från ^•OH var oberoende av pH. Fotokatalytisk blekning av indigokarmin med blacklight UV bestrålning av  Degussa P25 TiO2 suspensioner undersöktes sedan. Ett starkt pH-beroende av blekningsutbytet erhölls vilket tolkas som att kvantutbytet av OH-radikaler vid pH 3 är en fjärdedel jämfört med det vid pH 10.</p><p>    När ftalhydrazid reagerar med OH-radikaler bildas starkt kemiluminiscent 3-hydroxy-ftalhydrazid. Med denna  specifika OH-radikalprob, erhölls ett ännu starkare pH beroende. Vid pH 10 var kvantutbytet i paritet med det som erhölls med indigokarmin, medan kvantutbytet vid lågt pH var nära noll. Tillsats av fosfat-  och fluoridjoner visade sig avsevärt öka OH-radikalutbytet vid lågt pH-värde genom att blockera adsorption av ftalhydrazid på TiO2 ytorna. Adsorptionen av ftalhydrazid på TiO2 är således en viktig faktor när denna metod används.</p><p>    Fotokatalytiskt verksamma TiO2-filmer på metallplattor framställdes med sol-gel metoden med titan-isopropoxide som TiO2-prekursor och isopropanol som lösningsmedel. Den fotokatalytiska aktiviteten av TiO2-belagda plattor utvärderades genom blekning av indigokarmin vid pH 9 under blacklight UV-bestrålning. Effekten av olika proportioner mellan isopropanol, vatten och saltsyra till titan isopropoxide undersöktes. Det visade sig att denfotokatalytiska aktiviteten av TiO2-plattorna i hög grad påverkades av kalcineringstemperatur, beläggningscykler och materialet i plattorna.</p>

Contamination of surface and ground water from industrial wastes and anthropogenic activities represents one of the greatest challenges to the sustainable development of human society. Heterogeneous photocatalysis, a kind of advanced oxidation process characterized by the production of highly oxidative hydroxyl radicals, is a relatively novel subject with tremendous potential in water treatment applications.     The purpose of this research was first to develop feasible hydroxyl radical detection methods, which can be used to evaluate efficiency of photocatalytic process, and second to prepare immobilized TiO2 films with high photocatalytic activities by the sol gel method.     The feasibility of Indigo carmine and phthalic hydrazide as OH-radical probes was investigated. The organic dye Indigo carmine absorbs visual light strongly at 610 nm and its destruction can be monitored conveniently in a spectrophotometer. Results showed that both ·OH and HO2· can bleach Indigo carmine, and the bleaching yield of ·OH was pH independent. The photocatalytic dye bleaching in black light UV illuminated Degussa P25 TiO2 aerated suspensions was then investigated. A strong pH dependency of the bleaching yield was found.  This implies that the quantum yield of OH radical at pH 3 is one fourth compared to that at pH 10. The reaction of the OH radical with phthalic hydrazide will form strongly chemiluminescent 3-hydroxyphthalic hydrazide. Using the more specific phthalic hydrazide as OH radical probe, an even stronger pH dependent quantum yield of OH radical was found. At pH 10 the quantum yield reached the same magnitude as that obtained by using Indigo carmine, whereas the quantum yields at acidic pH were close to zero. However it was found that the addition of phosphate and fluoride anions can substantially enhance the OH radical yield at acidic pH by blocking the adsorption of phthalic hydrazide onto the TiO2 surfaces. Hence the adsorption of phthalic hydrazide to TiO2 is an important factor to consider when this method is used.     Photocatalytic TiO2 films coated on metal plates were prepared by a sol gel method using titanium isopropoxide as TiO2 precursor and isopropanol as solvent. The photocatalytic activity of the obtained films was evaluated by bleaching of indigo carmine at pH 9 under black light UV irradiation. The effect of the molar ratio of isopropanol, water and hydrochloric acid to titanium isopropoxide was studied. It was also shown that the activities of TiO2 films are considerably influenced by calcination temperature, coating cycles and the supporting materials. / Förorening av yt- och grundvatten från industrier och humana aktiviteter utgör en av de största utmaningarna för en hållbar utveckling av det mänskliga samhället. Heterogen fotokatalys, en slags avancerad oxidations process som kännetecknas av att starkt oxidativa hydroxylradikaler produceras, är en relativt ny teknik med stor potential för vattenrening.     Ett syfte med detta licentiatarbete var först att utveckla och genomföra olika metoder för att detektera bildningen av hydroxylradikaler såväl i laboratoriet som i tekniska miljöer. Det andra syftet med arbetet var att syntetisera immobiliserade TiO2 filmer med hög fotokatalytisk effektivitet med en sol-gel metod.     Möjligheten att använda indigokarmin och ftalhydrazid som OH-radikalprob undersöktes. Det organiska färgämnet indigokarmin absorberar synligt ljus starkt vid 610 nm vilket gör att dess nedbrytning lätt kan följas i en spektrofotometer. Resultaten av gammaradiolys visade att båda •OH och HO2• kan bleka indigokarmin och att den blekning som härrör från •OH var oberoende av pH. Fotokatalytisk blekning av indigokarmin med blacklight UV bestrålning av  Degussa P25 TiO2 suspensioner undersöktes sedan. Ett starkt pH-beroende av blekningsutbytet erhölls vilket tolkas som att kvantutbytet av OH-radikaler vid pH 3 är en fjärdedel jämfört med det vid pH 10.     När ftalhydrazid reagerar med OH-radikaler bildas starkt kemiluminiscent 3-hydroxy-ftalhydrazid. Med denna  specifika OH-radikalprob, erhölls ett ännu starkare pH beroende. Vid pH 10 var kvantutbytet i paritet med det som erhölls med indigokarmin, medan kvantutbytet vid lågt pH var nära noll. Tillsats av fosfat-  och fluoridjoner visade sig avsevärt öka OH-radikalutbytet vid lågt pH-värde genom att blockera adsorption av ftalhydrazid på TiO2 ytorna. Adsorptionen av ftalhydrazid på TiO2 är således en viktig faktor när denna metod används.     Fotokatalytiskt verksamma TiO2-filmer på metallplattor framställdes med sol-gel metoden med titan-isopropoxide som TiO2-prekursor och isopropanol som lösningsmedel. Den fotokatalytiska aktiviteten av TiO2-belagda plattor utvärderades genom blekning av indigokarmin vid pH 9 under blacklight UV-bestrålning. Effekten av olika proportioner mellan isopropanol, vatten och saltsyra till titan isopropoxide undersöktes. Det visade sig att denfotokatalytiska aktiviteten av TiO2-plattorna i hög grad påverkades av kalcineringstemperatur, beläggningscykler och materialet i plattorna.

Made available in DSpace on 2016-12-08T17:19:18Z (GMT). No. of bitstreams: 1 Andre Luiz Leite.pdf: 5779192 bytes, checksum: 04530876418d79bd340d3b48aad64e35 (MD5) Previous issue date: 2012-07-27 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The purpose of this study is to find out ways of coatings a SAE 10B30 steel with a TiO2 film, so it may have adhesion and may be known its wear resistance. In this study were investigated three kinds of coatings of TiO2, TiO2 with one on untreated steel, duplex and two treatments: TiO2 provided with nitriding in an atmosphere of 10% nitrogen, and TiO2 prior to nitriding in an atmosphere of 80% nitrogen, and the balance hydrogen gas, and were fixed temperature, pressure, and time of nitriding. The TiO2 film was deposited by triode magnetron reactive sputtering and the nitriding were made by plasma. The samples were characterized by optical microscopy, scanning electron microscopy (SEM), microhardness and roughness. Adherence was evaluated by the Rockwell C indentation method described in the VDI 3824 guidelines, and the images of evaluating were obtained by optical microscopy. The wear and the friction coefficient were evaluated through tests in a tribometer type pin on disc and wear surfaces evaluated trough images obtained by SEM. Of all configurations evaluated, the TiO2 duplex coating with sub layer nitrided in an atmosphere of 10% nitrogen resulted in better adhesion, and worse adhesion was observed in the sample with TiO2 deposited on steel without prior nitriding, although this is satisfactory. It was observed that the wear resistance was higher for samples with nitriding in an atmosphere of 10% nitrogen and wear performance was worst in the sample without treatment. The results showed that the TiO2 film has no good wear resistance for none of theconditions tested, but for applications where many cycles or large distances sliding is not required, duplex TiO2 treatment with pretreatment nitrided in an atmosphere of 10 % nitrogen is the most effective, by ensuring better adherence and wear resistance over short distances, compared with the other conditions. / O objetivo deste trabalho é determinar condições para depositar um filme de TiO2 sobre um aço SAE 10B30, de modo que este tenha boa adesão e seja conhecida sua resistência ao desgaste. Neste trabalho foram investigados três tipos de recobrimentos de TiO2, uma com TiO2 sobre aço sem tratamento, e dois tratamentos dúplex: TiO2 com previa nitretação em atmosfera com 10% de nitrogênio e 90% de hidrogênio, e TiO2 com prévia nitretação em atmosfera com 80% de nitrogênio e 90% de hidrogênio, e foram fixadas a temperatura, pressão, e o tempo de nitretação. O filme de TiO2 foi depositado por tríodo magnetron sputtering reativo e as nitretações foram feitas a plasma. As amostras foram caracterizadas através de microscopia ótica, microscopia eletrônica de varredura (MEV), microdureza e rugosidade. A adesão foi avaliada pelo método da identação Rockwell C descrito nas diretrizes da VDI 3824, e as imagens para avaliação foram obtidas através de microscopia ótica. O desgaste e coeficiente de atrito foram avaliados através de ensaios em um tribômetro do tipo pino sobre disco, e as superfícies de desgaste avaliadas através de imagens obtidas por MEV. De todas as configurações avaliadas, o recobrimento dúplex de TiO2 com subcamada nitretada em atmosfera com 10% de nitrogênio resultou na melhor adesão, e a pior adesão foi observada na amostra com TiO2 depositado sobre o aço sem prévia nitretação, embora esta ainda seja satisfatória. Foi observado que a resistência ao desgaste é maior para as amostras com nitretação em atmosfera com 10 % de nitrogênio, e o pior desempenho em desgaste foi da amostra sem tratamento. Os resultados mostram que em nenhuma das condições testadas o filme de TiO2 possui uma boa resistência ao desgaste, mas que para aplicações onde não se exigem muitos ciclos ou grandes distâncias de deslizamento, o tratamento dúplex de TiO2 com pré-tratamento nitretado em atmosfera com 10% de nitrogênio é o mais eficiente, por garantir a melhores adesão e resistência ao desgaste em pequenas distâncias, se comparado com as outras condições.

Today there is a great deal of interest in the development of gas sensors for various applications like monitoring of toxic gases, detection in oil reservoirs, mines, homes etc. Solid-state gas sensors have many advantages over the conventional analytical methods and hence are widely used. Amongst them, semiconducting metal-oxides based sensors are popular due to many advantages like low cost, small size, high sensitivity and long life. The present thesis reports a detailed work of TiO2 (Titania) thin film fabrication based on sol-gel method, study of their crystallization behavior and surface morphology, and characterizing them for alcohol sensing properties Sol-gel method is a wet chemical technique with many advantages over the conventional methods and offers a high degree of versatility to modify the film properties. Titania thin films were made with titanium isopropoxide as the precursor and ethanol and isopropanol as the solvents. Also effect of surfactants(PEG and CTAB) on the sol properties and film properties have experimentally examined. A in-house gas sensor testing setup has been designed and fabricated to characterize the sensors. Sensors with three different electrode configurations and also two different electrode material have been tested. The electrode geometry and material play a significant role on the sensing behavior and results for the same have been discussed.