Rozprawy doktorskie na temat „TiO2”

The removal or killing of microorganisms on surfaces is of concern in the health care setting, food preparation areas and general work environment. The use of TiO2 photosterilisation has been proposed as an alternative to chemical disinfection of surfaces as a means to reduce the need for increasingly concentrated and aggressive chemicals necessary to kill disinfectant-resistant organisms. The objective of this research was to evaluate the ability of photocatalytic oxidation to reduce bacterial and viral contaminants on surfaces coated with TiOa and Ag-TiC^, TiO2-Ag, Cu-TiC^, TiO2-Cu. There are no British Standards that cover evaluation of such surfaces. A method for evaluation of photocatalytic surfaces was therefore developed from BS EN 13697:2001 and used to evaluate the activities of a variety of catalytic surfaces coated with TiO2, Ag and Cu and multi-layers of Ag-TiO2,TiO2-Ag, Cu-TiO2,TiO2-Cu. The antimicrobial activities were found to be dependent on the nature of the coating. Highest killing activities were obtained with Ag and Cu alone but combinations of Ag or Cu with TiO2were more active than TiO2 alone and also retained some self- cleaning activity. The results showed that the developed method was adaptable for determination of the antimicrobial activity of coatings with a wide range of activities producing 100% killing of Escherichia coll in times from 3 min up to 4 h. The results showed that it was possible to produce self cleaning self disinfecting surfaces and that surfaces with TiO2 on top, although having reduced activity compared to Ag or Cu, were durable and may have applications in the prevention of transmission of infections on surfaces in a wide range of applications.

A atrazina (ATZ) é um herbicida utilizado em larga escala no Brasil de forma intensiva em culturas de cana-de-açúcar, milho e sorgo. A ATZ possui caráter persistente e recalcitrante, de forma que os tratamentos convencionais de efluentes não são capazes de removê-lo. Nesse contexto, os processos oxidativos avançados, como a fotocatálise heterogênea, têm se mostrado eficientes para remoção deste poluente. Este trabalho tem por objetivo avaliar o desempenho dos fotocatalisadores TiO2 P25 e C-TiO2 Kronos vlp 7000 modificado com carbono para a degradação do pesticida atrazina em solução aquosa, utilizando um reator fotoquímico com coletor parabólico composto irradiado por um simulador solar. Os catalisadores TiO2 P25 e C-TiO2 Kronos foram caracterizados por meio de difração de raios-X, espectroscopia de infravermelho, área superficial específica BET e análise de reflectância difusa. As concentrações de TiO2 P25 e C-TiO2 Kronos empregadas foram 500 e 100 mg L&-1, respectivamente. Os resultados obtidos mostraram significativa remoção de ATZ ao final de 120 minutos (100; 98; 98; 93; 86% para concentrações iniciais de ATZ de 1; 5; 10; 20 e 30 mg L-1, respectivamente) com emprego do catalisador TiO2 P25. No entanto, as análises de carbono orgânico total (COT) indicaram que não houve mineralização significativa da ATZ, com valores inferiores a 20% com o uso do TiO2 P25. Para o catalisador C-TiO2 Kronos não se obteve remoção importante da ATZ ao final de 120 minutos de experimento, quando comparado com o TiO2 P25. Neste caso, o catalisador C-TiO2 Kronos permitiu obter remoções do pesticida de 37; 35; 38; 39 e 45%, aproximadamente, para as concentrações iniciais de ATZ de 1; 5; 10; 20 e 30 mg L-1, respectivamente. Apesar disso, o catalisador C-TiO2 Kronos apresentou melhor desempenho em mineralizar a ATZ a CO2 e H2O em relação ao proporcionado pelo TiO2 P25, com aproximadamente 38% de mineralização. O modelo de Langmuir-Hinshelwood (LH) constitui uma aproximação adequada para a cinética de degradação da atrazina para ambos os catalisadores estudados, com valores de Kr e Kads iguais a 1,54 mg L-1 min-1 e 15,47 L mg-1, respectivamente, para o catalisador TiO2 P25 e de 1,34 mg L-1 min-1 e 132,95 L mg-1, respectivamente para o catalisador C-TiO2 Kronos vlp 7000.
Atrazine (ATZ) is a widely used herbicide in Brazil, where it is intensively applied in sugarcane, corn and sorghum cultivations. However, conventional wastewater treatments are not able to remove ATZ due to its persistent and recalcitrant properties. Advanced oxidation processes, such as heterogeneous photocatalysis, have been proved effective for the removal of this pollutant. This study aims to evaluate the performance of TiO2 P25 and carbon-modified TiO2 Kronos vlp 7000 photocatalysts in the degradation of ATZ in aqueous systems using a tubular photochemical reactor equipped with a compound parabolic collector (CPC) irradiated by simulated solar light. Catalysts TiO2 P25 and C-TiO2 Kronos were characterized by X-ray diffraction, infrared spectroscopy, BET analysis and diffuse reflectance analysis. The concentrations of TiO2 P25 and C-TiO2 Kronos were 500 and 100 mg L-1, respectively. For TiO2 P25, the results showed significant ATZ removals after 120 minutes of irradiation (100; 98; 98; 93; 86% for initial ATZ concentrations of 1; 5; 10; 20, and 30 mg L-1, respectively). In contrast, the total organic carbon (TOC) analyses indicated that no significant ATZ mineralization occurred, with values lower than 20% for TiO2 P25. In comparison with TiO2 P25, C-TiO2 was not able to completely remove ATZ at the end of 120 minutes of irradition. In this case, pesticide removals of about 37; 35; 38; 39 and 45% were obtained for initial ATZ concentrations of 1; 5; 10; 20, and 30 mg L-1, respectively. Nevertheless, C-TiO2 Kronos showed better performance for ATZ mineralization to CO2 and H2O in comparison with TiO2 P25, with approximately 38% total carbon organic removal. The Langmuir-Hinshelwood (LH) model was shown to be an appropriate approximation for the degradation kinetics of atrazine for both catalysts, with values of Kr and Kads equal to 1.54 mg L-1 min-1 and 15.47 mg L-1, respectively, for the P25 TiO2 and 1.34 mg L-1 min-1 and 132.95 mg L-1, respectively, for C-TiO2 Kronos vlp 7000.

Dans ce travail, nous avons prepare des oxydes mixtes: sio#2-zro#2, sio#2-tio#2, tio#2-zro#2, al#2o#3-tio#2 et al#2o#3-sio#2 par un procede sol-gel non hydrolytique base sur la condensation des chlorures metalliques et les alcoxydes metalliques ou entre des chlorures metalliques et des donneurs d'oxygene tels que les ethers. Les rendements en oxydes obtenus apres elimination des groupements organiques residuels sont eleves. Edx et icp nous ont permis de montrer que la composition des oxydes finaux dependait directement de la stoechiometrie des precurseurs. L'homogeneite des gels a ete determinee par leur comportement a la cristallisation et par rmn du #2#9si et ir. Les gels bicomposants obtenus par la voie sol-gel non hydrolytique sont homogenes sauf lorsque le taux de titane est superieur a 8. 5% dans le systeme sio#2/tio#2

Dans la premiere partie de cet ouvrage, sont etudies les transferts electroniques pour les systemes ti/tio2/electrolyte. La vitesse de reaction de transfert de charge a l'interface est liee a l'epaisseur de la couche d'oxyde. Le comportement semiconducteur de type (n) des oxydes de titane permet d'utiliser les structures ti/tio2 pour des reactions cathodiques. La modification des structures par un depot de platine modifie considerablement la cinetique du transfert electronique avec un couple redox en solution. Cette cinetique est etudiee dans la seconde partie par spectroscopie d'impedance. Pour les deux systemes etudies, un processus de transfert electronique par effet tunnel via des etats intermediaires est propose. La derniere partie du memoire regroupe les resultats des analyses physico-chimiques (esca, rbs, diffraction des rayons x, afm, meb) qui ont ete employees pour caracteriser les interfaces (epaisseur et composition des couches,)

In this thesis three studies of the geometric structure of the (110) surface of single crystal rutile TiO2 are presented. Firstly, quantitative low energy electron diffraction (LEED-IV) data acquired from TiO2(110)(1x1) are reanalysed to confirm the integrity of the previously reported optimized geometries by performing structural optimisation as a function of depth into the selvedge. The second study addresses the geometry of the x-linked (1x2) reconstruction of the same surface. Again, LEED-IV data are analysed to quantitatively determine the surface structure. Part of this effort involved substantial development of the code (SATLEED) employed for simulating the experimental data, to allow simultaneous optimisation of more than one surface termination. In contrast to recent scanning probe work, the analysis indicates that the surface consists of two differently relaxed Ti2O3 added rows. The last study concerns ab initio calculations of the structure of benzoate on TiO2(110)(1x1). Of particular interest is the impact of surface coverage on the orientation of the benzene ring. It is predicted that the benzene ring twists and tilts away from high symmetry with increasing coverage due to adsorbate-adsorbate interactions. No evidence is found to support the formation of benzoate dimers or trimers, as was concluded in earlier experimental work.

Orientador: Dayse Iara dos Santos
Resumo: O desenvolvimento de materiais cerâmicos é um campo de pesquisa cujos resultados são extremamente promissores para aplicações tecnológicas. Particularmente, no caso dos materiais nanoestruturados baseados no óxido titânio, observa-se grande potencial de aplicação em dispositivos optoeletrônicos, bem como, para processos de fotocatálise, visto que apresenta um bandgap direto de 3,2 eV. Além disso, o aperfeiçoamento das propriedades ópticas, por meio da interação entre óxidos de diferentes bandas eletrônicas, têm sido estudado por muitos autores. Por esta razão, compósitos nanoestruturados formados de dois ou mais óxidos, cujas propriedades são distintas quando isolados, têm sido sintetizados juntos e caracterizados a fim de avaliar possíveis interações sinérgicas. Neste trabalho, foram preparados e caracterizados os compósitos TiO2/CuO, TiO2/ZnO e TiO2/ZrO2. As sínteses foram realizadas pelo método Sol-gel original e pelo método Poliol modificado, e ambos os processos se mostraram propícios para a obtenção de nanocompósitos e óxidos nanoparticulados. O método Poliol produziu compósitos formados de partículas micrométricas de dióxido de titânio revestidas do segundo óxido, enquanto o processo Sol-gel resultou em material constituído de agregados de nanocristais com alta mesoporosidade. Por meio da difração de raios X dos pós tratados gradualmente até 1000 °C observou-se que a formação e cristalização dos óxidos ocorrem em temperatura mais alta quando o material é resultante do ... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: The development of ceramic materials is a field of research whose results are extremely promising for technological applications. Particularly, in the case of nanostructured materials based on titanium oxide, there is a great potential for application in optoelectronic devices, as well as for photocatalysis processes, since it has a direct bandgap of 3.2 eV. In addition, the improvement of the optical properties through the interaction between oxides of different electronic bands has been studied by many authors. For this reason, nanostructured composites formed of two or more oxides, whose properties are distinct when isolated, have been synthesized together and characterized in order to evaluate possible synergistic interactions. In this work the TiO2 / CuO, TiO2 / ZnO and TiO2 / ZrO2 composites were prepared and characterized. The syntheses were carried out using the original Sol-gel method and the modified Polyol method, and both processes proved to be suitable for nanocomposites and nanoparticulate oxides. The polyol method produced composites formed of micrometric titanium dioxide particles coated with the second oxide, while the sol-gel process resulted in material composed of nanocrystalline aggregates with high mesoporosity. By X-ray diffraction of the powders gradually treated to 1000 °C it was observed that the formation and crystallization of the oxides occur at a higher temperature when the material is produced by the Sol-gel process. With the observation of the ... (Complete abstract click electronic access below)
Doutor

Este trabalho relata a preparação dos materiais nanoestruturados SiO2/TiO2 (ST) e SiO2/TiO2/ZnO (STZ) pelo método sol-gel em catálise ácida. Os materiais ST foram preparados em diferentes proporções de Si:Ti e Si:Ti:Zn. A caracterização dos materiais ST e STZ foi realizada por análises químicas e por diversas técnicas como: microscopia eletrônica de varredura, espectroscopia de energia dispersiva, medida da área superficial específica, refletância difusa, microscopia eletrônica de transmissão em alta resolução, difração de raios-X e espectroscopia Raman. Pela caracterização foi possível constatar que os materiais são nanocristalinos com domínios entre 4 e 5 nm e com característica estrutural microporosa. No material ST foi identificado apenas domínios cristalinos da fase anatase (TiO2), enquanto no material STZ as fases nanocristalinas identificadas foram: a anatase e o rutilo (TiO2), a wurtzita (ZnO), o espinélio invertido titanato de zinco (Zn2TiO4) e na superfície do material STZ com maiores quantidades de Ti e Zn a fase α-quartzo. As propriedades fotocatalíticas destes materiais nanocristalinos foram estudadas utilizando-se corantes têxteis catiônicos e a luz solar natural sem a utilização de oxidantes fortes adicionais. O material STZ na maior proporção Ti:Zn apresentou a maior eficiência fotocatalítica, sendo capaz de degradar totalmente o corante azul de metileno após 30 minutos, o corante amarelo ouro GL após 150 minutos e o corante azul royal GRL após 180 minutos de irradiação solar natural. A mineralização total das moléculas orgânicas em solução aquosa foi confirmada pela análise de carbono orgânico total que mostrou resultado negativo no extrato após a irradiação solar. A cinética de fotodegradação dos corantes têxteis segue o modelo matemático de primeira ordem aparente.
This work reports the preparation of the SiO2/ZnO (ST) and SiO2/TiO2/ZnO (STZ) nanocomposites by the sol-gel in acid catalysis method. The ST materials were prepared in different Si:Ti and SI:Ti:Zn proportions. The characterization of the ST and STZ materials was made with chemical analysis and with several techniques such as: scanning electron microscopy, energy-dispersive spectroscopy, measurement of the specific surface area, difuse reflectance, high-resolution transmission electron microscopy, X-ray diffraction and Raman spectroscopy. It was possible with the characterization to verify that the materials are nanocrystalline with domains between 4 and 5 nm and with a microporous structural characteristic. In the ST material only crystalline domains of the anatase phase (TiO2) were identified, while in the STZ material the nanocrystalline phases identified were: anatase and rutile (TiO2), wurtzite (ZnO), the inverted zinc titanate spinel (Zn2TiO4) and in the surface of the STZ material with greater quantities of Ti and Zn in α-quartz phase. The photocatalytical properties of these nanocrystalline materials were studied using cationic textile dyes and natural sunlight without the use of additional strong oxidizers. The STZ material in the greater Ti:Zn proportion presented the greatest photocatalytical efficiency, being capable of completely degrade the methylene blue dye after 30 minutes, the yellow gold GL dye after 150 minutes and the royal blue GRL after 180 minutes of natural sunlight irradiation. The total mineralization of the organic molecules in aqueous solution was confirmed by the total organic carbon analysis which showed negative results in the extract after solar irradiation. The photodegradation kinetics of the textile dyes follows the mathematical model of apparent first order.

Developed rechargeable batteries are urgently required to make more efficient use of renewable energy sources to support our modern way of life. Among all battery types, lithium batteries have attracted the most attention because of the high energy density (both gravimetric and volumetric), long cycle life, reasonable production cost and the ease of manufacturing flexible designs. Indeed, electrode material characteristics need to be improved urgently to fulfil the requirements for high performance lithium ion batteries. TiO2-based anodes are highly promising materials for LIBs to replace carbon due to fast lithium insertion/extraction kinetics, environmentally-friendly behavior, low cost and low volume change (less than 4%) therewith, high structural stability as well as improved safety issues are obtained. Nevertheless, the low ionic and electric conductivity (≈ 10−12 S m−1) of TiO2 represent the main challenge. In short, the present work aims at developing, optimization and construction of novel anode materials for lithium ion batteries using materials that are stable, abundant and environmentally friendly. Herein, both of two-phase Ti80Co20 and single phase Ti-Sn alloys (with different Sn contents of 1 to 10 at.%) were used to fabricate highly ordered, vertically oriented and dimension-controlled 1D nanotubes of mixed transition metal oxides (TiO2-CoO and TiO2-SnO2) via a straight-forward anodic oxidation step in organic electrolytes containing NH4F. Surface morphology and current density for the initial nanotube formation are found to be dependent on the crystal structure of the alloy phases. Various characterization tools such as SEM, EDXS, TEM, XPS and Raman spectroscopy were used to characterize the grown nanotube films. The results reveal the successful formation of mixed TiO2-CoO and TiO2-SnO2 nanotubes under the selected voltage ranges. The as-formed nanotubes are amorphous and their dimensions are precisely controlled by tuning the formation voltage. The electrochemical performance of the grown nanotubes was evaluated against a Li/Li+ electrode at different current densities. The results revealed that TiO2-CoO nanotubes prepared at 60 V exhibited the highest areal capacity of ~ 600 µAh cm–2 (i.e. 315 mAh g–1) at a current density of 10 µA cm–2. At higher current densities TiO2-CoO nanotubes showed nearly doubled lithium ion intercalation and a coulombic efficiency of 96 % after 100 cycles compared to lower effective TiO2 nanotubes prepared under identical conditions. To further improve the electrochemical performance of the TiO2-CoO nanotubes, a novel ternary carbon nanotubes (CNTs)@TiO2-CoO nanotubes composite was fabricated by a two-step synthesis method. The preparation includes an initial anodic fabrication of well-ordered TiO2-CoO NTs from a Ti-Co alloy, followed by growing of CNTs horizontally on the top of the oxide films using a simple spray pyrolysis technique. The unique 1D structure of such a hybrid nanostructure with the inclusion of CNTs demonstrates significantly enhanced areal capacity and rate performances compared to pure TiO2 and TiO2-CoO NTs without CNTs tested under identical conditions. The findings reveal that CNTs provide a highly conductive network that improves Li+ ion diffusivity promoting a strongly favored lithium insertion into the TiO2-CoO NT framework, and hence results in high capacity and extremely reproducible high rate capability. On the other hand, the results demonstrate that TiO2-SnO2 nanotubes prepared at 40 V on a Ti-Sn alloy with 1 at.% Sn display an average 1.4 fold increase in areal capacity with excellent cycling stability over more than 400 cycles compared to the pure TiO2 nanotubes fabricated and tested under identical conditions. The thesis is organized as follows: Chapter 1: General introduction, in which the common situation of energy demand, along with the importance of lithium ion batteries in renewable energy systems and portable devices are discussed. A brief introduction to TiO2-based anode in lithium ion batteries and the genera strategies for developing TiO2 anodes are also presented. The scope of this thesis as well as the main tasks are summarized. Chapter 2: The basic concepts of lithium ion batteries with an overview about their main components are discussed, including a brief information about the anode materials and the crystal structure of TiO2 anode. A detailed review for TiO2 nanomaterials for LIBs including the fabrication methods and the electrochemical performance of various TiO2 nanostructures (nanoparticles, nanorods, nanoneedles, nanowires and nanotubes) as well as porousTiO2 nanostructures is presented. The fabrication of TiO2 nanotubes by anodic oxidation, along with the growth mechanism are highlighted. The factors affecting the electrochemical performance of anodically fabricated pure TiO2, TiO2/carbon composites and TiO2-mixed with another metal oxide are reviewed. Chapter 3: In this chapter, the synthesis of TiO2-CoO, (CNTs)@TiO2-CoO and TiO2-SnO2 nanotubes, along with the characterization techniques and the electrochemical basics and concepts are discussed. Chapter 4: Detailed results and discussion of synthesis, characterizations and the electrochemical performance of TiO2-CoO nanotubes and ternary (CNTs)@TiO2/CoO nanotube composites are presented. Chapter 5: Detailed results and discussion of synthesis, characterizations and the electrochemical performance of ternary (CNTs)@TiO2-CoO nanotube composites are explained. Chapter 6: Detailed results and discussion of synthesis, characterizations and the electrochemical performance of TiO2-SnO2 nanotubes are presented. Chapter 7: Summarizes the results presented in this work finishing with realistic conclusions, and highlights interesting work for the future
Um die zur Aufrechterhaltung unserer modernen Lebensweise unabdingbaren erneuerbaren Energiequellen effizient nutzen zu können, werden hochentwickelte wiederaufladbare Batterien dringend benötigt. Lithium-Ionenbatterien gelten aufgrund ihrer hohen Energiedichte (sowohl gravimetrisch als auch volumetrisch), ihrer langen Lebensdauer, moderater Produktionskosten und aufgrund der Möglichkeit, vielfältige Konzepte einfach herstellen zu können, als vielversprechend. Dennoch müssen die Elektrodenmaterialien dringend verbessert werden, um den Ansprüchen an zukünftige hochentwickelte Lithium-Ionenbatterien gerecht zu werden. TiO2-basierte Anoden gelten aufgrund ihrer schnellen Lade- und Entladekinetik, ihres umweltfreundlichen Verhaltens und niedriger Kosten als aussichtsreiche Alternativen zu Kohlenstoffen. Durch die geringe Volumenänderung beim Lithiumeinbau (unter 4%) werden außerdem eine hohe strukturelle Stabilität und erhöhte Sicherheit gewährleistet. Die hauptsächlichen Herausforderungen stellen die niedrige ionische und elektrische Leitfähigkeit (≈ 10−12 S m−1) von TiO2 dar. Zusammengefasst liegt das Ziel der vorliegenden Arbeit in der Entwicklung, Optimierung und Herstellung neuartiger Anodenmaterialien für Lithium-Ionenbatterien unter Verwendung stabiler, verfügbarer und umweltfreundlicher Materialien. In dieser Arbeit wurden sowohl zweiphasiges Ti80Co20 und einphasige Ti-Sn-Legierungen (mit verschiedenen Sn-Gehalten zwischen 1 und 10 at-%) zur Herstellung hochgeordneter, vertikal orientierter eindimensionaler Nanoröhren aus gemischten Übergangsmetalloxiden (TiO2–CoO und TiO2–SnO2) mittels anodischer Oxidation in NH4F-haltigen organischen Elektrolyten genutzt. Dabei wurden Abhängigkeiten der Oberflächenmorphologie und der Stromdichte für die Bildung der Nanoröhren von der Kristallstruktur der zugrundeliegenden Legierung beobachtet. Vielfältige Methoden wie REM, EDXS, TEM, XPS und Ramanspektroskopie wurden genutzt, um die Nanoröhren zu charakterisieren. Die Ergebnisse zeigen, dass gemischte TiO2-CoO und TiO2-SnO2 Nanoröhren in den gewählten Spannungsfenstern erfolgreich gebildet werden konnten. Die so hergestellten Nanoröhren sind amorph und in ihren Dimensionen präzise durch die Wahl der Spannung einstellbar. Eine elektrochemische Beurteilung der Nanoröhren erfolgte durch Tests gegen eine Li/Li+-Elektrode bei veschiedenen Stromdichten. Die Resultate zeigen, dass TiO2-CoO-Nanoröhren, welche bei 60 V hergestellt wurden, die höchsten Flächenkapazitäten von ~ 600 µAh cm–2 (d.h. 315 mAh g–1) bei einer Stromdichte von 10 µA cm–2 aufweisen. Bei höheren Stromdichten zeigen TiO2-CoO-Nanoröhren nahezu verdoppelte Lithiuminterkalation und eine Coulomb-Effizienz von 96 % nach 100 Zyklen, verglichen mit weniger effektiven TiO2–Nanoröhren, welche unter identischen Bedingungen hergestellt wurden. Um die elektrochemischen Eigenschaften der TiO2-CoO-Nanoröhren weiter zu verbessern, wurde ein neuer Komposit aus Kohlenstoff-Nanoröhren und TiO2-CoO-Nanoröhren ((CNT)s@TiO2/CoO) durch eine zweistufige Synthese hergestellt. Die Herstellung beinhaltet zunächst die anodische Bildung geordneter TiO2/CoO-Nanoröhren, ausgehend von einer Ti-Co-Legierung, gefolgt von einem horizontalen Kohlenstoff-Nanoröhren-Wachstum auf dem Oxid mittels einer simplen Sprühpyrolyse. Die einzigartige 1D-Struktur einer solchen hybriden Nanostruktur mit eingebundenen CNTs zeigt deutlich erhöhte Flächenkapazitäten und Belastbarkeiten im Vergleich zu Nanoröhren aus TiO2 und TiO2/CoO-Nanoröhren ohne CNTs, die unter identischen Bedingungen getestet wurden. Die Ergebnisse zeigen, dass die CNTs ein hochleitfähiges Netzwerk bilden, welches die Diffusion von Lithium-Ionen und deren Einbau in die TiO2/CoO-Nanoröhren begünstigt und somit hohe Kapazitäten und reproduzierbare hohe Belastbarkeiten bewirkt. Außerdem zeigen die Resultate, dass TiO2-SnO2 Nanoröhren, welche bei 40 V auf einer Ti-Sn-Legierung mit 1 at.% Sn hergestellt wurden, im Mittel eine 1,4-fache Erhöhung der Flächenkapazität und eine exzellente Zyklenstabilität über mehr als 400 Zyklen, verglichen mit unter identischen Konditionen hergestellten und getesteten TiO2-Nanoröhren, zeigen. Die Arbeit ist wie folgt organisiert: Kapitel 1: Allgemeine Einführung, in der die Energienachfrage und die Bedeutung von Lithium-Ionenbatterien in erneuerbaren Energiesystemen und tragbaren Geräten diskutiert wird. Eine kurze Einleitung zu TiO2-basierten Anoden in Lithium-Ionenbatterien und allgemeine Strategien zur Entwicklung von TiO2-Anoden werden ebenfalls gezeigt. Das Ziel der Arbeit und hauptsächliche Aufgaben werden zusammengefasst. Kapitel 2: Das grundlegende Konzept der Lithium-Ionenbatterie mit einem Überblick über ihre Hauptkomponenten wird diskutiert. Dies beinhaltet auch eine kurze Darstellung der Anodenmaterialien und der Kristallstruktur von TiO2-Anoden. Eine detaillierte Übersicht über TiO2-Nanomaterialien für LIB, welche Herstellungsmethoden und die elektrochemische Performance verschiedener TiO2-Nanostrukturen (Nanopartikel, Nanostäbe, Nanonadeln, Nanodrähte und Nanoröhren) und poröser TiO2-Nanostrukturen beinhaltet, wird gezeigt. Die Bildung von TiO2-Nanoröhren durch anodische Oxidation und der Wachstumsmechanismus werden hervorgehoben. Faktoren, welche die elektrochemische Performance anodisch hergestellter TiO2-Materialien, TiO2/Kohlenstoff-Komposite und TiO2 als Gemisch mit anderen Metalloxiden beeinflussen, werden diskutiert. Kapitel 3: In diesem Kapitel werden die Synthese von TiO2-CoO, (CNTs)@TiO2/CoO und TiO2-SnO2-Nanoröhren, die Charakterisierungsmethoden, elektrochemische Grundlagen und Konzepte diskutiert. Kapitel 4: Detaillierte Resultate und die Diskussion der Synthese, Charakterisierung und der elektrochemischen Performance der TiO2-CoO- Nanoröhren und der ternären (CNTs)@TiO2/CoO-Nanoröhrenkomposite werden gezeigt. Kapitel 5: Detaillierte Resultate und die Diskussion der Synthese, Charakterisierung und der elektrochemischen Performance der der ternären (CNTs)@TiO2/CoO-Nanoröhrenkomposite werden diskutiert. Kapitel 6: Detaillierte Resultate und die Diskussion der Synthese, Charakterisierung und der elektrochemischen Performance von TiO2-SnO2-Nanoröhren werden gezeigt. Kapitel 7: Eine Zusammenfassung der Resultate, die in dieser Arbeit gezeigt wurden und Schlussfolgerungen, sowie interessante Ansatzpunkte für zukünftige Arbeiten werden präsentiert

Orientador: Elson Longo
Banca: Sonia Maria Zanetti
Banca: Elaine Cristina Paris
Banca: Fenelon Martinho Lima Pontes
Banca: Ademir Geraldo Cavallari Costalonga
Resumo: Neste trabalho propôs-se sintetizar partículas fotocatalisadoras de óxido de titânio (TiO2), beta molibdato de prata (β-Ag2MoO4) e a heteroestrutura TiO2/Ag2MoO4 para principal aplicação em fotocatálise. As partículas de TiO2 e a heteroestrutura foram sintetizadas utilizando o método solvotérmico assistido por micro-ondas (SAMO), enquanto que as partículas de β-Ag2MoO4 foram sintetizadas pelo método de co- precipitação. As sínteses foram realizadas a partir das soluções diluídas dos sais de partida, em diferentes solventes, tempos de reação e temperaturas para o controle do tamanho e forma dos cristais. A atividade fotocatalítica destes materiais foi analisada para a degradação dos corantes orgânicos alaranjado de metila e rodamina 6G sob irradiação com lâmpada ultravioleta (UV) de 254 nm. Foram realizadas caracterizações por difração de raios X (DRX), espectroscopia vibracional na região do infravermelho, fotoluminescência (FL) e medida de área de superfície específica (método BET). As morfologias dos cristais foram analisadas por intermédio de microscopia eletrônica de varredura de alta resolução e feixe de íon focalizado (FIB). As propriedades ópticas foram investigadas por espectroscopia na região do ultravioleta-visível (UV-vis). Os resultados de DRX mostram uma estrutura tetragonal para os pós de TiO2 e uma estrutura cúbica do tipo espinélio para as partículas de β-Ag2MoO4. Os espectros de infravermelho apresentaram bandas de absorção caraterísticas para cada material. ... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: This research proposed to synthesize photocatalytic particles of titanium dioxide (TiO2), beta silver molybdate (β-Ag2MoO4), and TiO2/Ag2MoO4 heterostructures for application in photocatalytic processes mainly. TiO2 particles and heterostructures were synthesized using microwave-assisted solvothermal (SAMO) method, while β- Ag2MoO4 particles were synthesized via co-precipitation method. All syntheses were made from the starting dilute salt solutions in different solvents, temperatures, and reaction times in order to control the size and the shape of the crystals. Photocatalytic activity of these materials was analyzed for degradation of the organic dyes methyl orange and rhodamine 6G under ultraviolet light (UV) irradiation at 254 nm. Characterizations were performed using X-ray diffraction (XRD), infrared vibrational spectroscopy, photoluminescence (PL) and specific surface area determination (BET method). The morphologies of the crystals were examined by high resolution scanning electron microscopy (HRSEM) and focused ion beam (FIB). The optical properties were investigated by UV-Vis spectroscopy. XRD results showed a tetragonal structure for the powders of TiO2, and a cubic spinel structure for β-Ag2MoO4 particles. Infrared spectra presented characteristic absorption bands for each material. PL bands indicated a broad emission with a maximum at wavelength of 605 nm, which corresponds to the emission in the yellow region for TiO2 powder. Regarding the β-Ag2MoO4 powders emis... (Complete abstract click electronic access below)
Doutor

Esse trabalho teve por finalidade preparar, pelo método solvo térmico, fotocatalisadores a base de dióxido de titânio (TiO2) puro e modificado com prata (Ag/TiO2), na forma de filmes suportados em vidro a fim de obter materiais ativos em reações de fotodegradação de atorvastatina tanto sob luz visível como sob ultravioleta. Para sintetizar esses materiais foram utilizadas diferentes combinações de solventes (etilenoglicol, água deionizada, etanol e butanol) e de precursores de titânio (isopropóxido e butóxido de titânio). Também foi avaliado o efeito do aumento da concentração de precursor de titânio da solução de síntese e do tempo de tratamento para formação dos filmes. Os materiais obtidos foram caracterizados por difratometria de raios X (DRX), espectroscopia por refletância difusa (ERD), microscopia eletrônica de varredura (MEV) com espectroscopia por energia dispersiva (EDS), hidrofobicidade e perfilometria. Os catalisadores foram testados quanto a sua atividade fotocatalítica, mostrando-se promissores na fotodegradação do fármaco atorvastatina cálcica na região do visível e do ultravioleta. A síntese, pelo método solvo térmico, levou a formação de estruturas nano e micrométricas com diferentes formas, indicando que a interação solvente-precursor exerce papel crucial na morfologia do material. A análise de DRX indicou a presença apenas da fase cristalina rutilo. As energias de band gap (Eg) mostraram-se favoráveis à fotocatálise no UV e no visível. Todos os catalisadores se mostraram ativos no UV, sendo que a reação de degradação fotocatalítica da atorvastatina com o catalisador sintetizado com o par etilenoglicol e isopropóxido de titânio mostrou o melhor resultado: 28,0 % de remoção do fármaco em 30 minutos de experimento. A presença de prata nos catalisadores foi observada tanto na forma de cloreto de prata como também de prata metálica. A impregnação de prata nos filmes de titânia levou ao aumento da remoção do fármaco em 30 minutos de reação sob luz visível de 16,5 % (amostra não dopada) para 18,3 %. (amostra com prata).
This paper aims to prepare at solvothermal route, photocatalysts based on titanium dioxide (TiO2) and modified with pure silver (Ag/TiO2), in films supported on glass, in order to obtain active materials in photodegradation reactions of atorvastatin on visible light and on ultraviolet light. To synthesize these materials different combinations of solvents (ethylene glycol, deionized water, ethanol and butanol) and precursors of titanium (titanium isopropoxide and butoxide ) were used . The effect of increasing the concentration of the titanium precursor in the synthesis solution and reaction time of film formation was also evaluated. The materials were characterized by X-ray diffraction (XRD), diffuse reflectance spectroscopy (ERD), scanning electron microscopy (SEM) with spectroscopy energy dispersive (EDS) , hydrophobicity and perfilometry . The catalysts were tested for their photocatalytic activity, showing to be promising in the photodegradation of atorvastatin calcium on the visible and ultraviolet radiation. The synthesis by solvothermal route led to the formation of nano and micrometric structures with different shapes, indicating that the precursor - solvent interaction plays a crucial role in the morphology of the material. XRD analysis indicated the presence of only the rutile crystalline phase . The band gap energies ( Eg ) were favorable to the photocatalysis on visible or UV. The presence of silver helped in increasing the crystallinity of the material and the photocatalytic activity in visible light.

Ce travail est consacre a l'etude des mecanismes d'insertion d'ions lithium dans des couches minces de tio#2 et tio#2-ceo#2 elaborees par pulverisation cathodique rf magnetron. La premiere partie decrit l'influence des conditions de preparation des films (puissance, pression, composition du plasma, temperature de substrat). Pour tio#2 la taille des cristallites (anatase) est controlee par la temperature du substrat. Les caracterisations physico-chimiques des films sont realisees par met, meb, micro-diffraction d'electrons, dx, spectroscopies ir et raman et rbs. Un programme de simulation des reponses optiques de systemes multi-couches permet de relier le desordre structural des couches preparees sur substrat non chauffe a la presence d'une forte densite d'etats electroniques repondant a une distribution de type queue d'urbach. Les meilleures performances electrochimiques sont obtenues a faible puissance, forte pression et sous plasma d'oxygene. La seconde partie concerne la determination des processus d'insertion et de desinsertion dans tio#2 (pour differentes tailles moyennes des cristallites de structure anatase) et ce#0#. #1ti#0#. #9o#2 amorphe par spectrophotometrie et par spectroscopie d'admittance. Dans aucun cas nous n'avons observe d'effets attribuables a des oscillations plasma d'electrons libres. Pour tio#2 (anatase), l'insertion s'accompagne d'une absorption optique centree a 1,65ev, reversible en desinsertion et expliquee en termes de petit polaron ; les variations du coefficient d'absorption suivent une loi de type beer-lambert. Les films de tio#2 les mieux cristallises se distinguent par des reponses electrochimiques et optiques symetriques en insertion/desinsertion alors que les autres films piegent une quantite de charge, optiquement inefficace, dont l'importance decroit de cycle en cycle. Pour ce#0#. #1ti#0#. #9o#2 amorphe, l'accessibilite aux sites ce contribue a la decoloration des films aux hautes energies (occupation des etats 4f de ce). A partir de ces resultats et de mesures par spectroscopie d'admittance sur ito//al (processus electroniques) et ito//electrolyte/li (processus electrochimiques) un mecanisme d'insertion original est propose, adaptable a d'autres materiaux en ajustant le mode de preparation pour favoriser une conductivite ionique suffisante

Water is a vital natural resource. To develop more sustainable water systems, we must focus efforts on the removal of persistent contaminants. Aqueous organic contaminants include azo dyes, halogenated organics (e.g. pesticides), and algal and bacterial metabolites. The latter are common to surface waters and freshwater aquaculture systems and can cause taste and odor problems. Two of the principal organoleptic compounds are geosmin and 2-methylisoborneol (MIB). Traditional oxidation treatment methods, utilizing chlorine, hydrogen peroxide, and potassium permanganate, have been employed with varying levels of efficacy for removal of these and other organic contaminants. Advanced Oxidation Processes (AOPs) have greater potential for the removal of persistent contaminants than traditional methods due to their higher pollutant removal rates, their ability to degrade a variety of organic material, and their ability to completely mineralize compounds [1]. An emerging AOP technology is the use of titania based photocatalysts for water treatment. Titanium dioxide (TiO2) is an effective, inexpensive, and stable photocatalyst used for the decomposition of aqueous organics. Titania is primarily activated by the ultraviolet portion of the spectrum due to its energy band gap of 3.0-3.2 eV (depending upon crystalline structure). Photocatalytic efficiency can be enhanced or tuned through the use of semiconductor dopants and the variance of titania crystal structure (i.e. anatase to rutile ratios). Metal oxides, like indium vanadate (InVO4), may enhance reaction rates through new interfacial reaction sites and electron scavenging, transport, and storage. InVO4 has been shown to have four sub-bandgap transitions, of which three are in the visible range [2]. In this work, the synthesis of InVO4-TiO2 composite semiconductors is examined to shift photo-initiation into the visible portion of the spectrum. Parametric studies of the visible spectrum photodegradation of methyl orange, an azo dye, and 2-chlorophenol provide a basis for analysis. Methyl orange was utilized to ascertain the effect of pure and mixed phase titania in the semiconductor composites. The TiO2 photodegradation of geosmin and MIB has been previously demonstrated in small-scale batch slurry reactions. Slurry systems require the downstream separation of catalyst from the liquid. Laboratory trials use centrifugation or micro-filtration. Alternatively, immobilization of the photocatalyst could allow scale-up of the process. Here, titania was immobilized on glass plate substrates using an ethanol spray technique. Finally, naturally tainted waters may contain a number of constituents in addition to the target compounds. In recirculating aquaculture systems, the water contains natural organic matter (NOM), ammonia, nitrite/ nitrate, and carbonate species. These constituents may block light penetration, block reaction sites, scavenge hydroxyl radicals, or affect the surface chemistry of the catalyst. Further, geosmin and MIB concentrations are extremely low, in the ppt range. Naturally tainted waters from MOTE Marine Laboratory Aquaculture Research Park are treated in the laboratory and in situ to demonstrate TiO2 degradation efficiency for trace concentration geosmin and MIB degradation in a complex water matrix.

Orientadores: Inez Valeria Pagotto Yoshida, Wilson de Figueiredo Jardim
Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Quimica
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Resumo: Este trabalho relata a imobilização do TiO2 em matrizes de siloxano, como alternativa ao emprego do TiO2-pó em suspensão, para a fotodegradação de espécies orgânicas em solução aquosa, sob radiação UV-Vis ou radiação solar, tendo o ácido salicílico (AS) como modelo de poluente. Incorporou-se o TiO2-pó em uma matriz elastomérica de silicona com grau de reticulação relativamente baixo, obtida a partir de goma de poli(dimetilsiloxano) de alta massa molar, obtendo-se compósitos elastoméricos na forma de monólitos. O TiO2-pó também foi incorporado em uma matriz de silicona altamente reticulada, na presença de um agente porogênico, obtendo-se um compósito monolítico rígido e poroso, com características de ¿ceramer¿. Sintetizou-se ainda o TiO2 in situ na forma anatásio, por síntese hidrotérmica, empregando-se como matriz os compósitos contendo TiO2-pó, e placas porosas de vidro. Comparando-se a eficiência dos compósitos elastoméricos com diferentes composições, frente à fotodegradação do AS, sugeriu-se que apenas os sítios de TiO2 mais próximos da superfície iluminada tiveram acesso à radiação UVVis. Apesar das amostras com matriz elastomérica terem apresentado os maiores valores de sorção de AS, o material que apresentou a maior eficiência fotocatalítica sob radiação UV-Vis, superando inclusive o desempenho do TiO2-pó, foi o compósito poroso contendo também o TiO2 gerado in situ, provavelmente devido a sua maior área superficial. Os experimentos conduzidos com esse compósito sob radiação solar evidenciaram uma diminuição na porcentagem de fotodegradação do AS, provavelmente pela menor intensidade da radiação solar, em relação à lâmpada UVVis, associada ao efeito da atenuação da radiação no monólito. Observou-se um pequeno aumento na atividade fotocatalítica do TiO2 com o aumento no tamanho dos cristalitos de anatásio sintetizados in situ, após o tratamento térmico das placas porosas de vidro a 600°C. Os resultados apresentados neste estudo sugerem grande potencialidade na imobilização do TiO2 em matrizes de silicona, tanto pela incorporação do TiO2-pó, quanto pela síntese in situ da fase anatásio
Abstract: This study reports the immobilization of TiO2 in siloxane matrices, as an alternative to the use of TiO2-powder in suspension, for the photodegradation of organic species in aqueous solution, under UV-Vis radiation or solar radiation, having the salicylic acid (SA) as model pollutant. TiO2-powder was incorporated in an elastomeric silicone matrix with a relatively low crosslinking degree, obtained from a poly(dimethylsiloxane) gum with high molecular weight, giving rise to monolithic elastomeric composites. TiO2-powder was also incorporated in a silicone matrix with a high crosslinking degree, in the presence of a pore forming agent, resulting in a hard and porous monolithic composite, with ¿ceramer¿ characteristics. TiO2 in the anatase form was obtained in situ, by hydrothermal synthesis, on the previously prepared composites containing TiO2-powder, and also on glass porous plates. Comparing the efficiency of the elastomeric composites with different compositions, in relation to the SA photodegradation, the results suggested that only the TiO2 sites near the illuminated surface were accessed by the UV-Vis radiation. Although the samples with the elastomeric matrix presented the highest SA adsorption values, the porous composite containing the in situ obtained-TiO2 presented the highest photocatalytic efficiency, with better performance than the TiO2-powder, probably due to the high surface area of this material. When this porous composite was tested under solar radiation, the lower intensity of this radiation, in relation to the UV-Vis lamp, associated to the radiation attenuation effect in the monolith, promoted a decrease in the percentage of SA photodegradation. An increase in the size of the in situ obtained-anatase crystallites, promoted by the thermal treatment of the glass porous plates at 600°C, resulted in an increase in the photocatalytic activity of the TiO2. The results presented in this study suggest a great potential in the immobilization of TiO2 in silicone matrices, either by the incorporation of TiO2-powder, as by the in situ synthesis of the anatase form
Doutorado
Quimica Inorganica
Doutor em Ciências

TiO2 is a well investigated material due to its vast array of applications, from the most common white food colouring, to usage as an optical coating due to its high refractive index. When deposited as a thin film for use in solar control coatings using a magnetron sputtering device, TiO2 is found to form in rutile, anatase and amorphous phases, with the rutile (1 1 0) and anatase (1 0 0) crystal surfaces occurring most frequently. While the influence of deposition rate, substrate bias voltage, oxygen partial pressure and temperature have all been investigated experimentally, there are fewer simulated results. This seems to be primarily due to the lack of a suitable empirical potential through which dynamics can be accurately modelled. In this research project, the short-comings of the leading fixed and variable charge TiO2 potentials were revealed through comparison of binding energies and transition barriers for simple ad-clusters and interstitials to DFT. This led to the development of an improved variable charge potential, particularly when modelling the rutile (1 1 0) surface. It has been experimentally demonstrated that rutile growth results in a reduced surface due to the formation of large numbers of Ti interstitials and this was also suggested due to low Ti interstitial formation barriers found using DFT and the variable charge empirical potentials. The high interstitial formation probability was confirmed when performing large numbers of Tix Oy depositions at typical industrial energies. Correlations between impact site and numbers of interstitials and vacancies formed were found along with insight into typical penetration depths and common defect structures. Multilayer growth was successfully modelled using classical MD by accelerating the deposition rate. The large numbers of formed interstitials coupled with a high escape barrier resulted in defective growth and so it was necessary to increase the substrate temperature such that atoms were mobile on the computational time-scale. Multilayer growth was investigated as a function of deposition energy, cluster composition and stoichiometry on the rutile (1 1 0), anatase (1 0 0) and amorphous surfaces. The optimum conditions for forming defect free rutile were found along with more limited insight into the ideal growth conditions when depositing on anatase and amorphous substrates. Finally a long time-scale dynamics technique, the ‘on-fly-kinetic Monte Carlo' method, was developed, and using an efficient bespoke transition search algorithm, rutile TiO2 growth was successfully modelled at 350 K, with some caveats to avoid becoming entrenched in low activation diffusion processes. The final conclusion being that low energy depositions of large clusters with an oxygen excess would produce optimum film growth.

The remarkable characteristics of Ti02 are widely used, from everyday life applications (pigments, food/cosmetics additives) to more specialised systems, including photovoltaics and structural composites. Use in polymers is substantial (25% of all Ti02 produced), but most applications and research focus on commercial powders. A new generation of Ti02 nanoparticles has emerged, based on very small, single-crystals, with well-defined morphology and phase. A limited number of papers report the use of this new nanoscale Ti02 in polymer nanocomposites, and indicate improved properties. Although the synthesis of anisotropic nanoparticles (e. g. nanorods) has been well-reported, use in polymer nanocomposites remains largely unreported. This thesis broadly covers three topics: (1) synthesis of Ti02 nanorods using different sol-gel routes in presence of structure directing agents, (2) modification of the nanorod surface chemistry in order to control dispersion and surface properties and (3) fabrication of titania nanorod-polymer composites. Singlecrystal anatase nanorods were produced with variable aspect ratio (3-12), depending on the specific structure directing agent (SDA) used during synthesis. Due to organic functionalisation at the nanorod surface, nanorods could be well dispersed in chloroform. A new procedure, based on the self-cleaning ability of Ti02 under UV, was developed for removal of organics from the nanorod surface, without compromising the nanorod morphology, crystallinity or dispersibility. This powerful tool can be used to change the surface character of the nanorods to generate aqueous TNR dispersions. Stable dispersions were achieved using quaternary ammonium hydroxides to modify the surface electrostatically and sterically. Once dispersed individually, the surface can be further modified by sol-gel chemistry. Composite work involved blending both organic and water-soluble polymers with nanorod dispersions in chloroform and water, respectively, to produce composite films of exceptional optical transparency, even for nanorod loadings up to 30 wt%. The films possess very strong, wavelength-tuneable UV absorbance, which could be used in UV filters and optical limiting. The presence of SDAs or dispersants at the nanorodpolymer interface hinders strong adhesion, as evidenced by marginally lower tensile strength and thermal stability of the nanocomposites. The photo-stability of the nanorod composites is comparable to that of the pure polymer and better than that of composites with commercial equiaxed TiO2 nanoparticles.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Este trabalho traz o estudo das propriedades óticas, elétricas e morfológicas do material TiO2 de forma individual e acoplado com SnO2 dopado com 4at%Sb, formando uma heteroestrutura. Tanto TiO2 quanto a heteroestrutura foram trabalhados na forma de filmes finos depositados pelo método sol-gel-dip-coating, e, no caso do TiO2 também foi relevante sua análise em forma de pós prensados (pastilhas). No que diz respeito ao SnO2:4%Sb, este trabalho traz uma revisão literária de suas principais propriedades, buscando apresentar um panorama geral, pois com isto pode-se entender melhor os fenômenos que ocorrem na heteroestrutura. Os resultados das pastilhas de TiO2 indicam uma transição parcial de fase anatase/rutilo para tratamentos térmicos entre 500ºC e 1000ºC, confirmadas pela fotoluminescência, que apresentou bandas relacionadas a fase anatase ou rutilo, dependendo do processamento utilizado. Filmes de TiO2 mostraram boa foto sensibilidade, com a corrente elétrica respondendo imediatamente à excitação independente da energia, além de um rápido decaimento com relação ao valor excitado. Fora isto, medidas de decaimento da corrente foto induzida, realizadas em atmosfera de O2, indicaram que o decaimento se torna ainda mais rápido na presença do gás, estando associado ao aprisionamento de portadores de carga pelas moléculas adsorvidas na amostra, além da recombinação dos pares elétron-buraco. Com relação à heteroestrutura, quando a condução ocorre preferencialmente no TiO2, a amostra apresenta resultados muito similares às dos filmes de TiO2, tendo uma rápida resposta à excitação com fonte de luz acima do bandgap do TiO2 e um rápido retorno para seu estado de equilíbrio, no escuro. Entretanto, em atmosfera gasosa, o decaimento se torna muito mais rápido, o que também está associado ao aprisionamento de portadores pelas moléculas adsorvidas de gás. Porém, o aumento na taxa com que isto acontece, está relacionado à formação da heteroestrutura e às compensações de carga na interface, que podem ocorrer quando a excitação utiliza comprimento de onda adequado. A configuração lado a lado da heteroestrutura mostrou emissão Poole – Frenkel para tensões maiores que 40V, e quando irradiada com luz que simula o espectro solar apresentou uma região de resistência negativa para algumas potências de excitação que pode estar ligada ao aprisionamento de elétrons na interface. Desta forma, este trabalho visa trazer uma contribuição importante à compreensão do mecanismo de transporte elétrico dos materiais estudados. Por fim, pode-se dizer que os materiais aqui estudados podem ser aplicados como sensores de gás ou dispositivos retificadores/amplificadores desde que seja escolhida a melhor configuração para a aplicação desejada.
This work presents a study of the optical, electrical and morphological characterization of TiO2 thin films, deposited individually or coupled with SnO2 doped with 4at%Sb, forming a heterostructure. Both sort of samples, TiO2 and the heterostructure were studied in thin film form, deposited by sol-gel-dip-coating, and, in the case of TiO2, it was relevant the analysis of samples also in the form of pellets form (pressed powders). With regards to SnO2:4%Sb, this work brings a literary revision of its principal properties, trying to present a general overview, for the better understanding of the phenomena that occur in the heterostructure. The results of TiO2 pellets indicates a partial anatase/rutile phase transition to thermal annealing between 500 and 1000ºC, confirmed by the photoluminescence that presented bands related to anatase or rutile, depending the utilized processing. TiO2 films showed fair photo-sensibility, with immediate response on the electric current to light excitation, independent on the utilized energy, along with fast decay in relation to the excited value. Moreover, photo-induced current decay measurements, performed in O2 atmosphere, indicated that the decay becomes faster in gas presence, being associated to charge carriers trapping by the adsorbed molecules on sample, besides the electron-hole recombination. Concerning the heterostructure, when the conduction occurs preferentially in TiO2 layer, the sample shows very similar results to the TiO2 films, with a fast response to light excitation above the TiO2 bandgap and fast return to the equilibrium state, in dark. However, in gas atmosphere, the decay becomes much faster, which is also associated to the carriers trapping by the gas adsorbed molecules. Nevertheless, the rate increase in this phenomenon is related to the heterostructure formation and the charge compensations at the interface, which may occur when appropriate wavelength is used for excitation. The side by side heterostructure sample showed a Poole – Frenkel emission to bias higher than 40V, and presented a negative resistance region to some irradiation power when illuminated with solar light that can be associated to electrons trapping at the interface. In summary, this work aims to bring a contribution related to the electric transport mechanism of the studied materials. The materials investigated here may be applied in gas sensors or rectifiers/amplifiers devices, according the sample configuration.
CAPES: 1578735

Orientador: Luis Vicente de Andrade Scalvi
Banca: Luiz Carlos da Silva Filho
Banca: Emerson Aparecido Floriano
Resumo: Este trabalho traz o estudo das propriedades óticas, elétricas e morfológicas do material TiO2 de forma individual e acoplado com SnO2 dopado com 4at%Sb, formando uma heteroestrutura. Tanto TiO2 quanto a heteroestrutura foram trabalhados na forma de filmes finos depositados pelo método sol-gel-dip-coating, e, no caso do TiO2 também foi relevante sua análise em forma de pós prensados (pastilhas). No que diz respeito ao SnO2:4%Sb, este trabalho traz uma revisão literária de suas principais propriedades, buscando apresentar um panorama geral, pois com isto pode-se entender melhor os fenômenos que ocorrem na heteroestrutura. Os resultados das pastilhas de TiO2 indicam uma transição parcial de fase anatase/rutilo para tratamentos térmicos entre 500ºC e 1000ºC, confirmadas pela fotoluminescência, que apresentou bandas relacionadas a fase anatase ou rutilo, dependendo do processamento utilizado. Filmes de TiO2 mostraram boa foto sensibilidade, com a corrente elétrica respondendo imediatamente à excitação independente da energia, além de um rápido decaimento com relação ao valor excitado. Fora isto, medidas de decaimento da corrente foto induzida, realizadas em atmosfera de O2, indicaram que o decaimento se torna ainda mais rápido na presença do gás, estando associado ao aprisionamento de portadores de carga pelas moléculas adsorvidas na amostra, além da recombinação dos pares elétron-buraco. Com relação à heteroestrutura, quando a condução ocorre preferencialmente no TiO2, a amostra... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: This work presents a study of the optical, electrical and morphological characterization of TiO2 thin films, deposited individually or coupled with SnO2 doped with 4at%Sb, forming a heterostructure. Both sort of samples, TiO2 and the heterostructure were studied in thin film form, deposited by sol-gel-dip-coating, and, in the case of TiO2, it was relevant the analysis of samples also in the form of pellets form (pressed powders). With regards to SnO2:4%Sb, this work brings a literary revision of its principal properties, trying to present a general overview, for the better understanding of the phenomena that occur in the heterostructure. The results of TiO2 pellets indicates a partial anatase/rutile phase transition to thermal annealing between 500 and 1000ºC, confirmed by the photoluminescence that presented bands related to anatase or rutile, depending the utilized processing. TiO2 films showed fair photo-sensibility, with immediate response on the electric current to light excitation, independent on the utilized energy, along with fast decay in relation to the excited value. Moreover, photo-induced current decay measurements, performed in O2 atmosphere, indicated that the decay becomes faster in gas presence, being associated to charge carriers trapping by the adsorbed molecules on sample, besides the electron-hole recombination. Concerning the heterostructure, when the conduction occurs preferentially in TiO2 layer, the sample shows very similar results to the TiO2 films,... (Complete abstract click electronic access below)
Mestre

Ce travail de thèse examine une nouvelle méthode prometteuse pour la dépollution efficace des eaux contaminées par des polluants organiques insolubles de type toluène, 1-méthylnaphtalène, nitrobenzène,…. Cette méthode d’oxydation avancée repose sur la photocatalyse hétérogène dans des émulsions de Pickering. Dans ce type d’émulsions, les tensioactifs stabilisants des gouttelettes huileuses sont remplacés par des nanoparticules solides à propriétés photocatalytiques élevées. Par ailleurs, ces nanoparticules solides doivent remplir les conditions de mouillabilité partielle dans les deux phases aqueuse et huileuse grâce à un équilibre hydrophile-hydrophobe à leur surface. Pour cette raison, le dioxyde de titane (TiO2) anatase a été préparé par la méthode sol-gel puis modifié par fluoration pour obtenir le catalyseur TiO2-F. L’objectif est de formuler des émulsions de Pickering de type huile dans l’eau (H/E) à partir de polluants organiques de faible solubilité dans l’eau. Les catalyseurs synthétisés ont été caractérisés par XRD, BET, SEM, DRS, XPS, et TG-TD-MS. Il a été montré que la fluoration apporte des changements importants dans les propriétés optiques du TiO2 et a amélioré l’équilibre hydrophile/hydrophobe à sa surface de façon significative. Par ailleurs, les résultats obtenus indiquent que des émulsions de Pickering stables peuvent être formulées en utilisant des particules de TiO2 ou TiO2-F de taille nanométrique. Le type et la stabilité des émulsions dépendent de la mouillabilité des nanoparticules stabilisantes évaluées par des mesures d'angle de contact. La mouillabilité des nanoparticules a été trouvée fortement dépendante du type d’huile en raison des contributions de la polarité et des interactions spécifiques avec les polluants. L'étude des émulsions de Pickering par conductivité électrique, microscopie optique et diffusion de la lumière a montré qu'une stabilité élevée a été obtenue dans des conditions de mouillage partiel : angle de contact dans l'eau compris entre 70 et 110°. L’évolution de la taille des gouttelettes d'huiles avec le rapport de masse huile/photocatalyseur a confirmé une forte adsorption des nanoparticules de catalyseur sur les gouttelettes d'huiles. Finalement, les émulsions jugées stables ont été photodégradées sous rayonnement UV. La cinétique de photodégradation des polluants organiques mesurée par HPLC a montré que la dégradation a été intensifiée en utilisant les émulsions de Pickering par rapport aux systèmes non émulsionnés. Ces résultats ont prouvé que l’utilisation des émulsions de Pickering stabilisées par des nanoparticules de dioxyde de titane constituait un moyen efficace et innovateur pour intensifier la dégradation photocatalytique des polluants organiques
This thesis examines a promising new method for the effective depollution of water contaminated by insoluble organic pollutants such as toluene, 1-methylnaphthalene, nitrobenzene, etc. This advanced oxidation method is based on heterogeneous photocatalysis in Pickering emulsions. In this type of emulsion, the stabilizing surfactants of the oily droplets are replaced by solid nanoparticles having high photocatalytic properties. Moreover, these solid nanoparticles must fulfill the conditions of partial wettability in both aqueous and oily phases thanks to a hydrophilic-hydrophobic balance on their surface. For this reason, the titanium dioxide (TiO2) anatase was prepared by the sol-gel method and then modified by fluorination to obtain the TiO2-F catalyst. The objective is to formulate Pickering oil-in-water (O/W) emulsions from organic pollutants of low water solubility. The synthesized catalysts were characterized by XRD, BET, SEM, DRS, XPS, and TG-TD-MS. It has been shown that fluorination brings about important changes in the optical properties of TiO2 (change in band gap) and improves the hydrophilic / hydrophobic balance at its surface significantly. Moreover, the obtained results indicate that stable Pickering emulsions can be formulated using TiO2 or TiO2-F nanoparticles. The type and stability of the emulsions depend on the wettability of the stabilizing nanoparticles evaluated by contact angle measurements. The wettability of the nanoparticles has been found to be highly dependent on the type of oil due to the contributions of polarity and specific interactions with pollutants. The study of Pickering emulsions by electrical conductivity, optical microscopy and light scattering showed that high stability was obtained under partial wetting conditions: contact angle in water between 70 and 110°. The change in the size of the oil droplets with the oil/photocatalyst mass ratio confirmed a strong adsorption of the catalyst nanoparticles on the oil droplets. Finally, the judged stable emulsions were photodegraded under UV radiation. The photodegradation kinetics of organic pollutants measured by HPLC showed that degradation was intensified using Pickering emulsions compared to non-emulsified systems. These results have shown that the use of Pickering emulsions stabilized by titanium dioxide nanoparticles is an effective and innovative way to intensify the photocatalytic degradation of organic pollutants

Les photocatalyseurs à base de TiO2 ont été l’objet d’une grande attention comme une méthode durable de purification de l’air ou de l’eau, et de production d’hydrogène par décomposition de l’eau. Une stratégie avantageuse consiste à développer des héterostructures par couplage avec un autre oxyde métallique former une jonction de type Schottky ou avec un autre oxyde métallique pour créer une jonction p-n à l’interface de manière à prévenir les recombinaisons via une séparation de charge « vectorielle » à ces jonctions. De plus, les facettes cristallines jouent un rôle crucial dans le piégeage des porteurs de charge et, donc,dans les réactions rédox photoactivées. Ainsi, le dépôt sélectif de métal ou d’oxyde métallique sur des facettes spécifiques de nanocristaux de TiO2 devrait augmenter l’activité photocatalytique par l’amélioration de la séparation des charges. Dans ce travail, nous avons combiné l’emploi du cocatalyseur de type p NiO pour former des jonctions p-n avec son dépôt sélectif sur des nanocristaux de TiO2 anatase exposant des facettes bien définies. Par ailleurs, des expériences modèles de physique de surface ont été menées pour étudier les propriétés électroniques de ces hétérojonctions
TiO2 photocatalysts have attracted attention as a sustainable method for water/air purification and hydrogen production by water splitting. An advantageous strategy is the development of heterostructures by coupling metal oxides to create a p-n junction at their interface in order to prevent there combination by vectorial charge carrier separation at these energy junctions. In addition, crystal facets play a decisive role in the trapping of charge carriers and thus photocatalytic redox reactions. Thus, selective deposition of metal or metal oxides onto specific facets would enhance the photocatalytic activity by improving charge separation. In this work, we have combined the usage of p-type NiO co-catalyst to form p-n junction with its selective deposition onto the specific facet of oriented TiO2nanocrystal photocatalysts. Furthermore, the physical model experiments have been performed to investigate the electronic properties of these heterojunctions

Ce travail décrit la synthèse et le comportement de nouveaux photocatalyseurs à base de dioxyde de titane utilisés pour des applications environnementales. Dans la première partie, la pertinence des composés modèles testés, le colorant acide orange 7 (AO7) et le 4-Chlorophénol (4-CP), pour des traitements photocatalytiques à base de TiO2 a été étudiée et validée. Cette étude a été centrée sur l’effet de la concentration initiale en composé et sur la vitesse d’agitation pendant la réaction photocatalytique. La deuxième partie est consacrée principalement à la synthèse et la caractérisation des suspensions de particules colloïdales de TiO2. Leur séparation puis leur récupération après le traitement étant pratiquement impossible l’immobilisation de ces particules sur des supports de type hydroxydes doubles lamellaires (HDL) a été étudiée afin de préparer un matériau composite TiO2/HDL présentant une activité photocatalytique comparable à celle du dioxyde de titane pur. Un deuxième type de composite basé sur des mélanges de TiO2/SiO2 a également été envisagé et utilisé dans la préparation de fines couches efficaces pour la photodégradation de l’hexane. Enfin, le comportement photocatalytique d’HDL pur à base de zinc et de chrome, sans addition de TiO2, a également été étudié et est présenté dans la partie finale de cette thèse. Les matériaux préparés ont été caractérisés par différentes analyses chimiques, diffraction et fluorescence des rayons X, microscopie électronique à transmission et à balayage, spectroscopie IR à transformé de Fourier, analyse thermogravimétrique, mesure du potentiel Zeta, diffusion de la lumière, mesure d’adsorption N2. Les différents matériaux ont été testés photocatalytiquement via la photo-Oxydation en solution aqueuse de l’acide orange 7 (AO7), du 4-Chlorophénol (4-CP) ou du bleu de méthylène à différents pH. L’activité photocatalytique du matériau composite à base de TiO2/SiO2 sous forme de film fin a été évaluée en phase gaz en présence d’hexane
This work describes the behaviour and fabrication of new photocatalysts based on titaniumdioxide for the purpose of environmental applications. It consists of five closely connectedparts. In the first part the suitability of chosen model compounds, azo dye Acid Orange 7(AO7) and 4-Chlorophenol (4-CP), for photocatalytic activity assessment of TiO2 was studied.This study was focused on the effect of different initial concentrations of model compoundand different rates of stirring during photocatalytic reaction. The second part then focusedmainly on the synthesis and characterization of aqueous colloidal suspensions of TiO2. Theseparation of TiO2 particles in the form of colloidal suspensions and their regeneration afterthe reaction, while keeping the same photocatalytic properties, is almost not possible.Therefore, it was necessary to find an appropriate method how to immobilize these particleson the support or in the form of composite. The layered double hydroxides (LDH) werechosen as one of suitable supports for TiO2 photocatalyst. The focus was kept on thepreparation of TiO2/LDH composites with the same or higher photocatalytic activity as purecolloidal titanium dioxide. The second chosen type of composite was based on twocomponentTiO2/SiO2 material and these composites were used for the preparation of thinlayers. Photocatalytic behaviour of pure LDHs and their possible use as photocatalyst withoutTiO2 addition was also studied and described in a final part of this work. Prepared materials were characterized by chemical analysis, X-Ray diffraction andflorescence, transmition electron microscopy, scanning electron microscopy, Fouriertransform infrared spectroscopy, thermogravimetric analysis, dynamic light scattering, zetapotential measurement and N2 adsorption. As another step, materials were tested asphotocatalyst by the photooxidation of Acid Orange 7, 4-Chlorophenol and Methylene Blue indifferent pH in aqueous medium. Photocatalytic activity of TiO2/SiO2 composites in the formof thin films was tested in gaseous phase using hexane as a model pollutant. It was found that quantum yields of 4-CP degradation for all prepared alkaline colloidalsuspensions of TiO2 were lower than those obtained for acidic TiO2 colloidal suspensions. Inthe contrary to the quantum yield of acidic TiO2, the quantum yield of alkaline suspensionsdecreased during the aging. Prepared TiO2/Mg2Al1.5 nanocomposites exhibited higherphotocatalytic activity than the original TiO2 in basic conditions and also it was much easierto recover the photocatalyst after reaction by simple sedimentation. In the case of TiO2/SiO2composites, it was found that composite prepared with TiO2:SiO2 ratio 1:1 has higherphotocatalytic activity in aqueous media than starting pure TiO2 but with increasing SiO2content reaction rate of AO7 degradation decreases. Thin layers of TiO2:SiO2 compositeprepared from simultaneously co-Precipitated particles (they have improved crystallinity inrelation to pure TiO2) are able to photocatalyticaly degrade hexane. In the case of pure LDH,it was proved that even noncalcined Zn2CrCO3 LDH can produce HO• radicals. However,mixed oxides (containing ZnO) prepared by LDH calcination at temperatures higher than500°C, showed higher efficiency

L’objective est d’améliorer l’activité photocatalytique de TiO2 sous irradiations UV et Visible. Pour contourner les limites de TiO2 intrinsèque nous envisageons une fabrication de nanocomposite plasmonique à base de nanofils de TiO2 périodiquement organisés et assemblés avec des nanoparticules plasmoniques. Pour la fabrication des nanofils de TiO2 mécaniquement stables, deux approches ont été réalisées. La première approche est basée sur la croissance sélective en phase vapeur, la deuxième approche consiste en l’utilisation d’un moule de membranes AAO et d’un dépôt de films conformes par ALD. En parallèle les films de TiO2déposés par ALD sont assemblés avec les nanoparticules plasmoniques d’or. Les différentes architectures de TiO2 sont valorisées par des tests photocatalytiques (UV et Visible) sur les polluants modèles. Une nouvelle approche de la fabrication des films mesoporeux d’H-TiO2 avec efficacité photocatalytique à la fois sous irradiation UV et Visible est développée
The objective of this thesis is to improve the photo-response of well-known photocatalytic material such as TiO2, which is usually only active in the UV range. The basic idea is to assemble several approaches within one device to improve the photocatalytic properties: fabrication of periodically-organised TiO2 nanostructures and their assembly with plasmonic nanoparticles. Two fabrication strategies were investigated for these purposes. The first approach consists of selective vapour phase growth. The second approach implements the use of an AAO template. In parallel, TiO2 films deposited by ALD and assembled with plasmonic gold nanoparticles are investigated. The photocatalytic measurements on various TiO2 architectures were performed in both irradiation ranges UV and Vis. A new fabrication approach of mesoporous H-TiO2 films was developed giving promising results of photocatalytic efficiency improvement in both UV and Visible ranges

Parmi les différents systèmes de stockage d’énergie électrique étudiés depuis plus de 2 siècles, le stockage électrochimique de type batterie Li-Ion est vraisemblablement le plus pertinent et le plus efficace. Des verrous demeurent cependant pour avoir des batteries Li-Ion répondants aux besoins actuels, et une des limitations provient des matériaux d’électrodes. Le silicium est un candidat de choix pour répondre aux problématiques batteries posées, cependant sa tenue au cyclage est courte et les méthodes de synthèse sont souvent très contraignantes. Associant deux laboratoires de recherche acteurs majeurs dans le domaines des nanosciences (le LRN à l’URCA) et des matériaux et batteries (le LRCS à l’UPJV) le projet pluridisciplinaire NanoSiBL d’une durée de 36 mois se fixe pour objectif d’apporter des solutions aux deux points précédents par : 1, la réalisation d’électrodes négatives en Silicium par une voie de synthèse bas coût originale et innovante développée au LRN (l’électrodépôt en milieu liquide ionique), 2 un accroissement de la durée de vie de l’électrode grâce à deux types de structuration (soit une électrode constituée de nanofils/nanotubes de Si monolithique soit une électrode nanostructurée composite de Si/TiO2). L’expertise dans le domaine des batteries du LRCS devrait permettre sur ce deuxième point de déterminer la géométrie et configuration idéale de l’électrode en termes de performance. Basé des méthodes d’élaboration par électrochimie bas coût et originale, NanoSiBL a pour objectif, grâce au partage de compétences et de technologie entre physiciens et chimistes impliqués, d’initier une nouvelle thématique inter-établissement axée sur la valorisation de nanostructures de silicium et silicium composite nanostructuré. L’intérêt scientifique de ce projet réside dans la mise en œuvre et le contrôle des propriétés intrinsèques de ces nanostructures à base de silicium pour la réalisation d’électrodes négatives performantes de batterie Li-Ion. Dans la littérature, les électrodes négatives à base silicium ou silicium composite (type Si/TiO2) ont déjà démontré une amélioration par rapport aux électrodes de silicium massif. Néanmoins, le passage à des dispositifs opérationnels reste peu fréquent car les voies permettant de contenir l’expansion en volume du silicium restent à éprouver et car les méthodes utilisées pour élaborer ces nanofils de silicium (Chemical Vapor Deposition, évaporation réactive…) restent très contraignantes, tant au niveau des conditions de croissance (nécessité d’utiliser des précurseurs métalliques et des gaz très toxiques) que des coûts de fabrication (travail sous ultra-vide, nombreuses étapes pour la réalisation des dispositifs avec la nécessité de réaliser des contacts post-croissance…). NanoSiBL propose donc une alternative en réelle rupture technologique avec les méthodes de synthèse actuelles. Les techniques de croissance (électrodépôt en liquide ionique) et de nanostructuration (au sein de membranes polycarbonates ou nanotubes de TiO2) utilisées dans le projet permettront la mise au point d’électrodes à bas coût performantes pour l’application batterie Li-Ion visée. En outre la variété conséquente de géométries possibles proposées par les membranes nanoporeuses qui seront utilisées dans le projet (polycarbonate ou nanotubes de TiO2) permettra d’établir un comparatif essentiel de l’impact de la nanostructuration ou encore de la composition des électrodes pour contenir l’expansion en volume du silicium lors du cyclage et ainsi améliorer la durée de vie de telles électrodes (batterie)
Among the various electric energy storage systems studied for more than two centuries, the electrochemical storage battery type Li-Ion is probably the most relevant and most effective. however locks remain for Li-Ion batteries respondents to current needs, and limitations comes from the electrode materials. Silicon is a prime candidate to meet the challenges posed batteries, however its resistance to cycling is short and synthesis methods are often very restrictive. Combining two research laboratories major players in the fields of nanoscience (the LRN to URCA) and materials and batteries (the LRCS to UPJV) the multidisciplinary project NanoSiBL a period of 36 months set the objective of provide solutions to the above two points: 1, the realization of negative electrodes in silicon by a synthetic route down original and innovative cost developed LRN (electrodeposition in ionic liquid medium), 2 increased lifetime of the electrode through two types of structuring (or one electrode made of nanowires / nanotubes Si monolithic or a composite nanostructured electrode Si / TiO2). The expertise in the field of LRCS of batteries should allow this second point to determine the geometry and ideal configuration of the electrode in terms of performance. Based methods developed by electrochemistry low cost and original NanoSiBL aims, through the sharing of expertise and technology between physicists and chemists involved, to initiate an inter-establishment new theme focused on valuation and silicon nanostructures composite nanostructured silicon. The scientific interest of this project lies in the implementation and control of the intrinsic properties of these nanostructures based on silicon for making efficient negative electrodes of Li-Ion battery. In the literature, the negative electrodes based on silicon or silicon composite (type Si / TiO2) have already demonstrated improvement compared to bulk silicon electrodes. However, the transition to operational devices remains uncommon for ways to contain the expansion in volume of the silicon are experiencing and because the methods used to develop these silicon nanowires (chemical vapor deposition, reactive evaporation ...) remain very restrictive both in terms of growth conditions (the need to use metal precursors and highly toxic gases) that manufacturing costs (labor UHV, many steps for the realization of devices with the need for contacts post- growth…). NanoSiBL proposes an alternative in real technological break with the current methods of synthesis. growth techniques (electrodeposition in ionic liquid) and nanostructuring (in polycarbonates or TiO2 nanotube membranes) used in the project will enable the development of electrodes at low cost efficient for application referred Li-Ion battery. Furthermore the consequent variety of possible geometries offered by the nanoporous membranes to be used in the project (polycarbonate or TiO2 nanotubes) will establish a critical comparison of the impact of the nanostructure or composition of electrodes to contain expansion by volume of the silicon during the cycling and improve the life of such electrodes (battery)

Ispitana je kinetika i mehanizam fotokatalitičke razgradnje herbicida kvinmeraka i klomazona u prisustvu UV/TiO₂  Degussa P25, odnosno piklorama i  klopiralida primenom UV/TiO₂  Wackherr pri različitim eksperimentalnim uslovima. Praćena je i kinetika razgradnje odabranih herbicida direktnom fotolizom uz primenu sunčevog, UV i vidljivog zračenja, kao i u odsustvu svetlosti. Pored toga, upoređena je efikasnost UV/TiO₂  Degussa P25, odnosno UV/TiO₂  Wackherr sa vidljivim zračenjem, kao i direktnom fotolizom u prisustvu pomenutih izvora svetlosti.  U cilju procene citotoksičnosti klomazona i klopiralida, kao i smeše klomazona i klopiralida i njihovih intermedijera nastalih tokom fotokatalitičke razgradnje ispitan je  in vitro  rast ćelijskih linija  MRC-5 i H-4-II-E.  Nakon ispitivanja fotokatalitičke razgradnje odabranih herbicida u dvaput destilovanoj vodi, praćena je njihova razgradnja i u prirodnim vodama. Takođe, ispitan je uticaj dodatka hidrogenkarbonata i huminske kiseline na efikasnost razgradnje odabranih herbicida. Fotokatalitička razgradnja klomazona, piklorama i mekopropa je ispitivana i u prisustvu UV/TiO₂  nanocevi. Aktivnost katalizatora TiO₂ Wackherr  i TiO₂  nanocevi je upoređena sa TiO₂  Degussa P25.
The kinetics and mechanism of photocatalytic degradation of the herbicides quinmerac and clomazone in the presence of UV/TiO₂  Degussa P25, and of picloram and clopyralid using UV/TiO₂  Wackherr under different experimental conditions were studied. The kinetics of degradation of selected herbicides by direct photolysis using sunlight, UV and visible radiation, and in the absence of light were followed. In addition, the efficiencies of UV/TiO₂  Degussa P25 and UV/TiO₂ Wackherr  were compared with visible radiation and direct photolysis in the presence of the above mentioned light sources. In order to evaluate the cytotoxicity of clomazone and clopyralid alone and in their mixture with intermediates formed during the photocatalytic degradation, in vitro growth of cell lines, MRC-5 and H-4-II-E was followed. After examining  the photocatalytic degradation of selected herbicides in double distilled water, their decomposition in natural waters was also followed. Also, the influence of hydrogencarbonate and humic acid addition on the efficiency of degradation of selected herbicides was studied. Photocatalytic degradations of clomazone, picloram and mecoprop were investigated in the presence of UV/TiO₂ nanotubes. Activities of the catalysts TiO₂  Wackherr and TiO₂ nanotubes were compared to TiO₂ Degussa P25.

Orientador: Edson Tomaz
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química
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Resumo: Compostos orgânicos voláteis (COV) representam uma categoria de substâncias poluentes que geram diferentes impactos ambientais. Eles são responsáveis pelo aumento das concentrações de ozônio ao nível do solo e pela formação de aerossóis orgânicos secundários. Além disso, alguns deles contribuem para a degradação do ozônio estratosférico e a ampliação do efeito estufa. Alguns componentes têm um caráter carcinogênico, teratogênico ou mutagênico. Há estudos envolvendo o tratamento dos COV pelos mais diversos métodos, tais como: incineração, adsorção e absorção. Reatores fotocatalíticos, muito estudados em aplicação em fase aquosa e com grande sucesso na oxidação de contaminantes orgânicos, aparecem como uma alternativa pouco estudada. A fotocatálise em fase gasosa usando o TiO2 como catalisador se apresenta como uma solução interessante para o tratamento de compostos orgânicos voláteis, por não requerer operação em altas temperaturas, pelo baixo custo do TiO2, por ser seletiva na absorção de radiação e por gerar como produtos da reação CO2 e água, o que dispensa demais tratamentos. Estudos demonstram que a adição de metais nobres ao TiO2 comprova uma melhoria na eficiência fotocatalítica das reações de oxidação de compostos orgânicos voláteis. Dentro deste escopo, este trabalho tem como objetivo testar a eficiência do processo de oxidação de COV em fase gasosa por fotocatálise heterogênea com catalisador de dióxido de titânio (TiO2) impregnado com 1% de paládio (Pd) sob luz ultravioleta. O método de impregnação de paládio em TiO2 pela redução com NaBH4 mostrou-se adequado pelas técnicas de caracterização por DRX, XPS, UV ¿Vis, BET, MEV e Quimissorção de H2, pois há a impregnação do metal na superfície do catalisador sem promover modificações estruturais no TiO2 e não ocorreu alterações na razão de anatase/rutilo. Por XPS indicou a presença de metal em sua forma elementar. Além disso, os resultados da oxidação dos compostos n-hexano, ciclohexano, metil-ciclohexano, n-octano e iso-octano demonstraram aumento significativo na eficiência da conversão, pois foram obtidos valores acima de 90% em tempos de residência de aproximadamente 35 s
Abstract: Volatile organic compounds (VOCs) represent a category of pollutants substances that generate different impacts. They are responsible for increase concentrations of tropospheric ozone and also the formation of secondary organic aerosols. In addition, some of them contribute to the degradation of stratospheric ozone and greenhouse gas intensification. Some components have a carcinogenic, teratogenic or mutagenic character. There are studies involving the treatment of VOCs with various methods, such as: incineration, adsorption and absorption. Photocatalytic reactors, extensively studied in aqueous and with great success to destroy organic contaminants, appears as an alternative understudied. The photocatalysis gas phase using TiO2 as catalyst shows an interesting solution for the treatment of volatile organic compounds, because does not require operation at high temperatures, the low cost of TiO2, being selective in absorbing radiation and the products of reactions are CO2 and water, which eliminates other treatments. Studies prove that the addition of noble metals on TiO2 can improve the photocatalytic efficiency in the oxidation of volatile organic compounds. Therefore, this paper aims to test the efficiency of oxidation of volatile organic compounds (VOC) in gas phase catalysts through heterogeneous photocatalysis with titanium dioxide (TiO2), and their impregnation with 1% palladium (Pd) and UV light. The method for impregnate palladium on TiO2 with NaBH4 reduction was appropriated according to techniques for characterization like XRD, XPS, UV-vis, BET, SEM and H2 chemisorption, because all analysis confirmed that the impregnation of the metal on the catalyst surface do not structurally modify TiO2, neither changes occurred in the ratio of anatase/rutile. XPS indicated the presence of metal in elemental form. The results the oxidation of compounds n-hexane, cyclohexane, methyl cyclohexane, n-octane and iso-octane indicated a significant increase in conversion efficiency; the values were above 90% at residence times around 35 s
Mestrado
Desenvolvimento de Processos Químicos
Mestra em Engenharia Química

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
The need to control textile effluents due to contamination of rivers has led CONAMA to regulate and require a more efficient treatment process. Among the methods of treatment, heterogeneous catalysis stands out due to its high efficiency. The most used photocatalyst is TiO2. The combination of this material with other ones has been employed to improve its activity and/or its performance. Several systems have been tested, including the core-shell that constitutes a complete coverage of one material by another. In this work, TiO2@CoFe2O4 was synthesized by the modified-Pechini method with the addition of CoFe2O4 nanoparticles into the polymeric resin containing titanium. A magnetic material was obtained, which was characterized by X-ray diffraction (XRD), infrared spectroscopy (IR), ultraviolet - visible spectroscopy (UV-Vis), specific surface area by the BET method. The materials were applied in the photodiscoloration of an azo dye. The pure TiO2 calcined at 700 °C showed a mixture of phases anatase / rutile in the proportions 77/23%, which was the calcination temperature which led to the highest photocatalytic activity in the discoloration of the solution yellow gold remazol (RNL). A discoloration of 81% in color of the solution was attained after 6 h of exposure to UV light, while 94% was reached after 2 h of irradiation with sunlight. With the core@shell system CoFe2O4@TiO2 synthesized with 90 % of TiO2, a mixture of anatase and rutile of 92 : 8% was obtained for a calcination temperature of 500 °C. This material showed 76% discoloration after 16 h of exposure to UV light under the same conditions used for the test with pure TiO2
A necessidade do controle de efluentes têxteis devido à contaminação de águas fluviais tem levado órgãos como o CONAMA a regulamentar e exigir um processo de tratamento mais eficiente. Dentre os métodos de tratamento estudados, os Processos Oxidativos Avançados (POA) têm demonstrado grande eficiência, como na fotocatálise heterogênea utilizando materiais semicondutores, sendo o TiO2 um dos mais empregados. A combinação deste material com outros tem sido estudada com o objetivo de melhorar a atividade e/ou performance do mesmo. Para isso vários sistemas têm sido utilizados, dentre eles o core@shell, que consiste na completa cobertura de um material por outro. Neste trabalho o CoFe2O4@TiO2 foi sintetizado pelo método Pechini modificado, com a adição do CoFe2O4 nanoparticulado à uma resina polimérica de titânio, sendo obtido um material magnético, o qual foi caracterizado por difração de raios X (DRX), espectroscopia infravermelho (IV), espectroscopia na região ultravioleta e visível (UV-Vis), análise de área superficial específica pelo método de BET. Os materiais foram testados na fotodegradação de um corante azo. O TiO2 puro calcinado a 700 ºC, apresentou mistura de fases anatase / rutilo com proporção 77 / 23 %, sendo a temperatura de calcinação que levou à maior atividade fotocatalítica na descoloração da solução de amarelo ouro remazol (RNL). Foi obtida 81 % de redução da cor da solução em 6 h de exposição a luz UV e 94 % após 2 h com irradiação de luz solar. Com o sistema core@shell CoFe2O4@TiO2 sintetizado com 90 % de TiO2 foi obtida uma mistura de 92 % de anatase e 8 % de rutilo, para uma temperatura de calcinação de 500 ºC. Este material levou a 76 % de descoloração em 16 h de exposição à luz UV com as mesmas condições utilizadas para o teste com o TiO2 puro

Neste trabalho apresentamos a síntese e caracterização de nanoestruturas core/shell de TiO2/SiO2 e SiO2/TiO2. Visando aumentar a eficiência de DSSC’s, foi investigado o efeito das interfaces SiO2|TiO2 na diminuição de defeitos estruturais (trapping states) no TiO2, sem resultar no bloqueio da transferência de carga entre as partículas no fotoanodo. Foram obtidas nanoestruturas sintetizadas por diferentes períodos, pH, e tratamentos térmicos utilizando-se cores cristalinos e amorfos de SiO2 e TiO2. As amostras foram caracterizadas por Microscopia Eletrônica de Transmissão, UV-VIS, FTIR-ATR, Difratometria de Raios-X, Cronopotenciometria, Voltametria Linear e Impedância. Foram obtidos cores de TiO2 de cerca de 30 nm de diâmetro e shells de SiO2 de cerca de 5 nm de espessura, também obtivemos cores de SiO2 de 10 e 70 nm em diâmetro e encapsuladas com shell de TiO2 de 5 nm de espessura. Os resultados obtidos mostraram que há uma influência da fase polimorfica do material componente do core na fase polimorfica do material que compõe o shell, havendo um significativo retardo nas temperaturas de mudança de fase. Observou-se também uma correlação da fase polimórfica do TiO2 e a camada de SiO2 no bandgap das amostras. Constatamos que estruturas core/shell são eficientes na passivação de defeitos superficiais, embora a espessura da camada isolante deva ser controlada para não influenciar nos parâmetros elétricos do dispositivo.
In this work, we present the synthesis and characterization of core/shell structures of TiO2/SiO2 and SiO2/TiO2 nanoparticles. Aiming to improve the efficiency of DSSCs, the effect of SiO2|TiO2 interfaces to reduce the amount of trapping states on TiO2, without blocking charge transfer among nanoparticles across the photoanode, was investigated. Nanostructures were obtained trough different reaction periods, pH and thermal treatment temperatures using crystalline and amorphous cores of TiO2 and SiO2. The samples were characterized by transmission electron microscopy, UV-Vis, x-ray diffractometry, chronopotentiometry, linear sweep voltammetry and electrochemical impedance spectroscopy. TiO2 cores of ca. 30 nm in diameter were obtained an were encapsulated with a 5 nm thick SiO2 shell. SiO2 cores of ca. 70 nm in diameter were obtained and encapsulated in ca. 5 nm thick TiO2 shell. The results show an influence of polymorphic phase of the core material on the polymorphic phase of the shell material, resulting in a significative change in the phase transition temperatures. It was also determined a correlation between the polymorphic phase of TiO2 and the insulator layer on the samples bandgap. Finally we show that, even though core/shell structures are efficient in trapping states passivation, the thickness of the insulator layer must be controlled in order to not jeperdize the electric parameters of the photoelectrochemical device.

Filmes finos de TiO2 e N:TiO2, e multicamadas TiO2/N:TiO2 foram crescidos sobre substratos de aço AISI 316 e Si(100), por meio da técnica de deposição química de organometálicos em fase vapor (MOCVD). Foram produzidos filmes com diferentes espessuras, nas temperaturas de 400 e 500°C. Os filmes foram caracterizados utilizando-se técnicas de difração de raios X (DRX), espectroscopia de fotoelétrons excitados por raios x (XPS) e microscopia eletrônica de varredura (MEV). A resistência à corrosão foi avaliada por meio de testes de polarização potenciodinâmica em eletrólito 3,5%p NaCl. Filmes não dopados, crescidos a 400°C, apresentaram TiO2 anatase, enquanto que os crescidos a 500°C apresentaram a fase rutilo, além de anatase. Nos filmes dopados com nitrogênio (7,29 e 8,29 at% a 400 e 500°C, respectivamente), em ambas as temperaturas, houve a formação de TiO2 anatase, bem como de fases contendo nitrogênio. Os filmes de TiO2 crescidos a 400°C ofereceram melhor proteção contra a corrosão que os crescidos a 500°C. Filmes crescidos a 500°C apresentaram estrutura colunar, que representa alto nível de porosidade, enquanto que os filmes crescidos a 400°C apresentaram estrutura mais densa. A dopagem não foi eficiente para proteger o substrato contra corrosão, provavelmente devido à formação das fases contendo nitrogênio. Os resultados para os testes com filmes compostos por multicamadas sugerem que aqueles com mais interfaces apresentam melhor resistência à corrosão. O processo de corrosão das amostras se inicia na superfície do filme, que está em contato com o meio agressivo, originando pites, que permitem ao meio corrosivo acessar o substrato metálico. O metal é atacado e dissolvido sob o filme, e resulta na delaminação do filme.
TiO2 and N-doped TiO2 (N:TiO2) thin films, and TiO2/N:TiO2 multilayered films were grown on AISI 316 steel substrates, and Si (100) by using metallorganic chemical vapor deposition (MOCVD) technique. The growth of the films was carried out at 400 and 500°C, and films with different thicknesses and structures were obtained. Titanium dioxide films were produced by using only titanium isopropoxide IV as both titanium and oxygen sources. In order to obtain N:TiO2 films, NH3 was also added to the system. The films were characterized by using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM) The corrosion resistance was evaluated by potentiodynamic polarization tests in a 3.5wt% NaCl electrolyte. TiO2 undoped films, grown at 400°C, presented anatase, while those grown at 500°C showed the rutile phase, besides anatase. For nitrogendoped films (7.29 and 8.29 at% at 400 and 500°C, respectively), at both temperatures, TiO2 anatase was formed, as well as nitrogen-containing phases. TiO2 films grown at 400°C provided better protection against corrosion than those grown at 500°C. Films grown at 500°C showed a columnar structure, which represents a high level of porosity, while the films grown at 400°C presented a denser structure. Doping was not efficient to protect the substrate against corrosion, probably due to the formation of nitrogen containing phases. The corrosion results for tests with multilayered films suggest that those with more interfaces present better resistance to corrosion. The corrosion of the samples starts at the surface of the films, which is in contact with the aggressive medium, causing pitting in this film, which allows the corrosive medium to reach the metallic substrate. The metal is attacked and dissolved under the film, and results in film delamination.

碩士
明志科技大學
材料工程研究所
99
TiO2, TiOxNy thin films have been deposited on unheated glass substrates by a direct current (dc) reactive magnetron sputtering. TiO2-Ag, TiOxNy –Ag thin films were prepared using reactive co-sputtering with Ti and Ag targets on silicon substrates and Corning glass substrates. These films were annealed in Ar atmosphere, at 300 oC, 400 oC, 500 oC, 600 oC, 700 oC, and 800 oC. The studies on microstructural, optical, light degradable, anti-bacterial properties for TiO2-Ag, TiOxNy -Ag nano-composite films were then carried out. The films structures were examined with X-ray diffractometry, TEM (transmission electron microscopy), FESEM (field emission scanning electron microscopy). As for the optical properties, UV-Vis-NIR, PL spectrometry were used. Finally, hydrophilic test and MB degradation test were carried out to test the photocatalytic properties of these films. The results show that the absorption of the Ag-doped films would increase in the visible-light range. Some of the increase is clearly due to plasmon resonance effect. All Ag-doped TiOxNy are hydrophilic under visible light irradiation. As for the change of microstructure, Ag-doped TiO2 leads to amorphous structure. After being annealed at 500 oC, the films tend to become anatase phase first due to its fine grain structure. When the annealing temperature increased to 800 oC, the phase tends to become rutile. Ag-doped TiO2 and TiOxNy films are found to inhibit the recombination of electron-hole pairs. However, when the Ag contents reach a certain limit, no enhancement can be found. This is probably due to the light blocking effect.

博士
國立臺灣科技大學
電子工程系
97
In this dissertation, we have studied the growth conditions for the deposition of well-aligned anatase (A) and rutile (R) phases titanium dioxide (TiO2) nanocrystals (NCs) as well as IrO2/R-TiO2 and RuO2/R-TiO2 hetero-nanocrystals on various substrates via the technique of cold-wall metal organic vapor deposition (MOCVD). The source reagents used for TiO2, IrO2 and RuO2 deposition are Ti(OC3H7)4, (C6H7)(C8H12)Ir and bis(ethylcyclopentadienyl) ruthenium (II), respectively. Thermal-induced phase transformation from A-TiO2 to R-TiO2 was also studied. A detailed characterization focusing on the surface morphology, structural, orientations, optical and spectroscopy properties of A- and R-TiO2 NCs, IrO2/R-TiO2 and RuO2/R-TiO2 hetero-nanocrystals have been carried out by means of field emission scanning electron microscopy (FESEM), X-ray diffractometry (XRD), micro-Raman scattering (RS), photoluminescence (PL), surface photovoltage spectroscopy (SPS), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and selected-area electron diffractometry (SAED). Under the growth condition of 1.5 mbar and 60 牵C(chamber pressure and showerhead temperature), we have successfully deposited well-aligned A-TiO2 NCs on fused silica with a preferential orientation of (220). Raman spectrum confirmed the deposition of pure anatase phase TiO2 on fused silica. Luminescence of self-trapped excitons and oxygen vacancies were observed in anatase NCs. The indirect band gap of A-TiO2 was determined to be 3.14 ± 0.01 eV by analyzing the surface photovoltage spectrum. Energy-dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) analyses showed oxygen vs. titanium ratio of 2.0 ± 0.1 for the as-deposited A-TiO2 NCs. Further structural characterization of the well-aligned A-TiO2 NCs was studied using TEM technique. The formation of building units bonded along {112} facets with preferred (220) orientation of the well-aligned A-TiO2 NCs on fused silica were presented and the probable growth mechanisms were discussed. A detailed study of thermal-induced phase transformation in TiO2 NCs via XRD and RS spectroscopy has also been carried out. Vertically-aligned A-TiO2(220) NCs were grown on sapphire SA(100) substrate at 550 °C. The effects of thermal annealing of TiO2 NCs in oxygen atmosphere between 600 and 1000 °C were investigated. XRD and RS spectra showed the onset of the phase transformation process from the as-grown A-TiO2(220) NCs into R-TiO2(002) at the annealing temperature of 800 °C. At annealing temperature higher than 900 °C, pure R-TiO2(002) NCs were formed and the crystalline quality of TiO2 NCs can be further improved upon higher annealing temperature. The well-aligned densely-packed R-TiO2 NCs have been grown on SA(100) and (012) substrates. FESEM micrographs revealed the growth of vertically aligned NCs on SA(100), whereas the NCs on SA(012) were grown with a tilt angle of ~ 33牵 from the normal to the substrates. TEM and SAED measurements showed that the TiO2 NCs on SA(100) have their long axis directed along the [001] direction. The XRD results revealed TiO2 NCs with (002) orientation on SA(100) substrate or (101) orientation on SA(012) substrate. A strong substrate effect on the alignment of the growth of TiO2 NCs has been demonstrated and the probable mechanism for the formation of these NCs has been discussed. The optical characterization of well-aligned A- and R-TiO2 NCs grown on SA(100) substrate under different conditions have been carried out by using Raman scattering (RS), photoluminescence (PL) and surface photovoltage spectroscopy (SPS) techniques. Raman spectra confirmed the formation of pure phases of A- and R-TiO2. Comparing to the results of the single crystals, the luminescence features of A-TiO2 were assigned to the recombination of self-trapped excitons localized on TiO6 octahedra and oxygen vacancies. The emission spectrum of the R-TiO2 NCs contained features related to the visible- and near infrared-broad- bands centered on 1.5 and 2.7 eV, respectively. The visible band was attributed to the bound excitation emission due to the trapping of free excitons by TiO6 octahedra near oxygen vacancies and the near infrared band is associated with the emission centers of intrinsic defect in R-TiO2. The indirect band gaps for the as-grown A- and R-TiO2 NCs were estimated to be 3.14 ± 0.02 and 3.01 ± 0.02 eV, respectively, by analyzing near band edge surface photovoltage spectra. The study of the growth of IrO2/R-TiO2 and RuO2/R-TiO2 hetero-nanocrystals has been carried out as well. The IrO2 /RuO2 NCs were grown on top of well-aligned R-TiO2 templates. The FESEM images and XRD patterns indicated growth of V-shaped IrO2(101) nanowedges (NWs)/coexistence of vertically aligned (002) and V-shaped RuO2(101) nanorods (NRs) on top of R-TiO2 NRs. TEM and SAED characterizations of V-shaped IrO2/RuO2 NCs showed crystalline IrO2 NWs/RuO2 NRs with a twin plane of (101) and twin direction of at the V-junction. The probable mechanisms for the formation of well-aligned IrO2 NWs/ RuO2 NRs were discussed.

碩士
臺灣大學
物理研究所
95
In this thesis, a series of TiO2/Co/TiO2 trilayer samples were synthesized by high vacuum based co-sputtering in a RF magnetron system. The samples were grown on the Si(100) substrates. We try to synthesize the Co doped TiO2 dilute magnetic semiconductor structure via thermal treatments under vacuum environment, and study its magnetic property. The results reveal that during thermal treatments in a vacuum environment, the Co grains may form the oxide phase structure, and lose their magnetic properties. In the second part, we synthesize a series of Co/TiO2/Co trilayer films, with varying the TiO2 spacer layer thickness, and fixing the Co layer thickness to study their interlayer coupling effect. As analyzed from M-H results, the thickness of TiO2 spacer layer (X) strongly influences the ferromagnetic layers to be alignment in parallel or in antiparallel at low temperature. The ESR analysis results also reveal that the peaks of Hr versus angle shift from 90˚ under different TiO2 spacer layer thickness. At X=4~6 nm, it shows the largest shift which is very different from the result of single Co layer. Our experimental results suggest that Co/TiO2/Co may be a candidate for the tunneling magnetoresistance system. However the mechanism of interlayer coupling of Co-layer via TiO2 requires a further investigation.

碩士
國立清華大學
材料科學(工程)研究所
83
TiO2陶瓷經由適當的添加(Nb''Ba等),使其具有優良之電容及變阻效應本論 文主要研究不同結晶相粉末及添加劑對TiO2陶瓷體電性之影響另外因為一 般商業用金屬氧化物粉末由於其粉末粒度大故燒結時其緻密化程度較用化 學方法製備之粉末為差故本論文亦探討了添加劑與製程方法上之改變對燒 結試片緻密化的影響不同之煆燒溫度可獲得不同結晶相之粉末而不同結晶 相粉末會因其特性之不同造成燒結後電性之差異由實驗發現rutile 相粉 末燒結後試片其崩潰電場較低且非歐姆特性變差在1250℃燒結兩小時之試 片α值大約在6.4左右但其介電常數卻是同樣燒結溫度下最高的而其主要 因素在於空乏區寬度較薄而rutile+anatase 相粉末具有最佳之非線性指 數在1250℃燒結兩小時之試片其α值達7.6不同氧化物之添加(Cu、Sb)， 經由介電性質測試、阻抗分析、I-V測試，可直接或間接證實各種添加劑 對晶粒電阻率、晶界電阻率及晶界能障等之影響。另外，經由微觀結構之 觀察、X光繞射分析，可以得知微結構與析出物對電性之影響。此外亦就 試片做TEM之分析，發現其晶界 分是有玻璃相存在且已有多處成核結晶。 Cu之添加使得晶粒晶界電阻增大，非歐姆特性及介電常數降低，其主要原 因為空乏區寬度大幅增加；而Sb之添加，由於其在燒結時部份會由三價離 子轉變成五價離子，使晶粒、晶界電阻，非歐姆特性降低而介電常數提高 ，主要是由於空乏區寬度減小之故。另外，亦利用Sb低熔點之特性，來增 進燒結之密度，實驗發現Sb果然有幫助燒結之現象。最後利用製程方法之 改變，將欲留在晶粒與晶界部份之元素分開鍛燒，實驗發現其緻密化程度 穫得很大的提升，密度大約在理論密度之91%-99%之間。

碩士
國立中正大學
化學所
94
This study investigated the phase transfer of aqueous Au nanoparticles and Ag nanoparticles into the organic solution by adding different surfactant and ionic liquid and thereafter the preparation of Au@TiO2 and Ag@TiO2 nanocomposite materials.To prepare Au@TiO2 and Ag@TiO2 nanoparticles, metal nanoparticles have to be firstly prepared. Metal nanoparticles are usually produced in aqueous solution, due to the water-soluble nature of metal salt. In addition, synthesis of different sized and shaped nanoparticles in aqueous solutions is easier than that of in organic solutions. However, some applications of metal nanoparticles have to be performed in organic phase. For example, TiO2 coating of metal nanoparticle by hydrolysis-condensation of titanium dioxide，s precursor in water is very fast. Hence, the size and thickness of the Core-Shell composition are very difficult to control in water-based solution, as in contrast with that of in organic solution. This research examined the effect of organic solvent, modifier, precursor and concentration of ionic liquid on the formation of core-shell material. The results indicate that : (1) Ionic liquid can be employed to transfer the nanoparticles from aqueous phase into organic phase and the efficiency of phase transfer is proportion to the concentration of ionic liquid. The data implies that the ionic liquid behaves as an ion-pair reagent in the process of phase transfer. (2) Organic solvent and modifier are definitely required to form a stable core-shell structure. (3) The size of Au@TiO2 and Ag@TiO2 nanocomposite is proportion to the concentration of ionic liquid in organic solution.

碩士
明新科技大學
化學工程研究所
94
Textile industry will produce large amount of wastewater which is non-biodegradable and colorful and causes serious pollution problem to the environment. Therefore, the aim of this research will focus on the feasibility and treatment efficiency by Advance Oxidation Process（AOP）- UV/TiO2 for three different kinds of simulated dye wastewater. The first part of this study will investigate the treatment of simulated dye wastewater with UV/TiO2 by changing TiO2 dosages、TiO2 nanosizes and dye concentrations. The optimum conditions obtained for treatment of different dye wastewater are different. By the experimental result, the treatment of Indanthren red（FBB）by UV/TiO2 is best among others. Its TOC removal percentage is 99.68％, color removal near 100％. Because the photocatalysts, TiO2, used are nano powders, it is difficult to separate from wastewater. It will cause the secondary pollution. By this reason, the second part of the research will try to produce TiO2 film and then use UV light to treat dye wastewater. By the experimentals, the TiO2 films made in the laboratory prove its suitability for the dye wastewater treatment in low concentration.

碩士
明新科技大學
化學工程研究所
95
Surfactant is a very popular synthetic chemical material with some special nature , such as cleaning , emulsification , dispersion and wetness .Therefore it is widely applied in family's daily life and in industry. At present, the global consumption of surfactants approaches 2,700,000 metric tons per year and about 1 million metric tons in Asia. Among them the most common type is the anionic or nonionic surfactants which accounts for more than 90% of the total surfactant usage. Most wasted surfactants metabolize in domestic or industrial wastewater treatment plant. The general treatment technology includes chemical, physical or biological methods. But , more than 15％ of the surfactants will still directly or indirectly enter to the river or ocean which causes the environmental pollution problems. Therefore, the aim of this research will study the feasibility and treatment efficiency of Advanced Oxidation Processes (AOPs) - Solar/TiO2 method and UV/TiO2 method for simulated anionic surfactant wastewater. The first part of this research focuses on the treatment by studying the effect of TiO2 dosages、reaction time、light intensity、anion surfactant concentration and TiO2 nanosizes. Meanwhile, adsorption of surfactant on TiO2 was carried out by studying adsorption isotherm and L-H kinetic model. The experimental results by Solar/TiO2 treatment showed that the optimum conditions obtained were anionic surfactant concentration 100ppm , dosage 6g/L of TiO2 , and limited effect of nanosizes (7nm , 20nm ) of TiO2 . Both Langmuir adsorption isotherm and Langmuir-Hinshelwood kinetic model fit the experimental data well and their adsorption constants are quite close by either isotherm or L-H model. The second part of this research studied the simulated anionic surfactant wastewater treatment by UV/TiO2 method. The optimum conditions from Solar/TiO2 were used for the study of UV/TiO2 method. Finally Solar/TiO2 and UV/TiO2 were compared by their experimental results.

碩士
國立中正大學
化學工程研究所
90
In this study，these V2O5/TiO2/SiO2,V2O5/SiO2，TiO2/SiO2 catalyst were successfully prepared from two-steps impregnation，(i).wet impregnation of the support(SiO2) with a titanium isopropoxide aqueous solution was sintering at 500 ℃ for 4 hr to get TiO2/SiO2，(ii) grafting of TiO2/SiO2 dissolved in vanadium isopropoxide was sintering at 500℃ for 12hr。 than the V2O5/TiO2/SiO2 catalyst was obtained。The catalyst was application in ethanol oxidation reaction，to confer change of conversion and selectivity，and EXAFS (Extended X-Ray Absorption Fine Structure) was used to confer the role of TiO2 on V2O5/TiO2/SiO2 catalyst structure。 In oxidation reaction，the ethanol conversion in V2O5/TiO2/SiO2 catalyst system is higher 1.5~3 times than V2O5/SiO2，TiO2/SiO2。in TPR (Temperature Programmed Reduction) profile of catalyst，Tr was decrease 100 ℃ by using V2O5/TiO2/SiO2 catalyst。Therefore，form characterization result of the catalyst in EXAFS spectroscopy，the metal aggregate phenomenon in high temperature decrease by adding TiO2 on V2O5/SiO2 catalyst，and keep high metal dispersion and conversion。 A series of oxidation reaction，the effect of TiO2 in V2O5/TiO2/SiO2 were (1).in structure : TiO2 hold the metal aggregation in high temperature was decrease to present of TiO2，and high metal dispersion。(2). in TPR : Tr was decrease 100℃by using V2O5/TiO2/SiO2 catalyst。(3). In conversion : the ethanol conversion was increase 1.5~3 times。

碩士
國立中興大學
環境工程學系
91
This research studied the heterogeneous photocatalytic degradation of aqueous monochlorophenol solution by UV/TiO2 and UV/Pt-TiO2 processes in a batch reactor with coated TiO2 on pyrex tube. The experimental equipment was a batch recycle system. The controlled parameters included concentration of monochlorophenol and pHs. The reaction kinetic model could be established with the analyses of TOC, HPLC, and IC, varied with reaction time. Moreover, the effect of various parameters on reaction efficiency was expected to study. The TiO2 thin film was prepared by chemical vapor deposition (CVD), and then to be modified it with irradiation of 365nm UV for 24 hours in high concentration of H2PtCl6˙6H2O solution. In the experimental results of the photocatalyst preparation, it was suggested that loaded Pt on TiO2 thin film will not change the anatase percentage with the analysis of XRD. Photodegradation and mineralization were confirmed by HPLC and TOC measurements. After 240 minutes of reaction, the photodegradation ratio for 50ppm monochlorophenol reached 80% at high pH’s. There was no evidently increasing of the degradation of monochlorophenol. It could be due to the excess amount of Pt loaded on TiO2 thin film and form metallicity Pt during the modified process. It might result in the depression of the photon absorption efficiency and entirely inhibited the photocatalytic reaction. On the aspects of mineralization, there was better mineralization at low concentration of 3-CP and 4-CP, and decreased with the increased of original concentration. On the aspects of Cl- production, TiO2 and Pt/TiO2 system presented the same tendency of chloride formation.

碩士
明道大學
材料科學與工程學系碩士班
99
Investigation of anti-reflection coating using sol-gel method and dip coating technique were deposited on glass. We selected a sol-gel of TiO2(T)、SiO2 (S) and TiO2-SiO2(TS) mixture solution which different ratios of TiO2 and SiO2 solution were mixed. We main Research (1) changes withdrawal speed of different sol-gel solution thin film thickness. (2) influence of thin film thickness and adhesion on glass of changes baking temperature. (3) get the higher transmittance at vision region using different optical thickness stacking. Experimental results found that increase of withdrawal speed cause the film thickness increase but the film was non-uniform, increase of baking temperature cause the thin film thickness down and adhesion raise. SiO2 anti-reflection coating on glass substrate which the optical property the average transmission, was 96.3 % in wavelength range 400-800 nm and 93.8 % in wavelength range 400-1200 nm, and the highest transmittance at 558 nm with 98.3%. SiO2/TiO2-SiO2 double layer anti-reflection coating on glass substrate which the optical property the average transmission, was 96.8 % in wavelength range 400-800 nm and 94.4 % in wavelength range 400-1200 nm, and the highest transmittance at 544 nm with 97.9 %. These results show anti-reflection coating on glass assured increase transmission. Therefore expected to use sol-gel method on solar cell of anti-reflection coating on package glass and increase solar cell Efficiency.

博士
國立成功大學
化學工程學系碩博士班
97
This dissertation concerns the preparation of TiO2 nanoparticles and metal-TiO2 core-shell type nanocomposites, and their photocatalytic and photoelectrochemical applications. TiO2 nanoparticles were prepared though sol-gel process, coating on Ag or NiAg alloy nanoparticles, and the core-shell type Ag@TiO2 or NiAg@TiO2 nanocomposites were fabricated. The effects of preparation conditions on the particle size, structure, optical and surface state properties were investigated. The applications in UV-cut materials, photocatalysts and photoelectrochemical cells were also discussed. Three systems were studied, including “Catalyst-free low temperature synthesis of discrete anatase titanium dioxide nanocrystals with highly thermal stability and UVC-cut capability”, “Fabrication and photocatalytic activities of Ag@TiO2 and NiAg@TiO2 nanoparticles”, and “Visible light induced photoelectrochemical properties of Ag@TiO2 nanoparticle thin film as a novel photoelectrode”. A novel, facile, catalyst-free and low temperature process for the synthesis of discrete anatase TiO2 nanocrystals has been developed in the absence of stabilizing agent. By varying the water content and precursor concentration, the particle size could be tuned. Also, the resultant colloid solution was quite stable even in the absence of stabilizing agent because of the coverage of EG molecules on the particle surface. The product was shown to be discrete anatase TiO2 nanocrystals with a mean diameter of 4.97 ± 0.9 nm and a specific surface area of 393 m2/g. Also, as compared to Degussa P25 TiO2 powders, they exhibited stronger absorption at 200 ~ 350 nm and higher transmittance in the visible light region. In addition, the anatase TiO2 nanocrystals obtained in this work had highly thermal stability even at temperatures up to 800 oC. The new approach proposed in this work was practicable for the synthesis of anatase TiO2 nanocrystals, particularly for those requested to have highly thermal stability and UVC-cut capability. Completely discrete Ag@TiO2 and NiAg@TiO2 core-shell type nanocomposites were prepared by the hydrazine reduction of Ag+/Ni2+ ions and the followed sol-gel coating of TiO2 in the aqueous solution of CTAB. TEM analysis revealed that they had diameters of 11.91 ± 2.31 and 13.49 ± 2.58 nm, respectively, and the similar shell thickness of 5 nm. By the analyses of EDX, UV-VIS absorption spectra, FTIR spectra, and zeta-potential, their core-shell structure, crystal structure, optical property, and surface state were demonstrated. By measuring the photocatalytic degradation rate of Rhodamine B, Ag@TiO2 and NiAg@TiO2 nanoparticles were demonstrated to possess significantly higher photocatalytic activities than pure TiO2 nanoparticles in the visible light region because of the formation of Schottky barrier banding at the core-shell interface as well as the excitation of photogenerated electrons from the surface of Ag or NiAg cores to the conduction band of TiO2 shells. Although NiAg@TiO2 nanoparticles had lower photocatalytic activity than Ag@TiO2 nanoparticles owing to weaker surface plasmon resonance, they could be recovered magnetically from the treated solutions. The photoelectrochemical photoelectrodes were also prepared through Ag@TiO2 thin films coating on ITO conducting glass substrates. SEM analysis indicated that the thickness was about 2 µm and the surface morphology was a granular porouslike structure, which could assist the permeation of electrolytes and improve the photoelectrochemical properties. By measuring the photoelectrochemical properties, Ag@TiO2 photoelectrodes were demonstrated to possess significantly 8.33 and 68 folds higher photocurrent density than pure TiO2 photoelectrodes in the UV and visible light region, respectively, because of the formation of Schottky barrier banding at the core-shell interface as well as the excitation of photogenerated electrons or holes from the surface of Ag cores to the conduction or valance band of TiO2 shells. It was noted that different light illumination, UV or visible light, induced opposite photocurrent tendency of Ag@TiO2 photoelectrodes in the basic electrolytes. It enhanced the positive and negative photocurrent density under UV and visible light illumination, respectively. Ag@TiO2 photoelectrodes were effective in the photoelectrochemical applications both in the UV and visible light region. In addition, the trend of enhanced photocurrent in the basic electrolytes could be tuned by different light illumination. It might be utilized in the applications such as photo-switch, photo-sensor and so on.

碩士
逢甲大學
電子工程所
95
In this study, we tried to synthesize different phases TiO2 nanoparticle crystals by adjusting the pH value of the TiCl4 solution through the hydrolysis and condensation reaction at the room temperature, these products then treated with thermal process in different ambience and temperature. In order to measure variation of the crystalline property, surface morphology and optical properties of the different phases TiO2 nanoparticles, these particles were finally analyzed by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), utraviolet-visible spectrometer (UV) and photoluminescence spectrometer (PL). From XRD analysis, the results appeared that the first order crystal diameter of these TiO2 nanoparticles were affected by the variation of the experiment parameter, the crystal diameter increased with the increasing of the oxygen concentration and the annealing temperature but decreased at 450℃ high vacuum ambient environment. In optical properties, we could obviously find that the indirect band gap varied with the different ambiences from the absorption spectrum, it existed a blue shift phenomenon at the high vacuum thermal process environment. In the other hand, we could also find that there was a obviously blue shift on the direct band gap of the 550℃ high vacuum thermal process one. Eventually, the emission spectrum revealed that there existed a great quantities of oxygen vacancies of particles at the high vacuum condition, the vacancies had a strong emission light at the 465nm and 540nm wavelength.

碩士
國立東華大學
材料科學與工程學系
104
Several series of [TiO/TiO2] multilayer thin films were prepared by magnetron sputtering, including films of low deposited temperature, annealed in different temperature and [TiO/TiO2] multilayer of low deposited temperature period to investigate the relationship between composition, structure and room-temperature ferromagnetism property (RTFM). XRD and XPS were used to detect the film structure, composition and binding energy. FE-SEM and AFM were used to observe the surface morphology. SQUID measurement was used to investigate the magnetic property of the thin films. Our research shows that the various periodic thickness and crystal defect in the thin films both affect film magnetic property. For the series of various periodic thickness, amorphous [TiO/TiO2] multilayer thin films show very weak RTFM, and all of the films show RTFM after annealed in argon at 350°C. Also show that the structure, crystallinity and oxidation of pure titanium films all play important roles to the RTFM property. For the series of [TiO/TiO2] multilayers, single layer of TiO or TiO2 grow on Si wafer and c-sapphire do not show ferromagnetism, but multilayers of TiO and TiO2 exhibit RTFM. There is probably no distinct layer structure in the [TiO/TiO2] films because TiO and TiO2 could diffuse to each side at the growth temperature of 750°C. However, the interdiffusion of TiO and TiO2 made the Ti cations of multi-valence state (Ti2+,Ti3+,Ti4+), resulting in RTFM in the [TiO/TiO2] multilayers. According to the results mentioned above, the following observation and conclusion can be drawn: 1. Amorphous and highly crystalline titania films don’t show RTFM property. 2 TiO /TiO2 thin films with multilayer structure show RTFM property. 3 The origin of RTFM property in the titania film could be due to multi-valence、cations and defects exist on the film interface, grain boundary and surface.

碩士
國立成功大學
化學系
89
Adsorption and reactions of N2H4 and NH3 on powdered TiO2 have been studied by Fourier-transformed infrared spectroscopy. N2H4 decomposes on the surface to form NH3 and surface hydroxy groups at temperatures higher 423 K. Based on these findings, a N2H4 thermodecomposition pathway on TiO2 is established. NH3 decomposes on TiO2 and forms adsorbed azide N3(a) species at temperatures higher than 623 K. Photooxidation of NH3 is discussed in terms of N2H4 thermodecomposition pathway and recent reports for the reaction between NHx and NOx (x = 1, 2) in the gas phase. Adsorption and reactions of CH3CN on TiO2 (110) have been studied by combinatory techniques of X-ray photoelectron spectroscopy and temperature programmed desorption. CH3CN(a) desorbs molecularly at 186 and 137 K, respectively. No photodesorption of monolayer CH3CN(a) from TiO2 (110) has been observed after irradiation at 256 and 546 nm at 110 K. This is attributed to higher vertical electron affinity of CH3CN. No photooxidation of CH3CN has occurred on TiO2 (110) under such experimental conditions.