Advanced High Strength Steel (AHSS) has become a popular steel grade among automakers to produce vehicle bodies. With improvements in strength and elongation, AHSS has evolved to its 2nd generation, including high manganese steel. Even though it has outstanding strength, the 2nd generation of AHSS faces some production problems due to its high alloying elements. With continual improvement, the 3rd generation of AHSS is currently in production. In this generation, the steel types still have a competitive strength and elongation like the 2nd generation of AHSS while having lower alloying element contents and production costs. One of the types of 3rd generation AHSS is medium manganese steel. Research related to the 2nd and 3rd generation of AHSS mainly focuses on their mechanical properties and microstructures. As there is a strong correlation between mechanical properties and inclusion characteristics, further investigation of the evolution of inclusions is still required. In this study, high-temperature experiments were conducted to investigate the effects of metal chemistry on the inclusion evolution in liquid steel. The concentrations of manganese, aluminum, and nitrogen were varied systematically. Two and three-dimensional analysis techniques were applied to study the number, composition, and size distribution of inclusions. Electrolysis extraction was used to identify the oxide, sulfide, and nitride inclusions, whereas an automated SEM with an ASPEX feature was used to detect a larger number of inclusions for better representation of the steel matrix. This work has established inclusion classification rules to distinguish nitride inclusions from oxide inclusions. To the best of the authors’ knowledge, this is the first discussion of this type of inclusion classification in the open literature. Based on the automated SEM (ASPEX Feature) analysis, the type of detected inclusions in medium and high manganese steels were Al2O3(pure), Al2O3-MnS, AlN(pure), AlN-MnS, AlON, AlON-MnS, and MnS inclusions. As the manganese content in the steel increased from 2% to 20%, the total amount of inclusions, especially AlN-contained inclusions, was raised. This phenomenon occurred due to the increase in nitrogen solubility with increased manganese content in the steel. The thermodynamic calculation also predicted that AlN inclusions would form when the steel was cooled or during the solidification. Moreover, AlN and MnS inclusions were observed to co-precipitate together. Similar to manganese, the increase in the aluminum content (Al = 0.5-6%) increased the total amount of inclusions in the steel, and the dominant inclusion type is AlN. AlN and Al2O3 inclusions can be heterogenous nucleation sites for MnS inclusions. Furthermore, Al2O3 inclusions also became heterogeneous nucleation sites for AlN inclusions. The experimental set-up was further modified to investigate the effect of nitrogen on the formation of inclusions in the medium manganese steels. The nitrogen was introduced by purging or injecting N2 gas into the steel system. Similar to the effect of manganese and aluminum, the increase in the nitrogen content also increased the total amount of inclusions. Once the nitrogen content in the steel exceeded the critical limit for the formation of AlN inclusions, AlN inclusions can be stable in the liquid steel. Moreover, regardless of the nitrogen content in the steel, AlN-MnS inclusions were formed in the slow-cooled steels. In terms of morphology, AlN inclusions can be formed of plate-like, needle, angular, agglomerate, or irregular shapes. Furthermore, a brief investigation on the addition of calcium and nitrogen to the medium manganese steels found that calcium led to the formation of other complex inclusions, such as CAx and CAS-Other inclusions. In the medium manganese steel composition in the present study, the number of CAS-Other inclusions was dominated by (Ca,Mn)S-Oxide inclusions after the addition of Ca. However, with time and after introducing N2 gas into the steel, the number of (Ca,Mn)S-Nitride inclusions also increased. The formation of (Ca,Mn)S-Nitride inclusions resulted from the co-precipitation of CaS, MnS, and AlN. The current work provides a better understanding of the formation mechanism of inclusions in medium manganese steels and high manganese steels. It presents complete information on the characteristics of inclusions, such as the number density, type, and morphology of inclusions. This knowledge can help steelmakers improve the steelmaking process to control the formation of inclusions, which can be problematic for the manufacture and performance of medium manganese steels and high manganese steels. / Dissertation / Doctor of Philosophy (PhD)

<p> The distribution of manganese in blood serum and erythrocytes has been investigated using a combination of radioactive tracer method with both gel chromatography and disc gel electrophoresis. </p> <p> In serum, there are two manganese-binding proteins. The first is a(beta)1 globulin with a molecular weight of 70,000. This forms a relatively labile manganese complex both in vitro and in vivo, and is remarkably similar in both its chromatographic and electrophoretic behaviour to the iron-binding protein, transferrin. The second protein is a higher molecular weight (beta) globulin. It is found to incorporate radiomanganese in vivo only, thereupon forming a very stable entity. </p> <p> In erythrocytes, manganese occurs predominantly in a porphyrin bound to apoglobin, giving rise to a species similar to hemoglobin . </p> / Thesis / Doctor of Philosophy (PhD)

This study evaluated alternative sulfide treatment processes for potable water systems that rely on groundwater supplies. Research for this study was conducted at the Imperial Lakes (IL) and Turner Road (TR) water treatment plants (WTPs) in Polk County, Florida. These WTPs are in the process of refurbishment and expansion, and will require the installation of a new groundwater well. The IL and TR WTPs both rely upon groundwater sources that contain total sulfide at concentrations ranging from 1.4 to 2.6 mg/L. Sulfide is a concern because if left untreated it can impact finished water quality, corrosivity, create undesirable taste and odor, and oxidize to form visible turbidity. For this reason, the raw water will require treatment per Florida Department of Environmental Protection (FDEP) "Sulfide Rule" 62-555.315(5)(a). This rule does not allow the use of conventional tray aeration (currently in use at the IL and TR WTPs) for wells that have significant total sulfide content (0.6 to 3.0 mg/L). This research was commissioned because the potential water treatment method identified in the Sulfide Rule (i.e. forced-draft aeration) would not adequately fit within the confines of the existing sites and would pose undue burden to neighboring residents. In addition, an effective sulfide treatment process was desired that offered a low profile, did not necessitate the need for additional complex chemical feed systems, minimized the extent of electrical infrastructure upgrades, and was inexpensive to construct and operate. To meet these goals, several alternative technologies were evaluated at the desktop and bench-scale; these included anion exchange, various oxidation methods, and alternative media filtration processes. From that effort, several processes were selected for evaluation at the pilot scale: bleach (NaOCl) oxidation preceding electromedia filtration; manganese (IV) oxide (MnO2) filtration continuously regenerated with bleach; and ferrate (Fe(VI)) oxidation. Electromedia and MnO2 filtration were shown to be effective for total sulfide treatment. Both processes reduced total sulfide content to below detection levels ( > 0.1 mg/L) for groundwater supplies containing as much as 2.6 mg/L of total sulfide. The use of bleach oxidation ahead of media filtration also produced finished water with low turbidity ( > 1.0 NTU) as compared to conventional tray aeration and chlorination processes (6-16 NTU, as observed in this study). It was determined that the media filtration approach (electromedia and MnO2) was effective for sulfide treatment and met the County's site objectives established at the outset of the project. Ferrate was also shown to reduce total sulfide content to below detection levels ( > 0.1 mg/L) for groundwater supplies containing as much as 2.6 mg/L of total sulfide. An opinion of probable capital costs for installing a sulfide oxidation/filtration process at either the Imperial Lakes or Turner Road WTP was estimated to range from roughly $830,000 to $1,100,000. That equates to a $/kgal capital cost of $0.10 to $0.32 (at 8% for 20 years). An opinion of annual probable bleach chemical costs was estimated to range from $3,500 to $9,800 for the IL WTP and $3,500 to $5,800 for the TR WTP.

No description available.

<p>Transition metals, such as iron, manganese, and copper are essential in the development and function of biological systems. However, disrupted levels of transition metals are highly cytotoxic, and metal homeostasis is strictly maintained in cells under normal conditions. The neuropathology of several brain disorders, such as Alzheimer’s disease and Parkinson’s disease has been linked to altered metal levels. This work focused on the measurement of iron, manganese, and copper, with the aim of better elucidating their role in brain disease.</p> <p>Two experiments were carried out in C57Bl/6 mice looking at metal homeostasis: <em>1.</em> following manganese injections typically administered in manganese-enhanced MRI animal studies, and <em>2.</em> following copper deficiency in a cuprizone model of demyelination. Metal measurements were made in the brain and visceral organs using X-ray fluorescence to measure iron and copper concentrations, and neutron activation analysis to measure manganese concentrations.</p> <p>In the MEMRI study in this work, in addition to the expected manganese concentration increases in brain regions, a statistically significant decrease in iron concentration in the thalamus was found. This change in iron levels in the thalamus following manganese injections should serve as a caution that care should be taken when interpreting signal changes in brain regions.</p> <p>The cuprizone study in this thesis confirmed that copper levels are reduced following cuprizone administration. Surprisingly, manganese concentrations were significantly higher in several brain regions that have demyelination in this model, but not iron or copper. The mechanism of cuprizone toxicity was related to manganese neurotoxicity that may contribute to demyelination.</p> / Master of Science (MSc)

Metalorganic Chemical Vapour Deposition (MOCVD) is a versatile technique for the deposition of thin films of oxide materials as it offers advantages, such as deposition over large surface area, conformal coverage, selective area deposition, and a high degree of compositional control. The MOCVD process uses metalorganic (MO) complexes, such as β-diketonate and alkoxide-based complexes, as precursors. These complexes are stable and moderately volatile. Because of the direct bond between metal and oxygen, MO complexes are natural precursors for oxide coatings. As the process involves chemical reactions taking place on the substrate surface, growth of thin films by MOCVD depends on various parameters such as the chemical nature and concentration of precursors, reaction pressure, reaction temperature, and the nature of the substrate. Such a large parameter space of the CVD process, when combined with the dynamics (thermodynamics and fluid dynamics) and kinetics, makes it rather complex. This complexity allows one to make thin films of metastable phases, including amorphous materials. One of the important findings of the work is that MOCVD process is capable of making composite coatings of carbonaceous metal oxide. Manganese is multivalent and forms various stable oxides, such as MnO, Mn2O3, Mn3O4 and MnO2. There are various potential applications of manganese oxides. MnO2 is a very well studied material for its electrochemical applications in dry cells, lithium-ion batteries, and in supercapacitors. Hence, it becomes pertinent to explore the properties of thin films of manganese oxides prepared by MOCVD for various electrochemical and other applications. The thesis work is divided into two parts. Part 1 describes the synthesis of manganese complexes, their characterization, and their application to the CVD of coatings, especially those of carbonaceous MnO. Part 2 is devoted to a detailed study of electrochemical aspects of the carbonaceous MnO coatings, followed by a report on their unusual transport properties. Chapter 1 begins with a brief introduction to thin film deposition processes. In particular, the CVD process is described with reference to various parameters such as carrier gas flow, pressure, temperature and most importantly, the CVD precursor. The chapter ends with a description of the scope of the work undertaken for the present thesis. Chapter 2 deals with “Synthesis and Characterization of MO complexes”. It begins with a description of the classification of CVD precursors with the description of MO complexes such as β-diketonates, which are generally subliming crystalline solids. Manganese β-diketonate complexes are discussed in detail. Due to the multivalent nature of Mn, there are two possible complexes namely Mn(acac)2(H2O)2 and Mn(acac)3. These complexes have been synthesised and characterized (confirmed) by various techniques, such as elemental analysis (CHN), X-ray diffraction (XRD), FTIR spectroscopy, and mass spectroscopy. Thermal analysis of the complexes shows that they are suitable as MOCVD precursors. We have used Mn(acac)2(H2O)2 as a precursor in the present work. Metalorganic complexes, where metal ion is directly bonded with both nitrogen and oxygen, can be potential candidates for the precursor for oxynitrides coatings. We have therefore studied solid crystalline anthranilate complexes of various metal ions, such as Mn2+, Co2+, Cu2+ and Zn2+ and confirmed their formation. Thermal analysis shows that anthranilate complexes are fairly volatile below 250oC and decompose below 500oC. These complexes were pyrolysed in open air and in sealed tube at different temperatures, and the resulting powder product examined by XRD, SEM, EDAX and FTIR. This preliminary study shows that anthranilate complexes yield different oxides of Mn, Co and Cu under different pyrolysis conditions, with very interesting morphological features. Pyrolysis of Zn(aa)2 in a sealed tube leads to the formation of a nanocomposite of carbon and zinc oxide (wuerzite), rich in carbon, with potential for applications in catalysis. On the other hand, the pyrolysis of Zn(aa)2 in air at the same temperature leads to leads to crystalline, nanostructured zinc oxide (wuerzite). However, no attempt has been made to use these anthranilates as CVD precursors. Chapter 3 deals with “MOCVD of Manganese Oxides and their Characterization”. It begins with a brief review of various manganese oxides and their properties. This is followed by description of the CVD reactor used for the present work, together with the conditions employed for the deposition of MnOx films. Depositions have been carried out on different substrates such as SS-316, ceramic alumina and Si (111), while varying various deposition parameters, viz., substrate, reactor pressure, carrier gas (argon) flow rate, and the duration of deposition. Significantly, depositions are divided into two categories: one, carried out in argon ambient, in the absence of a supply of oxygen (or any other oxidant) and the second one, under oxygen flow, using argon as carrier gas. The films deposited in the absence of oxygen flow are thick, black in colour, and electrically conducting, indicating the presence of carbon. The growth rate follows a typical thermal pattern, with activation energy of ~ 1.7 eV. Detailed characterization by XRD, TEM/ED, Raman, FTIR and XPS (X-ray photoelectron spectroscopy) shows that these films are composed of MnO in a carbon-rich amorphous matrix. High-resolution SEM (fig. 1) reveals a fractal pattern of cauliflower morphology, comprising very fine particles (4 – 10 nm), characteristic of very large specific surface area of the film, which is confirmed by volumetric BET measurement (~2000 m2/g). We conclude that growth in argon ambient leads to a homogenous nanocomposite film of hydrated MnO in carbon-rich matrix. Thus, our study reveals that MOCVD is a novel one-step chemical method to produce homogenous composite thin films, wherein all components of the nanocomposite film emerge from the same chemical precursor. Carbon incorporation is generally avoided by empirical process design, as it is viewed as an impurity. The potential advantages of carbon incorporation are thus not examined and the composite nature of carbonaceous films not recognized in the literature. Carbonaceous nanocomposite film can be significant as an electrode in supercapacitors, as discussed in part 2 of the thesis. Chapter 3 describes films deposited under oxygen flow, which are no longer black and are highly resistive, indicating the absence of carbon in the film, as confirmed by Raman spectroscopy. XRD, FTIR and Raman spectroscopy reveal that the films obtained under oxygen flow are more crystalline than the ones obtained in the absence of oxygen flow, and that the films are generally nanocrystalline composites of two manganese oxides, such as MnO and Mn3O4. Given the context of the carbonaceous MnO films described above, chapter 4 begins with a review of electrochemical capacitors (also called supercapacitors or ultracapacitors), which are emerging as important energy storage devices. Until now, in the Mn-O system, hydrated MnO2 has been well-studied as an electrode material due to its low cost and environmental compatibility, but the low electrical conductivity of MnO2, together with irreversible redox reactions, reduces its performance. In electrochemical capacitor applications, metal-oxide/carbon composites are finding importance. Chapter 4 deals with “MnO/C Nanocomposite Coatings as Electrodes for Electrochemical Capacitor”. In this chapter, we have examined the novel EM, i.e., the hydrated MnO/C nanocomposite coating prepared by the MOCVD process on a conducting substrate (current collector) such as SS-316 as an electrode. Electrochemical measurements have been carried out for both the 3-electrode assembly (for basic aqueous electrolyte) and 2-electrode assembly (for gel polymer electrolyte) using cyclic voltammetry (CV), AC impedance and charge-discharge techniques. The studies lead to a maximum specific capacitance of 230 – 270 F/g at 1 mA/cm2 discharge current density for the MnO/C nanocomposite coating grown at 680oC. The Bode plot shows a maximum phase angle of around 74 – 82o, indicating capacitive behaviour. The MnO/C nanocomposite film shows a very small time constant (0.5 – 3 msec), which is good for high frequency applications. The pulse power figure of merit is found to be 650 – 2000 W/g. Capacitance determined for a large number of charge-discharge cycles (~20000), and at large current densities (50 mA/cm2) show promising results. The energy density (5 - 32 Wh/kg) and power density (2 – 4 kW/kg) estimated from charge-discharge data at 1 mA/cm2 shows the potential of the nanocomposite MnO/C as electrode for superior capacitor devices. Gel polymer electrolytes (GPE) offer the advantage of large electrochemical potential window due to its structural and chemical stability. Studies have been carried out to show that the MnO/C nanocomposite film is compatible with gel polymer electrolytes based on poly(methyl methacrylate) (PMMA) and poly(acrylonitrile) (PAN) with salts of magnesium triflate and magnesium perchlorate, respectively) and plasticizers (ethylene carbonate (EC) + propylene carbonate (PC)), in a 2-electrode assembly. Chapter 5 deals with “Magnetoconductance in MnO/C Nanocomposite Coatings on Alumina”. Amorphous systems, such as MnO/C composites wherein carbon is amorphous and MnO is nearly so, are highly symmetric condensed phases, which do not possess long range translational or orientational order. Disorder in the system creates Anderson localized states just above the valence band, which lead to reduced electrical conductivity. Amorphous systems show either a small negative magnetoresistance (~ 5%) or a small positive magnetoconductance (~ 7%) at very low temperatures (~ 10 K). As such, the transport properties of the MnO/C nanocomposite film have been investigated, and are reported in chapter 5. Transport and magnetotransport measurements have been made on the MnO/C nanocomposite film grown on alumina. It is found that the MnO/C nanocomposite coating exhibits a giant negative MR (22.3%) at a temperature as high as 100 K, which is unusual because pure MnO is anti-ferromagnetic and does not ordinarily show any magnetoresistance (MR), while amorphous carbon is known to show a small MR at very low temperatures (~7 K), due to weak-localization. The present results mean that a mechanism other than weak-localization plays a role in this nanocomposite material. Further study of this material is called for, which can perhaps lead to giant magnetoresistance (GMR) at room temperature in a metal-oxide/carbon nanocomposite. A summary of the work and an outlook for further research are given in the concluding chapter 6.

Made available in DSpace on 2015-03-26T13:53:35Z (GMT). No. of bitstreams: 1 texto completo.pdf: 2372218 bytes, checksum: c684476e0801238a67fe879e90544505 (MD5) Previous issue date: 2007-08-27 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The dusty from the siderurgical industry (PD) it is an industrial solid residue originating from the processes of the metallurgy of the ore of manganese (Mn). This material contains significant concentration of Mn. The responsible industrial unit for the production of approximately 2000 ton/month of PD's is Rio Doce Manganês (RDM), company of the group of the Company is Worth of Rio Doce (CVRD), nowadays, Company is Worth. PD's were characterized chemically (stage 1) and soon afterwards, appraised as source of Mn for soy plants (Glicine max L.), of the variety it Conquers and eucalyptus plants (Eucalyptus globulus), of the hybrid Urograndis, vegetation home (stage 2). Para the stage 1 of the research, they were chosen ten materials of PD's collected in the industrial units of Barbacena/MG, Ouro Preto/MG, Salvador/Ba and Corumbá/MS, respectively. The samples of PD's were analyzed according to the lixiviação procedures and solubilization of solid residues (ABNT NBR 10005 and 10006, 2004). The tenors of metals of PD &#769;s were quantified through espectrofotometry in optic emission with plasma coupled induced (ICP-OES) and espectrofotometry for atomic absorption (AAS). Soon afterwards, the experiment was accomplished vegetation home (stage 2), being used samples of two Latossolos (LVa), a loamy one (TG) and other sandy (TM), of the cities Viçosa/MG and Three Marias/MG, respectively. As sources of Mn, were appraised samples of PD's in natura originating from five industrial units of RDM/CVRD and two prepared fertilizers starting from PD's: the sulfate of manganese (SM-PD) and the oxide of manganese (OM-PD). it was included as treatment controls another fertilizer sulfate of commercial manganese (SM- with). The materials were applied in equivalent amount to the doses 0,0; 2,5; 5,0; 7,5 and 30,0 mg kg-1 of Mn, except for applied OM-PD just in the doses 2,5 and 30,0 mg kg-1 of Mn. The plants were collected and droughts in greenhouses with ventilation forced of hot air. Soon afterwards, they were determined the tenors of P, Mn, Zn, Ass, Faith, Cr, Ni, You and If, with xiextraction of nítric acid and percloric (3:1), for espectrofotometry of optical emission with plasma coupled induced (ICP-OES). The data were submitted to the analysis of multiple lineal regression, being evaluated the production of the mass of dry matter, concentration and accumulation of the chemical elements in the aerial part and roots of the soy plants and eucalyptus. The results obtained with the extracts solubilizados (stage 1), they presented tenors of The, Pb, If, Hg, Mn, Faith and Al in values above the maximum limits established by ABNT (I Enclose G, ABNT NBR 10004, 2004). on the other hand, the tenors of metals found in the leached extracts didn't result in high values, second referred her norm. There was not significant answer with the sources of applied Mn in the treatments, in what he/she concerns the production of the mass of dry matter of the soy plants and eucalyptus (stage 2). there also was not, accumulation of heavy metals in the fabrics of the same ones in levels that represented any risk to his/her development. PD's in natura made available Mn to the cultivated plants, in amounts comparable to liberated them to SM-PD, OM-PD and the SM-COM. It is ended that, so much PD's in natura, as for the materials produced starting from PD's (SM-PD and OM-PD) they were efficient as sources of Mn to the soy plants and eucalyptus cultivated vegetation home. The obtained results indicate that the use of PD can be viable, as source of Mn for the industry of fertilizers. / O Pó de Despoeiramento (PD) é um resíduo sólido industrial proveniente dos processos da metalurgia do minério de manganês (Mn). Este material contém concentração significativa de Mn. A unidade industrial responsável pela produção de aproximadamente 2000 toneladas/mês de PD s é a Rio Doce Manganês (RDM), empresa do grupo da Companhia Vale do Rio Doce (CVRD), atualmente, Companhia VALE. Os PD s foram caracterizados quimicamente (etapa 1) e em seguida, avaliados como fonte de Mn para plantas de soja (Glicine max L.), da variedade Conquista e plantas de eucalipto (Eucalyptus globulus), do híbrido Urograndis, em casa de vegetação (etapa 2). Para a etapa 1 da pesquisa, foram escolhidos dez materiais de PD s coletados nas unidades industriais de Barbacena/MG, Ouro Preto/MG, Salvador/Ba e Corumbá/MS, respectivamente. As amostras de PD s foram analisadas segundo os procedimentos de lixiviação e solubilização de resíduos sólidos (ABNT NBR 10005 e 10006, 2004). Os teores de metais dos PD &#769;s foram quantificados por meio de espectrometria em emissão ótica com plasma acoplado induzido (ICP-OES) e espectrometria por absorção atômica (AAS). Em seguida, foi realizado o experimento em casa de vegetação (etapa 2), utilizando-se amostras de dois Latossolos (LVa), um argiloso (TG) e outro arenoso (TM), das cidades Viçosa/MG e Três Marias/MG, respectivamente. Como fontes de Mn, foram avaliadas amostras dos PD s in natura proveniente de cinco unidades industriais da RDM/CVRD e dois fertilizantes preparados a partir dos PD s: o sulfato de manganês (SM-PD) e o óxido de manganês (OM- PD). Foi incluído como tratamento controle um outro fertilizante sulfato de manganês comercial (SM-Com). Os materiais foram aplicados em quantidade equivalente às doses 0,0; 2,5; 5,0; 7,5 e 30,0 mg kg -1 de Mn, com exceção do OM-PD aplicado apenas nas doses 2,5 e 30,0 mg kg -1 de Mn. As plantas foram coletadas e secas em estufas com ventilação forçada de ar quente. Em seguida, determinaram-se os teores de P, Mn, Zn, Cu, Fe, Cr, Ni, Ti e Se, com ixextração de ácido nítrico e perclórico (3:1), por espectrometria de emissão óptica com plasma acoplado induzido (ICP-OES). Os dados foram submetidos à análise de regressão linear múltipla, avaliando-se a produção da massa de matéria seca, concentração e acúmulo dos elementos químicos na parte aérea e raízes das plantas de soja e eucalipto. Os resultados obtidos com os extratos solubilizados (etapa 1), apresentaram teores de As, Pb, Se, Hg, Mn, Fe e Al em valores acima dos limites máximos estabelecidos pela ABNT (Anexo G, ABNT NBR 10004, 2004). Por outro lado, os teores de metais encontrados nos extratos lixiviados não resultaram em valores elevados, segundo a referida norma. Não houve resposta significativa com as fontes de Mn aplicadas nos tratamentos, no que diz respeito à produção da massa de matéria seca das plantas de soja e eucalipto (etapa 2). Não houve também, acúmulo de metais pesados nos tecidos das mesmas em níveis que representassem qualquer risco ao seu desenvolvimento. Os PD s in natura disponibilizaram Mn às plantas cultivadas, em quantidades comparáveis às liberadas ao SM-PD, OM- PD e o SM-Com. Conclui-se que, tanto os PD s in natura, quanto aos materiais produzidos a partir dos PD s (SM-PD e OM-PD) foram eficientes como fontes de Mn às plantas de soja e eucalipto cultivadas em casa de vegetação. Os resultados obtidos indicam que o uso do PD pode ser viável, como fonte de Mn para a indústria de fertilizantes.

by Tsai Yau Moon = 錳氧化物的金屬-絶緣體轉變 : 多層薄膜及異構結 / 蔡友滿. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2006. / Includes bibliographical references. / Text in English; abstracts in English and Chinese. / by Tsai Yau Moon = Meng yang hua wu de jin shu-jue yuan ti zhuan bian : duo ceng bo mo ji yi gou jie / Cai Youman. / Abstract / 論文摘要 / Acknowledgements / Table of Contents / List of Figures / List of Tables / Chapter Chapter 1 --- Introduction / Chapter 1.1 --- Perovskite-type structure / Chapter 1.2 --- Metal-insulator transition / Chapter 1.3 --- Magnetoresistance / Chapter 1.3.1 --- Giant magnetoresistance (GMR) / Chapter 1.3.2.1 --- Colossal magnetoresistance (CMR) in perovskite manganites / Chapter 1.3.2.2 --- Possible origin of CMR / Chapter 1.4 --- Brief review of p-n junction between perovskite manganites and STON (001) / Chapter 1.5 --- Our project / Chapter 1.6 --- Scope of this thesis work / References / Chapter Chapter 2 --- Preparation and characterization of manganite thin films / Chapter 2.1 --- Thin film deposition / Chapter 2.1.1 --- Facing-target sputtering (FTS) / Chapter 2.1.2 --- Vacuum system / Chapter 2.1.3 --- Deposition procedure / Chapter 2.1.4 --- Deposition conditions / Chapter 2.1.5 --- Oxygen annealing system / Chapter 2.1.6 --- Silver electrode coating system / Chapter 2.2 --- Characterization / Chapter 2.2.1 --- Alpha step profilometer / Chapter 2.2.2 --- X-ray diffraction (XRD) / Chapter 2.2.3 --- Transport property measurement / References / Chapter Chapter 3 --- [LCSMO/PCMO] multilayers / Chapter 3.1 --- [LCSMO (100 A)/PCMO (X A)] multilayers / Chapter 3.1.1 --- Sample preparation / Chapter 3.1.2 --- Results and discussion / Chapter 3.1.2.1 --- Structural analysis / Chapter 3.1.2.2 --- Transport properties / Chapter 3.2 --- [LCSMO (50 A)/PCMO (X A)] multilayers / Chapter 3.2.1 --- Sample preparation / Chapter 3.2.2 --- Results and discussion / Chapter 3.2.2.1 --- Structural analysis / Chapter 3.2.2.2 --- Transport properties / References / Chapter Chapter 4 --- [LSMO/PCMO] multilayers and LSMO/STON p-n junction / Chapter 4.1 --- [LSMO/PCMO] multilayers / Chapter 4.1.1 --- Sample preparation / Chapter 4.1.2 --- Results and discussion / Chapter 4.1.2.1 --- Structural analysis / Chapter 4.1.2.2 --- Magnetization / Chapter 4.2 --- LSMO/STON heterojunction / Chapter 4.2.1 --- Sample preparation / Chapter 4.2.2 --- Results and discussion / Chapter 4.2.2.1 --- Structural analysis / Chapter 4.2.2.2 --- Metal insulator transition of LSMO revealed by four point I-V measurement / Chapter 4.3 --- Conclusion / References / Chapter 5 Conclusion / Chapter 5.1 --- Conclusion / Chapter 5.2 --- Future outlook

"Manganese (Mn2+) has recently gained acceptance as a magnetic resonance imaging (MRI) contrast agent useful for generating contrast in the functioning brain. The paramagnetic properties of Mn2+, combined with the cell's affinity for Mn2+ via voltage-gated calcium channels, makes Mn2+ sensitive to cellular activity in the brain. Compared with indirect measures of brain function, such as blood oxygenation level dependent (BOLD) functional MRI, manganese-enhanced MRI (MEMRI) can provide a direct means to visualize brain activity. MEMRI of the brain typically involves osmotic opening of the blood-brain barrier (BBB) to deliver Mn2+ into the interstitial space prior to initiation of a specific neuronal stimulus. This method assumes that the BBB-disruption process itself does not induce any apparent stimuli or cause tissue damage that might obscure any subsequent experimental observations. However, this assumption is often incorrect and can lead to misleading results for particular types of MRI applications. One aspect of these studies focused on characterizing the confounding effects of the BBB-opening process on MRI measurements typically employed to characterize functional activity or disease in the brain (Chapters 4 and 5). The apparent diffusion coefficient (ADC) of tissue water was found to decrease (relative to the undisrupted contralateral hemisphere) following BBB opening, obscuring similar ADC changes associated with ischemic brain tissue following stroke. Brain regions exhibiting reduced ADC values following osmotic BBB disruption also experienced permanent tissue damage, as validated by histological measures in the same vicinity of the brain. Non-specific MEMRI-signal enhancement was also observed under similar conditions and was found to be correlated to regions with BBB opening as verified by Evans Blue histological staining. In this case, MEMRI may prove to be a useful alternative for monitoring BBB-permeability changes in vivo. MEMRI was also investigated as a method for visualizing regions of BBB damage following ischemic brain injury (Chapter 6). BBB disruption following stroke has been investigated using gadolinium-based MRI contrast agents (e.g., Gd-DTPA). However, as an extracellular MRI contrast agent, Gd-DTPA is not expected to provide information regarding cell viability or function as part of MR image contrast enhancement. By comparison, brain regions with ischemia-induced BBB damage, and blood-flow levels sufficient to deliver Mn2+, show MEMRI-signal enhancement that correlates to regions with tissue damage as verified by histological staining. This approach should allow us to better understand the factors responsible for ischemia-induced BBB damage. Furthermore, MEMRI should be a useful tool for monitoring therapeutic interventions that might mitigate the damage associated with BBB disruption following stroke. "

La forte progression démographique mondiale induit une demande d’énergietoujours en hausse. Ceci se traduit par un fort développement de nouvelles énergiesrenouvelables qui nécessitent, de par leur nature intermittente, des dispositifs de stockagede l’énergie. Parmi eux les supercondensateurs permettent un stockage électrostatique decharges (supercondensateurs à base de carbones activés), mais certains systèmes, ditspseudocapacitifs, font en outre intervenir des réactions redox rapides de surface.L’association des deux systèmes permettent d’accéder à des propriétés intéressantes, enparticulier pour le système MnO2/carbone activé. Cependant, les oxydes de manganèse sontd’excellents matériaux pseudocapacitifs mais assez peu conducteurs électroniques.L’objectif de ce travail est d’améliorer cette conductivité en les associant avec des oxydes decobalt conducteurs. Pour cela, une approche « architecturale » de synthèse de matériaux aété choisie. En partant d’oxydes de Mn et de Co lamellaires, ceux-ci sont exfoliés pourobtenir des nanofeuillets de nature différente. S’ensuit une étape de réempilement pouraboutir à un matériau lamellaire alterné. L’analyse structurale et morphologique desmatériaux prouve que des nanocomposites très finement divisés sont obtenus. Lespropriétés électrochimiques obtenues pour ces nanocomposites s’avèrent meilleures quecelles des matériaux initiaux, tant en densité d’énergie qu’en puissance. Cette stratégieoriginale est prometteuse et ouvre la voie à des réempilements de différente nature,notamment le graphène. / The ever increasing demand of renewable energies imposes, due to theirintermittent nature, the development of performant energy storage devices. Supercapacitorsare reliable devices that offer a high power density and numerous investigations are focusingon increasing their energy densities. In particular, asymmetric "metal oxides / activatedcarbons" supercapacitors are possible candidates. The MnO2/carbon system is the mostinvestigated system, due to its capability to work in aqueous medium at potentials up to 2 V,as well as to the low cost and environmental friendliness of manganese. Nevertheless, thissystem suffers from the poor electronic conductivity of manganese. This work reports anoriginal strategy for novel electrode materials involving exfoliation and restacking processesof lamellar “building blocks”: lamellar manganese oxides for their pseudocapacitiveproperties and lamellar cobalt oxyhydroxides for their high electronic conductivity. Thematerial engineering strategy focuses on the exfoliation of the lamellar materials intooligolamellae. The obtained suspensions are then restacked through various strategies andnew well defined mixed oxides are obtained. After structural and morphologicalcharacterization, it is clear that these nanocomposites present an intimate mix of the twoinitial phases. The electrochemical responses are hereby enhanced, proving the intertwinedrelationship between structure, morphology and properties. Furthermore, this architecturalapproach of building novel electrode materials is original and efficient and can easily betransposed to other “building blocks”, including graphene.