Thèses : « FePO4 »

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Intaranont, Noramon. « Selective lithium extraction from salt solutions by chemical reaction with FePO4 ». Thesis, University of Southampton, 2015. https://eprints.soton.ac.uk/382486/.

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The spectacular increase in lithium battery applications has raised the question of whether global lithium resources will be enough in the future. Experts in the field have estimated that the existing lithium resources will probably be sufficient to support demands until the year 2100, assuming that lithium batteries are recycled. Without lithium batteries being recycled, the resources are expected to be depleted in 50 years’ time. Therefore, there is a great interest in developing better methods of lithium recycling from batteries, and also, better methods of lithium extraction from natural resources. Currently, lithium is extracted from natural brines via the lime soda evaporation process, i.e. a solar evaporation plus chemical plant process, which takes between 12 and 24 months. The drawbacks of this process are that it is complex, slow and inefficient. Also, the currently available methods of lithium recycling from batteries are too complex and expensive. Thus, the main objective of this work is to develop a novel, inexpensive and less timeconsuming approach to recover lithium chemically, from the lithium salts (lithium sources) that contain other metal cations. The new process is also based on environmental concerns. A battery material, lithium iron phosphate (LiFePO4) has the olivine structure and heterosite structure once it discharges to iron phosphate (FePO4). This structure shows excellent properties of the charge/discharge reversibility. A few studies on the heterosite FePO4 have reported that it is more selective for lithium ions (Li+) over other cations. The main advantages of this structure are the small potential differences of the redox couple, i.e. Fe(II)/Fe(III), and the stability of LiFePO4 over a wide range of acid-based conditions in an aqueous solution. This work investigates a novel process that may be superior to the lime soda evaporation process for extracting lithium. Heterosite FePO4 was employed to selectively remove Li+ from lithium sources with the support of a reducing agent, i.e. sodium thiosulphate (Na2S2O3). The resulting LiFePO4 can be directly sent not only to lithium battery industries, but also to other industrial uses. In principle, the other cations could be retrieved back into their sources. The novel process was examined and demonstrated lithium insertion into a heterosite FePO4, working as a framework, in aqueous salt solutions. The evaluation of this process is presented by the Li+ uptake value. The amount of Li+ uptake can be up to 46 mgLi +/gsolid where other cations (i.e. sodium, potassium, and magnesium) can take less than 3 mg/gsolid, using this process. Furthermore. This work could also be developed for future lithium recycling processes.

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Zhu, Changbao [Verfasser], et Joachim [Akademischer Betreuer] Maier. « Size effects on lithium storage and phase transition in LiFePO4/FePO4 system / Changbao Zhu. Betreuer : Joachim Maier ». Stuttgart : Universitätsbibliothek der Universität Stuttgart, 2013. http://d-nb.info/1036874680/34.

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Aliouane, Nadir. « Transitions de phase α-β dans le quartz et FePO4 : relations avec la diffusion anomale de la lumière et mécanismes ». Toulon, 2002. http://www.theses.fr/2002TOUL0012.

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Lachal, Marie. « Etude des mécanismes d'insertion/désinsertion des cations alcalins (Li+/Na+) au sein de la structure olivine FePO4 pour accumulateurs Li-ion et Na-ion ». Thesis, Université Grenoble Alpes (ComUE), 2015. http://www.theses.fr/2015GREAI035/document.

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Dans le cadre du développement des technologies Na-ion, le composé NaFePO4, équivalent chimiquedu matériau très attractif LiFePO4, représente une alternative intéressante aux problèmes deressourcement du lithium. Toutefois, les composés LiFePO4 et NaFePO4 de structure olivineprésentent des divergences de comportement structural et électrochimique lors de l'insertioncationique. Ce travail présente une analyse des mécanismes de (dés)insertion des ions Li+ et Na+ ausein de la phase FePO4 par voie chimique et électrochimique. Les échantillons de LiFePO4 ont étésynthétisés par deux méthodes différentes (hydrothermale et précipitation), puis délithiéschimiquement via différents procédés. Dans un premier temps, les analyses structurales (DRX)associées aux analyses nucléaires ont permis d'effectuer un suivi de la cinétique de réaction. Nousavons montré que la présence de joints de grains, issus du traitement thermique effectué, limitefortement la vitesse de délithiation. L'analyse de l’évolution des domaines de cohérences a permis deproposer un mécanisme de délithiation original de type "Coeur-Coquille" avec un coeur de LiFePO4,confirmé par HRTEM et STEM-EELS. Dans un deuxième temps, afin de comparer les mécanismes dedélithiation chimique et électrochimique, l’insertion et la cyclabilité des ions Li+ et Na+ ont étécaractérisées en demi-cellules lithium et sodium. Bien que la signature électrochimique des matériauxLiFePO4 et NaFePO4 soit différente, les performances en termes de capacité restituée ou de tenue enpuissance s'avèrent similaires. Enfin, l'insertion électrochimique des ions Li+ et Na+ au sein d'unepoudre comportant des défauts structuraux a été caractérisée par DRX Operando durant un cycle decharge / décharge effectué à régime lent. Ces analyses ont révélées que la co-insertion cationiques'effectue via une solution solide de type LixNayFePO4 (0
As part of the development of Na-ion technology, NaFePO4 compound, chemical equivalent of theattractive LiFePO4 material, would be a promising option facing possible lithium shortage. However,olivine-type LiFePO4 and NaFePO4 display different structural and electrochemical behaviors duringcationic insertion. This thesis presents an analysis of the (de)insertion mechanisms of Li+ and Na+ ionswithin olivine-type FePO4 by chemical and electrochemical means. Samples of LiFePO4 weresynthesized by two different methods (hydrothermal and precipitation), then chemically delithiated bydifferent processes. In a first step, structural analysis (XRD) associated with nuclear analyses enabledfollowing the reaction kinetics. We have pointed out that the presence of grain boundaries, resultingfrom the heat treatment, strongly limits the delithiation kinetics. The analysis of the evolution of thecoherency domains enabled us to propose an original "Shrinking Core" type delithiation mechanismwith a core of LiFePO4, observed by HRTEM and STEM-EELS. In a second step, in order to comparechemical and electrochemical mechanisms, insertion and cyclability of Li+ and Na+ were characterizedin lithium and sodium half-cells. Although the electrochemical signature of LiFePO4 and NaFePO4materials is different, the performances in terms of restored capacity or power capability are similar.Finally, electrochemical insertion of Li+ and Na+ in a powder comprising structural defects wascharacterized by operando XRD, during a charge / discharge cycle performed at low rate. Theseanalyses revealed that the cationic co-insertion takes place via a solid solution LixNayFePO4(0

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Matos, Izabela Teles de. « Caracterização em escala atômica de nanopartículas magnéticas de magnetita e ferrita do tipo TMFe2O4 (TM = Co, Ni) para uso em biomedicina pela espectroscopia de correlação angular gama-gama perturbada ». Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/85/85131/tde-30012019-144245/.

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Este trabalho descreve, sob um ponto de vista atômico, a investigação das nanopartículas magnéticas (NPMs) de magnetita (Fe3O4) e ferritas do tipo TMFe2O4 (TM = Co, Ni), que são uma classe de materiais estruturados que atualmente tem um grande interesse devido à grande variedade de suas possíveis aplicações tecnológicas e biomédicas, pela Espectroscopia de Correlação Angular γ-γ Perturbada (CAP). Para a produção das NPMs foram utilizadas duas rotas químicas: o método de co-precipitação e o método de decomposição térmica. A co-precipitação apresenta as vantagens de ter temperaturas moderadas e custos relativamente baixos, porém não se consegue ter um controle da distribuição de tamanho das partículas. Por outro lado, a decomposição térmica possibilita uma amostra monodispersa com controle de tamanho e forma, mas este método necessita de reagentes tóxicos, caros e alta temperatura de reação. Para caracterização das amostras foi usada a técnica de Difração de Raio X (DRX) e a morfologia das NPs foi estudada por meio da Microscopia Eletrônica de Transmissão (MET). A partir desta técnica foi possível avaliar a distribuição do tamanho dos grãos, pois algumas características como, elevado valor de magnetização, alta anisotropia e um alto valor de coercividade são propriedades que dependem das nanoestruturas. As propriedades magnéticas foram estudadas localmente a partir da Correlação Angular Perturbada (CAP) que utiliza como sondas núcleos atômicos das medidas, como os núcleos de prova 111In (111Cd), 140La (140Ce) e 181Hf(181Ta). Estas propriedades foram complementadas por medidas de Magnetização.
This work describes, from an atomic point of view, the investigation of magnetic nanoparticles (MNPs) of magnetite (Fe3O4) and ferrites of the type TMFe2O4 (TM = Co, Ni), which are a class of structured materials that currently have a great interest due to the great variety of its possible technological and biomedical applications by Perturbed γ-γ Angular Correlation Spectroscopy (PAC). Two chemical routes were used to produce MNPs: the co-precipitation method and the thermal decomposition method. Co-precipitation has the advantages of having moderate temperatures and relatively low costs, but particle size distribution control is not achieved. On the other hand, the thermal decomposition allows a monodisperse sample with size and shape control, but this method requires toxic reagents, expensive and high reaction temperature. The X-Ray Diffraction (XRD) technique was used to characterize the samples and the morphology of the NPs was studied by Electron Transmission Electron Microscopy (TEM). From this technique it was possible to evaluate grain size distribution, because some characteristics such as high magnetization value, high anisotropy and a high coercivity value are properties that depend on the nanostructures. The magnetic properties were studied locally from the Perturbed Angular Correlation (CAP), which uses as probe nuclei of the measurements, such as 111In (111Cd), 140La (140Ce) and 181Hf (181Ta). These properties were complemented by Magnetization measurements.

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Ballesteros, Camilo Arturo Suarez. « Síntese e caracterização de nanopartículas Fe3O4@Au e desenvolvimento de sensores para aplicações em nanomedicina ». Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/76/76132/tde-23102012-101205/.

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Com o desenvolvimento de novos nanomateriais têm-se descoberto propriedades eletrônicas, elétricas, ópticas e catalíticas únicas para aplicações nanotecnológicas. Entre estes nanomateriais com caraterísticas singulares, estão as nanopartículas (Np) CoreαShell, as quais combinam propriedades físico-químicas de dois materiais diferentes, provendo maior eficiência em aplicações como nanoeletrônica, sensoreamento, biossensoreamento e biomédicas. Neste trabalho, Np CoreαShell são sintetizada com núcleo (Core) de Np Fe₃O₄ e com casca (Shell) de Np Au, formando as Nps Fe₃O₄αAu na presença do dendrímero poli(amidoamina) geração 4.0 (Pamam G4). As propriedades físico-químicas do nanomaterial core-shell são estudadas através de análises espectroscópicas, microscopias e eletroquímicas, além de medidas de magnetização. Essas técnicas revelam a formação das Nps Au nas cavidades do Pamam G4 e as interações eletrostáticas entre os grupos funcionais do Pamam G4 e os grupos OH ⁻ e H ⁺ da superfície das Nps magnéticas, as quais dão uma forte estabilidade na configuração da Np Fe₃O₄αAu. Evidencia-se propriedades óticas da Np Au e propriedades superparamagnéticas da Np Fe ₃ O ₄, as quais podem ser usadas para aplicações em nanomedicina. As propriedades electrocatalíticas das Nps são utilizadas na detecção de dopamina (DA). Foram fabricados sensores eletroquímicos das Nps Fe₃O₄αAu, Nps Fe₃O₄ e Nps Au, e caracterizados por técnicas de voltametria cíclica e voltametria de pulso diferencial. A fabricação dos sensores consistiu na deposição de camadas alternadas entre as nanopartículas com o poliânion poly(ácido vinil sulfônico) (PVS) no eletrodo de ITO, levando à configuração de três arquiteturas; ITO - (Fe₃O₄αAu ⁄ PV S), ITO - (Fe₃O₄ ⁄ PV S) e ITO - (Au ⁄ PV S). Um problema encontrado na detecção de DA é que esta tem potenciais de oxidação aproximadamente iguais ao ácido ascórbico (AA) e ao ácido úrico (AU). Portanto, os sensores utilizados na detecção de DA, devem ser altamente seletivos a DA em relação a seus interferentes. Os sensores desenvolvidos aqui mostraram uma boa seletividade e velocidade de resposta na detecção de DA, sendo o sensor ITO - (Fe₃O₄αAu ⁄ PV S) o mais eficiente. As Nps Fe₃O₄αAu revelam maior citotoxicidade nas células cancerígenas comparadas com as células saudáveis, já que as células cancerígenas são mais sensíveis ao estresse oxidativo produzido pelas nanopartículas no interior da célula.
Along with the development of nanomaterials came the knowledge and design of their unique eletronic, optical and catalitycal properties which may be used for a variety of nanotecnological applications. A special class of nanomaterials with interesting characteristics is represented by the CoreαShell nanoparticles, which combine the physicochemical properties of two differerent nanomaterials (including oxides, metals, semiconductors or polymers). This combination provides greater efficiency in applications such as nanoelectronics, sensing, biosensing and biomedical areas. This study reports the synthesis of Fe₃O₄ Np, which in the presence of the polyamido amine generation 4.0 (Pamam G4), is covered with Au Np forming the Fe₃O₄αAu Nps. The nanomaterials had been characterized using spectroscopic, microscopic and electrochemical techniques. The results revealed the formation of Au Nps in the cavities of PAMAM G4 and showed that the electrostatic interactions between the PAMAM functional groups and the OH ⁻ and H ⁺ groups on the surface of the magnetic nanoparticles lead to a strong stability in the configuration of Fe₃O₄αAu Nps. The optical properties of the Au Np (namely the Plasmon resonance band at 542 nm) as well as the superparamagnetic properties of the Fe₃O₄ Np were present in the core-shell nanostrutures. Due to their electrocatalytical properties, the core-shell nanoparticles were employed as active elements for dopamine (DA) detection. The fabrication of the modified electrodes for DA detection consisted in the deposition by LbL technique of alternating layers of nanoparticles and poly(vinyl sulfonic acid) (PVS) on the ITO eletrode, in three distinct architectures: ITO - (Fe₃O₄αAu Fe₃O₄ PV S), ITO - (Fe₃O₄ ⁄ PV S) and ITO - (Au ⁄ PV S). We found a good selectivity and rapid response toward the detection of DA, being the sensor ITO - (Fe₃O₄αAu ⁄ PV S) the most efficient. The effect of Fe₃O₄αAu Nps showed a higher cytotoxicity in cancer cells compared to healthy cells, because cancer cells are more sensitive to oxidative stress produced by the nanoparticles.

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Rodrigues, Marcos Renan Flores. « Estudo e caracterização de nanopartículas de Fe3O4, Fe2O3, Fe3O4/ Aunanop E Fe2O3/Aunanop ». reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2017. http://hdl.handle.net/10183/184573.

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Nanopartículas de Fe3O4 e Fe2O3 foram sintetizadas a partir da rota de coprecipitação, em atmosfera de N2, mantendo-se o pH entre 9 e 14 na temperatura ambiente e utilizando como precursores o FeCl2 e FeCl3. Após a síntese, as nanopartículas foram tratadas termicamente a 250, 500 e 800 oC. Para obtenção de um sistema híbrido, foram sintetizadas nanopartículas de ouro sobre as nanopartículas de óxido previamente tratadas em diferentes temperaturas. As amostras foram caracterizadas por UV-Vis, difratometria de Raios-X (DRX), microscopia eletrônica de transmissão (MET), microscopia eletrônica de transmissão de alta resolução (MET-AR), espectroscopia no na região do infravermelho (FTIR), magnometria de amostra vibrante (VSM) e espectroscopia Mossbauer (EM), e aplicadas para produção de hidrogênio promovendo a decomposição da hidrazina. Os resultados mostram a síntese de nanopartículas de óxido de ferro com diâmetro médio de cerca de 7 nm. Quando aquecidas a 250 oC o tamanho médio aumentou para ca. de 11 nm e foi observado uma pequena mudança no comportamento óptico e estrutural, mantendo o comportamento superparamagnetico. Quando aquecidas a 500 oC o tamanho médio aumenta para ca. de 50nm e são observadas mudanças significativas nas propriedades ópticas, morfológicas, estruturais. Adicionalmente observa-se transição de comportamento superparamagnetico para paramagnético. Quando aquecidas a 800 oC os efeitos nas propriedades dos materiais são ainda mais significativos; as partículas apresentam tamanho médio de 200 nm, o espectro de absorção no UV-Vis muda significativamente e as partículas passam a ter comportamento pagamagnético. Os resultados obtidos pelas diferentes técnicas e somadas ao Mossbauer sugerem que as amostras sintetizadas são uma mistura de Fe3O4 e -Fe2O3, quando aquecido a 250 e 500 oC uma mistura de -Fe2O3 e -Fe2O3 e a 800 oC somente -Fe2O3. As nanopartículas de ouro sintetizadas sobre as amostras de oxido de ferro apresentaram tamanho médio de 6,0 nm e não afetaram as propriedades magnéticas dos oxidos. As amostras de óxido com nanopartículas de ouro promoveram a decomposição da hidrazina por rota completa, levando a formação de hidrogênio com seletividade de até 33%.
Fe3O4 and Fe2O3 nanoparticles were synthesized by coprecipitation route carried out under N2 atmosphere, maintaining the pH between 9 and 14 at room temperature and using FeCl2 and FeCl3 as precursors. After synthesis the iron oxide nanoparticles were thermally treated at 250, 500 and 800 oC. To obtain a hybrid system, gold nanoparticles were synthesized on the thermally treated oxide nanoparticles. The samples were analyzed by UV-Vis, X-ray diffraction (XRD), transmission electron microscopy (TEM), high resolution transmission electron microscopy (MET-AR), spectroscopy in the region of Infrared (FTIR), vibrating sample magnitude (VSM) and Mossbauer, and applied to produce H2 through hydrazine decomposition. The results show the synthesis of Fe3O4 nanoparticles with average diameter of about 7 nm. When heated to 250 oC the average size increased to about 11 nm and a small change in the optical and structural behavior was observed, while the superparamegnetic behaviour was maintained. When heated to 500 °C, the average particle size increase to ca 51nm, significant changes in the optical, morphological and structural properties are observed, in addition to a transition from superparamegnetic to paramagnetic behaviour. When heated to 800 oC the effects on the properties are even more significant; the nanoparticles increase to ca. 200 nm, the absorption spectrum in UV-Vis changes significantly and the particles present paramagnetic behaviour. The results suggest that when heated to 250 and 500 oC a mixture of -Fe2O3 e -Fe2O3 is obtained, after heating at 800 oC only -Fe2O3 is observed. The gold nanoparticles synthesized on the iron oxides present average size of 6.0 nm, and did not affect the magnetic properties of the oxides. The iron oxides/gold nanoparticle samples were efficiently applied to produce hydrogen, promoting the decomposition of hydrazin. The selectivity to hydrogen reached up to 33%.

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Nunes, Eloiza da Silva [UNESP]. « Preparação e caracterização de nanocompósitos de Fe@SiO2, Fe@Fe3O4 e Fe3O4@PNIPAM ». Universidade Estadual Paulista (UNESP), 2015. http://hdl.handle.net/11449/124538.

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Neste trabalho foi investigada a obtenção de nanopartículas de ferro metálico em diferentes meios não aquosos (glicóis) e em água através da rota de redução com boroidreto e a obtenção de estruturas caroço@casca Fe@SiO2 e Fe@Fe3O4. Também são apresentados resultados da caracterização de nanocompósitos magnéticos à base poli(N-isopropilacrilamida) (PNIPAM) e de nanogéis poliméricos (controles) através do método de polimerização radicalar por precipitação. A composição dos nanocompósitos poliméricos foi variada quanto ao tipo de co-monômero (ácido acrílico e poli(etileno glicol) metiléter metacrilato (PEGMA)), reticulador (metileno bis-acrilamida (MBA) e poli(etileno glicol) diacrilato (PEGDA)) e nanopartícula magnética precursora. As nanopartículas metálicas e nanoestruturas Fe@SiO2 e Fe@Fe3O4 foram caracterizadas por DRX, espectroscopia Mössbauer, XPS, SEM e TEM. Os resultados obtidos demostraram que as nanopartículas de ferro metálico foram compostas de α-Fe e variáveis teores de liga de Fe1-xBx e a morfologia e tamanho de partícula variaram em função dos diferentes meios reacionais empregados. As metodologias de recobrimento das partículas metálicas precursoras foram eficazes na estabilização química do caroço magnético. O recobrimento com sílica para obtenção das estruturas Fe@SiO2 foi realizado empregando-se precursores alcoxissilanos através do processo sol-gel. A espessura da camada de sílica pode ser controlada mais eficientemente no caso de partículas maiores oriundas de redução no meio aquoso e no caso de nanopartículas pequenas observou-se a formação de agregados. As estruturas Fe@Fe3O4 foram obtidas pela passivação das nanopartículas metálicas em solvente glicol. A metodologia de passivação demostrou a possiblidade de oxidação controlada da superfície para fase de magnetita evitando a formação de óxi-hidróxidos não...
In this work the obtainment of metallic iron nanoparticles in several non-aqueous (glycols) and in aqueous media through chemical reduction with sodium borohydride and the obtainment of core@shell structures Fe@SiO2 and Fe@Fe3O4, was investigated. The characterization results of poly(N-isoproprylacrylamide) (PNIPAM) based magnetic nanocomposites and bare polymeric nanogels (controls) synthesized through radical precipitation polymerization were also presented. The composition of the polymeric nanocomposites was varied as the type of co-monomer (acrylic acid and poly(ethyleneglycol) methylether methacrylate (PEGMA)), crosslinker (methylene bis-acrylamide (MBA) and poly(ethyleneglycol) diacrylate (PEGDA)) and precursor magnetic nanoparticle. The metallic nanoparticles and the core@shell Fe@SiO2 and Fe@Fe3O4 nanostructures were characterized by XRD, Mössbauer spectroscopy, XPS, SEM and TEM. The results show that the iron nanoparticles were composed of α-Fe and varying amounts of Fe1-xBx alloy and the size and morphology of the particles was dependent of the reaction media used. The strategies for metallic nanoparticles coating was efficient and chemically stabilized the magnetic cores. The Fe@SiO2 nanostructures was prepared by using alkoxysilanes precursors through the sol-gel process to produce the silica coating. The silica thickness could be controlled more efficiently in the case of bigger particles produced from chemical reduction in aqueous media. In the case of small nanoparticles the formation of aggregates was observed. The Fe@Fe3O4 core@shell structures were obtained by passivation of the metallic iron nanoparticles in a glycol solvent. The method of passivation enabled good oxidation control of the metallic surface to magnetite phase, avoiding the formation of non-magnetic oxy-hydroxides. The metallic to oxide phase ratio was determined by Rietveld refinement and was dependent of the type...

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Cláudia, Vaz de Araújo Ana. « Síntese de nanopartículas de Fe3O4, nanocompósitos de Fe3O4 com polímeros e materiais carbonáceos ». Universidade Federal de Pernambuco, 2011. https://repositorio.ufpe.br/handle/123456789/9226.

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Universidade Federal Rural de Pernambuco
Nanopartículas magnéticas de Fe3O4 foram sintetizadas através do método da precipitação a partir de uma solução aquosa de sulfato ferroso, sob ultrassom. Um planejamento fatorial 23 em duplicata foi desenvolvido para determinar as melhores condições de síntese e obter o menor tamanho de cristalito. As condições selecionadas foram: freqüência do ultrassom de 593 kHz durante 40 min em 1,0 mol L-1 de hidróxido de sódio. Foi obtido tamanho médio do cristalito da ordem de 25 nm. A fase cristalina obtida foi identificada por difratometria de raios-X (DRX) como sendo a magnetita. A microscopia eletrônica de varredura (MEV) mostrou partículas polidispersas com dimensões em torno de 57 nm, enquanto a microscopia eletrônica de transmissão (MET) revelou um diâmetro médio das partículas em torno de 29 nm, na mesma ordem de grandeza do tamanho de cristalito determinado com a equação de Scherrer. Estas nanopartículas magnéticas foram utilizadas para a obtenção de nanocompósitos com polianilina (PAni). O material foi preparado sob exposição à luz ultravioleta (UV) ou sob aquecimento, a partir de dispersões das nanopartículas em solução ácida de anilina. Ao contrário de outras rotas sintéticas reportadas na literatura, esta nova rota não faz uso de um agente oxidante adicional. Análises de DRX mostraram o surgimento de uma segunda fase cristalina em todos os compósitos de PAni-Fe3O4, a qual foi indexada como goetita. Além disso, o tamanho de cristalito diminui quase 50% em função do aumento do tempo de síntese. Esta diminuição de tamanho sugere que as nanopartículas são consumidas durante a síntese. A análise termogravimétrica mostrou que a quantidade de polianilina aumenta com o aumento do tempo de síntese. A condutividade elétrica dos nanocompósitos foi de cerca de 10-5 S cm-1, aproximadamente uma ordem de grandeza mais alta que para a magnetita pura. A condutividade variou com a quantidade de PAni presente no sistema, sugerindo que as propriedades elétricas dos nanocompósitos podem ser ajustadas de acordo com a sua composição. Sob a aplicação de um campo magnético externo os nanocompósitos apresentam histerese a temperatura ambiente, característica de materiais ferromagnéticos. A magnetização de saturação (MS) observada para a magnetita pura foi cerca de 74 emu/g. Para os nanocompósitos PAni-Fe3O4, MS variou de aproximadamente 2,0 a 70 emu/g de acordo com as condições de síntese. Isto sugere que a composição do material também pode ser usada para controlar suas propriedades magnéticas. Um nanocompósito de PAni-Fe3O4-Quitosana foi obtido a partir de uma mistura das nanopartículas de Fe3O4 com uma solução de anilina e uma solução ácida de quitosana exposta à UV. O uso da quitosana permitiu a obtenção de filmes contendo PAni e nanopartículas de Fe3O4, as quais apresentaram diâmetro médio da ordem de 5 nm. A ausência de histerese nas medidas de magnetização indicou que o material possui características superparamagnéticas. A pirólise de misturas de PAni sintetizada quimicamente e nanopartículas de Fe3O4 foi utilizada para produzir materiais carbonáceos porosos. Morfologias fibrilares foram observadas por MEV e MET. Resultados mostraram que o material é mesoporoso (diâmetro de poro de 2 a 50 nm), com áreas superficiais de BET entre 200 e 400 m2/g

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Jesus, Ana Carla Batista de. « Síntese e caracterização de nanoestruturas Fe3O4 e Fe3O4@Ag para estudos com hipertermia magnética ». Pós-Graduação em Física, 2018. http://ri.ufs.br/jspui/handle/riufs/8037.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
Fundação de Apoio a Pesquisa e à Inovação Tecnológica do Estado de Sergipe - FAPITEC/SE
In this work we have performed a study of the structural and magnetic properties in Fe3o4@Agx nanostructures (x=0,1,5 and 10%), synthesized by thermal decomposition (DT) and co-precipitation (CP). The samples were characterized by measurements of X-ray diffraction (XRD) and transmission electron microscopy (TEM). The XRD patterns indicate the presence of the Fe3o4 and Ag phase. The mean crystallites size corresponding to the Fe3o4 estimated by using the Scherrer’s equation shows that the nanostructures present not change considerable in the size after insertion of Ag for both growth methods. The TEM images obtained for DT samples reveal that the nanostructures are a like-spherical shape and average sizes of 3 nm which are in good according with size estimated by XRD. The mass loss observed in TG analysis was used to estimate the amount of organic matter present in the samples and consenquently normalize the magnetic measurements. The magnetic characterization was carried out by magnetization measurements as a function of magnetic field (MvsH) and temperature in Zero Field Cooling – Field Cooling (ZFC/FC) modes. These results indicate that the samples present superparamagnetic behavior to start 220 K. Fits of the ZFC / FC curves allowed verify that the magnetic anisotropy constant decreasing as a function of Ag-concentration. Magnetic hyperthermia measurements were performed in the samples synthesized via CP and the specific absorption rate (SAR) was estimated between 8 and 40 W / g.
Neste trabalho foi realizado um estudo das propriedades estruturais e magnéticas em nanoestruturas Fe3o4@Agx (x=0,1,5 and 10%), sintetizadas pelos métodos de decomposição térmica (DT) e de co-precipitação (CP). As amostras foram caracterizadas estruturalmente através de medidas de difração de raios X (DRX) e microscopia eletrônica de transmissão (MET). Os padrões de DRX indicam a presença da fase cristalina de Fe3o4 para todas as amostras, mas nas amostras aonde foi inserida a Ag há presença de uma outra fase cristalina, ou seja, a fase da Ag. O tamanho médio dos cristalitos estimados utilizando a largura à meia altura dos picos de DRX e a equação de Scherrer, mostra que as nanoestruturas não sofreram alterações consideráveis de tamanho após o acréscimo da Ag, mesmo com o aumento da concentração de Ag para ambos os métodos. As imagens de MET obtidas para as amostras sintetizadas via DT revelam que as nanoestruturas apresentam formatos praticamente esféricos e com tamanhos médios de 3 nm, que estão de acordo com os tamanhos estimados por DRX. Análises termogravimétricas foram utilizadas para estimar as perdas de massa de orgânicos presente nas amostras e assim realizar a normalização das medidas de magnetização. A caracterização magnética foi feita através de medidas de magnetização em função do campo magnético (MvsH) e da temperatura no modo Zero Field Cooling – Field Cooling (ZFC/FC). Estas medidas indicam que as amostras apresentam um comportamento superparamagnético a partir de 220 K. A realização de ajustes nas curvas ZFC/FC permitiu verificar que a constante de anisotropia magnética diminui com a concentração de Ag. Também foram realizadas medidas de hipertermia magnética nas amostras sintetizadas via CP e através das análises foi estimada a taxa de absorção específica (SAR), com valores entre 8 e 40 W/g.
São Cristóvão, SE

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Huet, 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/.

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Neste trabalho foram estudadas as nanopartículas magnéticas (NPs) de interesse em biomedicina de Fe3O4 e de Fe3O4 dopadas com Gd 5% pela técnica de Espectroscopia de correlação angular gama-gama perturbada (CAP). As amostras de Fe3O4 foram sintetizadas pelos métodos de co-precipitação e decomposição térmica e as nanopartículas de Fe3O4 dopadas com Gd 5% foram sintetizadas pelo método da coprecipitação. As amostras de nanoparticulas foram caracterizadas quanto a sua estrutura pela difração de raios X (DRX) e quanto ao seu tamanho pela técnica de microscopia eletrônica de transmissão (TEM). Os resultados mostram que as nanoparticulas de ferrita mostram estrutura pertencente ao grupo espacial Fd3m e que seu tamanho é de 10 nm quando sintetizada por decomposição térmica e entre 7 e 15 nm quando sintetizada por co-precipitação. As nanopartículas de Fe3O4 sintetizadas pelo método de decomposição térmica apresentaram maior monodispersão do que as nanopartículas sintetizadas pelo método de co-precipitação, ou seja, o tamanho de grão estava mais homogêneo. A técnica CAP mostrou que a variação de tamanho das nanopartículas infuencia no comportamento magnético das mesmas e o dopante Gd atrapalha a introdução da sonda radioativa por competir pelos sítios de Fe.
In 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.

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Bataille, Alexandre. « Etude des propriétés physiques des films de Fe3O4 et de la polarisation en spin à l'interface Fe3O4/gamma-Al2O3 ». Paris 11, 2005. https://tel.archives-ouvertes.fr/tel-00085941.

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La magnétite Fe3O4 est un matériau prometteur pour l'électronique de spin, puisque des calculs de structure de bande la prédisent demi-métallique, c'est à dire totalement polarisée en spin au niveau de Fermi. Nous avons fait croître des films minces de Fe3O4 de 3 à 50 nm d'épaisseur sur γ-Al2O3 par épitaxie par jets moléculaires. Les films sont monocristallins mais présentent un grand nombre de parois d'antiphase qui sont responsables des anomalies magnétiques observées. Nous avons reproduit le comportement magnétique des films à l'aide d'un modèle unidimensionnel et confronté les résultats avec la taille caractéristique des parois mesurée par une analyse fractale. Nous avons d'autre part étudié la transition de Verwey des films minces; les effets de taille finie font disparaître la transition pour les films d'épaisseur inférieure à 20 nm et le magnétisme de tous les films présente des effets de dynamique lente. Nous avons de plus mis au point une méthode de dépôt de couches minces de γ-Al2O3 épitaxiée sur les films de Fe3O4, en contrôlant la stoechiométrie à l'interface entre oxydes. Les films de γ-Al2O3 d'épaisseur supérieure à 2 nm présentent toutes les propriétés requises pour une barrière tunnel (continuité électrique, découplage magnétique entre les électrodes). Nous avons enfin étudié la polarisation en spin à l'inierface Fe3O4/ γ-Al2O3 par deux méthodes distinctes: les mesures directes par photoémission résolue en spin conduisent à une polarisation en spin de -40% tandis que l'on mesure une magnétorésistancc tunnel de +3% à température ambiante pour les jonctions tunnel Fe3O4/ γ-Al2O3/Co
Magnetite Fe3O4 is a promising material for spintronics since band structure calculations predict it to be half-metallic, i. E. Fully spin-polarised at the Fermi level. One thus expects large magnetoresistance in magnetic tunnel junctions using Fe3O4 as electrode. We have grown 3 to 50 nm-thick Fe3O4 thin films onto γ-Al2O3 by molecular beam epitaxy. The films are single crystalline but comprise a large number of antiphase boundaries which are responsible for the magnetic anomalies of Fe3O4 thin films. We have qualitatively reproduced the magnetic behavior of our samples with a one-dimensionnal model, and compared the results with the characteristic size of the antiphase boundaries measured by a fractal analysis. We also studied the Verwey transitions of our thin films. The transition is not seen for thicknesses below 20 nm because of finite size effects and all samples show slow magnetization dynamics. We have also developed a growth method allowing us to deposit γ-Al2O3 epitaxially onto Fe3O4, and to control the stoichiometry at the interface. γ-Al2O3 thin films of thicknesses greater than 2 nm exhibit all the characteristics required for a tunnel barrier (electrical continuity, magnetic decoupling). We finally studied the spin polarization at the Fe3O4/γ-Al2O3 interface by too distinct methods. Direct measurements by spin resolved photoemission yields to -40 % for the spin polarization whereas the tunnel magnetoresistance is +3\% at room temperature for Fe3O4/ γ-Al2O3/Co

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Bataille, Alexandre. « Etude des propriétés physiques des films de Fe3O4 épitaxiés et de la polarisation en spin à l'interface Fe3O4/γ-Al2O3 ». Phd thesis, Université Paris Sud - Paris XI, 2005. http://tel.archives-ouvertes.fr/tel-00085941.

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La magnétite Fe3O4 est un matériau prometteur pour l'électronique de spin, puisque des calculs de structure de bande la prédisent demi-métallique, ce qui laisse supposer des effets de magnétorésistance importants pour des jonctions tunnel magnétiques utilisant Fe3O4 comme électrode. Nous avons fait croître des films minces de Fe3O4 de 3 à 50 nm d'épaisseur sur α-Al2O3 par épitaxie par jets moléculaires. Les films sont monocristallins mais contiennent des parois d'antiphase. Celles-ci sont responsables des anomalies magnétiques observées sur les films, que nous avons pu reproduire à l'aide d'un modèle unidimensionnel, les résultats ayant étés confrontés avec la taille caractéristique des parois mesurée par une analyse
fractale.

Nous avons de plus mis au point la croissance de couches minces de γ-Al2O3 épitaxiée sur les films de Fe3O4, en contrôlant la stoechiométrie à l'interface entre oxydes. Les films de γ-Al2O3 d'épaisseur supérieure à 2 nm sont continus, et assurent le découplage magnétique entre les électrodes. Les mesures directes par photoémission résolue en spin conduisent à une polarisation en spin de -40 % pour l'interface Fe3O4/ γ-Al2O3 tandis que l'on mesure
une magnétorésistance tunnel, réduite du fait du désordre magnétique induit par les parois d'antiphase, de +3 % à température ambiante pour les jonctions Fe3O4/ γ-Al2O3/Co, ce qui implique une polarisation effective positive pour l'interface Fe3O4/ γ-Al2O3 dans les mesures de transport tunnel.

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CATALANO, ENRICO. « Physicochemical and biological characterization of magnetic nanoparticles for biomedical applications ». Doctoral thesis, Università del Piemonte Orientale, 2015. http://hdl.handle.net/11579/81662.

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The overall goal of this project was the biological characterization by in vivo and in vitro testing of magnetic nanoparticles that can be used for various applications. The aim of this work was to understand which of the synthesized magnetic nanoparticles could be more suitable to be used as a carrier or platform for various applications in different scientific fields. Two different kinds of magnetic nanoparticles were developed: naked iron-oxide nanoparticles and silica or silica-based coated nanoparticles (core shell-type nanoparticles). Magnetic nanoparticles were prepared using a coprecipitation method. The structure, phase composition, physicochemical and surface properties, magnetic susceptibility, and release in vitro of MNPs were characterized by transmission electron microscopy, x-ray diffraction, scanning electron microscopy-energy dispersive x-ray spectroscopy, and a vibrating sample magnetometer. In vivo toxicity, in vitro toxicity, ROS production and genotoxicity were investigated. Therapeutic effects were evaluated by cell viability assays and flow cytometry assays. The tools developed in this thesis spanned a range of physical-chemical, biological and magnetic aspects and incorporate innovations on a nanometric range of scales. MNP-based technologies appear to hold a significant potential for a myriad of biomedical applications and the toxic potential of MNPs cannot be overlooked. For this reason we carried out different physicochemical and biological characterization of MNPs to identify a safe dose and formulation of MNPs. Understanding the relationship between the physicochemical properties of MNP constructs and their behavior will induce full translational potential of these nanoparticles. The magnetic nanoparticles prepared in this study have good biocompatibility and are suitable for further application in tumor hyperthermia.

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Lima, Bruno Henrique Ramos de. « Nanopartículas de Fe3O4 funcionalizadas e nanocompósitos de base epóxi ». Universidade Federal de São Carlos, 2015. https://repositorio.ufscar.br/handle/ufscar/7452.

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
The use of metal oxide nanoparticles in nanocomposite has provided new and interesting properties and is one of the most promising areas in composites. Compatibility between these nanoparticles and polymer matrix is the most critical fator on development of these materials. In this context, this thesis project has focused on study of synthesis and functionalization of magnetite nanoparticles (Fe3O4) aiming its incorporation into bisphenol A based diglycidyl ether based to produce nanocomposites with very high compatibility between dispersed and matrix phases. Synthesis and functionalization of nanoparticles were performed in a single step by thermodecomposition of iron (III) acetylacetonate in poly (1,4- butanediol) with molar weight 1000, which served both as a solvent for the reaction as a source of molecules for surface functionalization of the nanoparticles. Nanoparticles with an average size of 8,4 nm and with high volume fraction of organic layer were obtained and the synthesis was highly reproducible. The produced nanocomposite exhibited high homogeneity of nanoparticles dispersion and the absence of large agglomerates. The interaction between the nanoparticles and matrix occurred through the chemical reaction between the functional groups of the organic layer and the DGEBA, as was expected, and through intercalation of DGEBA molecules between the molecules from the organic layer, thereby creating a new interphase with unique properties. Due to the high volume fraction of this new phase, the density and modulus of elasticity exhibited behavior that could not be explained by traditional methods. A new approach was used to develop a model that considered this third phase and set more consistently to the experimental data obtained, and showing the domain of this new interphase on the nanocomposite`s properties.
O uso de nanopartículas de óxidos metálicos em nanocompósitos tem proporcionado novas e interessantes propriedades e é uma das áreas mais promissoras em compósitos. A compatibilização entre essas nanopartículas e a matriz polimérica é ainda um dos pontos mais críticos no desenvolvimento desses materiais. Nesse contexto, esse projeto de tese teve como foco estudar a síntese e funcionalização de nanopartículas de magnetita (Fe3O4) visando sua incorporação em matriz polimérica a base de diglicidil éter bisfenol A (DGEBA) para produção de nanocompósitos em que matriz e fase dispersa apresentam altíssima compatibilidade. A síntese e funcionalização das nanopartículas foram feitas em uma única etapa através da termodecomposição de acetilacetonato de ferro (III) em poli(1,4 butanodiol) de massa molar 1000, que atuou tanto como solvente da reação quanto fonte de moléculas para a funcionalização superficial das nanopartículas. Nanopartículas com tamanho médio 8,4 nm e com alta fração volumétrica de capa orgânica foram obtidas e a síntese se mostrou altamente reprodutível. Os nanocompósitos produzidos apresentaram uma alta homogeneidade de dispersão de nanopartículas e ausência de grandes aglomerados. A interação entre as nanopartículas e matriz ocorreu através da reação química entre os grupos funcionais da capa orgânica e do DGEBA, como era esperado, e também através da intercalação de moléculas de DGEBA entre as moléculas que formam a capa orgânica, criando assim uma nova interfase com propriedades únicas. Devido à altíssima fração volumétrica dessa nova fase, a densidade e o módulo de elasticidade apresentaram comportamentos que não puderam ser explicados pelos métodos tradicionais. Uma nova abordagem foi usada para desenvolver um modelo que considerou essa terceira fase e se ajustou de forma mais coerente aos dados experimentais obtidos, mostrando o domínio dessa nova fase sobre as propriedades do nanocompósito.

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León, Félix Lizbet. « Síntese e caracterização de nanopartículas de Fe3O4 recobertas com ouro ». reponame:Repositório Institucional da UnB, 2013. http://repositorio.unb.br/handle/10482/13862.

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Dissertação (mestrado)—Universidade de Brasília, Instituto de Física, Programa de Pós-Graduação do Instituto de Física 2013.
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Neste trabalho apresenta-se o estudo experimental de nanopartículas de magnetita com e sem recobrimento de ouro. As nanopartículas de magnetita foram sintetizadas pelo método de coprecipitação e o recobrimento com ouro foi realizado usando as nanopartículas em solução com citrato de sódio adicionando o colóide de ouro (HAuCl4). O estudo estrutural e o tamanho do cristalito foram determinados por difração de raios-X. O refinamento de Rietveld dos dados de raios-X revelou a formação de uma única fase cristalina. O tamanho médio das partículas sem recobrimento é de ~ 7 nm e de ~ 8 nm na amostra recoberta com ouro. Estes tamanhos foram corroborados com imagens de microscopia eletrônica de transmissão. Espectros Mössbauer à temperatura ambiente mostram evidências da relaxação térmica parcial dos momentos magnéticos. A ausência de um dubleto central em 297 K foi associada à ocorrência de interações partícula-partícula. Os espectros obtidos a 77 K foram modelados com quatro sextetos os quais foram atribuídos a íons de Fe3+ ocupando sítios tetraédricos e octaédricos e Fe2+ ocupando sítios octaédricos da estrutura cristalina. Evidências da ocorrência de desordem superficial foram também determinadas nas nanopartículas sem recobrimento. Esta desordem é reduzida nas nanopartículas recobertas com ouro. Curvas de histerese magnética obtidas a 300 K para as duas amostras apresentam um campo coercivo quase nulo, o que sugere um comportamento superparamagnético em altas temperaturas. O comportamento irreversível observado entre as curvas ZFC e FC abaixo de Tirr ~ 280 K e o máximo na curva ZFC são evidências da ocorrência de relaxação térmica dos momentos magnéticos. Determinou-se que a posição do máximo da curva ZFC é bem maior do que a temperatura de bloqueio para um sistema superparamagnético de partículas não interagente. Esse resultado foi associado com a ocorrência de interações entre as partículas, que retardam a relaxação térmica em baixos campos e aumentam a temperatura de bloqueio do sistema. Também foi estudado o efeito das interações sobre as propriedades magnéticas. Determinouse a presença de um momento magnético aparente que permite o "scaling"das curvas M/MS vs. MS(H/T). O crescimento deste momento magnético aparente com a temperatura (acima de 200 K) confirma a ocorrência de interações cuja natureza é dipolar. Estes resultados sugerem que acima de 200 K, os sistemas estudados se encontram num regime de superparamagnetismo interagente e que são necessárias temperaturas bem maiores (T > T*) para que os sistemas mostrem um comportamento superparamagnético convencional. As propriedades dinâmicas das amostras foram estudadas por medidas de susceptibilidade AC. Estas medidas confirmam a ocorrência de relaxações térmicas dos momentos magnéticos acima de 150 K. Para explicar a dependência na frequência da posição do máximo da curva X ’ vs. T é necessário incluir um parâmetro que represente as interações entre as partículas. Este analise confirmam os resultados obtidos por medidas de magnetização DC e espectroscopia Mössbauer em ambas as amostras. _______________________________________________________________________________________ ABSTRACT
In this work presents the experimental study of uncoated and gold-coated magnetite nanoparticles. Magnetite nanoparticles have been synthesized using the co-precipitation method and their coating with gold has been obtained adding (HAuCl4) into the solution of the nanoparticles containing sodium citrate. The structural characterization and crystallite size have determined by X-ray diffraction. The Rietveld refinement of the X-ray diffraction data reveals the formation of a single crystalline phase. The mean size of the uncoated nanoparticles is ~ 7 nm and ~ 8 nm for the gold coated nanoparticles. These sizes have been corroborated by transmission electron microscopy images. Mössbauer spectra at room temperature show evidences of the partial thermal relaxation of the magnetic moments. The absence of a central doublet at 297 K was assigned to the occurrence of particle-particle interactions. Spectra obtained at 77 K were modeled using four sextets which were associated with Fe3+ ions occupying tetrahedral and octahedral sites and Fe2+ occupying octahedral sites in the crystalline structure. Evidences of the occurrence of surface disorder were also determined for the uncoated nanoparticles. This disorder is lower for the gold coated nanoparticles. Magnetic hysteresis curves obtained at 300 K for the samples show an almost zero coercive field, which suggests a superparamagnetic behavior at high temperatures. The irreversible behavior observed for the ZFC and FC curves below Tirr ~ 280 K and the maximum of the ZFC curve are evidences for the occurrence of thermal relaxations of the magnetic moments. It has been determined that the position of the maximum of the ZFC curves is quite larger than the blocking temperature for a superparamagnetic system of non-interacting particles. This result was associated to the occurrence of particles interactions, which delays the thermal relaxation at low magnetic fields and increases the blocking temperature of the system. Also, the effect of the interaction on the magnetic properties was studied. It has been determined that the presence of an apparent magnetic moment which permits the scaling of M/MS vs. MS(H/T) curves. The increase of this apparent magnetic moment with the temperature (above 200 K) confirms the occurrence of particles interactions whose nature is dipolar. These results suggest that above 200 K, the studied systems are in a interacting superparamagnetic regime and high temperatures (T > T*) are necessary in order to appear conventional superparamagnetism in the systems. The dynamical properties of the samples were studied by AC susceptibility measurements. These measurements confirm the occurrence of thermal relaxations of magnetic moments above 150 K. In order to explain the frequency dependence of the maximum of the X ’ vs. T curve, it is needed to include a term to represent the particles interaction. These analyses confirm the results obtained by DC magnetization and Mössbauer spectroscopy in both samples.

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Руденко, Н. П. « Кинетика анодного растворения железа и сталей в растворах Р2SO4-FeSO4 ». Thesis, Издательство СумГУ, 2012. http://essuir.sumdu.edu.ua/handle/123456789/25987.

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Демчук, В. Б., В. А. Сидлецкий et В. А. Мащенко. « Влияние магнитного поля на электрические свойства ПВХ, наполненного дисперсным Fe3O4 ». Thesis, Издательство СумГУ, 2012. http://essuir.sumdu.edu.ua/handle/123456789/27577.

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Monnington, Amy Elizabeth. « Modelling magnetite biomineralisation : the interactions of proteins and Fe3O4 surfaces ». Thesis, University of Huddersfield, 2014. http://eprints.hud.ac.uk/id/eprint/23448/.

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The biosynthesis of magnetite is the earliest known example of biomineralisation; how-ever, much of the detailed atomistic mechanisms by which the process occurs are unknown. Within the bacterial strain Magnetospirillum magneticum AMB-1, the formation of mag-netite nanoparticles is thought to occur under the inﬂuence of the Mms6 protein. The C–terminal of this protein is highly acidic, containing dense carboxyl and hydroxyl groups, and exhibits direct interaction with the magnetite surface. In this thesis, a novel atomistic model of Mms6-driven magnetite formation was developed and the interactions of amino acids, dipeptide, tetrapeptide and pentapeptide sequences, related to the C-terminus of Mms6, with the{100}and{111}magnetite surfaces (both in vacu and solvated) have been investigated. Each study was split into two systems; a classic molecular dynamics system and a constrained molecular dynamics system utilising the Potential of Mean Force. Initially, the attachment of the individual amino acids to magnetite surfaces was consid-ered. From these results, it was established that the {111} surface was the favoured for surface for amino acid attachment and bonding occurred through octahedral iron ions, rather than tetrahedral iron ions. Furthermore, the charged amino acids demonstrated a higher aﬃnity for iron binding and solvation of unconstrained systems diminished the iron binding abilities of all the amino acids. Secondly, based on a glutamate repeat motif, the attachment of a series of di- and tetrapep-tides to the {100} and {111} magnetite surfaces was explored. It was hypothesised that if the negatively charged glutamate was substituted for a charge neutral alanine, the iron binding potential of the sequence would reduce. The results suggested that the substitu-tion of glutamate for alanine signiﬁcantly reduces the iron binding aﬃnity of the system on the {100} surface, irrespective of sequence length and composition. However, on the {111}surface, the introduction of alanine diﬀerentially modulates the iron binding activity of the sequences investigated. Sequential substitution in a two amino acid chain confers inhibition of iron binding, conversely, in a four amino acid chain, iron binding aﬃnity is enhanced. The ﬁnal chapter utilised pentapeptides taken from the Cterminal region, thus ensuring the full sequence was explored. The binding behaviour of these pentapeptides and their related mutants, were investigated. It was found that the diﬀerent sections behaved diﬀer-ently from each other, suggesting that the binding activity of the C-terminal sequence is partly dependent on how the amino acids interact with each other. It was theorised that sequence mutation would decrease iron binding; however, the data suggested that this was not always the case and was sequence dependent. Based on the constrained system data, mutation of the original sequences conﬁrmed the hypothesis for DIESA, LRDAL and EVELR on the {100} surface, and for SRDIE and SDEEV on the {111} surface, whereas, the theory was contradicted for the counterparts surfaces and for both surfaces of ELRDA. This data also suggests that the {111} surface was the preferred surface of attachment, with the exception of LRDAL. For the unconstrained systems, the observations diﬀered dependent on the data analysis technique utilised, as well as on the pentapeptide original sequence, with none of the sequences explored fully conﬁrming the hypothesis. Furthermore, the presence of water in the unconstrained systems was detrimental to the iron binding potential of the pentapeptides. The data from both the unconstrained and constrained systems propose that, there are many factors aﬀecting the iron binding ability other than sequence mutation, such as, surface type, iron type and sequence dependence.

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Haney, Carl Edwin. « Effects on Iron Nanoparticles on Pseudomonas Aeruginosa Biofilms ». University of Dayton / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1324058048.

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Liong, Silvia. « A Multifunctional Approach to Development, Fabrication, and Characterization of Fe3O4 Composites ». Diss., Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/7640.

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A unique approach for lightweight multifunctional composites was developed using Fe3O4 nanoparticles and polypyrrole-coated Fe3O4 particles as fillers. Fe3O4 particles are a good candidate for filler in a multifunctional composite system because they can reinforce mechanical properties of a polymer matrix and impart magnetic properties into a composite. Polypyrrole coating on Fe3O4 particles was utilized to incorporate electrical conductivity to the properties of composites. The effects of filler size and filler content were studied on both the mechanical and electromagnetic properties. Fe3O4 nanoparticles improved fracture toughness, but they compromised strength and modulus. Polypyrrole-coated Fe3O4 has potential for multifunctional material applications because the coating allows for concurrent increase in magnetic permeability and electrical conductivity in a composite. The polypyrrole coating also improved the strength of the composite. Fe3O4 nanoparticles were a major part of this work from their synthesis to their application in composites. The surface effect on magnetic properties was analyzed for Fe3O4 nanoparticles, resulting in a more accurate calculation of the magnetically dead layer thickness than previously reported. The results from this work contributed to further understanding of synthesis and characterization of magnetic nanoparticles, fabrication and characterization of nanocomposites, and design and development of lightweight multifunctional materials. Although the properties of the fabricated composites require further improvement, the methodology and approach provide a basis for future work in development of lightweight multifunctional composites.

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Bradley, Ruth. « Optimisation of Fe3O4 thin films and nanostructures for atom trapping applications ». Thesis, University of Sheffield, 2017. http://etheses.whiterose.ac.uk/19747/.

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Thin films and nanostructures of Fe3O4 have been investigated and analysed with the aim of being used for an exciting application where the stray magnetic field from domain walls in nanowires are used to trap ultra-cold atoms. In this thesis, polycrystalline Fe3O4 thin films have been successfully grown on Si using reactive dc magnetron sputtering from a Fe target. It has been shown that by using different growth temperatures produces different iron oxide phases. Fe3O4 was grown at substrate temperatures of 200 – 500 ºC with a mixed iron oxide phase of Fe3O4 & α-Fe2O3 produced at RT & 100 ºC. In contrast to the polycrystalline, granular films on Si, Fe3O4 thin films grown on MgO (100) have been shown to be textured with a smooth surface. However, multiple different surface morphologies have been found for the Fe3O4/MgO films. The coercivity of the Fe3O4 films has a negative trend with the film thickness for both substrates, whereas the grain size (Fe3O4/Si) has a positive trend with both film thickness and growth temperature. Following an annealing treatment of Fe3O4 thin films at 250 ºC the composition of the film was altered to become a mixed iron oxide of Fe3O4 & γ-Fe2O3. Dramatic changes in coercivity have been observed, with a large increase seen for the films on Si and negligible change seen for the films on MgO. However, a significant decrease in coercivity has been seen for a smooth film on MgO and the increase in coercivity on Si is dependent on the presence of Fe3O4 regions amongst the mixed iron oxide. Nanostructures of Fe3O4 were created from thin films on Si & MgO, with the nanorings remaining in a saturated state after an in-plane magnetic field is removed. Applying a small negative field to the nanorings on MgO produces a magnetic structure similar to that seen in nanostructures with a 4-fold magnetocrystalline anisotropy.

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MONSALVE, Johanna Gil. « Oscilação da magnetização em nanocompósitos de Fe3O4/PANI e γFe2O3/PANI ». Universidade Federal de Pernambuco, 2017. https://repositorio.ufpe.br/handle/123456789/22658.

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Estudos recentes mostram que o nanocompósito Fe3O4/PANI tem propriedades magnéticas interessantes, como oscilações sustentadas na magnetização, que foram interpretadas como o resultado de uma reação química oscilante que faz que uma fração do conteúdo de magnetita seja transformada em maghemita e vice-versa [1]. Neste trabalho fizemos estudos adicionais. Variamos parâmetros como temperatura, tipo e concentração de ácidos, além de usar como ponto de partida óxidos comerciais e de tamanho maior. Produzimos ainda nanocompósitos Fe2O3/PANI sob as mesmas condições usando Fe2O3 ao invés de Fe3O4. Para os nanocompósitos produzidos estudamos as propriedades magnéticas e estruturais e a cinética química da reação através da magnetização da solução precursora. Os nanocompósitos Fe3O4/PANI e Fe2O3/PANI foram preparados sob UV (365nm) a diferentes tempos de exposição e sob aquecimento (40, 60 e 80 °C), mediante a dispersão das nanopartículas de magnetita e maghemita em uma solução ácida de anilina. Para o estudo de suas propriedades foram usadas medidas de difração de raios X (DRX), análises termogravimétricas e de calorimetria de varredura diferencial (TGA e DSC). Para a caracterização magnética foi usado um magnetômetro de amostra vibrante (VSM) para obter curvas de histereses, plot de Henkel, verificação das mudanças na transição de Verwey e estudo da cinética química a partir da magnetização da solução líquida precursora dos nanocompósitos. Este último resultado foi analisado segundo modelo presa-predador de Lotka Volterra, um modelo simples, qualitativo, para esse sistema relativamente complexo e caótico. As curvas de histerese dos nanocompósitos sintetizados a 40 ºC mostraram oscilações na magnetização; enquanto que para 60 e 80 °C sob UV mostraram um decréscimo acentuado na magnetização máxima com o tempo de reação. As curvas do plot de Henkel mostraram que predominam efeitos de interação de natureza desmagnetizante. Foi observada a transição Verwey, mas deslocada da temperatura típica para os nanocompósitos sintetizados a 40 ºC, sugerindo que isso seja uma evidência das mudanças do número de oxidação do Fe provocados pela polimerização e radiação UV. Finalmente, usando o modelo Lotka-Volterra e suas propriedades matemáticas intrínsecas, verificamos o efeito nos parâmetros do modelo provocados pela mudança de alguns parâmetros importantes da reação. A caracterização estrutural mediante DRX mostraram que todas as nanopartículas são cristalinas exceto para as amostras de 80 ºC após de 1 h de reação. Os difratogramas para as amostras de Fe3O4/PANI tratadas a 60 ºC mostraram um deslocamento dos picos característicos indicando a transformação magnetita/maghemita/magnetita. Aparece também uma nova fase cristalina, a qual foi indexada como hematita. Por outro lado, não há variações muito significativas do tamanho de cristalito para Fe3O4/PANI, enquanto que para os nanocompósitos Fe2O3/PANI tratados a 60 ºC há um leve aumento no tamanho de cristalito com o tempo de síntese, assim como com o aumento na temperatura. A análise TGA e DSC mostrou que a polimerização é favorecida pelo calor e pelo tempo de reação. Além disso, conforme o esperado pelo modelo proposto por A. C. V de Araújo e col. [1], a polimerização para os nanocompósitos Fe2O3/PANI é mais acelerada que Fe3O4/PANI.
Recent studies show that the Fe3O4/PANI nanocomposite has interesting magnetic properties, such as sustained oscillations in magnetization, which have been interpreted as the result of an oscillating chemical reaction that causes a fraction of the magnetite content to be transformed into maghemite and vice-versa [1]. In this work we did additional studies. Where we had changed parameters such as temperature, type and concentration of acids, as well as using commercial oxides with larger sizes. We have also produced Fe2O3/PANI nanocomposites under the same conditions using Fe2O3 instead of Fe3O4. For the produced nanocomposites, we have studied the magnetic and structural properties as well as the chemical kinetics of the reaction through the magnetization of the precursor solution. The Fe3O4/PANI and Fe2O3/PANI nanocomposites were prepared under UV (365 nm) at different exposure times and under heating (40, 60 and 80 °C) by dispersing the nanoparticles of magnetite and maghemite in an acid solution of aniline. X-ray diffraction (XRD), thermogravimetric and differential scanning calorimetry (TGA and DSC) measurements were used to study their properties. For the magnetic characterization, a vibrating sample magnetometer (VSM) was used to obtain hysteresis curves, Henkel plot, verify changes in the Verwey transition and study the chemical kinetics from the magnetization of the liquid precursor solution of the nanocomposites. This last result was analyzed according to the prey-predator model of Lotka-Volterra, a simple, qualitative model for this relatively complex and chaotic system. The hysteresis curves of the nanocomposites synthesized at 40 ºC showed oscillations in the magnetization; while for 60 and 80 °C under UV showed a marked decrease in the maximum magnetization as function of the reaction time. Henkel plot curves showed that the interaction effects have a predominant demagnetizing nature. Verwey transition was observed, but displaced from the typical temperature for the 40 ºC synthesized nanocomposites, suggesting that this is an evidence of the changes in the oxidation number of Fe caused by polymerization and UV radiation. Finally, using the Lotka-Volterra model and its intrinsic mathematical properties, we verified the effect on the parameters of the model caused by the change of some important parameters of the reaction. The structural characterization by XRD showed that all the nanoparticles are crystalline except for the 80 ºC samples after 1 h of reaction. The diffractograms for the Fe3O4/PANI samples treated at 60 °C showed a shift of the characteristic peaks indicating a magnetite/maghemite/magnetite transformation. A new crystalline phase was observed, which was indexed as hematite. On the other hand, there are not significant variations of the crystallite size for Fe3O4/PANI, whereas for the Fe2O3/PANI nanocomposites treated at 60 °C there is a slight increase in the crystallite size over time as well as with the increase in temperature. The TGA and DSC analysis showed that polymerization is favored by heat and reaction time. In addition, as expected by the model proposed by A. C. V de Araújo et al. [1], the polymerization for the Fe2O3/PANI nanocomposites is more accelerated than for Fe3O4/PANI.

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Ciurli, Andrea. « FePO4 NANOPARTILCES AS SOURCE OF NUTRIENTS : EFFECTS ON THE PLANT-SOIL SYSTEM AND EVI-DENCE FOR A SAFE AND SUSTAINABLE NANO-FERTILIZATION ». Doctoral thesis, 2021. http://hdl.handle.net/11562/1044499.

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In the last decade, nanotechnology became a consistent part of the technological progress in modern agriculture, with applications in agri-food technology, nano-biosensoring, plant defence and plant nutrition. Nanomaterials which can provide one or more macro/micro-nutrient to the plant are commonly referred as nanofertilizers. Nevertheless, in the scientific literature there are still few evidence of a successful utilization of nanomaterials as fertilizers. In a previous work, it has been shown that iron phosphate (FePO4) nanoparticles (NPs) can provide either iron (Fe) or phosphate (P) to plants grown in hydroponic. The present study is aimed to highlight the effect of FePO4 NPs used as nanofertilizer in the whole plant-soil system, and to determine if they can represent a safe and effective alternative to conventional fertilizers. To investigate the plant early transcriptomic responses to FePO4 NPs exposure, microarray expression analyses have been performed in maize and cucumber roots grown in hydroponic for 24 hours. Responses of the plants treated with FePO4 NPs were shown to be associated mainly to biotic and abiotic stress, cell wall modulation and regulation of transcription, and triggered a different pattern of responses that was dependent on the nano-size. To evaluate the possibility to apply FePO4 NPs to the soil as fertilizer, two different bare soils were treated. Soil enzyme activities, CO2 respiration and DGGE analyses showed that there was not negative impact of FePO4 NPs onto soil microbial community and metabolic functions, neither toxic effects. Further, FePO4 NPs provided available P in bare soil in respect to triple superphosphate (TSP), even though the efficacy was dependent on the soil characteristics. Moreover, FePO4 NPs represented a source of available P for plant, which grown in soil in controlled condition without significant differences in respect to TSP, although P availability in the bare soil resulted lower for NPs than TSP. Microbial community associated to rhizosphere was not negatively affected by NPs and a stimulatory effect on enzyme activity was observed. In this work it was shown that FePO4 NPs can be applied to the soil without any negative consequence for the environment, enhancing plant growth and providing nutrients. These results encourage the hypothesis that the nanoparticulate nature of fertilizers could contribute to rationalize the chemical inputs in agriculture and increasing nutrient use efficiency

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Kinyanjui, Michael Kiarie [Verfasser]. « Electronic and structural properties of Li(1-x)FePO4 (X=0, 0.5, 1) / vorgelegt von Michael Kiarie Kinyanjui ». 2010. http://d-nb.info/1004984219/34.

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Sega, Davide. « FePO4 nanoparticles as a source of nutrients for plants : synthesis and evaluation of their effects on hydroponically grown cucumber and maize seedlings ». Doctoral thesis, 2018. http://hdl.handle.net/11562/977172.

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The nutrient use efficiency (NUE) of crops is typically low, in particular referring to the uptake of nutrients applied through fertilizers. A strategy to improve the NUE could be the development of new and more efficient fertilizers. A promising field in order to achieve this goal could be the use of nanotechnology. Nanomaterials are widely used in medical and pharmaceutical fields, but their application in agriculture and in particular in plant nutrition is at its infancy. A continuous method of FePO4 nanoparticles (FePO4 NPs) synthesis based on the extremely fine and rapid mixing of a FeCl3 solution with a K2HPO4 solution in a mixing chamber was tested for its effectiveness with a laboratory-made system. The proof-of-concept could produce FePO4 particles smaller than 100 nm, reaching the threshold of 50% of particles smaller of 100 nm, a value that is recommended by the European Union for the definition of nanomaterial. A pilot plant for the continuous FePO4 NPs synthesis was set up, using two dosing pumps for solutions pumping, and an HPLC mixing tee as mixing chamber. The system could produce 15 L•h-1 of raw FePO4 NPs suspension. Purification through dyalisis was optimized, together with a stabilization method of FePO4 NPs, called citrate capping, based on the adding of tribasic potassium citrate and thorough vortexing, in order to reduce aggregation and sedimentation of particles on long time periods. FePO4 NPs were then tested for their effectiveness as source of P and Fe on two hydroponically grown crop species, cucumber (Cucumis sativus) and maize (Zea mays). The experiments were designed in order to evaluate the effect of FePO4 NPs as source of both nutrients, or source of sole P and Fe. For this reason, as negative controls were used plants grown without P (-P), without Fe (-Fe), or without both nutrients (-P-Fe). In addition, in order to analyze if the size of FePO4 particles could cause different effects on plants, we included in the experiment a treatment with non-nanometric FePO4 (bulk FePO4). The results showed that nano-sized FePO4 improved the availability of P and Fe, if compared to the non-nano counterpart, as demonstrated by SPAD indexes of leaves and the determination of nutrients concentrations in tissues. Transmission Electron Microscopy (TEM) observations on cucumber roots treated with FePO4 NPs revealed that these particles did not enter into the plant, suggesting as mechanism of delivery of nutrients the dissolution in the apoplast. Gene expression analysis of homologs of AtPHR1, a key regulator of the response to P starvation in Arabidopsis, revealed in cucumber an upregulation of Csa3M608690 in plants grown with FePO4 NPs. The transcriptional behavior of Csa1M024210, homologs of AtBTS, suggested that plants grown with both forms of FePO4 are, with respect of Fe, in good nutritional conditions thus confirming physiological parameters. For maize, the negative modulation of ZmFER-Like gene in response to all treatments suggested a minor role of this gene in the regulation of Fe homeostasis in this plant species, while the upregulation of ZmIRO2 in plants grown with both forms of FePO4 confirmed the sub-optimal nutritional state of the plants.

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Shen, Ming-Zong, et 沈明宗. « Synthesis of Fe3O4，Fe3O4/SiO2，Fe3O4/TiO2 nano-particles and Its Applications ». Thesis, 2007. http://ndltd.ncl.edu.tw/handle/73914817140382431947.

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碩士
中原大學
化學研究所
95
Synthesis of Fe3O4 magnetic nanoparticles is carried out by microwave hydrothermal method. The size of Fe3O4 magnetic nanoparticles is controlled by changing solution’s concentration. We have prepared the Fe3O4/SiO2 Core/shell nanoparticles by using Stober process. In this study, Fe3O4 magnetic nanoparticles prepared by microwave hydrothermal method and is used for disposable glucose biosensor. The advantages such as excellent biocompatibility, low toxicity, superparamagnetic and biocatalytic properties of Fe3O4 nanoparticles was expected to increase electrode’s active area or promote electrons transfer, and hence improve the sensitivity of the biosensor. The disposable glucose electrodes were constructed by simple surface coatings of GOD and mixture of Fe3O4 nanoparticles onto gold electrodes. In this study, the modified processes of the gold electrodes and the related electrochemical characteristics were analyzed by cyclic voltammetry (CV).Purification and separation the DNA by the Fe3O4 nanoparticles modified with SiO2 or TiO2 was characterized by agarose gel electrophoresis.

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BERARDI, GINEVRA. « Multitasking Fe3O4@Cu@Au and Fe3O4@SiO2 nanoparticles for biomedical applications ». Doctoral thesis, 2018. http://hdl.handle.net/11573/1215256.

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Tra i nanomateriali utili in ambito biomedico, le nanoparticelle di magnetite offrono grandi vantaggi sia in campo diagnostico che terapeutico, permettendo di combinare le loro peculiari proprietà magnetiche con le note proprietà chimico fisiche che caratterizzano le nanoparticelle. Realizzando una struttura core-shell e funzionalizzando la superficie della nanoparticella con sostanze biologicamente o farmacologicamente attive, è possibile, da un lato, conservare le proprietà superparamagnetiche del nucleo e, dall'altro, ottenere nanosistemi multifunzionali più selettivi e/o efficaci nei confronti dei target biologici prescelti. Lo scopo di questa tesi ha riguardato, quindi, la progettazione e la realizzazione di nanosistemi basati su nanoparticelle core-shell costituite da Fe3O4@Cu@Au o Fe3O4@SiO2 utilizzabili per diverse applicazioni biomediche. La sintesi delle nanoparticelle è stata effettuata utilizzando reagenti biocompatibili mentre una approfondita caratterizzazione chimico-fisica dei nanosistemi è stata ottenuta tramite l'analisi con differenti tecniche microscopiche e spettroscopiche. Attraverso esperimenti biologici in vitro, è stata valutata l' efficacia terapeutica e/o l' internalizzazione in cellule immunitarie di nanosistemi opportunamente funzionalizzati con farmaci chemioterapici, macromolecole biologiche o metaboliti secondari con attivià antibiotica. Infine, nanoparticelle funzionalizzate con specifici anticorpi sono state utilizzate per lo sviluppo di strumenti diagnostici per la rivelazione di neurotrasmettitori in vitro.

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Jian, Chung-Chin, et 簡崇欽. « Magnetic Tunneling Effect in Co/CoO/Fe3O4 and Fe3O4/AlOx/Co Junctions ». Thesis, 2004. http://ndltd.ncl.edu.tw/handle/79838508059773261672.

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碩士
國立臺灣大學
物理學研究所
92
Abstract Magnetic trilayer junctions(MTJs) based on half metallic oxides have attracted much attention because of their potential in memory and logic device applications. Among half metallic materials, the magnetite(Fe3O4) is the most promising candidate due to its high ferrimagnetic Curie temperature(~856K). And an enhanced TMR effect has been expected for this sort of MTJ. However, up to now, the MR effect of MTJ with Fe3O4 as an electrode has been found to be negligibly small. Several causes have been speculated to explain the reduction. For examples, the spin flip processes on the interface would have a deleterious effect on the MR. A less-than ideal insulating barrier containing impurities and defects would also lead to spin scattering. In order to explore the major origins of reduction in MR, we have systematically investigated the TMR of MTJs prepared under various conditions. Our MTJs consist of Fe3O4 and Co as the electrodes sandwitched with cobalt oxide and AlOx thin layers as the tunneling barriers for comparison. The choice of Fe3O4 and Co as the electrodes is due to a large difference of coercivities from these two magnetic layers. Besides, a thin oxide layer can be directly obtained from oxidation of the metal layer right after deposition of the metal, where metals are Co and Al, respectively. We have adopted different oxidation time to acquire tunneling barrier of various thickness. Thus, the impact of tunneling barrier on TMR can be evaluated. Furthermore, since the polarization of Fe3O4 has been predicted to be negative, the inverse MR will be also studied. In Our MTJs, the resistance of electrode Fe3O4 is too large compared to the junction''s, then it would cause nonuniform current distribution over the junction area. Thus, negative resistance will be obtained by using four-probe measurement. We try to reduce the junction area from mm2-size to um2-size to pursuit a uniform coverage of the barrier on the electrode in MTJs. For this purpose, we learn to use E-beam lithography technique to make um2-size magnetic films. We also fabricate hundreds of nm size Co dot arrays to investigate its properties.

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MING, CHANG WEN, et 張文明. « Spin injection and accumulation in Au-Fe3O4 and Cu-Fe3O4 composite films ». Thesis, 2002. http://ndltd.ncl.edu.tw/handle/46165833493804300612.

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碩士
國立臺灣大學
物理學研究所
90
Abstract The magnetoresistance effect have been investigated in Au-Fe3O4 and Cu-Fe3O4 and compared with the results of Ag-Fe3O4. It has been found that in addition to the contribution of GMR from Fe3O4 and OMR from metal the spin injection and accumulation is the dominant factor that determines the MR value. The films were prepared by the dc magnetron sputtering with the substrate temperature set at 340℃ during sputtering. The film structure was determined from X-ray diffraction. The results indicate that the film essentially contains fcc phase from metal and inverse spinel phase from Fe3O4. Thus, the film is a composite film. The film morphology determined from TEM shows that the metal granules and Fe3O4 grains are intermixing in the films and the granular size of metal is increasing with the metal content. The resistivity was investigated by the four-probe method. The result shows that the metal granules and Fe3O4 grains form a connecting network. Furthermore, all films exhibit a Verwery transition at low temperatures. And the transition temperature is decreasing with increasing x. At small x, the sample shows a negative and isotropic MR effect and its value is reduced rapidly as more metal content is added. This phenomenon is associated with the appearance of a large difference between the peak field and coercive field. Thus, we can ascribe the anomalous MR to the spin injection and accumulation. The spin diffusion length at 300K determined from the MR measurement is 6 nm for Au and 25 nm for Cu. The result is consistent with the theory that the spin-orbital interaction is the dominant factor causing spin flip.

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Lin, Shih-che, et 林士哲. « Magnetic Compensation and Interfacial Coupling in Ferrimagnetic Spinel Oxide Fe3O4/Mn3O4/Fe3O4 Trilayers ». Thesis, 2010. http://ndltd.ncl.edu.tw/handle/41584184823177976691.

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碩士
國立中正大學
物理所
98
Fe3O4 and Mn3O4 are the most typical spinel ferrimagnetic oxides. The magnetic coupling between Fe3O4 and Mn3O4 has been studied through superlattices but with relatively smaller length scale of each constituent layer. In this thesis, a Fe3O4/Mn3O4/Fe3O4 trilayered structure on MgO(001), MgO(011) and STO(001) substrates, fabricated by molecular beam epitaxy(MBE), provides a simple system to test the magnetic response to a much larger length scale. These trilayered structure have been also characterized by X-ray diffraction(XRD) and scanning electron microscopy(SEM) for both crystalline quality and surface morphology. X-ray diffraction along the perpendicular direction reveals that the lattice parameters along the z-direction are off the bulk value -1.3% for Mn3O4 and over 4 % for Fe3O4, respectively indicating that both constituent layers are heavily under strain. This modification of the lattice parameters along the z-axis results from the in-plane matching which is due to probably similar oxygen sublattices. The in-plane matching is further confirmed by a model calculation and suggests a strong coupling between two constituent layers. The remanence magnetization vs. temperature (Mr-T) shows a magnetic compensation point at ~22K. Although this observation indicates antiparallel coupling at the interface and consistent with the previous superlattice results, this is unexpected for the present configuration. The compensation state is thus attributed to a domain wall structure formed in Fe3O4 along the perpendicular direction due to the strong anisotropic energy of the tetragonal Mn3O4 relative to cubic Fe3O4. Magnetic hysteresis measurements at various temperatures support this domain wall configuration and also map out an H-T diagram which includes a low-field compensation and a high-field spin flop phase.

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32

Huang, Ching-Yen, et 黃清彥. « Investigation of Surface Property of Magnetic Nano-particles Fe3O4 and SiO2 Coated with Fe3O4 ». Thesis, 2013. http://ndltd.ncl.edu.tw/handle/61751160626335530152.

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碩士
國立高雄應用科技大學
模具工程系碩士班
102
In this paper, the magnetic nanoparticles of Fe3O4 were prepared with a chemical co-precipitation method. The Fe3+ and Fe2+ solution was mixed with NH4OH by heating and stirring and using N2 to protect the reaction, after that the Fe3O4 magnetic nanoparticles were obtained. Next, the core-shell structures of SiO2 coated with Fe3O4 nanocomposite particles were prepared by sol-gel method, in which the hydrolysis of TEOS was conducted on the surface of Fe3O4 with the aid of basic catalyst at room temperature. In this study, the surface shape and component of Fe3O4 nanoparticles and Fe3O4 coated SiO2 nanocomposite particles were studied by ESEM, EDS and TEM. The crystal structure was studied by use of XRD. The magnetic nano-particles size before and after the modification with TEOS were studied with TEM. The results indicated that the magnetic nanoparticles were aggregate due to the particles attraction each other, and the magnetic nanoparticles had very small size. The average particles size of addition 5 ml ammonia solution were 10.303 nm and addition 20 ml ammonia solution was 8.86 nm. The results indicate that the Fe3O4 magnetic nano-particles size is smaller with addition of 20 ml ammonia solution. After Fe3O4 coated with SiO2 were observed by use of TEM, it was confirmed that the SiO2 were successfully coated on the surface of Fe3O4 magnetic nanopraticles.

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Ho, Chien-Hsin, et 何建新. « Shape-controlled Synthesis, Characterization, and Applications of Fe3O4 and FePt@Fe3O4 Core-shell Magnetic Nanoparticles ». Thesis, 2010. http://ndltd.ncl.edu.tw/handle/00723633832958956225.

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博士
國立清華大學
材料科學工程學系
98
摘要本論文主要著重於四氧化三鐵和鐵鉑-四氧化三鐵核殼結構磁性奈米微粒之合成、形狀控制、鑑定、與其應用之研究。首先，我們利用高溫注入前驅物的方法來製備四氧化三鐵的奈米微粒，注射時的反應溶液溫度為290 °C。我們發現溶液中鐵單體的濃度會影響著四氧化三鐵奈米微粒的形狀。當前驅物注射速度只有10 mL/h時，所還原出的有限鐵單體將優先成長於具有較高能量的晶面，而造成具有最低能量的{100}晶面變成主要外露面，最終得到立方體形的奈米微粒。然而，當注射速度增加到20 mL/h時，增加的鐵單體濃度會改變各主要晶面的相對成長速率。因此原本具有第二低能量的{110}晶面，也和{100}晶面一樣變成了主要外露面之一，最後形成了削菱截角立方體(Rhombicuboctahedron)。在我們的實驗中，這兩種四氧化三鐵奈米微粒的粒徑大約都在16奈米左右，並且都可以在TEM銅網上和矽基板上自組裝成具有優選晶體方向的奈米微粒超晶格結構。第二部分的研究主要是製備具由核殼結構的鐵鉑-四氧化三鐵奈米立方體。我們利用上述之高溫注入前驅物的方法搭配晶種成長法，來製備具有球形鐵鉑核和立方體形四氧化三鐵殼的複合式磁性奈米微粒。此複合式奈米微粒的最終形狀主要取決於四氧化三鐵殼的成長條件。並且經由HRTEM的分析可得知，鐵鉑核和四氧化三鐵殼並不需具備磊晶成長關係，此結果表示內核的材料並不需要具備與外殼四氧化三鐵相近之晶體常數。因此，不同材料的核可被選用來製備具有核殼結構的四氧化三鐵奈米立方體，以增進其應用價值。最後一部分則是探討四氧化三鐵和鐵鉑-四氧化三鐵奈米立方體的特性和前瞻應用。我們利用XMCD來量測鐵離子在四氧化三鐵內不同位置的分佈情形。在立方體形的四氧化三鐵奈米微粒內，我們發現三價鐵離子佔有八面體位置的比率比一般四氧化三鐵塊材還來的高。然而，在削菱截角立方體形的四氧化三鐵奈米微粒內，其鐵離子在不同位置上的分佈情形就比較接近於四氧化三鐵塊材。此鐵離子分佈位置的不同可能是由於這兩種形狀的奈米微粒具有不同的比表面積和外露面所致，此結果也將有助於進一步研究四氧化三鐵的催化特性。最後，我們也發現鐵鉑-四氧化三鐵奈米微粒能顯著地增強MRI影像對比，並且效果優於目前市售之影像顯影劑，此顯著效果應歸因於鐵鉑核的高單位磁化量。另外具有自組裝排列的鐵鉑-四氧化三鐵奈米立方體有機會成為前瞻性多頻譜的影像增強劑。

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陳柏安. « Fe3O4/polypyrrole composite for microwave absorption ». Thesis, 2014. http://ndltd.ncl.edu.tw/handle/789sq4.

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碩士
逢甲大學
化學工程學系
102
Fe3O4 nanoparticles, H-Fe3O4 and C-Fe3O4, were prepared by the hydrothermal and co-precipitation methods, respectively. Microwave absorption properties of composites using polypyrrole encapsulated Fe3O4 by different polypyrrole (Ppy) and carbon nanotube (CNT) content in an epoxy matrix were studied. The composites were characterized by FE-SEM, XRD, FTIR, TEM, magnetic hysteresis loops. For the study of microwave absorption properties, we measured the permittivity and permeability of the composites and simulated their reflection loss (RL) in the frequency ranges of 2-18 GHz. The results showed that epoxy based composite containing 20wt% H- Fe3O4/Ppy (HP3) with a thickness of 2 mm exhibits maximum reflection loss -41dB at 14.48 GHz, the epoxy based composite containing 30wt% C- Fe3O4/Ppy (CP3) with a thickness of 2 mm has maximum reflection loss -13 dB at 13.98 GHz. The microwave absorption ability of H- Fe3O4/Ppy is better than that of C- Fe3O4/Ppy. The H-Fe3O4 nanoparticles were synthesized by hydrothermal method has higher coercivity (Hc) than C-Fe3O4 nanoparticles prepared by co-precipitation method. Furthermore, the H- Fe3O4/Ppy/CNT composites have wider absorption bandwidth than C-Fe3O4/Ppy composite. After incorporating CNT, the bandwidth of H-Fe3O4/Ppy/CNT increased from 4.19 to 5.15GHz for RL<-10dB. Incorporating Fe3O4 nanoparticles with high coercivity can enhance the microwave absorption properties of Fe3O4/Ppy/epoxy composites. Adding CNT can extend the bandwidth for RL<-10dB.

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Hou, T. Y., et 侯宗佑. « [Mn3O4/Fe3O4]與[MgO/Fe3O4]超晶格之製成與磁性分析研究 ». Thesis, 1999. http://ndltd.ncl.edu.tw/handle/42386400203831573480.

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碩士
國立中正大學
物理系
87
The transition metal oxides have been studied for a long time due to their rich electromagnetic properties. Previos studies on oxide systems have been focusing in the anti-ferromagnetic/anti-ferromagnetic (AF/AF) and ferrimagnetic/anti-ferromagnetic (FM/AF)super lattices, such as NiO/CoO and Fe3O4/NiO. We extend the study to the superlattices of high quality [Mn3O4/Fe3O4] and [MgO/Fe3O4] , including the magnetic property. Using plasma-oxygen-assisted molecular beam epitaxy technique, we are able to grow both super lattices [Mn3O4/Fe3O4] and [MgO/Fe3O4] on MgO(100). This is the first time that an oxide ferrimagnetic/ferrimagnetic multilayered structure has been studied. We use a SQUID magnetometer to measure the magneic property. The magnetic response has been studied as a funttion of applied field (-5T~5T), temperature (5K~300K) and orientation of the applied field (parallel and perpendicular to the film). In [Mn3O4/Fe3O4] : a strong reduction of magnetic moment, from 120 emu/cm3 to 50 emu/cm3, has been observe at temperature below ~60K which is very close to the bluk magnetic transition temperature of Mn3O4 . This observation indicates that moment from two constituents is anti-parallel . The remanent magnetization as a function of the temperature further shows a compensation point at about 45K which the opposing spins are balanced. The magnetic moment switch sign when crossing this temperatue. Detail magnetic hysteresis measurements indicate the easy axis remain in the film plane but the coercivity shows a maximum at the composition temperature . Besides, a nonmagnetic/ferrimagnetic[MgO/Fe3O4]super lattices has been studied for comparison.

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Ho, Mao-Hsun, et 何茂熏. « Preparation and characterization of electrospun Fe3O4/poly(3-hydroxybutyrate) and Fe3O4/poly(3-hydroxybutyrate-co-3-hydroxyvalerate) nanofibers ». Thesis, 2012. http://ndltd.ncl.edu.tw/handle/77423046945366981078.

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碩士
國立中興大學
材料科學與工程學系所
100
This study is focused on the preparation of Fe3O4/poly(3-hydroxybutyrate) (PHB) and Fe3O4/poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) electrospun fiber containing high porosity and surface area with interconnected pore network. The structure of prepared PHB and PHBV fibers is similar to the dimension of extracellular matrix (ECM). The electrospun Fe3O4/PHB and Fe3O4/PHBV composite fibers were achieved with biocompatibility and magnetic properties. The micrographs of scanning electronic microscopy (SEM) illustrate that the fiber diameter was distributed in the range of 160 nm ~ 660 nm and 2.4 μm ~ 8.7 μm for PHB, PHBV5 and PHBV12 fiber in 2,2,2-trifluoroethanol (TFE) and chloroform (CHCl3) solvent, respectively. The structure and property of PHB, PHBV5 and PHBV12 fiber were investigated by different scanning calorimeter (DSC) and X-ray diffraction (XRD). The DSC results indicated that the melting endotherm slightly shifted to low temperatures as the content of PHV increased. At the same time, XRD analysis of PHBV fiber show the (110) diffraction peak became apparent with 12% PHV content under the electric field. The monodispersed 6 nm Fe3O4 nanoparticles have been prepared through thermal decomposition process. The structure and properties of fabricated nanoparticles can be analyzed by transmission electron microscopy (TEM), superconducting quantum interference device (SQUID), and XRD. The monodispersed 6 nm Fe3O4 nanoparticles contain superparamagnetic property. The electrospun Fe3O4/PHB and Fe3O4/PHBV fiber with high porosity and surface area with interconnected pore network have been suceessfully prepared. DSC analysis of Fe3O4/PHB and Fe3O4/PHBV composite fibers fabricated in TFE solvent presence of Fe3O4 nanoparticles will promote good arrangement of the molecular chain in PHB and PHBV5 under an electric field. XRD results of the PHB, PHBV, Fe3O4/PHB and Fe3O4/PHBV composite fibers show similar tendence, which indicates the Fe3O4 does not significantly affect the crystalline structure of PHB and PHBV in the electrospinning process. For the in vitro degradation experiments, the fibers soaked in a solution containing bacteria was observed by SEM. Experimental result showed that the structural changes of PHB and PHBV fiber occurred during the in vitro degradation, in which the fiber pore formed on the surface of PHB and PHBV. Erosion of both PHB and PHBV fibers increased with increasing incubation time. Compared to different PHV content of fiber, the SEM micrographs illustrate that the degradation rate was increased by increasing content of PHV. From the SEM results after decomposition for 2 days, the PHB fiber was significantly destroyed. Gel Permeation Chromatography (GPC) was used to investigate further the molecular weight changes of PHB. When weight percentage of molecular weight (Mw) started to decay to around 240000 ~ 230000 g/mole (after 6 hr), and the next step of degradation has been occured involving the weight loss. However, the system of PHBV showed little molecular weight changes, in which the degradation began to decompose from the surface of fibers. After the specimen was washer using water, the lower molecular weight of sample might be removed from the surface of fiber. Then the fibers soaked in a solution containing fungi in vitro degradation test showed that the fiber surface is gradually covered with mycelium as degradation time increases, which led to the residual amount. The result indicated that fungi do not significantly affect increasing the degradate rate of PHB and PHBV. These results can serve as a reference for future animal studies.

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Pei-Lun, Chien, et 簡培倫. « Synthesize and application of Fe3O4 nano particle ». Thesis, 2006. http://ndltd.ncl.edu.tw/handle/09666095080904376094.

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碩士
中國文化大學
材料科學與奈米科技研究所
94
In this dissertation, the study of synthesize and application of Fe3O4 nano particle the main purpose, divide the application into three following parts. In the first part, nanometer-sized magnetic materials have attracted the attention of many researchers, because magnetic nanoparticles exhibit unusual chemical and physical properties such as superparamagnetism and quantum tunneling of magnetization. A number of techniques, both chemical and physical, have been used to make magnetic particles. In this dissertation, ferrite nanoparticles [magnetite (Fe3O4)] were prepared using a simple chemical coprecipitation method. Oleic acid was added to protect nanoparticles from aggregation. The characteristics of nano-magnetic Fe3O4 particles were determined by various techniques, such as transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray absorption near edge structure spectroscopy (XANES) and X-ray magnetic circular dichroism (XMCD) In the second part, A method for manufacturing ferrous ferric oxide powder is disclosed, The method includes mixing ferrous ferric oxide powder with a coupling agent having a silane functional group in an organic solution for improving its quality. The ferrous ferric oxide powder with improved surface quality manufactured by the present invention can be dispersed and mixed steadily and uniformly in a nonpolur solvent . In addition to that, it has longer dispersion time and is hardly to precipitate, so it has relatively high production value and can be widely used in manufacturing all kinds of ferrous ferric oxide - containing stealth paint. In the third part, we study the preparation and properties of bio-compatible magnetic nanoparticles for immunoassay detection. The magnetite (Fe3O4) nanoparticles were prepared by a chemical co-precipitation method and dextran is selected as the surfactant to suspend the nanoparticles. Suspended particles associated with avidin followed by biotin were qualitatively analyzed by enzyme-linked immunosorbent assay (ELISA) method. We found further the ethylenediamine blocked activated residual groups efficiently, hence enhancing the attachment of biotin for probing the avidin.

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38

Chien, Yen-tao, et 錢彥滔. « Synthesis and Characterization of TiO2/Fe3O4 photocatalyst ». Thesis, 2011. http://ndltd.ncl.edu.tw/handle/7h27q5.

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碩士
明道大學
材料科學與工程學系碩士班
99
Our study is to explore how soluble gel ( Sol-Gel ) preparation TiO2/Fe3O4 Photocatalyst complex to destain Indigo in different content Fe3O4 molal ratio in variation situation, like different OD of Indigo and density of seawater at three color light source LED (blue ,white and red). We also used human brine pathogenic bacteria Edwardsiella tarda to measure TiO 2/Fe3O4 antibiotic activities. The data shows the best destained condition is in 4% Fe3O4 in different OD and 1% Fe3O4 in different density of seawater at blue light source. On marine pathogens Edwardsiella tarda, it has 36.6% sterilization in two hours. However, it still has sterilization activity at blue light. TiO 2 is non-toxicity and can be recycled by magnet of Fe3O4 . This material is difficult to cause secondary pollution and save some industry prime cost.

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39

Wang, Shi-Yu, et 王世育. « Characterization and Mechanism of Fe3O4/Carbon Supercapacitors ». Thesis, 2004. http://ndltd.ncl.edu.tw/handle/54488132506871444616.

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博士
國立臺灣大學
化學工程學研究所
92
Composite electrodes which comprise a non-conductive activated carbon of large surface area (1436 m2/g) and a conductive carbon black (CB) of small surface area (220 m2/g) have been prepared and studied for their capacitive properties in aqueous KOH and Na2SO4 electrolytes. For either electrolyte, maximum capacitance exists at the composition believed to correspond to the percolation threshold for CB, the conductive phase. At a CB content less than the threshold, the capacitance is limited mainly by the electronic resistance on the electrode side. The interfacial surface area becomes the limiting factor as the threshold is exceeded. A maximum capacitance of 108 F/g at a voltage sweep rate of 20 mV/s is obtained in 1 M KOH aqueous electrolyte with a CB content of 25 wt.% (or ~ 14 vol.%). Magnetite (Fe3O4) supercapacitor contained 10 wt.% CB as conductive additive (≧ percolation threshold), operating characteristics in aqueous electrolytes of Na2SO3, KOH and Na2SO4 were investigated. While the capacitance of the oxide was found to depend heavily on electrolyte composition, the self-discharge mechanism in these electrolytes appeared to be the same. Reduction in dissolved oxygen content (DOC) of electrolyte reduced leakage current and profoundly improved the cycling stability. In particular, Na2SO3(aq) gives the highest capacitance, nearly 30 F/g-Fe3O4 or 80 �媹/cm2 of actual surface area, with an operating range of 1.1 V and the electrode showed no deterioration after 104 cycles under a DOC < 0.1 ppm. Since the surface Fe3O4 particles will easily raise the reversible redox below the low sweep rates (≦ 20 mV/s), the specific capacitances of coprecipitated electrode increased as magnetite loading content. The contributive specific capacitances of magnetite increased as decreasing magnetite content because of the dispersion of magnetite. The largest specific capacitances of coprecipitated electrode and magnetite were 42.4 F/g (66.4 wt.%) and 375 F/g-Fe3O4 (5.6 wt.%), respectively. We found that the capacitive behavior of magnetite with the optimal Ni-doped content would be larger than that without Ni-doped magnetite at the lower sweep rate. The specific capacitance of thin film magnetite possess 130 F/g in 1 M Na2SO3(aq) which is due to higher conductivity by electroplating process. In order to explore the pseudocapacitive mechanism of magnetite in Na2SO3(aq), combined use of CV and EQCM affords a route to obtain the reversible oxdation and reduction reaction. We found that SO32- ions adsorbed on Fe atom of Fe3O4 surface structure, however, SO32- ions transformed into S2- ion (deoxidization) and adsorbed yet on Fe atom during the reduction process. During the oxidation process, S2- ions were returned to original SO32- ion on Fe atom site. On the other hand, the structure of Fe3O4 surface maybe has been transferred to another Fe2O3 phase during the oxidation or reduction process. The reaction of SO32- ions or phase transformations of Fe3O4 both take place on Fe3O4 surface structure and there was a consequent reversible pseudocapacitor.

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40

Chao, Pei-Yu, et 巢沛禹. « Exosomes purification based on PEG coated Fe3O4 ». Thesis, 2016. http://ndltd.ncl.edu.tw/handle/02074383761495791195.

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碩士
中原大學
機械工程研究所
104
Cancer also known as malignant tumors, is a group of diseases involving abnormal cell growth with the potential to invade or spread to other parts of the body, for many years, cancer is a disease of the highest mortality, over 100 cancers affect humans. When cancer metastasis, cancer cells secretes a kind of microvesicles called “Exosome” to create the microenvironment at the destination. So, if we can detect the quantity of exosomes in human body, perhaps have the opportunity to check out the cancer at an early stage. Exosomes appears in biological fluids like blood, but it is impurity that contain lots of protein like globulin and albumin, will reduce the accuracy of liquid biopsy. So this study focuses on exosome isolation with magnetic nanoparticles. The use of chemical co-precipitation method to synthesize Polyethylene glycol(PEG)-coated Fe3O4 nanoparticles, the surface of the Fe3O4 has the reticular structure of PEG, can produce space crowing effect to make protein precipitated from the original location. The particles are uniformly mixed with serum, let particles catch protein, then use magnet to separate the particles and the supernatant, the supernatant contain pure exosomes. In order to use the protein precipitation, the purification of exosomes can be achieved. The diameter of PEG-coated Fe3O4 nanoparticles is about 20 nm, and the agglomerates size is about several hundred nanometers. The use of FESEM, XRD and FTIR to check the PEG is indeed coated on the surface of Fe3O4 nanoparticles. In the experiment of protein isolation, through ELISA to detect, the particles can decline the protein concentration to 39.9% of stock solution. To confirm exosomes are still in the supernatant, the result of Nanosight shows the supernatant content 1.6x1010 particles/ml the size of 30-200nm inclusions, same as the stock solution, SDS-PAGE shows the CD63 exosomes band (~53kD) both are equally show in supernatant and stock solution clearly, the immunoglobulin and albumin band (160~188kD and ~66kD) are shown in stock solution but disappear in supernatant, the result shows the exosome still in the supernatant but the other impurity protein are filtered. As a result, the PEG-coated Fe3O4 nanoparticles indeed can catch the protein and retain the exosome, this is a practical method in exosome isolation.

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41

Kuo, Ying-Jeng, et 郭英傑. « Synthesis of Ag-Fe3O4 composite nano-particles ». Thesis, 2008. http://ndltd.ncl.edu.tw/handle/87441725318289026864.

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碩士
中原大學
化學研究所
96
Synthesis of Ag-Fe3O4 magnetic nanoparticles is carried out by coprecipitation method. The size of Ag-Fe3O4 magnetic nanoparticles is controlled by changing solution’s concentration and different preserver. The component and microstructure of Ag-Fe3O4 magnetic nanoparticles was characterized by XRD, UV, TEM, and EDS. The superparamagne- tism of Ag-Fe3O4 magnetic nanoparticles s was confirmed with a VSM. Synthesis of Ag-Fe3O4 magnetic nanoparticles was accomplished in two methods. Method one is Chemical reduction and oxidation. Silver ions were used as oxidation agent to oxidize ions of Fe(II) to form a solution containing both Fe(II) and Fe(III) ions. After precipitation with ammonia hydroxide, magnetic nanoparticles containing silver metals were obtained. Method two is synthesis of Fe3O4 magnetic nanoparticles using the microwave hydrothermal or coprecipitation method, then Synthesis of Ag-Fe3O4 magnetic nanoparticles were prepared by reducing silver nitrate on the surface of Fe3O4 nanoparticles using the coprecipitation method. Method two results in better efficiency than those of method one. The best size we obtained in this study is 10±5nm.

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42

Kao, Ting-Hsuan, et 高挺軒. « Preparation and properties of Fe3O4/ polybenzoxazine nanocomposites ». Thesis, 2011. http://ndltd.ncl.edu.tw/handle/87187316368696727307.

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碩士
南亞技術學院
材料應用科技研究所
99
The subject of this study is to develop a novel approach to modify the surface of Fe3O4 nanoparticles and to prepare Fe3O4/polybenzoxazine nanohybrids. Fe3O4 modification as been employed with N-(p-carboxyphenyl) maleimide(p-CPM) through the reaction between the hydroxyl groups of Fe3O4 nanoparticles and the carboxyl groups of p-CPM. The p-CPM modified Fe3O4 nanoparticals (Fe3O4-p-CPM) are then utilized in preparation of Fe3O4 nanopartical-cored star polymers and Fe3O4 nanoparticale/benzoxazine nanohybrides. The chemical structures of the prepared materials have been characterized with FTIR, SQUID, and thermal analysis. Then the benzoxazine-modified Fe3O4 nanoparticales are applied for the preparation of polybenzoxazine/Fe3O4 nanocomposites. The morphologies as well as the superparamagnetic properties of the nanocomposites have been characterized with electron microscopy and SQUID, respectively.

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43

Chen, Yi-hsun, et 陳誼勳. « Reaction Behavior of Nanoscale Fe3O4 and [Fe3O4]MgO with Different Inorganic Pollutants (NO3-, Cd2+ and Cr6+) in Simulated Groundwater ». Thesis, 2008. http://ndltd.ncl.edu.tw/handle/75374599593178756507.

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碩士
國立中山大學
環境工程研究所
97
This study was to investigate the reaction behavior of laboratory-prepared nanoscale adsorbents (Fe3O4 and H-[Fe3O4]MgO) and inorganic pollutants (NO3-, Cd2+and Cr6+) in simulated groundwater. First, Fe3O4 and the composites of nanoscale Fe3O4 and MgO were prepared using chemical co-precipitation method. Then they were characterized and verified by various apparatuses and methods including X-ray diffractometry, scanning electron microscopy, Zetasizer, and specific surface area measurements. Second, the nanoscale adsorbents were used to adsorb inorganic pollutants in simulated groundwater of different conditions. The relevant reaction behavior and mechanisms were also investigated. Results of this research showed that Fe3O4 and H-[Fe3O4]MgO had the greater adsorption amount when the initial concentration of inorganic pollutants was higher than lower. The adsorption rate of inorganic pollutants at 28℃ was greater than that of at 18℃. The experimental results also showed that at a higher pH environment or the existence of humic acid in simulated groundwater would increase the removal efficiency of Cd2+, but decrease the removal efficiency of NO3- and Cr6+. Analysis of inorganic pollutants adsorption on nanoscale adsorbents in simulated groundwater indicated that a Langmuir-type of chemical adsorption and pseudo-second-order reaction kinetic equation would have better fit. In this study, it was also found that nanoscale adsorbents not only adsorbed inorganic pollutants but also reduced NO3- and Cr6+ to NO2-, NH4+, and Cr3+ at pH=3, respectively. Thus, the nanoscale adsorbents (Fe3O4 and H-[Fe3O4]MgO) prepared and were capable of reductively adsorbing inorganic pollutants (e.g., NO3- and Cr6+) for environmental remediation.

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44

Kuschel, Olga. « From initial growth of ultrathin Fe3O4 films up to NiFe2O4 formation through interdiffusion of Fe3O4/NiO bilayers on Nb:SrTiO3(001) ». Doctoral thesis, 2020. https://repositorium.ub.uni-osnabrueck.de/handle/urn:nbn:de:gbv:700-202005083040.

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Within this thesis, a comprehensive study of the initial growth process of pure Fe3O4 films and Fe3O4/NiO bilayers on Nb:SrTiO3(001) substrates including the thermal interdiffusion behavior of these bilayers is presented. The sensitive interplay between magnetic, electronic and structural properties of these materials has been investigated in detail. In the first study, the initial growth behavior of high-quality ultrathin magnetite films on SrTiO3(001) deposited by reactive molecular beam epitaxy depending on the deposition temperature has been analyzed. For this purpose, the growth process has been monitored in situ and during the deposition by grazing incidence x-ray diffraction (GIXRD). The second part provides a comparative study of Fe3O4/NiO bilayers grown on both MgO(001) and Nb:SrTiO3(001) substrates exploring morphological, structural and magnetic properties. These structures have been investigated by means of x-ray photoelectron spectroscopy (XPS), low-energy electron diffraction (LEED), x-ray reflectivity (XRR) and diffraction (XRD), as well as vibrating sample magnetometry (VSM). Subsequently, thermal stability of these bilayers and the thermally induced interdiffusion process have been studied successively accompanied by a comprehensive characterization of the fundamental electronic, structural and magnetic properties using additional techniques such as angle resolved hard x-ray photoelectron spectroscopy (AR-HAXPES) and x-ray magnetic circular dichroism (XMCD). Finally, an alternative pathway for the preparation of ultrathin nickel ferrite films through interdiffusion is provided.

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45

Lee, Chih-Hung, et 李致竑. « The Study of Nylon 6/Fe3O4@Graphene Composites ». Thesis, 2012. http://ndltd.ncl.edu.tw/handle/s28s7g.

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碩士
國立臺北科技大學
有機高分子研究所
100
The method of ball-milling and oxidation were applied in this study to produce small-sized particle graphene, then the reduction of metal nano-particle was introduced to reduce Fe3O4 onto the graphene surface. By using Scanning Electron Microscope, Energy Dispersive Spectrometer, X-ray Diffractometer and also doing BET analysis, resistivity test and TGA test, we obtained the optimal ratio for Graphene Oxide to FeCl2 is 1 g to 0.5 g. The Fe3O4@Graphene powder at 0.1 wt%, 0.5 wt%, 1 wt%, 2 wt% and 3 wt% were added respectively to Nylon 6 through the in situ polymerization. The functional properties of these Nylon 6 composites were discussed by the results of FTIR, DSC, XRD, VSM, resistivity test and tensile test. Due to the results we understand that Fe3O4@Graphene powder not only has great conductivity, but possesses electromagnetic effects. Adding the powder to Nylon 6 could enhance its electromagnetic property. Adding 0.1 wt% Fe3O4@Graphene powder, it could strengthen the mechanical property of Nylon 6. Furthermore, while the adding amount was 3 wt%, it could reduce the resistivity by 2 levels, but VSM showed that the composites presented obvious electromagnetic property.

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46

TSAI, CHE-WEI, et 蔡哲維. « Characterization of (Ba0.8Pb0.2)TiO3-(Ni0.9Cu0.04Mn0.06)Fe2O4 magnetoelectric composites ». Thesis, 2014. http://ndltd.ncl.edu.tw/handle/21686146659007004735.

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碩士
東海大學
化學工程與材料工程學系
102
In this study, we reported on the thermal expansion coefficients, microstructures, dielectric properties, and magnetic properties of (Ba0.8Pb0.2)TiO3-(Ni0.9Cu0.04Mn0.06)Fe2O4 magnetoelectric composites prepared by sol-gel method and solid state method. The BPT percentage of BPT-NCMFO composites has a strong influence on the material properties. The composites were sintered for 3 hrs at various sintering temperatures. At the same BPT percentage, the relative density and permeability of the composites prepared by solid state method are higher than those of the composites prepared by sol-gel method. However, the loss tangent of the composites prepared by sol-gel method is lower than that of the composites prepared by solid state method. Except for the composites of 75 mol% and 100 mol% BPT, the thermal expansion coefficients of the composites prepared by solid state method are lower than that of the composites prepared by sol-gel method. Except for the composites of 0 mol%, 75 mol%, and 100 mol% BPT, the dielectric constant of the composites prepared by sol-gel method are higher than that of the composites prepared by solid state method. Except for the composites of 75 mol% BPT, the loss of permeability of the composites prepared by sol-gel method is lower than that of the composites prepared by solid state method. Besides, the magnetic properties of the magnetoelectric composites were obviously affected by applying a magnetic field at a frequency of 10 GHz.

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47

Cheng, Chun-Yang, et 鄭鈞陽. « Catalytic destruction of isopropanol by microwave/Fe3O4 system ». Thesis, 2009. http://ndltd.ncl.edu.tw/handle/50914783541600207247.

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碩士
明道大學
材料科學與工程學系碩士班
97
A microwave/Fe3O4 catalytic system was chosen for treatment of volatile organic compounds (VOCs). The system comprises a homemade microwave oven modified as the reactor in this study, which was fitted with a vertical, cylindrical quartz reactor comprising a catalytic packed column filled with granular Fe3O4, a microwave catalyst of iron (II, III) oxide. Experimental results showed that the destruction and removal efficiency (DRE) of isopropyl alcohol by microwave/Fe3O4 system reached to 99%, and the temperature of the catalytic packed column increased rapidly and reached thermal balance within 20-25 min. Analysis of the flue gas after combustion showed that most of the isopropyl alcohol was thermal oxidized into CO2 and H2O. The successful application of the microwave/Fe3O4 system on treatment of isopropyl alcohol will supply a new technology for treatment of VOCs.

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48

Sung, Ti-Wen, et 宋狄文. « Synthesis and Magnetic Property of Monodisperse Fe3O4 Nanoparticles ». Thesis, 2005. http://ndltd.ncl.edu.tw/handle/15500989874650386343.

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碩士
遠東技術學院
機械研究所
93
This study is about the synthesis of Fe3O4 nanoparticles with precisely controlled sizes and size distributions. The precursors are oxygen-containing organic materials such as Fe(acac)3 or inorganic materials such as FeO(OH), which are decomposed in high-boiling point solvents to provide the monodispersed Fe3O4 nanoparticles. Particle diameters can be tuned from 4 to 20 nm by varying reaction conditions or by seed-mediated growth methods. Fe3O4 nanoparticles are synthesized with narrow size distributions (σ ~ 5 to 10%). The size of nanoparticles are mainly controlled by the variety of solvents with different boiling point and the iron-reactant/surfactant mole ratios. The research is characterized by dynamic light scattering, powder X-ray diffraction, vibrating sample magnetometer and transmission electron microscopy.

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49

Chen, S. Y., et 陳尚煜. « Anomalous positive magnetoresistance in Fe3O4-Ag composite films ». Thesis, 2001. http://ndltd.ncl.edu.tw/handle/32506591733627718248.

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碩士
國立臺灣大學
物理學研究所
89
Abstract The anomalous positive magnetoresistance effect of Agx-(Fe3O4)1-x composite films have been investigated. Samples were prepared by dc magnetron sputtering with composite targets and the Si(100) wafer was used as the substrate. We have studied the composition, structure, and morphology of Agx- (Fe3O4)1-x composite films by EPMA, X-ray diffraction and SEM respectively. The resistivity of Agx-(Fe3O4)1-x films were measured by four-probe method. The MR was in general obtained with a maximum applied magnetic field of 0.8 Tesla at 350K, 300K and 225K. The value of MR ratio is defined to be MR={R(H)-R(0)}/R(0). The magnetic properties of the films were determined with SQUID between 150K and 350K. It has been found that a negative magnetoresistance of about 0.3% is observed for pure Fe3O4 films. With the incorporation of a small amount of Ag nanoparticles into Fe3O4 matrix, the MR value suddenly becomes positive. The MR ratio reaches a maximum value of about +0.5% at x=0.007. The positive MR effect disappears at x≒0.015. The MR value re-entries into negative region again. Furthermore, its magnitude is decreasing with increasing x. If the contribution from the negative MR effect of Fe3O4 and the OMR effect of Ag are subtracted, the anomalous positive magnetoresistance is present only in a very narrow region between 0.001＜x＜0.02. At x=0.02, the average granular size of Ag is about 10nm. This phenomenon of extra anomalous MR can be explained from spin current injected into Ag granules, inducing spin accumulation inside Ag granules. Therefore, using MR measurement, the spin diffusion length at room temperature in Ag particle was determined to be 9nm. And as the temperature decreases to 225K, the spin diffusion length increases to 10nm.

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Lu, Zhao-Ming. « Dielectric Properties of (CaCu3Ti4O12)1-x(Fe3O4)x ». 2007. http://www.cetd.com.tw/ec/thesisdetail.aspx?etdun=U0001-2607200717365000.

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