783 research outputs found
Data file for paper: Rubio Garcia, Javier; Kucernak, Anthony; Zhao, Dong; Li, Danlei; Fahy, Kieran; Yufit, Vladimir; Brandon, Nigel; Gomez-Gonzalez, Miguel, "Hydrogen/manganese hybrid redox flow battery", Journal of Physics: Energy, 2018
No full textThe data in this spreadsheet was used to produce the figures in the paper
Rubio Garcia, Javier; Kucernak, Anthony; Zhao, Dong; Li, Danlei; Fahy, Kieran; Yufit, Vladimir; Brandon, Nigel; Gomez-Gonzalez, Miguel, "Hydrogen/manganese hybrid redox flow battery", Journal of Physics: Energy, 2018
DOI: 10.1088/2515-7655/aaee17
Please cite the above reference if you wish to use this data</p
Study on the work of Massachusetts Institute of Technology Mechanical Engineering graduates
No full textThesis: S.B., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2015.Cataloged from PDF version of thesis.Includes bibliographical references (page 30).This study seeks to collect rich data about Mechanical Engineering alumni's work lives using qualitative and interpretive social research methods. Semi-structured interviews were conducted with several alumni from the MIT Mechanical Engineering department. Main topics discussed in theses interviews were current work activities, career motivations, important job skills, the value of an MIT education, and potential improvements to the MIT alumni experience.by Brandon Nigel Wright.S.B
Also By The Same Author: AKTiveAuthor, a Citation Graph Approach to Name Disambiguation
No full textThe desire for definitive data and the semantic web drive for inference over heterogeneous data sources requires co-reference resolution to be performed on those data. In particular, name disambiguation is required to allow accurate publication lists, citation counts and impact measures to be determined. This paper describes a graph-based approach to author disambiguation on large-scale citation networks. Using self-citation, co-authorship and document source analyses, AKTiveAuthor clusters papers, achieving precision of 0.997 and recall of 0.818 over a test group of eight surname clusters
Microstructural Degradation: Mechanisms, Quantification, Modeling and Design Strategies to Enhance the Durability of Solid Oxide Fuel Cell Electrodes
No full textElectrode microstructure is one of the main factors determining the performance and durability of solid oxide fuel cells (SOFCs). The degradation is intimately linked to the microstructure, which in turn depends upon manufacturing and operation conditions. In this chapter we discuss the main causes for degradation of electrodes, concentrating mainly on the anode and present the techniques-both typical and state-of-the-art to follow these changes. We emphasize the need to quantitatively link the microstructural properties (e.g., triple-phase boundaries, porosity, and tortuosity) with the electrochemical responses measured and, most importantly, to link the change in microstructure to the performance degradation via suitable models. The knowledge gained must then be used to design new electrodes that can extend the lifetime of SOFCs once the critical parameters have been identified
Optimization of dry reforming of methane over Ni/YSZ anodes for solid oxide fuel cells
No full textThis work investigates the catalytic properties of Ni/YSZ anodes as electrodes of Solid Oxide Fuel Cells (SOFCs) to be operated under direct dry reforming of methane. The experimental test rig consists of a micro-reactor, where anode samples are characterized. The gas composition at the reactor outlet is monitored using a mass spectrometer. The kinetics of the reactions occurring over the anode is investigated by means of Isotherm reactions and Temperature-programmed reactions. The effect of the variation of temperature, gas residence time and inlet carbon dioxide-methane volumetric ratio is analyzed. At 800 °C, the best catalytic performance (in the carbon safe region) is obtained for 1.5 < carbon dioxide/methane ratio < 2, which is an interesting result for prospective direct biogas fueled SOFCs. Conversion is stable over a period of 70 h. Both for temperatures lower than 450 °C and for carbon dioxide-methane ratios lower than equi-molar at 800 °C, conversion is poor due to low activity of the anode toward dry reforming and cracking reactions, respectively. In other ranges, dry reforming and reverse water gas shift are the dominant reactions and the inlet feed reaches almost the equilibrium condition provided that a sufficient gas residence time is obtaine
Modelling and advanced quantification of inhomogeneous 3D current distribution in SOFC electrodes at the particle level
No full textIt is widely accepted that electrode microstructural characteristics significantly affect the electrochemical performance as well as the durability of solid oxide fuel cells. 3D tomography allows for the reconstruction and simulation of electrochemical phenomena within the real three-dimensional electrode microstructures. However, despite the availability of the full three-dimensional structural details, so far the microstructural analysis has been largely focused to obtaining averaged properties, such as the three-phase boundary density or the tortuosity factor, while 3D simulations have been mainly used to predict polarization curves and voltage profiles, something that can also be done with high fidelity by 1D continuum models. In order to overcome these limitations, we have recently introduced a completely new methodology for advanced microstructural characterization [1]. First we solve for the transport and electrochemical reactions of charged and gas species within the 3D electrode microstructure (Figure 1a), thus obtaining the electric potential, current density and gas concentration in every point of the corresponding phase. Then, each phase is resolved into individual particles and pores, allowing for the quantification of the statistical distribution of current and other truly-three-dimensional quantities at the particle level. The analysis allows for the identification of two classes of particles: particles which transfer more current than average, characterized by 10-40% more contacts than average, and particles which produce more current than average, which show ~2.5 times more three-phase boundary length than average (Figure 1b). These two classes of particles are mutually exclusive, so that up to the 30% of solid electrode volume is shown to be underutilized. These behaviours are confirmed in both real and synthetic microstructures. The insight gained by the exploitation of all the information contained in 3D microstructural datasets enhances the understanding of the reasoning behind inhomogeneous current distribution, with its consequent impact on lifetime, suggesting strategies for the design of more durable SOFC electrodes. The approach is also applicable to lithium-ion batteries and other electrochemical energy systems
Characterization of Degradation in Nickel Impregnated Scandia-Stabilize Zirconia Electrodes during Isothermal Annealing
No full textThis study investigates the stability of nickel-impregnated scandia-stabilize zirconia composite electrodes during isothermal annealing at temperatures from 600 to 950°C in a humidified hydrogen atmosphere (3 vol % water vapor). Typically an initial rapid degradation of the electrode during the first 17 h of annealing is revealed by both an increase in polarization resistance and a fall in electronic conductivity. Secondary electron images show a shift in nickel particle size toward larger values after 50 h of annealing. The declining electrochemical performance is hence attributed to nickel coarsening at elevated temperatures. Nickel coarsening has two microstructural effects: breaking up nickel percolation; and reducing the density of triple phase boundaries. Their impact on electrode area specific resistance is explored using a physical model of electrode performance which relates the macroscopic electrochemical performance to measurable microstructural parameters
Simulated impedance of diffusion in porous media
No full textThis paper describes the use of a frequency domain, finite-difference scheme to simulate the impedance spectra of diffusion in porous microstructures. Both open and closed systems are investigated for a range of ideal geometries, as well as some randomly generated synthetic volumes and tomographically derived microstructural data. In many cases, the spectra deviate significantly from the conventional Warburg-type elements typically used to represent diffusion in equivalent circuit analysis. A key finding is that certain microstructures show multiple peaks in the complex plane, which may be misinterpreted as separate electrochemical processes in real impedance data. This is relevant to battery electrode design as the techniques for nano-scale fabrication become more widespread. This simulation tool is provided as an open-source MatLab application and is freely available online as part of the TauFactor platform
Multi-scale modelling of a Li-ion battery electrode with aligned pores
No full textThere is a growing interest in increasing the accessible capacity of Li-ion battery electrodes without compromising the power. This is a challenging task since as the electrode thickness increases, the ionic transport in the electrolyte becomes limiting. In order to facilitate ionic transport, we investigate the effect of the introduction of micro-channels aligned along the electrode thickness by using a multi-scale modelling approach. A volume-averaged electrochemical model is developed to take into account charge transport in concentrated solution, charge transfer at the solid/electrolyte interface, and electron migration and lithium diffusion in the electrode material [1]. Carbon nanoparticles are embedded within the electrode material to increase the effective electronic conductivity, which is evaluated through TauFactor [2] by simulating random dispersions of nanoparticles. A multi-scale optimisation strategy is adopted: at the micro-scale, the volume fraction of carbon nanoparticles is optimised in order to enhance the effective electronic conductivity
without compromising the electrode capacity; at the electrode level, the diameter, pitch and length of micro-channels are varied to maximise the power density. Results show that the electronic conductivity is significantly increased as soon as percolation of the carbon nanoparticles is achieved. At the electrode level, as long as the volume fraction of microchannels is constant, smaller pores lead to higher current densities. Finally, a positive electrode fabricated via freeze-casting according to optimised geometric parameters identified by the model is produced, tested and reconstructed with 3D X-ray
tomography. The difference between model predictions and real electrochemical performance may in part be attributed to the pore morphology of the actual sample, which is more complex than the prismatic forms captured in this model
A standing ovation for Nigel: An informal study
No full textThis article analyses a series of emails thanking Nigel for his stewardship of JASSS and the characteristics of their authors. It identifies a correlation between two measures of author activity in social simulation research, but no pattern between these activity measures and the email timing. Instead, the sequence suggests a classic standing ovation effect.</p
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