Detrital magnetite, although averaging less than I% of till volume, is a common constituent in glacial tills of eastern Indiana and western Ohio. Because of its abundance and ease of sampling, detrital magnetite was chosen to determine its potential as a tool to 1) determine provenance of the glacial tills and 2) to chemically fingerprint glacial sedimentary deposits for use in stratigraphic analysis. Two sampling programs were performed. First, glacial till samples were collected from a vertical section in western Ohio at the location of Doty's High Bank. Second, glacial tills were collected from a lateral distribution of five moraines in northeast and east central Indiana.Petrographic analysis of 946 detrital magnetite grains from eastern Indiana and western Ohio has shown that 81% of the magnetite grains are homogeneous, 15% have magnetite-ilmenite intergrowths, and 4% have exsolved phases of ulvospinel/pleonaste.Eighteen percent of all detrital magnetite grains have some level of hematite alteration. Chemical analyses were performed on 403 homogeneous detrital magnetite grains. These grains were analyzed for Fe, Ti, Mg, Mn, Cr, V, Al, and Si. The means and standard deviations of these eight elements, in weight percent oxide, are FeO (89.8087.696), TiO2 (1.58 ± 4.99), MgO ( 0.052 ± 0.200), MnO ( 0.172 ± 0.284), Cr2O3 (0.1942.256), V2O3 ( 0.241 ± 0.245), Al2O3 (0.455 ± 1.234), and SiO2 ( 0.035 ± 0.047).A Canadian source north of Lake Huron and south of James Bay is suggested based on previous studies of flow directions of the Laurentide Ice Sheet and bedrock geology in southern Canada. The bedrock in this area is primarily felsic plutonic and mafic volcanic. The petrographic and geochemical results of this study indicate this area as the source area for the detrital magnetite in eastern Indiana and western Ohio tills. Chemical fingerprints based on cluster analysis and bivariate plots were found within the vertical exposure of Doty's High Bank and the lateral moraines of eastern Indiana. Samples from the Muncie esker (unknown age) were found to correlate with the southernmost set of eastern Indiana moraines based on the chemical fingerprint analysis. / Department of Geology

Thermally activated shape memory polymers are a desirable material for use in dynamic structures due to their large strain recovery, light weight, and tunable activation. The addition of ferromagnetic susceptor particles to a polymer matrix provides the ability to heat volumetrically and remotely via induction. Here, remote induction heating of magnetite filler particles dispersed in a thermoset matrix is used to activate shape memory polymer as both solid and foam composites. Bulk material properties and performance are characterized and compared over a range of filler parameters, induction parameters, and packaging configurations. Magnetite filler particles are investigated over a range of power input, in order to understand the effects of particle size and shape on heat generation and flux into the matrix. This investigation successfully activates shape memory polymers in 10 to 20 seconds, with no significant impact of filler particles up to 10wt% on mechanical properties of shape memory foam. Performance of different particle materials is dependent upon the amplitude of the driving magnetic field. There is a general improvement in heating performance for increased content of filler particles. Characterization indicates that heat transfer between the filler nanoparticles and the foam is the primary constraint in improved heating performance. The use of smaller, acicular particles as one way to improve heat transfer, by increasing interfacial area between filler and matrix, is further examined.

De acordo com a literatura recente, a eletroquímica de partículas magnéticas e fenômenos de colisões em superfícies eletródicas resultam em curvas voltamétricas e amperométricas com perfis completamente destoados do convencional. Alguns modelos teóricos propõem explicações, no entanto, ainda se observa a necessidade de aquisição de mais dados experimentais. Visando contribuir com esta área, esta Dissertação de Mestrado aborda a manipulação de micropartículas e nanopartículas de magnetita modificadas com azul da Prússia (Fe3O4-PB), bem como o estudo das propriedades eletroquímicas das partículas na presença de um campo magnético externo. Filmes constituídos por micropartículas sobre eletrodos de carbono (grafite) foram obtidos por duas técnicas distintas, drop coating e magneto-deposição. Para ambos os métodos, os filmes apresentaram dois picos nos voltamogramas, um de oxidação (0,12 V) e outro de redução (-0,05 V), que estão associados ao par redox azul da Prússia/branco da Prússia. Para o filme obtido via drop coating, observaram-se correntes de pico mais elevadas. Também, micropartículas de Fe3O4-PB individuais foram isoladas (single particle) com auxílio de um microscópio óptico e analisadas por voltametria, onde se verificou o aparecimento de picos com os mesmos valores de potenciais. Utilizando os dois estados de comutação de campo (0,2 Tesla), ligado e desligado, foi possível controlar a presença e a ausência da partícula no eletrodo. Também, observaram-se diferenças nos valores de densidade de corrente nos cronoamperogramas para cada micropartícula de Fe3O4-PB e que a morfologia da micropartícula interfere significativamente na resposta eletroquímica. Por fim, e agora se tratando da eletroquímica de nanopartículas de Fe3O4-PB sobre um ultramicroeletrodo (UME) de ouro, controlaram-se as colisões das mesmas em diferentes condições experimentais, como na presença e na ausência de um campo magnético externo paralelo a superfície do eletrodo e com intensidades variadas (0,1 e 0,2 Tesla). Na ausência do campo, as nanopartículas que chegaram ao UME colidiram e se acumularam, gerando sinais eletroquímicos do tipo corrente staircase. Na presença de um campo de 0,1 T, observaram-se vários transientes de correntes (spikes) associados às colisões das nanopartículas, eventos esses não observados frequentemente na presença do campo de 0,2 T. Assim, esses resultados abrem a discussão da necessidade de se aperfeiçoarem os modelos que explicam os perfis das curvas voltamétricas e amperométricas para esses sistemas. / According to recent literature, the electrochemistry of magnetic particles and collision phenomena on surfaces result in unconventional voltammetric and amperometric responses. Some theoretical models has been proposed; however, experimental data are required for improve that. In order to contribute to this research area, this Master\'s Dissertation describes the manipulation of microparticles and nanoparticles of magnetite modified with Prussian blue (Fe3O4-PB), as well as the study of electrochemical properties of them in presence of an external magnetic field. Carbon (graphite) electrodes modified with microparticles were obtained by using two different techniques, (i) magneto-deposition and (ii) drop coating. For both, two peaks in the voltammograms were observed, related to oxidation (0.12 V) and reduction (-0.05 V), which are associated with redox couple Prussian blue / Prussian white. Higher peaks currents were observed for the film obtained via drop coating. Also, individual Fe3O4-PB microparticles (single particles) were isolated by using an optical microscope and analyzed by voltammetry, where there was the appearance of peaks with the same potential values. However, using two commutations magnetic states, \"switch on\" and \"switch off\", it was possible to monitor the presence and the absence of the particle on electrode. Also, there were differences in the values of current density in the chronoamperograms for each Fe3O4-PB microparticle, and the morphology of the microparticle significantly interfered in the electrochemical response. Finally, it was performed several electrochemical experiments regarding to collisions of Fe3O4-PB nanoparticles on a gold ultramicroelectrode. Controlled collisions in different experimental conditions were carried out, such as in the presence and absence of an external magnetic field parallel to the surface electrode, and also with intensities fields of 0.1 and 0.2 Tesla. In the absence of the field, the nanoparticles reached the UME and collided, resulting in electrochemical signals of this type staircase, due to accumulation of them. On the other hand, in the presence of a 0.1 T, we observed several transient currents (spikes) associated with the collisions of the nanoparticles. These events were not observed in the presence of the field of 0.2 T. Thus, these findings allow us to the discussion for improvements on the models for these systems, in order to explain the profiles of voltammetric and amperometric responses.

Lead's uptake on magnetite has been quantitatively evaluated in the present study at a temperature of 200°C and pH of 8.5 with lead concentrations ranging from 5 ppm to175 ppm by equilibrium adsorption isotherms. The pH independent sorption behavior suggested lead sorption due to pH independent permanent charge through weak electrostatic, non-specific attraction where cations are sorbed on the cation exchange sites. The permanent negative charge could be a consequence of lead substitution which is supported by increase in the lattice parameter values from the X-ray diffraction (XRD) results. Differential scanning calorimetry (DSC/TGA) results showed an increase of exothermic (magnetite to maghemite transformation) peak indicating substitution of lead ions due to which there is retardation in the phase transformation. Presence of outer sphere complexes and physical sorption is further supported by Fourier transformed infrared spectroscopy (FTIR). None of the results suggested chemisorption of lead on magnetite.

Marine vibrio MV-1 is a magnetotactic bacterium capable of aligning its cell in response to the Earth’s magnetic field. This ability is due to the presence of chainlike structures comprising magnetosomes, magnetite particles enclosed in a lipid membrane with associated proteins. Strain MV-1 differs from other, bettercharacterized strains of magnetotactic bacteria as the cells produce higher amounts of biomagnetite per litre of culture and its magnetosomes are unique in shape. This study investigates the presence and organisation of a gene cluster termed a “magnetosome island” within the genome of MV-1. In other magnetotactic bacteria this genomic region has been shown to contain many of the genes associated with magnetosome formation but has not been previously investigated for MV-1. One of the conserved fragments of this region was amplified using degenerate primers followed by extension of the known sequence using inverse PCR based technique and constructing plasmid libraries. Sequencing of the genome of strain MV-1 was accomplished as a part of this study. Significant work was done on comparison of the sequence quality obtained from SOLEXA, 454 and Sanger sequencing technologies. A number of obtained contigs were joined manually and the resulting sequence was automatically annotated using RAST. The obtained genome sequence of 3.6 Mb with a G+C content of 54.3 % was preliminarily analysed and used to search for magnetosome related genes. This study also analysed proteins associated with the magnetosomes of strain MV-1 using MALDI-TOF, LC-MS and Orbitrap mass spectrometry. These approaches allowed the identification of a number of proteins in the isolated magnetosome membrane fraction. Some of these proteins have very low similarity with other characterized proteins (either in magnetotactic bacteria or in other organisms). Another significant point is that genes that code for proteins such as MamR, MamK and MmsF were found to be present in several homologous copies within the “magnetosome island” of MV-1. Interestingly, this study shows that all homologous copies of these proteins were identified in the magnetosome membrane fraction. Generation of knock-out mutants of several specific genes from the “magnetosome island” of strain MV-1 was attempted; constructs were made based on suicide plasmids carrying the cre-lox or I-SceI systems. Despite altering numerous experimental conditions it was not possible to obtain conclusive evidence of the isolation of MV-1 transconjugants containing the integrated constructs. In order to investigate the cell localization of the magnetosome associated protein CAV30779.1, an enhanced green fluorescent protein (EGFP) fusion based construct was generated and transferred into MV-1 cells. The EGFP fluorescent protein fusions within the cells were detected by microscopy. This study reveals novel information about magnetosome formation in marine vibrio MV-1. The obtained results provide an important foundation for further investigation of this organism and contribute towards broadening the knowledge of the complex process of magnetosome formation in bacteria.

Master of Science / Department of Civil Engineering / Alexander P. Mathews / Nanoscale magnetite is being examined for possible uses as an adsorbent of heavy metals and for the enhancement of water treatment processes such as stripping of trichloroethylene (TCE) from contaminated water supplies and wastewaters. Methods for recovering nanoscale magnetite must be developed before the particles can be used in water treatment processes. This is necessary because expelling high amounts of particles into the environment will be unacceptable and costly; if captured they can be reused; additionally, they could potentially cause environmental impacts due to their stability in an aqueous environment and possible toxicity. Nanoscale magnetite is superparamagnetic, so it has a high magnetic susceptibility, and hence it is very attracted to magnetized materials. Utilizing the magnetic properties of magnetite may be one possible means of separating the particles from a treatment process. High Gradient Magnetic Separation (HGMS) has been studied for the separation of micron and even tenths of a micron size particles, but there is little experimental data for HGMS of nanoscale magnetite. This research looks to filter nanoscale magnetite through a HGMS and determine the capture efficiency of the filter. Subsequently, the filter was backwashed to determine particle recover efficiencies. The flow rate was adjusted to determine the dependency of particle capture efficiency on cross sectional velocity through the filter. Additionally, particle loading was changed to better understand the correlation of particle loading with capture efficiency. Filtrations for nanoscale magnetite dispersed with sodium tripolyphosphate were also completed as well as filtrations of nanoscale magnetite coated with silica and magnetite silica composites. Experimental data in this research indicates that magnetite nanoparticles can be captured at 99.8% efficiency or higher in a well-designed filtration system. Capture efficiencies around 99.8% have been found for magnetite. The silica coated magnetite and magnetite silica composites were captured at efficiencies as high as 96.7% and 97.9%, respectively. The capture efficiency of the dispersed magnetite is lower than non-dispersed magnetite and most promising at relatively low fluid flow velocities and particle loadings. The maximum capture efficiency for dispersed magnetite particles was 90.3%. Both magnetite and dispersed magnetite were successfully recovered using backwash at pH of 10 to 11.

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.

by Fung King-yuen Debera. / On t.p., "2+" is superscript. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1994. / Includes bibliographical references (leaves 102-112). / Acknowledgement --- p.i / Abstract --- p.ii / Table of Content --- p.iv / Chapter 1. --- Introduction --- p.1 / Chapter 1.1 --- Literature review --- p.1 / Chapter 1.1.1 --- Problems of heavy metals in the environment --- p.1 / Chapter 1.1.2 --- Methods of removal of heavy metal from industrial effluent --- p.5 / Chapter 1.1.3 --- The properties of magnetites --- p.10 / Chapter 1.1.4 --- Role of magnetites in water treatment --- p.12 / Chapter 1.1.5 --- The advantages of using magnetites and further application of magnetites --- p.16 / Chapter 1.2 --- Objectives of the study --- p.21 / Chapter 2. --- Materials and methods --- p.23 / Chapter 2.1 --- Selection of the organisms --- p.23 / Chapter 2.2 --- Culture media and chemicals --- p.23 / Chapter 2.3 --- Growth of the bacterial cells --- p.25 / Chapter 2.4 --- Immobilization of the bacterial cells on magnetites --- p.27 / Chapter 2.4.1 --- Effects of chemical and physical factors on the immobilization of the bacterial cells on magnetites --- p.27 / Chapter 2.4.2 --- Effect of pH on the desorption of cells from magnetites --- p.28 / Chapter 2.5 --- Nickel ion uptake experiments --- p.28 / Chapter 2.6 --- Effects of operational conditions on the nickel removal capacity of the magnetite-immobilized bacterial cells --- p.29 / Chapter 2 .6.1 --- Effect of physical factors --- p.29 / Chapter 2.6.2 --- Effect of chemical factors --- p.30 / Chapter 2.7 --- Optimization of the nickel removal efficiency --- p.30 / Chapter 2.8 --- Nickel adsorption isotherm of the magnetite- immobilized cells of Enterobacter sp4-2 --- p.30 / Chapter 2.9 --- Recovery of adsorbed Ni2+ from the magnetite- immobilized cells of Enterobacter sp4-2 --- p.31 / Chapter 2.9.1 --- Multiple adsorption-desorption cycles of Ni2+ by using citrate buffer --- p.32 / Chapter 2.9.2 --- Multiple adsorption-desorption cycles of Ni2+ by using ethylenediaminetetraacetic acid (EDTA) --- p.33 / Chapter 2.10 --- Effect of acidic treatment --- p.33 / Chapter 2.10.1 --- Effect of acidic treatment on the nickel removal capacity of the magnetites and the magnetite- immobilized cells of Enterobacter sp4-2 --- p.33 / Chapter 2.10.2 --- Effect of acidic treatment on the recovery of the adsorbed Ni2+ from magnetites and the magnetite- immobilized cells Enterobacter sp4-2 --- p.34 / Chapter 2.11 --- Removal and recovery of Ni2+ from the electroplating effluent --- p.34 / Chapter 3. --- Results --- p.36 / Chapter 3.1 --- Effects of chemical and physical factors on the immobilization of the bacterial cells on magnetites --- p.36 / Chapter 3.1.1 --- Effect of pH --- p.36 / Chapter 3.1.2 --- Effect of cells to magnetites ratio --- p.36 / Chapter 3.1.3 --- Effect of temperature --- p.39 / Chapter 3.2 --- Effect of pH on the desorption of cells from magnetites --- p.39 / Chapter 3.3 --- Nickel ion uptake experiments --- p.44 / Chapter 3.4 --- Effects of operational conditions on the nickel removal capacity of the magnetite-immobilized bacterial cells --- p.44 / Chapter 3.4.1 --- Effect of reaction temperature --- p.44 / Chapter 3.4.2 --- Effect of retention time --- p.44 / Chapter 3.4.3 --- Effect of pH --- p.47 / Chapter 3.4.4 --- Effect of the presence of cations --- p.50 / Chapter 3.4.5 --- Effect of the presence of anions --- p.50 / Chapter 3.5 --- Optimization of the nickel removal efficiency --- p.55 / Chapter 3.6 --- Nickel adsorption isotherm of the magnetite- immobilized cells of Enterobacter sp4-2 --- p.55 / Chapter 3.7 --- Recovery of adsorbed Ni2+ from the magnetite- immobilized cells of Enterobacter sp4-2 --- p.59 / Chapter 3.7.1 --- Multiple adsorption-desorption cycles of Ni2+ by using citrate buffer --- p.59 / Chapter 3.7.2 --- Multiple adsorption-desorption cycles of Ni2+ by using ethylenediaminetetraacetic acid (EDTA) --- p.63 / Chapter 3.8 --- Effect of acidic treatment --- p.63 / Chapter 3.8.1 --- Effect of acidic treatment on the nickel removal capacity of the magnetites and the magnetite-immobilized cells of Enterobacter sp4-2 --- p.63 / Chapter 3.8.2 --- Effect of acidic treatment on the recovery of the adsorbed Ni2+ from the magnetites and the magnetite-immobilized cells of Enterobacter sp4-2 --- p.66 / Chapter 3.9 --- Removal and recovery of Ni2+ from the electroplating effluent --- p.69 / Chapter 4. --- Discussion --- p.72 / Chapter 4.1 --- Selection of the organisms --- p.72 / Chapter 4.2 --- Effects of chemical and physical factors on the immobilization of the bacterial cells on magnetites --- p.72 / Chapter 4.2.1 --- Effect of pH --- p.72 / Chapter 4.2.2 --- Effect of cells to magnetites ratio --- p.74 / Chapter 4.2.3 --- Effect of temperature --- p.75 / Chapter 4.2.4 --- Effect of pH on the desorption of cells from magnetites --- p.76 / Chapter 4.3 --- Nickel ion uptake experiments --- p.78 / Chapter 4.4 --- Effects of operational conditions on the nickel removal capacity of the magnetite-immobilized bacterial cells --- p.80 / Chapter 4.4.1 --- Effect of reaction temperature --- p.80 / Chapter 4.4.2 --- Effect of retention time --- p.81 / Chapter 4.4.3 --- Effect of pH --- p.82 / Chapter 4.4.4 --- Effect of the presence of cations --- p.83 / Chapter 4.4.5 --- Effect of the presence of anions --- p.84 / Chapter 4.5 --- Optimization of the nickel removal efficiency --- p.85 / Chapter 4.6 --- Nickel adsorption isotherm of the magnetite- immobilized cells of Enterobacter sp4-2 --- p.86 / Chapter 4.7 --- Recovery of adsorbed Ni2+ from the magnetite- immobilized cells of Enterobacter sp4-2 --- p.87 / Chapter 4.7.1 --- Multiple adsorption-desorption of Ni2+ --- p.89 / Chapter 4.7.2 --- Effect of acidic treatment on the nickel removal capacity and recovery --- p.91 / Chapter 4.8 --- Removal and recovery of Ni2+ from the electroplating effluent --- p.93 / Chapter 5. --- Conclusion --- p.96 / Chapter 6. --- Summary --- p.99 / Chapter 7. --- References --- p.102

Batteries are ubiquitous in modern society, from the portable devices we use daily to the yet-to-be realized integration of batteries into the electrical grid and electrical vehicle markets. One of the primary roles of batteries to date has been to enable portability of devices, and as chemical energy storage becomes more affordable, batteries will play a larger role in how society cares for the environment by enabling technologies that are poised to decrease greenhouse gas emissions. Low cost and environmentally conscious materials are pivotal for the economic feasibility and widespread integration of batteries into new markets. Batteries operate far from equilibrium and may operate under extreme stress and varying loads, therefore, for a material to be successful in an operational battery it must meet multiple design criteria. Here, an in-depth analysis of magnetite, a low cost and abundant iron oxide studied for use as an electrode material in lithium-ion batteries, is presented. In the second Chapter, an in-depth analysis into how magnetite accepts lithium into the solid state at low depths of discharge is examined with density functional theory and a mechanistic understanding of a phase change from the parent spinel to a rocksalt-like material is presented. When magnetite is used as an electrode material in a lithium-ion battery, lithium must enter into and eject from the solid state of the host material, where the direction of lithium movement is a function of the current in the battery. In many electrode materials, magnetite included, large structural rearrangements can occur in the host material as lithium moves into and out of the lattice. These structural rearrangements can be irreversible and can contribute to overpotentials, decreasing efficiency and lifecycle for the battery. The structural rearrangements in bulk magnetite occurring due to lithium insertion are found to be driven primarily by Coulombic interactions. Additionally, the energetics and structural rearrangements for lithium insertion into defective magnetite and maghemite are examined, as these derivative structures commonly co-exist with magnetite, especially when the material is nanostructured. It is found that defective magnetite and maghemite accept lithium by a different mechanism, one that does not initially result in substantial structural rearrangement, as is the case in magnetite. In Chapter three, the effects of nanostructuring magnetite on the reversible potential are examined as a function of nanoparticle size. Due to solid-state mass-transport resistances, active electrode materials in batteries are commonly nanostructured. When a material is nanostructured, the bulk properties are often replaced due to interesting phenomena that can occur as a result of stark differences between the nanostructured material and the bulk counterpart. These differences are often attributed to surface area to volume ratios, the exaggerated role of surface energies, lattice defects, and the variation in electronic behavior, all properties which change between a bulk and nanostructured material. The reversible potential is found to be particle size dependent, and this dependence is explained, in part, by the cationic defective surfaces in the particles and the differences in surface area to volume ratio between varying particle sizes. Evidence for these defects is presented with materials characterization techniques such as XRD and EELS studies. Finally, the reversible potential at low lithiation states is predicted theoretically and found to match well to the experimentally measured potential. A study of the DFT predicted potentials and XRD characterization for multiple metastable pathways is examined in the fourth Chapter. Room temperature and long-time scale persistence of metastable phases is a pervasive phenomenon in nature. Magnetite is known to undergo both phase change and conversion reactions upon lithiation. Due to large mass transport and kinetic resistances, multiple phase changes are often observed in parallel during discharge, resulting in heterogenous phase formation in particles which can have large local lithium concentration variations. Phases which form during discharge can become kinetically trapped and the equilibrium state can therefore follow a metastable pathway. Theoretical potentials and XRD patterns are compared to the experimental patterns taken following 600 hours of relaxation following discharge at the slow rate of C/600. The evidence presented supports a metastable pathway occurring on the first voltage plateau. In the fifth Chapter, the methodologies for the density functional theory calculations are presented in full detail. This includes various studies on the more subtle electronic properties of magnetite and its lithiated derivates studied herein. These studies include examination of the charge and orbital ordering problem related to the Verwey transition in magnetite, the charge and magnetic order in the rocksalt-like lithiated magnetite, and a full theoretical description of the various phases in the Li-Fe-O ternary phase diagram that were calculated to make the relevant conclusions in Chapters 2-4. Finally, corrections to DFT predicted formation energy and volume are presented. The aim of this thesis is to use theoretical techniques to examine the lithiation of magnetite on the atomic scale and make meaningful connections to the experimentally observed electrochemical behavior of the material. To accomplish this, magnetite and the structural derivatives of magnetite that co-exist with the material under physically realistic conditions must be treated theoretically. In this thesis, ties between phenomena occurring on the atomic scale and the measurable properties of the macroscopic system, such as voltage, will be related. It will be illustrated that as a function of nanoparticle size, the magnetite system can vary in its atomic structure and the resultant electrochemistry and phase change characteristics are both affected. The findings indicate the relevance of the atomic properties and nanostructure for magnetite to the observed and measured electrochemical properties of the material.

Alguns estudos do emprego de compostos de ferro como material adsorvedor não- convencional são citados em literatura. Foram feitos alguns testes da utilização de hematita (Fe2O3), o lodo galvânico e a lama de alto forno como adsorvedores para a remoção de metais pesados de efluentes industriais. A utilização de resíduo siderúrgico abundante, composto predominantemente por magnetita (Fe3O4), como adsorvedor não - convencional em processos de remoção de metais representa uma alternativa, de baixo custo, para o tratamento e adequação do efluente aos padrões de descarte de efluentes industriais exigidos pela legislação. Neste trabalho estudou-se a utilização de resíduo siderúrgico composto basicamente por magnetita como material adsorvedor para remoção de metais pesados em solução. O trabalho se concentrou no estudo da adsorção de quatro metais: cobre (Cu2+) , níquel (Ni2+) , chumbo (Pb2+) e o cádmio (Cd2+). Estes metais foram escolhidos devido a sua alta toxicidade e por estarem freqüentemente relacionados com efluentes de atividades industriais poluidoras. Os resultados obtidos permitiram concluir que, nas melhores condições de adsorção, o resíduo apresenta características adsorvedoras favoráveis a sua utilização industrial, com 97,84 % de remoção dos íons de cobre, 96,20 % de íons de chumbo, 61,70 % de íons de níquel e 87,22 % de íons de cádmio em solução. A velocidade de adsorção é proporcional a aquelas obtidas para outros adsorvedores não convencionais, e para a remoção dos íons de chumbo varia entre (92 e 115) 10-3mg g1 min-1 , e o sistema de adsorção possui características espontâneas e endotérmicas em adsorção ativada com característica parcial de adsorção química e está de acordo com os modelos propostos por Langmuir e por Freundlich, característico de processo de adsorção em monocamada, com sítios de adsorção de mesma energia e calor de adsorção equivalente. / Various references on the use of ferrous compounds as non - conventional adsorption materials can be found in literature. According to the literature, such materials as hematite, galvanic slag and blast furnace slag were successfully used in liquid waste treatment for heavy metals removal. Thus, the use of abundant ferrous metallurgy slag may prove to be efficient for low cost treatment of liquid industrial waste. The main goal of the present work is the study of converter slag application as adsorber material for heavy metals removal from liquid waste. The present research was aimed at soluble copper ( Cu2+), nickel ( Ni2+ ) , cadmium ( Cd2+ ) , and lead (Pb2+) removal. These metals were chosen because of their high toxicity, and because they are considered as the most common pollutants present in liquid industrial waste. The obtained results on converter slag adsorption properties under optimized adsorption conditions show that 97,84 % of copper, 61,70 % of nickel, 87,22 % of cadmium and 96,20 % of lead can be removed from the liquid waste. The achieved adsorption rates are comparable to those of conventional adsorbers, and for soluble lead removal rates in the range of ( 92 - 115). 10 -3 mg g -1 min -1 were established. Additionally, if was shown that the investigated adsorption system presented spontaneous and endothermic behavior under conditions of activated adsorption with partial chemical adsorption characteristics. Such pattern is in good agreement with the models proposed by Langmuir and Freundlich for monolayer adsorption processes with adsorption centers having equal energy and specific heat of adsorption. Overall, the obtained results indicate the viability of the investigated material for commercial application.