To see the other types of publications on this topic, follow the link: Radiation on metals.
Dissertations / Theses on the topic 'Radiation on metals'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Radiation on metals.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Yellen, Duncan Howard. "Radiation damage in hexagonal-close-packed metals." Thesis, University of Liverpool, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.316660.
Full text
2
Rutherford, A. "Electronic effects in radiation damage simulations in metals." Thesis, University College London (University of London), 2009. http://discovery.ucl.ac.uk/15817/.
Full textAbstract:
Radiation damage has traditionally been modelled using classical molecular dynamics, in which the role of the electrons is confined to describing bonding via the interatomic potential. This is generally sufficient for low radiation energies. However high energy atoms lose a significant proportion of their energy to electronic excitations, therefore a simulation of the relaxation of a metallic lattice after a high energy event requires a description of the energetic interaction between atoms and electrons. The mechanisms of inelastic collisions between electrons and ions, coupling between electrons and phonons and the diffusion of energy through the electronic system to the rest of the lattice become signficant. We have coupled large scale MD simulations of the lattice to a continuum model for the electronic temperature evolution. Energy lost by the atoms due to elastic and inelastic electronic collisions is gained by the electronic system and evolves according to a heat diffusion equation. The electronic energy is coupled to the lattice via a modified Langevin thermostat, representing electron-phonon coupling. Results of the simulation of both displacement cascades and ion tracks, representing the low and high extremes of incident ion energy respectively, are presented. The effect of annealing of pre-existing damage by electronic excitation is studied and the behaviour under swift heavy ion irradiation in iron and tungsten is compared. In simulations of displacement cascades, the strength of coupling between the atoms and electrons emerges as the main parameter determining residual damage. Our new methodology gives rise to reduced damage compared to traditional methods in all cases. Ion track simulations demonstrated that the relaxation dynamics, and hence the residual damage, was dependent on the magnitude and temperature dependence of the electronic thermal parameters.
3
Gai, Xiao. "Radiation damage and inert gas bubbles in metals." Thesis, Loughborough University, 2015. https://dspace.lboro.ac.uk/2134/17927.
Full textAbstract:
Inert gases in metals can occur due to ion implantation, from a plasma in a magnetron device or as a result of being by-products of nuclear reactions. Mainly because of the nuclear applications, the properties of the inert gases, helium, argon and xenon in the body centred cubic (bcc) iron crystal are examined theoretically using a combination of molecular dynamics, static energy minimisation and long time scale techniques using empirical potential functions. The same techniques are also used to investigate argon and xenon in aluminium. The primary interest of the work occurred because of He produced in nuclear fission and its effect on the structural materials of a fission reactor. This structure is modelled with perfectly crystalline bcc Fe. In bcc iron, helium is shown to diffuse rapidly forming small bubbles over picosecond time scales, which reach a certain optimum size. In the initial phase of He accumulation, Fe interstitials are ejected. This occurs instantaneously for bubbles containing 5 He atoms and as the more He accumulates, more Fe interstitials are ejected. The most energetically favourable He to vacancy ratios at 0 K, vary from 1 : 1 for 5 vacancies up to about 4 : 1 for larger numbers of vacancies. An existing He bubble can be enlarged by a nearby collision cascade through the ejection of Fe interstitials, allowing more He to be trapped. Ar and Xe in bcc Fe prefer to be substitutional rather than interstitial and there are large barriers to be overcome for the inert gas atoms to diffuse from a substitutional site. Bubbles that form can again be enlarged by the presence of a nearby collision cascade or at very high temperatures. In this case the most energetically favourable vacancy ratios in the bubbles is 1: 1 for Ar and from 0.6: 1 to 0.8: 1 for Xe. For Ar and Xe, bubble formation is more likely as a direct result of radiation or radiation enhanced diffusion rather than diffusion from a substitutional site. Ar in aluminium is also studied. Ar atoms in fcc Al prefer to be substitutional rather than interstitial and evolution into substitutional occurs over picosecond time scales at room temperature. Bubble formation can occur more easily than in bcc iron, mainly because the barriers for vacancy diffusion are much lower but the time scales for bubble accumulation are much longer than those for He. A vacancy assisted mechanism is found which allows Ar to diffuse through the lattice. Finally some preliminary results on the energetics of different geometrical structures of larger Xe bubbles in Al are investigated since experiment has indicated that these can become facetted.
4
Chang, Zhongwen. "Multiscale modelling of radiation-enhanced diffusion phenomena in metals." Doctoral thesis, KTH, Reaktorfysik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-163279.
Full textAbstract:
A multiscale modelling framework and an experiment campaign are used to study void swelling and Cu precipitation under irradiation. Several aspects regarding defect and solute diffusion under irradiation have been studied in this thesis. First, a self-diffusion model in bcc Fe has been constructed in order to describe the non-linear effects, especially the magnetic transition, around the Curie temperature. First principles calculations are applied to obtain the parameters in the model. The paramagnetic state is simulated by statistical sampling of randomly arranged spin states on each atom. The model fits well with the experimental observations. Then, a combination of atomistic calculations and the finite element method (FEM) is developed in order to solve the diffusion equations of point defects, which are under the influence of a dislocation strain field. The dislocation bias, a key parameter in void swelling models, is hence obtained numerically. The method has been applied in different structural lattices. In the bcc materials, anomalous bias factors have been found for both edge- and screw dislocations. For the edge dislocations, the traditional assumption that the dislocation bias value is proportional to the Burgers vector has been proven not appropriate. For the screw dislocation, a negative bias value is obtained. This implies that vacancies, instead of self-interstitials, are preferentially absorbed into the screw dislocations. Thus a possible complementary mechanism is here introduced for explaining the long swelling incubation time before the steady swelling in bcc materials compared to that in fcc materials. Edge dislocations in fcc materials split into partial dislocations due to their relatively low stacking fault energy. This feature complicates the analytical derivation of the dislocation bias. However, by transforming the analytical dislocation-point defect interaction energies to discrete interaction maps numerically applied in the FEM method, it is possible to perform a systematic study on typical fcc materials, i.e. Cu, Ni and Al. The impacts on the dislocation bias from elastic constants and stacking fault energy have been studied. It is found that the partial splitting distance is the dominating factor that determines the dislocation bias. A prediction method has been hence developed to obtain the dislocation bias of the austenitic alloys, for which it is difficult to use an atomistic description of the interaction maps. A prediction of about 8% dislocation bias of a typical austenitic 316 alloy has been made without performing specific atomistic calculations in the austenitic alloys. Finally, Cu precipitation under irradiation has been studied using both experiment and simulations. Cast iron and FeCu alloy samples were irradiated for a week with 2 MeV electrons. The resistivity of the samples was measured in situ. The microstructure of the samples was then examined by atom probe tomography. No Cu precipitation was found in the cast iron sample while small Cu clusters are observed in the FeCu model alloy. To simulate the clustering process, Kinetic Monte Carlo (KMC) and rate theory methods are used. Both the KMC and rate theory simulations show clearly the Cu clustering process in the FeCu alloy but not in cast iron within the irradiation dose.QC 20150401
5
Carroll, Turhan Kendall. "Radiation Damage in GMR Spin Valves." The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1281633368.
Full text
6
Wooding, Stephen John. "Computer simulation of radiation damage in hexagonal close-packed metals." Thesis, University of Liverpool, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.321114.
Full textAbstract:
Two HCP metals, titanium and zirconium, have been modelled using molecular dynamics and recently developed many-body potentials. These two metals have similar lattice parameters, c/a ratios, melting temperatures, elastic and dislocation properties and, more importantly, responses to radiation damage(Griffith 1988,1989 & 1991, Hood 1988 & 1993), but differ by nearly a factor of two in atomic mass, thereby allowing the direct investigation of the effect of mass on radiation damage in the HCP system. Using the MOLDY code, successfully modified for the HCP structure, these two models w re rigorously investigated with respect to their point defect properties, displacement threshold energy response, and cascade processes. A marked preference for interstitial sites within the basal plane was found, in accordance with previous static studies on HCP metals. The displacement threshold energy showed a complex dependence on orientation within the HCP structure, but at higher energies this effect was swamped by structural disruptions during cascade development. The effect of mass was exhibited as a proportional increase in the mean displacement threshold energy, which carries over into cascade generation. Cascade morphology was seen to undergo a transition at energies of -1 keV, associated with the onset of true cascade conditions. This transition was reflected most markedly in the relaxation time for the recombination phase beyond the cascade peak, and explanation is presented for the transition in terms of ballistic, energetic and temporal effects. The dissimilarities between the two models were found to be mainly attributable to the mass difference. The condition of the cascade core at the peak was seen to be close to that of a liquid, with some discrepancies which indicate a lack of true melting, and an absence of the vacancy clustering often associated with a molten cascade core. The approximation of liquid-like structure was supported by the isotropy of the cascade-induced atomic mixing, despite the preference for basal-plane movement in the solid state. In agreement with modelling of other metals, the defect production efficiency for true cascade conditions was well below the NRT estimate, and an empirical relationship between final Frenkel-pair numbers and PKA energy is presented. SIA clustering occurred to a similar extent in both models, and small clusters were highly mobile and confined to single <1120> rows in the basal planes. The implications of these findings for microstructural evolution are discussed, along with comparisons of the results with other systems.
7
Zhang, Liang Ph D. Massachusetts Institute of Technology. "Modeling radiation-induced mixing at interfaces between low solubility metals." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/87493.
Full textAbstract:
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Nuclear Science and Engineering, 2014.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 123-139).
This thesis studies radiation-induced mixing at interfaces between low solubility metals using molecular dynamics (MD) computer simulations. It provides original contributions on the fundamental mechanisms of radiation-induced mixing and morphological stability of multilayer nanocomposites under heavy ion or neutron radiation. An embedded atom method (EAM) interatomic potential is constructed to reproduce the main topological features of the experimental equilibrium phase diagram of the Cu-Nb system in both solid and liquid states. Compared with two previously available EAM Cu-Nb potentials, the phase diagram of the current potential shows better agreement with the experimental phase diagram. The newly constructed potential predicts that the Cu-Nb liquid phase at equilibrium is compositionally patterned over lengths of about 2.3 nm. All three Cu-Nb potentials have the same solid phase behavior but different liquid phase properties, serving as a convenient set of model systems to study the effect of liquid phase properties on radiation-induced mixing. To study radiation-induced intermixing, a specialized MD simulation is developed that models multiple 10 keV collision cascades sequentially up to a total dose of ~5 displacements per atom (dpa). These simulations are comparable to experiments conducted at cryogenic temperatures. Mixing is modeled using all three Cu-Nb potentials and found to be proportional to the square root of dose, independent of interface crystallography, and highly sensitive to liquid phase interdiffusivity. It occurs primarily by liquid phase interdiffusion in thermal spikes rather than by ballistic displacements. Partial de-mixing is also seen within thermal spikes, regardless of liquid phase solubility, which is explained by segregation of impurities into the liquid core of the thermal spikes. Additional MD and phase field simulations are carried out on Cu-Nb multilayered nanocomposites with individual layer thicknesses above 1 nm. These simulations demonstrate that Cu-Nb multilayers with individual layer thicknesses above 2-4 nm remain morphologically stable when subjected to 100 keV collision cascades, characteristic of neutron or heavy ion irradiation. The probability of morphological instability rapidly increases as the layer thickness decreases to 1 nm, which is due to overlap of zones of liquid-like interdiffusion inside radiation-induced thermal spikes at neighboring interfaces in the multilayer. This work shows that to design morphologically stable radiation-tolerant nanocomposites, it is desirable to a) choose low solubility metals with small liquid phase interdiffusivity as the constituents, and b) use a microstructural length scale larger than twice the size of the interdiffusion zone inside thermal spikes.
by Liang Zhang.
Ph. D.
8
Race, Christopher Peter. "The modelling of radiation damage in metals using Ehrenfest dynamics." Thesis, Imperial College London, 2010. http://hdl.handle.net/10044/1/5730.
Full textAbstract:
In this thesis we use a time-dependent tight-binding model metal evolving under semiclassical Ehrenfest dynamics to explore the effects of electron-ion energy exchange on radiation damage phenomena. By incorporating an explicit model of quantum mechanical electrons coupled to a set of classical ions, our model correctly reproduces the interaction of excited ions with cooler electrons and captures phenomena absent in classical molecular dynamics simulations and in much-used analytical models. With our simple model we have been able to simulate large numbers of radiation damage cascades. We have directly explored the electronic excitations stimulated in such cascades and have found them to be well characterized by an elevated electronic temperature. We have also analysed the effect of these excitations in weakening the bonding interactions in our model metal, and the effect of these weakened interactions on the evolution of replacement collision sequences. By separating out components of the Hellmann-Feynman forces exerted by the electrons on the ions, we have identi ed the non-adiabatic force, resulting from the finite response time of the electrons to ionic motion and responsible for the accumulating electronic excitations. Based on simplifying physical arguments we have derived a temporallyand spatially-local expression for this force suitable for incorporation within a classical MD code at very low computational cost. Data from our simulations show that our new expression for the non-adiabatic force captures much of the microscopic detail of the direction and magnitude of the force. We find that it significantly outperforms commonly used viscous damping models of ion-electron energy transfer. At higher energies, our simulations of ion channelling reveal a new resonant enhancement of the electronic charge on the channelling ion and corresponding effects on the stopping force. We explain these phenomena with reference to the detailed atomic and electronic structure of our model.
9
Hardy, G. J. "A study of the interactions of point defects with dislocations." Thesis, University of Oxford, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.354836.
Full text
10
Goodband, John H. "Novel applications using neural networks and liquid metals in radiation therapy." Thesis, Coventry University, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.439109.
Full text
11
McClean, Brendan Anthony. "Temperature dependence of Doppler-broadened positron annihilation radiation in hexagonal-close-packed metals." Thesis, Queen's University Belfast, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.254232.
Full text
12
Ward, Ann Elizabeth. "Void swelling in ferritic steels." Thesis, Open University, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.277918.
Full text
13
KONDO, FERNANDO M. "Estudo do efeito da radiação ionizante na utilização dos catalisadores desativados de craqueamento." reponame:Repositório Institucional do IPEN, 2014. http://repositorio.ipen.br:8080/xmlui/handle/123456789/23494.
Full textAbstract:
Submitted by Maria Eneide de Souza Araujo (mearaujo@ipen.br) on 2015-02-23T19:40:28Z
No. of bitstreams: 0Made available in DSpace on 2015-02-23T19:40:28Z (GMT). No. of bitstreams: 0
Dissertação (Mestrado em Tecnologia Nuclear)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
14
KIKUCHI, OLIVIA K. "Efeitos de baixas doses de radiacao gama de cobalto-60 sobre sementes de feijao, arroz e rabanete." reponame:Repositório Institucional do IPEN, 1987. http://repositorio.ipen.br:8080/xmlui/handle/123456789/9873.
Full textAbstract:
Made available in DSpace on 2014-10-09T12:32:20Z (GMT). No. of bitstreams: 0Made available in DSpace on 2014-10-09T14:10:29Z (GMT). No. of bitstreams: 1 01537.pdf: 1505528 bytes, checksum: 79b06b0cf173671eeb859566744153c3 (MD5)
Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
15
Murphy, Susan Mary. "Theory of compositional effects in irradiation damage." Thesis, University of Oxford, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.670365.
Full text
16
Rosso, Aldana. "Free Molecular and Metal Clusters Studied by Synchrotron Radiation Based Electron Spectroscopy." Doctoral thesis, Uppsala universitet, Institutionen för fysik och materialvetenskap, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-9323.
Full textAbstract:
The main purpose of this Thesis is the experimental characterization of the electronic and geometric structures of objects called clusters. A cluster consists of a finite group of bound atoms or molecules. Due to its finite size, it may present completely different properties than those of the isolated atom and the bulk. The clusters studied in this work are constituted by rare-gas atoms, organic molecules, and metal atoms. Intense cluster beams were created using either an adiabatic expansion source or a gas-aggregation source, and investigated by means of synchrotron radiation based photoelectron spectroscopy. The reports presented in this Thesis may be divided into three parts. The first one deals with results concerning homogeneous molecular clusters (benzene- and methyl-related clusters) highlighting how molecular properties, such as dipole moment and polarizability, influence the cluster structure. The second part focuses on studies of solvation processes in clusters. In particular, the adsorption of polar molecules on rare-gas clusters is studied. It is shown that the doping method, i.e. the technique used to expose clusters to molecules, and the fraction of polar molecules are important factors in determining the location of the molecules in the clusters. Finally, a summary of investigations performed on metal clusters is presented. The applicability of solid state models to analyse the cluster spectra is considered, and the differences between the atomic, cluster and solid electronic structures are discussed.
17
Gilbert, Mark R. "BCC metals in extreme environments : modelling the structure and evolution of defects." Thesis, University of Oxford, 2010. http://ora.ox.ac.uk/objects/uuid:d972d28d-5d2d-4392-8cf5-fc5728dc74f6.
Full textAbstract:
Designing materials for fusion applications is a very challenging problem, requiring detailed understanding of the behaviour of materials under the kinds of extreme conditions expected in a fusion environment. During the lifetime of fusion-reactor components, materials will be subjected to high levels of neutron irradiation, but must still perform effectively at high operating temperatures and under significant loading conditions. Body-centred cubic (bcc) transition metals are some of the most promising candidates for structural materials in fusion because of their relatively high density, which allows for effective neutron-shielding with the minimum volume and mass of material. In this work we perform atomistic simulations on two of the most important of these, Fe and W. In this thesis we describe atomic-scale simulations of defects found in bcc systems. In part I we consider the vacancy and interstitial loop defects that are produced and accumulated as a result of irradiation-induced displacement cascades. We show that vacancy dislocation loops have a critical size below which they are highly unstable relative to planar void defects, and thus offer an explanation as to why they are so rarely seen in TEM observations of irradiated bcc metals. Additionally, we compare the diffusion rates of these vacancy loops to their interstitial counterparts and find that, while interstitial loops are more mobile, the difference in mobility is not as significant as might have been expected. In part II we study screw dislocations, which, as the rate limiting carriers of plastic deformation, are significantly responsible for the strength of materials. We present results from large-scale finite temperature molecular dynamics simulations of screw dislocations under stress and observe the thermally-activated kink-pair formation regime at low stress, which appears to be superseded by a frictional regime at higher stresses. The mobility functions fitted to the results are vital components in simulations of dislocation networks and other large-scale phenomena. Lastly, we develop a multi-string Frenkel-Kontorova model that allows us to study the core structure of screw dislocations. Subtle changes in the form of the interaction laws used in this model demonstrate the difference between the non-degenerate and degenerate core structures. We provide simple criteria to guarantee the correct structure when developing interatomic potentials for bcc metals.
18
Browne, Peter Anthony. "Determination of residual stress in engineering components using diffraction techniques." Thesis, University of Salford, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.365984.
Full text
19
Garmatz, Júlia Cristina. "Determinação de metais como contaminantes em formulações de eritropoetina empregando métodos voltamétricos." Universidade Federal de Santa Maria, 2007. http://repositorio.ufsm.br/handle/1/10644.
Full textAbstract:
The contamination of renal failure patients by metals can be associated to the presence of these metals in the medication, since they can be absorbed by the organism. The level of contamination caused by medication, in these cases, depends strongly on the quality of medication used in the treatment. Among the possible contaminants, there are metals such as aluminum, chromium and nickel. Therefore, the development of analytical methodologies for the quality control of medicaments used by anemic patients is of great importance. In the present work, the presence of Al, Cr and Ni as contaminants in erythropoietin formulations (EPO), a renal antianemic, was investigated by developing and optimizing an adsorptive cathodic stripping voltammetric (AdCSV) method. It involves the optimization of a pretreatment step of samples by using UV irradiation for decomposition of matrix organic components. The AdCSV method is based on the adsorptive deposition of the complex formed at the electrode surface and the subsequent reduction of ligand (or metal) during the cathodic potential scan. The results found for Al, Cr and Ni in the studied samples, after performing the pretreatment step, show the applicability of the method for the determination of Al, Cr and Ni as contaminants in this kind of samples. The developed voltammetric methods are advantageous in relation to other existing methods concerning the high sensitivity of measurement if associated to the pretreatment step by UV irradiation associated with the addition of H2O2.A contaminação de pacientes com insuficiência renal por espécies metálicas pode estar associada à presença destas na medicação empregada, uma vez que estas espécies podem ser absorvidas pelo organismo do paciente. O nível de contaminação através da medicação, nestes casos, dependerá da qualidade da medicação utilizada no tratamento. Dentre os possíveis contaminantes, estão metais como alumínio, cromo e níquel. Desta forma, o desenvolvimento de metodologias analíticas adequadas ao controle de qualidade dos medicamentos administrados ao paciente é de grande importância. No presente trabalho, investigou-se a presença de Al, Cr e Ni como contaminantes em formulações de eritropoetina (EPO), um antianêmico renal, através do desenvolvimento e otimização de um método voltamétrico adsortivo de redissolução catódica (AdCSV) com a otimização de uma etapa de pré-tratamento das amostras empregando radiação UV para a decomposição dos componentes orgânicos da matriz. O método está baseado na deposição adsortiva do complexo formado (metal-ligante) na superfície do eletrodo e na redução do ligante ou do metal durante a varredura catódica dos potenciais. Os valores de Al, Cr e Ni encontrados nas amostras estudadas, após a etapa de pré-tratamento, demonstram a aplicabilidade do método para a determinação de Al, Cr e Ni como contaminantes neste tipo de matriz. O método voltamétrico desenvolvido é vantajoso em relação a outros métodos existentes, devido à alta sensibilidade da medida quando associada a uma etapa de pré-tratamento da amostra com radiação UV combinado com adição de H2O2.
20
SZELES, MARLENE S. M. F. "Avaliacao da contaminacao radiologica de um solo agricola nas proximidades de uma mina de uranio." reponame:Repositório Institucional do IPEN, 1994. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10434.
Full textAbstract:
Made available in DSpace on 2014-10-09T12:38:42Z (GMT). No. of bitstreams: 0Made available in DSpace on 2014-10-09T14:05:21Z (GMT). No. of bitstreams: 1 05825.pdf: 11314587 bytes, checksum: 4c78dd49091b4bfc57c3ff1ed797e9e9 (MD5)
Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
21
Weber, Neto Jose. "Avaliação de metais pesados em emissões atmosfericas de industria automotiva por fluorescencia de raios X." [s.n.], 2007. http://repositorio.unicamp.br/jspui/handle/REPOSIP/258645.
Full textAbstract:
Orientador: Silvana MoreiraDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e Urbanismo
Made available in DSpace on 2018-08-11T18:03:07Z (GMT). No. of bitstreams: 1 WeberNeto_Jose_M.pdf: 3765791 bytes, checksum: d918dd0a186ccff6f6dfa814697be0f7 (MD5) Previous issue date: 2007
Resumo: A qualidade do ar está diretamente à qualidade de vida da sociedade. Nos últimos anos vários episódios de poluição nos grandes centros urbanos, bem como as doenças causadas pela baixa qualidade do ar têm feito com que os órgãos governamentais estabeleçam padrões de qualidade do ar e também para as emissões atmosféricas que geralmente são as responsáveis pela poluição atmosférica. O presente estudo tem como objetivo a determinação de metais pesados e outros elementos (Bário, Bromo, Cálcio, Chumbo, Cloro, Cobre, Cromo, Estrôncio, Ferro, Manganês, Níquel, Potássio, Silício, Titânio e Zinco), nos poluentes atmosféricos gerados em uma indústria automotiva localizada em Engenheiro Coelho no interior do estado de São Paulo. Os procedimentos adotados para a execução das amostragens e o preparo das amostras foram baseados nas normas definidas pela Companhia de Tecnologia de Saneamento Ambiental (CETESB) e, também pela Agência de Proteção Ambiental Americana (EPA). As análises foram realizadas pela técnica de Fluorescência de Raios X por Reflexão Total com Radiação Síncrotron (SR-TXRF) no Laboratório Nacional de Luz Síncrotron em Campinas (SP). Os resultados obtidos apresentaram concentrações na faixa de 30 mg/Nm³ para Zinco, Ferro, Bário, Cálcio e Potássio, enquanto que os outros elementos apresentaram concentrações próximas a 1 mg/Nm³. A técnica analítica apresentou limites de detecção bem inferiores (cerca de 1000 vezes) aos valores estabelecidos nas Resoluções CONAMA 264/1999 e SEMA 041/2002, que estabelecem valores máximos permitidos para emissões atmosféricas
Abstract: The air quality has a direct link with the life quality society, lately, a large number of cases of air pollution have been happening in the great urban centers, as well as diseases caused by the poor air quality. These facts have forced the government organs to create standards for the air regulations and also for the atmospheric emissions that generally are the main responsible for the air quality alterations. This study had as goal the determination of heavy metals and other elements (Barium, Bromine, Calcium, Lead, Chlorine, Copper, Chromium, Strontium, Iron, Manganese, Nickel, Potassium, Silicon, Titanium and Zinc) in the atmospheric pollutants generated by an automotive industry located in Engenheiro Coelho city, São Paulo State, Brazil. The sampling and sample preparation procedures were based on methods established by Company of Technology of Environmental Sanitation (CETESB L9.234) and also by the Environmental Protection Agency (EPA - Method 29). The analysis was performed at XRF Beamline (D09B-XRF) in the Synchrotron Light Source Laboratory (Campinas/SP). For zinc, iron, barium, calcium, potassium the values obtained were in the range of 30 mg/Nm³ and for other elements the concentrations were approximately 1 mg/Nm³. The analytical technique employed presented detection limits much smaller (1,000 times) than maximum permissive values established by Brazilian legislations (CONAMA 264/1999 and SEMA 041/2002)
Mestrado
Saneamento e Ambiente
Mestre em Engenharia Civil
22
Broleze, Silvana Turolla 1977. "Avaliação da qualidade do lodo das estações de tratamento de esgoto de parte da região metropolitana de Campinas empregando a fluorescência de raios X por reflexão total com radiação síncronrton." [s.n.], 2013. http://repositorio.unicamp.br/jspui/handle/REPOSIP/258556.
Full textAbstract:
Orientador: Silvana MoreiraDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e Urbanismo
Made available in DSpace on 2018-08-22T10:28:59Z (GMT). No. of bitstreams: 1 Broleze_SilvanaTurolla_M.pdf: 3879465 bytes, checksum: 55a0753c8198f927cfe15629d6203167 (MD5) Previous issue date: 2013
Resumo: O aumento da produção de lodo de esgoto é decorrente do crescimento do volume de esgoto tratado e do número de estações de tratamento de esgotos no Brasil e, tem exigido a busca de alternativas para a sua disposição final. Dentre as várias alternativas de disposição, a utilização agrícola e a compostagem são viáveis, uma vez que o lodo é rico em matéria orgânica, macro e micronutrientes necessários à fertilidade dos solos. Porém, devido aos lançamentos clandestinos e despejos industriais nas redes públicas de coleta de esgoto, pode haver a presença de elementos que causam danos à saúde humana e ambiental, como Pb, Hg, Cd, As, Cr e Se. Este trabalho avaliou as substâncias inorgânicas potencialmente tóxicas no lodo, previamente desaguado, das ETE Camanducaia em Jaguariúna; Vila Flora em Sumaré; Praia Azul e Carioba em Americana; Samambaia, Anhumas, Santa Mônica, Piçarrão e Barão Geraldo em Campinas, SP, por meio de SR-TXRF. Os lodos das estações de tratamento de esgoto da Região Metropolitana de Campinas atendem a Legislação CONAMA 375/06, com exceção do lodo da ETE Santa Mônica que, durante o período seco, excedeu os limites para o Cu (1500 mg kg-1) e Ni (420 mg kg-1). De acordo com a IN n° 27/06 do MAPA, os lodos das estações ultrapassam em, pelo menos, uma coleta o limite para os elementos Ni (70 mg kg-1), e Cr (200 mg kg-1). Durante o período seco, ocorreu uma maior concentração dos elementos, em relação ao período chuvoso. As amostras de lodo das ETE Vila Flora e Praia Azul, durante o período chuvoso, comparadas com um padrão certificado NIST 2781, apresentaram características de lodo doméstico. Para que o lodo de parte da RMC possa ter destinação agrícola, de acordo com as legislações ambientais vigentes no país, é necessário que haja uma redução do Ni, Cr e Cu. Uma das alternativas seria uma maior fiscalização nas fontes geradoras, de modo a melhorar a qualidade do afluente das estações, adequando o lodo de esgoto às legislações brasileiras
Abstract: The increased production of sewage sludge is due to the growth in the volume of sewage treated and the number of sewage treatment plants in Brazil and has demanded the search for alternatives for their final disposal. Among the various alternatives available, agricultural use and composting are viable, since the sludge is rich in organic matter, macro and micronutrients necessary for soil fertility. However, due to illegal releases and industrial waste at public sewage collection, there may be the presence of elements that cause damage to human and environmental health, as Pb, Hg, Cd, As, Cr and Se. This study evaluated the potentially toxic inorganic substances in the sludge, dewatered previously, the WWTP Camanducaia in Jaguariúna; Villa Flora in Sumaré; Praia Azul and Carioba in Americana; Samambaia, Anhumas, Santa Monica, and Piçarrão Barão Geraldo Campinas, SP, using SR-TXRF. The sludge from wastewater treatment plants in the metropolitan region of Campinas (MRC) attend Legislation CONAMA 375/06, except sewage sludge from the WWTP Santa Monica that, during the dry period, exceeded the limits for Cu (1500 mg kg-1) and Ni (420 mg kg-1). According to the Normative Ruling (IN) nº. 27/06 MAPA, the sludge from the stations exceeded in at least one collection limit for the elements Ni (70 mg kg-1), and Cr (200 mg kg-1). During the dry season, there was a higher concentration of elements in relation to the rainy season. The sludge samples of the WWTP Vila Flora and Praia Azul during the rainy period, compared with a standard certificate NIST 2781, showed characteristics of domestic sewage. For the sludge part of MRC may have agricultural destination, according to the environmental laws in force in the country, there must be a reduction of Ni, Cr and Cu. One alternative would be greater oversight in generating sources in order to improve the quality of tributary stations, adjusting the sewage sludge to Brazilian laws
Mestrado
Saneamento e Ambiente
Mestre em Engenharia Civil
23
Castin, Nicolas. "Atomistic kinetic Monte Carlo simulation of precipitation and segregation in metals for nuclear applications, using a novel methodology based on artificial neural networks." Doctoral thesis, Universite Libre de Bruxelles, 2011. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209893.
Full textAbstract:
La sécurité des installations nucléaires est constamment un souci majeur lors de leur exploitation, mais aussi lors de la conception de nouveaux réacteurs. Leurs durées de vie est limitée à cause des changements de comportement mécanique de leurs composants métalliques (principalement la cuve du réacteur mais aussi ses composants internes), qui sont accélérés ou induits par l’irradiation de neutrons. Une prédiction quantitative précise de ces changements, en fonction de la composition des matériaux et des conditions d'irradiation, est par conséquent un objectif de première importance pour la science des matériaux nucléaires. La modélisation est, de nos jours, considérée comme un complément vital aux approches expérimentales, avec l'objectif d’apporter une meilleure compréhension des processus physiques et chimiques qui se produisent dans les matériaux métalliques sous irradiation de neutrons.La modélisation des effets de l'irradiation de neutrons dans les aciers est par nature un problème multi-échelle. Le point de départ est la simulation des cascades de collisions atomiques initiées par les neutrons à hautes énergies qui pénètrent dans le matériau, créant ainsi des défauts ponctuels mobiles. Différents modèles physiques, considérant des échelles de temps et de longueur croissantes, doivent être développés afin de convenablement tenir en compte de tous les différents processus qui provoquent des changements de comportement macroscopique, à cause de la présence de ces défauts ponctuels mobiles. En outre, des liens entre les différents modèles doivent être créés, parce que les prédictions de chacun d'entre eux doivent servir de paramètres d'entrée pour les modèles qui travaillent aux échelles supérieures. Dans cette thèse, un tel lien est créé entre le niveau atomique et les modèles à gros-grains, en développant un nouvel algorithme Monte-Carlo cinétique atomistique (MCCA), où le matériau est décrit comme une collection d'atomes occupant des sites cristallographiques réguliers. Le processus simulé est dès lors naturellement décomposé en séries d'évènements élémentaires activés thermiquement, correspondant à la migration des défauts ponctuels (lacunes ou interstitiels) vers des positions de proches voisins, qui sont en permanence en compétition en fonction de leurs fréquences d'occurrences respectives. Ces dernières sont calculées en fonction des énergies de migrations, qui sont elles-mêmes calculées avec peu d'approximations par une méthode qui prend en compte tous les effets de la relaxation statique et des interactions chimiques à longue portée. Le nouvel algorithme MCCA est par conséquent un modèle physique, entièrement basé sur un potentiel inter-atomique approprié qui est utilisé de la manière la plus complète possible, sans définir de paramètres empiriques qui devraient être, par exemple, fittés depuis des données expérimentales. Finalement, l'algorithme est accéléré de plusieurs ordres de grandeur en utilisant des réseaux de neurones artificiels (RNA), entraînés à prédire les énergies de migrations des défauts ponctuels en fonction de leur environnement atomique local.
Le nouvel algorithme MCCA est utilisé avec succès pour simuler des expériences de recuits (pour lesquels une seule lacune doit être introduite dans la boîte), afin de valider le modèle grâce à une comparaison directe de ses prédictions avec des résultats expérimentaux trouvés dans la littérature. Une comparaison très satisfaisante est accomplie pour deux alliages modèles importants pour la science des matériaux nucléaires. Dans les deux cas, l'évolution avec le temps de recuit du rayon moyen des précipités formés, ainsi que de leur densité, est en très bonne adéquation avec les mesures expérimentales trouvées dans la littérature, contrairement à ce que d'autres auteurs avaient jusqu’à présent réussi. Ensuite, l'algorithme est généralisé avec succès afin de permettre l'introduction d'un grand nombre de lacunes, ce qui est un des deux ingrédients nécessaires pour la simulation des effets de l'irradiation de neutrons dans les métaux. Cet accomplissement permet la simulation de processus longs et complexes, par exemple le calcul de coefficients de diffusions et temps de vies d'amats de cuivre-lacunes, qui sont des paramètres d'entrée nécessaires pour des modèles de simulation à gros-grains. Finalement, des preuves convaincantes sont apportées que l'algorithme MCCA peut être, dans un futur proche, généralisé d'avantage et permettre la prise en compte des interstitiels, ouvrant ainsi la voie vers la simulation de cycles complets d'irradiation.
Doctorat en Sciences
info:eu-repo/semantics/nonPublished
24
OLIVEIRA, LAURA C. de. "Estudo da distribuição de íons e metais em sangue via metodologia nuclear." reponame:Repositório Institucional do IPEN, 2008. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11609.
Full textAbstract:
Made available in DSpace on 2014-10-09T12:53:49Z (GMT). No. of bitstreams: 0Made available in DSpace on 2014-10-09T13:58:49Z (GMT). No. of bitstreams: 0
Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP
25
Ferlazzo, Mélanie. "Impact du transit cytonucléaire de la protéine ATM en réponse aux radiations ionisantes : notions de pro- et anti-episkévie." Thesis, Lyon, 2017. http://www.theses.fr/2017LYSE1067/document.
Full textAbstract:
Plus d'un siècle après la découverte des rayons X, les effets biologiques des radiations ionisantes restent encore méconnus. En particulier, une meilleure connaissance des phénomènes liés à la radiosensibilité individuelle permettrait une meilleure prédiction du risque radioinduit tant en ce qui concerne les réactions tissulaires que la formation de cancers.Dans le cadre des recherches menées par le Groupe de Radiobiologie de l'UMR 1052 Inserm (Centre de Recherche en Cancérologie de Lyon), l'accumulation de données radiobiologiques issues de patients radiosensibles a permis d'initier une théorie basée sur le transit cytonucléaire de la protéine ATM. Acteur majeur de la réponse aux radiations ionisantes ATM est muté dans l'Ataxie Telangiectasie, syndrome génétique rare associé à la plus forte radiosensibilité. Plus précisément, les chercheurs du Groupe ont proposé le modèle suivant : l'irradiation produit une monomérisation des formes cytoplasmiques de la protéine ATM. Les monomères d'ATM diffusent dans le noyau pour assurer la reconnaissance et la réparation des cassures double-brin de l'ADN (CDB), dommages-clés de la réponse aux radiations. Tout retard dans ce transit conduirait à une certaine radiosensibilité.Le but de cette thèse est d'identifier d'une part, les protéines (appelées X) qui freinerait ce transit en s'associant à ATM dans le cytoplasme ; d'autre part, les agents chimiques (métaux, pesticides) qui influeraient sur ce processus.Les protéines X identifiées dans le cadre de cette thèse sont notamment la huntingtine, la neurofibromine, la tubérine qui, lorsqu'elles sont mutées, causent respectivement la maladie de Huntington, la Neurofibromatose de type 1 et la Tubéreuse de Bourneville. Les métaux étudiés sont les chlorures d'aluminium, de cuivre, de zinc, de fer, de nickel, de palladium, de cadmium ainsi que le nitrate de plomb, le selenium et le chrome. Les pesticides sont l'atrazine, le glyphosate, la permetrine, le thiabendazole et le pentachlorophénol.Cette thèse introduit la notion de pro-, dys- ou anti-épiskévie, c'est-à-dire la capacité de certains agents, protéines ou drogues à accélérer, ralentir ou interdire le transit cytonucléaire de la protéine ATMMore than a century after the discovery of X rays, the effects of ionising radiation are still misunderstood. In particular, a better knowledge of individual radiosensitivity could lead to a better prediction of radio induced risk of cancer and acute reactions after radiotherapy. As part of the research conducted by the Radiobiology Group of UMR Inserm 1052 (Cancer Research Center of Lyon), the accumulation of radiobiological data from radiosensitive patients allowed to initiate a theory based on the ATM protein transit from cytoplasm to nucleus. ATM a the major actor in the response to ionising radiation and is mutated in Ataxia Telangiectasia, a rare genetic syndrome associated with the highest radiosensitivity. Specifically, the researchers of the Group proposed the following model: irradiation produces monomerization of cytoplasmic forms of ATM protein. ATM monomers diffuse into the nucleus to ensure the recognition and repair of DNA double-strand breaks (DSBs), the key damage response to radiation. Any delay in this transit would lead to radiosensitivity.The aim of this thesis is to identify in one hand, the proteins (called X proteins), which would slow the transit by interracting with ATM in the cytoplasm; on the other hand, chemical agents (metals, pesticides) that would affect this process.X proteins identified in this thesis include huntingtin, neurofibromin, tuberin which, when mutated, cause, respectively, Huntington's disease, Neurofibromatosis type 1 and Tuberous Sclerosis. Studied metals are aluminum, copper, zinc, iron, nickel, palladium and cadmium chlorides, lead nitrate, selenium and chromium. Pesticides are atrazine, glyphosate, permethrin, thiabendazole and pentachlorophenol.This thesis introduces the concept of pro-, dys or anti- episkévia, that is to say the ability of some agents, proteins or drugs to speed up, slow down or inhibit the the ATM nucleoshuttling
26
CAMARGO, IARA M. C. de. "Estudo da influencia do coeficiente de particao de metais no solo de Figueira, Parana, no calculo de risco a saude humana, utilizando o modelo c-soil." reponame:Repositório Institucional do IPEN, 2005. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11356.
Full textAbstract:
Made available in DSpace on 2014-10-09T12:51:02Z (GMT). No. of bitstreams: 0Made available in DSpace on 2014-10-09T14:08:20Z (GMT). No. of bitstreams: 0
Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
27
Souza, Luciana Carla Ferreira de. "Avaliação de metais em esgoto e lodo gerado em estações de tratamento, nos municípios de Jaguariúna e Campinas, empregando a fluorescência de raios x por reflexão total com radiação síncrotron (SR-TXRF)." [s.n.], 2013. http://repositorio.unicamp.br/jspui/handle/REPOSIP/258555.
Full textAbstract:
Orientador: Silvana MoreiraTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e Urbanismo
Made available in DSpace on 2018-08-22T06:30:46Z (GMT). No. of bitstreams: 1 Souza_LucianaCarlaFerreirade_D.pdf: 23739098 bytes, checksum: 19ea527d066d2fff5ef81495ee85ff0f (MD5) Previous issue date: 2013
Resumo: O rápido crescimento urbano e industrial nas ultimas décadas provocou alterações no meio ambiente, dentre eles a poluição dos corpos d'água, principalmente por metais que podem causar danos a saúde humana. Os municípios de Campinas e Jaguariúna estão inseridos na Região Metropolitana de Campinas (RMC), uma das regiões mais dinâmicas no cenário econômico brasileiro. Portanto, visando estudar a influencia antropogenica das cidades, foi avaliada a qualidade do efluente bruto e tratado e, do lodo gerado na estação de tratamento de esgoto de Anhumas, no município de Campinas e na estação de tratamento Camanducaia no município de Jaguariúna, ambas no estado de São Paulo, principalmente no que se refere à contaminação por metais. As analises foram realizadas pela técnica de Fluorescência de Raios X por Reflexão Total com Radiação Sincrotron (SR-TXRF) e os resultados comparados com as legislações vigentes. Para o efluente tratado os dados foram comparados as legislações CONAMA 357 e 430 que estabelecem limites para o descarte de efluentes nos corpos d'água e todos os elementos Cr, Mn, Fe, Ni, Cu, Zn, Ba e Pb apresentaram concentrações em conformidade com a legislação. Para o reuso na agricultura, cujos limites são definidos pela Instrução Técnica CETESB alguns dos elementos apresentaram concentrações acima do permitido e desta forma o efluente tratado não pode ser empregado para reuso. No caso do lodo os teores de Cr, Ni, Cu, Zn, Ba e Pb foram comparados aos valores máximos permitidos das legislações CONAMA 357 e 430 e os teores de todos os elementos ficaram abaixo do valor Maximo permitido, e desta forma existe a possibilidade de aplicação do lodo no solo agrícola, para as duas estações de tratamento de esgoto estudadas, Anhumas (Campinas) e Camanducaia (Jaguariúna)
Abstract: The rapid urban and industrial growth in recent decades caused changes in the environment, including pollution of water bodies, mainly of metals that can cause harm to human health. The cities of Campinas and Jaguariuna are inserted in the Metropolitan Region of Campinas (MRC), one of the most dynamic regions in the Brazilian economy. Therefore, to study the influence of anthropogenic citiesit was evaluated the quality of raw and treated wastewater and sludge generated in the wastewater treatment plant of Anhumas, in Campinas and the treatment plant in the municipality of Camanducaia Jaguariuna, both in state of Sao Paulo, particularly with regard to metal contamination. Analyses were performed by the technique of X-ray Fluorescence by Total Reflection with Synchrotron Radiation (SR-TXRF) and the results compared with existing laws. For the treated effluent data were compared laws CONAMA 357 and 430 that set limits for the discharge of effluents into water bodies and all the elements Cr, Mn, Fe, Ni, Cu, Zn, Pb and Ba concentrations presented in accordance with legislation. To reuse in agriculture, whose limits are defined by the Technical Instruction CETESB some elements had concentrations above the permitted and thus the treated effluent can't be used for reuse. In the case of sludge contents of Cr, Ni, Cu, Zn, Ba and Pb were compared with maximum permissible values of the laws CONAMA 357 and 430 and the contents of all elements were below the maximum allowable value, and thus it is possible application of sludge to agricultural soil, for the two sewage treatment stations studied, Anhumas (Campinas) and Camanducaia (Jaguariuna)
Doutorado
Saneamento e Ambiente
Doutora em Engenharia Civil
28
Pinaeva, Uliana. "Functionalized track-etched PVDF membrane-electrodes for toxic metal determination in water." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLX048.
Full textAbstract:
Le greffage radio-induit de polymères fonctionnels, tels que le poly(acide acrylique) (PAA), la poly(4-vinyl pyridine) (P4VP) et le poly(bis[2-(methacryloyloxy)ethyl] phosphate (B2MP), dans la structure nanoporeuse de membranes en poly(fluorure de vinylidène) (PVDF) à traces attaquées est ici rapporté, l’objectif étant la pré-concentration sélective des ions Pb(II), Hg(II) et U(VI) en solution dans l’eau. Les membranes en PVDF à traces attaquées sont fabriquées par irradiation aux ions lourds rapides suivie par la révélation chimique des traces. Les membranes nanoporeuses en PVDF ainsi créées sont ensuite fonctionnalisées dans la porosité grâce à la présence de radicaux résiduels à la paroi des nanopores. La spectroscopie RPE a été utilisée pour déterminer la quantité et la réactivité des radicaux piégés, notamment dans le cas d’une fonctionnalité nouvelle comme le B2MP. Il a été montré que ces radicaux, alkyles et peroxyles, étaient en quantité suffisante pour initier une polymérisation radicalaire en présence des trois monomères étudiés. Le FESEM, le FTIR et une méthode moins conventionnelle comme le potentiel Zeta ont permis la caractérisation des groupes fonctionnels. Dans le cas du greffage de la P4VP dans les nanopores, la mesure des états de charges à la surface des nanopores versus le pH a montré que le greffage était uniforme et relativement dense tout au long des canaux poreux. L’objectif de ce travail étant de développer des capteurs électrochimiques innovants pour la détection des métaux toxiques, une étude en adsorption a confirmé des capacités de sorption très efficaces des membranes à traces en PVDF greffées dont les groupes fonctionnels facilitent les réactions de coordination partant d’une interaction électrostatique pure inhérente au PAA à la complexation chélatante avec la P4VP en passant par celle du B2MP. L’effet complexant modéré du B2MP dans le cas de l’adsorption de l’U(VI) est dû à la co-existence de groupements échangeurs d’ions et chélatants dans la structure du B2MP. Pour la détection électrochimique, les membranes en PVDF nanoporeuses radio-greffées sont converties en électrodes. La pré-concentration de métaux toxiques adsorbés dans la nanoporosité permet de diminuer la limite de sensibilité de la voltammétrie à redissolution à des concentrations sub-ppb (μg/L). Les données acquises en photoluminescence résolue en temps (TRPL) et en XPS ont approfondi la compréhension du mécanisme de coordination du complexe U(VI)-B2MPPresent work reports on radiation grafting of poly(acrylic acid) (PAA), poly(4-vinyl pyridine) (P4VP) and bis[2-(methacryloyloxy)ethyl] phosphate (B2MP) functional polymers inside nanoporous structure of track-etched poly(vinylidene fluoride) (PVDF) membranes for selective pre-concentration of Pb(II), Hg(II) and U(VI) from aqueous solutions. Track-etched PVDF membranes were made by means of swift heavy ion (SHI) irradiation followed by ion track revealing. The resulting nanoporous PVDF membranes were then functionalized through remained radicals at the nanopore walls. EPR spectroscopy was used to examine the amount and reactivity of the trapped radicals, notably towards a novel functionality inside the etched tracks, namely B2MP. It was found that these radicals, alkyl and peroxy ones, were sufficient to initiate free-radical polymerization in presence of the three studied vinyl monomers. FESEM, FTIR and a less conventional zeta-potential measurements were utilized for examination of functional group presence. In case of P4VP grafting, the measured nanopore surface charge versus pH demonstrated uniform and relatively dense grafting all along the nanopore channels. As the objective of this work is to develop innovative electrochemical sensors for toxic metal determination in water, adsorption experiments were performed confirming that efficient uptakes of the grafted track-etched PVDF membranes are due to the presence of functional groups that facilitate coordination reactions from pure inherent to PAA electrostatic interaction to chelating complexation with P4VP and B2MP complexation in between. The moderate interaction effect in case of U(VI) adsorption by B2MP is due to the co-existence of ion-exchange and chelating groups in B2MP. For electrochemical sensoring, membranes functionalized with abovementioned chelate polymers were converted into electrodes. The pre-concentration of toxic metal adsorbed inside the nanoporosity permit to below stripping voltammetry sensitivity limits to sub-ppb (μg/L) level. Time-resolved photoluminescence (TRPL) measurements accompanied with XPS were performed on uranyl adsorbed B2MP-g-PVDF membranes in order to understand deeper the U(VI)-B2MP coordination mechanism
29
Rander, Torbjörn. "Photoelectron Spectroscopy on Atoms, Molecules and Clusters : The Geometric and Electronic Structure Studied by Synchrotron Radiation and Lasers." Doctoral thesis, Uppsala University, Department of Physics, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-8343.
Full textAbstract:
Atoms, molecules and clusters all constitute building blocks of macroscopic matter. Therefore, understanding the electronic and geometrical properties of such systems is the key to understanding the properties of solid state objects.
In this thesis, some atomic, molecular and cluster systems (clusters of O2, CH3Br, Ar/O2, Ar/Xe and Ar/Kr; dimers of Na; Na and K atoms) have been investigated using synchrotron radiation, and in the two last instances, laser light. We have performed x-ray photoelectron spectroscopy (XPS) on all of these systems. We have also applied ultraviolet photoelectron spectroscopy (UPS), resonant Auger spectroscopy (RAS) and near-edge x-ray absorption spectroscopy (NEXAFS) to study many of the systems. Calculations using ab initio methods, namely density functional theory (DFT) and Møller-Plesset perturbation theory (MP), were employed for electronic structure calculations. The geometrical structure was studied using a combination of ab initio and molecular dynamics (MD) methods.
Results on the dissociation behavior of CH3Br and O2 molecules in clusters are presented. The dissociation of the Na2 molecule has been characterized and the molecular field splitting of the Na 2p level in the dimer has been measured. The molecular field splitting of the CH3Br 3d level has been measured and the structure of CH3Br clusters has been determined to be similar to the structure of the bulk solid. The diffusion behavior of O2, Kr and Xe on large Ar clusters, as a function of doping rate, has been investigated. The shake-down process has been observed from excited states of Na and K. Laser excited Na atoms have been shown to be magnetically aligned. The shake-down process was used to characterize the origin of various final states that can be observed in the spectrum of ground-state K.
30
Sampaio, Sergio Arnaud. "Quantificação de metais em aguas e sedimentos do reservatorio Billings por fluorescencia de raios X com reflexão total e radiação Sincrotron (SR-TXRF)." [s.n.], 2007. http://repositorio.unicamp.br/jspui/handle/REPOSIP/258641.
Full textAbstract:
Orientador: Silvana MoreiraDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e Urbanismo
Made available in DSpace on 2018-08-10T23:35:00Z (GMT). No. of bitstreams: 1 Sampaio_SergioArnaud_M.pdf: 1857794 bytes, checksum: b5584970c1ca196d93e07f5d3ea81396 (MD5) Previous issue date: 2007
Resumo: A Represa Billings é o maior reservatório de água da região metropolitana de São Paulo, com aproximadamente 100 km² em espelho de água. Sua bacia hidrográfica ocupa mais de 500km² em seis municípios da região. Ao seu redor concentra-se o maior parque industrial da América do Sul e somente suas margens são ocupadas por quase um milhão de habitantes. A qualidade de suas águas é, portanto, motivo constante de preocupação de toda a sociedade. Neste trabalho aplica-se a Espectrometria de Fluorescência de Raios X, com Reflexão Total e excitação por Radiação Síncrotron (SR-TXRF), para a identificação e quantificação de metais em águas e sedimentos da Represa Billings. Foram quantificados os metais Cr, Ni, Cu, Zn e Pb, freqüentemente investigados em trabalhos na área ambiental, já que são largamente usados em processos industriais e estão presentes em vários produtos de consumo doméstico. Para o trabalho de campo, foram coletadas amostras em dezoito pontos, incluídas as margens e a porção central da represa, localizados em regiões com ocupação residencial e industrial, como também em regiões preservadas, próximos de pontos de monitoramento adotados pela Companhia de Tecnologia de Saneamento Ambiental do Estado de São Paulo (CETESB). As amostras de água e de sedimentos, bem como as amostras certificadas e padrões, foram analisadas no Laboratório Nacional de Luz Síncrotron ¿ LNLS situado no pólo de alta tecnologia, em Campinas-SP. Foi estabelecida uma comparação entre as concentrações de metais obtidas e os valores de referência para águas e para sedimentos, recomendados pela legislação em vigor. Os resultados obtidos indicam concentrações acima dos valores permitidos para o cobre, generalizada para todos os locais de amostragem, como também para o chumbo na grande maioria desses locais. Os demais metais estudados também apresentaram concentrações acima do permitido para alguns dos pontos de amostragem. O trabalho destaca as vantagens e os aspectos relevantes da técnica de análise (SR-TXRF), considerada como não destrutiva e com baixos limites de detecção (partes por bilhão). Outras vantagens são: a sensibilidade analítica para uma ampla faixa de elementos, com um preparo simples e rápido de amostras e facilidade de operação, e que por isso tem apresentado grande desenvolvimento nos últimos anos, com crescente aceitação da comunidade científica. A finalidade de contexto social é contribuir para a preservação dos mananciais locais e o aproveitamento racional de suas águas
Abstract: The Billings dam is the largest water reservatory in the metropolitan region of Sao Paulo, with approximately 100 km2 of area. Its watershed takes up more than 500 km2 in 6 counties of the region. Around the dam is located the largest industrial region of South America and only its borders have about 1 million inhabitants. The water quality is a constant concern to society. On this study, it is applied the synchrotron radiation total reflection X-ray fluorescence (SRTXRF) analysis for identification and quantification of metals in water and sediments of the Billings dam. Metals such as Cr, Ni, Cu, Zn and Pb were analyzed and investigated by environmental work tasks, as they are largely used in industrial processes and are present in various domestic consumers¿ products. As far as experimental work, samples were collected in 18 locations, including the borders and in the central part of the dam, which were located in both residential and industrial regions, as well as in preserved regions, near the places where monitoring was adopted by the Technology and Environmental Company of São Paulo State (CETESB). The water and sediment samples, as well as the certified ones were analyzed in the Brazilian Synchrotron Light Laboratory (LNLS) located in the high technology pole in Campinas, SP. A comparison was established between the metal concentration obtained and the reference values for water and sediments, recommended by Brazilian laws. The results registered a concentration higher than permissive values for Cu, generalized to all sample locations, as well as to Pb in the majority of these places. Other metals studied also showed a concentration higher than permissive values in some points. The job features the advantages and relevant aspects of the SR-TXRF technique. Advantages as not destructive, with low detection limits, high sensitivity for several elements, simple and quick sample preparation, ease operation among others) that shows great development in the past years, with a growing acceptance in the scientific community. The purpose within the social context is to contribute to the local water sources preservation and the rational usage of its waters
Mestrado
Recursos Hidricos
Mestre em Engenharia Civil
31
Fazza, Elizete Vieira. "Avaliação da agua e do sedimento das microbacias dos Ribeirões Graminha e Aguas da Serra na cidade de Limeira, SP." [s.n.], 2007. http://repositorio.unicamp.br/jspui/handle/REPOSIP/258642.
Full textAbstract:
Orientador: Silvana MoreiraDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e Urbanismo
Made available in DSpace on 2018-08-11T03:52:29Z (GMT). No. of bitstreams: 1 Fazza_ElizeteVieira_M.pdf: 2172063 bytes, checksum: 9efe3c01da1dbb554288a537bfa44ea7 (MD5) Previous issue date: 2007
Resumo: A cidade de Limeira está localizada no Estado de São Paulo e possui economia expressiva, com indústrias em vários setores produtivos, entre elas, galvanoplastias voltadas para a produção de jóias, semijóias e bijuterias. Visando elucidar se há influência antropogênica nos mananciais da cidade, avaliou-se a qualidade das águas e as concentrações de metais presentes na água e nos sedimentos dos ribeirões Graminha e Águas da Serra, cujas nascentes estão na zona urbana de Limeira. As determinações de metais foram realizadas pela técnica de Fluorescência de Raios X por Reflexão Total com Radiação Síncrotron (SR-TXRF). Os limites de detecção para amostras de água estão na faixa de 0,50 a 0,05 µg.L-1 para Ca e Zn, respectivamente, enquanto que para as amostras de sedimento os limites de detecção obtidos foram iguais a 0,22 e 0,02 µg.g-1 para os mesmos elementos. Nas amostras de água dos dois mananciais e para ambos os períodos amostrados (seco e húmido) as concetrações de Al e Fe foram superiores aos limites máximos permissíveis estabelecidos pela legislação vigente. Os elementos Zn e Cu apresentaram o mesmo comportamento. Para o Cr e Ni apenas alguns pontos de amostragem apresentaram valores acima dos limites permitidos. No ribeirão Águas da Serra os valores foram superiores ao permitido para todos os pontos exceto pra dois pontos no período seco, enquanto que para o ribeirão Graminha os resultados foram superiores para quatro pontos no período úmido. Nas amostras de sedimento o elemento Cu ultrapassou o valor estabelecido pela legislação em ambos os mananciais. Os valores para Pb nas amostras de sedimento também foram ultrapassados para todas as amostras do ribeirão Águas da Serra e em alguns pontos do Graminha. Os resultados obtidos para Cr foram excedidos em três pontos no período húmido e em dois pontos no período seco para o ribeirão Águas da Serra, e no Graminha apenas no período seco os valores para dois pontos foram excedidos. Para Ni e Zn em apenas alguns pontos foram observados valores acima do permitido. A metodologia aplicada foi eficiente porque permitiu a determinação dos metais a níveis exigidos pela legislação brasileira. As concentrações dos metais foram superiores aos valores máximos permissíveis estabelecidos pela legislação vigente para vários elementos tanto nas amostras de água quanto nas amostras de sedimento. Os resultados apontam para a necessidade de ações para recuperar a qualidade dos mananciais bem como protegê-los de novas alterações antrópicas negativas. Palavras Chave: Metais pesado, Água ¿ Qualidade, Sedimentos, Poluição -- Aspectos Ambientais, Meio ambiente, Fluorescência de raio X, Síncrotron
Abstract: The city of Limeira is located in the State of São Paulo and has expressive economy, with industries in several productive sectors, as galvanization industries for the jewels, semi-jewels and bijoux production. Aiming to explain the anthropogenic influence in the sources, the water and sediment qualities of the Graminha and Águas da Serra brooks were evaluated whose springs are in the urban zone of Limeira. The metal determination was performed using Synchrotron Radiation Total Reflection X-Ray Fluorescence (SRTXRF). The detection limits for water samples were in the range of 0.50 to 0.05 µg.L-1 for Ca and Zn, respectively while for sediment samples the detection limits were 0.22 to 0.02 µg.g-1 for the same elements. For water samples in both brooks and for all periods (dry and humid) the concentrations of Al and Fe were higher than the maximum permissive values (MPV) established by the legislation. For Zn and Cu the same behaviour was observed. For Cr and Ni just some locations presented values higher than MPV for water samples. Moreover in Águas da Serra brook values higher than MPV were observed for all points except for two points in the dry period, for Graminha 12 stream the results were higher for four sample locations in the humid period. For sediment samples Cu surpass the value established by the legislation for both springs. For Pb the values surpass the limit for all samples in Águas da Serra and some points for Graminha stream. The results for Cr in sediment samples were surpassed for three points in the humid period and two points in the dry period for Águas da Serra brook, and in Graminha just in the dry period for two points the values were exceeded. For Ni and Zn only a few points surpassed the limits for both springs.The applied methodology was efficient because the detection limits turned possible the determination of the metals in levels in according to legislation. The metal concentrations were higher than the maximum permisse values established by the Brazilian Legislation for several elements in water and sediment samples. The results point to the action necessity to recover the quality of the sources as well as to protect the brooks of new negative anthropogenic alterations. Keywords: Heavy metals, Water quality, Sediment, Pollution, Environment, Synchrotron Radiation Total Reflection X-Ray Fluorescence (SR-TXRF)
Mestrado
Saneamento e Ambiente
Mestre em Engenharia Civil
32
Graça, Cátia Alexandra Leça. "DEGRADATION OF PERSISTENT PESTICIDES VIA ADVANCED OXIDATION AND REDUCTIVE PROCESSES." Doctoral thesis, Universidade de São Paulo, 2017. http://hdl.handle.net/10362/48570.
Full textAbstract:
In this Thesis either advanced oxidation or reductive processes are investigated for the degradation of two pesticides considered persistent in the environment: amicarbazone (AMZ) and chlorpyrifos (CP). In chapter I, different advanced oxidation processes (AOPs) driven by sulfate (SO4o-) and hydroxyl radicals (oOH) were applied to the degradation of AMZ. In the first study, several persulfate (PS) activated reactions were explored for AMZ degradation, namely activation with UVA radiation, Fe(II) and H2O2, as well as the combination of UVA radiation with Fe(II), Fe(III) and Fe(III)-complexes. Here, the influence of different reaction variables, such as solution pH, reactants and pesticide initial concentrations, addition of a second oxidant (H2O2) and the addition of different iron catalysts were also investigated. Control experiments regarding the photolysis of iron species in the absence of PS captured our interest and, with the aim of exploring more deeply this process on AMZ degradation, a second investigation was carried out. In this second study, a Doehlert experimental design was applied to investigate the simultaneous effects of two variables on AMZ degradation: pH and Fe(III):carboxylate ratio, where the carboxylate could be oxalate, citrate or tartrate. A response surface model for the observed degradation rate (kobs) as a function of pH and Fe(III):carboxylate ratio was obtained. The processes explored in both aforementioned studies revealed to be effective for AMZ removal, although nothing is known yet about their effectiveness regarding toxicity removal. Given that, a third study was carried out, where the toxicity of AMZ solutions, before and after submission to the processes studied was evaluated towards five microorganisms: Vibrio fischeri (acute toxicity), Tetrahymena thermophile, Chlorella vulgaris (chronic toxicity), Escherichia coli and Bacilus subtilis (antimicrobial activity). The last investigation detailed in chapter I is related with the application of zero-valent-metals on PS activation, which is a subject that links this chapter with the following one. For that, zero-valent-iron (ZVI) was investigated as a PS activator and the influence of variables that help to assess the environmental applicability of this process. In general, organochlorine pesticides reveal a higher resistance to oxidation than reduction, the latter process preferred when the aim is to degrade that important class of contaminants. Therefore, in chapter II the reductive degradation of CP by means of zero-valent-metals and bimetallic particles was investigated. ZVI has been extensively applied for that purpose. However, besides iron, other zero-valent metals can be potential reactive materials for reductive degradation and hence, in this study, the effectiveness of Zn0 and Cu0 was also explored in comparison to that widely reported for ZVI. Furthermore, two different ways of enhancing metals reactivity were here explored: i) by coating ZVI or Zn0 with a more noble metal (Cu), in order to analyze the copper catalytic effect on the bimetallic system; ii) by different surface pretreatments.Na presente Tese de Doutorado foram abordados tanto processos oxidativos avançados (POA), como processos redutivos por metais de valência zero, na degradação de dois pesticidas considerados persistentes no meio ambiente: amicarbazona (AMZ) e clorpirifós (CP). No capítulo I são apresentados os estudos realizados com diversos POA, mediados por radicais sulfato (SO4o-) e hidroxila (oOH), aplicados da AMZ. Num primeiro estudo foi explorada a ativação do oxidante persulfato (PS), de diferentes formas, tais como radiação UVA, H2O2 e Fe(II), assim como a combinação de radiação UVA com Fe(II), Fe(III) e complexos de Fe(III). Aqui também foram investigados os efeitos de diversas variáveis reacionais, tais como pH, concentração inicial de reagentes e de pesticida, adição de um segundo oxidante (H2O2) e adição de diferentes espécies de ferro. Os testes realizados, para efeito de controle, referentes à irradiação das espécies de Fe(III) na ausência de PS, despertaram o interesse para um estudo mais aprofundado sobre o efeito da fotólise destas espécies na degradação da AMZ, surgindo assim o segundo trabalho. Neste utilizou-se um projeto experimental de Doehlert, para avaliar o efeito de duas variáveis em simultâneo quanto à degradação da AMZ: pH e proporção Fe(III): ligante, sendo o ligante um dos seguintes carboxilatos: oxalato, citrato ou tartarato. Um modelo de superfície de resposta, que correlaciona a taxa de degradação observada (kobs) em função do pH e proporção Fe(III):ligante foi obtido para cada um dos complexos de Fe(III) estudados. Os processos explorados, tanto no primeiro como no segundo estudo, se mostraram eficazes na remoção da AMZ, porém nada se sabe acerca da remoção da toxicidade. Para tal, foi desenvolvido um terceiro estudo dedicado à avaliação da toxicidade da solução de AMZ, antes e após a aplicação de cada um dos processos anteriormente abordados, contra cinco micro-organismos: Vibrio fischeri (toxicidade aguda); Tetrahymena thermophila, Chlorella vulgaris (toxicidade crônica); Escherichia coli e Bacilus subtilis (atividade antimicrobiana). O último estudo abordado no capitulo I é referente à aplicação de metais de valência zero também nos POA, correlacionado assim o capítulo I e o capítulo II. Como tal, foi feito um estudo de ativação de PS por meio de ferro de valência zero (Fe0), em que se investigou a influência de diversas variáveis por forma a inferir sobre a aplicabilidade prática deste processo. Pesticidas organoclorados apresentam maior resistência à degradação por processos oxidativos do que redutivos, sendo preferível o último na degradação desta importante classe de contaminantes. Como tal, o capítulo II se refere à degradação redutiva, por meio de diferentes metais de valência zero e partículas bimetálicas, do pesticida organoclorado CP. Além do amplamente explorado Fe0, outros metais podem ser aplicados neste processo, pelo que, neste estudo, explorou-se a potencialidade de Zn0 e Cu0 comparativamente ao primeiro. Ainda neste estudo foram investigadas duas formas de aumentar a reatividade dos metais: i) no caso do Fe0 e Zn0, revestindo com um metal mais nobre (Cu), por forma a observar o efeito catalisador do último no sistema bimetálico; ii) realizando um pré-tratamento à superfície dos metais.
33
Hussain, Mallik Mohd Raihan. "Nonlinear Electromagnetic Radiation from Metal-Insulator-Metal Tunnel Junctions." University of Dayton / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1490823061190116.
Full text
34
Graça, Cátia Alexandra Leça. "Degradation of persistent pesticides via advanced oxidation and reductive processes." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/3/3137/tde-03082017-091224/.
Full textAbstract:
In this Thesis either advanced oxidation or reductive processes are investigated for the degradation of two pesticides considered persistent in the environment: amicarbazone (AMZ) and chlorpyrifos (CP). In chapter I, different advanced oxidation processes (AOPs) driven by sulfate (SO4o-) and hydroxyl radicals (oOH) were applied to the degradation of AMZ. In the first study, several persulfate (PS) activated reactions were explored for AMZ degradation, namely activation with UVA radiation, Fe(II) and H2O2, as well as the combination of UVA radiation with Fe(II), Fe(III) and Fe(III)-complexes. Here, the influence of different reaction variables, such as solution pH, reactants and pesticide initial concentrations, addition of a second oxidant (H2O2) and the addition of different iron catalysts were also investigated. Control experiments regarding the photolysis of iron species in the absence of PS captured our interest and, with the aim of exploring more deeply this process on AMZ degradation, a second investigation was carried out. In this second study, a Doehlert experimental design was applied to investigate the simultaneous effects of two variables on AMZ degradation: pH and Fe(III):carboxylate ratio, where the carboxylate could be oxalate, citrate or tartrate. A response surface model for the observed degradation rate (kobs) as a function of pH and Fe(III):carboxylate ratio was obtained. The processes explored in both aforementioned studies revealed to be effective for AMZ removal, although nothing is known yet about their effectiveness regarding toxicity removal. Given that, a third study was carried out, where the toxicity of AMZ solutions, before and after submission to the processes studied was evaluated towards five microorganisms: Vibrio fischeri (acute toxicity), Tetrahymena thermophile, Chlorella vulgaris (chronic toxicity), Escherichia coli and Bacilus subtilis (antimicrobial activity). The last investigation detailed in chapter I is related with the application of zero-valent-metals on PS activation, which is a subject that links this chapter with the following one. For that, zero-valent-iron (ZVI) was investigated as a PS activator and the influence of variables that help to assess the environmental applicability of this process. In general, organochlorine pesticides reveal a higher resistance to oxidation than reduction, the latter process preferred when the aim is to degrade that important class of contaminants. Therefore, in chapter II the reductive degradation of CP by means of zero-valent-metals and bimetallic particles was investigated. ZVI has been extensively applied for that purpose. However, besides iron, other zero-valent metals can be potential reactive materials for reductive degradation and hence, in this study, the effectiveness of Zn0 and Cu0 was also explored in comparison to that widely reported for ZVI. Furthermore, two different ways of enhancing metals reactivity were here explored: i) by coating ZVI or Zn0 with a more noble metal (Cu), in order to analyze the copper catalytic effect on the bimetallic system; ii) by different surface pretreatments.Na presente Tese de Doutorado foram abordados tanto processos oxidativos avançados (POA), como processos redutivos por metais de valência zero, na degradação de dois pesticidas considerados persistentes no meio ambiente: amicarbazona (AMZ) e clorpirifós (CP). No capítulo I são apresentados os estudos realizados com diversos POA, mediados por radicais sulfato (SO4o-) e hidroxila (oOH), aplicados da AMZ. Num primeiro estudo foi explorada a ativação do oxidante persulfato (PS), de diferentes formas, tais como radiação UVA, H2O2 e Fe(II), assim como a combinação de radiação UVA com Fe(II), Fe(III) e complexos de Fe(III). Aqui também foram investigados os efeitos de diversas variáveis reacionais, tais como pH, concentração inicial de reagentes e de pesticida, adição de um segundo oxidante (H2O2) e adição de diferentes espécies de ferro. Os testes realizados, para efeito de controle, referentes à irradiação das espécies de Fe(III) na ausência de PS, despertaram o interesse para um estudo mais aprofundado sobre o efeito da fotólise destas espécies na degradação da AMZ, surgindo assim o segundo trabalho. Neste utilizou-se um projeto experimental de Doehlert, para avaliar o efeito de duas variáveis em simultâneo quanto à degradação da AMZ: pH e proporção Fe(III): ligante, sendo o ligante um dos seguintes carboxilatos: oxalato, citrato ou tartarato. Um modelo de superfície de resposta, que correlaciona a taxa de degradação observada (kobs) em função do pH e proporção Fe(III):ligante foi obtido para cada um dos complexos de Fe(III) estudados. Os processos explorados, tanto no primeiro como no segundo estudo, se mostraram eficazes na remoção da AMZ, porém nada se sabe acerca da remoção da toxicidade. Para tal, foi desenvolvido um terceiro estudo dedicado à avaliação da toxicidade da solução de AMZ, antes e após a aplicação de cada um dos processos anteriormente abordados, contra cinco micro-organismos: Vibrio fischeri (toxicidade aguda); Tetrahymena thermophila, Chlorella vulgaris (toxicidade crônica); Escherichia coli e Bacilus subtilis (atividade antimicrobiana). O último estudo abordado no capitulo I é referente à aplicação de metais de valência zero também nos POA, correlacionado assim o capítulo I e o capítulo II. Como tal, foi feito um estudo de ativação de PS por meio de ferro de valência zero (Fe0), em que se investigou a influência de diversas variáveis por forma a inferir sobre a aplicabilidade prática deste processo. Pesticidas organoclorados apresentam maior resistência à degradação por processos oxidativos do que redutivos, sendo preferível o último na degradação desta importante classe de contaminantes. Como tal, o capítulo II se refere à degradação redutiva, por meio de diferentes metais de valência zero e partículas bimetálicas, do pesticida organoclorado CP. Além do amplamente explorado Fe0, outros metais podem ser aplicados neste processo, pelo que, neste estudo, explorou-se a potencialidade de Zn0 e Cu0 comparativamente ao primeiro. Ainda neste estudo foram investigadas duas formas de aumentar a reatividade dos metais: i) no caso do Fe0 e Zn0, revestindo com um metal mais nobre (Cu), por forma a observar o efeito catalisador do último no sistema bimetálico; ii) realizando um pré-tratamento à superfície dos metais.
35
Martis, V. "Synchrotron radiation studies of multicomponent metal oxides." Thesis, University College London (University of London), 2012. http://discovery.ucl.ac.uk/1388216/.
Full textAbstract:
The work described in this thesis is focused on the development of characterization methods for determining the structure of multicomponent metal oxides using synchrotron radiation techniques, in particular, X-ray Absorption Fine Structure (XAFS) and Energy Resolved Electron Yield X-ray Absorption Spectroscopy (EREY– XAS). XAFS is a superior technique for determining the local structure of, for example, transition metals that are used as dopants in very low concentrations. It also provides information on early stages of crystallization processes before a material develops sufficient long range order. Energy resolved XAS was developed as an alternative to conventional transmission and fluorescence techniques which probe mainly the bulk of materials. This techniques yield information about the local structure from the near surface region of materials. The other complementary techniques used for characterization of materials were XRD, Raman spectroscopy, X-ray Photoelectron Spectroscopy (XPS) and Scanning Electron Microscopy (SEM). New insights about formation of Bi2MoO6 crystallites from an amorphous gel below 200oC were obtained with a novel in situ setup, in which XAFS and XRD was combined with RAMAN spectroscopy in a single experiment. Combined XRD/XAFS technique was used for determining the growth mechanism of Bi2MoO6 formed under hydrothermal conditions from an amorphous gel. The reaction kinetics was quantified by using the Avrami-Erofe’ev formalism. The surface sensitive of EREY–XAS was performed on several materials in particular chromium doped Fe2O3 catalysts and cobalt substituted aluminophosphates such as CoAlPO-18 and CoAlPO-34. The sensitivity of technique was assessed by comparison with conventional XAS techniques and XPS. Finally, the interactions of a synchrotron X-ray beam with a sample were studied. In particular, the effects of exposure to a monochromatic 10 keV X-ray beam on thermally induced crystallization of lithium disilicate glass were investigated.
36
Collins, John L. "Radiation effects in metal-oxide-semiconductor capacitors." Thesis, Aston University, 1987. http://publications.aston.ac.uk/8078/.
Full textAbstract:
An investigation has been undertaken into the effects of various radiations on commercially made Al-SiO2-Si Capacitors (MOSCs). Detailed studies of the electrical and physical nature of such devices have been used to characterise both virgin and irradiated devices. In particular, an investigation of the nature and causes of dielectric breakdown in MOSCs has revealed that intrinsic breakdown is a two-stage process dominated by charge injection in a pre-breakdown stage; this is associated with localised high-field injection of carriers from the semiconductor substrate to interfacial and bulk charge traps which, it is proposed, leads to the formation of conducting channels through the dielectric with breakdown occurring as a result of the dissipation of the conduction band energy. A study of radiation-induced dielectric breakdown has revealed the possibility of anomalous hot-electron injection to an excess of bulk oxide traps in the ionization channel produced by very heavily ionizing radiation, which leads to intrinsic breakdown in high-field stressed devices. These findings are interpreted in terms of a modification to the model for radiation-induced dielectric breakdown based upon the primary dependence of breakdown on charge injection rather than high-field mechanisms. The results of a detailed investigation of charge trapping and interface state generation in such MOSCs due to various radiations has revealed evidence of neutron induced interface states, and of the generation of positive oxide charge in devices due to all of the radiations tested. In particular, the greater the linear energy transfer of the radiation, the greater the magnitude of charge trapped in the oxide and the greater the number of interface states generated. These findings are interpreted in terms of Si-H and Si-OH bond-breaking at the Si-SiO2 interface which is enhanced by charge carrier transfer to the interface and by anomalous charge injection to compensate for the excess of charge carriers created by the radiation.
37
Peters, Chris (Christopher Joseph) Carleton University Dissertation Engineering Electrical. "MOSFET based gamma radiation detector." Ottawa, 1992.
Find full text
38
Wahle, Peter Joseph 1961. "Radiation effects on power MOSFETs under simulated space radiation conditions." Thesis, The University of Arizona, 1989. http://hdl.handle.net/10150/277024.
Full textAbstract:
Application of power MOSFETs in spaceborne power converters was simulated by exposing devices to low-dose-rate ionizing radiation. Both radiation-hardened and nonhardened devices were tested with constant and switched gate biases during irradiation. In addition, some of the devices were under load. The threshold-voltage shifts were strongly bias dependent. The threshold-voltage shift of the nonhardened parts was approximately dose-rate independent, while the hardened parts exhibited significant dose-rate dependence. A pre-anneal dose-rate dependence was found for the interface-state buildup of the switched and positively biased devices, but the results for the switched devices were qualitatively different than those for the positively biased devices. The buildup of interface trapped charge was found to be the primary contributor to mobility degradation, which results in reduced drive capability and slower operation of the devices. These results indicate that new methods need to be utilized to accurately predict the performance of power MOSFETs in space environments.
39
Graziani, Luca. "Cosmological radiative transfer through metals in CRASH." Diss., lmu, 2012. http://nbn-resolving.de/urn:nbn:de:bvb:19-149355.
Full text
40
Falco, Tony. "Analysis of metalfilm and novel metala-Se portal detectors." Thesis, McGill University, 1999. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=35879.
Full textAbstract:
Measurements of modulation transfer function (MTF), noise power spectrum (NPS), and detective quantum efficiency (DQE) for metal/film portal detectors are reported for the Cobalt-60 and 10 MV spectra. The detectors consist of a double-emulsion portal film secured between plates of aluminum, copper, brass or lead with thicknesses from 0 to 4.81 mm. The study of MTF, NPS, and DQE shows that both photons and secondary electrons produced within the front-plate and backscattered electrons from the back-plate affect metal/film portal imaging. Study of DQE indicates that the best portal detectors are those without back-plates, and with high density front-plates with thicknesses less than the maximum electron range.This MTF data was modeled with the logit analysis. It is shown that the parameters resulting from the logit analysis depend on the mass thickness and the atomic number of the metal plates.
Metal/amorphous selenium (a-Se) electrostatic-based detectors have been developed for portal imaging. The detectors consist of a-Se photoconductive layers of varied thicknesses deposited on plates of varying thicknesses of aluminum, copper, and stainless steel. The metal-plates of the detectors face the incident 6 MV and Co-60 photon spectra during imaging. The sensitivity of the a-Se detectors to dose, electric field across the a-Se layer, plate type, and a-Se thickness is studied. A model showing a cubic relationship between the a-Se latent surface voltage and dose is derived and experimentally verified. A contrast-detail phantom is used to study the image quality and contrast-resolution characteristics of the metal/a-Se detectors. The metal/a-Se detectors produce better quality contrast-detailed images at a considerably lower dose than that offered by the other commercial available portal systems, mainly due to the low inherent noise of the novel detectors.
A semi-automatic technique for the direct set-up alignment of radiosurgical circular fields from an isocentric linac to treatment room laser cross-hairs is described. Because film or a-Se is each sensitive to laser and ionizing radiation, they are used to acquire images of the positioning lasers superimposed directly onto the radiosurgical circular fields. An algorithm extracts the coordinates of the center of the collimator image and of the intersection of the laser cross-hair image and subsequently determines the deviation, to within a precision of ∼0.04 mm. The technique is also used to perform quality assurance on a Clinac-18 linac and shows a (0.53 +/- 0.05) mm wobble from the nominal isocenter of the linac.
41
Guigues, Stéphanie. "Caractérisation des interactions physico-chimiques entre le cuivre et les racines comme base de développement d'un modèle d'évaluation de la phytodisponibilité des éléments traces." Thesis, Aix-Marseille, 2015. http://www.theses.fr/2015AIXM4307.
Full textAbstract:
Cette étude a été dédiée au développement d’une nouvelle approche de modélisation de la phytodisponibilité des éléments traces. Cette approche a été employée pour prédire l’adsorption du cuivre (Cu) sur des racines de blé et de tomate. Plusieurs techniques analytiques (titrages acido-basiques, résonance magnétique nucléaire, spectroscopie d’absorption X) ont été employées et croisées avec des résultats de modélisation. Dans un premier temps, la réactivité des racines a été caractérisée. Les racines étant constituées de parois apoplasmiques et de membranes plasmiques, la contribution respective de ces deux compartiments végétaux aux propriétés de complexation des racines a été évaluée. L’étude a ensuite été focalisée sur la complexation du Cu au sein des racines et sur l’évolution de cette complexation en fonction des conditions physico-chimiques du milieu. Grâce aux résultats obtenus sur la caractérisation des racines et à l’acquisition d’un jeu varié de données expérimentales sur la complexation du Cu, le modèle a pu être paramétré. Il a été montré que les propriétés de complexation des racines de blé et de tomate proviennent conjointement des membranes plasmiques et des parois apoplasmiques. La spéciation du Cu au sein des racines était partagée entre les composés pectiques des parois apoplasmiques et les protéines enchâssées à la fois dans les parois apoplasmiques et les membranes plasmiques. Un modèle propre aux racines a pu être développé sur la base d’un modèle existant dédié à la réactivité des substances humiques. Le modèle WHAM-THP, présenté dans cette étude, est un premier pas vers un nouvel outil d’évaluation de la phytodisponibilité des éléments tracesThis study has been dedicated to the development of a new modeling approach of trace element phytoavailability, focusing on binding reactions between trace element and plant roots. This approach was used to predict copper (Cu) adsorption on wheat and tomato roots. Several analytical techniques (acid-base titrations, nuclear magnetic resonance of carbon 13, X-ray absorption spectroscopy) were used and crossed with modeling results. At first, plant root reactivity was characterized. Because plant roots are consist of cell walls and plasma membranes, the relative contribution of these two compartments in root binding properties was evaluated. The study was then focused on Cu binding reactions on roots and the effects of physico-chemical conditions (pH, ionic strength, presence of cations) on copper binding. The model has been set thanks to results on root characterization obtained and the acquisition of a set of experimental data on Cu binding. It has been shown that binding properties of wheat and tomato roots came from both cell walls and plasma membranes. Copper speciation in roots was shared, almost evenly, between cell wall pectic compounds and proteins embedded in cell walls and plasma membranes. A model, specific to plant roots, has been developed on the basis of a current model dedicated to the humic substances reactivity. The WHAM-Terrestrial Higher Plants model presented in this study is a first step towards a new tool for assessing the availability of trace elements for plants
42
Baumer, Richard E. (Richard Edward). "Atomistic simulations of radiation damage in amorphous metal alloys." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/88363.
Full textAbstract:
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2013.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 121-131).
While numerous fundamental studies have characterized the atomic-level radiation response mechanisms in irradiated crystalline alloys, comparatively little is known regarding the mechanisms of radiation damage in amorphous alloys. Knowledge of collision cascade dynamics is lacking, both with respect to the possibility of sub-cascade formation and concerning the types of damage created in individual cascades. This Thesis resolves these knowledge gaps through a systematic simulation study of the radiation response of amorphous metal alloys. Using a molecular dynamics simulation of /2 MeV ion irradiation in a realistic 2 billion-atom molecular dynamics simulation in amorphous Cu₅₀Nb₅₀, I show that radiation creates isolated nanometer-scale zones with rapidly quenching liquids. Quenched liquids reach large pressures and emit stress pulses that trigger polarized plastic deformation in adjacent material. In order to identify liquid zones in irradiated amorphous Cu₅₀Nb₅₀, I use molecular dynamics simulations to characterize the properties and glass transition temperature of uniform liquid Cu-Nb alloys. I show that radiation-induced liquid zones rapidly quench to material with the same properties as a uniform liquid quenched at an equivalent quench rate approaching 1014 K/s. These "super-quenched zones" (SQZs) are approximately 10 nm in diameter and provide a mechanistic explanation for radiation-induced swelling and ductilization in metallic glasses. The identification of plasticity adjacent to SQZs is an unexpected damage mechanism that could prove a limiting factor for the application of amorphous alloys in radiation environments. To aid selection of amorphous alloys with resistance to collision-induced plasticity, I formulate a micro-mechanical model for collision-induced plasticity in irradiated metallic glasses. The analytical model successfully ranks the damage-resistance of irradiated Cu- Nb alloys and should enable selection of amorphous alloys with optimized radiation tolerance. Finally, through characterization of quenched Cu₅₀Nb₅₀, I reveal that glass transition in Cu₅₀Nb₅₀ occurs by gelation due to formation of a mechanically stiff, percolating network of atoms with icosahedral local packing at the interfaces between compositionally enriched regions. These features of glass transition are similar to gelation processes in polymeric and colloidal gels and suggest new approaches for understanding glass transition in bulk metallic glasses.
by Richard E. Baumer.
Ph. D.
43
Falco, Tony. "MTF, NPS and DQE analysis of portal metal-platefilm detectors." Thesis, McGill University, 1996. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=23885.
Full textAbstract:
Previous studies of modulation transfer function (MTF), noise power spectrum (NPS), and detective quantum efficiency (DQE) of metal-plate/film portal detectors have been performed on limited combinations of front and back metal-plates. We report on these parameters for an extensive set of forty-nine front-back metal-plate combinations. The portal detector consists of a double emulsion RP (Kodak localization therapy) film placed between metal-plates: Al, Cu, brass and Pb of thicknesses varying from 0.30 to 4.80 mm. Radiation sources included a Theratron Co-60 unit, and a Varian Clinac-18 linear accelerator delivering a polyenergetic 10 MV X-ray spectrum. In terms of the absolute efficiency of the detectors, the best DQE is obtained with the detector consisting of a 1.75 mm Cu front plate and a 1.62 mm Al back plate for the Clinac-18, and with the detector consisting of a 0.95 mm Cu front plate and a 0.80 mm Cu or a 1.62 mm Al back plate for the Co-60 gamma ray source.
44
Charron, Luc G. "Radiative properties of molybdenum sulfide and other transition metal dichalcogenides." Thesis, University of Ottawa (Canada), 2004. http://hdl.handle.net/10393/26599.
Full textAbstract:
Low temperature radiative properties of the layered transition metal dichalcogenides 2H-MoS2, 2H-WS2 and 2H-WSe 2 are investigated. Synthetically grown crystals of all three materials, natural 2H-MoS2 single crystals and several 2H-MoS2 and 2H-WS2 commercial powders are studied. Steady-state photoluminescence (PL) measurements performed on the samples reveal two distinct radiative regions in the near infrared. The first region consisting of several sharp lines is produced by bound excitons related to the halogen transport agent intercalated within the van der Waals gap of the layered compounds. The second weaker region, composed of a broad spectral band, originates from the radiative recombination between an intrinsic crystal lattice defect center and the valence band in the conditions of a strong electron-phonon coupling. Time decay analysis of the bound excitonic radiative transitions is performed with time-resolved and PL intensity ratio measurements. The spectral and temperature dependence of the total radiative emissions of all three compounds are described in the framework of a two-channel kinetic recombination model in thermal equilibrium conditions. A configuration coordinate diagram is also constructed for 2H-MoS 2. PL intensity measurements performed on the 2H-MoS2 and 2H-WS2 synthetic crystals reveal a sublinear PL dependence on excitation intensity. Finally a technique developed to intercalate halogen molecules in natural 2H-MoS2 single crystals is described.
45
Subahi, A. M. "Assessment and development of novel transition metal oxide radiation detectors." Thesis, University College London (University of London), 2011. http://discovery.ucl.ac.uk/1325634/.
Full textAbstract:
New radiation detector materials based on transition metal oxides [TMOs] are being developed for applications in radiation protection. The TMOs are cheap, simple to manufacture and have semiconducting properties, indicating either p-type or n-type characteristics. Thus, p-n hetrojunction diodes may be formed by combining p-type and n-type specific TMOs to produce radiation sensitive detectors. This is done by layering the materials in a flame-spraying process. Work by Mott on amorphous semiconductors has inspired this work to addressing the theoretical analysis of the disordered TMOs. It is found that charge carriers are polarons due to the presence of localised states in the TMOs. Moreover, the charge transport mechanism is ―Mott Hopping‖, whereby conductivity obeys the relationship of log σ ~ -[1/T]1/4. Practically, early studies have shown that TMO detectors perform successfully at room temperature as ionising radiation detectors. However, limitations existed in their very early design, which used Cu tape electrodes and, though demonstrated acceptable levels of response. This response did not meet the full expectation of the TMO detectors. New electrode deposition and materials, therefore, are sought to form ohmic and well-deposited electrodes. In this work, electrodes of Ag and Al were physically vapour deposited on either side of the detector. The electron microscope was used to fully evaluate the structure of the TMO materials. It is found that the flame-spray deposition is uniform with 3.56% of surface variation. Bulk and surface were scanned and were found to vary by 3.18% with variation in oxygen level of 0.55%. Mechanical polishing has shown a high level of validity to improve the surface by 94%. TMOs have demonstrated superior absorption efficiency of 19%, compared to Si [5%] of 200 μm thickness with 33 keV of incident photon energy. In contrast, CZT showed a superior intrinsic efficiency of 0.47%, compared to TMOs [0.02%] at 33 keV. In terms of x-ray and UV radiation tests, excellent correlations between TMO detectors, and IC and Si photodiode were observed. Also, detection was found to be uniform as expected across the p-n hetrojunction with a variation of 6% as an average. Finally, the TMO detectors were claimed to be feasible for detection of photons in the energy range of UV up to diagnostic x-ray.
46
Cui, Zhenpeng. "Radiation Induced Synthesis of Conducting Polymers and their Metal Nanocomposites." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLS165/document.
Full textAbstract:
L‘objectif du présent travail est de démontrer la versatilité de méthodologie radiolytique et de l‘étendre à la synthèse de différents PCs dans l‘eau. Le poly(3,4-ethylènedioxythiophène), PEDOT, et le polypyrrole, PPy, ont ainsi été préparés avec succès et caractérisés en solution aqueuse, ou après dépôt sur substrat, par des techniques spectroscopiques et microscopiques. La stabilité thermique et la conductivité électrique de ces matériaux radio synthétisés ont été étudiées et comparées aux propriétés des PCs produits par les méthodologies traditionnelles. Nous avons étudié l‘influence de la nature des espèces radiolytiques oxydantes, de la force ionique du milieu, du pH de la solution et de la présence de surfactants, sur le mécanisme de croissance des PCs, sur le rendement de polymérisation, sur la morphologie des matériaux radio synthétisés ainsi que sur les propriétés optiques et électriques de ces derniers. Nous avons utilisé la radiolyse pour la synthèse de nano composites hybrides à base de PCs et de métaux de transition. Plusieurs voies de synthèse ont été développées : synthèse en une ou deux étapes, par oxydation ou réduction des monomères. La nouvelle stratégie de synthèse par radiolyse, qui est décrite dans ce manuscrit, ouvre la voie à la préparation de très nombreuses familles de PCs et de leurs composites, que ce soit en solution aqueuse ou dans des environnements alternatifs (en milieu organique, sur support, en milieu hétérogène), ce qui laisse augurer de nombreuses applications fort prometteusesThe aim of the present work is to demonstrate the versatility of the gamma (γ)-rays based radiolytic method and to extend our methodology to the synthesis of various conducting polymers (CPs) in water in different experimental conditions. Poly(3,4-ethylenedioxythiophene) (PEDOT) and polypyrrole (PPy) conjugated polymers were successfully prepared and characterized in solution and after deposition by complementary spectroscopic and microscopic techniques. Also their thermal stability and their electrical conductivity were studied and compared with those of CPs prepared by conventional methods. The influence of the nature of radiation-induced oxidizing radicals, of the ionic strength, of the medium, of the pH, of the presence of surfactant-based soft templates on the growth mechanism, on the efficiency of polymerization, on the morphology of the obtained CPs as well as on their absorption and conducting properties was checked. Also, the radiolytic method was extend to the synthesis of CPs/noble metal nanocomposites. Different preparation methodologies were developed based on two-step method and one-pot method, by using oxidation route or reduction route. Our new radiolytic strategy described and extended in this manuscript opens the way for the preparation of different kinds of CPs and CPs nanocomposites not only in aqueous solutions but also in various environments foreshadowing many promising applications
47
Rodrigues, Luís Gustavo Pires. "Aplicação do modelo da soma-ponderada-de-gases-cinza na simulação da transferência radiativa em chamas difusivas laminares de metano diluído com CO2 e N2." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2016. http://hdl.handle.net/10183/151382.
Full textAbstract:
Simulações acopladas do escoamento reativo e dos processos de transferência de calor para o estudo de chamas são problemas dispendiosos computacionalmente. A transferência de calor por radiação em processos de combustão, devido às elevadas temperaturas, é o processo de troca energética dominante. Ainda, o comportamento altamente irregular do coeficiente de absorção com o comprimento de onda se constitui em uma dificuldade adicional na modelagem da transferência radiativa em meios participantes. Para contornar essa dificuldade modelos espectrais foram desenvolvidos com o objetivo de simular o comportamento de um gás real. Dentre esses modelos destacam-se o gás cinza (GG: Gray Gas), o mais simples, que negligencia o comportamento espectral do coeficiente de absorção, e o modelo da soma-ponderada-de-gases-cinza (WSGG: Weighted-Sum-of-Gray-Gases) onde a integração sobre todo o espectro é substituída por um número finito de gases cinza. Com o avanço de ferramentas computacionais, principalmente códigos CFD (Computational Fluid Dynamics), abordagens computacionais se tornaram atrativas frente ou em complemento às abordagens experimentais. Desse modo, o presente trabalho tem por objetivo a aplicação dos modelos WSGG e GG com novas correlações na simulação detalhada de chamas difusivas laminares de metano diluído com dióxido de carbono e nitrogênio com o código CFD comercial ANSYS/Fluent. Foram desenvolvidas rotinas de usuário (UDF: User-Defined Functions) para o acoplamento dos modelos espectrais ao código CFD. A verificação das rotinas de usuário foi realizada comparando os resultados obtidos via simulação Fluent com dados obtidos pelo modelo WSGG com um código FORTRAN próprio desenvolvido pelo grupo de pesquisa do Laboratório de Radiação Térmica (LRT/UFRGS) para o problema unidimensional de superfícies negras e infinitas preenchidas por um meio não-isotérmico e não-homogêneo. Os erros encontrados para o fluxo de calor radiativo nas superfícies e para o termo fonte radiativo ao longo do meio foram da ordem de 1% indicando o funcionamento correto das rotinas UDF acopladas ao Fluent. Por fim, as rotinas foram aplicadas na simulação numérica para chamas de potência constante com diluição dos reagentes e os dados obtidos com a solução numérica foram comparados com dados experimentais para a fração radiante e fluxo de calor radiativo. Os desvios médios encontrados para o fluxo de calor radiativo ficaram em torno de 10% para todas as chamas, excetuando as chamas com diluição de CO2 de 30%, 40% e 50%, em volume, para as quais os desvios médios ficaram em torno de 15%. O termo fonte para as chamas apontou para a predominância da emissão do meio em relação à absorção. Todas as chamas estudadas se encontram no regime opticamente fino (optically thin) para o qual, segundo apontam estudos da literatura, a escolha do modelo espectral possui impacto pequeno em resultados globais da chama como a temperatura e a concentração das espécies na mistura. Nesse aspecto os resultados encontrados concordaram com a previsão da literatura, entretanto para a transferência radiativa, o modelo GG se mostrou sensivelmente menos preciso em comparação ao modelo WSGG, principalmente para a fração radiante e para o fluxo radiativo na região da pluma aquecida, indicando a dependência do modelo espectral adotado.Coupled simulations of the reactive flow with the heat transfer processes for flame studying are computationally demanding problems. The radiative transfer in combustion processes is the main heat transfer mechanism due to the high temperatures involved. However, the highly irregular behavior o f the absorption coefficient with the wavenumber composes in an additional difficulty on modeling the radiative transfer in participating media. In order to overcome this issue, spectral models were developed with the objective of simulate the behavior of real gases. Some of the most known models are the gray gas (GG) for which the spectral behavior of the radiative properties of the medium is neglected and the weighted-sum-of-gray-gases (WSGG) for which the integration over the entire spectrum is replaced by a summation over a finite number of gray gases with constant absorption coefficients. With the development of computational tools, mainly Computational Fluid Dynamics (CFD) codes, numerical approaches became attractive instead or in complement of experimental set ups. In this way, the present work aims to couple the WSGG and the GG models with new correlations in a detailed simulation of diffusive laminar flames of methane diluted with carbon dioxide and nitrogen with the commercial CFD code ANSYS/Fluent. User-defined functions (UDF) were developed to the coupling of the spectral models. The verification was carried out through the WSGG model by comparing the Fluent solution with a solution obtained with a FORTRAN code developed by the Thermal Radiation Laboratory (LRT/UFRGS) research group for the one-dimensional system of black surfaces filled with a non-homogeneous and non-isothermal medium. The deviations for the radiative heat flux for the walls and the radiative heat source along the domain were of 1% or less, indicating the correct coupling between the UDF routines and the CFD code. Finally, the UDF were applied in the solution of constant power flames with fuel diluted with carbon dioxide and nitrogen. The obtained data was then compared with experimental measurements for the radiant fraction and the radiative heat flux along the flame axis. The average deviations found were in order of 10% for all flames, except for the flames with 30%, 40% and 50% of CO2 dilution, in volume, for which the deviatioms found were in order of 15%. The radiative heat source was plotted and indicated for the medium emission predominance in comparison with the medium absorption. All flames studied were optically thin flames for which, studies pointed, the spectral model have minor impact over global results as flame temperature and mixture concentration. For this aspect the results found showed agreement with the literature studies predictions, however the GG model showed itself less accurate in comparison with the WSGG model for the radiant fraction and the radiative heat flux computations. So the spectral models have influence on the radiative transfer even if its effect on flame structure can be negligible.
48
Phillips, Stanley D. "Developing radiation hardening by design." Thesis, Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/29640.
Full textAbstract:
Thesis (M. S.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2010.Committee Chair: Cressler, John; Committee Member: Citrin, David; Committee Member: Shen, Shyh-Chiang. Part of the SMARTech Electronic Thesis and Dissertation Collection.
49
Hardie, Christopher David. "Micro-mechanics of irradiated Fe-Cr alloys for fusion reactors." Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:a3ac36ba-ca6f-4129-8f37-f1278ef8a559.
Full textAbstract:
In the absence of a fusion neutron source, research on the structural integrity of materials in the fusion environment relies on current fission data and simulation methods. Through investigation of the Fe-Cr system, this detailed study explores the challenges and limitations in the use of currently available radiation sources for fusion materials research. An investigation of ion-irradiated Fe12%Cr using nanoindentation with a cube corner, Berkovich and spherical tip, and micro-cantilever testing with two different geometries, highlighted that the measurement of irradiation hardening was largely dependent on the type of test used. Selected methods were used for the comparison of Fe6%Cr irradiated by ions and neutrons to a dose of 1.7dpa at a temperature of 288°C. Micro-cantilever tests of the Fe6%Cr alloy with beam depths of 400 to 7000nm, identified that size effects may significantly obscure irradiation hardening and that these effects are dependent on radiation conditions. Irradiation hardening in the neutron-irradiated alloy was approximately double that of the ion-irradiated alloy and exhibited increased work hardening. Similar differences in hardening were observed in an Fe5%Cr alloy after ion-irradiation to a dose of 0.6dpa at 400°C and doses rates of 6 x 10-4dpa/s and 3 x 10-5dpa/s. Identified by APT, it was shown that increased irradiation hardening was likely to be caused by the enhanced segregation of Cr observed in the alloy irradiated with the lower dose rate. These observations have significant implications for future fusion materials research in terms of the simulation of fusion relevant radiation conditions and micro-mechanical testing.
50
Leghuel, Hatim A. "Radiation Backscatter of Zirconia." The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1377012297.
Full text