Dissertations / Theses on the topic 'Magnetite'
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Chatman, Shawn Michael Edward. "Morphological and magnetic characterization of electrodeposited magnetite /." Internet access available to MUN users only, 2005. http://collections.mun.ca/u?/theses,85053.
Full textMuxworthy, Adrian R. "Stability of magnetic remanence in multidomain magnetite." Thesis, University of Oxford, 1998. http://ora.ox.ac.uk/objects/uuid:bc70e665-4c54-4ab5-98fa-d43ccecd07a1.
Full textOwings, Paul C. "High Gradient Magnetic Separation of nanoscale magnetite." Thesis, Kansas State University, 2011. http://hdl.handle.net/2097/12020.
Full textDepartment of Civil Engineering
Alexander P. Mathews
Nanoscale magnetite is being examined for possible uses as an adsorbent of heavy metals and for the enhancement of water treatment processes such as stripping of trichloroethylene (TCE) from contaminated water supplies and wastewaters. Methods for recovering nanoscale magnetite must be developed before the particles can be used in water treatment processes. This is necessary because expelling high amounts of particles into the environment will be unacceptable and costly; if captured they can be reused; additionally, they could potentially cause environmental impacts due to their stability in an aqueous environment and possible toxicity. Nanoscale magnetite is superparamagnetic, so it has a high magnetic susceptibility, and hence it is very attracted to magnetized materials. Utilizing the magnetic properties of magnetite may be one possible means of separating the particles from a treatment process. High Gradient Magnetic Separation (HGMS) has been studied for the separation of micron and even tenths of a micron size particles, but there is little experimental data for HGMS of nanoscale magnetite. This research looks to filter nanoscale magnetite through a HGMS and determine the capture efficiency of the filter. Subsequently, the filter was backwashed to determine particle recover efficiencies. The flow rate was adjusted to determine the dependency of particle capture efficiency on cross sectional velocity through the filter. Additionally, particle loading was changed to better understand the correlation of particle loading with capture efficiency. Filtrations for nanoscale magnetite dispersed with sodium tripolyphosphate were also completed as well as filtrations of nanoscale magnetite coated with silica and magnetite silica composites. Experimental data in this research indicates that magnetite nanoparticles can be captured at 99.8% efficiency or higher in a well-designed filtration system. Capture efficiencies around 99.8% have been found for magnetite. The silica coated magnetite and magnetite silica composites were captured at efficiencies as high as 96.7% and 97.9%, respectively. The capture efficiency of the dispersed magnetite is lower than non-dispersed magnetite and most promising at relatively low fluid flow velocities and particle loadings. The maximum capture efficiency for dispersed magnetite particles was 90.3%. Both magnetite and dispersed magnetite were successfully recovered using backwash at pH of 10 to 11.
Harrison, Richard John. "Magnetic properties of the magnetite-spinel solid solution." Thesis, University of Cambridge, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.603779.
Full textMacêdo, Gleyguestone Lopes de 1983. "Síntese e caracterização magnética de nanopartículas do tipo dímero de Ag-Fe3O4." [s.n.], 2012. http://repositorio.unicamp.br/jspui/handle/REPOSIP/278116.
Full textDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin
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Resumo: Neste trabalho, seguindo uma nova rota de síntese, foram produzidas três amostras de nanopartículas do tipo dímero de prata com magnetita (Ag-Fe3O4), onde a única diferença entre elas é no valor da concentração de partículas de prata utilizadas na síntese. As amostras de tipo dímero possuem concentrações de prata iguais a 0,003 g/mL, 0,007 g/mL e 0,01 g/mL e foram chamadas, respectivamente, de AgFeO_1, AgFeO_2 e AgFeO_3. Sobre estes sistemas realizaram-se medidas da magnetização do tipo Zero Field cooling/Field cooling (ZFC-FC) onde se observou nos três sistemas um aumentou brusco da temperatura de irreversibilidade (Tirr) da magnetita quando unida a prata. Também se observou que somente na amostra com menor concentração de prata sofre um grande aumento em sua temperatura de bloqueio (T B), aproximadamente 130K, que pode ser devido a fatores como aumento do tamanho da partícula de magnetita contida no dímero, aglomerações e interações entre particulas. Porém, através de medidas de dicroísmo circular magnético de raios-X (XMCD) observou-se que com a união da prata a magnetita provoca nesta um aumento de seu momento orbital sendo mais intenso para a amostra com menor concentração de prata (AgFeO_1). Tal resultado pode explicar o aumento em Tirr e TB, já que o momento orbital é diretamente proporcional à anisotropia magnética. Por fim, gostaria de salientar que, em conjunto com meu orientador (Prof. Kleber Roberto Pirota) foi decidido optar por uma estrutura na qual inicio com descrição das bases teóricas de interesse, logo comento rapidamente sobre as técnicas experimentais utilizadas e, finalmente, anexo os trabalhos publicados. Porém, como alguns resultados obtidos neste trabalho ainda não foram publicados, decidi resumir-los no final da tese (capítulo 4)
Abstract: In this work, following a new synthesis route, three samples were produced nanoparticle type silver dimer with magnetite (Ag-Fe3O4), where the only difference between them is the value of the concentration of silver particles used in the synthesis. Samples of dimer type silver concentrations have equal 0,003 g/mL, 0,007 g/mL e 0,01 g/mL and were named, respectively AgFeO_1, and AgFeO_2 AgFeO_3. On these systems were expressed as the magnetization of the type Zero Field cooling/Field cooling (ZFC-FC) where it was observed in all three systems a sudden increase in temperature of irreversibility (T IRR) of magnetite attached to silver. It was also observed that the sample with only low silver concentration undergoes a sharp increase in its temperature block (TB), to approximately 130K, which may be due to factors such as increasing the particle size of magnetite contained in the dimer interactions and agglomerations. However, through measures of magnetic circular dichroism X-ray (XMCD) observed that with the union of silver magnetite causes this increased their orbital momentum being more intense for the sample with lower concentration of silver (AgFeO_1). This result may explain the increase in TB and TIRR, since the orbital momentum is directly proportional to the magnetic anisotropy. Finally, let me emphasize that, together with my advisor (Prof. Kleber Roberto Pirota) it was decided to opt for a structure in which beginning with a description of the theoretical bases of interest, just comment quickly on the experimental techniques used and eventually annex published works. However, as some results of this work have not yet been published, I decided to summarize them at the end of the thesis (Chapter 4)
Mestrado
Física
Mestre em Física
Arredondo, Melissa Gayle. "Zero-Dimensional Magnetite." Diss., Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/14151.
Full textVieira, Raquel Nadine Cadete. "Coating of magnetite nanoparticles with chitosan for magnetic hyperthermia." Master's thesis, Universidade de Aveiro, 2016. http://hdl.handle.net/10773/21895.
Full textO cancro é uma das doenças com maior ocorrência na população mundial e com uma elevada taxa de mortalidade. Os principais problemas na luta contra o cancro prendem-se com a dificuldade de diagnóstico precoce, a citotoxicidade associada aos fármacos anticancerígenos usados em quimioterapia convencional e a falta de tratamentos mais eficazes. Com o advento da nanotecnologia, tem havido um crescente interesse na aplicação de nanopartículas e nanoestruturas, nas mais diversas áreas da ciência, nomeadamente em aplicações biomédicas. Neste contexto em particular, as nanopartículas magnéticas apresentam propriedades interessantes, por exemplo, em sistemas de libertação controlada de fármaco e em hipertermia. A sua aplicação em áreas relacionadas com a saúde, como o tratamento de cancro por hipertermia magnética, passa necessariamente por uma boa caracterização das suas propriedades e pela correta avaliação das suas capacidades de libertação de energia sob a forma de calor por indução magnética. Nesse sentido, este trabalho teve como objetivo a síntese de nanopartículas de magnetite devido a sua compatibilidade com o organismo humano e propriedades magnéticas. No entanto, devido ao seu elevado grau de agregação assim como facilidade de oxidação em meios aquosos existe uma necessidade de revestir estas partículas. Para tal, foi utilizado um biopolímero: a quitosana. A ligação do revestimento da quitosana ao núcleo do óxido de ferro foi realizada através de dois tipos de ancoragem: através da dopamina, conhecida pela sua grande afinidade aos grupos aminas e através do ácido cafeico, por apresentar uma similaridade estrutural à dopamina. Para a caracterização estrutural e morfológica das partículas recorreu-se à difração de raios-X (DRX), à espetroscopia de infravermelhos com transformada de Fourier (FTIR), à dispersão dinâmica da luz (DLS), ao Potencial Zeta e à microscopia eletrónica de transmissão (TEM). As propriedades magnéticas foram medidas por magnetometria de SQUID (Superconducting Quantum Interferance Device). Por fim foi avaliada a capacidade das partículas sintetizadas para aplicação em hipertermia magnética.
Cancer is a disease with high incidence in the world population and equally with a high mortality rate. The main problems in the fight against cancer are linked to the difficulty of early diagnosis, the cytotoxicity associated with anticancer drugs used in conventional chemotherapy and the lack of more effective treatments. With the advent of nanotechnology, there has been increasing interest in the application of nanoparticles and nanostructures, in several areas of science, such as biomedicine. In this context, the magnetic nanoparticles have interesting properties in controlled drug release systems and hyperthermia. Its application in areas related to health, such as the treatment of cancer by magnetic hyperthermia, necessarily requires a good characterization of their properties and the correct assessment of their ability to release energy in the form of heat by magnetic induction. Therefore, this study aimed the synthesis of nanoparticles of magnetite due to their biocompatibility and magnetic properties. However, due to their high degree of aggregation as well as facile oxidation in aqueous media there is a need to coat these particles. For this purpose, a biopolymer was used: chitosan. The binding of the coat to the core of the iron oxide was accomplishment through two types of anchorages molecules: dopamine, knowing for their great affinity with amine groups and through caffeic acid due to structural similarity to dopamine. The structural and morphological characterization was performed using X-ray diffraction (DRX), Fourier transformed infrared spectroscopy (FTIR), dynamic light scattering (DLS), Zeta Potential; thermalgravimetric analysis and transmission electron microscopy (TEM). The magnetic properties were studied using a Superconducting Quantum Interference Device (SQUID) magnetometer. Finally, we evaluated the ability of some of the synthesized NPs for use in magnetic hyperthermia.
Dudchenko, N. O., A. B. Brik, Y. V. Kardanets, and O. E. Grechanivskyy. "Influence of Ultrasound Treatment on the Properties of Synthetic Magnetite Nanoparticles." Thesis, Sumy State University, 2013. http://essuir.sumdu.edu.ua/handle/123456789/35186.
Full textVirdee, D. "The influence of magnetostatic interactions on the magnetic properties of magnetite." Thesis, University of Edinburgh, 1999. http://hdl.handle.net/1842/14612.
Full textNewcombe, Lee. "The effects of screw dislocations on the magnetic properties of magnetite." Thesis, University of Edinburgh, 1998. http://hdl.handle.net/1842/15500.
Full textZhang, Rui. "Ionic Copolymer-Magnetite Complexes for Magnetic Resonance Imaging and Drug Delivery." Thesis, Virginia Tech, 2015. http://hdl.handle.net/10919/73648.
Full textMaster of Science
Stanley, Daniel C. "MAGNETIC DAMPING IN FE3O4 THROUGH THE VERWEY TRANSITION FOR VARIABLE AG THICKNESSES." Miami University / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=miami1376500586.
Full textTempleton, John Andrew. "Magnetite Oxidation in Aqueous Systems." Thesis, Virginia Tech, 2008. http://hdl.handle.net/10919/43468.
Full textMaster of Science
Fullem, Sharbani I. "Study of superspin-glass effect and superparamagnetic behavior in magnetite nanoparticles and gold-coated magnetite nanoparticles." Diss., Online access via UMI:, 2006.
Find full textThomson, Leslie Campbell. "A three-dimensional micromagnetic investigation of the magnetic properties and structures of magnetite." Thesis, University of Edinburgh, 1993. http://hdl.handle.net/1842/13127.
Full textDavila, Alfonso F. "Detection and function of biogenic magnetite." [S.l.] : [s.n.], 2005. http://edoc.ub.uni-muenchen.de/archive/00004614.
Full textFernandez, Davila Alfonso. "Detection and function of biogenic magnetite." Diss., lmu, 2005. http://nbn-resolving.de/urn:nbn:de:bvb:19-46145.
Full textMAIA, EDUARDO SILVA. "PELLETIZING AND REDUCING OF MAGNETITE CONCENTRATE." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2011. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=18544@1.
Full textA tendência mundial de aumento da quantidade de finos (sinter feed e pellet feed) nas lavras de minério de ferro tem elevado a importância dos processos de aglomeração, em especial a pelotização, que tem por característica produzir pelotas de excelente qualidade química e alta resistência mecânica, além de ser um processo menos poluente que a sinterização. Atualmente, as jazidas de minério de ferro em lavra no Brasil, exploram minérios predominantemente hematíticos (hematita e/ou itabirito). Apesar do país não possuir tradição na exploração de minérios magnetíticos, existem ocorrências destes que vêm despertando crescente interesse, sendo, contudo, necessário à adequação das etapas do beneficiamento mineral e dos parâmetros operacionais da pelotização. O presente trabalho, fruto de uma interação da empresa Metal Data S/A e o Grupo de Siderurgia do DEMa/PUC-Rio, trata do estudo da pelotização de um minério de ferro magnetítico, proveniente de uma jazida brasileira em fase de pesquisa mineral, com o objetivo de analisar sua viabilidade exploratória para produção de pelotas a serem utilizadas como matéria prima na indústria siderúrgica. Os procedimentos experimentais foram divididos em três etapas: tratamento do minério, pelotização e redução, buscando assim, definir uma rota de tratamento do minério e, posteriormente, a caracterização química, mecânica e metalúrgica das pelotas produzidas. Foram estudados três tipos de misturas para a pelotização, envolvendo oito diferentes concentrados. Os resultados indicaram que o minério magnetítico é passível de concentração e capaz de produzir um pellet feed de qualidade, utilizando rota de beneficiamento com operações unitárias típicas. Este material mostrou potencial para a formação de pelotas cruas em discos de laboratório e, após as operações de queima, produziu pelotas que apresentaram granulometria entre 9,5 e 16,0 mm, resistência à compressão de 126 a 339 kg/pelota, índice de tamboramento de 67,7 a 94,9 %, porosidades de 23,8 a 40,74%, grau de metalização de 30 a 75%, entre outras.
The global increasing trend of producing iron ore fines (sinter feed and pellet feed) has also increased the importance of the agglomeration processes, in particular the pelletizing, which has as main characteristic to produce high quality pellets with excellent mechanical resistance, besides being a less polluting process than the sintering. Currently, Brazilian mines exploit mainly hematite deposits (hematite and / or itabirite ores). Although the country has no tradition in exploiting magnetite minerals, there is a growing interest trend in magnetite occurrences, although it might be necessary to adequate mineral processing and pelletizing operating parameters when using such ore. This work is a result of an interaction between the company Metal Data S/A and the Siderurgy Group of the DEMa/PUC-Rio and describes the pelletizing process using magnetite iron ore from a Brazilian deposit in exploration stage, in order to evaluate its suitability for exploratory pellet production to be used as feedstock in the steel industry. The experimental procedures were divided into three steps - ore processing, pelletizing and reduction, aiming to define the ore treatment route and chemical, mechanical and metallurgical characteristics of the produced pellets. Three types of mixtures for pelletizing were analysed, involving eight different concentrates. The results indicated that the magnetite ore is likely to concentrate and capable of producing a pellet feed with adequate quality, using a processing route with typical unit operations. It was observed that this materal has a potential for the formation of green pellets in the laboratory pelletizing disc and, after burning operations, produced pellets that had particle size between 9.5 and 16.0 mm, compression strength from 126 to 339 kg / pellet, tumble index from 67.7 to 94.9%, porosity from 23.8 to 40.74%, degree of metallization from 30 to 75%, among others.
Stanislavov, A. S., L. B. Sukhodub, V. N. Kuznetsov, Леонід Федорович Суходуб, Леонид Федорович Суходуб, and Leonid Fedorovych Sukhodub. "Magnetite-polymer Nanoparticles: Structure and Properties." Thesis, Sumy State University, 2015. http://essuir.sumdu.edu.ua/handle/123456789/42573.
Full textCollyer, Stephen. "Crystallographic studies of magnetite and titanomaghemite." Thesis, Aston University, 1986. http://publications.aston.ac.uk/14360/.
Full textZhang, Qi [Verfasser]. "Humidity related magnetite alteration / Qi Zhang." Tübingen : Universitätsbibliothek Tübingen, 2020. http://d-nb.info/122159639X/34.
Full textRagheb, Ragy. "Synthesis and Characterization of Polylactide-siloxane Block Copolymers as Magnetite Nanoparticle Dispersion Stabilizers." Thesis, Virginia Tech, 2005. http://hdl.handle.net/10919/31687.
Full text
The synthesis of the triblock copolymers is comprised of three reactions. Difunctional, controlled molecular weight polymethylvinylsiloxane oligomers with either aminopropyl or hydroxybutyl endgroups were prepared in ring-opening redistribution reactions. These oligomers were utilized as macroinitiators for ring-opening L-lactide to provide triblock materials with polymethylvinylsiloxane central blocks and poly(L-lactide) endblocks. The molecular weights of the poly(L-lactide) endblocks were controlled by the mass of L-lactide relative to the moles of macroinitiator. The vinyl groups on the polysiloxane center block were further functionalized with carboxylic acid groups by adding mercaptoacetic acid across the pendent double bonds in an ene-thiol free radical reaction. The carboxylic acid functional siloxane central block was designed to bind to the surfaces of magnetite nanoparticles, while the poly(L-lactide)s served as tailblocks to provide dispersion stabilization in solvents for the poly(L-lactide). The copolymers were complexed with magnetite nanoparticles by electrostatic adsorption of the carboxylates onto the iron oxide surfaces and these complexes were dispersible in dichloromethane. The poly(L-lactide) tailblocks extended into the dichloromethane and provided steric repulsion between the magnetite-polymer complexes.
Master of Science
Santos, Germano Pereira dos. "Estudo eletroquímico de micropartículas individuais e colisões de nanopartículas de magnetita modificadas com azul da Prússia." Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/75/75134/tde-07052015-093611/.
Full textAccording to recent literature, the electrochemistry of magnetic particles and collision phenomena on surfaces result in unconventional voltammetric and amperometric responses. Some theoretical models has been proposed; however, experimental data are required for improve that. In order to contribute to this research area, this Master\'s Dissertation describes the manipulation of microparticles and nanoparticles of magnetite modified with Prussian blue (Fe3O4-PB), as well as the study of electrochemical properties of them in presence of an external magnetic field. Carbon (graphite) electrodes modified with microparticles were obtained by using two different techniques, (i) magneto-deposition and (ii) drop coating. For both, two peaks in the voltammograms were observed, related to oxidation (0.12 V) and reduction (-0.05 V), which are associated with redox couple Prussian blue / Prussian white. Higher peaks currents were observed for the film obtained via drop coating. Also, individual Fe3O4-PB microparticles (single particles) were isolated by using an optical microscope and analyzed by voltammetry, where there was the appearance of peaks with the same potential values. However, using two commutations magnetic states, \"switch on\" and \"switch off\", it was possible to monitor the presence and the absence of the particle on electrode. Also, there were differences in the values of current density in the chronoamperograms for each Fe3O4-PB microparticle, and the morphology of the microparticle significantly interfered in the electrochemical response. Finally, it was performed several electrochemical experiments regarding to collisions of Fe3O4-PB nanoparticles on a gold ultramicroelectrode. Controlled collisions in different experimental conditions were carried out, such as in the presence and absence of an external magnetic field parallel to the surface electrode, and also with intensities fields of 0.1 and 0.2 Tesla. In the absence of the field, the nanoparticles reached the UME and collided, resulting in electrochemical signals of this type staircase, due to accumulation of them. On the other hand, in the presence of a 0.1 T, we observed several transient currents (spikes) associated with the collisions of the nanoparticles. These events were not observed in the presence of the field of 0.2 T. Thus, these findings allow us to the discussion for improvements on the models for these systems, in order to explain the profiles of voltammetric and amperometric responses.
Pardoe, Heath. "In vivo measurement and imaging of ferrimagnetic particle concentrations in biological tissues." University of Western Australia. School of Physics, 2005. http://theses.library.uwa.edu.au/adt-WU2005.0060.
Full textPradhan, Anindya. "Synthesis and Characterization of Novel Nanoparticles for Use as Photocatalytic Probes and Radiotracers." ScholarWorks@UNO, 2008. http://scholarworks.uno.edu/td/689.
Full textUnibosi, Marco. "Studio delle proprieta magnetiche del sistema nanogranulare magnetite/idrossiapatite per potenziali applicazioni in nanomedicina." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2015. http://amslaurea.unibo.it/8349/.
Full textLucet, Isabelle. "Structure et proprietes magnetiques de nanoparticules de magnetite-dextran : analyse de leur efficacite sur la relaxation protonique." Angers, 1994. http://www.theses.fr/1994ANGE0503.
Full textMokhtari, Abbas. "On the growth, magnetic properties and Magneto-Optical Studies of ZnO based Dilute Magnetic Semiconductors and Magnetite." Thesis, University of Sheffield, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.500218.
Full textOrozco, Henao Juan Manuel 1989. "Efeitos de tamanho e geometria nas propriedades magnéticas e de hipertermia magnética em nanopartículas de Fe3O4." [s.n.], 2016. http://repositorio.unicamp.br/jspui/handle/REPOSIP/305751.
Full textDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin
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Resumo: Nanopartículas de magnetita com diâmetros entre 5nm e 19nm sintetizadas mediante um método de decomposição térmica são apresentadas. A caracterização estrutural é feita usando diferentes técnicas experimentais como a microscopia eletrônica de transmissão (TEM), difração de raios-X e espalhamento de raios-X a baixos ângulos (SAXS) de onde são obtidos os tamanhos e a forma das nanopartículas. As propriedades magnéticas e de magneto-hipertermia das nanopartículas são estudadas para diferentes parâmetros de produção como concentração dos surfactantes, temperaturas de refluxo e atmostfera de crescimento. A dependência com a temperatura das propriedades magnéticas são analisadas dentro do marco do modelo usual do superparamagnetismo e o modelo de interação superparamagnética (ISP), de onde os parâmetros magnéticos dependentes do tamanho como anisotropia magnética (1.06x10^4 J/m^3 até 9.91x10^4 J/m^3), momento magnético por partícula (2618?B até 11500?B), temperatura de bloqueio (18K até mais de 300K) e energia de ineração dipolar magnética (0.55x10^-21 J até 5.5x10^-21 J) são inferidos. Os resultados de magneto-hipertermia foram obtidos mediante a medição da resposta térmica das nanopartículas de magnetita suspendidas em tolueno. Valores da taxa de absorção específica (SAR) são calculados experimental e teoricamente utilizando a teoria de resposta linear para um sistema superparamagnético não interagente. Valores de SAR entre 3.0W/g e 40.3W/g e a sua dependência com a frequência e o campo aplicado são apresentados. Como resultado interessante, a resposta de magneto-hipertermia para as nanopartículas de 19nm preparadas na presença de oxigênio e mais de 10 vezes maior do que nanopartículas similares mas obtidas na ausência da atmosfera de oxigênio. Também é destacada a possibilidade de prever a resposta de magneto-hipertermia num sistema de nanopartículas magnéticas mediante a obtenção dos parâmetros de caracterização magnetica e estrutural
Abstract: Magnetite nanoparticles with diameters between 5nm and 19nm synthesized by means of a thermal decomposition method are presented. Structural characterization is made by different experimental techniques such as transmission electron microscopy (TEM), X-ray diffraction and Small Angle X-ray Scattering (SAXS) from where nanoparticles size and shape are obtained. Magnetic and magneto-hyperthermia properties of the nanoparticles are studied for different production parameters, such as surfactant concentrations, refluxing temperature and growth atmosphere. Temperature dependence of the magnetic properties are analyzed in the framework of the standard superparamagnetism model and the interacting superparamagnetic model (ISP), from where size dependent magnetic parameters for each sample such as anisotropy (1.06×10^4 J/m^3 to 9.91x10^4 J/m^3) magnetic moment per particle (2618?B to 11500?B), blocking temperature (18K to above 300K) and magnetic dipolar interaction energy on dried nanoparticle samples (0.55 × 10^?21 J to 5.5 × 10^?21 J) are inferred. Magneto-hyperthermia results are obtained by measuring the thermal response of magnetite nanoparticles dissolved in toluene. Specific absorption rate (SAR) values are theoretically and experimentally calculated by means of a linear response theory approach of a non-interacting superparamagnetic system. SAR values between 5.8W/g and 40.3W/g are reported; interestingly, the magneto-hyperthermia response for 19nm nanoparticles prepared in presence of an oxygen atmosphere is more than 10 times larger than similar particles obtained in absence of oxygen atmosphere. Also it is important to highlight the possibility to obtain the magneto-hyperthermia behavior of a magnetic nanoparticles system by knowing a priori its structural and magnetic characterization parameters
Mestrado
Física
Mestre em Física
1247647/2013
CAPES
Hargreaves, Joe. "The Verwey transition : neutron scattering studies of the vibrational and magnetic excitations in magnetite." Thesis, University of Manchester, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.505388.
Full textHuet, Sarah Damasceno Pinheiro. "Estudo das interações hiperfinas em nanopartículas de Fe3O4 e Fe3O4 dopadas com gadolínio pela espectroscopia de correlação angular perturbada." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/85/85131/tde-20062014-132040/.
Full textIn the work reported in this dissertation, magnetic nanoparticles of Fe3O4 and 5% Gddoped Fe3O4, which have applications in biomedicine, were studied by Perturbed Gamma-Gamma Angular correlation spectroscopy (PAC). Fe3O4 samples were synthesized by both, co-precipitation and thermal decomposition methods. Gd-doped Fe3O4 magnetic nanoparticles were synthesized only by co-precipitation method. Analysis of X-ray diffraction (XRD) showed that the samples belong to Fd3m space group. Transmission Electron Microscopy (TEM) showed that nanoparticles have sizes between 5 and 14 nm, suitable for biomedical applications. Fe3O4 nanoparticles synthesized by thermal decomposition method showed greater monodispersed nanoparticles than the samples synthesized by co-precipitation method. PAC technique using radioactive probe 111In (111Cd) showed that the size of the nanoparticles changes magnetic behavior and for the Gd-doped sample PAC measurements results showed that the introduction of radioactive probe is difficult due the presence of an impurity (Gd) and there is a competition for Fe sites between Gd and nuclear probe.
Fewell, Sean E. "The particle erosion of steel by magnetite." Master's thesis, University of Cape Town, 2002. http://hdl.handle.net/11427/4965.
Full textThis work addresses the problem of erosion of steel heat exchanger coils in a petroleum producing plant by magnetite catalyst particles entrained in the flowing gas stream.
Fortes, Júnior Cristiano Correia Silva. "Imobilização de lacase em nanopartículas de magnetite." Master's thesis, Universidade de Aveiro, 2014. http://hdl.handle.net/10773/14303.
Full textAs excelentes propriedades catalíticas têm aumentado o uso de enzimas na biocatálise industrial. Contudo, como normalmente são solúveis, apresentam desvantagens como a dificuldade de recuperação da enzima da solução reacional e a sua reutilização. De modo a reutilizar uma enzima solúvel, a sua imobilização tem sido utilizada, nos mais diversos tipos de suportes e usando metodologias variadas. Neste sentido, estudou-se a imobilização da lacase em nanopartículas magnéticas de magnetite, revestidas com sílica (Fe3O4-SiO2) e ativadas com glutaraldeído. Na primeira fase deste trabalho, com o objetivo de maximizar a recuperação de atividade enzimática, estudou-se a otimização das condições da imobilização, através do uso da metodologia de superfície de resposta, tendo como variáveis independentes o pH (4.5, 6.5 e 8.5), a concentração da enzima (0.03, 0.1 e 0.17 μL/mL) e o tempo de contato (1.0, 2.0 e 3.0h). As condições ótimas de imobilização encontradas foram a concentração de enzima 0.03 μL/mL, pH 5 e tempo de contato de 3h. Numa segunda fase, investigou-se a estabilidade térmica da lacase livre e imobilizada, estabilidade operacional ou capacidade de reutilização e o efeito do armazenamento na enzima imobilizada. Verificou-se que a estabilidade térmica da lacase imobilizada, em relação à lacase livre, foi ligeiramente melhorada. A retenção de 75,8 % da atividade inicial após 6 ciclos de reação mostraram claramente que a estabilidade operacional e a capacidade de reutilização do biocatalisador foi melhorada em relação à enzima livre. Na terceira fase determinou-se a cinética da reação de oxidação do ABTS, catalisada pela lacase imobilizada e comparou-se com a cinética da enzima livre. Os resultados foram modelados usando o modelo de Michaelis-Menten, e constatou-se que um aumento substancial do valor da constante de Michaelis-Menten, em relação à enzima livre, certamente provém de uma menor afinidade da enzima imobilizada para o substrato e ou por limitações de transferência de massa. Conclui-se que as propriedades melhoradas da lacase imobilizada em nanopartículas, assim como as vantagens de reutilização, aproveitando as propriedades magnéticas das nanopartículas, mostram que a lacase imobilizada nestes suportes apresenta potencial para aplicações industriais.
Due to their excellent catalytic properties, there is an increase of the use of enzymes in industrial biocatalysis. However because normally they are in the soluble state, there are disadvantages such as the difficulty of recovering the enzyme from the solution where occurs the reaction and its posterior reutilization. In order to reuse the soluble enzymein an industrial reactor, the enzyme can be immobilized in various supports using different immobilization methodologies. The main objective of this work was to study the immobilization of laccase on magnetic nanoparticles of magnetite coated with silica (Fe3O4-SiO2) and activated with glutaraldehyde. In the first stage of this work the optimization of the conditions for the immobilization of laccase was studied, through the use of a response surface methodology, taking as independent variables pH (4.5, 6.5 and 8.5), the concentration of the enzyme (0.03, 0.10 and 0.17 μL/mL) and contact time (1.0, 2.0 and 3.0h) with the purpose of maximizing the recovery of enzyme activity. The optimal experimental conditions for the immobilization were enzyme concentration 0.03 μL/mL, pH 5 and contact time of 3h. In a second stage, investigation of the thermal stability of laccase, operational stability and reusability and the effect of storage on the immobilized enzyme was carried out. It was found that the thermal stability of the immobilized laccase comparing to the free laccase was slightly improved. The retention of 75.8% of initial activity after 6 cycles of operation clearly showed the good operational stability and reusability. Later the kinetics of oxidation of ABTS, catalyzed by immobilized laccase was determined and compared with the kinetics of the free enzyme. The results of the oxidation of ABTS by laccase immobilized were modeled using the Michaelis-Menten model, and it was found that a substantial increase in the value of the Michaelis-Menten constant by comparing to the free enzyme, certainly comes from a lower affinity of the immobilized enzyme for the substrate or by limitation in mass tranfer. As conclusion, there was an improvement in the proprieties of immobilized laccase on magnetic nanoparticles as well as the benefits of reuse, taking advantage of the magnetic properties of the nanoparticles and showing that laccase immobilized in these carriers has enormous potential for industrial application.
Ye, Quan-Lin, Hirofumi Yoshikawa, Shunji Bandow, and Kunio Awaga. "Green magnetite (Fe3O4): Unusual optical Mie scattering and magnetic isotropy of submicron-size hollow spheres." American Institite of Physics, 2009. http://hdl.handle.net/2237/12624.
Full textLeibovitz, Natalie Ruth. "Magnetic Paleointensities in Fault Pseudotachylytes and Implications for Earthquake Lightnings." OpenSIUC, 2016. https://opensiuc.lib.siu.edu/theses/1980.
Full textSilva, Caio Luis Santos. "Efeito do gadolínio nas propriedades catalíticas de óxidos de ferro na reação de WGS." reponame:Repositório Institucional da UFBA, 2012. http://www.repositorio.ufba.br/ri/handle/ri/11726.
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Devido à necessidade de garantir o suprimento de energia através de tecnologias de conversão de energia mais limpas e mais eficientes, reduzindo a emissão de gases causadores do efeito estufa, o interesse pela reação de deslocamento de monóxido de carbono com vapor d´água (WGSR, water gas shift reaction) tem aumentado, especialmente devido ao seu papel nas células a combustível. A fim de obter catalisadores alternativos para essa reação, foi estudado o efeito da adição e do teor de gadolínio nas propriedades de catalisadores de óxido de ferro. As amostras foram preparadas pela hidrólise de nitrato de ferro e de gadolínio, seguida da lavagem do gel com uma solução de acetato de amônio para obter magnetita e com água para obter hematita. As amostras foram caracterizadas por termogravimetria, calorimetria diferencial de varredura, espectroscopia no infravermelho com transformada de Fourier, difração de raios X, medida da área superficial específica (B.E.T.) e redução à temperatura programada. Os catalisadores foram avaliados na WGSR a 1 atm, na faixa de 250 a 400 ºC, usando uma razão molar vapor d´água/gás de processo (3,7% CO, 3,7% CO2, 22,2% H2, 70,4% N2) igual a 0,6. As fases hematita e ferrita de gadolínio foram detectadas em todos os sólidos lavados com água, enquanto magnetita e ferrita de gadolínio foram encontradas naqueles lavados com acetato de amônio. No primeiro caso, a área superficial específica aumentou devido ao gadolínio, independente do seu conteúdo, um fato que foi relacionado ao seu papel como espaçador e/ou a uma causa de tensões na rede, produzindo partículas menores. Entretanto, em todos os sólidos baseados em magnetita, o gadolínio conduziu a uma diminuição da área superficial específica, devido à predominância da perovskita (ferrita de gadolínio), que apresenta valores tipicamente baixos. A adição de gadolínio facilita a redução de espécies Fe3+, em todos os catalisadores, mas aumenta a atividade apenas naquelas aquecidas sob ar. O sólido com Gd/Fe=0,1, aquecido sob ar, mostrou a mais alta atividade, provavelmente devido à area superficial específica aumentada devido ao gadolínio, que também facilitou a redução do ferro, tornando o ciclo redox mais fácil durante a WGSR. Além disso, os catalisadores baseados em hematita mostraram as atividades mais elevadas. Isto pode ser atribuído à predominância de hematita nesses sólidos, quando comparados a outros nos quais a ferrita de gadolínio foi a fase predominante. Isto significa que as espécies Fe3+, no ambiente da hematita, são mais ativas na reação de WGS que as espécies Fe4+, no ambiente da perovskita
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Khan, Latif Ullah. "Nanomateriais ópticos e magnéticos contendo matrizes de Fe3O4 e SiO2 funcionalizadas com calixareno e complexos de terras raras." Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/46/46136/tde-20072015-151110/.
Full textThe design and fabrication of sophisticated bifunctional luminescent and magnetic nanomaterials based on Fe3O4 and RE3+ complexes are sought for. Accordingly, novel red-green emitting superparamagnetic Fe3O4@calix-Eu(TTA) and Fe3O4@calix-Tb(ACAC) nanomaterials were prepared through on-pot method. In this regard, the chemically modified calixarene ligand was used as a surfactant to stabilize the Fe3O4 nanoparticles. The calixarene ligand provides colloidal stability and chemically modifiable surface to the magnetite nanoparticles. Thus, this ligand functionalized Fe3O4@calix nanoparticles were further coordinated to the RE3+ ions via one-pot synthesis, using TTA and ACAC ligands as sensitizers (antenna effect) to produce highly luminescent nanophosphors. In addition, bifunctional optical and magnetic Fe3O4@SiO2-TTA-Eu(L), L: TTA, TC, AB and AMB as well as Fe3O4@SiO2-TTA-Tb(AB or AMB) nanocomposites were also synthesized through multistep synthetic protocol, utilizing Fe3O4 nanoparticles as precursors. They were modified with silica shell, using modified Stöber method and further grafted with RE3+ complexes to produce the luminescent and magnetic nanocomposites. The X-ray powder diffraction (XPD), small angle x-ray scattering (SAXS), transmission electron microscopy (TEM) and scanning electron microscopy (SEM) techniques were used to determine the structures, morphologies, size distribution and monodispersity of the synthesized materials. These novel Fe3O4@calix-Eu(TTA) and Fe3O4@calix-Tb(ACAC) as well as Fe3O4@SiO2-TTA-Eu(L) and Fe3O4@SiO2-TTA-Tb(AB or AMB) magnetic luminescent nanomaterials show interesting superparamagnetic and photonic properties. The magnetic properties (M-H and ZFC/FC measurements) at temperatures of 2, 5 and 300 K were explored in order to investigate the extent of coating and crystalinity effect on the saturation magnetization and blocking temperatures. The influence of the RE3+ ions on the magnetization of the optical and magnetic nanomaterials was also studied. Even though magnetite is a strong luminescence quencher, the coating of the Fe3O4 nanoparticles with synthetically modified calixarene ligand (calix) and silica shell have overcome this difficulty. Moreover, the intramolecular energy transfer from the T1 excited triplet states of TTA and ACAC ligands to the emitting levels of Eu3+ and Tb3+ in the Fe3O4@calix-Eu(TTA) and Fe3O4@calix-Tb(ACAC) nanomaterials are discussed. The emission quantum efficiencies (η) for the Fe3O4@calix-Eu(TTA) and Fe3O4@SiO2-TTA-Eu(L) nanomaterials are also calculated and discussed, as well as the structural features based on the energy levels and experimental intensity parameters, in the case of the Eu3+ ion. These novel nanomaterials may act as the emitting layer for the red and green light for magnetic and light converting molecular devices (MLCMDs).
Panasiuk, Oleksander. "Phosphorus Removal and Recovery from Wastewater using Magnetite." Thesis, KTH, Industriell ekologi, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-58595.
Full textSiyambalapitiya, Chamila S. "Growth and physical properties of magnetite thin films." [Tampa, Fla] : University of South Florida, 2006. http://purl.fcla.edu/usf/dc/et/SFE0001676.
Full textEder, Stephan. "Magnetite in organisms and the biophysics underlying magnetoreception." Diss., Ludwig-Maximilians-Universität München, 2013. http://nbn-resolving.de/urn:nbn:de:bvb:19-161971.
Full textGhalamboran, M. R. "Symbiotic nitrogen fixation enhancement due to magnetite nanoparticles." Thesis, Cranfield University, 2011. http://dspace.lib.cranfield.ac.uk/handle/1826/8172.
Full textRóbert, Arató [Verfasser], and Hans [Akademischer Betreuer] Keppler. "Magnetite–melt oxybarometry / Arató Róbert ; Betreuer: Hans Keppler." Bayreuth : Universität Bayreuth, 2018. http://d-nb.info/1151203033/34.
Full textPalmer, J. W. "The solution chemistry of magnetite and mild steel." Thesis, University of Nottingham, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.371288.
Full textGibbs, Zoe Elizabeth. "The origin of fine grained magnetite in sediments." Thesis, University of Liverpool, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.368000.
Full textAkhtar, Mst Alpona. "Hydrophobicity of Magnetite Coating on Low Carbon Steel." Thesis, University of North Texas, 2018. https://digital.library.unt.edu/ark:/67531/metadc1248389/.
Full textTeng, Chien-Lung. "Investigation of Electrodeposited Magnetite Films : Formation and Characterization." Thesis, Imperial College London, 2008. http://hdl.handle.net/10044/1/4260.
Full textVialle, Greg. "Inductive activation of magnetite filled shape memory polymers." Thesis, Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/28104.
Full textCulpepper, Johnathan D. "Reduction of tetrachloroethylene and trichloroethylene by magnetite revisted." Thesis, University of Iowa, 2017. https://ir.uiowa.edu/etd/5741.
Full textBjork, Andreas. "Characterizing magnetic susceptibility and remanent magnetization of magnetite and hematite rich drill-core samples at Blötberget." Thesis, Uppsala universitet, Geofysik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-347975.
Full textLaboratorietekniska metoder kan användas som ett komplement till malmgeologi och geofysisk prospektering. I denna metodstudie karaktäriseras apatitjärnmalm från Blötberget, nära Grängesberg. En fyndighet bestående av linsformade malmkroppar rika på magnetit och ofta avskilda men komplexa hematitrika stråk. Studien är gjord 37 prover från totalt 8 borrkärnor, och lokaler som tillhörde produktion från gruvverksamhet under 1900-talet. Mätmetoderna fokuserar på att kartlägga malmens magnetiska egenskaper, och hur temperatur, frekvens, fältstyrka samt riktning påverkar dessa. Resultaten jämfördes med tidigare petrografisk studie av tillhörande tunnslip Resultaten visar att magnetit står för merparten av susceptibiliteten i proverna, men att även hematit kan urskiljas och kvantifieras. Temperaturberoende har påvisats vid övergångar för Verwey-temperatur; -153°C, Curie-temperatur; 580 °C, och Néeltemperatur; 680 °C. Den förväntade Morin-temperaturen vid -14°C, påträffades vid -60 °C eller saknas helt för flera av de hematitrika proverna. Magnetiskt anisotropa prover återfinns bland prover som identifierats som skarn eller hematitrika. Magnetisk granulometri visar karaktär av multidomäntyp med låg magnetisk coercivitet och hög satureringsförmåga. Högtemperaturmätningar av susceptibilitet visar på ren magnetit för prover från Blötberget. Samtidigt visar lågtemperaturemätningar att hematit sannolikt har inblandning av titanium eller bär på ett mer komplext förflutet. Studien visar också att det finns en risk i att enbart förlita sig på bulksusceptibilitet för prover rika på malm.
King, James Gagwane. "Magnetic properties of arrays of magnetite particles produced by the method of electron beam lithography (EBL)." Thesis, University of Edinburgh, 1996. http://hdl.handle.net/1842/15171.
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