In this PhD thesis, seawater desalination by Membrane Distillation (MD) has been explored from the perspective of process and membrane. Regarding the process, an innovative, energy efficient, and environmentally friendly Zero Thermal Input Membrane Distillation (ZTIMD) process was proposed. ZTIMD uses thermal energy stored in seawater, which makes the process sustainable by being independent of the external sources of thermal energy, which is one of the major contributors to the cost and energy consumption of conventional MD desalination processes. Economic feasibility study was carried out for the ZTIMD process, and it was demonstrated that drinking water could be produced with a cost of $0.28/m3, which is approximately half of the cost of conventional desalination processes. Regarding the membrane, novel MD membranes were developed through incorporation of nanomaterials in polyvinylidene fluoride (PVDF). Different nanomaterials including superhydrophobic SiO2, amine modified hydrophilic SiO2, CuO, and CaCO3 were used for this purpose. It was shown that membrane structure and consequently its performance could be affected by the nanoparticle properties, concentration, presence of backing material, PVDF blend ratio, and penetration time. In a best membrane developed in this work, almost 2500% increase was observed in the Vacuum Membrane Distillation (VMD) flux over that of the neat PVDF membrane at a feed temperature of 27.5 °C and vacuum pressure of 1.2 kPa, when 7.0 wt.% hydrophilic SiO2 nanoparticles were added into a PVDF membrane supported with Non-Woven Fabric (NWF) polyester. The membrane possessed near perfect selectivity.

Submitted by DANIEL FERNANDO DA SILVA null (danielprofessorengemec@gmail.com) on 2018-01-04T13:41:19Z No. of bitstreams: 1 Dissertação - Daniel Fernando - versão final.pdf: 4270080 bytes, checksum: a1076d940ede22de07f7319dd405f059 (MD5) / Approved for entry into archive by Cristina Alexandra de Godoy null (cristina@adm.feis.unesp.br) on 2018-01-04T17:07:06Z (GMT) No. of bitstreams: 1 silva_df_me_ilha.pdf: 4270080 bytes, checksum: a1076d940ede22de07f7319dd405f059 (MD5) / Made available in DSpace on 2018-01-04T17:07:06Z (GMT). No. of bitstreams: 1 silva_df_me_ilha.pdf: 4270080 bytes, checksum: a1076d940ede22de07f7319dd405f059 (MD5) Previous issue date: 2017-07-07 / O presente trabalho estudou a influência do aporte térmico do processo de soldagem GTAW automatizado nas propriedades mecânicas do aço inoxidável austenítico AISI 316L. Esse aço é amplamente utilizado na indústria alimentícia e de petróleo e gás, por ser muito resistente a corrosão. Utilizou-se chapas de 1,0 mm de espessura, soldadas por junta de topo sem chanfro. Os parâmetros de soldagem foram selecionados e ajustados através de pré-testes, pois existem poucas fontes de pesquisa sobre a soldagem de chapas finas de aço inoxidável. Para analisar a influência da variação do aporte térmico, variou-se a velocidade de soldagem na faixa de 375 a 500 mm/min, com incremento de 25 mm/min. O processo de soldagem foi autógeno. Foram realizadas análises macrográficas para avaliar a largura e profundidade do cordão de solda. Foram realizados também ensaios mecânicos de microdureza Vickers e ensaios de tração para avaliar as propriedades mecânicas do cordão de solda formado. Os valores encontrados nestes ensaios foram comparados com o aporte térmico de soldagem, para avaliar a influência do mesmo nas propriedades mecânicas da junta de solda. Os resultados obtidos com os ensaios descritos, mostraram que o controle da energia de soldagem, ou seja, do aporte térmico é essencial na soldagem de chapas finas de aço inoxidável austenítico AISI 316L, gerando juntas de solda livres de descontinuidades e com propriedades mecânicas próximas ao do metal puro. / The present research studied the influence of the thermal input of the automated GTAW welding process on the mechanical properties of AISI 316L austenitic stainless steel. This steel is widely used in the food and oil and gas industry because it is very resistant to corrosion. Panels of 1.0 mm thickness were used, welded by a non-chamfered top joint. The welding parameters were selected and adjusted through pre-tests, as there are few sources of research on the welding of stainless steel thin sheets. In order to analyze the influence of the variation of the thermal input, the welding speed was varied in the range of 375 to 500 mm / min, with an increase of 25 mm / min. The welding process was autogenous. Macrographic analyzes were performed to evaluate the width and depth of the weld bead. Mechanical tests of Vickers microhardness and tensile tests were also performed to evaluate the mechanical properties of the weld bead formed. The values found in these tests were compared with the thermal input of welding, to evaluate the influence of the same on the mechanical properties of the weld joint. The results obtained with the described tests showed that the control of the welding energy, that is, of the thermal input is essential in the welding of thin sheets of AISI 316L austenitic stainless steel, generating solder joints free of discontinuities and with mechanical properties close to the of the pure metal.

Orientador: Vicente Afonso Ventrella / Resumo: O presente trabalho estudou a influência do aporte térmico do processo de soldagem GTAW automatizado nas propriedades mecânicas do aço inoxidável austenítico AISI 316L. Esse aço é amplamente utilizado na indústria alimentícia e de petróleo e gás, por ser muito resistente a corrosão. Utilizou-se chapas de 1,0 mm de espessura, soldadas por junta de topo sem chanfro. Os parâmetros de soldagem foram selecionados e ajustados através de pré-testes, pois existem poucas fontes de pesquisa sobre a soldagem de chapas finas de aço inoxidável. Para analisar a influência da variação do aporte térmico, variou-se a velocidade de soldagem na faixa de 375 a 500 mm/min, com incremento de 25 mm/min. O processo de soldagem foi autógeno. Foram realizadas análises macrográficas para avaliar a largura e profundidade do cordão de solda. Foram realizados também ensaios mecânicos de microdureza Vickers e ensaios de tração para avaliar as propriedades mecânicas do cordão de solda formado. Os valores encontrados nestes ensaios foram comparados com o aporte térmico de soldagem, para avaliar a influência do mesmo nas propriedades mecânicas da junta de solda. Os resultados obtidos com os ensaios descritos, mostraram que o controle da energia de soldagem, ou seja, do aporte térmico é essencial na soldagem de chapas finas de aço inoxidável austenítico AISI 316L, gerando juntas de solda livres de descontinuidades e com propriedades mecânicas próximas ao do metal puro. / Abstract: The present research studied the influence of the thermal input of the automated GTAW welding process on the mechanical properties of AISI 316L austenitic stainless steel. This steel is widely used in the food and oil and gas industry because it is very resistant to corrosion. Panels of 1.0 mm thickness were used, welded by a non-chamfered top joint. The welding parameters were selected and adjusted through pre-tests, as there are few sources of research on the welding of stainless steel thin sheets. In order to analyze the influence of the variation of the thermal input, the welding speed was varied in the range of 375 to 500 mm / min, with an increase of 25 mm / min. The welding process was autogenous. Macrographic analyzes were performed to evaluate the width and depth of the weld bead. Mechanical tests of Vickers microhardness and tensile tests were also performed to evaluate the mechanical properties of the weld bead formed. The values found in these tests were compared with the thermal input of welding, to evaluate the influence of the same on the mechanical properties of the weld joint. The results obtained with the described tests showed that the control of the welding energy, that is, of the thermal input is essential in the welding of thin sheets of AISI 316L austenitic stainless steel, generating solder joints free of discontinuities and with mechanical properties close to the of the pure metal. / Mestre