bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of Cathode Catalyst Layer Structure on PEFC Performance Using Two-Dimensional Carbon Support for Pt Catalyst
Authors: Kachi Kazuhiro , Shimada Iori , Osada Mitsumasa , Takahashi Nobuhide , Fukunaga Hiroshi
Published: February 2020

Introduction

Polymer electrolyte fuel cell (PEFC) has been attracting much attention due to its high efficiency at low operating temperature. However, since platinum (Pt), which is used for the electrode catalyst in the cathode, is a metal of low abundance and high cost, reduction of the Pt usage is required. Generally, nano-size Pt particles supported on carbon black are used to increase the mass activity. However, nanoparticles have problems in durability. Moreover, since some Pt particles are located inside the pore of the support, diffusion of supplied oxygen and produced water are suppressed. Recently, nanostructured thin film (NSTF)1) and Pt thin film fabricated by atomic layer deposition (ALD)2) are reported as alternative catalysts. However, they are fabricated on non-conducting materials. Takenaka et al. fabricated metal oxide nanofilms using graphene oxide (GO) as a template to form two-dimensional (2-D) catalysts3). 2-D catalysts are expected to show high mass activity due to the high surface area, and high conductivity during power generation due to the reduced GO and/or metal oxide. In this study, membrane electrode assembly (MEA) was prepared using Pt/GO catalyst, and the relationship between the performance and the structure of the electrode catalyst layer using 2-D carbon support for Pt catalyst was investigated to obtain information towards low Pt loaded PEFC.

Experimental Catalyst inks were prepared by mixing Pt /Graphene oxide (Pt/GO), carbon black (CB), n-Propyl alcohol, and distilled water, and then the mixture was sonicated. 5 wt.% Nafion® solution was added to the mixture which was sonicated again. Catalyst ink was mixed by rotation revolution mixer. Then it was coated onto polytetrafluoroethylene (PTFE) sheet using doctor blade method to fabricate catalyst layer (CL). CL and Pt/carbon paper were hot-pressed onto each side of the Nafion® membrane. After the PTFE sheet was peeled off, carbon paper was hot-pressed onto CL to fabricate the MEA. Terminal voltage vs. current density of the MEA was measured at 80 ˚C.

Results and Discussion

Terminal voltage vs. current density of MEA with various ionomer/carbon ratios (I/C) using Pt/GO are shown in Fig. 1. As it can be seen in the figure, the cell performance in the low current density region was higher when I/C was higher. This indicates that reactive sites have increased due to the coating of catalyst by ionomer. On the other hand, MEA prepared with low I/C showed higher cell performance in the high current density region. It is considered that ohmic resistance was reduced due to the thin coating of catalyst by ionomer.

References

1) M. K. Debe, J. Electrochem. Soc, 160 (6), F522-F534 (2013)

2) M. Inaba, T. Suzuki, T. Hatanaka, Y. Morimoto, J. Electrochem. Soc, 162 (7), F634-F638 (2015)

3) S. Takenaka, S. Miyake, S. Uwai, H. Matsune, M. Kishida, J. Phys. Chem. C, 119 (22), 12445-12454 (2015)

Figure 1
Atomic-Scale Mechanisms for Electrolyte Decomposition in Li-Ion Battery Cathodes
Authors: Fuhst Mallory , Siegel Donald J
Published: February 2020

Li-ion batteries using high energy density LiCoO2 (LCO) intercalation cathodes are known to generate gaseous species inside the cell, which can lead to venting flammable solvent vapor. It has been hypothesized that reactions at the cathode/electrolyte interface catalyze the production of these gaseous species. To elucidate the underlying reaction mechanism, first principles calculations were used to model interactions between LCO surfaces and Ethylene Carbonate (EC), a commonly used solvent in Li-ion batteries. A Metropolis Monte Carlo algorithm was used to identify likely low energy adsorption configurations for EC on the (10-14) surface of LCO. Several of these geometries were further analyzed with DFT. The thermodynamics and kinetics of EC decomposition were evaluated for plausible reaction pathways and associated various solvent decomposition mechanisms, such as hydrogen abstraction. Preliminary results indicate that hydrogen abstraction may lead to the decomposition of EC into CO2 and other adsorbed species at the surface.
Novel Ir@Pt Core@Shell Nanoparticles As Catalysts for Ethanol Oxidation
Authors: Slaby Jachym , Ketabi Sanaz , El Sawy Ehab , Birss Viola
Published: February 2020

Ethanol is a promising fuel for transportation applications, given its low toxicity and easy access from feedstock fermentation. However, the combustion of ethanol to regain the stored energy is highly inefficient and thus a non-combustion process, such as the electrochemical oxidation of ethanol in a fuel cell, is desirable for utilizing the stored energy. To achieve high conversion efficiencies, an appropriate catalyst for ethanol oxidation must be developed. While Pt is a good material for this purpose, it is prone to poisoning by strongly adsorbed intermediates, e.g., CO. To address these shortcomings, Pt can be nanostructured and combined with other metals, resulting in superior activity and longer lifetimes.

In the present work, Ir core@Pt shell nanoparticles (NPs) were synthesized, with varying Pt shell coverages (less than one monolayer), ensuring that some Ir is exposed and thus allowing the bifunctional effect [1], electronic [2], and strain effects [3] to all play a role in the catalysis of the ethanol oxidation reaction. The core@shell NPs were synthesized using the polyol method [4], producing a core that was ca. 3 nm in diameter and then loaded (10 mass %) onto Vulcan Carbon powder. These catalysts were then characterized by wavelength-dispersive X-ray spectroscopy (WDS) and thermogravimetric analysis to determine the relative percentage of each metal present in each nanoparticle and to confirm the metal loading onto the carbon, respectively, while TEM analysis confirmed the expected NP size and distribution.

The electrocatalytic activity of these materials was evaluated using a three electrode system, all in 0.5 M H2SO4 + 0.01 - 1 M ethanol at room temperature. Overall, it is shown that these Ir core@Pt shell NPs are notably more active than Pt NPs of the same size and also produced using the polyol method. The activity of the catalysts increases with ethanol concentration, but less than linearly, and sweep rate studies revealed the presence of electroactive surface-bound reaction intermediates. The stability of the catalysts has also been investigated using cyclic voltammetry and chronoamperometry experiments. By studying the effect of Pt shell coverage on the Ir core NPs, the mechanism by which Ir enhances the activity of Pt during ethanol oxidation is now being determined.

References:

El Sawy, E. N.; Molero, H. M.; Birss, V. I. Electrochimica Acta (EAST13-0480)
2013.

Chen, Y. M.; Yang, F.; Dai, Y.; Wang, W. Q.; Chen, S. L. Journal of Physical Chemistry C
2008, 112, 1645-1649.

Zhang, X. T.; Wang, H.; Key, J. L.; Linkov, V.; Ji, S.; Wang, X. L.; Lei, Z. Q.; Wang, R. F. Journal of The Electrochemical Society
2012, 159, B270-B276.

Alayoglu, S.; Eichhorn, B. Journal of the American Chemical Society
2008, 130, 17479- 17486.
Microscale Fuel Cells for Portable Power Applications
Authors: Miller Kelly L , Burbules Mary Beth , DeLaney Scott C , Hollinger Adam S
Published: February 2020

The development of microscale fuel cells has been motivated by the increasing demand for high power density, portable electronic devices (i.e., smartphones, tablet computers) with a fast recharge [1]. In comparison to rechargeable batteries, microscale fuel cells demonstrate superior energy densities and the potential to provide longer off-grid run times [2]. Additionally, fuel cells enable nearly instantaneous recharging by refilling or replacing a liquid-based fuel cartridge. However, due to the size constraints and power demands of modern portable electronic devices, microscale fuel cells must be optimized to produce sufficient power for as long as possible before requiring refilling or replacing of a self-contained fuel cartridge. To perform this optimization, parameters such as catalyst area, catalyst loading, fuel molarity, temperature, and flow rate, electrolyte molarity and flow rate, and electrode geometry are modified, isolated, and tested experimentally until maximum performance is achieved.

Because the aforementioned process is laborious, we present a mathematical flow and diffusion model to simulate the effects of the experimental parameters [3]. The model outputs performance data, confirmed by experimental data, over a range of parameters without the use of curve fitting, resulting in significantly improved simulation accuracy compared to simple curve fits. The model is adjusted to replicate the experimental results for a given set of parameters by adjustment of a set of internal variables. Utilizing a design of experiment (DOE)-based analysis of the model’s governing equation, the model is modified to simulate other experimental parameters accurately, resulting in a tool for microscale direct methanol fuel cell (DMFC) optimization. DOE experimental protocol reveals interactions between parameters and ultimately, a more complete understanding of DMFC performance parameters.

[1] E. Kjeang, N. Djilali, D. Sinton, Journal of Power Sources, 186 (2009) 353-369.

[2] C. Potera, Environ. Health Perspect., 115 (2007) A38-A41.

[3] A.S. Hollinger, M.G. Willis, D.G. Doleiden, Proceedings of the ASME 2015 Power and Energy Conversion Conference, San Diego, CA, 2015.
Effect of Surface Nanocrystallization on the Sensitization and Desensitization Behaviors of the Novel Super304H Stainless Steel
Authors: Wang Rui.Kun
Published: February 2020

The newly developed Super304H austenitic stainless (SS) steel is being widely used in ultra supercritical fossil fired boilers because of its superior high temperature strength and oxidation resistance, but its high carbon content has increased greatly its intergranular corrosion susceptibility (IGCS). In the present paper, we have made an attempt to understand the sensitization and desensitization behaviors of the shot-peened Super304H SS during aging around service temperature. The shot peening on the Super304H SS resulted in its surface nanocrystallization accompanied with strain-induced αʹ-martensite. The strain-induced αʹ-martensite had good thermal stability at 600℃ and was blamed mainly for the significant increase of the degree of sensitization (DOS) of shot-peened Super304H SS when aged at 600℃ for different time. However, the DOS decreased greatly when aged at 650℃ for 24 h or 700℃ for 2 h, indicating the occurrence of a faster self-healing process of chromium depletion zones due to long range Cr diffusion enhancement by surface nanocrystallization and also the reverse transformation of αʹ-martensite to austenite at the same time.

Figure 1
Integrating Ultrafast Coherent Diffractive Imaging and Atomistic Simulations to Investigate Externally Stimulated Metallic Nanocrystals
Authors: Sasikumar Kiran , Cherukara Mathew , Clark Jesse N , Peterka Tom , Harder Ross , Sankaranarayanan Subramanian K. R. S.
Published: February 2020

Despite the increasing role of nanomaterials in technology, the mechanical and dynamical properties of single nanoparticles at picosecond timescales are not well understood. In particular, core-shell nanocrystals are an important class of nanoparticles for catalysis, biomedical and energy applications. The effect of the nanoscale interface between the core and shell material on coherent lattice vibrations (phonons) is yet to be investigated in detail. Understanding the temporal behavior of such nanomaterials under conditions of external thermal stimulation is crucially important for energy research. In addition, observing ultrafast lattice distortions can provide key insights into the behavior of nanomaterials and nanoscale interfaces.

Recently, experimental techniques have evolved to conduct time-dependent lattice dynamics measurements in nanomaterials. In particular, Bragg Coherent Diffraction Imaging (BCDI) in conjunction with optical pump-probe experiments via ultrafast x-ray lasers has been used to directly image the generation and subsequent evolution of coherent acoustic phonons within nanocrystals. In particular, experiments on bimetal (Au/Al) core-shell nanocrystals have revealed inhomogeneous effects in the lattice breathing upon heating with femtosecond x-ray lasers. Conventional theoretical models cannot be used to explain the physics of the phenomena in such non-equilibrium environments that involve extreme heat fluxes and temperature gradients.

Atomistic molecular dynamics (MD) simulation is an appropriate technique to investigate lattice dynamics in such environments, particularly in core-shell structures where interfacial effects can play an important role in phonon scattering. With the convergence of time and length scales accessible by both experiments and simulations, we are now able to integrate experimental observations with multi-million atom MD simulations to enhance the fundamental understanding of materials behavior under external stimulation.

In this talk, we demonstrate the workflow to integrate ultrafast time-resolved coherent diffractive imaging with large-scale atomistic molecular dynamics simulations to investigate lattice dynamics in externally stimulated core-shell bimetallic nanocrystals. We will focus, primarily, on the MD simulations performed on core-shell bimetallic nanocrystals under the influence of extreme heat fluxes. We explore the vibrational modes that dominate lattice breathing and look into the effect the nanoparticle size and shape have on the same. In addition, we attempt to identify the origin of the inhomogeneous effects, observed experimentally, in the lattice breathing of core-shell structures.

Figure 1
First-Principles Study on Mechanical Strain and Defect in Materials
Authors: Choi Minseok
Published: February 2020

Strain, a simple and predictive parameter, has been utilized to control the materials property. In various materials, drastic changes in chemical and physical properties are observed with an introduction of strains by lattice distortion or lattice mismatch. In this work, we investigate the correlation between mechanical deformation and defects/dopants in materials using first-principles calculations. First, we examine how mechanical deformation impacts on defect formation that is critical for the materials property. Our calculations predict that strain and hydrostatic pressure lower the formation energy of oxygen vacancies in SrTiO3, thereby enhancing the vacancy formation, which agrees with the experimental observation of oxygen vacancies at the strain-imposed regions in SrTiO3 bicrystals. Second, how dopants introduce strain via lattice distortion is examined. We find that chemical doping such as hydrogenation induces strong strain in the VO2 lattice. It is experimentally observed that the massive hydrogenation leads to the electronic phase transition and dramatic out-of-plane lattice expansion. Our calculations explain that the phase transition is originated from the heavily doped electrons with cooperative interaction of hydrogenation-induced strain, i.e., lattice expansion.
Atomistic Picture of the Catalytic Activity of Platinum Nanoparticles through Coherent Diffraction Imaging and Reactive Molecular Dynamics Simulations
Authors: Cherukara Mathew Joseph , Kim Dongjin , Cha Wonsuk , Kim Hyunjung , Narayanan Badri , Harder Ross , Sankaranarayanan Subramanian K. R. S.
Published: February 2020

Platinum nanoparticles are among the most widely used catalysts due to their high chemical stability, surface reactivity and electron transfer rate. They find applications in chemical and bio-sensing, fuel cells, photocatalysis and methanol formation. Elucidating the catalytic mechanism under in-situ conditions is vital to the structural and chemical design of more efficient catalysts that are urgently needed to meet the energy needs of today. Coherent X-ray diffraction imaging (CDI) is a powerful technique for operando characterization with the ability to provide evolving snapshots of defect structure, lattice dynamics and structural evolution at ~10 nm resolution, while reactive molecular dynamics (MD) simulations provide atomistic details of lattice dynamics, bond breakage and formation as well as reaction kinetics at experimentally inaccessible length and time scales. We present results from combined CDI experiments and reactive MD simulations on the atomistic processes underlying methanol formation from methane on Pt nanoparticles. We observe the preferential oxidation of edge and corner sites on the Pt nanoparticle in an O2 rich atmosphere, which when followed by the introduction of methane, leads to the binding of CH4 to disassociated O atoms. Fig. 1 a) shows the partially oxidized Pt particle in a methane atmosphere. O2 on surface sites is not seen to disassociate while oxygen at corner and edge sites disassociates due to the higher site reactivity at edges and corners. Fig 1. b)-c) shows a close-up of the surface during the binding of CH4 to the disassociated oxygen. Finally, the mechanism predicted by the reactive MD simulations is validated through CDI experiments, with the observation of local lattice strains at edge and corner sites, which arise due to the binding of O2 and CH4 molecules.

Figure 1
from Bare Metals to Metal Oxides Nanoparticles and Hierarchical Supramolecular Metal Oxide Nanoparticle Network Assemblies
Authors: Redel Engelbert
Published: February 2020

A unique, universal and general route to a library of different metal oxide nanoparticle materials starting from bare metal powders will be presented. Such metal oxide nanoparticles are further used to construct porous and hierarchical photonic multilayer assemblies or can be assembled into 1D supramolecular nanoparticle network structures.

Potential applications of such materials will be also presented, reaching from optical and tune able and porous 1D photonic crystals (PCs) to transparent and conductive oxides (TCOs) porous thin films, electrochromo-photonic switches as well as sensing devices.

REFERENCES:

E. REDEL, P. MIRTCHEV, C. HUAI, S. PETROV, G. A. OZIN

Nanoparticle Films and Photonic Crystal Multilayers from Colloidal Stable, Size-Controllable Zinc and Iron Oxide Nanoparticles. ACS NANO, 2011, 5, 2861-2869.

E. REDEL, S. PETROV, D. OMER, J. MOIR, C. HUAI, P. MIRTCHEV, G. A. OZIN

From Metal Powders to Metal Oxide Nanoparticles and Porous Thin Films.

SMALL
2012, 8, 68-72.

E. REDEL, J. MLYNARSKI, J. MOIR, A. JELLE, C. HUAI, S. PETROV, M. G. HELANDER, F. C. PEIRIS, G. V. FREYMANN, G. A. OZIN

“Electrochromic Bragg Mirror (ECBM)” Advanced Materials
2012, 24, OP265-OP269.

S. MAKUMIREA, V. S. K. CHAKRAVADHANULA, E. REDEL, A. SHONHAI

“The effect of colloidal and charge stabilized Zinc peroxide (ZnO2) and Titanium dioxide (TiO2) nanoparticles on the structural integrity of DNA and protein”

Toxicology Letters
2014, 227, 56-64.

E. REDEL, V. S. K. CHAKRAVADHANULA, Y. LANHUA, C. NATZEK, S. HEISSLER

“On the self-assembly of paramagnetic TiOx NPs to supramolecular TiO2 network structures”

Nanotechnology
2015, 26
, 051001.
Electrochemical Characterization of Lithium-Oxygen Cells Employing a Bi-Functional Metal-Free Catalyst Composed of Dual-Doped Graphene and Mesoporous Carbon
Authors: Kim Jae-Hong , G Kannan Aravindaraj , Woo Hyun-Sik , Kim Dong-Won
Published: February 2020

Rechargeable lithium-oxygen (Li-O2) batteries have received great attention due to their high theoretical energy density. The successful operation of the Li-O2 battery requires the reversible formation and decomposition of insoluble Li2O2 on the cathode surface during the discharge and charge processes. However, the large overpotential during the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) should be reduced to make this battery commercially viable. Recently, carbon-based nanomaterials have been widely explored as either a catalyst support or a catalyst for the ORR in different electrolytes. In particular, graphene nanosheets with their two-dimensional, sp2-hybridized carbon structure have received great interest due to desirable properties such as high surface area, high electronic conductivity and charge carrier mobility, high mechanical strength and chemical stability. In this work, mesoporous carbon was grown on graphene nanosheets by in situ nitrogen and sulfur co-doping using a two-step synthesis method (hereafter referred to as NSGC). The growth of mesoporous carbon on graphene nanosheets prevented the restacking of graphene, resulting in a higher active surface area and enhanced electronic conductivity. Furthermore, the presence of mesoporous structures could accommodate the insoluble Li2O2 formed during discharge. As a result, the synthesized NSGC exhibited enhanced bi-functional catalytic activities toward ORR and OER, and showed a high initial discharge capacity of 11,431 mAh g-1 and good cycling stability as an air cathode in Li-O2 batteries.
Gold Nanoparticles Supported over Low-Cost Adsorbents for Hydrogen Generation from a Solid Hydrogen Feedstock
Authors: Abdel-Fattah Tarek M , Horten Mitchell , Osborn Justin
Published: February 2020

Due to the rising concern of global warming and the limited supply of fossil fuels, hydrogen gas production for use as a clean and renewable energy source has been a rapidly growing field of research. A significant amount of work has been done in generating hydrogen gas from water [1-3]. However, this is an energy intensive process. Solid chemical storage of hydrogen using metal hydrides has been proposed as an attractive alternative. Sodium borohydride is considered one of the most viable hydrogen storage materials because it provides a safe and practical means of producing hydrogen and has a high hydrogen content (10.7% wt). Sodium borohydride produces hydrogen by slowly reacting with water to evolve 4 moles of hydrogen gas [3]. While a slow reaction is favorable for reduction, the use of sodium borohydride to produce hydrogen gas for energy generation necessitates the use of catalysis to accelerate the reaction to an appreciable rate. A significant amount of research has been conducted searching for catalysts of such reactions, often finding noble metals to be the most efficient. Nobel metals are often expensive, therefore price must be considered when deciding on a catalyst. A cost effective strategy to create noble metal catalysts is to synthesize nanoparticles of the metal of interest and adsorb them to low-cost supports.

Gold nanoparticles affixed to activated carbon and glasswool were tested for catalytic activity in the hydrogen evolution reaction of aqueous sodium borohydride and compared against the catalytic activity of uncoated activated carbon and glasswool supports. The evolved gas was measured through the use of a water-displacement system, Ohaus microbalance, and mass logging software. Preliminary data suggests that the gold nanoparticle supports are more efficient at generating hydrogen than non-coated substrates.

References:

[1] Abdel-Fattah T. M.; Wixtrom A. Catalytic Reduction of 4-Nitrophenol Using Nanoparticles on Carbon Nanotubes. 2014,
ECS J SOLID STATE SC 3(4) M18-M20.

[2] Schlesinger, H.; Brown, H.; Finholt, A.; Gilbreath, J.; Hoekstra, H.; Hyde, E. Sodium Borohydride, Its Hydrolysis and its Use as a Reducing Agent and in the Generation of Hydrogen. 1952,
J. Am. Chem. Soc. 75(1) 215-219.

[3[ Zahmakiran, M.; Özkar, S. Zeolite-Confined Ruthenium(0) Nanoclusters Catalyst: Record Catalytic Activity, Reusability, and Lifetime in Hydrogen Generation from the Hydrolysis of Sodium Borohydride. 2009, Langmuir. 25(5) 2667-2678.
Controlled Synthesis of BaTiO3 Nanofibers for Enhanced Piezoelectric Properties
Authors: Shirazi Paymon , Anderson Christopher S. , Ma Meghann C. , Myung Nosang Vincent
Published: February 2020

Reducing the size of piezoelectric energy harvesting devices – progressing from bulk materials, through the micro scale, and now into the nanoscale – is attracting interest in new size-based classifications of clean energy sources converting ambient, attenuated mechanical energy into electrical energy. Compared to the macro devices, nanostructures based transducer materials, with their exclusively large surface area-to-volume ratio, have shown enhanced piezoelectric properties. In this paper, electrospinning was used to fabricate nanofibrous structures by jetting a solution of barium and titanium precursors dissolved in poly (vinyl pyrrolidone) (PVP) with an applied voltage. Three separate full-factorial design of experiments (DOEs) (one 3-level, two 2-levels) were conducted to control and optimize the process to minimize fiber diameter with the least amount of beading defects. The three factor design focused on the optimization of the solution properties (viscosity, electrical conductivity, surface tension), one of the two factors focused on electrospinning parameters (voltage, flow rate), and the other on environmental conditions (temperature, absolute humidity). The viscosity was controlled by the polymer weight percentage, the electrical conductivity controlled by the salt to polymer ratio, and the surface tension controlled by the solvent. Low temperature and low absolute humidity produced the smallest fibers. Scanning electron microscopy (SEM) was utilized to characterize the morphology and diameter of the as-spun nanofibers. Micrographs of our best results showed as-spun nanofibers with an average diameter of 74.6 ± 15 nm with minimal beading. The as-spun nanofiber mats were subsequently calcinated and annealed to produce BaTiO3 nanofibers to be tested for their piezoelectric properties.
Non-Plasma Based Atomic Layer Dry Removal Technology for 10nm Node and Beyond
Authors: Su Yongzhuo , Suemasa Tomoki , Mosden Aelan , Biolsi Peter
Published: February 2020

The fabrication of nanoscale devices is increasingly relying on digital precision process engineering that goes well beyond conventional continuous etch and clean technology. Interest in atomic layer etch and clean (ALE/C) has been intensifying as it emerges as an enabling technology for advanced etch and clean applications. As features on a chip continue to decrease in size, the ability to precisely remove materials to create those features becomes increasingly difficult and vitally important. ALE/C can deliver the level of control needed by using cycles of multi-step processes that are self-limiting and remove a few atomic layers at a time, making it useful for manufacturing 3D, high aspect ratio, and other challenging structures requiring extreme precision and fidelity. COR (Chemical Oxide Removal) is a technique that removes thin layers of material using sequential self-limiting reactions and is considered one of the promising techniques for achieving the low process variability necessary in the nano-scale and atomic-scale era. The basic COR concept starts with a reaction step to form a byproduct layer, followed by a removal step to take off only this modified layer. Using gas distribution plate allows for the semi-directional etching and cleaning required to form deep, narrow structures. In this paper, non-plasma based dry removal processes such as COR is illustrated, and applications and prospects for COR will also be discussed.
A Study on Profile Control at Wafer Edge By CMP Head Separated Retainer Ring
Authors: Yoo Jinsu , Lee Dongjun , Yoon Hyunjoo , Jeon Joonbae , Kim Kyoungwoo , Hwang Hasub
Published: February 2020

CMP (chemical mechanical planarization) is a process in which both chemical and mechanical mechanisms act simultaneously to produce the planarized wafer.[1]

The wafer edge profile control is the most challenging issue in CMP process. Even much investigation has been tried to eliminate wafer edge profile control, the understanding the origins of the wafer edge profile control during polishing are still needed.

Fig1. shows the differences were compared with the single retainer ring and separated retainer ring.

Fig2. shows that the separated retainer ring can control wafer edge profile as the result of the simulation.

Fig3. is the removed wafer normalize amount as compared with the result of single retainer ring and separated retainer ring.

In this study, we examined the better wafer edge profile control was presented by changing the original form of RR(retainer ring) into having two individual pressure controls.

Based on experimental and simulation result, it was possible to achieve uniform surface even in the wafer edge area in the case of separated retainer ring by decreasing pad deformation.

REFERENCE

1. P. Singer, “Chemical-Mechanical Polishing : A new focus on consumable”, Semiconductor International, pp. 48-53, Feb, 1994.

2. Preston, F. W., “The Theory and Design of Plate Glass Polishing Machine”. Journal of the Society of Glass Technology, 11, p. 214, 1927.

3. Zhao, D., Wang, T., He, Y., and Lu, X., “Effect of Zone Pressure on Wafer Bending and Fluid Lubrication Behavior during Multi-zone CMP Process”, Microelectronic Engineering, 108, p. 33, 2013.

4. Wang, T., Lu, X., Zhao, D., & He, Y., "Contact Stress Non-uniformity of Wafer Surface for Multi-zone Chemical Mechanical Polishing Process." Science China Technological Sciences, 56(8), p.1974, 2013.

Figure 1
Influence of Nanopore Size on the Performance of Salinity Gradient Power
Authors: Tseng Shiojenn , Li Yu-Ming , Lin Chih-Yuan , Hsu J.P.
Published: February 2020

Retrieving energy based on a salt concentration difference between two liquid phases, such as sea water and fresh water, has emerged as one of the promising next-generation renewable energy techniques. Recent advances in nanotechnology and nanofabrication also make relevant applications attractive. According to the mechanisms involved, relevant results can be classified roughly into two technologies: pressure retarded osmosis and reverse electrodialysis (RED). The latter can be achieved by separating two liquids having different salt concentrations, for example, a fresh water and a sea water, by an ion-exchange membrane. Since the membrane attracts counterions and repels coions simultaneously, making the concentration of counterions inside the membrane higher than that of coions. Because it is easier for counterions to pass through the membrane, a net ionic flow is present so that Gibbs free energy is converted to electric energy. Considering the great potential of harvesting energy by RED, a detailed understanding of its performance under various conditions is highly desirable and necessary for design purposes. Among factors capable of influencing that performance, the size of a pore and its charged conditions are of particular significance. This is because the possible mechanisms involved, such as double layer overlapping, ion concentration polarization, and diffusioosmotic flow, are all related closely to those factors. In this study, we conduct a theoretical analysis on the influences of the size of a nanopore and its charged conditions on the performance of a RED system. Taking an aqueous KCl solution as an example, the results of numerical simulation reveal that for a positively charged nanopore, both the maximum power, P
max, and the ion selectivity, η, have a local maximum as its radius, R, and its length, L, varies. A negatively charged nanopore, however, shows different behaviors. Regression analyses are performed to provide the dependences of both P
max andη on R and L.
Additional Voltage Loss to Explain an Equilibration Process in Response to a Change in the Anode Gas Using Sm-Doped Ceria Electrolytes
Authors: Miyashita Tomofumi
Published: February 2020

The electronic conductivity of Sm-doped ceria is very low in air but increases substantially in H2 gas. We measured the equilibration process using a very thick (6.6 mm) samarium-doped ceria electrolyte in response to a change in the anode gas. For this purpose, Weppner’s approach was used to analyze the drift current and the electron diffusion current throughout the entire electrolyte. The direction of the electron drift current was the same as that of the ionic current. The electron drift current was recycled as the electrons diffused throughout the electrolyte. The open-circuit voltage (OCV) gradually increased to an equilibrium voltage of 0.80 V within 5 min. The time constant was only 1 min. According to Weppner’s approach, the equilibrium time should be much longer than 5 min. It is impossible to calculate the OCV at equilibration in response to a change in the oxygen activity of the anode gas. Assuming a current-independent constant anode voltage loss (approximately 0.35 V), the calculation revealed a significantly improved explanation of the experimental results, both quantitatively and qualitatively. Consequently, both Weppner’s approach and Wagner’s equation can coexist with this method. This proposed voltage loss does not contradict the model for very thin films but is necessary to improve the analysis of the experimental results. A hypothesis was developed to explain this voltage loss in the SDC electrolyte. Furthermore, a current-independent constant anode voltage loss is a general topic in electrochemistry and important to explain physical phenomena not only in the area of solid oxide fuel cells.
Electrochemistry Modeling for Energy Conversion and Storage
Authors: Lueth Chris
Published: February 2020

Renewable energy devices, such as fuel cells, flow batteries, and electrolyzers require reliable functioning of mass and energy transfer processes. For example, water management in fuel cells is tightly linked to their thermal and electrochemical operation. To better understand and predict these interactions, computer aided engineering (CAE) may provide a valuable tool. CAE in parallel with experimentation has proven invaluable for efficient design and theoretical insight in traditional engineering fields like automotive and aerospace. In many instances, it has even replaced the need for expensive prototyping. Combing the traditional flow, stress, and thermodynamic models with electrochemistry may provide the innovation required for the development of renewable energy technology and processes.

We will present recent electrochemistry developments in an industrial CAE software. The general framework provides unprecedented flexibility with the range of physics and length scales available with an extensive suite of compatible models. The general implementation allows for simulation of a wide array of processes, from pH effects on corrosion to water management in fuel cells.
Electrospun Polyimide Based Composite Fibrous Separator with High Heat Resistance for Lithium Ion Batteries
Authors: Jo Seong Mu , Joh Han-Ik , Lee Sungho
Published: February 2020

High heat-resistive nanofibrous membrane as new separator of future lithium ion battery was prepared by electrospinning of PVdF and Polyimide(PI) mixture solution. Electrospun PI/PVdF composite fibrous separators generally have mechanical performance with tensile strength of 32 MPa, and modulus of 700 MPa after post-process such as hot-pressing. The internal structure of the electrospun PVdF/PI composite fiber with a diameter of few hundreds nanometer were composed of a bundle of PI nanofiber with a diameter of few tens nanometer, which resulted from microphase separation and highly stretching of PI micro-domain during electrospinning. These composite fibrous separator show high ionic conductivity of 1.3× 10-3 S/cm at room temperature and sufficient electrochemical stability windows above 4.5 V ver. Li+/Li. From thermal stability tests, PE separator was melted above 130oC, but PI/PVdF blend membranes show good dimensional stability at above 200 oC. It indicates the membrane will still retain the mechanical integrity of membrane even after meltdown at high temperature. Also, the prototype cells with electrospun PI/PVdF composite membrane have good long term cycle performance over 500 cycles compared with PE separator at 1C rate.
Hydrogen Trap in Seashells
Authors: Kato Yoshimine , Tsuchida Hirotsugu , Dobara Kent , Aramaki Masatoshi , Furukimi Osamu
Published: February 2020

Hydrogen evolution and adsorption were found that from seashells at high temperature. Large quantities of seashells are abandoned as production waste and it is desired to make use of them. As it is well known that the component of seashell is mostly calcium carbonate CaCO3 layers which are bonded by conchiolin layers. In conchiolin layers there are many types of carbohydrates and those seem to be origin of hydrogen evolution during the heat treatment in N2 gas flow at temperature between 300 and 900°C. Hydrogen gas detection was conducted with gas chromatography mass spectrometer during the heat treatment flowing Ar gas of 50ml/min. The total evolution hydrogen amount from the Mizuhopecten yessoensis［scallop］shell was roughly about 0.05ml/g. It was observed by X-ray diffraction that the CaCO3 layers metamorphose to calcium hydroxide Ca(OH)2 above 450°C that may due to the hydrogen from conchiolin layers. It was also observed by FESEM that there are many nm-size holes on the surface of the seashells. These holes formation may due to hydrogen and etc. evolution from the conchiolin layers. Then after 800°C calcium oxide CaO was formed due to the Ca(OH)2 decomposition. It was also confirmed that surface area has increased up to about 11m2/g with increasing temperature using Specific Surface Area Analyzer (Shimazu Gemini VII 2390). After the heat treatment the hydrogen adsorption or chemical bind was observed in the seashells by using NMR analysis and oxidation-reduction potential (ORP) analysis.

 Commercial Ca(OH)2 powder was obtained and similar experiment was done for comparison. The Ca(OH)2 powder was heated at the temperature range from 600 to 1300°C in Ar based 3% hydrogen gas flow. The hydrogen adsorption from the gas was confirmed using NMR analysis and ORP analysis. It showed adsorption of hydrogen at annealing temperature of around 800°C to 900°C. nm-size holes on the surface of Ca(OH)2 powder was also observed by FESEM. Hydrogen adsorption may be caused by this large surface area due to these fine holes.
(Keynote) Japan's Policy and Activity on Hydrogen Energy
Authors: Ohira Eiji
Published: February 2020

This presentation will provide an overview of Japan’s hydrogen and fuel cell activities, focusing on the latest policy, market and NEDO’s research, development and demonstration programs. In June 2014, Japanese Ministry of Economy, Trade and Industry (METI) compiled the “Strategic Road Map for Hydrogen and Fuel Cells” toward the realization of a “hydrogen society.” This road map states how Japan would be able to make use of hydrogen, what are goals to be achieved in each step of production, transportation, storage and utilization of hydrogen, and what kind of collaborative efforts could be possible among industry, academia and government for achieving these goals.

Regarding market status, Japan has success to market introduction of hydrogen technology. Fuel cell micro combined heat and power system for household has been on market since 2009 and over 150,000 units are installed. Fuel cell vehicle was launched in December 2014 and around 70 hydrogen refueling stations have been operated now.

The New Energy and Industrial Technology Development Organization (NEDO) has been conducting comprehensive technology development and demonstrative research programs on hydrogen energy. The most recent result from NEDO’s program such as new materials for PEFC, analysis technology of morphology, electrochemical reaction and mass transfer in MEA, evaluation technology for long time fuel cell durability will be addressed. Following current topic, NEDO’s future challenge to develop hydrogen energy demand will be presented. NEDO just started R&D program to develop large scale n hydrogen supply chain with long-distance transportation of hydrogen and hydrogen gas turbine technology. NEDO is now also conducting Power to Gas which is a key technology to provide CO2 free hydrogen in the future.
Investigating the Effect of Chlorides on the Reaction Kinetics of a Copper Electrodeposition Process
Authors: Vyas Ritesh , Kubicsko Michael
Published: February 2020

Over the past two decades, the replacement of aluminum interconnects with copper is one of the biggest advances in semi-conductor industry. As the wiring density continues to increase, so does the demand for tighter control on the electrolytic copper deposition process for these industries. Apart from organic additives and other trace metals, one of the crucial component in plating baths mixtures for manufacturing PCB boards and photovolotaic cells is the intermediate cuprous ion composition, which is formed during the copper dispropornation reaction:

2
Cu

+

(aq)

⇌ Cu(s) + Cu2+
(aq)

 

The cuprous ion is typically unstable in normal acidic solution and it disproportionates into metallic copper and cupric ions. In the presence of chlorides however, the disproportionation reaction equilibrium is shifted and the cuprous ions are stabilized. Cuprous ions are also required in order for the other additives (brightener, suppressor, leveler) used in the process to operate at maximum efficiencies. It is therefore important to know if the Cu2+
intermediate is truly formed and present during the a copper electrodeposition process.

In this work, we used Autolab RRDE system to identify mechanisms governing copper electrodeposition process and study the influence of chloride concentration on the generation of intermediates.
Non-Isothermal Aging of Lithium-Ion Cells
Authors: Bloom Ira , Thomas Edward V , Christophersen Jon P , Robertson David C , Walker Lee K , Ho Chinh , Battaglia Vince
Published: February 2020

Lithium-ion batteries are rapidly being adopted for transportation applications, ranging from hybrid- to full-electric vehicles.  To assure that the automotive battery can meet the demands of these applications, the US Advanced Battery Consortium has established test manuals and performance targets for each application [1-3].  These manuals use accelerated tests to gather needed performance degradation information in a limited amount of time.  Models are then developed from these data that relate performance decline to the magnitude and duration of the stress.  Isothermal aging stresses the battery under a simple set of conditions and can be used to elucidate the underlying degradation mechanisms.  It is then generally assumed that a cumulative degradation model of aging under non-isothermal conditions would be a linear combination of the isothermal results.  However, this approach may not directly predict the non-isothermal behavior.  A model based on degradation rates may be a better predictor.  In theory, integrating the rate-based model over the temperature path can then express the cumulative degradation.  The results of this investigation will be discussed.

The work at Argonne National Laboratory was performed under the auspices of the U.S Department of Energy (DOE), Office of Vehicle Technologies, under Contract No. DE-AC02-06CH11357.  Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.  The efforts at Idaho National Laboratory and at Lawrence Berkeley National Laboratory were performed under Contract Numbers DE-AC07-05ID14517 and DE-AC03-76SF00098, respectively.

This article issue has been created by UChicago Argonne, LLC, Operator of Argonne National Laboratory (Argonne). Argonne, a DOE Office of Science Laboratory, is operated under Contract No. DE-AC02-06CH11357. The U.S. Government retains for itself, and others acting on its behalf, a paid-up, nonexclusive, irrevocable, worldwide license in said article to reproduce, prepare derivative works, distribute copies to the public, and perform publicly and display publicly, by or on behalf of the Government.

References

FreedomCAR Battery Test Manual for Power-Assist Hybrid Electric Vehicles, DOE/ID-11069, October 2003.

Battery Test Manual for Plug-In Hybrid Electric Vehicles, Rev. 3, INL/EXT-14-32849, September 2014.

Battery Test Manual for Electric Vehicles, INL/EXT-15-34184, Rev. 3, June 2015
Mechanistic Study of Parasitic Reactions on Cathodes of Lithium-Ion Batteries
Authors: Chen Zonghai , Zeng Xiaoqiao , Ma Tianyuan , Amine Khalil
Published: February 2020

The side reactions between the change electrode materials, delithiated cathodes or lithiated anodes, significantly contributes to the continuous and irreversible consumption of accessible lithium during the normal charge/discharge cycling, leading to a degradation on electrochemical performance of lithium-ion batteries. Understanding these side reactions, parasitic reactions, is crucial for the development of robust algorithm for predicting the remaining life of a specific battery and for the development of functional materials for long-life lithium-ion batteries.

Figure 1a shows a home-built high precision electrochemical testing system used to study the kinetics of parasitic reactions on LiNi0.6Mn0.2Co0.2O2. Figure 1b schematically shows the principle of the measurement. The working electrode was held at a specific potential using the source meter, maintaining a constant state-of-the-charge (SOC) for the working electrode. During this process, the electron obtained from the environment by the oxidation of the solvent, will be electrochemically collected by the external circuit. The measured leakage current is proportional to the reaction rate of parasitic (side) reactions between the working electrode and the electrolyte. Hence, the static leakage current can be used as a quantitative indicator for the reaction rate of the side reactions. Figure 1c shows a typical current relaxation curve collected, an exponential decay function was used to extract the static current (y0in Figure 1C), and to (1) minimize the impact of the high frequency noise, and (2) to get rid of the potential impact of slow intercalation/deintercalation reaction.

In this work, the reaction mechanisms between delithiated cathodes and the non-aqueous electrolyte will be discussed. 

Figure 1
Investigation on Electrochemical Properties and Degradation Mechanism of Cylindrical-Type Li-Ion Rechargeable Battery without Deconstruction
Authors: Kobayashi Hironori , Kuratani Kentaro , Koike Shinji , Saito Yoshiyasu
Published: February 2020

Recently Li-ion rechargeable battery (LIB) has been widely used as power source of not only portable device but also electric vehicle (EV). For LIBs in EVs, a long life of 10 years or more is required. Therefore, a great deal of effort has been made to develop the prediction method of life of LIB for EV. We have already started to measure battery performance for LIBs being used in practical EVs and developed the prediction method of battery life based on the degradation mechanism of the active materials in the batteries.

In this paper, we investigated battery performance of cylindrical-type cells with Sn-containing negative electrode. Sn-containing materials are promising negative electrode materials for LIB because of large theoretical capacity compared with that of conventional carbon materials. Both general cycle and storage tests were carried out for each 25 cells at 298 K and 318 K, and the capacity, DC resistivity and power density of these cells were checked every fixed period. We also applied the X-ray CT method to cells as an analytical technique without deconstruction, and confirmed visually to detect the internal structure in the cells definitely.

In the presentation, we will discuss the degradation mechanism of the cells using Sn-containing negative electrode mainly by the combination of the prediction method of battery life and the X-ray CT method without deconstruction of cells.

Acknowledgement

This work was partly supported by the New Energy and Industrial Technology Development Organization (NEDO).