SwePub - sökning: L773:1938 6737 OR L773:1938 58...

Numrering	Referens	Omslagsbild	Hitta
1.	Ayedh, H. M., et al. (författare) Controlling the carbon vacancy in 4H-SiC by thermal processing 2018 Ingår i: ECS Transactions. - : Electrochemical Society Inc.. - 1938-6737 .- 1938-5862. ; , s. 91-97 Konferensbidrag (refereegranskat)abstract The carbon vacancy (Vc) is perhaps the most prominent point defect in silicon carbide (SiC) and it is an efficient charge carrier lifetime killer in high-purity epitaxial layers of 4H-SÌC. The Vc concentration needs to be controlled and minimized for optimum materials and device performance, and an approach based on post-growth thermal processing under C-rich ambient conditions is presented. It utilizes thermodynamic equilibration and after heat treatment at 1500 °C for 1 h, the Vc concentration is shown to be reduced by a factor-25 relative to that in as-grown state-of-the-art epi-layers. Concurrently, a considerable enhancement of the carrier lifetime occurs throughout the whole of >40 urn thick epi-layers.
2.	Abedin, Ahmad, et al. (författare) Epitaxial growth of Ge strain relaxed buffer on Si with low threading dislocation density 2016 Ingår i: ECS Transactions. - : Electrochemical Society. - 1938-5862 .- 1938-6737. - 9781607685395 ; , s. 615-621 Konferensbidrag (refereegranskat)abstract Epitaxial Ge with low dislocation density is grown on a low temperature grown Ge seed layer on Si substrate by reduced pressure chemical vapor deposition. The surface topography measured by AFM shows that the strain relaxation occurred through pit formation which resulted in freezing the defects at Ge/Si interface. Moreover a lower threading dislocation density compared to conventional strain relaxed Ge buffers on Si was observed. We show that by growing the first layer at temperatures below 300 °C a surface roughness below 1 nm can be achieved together with carrier mobility enhancement. The different defects densities revealed from SECCO and Iodine etching shows that the defects types have been changed and SECCO is not always trustable.
3.	Carlson, Annika, et al. (författare) Kinetic parameters in anion-exchange membrane fuel cells 2019 Ingår i: ECS Transactions. - : Electrochemical Society Inc.. - 1938-6737 .- 1938-5862. - 9781607685395 ; , s. 649-659 Konferensbidrag (refereegranskat)abstract Understanding limitations in an operating AEMFC is essential to .enhance the technology. Here the electrode processes are studied experimentally as well as by two physics-based models taking the porosity of the electrodes into account. The aim is to use the models to determine kinetic parameters specific for in-situ operation. The models can also be used to explain the experimental .behavior. From the impedance model of a symmetric H2/H2 cell it is shown that the hydrogen oxidation reaction (HOR) proceeds through the Tafel-Volmer reaction pathway, with the hydrogen adsorption as the slower reaction step. Based on the HOR model a •steady-state model of an O2/H2 cell is used to evaluate data from 14 experimental I-V curves, obtained for different gas partial pressures and catalyst loadings, in order to study the effects of the oxygen reduction reaction and overall cell limitations. The results show that the oxygen reduction reaction kinetics limit the cell performance for low current densities. However, at higher currents the uneven current distribution and locally low hydrogen adsorption at the anode increasingly affect the overall performance. Uneven current distribution is also observed at the cathode and likely caused by insufficient effective ionomer conductivity.
4.	Chen, J. T., et al. (författare) Carbon-doped GaN on SiC materials for low-memory-effect devices 2016 Ingår i: ECS Transactions. - : The Electrochemical Society. - 1938-5862 .- 1938-6737. - 9781607685395 ; 75:12, s. 61-65, s. 61-65 Konferensbidrag (refereegranskat)abstract AlGaN/GaN on SiC HEMT structures suitable for high power, high frequency applications are demonstrated. The material manifests record breaking thermal management and electron mobility. Moreover, thanks to the fact that the buffer layer is doped with carbon, the memory effect of processed devices is very low making system design and manufacturing significantly easier and less expensive.
5.	Debela, A. M., et al. (författare) Functionalized deoxynucleotides and DNA primers for electrochemical diagnostics of disease predispostions 2017 Ingår i: ECS Transactions. - : Electrochemical Society Inc.. - 1938-6737 .- 1938-5862. - 9781607685395 ; , s. 1873-1883, s. 1873-1883 Konferensbidrag (refereegranskat)abstract Redox labeled DNAs are of increasing interest for the fabrication of next generation molecular tools. In the present work we are investigating the use of various redox labeled dNTPs, ddNTPs and DNA primers for use in detection of diseases. We have reported the use of Polyoxometalate (POM) labeled DNA primers and dNTPs for use in PCR and subsequently used for direct electrochemical detection of PCR products. The use of POM labeled DNAs in PCR enabled us to check the compatibility with polymerases and PCR incorporability of the modified DNAs. Furthermore we have investigated the solid-phase array based primer extension (é-PEX) with redox labelled ddNTPs (ferrocene (Fc), anthraquinone (AQ) phenothiazine (PTZ) and methylene blue (MB)) to prove the strategy of detection of single nucleotide polymorphisms using the labeled ddNTPs. This strategy will allow the development of cost-effective, rapid and user-friendly platform for the screening of known and unknown genetic mutations.
6.	Espinoza-Andaluz, M., et al. (författare) Pore-scale analysis of diffusion transport parameters in digitally reconstructed SOFC anodes with gradient porosity in the main flow direction 2017. - 1 Ingår i: ECS Transactions. - : The Electrochemical Society. - 1938-6737 .- 1938-5862. - 9781607685395 ; 78, s. 2785-2796 Konferensbidrag (refereegranskat)abstract One of the promising devices to obtain electrical and thermal energy with considerable high efficiency is the solid oxide fuel cell (SOFC). The electrical energy is the result of the electrochemical reactions that occur inside the fuel cell (FC) when the reactant gases reach the so-called three-phase boundary (TPB). The nonhomogeneous and anisotropic characteristics of the layer between the gas channel and the TPB region require a pore-scale analysis to understand the effect of microstructural configurations. The purpose of this paper is to provide understanding of the behavior of the fluid flow through the digitally reconstructed SOFC anodes, with gradient porosity in the main flow direction, using the lattice Boltzmann method (LBM). The impact of the porosity distribution over the fluid behavior is determined for different digitally created SOFC anodes. The SOFC anodes are analyzed keeping the total porosity constant, but varying the local porosity in the flow direction. The impact of a gradient porosity over the gas-phase tortuosity and the normalized effective diffusion coefficient are presented.
7.	Falk Windisch, Hannes, 1984, et al. (författare) Metallic thin-film Co- and Ce/Co-coated steels as interconnect material in IT-SOFC 2017 Ingår i: ECS Transactions. - : The Electrochemical Society. - 1938-5862 .- 1938-6737. - 9781607685395 ; 78:1, s. 1607-1614 Konferensbidrag (refereegranskat)abstract Cr vaporization, oxide scale growth, and the electrical scale resistance (ASR) were studied at 650°C on coated interconnects intended for IT-SOFC applications. The custom-made SOFC interconnect steel Sanergy HT was coated with thin-film Co- and Ce/Co-coatings and compared to the less expensive substrate steel AISI 441 which was coated with Ce/Co and a 15-20 μm thick commercial MCO-coating. All coated materials mitigated Cr vaporization, and due to the very thin chromia scales formed at the low exposure temperature, ASR values below 10 mΩcm 2 were measured for all materials after 500 h at 650°C. The results in this study show that thin-film metallic Co- and Ce/Co-coated steels show excellent properties as interconnect materials for IT-SOFCs. Thick MCO-coatings can also be used at low temperatures; however, the coating method might be a critical issue for lowtemperature applications.
8.	Falk Windisch, Hannes, 1984, et al. (författare) Pre-coated Ce/Co-coated steel: Mitigating Cr vaporization, increasing corrosion resistance at competitive cost 2015 Ingår i: ECS Transactions. - : The Electrochemical Society. - 1938-5862 .- 1938-6737. - 9781607685395 ; 68:1, s. 1617-1623 Konferensbidrag (refereegranskat)abstract Cr vaporization and oxide scale growth are probably the two most detrimental degradation mechanisms associated to Cr2O3-forming alloys as interconnect material in SOFC. Both issues can be improved by the application of coatings. However, the use of coatings increase material cost. To reduce coating costs it is suggested that large amounts of steel can be coated before shaping the pre-coated material into an interconnect. The present study investigates the effectiveness of thin Ce and Co coatings on the cost effective steel AISI 441 with respect to Cr vaporization and corrosion resistance. Furthermore, the effect of mechanical deformation of the coated steel is examined. The results revealed that when the pre-coated steel is deformed, large cracks are formed. However, upon exposure those cracks can heal forming a continuous surface oxide rich in Co and Mn. As an effect of the rapid healing, no increase in Cr vaporization was measured.
9.	Habib, K., et al. (författare) Resistance values of aluminum oxide film in situ during anodization of aluminum by fabry-pérot interferometry 2017 Ingår i: ECS Transactions. - : Electrochemical Society Inc.. - 1938-6737 .- 1938-5862. - 9781607685395 ; , s. 1221-1229 Konferensbidrag (refereegranskat)abstract A combination of Fabry-Pérot interferometry and the DC electrochemical method have been used for the first time, in situ, to measure the resistance of aluminum oxide films in 2% sulfuric acid solution. Values of the corresponding resistance of the obtained Al2O3 film thickness were determined during anodization of aluminum (Al) in 2% H2SO4. The obtained resistance values were verified by electrochemical impedance spectroscopy (EIS) and holographic interferometry. The corresponding resistance (2.4 x109 Ohms) to the final thickness of the aluminum oxide film was found in an agreement with the resistance value that was measured by holographic interferometry, 2.54x109 Ohms, in 2% H2SO4. On the contrary, the corresponding resistance (2.4 x109 Ohms) to the final thickness of the aluminum oxide film was found twice the value of the resistance that was measured by the electrochemical impedance spectroscopy (EIS), 1.25x109 Ohms, in 2% H2SO4.
10.	Hu, Lan, et al. (författare) Electrode kinetics of the Ni porous electrode for hydrogen production in the molten carbonate electrolysis cell (MCEC) 2015 Ingår i: ECS Transactions. - : The Electrochemical Society. - 1938-5862 .- 1938-6737. - 9781607685395 ; , s. 93-98 Konferensbidrag (refereegranskat)abstract The hydrogen evolution reaction in molten carbonate salts is an important process in the development of the molten carbonate electrolysis cell (MCEC). In the present study the kinetics of hydrogen production in the Ni porous electrode in a MCEC is investigated. The general procedure is to determine the reaction orders of hydrogen, carbon dioxide and water. For this purpose steady-state polarization data were recorded under different gas compositions and temperatures. The exchange current densities were calculated from the slopes of the polarization curves at low overpotential. On the basis of that, the partial pressure dependencies of hydrogen, carbon dioxide and water could be determined in the electrolysis operation.
11.	Jaramillo-Fernandez, Juliana, et al. (författare) Tuning of heat transport across thin films of polycrystalline AlN via multiscale structural defects 2015 Ingår i: ECS Transactions. - : Electrochemical Society. - 1938-5862 .- 1938-6737. - 9781607685395 ; , s. 53-64 Konferensbidrag (refereegranskat)abstract The effective thermal conductivity of nanocrystalline films of AlN with inhomogeneous microstructure is investigated experimentally and theoretically. This is done by measuring the thermal conductivity of the samples with the 3-omega method and characterizing their microstructure by means of electron microscopy. The relative effect of the microstructure and the interface thermal resistance on the thermal conductivity is quantified through an analytical model. Thermal measurements showed that when the thickness of an AlN film is reduced from 1460 to 270 nm, its effective thermal conductivity decreases from 8.21 to 3.12 WYm-1?K-1, which is two orders of magnitude smaller than its bulk counterpart value. It is shown that both the size effects of the phonon mean free paths and the intrinsic thermal resistance resulting from the inhomogeneous microstructure predominate for thicker films, while the contribution of the interface thermal resistance strengthens as the film thickness is scaled down. The obtained results demonstrate that the structural inhomogeneity in polycrystalline AlN films can be efficiently used to tune their cross- plane thermal conductivity. In addition, thermal conductivity measurements of epitaxially grown InP layers on silicon using Raman spectroscopy are reported.
12.	Nugehalli Sachitanand, Rakshith, 1984, et al. (författare) Coatings for SOFC interconnects in fuel side environments 2015 Ingår i: ECS Transactions. - : The Electrochemical Society. - 1938-5862 .- 1938-6737. - 9781607685395 ; 68:1, s. 1575-1580 Konferensbidrag (refereegranskat)abstract This study focuses on examining the effect of PVD coatings on the oxidation performance of interconnects in fuel side environments. The ferritic steels Sanergy HT and AISI 441 were coated with nanoscale thick rare earth oxides of Ce and La. Additionally, Sanergy HT was also coated with Cu, Co and Ce/Co. The samples were exposed at 850°C in Ar-5% H2-3% H2O in a tubular furnace. Chemical analysis on the samples was subsequently performed with SEM/EDX and XRD. It was established that the Ce and La coatings brought about a ≈4x reduction in the oxidation rate while the presence of a metallic phase in the oxide (Cu and Co) negatively affected oxidation performance. Further, the La coating resulted in the formation of a perovskite phase, showing that the intrinsic electronic properties of the oxide can be tailored using coatings.
13.	Wang, G., et al. (författare) Integration of selective epitaxial growth of SiGe/Ge layers in 14nm node FinFETs 2016 Ingår i: ECS Transactions. - : Electrochemical Society Inc.. - 1938-5862 .- 1938-6737. - 9781607685395 ; , s. 273-279 Konferensbidrag (refereegranskat)abstract In this study, the process integration of SiGe selective epitaxy on source/drain and SiGe/Ge bilayers selectively epitaxy on replacement Si channel regions for 14 nm node FinFETs has been presented. The epi-quality, layer profile and strain amount of the selectively grown SiGe and Ge layers were also investigated by means of various characterization tools. A series of prebaking experiments were performed for different temperatures in order to in-situ clean the Si fins prior to the SiGe S/D epitaxy. It was also found that a SiGe layer with graded Ge content was deposited as the strain relaxed buffer (SRB) layer in the channel trench prior to the Ge layer filling in the small trenches to make the void defect free.
14.	Zhang, Shidong, et al. (författare) Simple and complex polymer electrolyte fuel cell stack models : A comparison 2018. - 13 Ingår i: ECS Transactions. - : The Electrochemical Society. - 1938-6737 .- 1938-5862. - 9781607685395 ; 86, s. 287-300 Konferensbidrag (refereegranskat)abstract In this paper, two distinct polymer electrolyte fuel cell stack models are constructed: a detailed numerical model (DNM) employing a fine-scale computational mesh and a coarse-mesh approach based on a distributed resistance analogy (DRA) where diffusion terms in the transport equations are replaced by rate terms. Both methods are applied to a 5-cell, high-temperature polymer electrolyte fuel cell stack with an active area of 200 cm2 per cell. The polarization curve and local current density distributions from both the DRA and DNM are compared with experimental data, finding good agreement. Temperature, pressure, Nernst potential, and species distributions are also exhibited. The DNM displays details of fine-scale local extrema not captured by the DRA; however, the latter requires orders of magnitude less computer processor power and memory for execution. Both methods provide much finer-scale results than present experimental techniques.
15.	Andersson, M., et al. (författare) Coupling of lattice boltzmann and volume of fluid approaches to study the droplet behavior at the gas diffusion layer/gas channel interface 2018. - 13 Ingår i: ECS Transactions. - : The Electrochemical Society. - 1938-6737 .- 1938-5862. - 9781607688600 ; 86, s. 329-336 Konferensbidrag (refereegranskat)abstract A typical polymer electrolyte fuel cell (PEFC) flow field consists of micro/minichannels. The continues removal of liquid water from the cathode channels is a critical topic, as water droplets forming in the channels may block the transport of gaseous oxygen to the active sites, which not only gives an uneven current distribution and substantial loss of performance, but also, increases degradation rates and unstable operation. Water generated by the electrochemical reactions condenses, depending on temperature mainly, into liquid form, potentially flooding various part of the PEFC. The aim of this work is to obtain an increased understanding of the droplet behavior at the gas diffusion layer (GDL) interface with the gas channels in PEFCs by the coupling of Lattice Boltzmann (LB) and Volume of Fluid (VOF) approaches. A multiscale environment is established with input parameters in the VOF model being extracted from in-house LB calculations. It is clear that the contact angle as well as the size of the liquid droplet vary with positions at the GDL surface, depending on the stochastic GDL geometry. A VOF model describing one straight channel with one gas inlet, one liquid inlet (at the GDL surface) and one two-phase outlet is employed.
16.	Andersson, Martin, et al. (författare) Review on Dimensionless Numbers Relevant for Polymer Electrolyte Fuel Cells 2016 Ingår i: ECS Transactions. - : The Electrochemical Society. - 1938-6737 .- 1938-5862. ; 75:14, s. 547-552 Tidskriftsartikel (refereegranskat)abstract With the concern about global warming, air pollution and energy security, the prospect of using polymer electrolyte fuel cells (PEFCs) in future sustainable and renewable energy conversion systems has achieved substantial momentum. Dimensionless numbers can be determined before construction of a model is started, to make simple estimations on the transport processes, for example, within the porous PEFC GDL. Microstructural parameters, such as tortuosities and contact angles, are frequently treated as fitting parameters used in the respective governing equations, such that unrealistic values could be assumed or properties could not be representative of the corresponding microstructure. This treatment can be avoided if the origin of the expression is clearly clarified and if geometric properties are not used for fitting. Instead, it is recommended to, when needed, introduce parameters, without a geometrical meaning used only for fitting the model to experimental data, such as the pre-exponential factor in the advanced microstructural approach.
17.	Bessman, Alexander, et al. (författare) Investigating the aging effect of current ripple on lithium-ion cells 2015 Ingår i: ECS Transactions. - : Electrochemical Society. - 1938-6737. - 9781607685395 ; , s. 101-106 Konferensbidrag (refereegranskat)abstract We have built an experimental setup which exposes twelve cells to a well-defined ripple current. It consists of a system for cycling high capacity cells in parallel with a triangular current waveform superimposed on top of the direct current. The frequency of the waveform is variable up to 50 Hz, and the sum of the DC and AC components can have a magnitude of -40 A to 40 A. Current is measured over a 500 μω shunt resistor. The voltage and current of each cell is read simultaneously at a sample rate up to 4 MS/s, allowing for precise impedance measurements even for high frequency harmonics. The cells are cycled at 40 °C. The experiment has been designed to eliminate indirect effects of the AC harmonics as far as possible. This system is being used to test whether or not AC harmonics affect Li-ion aging.
18.	Dermenci, K.B., et al. (författare) Effect of cathode slurry composition on the electrochemical properties of Li-ion batteries 2015 Ingår i: ECS Transactions. - 1938-5862 .- 1938-6737. ; 66:9, s. 285-293 Tidskriftsartikel (refereegranskat)abstract The performance difference between commercial and laboratory scale cells remains a problem to be solved. Different way of battery electrode preparation is considered to be the main reason underlying various battery performance. In this work, the effect of slurry composition on electrochemical properties of Li-ion batteries is reported. Slurry preparation with various compositions of LiFePO4 active material (76-88%), PVdF binder (6-12%) and Super P Carbon conductive additive (6-12%) has been studied. Charge-discharge curves and capacity fade of electrodes are also investigated. Selected electrodes were pressed in order to see the effect of pressing on the final performance. Results showed that varying PVdF and carbon content mainly effects charge-discharge characteristics. For unpressed samples, higher amount of PVdF and carbon could result higher maximum specific capacity and lower internal resistance during lithiation and delithiation of positive electrode. Pressing reduces the distance between slurry particles, which enhances the conductivity of the prepared cell.
19.	Engström, Olof, 1943, et al. (författare) Properties of Metal/High-k Oxide/Graphene Structures 2017 Ingår i: ECS Transactions. - : The Electrochemical Society. - 1938-5862 .- 1938-6737. ; 80:1, s. 157-176 Konferensbidrag (refereegranskat)abstract The challenge of interpreting experimental data from capacitance versus voltage (C-V) measurements on metal/high-k oxide/graphene (MOG) structures is discussed. Theoretical expressions for the influence of interface states, bulk oxide traps, measurement frequency, temperature and puddles are derived and compared with experiments. The nature of oxide traps and their impact on C-V data is treated especially from the view of electron-lattice interaction at electron emission and capture and possible performance as border traps, resembling interface states. We find that characterization on detailed physical origins leading to effects on C-V data is a more complicated issue than the corresponding analysis of metal/oxide/semiconductor (MOS) structures.
20.	Esmaily, Mohsen, 1987, et al. (författare) Achieving superior corrosion resistance in friction stir processed AA6005-T6 aluminum alloy joints 2015 Ingår i: ECS Transactions. - : The Electrochemical Society. - 1938-5862 .- 1938-6737. ; 64:26, s. 29-43 Konferensbidrag (refereegranskat)abstract In this study, ultra-fine grained (UFG) structure was produced in the stir zone (SZ) of AA6005-T6 alloy joints using friction stir processing (FSP) cooled by liquid nitrogen (N 2 ). Conventional friction stir welding (FSW) was used to fabricate reference joints. The corrosion properties of the cooled joints were investigated by atmospheric corrosion tests. The corrosion exposures were carried out at a relative humidity (RH) of 95%, 400 ppm CO 2 and at 22°C. The rapidly cooled joints exhibited exceptional corrosion resistance in both corrosion experiments as well as better mechanical properties compared to those of the FSWed joints. The better corrosion resistance of the quenched sample was attributed to the microstructural modification of the joint.
21.	Espinoza Andaluz, Mayken, et al. (författare) Analysis of Porosity and Tortuosity in a 2D Selected Region of Solid Oxide Fuel Cell Cathode Using the Lattice Boltzmann Method 2015 Ingår i: ECS Transactions. - : The Electrochemical Society. - 1938-5862 .- 1938-6737. ; 65:1, s. 59-73 Konferensbidrag (refereegranskat)abstract The solid oxide fuel cell (SOFC) is one of the most promising devices for getting electrical energy. There are a lot of advantages in the use of SOFCs such as their efficiency, higher electrical and thermal power production and reduction of the emission of polluting gases. Modeling the SOFC at downscale is one of the most important challenges in fuel cell (FC) research. Knowing the behavior of materials to this scale is a helpful tool to predict the physical and chemical phenomena within the FCs, improve their efficiency and reduce material costs. At micro- and mesoscale, Lattice Boltzmann Method (LBM) appears as a powerful tool for modeling fuel cells. LBM has been proven suitable for solving several physical phenomena in complex geometries such as porous media. Using the D2Q9 LBM scheme, the velocity field for a selected section of an SOFC cathode is determined. This velocity field is shown in 2D and 3D graphics. The porosity and tortuosity for this selected region are calculated and compared with previous results.
22.	Espinoza-Andaluz, M., et al. (författare) Impact of carbon deposition on diffusion parameters in porous anodes of solid oxide fuel cells using the lattice Boltzmann method 2019 Ingår i: ECS Transactions. - : The Electrochemical Society. - 1938-6737 .- 1938-5862. ; 91:1, s. 2023-2030 Tidskriftsartikel (refereegranskat)abstract A solid oxide fuel cell (SOFC) is an electrochemical device that converts energy of a chemical reaction into electrical and thermal energy. Besides lack of pollutants and high electrical efficiency, one of the main advantages of SOFCs is the flexibility of using a wide range of fuels, i.e., natural gas, biogas, or any reactant with hydrogen as constituent. However, the use of hydrocarbon fuels can affect the transport phenomena within the SOFC porous anode due to carbon deposition. The purpose of this work is to investigate, at pore-scale level, the impact of carbon deposition on the microstructural parameters that describes the diffusion process. The single-phase fluid flow behavior through digitally generated SOFC anodes is obtained by the Lattice Boltzmann method (LBM). Diffusion transport parameters, i.e., porosity, gas-phase tortuosity and effective diffusion coefficient are computed for different content of carbon deposition to be able to evaluate its impact.
23.	ESPINOZA ANDALUZ, MAYKEN, et al. (författare) Impact on Diffusion Parameters Computation in Gas Diffusion Layers, Considering the Land/Channel Region, Using the Lattice Boltzmann Method 2016 Ingår i: ECS Transactions. - : The Electrochemical Society. - 1938-6737 .- 1938-5862. ; 75:14, s. 521-530 Tidskriftsartikel (refereegranskat)abstract Diffusion phenomena through the gas diffusion layer (GDL) at the microscale are one of the most complex physical phenomena to be described in proton exchange fuel cell (PEFC) numerical models. Predicting transport parameter behavior in GDLs is a valuable stage to propose micro-architectural designs, which can improve the efficiency and performance of fuel cells (FCs). The purpose of this paper is to propose an expression to estimate parameters involved in the diffusion process such as gas-phase tortuosity and effective diffusion coefficient when the effects of the land/channel region are considered. Three-dimensional GDL approximations are generated considering real characteristics of micro-porous layers employed in FCs. The fluid behavior through the porous media is simulated using the Lattice Boltzmann method (LBM), and the mentioned parameters are studied. The incidence of the land/channel presence over the gas-phase tortuosity is determined, and its effects over the effective diffusion are estimated.
24.	Goebel, Claudia, 1988, et al. (författare) Influence of pre-oxidation on dual atmosphere effect on AISI 441 interconnects for solid oxide fuel cell applications 2017 Ingår i: ECS Transactions. - : The Electrochemical Society. - 1938-5862 .- 1938-6737. ; 78:1, s. 1559-1563 Konferensbidrag (refereegranskat)abstract In previous studies an extreme dual atmosphere effect on the airfacing side of AISI 441 at 600°C was observed. However indications showed that pre-oxidation of the material might have a beneficial effect on the corrosion resistance in dual atmosphere. To examine this further we pre-oxidized AISI 441 samples for 0 min, 11 min, 45 min, 180 min and 280 min and subsequently exposed these at 600 °C for 500 h under dual atmosphere conditions. Photographs of the air-facing sides were taken throughout exposure to monitor the corrosion behavior. SEM analysis was performed on all samples after exposure.
25.	Goebel, Claudia, 1988, et al. (författare) Long term (4 years) performance of Co/Ce coated 441 for SOFC interconnect applications 2017 Ingår i: ECS Transactions. - : The Electrochemical Society. - 1938-5862 .- 1938-6737. ; 78:1, s. 1675-1679 Konferensbidrag (refereegranskat)abstract Co/Ce coated 441 samples were exposed at 800°C in laboratory air for up to 37 000 h and subsequently characterized using different techniques. Mass gain data of all samples were recorded throughout exposure. Cr-evaporation measurements were conducted and compared with unexposed Co/Ce coated AISI 441 as well as unexposed and uncoated AISI 441. Furthermore SEM analysis on BIB cross-sections was performed on 7 000 h, 23 000 h and 35 000 h exposed Co/Ce coated 441.
26.	Goebel, Claudia, 1988, et al. (författare) The influence of different factors on the dual atmosphere effect observed for AISI 441 interconnects used in solid oxide fuel cells 2019 Ingår i: ECS Transactions. - : The Electrochemical Society. - 1938-5862 .- 1938-6737. ; 91:1, s. 2261-2266 Konferensbidrag (refereegranskat)abstract Interconnects used in solid oxide fuel cells are subjected to dual atmosphere corrosion at 600 °C. In this work we show that the dual atmosphere effect is dependent on the thickness of the steel sheet. For this AISI 441 with varying thicknesses was exposed to dual atmosphere at 600 °C for 336 h. Before and after exposure photographs were taken to analyze the progress of corrosion on the air-facing side of the steel samples. Additionally, scanning electron microscopy and energy dispersive x-ray diffraction (SEM/EDX) analysis was conducted on all exposed samples. It was found that thinner samples showed increased breakaway oxidation than thicker samples.
27.	Gupta, Mohit Kumar, et al. (författare) Electrochemical performance of plasma sprayed metal supported planar solid oxide fuel cells 2015 Ingår i: ECS Transactions. - : The Electrochemical Society. - 1938-5862 .- 1938-6737. ; 68:1, s. 1791-1802 Tidskriftsartikel (refereegranskat)abstract High production cost is one of the major barriers to widespread commercialization of solid oxide fuel cells (SOFCs). Thermal spray techniques are a low cost alternative for the production of SOFCs. The objective of this work was to evaluate the electrochemical performance of half-cells produced by plasma spraying. The anode was deposited on a porous metallic support by atmospheric plasma spraying (APS) whereas the electrolyte was deposited by plasma spray-thin film (PS-TF) technique which can produce thin and dense coatings at high deposition rates. The cathode was deposited by screen-printing. The electrochemical tests were performed at 650-800Â°C. Current-voltage characteristics and impedance spectra were measured and analyzed. The impact of electrolyte composition and layer thickness on the gas tightness of the electrolyte and the area specific resistance of the cell is discussed. The results show that the applied thermal spraying techniques are a potential alternative for producing SOFCs. Â© The Electrochemical Society.
28.	Jannasch, Patric (författare) Tethering cations to aromatic polymers via flexible spacers to enhance the performance of alkaline fuel cell membranes 2015 Ingår i: ECS Transactions. - : The Electrochemical Society. - 1938-6737 .- 1938-5862. ; 69:17, s. 369-375 Forskningsöversikt (refereegranskat)abstract Conventional anion-exchange membranes based on aromatic polymers with cationic groups placed in benzylic positions on the polymer backbone normally suffer from poor alkaline stability and limited OH− conductivity. However, recently it has been shown that both the conductivity and alkaline stability of anion-exchange membranes can be significantly enhanced by instead placing the cationic groups on flexible and hydrolytically stable alkyl spacers. The present contribution briefly reviews the latest results and developments concerning this synthetic approach to improved alkaline membranes for fuel cells.
29.	Kovi, Kiran Kumar, et al. (författare) (Invited) Surface Passivation of High-k Dielectric Materials on Diamond Thin Films 2015 Ingår i: ECS Transactions. - : The Electrochemical Society. - 1938-5862 .- 1938-6737. ; 69, s. 61-65 Tidskriftsartikel (refereegranskat)abstract Single-crystalline CVD diamond films have excellent electrical and material properties with potential in high power, high voltage and high frequency applications that are out of reach for conventional semiconductor materials. For realization of efficient devices (e.g. MOSFET), finding a suitable dielectric is essential to improve the reliability and electrical performance of devices. In the current study, we present results from surface passivation studies by high-k dielectric materials such as aluminum oxide and hafnium oxide deposited by ALD on intrinsic and boron doped diamond substrates. The hole transport properties in the intrinsic diamond films were evaluated and compared to unpassivated films using the lateral time-of-flight technique. The MOS capacitor structure, which forms the basic building block of the MOSFET, is discussed.
30.	Kuhn, Joel, et al. (författare) The effect of fuel electrode roughness on the properties of plasma sprayed solid oxide cells 2017 Ingår i: ECS Transactions. - : The Electrochemical Society. - 1938-5862 .- 1938-6737. ; 78:1, s. 1477-1487 Tidskriftsartikel (refereegranskat)abstract Solid oxide cell electrolytes fabricated by atmospheric plasma spraying are frequently found to have nonzero gas leak rates. Electrode surface roughness is known to have an influence on electrolyte leak rates. A jet of high velocity air, produced with an air knife, was aimed at the plasma plume during fuel electrode deposition to reduce the surface roughness prior to electrolyte deposition. The resulting fuel electrode masses, electrode compositions, and electrode surface roughnesses were measured for varying air knife inlet pressures. Surface asperity populations and maximum heights were significantly reduced using air knife pressures of > 6 bar at the expense of deposition efficiency. The distribution of surface gradients was also improved with the use of the air knife, but some regions with steep gradients still remained in surfaces prepared with an air knife pressure of 8 bar. Â© The Electrochemical Society.
31.	Santhanam, S., et al. (författare) Transient operation strategies for MW-scale SOC systems 2019 Ingår i: ECS Transactions. - : The Electrochemical Society. - 1938-6737 .- 1938-5862. ; , s. 2571-2578 Konferensbidrag (refereegranskat)abstract High temperature reversible Solid Oxide cell (rSOC) systems can operate efficiently in both fuel cell and electrolysis mode for energy storage and sector coupling. They are expected to attain MW and multi-MW capacities for industrial applications. Fast dynamic operation is required to interact with a renewable energy driven grid without storage. The challenges associated with fast dynamic operation must be addressed to realize its true market potential. The system should be able to achieve fast transition within a single operation mode and also switch between electrolysis and fuel cell peak operation in less than 30 minutes for a secondary or tertiary energy market. A control strategy to enable the expected fast dynamic operation is presented. It accounts for the thermal behavior of the reactor module and safeguards it against hot spots and out of specification temporal and spatial temperature gradients.
32.	Taiwo, Oluwadamilola O., et al. (författare) In-Situ Examination of Microstructural Changes within a Lithium-Ion Battery Electrode Using Synchrotron X-ray Microtomography 2015 Ingår i: ECS Transactions. - : The Electrochemical Society. - 1938-6737 .- 1938-5862. ; 69:18, s. 81-85 Konferensbidrag (refereegranskat)abstract In this work, we use synchrotron X-ray microtomographic imaging to examine in-situ changes in a silicon / lithium half-cell before and after lithiation. We visualize volume expansion within the silicon electrode matrix and active particle fracturing as a result of the lithiation process. A change in volume fraction of silicon with respect to electrode state-of-charge was also characterized.
33.	Tomas, Matthieu, 1993, et al. (författare) Cu-based coatings for IT-SOFC applications 2019 Ingår i: ECS Transactions. - : The Electrochemical Society. - 1938-5862 .- 1938-6737. ; 91:1, s. 2291-2298 Konferensbidrag (refereegranskat)abstract Cu and Ce/Cu coated Sanergy HT samples were exposed at 650 °C and 850 °C for 500 h in air + 3 % water vapor and characterized. Mass gain data of all samples were measured throughout exposure. Cr-evaporation measurements were conducted and compared with uncoated Sanergy HT materials. Furthermore, SEM analysis on BIB cross-sections were performed on exposed samples. Results have shown higher mass gain for samples exposed at 850 ºC than 650 ºC as well as higher Cr evaporation. Microstructural analysis shows thinner oxide scales for samples coated with reactive elements.
34.	Wen, Rui-Tao, et al. (författare) Progress in Electrochromics: Towards Long-Term Durability and Materials Rejuvenation for Oxide-Based Thin Films 2015 Ingår i: ECS Transactions. - : Electrochemical Society. - 1938-5862 .- 1938-6737. ; , s. 9-16 Konferensbidrag (refereegranskat)abstract Most electrochromic devices, such as “smart windows” for energy efficient glazings, must be durable enough for many years of service life. Typical constructions use films based on thin films of W oxide and Nioxide, and this paper summarizes progress on durability-related issues for these materials. For W oxide, we describe recent and unexpected progress on galvanostatic rejuvenation of aged W oxide films, and we also discuss the beneficial effects of Ti addition. For Ni oxide, we report how charge exchange declination during extended voltammetric cycling can be modeled in terms of a power law and also demonstrate how modest additions of Ir can dramatically extend the cycling durability.
35.	Xu, Min, et al. (författare) Modeling of Solid Oxide Fuel Cell with Anisotropic Conductivity 2015 Ingår i: ECS Transactions. - : The Electrochemical Society. - 1938-6737 .- 1938-5862. ; 68:1, s. 3003-3011 Konferensbidrag (refereegranskat)abstract In recent years, significant advances have been made in the understanding of fabricated technology of solid oxide fuel cells (SOFCs). A three-dimensional model based on the finite element method (FEM) is developed for a single planar SOFC. The uniqueness of this paper is that both anode support electrode and anode active electrode layer fabricated by the freeze-tape-casting process with anisotropic conductivity property is taken into account. The parameter study demonstrates that grading the electron conductivity (increased in both anode and cathode active layers and support layers), in the principle direction to the electrode/electrolyte interface will increase the performance. On the other hand, the results also indicate that increased conductivity perpendicular with fuel transform of active electrode could significantly enhance the gas transport current density. It is concluded that an increased electric conductivity parallel to the electrode/electrolyte and perpendicular to the fuel and gases transport path in the active electrode raises the current density efficiently. Optimization of cell performance requires consideration of anisotropic conductivity that is needed to develop three-dimensional models.
36.	Beni, Valerio, 1972-, et al. (författare) Printed electrochemical instruments for biosensors 2015 Ingår i: ECS Transactions. - : The Electrochemical Society. - 9781607685395 ; , s. 1-13 Konferensbidrag (refereegranskat)abstract Mobile diagnostics for healthcare, food safety and environmental monitoring, demand a new generation of inexpensive sensing systems suitable for production in high volume. Herein we report on the development of a new disposable electrochemical instrument exploiting the latest advances in printed electronics and printed biosensors. The current system is manufactured under ambient conditions with all interconnections printed; electrochemical measurements and data elaboration are realized by the integration onto the platform of two chips: a MICROCHIP-PIC24F16KA101 and a Texas Instrument's LMP91000. A PEDOT.PSS vertical electrochromic display (VECD) is also incorporated into the system to visualize the data. A printed Enfucell 3V manganese dioxide battery was used to deliver the required power. Finally, in order to demonstrate the utility of the system, screen-printed sensors for the detection of glucose were added and the performance of the overall system was evaluated.
37.	Johansson, Malin, 1972-, et al. (författare) Nano crystals to micro crystals : Organolead triiodide perovskite crystal growth from isopropanol solution 2016 Ingår i: High Purity and High Mobility Semiconductors 14. - : Electrochemical Society. - 9781607685395 - 9781607687214 ; , s. 161-178 Konferensbidrag (refereegranskat)abstract The growth mechanism and dependence on precursor conditions are vital for creation of high quality crystalline materials in many fields. Here the growth from nano sized quantum dots to micro crystalline methyl ammonium lead tri-iodide (MAPbI3) perovskites prepared from isopropanol solution are reported. Isopropanol is more environmental friendly compared to the commonly used solvents DMF or DMSO, both with relatively high toxicity and the proposed method can be a useful new route to prepare hybrid perovskites. Three different molar ratios of MAPbI3 perovskite solution (MAI:PbI2 of 1:1, 2:1 and 0.5:1) were applied to give insights in the crystal formation mechanism also under nonstoichiometric conditions. Perovskite crystal growth is followed by TEM. From XRD powder diffraction the lattice constants have been determined and compared with results from electron diffraction (ED). Interestingly, there seems to be an occurrence of the cubic phase besides the common tetragonal phase at room temperature.
38.	Lang, Jenny, et al. (författare) Reliability study of a RF power amplifier with GaN-on-SiC HEMTs 2016 Ingår i: ECS Transactions. - Pennington, N.J. : The Electrochemical Society. - 9781607685395 ; , s. 49-59 Konferensbidrag (refereegranskat)abstract RF power amplifier demonstrators containing each one GaN-on- SiC, HEMT, CHZ015A-QEG, from UMS in SMD quad-flat noleads package (QFN) were subjected to thermal cycles (TC) and power cycles (PC) and evaluated electrically, thermally and structurally. Two types of lead-free solders (Sn63Pb36Ag2 and SnAgCu (SAC305)) and two types of TIM materials (NanoTIM and TgonTM 805) for PCB attachment to liquid cold plate were tested for thermo-mechanical reliability. Changes in electrical performance of the devices namely reduction of the current saturation value, threshold voltage shift, increase of the leakage current and degradation of the HF performance were observed as a result of an accumulated current stress during PC. No significant changes in the investigated solder or TIM materials were observed.
39.	Schöner, Adolf, et al. (författare) Progress in buried grid technology for improvements in on-resistance of high voltage SiC devices 2016 Ingår i: ECS Transactions. - : The Electrochemical Society. - 9781607685395 ; , s. 183-190 Konferensbidrag (refereegranskat)abstract Buried grid technology is suggested to protect field sensitive device areas from high electric field in order to improve the high temperature and high voltage performance of SiC devices. More than three orders of magnitude lower leakage currents have been demonstrated at high temperature operation. The drawback is that the total resistance increases due to the introduction of the buried grid leading to higher voltage drop at rated current and higher conduction losses. In this paper, we discuss doping and barrier engineering methods in order to take full advantage of the superior shielding effect of the buried grid technology and at the same time minimize the effect on the current conduction. As example, the design considerations for a 1200 V SiC buried grid JBS diode in terms of epi structure doping as well as buried grid properties is comprehensively investigated to optimize the on-state condition.
40.	Yakimova, Rositsa, et al. (författare) Growth, defects and doping of 3C-SiC on hexagonal polytypes 2017 Ingår i: ECS Transactions. - : Electrochemical Society. - 9781607685395 ; , s. 107-115, s. 107-115 Konferensbidrag (refereegranskat)abstract Technologies for the growth of 3C-SiC with crystalline quality and crystal size similar to hexagonal counterparts (6H- or 4H-SiC) are still at the laboratory stage. There are several challenges in the control of polytype stability and formation of structural defects which have to be eliminated to reveal the full potential of this material. Nevertheless, 3C-SiC has been explored for various energy, environment and biomedical applications which significantly benefit from the intrinsic semiconductor properties of this material. The future of 3C-SiC and its applications depends on the advances which will be made in improving crystalline quality, enlarging crystal size and controlling doping levels which have not been entirely explored due to the lack of high quality 3C-SiC substrates. This paper reviews recent progress in growth and doping of thick 3C-SiC layers on hexagonal SiC substrates using sublimation epitaxy. It covers the growth process on off-axis substrates and defects occurrence, as well as the issue of obtaining high resistivity material.
41.	Zurauskaite, Laura, et al. (författare) Investigation of Tm2O3 as a gate dielectric for Ge MOS devices 2018 Ingår i: ECS Transactions. - : Electrochemical Society. - 1938-5862. ; , s. 67-73 Konferensbidrag (refereegranskat)abstract In this work atomic layer deposited Tm2O3 has been investigated as a high-k dielectric for Ge-based gate stacks. It is shown that when Tm2O3 is deposited on high-quality Ge/GeO2 gates, the interface state density of the gate stack is degraded. A series of post-deposition anneals are studied in order to improve the interface state density of Ge/GeOx/Tm2O3 gates, and it is demonstrated that a rapid thermal anneal in O2 ambient can effectively reduce the interface state density to below 5-1011 cm-2eV-1 without increasing the equivalent oxide thickness. Fixed charge density in Ge/GeOx/Tm2O3 gates has also been investigated, and it is shown that while O2 post-deposition anneal improves the interface state density, the fixed charge density is degraded.
42.	Östling, Mikael, et al. (författare) Emerging graphene device technologies 2016 Ingår i: Emerging Nanomaterials and Devices. - : Electrochemical Society. - 9781607685395 ; , s. 17-35 Konferensbidrag (refereegranskat)abstract Graphene has a wide range of attractive electrical and mechanical properties. This unique blend of properties make it a good candidate for emerging and future device technologies, such as sensors, high frequency electronics, and energy storage devices. In this review paper, each of the aforementioned applications will be explored along with demonstrations of their operating principles. Specifically, we explore pressure and humidity sensors, graphene base transistor for high frequency applications, and supercapacitors. In addition, this paper provides a general overview of these graphene technologies and, in the case of pressure and humidity sensors, benchmarking against other competing technologies. This paper further shows possible and prospective paths that are suitable for future graphene research to take.

Skapa referenser, mejla, bekava och länka

Länka till träfflistan

Träfflista för sökning "L773:1938 6737 OR L773:1938 5862 OR L773:9781607685395 srt2:(2015-2019)"

Avgränsa träffmängd

År