bluuebunny/crossref_metadata_2025_split huggingface dataset:
Microstructual and Chemical Analysis of Surface Treated Metal Foam Anode for Li Rechargeable Battery
Authors: Ahn Tae-Young , Choi Yu Song , Kim Jiyoun , Cho Jang-Hyeon 
Published: December 2020

As the amount of power consumed by electronic products increases, a lot of studies focused on high capacity and miniaturization of batteries. In order to overcome the low capacity of carbon anode in Li rechargeable battery, researches on the development of high capacity anode material have been conducted. In particularly, it has been reported that pure lithium was adopted for high capacity of Li ion battery due to its light in weight and excellent theoretical capacity. However, when pure lithium is used, the capacity decreases rapidly as charging and discharging proceeded, which is reported to be formation of dendrite on the Li surface during charging/discharging. In order to suppress the growth of dendrite during charging/discharging, several researches have been focused on the Li impregnated metal foam for Li rechargeable battery. However, due to the poor wettability between metal foam and pure Li, adhesive materials had to be deposited by using expensive processes such as chemical vapor deposition to impregnate the Li into metal foam.
In this study we focus on the heat treatment effect on the microstructure and Li-impregnation property of Ni metal foam. We oxidized the metal foam in a high temperature(500-900oC) for 5 min using the furnace to improve the wettability between the Lithium and Ni metal foam. Heat treated metal foam was dip into melted Li at 400 oC in a glove box. As a result, the rate of Li-impregnation in the heat treated metal foam was more than 10 times faster than that of the untreated Ni metal foam. The surface of heat treated Ni metal foam was characterized using transmission electron microscopy (TEM) equipped with energy dispersive X-ray spectroscopy(EDS). Figure. 1 shows the TEM image of the untreated and heat treated Ni metal foam surface. It reveals that an additional layer having a thickness of 200 nm was observed in the heat treated Ni foam. The additional layer was identified as polycrystalline NiOx by EDS and selected area diffraction pattern (SADP). It is believed that formation of NiOx was greatly contribute to improvement of the impregnation characteristics. In addition, the impregnation characteristics of Ni alloy foam will be discussed in this presentation.

Figure 1
Investigation of Low Temperature Epitaxial SiGe:P in View of Source/Drain Application for 5nm Technology Node and Below
Authors: Hikavyy Andriy Yakovitch , Porret Clement , Vohra Anurag , Ayyad Mustafa , Douhard Bastien , Loo Roger 
Published: December 2020

After a long period of research and development high mobility Ge-based materials are being introduced as channel materials of pMOS transistors targeting 5nm node and below [1, 2]. Due to an aggressive scaling, transistors source/drain (S/D) areas are reduced dramatically along with the channel, which has a strong impact on epitaxial layers quality, strain introduction in the channel, contact resistivity, parasitic capacitances, etc. Although standard S/D materials such as SiGe:B and Si:P are being intensively used by the semiconductor industry, other options are being investigated in order to improve the contact resistivity. In the case of Ge based n-MOS transistors SiGe:P attracts attention since it allows a defect free growth on the Ge starting surface, the introduction of tensile stress in the Ge channel and comparably low Rc if sufficiently doped.
In this contribution we focus on SiGe:P growth at a very low temperature of 400oC in view of Ge-based devices processing and further 3D device integration which require a considerable reduction of thermal budget. We show that maximum achievable active P concentration (~1e20cm-3) of as grown layers strongly depends on the Ge concentration with the optimal Ge concentration below 45%. For higher Ge concentrations achievable active P concentration is lower. However, it can be significantly improved by means of post epi laser annealing which eventually allows to vary Ge concentration in a broad range of 30 – 70%. Finally, we will demonstrate a selective epitaxial growth, obtained by applying a cyclic deposition and etch routine using Cl2 as an etchant gas (Fig.1).
[1] E. Capogreco et al
., Symposium on VLSI Technology, 2019, pp. 94
[2] G. Yeap, et al., IEDM 2019, pp. 879
Fig.1. Maximal P active concentration as a function of Ge concentration in SiGe grown at 400oC (left), SiGe:P selectively grown in the Source/Drain areas of a Ge finFET device (right).

Figure 1
(Invited) Strain Engineering of Si/Ge Heterostructures on Ge-on-Si Platform
Authors: Sawano Kentarou , Youya Wagatsuma , Alam Md. M , Omata Kaisei , Niikura Kenta , Shibata Shougo , Hoshi Yusuke , Yamada Michihiro , Hamaya Kohei 
Published: December 2020

Si/Ge heterostructures with high Ge contents have attracted increasing interests for last few decades because of their various high potential applications in the microelectronics industry. Strain engineering is an additional key technology not only for electronic devices with enhanced carrier mobilities but also for photonic devices since efficient light emission can be made possible via strain-induced direct band transition. In addition to the conventional (100) orientation, Si/Ge with a (111) orientation is very attractive owing to the higher electron mobility and applicability to spintronic devices via lattice matched epitaxial growth of high-quality ferromagnetic materials.
As well known, however, it is a challenging issue to grow high-quality Ge-rich SiGe layers on the Si platform due to the large lattice mismatch between Si and Ge. Hence, strain engineered Si/Ge heterostructures with high Ge contents have to be created on Ge-on-Si virtual substrates, whereas strain states and crystallinities of the SiGe are expected to be highly influenced by those of the Ge-on-Si. Here, we show recent studies on heteroepitaxy of various Si/Ge heterostructures on Ge-on-Si with various surface orientations and discuss their strain states, stabilities, critical thickness and crystal qualities. Furthermore, their applications to optoelectronic and spin devices are overviewed.
(Invited) Various Strategies Using Protective Coating Layers for High-Performance Lithium Metal Batteries
Authors: Park Soojin 
Published: December 2020

Recently, a consensus has been reached that using lithium metal as an anode in rechargeable Li-ion batteries is the best way to obtain the high energy density necessary to power electronic devices. Challenges remain, however, with respect to controlling dendritic Li growth on these electrodes, enhancing compatibility with carbonate-based electrolytes, and forming a stable solid–electrolyte interface layer.
Herein, we suggest a groundbreaking solution to these challenges consisting in the preparation of a Li2TiO3 (LT) layer that can be used to cover Li electrodes via a simple and scalable fabrication method. Not only does this LT layer impede direct contact between electrode and electrolyte, thus avoiding side reactions, but it assists and expedites Li-ion flux in batteries, thus suppressing Li dendrite growth. Other effects of the LT layer on electrochemical performance were investigated by scanning electron microscopy, electrochemical impedance spectroscopy, and galvanostatic intermittent titration technique analyses. Notably, LT layer-incorporating Li cells comprising high-capacity/voltage cathodes with reasonably high mass loading (LiNi0.8Co0.1Mn0.1O2, LiNi0.5Mn1.5O4, and LiMn2O4) showed highly stable cycling performance in a carbonate-based electrolyte. Therefore, we believe that our approach based on the LT layer can boost the realization of high energy density lithium metal batteries and next-generation batteries.
Furthermore, functional organic protective layers are helpful to suppress the dendritic growth of Li metal. We would like to introduce two different polymer systems including ferroelectric poly(vinylidene fluoride) fiber mats and elastic polymer, poly(styrene-b-butadient-b-styrene) copolymer for this purpose.
Electrochromic Alarm System with Computer Vision in Smart Contact Lens
Authors: KIM Moobum , Jung Im Doo , Kim Yeongae , Yun Jeonghun , Gao Caitian , Lee Hyun-Wook , Lee Seok Woo 
Published: December 2020

Recent advances in smart healthcare system using IoT are becoming mandatory with continuous and real time healthcare monitoring system. This system can give signal to the user by sound or stimulation when health condition become severe. As one of them, smart contact lens can be used to monitor vital signals from glucose level of the tear related to diabetes1 and intraocular pressure related to glaucoma2. However, previous researches about smart contact lens used wireless communication for signal transfer which need external receiver and antenna inside. Moreover, research that deals with data transmission to the user by image visualization on the contact lens has not been yet published. Herein, we have demonstrated electrochromic alarm system which uses color change to give direct signal transfer to the user by electrochemical reaction with ions in tear. This system showed clear color change with curved shape in limited spaces. Also, diverse intensities and frequencies of color change were controlled by the various voltages and duration of voltage application to this system. In addition, various color changing patterns can be shown to the user by controlling the duration of voltage application and Morse code was used to transfer words to the user in specific purpose. With the help of computer vision, color changing patterns were detected and interpreted. We believe that our electrochromic alarm system with diverse patterns suggest new method for direct data transmission to the user with the help of computer vision. Also, it can be integrated into smart contact lens with battery and various sensors.
References

D. H. Keum, S.-K. Kim, J. Koo, G.-H. Lee, C. Jeon, J. W. Mok, B. H. Mun, K. J. Lee, E. Kamrani, C.-K. Joo, S. Shin, J.-Y. Sim, D. Myung, S. H. Yun, Z. Bao, S. K. Hahn, Wireless smart contact lens for diabetic diagnosis and therapy. Sci. Adv. 6, eaba3252 (2020).

J. Kim, M. Kim, M.-S. Lee, K. Kim, S. Ji, Y.-T. Kim, J. Park, K. Na, K.-H. Bae, H. K. Kim, F. Bien, C. Y. Lee, J.-U. Park, Wearable smart sensor systems integrated on soft contact lenses for wireless ocular diagnostics. Nat. Commun. 8, 14997 (2017).

Figure 1
An Assessment of Novel Graphene Foam and Graphene-Based Microporous Layers for Polymer Electrolyte Fuel Cells: Fabrication and Characterisation.
Authors: Lee Florence Cecilia , Ismail Mohammed S , Ingham Derek B , Hughes Kevin J , Ma Lin , Lyth Stephen Matthew , Pourkashanian Mohamed 
Published: December 2020

Polymer Electrolyte Fuel Cells (PEFC) are electro-chemical energy conversion devices capable of providing sustainable transport, stationary and portable solutions, owing to their high-power density and fast start-up time. However, water management remains one of the largest barriers limiting fuel cell efficiency and the wide scale deployment of PEFC. The microporous layer (MPL) of PEFC is widely acknowledged as a crucial, performance enhancing component; increasing cell efficiency and durability, largely by the improved management of liquid water and two-phase flow.
The purpose of this research is to develop a greater understanding of how composition affects MPL microstructure and morphology, and ultimately identifying strategies to improve fuel cell efficiency. Here we present the fabrication and characterisation of novel MPLs produced from graphene-based materials. Graphene-based materials are a highly promising MPL material, due to their unique physical structure and their excellent electric and thermal conductivity. MPLs were produced from graphene-based materials and compared to conventional carbon black. The graphene-based materials studied were; graphene foam, derived from pyrolysis of sodium ethoxide (GF); graphene nanoplatelets (GN); and multi-wall carbon nanotubes (CNT). The synergetic effect of carbons with different aspects was also studied by the fabrication of composite MPLs mixed with conventional carbon black. Analysis of the performance enhancement and water management capabilities of the MPLs was conducted through microstructural and physical ex-situ characterisation, and polarisation measurements at 100% and 20% relative humidity (RH).
Detailed analysis of the physical characteristics, morphology and microstructure provides an insight into how MPL architecture can be optimised to facilitate mass transport and negate flooding issues whilst maintaining membrane hydration. Thus, graphene-based materials hold the potential to optimise the MPL’s ability for reactant, heat and electron transport, over a range of operating conditions, and so improving overall cell efficiency.
Distribution of Water Molecules inside Proton Exchange Membrane in Transient State during Fuel Cell Operation Monitored By Operando Time-Resolved CARS Spectroscopy
Authors: Nishiyama Hiromichi , Takamuku Shogo , Iiyama Akihiro , Inukai Junji 
Published: December 2020

On the performance and stability of proton exchange membrane fuel cells (PEMFCs), the distribution of water inside the membrane during the power generation has a direct, profound influence, especially for the automotive applications. In this study, coherent anti-Stokes Raman scattering (CARS) spectroscopy was applied to investigating the distribution of water and its chemical states inside the membrane with high spatial (10 μm φ (area) ×1 μm (depth)) and time (0.5 s) resolutions during the power generation.
Figure 1 shows a schematic illustration of the measurement system. Two laser lights, pump light (ω
1: 532 nm) and Stokes light (ω
2: 550-700 nm), were set coaxial and irradiated to the membrane inside the single fuel cell having a glass window in the middle on the cathode-side endplate1. The CARS light emitted was separated by filters and introduced into a spectrometer. Five measurement locations were set from the membrane surface (0 μm) of the cathode side through the membrane to that of the anode side separated by 5μm. Each spectrum was recorded every 0.5 s at each location during the current-density jump from 0.1 to 1.0 A cm−2. The number of water molecules per sulfonic acid group,λ, was quantified using spectral information from a calibration curve created in advance2.
Figure 2 shows the number of water molecules per sulfonic acid group, λ, at five locations of the membrane with the ohmic resistance and the cell voltage during the current-density jump. Upon the jump, the cell voltage dropped abruptly but increased slowly and reached a steady state, whereas the ohmic resistance of the cell decreased abruptly and increased immediately to reach a steady state after the current density jump. Upon the jump, the λ value at 0 μm overshot with a peak at 4.5 s and reached a steady state at 7.0 s. At other locations, a gradual increase in λ was observed corresponding to the electro-osmosis drag and the back diffusion of water. The results of the analysis under conditions other than those in Fig. 2 will also be reported.

Nishiyama et al. J. Phys. Chem. C 2020, 124, 18, 9703–9711

Hara et al. Electrochim. Acta 2012, 82, 277-283

Figure 1
Fabrication and Evaluation of Catalyst Layers in Polymer Electrolyte Fuel Cells: A Comparison of Decal and Inkjet Printing Techniques
Authors: Shimizu Yuki , Murata Ryosuke , Kokogawa Riho , Suzuki Takahiro , Tsushima Shohji 
Published: December 2020

In polymer electrolyte fuel cells (PEFCs), an enhancement of oxygen transport with excess water removal in membrane electrode assemblies can lead to better cell performance especially in high current density operation. Controlling porous structure in the catalyst layers is of great concern, satisfying these demands as well as achieving less precious catalyst loading and reduction of overpotential that are necessitated for automobile application of PEFCs. Depositing and engineering the catalyst layers have been gathering much attention intensively in these two decades [1-2]. Porous electrodes in PEFCs are generally fabricated by either coating or spraying the electrode slurry on substrate materials. Mixing, coating and drying processes of the slurry inherently affect the structural formation of the porous electrode and thus cell performance [3].
In this study, we focused our attention on the inkjet printing technique as a versatile method to control catalyst layer structure. Catalyst layers (CL) with micro-grooves, which potentially provide liquid water channels in the electrodes, were fabricated by adjusting an electrode slurry injectable from a single capillary nozzle in a printing device (Fig.1). Catalyst layers made by a decal transfer technique were also prepared for comparison. The catalyst layers prepared by each method were controlled to gain the same amount of contents, i.e. platinum, ionomer and carbon, within 5% variation.
Porous structure and cell polarization of each catalyst layer were examined. A two-stage ion-beam method using ion milling and focused ion beam (FIB) [4] was applied to analyze the spatial distribution of both ionomer and pore in the catalyst layers as shown in Fig.1. In this technique, a relatively wide cross-section of the CL was firstly formed by a broad ion beam and then, the ionomer impregnated in the CL was removed selectively by a focused ion beam. It was revealed that the electrode thickness was affected by fabrication methods, presumably due to mixing and coating processes. Cell performance shows its variation, depending on fabrication methods and this suggests an optimized electrode structure for further cell performance improvements.

Acknowledgements

This work was supported by JSPS KAKENHI Grant Number 18H01383.

References

[1] A. Strong, C. Thornberry, S. Beattie, R. Chen, S. R. Coles, J. Fuel Cell Sci. Technol., 12(6), (2015), 064001.
[2] M. Breitwieser M. Klingele S. Vierrath R. Zengerle, S. Thiele, Adv. Energy Mater., 8, (2018), 1701257.
[3] T. Suzuki, S. Tsushima, S. Hirai, Int. J. Hydrogen Energy, 36(19), (2011), 12361.
[4] T. Suzuki, T. Koyama, S. Tsushima, ECS Trans., 80(8), (2017), 419-423..

Figure 1
A Computational Fluid Dynamics Analysis of Heat Transfer in an Air-Cooled Proton Exchange Membrane Fuel Cell with Transient Boundary Conditions
Authors: Lind Alexander , Yin Chungen , Berning Torsten 
Published: December 2020

In recent studies, it was found that the current density and power density in air-cooled proton exchange membrane fuel cells is limited by heat transfer. The air that serves as both reactant and coolant has a low thermal conductivity which leads to an early onset of membrane overheating at current densities that are typically in the range of 0.3 - 0.4 A/cm^2. In addition, the stoichiometric air flow ratios are in the regime that lead to laminar flow while it is known that turbulent flow leads to higher heat transfer rates and more efficient cooling. It has therefore been suggested to place a turbulence grid before the entrance of such an air-cooled fuel cell, and first experiments have shown that both the current density and power density can be increased while keeping the fan power constant.
In order to further improve the heat transfer, it has been suggested to induce pulsating flow to the air stream by sinusoidally varying the fan power as function of time. In this numerical study, a turbulence grid was placed before the entrance of a single air-cooled fuel cell channel with varying distances, and the velocity inlet of the air was varied periodically as function of time. One finding is that the choice of the numerical turbulence model is crucial in this analysis. Results indicate that the best distance between the grid and the cathode inlet is the closest at 2.5 mm which is in good agreement with prior experiments. The transient effects are small but show an additional cooling effect.

Figure 1
Feasibility Studies of Pulsed Oxidation Mitigation of CO Poisoning in Polymer Electrolyte Fuel Cells
Authors: Sarma Paran Jyoti , Gardner Christopher L , Chugh Sachin , Sharma Alok , Kjeang Erik 
Published: December 2020

Operation of low temperature polymer electrolyte fuel cells (PEFCs) require up to 99.97% purity hydrogen with CO concentrations mandated to be below 0.2 ppmv by ISO 14687-2 standards [1]. The production and application of such high purity hydrogen increases the fuel price and overall cost of fuel cell operation due to the requirement of additional pre-purification measures. Indian Oil Corporation is the largest producer of reformate hydrogen with up to 99.9% purity in India. It contains traces of methane, carbon monoxide and carbon dioxide as some of the major impurities. This low-cost hydrogen could conceivably be used in PEFCs subject to operando mitigation of CO poisoning with the aid of techniques such as pulsed oxidation [2] and air-bleeding [3] to deliver satisfactory performance [4]. However, the long term impacts of these techniques and their feasibility in terms of overall efficiency and cost must be carefully assessed.
In this work, we present a detailed investigation of the pulsed oxidation technique to mitigate the effect of CO poisoning in long term PEFC operation. A single cell PEFC with an active area of 25 cm2 and Pt-Ru as the anode electrocatalyst is subjected to 80 ppm CO fuel at a nominal operating current density. Pulsed oxidation operation for 4000 cycles showed a consistent performance recovery up to 90% compared with pure hydrogen potentials. Performance governing parameters such as average potential, peak potential and droptime are presented to show changes in cell performance and pulsed oxidation efficiency. A one-dimensional transient model is developed to detect variations in cell potential and surface coverages of species during poisoning and its pulsing process. The model results show up to 26 % increase in the overall efficiency of the cell with and without the application of pulsing process as a function of bleed rates (anode flow). The technical and economic feasibility of operating a PEFC with impure hydrogen with pulsing is demonstrated.
Acknowledgement: This work was supported by Indian Oil Corporation (R&D) and Simon Fraser University under the SFU-IOCL joint PhD program in clean energy.
[1] B. Shabani, M. Hafttananian, S. Khamani, A. Ramiar, A.A. Ranjbar, J. Power Sources. 427 (2019) 21–48.
[2] P. J. Sarma, C. L. Gardner, S. Chugh, A. Sharma, E. Kjeang, J. Power Sources (2020)
[3] L-Yu Sung, B-Joe Hwang, K-Lin Hsueh, W-Nien Su, C-Chung Yang, J. Power Sources 242 (2013) 264-272
[4] C.L. Gardner, D. Mehta, S. Chugh, E. Kjeang, J. Electrochem. Soc. 166 (2019) F3123–F3135

Figure 1