Efeito do laser de Nd:YAG do fluoreto de sódio na prevenção da erosão em dentina bovina através de perfilometria

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Influência de diferentes íons sobre a erosão dentária

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Síntese por reação em estado sólido de pós cerâmicos multifuncionais à base de CaCu3Ti4O12 modificados com estrôncio

The study of ceramic materials is constantly evolving, especially in research related to advanced ceramics. Once these have many applications, this paper relates to synthesis by solid state reaction of calcium copper titanate (CCTO) ceramic material means doping with strontium. The powders were characterized using thermal analysis techniques such as TG (thermogravimetry), DTA (differencial thermal analysis), dilatometry, X-ray diffraction (XRD) and scanning electron microscopy (SEM). The compositions have submitted weight loss at around 6% with respect to carbonates used, and was attributed a temperature of 950° C to perform the calcination according to thermogravimetric analysis. After the process of calcination and milling, the particles presented approximately spherical shapes and high percentages of substitution Ca2+ with Sr2+ was evident by the presence of necks between to particles due to the milling calcination. Analyses with Energy Dispersive Spectroscopy (EDS) showed stoichiometries in different samples very similar to the theoretical stoichiometry

Recycling scrap automotive heat shield insulation material

Automotive heat shields are usually composed of two metal sheets enclosing an insulating material with a paper-like texture that contains refractory ceramic particles. This article discusses the results achieved by recycling the scrap automotive insulation that is discarded in landfills, using the same concept as paper recycling. For comparison with the original product, tests of thickness, bulk density, weight loss on ignition, tensile strength, compressibility, and recovery were performed on recycled materials produced in a so-called "manual" process (involving little automation and performed in adapted facilities) without pressing, and pressed once, twice, and four times. Materials recycled in a so-called "industrial" process (in a paper recycling plant) without pressing, and pressed once were also tested. The recycled materials can be considered approved with respect to the main requirement, thermal insulation, since they dissipated the under-hood temperature by more than 300 A degrees C (like the original product). Like the heat insulation tests, the thermogravimetric analysis suggested that the recycled materials showed higher stability than the original product. Thermogravimetric, microscopy, and energy dispersive spectroscopy analyses indicated that the structural and compositional characteristics of the original product were preserved after recycling.

Anelastic behavior due to interstitial oxygen in SmBa(2)Cu(3)O7-delta

The composite SmBa2Cu3O7-delta (Sm-123), obtained by the substitution of the ion Y for Sm in the very well known and studied YBa2Cu3O7-delta (Y-123), is potentially attractive for better understanding superconductivity mechanisms and for its applications as electronic devices. Sm-123 samples show higher critical temperatures than Y-123 ones do and a larger solubility of Sm in Ba-Cu-O solvent, which makes their growth process faster. When oxygen is present interstitially, it strongly affects the physical properties of the material. The dynamics of oxygen can be investigated by anelastic spectroscopy measurements, a powerful technique for the precise determination of the oscillation frequency and the internal friction when atomic jumps are possible. Anelastic spectroscopy allows determining the elasticity modulus (related to the oscillation frequency) and the elastic energy loss (related to the internal friction) as a function of the temperature. The sample was also investigated by X-ray diffraction (XRD), scanning electronic microscopy (SEM), and electric resistivity. The results obtained show a thermally activated relaxation structure composed by at least 3 relaxation processes. These processes may be attributed to the jumps of oxygen atoms present of the Cu-O plane in the orthorhombic phase.

Oxygen Interstitial Dynamics in Bi(2)Sr(2)CaCu(2)O(8+delta) Oxides Measured by Mechanical Spectroscopy

Many researchers became interested in the discovery of Bi(2)Sr(2)CaCu(2)O(8+delta) oxides with critical temperature of around 80 K. It is known that the critical temperature is related to the CuO2 planes of the material. For this reason, the study of the interstitial oxygen in these oxides is of great relevance. The samples were prepared by means of conventional solid state reactions, through the stoichiometric mixture of precursory powders. After the sinterization, the samples were submitted to measurements of density, electrical resistivity, x-ray diffraction, scanning electron microscopy and energy dispersion spectroscopy, with the objective of performing their characterization. The measurements of mechanical spectroscopy were performed by a torsion pendulum. The results show three relaxation processes in the temperature range of 200 and 700 K, with activation energy of approximately 0.9 eV, which has been attributed to the dynamics of the interstitial oxygen present in the material.

Síntese e caracterização de complexos de lantanídeos pesados e ítrio(III) como o fármaco ibuprofeno no estado sólido

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Changes in the surface of four calcium silicate-containing endodontic materials and an epoxy resin-based sealer after a solubility test

Aim To compare the changes in the surface structure and elemental distribution, as well as the percentage of ion release, of four calcium silicate-containing endodontic materials with a well-established epoxy resin-based sealer, submitted to a solubility test. Methodology Solubility of AH Plus, iRoot SP, MTA Fillapex, Sealapex and MTA-Angelus (MTA-A) was tested according to ANSI/ADA Specification 57. The deionized water used in the solubility test was submitted to atomic absorption spectrophotometry to determine and quantify Ca2+, Na+, K+, Zn2+, Ni2+ and Pb2+ ions release. In addition, the outer and inner surfaces of nonsubmitted and submitted samples of each material to the solubility test were analysed by means of scanning electron microscopy and energy-dispersive spectroscopy (SEM/EDX). Statistical analysis was performed by using one-way anova and Tukeys post hoc tests (a = 0.05). Results Solubility results, in percentage, sorted in an increasing order were -1.24 +/- 0.19 (MTA-A), 0.28 +/- 0.08 (AH Plus), 5.65 +/- 0.80 (Sealapex), 14.89 +/- 0.73 (MTA Fillapex) and 20.64 +/- 1.42 (iRoot SP). AH Plus and MTA-A were statistically similar (P > 0.05), but different from the other materials (P < 0.05). High levels of Ca2+ ion release were observed in all groups except AH Plus sealer. MTA-A also had the highest release of Na2+ and K+ ions. Zn+2 ion release was observed only with AH Plus and Sealapex sealers. After the solubility test, all surfaces had morphological changes. The loss of matrix was evident and the filler particles were more distinguishable. EDX analysis displayed high levels of calcium and carbon at the surface of Sealapex, MTA Fillapex and iRoot SP. Conclusions AH Plus and MTA-A were in accordance with ANSI/ADAs requirements regarding solubility whilst iRoot SP, MTA Fillapex and Sealapex did not fulfil ANSI/ADAs protocols. High levels of Ca2+ ion release were observed in all materials except AH Plus. SEM/EDX analysis revealed that all samples had morphological changes in both outer and inner surfaces after the solubility test. High levels of calcium and carbon were also observed at the surface of all materials except AH Plus and MTA-A.

Subdivision of Hysteresis Loss in Mn-Zn Ferrite Toroidal Cores

The hysteresis loss subdivision method proved to be a strong tool to help in the analysis of different energy dissipation mechanisms along the quasi-static hysteresis loop measured on electrical steels. This paper used the samemethod to discuss the mechanisms involving the energy loss dissipation in Mn-Zn ferrite toroidal cores. The samples, sintered under controlled atmosphere in industrial conditions, were measured under triangular waveform excitation at very low frequency (5 mHz) and peak flux densities varying from 0.05 T to 0.45 T. The results show a different behavior between the low inductions hysteresis loss (WLI) and the high induction hysteresis loss (WHI) which proves the existence of different energy dissipation mechanisms affecting these loss components.

Outdoor bronze conservation: assessment of protective treatments by accelerated aging and of treatment removal procedures by laser cleaning

Outdoor bronzes exposed to the environment form naturally a layer called patina, which may be able to protect the metallic substrate. However, since the last century, with the appearance of acid rains, a strong change in the nature and properties of the copper based patinas occurred [1]. Studies and general observations have established that bronze corrosion patinas created by acid rain are not only disfiguring in terms of loss of detail and homogeneity, but are also unstable [2]. The unstable patina is partially leached away by rainwater. This leaching is represented by green streaking on bronze monuments [3]. Because of the instability of the patina, conservation techniques are usually required. On a bronze object exposed to the outdoor environment, there are different actions of the rainfall and other atmospheric agents as a function of the monument shape. In fact, we recognize sheltered and unsheltered areas as regards exposure to rainwater [4]. As a consequence of these different actions, two main patina types are formed on monuments exposed to the outdoor environment. These patinas have different electrochemical, morphological and compositional characteristics [1]. In the case of sheltered areas, the patina contains mainly copper products, stratified above a layer strongly enriched in insoluble Sn oxides, located at the interface with the uncorroded metal. Moreover, different colors of the patina result from the exposure geometry. The surface color may be pale green for unsheltered areas, and green and mat black for sheltered areas [4]. Thus, in real outdoor bronze monuments, the corrosion behavior is strongly influenced by the exposure geometry. This must be taken into account when designing conservation procedures, since the patina is in most cases the support on which corrosion inhibitors are applied. Presently, for protecting outdoor bronzes against atmospheric corrosion, inhibitors and protective treatments are used. BTA and its derivatives, which are the most common inhibitors used for copper and its alloy, were found to be toxic for the environment and human health [5, 6]. Moreover, it has been demonstrated that BTA is efficient when applied on bare copper but not as efficient when applied on bare bronze [7]. Thus it was necessary to find alternative compounds. Silane-based inhibitors (already successfully tested on copper and other metallic substrates [8]), were taken into consideration as a non-toxic, environmentally friendly alternative to BTA derivatives for bronze protection. The purpose of this thesis was based on the assessment of the efficiency of a selected compound, to protect the bronze against corrosion, which is the 3-mercapto-propyl-trimethoxy-silane (PropS-SH). It was selected thanks to the collaboration with the Corrosion Studies Centre “Aldo Daccò” at the Università di Ferrara. Since previous studies [9, 10, 11] demonstrated that the addition of nanoparticles to silane-based inhibitors leads to an increase of the protective efficiency, we also wanted to evaluate the influence of the addition of CeO2, La2O3, TiO2 nanoparticles on the protective efficiency of 3-mercapto-propyl-trimethoxy-silane, applied on pre-patinated bronze surfaces. This study is the first section of the thesis. Since restorers have to work on patinated bronzes and not on bare metal (except for contemporary art), it is important to be able to recreate the patina, under laboratory conditions, either in sheltered or unsheltered conditions to test the coating and to obtain reliable results. Therefore, at the University of Bologna, different devices have been designed to simulate the real outdoor conditions and to create a patina which is representative of real application conditions of inhibitor or protective treatments. In particular, accelerated ageing devices by wet & dry (simulating the action of stagnant rain in sheltered areas [12]) and by dropping (simulating the leaching action of the rain in unsheltered areas [1]) tests were used. In the present work, we used the dropping test as a method to produce pre-patinated bronze surfaces for the application of a candidate inhibitor as well as for evaluating its protective efficiency on aged bronze (unsheltered areas). In this thesis, gilded bronzes were also studied. When they are exposed to the outside environment, a corrosion phenomenon appears which is due to the electrochemical couple gold/copper where copper is the anode. In the presence of an electrolyte, this phenomenon results in the formation of corrosion products than will cause a blistering of the gold (or a break-up and loss of the film in some cases). Moreover, because of the diffusion of the copper salts to the surface, aggregates and a greenish film will be formed on the surface of the sample [13]. By coating gilded samples with PropS-SH and PropS-SH containing nano-particles and carrying out accelerated ageing by the dropping test, a discussion is possible on the effectiveness of this coating, either with nano-particles or not, against the corrosion process. This part is the section 2 of this thesis. Finally, a discussion about laser treatment aiming at the assessment of reversibility/re-applicability of the PropS-SH coating can be found in section 3 of this thesis. Because the protective layer loses its efficiency with time, it is necessary to find a way of removing the silane layer, before applying a new one on the “bare” patina. One request is to minimize the damages that a laser treatment would create on the patina. Therefore, different laser fluences (energy/surface) were applied on the sample surface during the treatment process in order to find the best range of fluence. In particular, we made a characterization of surfaces before and after removal of PropS-SH (applied on a naturally patinated surface, and subsequently aged by natural exposure) with laser methods. The laser removal treatment was done by the CNR Institute of Applied Physics “Nello Carrara” of Sesto Fiorentino in Florence. In all the three sections of the thesis, a range of non-destructive spectroscopic methods (Scanning Electron Microscopy with Energy Dispersive Spectroscopy (SEM-EDS), μ-Raman spectroscopy, X-Ray diffractometry (XRD)) were used for characterizing the corroded surfaces. AAS (Atomic Absorption Spectroscopy) was used to analyze the ageing solutions from the dropping test in sections 1 and 2.

Using the Franck-Hertz Experiment To Illustrate Quantization Energy States of the Neon Atom by Electron Impact

na provide students with motivation for the study of quantum mechanics. That microscopic matter exists in quantized states can be demonstrated with modem versions of historic experiments: atomic line spectra (I), resonance potentials, and blackbody radiation. The resonance potentials of mercury were discovered by Franck and Hertz in 1914 (2). Their experiment consisted of bombarding atoms by electrons, and detecting the kinetic energy loss of the scattered electrons (3). Prior to the Franck-Hertz experiment, spectroscopic work bv Balmer and Rvdbere revealed that atoms emitted radiatibn at discrete ekergiis. The Franck-Hertz experiment showed directly that auantized enerm levels in an atom are real, not jist optiEal artifacts. atom can be raised to excited states by inelastic collisions with electrons as well as lowered from excited states by emission of photons. The classic Franck-Hertz experiment is carried out with mercury (4-7). Here we present an experiment for the study of resonance potentials using neon.

Thermal Energy Storage for Solar Power Production

Solar energy is the most abundant persistent energy resource. It is also an intermittent one available for only a fraction of each day while the demand for electric power never ceases. To produce a significant amount of power at the utility scale, electricity generated from solar energy must be dispatchable and able to be supplied in response to variations in demand. This requires energy storage that serves to decouple the intermittent solar resource from the load and enables around-the-clock power production from solar energy. Practically, solar energy storage technologies must be efficient as any energy loss results in an increase in the amount of required collection hardware, the largest cost in a solar electric power system. Storing solar energy as heat has been shown to be an efficient, scalable, and relatively low-cost approach to providing dispatchable solar electricity. Concentrating solar power systems that include thermal energy storage (TES) use mirrors to focus sunlight onto a heat exchanger where it is converted to thermal energy that is carried away by a heat transfer fluid and used to drive a conventional thermal power cycle (e.g., steam power plant), or stored for later use. Several approaches to TES have been developed and can generally be categorized as either thermophysical (wherein energy is stored in a hot fluid or solid medium or by causing a phase change that can later be reversed to release heat) or thermochemical (in which energy is stored in chemical bonds requiring two or more reversible chemical reactions).

Low-temperature experiments of sediment core GeoB6229-6 at the South American continental margin off the Rio de la Plata estuary

With various low-temperature experiments performed on magnetic mineral extracts of marine sedimentary deposits from the Argentine continental slope near the Rio de la Plata estuary, a so far unreported style of partial magnetic self-reversal has been detected. In these sediments the sulphate-methane transition (SMT) zone is situated at depths between 4 and 8 m, where reductive diagenesis severely alters the magnetic mineral assemblage. Throughout the sediment column magnetite and ilmenite are present together with titanomagnetite and titanohematite of varying compositions. In the SMT zone (titano-)magnetite only occurs as inclusions in a siliceous matrix and as intergrowths with lamellar ilmenite and titanium-rich titanohematite, originating from high temperature deuteric oxidation within the volcanic host rocks. These abundant structures were visualized by scanning electron microscopy and analysed by energy dispersive spectroscopy. Warming of field-cooled and zero-field-cooled low-temperature saturation remanence displays magnetic phase transitions of titanium-rich titanohematite below 50 K and the Verwey transition of magnetite. A prominent irreversible decline characterizes zero-field cooling of room temperature saturation remanence. It typically sets out at ~210 K and is most clearly developed in the lower part of the SMT zone, where low-temperature hysteresis measurements identified ~210 K as the blocking temperature range of a titanohematite phase with a Curie temperature of around 240 K. The mechanism responsible for the marked loss of remanence is, therefore, sought in partial magnetic self-reversal by magnetostatic interaction of (titano-)magnetite and titanohematite. When titanohematite becomes ferrimagnetic upon cooling, its spontaneous magnetic moments order antiparallel to the (titano-)magnetite remanence causing an drastic initial decrease of global magnetization. The loss of remanence during subsequent further cooling appears to result from two combined effects (1) magnetic interaction between the two phases by which the (titano-)magnetite domain structure is substantially modified and (2) low-temperature demagnetization of (titano-)magnetite due to decreasing magnetocrystalline anisotropy. The depletion of titanomagnetite and superior preservation of titanohematite is characteristic for strongly reducing sedimentary environments. Typical residuals of magnetic mineral assemblages derived from basaltic volcanics will be intergrowths of titanohematite lamellae with titanomagnetite relics. Low-temperature remanence cycling is, therefore, proposed as a diagnostic method to magnetically characterize such alteration (palaeo-)environments.

Desenvolvimento de hidroxiapatita contendo prata via precipitação e imersão: avaliação do efeito antimicrobiano

A utilização de substitutos ósseos para recuperação da função perdida é uma constante busca dentro da área médica. Por isso os biomateriais têm recebido uma atenção muito grande por parte da comunidade científica, dentre eles os materiais a base de fosfato de cálcio. A hidroxiapatita, Ca10 (PO4)6 (OH) 2, tem sido muito estudada, pois além de representar a constituição da massa dos ossos naturais e dentes em 30 a 70%, possui propriedades de bioatividade e osteocondutividade, favorecendo e auxiliando o crescimento do tecido ósseo. Em contrapartida, infecções bacterianas podem surgir após o implante ocasionando a perda da funcionalidade a curto e médio prazo. Várias alternativas estão sendo testadas, geralmente associadas ao uso de antibióticos convencionais incorporados aos biomateriais. Uma alternativa a tais antibióticos seria a utilização de metais que possuem propriedades antibacterianas. A prata (Ag) é conhecida como um metal bactericida e por isso ganhou lugar de destaque dentre os estudos como um aliado importante no controle das infecções pós-cirúrgicas. Este trabalho teve como objetivo sintetizar, caracterizar e avaliar o efeito antimicrobiano da adição de íons de prata em hidroxiapatita. Foram obtidos pós de hidroxiapatita contendo prata (HAAg), nas concentrações de 0,1M; 0,01M e 0,001M pelo método de precipitação em temperatura ambiente e por imersão do pó de hidroxiapatita em soluções aquosas. As fases cristalinas e os grupamentos iônicos foram analisados para cada condição por técnicas de difração de raios X (DRX) e espectroscopia no infravermelho (IV) respectivamente. As informações sobre a morfologia e identificação de elementos químicos foi realizado pela técnica de microscopia eletrônica de varredura com espectroscopia de energia dispersiva (MEV EDS). As avaliações antimicrobianas foram realizadas por ensaios qualitativos e quantitativos, o ensaio qualitativo utilizou o teste de halo de difusão em disco para Staphylococcus aureus e Escherichia coli e o ensaio quantitativo utilizou contagem de bactérias para as cepas de Staphylococcus aureus. Os resultados de DRX e IV indicaram que independentemente do método de obtenção da HAAg foi possível observar a presença de prata metálica caracterizada pelos picos em 2θ=38,1º e 44,3º nas amostras HAAg0,1Im, HAAg0,1Pr e HAAg0,01Pr. Observou-se também a presença de AgO, correspondente ao pico em 2θ=37,5º nas amostras de HAAg0,01Pr e HAAg0,001Pr. Nos espectros de IV estão presentes as bandas que caracterizam a fase HA, referentes aos grupamentos PO43-, OH- e CO32-. Analisados em conjunto os ensaios qualitativos e quantitativos, as amostras HAAg0,01Im e HAAg0,001Im sintetizadas por imersão indicaram os melhores resultados para o ensaio de disco difusão, por apresentarem formação de halo inibição do crescimento bacteriano para a bactéria S. aureus. Para os ensaios quantitativos as amostras obtidas por precipitação com concentrações 0,1M e 0,01M de prata apresentaram melhor resultado por inibirem o crescimento bacteriano para as cepas S. aureus.

Utilização de resíduo de mármore e de óxido de boro em escórias sintéticas dessulfurantes para aços.

O mercado atual exige das indústrias siderúrgicas aços de melhor qualidade produzidos por meio de processos que causem menor impacto ao meio ambiente. Dessa forma, este trabalho teve como objetivo reciclar o resíduo de mármore gerado na indústria de rochas ornamentais, que possui em sua composição óxido de cálcio (CaO) e óxido de magnésio (MgO). O CaO é suficiente para substituir a cal nas escórias e o MgO contribui para a diminuição do desgaste dos refratários, através do emprego do resíduo no processo produtivo do aço. Além disso, foi realizada a substituição da fluorita por óxido de boro como fluxante na composição de misturas dessulfurantes. O resíduo de mármore foi caracterizado utilizando as seguintes técnicas: análise química via EDXFR, análise granulométrica via espalhamento de luz, área de superfície específica pelo método BET, difração de raios-X, microscopia eletrônica de varredura (MEV) e análise de micro-regiões por EDS. Visando verificar a eficiência na dessulfuração, foram formuladas misturas sintéticas utilizando a cal convencional ou resíduo de mármore, e a fluorita ou o óxido de boro. As misturas foram formuladas com o auxílio dos programas de termodinâmica computacional, Thermo-Calc e FactSage. Estas misturas foram adicionadas no aço fundido a temperatura de 1600°C sob atmosfera de argônio e agitadas por meio de um rotor de alumina. Amostras de metal foram retiradas para verificar a variação do teor de enxofre durante o experimento. O resíduo de mármore caracterizado, apresentou em sua composição 40% de CaO e 14% de MgO, na forma dos carbonatos CaCO3 e MgCO3. Obteve uma perda de massa de 42,1%, na forma de CO2 a temperatura de 780°C. Os experimentos mostraram que, as misturas testadas apresentaram, na maioria dos casos, eficiência de dessulfuração acima de 60%.