bluuebunny/crossref_metadata_2025_split huggingface dataset:
(Keynote) Accelerating Commercialization of SiC Power Devices through Low-Cost US Manufacturing
Authors: Veliadis Victor 
Published: February 2020

The U.S Department of Energy launched the PowerAmerica (PA) Institute under the initiative of “National Network of Manufacturing Institutes” to commercialize SiC and GaN wide bandgap (WBG) power devices. PowerAmerica started operations in 2015 with $140M funds over 5 years, and is managed by North Carolina State University in Raleigh, NC. PA’s mission is to create U.S. high-tech manufacturing jobs and save energy through accelerated large-scale adoption of WBG semiconductor devices in power electronics systems. To achieve its goals, PowerAmerica funds strategic projects and brings together a range of companies – from startups to major corporations – as well as national labs and universities that work on every facet of the supply chain, from research and development to manufacturing and commercialization. Through membership in the PowerAmerica institute, industry members grow their business by accelerated wide bandgap product introduction to market, and University members gain by engaging in collaborative projects with industry.
Projects launched in 2016 covered low cost WBG device fabrication and a range of promising power electronics applications including a faster circuit breaker, a fast charger, electric vehicle traction drives, photovoltaic inverters, more efficient data centers, and heavy-duty vehicle electrification.
PowerAmerica’s largest project to date has focused on lowering the barrier to market entry for fabless SiC device companies, thereby contributing to building a stronger overall manufacturing ecosystem for this technology. The PA Institute partnered with Texas-based X-Fab to form the world’s first “open foundry” capable of supporting 6-inch SiC wafers. By leveraging mature Si fabrication practices and qualifying SiC specific processes, XFAB has enabled high-yield volume manufacturing at the economy scale of silicon. This capability enables fabless semiconductor companies to economically fabricate silicon carbide devices and compete in new ways. The conversion of an existing silicon factory into one capable of additionally fabricating SiC has produced significant benefits for the SiC ecosystem.
In addition to facilitating volume manufacturing, PA is accelerating WBG adoption by training the workforce through short course offerings, and preparing the next generation of high-skilled WBG technologists through hands-on projects at leading US Universities.
The presentation will outline the model for low cost SiC manufacturing in the US, and describe select projects that exemplify the performance advantages of SiC based power electronic systems.
(Invited) Dirac Fermions in Layered Topological Material ZrTe5
Authors: Jiang Zhigang , Jiang Yuxuan , Smirnov Dmitry 
Published: February 2020

Finding a large band gap topological insulator (TI) is crucial to future room-temperature (corresponding to ~25 meV) device applications. Recently, monolayer ZrTe5 has been predicted to be new functional two-dimensional (2D) TI [1], with a large (bulk) band gap far surpassing their predecessors, e.g., HgTe/CdTe and InAs/GaSb quantum wells. However, its electronic structure in the bulk is currently under heated debate, with interpretations ranging from weak/strong TI to Dirac semimetal.
Here, we report on a “bulk-sensitive” magneto-infrared transmission study of ZrTe5 thin flakes in magnetic fields up to 17T. At zero magnetic field, our samples exhibit graphene-like optical absorption, which signifies their 2D nature. In a magnetic field, we observed a series of inter-band Landau level (LL) transitions that can be described by a massive Dirac fermion model with a small mass. More interestingly, we observed a four-fold splitting of low-lying LL transitions. Thanks to the newly developed circular polarized magneto-infrared capability, we were able to separate the σ+ and σ- active transitions. These observations enable further exploration of the origin in the splitting: (i) the band asymmetry breaks the degeneracy of the dipole allowed inter-band LL transitions, and (ii) the remaining two-fold degeneracy is due to a combined effect of large g-factor and a small energy gap in this system. Our results support a 2D Dirac semimetal interpretation, consistent with recent electronic transport studies [2,3]. Finally, we compare the LL structure of Dirac fermions in ZrTe5 and in other topological materials that we systematically investigated over last few years, such as HgCdTe and InAs/GaSb [4, 5, 6].
1. H. Weng, X. Dai, and Z. Fang, Physical Review X
4, 011002 (2014).
2. W. Yu et al. Scientific Reports
6, 35357 (2016).
3. X. Yuan et al. NPG Asia Mater
8, e325 (2016).
4. J. Ludwig et al. Physical Review B
89, 241406(R) (2014).
5. F. Teppe et al. Nature Communications
7, 12576 (2016).
6. Y. Jiang et al. Physical Review B
95, 045116 (2017).
Influence of the Design of High-Energy-Density Graphite Negative Electrodes on the Electrochemical Performance
Authors: Malifarge Simon , Franco Alejandro A. , Delobel Bruno , Delacourt Charles 
Published: February 2020

Energy density of current Li-ion cells still need improvement for wide-spreading sales of electric vehicles. One can increase energy density of cells based on state-of-the-art active materials, such as graphite, by using thicker and/or lower-porosity electrodes, which contain a higher active-material loading. A downside of this approach is that in addition to enhancing the cell energy density, these thick/dense porous electrodes suffer lower cell power capability because of higher electrolyte transport limitations across the electrode. Large concentration and potential gradients develop across the electrode, leading to significant polarization increase and the possible occurrence of side reactions, such as Li plating. Active particle shape may also contribute to electrolyte transport limitations; Anisotropic particles may stack in a preferred direction that likely impede ionic transport. When studying high-energy-density porous electrodes, it is then essential to correlate the electrochemical performance with design parameters. Physics-based models, such as the Newman porous electrode model [1], prove effective to attempt such a correlation.
In this work, industry-grade graphite porous electrodes with different thicknesses and porosities are studied by a variety of electrochemical techniques such as rate-capability tests, pulse tests and electrochemical impedance spectroscopy. Electrode tortuosities are estimated with a model analysis of impedance diagrams of symmetric graphite/graphite cells. Tortuosity values lie well above what is predicted by the Bruggeman relation possibly because the graphite particles have a platelet-like shape that promotes a stacking perpendicular to ionic pathways. Cycling and rate performance as well as electrochemical impedance of several high-loading-electrode designs are compared.
[1] T.F. Fuller, M. Doyle, J. Newman, Simulation and Optimization of the Dual Lithium Ion Insertion Cell, J. Electrochem. Soc. 141 (1994).

Figure 1
Coupling of Pore-Phase and Solid-Phase Networks for Simulating Heat and Mass Transport in Porous Transport Layers
Authors: Konduru Vinaykumar , Allen Jeffrey S 
Published: February 2020

Reactant, water, and heat transport through Porous Transport Layers (PTL), also known as Gas Diffusion Layers (GDL), can be simulated using a variety of computational architectures and transport models. A common approach is to create detailed reconstruction of geometry from tomographic data and use a Lattice-Boltzmann model for computing transport within the material. Another common approach is to simulate the material using a network of transport resistance elements and then use continuum, phenomenological, or Lattice Boltzmann models for computing transport through the network.
For either approach the computational domain should be representative of the morphology and structure of the PTL being simulated. Geometric reconstructions of tomographic data naturally capture the morphology and structure, but at great computational expense when simulating heat and mass transport. A computationally efficient method is to create an abstraction of the PTL in a simple, regularized domain known as a pore-network model (PNM). This latter approach resolves the issue of computational expense, but lacks a clear relationship to the original structure and morphology of the PTL that is generally stochastic.
The stochastic morphology of a PTL can be characterized using a probability distribution of void volume size, known as a pore size distribution, which is invariant with respect to sample size. Pore size distribution data can be obtained using porosimetry or tomography and is almost universally based on spherical pore volumes.
This presentation discusses a methodology for transforming a spherical pore size distribution data into a pore-network model domain. This methodology maintains the appropriate stochastic distribution, physical size and bulk porosity of the original PTL. The resulting PNM domain is unique to the original PTL sample; meaning that the pore-network is material or manufacturer specific. Thus, simulation of reactant and water transport is also material or manufacturer specific.
The methodology developed transforms a spherical-pore size distribution into a regularly-spaced network of pore cylinders; referred to as the pore-phase network. In order to simulate thermal transport in a PTL using the PNM architecture, the solid portion of the original material must also be transformed into a complimentary solid-phase network. The solid-phase network should also preserve the original stochastic morphology and bulk porosity of the PTL. In this methodology, the two networks (pore-phase and solid-phase) are generated independent of one another, connected only through the distribution of unit cell porosities. In this manner thermal transport through the solid-phase network can be validated independently of liquid water transport through the pore-phase network and vice-versa. When combined, the dual PNM networks capture the coupled thermal and mass transport through the PTL.
Numerical Predicting of Liquid Water Transport inside Gas Diffusion Layer for PEMFC Using Lattice Boltzmann Method
Authors: Satjaritanun Pongsarun , Shimpalee Sirivatch , Weidner John W. , Hirano Shinichi , Lu Zijie , Shum Andrew , Zenyuk Iryna V. , Ogawa Shohei , Litster Shawn 
Published: February 2020

The purpose of this work is to use a numerical simulation applying the Lattice Boltzmann Method (LBM) [1-2] technique to understand the two-phase transport of liquid water and air inside the gas diffusion layers (GDLs) used in polymer electrolyte membrane fuel cells (PEMFC). The liquid water breakthrough dynamics described by the capillary pressure across the GDLs with and without a microporous layer (MPL) are the major focus in this work. The model geometries of GDLs and MPLs used in this study were obtained by three dimensional reconstructed micro-structure from both Nano and Micro X-ray computed tomography (CT). The overall predictions of water breakthrough pressure agree with the data observed in the experiment. They also reveal that the breakthrough pressure and liquid water evolution inside the GDL samples are different when the wetting properties of GDL and/or MPL are changed. Figure 1 gives an example of model geometries for the simulation. It consists of both GDL and MPL those were taken from Nano X-ray CT. This also includes a crack that was observed from the image. Figure 2 shows an example of the predictions of water evolution inside the GDL and MPL. When the liquid water was pushed from MPL to GDL, liquid water spread all over the MPL before it moves toward the GDL. This is because the pressure required to push the liquid water thru the MPL structure or the crack in MPL is higher than the pressure used for liquid water spreads on the top of MPL [3].
References:

U. Frisch, B. Hasslacher, Y. Pomeau, Physical review letters 56 (14) (1986) 1505-1508.

G. R. McNamara, G. Zanetti, Physical Review Letters 61 (1988) 2332-2335.

P. Satjaritanun et al., J. Electrochem. Soc., submittied (2017).

Figure 1
Transport Resistances in Fuel-Cell Catalyst Layers
Authors: Chowdhury Anamika , Radke Clayton J. , Weber Adam Z. 
Published: February 2020

Catalyst layers (CLs) in polymer-electrolyte fuel cells have garnered the attention of researchers due to their association with high local mass-transport resistance at low catalyst loadings [1, 2]. Nevertheless, the genesis and nature of CL resistance(s) is still under debate. CLs are only a few micrometers thick with complex geometry and heterogeneous phases making in-situ examination of CL transport processes extremely difficult.
In this study, we probe the nature of CL resistances experimentally and theoretically. Using a hydrogen-pump limiting-current modality, we deconvolute the various gas-transport-related resistances without the impact of those associated with the oxygen-reduction reaction (e.g., water production) [3]. An analytical model to quantify the experimental measurements is developed to analyze the data and to elucidate limiting regimes. Our new results are in agreement with literature limiting-current measurements.
Similar to previously reported studies [4], the model demonstrates that the transport of the reactant to the surface through the ionomer film tends to be the dominant resistance in CLs with a linear dependence on the inverse of Pt loading (i.e., roughness factor) [5]. Further, we study the dependence of this resistance on operational parameters including pressure, RH, temperature, gas molecular mass, and ionomer type. The garnered information exposes the controlling resistances, especially in comparison to ex-situ ionomer thin-film properties. Our efforts can be utilized to understand and develop mitigation strategies for local CL resistances.

Acknowledgements

We would like to thank helpful discussions and data provided by KC Neyerlin at NREL. This work was funded under the Fuel Cell Performance and Durability Consortium (FC PAD) funded by the Energy Efficiency and Renewable Energy, Fuel Cell Technologies Office, of the U. S. Department of Energy under contract number DE-AC02-05CH11231.

References:

A. Weber and A. Kusoglu, Journal of Material Chemistry A, 2,17207–17211 (2014).

A. Kongkanand and M. F. Mathias, The Journal of Physical Chemistry Letters, 7, 1127 (2016).

F. Spingler, A. Phillips, T. Schuler, M. Tucker and A. Weber, International Journal of Hydrogen Energy (2017), http://dx.doi.org/10.1016/j.ijhydene.2017.01.036

N. Nonoyama, S. Okazaki, A. Weber, Y. Ikogi and T. Yoshida, Journal of The Electrochemical Society, 158 (5), B416 (2011).

T. Greszler, D. Caulk and P. Sinha, Journal of The Electrochemical Society, 159, F831 (2012).
Investigation of PEMFC Performance and Property of the Gas Diffusion Layers Utilizing the Numerical Model
Authors: Hirano Shinichi , Shimpalee Sirivatch , Lu Zijie , Satjaritanun Pongsarun , Weidner John W. 
Published: February 2020

The overpotential at the cathode is significantly large in the proton exchange membrane fuel cells; therefore, the oxygen concentration in the oxygen reduction reaction (ORR) area is vital. Condensed water in the flow field and the gas diffusion layer (GDL) reduces oxygen transport to the ORR area. The enhancement of the mass transport of liquid water and oxygen is critical to improve fuel cell performance particularly at the high current density operations. It is required to reduce the total active area in the fuel cell stack and also it is leading to the significant cost reduction. Experimental investigation of oxygen transport has been limited by an inability to resolve water saturation-dependent properties. The two-phase thermos-fluid dynamics model of GDL was developed with Lattice Boltzmann Method (LBM) and it was integrated with computational fluid dynamics (CFD) based proton exchange membrane fuel cell (PEMFC) model to simulate the fuel cell performance with given design parameters and operational conditions [1, 2]. This work, utilizing the developed model, investigates the correlations between fuel cell performance and GDL structures and material properties. Some empirical studies were pursued and structure and property of the micro porous layer (MPL) in the GDL is correlated to the fuel cell performance particularly high current densities [3-5]. The model simulates the fuel cell performance with various porosity and permeability of MPL in the cathode GDL to investigate those correlations. Also the two-phase model can show the presence of residual liquid water in the cathode GDL which effects on the fuel cell performance. It can distinguish the residual liquid water in the GLD underneath of the flow field channel ribs and under the channels. Figure 1 gives an concept of integrated CFD based PEMFC model with micro-scale GDL model with LBM. Figure 2 shows residual liquid water in the cathode GDL with various operating conditions. In this fuel cell design, residual liquid water is correlated with cathode conditions, relative humidity, rather than the current density. It shows the potential capability of a model-based investigation of mass-transport to find solution of design and operational conditions in the PEMFC.

References:

1. S. Shimpalee, et. al., ECS Trans., 6493): 693-654 (2014)

2. S. Shimpalee, et. al., Multi-scale Modeling of Transports inside PEMFC By Combining Multiphase, Abstract 2387, 230th ECS Meeting, Honolulu, HI, Oct. 2, 2016.

3. Y. Aoyama, et. al., ECS Trans., 69 (I7): 743-752 (2015)

4. J. Eller, et. al., ECS Trans., 50(2): 477-486 (2013)

5. J. Eller, et. al., ECS Trans 69(17): 523-531 (2015)

Figure 1
A 1D+1D Model of Direct Ethanol Fuel Cells Based on an Optimized Kinetic Mechanism for Ethanol Electro-Oxidation Involving Free and Adsorbed Intermediate Species
Authors: Sánchez-Monreal Juan , García-Salaberri Pablo A. , Vera Marcos 
Published: February 2020

Ethanol electro-oxidation is known to proceed through a series of elementary reactions that involve free and adsorbed species, like acetyl, hydroxyl, and carbon monoxide, and lead to a mixture of oxidation products such as acetaldehyde, acetic acid, carbon dioxide and methane. The major electro-oxidation products of ethanol on Pt electrodes are acetaldehyde and acetic acid, instead of carbon dioxide, making incomplete oxidation of ethanol one of the main challenges for the development of Direct Ethanol Fuel Cells (DEFCs). As recently shown by the authors [1], acetaldehyde plays an important role because it is not a truly final product of the reaction, but a free intermediate species that can be oxidized to acetic acid or, even further, to carbon dioxide. The kinetic model presented in [1] showed its capability to be adapted, via genetic algorithm optimization, to different binary Pt-based catalyst compositions, reproducing the anode overpotential and product selectivity in a wide range of operation conditions. Moreover, the consideration of several intermediate species enabled improved modeling of the crossover flux and the resulting mixed potentials induced at the cathode side.
In this work, we present a 1D + 1D model for liquid-feed DEFCs. One-dimensional convective transport along the channel is coupled to a one-dimensional model that accounts for species transport through the MEA, as well as electrochemical kinetics, including the mixed potential due to ethanol/acetaldehyde crossover. The complex kinetics of the multi-step ethanol oxidation reaction is described with the model proposed in [1]. A simple along-the-channel convective model is used to describe the downstream variation of the concentrations of the different species. This provides, in particular, the variation of the local current density. The results show that the current density distribution is highly dominated by the decrease of the ethanol concentration down the anode channel, together with the change of the production/consumption rate of free species. The variation of the ethanol and acetaldehyde concentration impacts the anode reaction rates and the ethanol/acetaldehyde crossover flux, which affects the cathode reaction rates.

References

[1] J. Sánchez-Monreal, P. A. García-Salaberri, M. Vera, Mathematical Modeling of Direct Ethanol Fuel Cells Using a Multi-Step Chemical Kinetic Mechanism, ECS Trans. 72 (2016) 1-16.
Synthesis of a Polymer Electrolyte Based on Silicotungstic Acid, Performance, and Mechanical Durability in a Proton Exchange Membrane Fuel Cell
Authors: Motz Andrew R , Kuo Mei-Chen , Herring Andrew M 
Published: February 2020

While perfluorinated sulfonic acids (PFSA)s have many desirable qualities for use as a membrane separator in a polymer electrolyte membrane fuel cell (PEMFC), they suffer from decomposition via radical attack and excessive swelling. These two properties reduce the chemical and mechanical durability, respectively, of PFSA materials in the operating environment of a fuel cell. Through using heteropoly acids (HPA)s as an ion-conducting, crosslinking moiety, these short comings of PFSA membranes can be overcome. HPAs are known to be highly conductive [1] and are able to react with radicals. Our approach is to use a commercially available fluoroelastomer and functionalizes using HPA crosslinks. First, FC-2178 (polyvinylidene-co-hexafluoropropylene) is functionalized with phosphonic acid containing sidechains. Next, lacunary silicotungstic acid is covalently bonded to acidic sicechains. This material is stable in aqueous environments, unlike blends of HPA and PFSA. The results of in-situ evaluation of these membranes show impressive durability in accelerated stress test (AST). The loss of open circuit voltage (OCV) in the chemical degradation test is much less than traditional films, resulting in >0.8V OCV after 500 hrs. Also, the minimal swelling of this material leads to greater durability in humidity cycling ASTs with negligible H2 crossover after 20,000 dry wet cycles. Overall, this material shows great promise in outperforming PFSAs in chemical and mechanical ASTs.

References:

[1] Nakamura, O.; Kodama, T.; Ogino, I.; Miyake, Y., High-Conductivity Solid Proton Conductors - Dodecamolybdophosphoric Acid and Dodecatungstophosphoric Acid Crystals. Chemistry Letters 1979, 17-18.
Understanding the Effect of the Anion of the Ionic Liquid on the Activity of the Oxygen Reduction Reaction on Pt/C
Authors: Huang Kan , Song Tangqiumei , Morales-Collazo Oscar , Jia Hongfei , Brennecke Joan F 
Published: February 2020

The efficiency of the oxygen reduction reaction (ORR) is determined by many factors, among which the adsorption of non-reactive species on the Pt surface and oxygen concentration near the Pt interface are considered the most important. Extensive research has focused on developing novel Pt based catalysts with sophisticated structures designed to weaken the adsorption of oxygenated species and enhance ORR activity. Recently, ionic liquid (IL) with high oxygen concentration have been proposed as another countermeasure to accelerate the reaction rate. (1, 2)
The choice of anion of the IL, in particular, can have a significant effect on the oxygen solubility. To investigate how oxygen solubility in the IL improves the ORR activity and durability, a series of ILs with various anions designed to enhance oxygen solubility were synthesized and characterized. Surprisingly, the electrochemical studies showed that the ORR activity was not sensitive to the oxygen solubility in the ILs, but showed significant dependence on the oxides free Pt sites (1- θ
OHad). (Fig.1)
The degree of IL coverage on the Pt was quantitatively estimated using (bi)sulfate ion as an indicator. It was found that the ORR activity was promoted when there was partial IL coverage, while full IL coverage resulted in degradation of the performance. Durability studies showed that in the presence of the IL Pt dissolution can be mitigated. A balance between activity and stability can be achieved with an optimized IL coverage.
1. J. Snyder, T. Fujita, M. W. Chen and J. Erlebacher, Nat Mater, 9, 904 (2010).
2. J. Snyder, K. Livi and J. Erlebacher, Advanced Functional Materials, 23, 5494 (2013).

Figure 1