Prior to the long-term utilization of solid oxide fuel cell (SOFC), one of the most remarkable el... more Prior to the long-term utilization of solid oxide fuel cell (SOFC), one of the most remarkable electrochemical energy conversion devices, a variety of difficult experimental validation procedures is required, so it would be time-consuming and steep to predict the applicability of these devices in the future. For numerous years, extensive efforts have been made to develop mathematical models to predict the effects of various characteristics of solid oxide fuel cells (SOFCs) components on their performance (e.g., voltage). Taking advantage of the machine learning (ML) method, however, some issues caused by assumptions and calculation costs in mathematical modeling could be alleviated. This paper presents a machine learning approach to predict the anode-supported SOFCs performance as one of the most promising types of SOFCs based on architectural and operational variables. Accordingly, a dataset was collected from a study about the effects of cell parameters on the output voltage of a ...
In the manufacturing process of solid oxide fuel cells (SOFCs), the residual stresses and curvatu... more In the manufacturing process of solid oxide fuel cells (SOFCs), the residual stresses and curvature are developed in components due to the differences in material properties of cell layers. Residual stress may lead to the crack formation in the cell layers and facilitates cell fracture. In this work, the changes of the residual stress in the electrolyte layer of the anode-supported planar solid oxide fuel cells are experimentally determined at room temperature. The “sin2ψ” technique of X-ray diffraction method is employed to measure the residual stress in the half-cell samples. Investigation on the changes of the residual stress and curvature state in the scaling-up process of the cell is crucial for commercial use. Therefore, several cells with different sizes and shapes are investigated to evaluate the potential impact of cell size and cell shape on the residual thermal stress. Values of about −610 MPa are determined for the electrolyte layer on an oxidized ∼400 μm thick anode sub...
Background: Leishmaniasis is an expanding neglected tropical disease in the world reporting from ... more Background: Leishmaniasis is an expanding neglected tropical disease in the world reporting from 98 countries including Iran. This study focused on eco-epidemiological determinants of the disease following a rapid and unexpected increase of leishmaniasis incidence in a strategic residential district in North-East of Isfahan County, Iran. Methods: This study was accomplished from Apr 2012 to Jan 2014 in a strategic residential zone in North-East of Isfahan County, Esfahan, Iran. Monthly activity, parity, Leishmania infection and susceptibility tests, were determined on sand flies. Some portion of inhabitants and school children were surveyed to find active or passive cases of leishmaniasis and also wild rodents were collected to determine reservoir host. Results: Totally 5223 sand flies belonging to Phlebotomus and Sergentomyia genus were collected and identified; Ph. papatasi was the dominant species and started to appear in May and disappeared in Oct. The majority of living dissect...
Abstract<br /> Background and purpose: This study was done from October 2016 to October 201... more Abstract<br /> Background and purpose: This study was done from October 2016 to October 2017 to determine funa and distribution of ectoparasites of zoonotic cutaneous leishmaniasis reservoirs to prevent and control of zoonotic diseases in the hyperendemic area (Segzi area), in Esfahan Province in the future.<br /> Materials and methods: Rodents were collected by Sherman's Living Traps during different seasons and were identified by the standard morphological keys and comparison of morphometric characteristics with standard specimens. The collected rodents were anesthetized and ectoparasites were removed and conserved in 96% Alcohol. Then the ectoparasites were identified by the standard keys. <br /> Results: Ninety-two Rhombomys opimus and 1 Nesokia indica were captured. 50 out of 93 rodents (53.88%) were infested by the ectoparasites and a total of 527 ectoparasites were collected from them. The 9 species of identified ectoparasites were included 1 tick (0.19%...
Background: Sand flies of subgenus Adlerius has a wide geographical distribution in Iran and are ... more Background: Sand flies of subgenus Adlerius has a wide geographical distribution in Iran and are mostly found in wild form in mountainous areas. They are always considered as probable vectors of visceral leishmaniasis. The objective of this study was to determine the Adlerius species and its composition in an endemic focus of zoonotic vis-ceral leishmaniasis in northwest of the country. Methods: Sand flies were collected from 6 different areas of Azarbaijan-e-Sharqi Province using sticky paper traps from August to September which is active season for sand flies in this area, in 2009. The flies were mounted and identified. The length of third antennal segments, ascoid, labrum, coxite, surstyle, style, aedeagus, genital filament, genital pump, width of style, and the end of aedeagus were measured and the number of costal hairs group was also counted as the morphological characters. Results: A total of 30 adult sand flies, (26 males and 4 females) including Phlebotomus halepensis (46.8...
2019 International Power System Conference (PSC), 2019
Residual stresses in solid oxide cell (SOC) stacks or components are potential fracture sources w... more Residual stresses in solid oxide cell (SOC) stacks or components are potential fracture sources which needs to be investigated in order to enhance the reliability of the stacks. One of the most important joint materials in solid oxide cell stacks are glass sealants/steel interconnects at which chemical and mechanical characteristics are changed during service. Chemical reactions occur at the interface and change its chemistry. Mechanical stresses are formed with changing materials chemistry. Moreover, thermos-mechanical behavior mismatches lead to residual mechanical stress upon cooling/heating. An analytical model based on the classical beam bending theory was used in this study for calculating the residual stresses in this joint hybrid structure when the device is cooled down to room-temperature. Two potential commercial steel materials (SS430 and Crofer 22APU) were considered as the glass sealant counterpart.
Several theories have been presented about the corporate capital structure; some researchers beli... more Several theories have been presented about the corporate capital structure; some researchers believe that the structure of capital and firm value depend on each other. Moreover, others believe that the firm value is not influenced by any changes in the structure of capital, and with the change in the structure of capital, the value of the firm remains constant. The present research studies the historical theories of capital structure and presents the classification of existing theories in terms of the optimal capital structure. This classification is subdivided into two categories: the presence of an optimal capital structure and the absence of an optimal capital structure. With the historical review of theories of capital structure and the presence of an optimal capital structure or the lack of an optimal capital structure, it seems that none has been a complete model and so far, no one has been able to provide an optimal capital structure. In this research, from the system dynamic...
In the manufacturing process of solid oxide fuel cells (SOFCs), the residual stresses and curvatu... more In the manufacturing process of solid oxide fuel cells (SOFCs), the residual stresses and curvature are developed in components due to the differences in material properties of cell layers. Significant residual stress may lead to the formation of cracks in the cell layers and facilitates cell fracture. In this work, the changes of the residual stress in the electrolyte of the anode-supported planar solid oxide fuel cells are experimentally determined at room temperature. The “sin2ψ” technique of X-ray diffraction method is employed to measure the residual stress in the half-cell samples. Several cells with different sizes and shapes are investigated to evaluate the potential impact of cell size and cell shape on the thermal residual stress. Because investigation on the changes of the residual stress and curvature state in the scaling up process of cell is crucial for commercial use. Values of about − 610 MPa are determined for an electrolyte layer on an oxidized ∼400µm thick anode s...
The structural integrity of the sealant is critical for the reliability of solid oxide cells (SOC... more The structural integrity of the sealant is critical for the reliability of solid oxide cells (SOCs) stacks. In this study, elastic modulus (E), hardness (H) and fracture toughness (K IC) of a rapid crystallizing glass of BaO-CaO-SiO 2 system termed "sealant G" are reported as determined using an indentation test method at room temperature. A wide range of indentation loads (1 mN-10 N) was used to investigate the load-dependency of these mechanical properties. Values of 95 ± 12 GPa, 5.8 ± 0.2 GPa and 1.15 ± 0.07 MPa m 0.5 were derived for E, H and K IC using the most suitable indentation loads. An application relevant annealing treatment of 500 h at 800 • C does not lead to a significant change of the mechanical properties. Potential self-healing behavior of the sealant has also been studied by electron microscopy, based on heat treatment of samples with indentation-induced cracks for 70 h at 850 • C. Although the sealant G is considered to be fully crystallized, evidence indicates that its cracks can be healed even in the absence of a dead load.
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Low-temperature deposition of electroceramic thin films allows the construction of new devices an... more Low-temperature deposition of electroceramic thin films allows the construction of new devices and their integration with existing large-scale fabrication methods. Developing a suitable low-cost deposition method is important to further advance the development of microdevices. In this work, we deposited a 1-lm-thick La 0.6 Sr 0.4 CoO 3Àd (LSC) perovskite with high electrical conductivity on sapphire substrates at 400°C and analyzed its electrical, morphological and structural properties as a function of temperature in the range of 400-1100°C. The results show that spray pyrolysis can be used to deposit highquality reproducible layers with the desired chemical and phase composition. Upon heating to around 600°C, the residual CO and C=O species are removed, and the deposited layers crystallize and become conducting. The dependence of electrical conductivity versus processing temperature has a complex character-the maximum conductivity is found for layers processed at 800°C. An analytical model of stress distribution was used to predict stress to which the bi-layer material would be exposed to while being cooled down from the annealing temperature to room temperature. The high electronic conductivity and high-quality microstructure of the LSC layers, which can be adjusted with the appropriate heat treatment procedure, make them suitable for applications in electrochemical devices applied in integrated energy modules, including electrodes or contacts.
Cell temperature and selection of the reactant gases are crucial parameters for the design and op... more Cell temperature and selection of the reactant gases are crucial parameters for the design and optimization of fuel cell performance. In this study, effect of operating conditions on the performance of Solid Oxide Fuel (SOFC) has been investigated. Application of Response Surface Methodology (RSM) was applied to optimize operations conditions in SOFC. For this purpose, an experimental set up for testing of SOFC has been established to investigate the effect of Hydrogen, Oxygen, Nitrogen flow rates and cell temperature parameters on cell performance. Hydrogen flow rate, oxygen flow rate, nitrogen flow rate and cell temperature were the main parameters considered and they were varied between 0.25 and 1 L/min, 0.5 and 1 L/min, 0 and 1 L/min and 700-800 oC in the analyses respectively. The maximum power density was found as 0.572 W/cm2 in the experiments.
The compressibility behavior of Al-AlN nanostructured composite powder with different amount of r... more The compressibility behavior of Al-AlN nanostructured composite powder with different amount of reinforcement content was studied. The composite powder was synthesized by blending and high-energy milling process for 25 h. Williamson-Hall method was applied to determine the crystallite size after milling process. To investigate the role of reinforcement particles in consolidation of composite powders, monolithic aluminum powder was examined. Samples were made at different pressures and relationships were established between the compaction pressure and the density of the compacts. The modified Heckel equation was used to assume the pressure effect on yield strength and then was compared with other common equations. The best correlation was obtained when the effect of compaction pressure was considered. Due to lower plastic deformation capacity, the powders with higher content of hard reinforcements exhibited lower compressibility. The results also revealed that the yield strength of compacts, predicted by the mathematical equation, increases with reinforcement addition.
The thermal stability of nanostructured aluminum powder synthesized by high energy milling was st... more The thermal stability of nanostructured aluminum powder synthesized by high energy milling was studied through isothermal annealing at high temperatures for various times. Strain relaxation and grain growth of milled powders were studied at different milling times by differential scanning calorimetry (DSC). The results showed a high level of stored enthalpy due to milling procedure. After 25 h milling, powder particles reached a steady state with equiaxed morphology and 90 nm crystallite size in average. Isothermal grain growth kinetics of nanocrystalline Al powder was investigated using X-ray diffraction (XRD). A critical temperature (∼0.8 of melting point) was distinguished at which a considerable increase was observed in the grain size. At below this temperature, the mean grain size remains almost stable for long annealing times due to small amounts of interstitial and substitutional impurities. However, grain growth was pronounced significantly depending on settling time above it. Stability of powder hardness after annealing was evaluated by micro-indentation. The results revealed a down-shift of the hardness beyond the critical temperature.
Glass and glass-ceramics are versatile materials and have been widely used for sealing in the ong... more Glass and glass-ceramics are versatile materials and have been widely used for sealing in the ongoing development of intermediate temperature solid oxide fuel cell (SOFC) technology where its integrity is crucial for reliable operation of the stack. The fracture toughness is a key parameter required for the prediction of the mechanical performance of a seal glass. A comparative indentation study on two REglasses (RE¼ La and Y) was performed to evaluate their fracture toughness. Indentation toughness was calculated both through measurements of the indentation crack lengths and of crack-opening displacements in the near regions of a crack tip. Both approaches exhibited good agreement. La-containing glass showed higher stiffness, hardness and fracture toughness, which has been related to the in-situ toughening mechanism caused by devitrification and formation of crystalline phases.
ABSTRACT Thermo-mechanical properties of a silicate based glass and its potential use for sealing... more ABSTRACT Thermo-mechanical properties of a silicate based glass and its potential use for sealing application in intermediate temperature solid oxide cell (SOC) are presented in this paper. Effects of thermal aging are discussed on structural and microstructural evolution, thermal expansion, viscosity, modulus of elasticity, and high-temperature deformation of the glass. The balance between the viscosity and viscous flowing behavior was explored for the non-aged and aged glasses as it is essential to have a successful sealing for a SOC stack. The results reveal a temperature dependence of Young&amp;#39;s modulus in which a transition between a slow softening (elastic) regime and a rapid softening one was observed. Crystallization induced by thermal aging led to higher creep resistance, but lower capability of crack healing when inspected by electron microscopy. However, potential of stress relaxation in the aged material was confirmed by the constitutive mechanical models of viscoelasticity.
Prior to the long-term utilization of solid oxide fuel cell (SOFC), one of the most remarkable el... more Prior to the long-term utilization of solid oxide fuel cell (SOFC), one of the most remarkable electrochemical energy conversion devices, a variety of difficult experimental validation procedures is required, so it would be time-consuming and steep to predict the applicability of these devices in the future. For numerous years, extensive efforts have been made to develop mathematical models to predict the effects of various characteristics of solid oxide fuel cells (SOFCs) components on their performance (e.g., voltage). Taking advantage of the machine learning (ML) method, however, some issues caused by assumptions and calculation costs in mathematical modeling could be alleviated. This paper presents a machine learning approach to predict the anode-supported SOFCs performance as one of the most promising types of SOFCs based on architectural and operational variables. Accordingly, a dataset was collected from a study about the effects of cell parameters on the output voltage of a ...
In the manufacturing process of solid oxide fuel cells (SOFCs), the residual stresses and curvatu... more In the manufacturing process of solid oxide fuel cells (SOFCs), the residual stresses and curvature are developed in components due to the differences in material properties of cell layers. Residual stress may lead to the crack formation in the cell layers and facilitates cell fracture. In this work, the changes of the residual stress in the electrolyte layer of the anode-supported planar solid oxide fuel cells are experimentally determined at room temperature. The “sin2ψ” technique of X-ray diffraction method is employed to measure the residual stress in the half-cell samples. Investigation on the changes of the residual stress and curvature state in the scaling-up process of the cell is crucial for commercial use. Therefore, several cells with different sizes and shapes are investigated to evaluate the potential impact of cell size and cell shape on the residual thermal stress. Values of about −610 MPa are determined for the electrolyte layer on an oxidized ∼400 μm thick anode sub...
Background: Leishmaniasis is an expanding neglected tropical disease in the world reporting from ... more Background: Leishmaniasis is an expanding neglected tropical disease in the world reporting from 98 countries including Iran. This study focused on eco-epidemiological determinants of the disease following a rapid and unexpected increase of leishmaniasis incidence in a strategic residential district in North-East of Isfahan County, Iran. Methods: This study was accomplished from Apr 2012 to Jan 2014 in a strategic residential zone in North-East of Isfahan County, Esfahan, Iran. Monthly activity, parity, Leishmania infection and susceptibility tests, were determined on sand flies. Some portion of inhabitants and school children were surveyed to find active or passive cases of leishmaniasis and also wild rodents were collected to determine reservoir host. Results: Totally 5223 sand flies belonging to Phlebotomus and Sergentomyia genus were collected and identified; Ph. papatasi was the dominant species and started to appear in May and disappeared in Oct. The majority of living dissect...
Abstract<br /> Background and purpose: This study was done from October 2016 to October 201... more Abstract<br /> Background and purpose: This study was done from October 2016 to October 2017 to determine funa and distribution of ectoparasites of zoonotic cutaneous leishmaniasis reservoirs to prevent and control of zoonotic diseases in the hyperendemic area (Segzi area), in Esfahan Province in the future.<br /> Materials and methods: Rodents were collected by Sherman's Living Traps during different seasons and were identified by the standard morphological keys and comparison of morphometric characteristics with standard specimens. The collected rodents were anesthetized and ectoparasites were removed and conserved in 96% Alcohol. Then the ectoparasites were identified by the standard keys. <br /> Results: Ninety-two Rhombomys opimus and 1 Nesokia indica were captured. 50 out of 93 rodents (53.88%) were infested by the ectoparasites and a total of 527 ectoparasites were collected from them. The 9 species of identified ectoparasites were included 1 tick (0.19%...
Background: Sand flies of subgenus Adlerius has a wide geographical distribution in Iran and are ... more Background: Sand flies of subgenus Adlerius has a wide geographical distribution in Iran and are mostly found in wild form in mountainous areas. They are always considered as probable vectors of visceral leishmaniasis. The objective of this study was to determine the Adlerius species and its composition in an endemic focus of zoonotic vis-ceral leishmaniasis in northwest of the country. Methods: Sand flies were collected from 6 different areas of Azarbaijan-e-Sharqi Province using sticky paper traps from August to September which is active season for sand flies in this area, in 2009. The flies were mounted and identified. The length of third antennal segments, ascoid, labrum, coxite, surstyle, style, aedeagus, genital filament, genital pump, width of style, and the end of aedeagus were measured and the number of costal hairs group was also counted as the morphological characters. Results: A total of 30 adult sand flies, (26 males and 4 females) including Phlebotomus halepensis (46.8...
2019 International Power System Conference (PSC), 2019
Residual stresses in solid oxide cell (SOC) stacks or components are potential fracture sources w... more Residual stresses in solid oxide cell (SOC) stacks or components are potential fracture sources which needs to be investigated in order to enhance the reliability of the stacks. One of the most important joint materials in solid oxide cell stacks are glass sealants/steel interconnects at which chemical and mechanical characteristics are changed during service. Chemical reactions occur at the interface and change its chemistry. Mechanical stresses are formed with changing materials chemistry. Moreover, thermos-mechanical behavior mismatches lead to residual mechanical stress upon cooling/heating. An analytical model based on the classical beam bending theory was used in this study for calculating the residual stresses in this joint hybrid structure when the device is cooled down to room-temperature. Two potential commercial steel materials (SS430 and Crofer 22APU) were considered as the glass sealant counterpart.
Several theories have been presented about the corporate capital structure; some researchers beli... more Several theories have been presented about the corporate capital structure; some researchers believe that the structure of capital and firm value depend on each other. Moreover, others believe that the firm value is not influenced by any changes in the structure of capital, and with the change in the structure of capital, the value of the firm remains constant. The present research studies the historical theories of capital structure and presents the classification of existing theories in terms of the optimal capital structure. This classification is subdivided into two categories: the presence of an optimal capital structure and the absence of an optimal capital structure. With the historical review of theories of capital structure and the presence of an optimal capital structure or the lack of an optimal capital structure, it seems that none has been a complete model and so far, no one has been able to provide an optimal capital structure. In this research, from the system dynamic...
In the manufacturing process of solid oxide fuel cells (SOFCs), the residual stresses and curvatu... more In the manufacturing process of solid oxide fuel cells (SOFCs), the residual stresses and curvature are developed in components due to the differences in material properties of cell layers. Significant residual stress may lead to the formation of cracks in the cell layers and facilitates cell fracture. In this work, the changes of the residual stress in the electrolyte of the anode-supported planar solid oxide fuel cells are experimentally determined at room temperature. The “sin2ψ” technique of X-ray diffraction method is employed to measure the residual stress in the half-cell samples. Several cells with different sizes and shapes are investigated to evaluate the potential impact of cell size and cell shape on the thermal residual stress. Because investigation on the changes of the residual stress and curvature state in the scaling up process of cell is crucial for commercial use. Values of about − 610 MPa are determined for an electrolyte layer on an oxidized ∼400µm thick anode s...
The structural integrity of the sealant is critical for the reliability of solid oxide cells (SOC... more The structural integrity of the sealant is critical for the reliability of solid oxide cells (SOCs) stacks. In this study, elastic modulus (E), hardness (H) and fracture toughness (K IC) of a rapid crystallizing glass of BaO-CaO-SiO 2 system termed "sealant G" are reported as determined using an indentation test method at room temperature. A wide range of indentation loads (1 mN-10 N) was used to investigate the load-dependency of these mechanical properties. Values of 95 ± 12 GPa, 5.8 ± 0.2 GPa and 1.15 ± 0.07 MPa m 0.5 were derived for E, H and K IC using the most suitable indentation loads. An application relevant annealing treatment of 500 h at 800 • C does not lead to a significant change of the mechanical properties. Potential self-healing behavior of the sealant has also been studied by electron microscopy, based on heat treatment of samples with indentation-induced cracks for 70 h at 850 • C. Although the sealant G is considered to be fully crystallized, evidence indicates that its cracks can be healed even in the absence of a dead load.
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Low-temperature deposition of electroceramic thin films allows the construction of new devices an... more Low-temperature deposition of electroceramic thin films allows the construction of new devices and their integration with existing large-scale fabrication methods. Developing a suitable low-cost deposition method is important to further advance the development of microdevices. In this work, we deposited a 1-lm-thick La 0.6 Sr 0.4 CoO 3Àd (LSC) perovskite with high electrical conductivity on sapphire substrates at 400°C and analyzed its electrical, morphological and structural properties as a function of temperature in the range of 400-1100°C. The results show that spray pyrolysis can be used to deposit highquality reproducible layers with the desired chemical and phase composition. Upon heating to around 600°C, the residual CO and C=O species are removed, and the deposited layers crystallize and become conducting. The dependence of electrical conductivity versus processing temperature has a complex character-the maximum conductivity is found for layers processed at 800°C. An analytical model of stress distribution was used to predict stress to which the bi-layer material would be exposed to while being cooled down from the annealing temperature to room temperature. The high electronic conductivity and high-quality microstructure of the LSC layers, which can be adjusted with the appropriate heat treatment procedure, make them suitable for applications in electrochemical devices applied in integrated energy modules, including electrodes or contacts.
Cell temperature and selection of the reactant gases are crucial parameters for the design and op... more Cell temperature and selection of the reactant gases are crucial parameters for the design and optimization of fuel cell performance. In this study, effect of operating conditions on the performance of Solid Oxide Fuel (SOFC) has been investigated. Application of Response Surface Methodology (RSM) was applied to optimize operations conditions in SOFC. For this purpose, an experimental set up for testing of SOFC has been established to investigate the effect of Hydrogen, Oxygen, Nitrogen flow rates and cell temperature parameters on cell performance. Hydrogen flow rate, oxygen flow rate, nitrogen flow rate and cell temperature were the main parameters considered and they were varied between 0.25 and 1 L/min, 0.5 and 1 L/min, 0 and 1 L/min and 700-800 oC in the analyses respectively. The maximum power density was found as 0.572 W/cm2 in the experiments.
The compressibility behavior of Al-AlN nanostructured composite powder with different amount of r... more The compressibility behavior of Al-AlN nanostructured composite powder with different amount of reinforcement content was studied. The composite powder was synthesized by blending and high-energy milling process for 25 h. Williamson-Hall method was applied to determine the crystallite size after milling process. To investigate the role of reinforcement particles in consolidation of composite powders, monolithic aluminum powder was examined. Samples were made at different pressures and relationships were established between the compaction pressure and the density of the compacts. The modified Heckel equation was used to assume the pressure effect on yield strength and then was compared with other common equations. The best correlation was obtained when the effect of compaction pressure was considered. Due to lower plastic deformation capacity, the powders with higher content of hard reinforcements exhibited lower compressibility. The results also revealed that the yield strength of compacts, predicted by the mathematical equation, increases with reinforcement addition.
The thermal stability of nanostructured aluminum powder synthesized by high energy milling was st... more The thermal stability of nanostructured aluminum powder synthesized by high energy milling was studied through isothermal annealing at high temperatures for various times. Strain relaxation and grain growth of milled powders were studied at different milling times by differential scanning calorimetry (DSC). The results showed a high level of stored enthalpy due to milling procedure. After 25 h milling, powder particles reached a steady state with equiaxed morphology and 90 nm crystallite size in average. Isothermal grain growth kinetics of nanocrystalline Al powder was investigated using X-ray diffraction (XRD). A critical temperature (∼0.8 of melting point) was distinguished at which a considerable increase was observed in the grain size. At below this temperature, the mean grain size remains almost stable for long annealing times due to small amounts of interstitial and substitutional impurities. However, grain growth was pronounced significantly depending on settling time above it. Stability of powder hardness after annealing was evaluated by micro-indentation. The results revealed a down-shift of the hardness beyond the critical temperature.
Glass and glass-ceramics are versatile materials and have been widely used for sealing in the ong... more Glass and glass-ceramics are versatile materials and have been widely used for sealing in the ongoing development of intermediate temperature solid oxide fuel cell (SOFC) technology where its integrity is crucial for reliable operation of the stack. The fracture toughness is a key parameter required for the prediction of the mechanical performance of a seal glass. A comparative indentation study on two REglasses (RE¼ La and Y) was performed to evaluate their fracture toughness. Indentation toughness was calculated both through measurements of the indentation crack lengths and of crack-opening displacements in the near regions of a crack tip. Both approaches exhibited good agreement. La-containing glass showed higher stiffness, hardness and fracture toughness, which has been related to the in-situ toughening mechanism caused by devitrification and formation of crystalline phases.
ABSTRACT Thermo-mechanical properties of a silicate based glass and its potential use for sealing... more ABSTRACT Thermo-mechanical properties of a silicate based glass and its potential use for sealing application in intermediate temperature solid oxide cell (SOC) are presented in this paper. Effects of thermal aging are discussed on structural and microstructural evolution, thermal expansion, viscosity, modulus of elasticity, and high-temperature deformation of the glass. The balance between the viscosity and viscous flowing behavior was explored for the non-aged and aged glasses as it is essential to have a successful sealing for a SOC stack. The results reveal a temperature dependence of Young&amp;#39;s modulus in which a transition between a slow softening (elastic) regime and a rapid softening one was observed. Crystallization induced by thermal aging led to higher creep resistance, but lower capability of crack healing when inspected by electron microscopy. However, potential of stress relaxation in the aged material was confirmed by the constitutive mechanical models of viscoelasticity.
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