Investigation of photoinduced electrical properties in the heterojunction TiO2/SnO2

TiO2/SnO2 thin films heterostructures were grown by the sol-gel dip-coating technique. It was found that the crystalline structure of TiO2 depends on the annealing temperature and the substrate type. TiO2 films deposited on glass substrate, submitted to thermal annealing until 550 degrees C, present anatase structure, whereas films deposited on quartz substrate transform to rutile structure when thermally annealed at 1100 degrees C. When structured as rutile, this oxide semiconductor has very close lattice parameters to those of SnO2, making easier the heterostructure assembling. The electrical properties of TiO2/SnO2 heterostructure were evaluated as function of temperature and excitation with different light sources. The temperature dependence of conductivity is dominated by a deep level with energy coincident with the second ionization level of oxygen vacancies in SnO2, suggesting the dominant role of the most external layer material (SnO2) to the electrical transport properties. The fourth harmonic of a Nd:YAG laser line (4.65 eV) seems to excite the most external layer whereas a InGaN LED (2.75 eV) seems to excite electrons from the ground state of a quantized interfacial channel as well as intrabandgap states of the TiO2 layer.

Influência do espaçamento do feixe de laser Nd: YAG na obtenção de óxidos e nitretos na superfície do titânio em pressão atmosférica

Neste trabalho investigou-se a modificação de superfície do titânio pela irradiação com feixe de Laser Nd:YAG. Os parâmetros do laser como a potência, o comprimento de onda, a frequência, a velocidade de varredura e a área de exposição foram mantidos constantes, exceto o espaçamento da matriz, o qual foi de 0,01 e 0,02 mm. A caracterização da superfície foi realizada por Microscopia Eletrônica de Varredura (MEV) e Difração de Raios X (DRX), sendo que os espectros foram refinados pelo método Rietveld. Pela análise de MEV, observou-se uma mudança na topografia, obtendo uma superfície rugosa produzida pelo fenômeno de ablação. As análises por Rietveld dos espectros de difração de raios X detectaram TiN, Ti2N, TiO2 (anatásio e rutilo), sendo que a amostra com espaçamento 0,01 mm apresentou uma maior quantidade de óxidos e nitretos. Isso pode ser devido à sobreposição do feixe, induzindo à formação de uma superfície com maior estabilidade termodinâmica. Os óxidos e nitretos obtidos são de grande importância, pois são responsáveis por produzir uma maior interação entre o osso-implante.

Photoelectrocatalytic/photoelectro-Fenton coupling system using a nanostructured photoanode for the oxidation of a textile dye: kinetics study and oxidation pathway

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Otimização dos parâmetros para obtenção de nanotubos em Ti-Cp por anodização eletroquímica e aplicação na liga experimental Ti-35Nb-7Zr

Pós-graduação em Engenharia Mecânica - FEG

Structural study of copper oxide supported on a ceria-modified titania catalyst system

A structural study of CuO supported on a CeO2-TiO2 system was undertaken using X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS) techniques. The results of XRD revealed the presence of only two phases, TiO2 anatase and CeO2 cerianite. A trend towards smaller TiO2 crystallites was observed when cerium content increased. When the amount of cerium increased, Ti K-edge XANES analysis showed an increasing distortion of Ti sites. The results of Ce LIII-edge EXAFS showed that Ce atoms are coordinated by eight oxygen atoms at 2.32 Å. For the sample containing a small amount of cerium, the EXAFS analysis indicated that the local structure around Ce atoms was highly distorted. The catalysts presented quite different Cu K-edge XANES spectra compared to the spectra of the CuO and Cu2O reference compounds. The Cu-O mean bond length was close to that of the CuO and the Cu atoms in the catalysts are surrounded by approximately four oxygen atoms in their first shell. Copper supported on the ceria-modified titania support catalysts displayed a better performance in the methanol dehydrogenation when compared to copper supported only on titania or on ceria. © 2002 Plenum Publishing Corporation.

Estudo da relação de ordem-desordem estrutural em nanopartículas de TiO2

Pós-graduação em Química - IQ

Efeito na osseointegração de um novo método de nanotexturização de superfície de implantes através de anodização

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Produção do monóxido de titânio em estrelas variáveis

Mira are pulsating variable stars in advanced stages of evolution. Their atmospheres are sources of intense absorption bands attributed to molecular titanium monoxide (TiO). It has been suggested that the abundance of TiO reaches its maximum value near the minimum light. In this sense, the study of the processes of formation and destruction of TiO in circumstellar envelopes of Mira stars, not only allows us to understand the physical and chemical processes that occur in these environments, as it allows to verify the correlation between the abundance of TiO and its light curve. However, the main mechanisms of formation and destruction of TiO are poorly known and, consequently, the possible correlation between the abundance of this species and the light curve. In these sense, we studied the main processes of formation and destruction of titanium monoxide in molecular layers of Mira atmospheres and determined its temporal variation as function of the stellar radius. The TiO profile along the radius was expected for the different stellar phase, however its abundance is not enough to explain the light curve. The reasons behind it are discussed in details

Preparação, caracterização e estudo da eficiência na fotodegradação e adsorção de Rodamina B de heteroestruturas de TiO2/α-Fe2O3

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Radiative association of Ti and O atoms

Rate coefficients for the radiative association of titanium and oxygen atoms to form the titanium monoxide (TiO) molecule are estimated. The radiative association of Ti(F-3) and O(P-3) atoms is dominated by an approach along the C-3 Delta potential energy curve, accompanied by spontaneous emission into the X-3 Delta ground state of TiO. For temperatures ranging from 300-14 000 K, the total rate coefficients are found to vary from 4.76 x 10(-17) to 9.96 x 10(-17) cm(3) s(-1), respectively.

Advanced prostate cancer as a cause of oncogenic osteomalacia: an underdiagnosed condition

Tumor-induced osteomalacia (TIO) is a paraneoplastic bone mineral disturbance related to fibroblast growth factor 23 (FGF23) overproduction by the tumor, usually from mesenchymal origin. Such condition leads to high phosphate renal wasting and, consequently, to cumbersome symptoms as weakness, bone pain, and fractures. Case report. We report a case of an advanced castration-refractory prostate cancer patient, which developed severe hypophosphatemia with elevated phosphate excretion fraction. TIO was suspected, and increased levels of FGF23 reinforced such diagnosis. The patient died 4 months after being diagnosed with TIO. This case suggests that TIO has a dismal prognosis in prostate cancer patients. The clinical oncology community must be aware about such disturbance that can be present in those patients with weakness, bone pain, and hypophosphatemia.

Vanadium and Titanium Mixed Oxide Films: Synthesis, Characterization and Application as Ion Sensor

Vanadium/titanium mixed oxide films were produced using the sol-gel route. The structural investigation revealed that increased TiO2 molar ratio in the mixed oxide disturbs the V2O5 crystalline structure and makes it amorphous. This blocks the TiO2 phase transformation, so TiO2 stabilizes in the anatase phase. In addition the surface of the sample always presents larger amounts of TiO2 than expected, revealing a concentration gradient along the growth direction. For increased TiO2 molar ratios the roughness of the surface is reduced. Ion sensors were fabricated using the extended gate field effect transistor configuration. The obtained sensitivities varied in the range of 58 mV/pH down to 15 mV/pH according to the composition and morphology of the surface of the samples. Low TiO2 amounts presented better sensing properties that might be related to the cracked and inhomogeneous surfaces. Rising the TiO2 quantity in the films produces homogeneous surfaces but diminishes their sensitivities. Thus, the present paper reveals that the compositional and structural aspects change the surface morphology and electrical properties accounting for the final ion sensing properties of the V2O5/TiO2 films. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.053206jes] All rights reserved.

Enhancement of optical absorption by modulation of the oxygen flow of TiO2 films deposited by reactive sputtering

Oxygen-deficient TiO2 films with enhanced visible and near-infrared optical absorption have been deposited by reactive sputtering using a planar diode radio frequency magnetron configuration. It is observed that the increase in the absorption coefficient is more effective when the O-2 gas supply is periodically interrupted rather than by a decrease of the partial O-2 gas pressure in the deposition plasma. The optical absorption coefficient at 1.5 eV increases from about 1 x 10(2) cm(-1) to more than 4 x 10(3) cm(-1) as a result of the gas flow discontinuity. A red-shift of similar to 0.24 eV in the optical absorption edge is also observed. High resolution transmission electron microscopy with composition analysis shows that the films present a dense columnar morphology, with estimated mean column width of 40nm. Moreover, the interruptions of the O-2 gas flow do not produce detectable variations in the film composition along its growing direction. X-ray diffraction and micro-Raman experiments indicate the presence of the TiO2 anatase, rutile, and brookite phases. The anatase phase is dominant, with a slight increment of the rutile and brookite phases in films deposited under discontinued O-2 gas flow. The increase of optical absorption in the visible and near-infrared regions has been attributed to a high density of defects in the TiO2 films, which is consistent with density functional theory calculations that place oxygen-related vacancy states in the upper third of the optical bandgap. The electronic structure calculation results, along with the adopted deposition method and experimental data, have been used to propose a mechanism to explain the formation of the observed oxygen-related defects in TiO2 thin films. The observed increase in sub-bandgap absorption and the modeling of the corresponding changes in the electronic structure are potentially useful concerning the optimization of efficiency of the photocatalytic activity and the magnetic doping of TiO2 films. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4724334]

UNG OCH UTBRÄND- sex unga personers berättelser om hur det är att vara ung och utbränd

Vi har valt att göra en kvalitativ studie om utbrändhet bland unga människor i åldrarna 19-25 år i Sverige. Syfte med denna studie är att få en inblick i och ökad förståelse över hur utbrändhet påverkar unga i Sverige. Vi ville belysa orsakerna till varför allt fler unga människor i Sverige drabbas av utmattningssyndrom. Vi utgick från ett hermeneutiskt synsätt och en narrativ metod. Under de senaste tio åren har den psykiska ohälsan och sjukskrivningsantalet i Sverige ökat och då framförallt bland ungdomar. Forskningen talar om ett nytt sjukdomsfenomen, utbrändhet. Det är en stressrelaterad sjukdom som framförallt handlar om en känslomässig utmattning. Varje människa kan uppleva stress men det är endast de som går in i arbetet med höga förväntningar och som arbetar hårt för att uppnå dessa förväntningar som kan bli utbrända. Intervjupersonenerna grundade sin självkänsla och identitet i sina arbetsprestationer. Vi tror att alla intervjupersonerna saknade en grundläggande självkänsla vilket gjorde att de hela tiden sökte bekräftelse utifrån sina prestationer. Om en person blir utbränd eller inte beror såväl på fysiologiska, biologiska som psykologiska faktorer. Risken är större för personer som redan har drabbats av utbrändhet att drabbas igen. Kraven och pressen som unga människor känner idag kan härstamma från både familjen och samhället. Dagens samhälle är uppbyggt på så sätt att vi hela tiden måste göra en massa val. Ingenting är längre som det var förr då allt och alla hade sin plats i samhället. Den ökade individualiseringen kanske inte alltid är positiv. I socialt arbete kan vi hjälpa till med att förebygga utbrändhet bland ungdomar genom att finnas ute i skola och andra miljöer där ungdomar vistas för att hjälpa dem in i vuxenlivet.

Rehabiliteringsprocessen som lärande, styrning och organisering : En kvalitativ studie om upplevelser av rehabilitering efter utmattningssyndrom

Sjukskrivningarna för utmattningssyndrom har de senaste åren ökat dramatiskt i Sverige. Detta har lett till allt mer komplexa och långvariga rehabiliteringar. Syf-tet med denna studie var att beskriva och analysera hur ett antal individer upplev-de sin rehabilitering efter sjukskrivning för utmattning. Delsyften var att öka kun-skapen om hur rehabiliteringen efter utmattning kunde förbättras samt belysa kvinnors och mäns skilda förutsättningar till rehabilitering beroende på kulturell kontext. Tio personer som kommit åter till arbete efter sjukskrivning djupintervju-ades om rehabiliteringen. Resultaten från studien antydde att det var viktigt att vidga perspektiven på rehabilitering genom att använda ett kontextberoende syn-sätt. Studien resulterade i tre teman; Lärande, Styrning och Organisering. I samtli-ga teman var timing betydelsefullt. Lärandet och strategier att hitta nya insikter var viktigt både för individ och organisation för att en lyckad rehabilitering skulle ske, där strategierna blev olika för kvinnor och män. När det gällde rehabilitering-ens styrning visade det sig hur viktig balansen mellan att få stöd och att själv få agera var. Rehabiliteringens organisering visade sig i denna studie vara grund-läggande och central för rehabiliteringen, där möjligheten att kunna återskapa goda sociala möten var avgörande.