Lai Chun Hei Gary = 錳氧化物-鈮摻雜之鈦酸鍶異構結的輸運特性 / 黎鎮禧. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references. / Text in English; abstracts in English and Chinese. / Lai Chun Hei Gary = Meng yang hua wu-ni shan za zhi tai suan si yi gou jie de shu yun te xing / Li Zhenxi. / Acknowledgement --- p.i / Abstract --- p.ii / 論文摘要 --- p.iv / Table of contents --- p.vi / List of Figures --- p.x / List of Tables --- p.xv / Chapter Chapter 1 --- Introduction / Chapter 1.1 --- Introduction to perovskite manganites and niobium doped strontium titanate --- p.1-1 / Chapter 1.1.1 --- Structure and properties of perovskite manganites --- p.1-1 / Chapter 1.1.2 --- Structure and properties of niobium doped strontium titanate --- p.1-4 / Chapter 1.1.3 --- Phase transition in perovskite manganites --- p.1-9 / Chapter 1.1.4 --- Charge ordering and small polaron theory in PCMO --- p.1-15 / Chapter 1.1.5 --- Colossal Magnetoresistance (CMR) in perovskite manganites --- p.1-19 / Chapter 1.16 --- Review of semiconducting junction between perovskite manganites and niobium doped strontium titanate --- p.1-23 / Chapter 1.2 --- Research motivation --- p.1-28 / Chapter 1.3 --- Scope of this thesis --- p.1-29 / References --- p.1-31 / Chapter Chapter 2 --- Experimental details / Chapter 2.1 --- Thin film deposition --- p.2-1 / Chapter 2.1.1 --- Facing-target sputtering --- p.2-1 / Chapter 2.1.2 --- Vacuum system --- p.2-3 / Chapter 2.1.3 --- Fabrication and characterization of manganites targets --- p.2-4 / Chapter 2.1.4 --- Substrate --- p.2-7 / Chapter 2.1.5 --- Deposition procedure --- p.2-8 / Chapter 2.1.6 --- Silver electrode coating apparatus --- p.2-10 / Chapter 2.2 --- Annealing systems --- p.2-12 / Chapter 2.2.1 --- Vacuum annealing system --- p.2-12 / Chapter 2.2.2 --- Oxygen annealing system --- p.2-14 / Chapter 2.3 --- Characterization --- p.2-16 / Chapter 2.3.1 --- Profilometer --- p.2-16 / Chapter 2.3.2 --- X-ray diffractometer --- p.2-16 / Chapter 2.3.3 --- Resistance measurement system --- p.2-18 / Chapter 2.3.4 --- Current-voltage characteristics measurement system --- p.2-20 / References --- p.2-23 / Chapter Chapter 3 --- Epitaxial LCMO/STON heterojunction / Chapter 3.1 --- Four point and two point I-V measurement --- p.3-1 / Chapter 3.2 --- Magnetic phase transition of LCMO revealed by four point I-V measurement of LCMO/STON heteroj unction --- p.3-8 / Chapter 3.3 --- Oxygen annealing effect on LCMO/STON heteroj unction --- p.3-14 / Chapter 3.4 --- Positive colossal Magnetoresistance in LCMO/STON heteroj unction --- p.3-16 / References --- p.3-23 / Chapter Chapter 4 --- Epitaxial PCMO/STON heterojunction / Chapter 4.1 --- Ohmic contact for PCMO thin films --- p.4-1 / Chapter 4.2 --- PCMO charge ordering and magnetic phase transition --- p.4-9 / Chapter 4.3 --- Four point I-V measurement of PCMO/STON heterojunction --- p.4-14 / References --- p.4-16 / Chapter Chapter 5 --- Epitaxial LCMO/PCMO/STON junction / Chapter 5.1 --- Tunneling junction fabrication --- p.5-1 / Chapter 5.2 --- Structural characterizations --- p.5-2 / Chapter 5.3 --- PCMO magnetic phase transition revealed by I-V measurement of LCMO/PCMO/STON tunneling junction --- p.5-3 / Chapter 5.4 --- Energy band structure of perovskite manganites --- p.5-11 / Chapter 5.4.1 --- Introduction to energy band of perovskite manganites and STON --- p.5-11 / Chapter 5.4.2 --- Temperature dependent band structure of LCMO explained by diffusion voltage of LCMO/STON heterojunction --- p.5-18 / References --- p.5-22 / Chapter Chapter 6 --- Conclusions / Chapter 6.1 --- Conclusion --- p.6-1 / Chapter 6.2 --- Future outlook --- p.6-3

Cheung, Wing Kin = 應變及間隔效應對La0.67Sr0.33MnO3摻雜Pr0.67Ca0.33MnO3的傳導特性的影響之研究 / 張榮健. / On t.p. "0.67", "0.33" and "3" are subscripts. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2007. / Includes bibliographical references (leaves 89-93). / Text in English; abstracts in English and Chinese. / Cheung, Wing Kin = Ying bian ji jian ge xiao ying dui La0.67Sr0.33MnO3 shan za Pr0.67Ca0.33MnO3 de chuan dao te xing de ying xiang zhi yan jiu / Zhang Rongjian. / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Development of magnetoresistance materials --- p.1 / Chapter 1.2 --- What is magnetoresistance? --- p.1 / Chapter 1.2.1 --- Anisotropic magnetoresistance --- p.2 / Chapter 1.2.2 --- Giant magnetoresistance (GMR) --- p.3 / Chapter 1.2.3 --- Colossal magnetoresistance (CMR) --- p.4 / Chapter 1.3 --- Possible origins of CMR in manganites --- p.6 / Chapter 1.3.1 --- Tolerance factor --- p.6 / Chapter 1.3.2 --- Double exchange mechanism --- p.8 / Chapter 1.3.3 --- Jahn-Teller distortion --- p.11 / Chapter 1.3.4 --- Charge-ordering and phase separation --- p.13 / Chapter 1.4 --- Movtiation --- p.17 / Chapter 1.5 --- Literature review --- p.18 / Chapter 1.5.1 --- Single-layer manganite thin films --- p.18 / Chapter 1.5.2 --- Multilayer system - manganites with insulating spacers --- p.19 / Chapter 1.6 --- Scope of thesis --- p.20 / Chapter 2 --- Instrumentation --- p.21 / Chapter 2.1 --- Sample preparation --- p.21 / Chapter 2.1.1 --- Facing-target sputtering technique (FTS) --- p.21 / Chapter 2.1.2 --- Deposition system --- p.24 / Chapter 2.2 --- Annealing system --- p.26 / Chapter 2.2.1 --- Oxygen annealing --- p.26 / Chapter 2.3 --- Sample characterization --- p.28 / Chapter 2.3.1 --- X-ray diffraction (XRD) --- p.28 / Chapter 2.3.2 --- Alpha - step profiler --- p.30 / Chapter 2.3.3 --- Transport property measurement --- p.30 / Chapter 3 --- Preparation and characterization of single-layer thin films --- p.32 / Chapter 3.1 --- Introduction --- p.32 / Chapter 3.2 --- Fabrication and characteristization of the sputtering targets --- p.32 / Chapter 3.3 --- Deposition procedure --- p.36 / Chapter 3.3.1 --- Preparation of substrate --- p.36 / Chapter 3.3.2 --- Deposition process --- p.36 / Chapter 3.4 --- Parameters related to epitaxial growth of LPSCMO thin films --- p.37 / Chapter 3.4.1 --- Substrate materials --- p.37 / Chapter 3.4.2 --- Substrate temperature --- p.38 / Chapter 3.4.3 --- Oxygen partial pressure --- p.38 / Chapter 4 --- Thickness and strain effects in epitaxial LPSCMO thin films --- p.43 / Chapter 4.1 --- Introduction --- p.43 / Chapter 4.2 --- Structural characterization of LPSCMO thin films --- p.45 / Chapter 4.2.1 --- Thickness effect --- p.45 / Chapter 4.2.2 --- Strain effect --- p.49 / Chapter 4.3 --- Transport properties and magnetoresistance measurement --- p.51 / Chapter 4.3.1 --- Thickness effect --- p.51 / Chapter 4.3.2 --- Strain effect --- p.60 / Chapter 4.4 --- Discussion --- p.63 / Chapter 5 --- Effect of spacer in [LPSCMO/SCuO] multilayer --- p.65 / Chapter 5.1 --- Sample preparation --- p.65 / Chapter 5.2 --- Characterization of as-deposited multilayer samples --- p.67 / Chapter 5.2.1 --- Structural anaylsis --- p.67 / Chapter 5.2.2 --- Resistance measurement --- p.72 / Chapter 5.3 --- Oxygen-annealing treatment --- p.76 / Chapter 5.3.1 --- Introduction --- p.76 / Chapter 5.3.2 --- Structural anaylsis --- p.77 / Chapter 5.3.3 --- Resistance measurement --- p.78 / Chapter 5.4 --- Discussion --- p.85 / Chapter 6 --- Conclusion --- p.87 / Chapter 6.1 --- Summary --- p.87 / Chapter 6.2 --- Future outlook --- p.88 / Bibliography --- p.89

Realizaram-se estudos potenciométricos, em combinação com medições espectrofotométricas, para caracterizar a espécie de íon manganês obtida a partir de oxidação coulométrica a corrente constante utilizando-se solução de Mn(II) (0,050 mol.L-1) em N3- (0,50 a 2,0 mol.L-1) e H+ (0,01 mol.L-1). Graficamente foi possível concluir que a espécie gerada é Mn(III) e obter os valores dos potenciais condicionais de redução, E0\'x, do par Mn(III)/Mn(II), em soluções tampão N3-/HN3, de concentração de N3- 0,50; 1,0; 1,5; 2,0 e 4,0 mol.L-1 e H+ 0,010 mol.L-1, sendo 0,468, 0,421, 0,396, 0,377 e 0,336 V (vs. ECS), respectivamente. Esses valores de E0\'x permitiram o cálculo das constantes de equilíbrio para os complexos no sistema Mn(III)/N3-, sendo: β1 = 1,23.105 M-1, β2 = 6,03.108 M-2, β3 = 2,37.1011 M-3, β4 = 1,54.1011 M-4 e β5 = 9,57.1011 M-5 (T = 25,0 ± 0,1 ºC, I = 2,0 mol.L-1 com NaClO4). Os valores calculados para as absortividades molares, em 430 nm, para as espécies [Mn(N3)3], [Mn(N3)4]- e [Mn(N3)5]2- foram 226, 3.680 e 6560 mol-1.L.cm-1, respectivamente. Para o estudo do cátion Co(II), foram efetuadas oxidações coulométricas da mesma forma e nas mesmas condições que para o cátion Mn(II). Os valores de E0\'x encontrados para o par Co(III)/Co(II) foram 0,400, 0,338, 0,302, 0,277 e 0,228 V (vs. ECS), para as concentrações de N3- 0,50; 1,0; 1,5; 2,0 e 4,0 mol.L-1 e H+ 0,010 mol.L-1. Com os valores de E0\'x obtidos para os pares Co(III)/Co(II) e Mn(III)/Mn(II), calcularam-se as constante de equilíbrio global, K, para a reação redox entre [Co(N3)n]3-n e [Mn(N3)n]2-n, encontrando-se os valores 7,1xl0-2, 4,0x10-2, 2,6x10-2, 2,0x10-2 e l,5x10-2, para os tampões acima descritos, respectivamente. Outros estudos revelaram a possível formação da espécies Mn(VI) quando KMnO4 e K2MnO4 são adicionados, separadamente, a uma solução tampão azoteto, por exemplo, N3- = 1,5 mol.L-1 e HN3 = 0,05 mol.L-1. / Spectrophotometric studies combined with coulometric generation of Mn(III), in presence of large excess of Mn(II), showed a maximum absorbance peak at 430 nm. The average molar absorptivity increases with azide concentration (0.44 to 3.9 mol.L-1) from 3,100 to 6,300 mol-1.L.cm-1, showing a stepwise complex formation. Potential measurements of the Mn(III)/Mn(II) system in several azide aqueous buffers solutions: 1.0x10-2 mol.L-1 HN3, (0.50 to 2.0 mol.L-1) N3- and 5.0x10-1 mol.L-1 Mn(II) and constant ionic strength 2.0 mol.L-1, kept with sodium perchlorate, leads to the conditional potential, E0\'x, in several azide concentrations at 25.0 ± 0.1 ºC (0.468, 0.421, 0.396, 0.377 e 0.336 V (vs. SCE) for the 0.50; 1.0; 1.5; 2.0 and 4.0 mol.L-1 N3- concentration, respectively). Considering the overall formation constants of Mn(II)/N3-, from former studies, and the potential, E0\'s = 1.063 V vs. SCE, for Mn(III)/Mn(II) system in non-complexing medium, it was possible to calculate the Fronaeus function, F0(L), and the following overall formation constants: β1 = 1.2x105 M-1, β2 = 6.0x108 M-2, β3 = (2.4±0.7)x1011 M-3, β4 = (1.5±0.5)x1011 M-4 and β5 = (9.6±.0.8)x1011 M-5 for the Mn(III)/N3- complexes. The molar absorptivity values, at 430 nm, found for the species [Mn(N3)3], [Mn(N3)4]- and [Mn(N3)5]2- were 226, 3,680 and 6,560 mol-1.L.cm-1, respectively. Similar studies with Co(II) in the same conditions, lead to the following conditional potentials, E0\'x, for the Co(III)/Co(II) system: 0.400, 0.338, 0.302, 0.277 e 0.228 V (vs. SCE). Using the E0\'x values obtained for both systems, Co(III)/Co(II) and Mn(III)/Mn(II), it was possible to calculate the equilibrium constant for the redox reaction between [Co(N3)n]3-n and [Mn(N3)n]2-n. The values found were 7.1xl0-2, 4.0x10-2, 2.6x10-2, 2.0x10-2 and 1.5x10-2, for 0.50; 1.0; 1.5; 2.0 and 4.0 mol.L-1 N3- concentration, respectively, in the same acidity (1.0x10-2 mol.L-1 HN3).

One of the largest environmental liabilities facing the Canadian and international mining industry includes the effects of acidic drainage to water resources. This thesis sought to determine biogeochemical mechanisms of rare earth element and yttrium (REY) enrichment in mine drainage, linkages between REYs and microbial populations, and whether REYs were present in water or biofilm at mineable quantities or toxic levels. Water and co-occurring biofilm samples were collected from North and South American mining and control sites, and a passive water treatment system in Pennsylvania. REY concentrations within mineralized biofilm were observed to occur at borderline mineable quantities within biofilm in coal mine drainage (1,000 mg/kg dry weight total REYs), where REYs were bound predominately to particulate organic matter, manganese and iron, limiting their bioavailability. Within the passive treatment system, REYs showed the greatest maximum water-biofilm partitioning coefficients after Al and Fe, and a strong inverse relationship with aqueous REY concentration. Photosynthetic eukaryotes were observed to occur within biofilms that contained an abundance of neutrophilic iron oxidizing bacteria.

Incorporation of magnetic microparticles (~ 1 um) at electrode structures increases electron transfer e¢ ciency, observed as increased current, for multiple electrochemical systems. Current increases occur with magnetic field. Inclusion of magnetic materials into the cathode matrix of alkaline MnO2 batteries requires the materials to be stable in the strong base electrolyte, typically 6 to 9 M KOH. Samarium cobalt magnetic particles sustain strong permanent magnetic fields and are stable in base without surface modification. Studies were undertaken at fast (C/2), moderate (C/3), and slow (C/5) constant current discharges. Here, alkaline MnO2 batteries generated increased power and energy when magnetic microparticles are incorporated into the cathode of the battery. Because of anode limitations in the battery, total coulombic output is not increased for the first electron discharge, but the available power and energy is significantly higher compared to nonmagnetic batteries at voltages above 0.9V. Constant current discharge curves of magnetic batteries demonstrate higher voltages than nonmagnetic batteries at a given time, which translates to greater power output. This effect is also observed by electrochemical impedance spectroscopy, where charge transfer resistance is less for magnetically modified cells. This work also developed voltammetric measurement protocols for acetone concentration collected in the liquid and vapor phase and measured in solution. Acetone on the breath is an indicator for physiological dysregulation. Measurements are demonstrated for acetone concentrations across the human physiological range, 1 uM to 10 mM at platinum electrodes in 0.5 M H2SO4. Effects arise through adsorption of acetone from the gas phase onto a platinum surface and hydrogen in acidic solution within the voltammetric butterfly region. The protocol is demonstrated to yield breath acetone concentration on a human subject within the physiological range and consistent with ketone urine test strip.

>Magister Scientiae - MSc / Lithium iron manganese phosphate (LiFe0.5Mn0.5PO4), is a promising, low cost and high energy density (700 Wh/kg) cathode material with high theoretical capacity and high operating voltage of 4.1 V vs. Li/Li+, which falls within the electrochemical stability window of conventional electrolyte solutions. However, a key problem prohibiting it from large scale commercialization is its severe capacity fading during cycling. The improvement of its electrochemical cycling stability is greatly attributed to the suppression of Jahn-Teller distortion at the surface of the LiFe0.5Mn0.5PO4 particles. Nanostructured materials offered advantages of a large surface to volume ratio, efficient electron conducting pathways and facile strain relaxation. The LiFe0.5Mn0.5PO4 nanoparticles were synthesized via a simple-facile microwave method followed by coating with multi-walled carbon nanotubes (MWCNTs) nanoparticles to enhance electrical and thermal conductivity. The pristine LiFe0.5Mn0.5PO4 and LiFe0.5Mn0.5PO4-MWCNTs composite were examined using a combination of spectroscopic and microscopic techniques along with electrochemical techniques such as cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Microscopic results revealed that the LiFe0.5Mn0.5PO4-MWCNTs composite contains well crystallized particles and regular morphological structures with narrow size distributions. The composite cathode exhibits better reversibility and kinetics than the pristine LiFe0.5Mn0.5PO4 due to the presence of the conductive additives in the LiFe0.5Mn0.5PO4-MWCNTs composite. For the composite cathode, D = 2.0 x 10-9 cm2/s while for pristine LiFe0.5Mn0.5PO4 D = 4.81 x 10-10 cm2/s. The charge capacity and the discharge capacity for LiFe0.5Mn0.5PO4-MWCNTs composite were 259.9 mAh/g and 177.6 mAh/g, respectively, at 0.01 V/s. The corresponding values for pristine LiFe0.5Mn0.5PO4 were 115 mAh/g and 44.75 mAh/g, respectively. This was corroborated by EIS measurements. LiFe0.5Mn0.5PO4-MWCNTs composite showed to have better conductivity which corresponded to faster electron transfer and therefore better electrochemical performance than pristine LiFe0.5Mn0.5PO4. The composite cathode material (LiFe0.5Mn0.5PO4-MWCNTs) with improved electronic conductivity holds great promise for enhancing electrochemical performances and the suppression of the reductive decomposition of the electrolyte solution on the LiFe0.5Mn0.5PO4 surface. This study proposes an easy to scale-up and cost-effective technique for producing novel high-performance nanostructured LiFe0.5Mn0.5PO4 nano-powder cathode material. / 2023-12-01

Orientador: Renato de Mello Prado / Banca: Anelisa de Aquino Vidal Lacerda Soares / Banca: Jairo Osvaldo Cazetta / Resumo: A pulverização foliar de manganês (Mn) é amplamente utilizada em cultivos anuais dada a deficiência do micronutriente no solo. A adição de silício (Si) na calda com o Mn poderia favorecer aspectos fisiológicos e nutricionais e a produção de plantas de milho e sorgo. Objetivou-se avaliar os efeitos do Mn e Si fornecidos via pulverização foliar na nutrição foliar de plantas de milho e de sorgo sob deficiência de Mn. Foram desenvolvidos dois experimentos, um com a cultura do milho (experimento milho) em casa de vegetação e outro com a cultura do sorgo granífero (experimento sorgo) em sala climatizada. O experimento milho foi composto de arranjo fatorial 4x2, sendo concentrações de Mn 0,0; 0,29; 0,58 e 0,87 g L-1na ausência e presença de Si (0,476 g L-1de Si) aplicados via foliar no estágio V4 e V6.O experimento sorgo foi realizado em arranjo fatorial 4x2 com concentrações de Mn 0,0; 0,17; 0,34 e 0,51 g L-1 na ausência e presença de Si (0,476 g L-1de Si) aplicados via foliar no estágio V4 e V6. Em ambos os experimentos avaliaram-se variáveis fisiológicas e de produção de massa seca para verificar efeito do Si e Mn na nutrição das plantas. A pulverização foliar de Mn com adição de Si na calda incrementou o acúmulo do micronutriente, o índice relativo de clorofila, a eficiência quântica do FSII, a eficiência do uso da água e refletiu na produção de massa seca das plantas de milho e sorgo. A pulverização foliar de Mn com adição de Si na calda é viável para as plantas de milho e de ... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Foliar spraying of manganese (Mn) is widely used in annual crops due to micronutrient deficiency in the soil. The addition of silicon (Si) in the application liquid with Mn could favor physiological and nutritional aspects and the production of maize and sorghum plants. The objective of this study was to evaluate the effects of Mn and Si supplied by foliar spraying on leaf nutrition of maize and sorghum plants under Mn deficiency. Two experiments were carried out, one with maize (corn experiment) in greenhouse and the other with sorghum (sorghum experiment) in climatized room. The corn experiment was composed of factorial arrangement 4x2, with concentrations of Mn 0,0; 0.29; 0.58 and 0.87 g L-1 in the absence and presence of Si (0.476 g L-1 of Si) applied via leaf in stage V4 and V6. The sorghum experiment was performed in a 4x2 factorial arrangement with concentrations of Mn 0,0; 0.17; 0.34 and 0.51 g L-1 in the absence and presence of Si (0.476 g L-1 of Si) applied via foliar in stage V4 and V6. In both experiments were evaluated the physiological and dry mass production variables to verify the effect of Si and Mn on plant nutrition. Foliar spraying of Mn with addition of Si in application liquid increased micronutrient accumulation, relative chlorophyll index, FSII quantum efficiency, water use efficiency, and reflected in the dry mass production of corn and sorghum plants. Foliar spraying of Mn with addition of Si in application liquid is viable for maize and sorghum ... (Complete abstract click electronic access below) / Mestre

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Includes bibliographies / 201 leaves : ill. (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Agronomy, 1987

<p>This thesis deals with the synthesis and characterisation of a series of dinuclear manganese complexes. Their ability to donate electrons to photo-generated ruthenium(III) has been investigated in flash photolysis experiments followed by EPR-spectroscopy. These experiment shows several consecutive one-electron transfer steps from the manganese moiety to ruthenium(III), that mimics the electron transfer from the oxygen evolving centre in photosystem II.</p><p>The redox properties of these complexes have been investigated with electro chemical methods and the structure of the complexes has been investigated with different X-ray techniques. Structural aspects and the effect of water on the redox properties have been shown.</p><p>One of the manganese complexes has been covalently linked in a triad donor-photosensitizer-acceptor (D–P–A) system. The kinetics of this triad has been investigated in detail after photo excitation with both optical and EPR spectroscopy. The formed charge separated state (D^––P–A⁺) showed an unusual long lifetime for triad based on ruthenium photosensitizers.</p><p>The thesis also includes a study of manganese-salen epoxidation reactions that we believe can give an insight in the oxygen transfer mechanism in the water oxidising complex in photosystem II.</p>