bluuebunny/crossref_metadata_2025 huggingface dataset:
All-Solid-State Lithium Cells Assembled with Solid Polymer Electrolytes Based on Poly(ε-caprolactone)
Authors: Seo Yerin , Jung Yun-Chae , Park Myungsoo , Kim Dong-Won
Published: February 2020

Lithium-ion batteries (LIBs) are one of the promising power sources for mobile electronics, electric vehicles and energy storage systems. Recently, the safety issues of the LIBs have become a considerable concern for utilization of batteries in large capacity applications. Although liquid electrolytes currently used in LIBs show the high ionic conductivity and good electrochemical properties, they have drawbacks such as flammability, solvent leakage and growth of lithium dendrite in case of lithium metal anode. Accordingly, the development of non-flammable solid electrolytes can give a solution in consideration of safety issue of LIBs.1 Solid polymer electrolytes based on poly(ethylene oxide) have received great attention so far owing to their flexibility in the shape of battery design, an absence of leakage and enhanced safety. However, their low ionic conductivities at ambient temperatures, which range from 10-8 to 10-5 S cm-1 due to their high degree of crystallinity, preclude their practical applications at room temperature. Moreover, their poor mechanical properties resulting from their melting transition may cause short circuits between two electrodes if unexpected heat is generated.2 In our study, poly(ε-caprolactone) (PCL)-based solid polymer electrolytes supported by porous membrane were prepared and their electrochemical properties were investigated. The PCL-based solid polymer electrolyte was applied to the all-solid-state lithium cells composed of a lithium anode and a layered LiNi0.6Co0.2Mn0.2O2 cathode, and their electrochemical performance was evaluated.

J. Janek and W.G. Zerier, Nature Energy, 1, 16141 (2016).

Y. Tominaga, K. Yamazaki, and V. Nanthana, Journal of The Electrochemical Society, 162, A3133 (2017).
Zwitterionic Based Single-Ion Conducting Hydrogel Electrolyte for Flexible Supercapacitor
Authors: Park Jeong Hee , Rana Harpalsinh H. , Park Ho Seok
Published: February 2020

The performance of conventional energy storage with liquid electrolytes have made great progress in the last twenty years, but the inherent instability and leakage issues of liquid electrolytes leads to safety problems. The polymer gel electrolytes (PGEs) offer a perfect solution to these safety concerns and device design due to their flexibility. PGEs are dual ion conductors, in which both cations and anions are mobile and lead to concentration polarization, which leads to poor performance of devices. Hence, the attempt to develop new polymer electrolytes with high single ion transport rates has emerged as a primary strategy for enhancing device performance. But still these systems display ionic conductivities far lower than their polymer/salt mixture counterparts. In order to address these issues, there is need of electrolyte additive which can improve the ionic conductivity of single ion conducting polymer gel electrolyte. Zwitterions, being charged molecules known to enhance the water retention ability, can provide ion migration channel to enhance the charge transportation. Accordingly, in this work we have synthesized single ion conducting hydrogel based polymer gel electrolyte, which has anion covalently bound to the polymer backbone. Furthermore, the synergistic effect of zwitterion as an electrolyte additive has been evaluated by fundamental electrochemical measurement of supercapacitor such as CV, GCD, and EIS measurements.
Electrical Properties of Al-Doped SrTiO3 Films Grown Via Atomic Layer Deposition on Ru Electrodes
Authors: Kim Sang Hyeon , An Cheol Hyun , Kwon Dae Seon , Cha Soonhyung , Cho Seong Tak , Hwang Cheol Seong
Published: February 2020

Atomic layer deposition (ALD) of Al2O3-inserted SrTiO3 (STO) dielectric thin films were investigated in metal-insulator-metal capacitors for dynamic random access memory. STO thin films exhibit much higher dielectric constant compared with currently used ZrO2-based films, but the leakage current density is generally higher due to their low band-gap. To decrease the leakage current density, insertion of the ALD-Al2O3 could be adopted as for the current ZrO2-Al2O3-ZrO2 dielectric layer. One ALD cycle of the Al2O3 film was performed during the ALD of the bottom region of the STO film. As a result, the leakage current of the STO thin film with a thickness of 8nm decreased from 8.1 X 10-6 A/cm2 to ~2.8 X 10-8 A/cm2 at 0.8V, whereas the equivalent oxide thickness (EOT) of the (top) RuO2/STO/Ru (bottom) capacitor slightly increased from 0.8nm to 0.9nm. Al2O3 can exhibit a sufficient leakage current reduction effect at a small insertion ratio, but the increased Al portion deteriorates the dielectric constant and leakage current due to the inhibited crystallization. The lower crystallization during the ALD requires higher annealing temperature, which caused the nano- or micro-cracks in the film and consequent increase in the leakage current. Therefore, careful optimization of the Al insertion was performed to improve the leakage current performance while maintaining the high dielectric constant.

Figure 1
Probing the Interactions between CeO2 Nanoparticles and Cleaning Chemistry Relevant to Post STI CMP Cleaning
Authors: Zubi Tala B , Graverson Carolyn F , Sherry Brian M , Keleher Jason J. , Dickmann Dan S , Her Bob , Urban Nathaniel D
Published: February 2020

Fabrication of integrated circuits (IC) in the sub-micron regime utilizes shallow trench isolation (STI) to separate active circuits with a dielectric material, tetraethyl orthosilicate (TEOS). CMP is used to remove the excess TEOS layer to achieve planarity and expose the underlying structure without inducing defects. In an ideal system, the removal of TEOS is facilitated by colloidal suspensions (slurries) containing abrasive ceria (CeO2) nanoparticles and chemistry to produce defect free substrates. However, residual CeO2 particles can become embedded at the interface leading to defects impacting device performance. Current industrial methods of removing particles use Standard Clean-1 (SC-1), incorporating concentrated NH4OH and H2O2 to chemically remove organic contaminants and abrasive particles. This work set out to investigate particle encapsulation using novel polyelectrolyte and surfactant based chemistry to enhance electrostatic repulsions that occur at the interface during post-CMP cleaning. In-situ studies utilizing dynamic light scattering and turbidity measurements have provided insight regarding the role of polyelectrolyte and surfactant concentration during the cleaning process. The formulated cleaning chemistry was evaluated under small scale brush cleaning to clean polished TEOS wafers, which were then processed with fluorescence microscopy to determine particle removal efficiency. Analogous to SC-1, the cleaning chemistry shows comparable particle removal; however at an increased efficiency, making it a viable alternative to traditional cleaning methods.
Preparation and Characterization of Cross-Linked Anion Exchange Composite Membrane for Alkaline Exchange Membrane Fuel Cell
Authors: Son Tae Yang , Han Song I , Nam Sang Yong
Published: February 2020

Alkaline exchange membrane fuel cell (AEMFC) was attracting much attention in the fuel cell market. In the AEMFC using non-precious metal catalyst, the anion exchange membrane is key component. The anion exchange membrane should have high electrochemical and mechanical properties. First, for preparing composite membrane, synthesized anion exchange polymers were dissolved in solvent. Then, a support was added to impregnate in the solution. The impregnated composite membrane was taken out and the solvent was volatilized on a glass plate. Then, cross-link was carried out through a post-treatment cross-linking method so as to have physical and chemical stability. After the cross-linked composite membrane was prepared, the properties of the membrane were evaluated to confirm applicable to AEMFC.
Graphene-PEDOT-Platinum Tertiary Composite Material Based Catalyst for Hydrogen Evolution Reaction
Authors: Wang Haosen , Hou Runfang , Li Mengping , El-kady Maher , Kaner Richard B.
Published: February 2020

We fabricated a Laser Scribed Graphene-PEDOT-Platinum (LSG-PEDOT-Pt) tertiary composite material, using a three-step synthesis process, to investigate its catalytic hydrogen evolution reaction (HER) performance: 1. Graphene oxide film was photo-thermally reduced via a CO­­2 laser into laser-scribed graphene (LSG). 2. A layer of PEDOT polymer was grown on top of the LSG film using vapor assisted polymerization methods to yield a LSG-PEDOT composite film. 3. Platinum nanoparticles were deposited on the LSG-PEDOT composite via pulse-potentiometry. The vapor-assisted polymerized PEDOT decorates the surface of the LSG, forming nanoribbon/wire like structures. The pulse potentiommetry enables platinum to grow vertically on top of the LSG-PEDOT substrate, forming arrays of nanowires. The composite material shows better HER performances than metal platinum in 0.5M H2SO4 solution, with a very low Tafel slope of 29mV/decade, 15mV (vs. RHE) onset overpotential, and achieves 10mA/cm2 current density at a low overpotential of 35mV (vs. RHE). Even though LSG-PEDOT is an intrinsically poor HER catalyst, its high surface area, high conductivity and low charge transfer resistance make LSG-PEDOT a good substrate for HER catalysis material, as demonstrated by the performances of LSG-PEDOT-Pt. LSG-PEDOT composite material could be a promising base material for developing non-noble metal based catalysts.

Figure 1
Microstructural Effects on Disorder and Transport in Irradiated Pyrochlore Thin Films
Authors: Parker Nia , Kreller Cortney R. , Valdez James Anthony , Holesinger Terry , Wang Yongqiang , Tang Ming , Uberuaga Blas
Published: February 2020

Complex oxides exhibiting fast ion conduction have surfaced as attractive materials for various applications such as fuel cells, electrolyzers, sensors and gas separation membranes. Literature shows that many of the studies of these materials place emphasis on improving ionic conductivity. Here we focus on improving our understanding of how defects within the microstructure impact ionic transport.

We employ irradiation as a tool to induce disorder in oxide materials, then utilize a number of different characterization techniques to determine the relationship between disorder and oxygen ion conduction. In this study, Gd2Ti2O7 (GTO) pyrochlore thin films are prepared on single and polycrystalline Yttria Stabilized Zirconia (YSZ) substrates using RF Magnetron sputtering. Electrochemical Impedance Spectroscopy measurements are performed as a function of temperature in the through-plane configuration using a Cascade Microtech Microprobe Test Station equipped with a Linkam high temperature stage. The EIS data is used to determine the conductivity of GTO films with varying degrees of irradiation induced structural disorder. This work examines how the underlying microstructure in polycrystalline and highly oriented thin films (grown on polycrystalline and single crystal YSZ substrates, respectively) influences irradiation induced disordering and transport properties.

Acknowledgements

This work was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division.
Layered and Scrolled Nanocomposites with Aligned Semi-Infinite Graphene Inclusions at the Platelet Limit
Authors: Liu Pingwei , Strano Michael S
Published: February 2020

Graphene and other two-dimensional (2D) materials are distinct among nanoscale inclusions or fillers for composites in that they can potentially span the physical dimensions of the enclosing solid. However, alignment and assembly of continuous 2D components at high volume fraction and macroscopic dimensions remains an unsolved challenge in material science. Herein, we introduce a stacking and folding method that generates layer numbers that scale as 4j and lateral area decrease as 4-j where j and is the number of successive quadrant segmentations of a 2D inclusion, to generate aligned graphene/polycarbonate composites with as many as 320 parallel layers spanning 0.032 to 0.11 mm thickness. An analogous transverse shear scrolling method generates Archimedean spiral nanocomposite fibers 0.10-0.16 mm in diameter and 2 cm in length. The process significantly increases the effective elastic modulus approximately 1.9-fold to nearly 1 GPa, approaching the limit of platelet filler theory, and increases the ultimate tensile strength to 40 MPa even at exceptionally low graphene volume fraction of only 0.00185. Graphene spiral fibers demonstrate exotic, telescoping elongation at break of 110%, or 30 times greater than Kevlar. Both composite types retain anisotropic electrical conduction along the graphene planar axis with a percolation threshold VG < 0.003 vol%, and layer numbers less than 36 remain transparent with optical density < 42%. These results highlight new combinations of material properties available at this extreme platelet filler limit for nanocomposites.
Two-Dimensional MoTe­2 PN Diode and CMOS Inverter By Atomic Layer Deposition-Induced Hydrogen Doping
Authors: Lim June Yeong , Jeong Yeonsu , Ahn Jongtae , Im Seongil
Published: February 2020

Recently, 2D transition metal dichalcogenides(TMDs) MoTe2 has shown outstanding properties for future electronic devices. Such TMD structures without surface dangling bonds make the 2D MoTe2 more favorable candidate than conventional 3D Si in a few nanometer scale. The band gap of thin MoTe2 appears close to that of Si and quite smaller than those of other typical TMD semiconductors. Even though there have been a few attempts to control charge carrier polarity of MoTe2, functional devices such as complementary metal–oxide–semiconductor (CMOS) inverter have not been reported. Here we demonstrate a 2D CMOS inverter in a single MoTe2 nanosheet by straightforward selective doping technique. In a single MoTe2 flake, initially p-doped channel was selectively converted to n-doped region with high electron mobility of 18 cm2/Vs by atomic layer deposition-induced H-doping. Our ultrathin CMOS inverter exhibited a high DC voltage gain of 29, AC gain of 18 at 1 kHz, and a low static power consumption of a few nW. Our results show a great potential of MoTe2 for future electronic devices based on 2D semiconducting materials

Figure 1
Room-Temperature Atomic Layer Deposition of Aluminum Silicate for Molecule Sorption
Authors: Mori Yoshiharu , Imai Takahiro , Kanomata Kensaku , Miura Masanori , Ahmmad Bashir , Kubota Shigeru , Hirose Fumihiko
Published: February 2020

A room-temperature atomic layer deposition (RT-ALD) of aluminum silicate for molecule sorption is developed using trimethylaluminum (TMA) and trismethylaminosilane (TDMAS) using a plasma excited humidified argon. The aluminum-silicate is a main material of zeolites that is used for cation sorption. If we achieved the aluminum silicate deposition on flexible films, we could expect the film used as a regenerable ion exchange filter.

The schematic of ALD system is shown in Fig.1. TMA and TDMAS were introduced with mass flow controllers. A remote plasma system generating excited humidified argon was installed to the ALD chamber. The source gas for the oxidizing gas is a mixture of water vapor and argon. The plasma was generated in a glass tube with an induction coil with a frequency of 13.56 MHz and a RF power of 100 W. For the deposition, we repeated the cycle of TDMAS and TMA saturation and oxidizing gas treatment at RT. To control the aluminum to Si atomic ratio in the aluminum silicate, we adjusted the initial exposure of TDMAS.

To confirm the Na sorption ability of the aluminum silicate film deposited by the present technology, we immersed the aluminum silicate coated Si sample in a 100 mM NaCl solution for 3h. The dried sample was evaluated by X-ray photoelectron spectroscopy. As shown in Fig. 2, the enhanced Na adsorption is confirmed. In the conference, we discuss the mechanism of Na sorption on the RT deposited aluminum silicate.

Acknowledgements

This work was partly supported by JSPS KAKENHI Grant Numbers 15H03536. It was also partly supported by JST-CREST Grant Number JPMJCR14F3, Japan.

Figure 1
Aqueous Phase Synthesis Method of Fe Metal Nanoparticles and Its Application for Commercial Materials
Authors: Takahashi Hideyuki
Published: February 2020

It is well known that the melting point of metal element drastically change with decreasing the diameter of its particle into nano level, by obeying to the equation as follows,

Tnano = Tbulk (1-2σ/(ΔH*R))

Here, Tnano is melting point of nanoparticles. Tbulk is melting point of bulk material, σ is surface energy, ΔH is enthalpy change of melting, and R is radius.

Thus, the development of effective and green synthesis method of Fe nanoparticles means the development of new bonding method of Irons at low temperature, since Fe is most basic materials in resent world.

Fe nanoparticles were synthesized only in acidic solution by using strong reducing reagent, while it cannot be achieved in basic solution since iron hydroxide, which is easily formed in this condition, cannot be reduced into metals. However, former is not suitable for commercial synthesis method because of its intense reducing process. Thus, the reducing rout of Fe species under basic condition should be developed.

Here, until now, we tried to synthesized various metal/alloy nanoparticles, such as Pd20Te7 nanoparticles and uniform Cu-In (CI) alloy nanoparticles, by utilizing the restrict metallic complexes controlling method in an aqueous solution under room temperature. In this method, reduction potential of the metal species can be controlled under the room temperature, consequently metal/alloy nanomaterials with uniform and well crystallized structure can be successfully synthesized.

Therefore, in this study, aqueous phase synthesis method of Fe metal nanoparticles were developed.

To achieve the homogeneous reaction condition, metal complex species in the aqueous phase were restricted into single species by using calculation. Reduction potential of homogenized metal complex were analyzed by using cyclic voltammetry. Fe nanoparticles were synthesized by using chemical reduction method under ambient conditions using metal chlorides as metal sources and sodium borohydride as a reducing agent.

Calculation results indicated that Fe complex can be restricted into one species as the function of pH, complexing reagent species and/also concentration. For example, Fe complex can be restricted into Fe(NTA)2 only, in the case of 8<pH<11.

By using these homogeneous condition, metal Fe nanoparticles were successfully synthesized.

Other results, such as melting and/or bonding condition of synthesized materials, will present in our presentation.

[1] H. Takahashi et.,al, Applied Catalysis A: General 392 (2011) 80–85
Molecular Dynamics Simulation Study of Ion Exchange Membranes for Fuel Cell Application
Authors: Nam Sang Yong , Park Chi Hoon , Hong Young Taik
Published: February 2020

The ion exchange membrane is one of the key components of membrane-electrode assembly (MEA) at PEMFC and AEMFC systems, which plays important role in fuel cell performance together with catalysts. It is widely accepted that water channel morphology inside ion exchange membranes as ions pathway significantly affects the ion exchange membrane performance. So, molecular dynamics (MD) simulations are a very useful tool to understand molecular and atomic structures of materials, so that many related researches are currently being studied. In this paper, we summarize the current research trend in MD simulations, present which properties can be characterized, and finally introduce the usefulness of MD simulations to the researchers for ion exchange membranes.
Effect of Ti Content on Physical Properties and Electrical Characteristics of High-k Yb2TiO5 Gate Dielectrics for InZnSnO Thin-Film Transistors
Authors: Chen Ching-Hung , Her Jim Long , Koyama Keiichi , Pan Tung Ming
Published: February 2020

In this study, we investigated the impact of Ti content on structural properties and electrical characteristics of high-k Yb2TiO5 gate dielectrics for amorphous indium–zinc–tin-oxide (a-InZnSnO) thin-film transistor (TFT) devices. The Yb2TiO5 thin films with different Ti plasma conditions were integrated in metal-insulator-metal structures to check the electrical capabilities. The Yb2TiO5 a-InZnSnO TFT device fabricated at the 120 W condition exhibited excellent electrical characteristics in terms of a small threshold voltage (VTH) of 0.14 V, a low subthreshold swing of 202 mV/decade, a large field-effect mobility of 29.8 cm2/V-s, and a high Ion/Ioff current ratio of 2.7×108. In addition, the VTH stability of Yb2TiO5 a-InZnSnO TFT device was studied under both positive bias stress and negative bias stress conditions. The Yb2TiO5 thin film is a promising gate dielectric material for the fabrication of a-InZnSnO TFTs.
Investigation on Electrical Properties of Hydrogen Doped Boron Carbide Thin Films
Authors: Nehate Shraddha , Sundaram Kalpathy B
Published: February 2020

The ever-increasing advancements in semiconductor technology and continuous scaling of CMOS devices demands need for new low-k dielectric materials. Boron Carbide (B4C) has attracted recent attention due to its complicated crystalline structure and interesting properties. B4C is the third hardest material with a hardness > 30GPa after diamond and cubic boron nitride [1]. However, with increase in temperature, the hardness of diamond and cubic boron nitride decreases gradually. B4C is characterized to be the hardest material at even above 1100°C [2]. Other interesting properties exhibited by boron carbide are low specific weight, high modulus, high chemical stability and good wear resistance. These properties make boron carbide a promising material for applications in cutting tools.

In this study, electrical properties of hydrogen doped boron carbide thin films will be investigated. Boron carbide films are deposited by magnetron RF sputtering of B4C target. Films are deposited at different temperatures in presence of hydrogen/argon gas to investigate the influence of temperature and hydrogen on electrical properties of boron carbide thin films.

References

[1] T. Eckardt ,U, K. Bewiloguaa , G. van der Kolkb , T. Hurkmansb , T. Trinhb , W. Fleischer, Improving tribological properties of sputtered boron carbide coatings by process modifications., Surf. Coat. Technol., 123 (2000), p. 69

[2] S. Ulrich, H.Ehrhardt, J.Schwan, R.Samlenski, R.Brenn, Subplantation effect in magnetron sputtered superhard boron carbide films, Diamond Relat. Mater., 7 (1998), p. 838
Electrochemical Reduction of Metal Oxides
Authors: Shi Meng , Li Shelly , Zhao Haiyan
Published: February 2020

Electrochemical reductions of metal oxides were investigated in molten salt electrolyte consisting of Li2O and LiCl at 650 °C with a three-electrode electrochemical cell, namely, a fuel basket cathode loaded with metal oxides (TiO2, NO, etc.), a glassy carbon crucible anode, and a Ni/NiO reference electrode. Reductions were carried out in an interrupted mode at various cathodic potentials and total applied charges. Current-time profiles were recorded during reductions, where current increase and decrease indicated formation and reduction of lithium intermediates. Reduction pathways have been derived by analyzing reduced products with X-ray diffraction (XRD). It is shown that the reductions follow a stage-wise reaction process with intermediates such as LiTiO2 in TiO2 reduction, and different metal oxides reductions follow different reduction routes. Cyclic voltammetry (CV) of lithium salts were measured before and after reductions. The possibility of reutilizing salts after reductions is determined by comparing CV measurements before and after reductions, and the results are different for reduction of different metal oxides. It is found that a higher applied reduction potential (in magnitude), more charges and fresh lithium electrolyte are preferred in metal oxides reductions. Moreover, one of the keys to improve reduction efficiency is discussed to be the enhancement of oxygen diffusion outward the fuel basket.
Synthesis and Photoluminescence Properties of (Sr, Ba)2-XEuxSiO4 Phosphors with High Eu2+ Concentration for White LED Applications
Authors: Sato Yasushi , Tomita Koji , Kakihana Masato
Published: February 2020

Recently, several oxide-based phosphors with excellent luminescence properties have been reported. Especially, the deep-red emitting Ca1.2Eu0.8SiO4 has been prepared by the basis on crystal-site engineering, which shows an emission peak at 653 nm under excitation at 450 nm [1]. The emission wavelength of Ca1.2Eu0.8SiO4 is quite similar to those of commercial red-emitting CaAlSiN3:Eu2+ and Sr2Si5N8:Eu2+. The crystal structure of Ca2-x
Eu
x
SiO4 is analogous to those of Sr2-x
Eu
x
SiO4 and Ba2-x
Eu
x
SiO4. Therefore, it is expected that the addition of large amounts of Eu2+ ions to Sr2-x
Eu
x
SiO4 and Ba2-x
Eu
x
SiO4 can also lead to large redshifts in their emission and excitation spectra. In this study, we prepared and characterized Sr2-x
Eu
x
SiO4 and Ba2-x
Eu
x
SiO4 with a high concentration of Eu2+ ions. In the case of Sr2-x
Eu
x
SiO4, the emission peak was shifted from 585 nm for Sr1.9Eu0.1SiO4 to 611 nm for Sr1.2Eu0.8SiO4. On the other hand, in the case of Ba2-x
Eu
x
SiO4, the emission peak was shifted from 513 nm for Ba1.9Eu0.1SiO4 to 545 nm for Ba1.2Eu0.8SiO4. The right-hand edges of the excitation spectra for both the samples were significantly shifted, by 40-55 nm, to longer wavelengths, allowing for excitation by blue light. The induction of large redshifts in the emission and excitation spectra of both samples could be attributed to the occupancy of Eu2+ ions in the polyhedra of Sr(2) or Ba(2) sites, which are smaller and more distorted than the Sr(1) or Ba(1) sites. These results indicate that Sr1.2Eu0.8SiO4 and Ba1.2Eu0.8SiO4 are suitable as red- and green-emitting phosphors for next-generation white-LED applications.

[1] Y. Sato and M. Kakihana et al., Angew. Chem. Int. Ed.
53 (2014) 7756.
BaFeO3-Δ-Based Materials for Intermediate-Temperature Solid Oxide Fuel Cells and Beyond
Authors: Ciucci Francesco
Published: February 2020

Energy conversion and storage is a central problem to modern society, requiring the deployment of novel “green” technologies. Solid oxide fuel cells (SOFCs) are very promising because they can convert chemical energy directly to electricity with efficiencies as high as 60%. However, one of the bottlenecks of this technology is the limited activity of typical cathode materials. In this presentation, we will overview doped-BaFeO3-δ (BFO) as a potential high-activity SOFC cathode material.

We first fabricate Ba0.95La0.05FeO3-δ (BLF) single crystal thin films by pulsed laser deposition (PLD) on yttria-stabilized zirconia (YSZ) substrates. The phase structure, surface morphology and roughness of the BLF thin films are characterized by X-ray diffraction and atomic force microscopy. X-ray photoelectron spectroscopy is used to analyze the elemental composition and chemical state of the deposited thin film [1-2]. Electrochemical impedance spectra measurements obtained from the symmetric cells with the configuration of BLF /SDC/YSZ/SDC/ BLF reveal that polarization resistance of BLF (001) thin films (100 nm) is as low as ~0.1 Ω cm2 at 700 °C and 0.21 atm oxygen pressure. The polarization resistances of BLF are lower than those of other perovskite electrodes. Furthermore, our computational results, including density functional theory and molecular dynamics simulations, show that the BLF has a low vacancy formation energy and fast oxygen transport [3-4].

The effect of various A- and B-site substitutions on the BFO’s activity from both an experimental [5, 6] and computational [7] perspective are then explored. Finally, opportunities to develop ferrites are discussed together with their use as low temperature electrocatalysts.

Acknowledgements

The authors gratefully acknowledge the Research Grants Council of Hong Kong for support through the project 16207615 and 16227016.

References

[1] D. Chen, C. Chen, F. Dong, Z. Shao, F. Ciucci, J. Power Sources, 250, 188-195 (2014)

[2] C. Chen, D. Chen, Y. Gao, Z. Shao, & F. Ciucci. J. Mater. Chem. A, 2, 14154-14163 (2014)

[3] Z.M. Baiyee, C. Chen, & F. Ciucci. Phys. Chem. Chem. Phys. Phys. Chem. Chem. Phys., 17, 23511-23520 (2015)

[4] C. Chen, Z.M. Baiyee, & F. Ciucci. Phys Chem Chem Phys., 17, 24011-9 (2015)

[5] J. Wang, M. Saccoccio, D. Chen, Y. Gao, C. Chen, & F. Ciucci, J. Power Sources, 297, 511-518 (2015)

[6] J. Wang, K.Y. Lam, M. Saccoccio, Y. Gao, D. Chen, & F. Ciucci. J. Power Sources, 324, 224–232 (2016)

[7] C. Chen & F. Ciucci. Chem. Mat. 28 (19), 7058-7065 (2016)

[8] H. Zhao, C. Chen, D. Chen, M. Saccoccio, J. Wang, Y. Gao, T.H. Wan, & F. Ciucci, Carbon, 90, 122-129 (2015)
A Low-Cost Ion Exchange Membrane Separator for Rechargeable Aqueous Batteries
Authors: Liu Ping , Lee Byoung-Sun , Xing Xing
Published: February 2020

Zinc metal based aqueous batteries are actively explored as promising alternatives to lithium rechargeable batteries owing to their benefits in cost, safety, nontoxicity, and abundance. Zinc dendrite growth and resultant short lifespan are, however, major issue to overcome. Here, we propose a strategy to suppress the zinc dendrite growth by designing an ionic transport regulating membrane separator. The membrane is synthesized by reacting a low cost polyacrylonitrile with lithium polysulfide followed by hydrolysis. The reaction with lithium polysulfide leads to both cross-linking and functionalization of the polymer by sulfur containing groups. Hydrolysis results in a membrane with preferred cation transport and uniform ionic flux distribution. The membrane is mechanically robust and can be cast as 30 micron-meter-thick films. The membrane separator enables effective dendrite suppression and long cyclability of Zn/Zn symmetric cells.
Development of Bi-Functional Oxygen Electrode By Low Temperature Roll Press Method for Aqueous Air Secondary Battery
Authors: Kino Shizuki , Kawaguchi Kenji , Morimitsu Masatsugu
Published: February 2020

A bi-functional oxygen electrode is the key component of aqueous air secondary batteries, and a low overpotential for oxygen evolution and reduction and a bi-functionality for a long-term charge-discharge cycles are required. The oxygen electrode often consists of carbon material as the conducting matrix, oxygen catalyst, and PTFE, which are mixed, pressed to form a sheet, and finally heated at the temperature close to the melting point of PTFE, e.g., 370 oC, and oxygen in air is reduced during discharge and oxygen evolution occurs during discharge inside of the electrode. For the reactions, the electrode’s structure needs to be porous and optimized for oxygen permeability, and the inside should provide active sites for O2 and OH-. The polarization behaviors of the bi-functional oxygen electrode strongly depend on not only the materials but also the process and condition of the electrode preparation. The purpose of this study is to control and improve the gas diffusion behaviors of the oxygen electrode prepared by low temperature roll press at 80 oC, which was developed by our group [1].

The electrode used graphite as conductive material, Bi2-xRu2O7-z as bi-functional catalyst, and PTFE as binder, which were mixed and pressed to form a sheet by heated roller at 80 oC, and pressed again onto a nickel mesh. The polarization behaviors of the electrode were examined by cyclic voltammetry using a three-electrode cell, in which one side of the electrode was exposed to air and the other side to 6 mol/L KOH solution. The surface and cross section of the electrodes were examined by SEM.

SEM observation of the obtained electrodes at various roll press conditions indicated that the shape of PTFE changed depending on the pressure, temperature, and clearance of the rollers, and PTFE particles were fiberized even at 80 oC when the clearance between the two rollers was reduced at constant pressure. The cathodic polarization curves of the electrodes revealed that the onset potential of oxygen reduction hardly depended on the preparation condition, while the polarization in the potential region under mass transfer control, i.e., oxygen diffusion inside of the electrode, was strongly affected by the preparation condition. Oxygen evolution was also seen differently in polarization depending on the electrode, suggesting that the oxygen permeability seems to affect anodic polarization because evolved oxygen should be discharged from the electrode. In this work, detailed relationship between the internal structure of the electrode and the polarization behaviors for oxygen reactions will be presented.

Reference

[1] Y. Ujino, M. Morimitsu, TMS 2017, San Diego (2017).
(Corrosion Division H. H. Uhlig Award) Non-Faradaic Release of Copper during Corrosion of Engineering Alloys
Authors: Buchheit Rudolph
Published: February 2020

The phenomenon of “deposition corrosion” involving dissolution and replating of copper on aluminum alloys during corrosion has been known for decades. While the reduction of Cu ions onto aluminum alloys during corrosion was easily understood from an electrochemical point of view, how Cu ions were generated in the first place by a corrosion process occurring hundreds of millivolts below the copper oxidation process lacked a satisfying explanation. The advent of high brightness, high resolution electron sources in commercial scanning electron microscopes in the late-1980s and early-1990s enabled critical clues to be found as to how copper parted from the alloy. High resolution scanning electron imaging of corroded 2024-T3 surfaces suggested physical emission Cu nanoparticles by a non-faradaic process involving coarsening of dealloyed intermetallic particles. Subsequent electrochemical and surface analytical measurements validated the hypothesis that Cu nanoparticles emitted from the alloy were not constrained to be at the alloy corrosion potential and could be directly oxidized in aerated electrolyte conditions to form Cu ions. Further investigation demonstrated non-faradaic emission of Cu from several different intermetallic compounds, and dilute Al-Cu solid solutions with as little as 0.2wt.% Cu. Recent evidence of Cu release during corrosion of magnesium alloys and Cu-bearing stainless steels suggests that non-faradaic release of Cu from reactive engineering alloys is a corrosion characteristic to be expected when alloying with copper. In this presentation, the electrochemical framework for non-faradaic release of Cu will be descried along with key supporting experimental evidence. Examples of non-faradaic release from a number of different materials will be shown to underscore the ubiquity of this fascinating and technologically relevant phenomenon.
Corrosion Behavior of Highly As-Doped <100> Oriented Si-Wafer Anodes in Alkaline Si–Air Batteries
Authors: Durmus Yasin Emre , Montiel Guerrero Saul Said , Tempel Hermann , Hausen Florian , Kungl Hans , Eichel Rüdiger-Albert
Published: February 2020

One line of development to establish resource-efficient metal–air batteries is focusing on silicon materials as anode electrodes. While operation of primary Si–air batteries with ionic liquid electrolytes is one possible approach [1], employing conventional alkaline electrolyte is also considered by the recent investigations [2]. At the current state of development, the alkaline Si–air batteries suffer from high corrosion rates that reduce the theoretical specific capacity of 3820 mAh/g to 120 mAh/g [3]. Thereby, corrosion as being the major challenge has to be overcome in order to establish practical application of primary alkaline Si–air batteries.

The objective of the present work is to investigate the corrosion behavior of highly As-doped <100> oriented silicon wafer anodes in alkaline solutions for a scope of conditions that may arise in battery operation. Firstly, the influence of the immersion times on the open-circuit corrosion rates are discussed in combination with the surface morphology development in 72 h. Secondly, the impact of KOH electrolyte concentration on the open-circuit corrosion rates is investigated and three ranges of KOH concentrations are identified with different limiting mechanisms. Moreover, basing on the electrochemical corrosion rates obtained from potentiodynamic polarization method, the comparison between the chemical and electrochemical corrosion mechanisms are pointed out. Further investigations are carried out on the corrosion behavior of Si wafers under anodic voltages as present during the discharge of batteries. The dependency of the discharge characteristics as the discharge voltage, corrosion rates, and mass conversion efficiencies on the KOH concentrations and current densities are analyzed and accordingly, optimum conditions for the battery application are discussed.

References:

[1] Cohn, G., Ein-Eli, Y., Journal of Power Sources, 195, 4963–4970 (2010).

[2] Zhong, X., Zhang, H., Liu, Y., Bai, J., Liao, L., Huang, Y., Duan, X., ChemSusChem 5, 177–180 (2012).

[3] Durmus, Y.E., Montiel Guerrero, S.S., Aslanbas, Ö., Tempel, H., Hausen, F., de Haart, L.G.J., Ein-Eli, Y., Eichel, R.-A., Kungl, H., Electrochimica Acta 265, 292–302 (2018).
Evaluation of the Corrosion of AISI 304 Stainless Steel Embedded in Sustainable Concrete with High Volumes of Scba-SF Exposed in Marine Environment
Authors: Landa-Gómez Aldo , Castillo Aguilar Saul , Reyes Jimenez Jose Alberto , Villegas Apaez Rafael , Galván-Martínez Ricardo , Cabral-Miramontes Jose A. , Tiburcio Citlalli Gaona , Almeraya Facundo , Baltazar-Zamora Miguel Angel
Published: February 2020

The present study evaluates corrosion by electrochemical techniques of AISI 304 Stainless Steel and AISI 1018 Steel, embedded in sustainable concrete mixtures made with high volumes of SCBA-SF as a partial substitute for Portland Cement, the substitutions were 0%, 30%, 40% and 50%. The design of the concrete mixtures was made according to ACI 211.1, for a ratio w/ c = 0.65. The specimens to be evaluated were exposed in a marine or aggressive environment (Seawater) and water (Medium Control). The electrochemical techniques used were that of Corrosion Potential, Ecorr (ASTM C-876-15) and Corrosion Kinetics, Icorr (ASTM-G59). According to the results obtained after more than 150 days of monitoring, AISI 1018 Steel presents Ecorr values that indicate a 90% probability of corrosion and Severe Corrosion, depending on the percentage of substitution of SCBA-SF used. The AISI 304 Stainless Steel presented a significantly higher corrosion resistance than AISI 1018 Steel, reporting values of Ecorr that indicate a 10% probability of corrosion and magnitudes of Icorr indicating a negligible to moderate corrosion level, with a better performance in the mixes with 30% and 50% the substitutions of SCBA-SF.
(Invited) TiO2 Nanotubes: Electrochemical Growth, Modification, and Functional Properties
Authors: Schmuki Patrik
Published: February 2020

TiO2 nanomaterials, in general, have over the last 30 years attracted tremendous scientific and technological interest, due to a wide range of functional properties of TiO2 which make it promising for instance for photocatalysis, use in Grätzel type solar cells, electrochemical devices, or in biomedical applications. For many functional applications, 1D and highly defined TiO2 nanomorphologies can be superior to nanoparticles. A highly elegant route to grow TiO2 nanotube arrays is by self-organizing anodic oxidation. This approach is not limited to TiO2, as a full range of other functional oxide structures on various metals and alloys can be formed, and the chemical composition and morphology of the structures can be varied in a large range. As the structures can be grown on conductive substrates as ordered layers, they can be directly used as functional electrodes (e.g. photo-anodes). The presentation will focus on these highly ordered nanotube arrays of TiO2 and discuss most recent progress in synthesis, modification and applications.
(Invited) Growth of Anodic Nanotubular Oxides: The Influence of Substrate
Authors: Tsuchiya Hiroaki , Fujimoto Shinji
Published: February 2020

In the present work, we examined the growth of nanotubular oxide layers by anodization in fluoride containing electrolytes, focusing on the influence of substrate. The properties of substrate such as defect density and the size of microstructure were varied. The defect density and the size of microstructure were controlled by cold work and heat-treatment. Cold work increased the defect density of Ti substrate whereas heat-treatment decreased the defect density within Ti. These substrates were subjected to the anodization in ethylene glycol containing ammonium fluoride and water. Cross-sectional observations revealed that the defect density affected the growth of nanotubular oxide layers on Ti substrate, that is, on Ti substrate with increased defect density by cold work, the thickness of nanotubular oxide layer increased while on Ti substrate with decreased defect by heat treatment, the thickness decreased. The size of microstructure also exhibited strong influence on the growth of nanotubular oxide layer. For this purpose, lamellar Ti-41at.%Al alloys consisting of Ti3Al and TiAl were prepared. The width of the lamellas was controlled by heat treatment. On the alloy with wider lamellas, nanotubular oxide layers were formed on each phase. On the other hand, selective growth of pore was achieved when the width of lamella was below critical size. Therefore, these results indicate that the properties of substrate strongly affect the growth of anodic nanotubular oxide layers.
(Invited) Emerging Applications of Nanostructured Porous Silicon
Authors: Koshida Nobuyoshi
Published: February 2020

Porous silicon (PS) prepared by the appropriate electrochemical anodization consists of a nanopore structure and residual quantum-size nanocrystalline silicon (nc-Si). It has tunable physical properties that can be radically different from those of single-crystalline bulk silicon and plays a role as a platform of functional devices. Possible applications are discussed here and some recent developments highlighted: efficient route for nc-Si colloid formation, quasiballistic electron emission, and thermo-acoustic effect.

Using self-standing PS layer flakes as a base material, nc-Si dot colloid has been formed efficiently by either optical or thermal energy. Highly luminescent (35% in quantum efficiency) colloidal nc-Si dots can be produced with a considerably higher yield (85%) from target than the values (1-10%) in the conventional processes.

A multiple-tunneling transport mode through nc-Si dot chain induces efficient quasiballistic hot electron emission from an nc-Si diode. Being a relatively low operating voltage device compatible with silicon planar fabrication process, the emitter is applicable to mask-less parallel lithography under an active matrix drive. It has been demonstrated that the integrated 100×100 PS emitter array is useful for multibeam lithography and that the selected emitter pattern is delineated corresponding to the activated emitters [1]. In addition, highly reducing activity of emitted electrons is applicable to liquid-phase thin film deposition of metals and semiconductors under a printing mode [2,3]. Both the efficiency and the energy distribution are remarkably improved by using monolayer graphene as a surface electrode [4].

Due to a complete thermal insulating property of nc-Si layer retaining a low volumetric heat capacity, on the other hand, thermo-acoustic conversion is significantly enhanced. When a temperature fluctuation is produced at the surface of nc-Si layer, an acoustic wave is generated near the device surface without any mechanical vibrations. The non-resonant and broad-band emissivity with no harmonic distortions makes it possible to use the emitter for generating audible sound under a full digital drive [5] and reproducing complicated ultrasonic communication calls between mice [6].

References

1. A. Kojima et al., Proc. SPIE Adv. Lithography Symp. 9777, 977712 (2016).

2. R. Suda et al., J. Electrochem. Soc. 163(6), E162 (2016).

3. R. Suda et al., Mater. Sci. Semicond. Process 70, 44 (2017).

4. A. Kojima, R.Suda, and N. Koshida, Appl. Phys. Lett. 112 (2018) (accepted for publication).

5. N. Koshida et al., Appl. Phys. Lett. 102, 123504 (2013).

6. K. Mogi et al., Behav. Brain Res. 325, 138 (2017).
Cryogelated Superstructures for Electrochemical Applications
Authors: Müller Dennis , Freytag Axel , Bigall Nadja
Published: February 2020

The cryogelation method represents a simple and sophisticated way for producing highly porous aerogel materials of nanoparticles with extremely large specific surface areas. Therefore, an aqueous dispersion of nanoparticles, which are serving as building blocks, is frozen rapidly by the use of liquid nitrogen. A sudden crystallization of the solvent leads to a formation of many small ice crystals. In this process, the previously dispersed particles are excluded from the ice, so that a network of crystal boundaries filled with nanoparticles is formed. In a subsequent step, the solvent is sublimed and removed by lyophilization, to finally obtain a self-supported monolith. Providing a sufficiently high nanoparticle concentration, the shape of the resulting aerogel resembles the frozen colloid.[1] This fact offers the opportunity to prepare thin films on substrates by means of doctor blading or, on the other hand, to use molds for the fabrication of other macroscopic shapes.[2] Besides, a time-consuming hydrogelation step, which would be necessary for a conventional chemical gelation, is avoided. In the end, this procedure is applicable for a variety of nanoparticle systems, due to the fact that there is no chemical selectivity.[3] Here, we will present the chemical and physical properties of these superstructures and discuss their benefits in consideration of applications in the field of electrochemistry.

[1] A. Freytag, M. Colombo, N. C. Bigall, Z. Phys.
Chem., 2017, 231(1), 63-75.

[2] T. Kodanek, Axel Freytag et al., Z. Phys. Chem.,
2018, aop.

[3] A. Freytag et al., Angew.
Chem. Int. Ed., 2016, 55, 1200-1203.

Figure 1