bluuebunny/crossref_metadata_2025 huggingface dataset:
A New Mn-Based Cathode for Energy Dense Zn-Anode Batteries
Authors: Yadav Gautam Ganapati , Huang Jinchao , Turney Damon , Hawkins Brendan , Nyce Michael , Banerjee Sanjoy
Published: February 2020

Research interest on zinc (Zn)-anode aqueous-based batteries have renewed recently because of its low equilibrium potential in aqueous electrolyte, low cost, non-toxic and nonflammable characteristics compared to lithium-ion batteries. Zn has a high theoretical capacity of 820mAh/g based on two electron reactions, thus it has the capacity to deliver high energy density if it is paired with an equally high capacity cathode. Silver and nickel are high capacity cathodes; however, they are very expensive and require the addition of expensive additives like cobalt in nickel to increase the rate of the battery. MnO2 is the best cathode to be paired with Zn because it has a high two electron capacity of 617mAh/g and it is extremely safe and economical. Recently, we showed that attaining the two electron capacity of 617mAh/g for over 3000 cycles was possible with the used of bismuth and copper additives. Energy densities >160Wh/L were attainable when the cathodes were paired with Zn at 15% utilization.1-4 However, they are still susceptible to Zn poisoning which lead to the formation of inactive phase called haeterolite (ZnMn2O4). To improve the energy densities of Zn-anode batteries new inexpensive and safe cathodes with higher capacity than MnO2 and increasing Zn utilizations to >20-25% are a must.

In this presentation, we will report the synthesis of a new Mn-based cathode that delivers capacity ~800mAh/g, which is almost comparable to the Zn anode theoretical capacity. This new Mn-based cathode is able to deliver its capacity at high rates and maintain its capacity at high cycle life. We will present the reaction mechanism of this Mn-based cathode through real time microscopy videos and images, high resolution transmission microscopy and electroanalytical methods. We also report on the use of new Zn-based anodes that utilize >20% of its theoretical capacity and, at the time of this writing, still cycle with much deterioration in capacity due to shape change or passivation. The combination of the new high capacity Mn-based cathode and high utilization Zn-based anode results in a cell that delivers energy density >200Wh/L.

Funding:

This work was supported by the New York State Research and Development Authority (NYSERDA) under Project Number 58068.

References:

1] Yadav, G. G.; Gallaway, J. W.; Turney, D. E.; Nyce, M.; Huang, J.; Wei, X.; Banerjee, S., Nat. Commun., 2017, 8, 14424

2] Yadav, G. G.; Wei, X.; Huang, J.; Gallaway, J. W.; Turney, D. E.; Nyce, M.; Secor, J.; Banerjee, S., J. Mater. Chem. A, 2017, 5 (30), 15845-15854

3] Yadav, G. G.; Wei, X.; Gallaway, J. W.; Chaudhry, Z.; Shin, A.; Huang, J.; Yakobov, R.; Nyce, M.; Vanderklaauw, N.; Banerjee, S. Materials Today Energy, 2017, 6, 198-210.

4] Yadav, G. G.; Wei, X.; Huang, J.; Turney, D.; Nyce, M.; Banerjee, S. International Journal of Hydrogen Energy, 2018, https://doi.org/10.1016/j.ijhydene.2018.03.061
Standard Hydrogen Electrode Potential Referenced to Inner Potential from Density Functional + Implicit Solvation Theory
Authors: Haruyama Jun , Ikeshoji Tamio , Otani Minoru
Published: February 2020

Electrode potential is a general concept, in electrochemistry, which governs the charge transfer reactions such as ion insertion/extraction and reduction-oxidation at electrode/solution interfaces; the electrode potential should be appropriately included in the computational model. In this study, we consider how the standard hydrogen electrode (SHE) potential, which is the equilibrium potential of the charge transfer reaction of H+/H2, is theoretically evaluated.

Methods

We employed density functional theory (DFT) calculations combined with the effective screening medium (ESM) technique1 + the reference interaction site method (RISM);2 ESM-RISM formulation3 makes it possible to simulate the electrode (+ reactive ions) and the solution based on quantum mechanics and implicit classical solvation model, respectively. ESM-RISM calculations were performed on the configuration of a vacuum/slab/solvent system as shown in Figure 1, where the DFT slab domain is on the left-hand side, and the RISM solvents, that is, H2O, H3O+, and Cl− treated by the RISM equations, are on the right-hand side. Changing the chemical potential of electron, µ
e, referenced to the inner potential ΦS at the bulk solution region, we compared the grand potentials Ω for the following reaction R:

H3O+ (1M HCl aq.) + e− (electrode M, M=Pt, Al) ↔︎ 1/2 H2 (gas) + H2O (1M HCl aq.) (R).

Results

ESM-RISM calculations revealed Ω of the left side state of reaction R and that of the right state on Pt(111) electrode. They cross at µ
e = −5.27 eV, which is equilibrium chemical potential of electron at SHE reaction (= µ
SHE). This indicates that the electrode potential vs. SHE, E(SHE), is evaluated as E(SHE) = −(µ
e − µ
SHE)/e. We also obtained the almost same value of µ
SHE on Al(111) electrode. On the other hand, Pt(111) and Al(111) is negatively and positively charged at µ
e
=
µ
SHE, respectively. In the presentation, we will compare the potential profile of metal/solution/vacuum region obtained from ESM-RISM and the first-principles molecular dynamics calculation using ESM.4 We further discuss on the difference between µ
SHE and the absolute SHE obtained by Trasatti.5

References

M. Otani, O. Sugino, Phys. Rev. B
73, 115407 (2006).

F. Hirata, P. J. Rossky, Chem. Phys. Lett.
83, 329, (1981).

S. Nishihara, M. Otani, Phys. Rev. B
96, 115429 (2017).

M. Otani, I. Hamada, O. Sugino, Y. Morikawa, Y. Okamoto,T. Ikeshoji, J. Phys. Soc. Jpn.
77, 024802 (2008).

S. Trasatti, Pure Appl. Chem.
58, 955 (1986).

Figure 1
Galvanic Corrosion between AA5052 Aluminum-Magnesium Alloy and SS400 Carbon Steel in Aqueous NaCl Solutions
Authors: Ota Kengo , Tada Eiji , Ooi Azusa , Nishikata Atsushi
Published: February 2020

Aluminum alloys (AAs) such as 5000 and 6000 series have relatively good corrosion resistance and plastic workability. The use of these alloys for automobile body parts have been increased significantly because of reducing the weight of the body and improvement of fuel consumption. Although aluminum alloys themselves have relatively good corrosion resistance in atmospheric environments, galvanic corrosion between aluminum alloys and other materials should be taken into consideration in automotive application. This is because the body parts made of Al alloys should be jointed with other materials such as steel parts by welding or other methods and because the jointed parts can be exposed to atmospheric corrosion environments. In this study, galvanic corrosion between AA5052 aluminum-magnesium alloy and SS400 carbon steel is investigated in aqueous NaCl solutions.

A galvanic couple used in this study was made of AA5052 Al-Mg alloy (Mg: 2.65, Si: 0. 08, Fe: 0.27, Cu: 0.01, Cr: 0.17, Zn: 0.01, Al: bal. (mass%)) and carbon steel (JIS SS400). The plate of both materials was 10-mm width and 15-mm length and 3-mm thickness. After lead wire was connected on the surface of the plates, they were embedded in an epoxy resin. At this time, both materials were separated with a 500-um gap. The surface of the galvanic couple was polished with SiC papers up to JIS 2000 grit and rinsed in EtOH. Galvanic corrosion experiments were performed for 2 hours in aqueous NaCl solutions at various concentrations ranging from 5 mM to 500 mM. Galvanic current and corrosion potential of the couple were measured during the immersion in the solutions.

Corrosion potentials measured during the immersion in various concentrations of NaCl were almost constant for 2 h. The corrosion potentials changed in the less noble direction with increasing NaCl concentrations. Galvanic currents between AA5052 and SS400 showed positive values during the immersion in the solutions, indicating that aluminum-alloy side was basically an anode. However, the galvanic currents were almost the same independent of NaCl concentrations. From the results of polarization behaviors for AA5052 and SS400, a significant anodic current increase due to the propagation of localized corrosion on aluminum alloy and a diffusion-limiting current for the reduction of dissolved oxygen on steel were observed at the corrosion potentials of the galvanic corrosion tests. These results indicated that galvanic corrosion between AA5052 and SS400 in the early stage of immersion progressed under a diffusion-limiting condition for the reduction of dissolved oxygen on steel.
(Corrosion Division Morris Cohen Graduate Student Award) Local Hydrogen Detection Techniques for Atmospheric Uptake in Ultra-High Strength Steels
Authors: Schaller Rebecca Filardo , Thomas Sebastian , Birbilis Nick , Scully John R.
Published: February 2020

Hydrogen embrittlement (HE) is a concern specifically in ultra-high strength steels (UHSS) prevalent in key structural and vehicle components. In full immersion environments, hydrogen production and uptake in high strength materials has been well documented, such as in the case of cathodic protection. However, for atmospheric exposures, there is a large lack of information regarding hydrogen production and uptake. Under atmospheric conditions, acidic pits can form in UHSS due to the breakdown of the passive film, metal dissolution, hydrolysis, and acidification which are prone to local H production and uptake. An understanding of the effects of marine aerosols, industrial pollutants, and other environmental factors, such as UV and relative humidity, on hydrogen production and uptake in UHSS is necessary to develop new alloys with improved corrosion resistance as well as to anticipate and manage the effects of environment severity on embrittlement susceptibility of currently employed UHSS.

However, at present, the majority of available techniques for the measurement of hydrogen dissolved in metals and effective hydrogen diffusivity (DH,eff) lack spatial resolution at the micrometer scale. This is not only of significance for atmospheric exposures, with localized H uptake occurring at pits and/or within droplets, but is also of great importance since the hydrogen-metal interactions and processes occurring at the micrometer to nanometer length scales govern hydrogen embrittlement (HE). This presentation discusses and demonstrates select novel local hydrogen probes; the Scanning Kelvin Probe (SKP) and the Scanning Electrochemical Microscope (SECM). The detection of the spatial distribution of diffusible H concentrations was demonstrated on pre-exposed metallic surfaces with the SKP and SECM. SKP and SECM scans of H uptake in samples from controlled atmospheric pre-exposures are also presented. The application of these techniques is shown to provide local and spatial information on H concentrations produced through atmospheric corrosion. An understanding of the H severity at this local scale can provide significant information on severity of atmospheric exposure environments in terms of H production, uptake, and transport. Furthermore these techniques are adaptable to even higher resolution measurements with the application of the SKP atomic force microscope (SKPFM) or SECM-AFM.

Acknowledgement:

Research was sponsored by the US Air Force Academy under agreement number FA7000-13-2-0020 and ONR under PROJ0007990. The authors would like to acknowledge the Army Research Laboratories, as well as Monash University, in particular Dr. Sebastian Thomas and Prof. Nick Birbilis. The research was partially supported by a 2014 Australia Endeavour Award Research Fellowship with support from Dr. Kishore Venkatesan and Dr. Ivan Cole at CSIRO.
Ascorbic Acid as Antioxidant
Authors: Agrisuelas Jeronimo , Cuenca Alejandro , García Jose , Vicente Francisco
Published: February 2020

The use of ascorbic acid as a food additive is well known in health fields because it is a natural substance that is present in many fruits and vegetables, especially citrus fruits. Its beneficial actions in living beings is frequently associated with its inhibitory action of oxidative biochemical processes. On the other hand, it has also been found to inhibit the corrosion of metal alloys despite the fact that the metals in contact with acidified aqueous media react with the hydrogen ions to give molecular hydrogen and metal derivatives.

When checking in our laboratory that the juice of different citrus fruits and solutions of ascorbic acid and citric acid cause this effect on different technological metals and also check the protective action of ascorbic acid on the superficial atmospheric oxidation of carbonaceous particles, such as those of graphene or graphite, the idea arose to analyze the inhibitory effect of the anodic solution of a known system easy to study using electrochemical techniques that could be model of the inhibitory mechanism caused by ascorbic acid. In this work the inhibitory effect of ascorbic acid on copper anodic dissolution is studied by means of spectrum-electro-gravimetric techniques, since the Cu / acid solution system is a relatively simple model of possible utility to interpret the inhibitory effect of ascorbic acid on other more complicated systems.

The spectro-electro-gravimetric studies are useful to explain the corrosion and electrodeposits kinetics of copper in acid media [1,2]. If we analyze the mass evolution at open circuit potential of copper in sulfuric and ascorbic media, it is showed that in the chase of sulfuric media the mass decreases, but the process is slower at the end attending to the passive layer formation. However, when we analyze the mass evolution for the ascorbic acid dissolution, we can see that the mass grows proportionally to the acid concentration. First, takes place the adsorption on non-charged species over the electrode surface. This fact increases the rigidity over the electrode surface decreasing the values of the motional resistance. When the electrochemical process begins, there is an accumulation of copper ions over the electrode surface. The accumulation of copper ions allows the catalytic oxidation of the ascorbic acid.

1) D. Giménez-Romero, C. Gabrielli, J.J. García-Jareño, H. Perrot, F. Vicente Electrochemical quartz crystal microbalance study of copper electrochemical reaction in acid medium containing chlorides,. J. Electrochem. Soc. 153 (2006) J32-J39.

2) A. Cuenca, J. Agrisuelas, J.J. García-Jareño, F. Vicente, Oscillatory Changes of the Heterogeneous Reactive Layer Detected with the Motional Resistance during the Galvanostatic Deposition of Copper in Sulfuric Solution, Langmuir.31(46) (2015) 12664-12673.
EBSD Characterization of IGSCC Crack Initiated on Alloy 600 in Simulated PWR Primary Water Environment
Authors: Jung Ki-Taek , Tsuchiya Hiroaki , Fujimoto Shinji
Published: February 2020

In the present work, we crystallographically examined intergranular cracks initiated on Alloy 600 in a simulated PWR environment by using EBSD. The cracks initiated on a flat tensile specimen of the alloy in a short period of slow strain rate tests (SSRTs), that is, the initiation of cracks was accelerated due to the asperity of the specimen surface induced by mechano-chemical polishing with colloidal silica suspension prior to the SSRTs. As thick oxide films were formed on the specimen surface during the SSRTs, the sputtering of the films was carried out for the removal of the film. After the sputtering, clear crystallographic information such as inverse pole figures (IPFs) on the specimen surface could be obtained. Based on the information, the intergranular cracks were crystallographically analyzed. Furthermore, three-dimensional characterization of the cracks was also performed.
Arrays of Permanent Nanomagnets Produced By Bi-Metal Deposits within Nanostructured Silicon
Authors: Rumpf Klemens , Granitzer Petra , Gonzalez-Rodriguez Roberto , Coffer Jeffery , Poelt Peter , Michor Herwig
Published: February 2020

This work presents the investigation of the magnetic behavior of bi-metal nanostructures within nanostructured silicon with the aim to exploit the magnetic properties of both metals and gain control of the exchange coupling between the two metals especially with respect to their volume ratio. Furthermore a variation of the structure size and the proximity of the metal deposits modify the exchange coupling and thus the energy product. Finally nanocomposite systems with an energy product as high as possible are achieved to give rise to on-chip applications using permanent nanomagnets, especially arranged in arrays.

Magnetic nanostructures of two different metals are deposited within nanostructured silicon to control the magnetic switching behavior of the silicon/metal nanocomposite. Two different templates, porous silicon and porous silicon nanotubes are utilized to achieve such nanocomposites. The morphology (pore diameter, tube diameter) of the two systems is comparable. In the case of the utilization of porous silicon templates a mesoporous morphology with average pore diameters of 50 nm is used and these oriented and separated pores are filled with two different metals, namely Ni and Co. The two metals are deposited alternatingly by electrodeposition. A further approach is the chemical growth of Co nanoparticles within porous silicon nanotubes (SiNTs) and the additional deposition of a Ni layer on the outer surface of the tubes. The inner diameter of the silicon tubes is around 50 nm and the wall thickness is about 10 nm. Since the silicon wall of the tubes offers a porous structure the Co particles, which are localized near the pore surface on the wall of a given nanotube, can touch the Ni layer. An alternative structure involves the deposition of an additional Si layer (after the growth of Co particles inside the tubes) as a spacer before the Ni deposition.

The morphology of the deposited bi-metal Ni/Co structures is figured out by SEM and EDX.

In the presented work the dependence of the magnetic properties of a nanostructured silicon/bi-metal nanocomposite on the volume ratio of the metals, on the proximity of the nanostructures and also on the size of the metal deposits has been figured out. If the distance between the deposited bi-metal structures is small enough magnetic exchange coupling between them is present which could be observed. By tuning the bi-metal deposition an optimized energy product is achieved which gives rise to self-assembled nanocomposite systems containing permanent nanomagnets and arrays of them, respectively for on-chip applications.
Nanopore-Organized Nanoparticle Arrays for Tunable Optical Materials Using Nanobioplar Electrodeposition
Authors: Crouch Garrison , Han Donghoon , Fullerton Susan , Go David B. , Bohn Paul W.
Published: February 2020

The combination of polymers with nanopores has been of interest recently in many areas, from polymer-hybrid nanotube materials to functionalized membranes. Tightly-controlled nanopore arrays fabricated via Focused-Ion Beam (FIB) have demonstrated advantages in isolating small numbers of molecules or nanoscale objects, as with single molecule electrochemistry, and are well-suited to further engineering including multiple electrode rings and advanced surface functionalization techniques.

In this work, we discuss the ability of nanopore arrays to create ordered polymer cylinder arrays for testing the formation of nanofilaments in constrained polymer conditions as well as bipolar electrodeposition using nanoparticles. Previous work examined the kinetics of nanoscale bipolar electrodeposition by creating conductive filaments through a single nanoparticle, which demonstrated unique behavior due to the inherent limitations of nanoscale mass transport. Bipolar electrochemistry has demonstrated advantages in examining electrochemical effects under high electric fields, optically-coupled experiments, and other geometries where conventionally-connected electrodes would be prohibitively complex. In macro-scale bipolar electrochemistry, the difference in electric potential between the electrode and the surrounding electrolyte provides the driving force for a chemical reaction, such as the deposition of a metal ion from solution onto a surface. If that deposition is suitably controlled, a conductive filament may be created by electrodeposition, for example, in a nanoscale gap between two electrodes to create an atomic-scale junction.

This work examines the connection of multiple nanoparticles constrained in a nanopore array via the creation of conductive filaments, and the resultant change in optical behavior due to modified nanoparticle plasmonics. Preliminary theory suggests that the optical permittivity of the nanoparticle array may be tuned via formation and dissolution of the filaments. With application areas ranging from massively-parallel chemical sensing arrays to non-contact tunable metamaterials, this work uses advanced nanopore arrays to further the mechanistic understanding of nanoelectrodeposition and explore the unique challenges involved, both aspects vital to advancing the use of similar technology in real-world devices.

Special thanks to the Defense Advanced Research Projects Agency (DARPA) FA8650-15-C-7546 and the NASA Space Technology Research Fellowship (NSTRF) NNX16AM45H for providing funding for this research.
Ex-Situ Evidence on the Transition of Anodic Nanopores into Nanotubes Formed on Iron
Authors: Shahzad Khurram , Fadillah Laras , Kowalski Damian , Zhu Chunyu , Aoki Yoshitaka , Habazaki Hiroki
Published: February 2020

Anodizing is a high voltage electrochemical conversion process that forms barrier-type oxide layers or self-organized nanoporous/nanotubular structures. So far, the Al2O3-like nanopores and TiO2-like nanotubes could be successfully synthesized on many valve metals and alloys. The proposed models of anodic oxide nanotubes growth, however, sacrifice from lack of evidence on the transition from nanopores to nanotubes. Recently, anodizing become possible for more oxidizable metals such as iron and its alloys. The challenge in anodizing of iron lies in the proper control of corrosion/passivity of iron which can be successfully realized in organic electrolytes containing small amount of water. 1-3

Herein, we investigate the origin of the growth of nanotubes on iron in ethylene glycol electrolyte containing ammonium fluoride and desired amount of water. The composition of the nanoporous/ nanotubular anodic films formed on iron at various water concentrations is examined by high resolution electron microscopy/EDS elemental mapping.

The anodizing of iron in organic electrolytes containing fluorides typically leads to formation of nanopores and nanotubes depending on anodizing voltage. The kinetics of transition from nanopores to nanotubes is relatively slow for iron oxide and therefore allows for ex-situ observation of metal-fluoride layer upon nanopores/nanotubes transition. The TEM image shows pseudoporous structure in which anodic oxide is surprisingly in the form nanotubes as demonstrated by corresponding compositional TEM/EDS mapping. 4 The oxide nanotubes are separated by metal fluoride matrix which dissolves during anodizing process. The presented compositional fingerprints of the transition of nanopores into nanotubes are an evidence on the role of fluorides in the growth of anodic nanotubes.

References:

H. E. Prakasam, O. K. Varghese, M. Paulose, G. K. Mor and C. A. Grimes, Nanotechnology, 2006, 17, 4285-4291.

H. Habazaki, Y. Konno, Y. Aoki, P. Skeldon and G. E. Thompson, Journal of Physical Chemistry C, 2010, 114, 18853-18859.

Y. Konno, E. Tsuji, P. Skeldon, G. E. Thompson and H. Habazaki, J. Solid State Electrochem., 2012, 16, 3887-3896.

K. Shahzad, D. Kowalski, C. Y. Zhu, Y. Aoki and H. Habazaki, Chemelectrochem, 2018, 5, 610-618.

Figure 1 Bright field TEM micrograph for FIB cross-section of anodic iron formed at 100V in ethylene glycol electrolyte containing 1.5M H2O and 0.1M NH4F. The corresponding EDS maps show the elemental distribution of oxygen (green) and superimposed fluorine (red) and oxygen (green).

Figure 1
In-Situ Observations of Anodic Alumina Nanopore Growth and Self-Organisation
Authors: Harlow Gary Steven , Vinogradov Nikolay , Evertsson Jonas , Linpe Weronica , Carlà Francesco , Felici Roberto , Lundgren Edvin
Published: February 2020

Traditional surface science studies have been quite successful in determining several surface structures for alumina films, in particular those grown on NiAl, where the bulk structure consists of a combination of several building blocks but the surface Al atoms are found to occupy sites with either tetrahedral or pyramidal coordination [1]. However, the naturally forming ‘native oxide’ layers are found to be largely amorphous. The thickness of this layer can be increased electrochemically, i.e. by the industrial process of anodization, and to some extent the degree of crystallinity found depends on the applied voltage [2]. This type of oxide layer is called an anodic barrier layer and forms in neutral type electrolytes. In acidic electrolytes a porous oxide film is found, in which case the oxide has many nanometer sized pores and forms the base of most industrial aluminum coloring processes. Furthermore, under certain conditions these pores are found to be self-ordering [3]. They form hexagonal arrays and the pore diameter can be tuned by changes in potential, making excellent nanoscale templates.

We have investigated the formation and self-ordering behavior of porous type anodic alumina films in situ using Grazing Transmission Small-Angle X-Ray Scattering (GTSAXS) [5]. We observe the that the in-plane arrangement of the nanopores is independent of substrate crystallographic orientation whereas the oxide growth rate is not. The self-ordering behavior is studied in a variety of electrolytes and at several potentials in-order to explore the dynamics of self-ordering both below and above the breakdown potential (UB) at which optimal ordering is achieved [4]. It is also possible to follow the chemical etching of the oxide (pore widening) and subsequent metal deposition within the nanopores. The experimental approach presented can be applied to the study of a large variety of electrochemically produced materials such as magnetic nanowires, novel solar cell designs and catalysts.

[1] G. Prevot, et al. Phys. Rev. B, 85, 205450 (2012)

[2] J.W. Diggle, et al. Chem. Revs., 69(3), 365 (1969)

[3] H. Masuda, K. Fukuda, Science. 268, 1466–1468 (1995)

[4] Chu S.Z, et al. A. J. Electrochem Soc., 153, B384 (2006)

[5] Vinogradov, N.Am et al. ACS Applied Nano Materials, Article ASAP, (2018)

Figure 1: GTSAXS pattern during a 2nd anodoization of PAA. The oscillations correspond to the height of the pores.

Figure 1
Degradation Behavior of High-Phosphorus Ni-P Coating for Application in Oil and Gas Industry
Authors: Sun Chong , Fattahpour Vahid , Zeng Hongbo , Luo Jing-Li
Published: February 2020

Carbon steel casing and tubing, utilized for oil and gas production, may potentially experience severe corrosion due to the presence of corrosive gases (e.g., CO2 and H2S) and chlorine compounds in the production wells. To mitigate the corrosion of carbon steel, the Ni-P coating has been applied to the carbon steel surface using electroless deposition method. The extensive studies have suggested that Ni-P coating can effectively protect the substrate through isolating the substrate from the corrosive environment, and exhibits good corrosion resistance in the environment containing brine, acid, CO2 or even H2S. However, some internal microdefects derived from the deposition process as well as some external defects originated from the mechanical effect during the production process will inevitably be present in the coating. These defects are likely to pose great risks to the reliability of the coating and negatively affect its durability in the corrosive environments, especially in the coexistence of CO2 and Cl-.

In this work, the degradation behavior of a high-phosphorus Ni-P coating with microdefects or an artificial defect in CO2/Cl- environments was systematically investigated using electrochemical methods and surface characterizations. The results show that although the corrosion occurs at the microdefects and extends towards the inside of Ni-P coating, the coating has a good resistance to corrosion disbonding in the CO2/Cl- environment, even with an artificial defect in the coating. Under the cathodic polarization condition (to accelerate the corrosion process), the defects in the coating provide effective pathways for the electrolyte to transport through the coating and along the coating/substrate interface laterally from the defects, thereby, causing the localized corrosion and disbonding of the coating. Finally, a corrosion model is proposed to well interpret the degradation process of the coating with microdefects in CO2/Cl- environment. The electrolyte penetrates into the micropores and causes the corrosion of coating at the micropores, promoting the initiation of the pits. As the corrosion proceeds, the accumulation of corrosive species in the pits increases the localized corrosion rate. After the pits penetrate through the entire coating, the corrosion process is governed by the substrate dissolution and the mass diffusion between the substrate interface and the electrolyte. The corrosion of the substrate propagates along the coating/substrate interface laterally and towards the depth direction due to the accumulation of the electrolyte at the exposed substrate surface, which causes local corrosion disbonding of the coating.
Effects of Oil Viscosity on the Anti-Corrosion and Self-Healing Properties of Oil-Impregnated Nanoporous Anodic Aluminum Oxide
Authors: Choi Chang-Hwan , Lee Junghoon
Published: February 2020

Oil-impregnated nanoporous metal oxide surfaces such as anodic aluminum oxide showed significantly enhanced corrosion resistance and durability compared to hydrophilic or hydrophobic/superhydrophobic surfaces with no oil impregnation. Especially, the efficacy and durability of the oil-impregnated porous surfaces depend on the stability and retentivity of oil within the nanopores, where nanopores serve as reservoirs to hold the water-repelling and corrosion-protective oil in liquid phase. Previously, we demonstrated that the shape of nanopores should be an important factor to influence the stability and retention of oil. For example, it was demonstrated that the bottle-shaped nanopore featured with a smaller pore diameter at the upper layer than at the lower layer could immobilize the oil in the nanopores more stably than simply vertical nanopores, showing the greater corrosion resistance and robustness. In this study, we further report the effects of the oil viscosity on corrosion behaviors by testing bottle-shaped nanoporous anodic aluminum oxide surfaces impregnated with perfluorinated oils having various viscosities. Potentiodynamic polarization, salt fog and salt-water immersion tests show that the bottle-shaped nanoporous anodic aluminum oxide surfaces impregnated with more viscous oils result in the greater corrosion resistance and durability due to the enhanced oil retentivity. Despite the increased viscosity, the liquid oil still maintains the fluidity so that it fills physically damaged areas and allows the oil-impregnated surfaces to keep the self-healing capability. The result suggests that the anti-corrosion efficacy and durability of oil-impregnated porous surfaces can be optimized by modulating not only the pore geometry but also the oil viscosity.
Effect of Fe3+ Ion on Corrosion Behavior of 5083 Aluminum Alloy in Neutral Environment
Authors: Shinozaki Ippei
Published: February 2020

5000 series aluminum alloys are wildly used as high corrosion resistance aluminum alloys for Marine structures. As atmospheric corrosion test, iron powder and artificial sea water were spread on 5083 Aluminum alloy plate. A plate with only artificial sea water was also prepared. And the plates were kept in a humid environment for one week. After testing, pitting corrosion was only observed in plate with iron powder and artificial sea water. However, Fe3+ that is stable Fe ion was reported not to effect on corrosion of aluminum alloys.Cations derived from salts such as Na and Mg are investigated in detail as their effect on the corrosion resistance of aluminum alloys. On the other hand, the effect of Fe ions derived from steel materials, which are often used together in structural materials, on aluminum alloys is not clear. So, this study focused on effect of Fe ion on corrosion behavior of 5000 series aluminum alloy.

Then, the effect of Fe ion on the corrosion resistance of aluminum alloys was investigated through electrochemical method in beaker test. Open circuit potential in Fe3+ and Cl- solution was measured. FeCl3 aq which contained 0.53% Fe3+ and 1.0%Cl- was prepared. Its pH was adjusted to 7.0 with NaOH. NaCl aq (1%Cl-) was also prepared. OCP of 5083 Aluminum alloy in NaCl aq was -0.8 V vs SCE. However, OCP of FeCl3 aq was gradually lowered and -1.2V at last. Comparing the surfaces after 500hrs in FeCl3 aq and NaCl aq, Surface of 5083 Aluminum alloy in FeCl3 aq showed general corrosion. Surfaces at 0.5 hrs, 30 hrs, and 160 hrs in FeCl3 aq were also observed. The matrix arounds precipitations were dissolved at 0.5hrs. Dissolved area expanded after 30hrs. At last, Discoloration appeared at free surface after 160hrs. Al and O were detected at discoloration area by EDS. It implied that aluminum oxide likely was produced as corrosion product.

Anodic polarization curve in Fe3+ and Cl- solution was measured. The anodic polarization curve in FeCl 3 aq after 0.5hrs was the same as in the NaCl aq.However, OCP lowered after 24hrs. Anode current increment is necessary to lower the OCP. Then, activation of precedence dissolution caused OCP lowering as anodic reaction.Anodic polarization curve in 160 hrs had slightly higher activation potential and lower passivity current than that of 24hrs. So, Al oxide on the surface might possibly protect matrix from corrosion. However OCP kept lower and it did not return to the potential after 0.5hrs.So, the anode reaction was probably kept active even after the oxide was formed on the surface.

Therefore Fe3+ ion accelerated anode reaction that caused OCP lowering and corrosion acceleration of 5083 Aluminum alloy.
Effect of Inhibitor Modifications on Initial Localized Dealloying of Metallic Alloy Surfaces
Authors: Neupane Shova , Losada-Perez Patricia , Renner Frank Uwe
Published: February 2020

Despite a substantial number of reports on corrosion testing is available, only a few projects aim to understand the basic processes driving materials degradation. A special type of corrosion, localized dealloying, takes place on metallic alloy surfaces modified with self-assembled monolayers (SAMs) of organic inhibitors[1-2]. Corrosion initiation at the nanoscale can be addressed by controlling the spatial distribution and molecular organization of inhibitor-molecule SAMs at nano and micro length scales. We use micro-contact printing on model ultra-flat gold surfaces and obtain well-defined complex organic layers following a multi-step approach [3]. This approach was applied on locally atomically flat Cu3Au (100) surfaces to study initial localized dealloying which results in the initiation of localized dealloying being strongly dependent on the nanoscale surface morphology (Figure 1) [4]. In addition, different organic inhibitors containing -SH (thiol end) films were subsequently applied on polycrystalline Cu and CuZn alloys to analyse inhibitor film stabilities. Force Spectroscopy of Atomic Force Microscopy (FS-AFM) provides a stability status of such inhibitor layers by analysing AFM tip sample force interaction on inhibitor-modified metallic surfaces.

References:

[1] B. R. Shrestha et al, Farad. Discuss. 180 (2015) 191–204.

[2] F. U. Renner et al, Adv. Mater. 27 (2015) 4877–4882.

[3] S. Neupane et al, Langmuir. 34 (2018) 66–72.

[4] S. Neupane et al, to be published.

Figure 1
Single Event Experiment: A Powerful Approach for Studying Passivity Breakdown and Pitting Corrosion
Authors: Heurtault Stéphane , Joiret Suzanne , Vivier Vincent , Rouillard Fabien
Published: February 2020

Prediction of material lifetime such as stainless steels requires a clear understanding of passivation, corrosion, and pitting mechanisms. Despite its ubiquity and its history, the mechanisms of pitting are poorly understood, mainly because the stochastic behavior of the phenomenon, which results in many individual processes occurring simultaneously on the material surface. It is thus necessary to devise experiments which allow to work on a single pit for a better understanding of mechanisms governing pitting from its initiation to the propagation or its repassivation. Different experimental setup allowing the local injection of aggressive species such as chloride ions, have thus been developed [1-3], including a flow micro-device allowing a single pit to be initiated and then propagated over long time [4-6].

In this work, we show that we were able to reproduce, at will, the pitting of 316L stainless steel in order to study its propagation at various stages and to revisit the different parameters involved in the pitting process. Thanks to a statistical analysis performed on identical experiments, it was possible to build some zone diagrams showing the stability of pits as a function of the chloride concentration, the pit dimensions, and the electrode potential. Interestingly, the chemistry inside the pit was also studied as a function of the electrode potential. These experiments were performed with a specific experimental setup in order to measure the pitting current of a single pit simultaneously with the Raman spectrum thus opening new insight in the identification of species inside the pit. It was also possible to link the sulphate concentration (and thus the pH variation) inside the pit to the current as a function of time.

[1] K. Fushimi, K. Azumi, M. Seo, Use of a liquid-phase ion gun for local breakdown of the passive film on iron, J. Electrochem. Soc., 147 (2000) 552-557.

[2] K. Fushimi, M. Seo, Initiation of a local breakdown of passive film on iron due to chloride ions generated by a liquid-phase ion gun, J. Electrochem. Soc., 148 (2001) B450-B456.

[3] C. Gabrielli, S. Joiret, M. Keddam, H. Perrot, N. Portail, P. Rousseau, V. Vivier, Development of a Coupled SECM-EQCM Technique for the Study of Pitting Corrosion on Iron, J. Electrochem. Soc., 153 (2006) B68-B74.

[4] N. Aouina, F. Balbaud-Celerier, F. Huet, S. Joiret, H. Perrot, F. Rouillard, V. Vivier, A flow microdevice for studying the initiation and propagation of a single pit, Corros. Sci., 62 (2012) 1-4.

[5] S. Heurtault, R. Robin, F. Rouillard, V. Vivier, Initiation and propagation of a single pit on stainless steel using a local probe technique, Faraday Discuss., 180 (2015) 267-282.

[6] S. Heurtault, R. Robin, F. Rouillard, V. Vivier, On the Propagation of Open and Covered Pit in 316l Stainless Steel, Electrochim. Acta, 203 (2016) 316-325.
Effect of Environment Variables and Material Properties on the Limiting Current Density for Oxygen Reduction
Authors: Anderson Rachel , Hangarter Carlos , Policastro Steve
Published: February 2020

For aircraft alloys that have received surface treatments, primers, and topcoats to control self-corrosion due to precipitate phases, high-strength fasteners made of stainless steel or titanium alloys are the most obvious point of attack due to galvanic mismatches between the materials. However, the electrolytes that form from atmospheric processes can differ widely in composition and thickness. Dissolved oxygen concentrations vary due to temperature and salinity changes in the electrolyte. Recent attempts to model atmospheric corrosion have suggested that, at high salt loadings on the surface, electrolytes can form that have water layer thicknesses that appear as bulk electrolytes in terms of oxygen transport1. Experiments using rotating disk electrode (RDE) measurements and polarization curve data,2 have suggested an upper bound of approximately 800 mm on the diffusion layer thickness for oxygen that can be expected to form in a thin film of water. At distances beyond this thickness, convective flow is expected to dominate oxygen transport. In this report, we compare the results of RDE experiments that simulate thin film behavior on different substrate materials in different electrolytes with polarization data obtained under actual electrolyte thin films equilibrated at different relative humidity values, and bulk polarization measurements, as shown in Figure 1, in order to determine the effects of ohmic drop on the measurements and isolate relevant kinetic parameters. Isolating these effects is important in order to accurately model the corrosion currents arising from galvanic couples in which the oxides at which the reduction reactions are occurring can be changing in response to the changes in the electrolyte as the environment changes.

Figure 1. Bulk cathodic polarization curves in 0.6M NaCl at 25◦C for Pt, UNS S31600, and UNS R56400.

This work was sponsored by the Office of Naval Research, ONR, under grant/contract number N0001418WX00826; the views and conclusions contained herein are those of the authors and should not be interpreted as necessarily representing the official policies or endorsements, either expressed or implied, of the Office of Naval Research, the U.S. Navy or the U.S. government.

References

1 Van den Steen, N., Simillion, H., Dolgikh, O., Terryn, H. & Deconinck, J. An integrated modeling approach for atmospheric corrosion in presence of a varying electrolyte film. Electrochimica Acta
187, 714-723, doi:10.1016/j.electacta.2015.11.010 (2016).

2 Liu, C., Srinivasan, J. & Kelly, R. G. Electrolyte Film Thickness Effects on the Cathodic Current Availability in a Galvanic Couple. J Electrochem Soc
164, C845-C855, doi:10.1149/2.1641713jes (2017).

Figure 1
(Invited) Using Image Recognition to Identify Platinum Surfaces with Cyclic Voltammetry Scans
Authors: Baroody Heather A. , Muzaffar Tasleem Ahmad
Published: February 2020

Platinum is a key component in the catalyst layers of polymer electrolyte fuel cells where there continues to be major challenges delaying the full commercialization of fuel cell vehicles including platinum durability and lifetime.
Investigation of the Nanomechanical Properties of Titanium Oxide Films Synthesized Using Atomic Layer Deposition
Authors: Mohammed Yousuf , Zhang Kai , Baumgart Helmut , Elmustafa A A
Published: February 2020

Titanium oxides thin films are used in artificial heart valves due to their superb biocompatibility. They are used as photocatalysts in solar cells for the production of hydrogen and electric energy due to their stability, nontoxicity, and excellent photocatalytic properties [1]. TiO2 films are also used in heterogeneous catalysis, as a corrosion protective coating [2] and as electrode material in lithium rechargeable batteries. Above all TiO2 is utilized in massive amounts as white pigments in paints and toothpaste and cosmetic products.

It is reported that TiO2 exists in three different crystalline structures: rutile, anatase (both tetragonal) and brookite (rhombohedral). Many of the properties in these applications are strongly dependent on titanium oxide’s crystal morphology, surface area, and mechanical properties. TiO2 films of 500 nm thickness were synthesized using atomic layer deposition (ALD) on p-type Si (100). The films are tested for surface morphology, crystal structure and nanomechanical properties. The nanomechanical properties are tested using a nanoindenter from Keysight equipped with a three sided Berkovich diamond tip. The crystalline structure is verified using X-ray diffraction. The surface morphology is examined using atomic force microscopy (AFM) and the film thickness was verified using field emission scanning electron microscopy (FE-SEM) as indicated by the cross sectional FE-SEM image, shown in Figure 1.

We will discuss the structural and mechanical properties of the films citing the superiority of the ALD technique that is particularly used in the fabrication of the films that are presented in this study.

References

-Q. Hou, D.-M. Zhuang, G. Zhang, M. Zhao, and M.-S. Wu, Applied Surface Science, 218, 97 (2003).

Diebold, Surface Science reports, 48, 53 (2003).

X. Feng,G. Q.Xu, J. Lv,Q. M. Huang, Z. X. Zheng, andY. C.Wu, J. Electrochem. Soc, 160, H727 (2013).

Figure 1
(Invited) Homogeneous and Heterogeneous Material Based Nanotube Tunnel Field Effect Transistor with Core-Shell Gate Stacks
Authors: Hussain Muhammad Mustafa , Elatab Nazek , Hanna Amir N. , Hussain Aftab M. , Fahad Hossain M , Shaikh Sohail
Published: February 2020

In the last forty years, complementary metal oxide semiconductor (CMOS) technology has made tremendous progress and its advancement has enabled physical scaling of CMOS electronics technology. Physical scaling has offered us higher data processing performance but with the increased penalty of power consumption. As we approach physical scaling, alternative materials, device architecture, physics and integration strategies have been proposed to overcome this fundamental physical roadblock. This problem specially exaggerates for implantable and bioelectronics where we need higher data performance but at the same time lower power consumption. Specially body integration restricts heat dissipation related power consumption to 40 mW/cm2. Therefore, we have conceptualized a newly minted nanotube architecture with the classical crystalline material such as silicon (Si), Silicon-Germanium (SiGe), Germanium (Ge), III-V materials and applying tunnel physics we have developed an integration strategy where a core-shell gate stacks in a coin like configuration (sensors on sensing surface connected via through-polymer-via (TPV) to homo and heterogeneous crystalline materials based nanotube tunnel FETs with core-shell gate stacks on the other side for higher information processing performance and lower power consumption. In this talk, we will discuss this novel device architecture, its physics, choice of materials and integration strategy specially for brain-machine interfacing.
Development of Printable Organic Solar Cells in a Large Area
Authors: Son Hae Jung
Published: February 2020

Solar cells based on the photovoltaic effect are an effective method to convert solar energy into electricity. It has become attractive to find solar cell technologies which exhibit lower manufacturing costs by utilizing inexpensive and abundant materials. Some additional advantages conveyed by organic solar cells are that they are lightweight and flexible and allow for scalable material production and cost effective roll-to-roll coating and printing techniques. Efficiency of >10% was disclosed in small area solar cells with various device architectures, which indicated the rapid progress over the last several years and the great potential of organic solar cells as an alternative source of energy. In order for organic solar cells to fully mature from research and development into cost effective products, solar cell technology at a small size needs to be realized at a large scale. And for this, it is highly important to develop new conjugated polymers and understand the fundamental working mechanism of the materials. In the presentation, we developed new conjugated polymers for large-area solar cell technologies and studied the effects of conjugated polymers on solution processing and photovoltaic performance in large area organic solar cells.