Dissertations / Theses on the topic 'Carbothermal solid state reduction'

The aim of the project was to establish rate and mechanisms of solid state reduction of manganese ores. The project studied carbothermal reduction of manganese oxide MnO, two Groote Eylandt (Australian) and Wessels (South African) manganese ores in hydrogen, helium and argon atmospheres at temperatures up to 1400C for MnO and 1200C for manganese ores. Experiments were conducted in the fixed bed reactor with on-line off-gas analysis. The major findings are as follows. ?? Rate and degree of reduction of MnO and ores increased with increasing temperature. ?? Reduction of MnO and manganese ores at temperatures up to 1200C was faster in helium than in argon, and much faster in hydrogen than in helium. The difference in MnO reduction in hydrogen and helium decreased with increasing temperature to 1400C. ?? Addition of up to 7 vol% of carbon monoxide to hydrogen had no effect on MnO reduction at 1200C. ?? In the process of carbothermal reduction of ores in hydrogen at 1200C, silica was reduced. ?? Reduction of both GE ores was slower than of Wessels ore. This was attributed to high content of iron oxide in the Wessels ore. ?? Carbon content in the graphite-ore mixture had a strong effect on phases formed in the process of reduction; thus, in the reduction of Wessels ore with 12-16 wt% C, a-Mn and Mn23C6 were formed; when carbon content was above 20 wt%, oxides were reduced to carbide (Mn,Fe)7C3. ?? Kinetic analysis showed that mass transfer of intermediate CO2 from oxide to graphite in carbothermal reduction in inert atmosphere was a contributing factor in the rate control. ?? High rate of reduction of manganese oxide in hydrogen was attributed to formation of methane which facilitated mass transfer of carbon from graphite to oxide. Hydrogen was also directly involved in reduction of manganese ore reducing iron oxides to metallic iron and higher manganese oxides to MnO. Reduction of Wessels and Groote Eyland Premium Fines ores in the solid state is feasible at temperatures up to 1200C; while temperature for solid state reduction of Groote Eyland Premium Sands is limited by 1100C.

An experimental and theoretical analysis has been carried out into normal force reduction in electronic contact springs. This is a phenomenon whereby the force produced by the contact spring reduces with time. A series of ten elevated temperature heat age tests were carried out for time periods of up to three months. Over 6,500 normal force reduction measurements have been made. Examination of the data revealed a high correlation for the normal force to exhibit a logarithmic relationship with time. Theoretical analysis showed that this could be explained by assuming that the phenomenon of normal force reduction is thermally activated with an activation energy that is variable and related to the amount of stored energy in the contact spring. A theoretical model for the process has been proposed, and the values of the parameters calculated for the ten temperatures for which data has been collected. This model can be used to predict end of life normal forces for electrical contacts, provided that the model parameters are determined experimentally at the required temperature. In addition, it is also possible to obtain confidence levels associated with these predictions.

ZnO nanowires are a promising material with great semiconductor properties. ZnO nanowires were prepared by carbothermal reduction and vapor-liquid-solid growth mechanism. Altering a variety of parameters ranging from mole to mole ratio of ZnO to C all the way to gas flow rate was examined. The nanowires were then characterized and their morphology examined under a SEM to observe what effect the parameter had on the morphology of the nanowires. From the experiments and the parameters tested it was observed that in order to produce the highest quality straight nanowires one should use a mole to mole ratio of ZnO to C graphite of 1 to 3. With a dwell temperature and time of 900 °C for 3 hours. A gold seed catalyst of 4nm and a gas flow rate of 50 to 100sccm of Ar provides the straightest nanowires. Understanding the effect of each parameter on the morphology of ZnO nanowires is vital for the current research. This will only lead to further the research and provide a better understanding of the growth mechanism of these wires and how the production of specific wires with certain morphologic features and characteristics can be achieved.

Solid state fermentation of canola meal has been carried out for the reduction of its phytic acid content. Several microorganisms were surveyed for this purpose. The phytic acid content of canola meal was reduced by 26%, 60% and 66% using Saccharomyces cerevisiae, Rhizopus oligosporus NRRL 2990 and Aspergillus niger NRC 401121 respectively after 120 hours of fermentation. Aspergillus ficuum NRRL 3135 was found to be the best for the reduction of phytic acid content. For this reason, this microorganism was studied more extensively. In the study of the phytase (EC 3.1.3.8) from Aspergillus ficuum NRRL 3135, it was found that the production of the enzyme in a submerged batch process was inhibited by high concentrations of glucose. The inhibition was overcome by applying a fed batch technique in the production of the enzyme. Tests carried out at different oxygen concentrations revealed that aeration had a beneficial effect on the production of the enzyme. (Abstract shortened by UMI.)

This investigation is based on the topotactic reduction reactions of 3 sets of phases: La₁_-ₓSrₓMnO₃ (0.6 ≤ x ≤ 1), La₁_-ₓCaₓMnO₃ (0.6 ≤ x ≤ 1) and Sr₃Fe₂_-ₓCoₓO₅Cl₂ (0 ≤ x ≤ 1). The topotactic reduction reactions of La₁_-ₓSrₓMnO₃ (0.6 ≤ x ≤ 1) perovskite phases using NaH as a solid state reducing agent result in the formation of reduced phases which contain manganese centres with a constant average oxidation state of +2.5, thus leading to an empirical composition of La₁_-ₓSrₓMnO₃_-(0.5+x)/2. The structures of the reduced phases contain a 6-layer OOTOOT’ stacking sequence of the octahedral (O) and tetrahedral (T) sheets and so are closely related to the 4-layer OTOT’-stacked brownmillerite structure. Close inspection reveals that the structures of the La₁_-ₓSrₓMnO₃_-y (x = 0.67, 0.7 and 0.75) reduced phases contain an intralayer ordered arrangement of twisted tetrahedral chains, and are the first instances of refined 6-layer structures containing such an arrangement. The driving force dictating the arrangement of the twisted tetrahedral chains in these 6-layer structures are shown to be the size of the tetrahedral chain dipole moment and the coupling between neighbouring tetrahedral layers in a similar manner to the brownmillerite structure. This logic has been applied to rationalise the ordering arrangement of the twisted tetrahedral chains in other structures containing tetrahedral layers. Variable temperature neutron diffraction data reveal that the La₁_-ₓSrₓMnO₃_-y (0.67 ≤ x ≤ 0.83) reduced phases adopt magnetically ordered structures incommensurate with the nuclear structures below T_N. In contrast, the structures adopted by reduced phases formed by topotactic reduction reactions of La₁_-ₓCaₓMnO₃ (0.6 ≤ x ≤ 1) perovskite phases using NaH are split into 2 groups as a function of the La:Ca ratio: The reduction of perovskite phases in the range (0.6 ≤ x ≤ 0.8) result in the formation of reduced phases with an empirical composition of La₁_-ₓCaₓMnO₂ which adopt structures containing a disordered arrangement of layers of edge-sharing MnO₆ octahedra and layers of vertex-sharing MnO₄ tetrahedra. In contrast, reduction of the perovskite phases in the range (0.9 ≤ x ≤ 1) result in the formation of reduced phases with an empirical composition of (La₁_-ₓCₓx)_0.5MnO which adopt the rock salt structure with a disordered arrangement of the cations. The (x < 1) reduced phases are the first reported examples of extended oxides which contain manganese centres with an average oxidation state of below 2. Variable temperature neutron diffraction data reveal that the La₁_-ₓCaₓMnO₃_-y (x= 0.6, 0.67 and 0.7) reduced phases adopt G-type antiferromagnetically ordered magnetic structures below approximately T_N ~ 220 K. The structure of Sr₃Fe₂O₅Cl₂ is closely related to that of the A₃B₂O₇ n = 2 Ruddlesden-Popper structure. The topotactic reduction reaction of Sr₃Fe₂O₅Cl₂ with LiH results in the formation of the Fe(II) phase Sr₃Fe₂O₄Cl₂. Neutron powder diffraction data show that Sr₃Fe₂O₄Cl₂ adopts a body-centred tetragonal crystal structure with anion vacancies located within the central SrO layer of the phase. The structure of Sr₃Fe₂O₄Cl₂ is therefore a rare example of a structure consisting of infinite sheets of corner-sharing Fe(II)O₄ square planes. In addition, the effect of cobalt-doping on the magnetic properties of the isostructural Sr₃Fe₂_-ₓCoₓO₄Cl₂ (0 ≤ x ≤ 1) series of reduced phases was investigated. Cobalt-doping was found to frustrate the antiferromagnetic order initially leading to a decrease in the magnetic ordering temperature but ultimately leading to spin glass behaviour.

Part I. Reduction of the 1-methylpentacyclo [5.4.0.0²,⁶.0³,¹⁰,0⁵,⁹]undecane-8, 11-dione (9) with solid NaBH₄ resulted in highly stereoselective reduction of both C=O groups in the substrate, thereby affording the corresponding endo-8, endo-11-diol (11a). The configuration of 11a was established unequivocally by converting 11a into the corresponding cyclic thiocarbonate ester, 12. Part II. Z-1,2-Di(1'-adamantyl)ethene (14) was synthesized with a high degree of stereoselectively in four steps (Scheme 9 in Chapter 2). E-1,2-di(1'-adamantyl)ethene (15) was synthesized by iodine promoted isomerization of 14. Both structures were established unequivocally via single-crystal X-ray structural analysis. E-1-(exo-8'-Pentacyclo[5.4.0.0²,⁶.0³,¹⁰,0⁵,⁹]undecyl)-2-phenylethylene (16a) was synthesized, and its structure was established via analysis of its 1H, 13C, and 2D COSY NMR spectra. Part III. Reactions of electrophiles, i.e.,:CCl_2, PhSCl, and Br_2, to Z- and E-1,2-di(1'-adamantyl)ethenes (14 and 15, respectively) are described (Scheme 5, 8, 10, and 13 in Chapter 3). Structures of the corresponding products were established unequivocally via analysis of their respective one- and two-dimensional NMR spectra and/or single-crystal X-ray structural analysis. Part IV. An improved asymmetric synthesis of optically active (S)-4-hydroxy-2-cyclohexenone 1 (64%ee, determined via Mosher's method) has been developed (Scheme 5 in Chapter 4). The key step in this synthesis involves the baker's yeast reduction of 13. The absolute configuration of the major product, (S)-1, was established unequivocally via single-crystal X-ray structural analysis of a precursor. The optical purity of the major product 14a (80%de, 67%ee) was established via careful integration of relevant gated-decoupled 13C NMR spectra.

A static state technique for fermentation was applied using Aspergillus ficuum NRRL 3135 on canola meal for the production of phytase and for the reduction of the phytic acid content in the meal. Aspergillus ficuum was chosen as a result of its high phytase producing capacity. In the study of the effects of physical and nutritional factors on the enzyme production and the phytic acid content reduction, it was found that moisture content was a critical factor and 64% water in the medium was found to be the optimum moisture content for both enzyme production and phytic acid content reduction. Increasing time of homogenization of inoculum up to 240 seconds improved enzyme production and phytic acid reduction. Increase in both inoculum concentration (biomass) and inoculum age up to 7-days old increased enzyme production and rate of phytic acid content reduction. With increase in initial pH of medium of up to 5.7, increased enzyme production and rate of phytic acid reduction were achieved. In the addition of surfactants to medium, sodium oleate was found to significantly increase enzyme production and the rate of phytic acid content reduction while Triton X-100 gave a negative effect. The addition of 1 mg phosphate remarkably increased the enzyme production and phytic acid content reduction; though a negative effect was obtained for systems containing combined portions of oleate and phosphate. Biomass in the solid culture was found to increase during fermentation up to 144 h of incubation and the protein content of culture also increased to about 18% after 96 h of incubation; hence this method of fermentation could be used to improve the nutritional quality of the meal for animal feed.

Over the past decade, solid-state nanopores have emerged as a versatile tool for the detection and characterization of single molecules, showing great promise in the field of personalized medicine as diagnostic and genotyping platforms. While solid-state nanopores offer increased durability and functionality over a wider range of experimental conditions compared to their biological counterparts, reliable fabrication of low-noise solid-state nanopores remains a challenge. In this thesis, a methodology for treating nanopores using high electric fields in an automated fashion by applying short (0.1-2 s) pulses of 6-10 V is presented which drastically improves the yield of nanopores that can be used for molecular recognition studies. In particular, this technique allows for sub-nanometer control over nanopore size under experimental conditions, facilitates complete wetting of nanopores, reduces noise by up to three orders of magnitude and rejuvenates used pores for further experimentation. This improvement in fabrication yield (over 90%) ultimately makes nanopore-based sensing more efficient, cost-effective and accessible. Tuning size using high electric fields facilitates nanopore fabrication and improves functionality for single-molecule experiments. Here, the use of nanopores for the detection of DNA-protein complexes is examined. As proof-of-concept, neutravidin bound to double-stranded DNA is used as a model complex. The creation of the DNA-neutravidin complex using polymerase chain reaction with biotinylated primers and subsequent purification and multiplex creation is discussed. Finally, an outlook for extending this scheme for the identification of proteins in a sample based on translocation signatures is presented which could be implemented in a portable lab-on-a-chip device for the rapid detection of disease biomarkers.

Main purpose of this study was to find the optimum conditions to produce a charge material for ferromanganese production or steelmaking with high content of iron and manganese carbides from Denizli-Tavas manganese ore by carbothermic reduction and investigate the effects of temperature, time, amount of active carbon addition and CaO addition on this reduction. The ore was calcined and then mixed with active carbon and CaO. Experiments were performed in a horizontal tube furnace that can be heated up to 1700 º
C with MoSi2 heating elements. After each experiment weight loss data were obtained and converted to percentage reduction. X-Ray, SEM-EDS and chemical analyses were done in order to determine whether or not carbide phases have been obtained, and calculate the composition of the product. Considering the experimental results, the optimum conditions found for reduction of Denizli-Tavas manganese ore were 1250 °
C, 4 hours, 100% of stoichiometric amount of active carbon and 5% CaO addition. Under the optimum conditions 83.85% reduction of calcined ore was obtained.

Solid state fermentation (SSF) with canola meal as substrate was carried out to study the production of phytase and the reduction of the phytic acid content in the meal using Aspergillus carbonarius NRC 401124. Some characteristics of the phytase were studied. $K\sb{\rm m}$ and $\nu\sb{max}$ values of 0.345 mM and 0.8071 units were determined when sodium phytate was used as the substrate for this enzyme. The enzyme showed an optimum pH and temperature of 4.7 and 53$\sp\circ$C respectively. It was found that the production of phytase was growth associated and that the maximum activity was attained after 72 h of incubation during SSF process. Apparent increases of about 25% and 10% of protein content of canola meal were noticed after 48 h and 72 h of the process respectively. A 25% reduction in the total carbohydrate concentration was reached at the end of fermentation. The rate of the reduction of phytic acid content of the meal depended on the physical parameters of the SSF. The optimum particle size of the meal for this process was found to be 1.4 mm, and negative results are noticed with particle sizes higher than 1.4 mm. It was found that the increase in glucose amount up to and including 6 g per system in the initial medium resulted in an increase in the rate of the biomass growth, enzyme concentration and the rate of phytic acid content reduction in canola meal. The addition of 1 mg of phosphate per system remarkably increased the biomass and enzyme productions and phytic acid content reduction. Sodium oleate increased the biomass and enzyme productions and the rate of phytic acid content reduction, while Triton X-100 gave a negative effect. (Abstract shortened by UMI.)

ITC/USA 2005 Conference Proceedings / The Forty-First Annual International Telemetering Conference and Technical Exhibition / October 24-27, 2005 / Riviera Hotel & Convention Center, Las Vegas, Nevada
Solid State On-Board Recording is becoming a revolutionary way of recording airborne telemetry data and IRIG 106 Chapter 10 “Solid State On-Board Recorder Standard” provides interface documentation for solid state digital data acquisition. The Reduction and Analysis Program for Telemetry Recordings (RAPTR) is a standardized and extensible software application developed by the 96th Communications Group, Test and Analysis Division, at Eglin AFB, and provides a data reduction capability for disk files in Chapter 10 format. This paper provides the system description and software architecture of RAPTR and presents the 96th Communication Group’s total solution for Chapter 10 telemetry data reduction.

Les lasers à état solide bi-fréquences constituent des sources de choix pour de nombreux domaines (métrologie, photonique micro-onde, Lidar-Radar, horloges atomiques). Cependant, de tels lasers souffrent d'excès de bruit d'intensité difficiles à supprimer avec les méthodes habituelles. Dans ce contexte, nous développons une nouvelle approche baptisée « buffer reservoir » pour la réduction de l'excès de bruit d'intensité des lasers à état solide. Cette méthode repose sur le changement du comportement dynamique du laser par insertion d'un mécanisme d'absorption non-linéaire faiblement efficace dans la cavité. Tout d'abord, nous étudions cette approche dans des lasers solides mono-fréquence en exploitant deux types d'absorption non-linéaire : l'absorption à deux photons (TPA) et l'absorption par génération de seconde harmonique (SHGA). Nous montrons qu'il est possible de réduire de 50 dB le bruit d'intensité à la fréquence des oscillations de relaxation d'un laser Er,Yb:verre sans en dégrader la puissance de sortie ni le bruit de phase. Nous explorons les mécanismes physiques sous-jacents en développant un modèle analytique décrivant le comportement dynamique du laser. L'effet de l'absorbant non-linéaire sur les pics de bruit à haute fréquence à l'intervalle spectrale libre de la cavité est également étudié. Nous démontrons l'intérêt de telles sources lasers auto-régulées en intensité pour la distribution d'oscillateurs locaux sur porteuse optique. Nous mettons ensuite en application l'approche « buffer reservoir » dans des lasers bi fréquences. En développant un modèle analytique prédictif, nous montrons expérimentalement que l'utilisation de TPA engendre, sous certaines conditions, une réduction de 40 dB de l'amplitude des pics de bruit en-phase et en anti-phase. Nous vérifions en outre les propriétés de couplage des modes dans le milieu actif lorsque les pertes non-linéaires sont présentes. Enfin, nous abordons l'utilisation de SHGA comme ''buffer reservoir'' dans les lasers bi-fréquences. Plus particulièrement, nous explorons expérimentalement et théoriquement le comportement du laser lorsque les pertes non-linéaires ne sont introduites que sur un seul mode propre du laser. Dans cette configuration, nous montrons qu'il est possible d'obtenir pour les deux modes à la fois une forte diminution des pics de bruit d'intensité résonants
Dual-frequency solid-state lasers are attractive for numerous domains (metrology, microwave photonics, Lidar-Radar, optical clocks). However, such lasers suffer from excess intensity noise which is difficult to cancel with usual methods. In this context, we develop a new approach called “buffer reservoir” for reducing the excess intensity noise. This method relies on the change of the laser’s dynamical behavior by inserting a low efficient nonlinear absorption mechanism in the cavity. First, this approach is studied on single frequency solid-state lasers by using two types of non-linear absorption: two-photon absorption (TPA) and second harmonic generation absorption (SHGA). We show a possible reduction of the intensity noise at the relaxation oscillations frequency of an Er,Yb:glass laser up to 50 dB without degrading neither its power nor its phase noise. We explore the underlying physics by developing an analytical model describing the laser dynamical behavior. The effect of the nonlinear absorber on the noise peaks lying at high frequency at the free spectral range of the cavity is also studied. We demonstrate the relevance of such self-regulated lasers for the distribution of optically carried local oscillators. We then extend the “buffer reservoir” approach to dual-frequency lasers. By developing a predictive analytical model, we show experimentally that the use of TPA enables 40 dB reduction of both in-phase and anti-phase noise under certain conditions. The mode coupling in the active medium is analyzed when the nonlinear losses are present. Finally, we address the use of SHGA as a ''buffer reservoir'' in dual-frequency lasers. In particular, we experimentally and theoretically explore the laser behavior when the nonlinear losses are inserted on one eigen-mode of the laser only. This configuration enables a strong reduction of resonant noise peaks for both modes

High carbon ferrochromium serves as the main chromium source for almost all chromium containing steel alloys. The traditional method for the production of high carbon ferrochromium via the reduction of chromite using coke in electric arc furnaces, draws its considerable energy requirement from electrical power. The escalation in cost of electric power in South Africa has motivated research into alternative, fuel fired, reduction processes. One such process involves the partial solid state reduction of chromite in coal fired rotary kilns at temperatures between 1200 and 140rrc, prior to electric smelting. such processes are currently operated on a commercial scale and result in considerable savings in electrical energy, despite slow reduction kinetics and low reaction extents. A large amount of research conducted in the past, . aimed at establishing the fundamentals of the reduction process, has not provided satisfactory answers to questions regarding the mechanism of reduction. It was therefore necessary to conduct further test work on the process to establish the mechanism and factors limiting the rate and extent of reduction. Thermodynamic analysis of the reaction system indicates that at temperatures above 1050C reduction of the ore will proceed, and should reach an extent of approximately 90% reduction at 1200C. Complete reduction should be achievable at approximately 125ifc. However experimental results indicate the persistence of a stable magnesiochromite spinel under normal reducing conditions even at 140ifc. This limits the degree of chromium reduction to approximately 65%. Kinetic data from thermobalance studies and electron microscope examination of the reduction product showed independent reduction of iron and chromium. The rate of iron reduction was found to be relatively rapid and to go to completion, compared to that of chromium where the formation of a relatively inert picrochromite- spinel solid solution (MgO(Cr,AI)203) at the surface of the grain liinited the rate and extent of reduction to approximately 65% in the case of LG6 chromite. These findings suggested that the only way in which the kinetics of the process might be improved was through the addition of a component capable of disrupting the spinel layer at the surface of the chromite grain. In this study, fluoride containing mixtures such as CaF2 - NaF and fluorspar- feldspar- silica were successfully used to accelerate the reaction. Such mixtures are commercially interesting and highly effective even at low additions (4- 10%) . The mechanism whereby such mixtures operate was shown to involve the dissolution of all the spinel components in the liquid flux phase. Following dissolution, rapid i i recrystallization of spinel (Mg . Al2 ~) occurs , simultaneous to the transport of Fe 2+ and cr 3+ ions through the liquid to a site where reduction can take place. The main effect of this is to increase the rate and extent of chromium reduction to the point where virtual total reduction can be achieved in less than 90 min at temperatures as low as 1200C. Although the reduction kinetics in the presence of such solvent flux phases are still largely limited by the rate of solid state diffusion, the disruption of the surface enables faster overall diffusion rates to be achieved. Ultimately as the particle size and separation between oxide and reductant is increased, the rate of dissolution and transport through the flux phase become rate limiting.
Thesis (Ph.D.)-University of Natal, Durban, 1989.

碩士
元培醫事科技大學
醫學影像暨放射技術系碩士班
107
Purposes: With the use of clinical interventional angiography and transcatheter arterial embolization (T.A.E) .Patients receiving interventional special photographic examinations have radiation exposure, and skin dose is a topic worth exploring. In this study, a tissue equivalent (Bolus) was used between the sources, and the dose of the incident skin measured using a solid-state illuminating dose and the image quality was evaluated using the prosthesis. Materials and Methods: In this study, a solid-state dosimeter was used as a measuring tool for digital fluoroscopy photographic skin dose. The Siemens Artis Z Biplane System was used to set the inspection time used for routine examinations. The dose and irradiation time were measured under different tissue thicknesses of the tissue filler for statistical and data analysis, and the image quality after tissue equivalents was measured using a nuclear associates test Patterns 07-501 prosthesis. Result: According to the data obtained, it was found that when the dose measurement was performed using the thickness of the tissue filler, it was found that the surface dose decreased more as the thickness of the tissue equivalent increased in the same output dose, the tissue equivalent thickness was used from 0.5 cm to 3.5 cm, and the surface percent dose was significantly reduced from 100% to 91.1%, a total decrease of 8.9%. In terms of image quality, when measuring the image resolution, it is found that the thickness of the tissue equivalent of 3 cm or more is used, and the interpretation of the line pair in the spatial resolution is decrease, and the resolution line is less than 2 lp/mm and the image noise is obviously increase. Conclusion: The use of appropriate thickness of tissue equivalents, is expected to effectively reduce the skin dose to reduce the damage caused by radiation, the system can be applied to other interventional surgery in the future, in clinical research significance. Keywords: Angiography、Skin dose、Image quality、Bolus、Solid state dosimeter

碩士
國立清華大學
動力機械工程學系
101
In low temperature fuel cells, the cathodic reaction, oxygen reduction reaction (ORR), is the main rate-limited step. Normally, the kinetics of oxygen reduction reaction is very slow. For the purpose of speeding up the reaction to reach a practical usable level in a low temperature fuel cell, cathode catalysts are needed to be further investigated. Pt-based materials are the most practical catalysts currently. Because these Pt-based catalysts are too expensive for making commercially viable low temperature fuel cells, extensive research over the past several decades has focused on developing alternative catalysts. This thesis focuses on the reaction processes, and points out the key of improving efficiency. Some steps which influence the efficiency of low temperature fuel cells includes; oxygen adsorption, oxygen dissociation, protonation, charge transfer, and water desorption among others. we use the method of density functional theory (DFT) to build the nano structures including graphene, single walled and multi-walled carbon nanotube. In addition, We apply adsorption and doping methods to add the cathodic catalysts, Platinum and Nitrogen atoms into the nano structures. Then, we try to use the CASTEP platform to optimize the molecular structures during the oxygen reduction reaction process and analyze about the catalytic properties such as adsorption energy, work function, reorganization energy and rate of electron transfer. In conclusion, we obtain the improvement of catalyst in most of the selected nano structures and cathodic catalysts .

Over the last decade progress towards step-wise structural transformations in solid state chemistry has been made using metal hydride reductants. Alkali and alkali-earth metal hydrides can effectively reduce transition metal oxides resulting frequently in novel oxygen defect structures. This provides access to control over cation oxidation states and magnetic exchange pathways, and thus electronic and magnetic properties. The goal for this research was to investigate a representative system that could be used both for exploration of novel oxygen defect phases and for investigating the fundamental parameters governing successful solid state reductions. The systems chosen for investigation were Sr2-xCaxMnO4 (0