Artifacts made of durable materials, such as stone, can provide valuable clues to reconstruct the past. Marble sourcing, in particular,provides information about contact, trade, and other activities in the greater Mediterranean area. The Worcester Art Museum of Massachusetts (WAM) initiated a provenance study by requesting that an analysis of several marble artifacts occur at the University of South Florida's Archaeological Science Laboratory. The 55 marble samples used in this study are from the Worcester Art Museum's collection of Antioch mosaics. Positive results might reveal: 1) preferred sources of tesserae, 2) information about trade of specialized stone, 3) changes in preferred sources during different chronological periods, and 4) workshop preferences. The requested analysis had two objectives. First, once the provenance of the materials is determined, then the results could reveal meaning behind the images contained within the mosaic floor. Second, the results could reveal new trade routes in the Mediterranean. The first step in this analysis was X-ray diffraction (XRD),which differentiates dolomite and calcite marbles. The second step used stable isotope ratio analysis (SIRA), which measures carbon-13 and oxygen-18 isotopic ratios. These two steps have helped to identify Mediterranean marble sources in previous studies. Most of the ancient Mediterranean marble sources have been identified. They have different isotopic values and other characteristics that allow for differentiation. Only one source of dolomite marble exists, which is located in the eastern Mediterranean. It has been identified through XRD in previous studies. Many of the calcite marble sources have different carbon and oxygen isotopic values, which were provided from the SIRA. Those marble artifacts with overlapping carbon and oxygen values can be further analyzed using archaeological, historical, and other information and by using other scientific techniques including cathodoluminescence, electron paramagnetic resonance, and strontium isotope analysis. This thesis discusses the methods used to prepare the samples and analysis conduction; it also discusses the results of the analyses, and presents interpretations regarding the provenance and trade of the marble used for mosaics at Antioch. The results of the SIRA and XRD analysis showed that the materials used for mosaic tesserae come from a variety of sources. Although no definitive matches were found, the results provide the basis for the collection of a colored marble database of sources and artifacts.

Η υδροχλωρική δονεπεζίλη (Donepezil.HCl, DPZ) είναι ένα φάρμακο που λαμβάνεται για τη θεραπεία της νόσου Altzheimer. Δρα ως ανασολέας της ακετυλοχοληστερινάσης, ενός ενζύμου υπεύθυνου για την καταστροφή του νευροδιαβιβαστή ακετυλοχολίνη, αυξάνοντας το ποσό της ακετυλοχολίνης στον εγκέφαλο. Παρουσιάζει διάφορες κρυσταλλικές μορφές, συμπεριλαμβανομένων δύο ένυδρων, καθώς και μια άμορφη φάση. Τα δισκία Υδροχλωρικής Δονεπεζίλης λαμβάνονται από το στόμα και μπορεί να αποθηκευθούν για κάποιο χρονικό διάστημα πριν χρησιμοποιηθούν. Τα δισκία DPZ ισχύος 10 mg περιέχουν 3.6 % API, ενώ στις περιπτώσεις όπου λαμβάνει χώρα πολυμορφική μετατροπή, η επιμέρους περιεκτικότητα κάθε πολυμόρφου είναι ακόμα μικρότερη. Η ταυτοποίηση και ποσοτική ανάλυση των πολυμόρφων ή ένυδρων μορφών είναι δυνατή μόνο με τη χρήση περίθλασης ακτίνων Χ και δονητικών φασματοσκοπικών τεχνικών. Λόγω του μικρού ποσοστού της δραστικής ουσίας στα δισκία και της πιθανής παρουσίας περισσοτέρων του ενός πολυμόρφου αλλά και του μεγάλου σχετικά ορίου ανίχνευσης αυτών των τεχνικών η ταυτοποίηση και ποσοτική ανάλυση είναι μια αναλυτική πρόκληση. Στην παρούσα εργασία έγινε προσπάθεια ταυτοποίησης των κρυσταλλικών μορφών του DPZ σε δισκία και έλεγχος της σταθερότητάς τους μετά από διάφορες διαδικασίες παρασκευής των δισκίων, καθώς και μετά από αποθήκευση σε διάφορες συνθήκες υγρασίας και θερμοκρασίας, χρησιμοποιώντας τις πειραματικές τεχνικές XRD, FT-IR και FT-Raman. Παρατηρήθηκε ότι η προέλευση του API, οι συνθήκες αποθήκευσης και κυρίως η μέθοδος παρασκευής των δισκίων επηρεάζουν τη σταθερότητα των φαρμακευτικών σκευασμάτων. Με στόχο τη διερεύνηση της δυνατότητας ανάπτυξης ποσοτικών αναλυτικών μεθόδων προσδιορισμού των πολυμόρφων Ι και ΙΙΙ του DPZ σε δισκία, οι παραπάνω τεχνικές χρησιμοποιήθηκαν για τον υπολογισμό των ορίων ανίχνευσης των δύο πολυμόρφων (0.35% κ.β. για το πολύμορφο Ι και 0.44 % κ.β. για το πολύμορφο ΙΙΙ με την τεχνική Raman, 0.95% κ.β. για το πολύμορφο Ι και 1.3 % κ.β. για το πολύμορφο ΙΙΙ με την τεχνική XRD, 1.2% κ.β. για τη μορφή Ι και 1.0 % κ.β. για τη μορφή ΙΙΙ με την τεχνική IR, όπως προέκυψαν μετά από στατιστική επεξεργασία των πειραματικών δεδομένων των διαφόρων τεχνικών), καθώς και για τον ποσοτικό τους προσδιορισμό. Η τεχνική Raman φαίνεται να μπορεί χρησιμοποιηθεί για ποσοτική ανάλυση των πολυμόρφων Ι και ΙΙΙ του DPZ σε δισκία, ενώ επιπλέον η ποσοτική μέθοδος που παρουσιάσθηκε εδώ είναι απλή και μη καταστροφική για τα δείγματα. Η μέθοδος XRD μπορεί πιθανόν να χρησιμοποιηθεί για την ποσοτική ανάλυση δισκίων DPZ, με μεγαλύτερο όμως σφάλμα σε σύγκριση με την τεχνική Raman, ενώ η μέθοδος FT-IR ATR, παρέχει τα λιγότερο καλά ποσοτικά αποτελέσματα, ακόμα και στην περίπτωση που το δισκίο περιέχει αποκλειστικά το ένα από τα δύο πολύμορφα. Τέλος, με στόχο την ερμηνεία των φασμάτων δόνησης που καταγράφησαν στην παρούσα εργασία, υπολογίστηκαν η σταθερή δομή του μορίου της Δονεπεζίλης και της ένυδρης Δονεπεζίλης (με ένα μόριο νερού ανά μόριο Δονεπεζίλης) και τα φάσματα δόνησης (IR και Raman) με τις μεθόδους Hartree-Fock ab-initio και DFT (Density Functional Theory) και χρήση του υπολογιστικού πακέτου Gaussian09. / Donepezil hydrochloride (DPZ) is a medication used to treat Altzheimer’s disease. It acts as an inhibitor of acetylcholisterinase, an enzyme responsible for the destruction of the neurotransmitter acetylcholine, thus increasing the level of acetylcholine in the brain. As most of the pharmaceutical solids, DPZ exhibits polymorphism. Donepezil hydrochloride has different crystalline forms, including two hydrates, as well as an amorphous phase. DPZ is available for oral administration in tablets which can be stored for some time before use. In the present study, an effort was made to identify the crystal form of DPZ in tablets, as well as to test its stability against time, temperature and humidity, after various manufacturing processes, using XRD, FT-IR and FT-Raman techniques. The data showed that the origin of the API, the storing conditions and mainly the manufacturing process of the tablets affect the stability of the API. Quantitative determination of polymorphs I and III of DPZ in tablets was also attempted using the above experimental methods. Calibration models were constructed and applied in DPZ tablets. The detection limits of polymorphs I and III of DPZ for each technique, derived after statistical treatment of the experimental data, were calculated. Raman spectroscopy exhibited the lower detection limit (0.35 weigh % for polymorph Ι and 0.44 % weigh % for polymorph ΙΙΙ) compared with XRD (0.95% weigh % for polymorph Ι and 1.3 % weigh % for polymorph ΙΙΙ) and IR spectroscopy (1.2% weigh % for polymorph Ι and 1.0 % weigh % for polymorph ΙΙΙ). The data suggest that Raman spectroscopy could be applied to quantify polymorphs I and III in DPZ tablets; moreover, the Raman quantitative method presented in this work is simple and non-destructive for the tablets. The application of the X ray diffraction method for the quantitative analysis of polymorphs I and III in tablets yielded larger errors compared with Raman spectroscopy, while the FT-IR ATR technique yielded poor quantitative results, even in the case that only one polymorph was present in DPZ tablets. Finaly, in order to facilitate the assignment of the vibrational spectra recorded in this study, the optimized structure and the vibrational spectra (IR and Raman) of Donepezil and Donepezil hydrate (Donepezil:H20 = 1:1) molecules were calculated at the Hartree-Fock and DFT (Density Functional Theory) level of theory using the Gaussian 09 program package. The weigh % of the API in the tablets containing 10 mg of DPZ is 3.6 %. In cases where two or more polymorphs are present, the weigh % of each polymorphic form is lower. The difficulty in the identification and quantification of the crystal phase of DPZ is stemming from the small percentage of the API in the tablets, the considerable overlapping of DPZ XRPD patterns and IR and Raman spectra of the polymorphs and the excipients and the availability of various polymorphs.

>Magister Scientiae - MSc / Organic-inorganic lead-based perovskite has exhibited great performance in the past few years. However, the lead (Pb) embedded in those compounds is a significant drawback to further progress, due to its environmental toxicity. As an alternative, tin (Sn) based-perovskites have demonstrated promising results in terms of electrical and optical properties for photovoltaic devices, but the oxidation of tin ion- from stannous ion (Sn2+) to stannic ion (Sn4+) presents a problem in terms of performance and stability when exposed to ambient conditions. A more feasible approach may be in a Pb-Sn binary metal perovskite in pursuit of efficient, stable perovskite solar cells (PSCs) with reduced Pb-content, as compared to pure Pb- or Sn-based PSCs. Here, we report on the deposition of a Pb-Sn binary perovskite by sequential chemical vapor deposition.

Submitted by Emanuel Varela Cardoso (emanuel.varela@ufcg.edu.br) on 2018-06-26T19:38:51Z No. of bitstreams: 1 POLYANA TARCIANA ARAÚJO DOS SANTOS – TESE (UAEMa) 2015.pdf: 2974694 bytes, checksum: 08e52baa2c42ce5e7b0e35cbf00934bd (MD5) / Made available in DSpace on 2018-06-26T19:38:51Z (GMT). No. of bitstreams: 1 POLYANA TARCIANA ARAÚJO DOS SANTOS – TESE (UAEMa) 2015.pdf: 2974694 bytes, checksum: 08e52baa2c42ce5e7b0e35cbf00934bd (MD5) Previous issue date: 2015-01-29 / CNPq / Neste trabalho de pesquisa foi obtido um material híbrido a base de nanoferritas Ni0,5Zn0,5Fe2O4 e CoFe2O4 modificada a superfície com agente silano e funcionalizadas com quitosana visando seu uso como biossensores. Para este fim, as nanoferritas foram sintetizadas por reação de combustão e silanizadas com o 3-aminopropiltrimetoxissilano. A funcionalização foi realizada pelo método de evaporação do solvente usando o biopolímero quitosana. Todas as amostras foram caracterizadas por difração de raios X, espectrometria de infravermelho por transformada de Fourier, espectroscopia por energia dispersiva de raios X, análise termogravimétrica, microscopia eletrônica de varredura, microscopia eletrônica de transmissão, teste de sedimentação e separação magnética, medidas magnéticas e análise in vitro por citotoxidade. As amostras como sintetizadas apresentaram a formação da fase única do espinélio em estudo com característica nanométrica e após a formação do híbrido a estrutura do material foi mantida. Nos espectros de infravermelho observaram-se bandas de absorção características das nanoferritas e bandas referentes à presença do agente silano e da quitosana. Por meio das micrografias observou-se a formação de aglomerados de aspecto frágil, e após silanização e funcionalização observou-se uma morfologia com aglomerados de aspecto mais rígido constituídos de nanopartículas fortemente ligadas. A análise termogravimétrica mostrou que as nanoferritas apresentaram baixa perda de massa e que após formação do híbrido houve um aumento da perda de massa comprovando assim, a presença do agente silano e da quitosana. Quanto ao comportamento magnético, ambas as nanoferritas apresentaram elevada magnetização de saturação típica de materiais ferrimagnéticos, este comportamento foi mantido após formação do híbrido sendo adequado para aplicações biotecnológicas. A viabilidade celular das nanoferritas mostrou característica citotóxica para a ferrita Ni0,5Zn0,5Fe2O4 e não citotóxica para a ferrita CoFe2O4, a formação do híbrido favoreceu aumento da viabilidade celular em ambas as nanoferritas. Os materiais híbridos obtidos são promissores para o uso na nanobiotecnologia como biossensores e/ou em tratamento como diagnóstico clinico. / In this research was obtained a hybrid material nanoferrit es base Ni0,5Zn0,5Fe2O4 and CoFe2O4 modified the surface with silane agent and functionalized chitosan aiming their use as biosensors. To this end, nanoferritas were synthesized by combustion and silanized with 3-aminopropyltrimethoxysilane. The functionalization was carried out by the solvent evaporation method using the biopolymer chitosan. All samples were characterized by X-ray diffraction, infrared spectroscopy by Fourier transform spectroscopy energy dispersive X-ray, thermal analysis, scanning electron microscopy, transmission electron microscopy, sedimentation test and magnetic separation, magnetic measurements and Analysis by in vitro cytotoxicity. The samples showed synthesized as the formation of spinel single phase with nanometer feature under study and after the formation of the hybrid structure of the material has been maintained. In the infrared spectra there were absorption bands characteristic of nanoferritas and bands related to the presence of the silane agent and chitosan. Through micrographs showed the formation of agglomerates frail and after silanization and functionalization was observed with a morphology more rigid aspect of tightly bound agglomerates of nanoparticles. Thermogravimetric analysis showed that the nanoferritas showed low weight loss and that after hybrid formation was increased mass loss thereby proving the presence of the silane agent and chitosan. As for the magnetic behavior, both nanoferritas had high magnetization typical saturation ferrimagnetic materials, this behavior continued after the hybrid formation is suitable for biotechnological applications. Cell viability nanoferritas showed characteristic for cytotoxic and non-cytotoxic ferrite Ni0,5Zn0,5Fe2O4 to CoFe2O4 ferrite, the formation of hybrid favored increased cell viability in both nanoferritas. The obtained hybrid materials are promising for use in nanobiotechnology as biosensors and / or treatment and clinical diagnosis.

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No. of bitstreams: 1 curcio_al_me_rcla.pdf: 1672370 bytes, checksum: fd59b862449a04ac385f3661da6430f3 (MD5) Previous issue date: 2016-02-29 / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Nanocristais tem sido extensivamente investigados nos últimos anos devido à sua ampla gama de aplicações em vários dispositivos tais como sensores, células solares, lasers, fotocatalisadores, fotodetectores, detectores de infravermelhos, diodos emissores de luz, materiais eletroluminescentes e outros materiais emissores de luz. Semicondutores nanocristalinos apresentam propriedades eletrônicas intermediárias entre aqueles de estrutura molecular e sólidos macrocristalinos, proporcionando uma ampla gama de aplicações. Entre estes materiais, o sulfeto de zinco (ZnS) puro ou dopado tem recebido notável atenção por causa de suas propriedades estruturais ópticas, versatilidade e potencial para várias aplicações tecnológicas. O ZnS é um típico semicondutor II-VI, com um gap direto de 3,6 eV à temperatura ambiente e aproximadamente 40 meV de energia de gap, sendo um bom material luminescente utilizado em telas, sensores e lasers. Como material de gap largo, o ZnS pode facilmente hospedar diferentes metais de transição como centros luminescentes. Entre estes íons de metais de transição para estruturas dopadas, os íons Cu2+e Mn2+ são atraentes pelas emissões de luz características e por apresentarem propriedades eficientes para aplicações como luminóforos. A inserção desses íons na estrutura do ZnS proporcionam defeitos que resultam em emissão no verde para os íons Cu2+e emissão no laranja para os íons Mn2+. Neste estudo, as amostras de ZnS pura e dopadas com Cu2+ e Mn2+ foram preparados pelo método solvotermal, que demonstra ser um processo eficaz para preparar nanopartículas. Uma vez preparadas, as estruturas das amostras nanoestruturadas foram caracterizadas e correlacionada s com propriedades fotoluminescentes. Os resultados de difração de raios X mostram que as amostras de ZnS foram cristalizadas completamente sem a presença de fases secundárias e os difratogramas correspondem à estrutura blenda cúbica de zinco com grupo espacial F-43m. Os espectros de XANES (X-ray Absorption Near Edge Structure) teóricos e experimentais na borda K do Zn indicam que a incorporação de átomos de Mn na matriz ZnS causam a formação de vacâncias de Zn e S, a qual é confirmada por ajustes de espectros EXAFS (Extended X-ray Absorption Fine Structure). Estas vacâncias estão relacionadas com um desvio para o vermelho observado no pico do espectro de fotoluminescência devido a adição de Mn na estrutura do ZnS. Para o ZnS puro, o pico é centrado em ~ 504 nm, relativo as vacâncias de S na amostra nanoestruturada. À medida que se aumenta a porcentagem de Mn na matriz ZnS, uma emissão no amarelo-laranja centrada em ~ 590 nm pode ser observada, associada com a transição 4T1-6A1 no interior de níveis 3d de Mn2+. A adição de íons Cu2+ ao ZnS resulta em um alargamento no pico do espectro de fotoluminescência decorrente de emissão no azul-verde, que está relacionada a recombinação de elétrons de níveis de defeitos mais profundos dos estados t2 do Cu próximos da banda de valência. / Nanocrystals has been extensively investigated in recent years due to its wide range of applications in various devices light emitting materials such as sensors, solar cells, lasers, photocatalysts, photodetectors, IR detectors, light emitting diodes and others. Nanocrystalline Semiconductors have electronic properties between those intermediate molecular macrocristalinos and solid structure, providing a wide range of applications. Among these materials, zinc sulfide (ZnS) pure or doped has received considerable attention because of its optical structural properties, versatility and potential for several technological applications. The ZnS is a typical II-VI semiconductor with a direct band gap of 3.6 eV at room temperature and about 40 meV in energy gap, and a good luminescent material for constrution of displays, lasers and sensors. As wide band gap material, ZnS can easily host different transition metals as luminescent centers. Among these ions of transition metal doped structures, Cu2+ and Mn2+ ions are attractive for light emission characteristics and for having effective properties for applications such as phosphors. The addition of these ions in ZnS structure provide defects that result in emission in the green for the Cu2+ ions and emission in orange for the Mn2+ ions. In this study, samples of pure ZnS and doped with Cu2+ and Mn2+ ions were prepared by solvotermal method, which demonstrate to be an effective process for preparing nanoparticles. Once prepared, the structures of the nanostructured samples were characterized and correlated with photoluminescent properties. The results of X-ray diffraction showed that the ZnS samples were completely crystallized without the presence of secondary phases and XRD patterns correspond to the structure of zinc blende to cubic space group F-43m. spectra XANES (X-ray Absorption Near Edge Structure) theoretical and experimental in the Zn K edge indicates that the inclusion of Mn atoms in the ZnS matrix cause the formation of Zn and S vacancies, which is confirmed by spectral adjustments EXAFS (Extended X-ray Absorption Fine Structure). These vacancies are associated with a red shift observed in the photoluminescence spectrum peak due to the addition of Mn in ZnS structure. For pure ZnS, the peak is centered at ~ 504 nm concerning the vacancies in the S nanostructured sample. As it increases the percentage of Mn in the ZnS matrix, in yellow-orange emission centered at ~ 590 nm can be observed, associated with the transition 4 T1- 6A1 inside 3d levels of Mn2+. Adding Cu2+ to the ZnS results in a broadening of the peak of the photoluminescence spectrum due to emission in blue-green, which is related to recombination deeper defect levels of electrons of t2 Cu states near the valence band.

Diploma thesis deals with the methodology of preparation of Alit – the main clinker mineral. The content of this work involves design and optimization of the methodology of preparation of pure Alit polymorphs, analysis of their properties by available analytical methods and evaluation of the change of crystallinity in the process of preparation of these polymorphs by XRD-analysis.

Electron Backscatter Diffraction (EBSD) is a well-developed technique used to perform quantitative microstructure analysis in the Scanning Electron Microscope (SEM); however, it has not been widely applied towards studying nanostructures. This work focuses on the use and limitations of EBSD in the characterization of Au nanoparticles on an MgAl2O4 substrate. Samples under investigation are prepared by depositing a thin film of Au on an MgAl2O4 substrate, and then finally heated in a furnace to induce dewetting and cluster formation. The challenges of obtaining crystallographic information from nanoparticles using EBSD are qualitatively and quantitatively described through an evaluation of the quality of the diffraction pattern at various locations of the primary electron beam on the nanoparticle. It is determined that for a high quality Electron Backscatter Diffraction Pattern (EBSP), the production of diffracted backscattered electrons travelling towards the detector must be high and the depth of the source point must be low. The top of the nanoparticle, where the local geometry of the system is similar to the geometry of a macroscopically flat sample, is found to produce diffraction patterns of the highest quality. On the other hand, reversed-contrast EBSPs are observed when the beam is positioned near the bottom of the nanoparticle. In addition, crystallographic information for each individual nanoparticle is gathered using EBSD. Each individual AuNP is observed to be single crystalline. Finally, the complete ensemble of crystalline orientations for individual nanoparticles is then compared to the global averaged crystallinity of the sample, as measured by X-ray diffraction. These results show that EBSD promises to be a powerful and robust technique in the characterization of nanoparticles. / Thesis / Master of Applied Science (MASc)

This thesis reports both the optimizations of the vanadium oxide (VOx) thin film as an active infrared detector material by the magnetron sputtering deposition method and its use during fabrication of proper resistors for the microbolometers. Vanadium oxide is a preferred material for microbolometers, as it provides high TCR value, low noise, and reasonable resistance, and a number of high-tech companies have used this material to obtain state-of-the-art microbolometer arrays. This material is first used in microbolometers by Honeywell, who provides its recipe with license agreements, and there is not much information in the literature for its deposition recipe. This is the first study at METU for development of vanadium oxide thin film for microbolometers. The VOx material deposition studies started by identifying the deposition parameters of the magnetron sputtering system in order to obtain proper VOx resistors for the readout electronics. The obtained recipe includes high temperature deposition conditions of VOx, however, this causes a diffusion problem on the electrodes, preventing to obtain a good contact to VOx. Also, high oxygen level in the depositions makes a contamination on the electrodes. A number of studies were done to determine a proper electrode material which is proper with the deposition conditions of the VOx. Characterization of the vanadium oxide samples is done by XRD and XPS measurements to see the relation between the phases and resistivity of the vanadium oxide. It is known that V2O5 phase provides a high TCR and resistivity value, and the XRD results show that this phase is dominant in the highly-oxygen doped or annealed resistors. The TCR and noise measurements are done using resistors implemented with the developed VOx film, after the etching processes of the both VOx and the electrodes are optimized. The contamination on the electrodes is prevented by the help of a newly designed process. The TCR measurement results show that annealing of the resistors affect the TCR values, i.e., increasing the annealing duration increases the TCR values of the resistors. Two different resistors with different deposition conditions are annealed to see the effect of annealing, where TCR results of the resistors are -0.74%/K and -0.8 %/K before annealing. The TCR values of these resistors increase to -1.6 %/K and -4.35 %K, respectively, after annealing in same conditions, showing that both the deposition conditions and annealing change the TCR significantly. Although good TCR values are obtained, the noise values of the VOx resistors are much higher than the expected values, which suggest a further study to determine the cause of this noise.

This thesis reports the development of Vanadium Tungsten Oxide (VWO) film as an active detector material for uncooled infrared detectors by using the reactive DC magnetron co-sputtering method. VWO is a doped form of the Vanadium Oxide (VOx) which is known as a prominent material for uncooled infrared detectors with its high TCR, low resistivity, and low noise properties. VOx is a widely preferred material for commercialized uncooled infrared detectors along with its drawbacks. Fabrication is fairly difficult due to its unstable material properties and the need for low process temperatures for a monolithic, CMOS compatible surface micromachining process. Hence, a new material with high performance and easier fabrication is needed. This thesis is the first study at METU on the development of high-performance VWO as an active detector material for uncooled infrared detectors. Deposition studies of VWO primarily started by measuring the effects of deposition parameters upon the magnetron sputtering system. Because the high effectiveness of the tungsten doping has been obtained for the doping level below 10% according to literary information, maximum vanadium (V) deposition rate together with minimum tungsten (W) deposition rate has been initially aimed. TCR of the VWO films has been measured between -2.48 %/K and -3.31 %/K, and the variation of noise corner frequency from 0.6 kHz to 8 kHz has been observed. In addition to these results of VWO, a favorable VOx recipe which has the highest performance done at METU in terms of resistance, TCR, noise and uniformity has also attained during the studies. Structural characterization of VWO is achieved using XPS, XRD, and AFM characterization techniques. Other than the sputtering parameters, post-annealing process and oxygen plasma exposure was examined as well. A general observation of the post-annealing is that it decreases not merely the TCR but also the noise of the deposited film. A short-period oxygen plasma exposure has a constructive effect on the noise behavior. Fabricated vanadium tungsten oxide with sandwich type resistor structure shows very close but better bolometric properties when compared with the yttrium barium copper oxide (YBCO), which is another material being studied in scope of other theses at METU. XPS, XRD and AFM characterization methods have been used for the structural characterization of vanadium-tungsten-oxide.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / In this work we study the structural and magnetic properties of pure and TM-doped CeO2 nanoparticles (TM: Mn, Cr, Co and Fe) obtained by the co-precipitation and hydrothermal methods. X-ray diffraction (XRD) results allied to the Rietveld refinement method indicate that all samples present single-phase with structure isomorphous to the CeO2. Average crystallites size was determined using the full width at half maximum from XRD patterns and their sizes were from of 7 to 13 nm. Transmission electron microscopy (TEM) images 10% doped samples show the presence of particles with spherical-like morphology and average sizes in good agreement with the estimated by XRD. From ultraviolet–Visible (UV–Vis) spectroscopy absorption measurements we estimated the optoelectronic gap of the samples, which vary between 2.87 and 3.44 eV. Analyses from magnetization curves as a function of temperature (MvsT) using Curie-Weiss law show that the number of paramagnetic ions per molecule (n) increases with the increasing of the Mn concentration. Already for 10% doped samples with different ions the (n) obeys the following order Mn ˂ Fe ˂ Cr ˂ Co for samples obtained by co-precipitation and Co ˂ Cr ˂ Mn ˂ Fe for the samples obtained by hydrothermal synthesis. Magnetization curves as a function of the magnetic field (MvsH) show that the the systems present a weak ferromagnetic behavior at 5K and paramagnetic at temperature higher than 200 K. / Neste trabalho estudamos as propriedades estruturais e magnéticas de nanopartículas de CeO2 pura e dopadas com diferentes concentrações de metais de transição (MT: Mn, Cr, Co e Fe) obtidas pelo método de co-precipitação e de síntese hidrotérmica. Resultados de difração de raios X (DRX) aliados ao método de refinamento Rietveld indicam a formação de uma única fase isomorfa ao CeO2, cujos tamanhos médios das nanopartículas variam entre 7 e 13 nm quando sintetizadas por co-precipitação e entre 8 e 12 nm quando obtidas por síntese hidrotérmica. Imagens de microscopia eletrônica de transmissão (MET) das amostras dopadas com 10% dos metais de transição mostram a presença de partículas com morfologia tendendo à esferas e tamanhos médios das partículas em bom acordo com os tamanhos estimados por DRX. Através de medidas de absorção na região do ultravioleta ao visível (UV-vis) estimamos o gap optoeletrônico das amostras, os quais variam entre 2,87 e 3,44 eV. Resultados das medidas de magnetização em função temperatura (MvsT) usando a lei de Curie-Weiss indicam que o número de íons paramagnéticos por molécula cresce de forma sistemática com o aumento da concentração de Mn nos dois métodos de síntese. Já para o caso das amostras dopadas com 10% do MT, esse número obedece a seguinte ordem Mn ˂ Fe ˂ Cr ˂ Co para o sistema obtido por co-precipitação e Co ˂ Cr ˂ Mn ˂ Fe para o sistema obtido por síntese hidrotérmica. Medidas de magnetização em função do campo magnético (MvsH) mostram que as nanopartículas apresentam um possível ordenamento ferromagnético fraco em 5K e um comportamento típico de um material paramagnético acima de 200K. / São Cristóvão, SE