bluuebunny/crossref_metadata_2025 huggingface dataset:
Molten Salt Corrosion of SiC Fibers
Authors: Opila Elizabeth J. , Herweyer Lucas
Published: February 2020

The Na2SO4-assisted hot corrosion resistance of Hi-Nicalon, Hi-Nicalon S, Sylramic and Sylramic iBN SiC fibers was characterized as a function of time and temperature. Na2SO4-loaded fibers were exposed in a tube furnace with 0.1% SO2/O2 flowing gas for times between 45 minutes and 24 hours, at temperatures between 900 and 1100C. Fibers were characterized after hot corrosion exposure, and after 24 hour water and HF soaks, by weight change measurements, Scanning Electron Microscopy, and Energy Dispersive X-Ray Spectroscopy. Inductively Coupled Plasma Optical Emission Spectroscopy was used to determine the elemental composition and concentration of dissolved corrosion products found in the water and HF soaks. It was observed across all fiber types that hot corrosion attack was rapid and severe, with fiber fusion, surface pitting and non-uniform scale build-up as common microstructural features. Differences in hot corrosion reactions were observed in surface morphologies and weight change measurements. Time dependence revealed that Hi Nicalon fibers exhibited the largest weight gain, while Sylramic, Sylramic iBN and Hi Nicalon S fibers had similar weight gains.
Soaking Experiments for Understanding Corrosion Behavior of Zircaloy with Molten Stainless Steel−B4c at Elevated Temperatures
Authors: Matsuura Suguru , Nanko Makoto , Kurata Masaki
Published: February 2020

Abstract:

 Recently nuclear power reactors have been commonly used for generation of electricity as well as thermal power generation and hydroelectric generation. Boiling water-type nuclear reactors include fuel rods consisting of uranium pellet fuels cladded with Zircaloy (Zrc) tube and control rods consisting of boron carbide (B4C) powder cladded with stainless steel (SS) plates in the pressure vessel..

When severe accident occurs, water coolant circulation is halted, leading to increase temperature of these fuel rods. Thermal radiation from the fuel rods results in melting the control rods comprised of SS and B4C. The SS-B4C melts can react with Zrc cladding of the fuel rods. Nuclear fuels will be exposed into the ambient atmosphere. However reaction behavior of Zrc cladding with SS-B4C melts has not been researched. Previous study were mainly on solid state reaction of Zrc cladding and control rods [1-3].　In order to study corrosion behavior of Zrc cladding with molten control rods, the soaking experiments of Zrc into molten SS-B4C were conducted.

A powder mixture of SS and 5mol%B4C was heated at 1400°C for 12 h to synthesize the melt. After decreasing temperature to test temperature of 1175, 1200, 1225 and 1250°C, plates made of Zircaloy-4 were soaked to melted SS-B4C for 0 to 60 min. After soaking, the plates were removed from the melt. Thickness of the plates was measured by using an optical microscope. Reaction products on the plates were evaluated by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), electron probe micro-analyzer (EPMA) and X-ray diffraction (XRD).

The value of thickness reduction of Zrc was increased linearly with increasing the soaking time. The reduction rate of Zrc was increased with increasing temperature. The value of apparent activation energy on the thickness reduction rate was equal to 333 kJ/mol.

References:

[1] Steinbruck M., J. Nuclear Material 400 (2010) 138.

[2] Hofmann P., Markiewicz M., Spino J., KfK 4598, Kernforschungszentrum Karlsruhe GmbH,Karlsruhe, Germany, (1989).

[3] Nagase F., Uetsuka H. and Otomo T., JAERI-Research 95-085 (1995).

Acknowledgements

This study is performed in “Advanced Multi-scale Modeling and Experimental Tests on Fuel Degradation in Severe Accident Conditions", Ministry of Economy, Trade and Industry.
(Invited) Preparation of Ordered Anodic Porous Alumina Through-Hole Membrane and Its Applications
Authors: Yanagishita Takashi , Masuda Hideki
Published: February 2020

Anodic porous alumina, which is a typical self-ordered nanohole array material formed by anodization of Al in an appropriate acid solution, has recently attracted increasing interest as a key material for the fabrication of functional devices1,2). For the various applications of ordered anodic porous alumina, the preparation of through-hole membranes is important. The fabrication process for porous alumina through-hole membranes has been investigated for a long time3). However, a facile and reliable process that does not require special techniques has not yet been established. To overcome this problem, we have been developing a new high-throughput process for fabricating through-hole alumina membranes4). This process is based on the new finding that through-hole membranes can be easily obtained by dissolving a two-layered sample in an appropriate etchant, which was formed by a first anodization under standard anodizing conditions and a subsequent anodization in concentrated H2SO4. This is because the oxide layer formed in the concentrated H2SO4 can be easily dissolved in an appropriate etchant. After the detachment of the membrane, the residual Al substrate could be repeatedly used for the preparation of ordered through-hole membranes. In this report, recent results of the preparation of ordered anodic porous alumina through-hole membranes and its applications will be presented.

References

1) T. Yanagishita and T. Hidaka, M. Suzuki, and H. Masuda, J. Vac. Sci. Technol. B, 34, 021804 (2016).

2) H. Masuda and K. Fukuda, Science, 268, 1466 (1995).

3) H. Masuda and M. Satoh, Hpn. J. Appl/ Phys., 35, L126 (1996).

4) T. Yanagishita and H. Masuda, Electrochim. Acta, 184, 80 (2015).
(Invited) Systematic Engineering of Structured Magnetic Nanowire Arrays for Three-Dimensional Data Storage
Authors: Bachmann Julien , Bochmann Sebastian , Lee Jihyun , Fernandez-Pacheco Amalio , Wartelle Alexis , Trapp Beatrix , Cowburn Russell , Fruchart Olivier
Published: February 2020

A preparative strategy is presented towards a three-dimensional magnetic data storage medium based on arrays of parallel, cylindrical metallic nanowires structured along their length. The preparation utilizes porous anodic alumina as an inert template that defines the geometry (cylinder length, diameter and pitch), combined with galvanic deposition of the functional materials inside the pores. We demonstrate that the composition of nickel-cobalt alloys can be tuned systematically at one constant deposition potential, whereby the magnetocrystalline anisotropy can be minimized. The wires then display maximal shape anisotropy. The definition of bits along the 'vertical' direction of each wire is performed either by the introduction of non-magnetic segments or by modulation of the pore diameter. The former strategy is made possible by pulsed electrodeposition from a ternary electrolyte. The latter structure is achieved by combining several anodization steps. We demonstrate the presence of magnetic domain boundaries at such designed pinning points using bulk magnetometry and single-wire imaging techniques. As future read/write elements we embed ultrathin oxide layers at mid-height of the wires by atomic layer deposition, and we demonstrate a measurable magnetoresistance effect of these layers.

Figure 1
Control of the Magnetic Properties of a Magnetic Field Guidable Biocompatible Nanovehicle
Authors: Granitzer Petra , Rumpf Klemens , Reissner Michael , Poelt Peter
Published: February 2020

Within this work a biocompatible magnetic nanovehicle which is movable in aqueous solutions by a magnetic field is presented. The nanovehicle consists of a porous silicon template and encapsulated iron oxide nanostructures. Both materials employed, porous silicon (PSi) as well as iron oxide are known to be biocompatible (1, 2). Mainly the synthesis of the nanocomposite as well as the magnetic properties of the systems will be discussed.

Two routes are employed to produce various iron oxide phases of the embedded nanostructures within PSi. On the one hand, readily synthesized magnetite nanoparticles (NPs) which are superparamagnetic (SPM) due to their size, are infiltrated into the pores. On the other hand chemical deposition of iron oxide inside the PSi templates is used. The loading process of the templates depends not only on the pore-diameter/particle-size ratio but also on the particle-template interactions due to different surface treatments (e.g. as etched or oxidized PSi). Considering the chemically grown iron oxide, it does not form monodisperse particles but mainly clusters of particles. An increase of the temperature during the deposition resulted in a decrease of the coercivity which can be due to an iron oxide phase modification or due to a modification of the shape of the deposits.

An adjustability of the magnetic properties of the system is achieved by a variation of the iron oxide loading within the PSi. An investigation of the iron oxide deposition dependent on the template and on the chemical parameters as well as of the magnetic properties in dependence on the particle size and on the template morphology of the nanocomposite will be presented.

Temperature dependent magnetization measurements give information about the nature of the particle filling (packing density, spatial distribution), from field dependent magnetization measurements characteristics such as saturation magnetization, coercivity and remanence can be evaluated.

For a sample containing a moderate filling with 8 nm Fe3O4 NPs the saturation magnetization has been estimated in using the measured hysteresis curves and considering the 1/H approach to be in the order of 6×10-3 emu/cm2. The amount of iron oxide particles inside the pores of the PSi matrices has been estimated in taking the magnetic moment of an individual iron oxide NP which is about 1.49 × 10-18 emu. In this case this leads to a number of about 1.3 × 1019 particles/cm3. The coercivity HC of the nanocomposite systems below TBdecreases with decreasing particle size which is due to SPM relaxation effects.

The fabricated magnetic nanovehicles can be tuned in its magnetic behavior (e.g. coercivity, TB) due to the morphology of the template, the particle size and the filling conditions. The resulting magnetic moment of the samples is high enough to be moved within aqueous surroundings by a magnetic field of 0.1 T.

(1) D. Ling, T. Hyeon, Small 9, 2013.

(2) L.T. Canham, Adv. Mater. 7, 1033, 1995.
Dealloying Mechanism of Bulk-AlCu Intermetallic Phases (Al2Cu, Al7Cu2Fe, Al2CuMg) : Effect of Crystallographic Structure and Electrolyte
Authors: Rocca Emmanuel , Tardelli Joffrey
Published: February 2020

The aluminum alloys with high mechanical properties, the 2xxx and 7xxx series, are very sensible to corrosion because of the presence of numerous coarse intermetallic phases in the aluminum matrix. These phases are often responsible of the formation of pits in corrosion conditions, or the formation of defects in the anticorrosion coatings such as anodized layers.

The objective of this work is to study the behavior of different AlCu intermetallic phases (Al2Cu, Al7Cu2Fe, Al2CuMg) in the 7XXX and 2XXX alloys in NaCl electrolyte and H2SO4 electrolyte.

Firstly, bulk-samples of phases (centimeter size) were synthesized by quick melting in an induction furnace followed by several annealing steps under argon. The electrochemical behavior of the three phases was characterized by stationary electrochemical measurements and electrochemical impedance spectroscopy in function of immersion time at open-circuit potential. The surface layers on each phase were observed on surface and metallographic cross-section by FEG-SEM, EDX spectroscopy and X-ray Photoelectron Spectroscopy.

In NaCl electrolyte, all the studied intermetallic phases undergo a dealloying phenomenon which leads to the formation of a pure copper nanometer sponge. On the surface, the copper sponge can be partially embedded and covered in an aluminum hydroxide gel according to the hydrodynamic conditions. In sulfuric acid, the dealloying phenomenon depends on the copper content in the intermetallic phase and on its crystallographic structure. According to the density of the Cu plan, some phases can form a compact layer of copper that passivate the phase, some others form a nanometer sponge of copper.

In conclusion, after the dissolution of aluminum, magnesium or iron atoms, copper atoms diffuse on the surface of phases to form either crystalline copper nanometer particles, or compact copper layer according to the electrolyte properties and their crystallographic structure.
Enhanced Electrocatalytic Activity on Water Splitting with Niox Nanoflakes Electrode Fabricated Via Selective Etching and Reconstruction of Niw Amorphous Films
Authors: Ling Yunhan , Qin Fei , Yu Siqi , Gu Yanhong
Published: February 2020

Hydrogen is now widely regarded as most suitable to replace fossil fuels for it burns clean, producing only water and has the highest energy density per unit mass. However, hydrogen is not freely available in nature and needs to be produced, either from water or other compounds. Alkaline water electrolysis offers a simple method for mass production of hydrogen but suffers from the sluggish kinetics of the anodic oxygen evolution reaction, calling for the development of low-cost and durable oxygen evolution electrocatalysts with high activity.

In this work, we report an enhanced electrocatalytic activity on water splitting with NiOx nanoflakes electrode fabricated via selective etching and reconstruction of NiW amorphous films. It was found that the highly electrocatalytic activity was attributed to the increase of specific surface area of the electrode as well as the change of valence states of nickel. It is anticipated that the modification of as-fabricated nanostructured electrodes with bandgap engineering which is under way will further improve the efficiency and prolong the durability, making them potential and more attractive in addressing the pressed technological issues.
Atmospheric Corrosion Monitoring of Carbon Steel in Snowy Cold Region
Authors: Katayama Hideki
Published: February 2020

Atmospheric corrosion is a complex phenomenon that proceeds under thin water film while influencing a variety of environmental factors. Most of atmospheric corrosion researches generally have been conducted by exposure test. However, the sampling after exposure test are regularly carried out, so it is not possible to catch the changes in the corrosion resistance of samples to environmental factors continuously. In addition, many results are obtained from the data of atmospheric corrosion test in the subtropical region, and there is not much corrosion data in the cold snowy regions. In this study, atmospheric corrosion rate of carbon steel has been monitored in snowy cold region.

Concentric ring type corrosion sensors were used for the corrosion monitoring. The sensor consists of two carbon steel electrodes embedded concentrically in epoxy resin. The exposed areas of both electrodes are the same. Two test racks for outdoor exposure test were placed in Ishikari exposure test site. The height of the test rack was adjusted in consideration of the average snow accumulation, in order to investigate the influence of snow. The exposure test was started in December 2015. There was little snow at the start of the exposure test in Ishikari because snowfall in 2015 was less by the mild winter. The corrosion sensors were set on the test rack at an inclination of 45 degree to the south. The impedances at two different frequencies of 10kHz and 10mHz were measured continuously for corrosion monitoring. The impedances at 10kHz and 10mHz correspond to the solution resistance and the sum of the solution resistance and the corrosion resistance, respectively.

Relationship between snowfall and the solution resistance was investigated in the initial process of exposure test. The solution resistance during snowfall showed a low value, which suggests that the surface was getting wet by snowfall. Further, the solution resistance of a few hundred ohms was obtained during wetting. This means the electrical conductivity of the snow is relatively high. The test site is away only about 500 meters from the sea. Therefore, the electrical conductivity is attributed to airborne sea salt in snow. On the other hand, the corrosion sensor also gave a high corrosion rate during snowfall, indicating that the corrosion is in progress. Although the temperature is very low during snowfall, even the wetting of the surface by snow causes corrosion.
AE Monitoring of Hydrogen Embrittlement Crack in Maraging Steel
Authors: Shinozaki Ippei , Nakayama Gen , Sakakibara Yohei
Published: February 2020

AE (Acoustic Emission) result from initiation and propagation of cracks in materials. Then AE monitoring can detect the micro cracks.

Maraging steels witch have superior strength are used as structural materials. However, these have hydrogen embrittlement problem under humid air.

Hydrogen embrittlement resistance of maraging steels is usually estimated by visual testing (VT) which checks whether rupture or not in laboratory. However the testing method is batch style testing. Then it is difficult to estimate the exact rupture time through VT. Then the AE monitoring applied to detect hydrogen embrittlement of maraging steel.

Hydrogen embrittlement crack accelerated by a droplet of NaCl solution that was set on the center of the maraging steel thin plate. In this case, the droplet was too small to determine the hydrogen embrittlement crack through the electrochemistry method.AE sensor also set on the plate and detected AE signals.AE signals were classified as to amplitude, frequency, and wave form. AE event rate was also focused. The surface crack propagation was also recorded by digital camera. Crack growth was confirmed from the pictures.

AE event counts separate 3 regions. At first region, AE event counts detect before surface cracks were able to be observed. In this region, cracks may initiate under the droplet. At Second region, AE event counts were constantly increased. In this region it was observed that increment by crack growth was constant by digital camera. It shows that means the second region was the crack growth stage. At third region, AE event rate was increased twice. The second crack growth was observed in digital camera images. Then AE event rate reflected the number of cracks. There was good relation between crack propagation and AE event rate. AE event rates were difference between types of steels. The other steel which has high hydrogen embrittlement resistance tend to have low AE events rate.
Effect of Mg2+ on the Corrosion Behavior of Zinc
Authors: Tada Eiji , Tsurumaki Yumiko , Nishikata Atsushi
Published: February 2020

Zinc-coated steels have been widely used in various industrial fields such as automobiles and construction since they have excellent corrosion protection in atmospheric corrosion environments. To improve corrosion resistance of the coating, zinc-alloy coatings containing Mg have been develped and they have demonstrated superior corrosion resistance in terms of duration to appearance of red rusts on steel compared with zinc coatings. However, the effect of Mg on the improvement of corrosion resistance of the zinc-alloy coatings is still unclear. In this study, the effect of Mg2+on the corrosion behavior of zinc in Cl-containing aqueous environmnts is investigated by electrochemical measurments and surface analysis.

A pure zinc plate (purity: 99.5%) was used as a sample. The zinc plate was grounded with SiC papers up down to JIS #2000 grit and then rinsed in EtOH for several minutes. Test solutions used in this study were aqueous solutions of 1 M MgCl2and 2 M NaCl. Corrosion potential and polarization resistance for zinc were monitored during the immersion in the test solutions. The reciprocal of polarization resistance was used as a measure to evaluate corrosion rate. After the immersion, the surface of zinc was investigated by SEM-EDX, XRD and FE-AES.

From the results of the reciprocal of polarization resistances measured in the test solutions, it was confirmed that corrosion rate of zinc in MgCl2 is lower than that in NaCl during the immersion. Furthermore, it was also found that the corrosion rate in MgCl2 decreases obviously ca. 4 h after immersion in the solution. At this time, corrosion potential for zinc in MgCl2 shifted in the noble direction. These results indicate that corrosion rate of zinc is decreased due to the inhibition of anodic dissolution of zinc. From the results of surface observation and anaysis of zinc after the immersion, it was found that finer corrosion products of zinc were formed in the case of MgCl2 compared with that of NaCl. This result suggests that the differenrce in the morphology of zinc corrosion products can be related to the difference in the corrosion resistances in both solutions.
Improving the Corrosion Resistance of Magnesium-Aluminum Alloys Using Microstructural Design
Authors: Esmaily Mohsen , Svensson Jan-Erik , Johansson Lars-Gunnar
Published: February 2020

Magnesium-aluminum (Mg-Al) alloys are crucial lightweight materials with exceptional properties. However, unfortunately, they exhibit rather poor corrosion resistance, and, thus, they have attracted enormous research efforts and triggered a great deal of technological developments during the last decade. Despite the impressive progress in understanding the corrosion mechanism of Mg and Mg alloys, several shortcomings and bottlenecks still exist, preventing more widespread use of Mg alloys in various applications. Recent studies have shown that the corrosion properties of commercial Mg-Al alloys can be greatly improved by applying a semi-solid casting procedure. This promising method involves the rheocasting (RC) technique, in which the required slurry is prepared by the RheoMetal process, enabling the manufacturers to design the alloys’ microstructure with a rather high degree of freedom. A series of comprehensive accelerated corrosion tests in constant/cyclic relative humidity and temperature show that the alloys produced by the RC technique exhibit up to four times better corrosion resistance than their high pressure die-cast (HPDC) counterparts. In this study, the influence of alloy microstructure, in terms of the effect of all the microstructural constituents (α, β, η and casting pores), on the mechanisms of degradation of the RC and HPDC Mg-Al alloys in ambient atmosphere is discussed in detail. The results imply that it is (in principle) possible to use the component fabrication step (i.e., casting) to modify alloy microstructure so as to mitigate corrosion properties. The idea is generic and may also be applicable to other alloy systems.
Effect of Sulfate Ions on Repassivation Behavior of Crevice Corrosion on Type 316L Stainless Steel
Authors: Aoyama Takahito , Sugawara Yu , Muto Izumi , Hara Nobuyoshi
Published: February 2020

Crevice corrosion is known to be a serious problem of stainless steel structures in Cl- containing environments. The growth and repassivation behavior of crevice corrosion are significantly influenced by the solution composition of corrosion environments. To clarify the repassivation behavior of crevice corrosion, an in situ observation is a promising technique. This is because the quantitative relationship between current values and corrosion morphology could be analyzed. The current distribution inside the crevice can be estimated from the spreading of crevice corrosion depth. In this study, an in situ observation technique was applied to the study of the crevice corrosion of stainless steel. In addition, to clarify the effect of the solution composition outside the crevice on repassivation behavior, an electrochemical flow cell was newly designed.

Type 316L stainless steel was used as specimens. The specimens were heat-treated at 1373 K for 3.6 ks and then water-quenched. An electrochemical flow cell was fabricated (Fig. 1). The crevice was made by pressing a glass sheet to the specimen surface, and the specimen was polarized at 0.25 V (vs. Ag/AgCl, 3.33 M KCl). Crevice corrosion tests were initially performed in a flowing 1 M NaCl solution (298 K). During the corrosion tests, the corrosion behavior of the specimen surface inside the crevice was observed using an optical microscope through the glass sheet, and then the time-lapse video was produced by capturing one frame per 10 seconds. In some cases, the flowing solution was changed from 1.0 M NaCl to 0.88 M Na2SO4, after the initiation of the crevice corrosion. The solution was changed when the current reached a value of 100 µA.

Figure 2a shows the time variations of the current during the crevice corrosion tests. In the case of test A, the solution was not changed. In test B, the solution was changed from NaCl to Na2SO4 when the current reached the value of 100 µA. In both cases, the current first decreased to ca. 5 µA with the lapse of time and at about 400 s, it became to increase rapidly due to the initiation of crevice corrosion. In test A, the current increased up to ca. 5 mA. On the other hand, in test B where the solution was changed, the current decreased after reaching a maximum value of 3 mA at ca. 2.5 ks. The results of in situ observation of the specimen surface are shown in Fig. 2b. In test A, the corroded area propagated along the crevice mouth (Fig. 2b). At the beginning of crevice corrosion in test B, its propergation was similar to that of test A. When the current began to decrease at ca. 2.5 ks, the direction of corrosion propagation changed toward the inside of crevice (Fig. 2c). Finally, when the current decreased to ca. 1.2 µA, no lateral propagation of the corroded area was observed, suggesting that the repassivation inside the crevice was completed.

Figure 1
Extending the Life-Time of Low Cost Fuel Cells
Authors: Bedouet Max
Published: February 2020

Extending the bipolar plate lifetime of low-cost fuel cell.

Energy conversion sources that offer lower carbon emissions, increased efficiency and reduced environmental impact at a competitive cost are a key requirement for future low carbon transport and stationary power generation applications.Fuel cells are promising candidates but widespread uptake has so far been hindered by the high cost of materials and manufacturing in addition to limited durability under realistic operating conditions. There is a clear need for a lower cost approach but without sacrificing performance or durability.

Bipolar plates are responsible for collecting current, supplying the fuel to the MEA as well as exhausting water produced at the cathode side1. Metallic bipolar plates must be resilient, non-porous, conductive with a low contact resistance and obviously cheap for mass market penetration2. The US Department of Energy (DoE) has introduced target cost plans for 2020 on different PEM fuel cell components, including bipolar plates3. The technical plan states that the corrosion rate must be below 1 µA.cm-2 and that an interfacial contact resistance must be below 10 mΩ.cm2 at a compaction pressure of 140 N.cm-2. These condition has to be attained with a cost below 3 $kW-1. Bipolar plates account for 45-60 % of the stack cost, 80 % of the weight, and almost all the volume of the PEM fuel cell stack.

The flexiplanar approach uses a metallic substrate mounted on a printed circuit board (PCB) in order to produce a low cost cell. Copper is a strong candidate for this purpose: it is robust, has a high conductivity and a low contact resistance as well as a possibility of scalable hydroforming or stamping4, which is an important feature in order to produce a flow field plate. However, due to the harsh conditions within the fuel cell stack such as a high potential and temperature, the copper interface must be protected by a coating. Coatings applied on the flow field plate must have a good electrical conductivity, a low contact resistance and also have to be resilient to fuel cell operating conditions i.e. 120 °C and 1.2 V. In recent years, there has been an increasing amount of literature on carbon polymer blend used as metallic substrate protector19
,
20
,
21. Carbon-polymer mixtures are commercially available at reasonably affordable prices. Nevertheless, they are also likely to be corroded due to carbon micro-particles dispersed in the polymer. Hence further investigation needs to be done in this poorly understood area.

1            Polymer Fuel Cells - Cost reduction and market potential, C. Trust, 2012.

2            C. Spiegel, Designing and Building Fuel Cells, 2007.

3            T. Plan and F. Cells, 2015, 1–49.

4            ASM International, Copper and Copper Alloys, ASM International, 2001.

5            W. L. Wang, S. M. He and C. H. Lan, Electrochim. Acta, 2012, 62, 30–35.

6            Y. Show and K. Takahashi, J. Power Sources, 2009, 190, 322–325.

7            Y. B. Lee and D. S. Lim, Curr. Appl. Phys., 2010, 10, S18–S21.
Corrosion Protection of Zinc Alloy Coated Steel By Organic Coatings Pigmented with Strontium Aluminium Polyphosphate
Authors: Liu Yanwen , Zhou Xiaorong , Lyon Stuart B , Emad Reza , Hashimoto Teruo , Gholinia Ali , Graham Derek , Gibbon Simon R , Francis David
Published: February 2020

Strontium aluminium polyphosphate (SAPP) inhibitive pigment formulated into an organic primer for corrosion protection of zinc alloy coated steel in 0.6 M sodium chloride solution was investigated by serial block face imaging using scanning electron microscopy, which provided detailed information on inhibitor releasing, transportation and reaction with zinc alloy substrate. It was found that SAPP contains at least two distinct particle types, one which is strontium rich and another which is aluminium rich. These particles have different release characteristics which are dependent on the local environment. The strontium rich particles release their components faster in near neutral and acidic environment compared with the aluminium rich particles whilst in an alkaline environment the reverse is found. The pH related inhibitor release process and the mixture of the inhibitive pigment with different strontium to aluminium ratios ensure the availability of the inhibitor at both anodic and cathodic locations, which consequently reduced/retarded the corrosion of zinc alloy coated steel.
Adhesion and Interface Study of Cu/Ni/Polyimide Film
Authors: Kim Seung Min , Lee Jeong Gil , An Joong Kyu , Jin Shan hua , Jun Sang Hyun , Kim Young Tae , Park Joon Woo
Published: February 2020

The aim of this study is to achieve a better understanding of copper and polyimide film interfacial properties, such as bonding strength between two materials. The effect of nickel electroplating on the surface of copper foil on adhesion between two materials also discussed. These interfacial studies of nickel layers electroplated on the copper foil have been investigated using SEM, XPS, ToF-SIMS, and so on. The bonding strength of copper foil was proportion to the amount of nickel on the copper foil. In addition, the fracture location varied according to the amount of nickel on the surface of copper foil and occurred in the middle of the polyimide film of the high adhesion strength.
Novel Silane-Polymer Composite Coating for Corrosion Protection of Mg-Zn-Al Alloy Against Corrosion in NaCl Solution
Authors: BinSabt Mohammad , Al-Kharafi Faizah M , Abditon Maryam , Galal Ahmed
Published: February 2020

The electrochemical behavior of magnesium-aluminum-zinc alloy with composition Mg(93)-Zn(1)-Al(6) alloy is studied in 3.5% NaCl containing aqueous electrolytes. Potentiodynamic polarization and electrochemical impedance (EIS) measurements show a noticeable decrease in polarization resistance indicating the spontaneous dissolution of the alloy. The alloy was treated with a novel silane-polymer coating that proved effective in protecting the surface against corrosion. The protecting film is composed of 1,2-bis(triethoxysilyl)ethane-poly(vinyl alcohol) hybrid (TESE-PVA). The hybrid film was administered to the alloy surface using different approaches; sequential mechanical dropping and spin-coating of TESE-PVA or PVA-TESE, a mixture of TESE-PVA, and PVA was cross-linked and sequentially administered with TESE.

The alloy surface was examined before and after exposure to the NaCl solution using field emission electron microscopy/energy dispersive analysis with x-ray and x-ray photoelectron spectroscopy. Severe surface damage is noticed for the bare alloy with the formation of oxides, hydroxides and oxy-salts mainly of magnesium. The film is optimized using different concentration ratios between PVA-TESE, sequence of application and film thickness. The Mg-alloy coated with the “optimized” hybrid coating was tested for extended time exposure in the chloride solution and the coating proved effective in protecting the Mg-alloy. The film thickness and surface wettability were also determined with the film displaying relative increase in the hydrophobic character. Surface enhanced Raman spectroscopy (SERS) was used to characterized the structure of the film coating over the surface before and after exposure to the corroding medium.
In Situ Small-Angle Neutron Scattering of Mesoporous Electrode Materials
Authors: Bridges Craig A , Sun Xiao-Guang , He Lilin , Dai Sheng
Published: February 2020

A wide variety of techniques have been developed in the past 5-10 years to better understand changes in the interfacial chemistry and bulk structure of electrode materials during in situ cycling. Small angle scattering is particularly suited to studying changes in the microstructure of electrodes for length scales on the order of 1-300nm. When mesoporous electrodes are employed, sufficient signal may be present for the SANS technique to provide information on electrode-electrolyte interfacial surface layers. Having demonstrated the utility of small angle neutron scattering (SANS) to study the lithiation process in ordered mesoporous hard carbon, we have expanded this work to examine other electrode systems (e.g., TiO2), electrolytes, and counter electrodes. Here we examine the time-dependent changes in pore structure and interfacial chemistry with respect to electrolyte formulation using in situ SANS studies of mesoporous electrodes.
Behaviour of Nanostructured Si-Based Anode Materials Studied By Atom Probe Tomography and Hard X-Ray Photoelectron Spectrocopy
Authors: Renner Frank Uwe , Pradeep Konda Gokuldoss , Zheng Yueming
Published: February 2020

Lithium-ion batteries (LIB) are considered for electric vehicles (EV) as well as for home or off-grid energy storage for example in combination with photovoltaics. These specific applications drive the research on high energy density, cost-effective, safe and environmental friendly battery materials. To obtain deeper insight into the reaction mechanisms advanced characterization such as in-situ TEM or in-situ XRD1 are often used in combination with simplified model systems. For LIB anodes Si has the highest specific capacity among all anode materials. However, the mechanical fatigue (lack of microstructural integrity) associated with large volume expansion of pure Si during the lithiation process has hindered their wider use for commercial applications so far. Also, there are a series of side reactions which happen at the surface forming the solid electrolyte interface (SEI). In this work we investigate the role of mechanically confined nanocrystalline Si particles being embedded in a SiTiNi matrix2. Samples are produced by melt-spinning from a rapidly solidified SiTiNi alloy. The ribbon exhibits a nanocomposite microstructure with nano-Si particles (~50-200 nm) as potential sites for Li-storage embedded in an amorphous matrix of SiTiNi (STN). Such alloys have shown potential for anode materials in high capacity Li-ion batteries. Systematic lithiation and de-lithiation cycles were performed and selected samples after different cycles were investigated using Atom Probe Tomography (APT) to understand the Li diffusion mechanism in and out of the Si particles. We consider Atom Probe Tomography as a powerful tool to understand the phase changes at an atomic level3. Aided by Focus Ion Beam (FIB), we can address the nm-scale element distribution in any local structure. On the other hand, Hard X-Ray Photoelectron Spectroscopy (HAXPES) is adopted for a detailed SEI study. The employed high energy X-ray beams can probe deeper information of core level photoemission

[1] Bach, P.; Valencia-Jaime, I.; Ruett, U.; Gutowski, O.; Romero, A.H.; Renner, F.U. Chemistry of Materials (2016), doi: 10.1021/acs.chemmater.5b04719;

Renner, F.U.; Kageyama, H.; Siroma, Z.; Shikano, M.; Schröder, S.; Gründer, Y.; Sakata, O. Gold Model Anodes for Li-Ion Batteries: Single Crystalline Systems Studied by In Situ X-ray Diffraction, Electrochim. Acta 2008, 53, 6064-6069.

[2] Son et al. “A Highly Reversible Nano Si Anode Enabled by Mechanical Confinement in an Electrochemically Activated LiXTi4Ni4Si7 Matrix.” Advanced Energy Materials 2 (2012), 1226.

[3] Diercks et al., Microscopy of Chemical and Mechanical Heterogeneities in Lithium Cobalt Oxide, Microscopy and Microanalysis 21 (2015), 523.
(Invited) Electrochemical Impedance Study on Anodic Dissolution of Magnesium in Sodium Sulfate Solution
Authors: Umetsu Keita , Hoshi Yoshinao , Shitanda Isao , Itagaki Masayuki
Published: February 2020

Magnesium and its alloys are widely used in the industrial field such as the auto-mobile and electronic devices. However, the high reactivity of Mg and its alloys in the aqueous solution limits the application of magnesium. The hydrogen evolution rate on dissolving magnesium is increased when the applied anodic potential is increased, which is called the Negative Difference effect (NDE)1). Some mechanisms related to the anodic dissolution and hydrogen evolution of magnesium have been proposed in previous researches 1-3). Williams et al.2) investigated the local current on the anodically polarized magnesium surface by in-situScanning Vibrating Electrode Technique (SVET). They found that the anodic dissolution of magnesium is shown to be highly localized in nature and accompanied by significant cathodic activity. The reactions for the anodic dissolution of magnesium and hydrogen evolution occurred on the magnesium surface are expressed by the following reactions.

Mg → Mg2+ + 2e
-(1)

2H2O + 2e
- → H2 + 2OH-(2)

They2) implied that the hydrogen evolution on the magnesium surface is accelerated by the applied anodic potential. Cain et al.3)supported this theory by investigation using inductively coupled plasma optical emission spectroscopy (ICP-OES) and Rutherford backscattering spectrometry (RBS). However, the anodic dissolution mechanisms of magnesium are not well understood yet.

Our group have been investigating magnesium dissolution by 3D impedance spectroscopy. In our previous research, it was found that the inductive loops appeared in impedance spectra of magnesium are originated from Volmer and Heyrovsky reaction by calculating Faraday impedance 4). In the present study, we focus on the localized reaction of magnesium dissolution and hydrogen evolution. The local electrochemical impedance spectroscopy (LEIS)5)combined with 3D impedance spectroscopy was applied to the investigation of anodic dissolution of Mg.

Reference:

[1] G. Song, A. Atrens, D. Stjohn, J. Nairn, Y. Li, Corrosion Science, 39, 855-875 (1997).

[2] G. Williams, N. Birbilis, H.N. McMurray, Electrochemistry Communications, 36, 1-5 (2013).

[3] T. Cain, S. B. Madden, N. Birbilis, J. R. Scully, Journal of the Electrochemical Society, 162, C228-C237 (2015).

[4] K. Umetsu, Y. Hoshi, I. Shitanda, M. Itagaki 228th ECS meeting abstract, #659 (2016).

[5] V. M. Huang, S. Wu, M. E. Orazem, N. Pébère, B. Tribollet, V. Vivier, Electrochimica Acta, 56, 8048-8057 (2011) .
Quantitative Reconstruction of Half-Cell Impedances of Commercial Lithium-Ion Cells By Three Electrode Measurements and Impedance Modeling
Authors: Schindler Stefan , Danzer Michael A.
Published: February 2020

Impedance spectroscopy is a powerful tool for rating the performance and degradation of battery cells [1]. With regard to commercial cell formats, impedance acquisition and analysis is limited to the full cell impedance due to absence of an appropriate lithium reference potential to separate the shares of both half-cells. In consideration of this limitation, the equivalent electrodes are usually examined separately in symmetrical or three electrode arrangements [2, 3]. While this approach is generally suitable for qualitative estimations of the half-cell ratios, a quantitative reconstruction requires detailed knowledge of impedance contributions from the cell geometry and electrical contacts as well as an appropriate model approach to subtract the latter from the actual half-cell data.

In this study, we introduce a model-based reconstruction methodology based on a mathematical treatment of measurement data recorded on experimental full cells with suitable reference electrode. The methodology includes impedance scaling equivalent to the ratio of electrochemically active areas of experimental and commercial cell, a modulation of the geometrical contribution to the cell impedance and a correction of the purely ohmic impedance ratio to compensate the deviation of electrolyte volumes. It is shown that the subsequent application of these modification steps already yields an excellent reconstruction which can even be further refined by increasing the model discretization. The validity of the proposed methodology is cross-checked by application of distribution of relaxation times (DRT) analysis, which is a powerful mathematical tool to separate polarization contributions by their characteristic time constants [4]. Here, DRT is utilized to demonstrate the reproduction fidelity of the impedance modulation.

The presented methodology opens the door for a great bandwidth of new applications, for instance to develop iterative half-cell degradation models which can be parametrized from impedance data recorded on the (commercial) full cell at any state of degradation. Thus, it constitutes a completely refined opportunity for online applicable, non-invasive diagnosis of lithium-ion cells.

References

[1] Osaka, T.; Daikichi, M.; Hiroki, N.; J. Electrochem. Soc. 162 (2015) A2529-A2537

[2] Song, J.; Lee, H.; Wang, Y.; Wan, C.; J. Power Sources 111(2002) 255-267

[3] Chen, C.; Liu, J.; Amine, K.; J. Power Sources 96 (2001) 321-328

[4] Illig, J.; Schmidt, J.P.; Weiss, M.; Weber, A., Ivers-Tiffée, E.; J. Power Sources 239 (2013) 670-679

Figure Captions

Fig. 1: a) Exemplary nyquist plot recorded for commercial and experimental full cell (T = 25°C, SOC = 50 %). Simplified equivalent circuit structures used in the reconstruction for b) experimental full cell c) commercial cell. A reference electrode is implemented in the experimental cell to separate half-cell impedances.

Figure 1
(Invited) Evaluating Corrosion Processes in an Aluminum Alloy, AA2024, Assisted By a Consortium of Microorganisms
Authors: Paez Maritza Angelica , Alvarado Claudia , Gulppi Miguel , Gomez Grace , Sancy Mamie , Azocar Manuel Ignacio , Vejar Nelson , Blamey Jenny , Molina Paulo , Zagal Jose H
Published: February 2020

The influence of microorganisms in the deterioration of metal surfaces is an important issue in relation to the life of metal structures, equipment, and in terrestrial, marine, and aerospace transportation. In addition, changes in processes and formulations in surface treatments, in order to respond to environmental requirements, have reduced the protective quality of anti-corrosion coatings. A good example of this is the restriction in the use of Cr (VI) in surface treatments of aluminum alloys for aeronautical applications. To this we add the fact of climate change on a global level which can make the situation moredramatic. Therefore, there is growing interest in the phenomenon of microbiologically influenced corrosion in order to design intelligent solutions and long service life.

In this we have studied the electrochemical behavior of an aluminum alloy exposed to a bacterial consortium. We have also considered the electrochemical responses of aluminum alloys exposed to some of the bacteria that make up the consortium. Thus, potentiodynamic polarization measurements and electrochemical impedance spectroscopy were performed. Moreover, the morphological changes associated to the corrosion phenomena were followed by optical microscopy and scanning electron microscopy. Furthermore, we check indirectly the enzymatic biocorrosion process, using macromolecules of a molecular catalyst adsorbed on the surface of a carbon electrode.

The identification of microorganisms was performed by sequencing of the 16S gene of ribosomal DNA (rDNA), which allowed to distinguish a number of bacteria belonging to the genera Staphylococcus, Kocuria, Nosocomiicoccus and Tersicoccus. For all microorganisms, the catalase test was positive. Electrochemical measurements and morphological characterization (SEM and AFM) of the surfaces were performed before, and after, different immersion times (1, 2, 3, 7 and 14 days) in minimum culture media, Twin (MMT), sterile and inoculated with the consortium and also, with each isolated microorganism. Impedance diagrams for all immersion times showed a capacitive behavior characterized by a single time constant. Although for short exposure times no corrosion process was evident, for longer times the resistance of aluminum oxide (Rox) decreased significantly. The enzymatic approach of corrosion was studied using pyrolytic carbon electrodes modified with cobalt phthalocyanine. These results show that the presence of microorganisms significantly alter the mechanism of oxygen reduction, particularly the reduction of oxygen to hydrogen peroxide, confirming the enzymatic approach mechanism in MIC.

Ackowledgements: The authors are grateful to CONICYT (Grant ACT1412) for financial support.
(Invited) Correlation of Electrochemical Dissolution and Impedance of Active Implant Electrodes from Platinum and Iridium
Authors: Hassel Achim Walter , Kollender Jan Philipp , Sprinzl Georg , Doll Theo
Published: February 2020

Cardiac pacemakers and cochlear implants are examples for medical devices that make use of active electrodes from platinum, iridium or their alloys. They require relatively high voltages to stimulate body functions such as muscle contraction or nerve stimulation. From an electrochemical point of view the electrochemical window of the water based body fluids is exceeded and thus water splitting can occur. However, there is an important side reaction which has not been proven so far, that is the electrochemical dissolution of the noble metal electrodes. From a financial point of view these losses could be easily accepted in relation to other costs such as the required surgery or the hospital stay. The important point is that the minor dissolution is under suspect of being responsible for the nerve degeneration that leads to a malfunction of these devices.

In an attempt to clarify the mechanism combined experiments were performed in which electrochemical impedance spectroscopy at certain bias potentials was performed and the resulting noble metal dissolution was quantitatively monitored by an extremely sensitive analytical method the so called inductively coupled plasm mass spectroscopy (ICP-MS).

For a simulation of the in operando conditions large amplitude frequency measurements were performed to understand the relationship between dissolution rate and frequency.