bluuebunny/crossref_metadata_2025 huggingface dataset:
Multifunctional Electrospun Separators for Structural Battery Applications
Authors: Keaswejjareansuk Wisawat , Liang Jianyu
Published: February 2020

Lithium-ion battery (LIB) has been utilized in variety applications as energy source. Structural battery is a new approach that employs multifunctional material concept to use LIB with load-bearing capability to minimize the weight of the complete energy consumption system and maximize the efficiency. Separators are polymeric materials that have been known as the weakest component of conventional LIB. This work aims at creating electrospun membranes with multifunction, improved thermal resistance and mechanical properties as the next generation LIB separator. Electrospinning process (ES) is known as simple, flexible, versatile also cost-effective at all scales. The ES employs an electrostatic force to control the production of nanofibers from polymer solutions. Solution and process parameters, such as type of polymer and cross-linking additives, concentration of polymer solution, acceleration voltage, and solution feed rate, have been studied to achieve the desirable membrane properties. Many characteristics of ES polymer membrane would affect performance of it as the separator in LIB. In this study, design of experiments techniques has also been utilized to optimize the parameters in creating an improved multifunctional separator for structural battery applications.
Understanding Performance Fade in High Energy Density Li Batteries
Authors: Dufek Eric J. , Nagpure Shrikant C , Wood Sean M , Dickerson Charles C , Tanim Tanvir , Liaw Bor Yann
Published: February 2020

The desire to develop higher performing batteries can be linked with greater demand for long range electric vehicles, longer lasting consumer electronics, and increased use of energy storage technologies in applications such as grid storage. A key to enhancing battery energy density and specific energy for many of these applications is to reduce battery pack size while maintaining or even increasing total capacity. The first attempts at commercializing secondary Li metal batteries occurred over three decades ago.1,2 However, despite this long history there is still a significant gap between desired high energy density Li metal batteries and what can be effectively achieved.

One potential route to enhance energy density is the use of a high energy cathode such as nickel-rich lithium nickel manganese cobalt oxide (NMC) in conjunction with a liquid electrolyte and a Li metal negative electrode. In such a configuration, high theoretical energy densities of at least 500 Wh/kg can be realized with optimal utilization of active materials in both the positive and negative electrodes and minimized electrolyte volume.

With increased utilization of active materials, there is a respective decrease in volume of electrolyte and other non-active components such as conductive carbon and binder. Each of these reductions has the potential to shift the equilibrium of degradation processes and alter the accumulation of degradation byproducts in higher energy battery systems. This presentation will discuss some of the implications associated with this shift in degradation as the balance of materials transitions from having multiple components in excess to a more energy dense setting with minimal excesses.

1. Whittingham, M. S. History, Evolution, and Future Status of Energy Storage. Proc. IEEE
100, 1518–1534 (2012).

2. Brandt, K. Historical development of secondary lithium batteries. Solid State Ion.
69, 173–183 (1994).
Illuminating Heterogeneous Mass Transport in Commercial Porous Electrodes for Aqueous Flow Batteries By Fluorescence Microscopy
Authors: Wong Andrew A. , Rubinstein Shmuel , Aziz Michael J.
Published: February 2020

There are numerous styles of porous electrodes commercially available that can be used in flow batteries, yet there is no clear consensus as to what styles perform optimally, let alone which physical and chemical properties to select for in future iterations. There are apparent tradeoffs between electrochemically active surface area and electrical conductivity; however, physical heterogeneities leading to mass transport inefficiencies might also produce limited performance. In this study, we investigate the mass transport and electrochemical properties of several commercial porous electrodes in operating aqueous flow batteries using fluorescence microscopy, comparing various figures of merit for their performance. This is enabled using redox-active soluble quinones, which have distinct fluorescence signatures in their oxidized and reduced forms, as a direct measure for in-situ reaction flow mapping. These observations provide insights for future designs of porous electrodes, enabling improved flow battery performance.

Figure 1
A Fully Regenerable Thermal Silver Ammonia Battery to Convert Low-Grade Waste Heat to Electricity
Authors: Rahimi Mohammad , Kim Taeyoung , Gorski Christopher A. , Logan Bruce E.
Published: February 2020

A vast amount of low-grade thermal energy (temperature < 130 ⁰C) is available globally at industrial plants and from solar and geothermal sources. Converting these sources of energy to electricity has drawn increasing attention in recent years. Solid-state thermoelectrics (SSTs) and liquid-based thermoelectrochemical systems (TECs) have been widely investigated as means of converting low-grade waste heat to electrical energy. However, despite much progress in both the methods, these systems have failed to produce high power densities, and have not been cost-effective. A recently developed thermally regenerative ammonia batteries (TRAB) showed a significantly higher power production (~12 times more) than both SSTs and TECs. In a TRAB, electrical power is obtained from the formation of metal ammine complexes, which are produced by adding ammonia to the anolyte, but not to the catholyte. After the cell discharges, ammonia is separated from the anolyte using a conventional technology, such as distillation with low-grade waste heat, and then added to the other electrolyte for the next discharge cycle. The previous TRAB based on copper electrodes and a copper salt electrolyte showed a relatively high power production. However, unbalanced rates of anode dissolution and deposition of copper on the cathode limited the use of copper in closed-loop cycles. To address the reversibility issue, a silver-based TRAB was developed as an alternative to the copper-based TRAB. With silver, the cathodic and anodic coulombic efficiencies of the TRAB were the same (~100%), resulting in a reversible system for converting low-grade waste heat into electricity over many successive cycles. The developed silver system produced a net maximum power density of 30 W m−2-electrode area, with a net energy production of 490 Wh m−3-anolyte in a flow cell with an optimal hydraulic retention time (HRT) of 2 s. Successive deposition and dissolution cycling (i.e., the electrode reversibility) showed the system was stable over a hundred cycles. An initial economic analysis of the system showed that the price of electricity produced based on materials costs was 1.8 times more than the average electricity price is the U.S. ($ 120 MWh−1), due primarily to the cost of the membrane as well as sliver. However, this could be reduced to $ 120 MWh−1 if the cost of a membrane used in the system could be reduced to $10 m–2. Other potential benefits, such as elimination of air pollution, and beneficial issues related to health and climate change were not included in the comparison. Although the cost of building and operation relative to energy production of Ag-TRAB is currently higher than that of conventional technologies, this approach could generate a cleaner method of electrical power generation using a waste source of heat if the commercial cost of ion exchange membranes could be significantly reduced.
Complex Hydride Solid-State Electrolytes for Li, Na and Mg Batteries
Authors: Kühnel Ruben-Simon , Yan Yigang , Duchêne Léo , Roedern Elsa , Cuervo Reyes Eduardo , Remhof Arndt , Battaglia Corsin
Published: February 2020

The identification of a solid-state electrolyte that fulfills all the requirements to enable a competitive bulk-type all-solid-state battery remains a challenging task. The electrolyte should display high ionic conductivity, high thermal stability, good processability and importantly a large electrochemical stability window that ideally spans the redox potential of the conducted metal ion. Several electrolytes within the class of complex hydrides display such a favorable combination of battery relevant properties. Here, we will discuss our recent results for Li-, Na- and Mg-ion conductors.

We identified several compositions within the lithium-amide borohydride (Li(BH4)1-x
(NH2)
x
) system that display near room temperature conductivities of >6 mS/cm, comparable to the ones of typical carbonate-based liquid electrolytes used in commercial lithium-ion batteries. An Li4Ti5O12 half-cell based on such an electrolyte displays >60% capacity retention at 3.5 mA/cm2 (5C) and stable cycling for 400 cycles.[1] The mixed closo-borate Na2(B12H12)0.5(B10H10)0.5 displays a conductivity of 0.9 mS/cm at 20 °C, excellent thermal stability of up to 300 °C and an electrochemical stability window of 3 V that enables reversible plating of sodium.[2] We will also report on the preparation and characterization of magnesium ethylenediamine borohydride (Mg(en)1(BH4)2), which displays a very high conductivity of 6x10-5 S/cm at 70 °C for a magnesium-ion solid-state electrolyte.[3]

[1] Y. Yan, R.-S. Kühnel, A. Remhof, L. Duchêne, E. Cuervo Reyes, D. Rentsch, Z. Łodziana, C. Battaglia, Adv. Energy Mater., accepted.

[2] L. Duchêne, R.-S. Kühnel, D. Rentsch, A. Remhof, H. Hagemann, C. Battaglia, Chem. Commun. 2017, 53, 4195.

[3] E. Roedern, R.-S. Kühnel, A. Remhof, C. Battaglia, Sci. Rep. 2017, 7, 46189.
Organosulfide-Plasticized Solid-Electrolyte Interphase Layer for Stable Lithium Metal Anodes
Authors: Li Guoxing , Gao Yue , He Xin , Huang Qingquan , Chen Shuru , Kim Seong , Wang Donghai
Published: February 2020

Lithium metal is a promising anode candidate for the next generation rechargeable battery due to its highest specific capacity (3860 mA h g-1) and lowest potential, but low Coulombic efficiency (CE) and formation of lithium dendrites hinder its practical application. Here we report a self-formed flexible hybrid solid-electrolyte interphase (SEI) layer through co-deposition of organosulfides/organopolysulfides and inorganic lithium salts using sulfur-containing polymers as additive in the electrolyte. The organosulfides/organopolysulfides serve as “plasticizer” in the SEI layer to improve its mechanical flexibility and toughness. The as-formed robust SEI layers enable dendrite-free Li deposition and significantly improve CE (99% over 400 cycles at a current density of 2 mA cm-2). A lithium-sulfur battery based on this strategy exhibits long cycling life (1000 cycles) and good capacity retention. This study reveals a new avenue to effectively fabricate stable SEI layer for solving the issues associated with lithium metal anodes.
Free Standing Silicon Microparticle and Self-Healing Polymer Composite for High-Energy Lithium-Ion Anode Applications
Authors: Kim Donghyuk , Hyun Seungmin , Han Seung Min
Published: February 2020

Developing a commercially viable silicon anode as a replacement for graphite has been the topic of intense research and discussion. Numerous attempts have been made including the use of nanoscale structures smaller than silicon’s critical fracture size (e.g. nanoparticles, nanowires, nanotubes, etc.). However, nanoscale structures, while sufficiently effective in lab scale, are difficult and expensive to scale up. To address this issue, applying a thin coat of polymer with self-healing chemistries has been reported as an effective remedy to enhance the cycle life of the silicon microparticle anode. The self-healing chemistry enabled mechanical fractures generated during the cycling process to self-heal. As a result, excellent cycle life was obtained compared to conventional microscale anodes. However, there still is room to improve the mechanical and electrochemical performances of the anode, most notably areal capacity and flexibility, while using large scale processes. In this study, a free standing silicon microparticle and self-healing polymer (SiSHP) composite is fabricated demonstrating long cycle life while still retaining high capacity (up to ~2,800mAhg-1 and ~3.5mAhcm-2) without a metal foil current collector. SiSHP composite is prepared by simple, inexpensive, and scalable approach. The SiSHP composite consists of silicon microparticles embedded within a self-healing polymeric matrix providing sufficient space for volume expansion during lithiation. The self-healing chemistry reduces irreversible loss of electric contact due to mechanical degradation prevalent in conventional slurry cast silicon electrode design. In addition, because the SiSHP composite eliminates the need for a metal current collector, adhesion issues between the electrode and current collector that arise with repeated bending are eliminated, thereby ensuring minimal loss in mechanical and electrochemical properties even after undergoing repeated bending. We found that a 1:1 Si/SHP weight ratio with 10 wt. % carbon conductive additive exhibits the optimal balance between high capacity and providing sufficient polymer matrix for stable cycling behavior. The fabricated SiSHP composite is moldable into the required shape and dimension ranging from millimeter to tens of centimeter-scale. The freestanding feature of the SiSHP composite anode eliminates the need for a metal foil current collector thereby reducing the non-active mass, which is beneficial to enhancing capacity and energy density of Lithium-ion cells.
New Fluorinated Carbon Materials for Binder-Free Ultra-High Capacity Cathodic Materials
Authors: Sun Haoran
Published: February 2020

Low capacity of current cathodic materials is a bottle-neck for the next generation electrochemical energy storage devices. LiMO2, LiMPO4, and mixed metal oxide lithium salts are commonly used in current lithium batteries. The heavy nature of these transition metal elements limits their capacity below 300 mAh/g. Fluorinated carbon materials are mainly used in primary lithium batteries since the 1970s. It is a high capacity cathodic material that surfers low conductivity and slow electron transfer kinetics. The preparation method, high temperature reaction between graphite and fluorine gas, also possesses significant safety threat for the production of current carbon fluoride materials.

To solve the low conductivity and low discharge rate problem for carbon fluoride based cathodic materials, we designed a new type of fluorinated carbon materials that integrate conducting polymers, electron-transfer catalysts, and energy storage units, yet still have the similar composition of carbon fluoride to maintain the high specific capacity. Thus, this materials does not require additional mechanical binder and conducting materials for the cathode.

The materials were characterized by electrochemical, spectroscopic, and scanning electron microscopic (SEM) methods. Electrochemical experiments were done in an Argon filled glovebox with residual O2 level less than 1 ppm. Three electrode systems were used for the characterization of this carbon fluoride cathodic materials on glassy carbon (GC) and aluminium electrodes in both 1,2-difluorobenzene (DFB)/TBAPF6 and propylene carbonate (PC)/LiPF6solution.

Figure 1 shows galvanostatic discharge curve of the new carbon fluoride materials on GC WE in PC/1.0 M LIPF6 with two pieces of Li foil as CE and RE respectively at C/8 rate. The discharge result shows that this new cathodic material possesses specific capacity of 1.03 Ah/g with average voltage of 2.1 V (vs. Li+/Li) at 0.125 C rate, giving specific energy of 2.16 Wh/g. We also observed that the galvanostatic discharge of this material does not involve an initial voltage dipping as observed with current carbon fluoride materials. Searching and optimizing the electrolyte solution for rechargeable application is currently underway in this laboratory. We hope that this presentation will shed new light to the discovery of new cathodic materials.

Figure 1
Prediction of Electrochemical Performance of Lower Temperature Operating Na-NiCl2 Battery
Authors: Jung Keeyoung , Park Yoon-Cheol , Li Guosheng , Xu Yihan , Kim Chang-Soo
Published: February 2020

Sodium nickel chloride (Na-NiCl2) batteries are gaining growing attentions as a strong potential contender for advanced electric vehicle (EV) and stationary energy storage system (ESS) applications. The cathode compartment of a Na-NiCl2 battery features by a mixture of solid NaCl and Ni granules impregnated with a liquid NaAlCl4 catholyte. During charge-discharge cycles, complicated electrochemical reactions take place, including transportation of Na+ ions through NaAlCl4 catholyte, the dissolution/coarsening of NaCl particles, formation/decomposition of NiCl2 layers on the active Ni surface, and electron transport through the Ni granules. We are developing advanced Na-NiCl2 batteries that operate at relatively lower temperatures of below 200 °C to minimize its cell degradation typically observed at high operation temperature (over ~270 °C) and to enable application of simple and cheaper polymer seals for cell manufacturing. However, the diffusion and the ionic migration kinetics of active Na+ ions are restricted at the lower temperatures that may limit cell performance. In this presentation, we introduce a multi-physics continuum computational model to capture the electrochemical behaviors of planar lower temperature Na-NiCl2 batteries. The computational results will elucidate impacts of (i) cell operation temperatures, (ii) current densities, and (iii) cathode dimensions on the electrochemical performance of prototype planar Na-NiCl2 cells. The developed prediction model is expected to provide a useful guideline for the experimental fabrication of advanced Na-NiCl2 batteries with maximized cell performance at relatively lower temperatures.
A Flavin-Based pH Flow Battery That Recharges with Waste Heat or Carbon Dioxide Emissions
Authors: Fortunato Jenelle , Zhu Xiuping , Rahimi Mohammad , Gorski Christopher A.
Published: February 2020

Currently, two enormous potential energy sources remain largely untapped: waste heat from energy production and industrial processes and carbon dioxide emissions from power plants. Industrial sites and nuclear plants produce enough potential energy in the form of waste heat to meet approximately half the U.S. energy demand (29000 TWh in 2013), and CO2 emissions can theoretically provide over one-third of the electricity demand (4078 TWh in 2015). Current technologies used to capture this potential energy are inefficient and/or use expensive materials. Here we propose a novel pH flow battery, which uses pH-dependent redox couples to extract energy from a pH gradient created from either low-grade waste heat or CO2 flue gases. For waste heat, ammonia (NH3) is dissolved in water to create a pH gradient that can be reversed by distillation using low-grade waste heat. Similarly, CO2 dissolved in water forms carbonic acid (H2CO3), which dissociates into bicarbonate (HCO3
-) and protons (H+) to create an acidic solution that can be subsequently removed by sparging with air. The goal of the study is to test the viability of the pH flow battery compared to other technologies. Cyclic voltammetry was used to test a suite of compounds to determine the pH dependency of reduction potentials, electrode kinetics, and compound stability. For sparingly soluble compounds, we evaluated the use of a hydrotropic agent, nicotinamide (vitamin B3), to increase solubility. Ideal compounds were then tested in a pH flow battery to evaluate power production, the ability to recharge the battery with waste heat or CO2, and cycling stability. From the compound survey, several Flavin-based compounds were identified as candidates due to fast electrode kinetics, pH-dependent reduction potentials over a wide pH range, and stability in oxygen. Nicotinamide added in high concentrations was shown to increase solubility of Flavin compounds at low pH and promising results were obtained from preliminary tests of the pH flow battery.
High Conductive Two-Dimensional Covalent Organic Frameworks for Anodes of Lithium-Ion Batteries
Authors: Yang Hui , Huang Changshui , Liu Huibiao
Published: February 2020

Two-dimensional covalent organic framework (COF) nanosheets based on 5,10,15,20-tetra(4-thiophenephenyl)- porhyrin (TThPP) featuring high conductivity were synthesized using an in-situ chemical oxidative polymerization method. Here, we show for the first time a 2D COF used as the anode for lithium-ion batteries. When used as anode material for lithium ion batteries, the TThPP anode displayed good lithium-ion storage properties with high specific capacities, excellent rate performances, and long cycle lives compared with that of graphitic (372 mAh g−1) and other organic anodes. The reversible capacity is up to 666 mAh g−1. The TThPP also exhibited high energy and power densities of 48.44 Wh kg−1 and 700.36 W kg−1 respectively when used as the anode of a hybrid capacitor. The unique nanosheet morphology of the TThPP anode films provide efficient adsorption sites for Li atoms, short-ended paths for the fast lithium-ion diffusion, and open nanopores for holding electrolyte that contribute to the excellent electrochemical performance.
Atmospheric Pitting Corrosion Studies of AA7075-T6 Under Electrolyte Droplets
Authors: Thomson Mark S. , Frankel Gerald S.
Published: February 2020

Pitting corrosion of AA7075-T6 was investigated in situ by Scanning Kelvin Probe (SKP) under droplets containing MgCl2and NaCl. The corroded samples were analyzed by optical microscope and optical profilometer. The SKP results indicated that single regions of sustained pitting attack formed with preference at the edge of the droplets due to shortened distance of oxygen diffusion. The pits at the sustained attack sites formed anodes with supporting cathodic reactions at the surrounding sample surface. As the pits grew, the cathodic region was observed to expand, leading to elevated potentials measured at the center of the droplets. Droplets with greater initial volume formed larger areas of contact with the sample surface and accelerated corrosion attack. Overall, sustained pitting attack was observed along groups of surface particles oriented along the rolling direction. In many cases, pitting led to the formation of a secondary droplet at the periphery of the primary droplet. A mechanism is proposed for the pitting behavior of AA7075-T6 under the studied electrolyte droplets, as well as a new mechanism for the formation of secondary droplets.

This work was supported by Office of the Secretary of Defense Technical Corrosion Collaboration through the United States Air Force Academy.
An Svet Study of the Localised Corrosion of ZE20 Mg Alloy in Chloride Containing Electrolyte
Authors: Glover Carol Frances , Kish Joseph , Williams Geraint
Published: February 2020

The localised corrosion behaviour of ZE20 magnesium alloy (composition Mg-2.4Zn-0.2Ce) is studied by a scanning vibrating electrode technique (SVET) in immersion conditions. Such alloys have improved ductility compared to commercial alloys due to the random structure produced by Ce additions, making them suitable for lightweight automotive parts. The alloy has been developed such that ductility and strength are optimised (27% elongation, 135 MPa yield strength; 225 MPa ultimate tensile strength) for such applications where ‘crashworthiness’ and formability are key. The corrosion resistance of magnesium alloys is still a significant challenge and understanding the mechanism by which corrosion occurs is fundamental to advancing performance. In the current study, SVET is used to measure the time-resolved local current density distributions in situ over freely corroding sample surfaces. The localised corrosion rates of ZE20 are studied in terms chloride concentration and pH. Figure 1 shows representative current density maps of the alloy freely corroding in immersion conditions.

Figure 1 Surface plot showing the distribution of normal current density (jz) above a ZE20 magnesium alloy sample at times (a) 5 h and (b) 6.5 h following immersion in aerated 2 M aqueous NaCl at pH 7.

Figure 1
Experiment-Supported Model Development for Data Treatment of Diffusion and Activation Limited Polarization Curves of Magnesium and Steel Alloys
Authors: Stephens Lisa , Perry Samuel C , Lacasse Robert , Mauzeroll Janine
Published: February 2020

Characterization of any corroding system begins with determining its corrosion potential and rate. These two values serve as a preliminary measure of its surface passivation and kinetic activity which may then be investigated in more detail using local electrochemical or spectroscopic techniques. The potentiodynamic polarization curve (PDP) is the most common technique for simultaneous extraction of these two values, since it provides additional kinetic information in the form of Tafel slopes and can further be used to measure the pitting potential of a system. In the past, numerical analysis of these curves has proven challenging where mass transport limitations influence the currents measured. In this presentation we discuss a finite element model that has been developed to analyse the kinetics of corroding magnesium and steel alloys during PDP’s where both activation and diffusion-controlled currents are present. Furthermore, the origins of the mass transport limitations present in these systems have been investigated in more detail through an analysis of the concentration profiles involved.
Alternating Current Phosphoric Acid Etching of Aluminium
Authors: Burmas Bruno , Lein John Erik , Lunder Otto , Nisancioglu Kemal
Published: February 2020

Alkaline etching is a common pretreatment process for aluminium alloys before anodising or application of organic coating. Removal of the mill-finish surface layer is performed by a simple dipping process, which also gives the matt finish normally required for aesthetic appearance before conventional anodising. Major disadvantage of alkaline treatment is the surface enrichment of the alloying and trace elements more noble than the aluminium substrate by dealloying. This may reduce corrosion resistance and deteriorate the optical properties of the surface. The purpose of this work is to investigate fluoride-free acid etching for aluminium alloys as an alternative to alkaline etching to prevent or reduce heavy metal enrichment, while achieving matt appearance. Alternating current is applied to increase the rate of etching as the dissolution rate of aluminium in acid solutions is slower than in alkaline solutions. The principle is based on anodic oxidation of the heavy metal components, as well as aluminium, during the anodic cycle and removal of the corrosion products and concentration gradients by hydrogen evolution during the cathodic cycle. The materials used for this study were hot-rolled aluminium alloy AA3105 (Si 0.3%, Fe 0.6%, Cu 0.1%, Mn 0.7%, Mg 0.3%) and extrusion AA6060 (Si 0.4%, Fe 0.2%, Cu 0.01%, Mn 0.02%, Mg 0.5%). Phosphoric acid was used as the etching electrolyte. Consumption of aluminium was calculated from weight loss. Appearance was analysed visually and by gloss measurements. SEM was used to study surface microstructure and morphology. Aluminium oxidation rate increased with increasing temperature, current density, electrolyte concentration and etching time. Intermetallic Al-Mn-Fe-Si particles were selectively and rapidly removed by 1 min etching at 80⁰C. In contrast, particles were exposed and remained on the surface by alkaline etching. Matt appearance without visible defects was achieved after 10 min etching at 80⁰C. Presence of phosphorus in thin oxide film formed was determined by glow discharge optical emission spectroscopy (GD-OES). Advantages foreseen of acid-based AC pretreatment over alkaline dip processes in practice are suitability for in-line coil processing, superfluity of the desmutting step, low gloss achievable with reduced metal loss, improved corrosion resistance and adhesion properties.

Acknowledgements

This work was supported by Hydro Aluminium and The Research Council of Norway.
Coatings and Corrosion Behavior of the Magnesium Alloy WE43 Under Simulated Physiological Conditions
Authors: Höhlinger Michael , Wagener Victoria , Heise Svenja , Boccaccini Aldo R. , Virtanen Sannakaisa
Published: February 2020

Various coating approaches have been studied to achieve a better, controllable degradation of the Mg alloy WE43. For its use as a biomedical, biodegradable implant it is also necessary to diminish initial hydrogen evolution. Therefore it is beneficial to coat samples before using them in vivo.

Thus, in the current study, on top of a primary coating, an additional chitosan-bioglass layer was applied by electrophoretic deposition. Corrosion of the alloy and the coatings under physiological conditions was investigated by immersion tests under a controlled atmosphere in DMEM.

The methods used in this study include cross-sectional characterization (SEM) of the coated and corroded samples, EDX, XPS, and electrochemical measurements. Mass loss measurements were carried out to study the progress of corrosion under different immersion conditions. The information gathered by a combination of the aforementioned methods leads to a better understanding on the corrosion rate and mode as well as on the type of corrosion products forming under different conditions. In addition, the influence of corrosion and the formed corrosion products on the further performance, e.g. biocompatibility, are being considered.
Corrosion of Ti and Its Alloys Under Aggressive Conditions
Authors: Virtanen Sannakaisa
Published: February 2020

Ti and its alloys, for instance Ti-6Al-4V, are generally highly corrosion resistant, due to very stable passivity in various environments. These materials are widely used in biomedical applications for permanent implants, and they have an excellent reputation for biocompatibility. Some problems related to the corrosion resistance of Ti-based implants can be encountered in practical applications, mainly due to the conjoint action of chemical and mechanical attack, i.e. fretting corrosion. This can lead to release and accumulation of Ti (and alloying elements) in tissue adjacent to titanium implants. However, it is also known that depassivation of Ti can take place under deaerated acidic conditions. Even though the typical chemistry in a "bulk" biological environment is pH-neutral (buffered to pH 7.4), under certain conditions more aggressive environments can be present. Local acidification, for instance in crevices, could take place by metal cation hydrolysis reactions, but also by possible inflammation reactions (such as following a surgery). Biological reactions can also generate H2O2, possibly accelerating dissolution of Ti based materials.

This presentation will discuss the corrosion behavior of Ti and selected Ti alloys under different conditions, such as in deaerated acidic solutions, simulated biological environments (including slightly acidified and H2O2-containing solutions). Deactivation can take place in deaerated acidic solutions, especially for Al-containing Ti alloys. Electrochemical measurements and metal release studies indicate drastically increased dissolution rates in presence of H2O2. For Ti-6Al-4V alloy, selective phase etching is observed in H2O2-containing solutions.
In Situ Electrochemical-AFM Study of Local Dissolution Processes of Al
x
Co Cr Fe Ni High-Entropy Alloys
Authors: Shi Yunzhu , Collins Liam , Come Jeremy , Balke Nina , Liaw Peter , Yang Bin
Published: February 2020

The multiple compositionally-equivalent high-entropy alloys (HEAs) have shown remarkable potential in structural and energy-related applications. Their intrinsic random arrangement of elements results in homogeneous chemical distribution, which is expected to be beneficial for improving the corrosion resistance. However, with the increased Al content in the objective Al
x
CoCrFeNi (x = 0.3, 0.5, and 0.7, molar ratios) HEAs, the multi-phase microstructure with chemical segregations is inevitable. The microstructure changes from single FCC solid-solution to FCC + disordered/ordered BCC phases. The FCC and disordered BCC phases are (Cr, Co, Fe)-rich, while ordered BCC phase is (Al, Ni)-rich. This chemical segregation would lead to the localized corrosion, which evidently impact the corrosion resistance. To investigate the detailed localized corrosion mechanism, the in-situ electrochemical-AFM (EC-AFM) measurements are performed at consecutively applied anodizing potentials in a 3.5 wt.% NaCl solution in the present study. The topography changes on the surface at micro/sub-micro scale are monitored in real-time. The results show that in the single phase Al0.3CoCrFeNi alloy, at the passive region, the surface roughness increases slightly due to the formation of oxide film. While increasing the potential continuously, deposition of the corrosion products results in increased sample roughness. At the active potential region, severe local dissolution is observed as the onset of pitting. For the Al0.5CoCrFeNi alloy, the FCC matrix performs similar corrosion behavior as the single FCC phase of the Al0.3CoCrFeNi alloy. However, the active potential is easier to reach due to the preferential formation of pits at the FCC/BCC phases boundaries. For the Al0.7CoCrFeNi alloy, the critical breaking down potential of passive film decreases dramatically. No pitting-like corrosion is observed, but a large amount of selective dissolution occurred at the FCC and BCC phase boundaries at the active potential region. Local selective dissolution of the (Al, Ni)-rich ordered BCC phases is observed as well. The XPS results indicate that the oxide film with the higher Cr content is more protective, therefore, pitting and selective corrosion prefer to initiate at the (Al, Ni)-rich phases. Moreover, the trenches formed along the phase boundaries indicate that the galvanic cell formed between the FCC and BCC phases accelerate the alloy dissolution as well. Overall, in situ EC-AFM is shown to be a useful tool to explore details of the anodic oxidation/dissolution behavior of the Al
x
CoCrFeNi HEAs. The in-depth understanding of the local dissolution activity and corrosion behavior obtained in the present study is of importance for the future design of high performance HEAs.

Figure 1. In situ EC-AFM images of (a-c) Al0.3CoCrFeNi, (d-f) Al0.5CoCrFeNi, and (g-i) Al0.7CoCrFeNi HEAs at increasing potentials.

Figure 1
Non Toxic Functional Hydrophobic Anticorrosion and Antifouling Coating for Application in Marine Structures
Authors: Sumalatha Devi P , Sreejakumari S.S , Gouthami S , Arumugam Elango
Published: February 2020

The main aim of this work is to prepare a multifunctional coating for marine applications by modifying the surface properties without the use of toxic elements. Non-toxic, non-biocidal, economical and eco-friendly Antifouling coating was fabricated with silicone acrylic resin, Nano silica, Titanium dioxide and other pigments possessing functional properties by mixing in an attritor and applied by simple spray coating method. The physical and chemical properties of the coated film surface was characterized by Contact angle measurement, SEM, FTIR, Abrasion test, Impedance test and Salt spray test. The antifouling property was evaluated through field immersion studies in sea water. Hydrophobicity of the coating is substantiated from 135˚water contact angle.The SEM image shows hierarchical structures responsible for hydrophobicity. FTIR analysis reveals the presence of functional elements. The anticorrosive property of the coating was predominant on continuous exposure for several hours in the salt spray chamber. Impedance spectra also proves that the coating is corrosion resistant even after several days of exposure in NaCl solution. The antifouling behavior evaluated for a duration of 45 days of immersion in sea water confirms sustained antifouling protection without the use of biocides and toxic volatile compounds. There was no macro-fouling present on the surface of the exposed panels. The coating possess better functional properties and exhibits better resistance to corrosion and fouling.
A Novel Inhibitor for L921A Alloy Steel in a 3.5 % NaCl Solution
Authors: Yong Xingyue , Chen Zhenglin , Zhou Lin , Jiang Lin , Chen Rihui
Published: February 2020

Corrosion inhibitors, acting as an effective method at lower operating cost, are often used to protect metallic materials from corrosion. Although many kinds of corrosion inhibitors have been used in circulating cooling water systems, a few papers have been published for introducing the applications of corrosion inhibitors in chloride media. By comparison, it is difficult to develop a novel inhibitor for alloy steels in chloride solutions or sea water.

In this paper, a novel corrosion inhibitor for L921A alloy steel in a 3.5% NaCl solution was formulated by weight loss in conjunction with orthogonal tests. The inhibitory efficiency of this novel inhibitor was over 95.0%. It was found by electrochemical polarization that this novel inhibitor was a mixed type of inhibitor which had an ability to improve the pitting corrosion resistance of L921A alloy steel in a 3.5% NaCl solution. EIS spectra showed that L921A alloy steel in a 3.5% NaCl solution was subjected to pitting corrosion, due to that EIS spectrum of L921A alloy steel in a 3.5% NaCl solution was composed of a capacitive loop at high frequency region and an inductive loop at low frequency region. However, EIS spectrum with two time constants consisted of a capacitive loop at high frequency region and a Warburg line at low frequency region when the novel inhibitor was added into a 3.5% NaCl solution. The thickness of inhibitory film increased with increasing immersion time, resulting in the increment of the electrochemical impedance of corrosion process of L921A alloy steel in a 3.5% NaCl solution. Finally, the formation of the inhibitory film was further studied by EDX and XPS technology.
Acceleration of Fe Corrosion in Cement Paste and Mortar By Enhancing Oxygen Supply
Authors: Doi Kotaro , Hiromoto Sachiko , Akiyama Eiji
Published: February 2020

Generally, in concrete, alkalinity of the environment is maintained and reinforcing steels exhibit superior corrosion resistance owing to passive film. Therefore, it is difficult to demonstrate Fe corrosion in concrete in the laboratory in a short time. A new method for acceleration of Fe corrosion is necessary.

Recently, some researchers tried to accelerate the Fe corrosion in concrete. They accelerated Fe corrosion by anodic polarization and cyclic corrosion test. In this study, an accelerated corrosion test method with enhancing oxygen supply was developed to enhance oxygen reduction on Fe surface and Fe corrosion in concrete. The effect of amount of oxygen supply on Fe corrosion in cement paste and mortar will be discussed in our presentation.

The sample was 99.5% Fe sheet with 7×7 mm2and 1 mm thickness. The Fe sample was embedded in cement paste or mortar with 5 mm cover thickness and cured for 28 days. In order to prompt breakdown of passive film on the Fe sample, 2.06 M NaCl solution was mixed to the cement paste and mortar. Fig. 1 shows the schematic image of Hyperbaric-oxygen accelerated corrosion test we developed. In the gas pressure chamber, Fe in cement and Fe in mortar were immersed in 2.06 M NaCl solution under the pressured oxygen of 0.5 or 2.0 MPa for 14 days. For comparison, corrosion of Fe in cement and Fe in mortar immersed in the NaCl solution under ambient air was also discussed. After finishing the immersion under pressured oxygen or ambient air, surface and cross section of Fe sample were observed using an optical microscope and SEM. In addition, composition of the rust on Fe sample was analyzed using Raman spectroscopy measurement.

Corrosion of the Fe in cement and Fe in mortar was obviously accelerated under the pressured oxygen of 0.5 MPa, and the corrosion of Fe in mortar was further enhanced than that of Fe in cement. Composition of the rust formed under the pressured oxygen of 0.5 MPa was similar to those formed in the real environment. It is thus demonstrated that the enhancement of oxygen supply is beneficial and effective to validly accelerate Fe corrosion in concrete.

Corrosion of the Fe in cement and Fe in mortar was suppressed under the pressured oxygen of 2.0 MPa compared to corrosion under the pressured oxygen of 0.5 MPa. It is considered that corrosion of Fe in cement and Fe in mortar is dominated by oxygen reduction reaction under the pressured oxygen of 0.5 MPa, while the excess oxygen makes passive films more protective and corrosion of Fe is suppressed under the pressured oxygen of 2.0 MPa.

Figure 1
Indirect Impedance Measurement to Assess Corrosion of Tendons
Authors: Alexander Christopher L. , Orazem Mark E
Published: February 2020

As application of an electric field to the surface of an electrolytic medium can indirectly polarize a metal, an indirect impedance measurement has been proposed as a means to assess the properties of a conductive element contained within a resistive medium without a direct connection to the conductive element [1-3]. The indirect impedance technique was studied by Zhang et al. [4] to determine the location and the condition of steel rebar within concrete slabs. They were able to determine qualitatively that the measured surface impedance was a function of the corrosion state of the steel as well as the resistance of the concrete. However, extracting the true impedance of the conductive element from the impedance of the whole system was difficult.

Andrade et al. [5] used results of finite element models to propose an analogue circuit that accounts for the polarization behavior of the steel and the properties of the mortar in which the steel is embedded. They determined that a suitable circuit must contain a parallel, as well as, a series resistance term associated with the resistivity of the concrete in relation to the impedance of the steel.

Our work has shown that the nonuniform current distributions and ill-defined geometries associated with the grout gives rise to a complex ohmic impedance associated parallel to the steel and another complex ohmic impedance that is in series with the steel. The complex ohmic impedance of the steel limits the indirect impedance measurement to providing only a qualitative assessment of the corrosion of bridge tendons.

References

C. Andrade, I. Martnez, “Metal corrosion rate determination of diﬀerent solutions and reinforced concrete specimens by means of a noncontacting corrosion method,” Corrosion
66 (2010) pg. 056001-056001.

P. J. Monteiro, H. Morrison, Non-destructive method of determining the position and condition of reinforcing steel in concrete, 1999. US Patent 5,855,721.

M Keddam, X. R. Novoa, V. Vivier, “The concept of floating electrode for contact-less electrochemical measurements: Application to reinforcing steel-bar corrosion in concrete,” Corrosion Science,
51 (2009) pg. 1795-1801.

J. Zhang, P. J. Monteiro, F.H. Morrison, “Noninvasive surface measurement of corrosion of reinforcing bar in concrete: Part I Experimental results”, ACI Materials Journal,
98 (2001) pg. 116-125.

C. Andrade, J. Sanchez, I. Martinez, N. Rebolledo, Analogue circuit of the inductive polarization resistance,” Electrochimica Acta
56 (2011) pg. 1874-1880.
(Invited) High-K Dielectrics: A Perspective on Applications from Silicon to 2D Materials
Authors: Wallace Robert M
Published: February 2020

In the 1990’s, research accelerated on addressing the limits of the industry standard gate dielectric: SiO2. With the most aggressive integrated circuit scaling, it became clear that standby power for MOSFETs required the insertion of a gate dielectric material that reduced tunneling leakage while enabling performance expectations. Leveraging prior dielectric research and after exploring several dielectric material candidates, [1,2] Hf-based dielectrics became the dominant choice and were established in commercial Si technology fabrication processes in 2007 after at least a decade of research. [3] Although perhaps forgotten among today’s 3D FET technologies, the introduction of a new gate dielectric, simultaneously with metal gate materials, was considered quite revolutionary in its day, and this development, in conjunction with other device engineering aspects like strain, enabled the continued march of industry along Moore’s original predictions. Since that time, the research on incorporating high-k dielectrics has expanded to address alternative channel materials including Ge, III-V, wide band gap semiconductors, and, most recently, perhaps the ultimate limit in channel scaling – atomically thin 2D materials. This talk, from the author’s perspective, will review some of these developments, many presented at the annual ECS high-k gate dielectric symposia led by Prof. Kar, and provide some context on the resilience of the materials research as well as the challenges and opportunities that lie ahead.

This work is supported in part by: (i) the SWAN Center, a SRC center sponsored by the Nanoelectronics Research Initiative and NIST, (ii) the Center for Low Energy Systems Technology (LEAST), one of six centers supported by the STARnet phase of the Focus Center Research Program (FCRP), a Semiconductor Research Corporation program sponsored by MARCO and DARPA, (iii) the US/Ireland R&D Partnership (UNITE) under the NSF award ECCS-1407765, and (iv) the Erik Jonsson Distinguished Chair in the Erik Jonson School of Engineering and Computer Science at the University of Texas at Dallas.

[1] J. Robertson and R.M.Wallace, “High-K materials and metal gates for CMOS applications,” Materials Science and Engineering R, 88, 1-41 (2015)

[2] G.D.Wilk, R.M.Wallace, and J.M.Anthony, “High-k Gate Dielectrics: Current Status and Materials Properties Considerations”, Journal of Applied Physics
895243 (2001)

[3] M.T. Bohr, R.S. Chau, T. Ghani, K. Mistry, “The High-k Solution,” IEEE Spectrum. 44 (29) (2007).