CuNi nanoparticles were synthesized using a new polyol synthesis method. Three different CuxNi1-x catalysts were synthesized where x = 20, 50 and 80. The nanoparticles were deposited on carbon, C, gamma-alumina, γ-Al2O3, yttria-stabilized zirconia, YSZ, and samariumdoped ceria, SDC. Each set of catalysts was tested using the Reverse Water Gas Shift, RWGS, reaction under atmospheric pressure and at temperatures ranging from 400°C-700°C. The experiments were repeated 3 times to ensure stability and reproducibility. Platinum nanoparticles were also deposited on the same supports and tested for the RWGS reaction at the same conditions. The CuNi nanoparticles were characterized using a variety of different techniques. Xray diffraction, XRD, measurements demonstrate the resence of two CuNi solid solutions: one Cu rich solid solution, and the other a Ni rich solid solution. X-ray photo electron spectroscopy, XPS, measurements show Cu enrichment on all catalytic surfaces. Scanning electron microscopy, SEM, measurements show CuNi nanoparticles ranging in size from 4 nm to 100 nm. Some agglomeration was observed. SDC showed the best yield with all catalysts. Furthermore, high oxygen vacancy content was shown to increase yield of CO for the RWGS reaction. Cu50Ni50/SDC shows the combination of highest yield of CO and the best stability among CuNi catalysts. It also has similar yields (39.8%) as Pt/SDC at 700°C, which achieved the equilibrium yield at that temperature (43.9%). The catalyst was stable for 48 hours when exposed to high temperatures (600-700°C). There was no CH4 observed during any of the experiments when the partial pressure of the reactant gases was fed stoichiometrically. Partial pressure variation experiments demonstrated the presence of CH4 when the partial pressure of hydrogen was increased to twice the value of the partial pressure of CO2.

Zinc-nickel ?-phase silicate and copper-nickel silicate corrosion resistant coatings have been prepared via electrochemical methods to improve currently available corrosion resistant materials in the oil and gas industry. A layered silicate, montmorillonite, has been incorporated into the coatings for increased corrosion protection. For the zinc nickel silicate coatings, optimal plating conditions were determined to be a working pH range of 9.3 -9.5 with a borate based electrolyte solution, resulting in more uniform deposits and better corrosion protection of the basis metal as compared to acidic conditions. Quality, strongly adhering deposits were obtained quickly with strong, even overall coverage of the metal substrate. The corrosion current of the zinc-nickel-silicate coating is Icorr = 3.33E-6 for a borate based bath as compared to a zinc-nickel bath without silicate incorporation (Icorr = 3.52E-5). Step potential and direct potential methods were examined, showing a morphological advantage to step potential deposition. The effect of borate addition was examined in relation to zinc, nickel and zinc-nickel alloy deposition. Borate was found to affect the onset of hydrogen evolution and was examined for absorption onto the electrode surface. For copper-nickel silicate coatings, optimal conditions were determined to be a citrate based electrolytic bath, with pH = 6. The solutions were stable over time and strong adhering, compact particle deposits were obtained. The corrosion current of the copper-nickel-silicate coatings is Icorr = 3.86E-6 (copper-nickel coatings without silicate, Icorr = 1.78E-4). The large decrease in the corrosion current as the silicate is incorporated into the coating demonstrates the increase in corrosion resistance of the coatings with the incorporation of silicates.

The formation of nano–sized precipitates is considered to be the origin of hardening and embrittlement of ferritic steel used as structural material for pressure vessels of nuclear reactors, since these nanoclusters hinder the motion of dislocations within the grains of the polycrystalline bcc–Fe matrix. Previous investigations showed that these small precipitates are coherent and may consist of Cu, Ni, other foreign atoms, and vacancies. In this work a combination of on–lattice simulated annealing based on Metropolis Monte Carlo simulations and off–lattice relaxation by Molecular Dynamics is applied in order to determine the structure, energetics and thermodynamics of coherent clusters in bcc–Fe. The most recent interatomic potentials for Fe–Cu–Ni alloys are used. The atomic structure and the formation energy of the most stable configurations as well as their total and monomer binding energy are calculated. Atomistic simulation results show that pure (vacancy and copper) as well as mixed (vacancy-copper, copper-nickel and vacancy-copper-nickel) clusters show facets which correspond to the main crystallographic planes. Besides facets, mixed clusters exhibit a core-shell structure. In the case of v_lCu_m, a core of vacancy cluster coated with copper atoms is found. In binary Cum_Ni_n, Ni atoms cover the outer surface of copper cluster. Ternary v_lCu_mNi_n clusters show a core–shell structure with vacancies in the core coated by a shell of Cu atoms, followed by a shell of Ni atoms. It has been shown qualitatively that these core–shell structures are formed in order to minimize the interface energy between the cluster and the bcc-Fe matrix. Pure nickel consist of an agglomeration of Ni atoms at second nearest neighbor distance, whereas vacancy-nickel are formed by a vacancy cluster surrounded by a nickel agglomeration. Both types of clusters are called quasi-cluster because of their non-compact structure. The atomic configurations of quasiclusters can be understood by the peculiarities of the binding between Ni atoms and vacancies. In all clusters investigated Ni atoms may be nearest neighbors of Cu atoms but never nearest neighbors of vacancies or other Ni atoms. The structure of the clusters found in the present work is consistent with experimental observations and with results of pairwise calculations. In agreement with experimental observations and with recent results of atomic kinetic Monte Carlo simulation it is shown that the presence of Ni atoms promotes the nucleation of clusters containing vacancies and Cu. For pure vacancy and pure copper clusters an atomistic nucleation model is established, and for typical irradiation conditions the nucleation free energy and the critical size for cluster formation have been estimated. For further application in rate theory and object kinetic Monte Carlo simulations compact and physically–based fit formulae are derived from the atomistic data for the total and the monomer binding energy. The fit is based on the structure of the clusters (core-shell and quasi-cluster) and on the classical capillary model.

Thesis (Ph. D.)--Ohio State University, 2009. / Title from first page of PDF file. Includes bibliographical references (p. 229-238).

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1992. / Vita. Abstract. Includes bibliographical references (leaves 131-139). Also available via the Internet.

Made available in DSpace on 2016-03-15T19:36:31Z (GMT). No. of bitstreams: 1 Marcelo de Almeida Carvalhal.pdf: 4038630 bytes, checksum: 7060afa045e45cc87fb603998f21fe92 (MD5) Previous issue date: 2011-06-17 / Fundo Mackenzie de Pesquisa / In this work were synthesized several samples of ternary alloys of Cu-Ni-Cr by powder metallurgy. The alloys were submitted to different thermal treatments of sintering and homogeneizing and all of them were metallographic characterized. In various compositions were performed micro hardness and electrical resistance measurements. Samples with the compositions 98,5%Cu-1,0%Ni-0,5%Cr and 97,0%Cu-1,5%Ni-1,5%Cr presented electrical conductivity higher than 70% IACS and high mechanical resistance, which indicates proper thermal treatments for these compositions. From Rietveld Method refinements, a structural and micro structural study was performed for some samples, from which X rays diffraction data were collected with synchrotron and conventional radiation. The average crystallite size determined for samples with the composition 98,5%Cu-1,0%Ni-0,5%Cr was approximately of 100 nm. For these samples the grain size lies between 15 e 25 μm. / Neste trabalho foram sintetizadas diversas amostras de ligas metálicas ternárias de Cu-Ni-Cr por metalurgia do pó. As ligas receberam diferentes tratamentos térmicos de sinterização e homogeneização e todas foram caracterizadas metalograficamente. Foram realizadas medidas de micro- ureza e de resistência elétrica de amostras de varias composições. Amostras das composições 98,5%Cu-1,0%Ni- 0,5%Cr e 97,0%Cu-1,5%Ni-1,5%Cr apresentaram condutividades elétricas maiores que 70% IACS e alta resistência mecânica, o que indica que os tratamentos térmicos para estas composições foram adequados. A partir de refinamentos realizados pelo Método de Rietveld, foi realizado um estudo estrutural e microestrutural de algumas amostras, com as quais foram coletados dados de difração de raios x com radiação convencional e radiação síncrotron. O tamanho de cristalito médio determinado para amostras da composição 98,5%Cu-1,0%Ni-0,5%Cr foi de aproximadamente 100 nm. Para estas amostras o tamanho de grão se encontra entre 15 e 25 μm.

Made available in DSpace on 2016-03-15T19:37:00Z (GMT). No. of bitstreams: 1 Claudio Domingos de Abreu.pdf: 1743924 bytes, checksum: bdedae433f0895da882b52b84aac8e5b (MD5) Previous issue date: 2010-02-09 / Fundo Mackenzie de Pesquisa / Copper and its alloys have various applications from manufactured artefacts to sophisticated equipments and stands out as conductive material due to high electrical and thermal conductivity. Its mechanical properties are moderate, as high corrosion resistance, high ductility. The choice of copper as a study material was motivated by the high consumption, since copper is the third most used metal in the world. Copper can be used alone or combined with other metal and depending on the concentration, can change it is characteristics. In situations where it is required greater mechanical strength, without changing its electrical and thermal properties, one or more elements cam be used in specific concentrations to achieve the desired result. In cast materials increase the percentage of alloying elements can cause a decrease in electrical conductivity. In the process of powder metallurgy the presence of porosity within a structure, indicates inadequate dissolution of the alloy elements, resulting in low electrical conductivity which cam be fixed with thermal treatment. In order to observe the dependence of the conductivity with the microstructure, Cu-Ni alloys were doped with Cr, Al, Sn and Pt. The metallic powder were mixed or and compressed in cold uniaxial pressure of 300 MPa. After that, the samples were sintered at temperatures between 700 and 800 º C for a period of 5400 seconds. The alloys were characterized by optical microscopy, electrical conductivity and Vickers hardness, infrared spectroscopy and x-ray diffraction. The conductivity results already achieved in materials prepared by the casting process and the resulting determined by powder metallurgy, there was a comparative study between these two technologies. It can be observed that the increase in cast materials of alloys and plastic deformation affect the electrical conductivity and powder metallurgy, the less porosity have the final material, the better the results of conductivity. / O cobre e suas ligas têm diferentes aplicações sendo usado desde a produção artesanal de utensílios e esculturas até o processamento de componentes elétricos ou eletrônicos empregados em equipamentos sofisticados e destaca-se como material condutor devido à alta condutividade elétrica e térmica. Suas propriedades mecânicas são moderadas, tais como, alta resistência à corrosão e elevada ductilidade. A escolha do cobre como material de estudo foi motivada por seu alto índice de consumo, pois o cobre é o terceiro metal mais utilizado no mundo. O cobre pode ser usado puro ou ligado a outro metal e dependendo da concentração, pode ter suas características alteradas. Em situações onde é necessária maior resistência mecânica, sem alteração das propriedades elétricas e térmicas, pode-se utilizar um ou mais elementos em concentrações especificas para se obter o resultado pretendido. Nos materiais fundidos o aumento percentual dos elementos de liga em busca da melhoria da propriedade mecânica pode causar uma diminuição da condutividade elétrica. No processo de metalurgia do pó a presença de porosidade no interior de uma estrutura, indica dissolução inadequada dos elementos de liga, que pode resultar numa baixa condutividade elétrica, levando a necessidade de corrigir com tratamentos térmicos. Com objetivo de observar a dependência da condutividade com a microestrutura de ligas Cu-Ni, dopadas com Cr, Al, Sn, Pt com diferentes dopagens os pós-metálicos foram misturados e compactados em pressão uniaxial a frio de aproximadamente 300MPa e as amostras foram sinterizadas com temperaturas entre 700 e 800ºC por um período de 5400 segundos. As ligas foram caracterizadas por microscopia ótica, por condutividade elétrica, dureza Vickers, espectroscopia de infravermelho e difratometria de raio x. A partir dos resultados de condutividade, já alcançados em materiais preparados por processo de fundição e os decorrentes, determinados por metalurgia do pó, realizou-se um estudo comparativo entre essas duas tecnologias. Pode-se observar que em materiais fundidos o aumento dos elementos de liga e a deformação plástica prejudica condutividade elétrica e em metalurgia do pó, quanto menos porosidade tiver o material final, melhor será o resultado de condutividade.

In the oil and gas industry, high corrosion resistance and hardness are needed to extend the lifetime of the coatings due to exposure to high stress and salt environments. Electrodeposition has become a favorable technique in synthesizing coatings because of low cost, convenience, and the ability to work at low temperatures. Electrodeposition of metal matrix composites has become popular for enhanced corrosion resistance and hardness in the oil and gas industry because of the major problems that persist with corrosion. Two major alloys of copper-nickel, 90-10 and 70-30, were evaluated for microbial corrosion protection in marine environments on a stainless steel substrate. Copper and copper alloys are commonly used in marine environments to resist biofouling of materials by inhibiting microbial growth. Literature surveying the electrodeposition of Cu-Ni incorporated with nano- to micro- particles to produce metal matrix composites has been reviewed. Also, a novel flow cell design for the enhanced deposition of metal matrix composites was examined to obtain the optimal oriented structure of the layered silicates in the metal matrix. With the addition of montmorillonite into the Ni and Cu-Ni matrix, an increase in strength, adhesion, wear and fracture toughness of the coating occurs, which leads to an increase corrosion resistance and longevity of the coating. These coatings were evaluated for composition and corrosion using many different types of instrumental and electrochemical techniques. The overall corrosion resistance and mechanical properties were improved with the composite films in comparison to the pure metals, which proves to be advantageous for many economic sectors including the oil and gas industry.

Made available in DSpace on 2014-12-17T15:42:28Z (GMT). No. of bitstreams: 1 MonicaRO_TESE.pdf: 4155777 bytes, checksum: 6bff63b5cb0f37e64dfe6fcb144dae79 (MD5) Previous issue date: 2014-01-23 / The environmental impact due to the improper disposal of metal-bearing industrial effluents imposes the need of wastewater treatment, since heavy metals are nonbiodegradable and hazardous substances that may cause undesirable effects to humans and the environment. The use of microemulsion systems for the extraction of metal ions from wastewaters is effective when it occurs in a Winsor II (WII) domain, where a microemulsion phase is in equilibrium with an aqueous phase in excess. However, the microemulsion phase formed in this system has a higher amount of active matter when compared to a WIII system (microemulsion in equilibrium with aqueous and oil phases both in excess). This was the reason to develop a comparative study to evaluate the efficiency of two-phases and three-phases microemulsion systems (WII and WIII) in the extraction of Cu+2 and Ni+2 from aqueous solutions. The systems were composed by: saponified coconut oil (SCO) as surfactant, n-Butanol as cosurfactant, kerosene as oil phase, and synthetic solutions of CuSO4.5H2O and NiSO4.6H2O, with 2 wt.% NaCl, as aqueous phase. Pseudoternary phase diagrams were obtained and the systems were characterized by using surface tension measurements, particle size determination and scanning electron microscopy (SEM). The concentrations of metal ions before and after extraction were determined by atomic absorption spectrometry. The extraction study of Cu+2 and Ni+2 in the WIII domain contributed to a better understanding of microemulsion extraction, elucidating the various behaviors presented in the literature for these systems. Furthermore, since WIII systems presented high extraction efficiencies, similar to the ones presented by Winsor II systems, they represented an economic and technological advantage in heavy metal extraction due to a small amount of surfactant and cosurfactant used in the process and also due to the formation of a reduced volume of aqueous phase, with high concentration of metal. Considering the reextraction process, it was observed that WIII system is more effective because it is performed in the oil phase, unlike reextraction in WII, which is performed in the aqueous phase. The presence of the metalsurfactant complex in the oil phase makes possible to regenerate only the surfactant present in the organic phase, and not all the surfactant in the process, as in WII system. This fact allows the reuse of the microemulsion phase in a new extraction process, reducing the costs with surfactant regeneration / O impacto ambiental gerado pelo descarte de efluentes industriais carregados de metais pesados imp?e a necessidade do tratamento desses rejeitos, uma vez que s?o t?xicos e n?o biodegrad?veis, podendo causar s?rios danos ? popula??o e ao meio ambiente. O processo de extra??o de c?tions met?licos utilizando microemuls?es ? eficaz quando acontece em WII, onde a fase microemulsionada encontra-se em equil?brio com uma fase aquosa em excesso. No entanto, a microemuls?o formada nesse sistema possui uma maior quantidade de mat?ria ativa quando comparada ao equil?brio de WIII (microemuls?o em equil?brio com fases aquosa e oleosa, ambas em excesso), ainda pouco estudado, motivando, assim, o desenvolvimento de um estudo comparativo da efici?ncia de extra??o dos ?ons Cu2+ e Ni2+ por sistemas microemulsionados bif?sicos e trif?sicos (WII e WIII). Os constituintes utilizados nos sistemas de extra??o foram: ?leo de coco saponificado - OCS (Tensoativo), n- Butanol (Cotensoativo), querosene (Fase Oleosa) e solu??es sint?ticas de CuSO4.5H2O e NiSO4.6H2O com NaCl 2% (fases aquosas). Foram obtidos os diagramas de fases pseudotern?rios e os sistemas microemulsionados foram caracterizados atrav?s das t?cnicas de tens?o superficial, tamanho de part?culas e microscopia eletr?nica de varredura (MEV). A concentra??o dos ?ons foi determinada por espectrometria de absor??o at?mica. O estudo da extra??o dos c?tions met?licos Cu2+ e Ni2+ na regi?o de WIII contribuiu para um melhor entendimento dos processos de extra??o por microemuls?o, elucidando os v?rios comportamentos apresentados na literatura para esses sistemas. Al?m disso, uma vez que houve uma alta efici?ncia de extra??o, similar aos sistemas de Winsor II, o sistema trif?sico (WIII), por apresentar uma menor quantidade de tensoativo e cotensoativo, e um menor volume de fase aquosa ap?s a extra??o, levou a uma maior concentra??o do metal, representando uma vantagem econ?mica e tecnol?gica do processo. Assim, a extra??o em sistema trif?sico ? vi?vel e, apesar dos percentuais de extra??o em WII e WIII serem semelhantes, o sistema de WIII leva a uma maior concentra??o do metal na fase extrato. O presente trabalho mostrou, ainda, que a etapa de reextra??o para os sistemas em WIII ? mais eficaz pois, diferentemente da extra??o em Winsor II, ela ? realizada na fase oleosa, onde est? depositado o complexo metal/tensoativo, regenerando somente o tensoativo que complexa com o metal na fase org?nica, e n?o todo o tensoativo utilizado, como ? o caso do equil?brio em Winsor II. Este fato viabiliza a reutiliza??o da fase microemuls?o no processo de extra??o, diminuindo os custos de regenera??o do tensoativo

Made available in DSpace on 2016-03-15T19:36:50Z (GMT). No. of bitstreams: 1 Leilah Delaretti Luongo.pdf: 2162579 bytes, checksum: 76c30f5d2ee2f42b33cf84bd04999ac2 (MD5) Previous issue date: 2015-05-22 / In this work, samples of copper-silver and silver-copper-nickel alloys were synthesized by powder metallurgy. The alloys have received sintering and all of them were characterized metallographically. Different and significant effects were observed in the microstructure and conductivity of the samples studied. The influence of silver on the conductivity of the samples with nickel resulted to be lower than the alloy with chromium and nickel, studied in previous work of the research group, where the same procedures were applied to the same precursors. An interesting result is that the larger crystallite size favored the high electrical conductivity, which is presented in the samples without nickel. The presence of nickel helped to inhibit oxidation and the difference in the amount of nickel influenced the alloys behavior, however, it did not guarantee high conductivity observed in the aforementioned alloys copper-nickel-chromium. The structure of the samples was studied by the Rietveld Method, using data from x-ray diffraction. The differences in microstructure were investigated by comparing the parameters of the pure copper used as a precursor profile. / Neste trabalho foram sintetizadas amostras de ligas metálicas de cobre-prata e cobre-níquel-prata obtidas por metalurgia do pó. As ligas receberam tratamentos térmicos de sinterização e foram caracterizadas metalograficamente. Foram observados efeitos diferentes e significativos na microestrutura e na condutividade das amostras estudadas. A influência da prata na condutividade das amostras com níquel resultou ser inferior à de ligas com cromo e níquel, estudadas em trabalhos precedentes do grupo de pesquisa, onde se aplicaram os mesmos procedimentos aos mesmos precursores. Um resultado interessante é que o maior tamanho de cristalito favoreceu a condutividade elétrica, o qual se apresentou nas amostras sem níquel. A presença do níquel ajudou a inibir a oxidação e a diferença na quantidade de níquel se mostrou importante no comportamento das ligas, porém, não garantiu a alta condutividade verificada nas mencionadas ligas de cobre- níquel-cromo. A estrutura das amostras foi estudada pelo Método de Rietveld, usando dados de difração de raios x. As diferenças na microestrutura foram estudadas através da comparação com os parâmetros de perfil do cobre puro usado como precursor.