LaNi（0.6）Fe（0.4）O（3-δ） （LNF） powders were synthesized by the glycine-nitrate process and LNF-gadolinium-doped ceria （GDC） nanocomposite cathodes for solid oxide fuel cells （SOFCs） were fabricated by infil...LaNi（0.6）Fe（0.4）O（3-δ） （LNF） powders were synthesized by the glycine-nitrate process and LNF-gadolinium-doped ceria （GDC） nanocomposite cathodes for solid oxide fuel cells （SOFCs） were fabricated by infiltration from LNF porous backbones. Electrochemical properties and Cr-poisoning behavior of LNF-GDC cathodes were studied. Single phase perovskite LNF could be obtained at the glycine to nitrate molar ratio of 1：1. The polarization resistance of the LNF-GDC nanocomposite cathode was significantly decreased in comparison with the LNF. This phenomenon was associated with enhanced catalytic activity and enlarged triple-phase boundary （TPB） length by GDC nano particles. In addition, the nanocomposite cathode showed good Cr tolerance under open circuit condition. The LNF-GDC nanocomposite cathodes were expected for use as a potential cathode in intermediate- temperature solid oxide fuel cells （IT-SOFC）.展开更多
In many communities, residential wood burning is the source of a significant fraction of wintertime PM2.5 and produces exposures to nearby residents inside their homes. To evaluate the magnitude of this effect, black ...In many communities, residential wood burning is the source of a significant fraction of wintertime PM2.5 and produces exposures to nearby residents inside their homes. To evaluate the magnitude of this effect, black carbon particles were measured as a proxy for woodsmoke indoors and outdoors in a community where residential woodsmoke is the only significant particle source. Thirteen indoor/outdoor measurement pairs were obtained at 4 different residences and showed an average indoor/outdoor concentration ratio of 0.78 ± 0.21 for residences without indoor generation. In addition, a time dependent mass balance model was used in conjunction with aethalometer measurements taken over 16 nights at a single residence to estimate an average air exchange rate of 0.26 ± 0.08 h-1, an average deposition loss rate of 0.08 ± 0.03 h-1, and an average penetration factor of 0.97 ± 0.02. Using a mechanistic approach which utilizes these average values in a steady state model, the predicted average infiltration factor was 0.74 for the residence studied. The high values for both measured I/O ratio and modeled infiltration factor show that residential environments provide inhabitants with relatively little protection from recently generated wood smoke particles.展开更多
The pressureless infiltration process to synthesize a silicon nitride composite was investigated. An Al-2wt%Mg alloy was infiltrated into silicon nitride preforms in the atmosphere of nitrogen. It is possible to infil...The pressureless infiltration process to synthesize a silicon nitride composite was investigated. An Al-2wt%Mg alloy was infiltrated into silicon nitride preforms in the atmosphere of nitrogen. It is possible to infiltrate the Al-2wt%Mg alloy in silicon nitride preforms, The growth of the composite with useful thickness was facilitated by the presence of magnesium powder at the interface and by flowing nitrogen. The microstructure of the Si3N4-Al composite has been characterized using scanning electron microscope. During the infiltration of Si3N4 preforms, Si3N4 reacted with aluminium to form silicon and AIN. The silicon produced during the growth consumed in the formation of MgSiAIO, MgSiAlN and Al3.27Si0.47 type phases. The growth of the composite was found to proceed in two ways, depending on the oxide content in the initial preforms, First, less oxide content preforms gave rise to MgAlSiO and MgAlSiN type phases after infiltration. Second, more oxide content preforms gave rise to AlN-Al2O3 solid solution phase （AlON）, The AlON phase was only present in the composite, containing 10% aluminium in the silicon nitride preforms before infiltration.展开更多
Mixed ionic-electronic conductors in the family of LaxSr1-xCoyFe1-y O3-δ have been widely studied as cathode materials for solid oxide fuel cells （SOFCs）. However, the long-term stability was a concern. Here we rep...Mixed ionic-electronic conductors in the family of LaxSr1-xCoyFe1-y O3-δ have been widely studied as cathode materials for solid oxide fuel cells （SOFCs）. However, the long-term stability was a concern. Here we report our findings on the effect of a thin film coating of La0.85Sr0.15MnO3-δ （LSM） on the performance of a porous La0.6Sr0.4Co0.2Feo.8O3-δ（LSCF） cathode. When the thicknesses of the LSM coatings are appropriate, an LSM-coated LSCF electrode showed better stability and lower polarization （or higher activity） than the blank LSCF cathode without LSM infiltration. An anode-supported cell with an LSM-infiltrated LSCF cathode demonstrated at 825 ℃ a peak power density of -1.07 W/cm2, about 24% higher than that of the same cell without LSM infiltration （-0.86 W/cm2）. Further, the LSM coating enhanced the stability of the electrode; there was little degradation in performance for the cell with an LSM-infiltrated LSCF cathode during 100 h operation.展开更多
SiC particulates reinforced alumina matrix composites were fabricated using Directed Metal Oxidation (DIMOX) process. Continuous oxidation of an Al-Si-Mg-Zn alloy with different interlayers (dopents) as growth promote...SiC particulates reinforced alumina matrix composites were fabricated using Directed Metal Oxidation (DIMOX) process. Continuous oxidation of an Al-Si-Mg-Zn alloy with different interlayers (dopents) as growth promoters, will encompasses the early heating of the alloy ingot, melting and continued heating to temperature in the narrow range of 950°C to 980°C in an atmosphere of oxygen. Varying interlayers (dopents) are incorporated to examine the growth conditions of the composite materials and to identification of suitable growth promoter. The process is extremely difficult because molten aluminum does not oxidize after prolonged duration at high temperatures due to the formation of a passivating oxide layer. It is known that the Lanxide Corporation had used a combination of dopents to cause the growth of alumina from molten metal. This growth was directed, i.e. the growth is allowed only in the required direction and restricted in the other directions. The react nature of the dopants was a trade secret. Though it is roughly known that Mg and Si in the Al melt can aid growth, additional dopents used, the temperatures at which the process was carried out, the experimental configurations that aided directed growth were not precisely known. In this paper we have evaluated the conditions in which composites can be grown in large enough sizes for evaluation application and have arrived at a procedure that enables the fabrication of large composite samples by determining the suitable growth promoter (dopant). Scanning electron microscopic, EDS analysis of the composite was found to contain a continuous network of Al2O3, which was predominantly free of grain-boundary phases, a continuous network of Al alloy. Fabrication of large enough samples was done only by the inventor company and the property measurements by the company were confirmed to those needed to enable immediate applications. Since there are a large number of variable affecting robust growth of the composite, fabrication large sized samples for measurements is a difficult task. In the present work, to identify a suitable window of parameters that enables robust growth of the composite has been attempted.展开更多
基金supported by a grant from the Fundamental R&D Program for Core Technology of Materials (No.10051006)funded by the Ministry of Knowledge Economy, Republic of Koreasupported by the New & Renewable Energy Core Technology Program of the Korea Institute of Energy Technology Evaluation and Planning (KETEP), granted financial resource from the Ministry of Trade, Industry & Energy, Republic of Korea (No. 20113020030050)
文摘LaNi（0.6）Fe（0.4）O（3-δ） （LNF） powders were synthesized by the glycine-nitrate process and LNF-gadolinium-doped ceria （GDC） nanocomposite cathodes for solid oxide fuel cells （SOFCs） were fabricated by infiltration from LNF porous backbones. Electrochemical properties and Cr-poisoning behavior of LNF-GDC cathodes were studied. Single phase perovskite LNF could be obtained at the glycine to nitrate molar ratio of 1：1. The polarization resistance of the LNF-GDC nanocomposite cathode was significantly decreased in comparison with the LNF. This phenomenon was associated with enhanced catalytic activity and enlarged triple-phase boundary （TPB） length by GDC nano particles. In addition, the nanocomposite cathode showed good Cr tolerance under open circuit condition. The LNF-GDC nanocomposite cathodes were expected for use as a potential cathode in intermediate- temperature solid oxide fuel cells （IT-SOFC）.
文摘In many communities, residential wood burning is the source of a significant fraction of wintertime PM2.5 and produces exposures to nearby residents inside their homes. To evaluate the magnitude of this effect, black carbon particles were measured as a proxy for woodsmoke indoors and outdoors in a community where residential woodsmoke is the only significant particle source. Thirteen indoor/outdoor measurement pairs were obtained at 4 different residences and showed an average indoor/outdoor concentration ratio of 0.78 ± 0.21 for residences without indoor generation. In addition, a time dependent mass balance model was used in conjunction with aethalometer measurements taken over 16 nights at a single residence to estimate an average air exchange rate of 0.26 ± 0.08 h-1, an average deposition loss rate of 0.08 ± 0.03 h-1, and an average penetration factor of 0.97 ± 0.02. Using a mechanistic approach which utilizes these average values in a steady state model, the predicted average infiltration factor was 0.74 for the residence studied. The high values for both measured I/O ratio and modeled infiltration factor show that residential environments provide inhabitants with relatively little protection from recently generated wood smoke particles.
文摘The pressureless infiltration process to synthesize a silicon nitride composite was investigated. An Al-2wt%Mg alloy was infiltrated into silicon nitride preforms in the atmosphere of nitrogen. It is possible to infiltrate the Al-2wt%Mg alloy in silicon nitride preforms, The growth of the composite with useful thickness was facilitated by the presence of magnesium powder at the interface and by flowing nitrogen. The microstructure of the Si3N4-Al composite has been characterized using scanning electron microscope. During the infiltration of Si3N4 preforms, Si3N4 reacted with aluminium to form silicon and AIN. The silicon produced during the growth consumed in the formation of MgSiAIO, MgSiAlN and Al3.27Si0.47 type phases. The growth of the composite was found to proceed in two ways, depending on the oxide content in the initial preforms, First, less oxide content preforms gave rise to MgAlSiO and MgAlSiN type phases after infiltration. Second, more oxide content preforms gave rise to AlN-Al2O3 solid solution phase （AlON）, The AlON phase was only present in the composite, containing 10% aluminium in the silicon nitride preforms before infiltration.
基金supported by the Department of Energy (National Energy Technology Laboratory) SECA Core Technology Program under Award Number DE-NT0006557 and DE-FE0009652by NSFC under grant No.51002182
文摘Mixed ionic-electronic conductors in the family of LaxSr1-xCoyFe1-y O3-δ have been widely studied as cathode materials for solid oxide fuel cells （SOFCs）. However, the long-term stability was a concern. Here we report our findings on the effect of a thin film coating of La0.85Sr0.15MnO3-δ （LSM） on the performance of a porous La0.6Sr0.4Co0.2Feo.8O3-δ（LSCF） cathode. When the thicknesses of the LSM coatings are appropriate, an LSM-coated LSCF electrode showed better stability and lower polarization （or higher activity） than the blank LSCF cathode without LSM infiltration. An anode-supported cell with an LSM-infiltrated LSCF cathode demonstrated at 825 ℃ a peak power density of -1.07 W/cm2, about 24% higher than that of the same cell without LSM infiltration （-0.86 W/cm2）. Further, the LSM coating enhanced the stability of the electrode; there was little degradation in performance for the cell with an LSM-infiltrated LSCF cathode during 100 h operation.
文摘SiC particulates reinforced alumina matrix composites were fabricated using Directed Metal Oxidation (DIMOX) process. Continuous oxidation of an Al-Si-Mg-Zn alloy with different interlayers (dopents) as growth promoters, will encompasses the early heating of the alloy ingot, melting and continued heating to temperature in the narrow range of 950°C to 980°C in an atmosphere of oxygen. Varying interlayers (dopents) are incorporated to examine the growth conditions of the composite materials and to identification of suitable growth promoter. The process is extremely difficult because molten aluminum does not oxidize after prolonged duration at high temperatures due to the formation of a passivating oxide layer. It is known that the Lanxide Corporation had used a combination of dopents to cause the growth of alumina from molten metal. This growth was directed, i.e. the growth is allowed only in the required direction and restricted in the other directions. The react nature of the dopants was a trade secret. Though it is roughly known that Mg and Si in the Al melt can aid growth, additional dopents used, the temperatures at which the process was carried out, the experimental configurations that aided directed growth were not precisely known. In this paper we have evaluated the conditions in which composites can be grown in large enough sizes for evaluation application and have arrived at a procedure that enables the fabrication of large composite samples by determining the suitable growth promoter (dopant). Scanning electron microscopic, EDS analysis of the composite was found to contain a continuous network of Al2O3, which was predominantly free of grain-boundary phases, a continuous network of Al alloy. Fabrication of large enough samples was done only by the inventor company and the property measurements by the company were confirmed to those needed to enable immediate applications. Since there are a large number of variable affecting robust growth of the composite, fabrication large sized samples for measurements is a difficult task. In the present work, to identify a suitable window of parameters that enables robust growth of the composite has been attempted.
