bluuebunny/crossref_metadata_2025_split huggingface dataset:
Simulations of a New Flow Channel Design of Bipolar Plates for a Fuel Cell Type PEM By CFD
Authors: Castañeda Ulloa Locksley Fabiàn , Nava José Luis , Pérez-Segura Tzayam , Romero Tatiana 
Published: February 2020

Nowadays, there is an increasing tendency towards renewable energy due to the limitation and pollution of fossil fuel. Among these energies, the fuel cell is a suitable technology with its high-power density converting chemical energy to electricity. Fuel cells are a highly efficient, environmentally friendly power source with broad applications in many industries including transportation as well as portable and stationary power generation, which will translate the chemical energy stored directly in the fuel and oxidizer into electrical energy. The proton exchange membrane fuel cell (PEMFC) is a useful type of fuel cell due to its high efficiency, high energy densities and low corrosion [1]. Other advantages of PEMFCs are their low operating temperature (40-90°) and planar geometry which allows many cells to be stacked together in order to obtain an appropriate size. Manufacturing and operating costs of this type of fuel cell can be reduced by optimizing the efficiency of fuel cells through detailed analysis of complex electrochemical and mass transport phenomena that occur within the cells [2]. It is very well known that the bipolar plate is an important component of the fuel cell, the design of the fuel cell is largely bipolar plate design, and especially the design of the flow field is a top priority [3]. In this context, this work deals with the simulation of a complete PEM fuel cell, emphasizing the novel design of the flow channels of the bipolar plates. The simulation was performed in a single cell configuration using the Navier-Stokes equations for the flow channels, the Brinkman equation for the gas diffusion layer, and for the mass transport the Maxwell-Stefan equations. Finally, for the simulation of the current distribution in the catalytic layer, the Butler-Volmer equation was adapted to the mass transport. The new design allowed a better dispersion of the gases inside the channels, avoiding water stagnation and increasing the efficiency of the fuel cell.
References
[1] Caglayan D.G., Sezgin B., Devrim Y., Eroglu I. Three-dimensional modeling of a high temperature polymer electrolyte membrane cell at different operation temperatures. Int. J. Hyd. Ener. 41 (2016) 10060-10070.
[2] Haghayegh M., Eikani M., Rowshanzamir S. Modeling and simulation of a proton exchange membrane fuel cell using computational fluid dynamics. Int. J. Hyd. Ener. 42 (2017) 21944-21954.
[3] Hermann A., Chaudhuri T., Spagnol P. Bipolar plates for PEM fuel cells: A review. Int. J. Hyd. Ener. 30 (2005) 1297-1302.
Exploring the Effect of Strong Complexing Agents As Electrolyte Additives on Anode Performance in Mg-Air Primary Batteries
Authors: Vaghefinazari Bahram , Hoeche Daniel , Lamaka Sviatlana V , Snihirova Darya , Wang Linqian , Deng Min , Zheludkevich Mikhail L 
Published: February 2020

Mg-air primary batteries have drawn increasing attention recently due to their low cost, safety, and high theoretical specific power density. However, high self-corrosion rate and anode fouling during discharge (mainly due to the formation of Mg(OH)2/MgO) lead to particularly lower delivered voltage and utilization efficiency. Modification of the battery electrolyte chemistry plays a crucial role in tackling these shortcomings and improving battery performance. Remarkable enhancements to the Mg anode’s performance by addition of group of organic complexing agents in the Mg-air battery electrolyte has recently been reported [1]. In this study, the effect of two strong organic complexing agents (i.e. disodium 4,5-dihydroxy-1,3-benzenedisulfonate(Tiron) and Nitrilotriacetic acid(NTA)) as additives to the Mg-air battery electrolyte was investigated. Commercially pure magnesium with relatively high Fe impurity level (i.e. 220ppm) has been chosen as the anode material in order to have a better understanding of the interaction of the complexing agents with pure Mg and the common Fe impurity.
Half-cell measurements were conducted to evaluate the discharge performance of the anode in the presence of the complexing agents. The electrochemical and corrosion behavior were studied by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization curve. The morphology of the anode surface after discharge was investigated by scanning electron microscope (SEM).
The results indicate that strong complexing agents can remarkably improve the discharge potential by activating the Mg anode surface and mitigating the high cathodic activity stemmed from Fe impurities. A possible downside of adding strong complexing agents is the tendency to accelerate the corrosion rate of the Mg anode. However, tuning the complexing agent concentration in the electrolyte can significantly improve the utilization efficiency at the expense of a slight decrease in the battery delivered voltage.
[1] D. Höche, S.V. Lamaka, B. Vaghefinazari, T. Braun, R.P. Petrauskas, M. Fichtner, M.L. Zheludkevich, Performance boost for primary magnesium cells using iron complexing agents as electrolyte additives, Scientific Reports, 8 (2018).
Plastic Crystal Polymer Electrolytes with Anion-Trapping Boron Moieties for Room Temperature All-Solid-State Sodium Batteries
Authors: Chen Suli , Che Haiying , Feng Fan , Yin Yimei , Ma Zi-Feng 
Published: February 2020

Sodium-ion batteries (SIBs) have been considered as promising alternatives to lithium-ion batteries (LIBs) particularly in large scale electric energy storage applications for renewable energy and grid due to low cost and the huge abundance of sodium resources. However, increasing safety issues caused by the use of conventional organic liquid electrolytes (LEs) greatly hinder the commercial application of SIBs in electric vehicles or hybrid electric vehicles [1]. Replacing LEs with solid electrolytes (SEs) can inherently address such safety problems. However, it is a compelling challenge to develop SEs with superior room-temperature ionic conductivity, high ion transference number, considerable mechanical property, and low electrolyte/electrode interfacial resistance [2]. Recently, we developed a new type of nonwoven supported plastic crystal polymer electrolyte containing anion-trapping boron moieties (B-PCPE), which prepared by in situ growth method using UV-curing technique. In addition, the plastic crystal electrolyte modified electrodes were also designed to reduce interfacial resistance. The B-PCPE shows excellent room temperature ionic conductivity (0.36 mS/cm) and greatly enhanced sodium transference number (0.62) due to the presence of anion-trapping boron moieties. All-solid-state SIB assembled using the B-PCPE with anion acceptor exhibits excellent cycle performance and rate capability at room temperature. The cell delivers first discharge capacity of 104.8 mAh/g with Coulombic efficiency of 94.1% and the capacity retention is about 80.1% after 120 cycles at 0.1 C. We believe this B-PCPE is a promising candidate for practical application and our work provides a new perspective to design high-performance solid electrolyte for ambient-temperature all-solid-state batteries with exceptional rate capability and cycle stability.

References

[1] H. Che, S Chen, Y. Xie, H. Wang, K. Amine, X. Liao, Z-F. Ma, Energ. Environ. Sci., 10, 1075(2017)
[2] Z. Y. Lin, X. Y. Guo, H. J. Yu, Nano Energy, 41, 646( 2017)
(Invited) Origin of Weak Points in Surface Oxides at the Atomic Scale on Cr-Containing Alloys
Authors: Marcus Philippe , Ma Li , Wiame Frédéric , Maurice Vincent 
Published: February 2020

Stainless steels (SS) are widely used in various industrial sectors because they are protected against corrosion by an oxide film formed at the surface, only a few nanometers thick and strongly enriched in Cr(III).
Despite numerous studies of stainless steel passivity at the macroscopic scale, only recent surface analytical works have attempted to characterize the nature and elucidate the origin of sub-microscopic chemical and structural heterogeneities in surface oxide layers.
In this work, the topographic, structural and chemical alterations of a (100)-oriented model 304 austenitic stainless steel single crystalline surface have been investigated at the nanometer/ atomic scales during early stage oxidation by Scanning Tunneling Microscopy (STM) combined with X-ray Photoelectron Spectroscopy. The experiments were performed by exposing an oxide-free Fe-18Cr-13Ni(100) surface to oxygen.
The results presented first will be on the oxide-free alloy surface structure, with STM data revealing the presence of ordered vacancies under equilibrium conditions. Then the evidence of nucleation of chromium oxide at multi-atomic surface steps will be presented. A chromium pumping effect creates Cr enrichment in the oxide nuclei at the steps, and Cr-depleted zones at the border of the oxidized steps, allowing less protective iron oxide to be formed locally. Weak points in the surface oxide layers originate from this atomic scale surface process.
The further discussion of the presented data will emphasize the importance of this observation for the understanding of the role of the oxidation mechanisms in the nanoscale heterogeneity of the growing surface oxide on Cr-containing alloys such as stainless steel, providing a new insight into the mechanisms of pit initiation at weak points of passive films.

This project has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program (grant agreement No. 741123, CIMNAS : Corrosion Initiation Mechanisms at Nanometric/Atomic Scale). Région Ïle-de- France is acknowledged for partial funding of the STM and XPS equipments. China Scholarship Council (CSC) is acknowledged for a scholarship to Li Ma (No. 201606380129).
(Invited) Rapid Cathodic Process on Anodized Metals By Fast Current-Controlled Polarization
Authors: Fujimoto Shinji , Kurokawa Tetsuya , Tsuchiya Hiroaki , Miyabe Sayaka 
Published: February 2020

It is well known that oxygen reduction is one of the most important reactions in corrosion process. Therefore, oxygen reduction has been extensively studied on metals and alloys, the surface of which is covered with oxide film. In general, the oxygen reduction reaction during localized corrosion is considered to occur extremely fast, but such rapid cathodic process has not been reported. In the present work, we propose an approach to investigate rapid oxygen reduction reaction, so-called a fast current-controlled polarization, where a fast cathodic current transient is applied to metals and alloys covered with oxide film and from the resulting potential variation, the kinetics of the oxygen reduction on the surface is analyzed.
Materials examined were several valve metals such ad Ti, Al, and Zr. Anodic oxide films were produced by anodization on the metals in a phosphate buffer solution at various voltages. In the first current-controlled polarization, a triangle form of cathodic current was applied to the anodized metals, monitoring the resulting potential variation. The potential for all the anodized metals shifted in the less noble direction steeply and then recovered back gradually to the original potential. The potential variation was analyzed based on the assumption that the applied current was consumed as charge-discharge in the space charge layer in the oxide film and the oxygen reduction reaction. As a result, it was found that the oxygen reduction current was clearly different depending on the type of valve metal as well as anodization voltage. In this presentation, details on the fast current controlled polarization will be presented and the different reduction kinetics will be discussed.
A New Framework for Pit Growth Stability and Its Experimental Validation
Authors: Li Tianshu , Scully John R. , Frankel Gerald S. 
Published: February 2020

A new framework has been developed in recent works to describe pit growth stability 1-4. In this framework, the concept of maximum pit dissolution current density, i
diss,max, was proposed to consider the competition between the dissolution and diffusion processes within a pit 2, 3, an issue that has not been satisfactorily addressed previously. The quantity i
diss,max is the rate of dissolution in a pit in the absence of a salt film. According to this new framework, the pit stability and salt film formation can be defined by the critical conditions of i
diss,max = i
diff,crit and i
diss,max = i
lim, respectively, where i
diff,crit and i
lim are diffusion current densities related to maintain critical and saturated pit concentration 3. Unifying sets of principal parameters for pit stability and salt film formation were developed based on these critical conditions: (T
crit, E
crit, r
crit) and (T
sat, E
sat, r
sat), respectively 3.
This talk described experiments using 1D artificial pit electrodes that validate this new framework for pit stability. According to the model prediction, the critical potential for salt film formation (E
sat) should decrease with the log of pit depth. The results from experiments on 1D pits followed this relationship exactly, which provides strong support of the validity of the new model. Additionally, a critical pit concentration equal to 43% of the saturation concentration, C
sat, was determined, which is much lower than the critical concentration determined by others. Furthermore, i
diss,max values at fixed pit surface solution concentrations (100%C
sat and 70%C
sat) were determined using pits of varying depth. The Tafel slope was found to be about 116 mV in both environments. This is the first ever determination of pit dissolution kinetics in pit solutions of fixed concentration.
This new framework provides an opportunity to revisit several key topics of this field and generates new insights to interpret previous observations in a self-consistent way, such as to understand the effects of alloy composition, bulk chloride concentration, ohmic potential drop of the solution, etc.

Acknowledgments: This work was supported as part of the Center for Performance and Design of Nuclear Waste Forms and Containers, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences under Award # DE-SC0016584.
Reference

G. S. Frankel, T. Li and J. R. Scully, Journal of the Electrochemical Society
164, C180-C181 (2017).

T. Li, J. R. Scully and G. S. Frankel, Journal of The Electrochemical Society
165, C484-C491 (2018).

T. Li, J. R. Scully and G. S. Frankel, Journal of The Electrochemical Society
165, C762-C770 (2018).

T. Li, J. R. Scully and G. S. Frankel, Journal of The Electrochemical Society
166, C115-C124 (2019).
(Invited) High-Performance 2D Tellurium Transistors Towards CMOS Logic Applications
Authors: Qiu Gang , Wang Yixiu , Wu Wenzhuo , Ye Peide D 
Published: February 2020

The thirst for novel two-dimensional (2D) materials for ultra-scaled electronics keeps growing during the last decade as the downsizing trend of silicon-based conventional semiconductors is approaching its physical limit. An ideal paradigm of 2D materials suitable for logic device applications should possess high carrier mobility for both type of carriers, good air-stability, controllable doping scheme and a reasonable bandgap.
Recently reported hydrothermal growth technique of 2D tellurium (Te) thin films, which meet all the above criteria, offers a new option for 2D material-based CMOS applications. Tellurium is a narrow bandgap p-type semiconductor (0.35 eV) with nearly symmetric mobilities for both electrons and holes of around 700 cm2/Vs at room temperature. It has one-dimensional chiral crystal structure and can be grown into 2D films under right conditions. Just like other 2D materials, these 2D facets of Te also contain no dangling bonds and therefore the 2D films can preserve the material properties and have great potential for miniaturizing device geometry in principle. Here we first report systematic investigation of 2D Te p-type transistor performance approaching atomic-thin limit. The device key parameters, such as field-effect mobility, on/off ratio and stability were thoroughly studied as a function of film thickness. The device performance was then optimized through contact and dielectric engineering, and large drive current over 1 A/mm was achieved. We further employed photo-current mapping method to show that rare accumulation-type ohmic contacts were formed using high work function metal (palladium). Finally, we present an atomic layer deposited (ALD) dielectric doping technique to effectively dope the intrinsically p-type channel into n-type with almost symmetric operations for both NMOS and PMOS. Prototypical inverters based on Te CMOS demonstrate great potential of constructing Te-based high-speed CMOS logic circuits. Our work not only established a comprehensive guideline for designing and optimizing 2D Te based CMOS devices, but also provided a device platform to explore versatility of 2D Te from many other perspectives, such as condensed matter physics and thermoelectronics.
Data-Driven Modeling of Dielectric Breakdown Phenomena in Polymers
Authors: Shetty Pranav , Chen Lihua , Batra Rohit , Wu Chao , Li Zongze , Cao Yang , Ramprasad Rampi 
Published: February 2020

Polymers are widely used as dielectrics in devices ranging from capacitors to multi-layered IC’s and as insulation for high voltage cables. In these applications, the dielectric breakdown strength is a critical parameter affecting device performance [1]. In this work, we study the dielectric breakdown properties of common polymers using machine learning. The complex nature of the dielectric breakdown process makes it analytically intractable for real systems and thus ideal for application of machine learning.
The input to the machine learning model consists of material property values and the model outputs dielectric breakdown. For our training data, dielectric breakdown of polymer thin films is experimentally measured using small area breakdown measurements [2] at multiple temperatures ranging from -100 °C to 100 °C. The input to our model are property data that are known to influence dielectric breakdown. Selecting a subset of our original feature space using variable selection algorithms, we train a machine learning model using gaussian process regression.
We test our model on unseen experimental data and find that it predicts dielectric breakdown of unseen polymers accurate to the experimental error of measurement. In addition we find that the underlying physics of the temperature dependence of dielectric breakdown is captured well in the training domain. Our model can be used to systematically search polymer spaces to accelerate discovery of high breakdown strength polymers.

References

[1] Zulkifli Ahmad (October 3rd 2012). Polymer Dielectric Materials, Dielectric Material, Marius Alexandru Silaghi, IntechOpen, DOI:10.5772/50638
[2] Rytoluoto, I., et al. ”Large-area dielectric breakdown performance of polymer films-part i: measurement method evaluation and statistical considerations on area-dependence.” IEEE Transactions on Dielectrics and Electrical Insulation 22.2 (2015): 689-700.
Appraising the Extensibility of Optics-Based Metrology for Emerging Materials
Authors: Barnes Bryan M , Henn Mark-Alexander , Sohn M Y , Zhou Hui , Silver Richard M 
Published: February 2020

Over the last decade, our group at the National Institute of Standards and Technology (NIST) has explored novel ways to overcome the perceived limitations of applying optical scattering and imaging in the characterization of small silicon features. As a result, we were able to both qualitatively and quantitatively characterize features that are well-below the resolution limit, namely small groupings of well-ordered, periodic nanoscale features. This was achieved by specifying a limited number of parameters to describe these structures and comparing the measurements to extensive electromagnetic simulations with varying parameters. Such imaging simulations, which have yielded quantitative measurements of features less than λ/30 in size, require a priori knowledge of the nominal geometry, number of features, and optical constants of these materials; quantitative information from another tool set can augment such optical parametric fitting through “hybrid metrology,” pioneered by our group at NIST.
In the next decade, as the nanoelectronics industry further expands its palette of key emerging materials, it is critical to accurately establish their optical properties. Similar challenges exist for other optics-based, deep-subwavelength measurements, e.g., thickness determination via ellipsometry and parametric fitting via scatterometry. Specifically, the model-based metrology often employed for optics-based methods is challenged by the anisotropy and eventual thickness dependence of the dielectric tensor for two-dimensional materials and ultrathin films. Proper characterization of this tensor empirically or computationally will grow in importance as dimensions continue to decrease. The required steps, known limitations, and potential benefits of atomistic density-functional theory (DFT) simulations are discussed with respect to determining the macroscopic optical response due to feature dimensions only a few atoms in width.
(Invited) Plasma Etching at Ultra-Low Temp, Pressure and Radical Conditions for Next Generation Nano Chip Fabrication
Authors: Park Jongchul 
Published: February 2020

The memory and logic chips are essential for the expansion of big data processing and AI related technologies in the near futrure.
The needs for high density cell and high aspect ratio cell structure and even EUV patterning for the next generation memory and logic chips are increasing more and more.
The conventional etching technologies cannot porvide the appropriate solutions for the next generation nano chip fabrication anymore.
I researched some innovative new etching technologies recently.
- ultra low pressure plasma ( < 1mTorr)
- ultra low temperature ESC ( < -100 degree)
- ultra low radical plasma (Ion beam etch)
The above new technologies will give the breakthrough against current process limitations on the nano chip fabrication.
(Invited) Characterization of Isotropic Thermal ALE of Oxide Films in Nanometer-Size Structures
Authors: Fischer Andreas , Routzahn Aaron , Lill Thorsten 
Published: February 2020

Isotropic atomic layer etching (ALE) is increasingly becoming an option and even a necessity for modern chip manufacturing. Especially for application such as 3D-NAND memory, the ability to perform isotropic etches will be a critical addition to the established suite of reactive ion etching.
In this work, we have characterized the reaction of aluminum oxide (Al2O3) via the vapor-based DMAC ligand exchange mechanism in nanometer-size structures in which the oxide is buried below a silicon nitride mask. In the oxide, we measured vertical and horizontal etch rates and found that the etch showed some residual anisotropy even though all elements of the etch itself (flow, no plasma) were none-directional.
We applied a simple Monte-Carlo simulation to show that anisotropy is caused by a delay in the onset of the horizontal etch beneath the mask and by molecular scattering effects in the vapor phase above the nano-structures.
We are contrasting these results with experimental findings in structures without an anisotropy of the etch.