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Annie, Lundberg. "Environmental transformations of Manganese and Manganese oxide nanoparticles." Thesis, KTH, Materialvetenskap, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-289637.
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Engineered nanoparticles (NPs) are produced in increased quantities. Due to this increase, itis vital to understand the full lifecycle and fate of these NPs to prevent any possible environmental stress. As a result of their size, NPs may interact differently with their environment compared to bulk materials with the same composition, this both gives NPs their usage as well as risks. The risks often include unwanted interaction with biological systems which may lead to generation of toxicity. This study focused on environmental transformations of manganese and manganese oxide (Mn3O4) NPs. Applications these nanoparticles are often in battery technology and catalysis. A solution intended to mimic the composition of freshwater was used as the environmental media to study these transformations. Exposure of NPs was performed both with and without added natural organic matter (NOM). Several experiments were preformed such as Atomic absorption spectroscopy (AAS) for dissolution of the NPs, Nanoparticle Tracking Analysis (NTA) for particle size, and Attenuated total reflection Fourier transform infrared spectroscopy (ATR- FTIR) for adsorption studies. The production of reactive oxygen species (ROS) was also investigated, and simulations of metal speciation using Visual MINTEQ were also performed. The results from NTA and AAS (for Mn3O4) were not very reliable due to inconsistencies in the results which were probably caused by problems with preparation. However, for both, the results point towards that the dissolution rates of the particles are slightly slowed down when NOM is added. From ATR-FTIR and the simulations it was confirmed that NOM, carbonate, and sulfur will adsorb onto both particles, possibly in multiple layers. As for increased ROS development, no evidence of such an increase was found. However, the method used does not test for increased hydrogen peroxide development so this would in interesting test as well. Other studies which also would contribute to a more nuanced picture of this system is studies regarding zeta potential and studies which furtherinvestigates the type of adsorption mechanism which occurs at the particles surface.Industriella nanopartiklar används i allt större utsträckning. Därför är det av stor vikt attundersöka hela livscykeln som dessa produkter går igenom for att säkerhetsställa att de inte utgör någon fara för miljön och ekosystemen som de kan komma att hamna i. Som ett resultat av deras storlek interagerar nanopartiklar annorlunda med sin omgivning om man jämför med bulkmaterial av samma sammansättning, detta nanopartiklar både sina unika fördelar och risker. Riskerna innefattar ofta oönskade interaktioner med biologiska kretslopp som kan resultera i toxicitet. I den här rapporten läggs fokus på just denna typ av kemiska omvandlingar som nanopartiklar av mangan och manganoxid kan tänkas genomgå i det naturliga kretsloppet. Applikationer man ofta ser dessa partiklar i är batteriteknologi och katalys. De medium som används för att studera omvandlingarna är en lösning som efterliknar ytvatten från en klar sjö. Exponeringar gjordes både med denna lösning så som den är och med tillsatt naturligt organiskt material, NOM.En rad olika experiment gjordes så som analyser med AAS för att undersöka partiklarnas upplösning, NTA för partikelstorlekar och ATR-FTIR som undersökte adsorption på partiklarna. Även en studie med en DCFH metod där ökat ROS aktivitet undersöktes och en rad med SHM simuleringar gjorda i Visual MINTEQ utfördes. Resultaten från NTA och AAS analysen visade sig inte vara särskilt tillförlitliga på grund av tvetydliga resultat som troligen orsakats av problem med provpreparationen. Men resultaten från båda dessa pekar mot att upplösningshastigheten blir något hämmad då man tillsätter naturligt organiskt material, för båda partiklarna. Från ART-FTIR och simuleringarna kunde de säkerhetsställas att adsorption av NOM, karbonat och svavel sker på båda partiklarna, möjligen i fler än ett lager. När det kommer till ROS studien kunde inga bevis på ökad ROS aktivitet hittas med den använda metoden. Dock så kunde inte ökat väteperoxid aktivitet mätas med den metod som användes så detta hade varit av intresse att testa i framtiden. Andra studier som också skulle vara hjälpsamma för att ge en mer nyanserad bild av detta system är en studie om partiklarnas zeta potential och merundersökningar om vilken typ av adsorptions mekanism som sker vid partiklarnas yta.
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Chandrakumar, Thambirajah. "The high resolution spectroscopy of manganese oxide." Thesis, University of British Columbia, 1989. http://hdl.handle.net/2429/27405.
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This thesis reports studies of the electronic spectrum of gaseous MnO. The (0,0) band of the A⁶Σ +-X⁶ Σ+ electronic transition of MnO was recorded by intermodulated laser-induced fluorescence over the range 17770 - 17970 cm⁻¹. The hyperfine structure caused by the ⁵⁵Mn nucleus (I = 5/2) is almost completely resolved. Internal hyperfine perturbations between the F₃ and F₄electron spin components (where N = J - 1/2 and N = J + 1/2, respectively) occur in the ground state of MnO. These are caused by hyperfine matrix elements of the type ΔN = ΔF = 0.ΔJ = ± 1. Extra lines obeying the selection rules ΔJ = 0, ± 2 are also induced. Therefore, [sup P]Q₃₄, [sup R]Q₄₃, [sup P]Q₄₃ and [sup R]S₃₄ branches appear in the spectrum although they are not allowed in parallel transitions.
The reason for the great complexity of the spectra is the occurrence of a large avoided crossing near N = 26 in the A⁶Σ + v = 0 level by another electronic state, B⁶Σ +, with the same multiplicity and symmetry. The perturbation between the A⁶Σ + and B⁶Σ + states arises from electrostatic interaction. The selection rules for electrostatic perturbations are ΔJ = ΔS = Δ∧ = ΔΩ = 0. The perturbing state B⁶Σ + state has a considerably longer bond length so that it must come from a "charge transfer transition", possibly by electron transfer either from the 3π to the 4π orbital or from 8σ to 10σ. However, the A⁶Σ + state has only a small bond length change compared to the ground state so that it comes from a "Valence state transition". The Fermi contact constant b was found to be negative for the A⁶Σ + state and this confirms the electronic configuration as being (8σ² 3 π⁴) 1δ² 4 π ² 10σ¹.
The ground state is free of perturbations, except for the internal hyperfine perturbations, and is in nearly pure case (b) coupling. Various satellite branches which were observed in the B-X transition confirm the case (a) nature of the B⁶Σ + state at low N. The spacing between the main branches and the satellite branches gives values for the spin-spin parameter λ and the spin-rotation parameter γ of the ground state.Science, Faculty of
Chemistry, Department of
Graduate
3
Eames, Douglas J. "Direct causticizing of sodium carbonate with manganese oxide." Diss., Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/7026.
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Chan, Yiu-ming. "The chemistry and in vitro cytotoxicity study of manganese oxide nanostructures." Click to view the E-thesis via HKUTO, 2007. http://sunzi.lib.hku.hk/HKUTO/record/B39557121.
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Taujale, Saru. "INTERACTIONS BETWEEN METAL OXIDES AND/OR NATURAL ORGANIC MATTER AND THEIR INFLUENCE ON THE OXIDATIVE REACTIVITY OF MANGANESE DIOXIDE." Diss., Temple University Libraries, 2015. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/347169.
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Civil EngineeringPh.D.
Mn oxides have high redox potentials and are known to be very reactive, rendering many contaminants susceptible to degradation via oxidation. Although Mn oxides typically occur as mixtures with other metal oxides (e.g., Fe, Al, and Si oxides) and natural organic matter (NOM) in soils and aquatic environments, most studies to date have studied the reactivity of Mn oxides as a single oxide system. This study, for the first time, examined the effect of representative metal oxides (Al2O3, SiO2, TiO2, and Fe oxides) and NOM or NOM-model compounds (Aldrich humic acid (AHA), Leonardite humic acid (LHA), pyromellitic acid (PA) and alginate) on the oxidative reactivity of MnO2, as quantified by the oxidation kinetics of triclosan (a widely used phenolic antibacterial agent) as a probe compound. The study also examined the effect of soluble metal ions released from the oxide surfaces on MnO2 reactivity. In binary oxide mixtures, Al2O3 decreased the reactivity of MnO2 as a result of both heteroaggregation and complexation of soluble Al ions with MnO2. At pH 5, the surface charge of MnO2 is negative while that of Al2O3 is positive resulting in intensive heteroaggregation between the two oxides. Up to 3.15 mM of soluble Al ions were detected in the supernatant of 10 g/L of Al2O3 at pH 5.0 whereas the soluble Al concentration was 0.76 mM in the mixed Al2O3 + MnO2 system at the same pH. The lower amount of soluble Al in the latter system is the result of Al ion adsorption by MnO2. The experiments with the addition of 0.001 to 0.1 mM Al3+ to MnO2 suspension indicated the triclosan oxidation rate constant decreased from 0.24 to 0.03 h-1 due to surface complexation. Fe oxides which are also negatively charged at pH 5 inhibited the reactivity of MnO2 through heteroaggregation. The concentration of soluble Fe(III) ions ( 4 mg-TOC/L or [alginate/PA] > 10 mg/L, a lower extent of heteroaggregation was also observed due to the negatively charged surfaces for all oxides. Similar effects on aggregation and MnO2 reactivity as discussed above were observed for ternary MnO2‒Al2O3‒NOM systems. HAs, particularly at high concentrations (2.0 to 12.5 mg-C/L), alleviated the effect of soluble Al ions on MnO2 reactivity as a result of the formation of soluble Al-HA complexes. Alginate and PA, however, did not form soluble complexes with Al ions so they did not affect the effect of Al ions on MnO2 reactivity. Despite the above observations, the amount of Al ions dissolved in MnO2+Al2O3+NOM mixtures was too low, as a result of NOMs adsorption on the surface to passivate oxide dissolution, to have a major impact on MnO2 reactivity. In conclusion, this study provided, for the first time, a systematical understanding of the redox activity of MnO2 in complex model systems. With this new knowledge, the gap between single oxide systems and complex environmental systems is much narrower so that it is possible to have a more accurate prediction of the fate of contaminants in the environment.
Temple University--Theses
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Williams, Anthony James. "Synthesis and neutron diffraction studies of manganese oxide perovskites." Thesis, University of Cambridge, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.615786.
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Rodríguez-Martínez, Lide Mercedes. "The effects of cation disorder in manganese oxide perovskites." Thesis, University of Cambridge, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.624354.
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Reed, Corey William. "VOC Catalytic Oxidation on Manganese Oxide Catalysts Using Ozone." Diss., Virginia Tech, 2005. http://hdl.handle.net/10919/28000.
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This dissertation describes the current and common problem of removing low concentrations of pollutants known as volatile organic compounds (VOCs) from large volume gas emissions. Silica-supported manganese oxide catalysts with loadings of 3, 10, 15, and 20 wt. % (as MnO2) were characterized using x-ray absorption spectroscopy and x-ray diffraction (XRD). The edge positions in the x-ray absorption spectra indicated that the oxidation state for the manganese decreased with increasing metal oxide loading from a value close to that of Mn2O3 (+3) to a value approximating that of Mn3O4 (+2⅔). The XRD was consistent with these results as the diffractograms for the supported catalysts of higher manganese oxide loading matched those of a Mn3O4 reference. The reactivity of the silica-supported manganese oxide catalysts in acetone oxidation using ozone as an oxidant was studied over the temperature range of 300 to 600 K. Both oxygen and ozone produced mainly CO2 as the product of oxidation, but in the case of ozone the reaction temperature and activation energy were significantly reduced. The effect of metal oxide loading was investigated, and the activity for acetone oxidation was greater for a 10 wt. % MnOx/SiO2 catalyst sample compared to a 3 wt. % MnOx/SiO2 sample. A detailed mechanistic study of acetone oxidation using ozone was performed on a 10 wt. % silica-supported manganese oxide catalyst utilizing Raman spectroscopy, temperature programmed desorption (TPD), and kinetic measurements. In situ Raman spectroscopy at reaction conditions identified a band at 2930 cm-1 due to an adsorbed acetone species on the silica support and a band at 890 cm-1 due to an adsorbed peroxide species on the manganese oxide. A steady-state kinetic analysis, which varied acetone partial pressure (101 â 405 Pa), ozone partial pressure (101 â 1013 Pa), and temperature (318, 333, 343, and 373 K), was used to determine reaction rate expressions, while a transient kinetic study (318 K) was used to determine the role of the adsorbed species in the reaction mechanism. It was found that the rates of the acetone and ozone reactions were equally well described by both a power rate law and a Langmuir-Hinshelwood expression. The transient experiments showed that the rates of formation and reaction of the observed peroxide surface species did not correspond to the overall reaction rate, and it was concluded that it was not directly involved in the rate determining step of the reaction. A mechanism is proposed involving the reaction of an adsorbed acetone intermediate with an atomically adsorbed oxygen species via a dual site surface reaction to form complete oxidation products.Ph. D.
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Xi, Yan. "Ozone Decomposition and Acetone Oxidation on Manganese Oxide Catalysts." Thesis, Virginia Tech, 2005. http://hdl.handle.net/10919/33112.
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This thesis describes the preparation and characterization of manganese oxide catalysts and their application in the oxidation of acetone, a typical volatile organic compound (VOC), and ozone decomposition. This topic is of great value because of environmental concerns of the elimination of the harmful VOCs and ozone. Manganese oxide was chosen because it is a well-known complete oxidation catalyst for VOCs and also an active catalyst for ozone decomposition. Two cases of studies were carried out in this work.
The first study involved the oxidation of acetone using ozone on silica- and alumina-supported manganese oxide catalysts deposited on aluminum oxide foam substrates. The characteristics of the catalysts were determined through various techniques, including x-ray diffraction (XRD), x-ray absorption spectroscopy (XAS), Brunauer-Emmett-Teller (BET) surface area analysis, temperature-programmed reduction (TPR), and oxygen chemisorption. The use of these techniques allowed better understanding of the nature of the catalysts. Activity tests were carried out in the acetone oxidation reaction and it was found that the usage of ozone substantially reduced the oxidation temperature. Steady-state in situ Raman spectroscopy was also carried out to better understand the mechanism of the acetone oxidation reaction using ozone.
The second study involved an investigation of structural and electronic properties of manganese centers of the MnOx/SiO2 and MnOx/Al2O3 catalysts during the ozone decomposition reaction using in situ x-ray absorption spectroscopy (XAS). The number of surface active sites was again determined through TPR and oxygen chemisorption measurements. The performance of the catalysts with different loadings and supports were also compared.Master of Science
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Shumlas, Samantha Lyn. "Characterization of Carbon Nanomaterial Formation and Manganese Oxide Reactivity." Diss., Temple University Libraries, 2016. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/419544.
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ChemistryPh.D.
Characterization of a material’s surface, structural and physical properties is essential to understand its chemical reactivity. Control over these properties helps tailor a material to a particular application of interest. The research presented in this dissertation focuses on characterizing a synthetic method for carbon nanomaterials and the determination of structural properties of manganese oxides that contribute to its reactivity for environmental chemistry. In particular, one research effort was focused on the tuning of synthetic parameters towards the formation of carbon nanomaterials from gaseous methane and gaseous mixtures containing various mixtures of methane, argon and hydrogen. In a second research effort, photochemical and water oxidation chemistry were performed on the manganese oxide, birnessite, to aid in the remediation of arsenic from the environment and provide more options for alternative energy catalysts, respectively. With regard to the synthesis of novel carbonaceous materials, the irradiation of gaseous methane with ultrashort pulse laser irradiation showed the production of carbon nanospheres. Products were characterized with transmission electron microscopy (TEM), scanning electron microscopy (SEM), ultraviolet (UV) Raman spectroscopy, and infrared spectroscopy. Increasing the pressure of methane from 6.7 to 133.3 kPa showed an increase in the median diameter of the spheres from ~500 nm to 85 nm. Particles with non-spherical morphologies were observed by TEM at pressures of 101.3 kPa and higher. UV Raman spectroscopy revealed that the nanospheres were composed of sp2 and sp3 hybridized carbon atoms, based on the presence of the carbon D and T peaks. A 30% hydrogen content was determined from the red shift of the G peak and the presence of a high fluorescence background. Upon extending this work to mixtures of methane, argon, and hydrogen it was found that carbon nanomaterials with varying composition and morphology could be obtained. Upon mixing methane with other gases, the yield significantly dropped, causing flow conditions to be investigated as a method to increase product yield. Raman spectra of the product resulting from the irradiation of methane and argon indicated that increasing the argon content above 97% produced nanomaterial composed of hydrogenated amorphous carbon. In a second research effort, the effect of simulated solar radiation on the oxidation of arsenite [As(III)] to arsenate [As(V)] on the layered manganese oxide, birnessite, was investigated. Experiments were conducted where birnessite suspensions, under both anoxic and oxic conditions, were irradiated with simulated solar radiation in the presence of As(III) at pH 5, 7, and 9. The oxidation of As(III) in the presence of birnessite under simulated solar light irradiation occurred at a rate that was faster than in the absence of light at pH 5. At pH 7 and 9, As(V) production was significantly less than at pH 5 and the amount of As(V) production for a given reaction time was the same under dark and light conditions. The first order rate constant (kobs) for As(III) oxidation in the presence of light and in the dark at pH 5 were determined to be 0.07 and 0.04 h−1 , respectively. The As(V) product was released into solution along with Mn(II), with the latter product resulting from the reduction of Mn(IV) and/or Mn(III) during the As(III) oxidation process. Experimental results also showed no evidence that reactive oxygen species played a role in the As(III) oxidation process. Further research on the triclinic form of birnessite focused on its activation for water oxidation. Experiments were performed by converting triclinic birnessite to hexagonal birnessite in pH 3, 5, and 7 DI water with stirring for 18 hrs. Once the conversion was complete, the solid samples were characterized with TEM and x-ray photoelectron spectroscopy (XPS). The resulting hexagonal birnessites from experiment at pH 3, 5, and 7 possessed the same particle morphology and average surface oxidation states within 1% of each other. This observation supported the claim that upon transformation, Mn(III) within the sheet of triclinic birnessite migrated into the interlayer region of the resulting hexagonal birnessite. Furthermore, the migration of Mn(III) into the interlayer and formation of the hexagonal birnessite led to an increased chemical reactivity for water oxidation compared to the bulk. Electrochemical studies showed that the overpotential for water oxidation associated with the pH 3, 5, and 7 samples was 490, 510, and 570 mV, respectively. In another set of experiments, ceric ammonium nitrate was used to test birnessite for water oxidation reactivity. These experiments showed that the pH 3 birnessite produced the most O2 of all the samples, 8.5 mmol O2/mol Mn, which was ~6 times more than hexagonal birnessite which did not undergo post-synthesis exposure to low pH conditions.
Temple University--Theses
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Chan, Yiu-ming, and 陳耀明. "The chemistry and in vitro cytotoxicity study of manganese oxide nanostructures." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2007. http://hub.hku.hk/bib/B39557121.
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Ovalle, Alejandro. "Manganese titanium perovskites as anodes for solid oxide fuel cells." Thesis, St Andrews, 2008. http://hdl.handle.net/10023/567.
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Shen, Ruihua Materials Science & Engineering Faculty of Science UNSW. "Reduction of zinc oxide in sintering of manganese furnace dust." Awarded by:University of New South Wales. Materials Science & Engineering, 2009. http://handle.unsw.edu.au/1959.4/44542.
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Manganese furnace dust is made up of volatiles and fine particles of the raw materials collected from the off-gas during smelting of manganese alloys. Impediments to the recycling of the manganese furnace dust back to the ferroalloy furnaces are handling due to the presence of tar, and the potential accumulation of zinc in the furnaces, which can cause irregularities in their operation. The aim of the thesis was to establish conditions for zinc removal from the dust and assess the feasibility of the dust recycling in the Tasmanian Electrometallurgical Company sinter plant. Major findings are: - Manganese furnace dust taken from the settling ponds contained water, carbonaceous materials (tar), and metal oxides. The carbon content of the dried furnace dust was about 20% and the average manganese and zinc contents were 33.4 and 1.29%, respectively. Moisture content was 30-60%. - The tar components were aliphatic hydrocarbons and polyaromatic hydrocarbons, their derivatives, and sulphur- and oxygen-containing compounds with a wide range of carbon number (15-28) and boiling point (230-530oC). Light hydrocarbons were not detected. - If manganese furnace dust was recycled to ferroalloy furnaces through the sintering plant, the overall zinc input had increased by 51-143%. Sustainable utilisation of manganese furnace dust should include enhanced zinc removal. - Reduction of zinc oxide from manganese furnace dust pellets started at 800oC. Zinc oxide was reduced to zinc vapour by tar in the dust. Temperature and gas atmosphere were key parameters affecting the zinc removal from the dust. The zinc removal rate increased with increasing temperature and was close to completion at 1100oC. - Optimal conditions for removal of zinc from the furnace dust include: temperature in the range 1000-1150oC, inert gas atmosphere and furnace dust fraction in the furnace dust-manganese ore mixture above 60%. - Zinc removal in the processing of manganese furnace dust in the sinter plant was low because of zinc reoxidation in the sinter bed. This makes the sinter plant unsuitable for recycling of the dust. More suitable conditions for utilisation of manganese furnace dust exist in the rotary hearth furnace, which development is recommended for further study.
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Kötschau, Immo. "In situ x-ray study of orthorhombic lithium manganese oxide." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp04/mq24175.pdf.
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Eley, Mark John. "Manganese oxide deposits in water treatment facilities, North East Scotland." Thesis, Robert Gordon University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.388813.
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Radhakrishnan, Rakesh. "Structure and Ozone Decomposition Reactivity of Supported Manganese Oxide Catalysts." Diss., Virginia Tech, 2001. http://hdl.handle.net/10919/26033.
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Manganese oxide catalysts supported on Al2O3, ZrO2, TiO2 and SiO2 supports were used to study the effect of support on ozone decomposition kinetics. X-ray diffraction (XRD), in-situ laser Raman spectroscopy, temperature programmed oxygen desorption, surface area measurements, extended and near edge x-ray absorption fine structure (EXAFS and NEXAFS) showed that the manganese oxide was highly dispersed on the surface of the supports. EXAFS spectra suggest that the manganese active centers on all of the surfaces were surrounded by five oxygen atoms. These metal centers were of a mononuclear type for the Al2O3 supported catalyst and multinuclear for the other supports. NEXAFS spectra for the catalysts showed a chemical shift to lower energy and an intensity change in the L-edge features which followed the trend Al2O3 > ZrO2 > TiO2 > SiO2. The trends provided insights into the positive role of available empty electronic states required in the reduction step of a redox reaction.
The catalysts were tested for their ozone decomposition reactivity and reaction rates had a fractional order dependency (n < 1) with ozone partial pressure. The apparent activation energies for the reaction was low (3-15 kJ/mol). The support influenced the desorption step (a reduction step) and this effect manifested itself in the pre-exponential factor of the rate constant for desorption. Trends for this pre-exponential factor correlated with trends in NEXAFS features and reflected the ease of electron donation from the adsorbed species to the active center.Ph. D.
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Tsai, Chung-Ying. "SYNTHESIS, CHARACTERIZATION AND PSEUDO-CAPACITIVE PERFORMANCE OF MANGANESE OXIDE NANOSTRUCTURES." OpenSIUC, 2012. https://opensiuc.lib.siu.edu/theses/1029.
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In this research, manganese oxide based nanoparticles were synthesized by sol-gel process. Methanol, ethanol, and propanol were used as alternative solvents during sol-gel process with manganese acetate as precursor for the preparation of pristine manganese oxide. Hybrid manganese oxide modified by additions of carbon nanotubes was further prepared. The effects of different solutions and heat treatment temperatures on the morphology, physical characteristics, and electrochemical properties of the manganese oxide based materials were investigated. Particle size of pristine manganese oxide samples prepared from methanol, ethanol, and propanol were compared by SEM and TEM image analysis. Smallest particle size was observed for manganese oxide prepared from propanol, with diameters range from 16 nm to 50nm. XRD results showed that the as-prepared manganese oxide based samples treated at calcination temperature of 300ºC and above were composed of Mn2O3 as dominant phase, with Mn3O4 as minor phase. Specific capacitance of manganese oxide prepared from methanol, ethanol, and propanol at scan rate of 10 mV/s measured using two electrode systems were 88.3, 66.0, and 104.8 F/g, respectively and that for the hybrid sample was 140.5 F/g. Results from electrochemical impedance spectroscopy (EIS) also showed superior electrochemical properties of the hybrid sample over pristine manganese oxide samples. It is evident that the addition of carbon nanotubes not only improved the specific capacitance but also the overall electrochemical properties of the manganese oxide supercapacitor.
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Kononov, Ring Materials Science & Engineering Faculty of Science UNSW. "Carbothermal solid state reduction of manganese oxide and ores in different gas atmospheres." Publisher:University of New South Wales. Materials Science & Engineering, 2008. http://handle.unsw.edu.au/1959.4/41459.
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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.
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Apostolopoulos, D. G. "The manganese oxide ore deposits of the Nevrokopi district, Macedonia, Greece." Thesis, University of Reading, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.374035.
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Jang, Young-Il 1968. "Stability of lithium aluminum manganese oxide cathodes for rechargeable lithium batteries." Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/9162.
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Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1999.Includes bibliographical references.
Lithium manganese oxides have attracted wide attention as low-cost, nontoxic intercalation cathode materials for rechargeable lithium batteries. In this work, the stability of these compounds during synthesis and in use has been studied in several respects. (1) Phase stability of LiMnO2 polymorphs has been determined under the high temperature synthesis conditions. Effects of temperature, oxygen partial pressure, and dopant (Al) content on the phase stability have been discussed based on a possible stability mechanism. (2) The mechanism of improved cycling stability of electrochemically transformed spinel compared to conventional spinel has been identified. Atomic rearrangement from the ordered rocksalt to spinel type cation ordering results in an antiphase nanodomain structure, which becomes a ferroelastic domain structure during the cubic ---> tetragonal Jahn-Teller transformation, and thereby accommodates the transformation strains. (3) Al-doped spinels exhibit much improved capacity stability at elevated temperatures compared to undoped spinels. This effect has been discussed with respect to proposed mechanisms of Mn dissolution and capacity loss. (4) Magnetic properties are critically influenced by phase stability, cation ordering, and Mn valence in lithium manganese oxides. In the paramagnetic temperature regime, it has been observed that antiferromagnetic interactions between the Mn ions are strongest in the orthorhombic phase among LiMnO2 polymorphs having the average Mn valence of 3+, while decreasing Mn valence strengthens the antiferromagnetic interactions in LixMn2O4 spinel. At temperatures below the paramagnetic temperature regime, spin-glass behavior is observed in both LixMn2O4 and monoclinic LiMnO2 compounds, which is attributed to geometrical frustration due to structure ( cation ordering) and magnetic disorder due to a disordered distribution of Mn valence. As spin-glass behavior is commonly observed in both well-crystallized, conventional spinel and highly disordered, transformed spinel, magnetic characterization cannot easily be used to distinguish the two different spinels.
by Young Il-Jang.
Ph.D.
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Lekitima, Joel Ntotole. "Supercapacitive Properties of Nanocarbons Modified with Manganese Oxide Nanoparticles and Metallotetrapyrazinoporphyrazines." Diss., University of Pretoria, 2013. http://hdl.handle.net/2263/79269.
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This dissertation describes the electrochemical properties of nanocarbons (multiwalled
carbon nanotubes (MWCNTs) and graphene oxide (GO)) incorporated with
manganese dioxide (MnO2) and metallotetrapyrazinoporphyrazines (MTPyzPz,
where M = Co, Fe) as electrochemical capacitors. Supercapacitive properties of the
composites formed were investigated using cyclic voltammetry (CV), galvanostatic
charge-discharge and electrochemical impedance spectroscopy (EIS) in both threeand
two-electrode systems using 1.0 M H2SO4 and 1.0 M Na2SO4 as electrolytes. This
study showed that acid functionalized MWCNTs (MWCNTaf) enormously increased
the specific capacitance of MnO2 from 45 F.g-1 to 1209 F.g-1. Supercapacitive
properties of nanocarbons modified with cobalt(II)tetrapyrazinoporphyrazine(
CoTPyzPz) and Iron(II)tetrapyrazino-porphyrazine (FeTPyzPz) were
explored. MWCNTaf modified with CoTPyzPz and FeTPyzPz gave higher capacitances
than phenylamine-functionalised MWCNTs (MWCNTPhNH2) modified MTPyzPz
nanocomposites in acidic electrolyte. The specific capacitance obtained for
MWCNTaf-CoTPyzPz at 1 A.g-1 was 1642 F.g-1 in 1.0 M H2SO4 while 410 F.g-1 was
obtained for MWCNTaf-FeTPyzPz at 3 A.g-1. This large specific capacitance was
attributed to the protonation and deprotonation of the porphyrazine
macromolecule. FeTPyzPz nanocomposites gave higher specific capacitance in acid
electrolyte than in a neutral electrolyte.
An asymmetric capacitor cell (coin cell) was made to further investigate the
suitability of MTPyzPz compounds as electrode capacitor material. A novel
v
asymmetric electrochemical capacitor (AEC) using functionalised MWCNTs and
MTPyzPz nanocomposite as the positive electrode and functionalised MWCNTs and
carbon black (CB) as the negative electrode in a neutral aqueous Na2SO4
electrolyte was investigated. CoTPyzPz//CB-MWCNTaf was the best AEC with specific
capacitance of 70 F.g-1. This AEC cell exhibited energy density and power density of
8.5 kW.kg-1 and 4.3 KW.kg-1 respectively. A novel AEC with high energy and power
densities was successfully developed using GO/CoTPyzPz as the positive electrode
and GO/CB as the negative electrode in 1.0 M Na2SO4. The excellent energy and
power densities (44 Wh.kg−1 and 31 kW.kg−1 obtained at high current density, 2.4
A.g-1) coupled with excellent long cycle life, short response time, and low equivalent
series resistance (ESR) clearly indicate that this asymmetric electrochemical
capacitor has a considerable potential in developing low-cost and green energy
storage devices that operate at high energy and power densities. Interestingly, the
energy density of the GO/CoTPyzPz//GOCB based AEC falls within the range usually
seen for nickel metal hydride (NiMH) batteries (30 – 100 Wh.kg-1), but, more
importantly, has a much better power performance than NiMH batteries (0.25 – 1
kW.kg-1) widely used in hybrid vehicles such as Toyota Prius and Honda Insight. In
summary, the findings in this work clearly indicate that CoTPyzPz and FeTPyzPz are
potentially useful in developing low-cost and ‘green’ electrochemical energy storage
devices with high capacitance, energy and power densities. The work has indeed
opened a door of opportunity that will permit the study of other MTPyzPz complexes
for the development of electrochemical capacitors.Dissertation (MSc)--University of Pretoria, 2013.
Chemistry
MSc
Unrestricted
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Crowe, Andrea L. "Assessment of the fate of manganese in oxide-coated filtration systems." Thesis, This resource online, 1997. http://scholar.lib.vt.edu/theses/available/etd-08222008-063718/.
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Zhang, Huichun. "Metal oxide-facilitated oxidation of antibacterial agents." Diss., Available online, Georgia Institute of Technology, 2004:, 2004. http://etd.gatech.edu/theses/available/etd-07072004-152317/unrestricted/zhang%5Fhuichun%5F200407%5Fphd.pdf.
Full textAbstract:
Thesis (Ph. D.)--School of Civil and Environmental Engineering, Georgia Institute of Technology, 2005. Directed by Ching-Hua Huang.Wine, Paul, Committee Member ; Pavlostathis, Spyros, Committee Member ; Mulholland, James, Committee Member ; Yiacoumi, Sotira, Committee Member ; Huang, Ching-Hua, Committee Chair. Includes bibliographical references.
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Zhao, Qiang. "The thermal stability and catalytic application of MnOx-ZrO2 oxide powders /." Philadelphia, Pa. : Drexel University, 2004. http://dspace.library.drexel.edu/handle/1860/286.
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Sihaib, Zakaria. "Oxidation of toluene traces in gas phase in presence of manganese-oxide based catalysts : relationship structure-activity." Thesis, Lyon, 2018. http://www.theses.fr/2018LYSE1029.
Full textAbstract:
Dans la première partie de mon travail, j'ai préparé quatre catalyseurs différents à base d'oxydes de manganèse: une perovskite (LaMnO3), par voie sol-gel; un oxide simple (Mn2O3), par méthode rapide et un tamis moléculaire octahedrique (OMS-2) par deux méthodes de préparation différentes, via l'état solide (OMS) et la méthode hydrothermale (OMSh). Les propriétés physicochimiques de ces catalyseurs ont été caractérisées par diffraction des rayons X (DRX), adsorption-désorption de N2, analyses thermogravimétriques (ATD/ATG), analyses chimiques (ICP-OES) et réduction en température programmée (H2-RTP). Leurs performances catalytiques ont été évaluées dans la réaction d’oxydation du toluène. Trois cycles catalytiques consécutifs ont été réalisés pour chaque catalyseur afin de confirmer les performances. Afin d'évaluer la stabilité des catalyseurs dans des conditions réactionnelles, les performances catalytiques ont été étudiées sur des expériences de longue durée à température constante, pendant 24 h à 25% de conversion du toluène. Des tests d'oxydation du toluène sur un catalyseur de référence, type Pd/Al2O3 contenant 0,78% en poids de Pd, ont également été effectués à des fins de comparaison. Les caractéristiques cristallines détectées dans les modèles DRX sont bien compatibles avec la formation des structures désirées. Sur la base de leur surface spécifique et de leur réductibilité à basse température, les catalyseurs ont été classés comme suit : OMSs > Mn2O3 > OMS > LaMnO3. Cette tendance est en bon accord avec les performances observées dans l'élimination catalytique du toluène. Un modèle cinétique a été proposé et un bon accord a été obtenu lors de l'ajustement avec les données expérimentales. Dans la seconde partie de mon travail, des catalyseurs LaMnO3 (LM) avec un rapport molaire acide citrique (CA) sur nitrates métalliques (Mn et La) allant de 0,5 à 2 (LM 0,5 à LM 2) ont été synthétisés par méthode sol-gel citrate, afin d'étudier l'effet du rapport de l'acide citrique sur les propriétés physico-chimiques et les performances catalytiques. Les propriétés physicochimiques de ces catalyseurs ont été caractérisées par diffraction des rayons X (DRX), adsorption-désorption de N2 et par spectroscopie d'émission atomique de plasma à couplage inductif (ICP-AES). Sur des échantillons sélectionnés, des caractérisations supplémentaires par analyse thermogravimétrique et thermique différentielle (ATD/ATG), une réduction programmée en température par de l'hydrogène (H2-TPR) et une spectroscopie de photoélectrons X (XPS) ont été réalisées. Les résultats montrent que le rapport molaire acide citrique sur nitrates métalliques influence significativement le profil obtenu en ATD/ATG des solides non calcinés ainsi que les propriétés physico-chimiques des catalyseurs. Les caractéristiques cristallines détectées par DRX sont bien compatibles avec la formation de la phase perovskite LaMnO3. De petites caractéristiques de Mn2O3 ont été détectées dans les diagrammes de diffraction de tous les catalyseurs LM, à l'exception du rapport molaire élevé des nitrates CA / (Mn + La) (1,9 et 2,0). Inversement, des pics La2O3 sont observés pour des valeurs allant de 1,6 à 2, l'intensité la plus élevée étant détectée au rapport molaire égal à 2. Les performances catalytiques ont été évaluées dans l'oxydation du toluène en réalisant trois cycles catalytiques consécutifs pour atteindre des performances stables. Afin d'évaluer la stabilité des catalyseurs dans des conditions de réaction, des expériences à température constante ont été effectuées pendant 24 h à 17% de conversion du toluène. Les catalyseurs LM1.2, LM1.3 et LM1.5 ont montré les meilleures performances catalytiques en oxydation totale du toluène, tandis que LM1 et LM1.7 présentaient un comportement intermédiaire et LM0.8 était peu actifIn the first part of my work, I have prepared four different catalysts based on manganese oxides: a perovskite (LaMnO3), via sol-gel method; a simple oxide (Mn2O3), by rapid method and an Octahedral Molecular Sieve (OMS-2) by two different preparation methods, via solid state (OMSs) and hydrothermal method (OMSh). The physicochemical properties of these catalysts were characterized by X-ray diffraction (XRD), N2 adsorption–desorption, TGA/DTA, ICP-OES and H2-TPR. Their catalytic performances were evaluated in the oxidation of toluene. Three consecutive catalytic cycles were performed for each catalyst in order to reach steady state performances. In order to assess the stability of the catalysts under reaction conditions, the catalytic performances were studied upon long-term experiments running for 24 h at 25% of toluene conversion. Tests of toluene oxidation over a typical industrial catalyst, such as a commercial Pd/Al2O3 catalyst containing 0.78 wt% Pd, were also performed for comparison purposes. The crystalline features detected in the XRD patterns are well consistent with the formation of the desired structures. Based on their specific surface area and their low-temperature reducibility, the catalysts were ranked as follows: OMSs> Mn2O3> OMSh> LaMnO3. This trend was in good agreement with the performances observed in the catalytic removal of toluene. A kinetic model was proposed and a good agreement was obtained upon fitting with the experimental data. In the second part of my work, LaMnO3 (LM) catalysts with molar ratio of citric acid (CA) to metal nitrates (Mn and La) ranging from 0.5 to 2 (LM 0.5 to LM 2) were synthesized by citrate sol–gel method, in order to study effect of citric acid ratio on the physico-chemical properties and the catalytic performances. The physicochemical properties of these catalysts were characterized by X-ray diffraction (XRD), N2 adsorption–desorption and by inductively coupled plasma atomic emission spectroscopy (ICP-AES). Over selected samples, additional characterizations by thermogravimetric and differential thermal analysis (TGA/DTA), temperature-programmed reduction by hydrogen (H2-TPR) and X-ray photoelectron spectroscopy (XPS) were carried out. The results show that the molar ratio of citric acid to metal nitrates significantly influenced the TGA/DTA profile of gels along with the physico-chemical properties of the catalysts. The crystalline features detected by XRD are well consistent with the formation of LaMnO3 perovskite phase. Small features of Mn2O3 were detected in the diffraction patterns of all LM catalysts except for high CA/Mn+La nitrates molar ratio (1.9 and 2.0). Conversely, La2O3 peaks appeared for values ranging from 1.6 to 2, the highest intensity being detected at molar ratio equal to 2. The catalytic performances were evaluated in the oxidation of toluene, performing three consecutive catalytic cycles in order to reach steady-state performances. In order to assess the stability of the catalysts under reaction conditions, long-term experiments running for 24 h at 17 % of toluene conversion were carried out. The catalysts LM1.2, LM1.3 and LM1.5 showed the best catalytic performances in terms of toluene conversion, LM0.8 was poor performing, while LM1 and LM1.7 exhibited an intermediate behaviour
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Antoni, Hendrik [Verfasser], Martin [Gutachter] Muhler, and Wolfgang [Gutachter] Schuhmann. "Nanoscale manganese oxide and manganese oxide-carbon hybrid materials for water electrolysis : synthesis, characterization and elektrocatalysis / Hendrik Antoni ; Gutachter: Martin Muhler, Wolfgang Schuhmann ; Fakultät für Chemie und Biochemie." Bochum : Ruhr-Universität Bochum, 2019. http://d-nb.info/120156025X/34.
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Gilbert, Hanna Loraine, and Hanna Loraine Gilbert. "An Investigation of Biofilms and Manganese Oxide Formation in Pinal Creek, Arizona." Thesis, The University of Arizona, 2003. http://hdl.handle.net/10150/305290.
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Soo, Haw Yun. "Commercialization of cryptomelane-type manganese oxide (OMS-2) nanowire paper oil sorbent." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/42158.
Full textAbstract:
Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2007.Includes bibliographical references (leaf 36).
Cryptomelane-type Manganese oxide (OMS-2, a group of Octahedral Molecular Sieves) nanowire paper exhibits interesting properties: reversible wettability, oleophilic while being hydrophobic, and high thermal stability. These properties open up possible markets for commercialization. This thesis reviews the market potential of each of these properties and explores the competitiveness of the nanowire paper in the proposed markets. The proposed values of this technology are in its high selective absorbency towards oil, high performance over cost metric and its high thermal stability. Its thermal stability enables a thermal desorption type process to regenerate and recycle the sorbent for reuse. This translates into further differentiation and provides greater value for the users.
by Haw Yun Soo.
M.Eng.
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Jones, Christopher D. "Ambient temperature oxidation of carbon monoxide by copper-manganese oxide based catalysts." Thesis, Cardiff University, 2006. http://orca.cf.ac.uk/56078/.
Full textAbstract:
The catalytic oxidation of carbon monoxide is an important reaction both commercially and scientifically. Copper-manganese oxides in the form of hopcalite have formed a cheap and accessible carbon monoxide abatement catalyst for the last 80 years. This thesis outlines the robust and reproducible preparation methods necessary for the formation of highly active species, with the heat treatment applied during the catalyst drying steps being identified as crucial for the formation of active species. The addition of metal cations (Co3+, Ni2+, Fe3+, Ag+) to the standard hopcalite formulation has given rise to many interesting properties including increased intrinsic activity, increased surface area and greater stability of catalytic activity with increased usage. The results of doping with a small quantity of cobalt produced materials that were amorphous to X-Ray Diffraction studies and with increased surface areas over the standard hopcalite. The dual positive effects of increased activity and prolonged catalyst stability were also brought about by the addition of cobalt (1-5% with respect to the quantity of copper present). The joint effect of precipitate ageing time and level of cobalt doping is also probed. The poisoning effect of water on the hopcalite and cobalt-doped hopcalite is reported, with the effect being identified as temporary and reversible in many cases. The mechanisms of oxidation and deactivation over hopcalite are probed using the Temporal Analysis of Products technique with the important relationship between lattice oxygen and catalytic activity being identified. The presence of cobalt is also shown to be important to the re-oxidation of a reduced hopcalite surface. Catalysts were produced that rivalled and often improved on the activity and stability of a presently available commercial catalyst.
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Zimmermann, Nina Tamara [Verfasser]. "Manganese oxide cluster : Gas phase reactions and IR spectroscopy / Nina Tamara Zimmermann." Ulm : Universität Ulm, 2021. http://d-nb.info/1231916494/34.
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Rossouw, Margaretha Hendrina. "Synthesis and characterization of lithium-manganese-oxide electrodes for lithium battery applications." Master's thesis, University of Cape Town, 1994. http://hdl.handle.net/11427/18339.
Full textAbstract:
As the electronics industry moves more towards portable equipment the demand for batteries, especially rechargeable batteries, is increasing. Lithium batteries have several advantages over other competitive systems. Coupled with the inexpensive and environmentally friendly manganese dioxide, Li/MnO₂ batteries are being used extensively for powering a range of devices, but particular electronic systems.
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Madireddy, Sai Sidhardha. "Structural effects on Pseudocapacitive response in Manganese oxide (MnO2) super capacitive system." University of Cincinnati / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1479476408027058.
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Debnath, Sudeep. "Surface/Geochemistry of Iron and Manganese Oxide Nano-Materials in the Environment." Diss., Temple University Libraries, 2009. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/30879.
Full textAbstract:
ChemistryPh.D.
Nanomaterials possess physical and chemical properties that may benefit medicine, catalysis, and environmental remediation. Apart from understanding the structure of nanomaterials, significant amount of research has focused on understanding the structural properties of nanoparticles that lead to their unique reactivity. Ferric hydroxides are important mineral components and the subject of much scientific research in environmental and soil sciences because of their ubiquity in soil, ground water and aquatic sediments Iron oxide nanoparticles found in the environment exhibit size-dependent behavior. Iron oxides also play an important role in environmental chemistry. Ferrihydrite is an important iron oxide mineral as they exist in most of the sediment environment, necessary precursors for more stable iron oxides like hematite. Iron oxides are also important in many living organisms and stored as protein-encapsulated iron(III) oxyhydroxide nanoparticles. Because of the ubiquitous nature of ferrihydrite in soil and sediments, understanding correlation between the surface reactivity and the structure, phase of ferrihydrite ie. homogeneous or heterogeneous phase dependent reaction is important from environmental point of view. Iron oxides also play an important role in atmospheric chemistry and size dependent surface catalytic properties towards atmospheric gases. Green house gases are frequently generated during the burning of fossil fuels in factories and power plants, or derived from natural processes such as volcanic eruptions. Both natural and engineered metal oxides have been utilized as catalysts or sorbents for removal or minimization of green house emissions. In an attempt to understand the structure and reactivity relationship, we have presented ferrihydrite dissolution under reducing conditions and in situ kinetic studies were performed on isolated individual single particles of ferrihydrite using AFM. Bulk batch studies are also presented, where particles exist as agglomerates. Interface dissolution reaction has been characterized with FTIR and results were confirmed with theoretical calculations. Normalized dissolution rate of individual ferrihydrite particle sheds light on the phase behavior of this material. This study indicates that the ferrihydrite is uniform in composition and supports the Michel et al model. The size-dependent reactivity of ferrihydrite toward the environmentally important gas sulfur dioxide SO2 was also studied as atmospheric emission of SO2(g) affects the environment because it promotes the production of acid rain. In this investigation, nano-ferrihydrite particles were synthesized with a narrow size distribution. The surface chemistry and reactivity (SO2(g) sorption) was studied with attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy in combination with molecular orbital/density functional theory (MO/DFT) frequency calculations. Results showed that SO2(g) sorption may be a sensitive function of the structural properties and size of the nanoparticles. Like Iron oxides, Manganese oxides also play a distinctive role in superficial soil or near surface environments. Birnessite is one of the most commonly occurring manganese oxides in the soils and sediments. Birnessite are known to provide a suitable surface for heterogeneous oxidation of As(III) to As(V), and thus contribute to the environmental fate of arsenic species in soil and sediments. In the present study we have made an effort to understand this fundamental geochemistry occurring at birnessite surface at the molecular scale using advanced surface sensitive tools like AFM and spectroscopic techniques like FTIR and XPS. Nano size manganese oxide was also prepared via biological routes. Nano-size manganese oxide was prepared using ferritin protein as the biological precursor. Solution phase arsenic oxidation studies were performed with Ferritin Manganese oxide. Ion chromatography is performed to investigate oxidation of As(III) and reduction of manganese, along with XPS analysis to monitor the oxidation states of arsenic and manganese species. Results were also verified with FTIR spectroscopy for interface speciation.
Temple University--Theses
34
Im, Dongmin. "Manganese oxide cathodes for rechargeable batteries." Thesis, 2002. http://wwwlib.umi.com/cr/utexas/fullcit?p3110622.
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Liu, Bing-Shen, and 劉柄伸. "Removal of amoxicillin by manganese oxide." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/49557457190229582766.
Full textAbstract:
碩士明志科技大學
生化工程研究所
99
The removal of antibiotics amoxicillin (AMO) using manganese oxide was investigated in this study. Amoxicillin, one kind of β-lactam and semi-synthesis of penicillin, is used to cure streptococcus, staphylococcus, pneumococcus, meningococcal, and others that are infected by bacteria. The antibiotics is manufactured and widely used in great amount that affect the environment and ecosystem directly and indirectly. Many antibiotics are metabolized by organisms and then excreted through fecal matter to natural water body. The concentration of antibiotics in the environment is low; however, it is the emerging pollutant today because its high impact on ecosystems and human beings. Therefore, this study adopted manganese oxide, which is abundant in nature, to adsorb and/or to oxidize the target pollutant. The control factor includes reaction time (0 to 48 hours), AMO concentrations (1× 10^-4 to 1× 10^-3 mole), pH (2 to 9), and temperatures (15, 25 and 35℃). The pH zero point of charge of pyrolusite manganese oxide before is 5.2. The reaction between AMO and manganese oxide almost approaches pseudo-equilibrium at 36 hr, and the reaction kinetics obeys pseudo-second-order equation. The nitrogen purged before and during reaction did not significantly influences the AMO removal. At near neutral pH (6 ~ 7), the maximun removal of AMO approximate 90 % was obtained. The removal of AMO decreased with both pH increasing and decreasing. At acidic pH, that appeared to be only 40 % removal of AMO. Besides, at acidic condition AMO significantly enhances the dissolution of manganese oxide compared to that at alkalinity condition. AMO removal slightly increases with the temperature elevating. The prevalent buffer solution of sodium phosphate could successfully maintain the desired pH, but significantly influences the AMO removal. However, the buffer solution of sodium bicarbonate is vice versa, especially at acidic conditions the pH varies during the reaction. The results of LC-MS analysis displays that the, AMO could be hydrolyzed to amoxicillin penicilloic acid (m/z=383) and amoxicillin penilloic acid (m/z=339). Moreover, at alkaline condition, the new product with m/z 160 is yield and the concentration of amoxicillin penicilloic acid increases with reaction progressing; at acidic condition, the concentration of amoxicillin penilloic acid increases. Pyrolusite manganese oxides amoxicillin could plays the role of catalyst. Furthermore, FTIR-ATR analysis indicated that amoxicillin could be adsorbed by manganese oxides.
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Chan, Yen-Chuan, and 詹晏權. "Removal of methylene blue using manganese oxide." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/34007912157776652868.
Full textAbstract:
碩士明志科技大學
生化工程研究所
99
This research is about methylene blue (MB) removal mechanism with manganese oxide at different oxygen concentrations (opened-container, nitrogen aeration, oxygen aeration) and pH values. Use inductively coupled plasma (ICP) to analysis dissolved manganese ion, and UV/Vis spectrometer all-wavelength analysis, high performance liquid chromatography-mass spectrometer (HPLC-MS) to analysis the reactive intermediates and final products qualitatively. Then, study the roles of adsorption mechanism and manganese oxide with data results. As a result, the ICP data showed that pH4 had the highest dissolved manganese ion concentration, and the UV/Vis all-wavelength scan result indicated that after manganese oxide react with methylene blue, there was a blue-shift appears at the acidic environment, which was determined as thionin (Th). Furthermore, manganese oxide is the major oxidant at pH4 in all three different oxygen concentrations. However, compare the different oxygen concentrations with all-wavelength analysis in the nitrogen aeration of pH6 system, the adsorption peak increases with time, which was speculated that the initial state of manganese oxide was adsorbed and processed oxidation in the final state. Under the alkaline condition, dissolved manganese ion concentration decreases after the reaction, and unable to find efficient color removal with the all-wavelength analysis. Particularly, the methylene blue specific absorbing peak is 665nm and had noticeable decrease trends at pH8 and pH10. In the meantime, the HPLC-MS analysis results showed that there is only one single reactive intermediate, thionin(228) in the environment of pH6 and pH 8 after manganese oxide react with methylene blue. However, there were many reactive intermediates, such as azure A, azure C and the final dye thionin in pH4 and pH6 environments that proved the electron transfer phenomenon between dye molecules and manganese oxide. In summary, the main reaction mechanics of methylene blue are: (1) adsorption and the fall off stage of auxochrome, (2) further degradations of reactive intermediates.
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Chen, Chien-Ming, and 陳建銘. "Synthesis and Characterizations of Manganese Oxide Nanostructures." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/87404231311685608557.
Full textAbstract:
碩士國立中正大學
化學工程所
96
This research was to use the redox reaction of Mn2+ and/or MnO4- and PEG-20000 as dispersant for the synthesis of MnO2 nanostructures, such as ?MnO2 nanoparticles/nanorods, hydrangea-like MnO2 spheres and urchin-like β-MnO2 nanowires. Experimental parameters, such as amounts of PEG-20000, concentrations of HCl, calcination temprerature, calcination time, and ramping rate were discussed for the influence of morphology of the structure. According to the intermediate of different conditions, the possible formation mechanism was purposed. In the synthesis of hydrangea-like MnO2 spheres and urchin-like β-MnO2 nanowires, the results showed that the anion and PEG-20000 play an important role on the formation of MnO2. Field emission scaning electron microscopy, high resolution transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy were employed to characterize the morphology, structure, composition, and elemental composition of the nanostructure.
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Lee, Kuang-Tsin, and 李光正. "Synthesis and Characterization of Manganese Oxide Supercapacitors." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/32568097157639844992.
Full textAbstract:
博士國立臺灣大學
化學工程學研究所
99
For the first time, aqueous gel electrolytes have been successfully applied to the MnO2‧nH2O and MnFe2O4‧nH2O supercapacitors. Each gel polymer electrolyte consists of polymer, salt, and water. Potassium polyacrylic acid (PAAK), potassium polyacrylic acid-co-polyacrylamide (PAAK-co-PAAM), and polyacrylamide (PAAM) were used as polymers in the gel electrolytes. These gel electrolytes all show no fluidity, but they still main high ionic conductivities in the order of 10-1 Scm-1. The capacitances of two Mn-based oxides were all enhanced remarkably in gel polymer electrolytes compared to these in the liquid electrolytes. In-situ X-ray absorption near-edge structure (XANES) analysis indicates that the oxide electrodes of gel electrolyte cells possess higher Mn valances and are subjected to greater extent of valance variation than that of liquid electrolyte cell upon charging/discharging over the same potential range. On the other hand, for the MnO2 supercapacitor, the problem of capacitance reduction with increasing oxide loading can be solved to a great extent by introducing superabsorbent polymer, namely polyacrylic acid (PAA), to form new composite powders composed of MnO2, carbon black, and PAA. Besides, the capacitance of oxide in the composite electrode is also much higher than that of the original electrode. The success in combining both high capacitance and high active-material loading results in geometric capacitance density (GCD) of ca. 1.8-1.4 F cm-2 even under very high current densities (ca. 35-260 mA cm-2 or 5-40 A g-1 – MnO2).
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Kuo, Chung-Lun, and 郭仲倫. "The effects of carbon nanotube modification and manganese oxide annealing on capacitive characteristics of manganese oxide / carbon nanotube composite electrodes." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/58540311873972928094.
Full textAbstract:
碩士國立雲林科技大學
化學工程與材料工程系碩士班
100
In recent years with the 3C industry (computers, communications and consumer electronic products)''s flourish, industry for efficient can and high reliability level of the energy storage element needs also will increase, but the purpose of this thesis, the text of for the development of high power density level,electrochemical capacitors for high energy density and long life to take this future increase 3C products in performance, reliability, and cost competitive advantage; this study is to dip way through the thermal decomposition to graft manganese metal oxide nanothe carbon control preparation nanoscale electrochemical capacitor electrodes. The experiment will be to cobalt catalyst plating aluminum foil substrate using chemical vapor deposition method prepared carbon nanotubes, CNTs aluminum foil the pickling or atmospheric heat treatment modified immersion manganese nitrate solution, and then through thermal decomposition of manganese oxide, explore the different thermal decomposition temperature and of its drape manganese oxide capacitance value; CNTs manganese oxide composite electrode prepared in different conditions, cyclic voltammetry and the chronopotentiometry future investigate the capacitor, cycle life, trying to figure out the preparation of the best conditions. The best parts of the experiment: carbon nanotube aluminum foil electrode by 61wt.% HNO3 pickling 5min disseminated 50wt.% Mn(NO3)2 solution 5min, place a high temperature furnace to 300℃ heat treatment generated manganese oxide. The test via cyclic voltammetry, the potential range of 0-1 V, scan rate of 0.1 V/s, electrolyte 0.5M Na2SO4, measured the highest specific capacitance 494.65 mF/cm2
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Jin, Sang-wan. "Directed vapor deposition of lithium manganese oxide films /." 2008. http://wwwlib.umi.com/dissertations/fullcit/3329755.
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Lin, Chia-yen, and 林加岩. "Capacitive Properties of Porous Nanocrystalline Manganese Oxide Films." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/94152609967865997289.
Full textAbstract:
碩士逢甲大學
材料科學所
94
The manganese oxide electrodes with promising pseudo-capacitive behavior were prepared successfully by sol-gel process. The precursors were manganese acetate and citric acid, and ammonium hydroxide was added into the solution to adjust the pH value. Effects of heat treatment on material characteristics and electrochemical properties of the manganese oxide electrodes were investigated. In addition, electrophoretic deposition (EPD) process was adopted to deposit manganese oxide electrodes starting from powders with three different sources. The effect of structure and surface morphology of the manganese oxide electrodes was investigated. The experimental results showed that manganese oxide film prepared by sol-gel technique composed of Mn2O3 and Mn3O4 phases after heat treating at 300 oC. The surface morphology of the heat treated film exhibited a porous structure due to the burnout of organic. The specific capacitance of sol-geled manganese oxide electrodes was 53.2, 230.5, 185.6, and 189.9 F/g after heat treating at 250, 300, 350, and 400 oC, respectively. In addition to the sol-gel process, manganese oxide films were prepared by electrophoretic deposition starting from commercial-available, sol-gel, and spray pyrolysis derived powders and the specific capacitance was 201.4, 141.2, and 262.9 F/g, respectively. This indicated that the capacitive properties of manganese oxide films were influenced by its structure and surface morphology. Synchrotron X-ray absorption spectra showed that manganese oxide electrodes prepared either sol-gel or electrophoretic deposition process with different structure and morphology exhibited the same trend where the trivalent manganese was transited into tetravalent manganese after cyclic voltammetry.
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歐姿曼. "Na-intercalating manganese oxide for the supercapacitor application." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/45600172138290542776.
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CHEN, TE-WANG, and 陳德旺. "Manganese Oxide Mesoporous Sphere as Supercapacitor for Deionization." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/80755244157936838390.
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碩士國立宜蘭大學
環境工程學系碩士班
104
Recently, numerous studies have focused on water desalination by Capacitive deionization to create the advantages of low-cost, non-secondary polluted and clean water. In order to realize the situation of charged particle absorbed by electric field between two electrodes, varieties of model have been put forward. Researchers considered the material of electrode as most important factor for desalination capacity. As a trend, an increase in the capacitance of electrode results in a higher salt adsorption capacity. Activated carbon (AC) is the commonly used material, as it is the most cost efficient option and it has a high specific surface area. A few researches find that porous material modified by metal oxides could increase cell electrosorption by combined pseudocapacitance and double-layer capacitance both contribute inseparable to the total capacitance value. In this study, manganese oxide mesoporous sphere (MOS) were synthesized by a rapid AASA (Aerosol-Assisted Self Assembly) process which different from traditional process. Then we prepared film drop on titanium plate as electrode by combined porous sphere with carbon black and PTFE binder. We applied 0.8 voltage for the CDI cell and the opposed ions are forced toward the electrode surfaces. The MOS were characterized by SEM, TEM, BET, XRD, TPR and XPS for its structure and morphology. Then film were experimented for electrochemical properties by CV, CP, EIS and electrosorption. According to characterization, when the temperature of MOS calcined from 250 ℃ to 650 ℃, the crystalline structure of MOS been changed with different oxidation state. As calcined temperature equal to 250 ℃, the surface area were 102.2 (m2/g) and most of them were manganese dioxides. As temperature increased, the oxidation number of manganese ions were decreased. We could find the surface of material calcined temperature raised to 450 ℃ become sintering and converted into dimanganese trioxide. The capacitance of material also effected by calcined temperature. In conclusion, the MOS250 has maximum capacitance, stability and electrosorption were obtained for high surface area and more manganese dioxide. XPS was used to distinguish between double-layer capacitance and pseudocapacitance by electrode after eletrosorption. As a result MOS250 has both capacitance but pseudocapacitance much more than double-layer capacitance. It’s caused MOS250 have good performance in desalination.
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陳雅卿. "= Electronic structure of double-layered manganese oxide perovskites." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/38175926555642340616.
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Meena, Shanu. "Synthesis and Characterization of Gd Based Manganese Oxide." Thesis, 2015. http://ethesis.nitrkl.ac.in/7322/1/Synthesis_Meena_2015.pdf.
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In this project, we investigate the details of the structure and morphology (XRD, UV-visible spectroscopy, FESEM) of Gd0.5 Sr0.5MnO3. The sample is synthesized by wet chemical method, known as sol-gel process. The information about molecular bonding and structure is obtained from the x-ray diffractions. We also study its band gap properties from UV-Visible spectroscopy and the morphology of the material through FESEM.
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Liu, Guoliang. "Characterization of manganese-oxide perovskites, exhibiting a colossal magnetoresistance." Thesis, 2003. http://wwwlib.umi.com/cr/utexas/fullcit?p3118046.
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Yuan, Jian-Jie, and 袁薦傑. "The Preparation and Thermoelectric Properties of Calcium Manganese Oxide." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/48895655224655376684.
Full textAbstract:
碩士國立彰化師範大學
物理學系
98
This reports includes the crystal structure and high-temperature transport properties of element-doped perovskite calcium manganese oxide. Under high temperature, Calcium manganese oxide series are the most respected N-type thermoelectric materials. CaMnO3+δ exhibits a high thermoelectric power, but the electric resistivity and thermo conductivity exhibits high value as well. Hence, the thermoelectric performance (ZT) of the polycrystalline samples is small and unsuitable for practical utilization. The ZT of calcium manganese oxide would require improvement to become acceptable for practical application. It will become a promising thermoelectric material for high temperature power generation. This experiment attempts to enhance the thermoelectric properties by element doping. The samples used in this experiment includes CaMn1-ySiyO3+δ、Ca1-xBixMnO3+δ、Ca1-xBixMn1-ySiyO3+δ、Ca0.98R0.02MnO3+δ (R = Sm, Eu, Gd, Dy) and Ca1-xGdxMnO3+δ. All the samples are crystallized into orthorombic distorted perovskite structures (space group Pnma(No.62)). All the samples were prepared by conventional solid-state reaction method. The homogeneity was confirmed by X-ray diffraction (XRD), and the XRD data is used to refine the cell parameters. The electric resistivity and thermoelectric power is measure in respect of temperature from 300K to 700K. The thermal conductivity was measured by Kapton sensor at room temperature (~300K) and Mica sensor at high temperature (from 300K to 620K). The average valence of manganite and oxygen content is determined by iodometric titration. SQUID is use to measure some samples from 5K to 400K. From the SQUID data, we yield effective magnetic moment by applying Curie-Weiss law. The electric resistivity is reduces significantly and displays metallic property when Ca is substituted with Bi, Sm, Eu, Gd, or Dy. In the substitution of Si with Mn, electric resistivity data still exhibits semiconductor property. When we combine the substitution of Bi and Si with Ca and Mn, electric resistivity data differs by substitution ratio. At Ca0.98R0.02MnO3+δ (R = Sm, Eu, Gd, Dy) part, the maximum values is recorded with Dy substitution, in which the power factor (PF) was 2.217 μW/cmK2 and dimensionless figure of merit (ZT) was approximately 0.0723 at 618K. In this experiment, Ca0.95Bi0.05MnO3+δ showed the highest value recorded. The power factor (PF) was 3.122 μW/cmK2 at 620K.
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Lin, Yu-Hsun, and 林佑勳. "Applications of Manganese Oxide Containing Composite Aerogels in Supercapacitors." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/78692357690863189149.
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碩士國立清華大學
化學工程學系
98
Manganese oxide aerogels were successfully synthesized with an epoxide addition procedure by using MnCl2‧4H2O as the precursor. The as-prepared aerogels possessed the crystalline phase of hausmannite of Mn3O4 and a BET specific surface area of 79m2/g. After heat treatment at 300 oC, the aerogels gave specific capacitances (SC) of up to 122F/g in 0.5M Na2SO4 solution, at a scan rate of 25mV/s, and within the window of 0.1~0.9V vs. Ag/AgCl. The resulting cyclic voltammetry (CV) loops appeared rectangular, implying high reversibility. After 2000 cycles of CV scans, the aerogels showed excellent cycle stability, retaining at least 96% of the maximum SC value. In order to improve on the issue of low electrical conductivity of manganese oxides, tin oxide aerogels (317m2/g) and carbon aerogels (577m2/g) of high specific surface areas and better electrical conductivities were used as the porous template to accommodate the functioning manganese oxides. Manganese oxides were electrodeposited into the aerogel templates with a simple 2-electrode potentiostatic procedure operated at different potentials. These composite electrodes, possessing high electrical conductivity backbone and rich redox reactions of transition metal oxides were found promising for supercapacitors. The SC of the manganese oxide (deposited at 2V)/tin oxide aerogel composite electrode was 253F/g, a significant enhancement over that of the plain manganese oxide aerogel, mainly because of the enlarged specific surface area provided by the tin oxide aerogel template. To seek further improvement, carbon aerogels of high conductivity (0.00148Ω/□) and high surface area were used as the template for manganese oxides. The SC value of this MnOx/CA, with MnOx deposited at 1.5 V, was as high as 503F/g, and retained 99% of the maximum SC value after 6000 cycles of CV scans, indicating the further boost in SC and excellent cycle stability. The SC value of this composite electrode remained high at 243F/g even at a very high scan rate of 500mV/s, retaining 62.8% of the SC values obtained at a scan rate of 25mV/s, and achieving a high specific energy density of 21.6Wh/kg and a high specific power density of 48.5kW/kg. This work demonstrates the advantages of using composite electrodes for the next-generation supercapacitors.
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Liang, Hsu-sheng, and 梁旭昇. "Chlorobezene oxidation with ozone over supported manganese oxide catalyst." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/54747983818472470803.
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碩士國立中央大學
環境工程研究所
98
PCDD (Polychlorinated dibenzodioxin) and PCDF (Polychlorinated dibenzofuran) are commonly known as dioxins which have received great concerns due to their persistency and toxicity. In this study, chlorobenzene (CB) was employed as dioxin model molecule to evaluate the destruction behavior due to the high toxicity of dioxin. In this study, 10 wt % MnOx/SiO2 was prepared by impregnation method. The surface area of MnOx/SiO2 measured by the BET method was 286 m2/g. No distinct peaks were observed in the XRD pattern, indicating that manganese oxide was of an amorphous structure. Catalytic oxidation of gaseous chlorobenzene with ozone over 10% MnOx/SiO2 was experimentally carried out with a packed bed reactor to investigate the feasibility of the low-temperature decomposition process. The effects of reaction parameters (i.e reaction temperature, ozone concentration and space velocity (SV)) on the chlorobenzene oxidation were discussed. The conversion of chlorobenzene achieved with MnOx/SiO2 in the absence of ozone was only 2.7% at 120℃. On the other hand, the conversion increased to 90.4% over MnOx/SiO2 with 900 ppm ozone at 120℃. CB conversion slightly increases from 90.4% to 92.7% with the decrease of space velocity from 300,000 to 60,000 h-1 due to the fact that longer reaction time results in higher CB conversion. The results of the long-term operation indicate that the conversion of chlorbenzene shows a little drop from 90.8% to 79.6% after 96 h operation. At the steady state, CO and CO2 were the only carbon-containing products detected in gas streams at the outlet of the reactor. The selectivities of CO2 and CO were 58.5 and 41.5%, respectively. The average carbon and chlorine balance were 76.2 and 74.1%, respectively.
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Yu-LunLi and 黎友倫. "Development of Manganese Oxide Catalysts for HTP Monopropellant Thrusters." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/64969099701562395825.
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碩士國立成功大學
航空太空工程學系
103
Recently, hydrogen peroxide finds renewed interests and attention in space propulsion community due to the strong growing demand of non-toxic and environment-friendly “green” propellants. For monopropellant thrusters used in space propulsion applications, silver and manganese oxides are generally used as the catalyst to decompose hydrogen peroxide to generate thrust. The problem with the silver catalyst is that the melting temperature for silver is low and close to the maximum decomposition temperature of hydrogen peroxide that limits silver catalyst in very high concentration hydrogen peroxide applications. The purpose of this thesis is to re-examine the catalyst formation and fabrication process to develop the manganese oxides catalysts superior in catalytic performance and sustainable in high temperature decomposition of hydrogen peroxide for space propulsion applications. By adjusting key parameters of distinct catalyst fabrication steps such as calcination temperatures, precursors and solvents, we examine and analyze the constituents of the different resultant manganese oxides catalysts by using different instruments of SEM、XRD、EDS. The comparison and selection of the resultant manganese oxides catalysts is based on catalytic activity test in a reactor with 50% and 70% concentration H2O2 solution and the performance of the catalyst bed made of the selected catalyst is demonstrated on a 1N grade monopropellant thruster. The experimental results show that the active material load on γ-Al2O3 prepared by acetone solvent is greater than that on support prepared by using water as solvent,and it has superior uniformity of catalyst distribution on the support. The nominal catalyst content can be expressed as α-type Na0.07MnO2.05(PDF-270751) by XRD after regression analysis. The reactivity of the selected catalysts based on the decomposition of the hydrogen peroxide is found to decrease with increase of the calcination temperature of the catalyst for all the cases tested. The results of the thruster performance tests show that the selected manganese oxide catalysts can achieve comparable performance with the parameters of C* efficiency about 92.8%, the average atmospheric Isp 97.84sec, and ignition delay time about 300ms. In summary, (1) the active material loads on γ-Al2O3 prepared by acetone solvent could reach 10-15% of the total catalyst, and it is greater than the prepared by using water. (2) the nominal catalyst content is α-type Na0.07MnO2.05(PDF-270751) with t stable the oxidation state of and the average diameter of the active material about 8.023nm, (3) tetravalent manganese is more active than trivalent manganese through the activity tests, (4) the outstanding performance of catalytic bed to decompose the hydrogen peroxide is performed on the monopropellant thruster. The manganese oxides really find potential applications in space propulsion system to overcome the sintering problem from the silver.