Дисертації з теми "Molybdenum carbides"
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Clark, Christopher H. "Characterization and investigation of molybdenum carbides on activated carbon as hydrogenation catalysts." Morgantown, W. Va. : [West Virginia University Libraries], 2005. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=4281.
Title from document title page. Document formatted into pages; contains viii, 76 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 54-57).
McCauley, Robert Lowry. "The effects of molar flux, pressure, and product gases on the stability of molybdenum carbide during steam methane reforming." Online access for everyone, 2005. http://www.dissertations.wsu.edu/Thesis/Fall2005/r%5Fmccauley%5F120105.pdf.
Susanto, Benny Laurensius Materials Science & Engineering Faculty of Science UNSW. "Kinetics of carbide dissolution in chromium + molybdenum steels during oxidation." Awarded by:University of New South Wales. Materials Science and Engineering, 2004. http://handle.unsw.edu.au/1959.4/19385.
Perret, Noemie. "New catalyst formulations based on gold and molybdenum nitrides and carbides : application in selective hydrogenation." Thesis, Heriot-Watt University, 2012. http://hdl.handle.net/10399/2657.
Cunha, Adilto Pereira Andrade 1981. "Caracterização mecânica e microestrutural de aços médio carbono microligados ao nióbio e molibdênio." [s.n.], 2013. http://repositorio.unicamp.br/jspui/handle/REPOSIP/265015.
Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica
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Resumo: Neste trabalho foi estudada a influência da adição de molibdênio e nióbio na microestrutura e propriedades mecânicas de aços com 0,5 e 0,6 %C, utilizado na fabricação de rodas ferroviárias. A deformação dos aços foi aplicada através da laminação, em escala de laboratório, simulando o forjamento no processo real de fabricação. As amostras foram aquecidas a 1250 °C para solubilização do nióbio, sendo então laminadas em 4 passes, a partir de 1200 °C, sofrendo uma deformação total (redução em altura) de 67%, seguida de resfriamento ao ar. Posteriormente, os aços C5 e C5Nb foram submetidos a um tratamento térmico de têmpera e revenimento. Foram analisadas amostras dos aços por microscopia óptica, eletrônica de varredura e transmissão e também foram realizados ensaios mecânicos em todas as condições. Após a laminação entre 1200 e 1120 °C, observou-se que a adição de molibdênio e nióbio promoveu um aumento da resistência mecânica em 171 e 119 MPa no limite de escoamento e 61 e 66 MPa no limite de resistência à tração, nos aços C5Nb e C6Nb, respectivamente, devido à precipitação de carbonetos de nióbio, mantendo a mesma ductilidade e tenacidade para o aço C5Nb, mas houve uma queda dessas propriedades para os aço C6Nb. Após a laminação com posterior têmpera e revenimento a 500°C, simulando o mesmo tratamento feito na roda ferroviária, o aço C5 apresentou dureza, resistência mecânica e alongamento iguais à do aço da MWL, porém com redução de área e energia absorvida maiores que o aço da MWL. O aço C5Nb apresentou maiores valores de resistência mecânica, ductilidade e tenacidade que o aço da MWL, o que demonstra seu potencial para melhorar a qualidade das rodas ferroviárias atualmente produzidas
Abstract: The influence of molybdenum and niobium addition on the microstructure and mechanical properties of 0,5 and 0,6 %C steels used in railway wheels was studied. The deformation was applied by rolling, in a thermo mechanical processing laboratory, simulating the forging in the real process of manufacture. The samples were heated to 1250 °C to ensure dissolution of niobium and hot rolled in four passes, starting at 1200 °C, undergoing a total reduction of 67%, followed by air cooling. Steels were water quenched and tempered (heat treatment). Steel samples, before and after rolling and heat treated were analyzed by optical and scanning electron microscopy. Mechanical tests were performed on the all conditions. After rolling between 1200 and 1120 ° C, it was found that the addition of molybdenum and niobium resulted in an increase of mechanical strength at 171 and 119 MPa in yield strength and 61 and 66 MPa in tensile strength, respect due to precipitation of niobium carbides, while maintaining the same ductility and toughness for C5Nb steel, but there was a decrease of these properties for C6Nb. After rolling with subsequent quenching and tempering at 500 ° C, simulating the same treatment done in the railway wheel, steel C5 showed the same toughness, strength and elongation in comparison with MWL rail wheels steel, but with reduced area and absorbed energy greater than the MWL steel. C5Nb steel showed higher strength, ductility and toughness than MWL steel, which demonstrates its potential to improve the quality of railway wheels currently produced
Doutorado
Materiais e Processos de Fabricação
Doutor em Engenharia Mecânica
Posada, Pérez Sergio. "Heterogeneous catalysis of green chemistry reactions on molybdenum carbide based catalysts." Doctoral thesis, Universitat de Barcelona, 2018. http://hdl.handle.net/10803/552405.
En aquesta tesi es mostra un treball computacional sobre l'ús de catalitzadors econòmics per a la conversió de CO2, un perillós gas d'efecte hivernacle i també per a la producció d'hidrogen, el combustible del futur. En la recerca actual de nous catalitzadors, els carburs de metalls de transició (TMC) han sorgit com una alternativa atractiva pel el seu baix cost i per exhibir excel·lents propietats físiques i químiques. En aquest treball utilitzarem com a catalitzadors les superfícies cúbica δ-MoC (001) i ortoròmbica β-Mo2C (001). L'adsorció de la molècula de CO2 mostra que ambdues superfícies són capaces d'activar i doblegar la molècula. La superfície β-Mo2C (001) és capaç de dissociar fàcilment la molècula de CO2, mentre que la superfície δ-MoC (001) activa CO2 però no la dissocia. Els experiments realitzats pel grup del Dr. Jose Rodriguez van revelar que el CO i el metà són els principals productes de la hidrogenació de CO2 utilitzant β-Mo2C (001) com a catalitzador, i la quantitat de metanol és menor. D'altra banda, només es produeixen CO i metanol utilitzant δ-MoC (001). La deposició de partícules de coure a les superfícies del carbur augmenta dràsticament l'activitat dels catalitzadors, cosa que es va demostrar mitjançant càlculs teòrics. A la superfície β-Mo2C, la quantitat de CO i metanol augmenten mentre que la quantitat de metà disminueix. D'altra banda, la deposició de coure a δ-MoC (001) augmenta molt la quantitat de CO i metanol. En resum, el nostre estudi proposa el Cu/δ-MoC com a prometedor catalitzador de la hidrogenació de CO2 a causa de la seva activitat (la quantitat de productes és superior a la resta de TMCS, metalls i el model de catalitzadors comercials), selectivitat (només el CO i el metanol es produeixen) i l'estabilitat (aquests catalitzadors no es desactiven per la deposició d'oxigen). Tenint en compte els resultats previs, es va proposar la deposició d'or en la superfície δ-MoC per a la producció d'hidrogen. Els càlculs teòrics demostren que la superfície δ-MoC (001) no és un bon catalitzador per WGS, però la deposició dels clústers d'or canvia el mecanisme de reacció i augmenta la quantitat d'H2 produïda.
Fonseca, Solange Tamara da 1978. "Efeito de adições de vanádio, nióbio e molibdênio na estrutura e propriedades mecânicas de aços com 0,7 % C utilizados na fabricação de rodas ferroviárias." [s.n.], 2015. http://repositorio.unicamp.br/jspui/handle/REPOSIP/265830.
Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica
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Resumo: Uma das maneiras de se reduzir os custos no transporte de cargas é aumentando a quantidade de carga transportada por vagão, isto eleva a tensão no eixo do vagão e, consequentemente, a roda deve possuir maior dureza sem perda da tenacidade para suportar o desgaste. Para atingir os níveis de dureza necessários estão sendo desenvolvidas rodas ferroviárias com aços microligados que são definidos como aços carbono-manganês contendo pequenos teores (menores que 0,5% em massa) de elementos de liga, que são fortes formadores de carbonetos como o nióbio (Nb), vanádio (V), molibdênio (Mo) e titânio. Em 2008, a MWL do Brasil iniciou o desenvolvimento de rodas ferroviárias fabricadas com aços microligados, e a partir de 2012, com a colaboração da EPUSP foi necessário o desenvolvimento de uma máquina de ensaio de desgaste tipo disco contra disco que atendesse as especificações da norma AAR (Association of American Railroads). Além disso, havia interesse em se conhecer o comportamento desses aços, sendo assim, seria necessário obter as curvas de resfriamento contínuo (CRC) dos mesmos. A análise destas mostrou que a adição dos elementos microligantes refinou o grão austenítico por formação de finos carbonetos de Nb e V, retardou a formação de ferrita e perlita, o que reduziu o espaçamento interlamelar da perlita; e elevou a temperabilidade dos aços. Entretanto, a adição de microligantes não alterou as temperaturas de início de formação de martensita, mas melhorou a temperabilidade. A formação de martensita não foi finalizada até a temperatura ambiente e todos os aços apresentaram austenita retida junto com a martensita. A análise de corpos de prova retirados das pistas de rolamento das rodas ferroviárias prontas para uso, com estrutura ferrítica-perlítica, revelou que o aço ao V apresentou os melhores resultados em todos os ensaios (tração na temperatura ambiente e 540 ºC, energia absorvida no ensaio Charpy e KIC) quando comparado ao aço sem microligantes ou com a adição de Nb+Mo. O melhor desempenho do aço ao V foi atribuído ao seu menor tamanho de grão austenítico e espaçamento interlamelar da perlita mais refinado. No ensaio de desgaste por deslizamento, a perda de massa foi maior no aço Nb. O primeiro protótipo construído da máquina de desgaste tipo disco contra disco forneceu resultados confiáveis até 250.000 ciclos, não atingindo o valor minímo especificado pela AAR. Entretanto a experiência adquirida foi essencial para projetar um novo protótipo que está em comissionamento
Abstract: One of the main strategies to reduce cost in load transportation is through the increase of the load transported a railroad car. This increase of tension in the wagons axes, require wheels with higher hardness but without loss of ductility and toughness. Thus, to achieve the required levels of hardness, the developments are now focusing on railway wheels composed by microalloyed steels that are defined as carbon-manganese steels containing a small amount (less than 0.5% by mass) of strong carbide-forming elements such as niobium (Nb), vanadium (V), molybdenum (Mo) and/or titanium. The MWL Brazil began in 2008, together with Unicamp, a research project on the development of railway wheel made of microalloyed steel and, later on 2012, EPUSP joined to the project reinforcing the importance of the project. During this work, project developed a disk-on-disk wear test machine that would attend the specifications of the standard AAR (Association of American Railroads). Besides, there was also an interest on further knowing the behavior of these steels, that is, it would be necessary to obtain the continuous cooling curves (CCC). In this work, the analysis of CCC showed that the addition of microalloying elements contributed in refining the austenitic grain size due to fine Nb and V carbides formation; delayed the formation of ferrite and pearlite, which reduced the interlamellar spacing of pearlite; and increased the hardenability of steels. However, the addition of microalloying did not change the starting martensite formation temperature, but increased the hardenability. It was also observed that the formation of martensite was not finished at room temperature and all studied steels presented retained austenite. The analysis of samples taken from the tread of railway wheels, with ferritic-pearlitic structure revealed that the vanadium steel showed the best results in all tests of strength (at room temperature and 540 °C), K1C and Charpy test if compared to steels without microalloying or with the addition of Nb+Mo. The superior performance vanadium steel was attributed to the smallest austenite grain size and the finest interlamellar spacing of the pearlite. In the wear test, the weight loss was greater in the niobium microalloyed steel. The developed prototype of the disk-on-disk wear test machine only provided reliable results up to 250,000 cycles; it not reached the minimum value specified by the AAR. However, the experience was essential to enhance a new prototype that is commissioning
Doutorado
Materiais e Processos de Fabricação
Doutora em Engenharia Mecânica
Sosa, Letícia. "Hydrodésoxygénation du furfural en 2-methylfurane à l’aide de catalyseurs à base de carbures de molybdène." Electronic Thesis or Diss., Centrale Lille Institut, 2023. http://www.theses.fr/2023CLIL0004.
Molybdenum carbides were synthesized, characterized, and evaluated for the hydrodeoxygenation reaction of furfural to 2-methylfuran at 30 bar of H2 and 200 °C in 2-butanol and cyclopentyl methyl ether. In this thesis, several factors concerning the nature of carbides were evaluated: (i) the effect of crystallographic phases (α-MoC and β-Mo2C); (ii) the effect of the addition of Ni and Cu promoters; (iii) the effect of passivation and reactivation; (iv) effect of support (SiO2, TiO2, ZrO2, ZSM-5). The results show that the β-Mo2C phase is more active than the α-MoC phase, but the same distribution of products is observed in iso-conversion. The addition of Ni and Cu had a positive and negative effect, respectively, on the carbide activity. Different degrees of oxidation occurred during the passivation of carbides, which was related to their dispersion and reactivation did not regenerate them. The different supports mainly affected the first step of the reaction, as well as the final state of the Mo carbides
Murugappan, Karthick. "Molybdenum trioxide and molybdenum carbide as promising hydrodeoxygenation catalysts for biomass conversion." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/111404.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 171-176).
Growing concerns due to rising CO2 emissions have made biomass an indispensable source of renewable fuels and chemicals. However, biomass inherently has high oxygen content, which translates to low energy density, thereby necessitating a deoxygenation step before being utilized as fuels. Recently, MoO3 and Mo2C have emerged as promising earth-abundant cheap catalysts that perform hydrodeoxygenation (HDO) at relatively low temperatures ( 673 K) and ambient H2 pressures wherein oxygen is selectively removed as water. However, there exists a significant knowledge gap in understanding the stability and the active phases responsible for HDO of these catalysts. Furthermore, their applicability for real biomass conversions has not been largely demonstrated. In this thesis, first, HDO of m-cresol, a biomass-derived model compound, is investigated over bulk and supported MoO 3 catalysts. Detailed reactivity and characterization studies reveal that Mo5+ species plays a critical role during HDO. Specifically, TiO2 and ZrO2 are identified as ideal supports as they feature superior HDO reactivity and stability over bulk MoO3 by stabilizing intermediate Mo oxidation states (i.e. Mo5+) while bulk MoO 3 over-reduces to inactive metallic Mo. Translating from model compound studies, supported MoO3 catalysts are demonstrated to be effective in converting biomass (pine) pyrolysis vapors to hydrocarbons (ca. 30 % yield). In comparison with MoO 3, Mo2C is significantly more stable and selective for HDO of 4-methylanisole to toluene under identical reaction conditions. Mo2C predominantly breaks the stronger phenolic C-0 bond while MoO 3 also breaks the weaker aliphatic C-0 bond, likely due to the presence of Bronsted acid sites. To gain insights into the surface active sites, operando near-ambient XPS is employed during HDO and this technique revealed that HDO seems to operate via distinct active sites over both these materials. Finally, Mo2C is shown to be effective in upgrading real lignin streams to a single product propylbenzene, a precursor for renewable polymer. Overall, this thesis demonstrates the applicability of MoO3 and Mo2C in real biomass conversions and provides insights on the working nature of these catalysts, which will enable the design of more effective HDO catalysts.
by Karthick Murugappan.
Ph. D.
Yu, Jenwei Roscoe. "Methane activation over molybdenum disulfide, molybdenum carbide, and silver(110). Molecular orbital theory." Case Western Reserve University School of Graduate Studies / OhioLINK, 1990. http://rave.ohiolink.edu/etdc/view?acc_num=case1059138320.
Lugge, John J. "Molybdenum carbide synthesis using plasmas for fuel cells." Monterey, California: Naval Postgraduate School, 2013. http://hdl.handle.net/10945/34700.
Currently, carbon is the preferred support material for platinum catalyst particles used in polymer electrolyte fuel cells (PEFCs). Carbon possesses qualities needed for a fuel cell catalyst: high surface area and conductivity, but is unacceptable as it is prone to oxidization by carbon dioxide in the fuel cell environment. Molybdenum Carbides is known to have the required conductivity. However, making Mo2C with sufficient surface area and with stabilized platinum remains a materials challenge. In this work a novel approach, a variation on the Aerosol-Through-Plasma (ATP) method was employed for making Mo2C with high surface area and stable supported platinum particles. An ammonium molybdate precursor was processed through different ATP conditions to generate the catalyst. These particles were then characterized using X-ray diffraction and SEM techniques in order to produce a support material with the highest concentration of Mo2C. Using the ideal conditions for the ATP, precursor was loaded with platinum and then processed through the ATP. This sample was then characterized using X-ray and SEM techniques to insure that the material was suitable prior to testing the electrochemical properties under PEFC operating conditions. The results were then compared to other leading support catalysis.
Hantzer, Sylvain. "Nouveaux materiaux pour la reaction d'hydrodesulfuration (hds)." Université Louis Pasteur (Strasbourg) (1971-2008), 1988. http://www.theses.fr/1988STR13120.
Al-Megren, Hamid. "Hydrodenitrogenation of pyridine over bulk and supported molybdenum carbide." Thesis, University of Oxford, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.249636.
Naredla, Sai Bhargav. "Electrical Properties of Molybdenum Silicon Carbide Schottky Barrier Diodes." Youngstown State University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ysu155901806279725.
Martinelli, Antonio Eduardo. "Diffusion bonding of silicon carbide and silicone nitride to molybdenum." Thesis, McGill University, 1995. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=40191.
SiC was solid-state bonded to Mo at temperatures ranging from 1000$ sp circ$C to 1700$ sp circ$C. Diffusion of Si and C into Mo resulted in a reaction layer containing two main phases: $ rm Mo sb5Si sb3$ and Mo$ sb2$C. At temperatures higher than 1400$ sp circ$C diffusion of C into $ rm Mo sb5Si sb3$ stabilized a ternary phase of composition $ rm Mo sb5Si sb3$C. At 1700$ sp circ$C, the formation of MoC$ rm sb{1-x}$ was observed as a consequence of bulk diffusion of C into Mo$ sb2$C. A maximum average shear strength of 50 MPa was obtained for samples hot-pressed at 1400$ sp circ$C for 1 hour. Higher temperatures and longer times contributed to a reduction in the shear strength of the joints, due to the excessive growth of the interfacial reaction layer. $ rm Si sb3N sb4$ was joined to Mo in vacuum and nitrogen, at temperatures between 1000$ sp circ$C and 1800$ sp circ$C, for times varying from 15 minutes to 4 hours. Dissociation of $ rm Si sb3N sb4$ and diffusion of Si into Mo resulted in the formation of a reaction layer consisting, initially, of $ rm Mo sb3$Si. At 1600$ sp circ$C (in vacuum) Mo$ sb3$Si was partially transformed into $ rm Mo sb5Si sb3$ by diffusion of Si into the original silicide, and at higher temperatures, this transformation progressed extensively within the reaction zone. Residual N$ sb2$ gas, which originated from the decomposition of $ rm Si sb3N sb4,$ dissolved in the Mo, however, most of the gas escaped during bonding or remained trapped at the original $ rm Si sb3N sb4$-Mo interface, resulting in the formation of a porous layer. Joining in N$ sb2$ increased the stability of $ rm Si sb3N sb4,$ affecting the kinetics of the diffusion bonding process. The bonding environment did not affect the composition and morphology of the interfaces for the partial pressures of N$ sb2$ used. A maximum average shear strength of 57 MPa was obtained for samples hot-pressed in vacuum at 1400$ sp circ$C for 1 hour.
Oloye, Femi Francis. "Synthesis and characterisation of zirconia supported molybdenum oxide and molybdenum carbide catalysts for hydroconversion of n-heptane." Thesis, University of Aberdeen, 2016. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=230933.
Abou, Hamdan Marwa. "Hydrogenation of succinic acid and carbon dioxide over molybdenum carbide catalysts." Thesis, Lyon, 2019. http://www.theses.fr/2019LYSE1065.
This work focuses on the synthesis of supported molybdenum carbides and evaluating their catalytic performance in succinic acid hydrogenation reactions in aqueous phase using batch reactor and carbon dioxide hydrogenation in gas phase using continuous flow reactor. The catalysts were prepared by the temperature programmed reduction carburization method, where the parameters were modified leading to different molybdenum to carbon ratios. The different catalysts tested were active in converting succinic acid to gamma butyrolctone and more remarkably butyric acid which is not reported in significant quantities in this reaction with precious metal based catalysts. The catalysts containing more carbon contents that were prepared by increasing the gas hourly space velocity showed higher activity in converting succinic acid and higher selectivity to butyric acid. The intermediates were then converted to tetrahydrofuran, butanol, 1,4-butanediol and butane gas. The deactivation observed while recycling the catalyst was mainly attributed to a decrease in the amounts of carbidic molybdenum and carbidic carbon, as demonstrated by XPS analysis. Preliminary tests for these catalysts in carbon dioxide hydrogenation showed that they functioned mainly as reverse water gas shift catalysts, and the excess of carbon hinders the catalytic activity in an opposite manner of the reaction in aqueous phase. The support seems playing a role in the reactivity of the catalysts, carbon dioxide conversion as well as methane and methanol selectivity increased in the order: molybdenum carbide supported on DT51 TiO2 > P25 TiO2 ˜ ZrO2
Björklund, Kajsa. "Microfabrication of Tungsten, Molybdenum and Tungsten Carbide Rods by Laser-Assisted CVD." Doctoral thesis, Uppsala University, Department of Materials Chemistry, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-1593.
Thin films of refractory metals and carbides have been studied extensively over many years because of their wide range of application. The two major techniques used are Chemical Vapour Deposition (CVD) and Physical Vapour Deposition (PVD). These can result in the deposition of two-dimensional blanket or patterned thin films. Laser-assisted Chemical Vapour Deposition (LCVD) can provide a maskless alternative for localised deposition in two and three dimensions. This thesis describes LCVD of micrometer-sized tungsten, molybdenum and tungsten carbide rods. The kinetics, phase composition and microstructure have been studied as a function of in situ measured laser induced deposition temperature.
Tungsten and molybdenum rods were deposited by hydrogen reduction of their corresponding hexafluorides, WF6 and MoF6, respectively. Single crystal and polycrystalline tungsten rods were obtained, depending on the H2/WF6 molar ratio and deposition temperature. The molybdenum rods were either single crystals or dendritic in form depending on experimental conditions. The field emission characteristics of the tungsten single crystals were investigated. The results showed LCVD to be a potential fabrication technique for field emitting cathodes.
Nanocrystalline tungsten carbide rods were deposited from WF6, C2H4 and H2. TEM analysis showed that the carbide rods exhibited a layered structure in terms of phase composition and grain size as a result of the temperature gradient induced by the laser beam. With decreasing WF6/C2H4 molar ratio, the carbon content in the rods increased and the phase composition changed from W/W2C to WC/WC1-x and finally to WC1-x/C.
Björklund, Kajsa. "Microfabrication of tungsten, molybdenum and tungsten carbide rods by laser-assisted CVD /." Uppsala : Acta Universitatis Upsaliensis : Univ.-bibl. [distributör], 2001. http://publications.uu.se/theses/91-554-5197-7/.
St, Clair Todd P. "Characterization and Reactivity of Mo2C." Diss., Virginia Tech, 1998. http://hdl.handle.net/10919/40502.
Ph. D.
Lucazeau, Emmanuelle. "Contribution à l'étude de la formation du carbure de molybdène sur le diamant." Grenoble INPG, 1997. http://www.theses.fr/1997INPG0110.
Darujati, Anna Rini Sekar. "Oxidation stability and activity of bulk, supported and promoted molybdenum carbide catalysts for methane reforming." Online access for everyone, 2005. http://www.dissertations.wsu.edu/Dissertations/Spring2005/A%5FDarujati%5F050405.pdf.
Hanif, Ahmad. "Partial oxidation and COâ†2 reforming of methane to valuable products over molybdenum and tunsten carbide." Thesis, University of Oxford, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.343512.
Лалетіна, К. І., та Б. М. Ярмош. "Кристалічна структура та електрофізичні властивості плівок карбідів молібдену". Thesis, Видавництво СумДУ, 2008. http://essuir.sumdu.edu.ua/handle/123456789/4420.
Zhang, Tianyu. "DENSITY FUNCTIONAL THEORY STUDIES ON THE STRUCTURAL EVOLUTION AND CATALYTIC REACTIVITY OF MOLYBDENUM-BASED CATALYSTS FOR METHANE CONVERSION." OpenSIUC, 2019. https://opensiuc.lib.siu.edu/dissertations/1768.
Kong, Jia Huey. "SINTERING PROPERTIES OF TiC-Ni-Mo CERMET USING NANOSIZED TiC POWDERS." OpenSIUC, 2016. https://opensiuc.lib.siu.edu/theses/1898.
Okatsu, Hiroko. "New synthetic methods to alter catalytic properties of supported K/MoS₂ catalysts for syngas conversion to higher alcohols." Thesis, Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/48996.
Li, Liwei. "Density functional theory study of alcohol synthesis reactions on alkali-promoted Mo2C catalysts." Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/53456.
Holl, Tobias [Verfasser], and Jens [Akademischer Betreuer] Weitkamp. "Competitive hydroconversion of decalin and n-decane on noble-metal catalysts and the evaluation of molybdenum carbide as ring-opening catalyst / Tobias Holl. Betreuer: Jens Weitkamp." Stuttgart : Universitätsbibliothek der Universität Stuttgart, 2014. http://d-nb.info/1049688864/34.
Buckley, James. "The manufacture and characterisation of composite nuclear fuel for improved in-reactor performance." Thesis, University of Manchester, 2017. https://www.research.manchester.ac.uk/portal/en/theses/the-manufacture-and-characterisation-of-composite-nuclear-fuel-for-improved-inreactor-performance(b5ea0339-7c5b-46d2-a696-743007b9e94b).html.
Strahin, Brandon L. "The Effect of Engineered Surfaces on the Mechanical Properties of Tool Steels Used for Industrial Cutting Tools." University of Akron / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=akron1506692623324192.
Trueman, Anthony Roger. "Characterization and corrosion studies of high carbon tool steel/tungsten carbide metal matrix composites." Thesis, Queensland University of Technology, 1999.
Kolb, Veronika [Verfasser], Andreas [Akademischer Betreuer] Jess, and Bastian [Gutachter] Etzold. "Synthesis of a Molybdenum Carbide Catalyst for the Application in the Reductive Carbonyl Coupling of trans-Cinnamaldehyde to the all-trans Polyene Diphenyl-hexatriene / Veronika Kolb ; Gutachter: Bastian Etzold ; Betreuer: Andreas Jess." Erlangen : Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 2018. http://d-nb.info/1172072450/34.
Pasqualeti, Aniélli Martini. "Eletrocatalisadores formados por nitretos, carbetos e óxidos metálicos para o eletrodo de oxigênio." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/75/75134/tde-14062017-102848/.
The development of conductive electrocatalysts with high activity for the oxygen reduction and evolution reactions (ORR and OER) is of extremely importance for devices that electroconvert energy, such as fuel cells and electrolizers, which work in alkaline and acid media. A substantial amount of metals can be employed in alkaline electrolytes once the latter do not require the use of noble metals. The acid medium asks for stable materials, since they are exposed to a high oxidative environment and potentials during the start-up/shutdown events of the device. On the base of these facts, this research work has been divided into three parts: Part I - bifunctional electrocatalysts studies for the ORR and OER in alkaline electrolyte, the materials were composed of spinel manganese-cobalt oxide combined with gold nanoparticles (MnCo2O4/Au). Part II - studies of alternative electrocatalysts for the ORR in acid electrolyte, which included molybdenum carbides and nitrides (Mo2C-MoN), and tantalum oxynitrides (Ta-ON). Part III - alternative supports to the carbon for the ORR in acid electrolyte, which included tantalum and titanium carbonitrides (Ta-CN and Ti-CN). The results for MnCo2O4/Au, in Part I, showed that the addition of gold on the surface of the oxide improved the latter activity for both reactions. The combination of conductive nanoparticles (gold) with active, but non-conductive, nanoparticles (MnCo2O4) seems promising for the development of active electrocatalysts for the ORR and OER. In Part II, the materials composed of Mo2C-MoN were synthesized through carbon and nitrogen insertion, in a high temperature heat treatment, in the presence of Vulcan carbon and NH3. Among the gotten materials, the so called MoN + Mo2C (molybdate) showed the better electrocatalytic activity for the ORR, which could be attributed to its smaller crystallite size and the greater amount of its MoN phase, along with the synergistic effect between MoN and Mo2C. In this way, tantalum oxynitrides materials were obtained via a urea synthesis. The catalyst referred to as Ti-Ta-ON showed the better ORR activity among all the others studied oxynitrides materials. In Part III, besides the activity for the ORR of platinum supported on titanium carbonitride (Pt/Ti-CN) was similar to the activity of platinum supported on carbon (Pt/C), Pt/Ti-CN was also more stable than the latter, after the stability tests.
Heckman, Elizabeth Pierce. "Functionalizing Ceramic Matrix Composites by the Integration of a Metallic Substructure with Comparable Feature Size." Wright State University / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=wright1621451032485832.
Gomes, Kalyanne Keyly Pereira. "S?ntese e caracteriza??o do carbeto de molibd?nio nanoestruturado para fins catal?ticos na rea??o de oxida??o parcial do metano." Universidade Federal do Rio Grande do Norte, 2006. http://repositorio.ufrn.br:8080/jspui/handle/123456789/15789.
Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico
The nanostructures materials are characterized to have particle size smaller than 100 nm and could reach 1 nm. Due to the extremely reduced dimensions of the grains, the properties of these materials are significantly modified relatively when compared with the conventional materials. In the present work was accomplished a study and characterization of the molybdenum carbide, seeking obtain it with particles size in the nanometers order and evaluate its potential as catalyst in the reaction of partial methane oxidation. The method used for obtaining the molybdenum carbide was starting from the precursor ammonium heptamolybdate of that was developed in split into two oven, in reactor of fixed bed, with at a heating rate of 5?C/min, in a flow of methane and hydrogen whose flow was of 15L/h with 5% of methane for all of the samples. The studied temperatures were 350, 500, 600, 650, 660, 675 and 700?C and were conducted for 0, 60, 120 and 180 minutes, and the percent amount and the crystallite size of the intermediate phases were determined by the Rietveld refinement method. The carbide obtained at 660?C for 3 hours of reaction showed the best results, 24 nm. Certain the best synthesis condition, a passivating study was accomplished, in these conditions, to verify the stability of the carbide when exposed to the air. The molybdenum carbide was characterized by SEM, TEM, elemental analysis, ICP-AES, TG in atmosphere of hydrogen and TPR. Through the elemental analysis and ICP-AES the presence carbon load was verified. TG in atmosphere of hydrogen proved that is necessary the passivating of the molybdenum carbide, because occur oxidation in room temperature. The catalytic test was accomplished in the plant of Fischer-Tropsch of CTGAS, that is composed of a reactor of fixed bed. Already the catalytic test showed that the carbide presents activity for partial oxidation, but the operational conditions should be adjusted to improve the conversion
Os materiais nanoestruturados s?o caracterizados por terem um tamanho de cristalito inferior a 100 nm podendo atingir 1 nm. Devido ?s dimens?es extremamente reduzidas dos cristalitos, as propriedades destes materiais s?o significativamente modificadas relativamente ?s dos materiais convencionais. No presente trabalho foi realizado um estudo de s?ntese e caracteriza??o do carbeto de molibd?nio, visando obt?-lo com tamanho de part?culas na ordem de nan?metros e avaliar seu potencial como catalisador na rea??o de oxida??o parcial do metano. O m?todo utilizado para obten??o do carbeto de molibd?nio foi a partir do precursor heptamolibdato de am?nio que foi desenvolvida em forno bipartido, em reator de leito fixo, com uma taxa de aquecimento de 5?C/min, em um fluxo de metano e hidrog?nio cuja vaz?o foi de 15L/h com 5% de metano para todos os ensaios. As temperaturas estudadas foram 350, 500, 600, 650, 660, 675 e 700?C e nos tempos de isoterma de 0, 60, 120 e 180 minutos, sendo que a determina??o das fases presentes, estrutura cristalina e tamanho de cristalitos foram obtidos por refinamento de estrutura pelo m?todo de Rietveld. O carbeto obtido a 660?C e 3 horas de rea??o foi o que apresentou menor tamanho de cristalito 24 nm. Determinada a melhor condi??o de s?ntese foi realizado um estudo de passivac?o, nestas condi??es, para verificar a estabilidade do carbeto ao ser exposto ao ar. O carbeto de molibd?nio foi caracterizado por MEV, MET, an?lise elementar, ICP-AES, TG em atmosfera de hidrog?nio e RTP. Atrav?s da an?lise elementar e ICP-AES foi verificada a presen?a de carbono livre. A TG em atmosfera de hidrog?nio comprovou que ? necess?ria a passivac?o do carbeto de molibd?nio, pois ele ? oxidado em temperatura ambiente. O teste catal?tico foi realizado na planta semipiloto de Fischer-Tropsch do CTGAS, que ? composta de um reator de leito fixo. O teste catal?tico mostrou que o carbeto apresenta atividade para oxida??o parcial, mas as condi??es operacionais devem ser ajustadas para melhorar a convers?o
Susanto, Laurensius Benny. "Kinetics of carbide dissolution in chromium + molybdenum steels during oxidation /." 2004. http://www.library.unsw.edu.au/~thesis/adt-NUN/public/adt-NUN20040817.151942/index.html.
Tsai, Chih-yao, and 蔡智堯. "High Silicon Molybdenum Ductile Iron Differential Scanning Calorimetry and Eutectic Carbide M6C Growth Morphology." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/18390124425505149259.
國立臺灣科技大學
機械工程系
101
Ductile iron, with superior mechanical properties, has been applied in various industrial fields; high silicon ductile iron has a good resistance to high temperature oxidation, but with the adding of molybdenum elements will result in the increasing of high temperature strength. In this paper, using a water-cooled copper mold to achieve unidirectional solidification of high silicon molybdenum ductile iron castings, quality of spheroidal graphite and microstructure of eutectic carbides are presented. Thermal analysis of the casting by using Differential Scanning Calorimetry (DSC) analysis was conducted to calculate value of latent heat of this grade of ductile iron. Electrolytic deep etching technique was used to study the stereo structure of fish-bone M6C structure in the eutectic carbide. The Results shows regardless of the cooling rate is high or low, fish bone-like eutectic carbides appears between grain boundaries, at that vicinity which precipitates with tiny granular carbide; several stereo morphologies of this eutectic carbides were studied and based on that a growth model is proposed in this thesis; DSC analysis of high silicon molybdenum ductile iron in the heating and cooling process latent heat average value with the literature is equivalent.
Liu, Bo-Liang, and 劉柏良. "Production of Bio-Oil by Hydrocracking of Tung Oil with Molybdenum Carbide Catalyst in Batch System." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/hw6de5.
國立臺灣大學
環境工程學研究所
105
This study took advantages of using self-manufactured catalysts which were made by adding Mo2C on the surface of γ-Al2O3 particles to conduct the catalytic hydrocracking of tung oil. Tung oil was converted to bio-fuel oil (BFO) as an alternative of aviation fuels or fuel oils. The batch system was designed for the catalytic hydrocracking with a removal packed bed filled with catalyst at a present temperature. By varying experimental conditions, this study was performed to investigate the effects of reaction temperature (T), hydrogen pressure (PH2), holding time (t), types of catalysts, amount of catalyst added (MC), volume of raw tung oil (VLO), and two-stage reaction on the system performances. These include yields of the produced BFOs (YBFO) and their characteristics, such as acid value (AV), iodine value (IV), density (ρLO), heating value (HV), distribution of carbon numbers, and content of (MC1C9), C1~C9 elemental composition. In the same time, products of solid and gas were also analyzed for the related characteristics. The study consists of four parts. The first part was the development of method for preparation of Mo2C based catalysts. The second part was catalytic cracking of tung oil with different reaction temperatures and catalysts (γ-Al2O3 and Mo2C/γ-Al2O3). For the third part, direct cracking of tung oil under different nitrogen pressures was conducted. The forth part was catalytic hydrocracking of raw tung oil with different hydrogen pressures, holding times, volumes of raw tung oil, amounts of catalyst added, and types of processes with one or two stages of reactions. The results showed that tung oil is mainly composed of C16 ~ C22 unsaturated fatty acids. In the catalytic cracking with Mo2C/γ-Al2O3, it achieved MC1C9 = 73 wt%, HV = 47 MJ/kg, and YBFO = 65 vol% at 623 K, 100 psig Ar, 20 min, and MC = 1 wt%. For the direct cracking, the higher the nitrogen pressure, the better the effect of cracking giving higher MC1C9 and HV. At 623 K, 100 psig N2, and 20 min, MC1C9 in BFO was 66 wt% and HV and YBFO of BFO were 58 MJ/kg and 78 vol%, respectively. In the catalytic hydrocracking test, an increasing of catalyst reduced the oxygen content while enhanced the heating value of BFO. At 623 K, 100 psig H2, 40 min, and MC = 5wt%, the oxygen content was 1.5wt%, while MC1C9 = 82 wt%, HV = 38 MJ / kg, and YBFO = 53 vol%. In the stage-wise catalytic hydrocracking , HV and YBFO of BFO of the two-stage reaction were moderate while with high MC1C9. If applying one stage reaction at 623 K, 100 psig H2, 40 min, and MC = 1 wt%, values of MC1C9, HV, and YBFO of BFO were 76 wt%, 34 MJ/kg, and 65 vol%, respectively. For the two-stage reaction, at 623 K, 100 psig N2 (20 min, first stage), 100 psig H2 (40 min, second stage), and MC = 1 wt%, the values of MC1C9, HV, and YBFO were 83 wt%, 30 MJ/kg, and 52 vol%, respectively. For the case with highest overall performance index (PIt) of 0.80 at 623 K, 100 psig H2, 20 min, and MC = 1 wt%, the BFO had MC1C9 = 73 wt%, HV = 54 MJ/kg, and YBFO = 67 vol% with the AV and HV satisfying with the standards of aviation fuel oil. Further, from the results of species analysis, it was found that there were C7 ~ C17 straight chain alkanes in the products. Thus, it is feasible to produce the available BFO via the catalytic hydrocracking used in this study. Therefore, by fractionating the BFO, it can be blended in aviation fuel or gasoline or used directly as fuel oil.
Das, Debanjan. "New Avenues to Transition Metal-Based Water Splitting Electrocatalysts." Thesis, 2019. https://etd.iisc.ac.in/handle/2005/4399.