<p>It is widely believed that hydrogen will, within a few years, become the means of storing and transporting energy. The reason is the depletion of hydrocarbons and the relatively facile production of hydrogen from various renewable sources of energy. Hydrogen can be combusted in an efficient way in a fuel cell with water as emission product. The overall goal of the project was to deevlop the knowledge base for solid-state hydrogen storage technology suitable for stationary and mobile applications. The aim of this research was to develop a novel composite hydrogen storage material with high wt% storage capacity, high intrinsic safety, appropriate thermodynamics, high mechanical strength, reversibility of the system and fast kinetics based on a well known &quot / low temperature&quot / intermetallic alloy (Ti/Fe) as the core.</p>

<p>It is widely believed that hydrogen will, within a few years, become the means of storing and transporting energy. The reason is the depletion of hydrocarbons and the relatively facile production of hydrogen from various renewable sources of energy. Hydrogen can be combusted in an efficient way in a fuel cell with water as emission product. The overall goal of the project was to deevlop the knowledge base for solid-state hydrogen storage technology suitable for stationary and mobile applications. The aim of this research was to develop a novel composite hydrogen storage material with high wt% storage capacity, high intrinsic safety, appropriate thermodynamics, high mechanical strength, reversibility of the system and fast kinetics based on a well known &quot / low temperature&quot / intermetallic alloy (Ti/Fe) as the core.</p>

Magister Scientiae - MSc / It is widely believed that hydrogen will within a few tens of years become the means of storing and transporting energy. The reason is the depletion of hydrocarbons and the relatively facile production of hydrogen from various renewable sources of energy. Hydrogen can be combusted in an efficient way in a fuel cell with water as emission product. As concerns over air pollution and global warming increase, the incentive to switch to clean and efficient hydrogen economy becomes greater and the transition may occur well before hydrocarbon reserves are extinct. The overall goal of the project is to develop the knowledge base for solid-state hydrogen storage technology suitable for stationary and mobile applications. In order to accomplish this goal, the project will have a dual focus which includes the synthesis of novel nano-structured hydrogen storage materials and systems that can accurately analyze the materials. The aim of this research is to develop a novel composite hydrogen storage material with high wt% storage capacity, high intrinsic safety, appropriate thermodynamics, high mechanical strength, reversibility of the system and fast kinetics based on a well known “low temperature” intermetallic alloy (Ti/Fe) as the core. In the course of achieving this objective, the structural, thermal, chemisorptive and physisorptive attributes of this material on a nanoscale have been evaluated considering that nano-structuring is a potentially promising approach for controlling bond strength, kinetics, and sorption temperatures and pressures. By combining different materials with suitable catalytic and thermodynamic properties, a new class of hybrid hydrogen storage material has been developed. More importantly, the focus was to increase the capacity of hydrogen sorption in this material. This goal was achieved with the mechano-chemical pre-treatment of Ti/Fe alloy and surface modification with carbon nanotubes, binary palladium and magnesium metals via a layer-by-layer modification technique. The chemical and mechanical stability of hydrogen storage materials is of great importance because hydrogen storage materials must withstand repeated adsorption and desorption cycles. The layer by layer approach that was used in this project allowed the investigation of the chemical and mechanical stability of the materials as each layer was added. Through this layer by layer approach suitable nano-particles were introduced that are chemically and mechanically stable. The knowledge emanating from this investigation is expected to allow the directed design of new, higher-efficiency, recyclable hydride-based materials in pursuance of the 6.0 wt% goal set forth by the US Department of Energy. / South Africa

Made available in DSpace on 2014-06-11T19:29:09Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-03-11Bitstream added on 2014-06-13T19:17:18Z : No. of bitstreams: 1 segura_df_me_araiq.pdf: 1112989 bytes, checksum: 57dcb9d71e40b067b4378bde80885bbe (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Neste trabalho fibras ópticas de PMMA foram preparadas a partir de amostras de PMMA disponíveis comercialmente. As amostras foram termoprensadas a uma temperatura de 230 ºC na forma de bastões homogêneos e livre de bolhas. Desses bastões foi possível obter preformas cilíndricas com diâmetro de aproximadamente 10 mm. Para a obtenção de fibras foi utilizado o método de puxamento de preforma em uma torre de puxamento de características industriais. O puxamento das fibras foi conseguido em temperaturas próximas a 200 ºC possibilitando a confecção de fibras de diâmetro entre 200 µm a 1000 µm, essas fibras possuem uma atenuação entre 23 dB/m e 13 dB/m respectivamente. Esses valores são superiores ao encontrado para uma fibra comercial que é de 4 dB/m. Numa segunda parte do trabalho um novo material híbrido orgânico inorgânico foi preparado, constituído de PMMA e nanopartículas inorgânicas luminescentes de vanadato de ítrio dopado com európio (YVO4:Eu). Para isso foi empregado dois métodos diferentes: a moagem conjunta do PMMA com as nanopartículas com a posterior termoprensagem dessa mistura e a suspensão em solvente, que consistia em solubilizar o PMMA em um solvente contendo uma suspensão das nanopartículas com a sua posterior secagem. Ambos os métodos produziram materiais transparentes e homogêneos. As propriedades espectroscópicas sugerem que a identidade das nanopartículas tenha sido preservada nos compósitos finais. Alguns ensaios de puxamento de fibras a partir dos compósitos foram realizados / In this work PMMA optical fibers were prepared from samples of commercially available PMMA. The samples were processed at 230 ºC to make rods homogeneous and without bubbles. With these rods was possible to obtain cylindrical preforms with a diameter of approximately 10 mm. The drawing of the fibers was achieved at temperatures around 200 ° C enabling the manufacture of fibers with diameters of 200 μm to 1000 μm these fibers have an attenuation between 23 dB/m and 13 dB/m respectively. These values are higher than found for a commercial fiber that is 4 dB/m. In a second part of the work a new organic inorganic hybrid material was prepared, consisting of PMMA and inorganic luminescent nanoparticles of yttrium vanadate doped with europium (YVO4:Eu). For this he was employed two different methods: the joint milling of PMMA nanoparticles with subsequent thermopressing the mixture and suspended in solvent, which was to solubilize the PMMA in a solvent containing a suspension of nanoparticles with subsequent drying. Both methods produced transparent and homogeneous materials. The spectroscopic properties suggest that the identity of nanoparticles has been preserved in the final composite. Some tests of pulling fiber from the composite were performed

Orientador: Sidney José Lima Ribeiro / Banca: Karim Dahmouche / Banca: Bluma Guenther Soares / Resumo: Neste trabalho fibras ópticas de PMMA foram preparadas a partir de amostras de PMMA disponíveis comercialmente. As amostras foram termoprensadas a uma temperatura de 230 ºC na forma de bastões homogêneos e livre de bolhas. Desses bastões foi possível obter preformas cilíndricas com diâmetro de aproximadamente 10 mm. Para a obtenção de fibras foi utilizado o método de puxamento de preforma em uma torre de puxamento de características industriais. O puxamento das fibras foi conseguido em temperaturas próximas a 200 ºC possibilitando a confecção de fibras de diâmetro entre 200 µm a 1000 µm, essas fibras possuem uma atenuação entre 23 dB/m e 13 dB/m respectivamente. Esses valores são superiores ao encontrado para uma fibra comercial que é de 4 dB/m. Numa segunda parte do trabalho um novo material híbrido orgânico inorgânico foi preparado, constituído de PMMA e nanopartículas inorgânicas luminescentes de vanadato de ítrio dopado com európio (YVO4:Eu). Para isso foi empregado dois métodos diferentes: a moagem conjunta do PMMA com as nanopartículas com a posterior termoprensagem dessa mistura e a suspensão em solvente, que consistia em solubilizar o PMMA em um solvente contendo uma suspensão das nanopartículas com a sua posterior secagem. Ambos os métodos produziram materiais transparentes e homogêneos. As propriedades espectroscópicas sugerem que a identidade das nanopartículas tenha sido preservada nos compósitos finais. Alguns ensaios de puxamento de fibras a partir dos compósitos foram realizados / Abstract: In this work PMMA optical fibers were prepared from samples of commercially available PMMA. The samples were processed at 230 ºC to make rods homogeneous and without bubbles. With these rods was possible to obtain cylindrical preforms with a diameter of approximately 10 mm. The drawing of the fibers was achieved at temperatures around 200 ° C enabling the manufacture of fibers with diameters of 200 μm to 1000 μm these fibers have an attenuation between 23 dB/m and 13 dB/m respectively. These values are higher than found for a commercial fiber that is 4 dB/m. In a second part of the work a new organic inorganic hybrid material was prepared, consisting of PMMA and inorganic luminescent nanoparticles of yttrium vanadate doped with europium (YVO4:Eu). For this he was employed two different methods: the joint milling of PMMA nanoparticles with subsequent thermopressing the mixture and suspended in solvent, which was to solubilize the PMMA in a solvent containing a suspension of nanoparticles with subsequent drying. Both methods produced transparent and homogeneous materials. The spectroscopic properties suggest that the identity of nanoparticles has been preserved in the final composite. Some tests of pulling fiber from the composite were performed / Mestre