bluuebunny/crossref_metadata_2025 huggingface dataset:
Correlating Trajectories in Voltage Fading to Molecular Transformation in Ramsdellite MnO2 Cathode of Lithium Ion Battery
Authors: Gupta Prashant Kumar , Bhandari Arihant , Sharma Ashutosh , Bhattacharya Jishnu , Pala Raj Ganesh
Published: February 2020

The transition metal oxides are extensively utilized as cathode materials in Lithium ion batteries. These oxides occur as different polymorphs that have varied structures, stabilities and affinities for Li+ and consequently, it is desirable to develop heuristics for the choice of the optimal polymorph. In order to address these issues, exploring MnO2 can be useful as it has more than 10 polymorphic structures, besides being earth abundant inexpensive transition metal oxide. While some of these polymorphic structures have been studied in detail, we present analysis for less explored Ramsdellite MnO2 (R-MnO2) structure, which is part of inter growth structure of most electrochemically active polymorph ϒ-MnO2. Highly crystalline R-MnO2 have been synthesized and experimentally obtained discharge features are compared against density functional-cluster expansion calculations to obtain molecular insights into the intercalation process. The material shows voltage fading beyond Li concentration of 0.5 in R-MnO2 and the computations suggests that changes in Li-coordination environment from tetrahedral to octahedral beyond x=0.5 is critical towards rationalizing trajectories in voltage fading. Voltage fading is also correlated to Mn 2p and O 1s XPS spectra and the modulation of experimentally obtained valence band spectra compares well with the spectra obtained computationally. Volume expansion of about ~20% at full lithiation is accompanied by Jahn-Teller distortion of MnO6, which further rationalizes changes in the valence band-edge. Computations reveal a diffusional barrier of ~ 0.2 eV, which is lesser compared to the barriers in other polymorphs of MnO2 and structural rationale for the smaller barrier is developed. Finally, the results are presented in a more general framework of other polymorphic structures of Cobalt Oxide and Nickel Oxide in light of their importance to the state of the art cathode materials for Lithium Ion batteries.

Keywords:

R-MnO2, Lithium ion battery, Cluster expansion, DFT, XPS, Jahn-Teller effect
A Parametric Study of Sensitivity Analysis of All-Vanadium Redox-Flow Battery Systems
Authors: Al-yasiri Mohammed
Published: February 2020

Vanadium redox-flow batteries (VRFBs) are mainly used in large –scale grid storage. One of the great features of (VRFBs) is the ability to separate energy (amount of stored electrolyte) and power (number of utilized cells and electrode size) of each other. Thus, the flow battery can be improved for either energy and/or power delivery.

In this work, a 3D numerical model by COMSOL software (validated in previous work) of multidisciplinary problem is implemented to study the overall cell efficiency under different operating flow rate and current conditions. Next, we introduce a comprehensive sensitivity analysis study of many input parameters in our model such as (cell channel dimension and electrode material properties) to investigate the impact of the variation in each parameter on the output cell performance.

Based on the sensitivity results, only three input parameters dominate the simulation results, which are solid conductivity of porous electrode, diffusivity of proton in electrolyte, and reaction rate for both electrodes.

Figure 1
Modeling the Effect of Fast Charge Protocol on the Thermal Behavior of a Lithium-Ion Battery for Electric Vehicle Applications
Authors: Lee Dongcheul , Koo Boram , Shin Chee Burm
Published: February 2020

The battery is the primary reason that hampers a mass adoption of electric vehicles (EVs). Although lithium ion battery (LIB) is a preferred power source for EV, there is still a plenty of room to be improved for the cost, life and safety of the LIB in EV applications. Another important issue to be overcome for the EV battery is searching for an appropriate fast charge protocol to alleviate “range anxiety” for the driver of passenger EV and thus to enable a rapid growth of EV market. A short charge time is, however, reported to be achieved always at the expense of cycle life regardless of the charge techniques. It is, therefore, essential to find an optimized fast charge protocol that can balance fast charge and healthy cycling for the LIBs.

In this work, the thermal behaviors of LIB cell under various fast charge protocols are analyzed based on the two-dimensional modeling of the nonuniform temperature distribution in LIB cell during fast charge. The thermal modeling during fast charge is validated by the comparison of the modelling results with the experimental measurements using IR thermal images and thermocouples. The fast charge protocols are evaluated based on the peak temperature of LIB cell and the thermal imbalance within LIB cell during fast charge.

The maximum, average, and minimum temperatures obtained from the experimental measurements are compared with those predicted by the model in Fig. 1. The maximum, average, and minimum temperatures obtained from the experiment and modelling are in good agreement with each other at charge rate of 5C during CC-CV charging. Fig. 2 shows the temperature distributions based on the experimental IR image and the modeling for a 14.6 Ah LIB at an environmental temperature of 25℃ at charge time of 180, 480, 1140 s during CC-CV charging with CC charge at 5C. The overall temperature distributions obtained from the experiment agree well with those from the modeling in Fig. 2.

Figure 1
(Invited) Vertical Transport through Multi-Layer Van Der Waals Structures
Authors: Appenzeller Joerg
Published: February 2020

Electronic transport in low-dimensional systems such as carbon nanotubes, nanowires and more recently transition metal dichalcogenides (TMDs) and black phosphorus (BP) has attracted considerable attention over the years due to the unique properties that these classes of materials offer. In particular, the fact that these materials can be semiconducting with body thicknesses of sub-nanometers with appreciable carrier mobilities makes them relevant for various electronic applications. Consequently, many research activities have been focusing on the lateral transport through these structures, often in three-terminal device geometries. By utilizing a gate, ideal electrostatics conditions can be enabled in the low-dimensional semiconducting channel, due the aforementioned thin body, and field-effect transistors (FETs) can be built to explore their transport properties as a function of gate and drain voltage. In doing so, it was found that most devices behave as Schottky barrier transistors and that the total number of layers in case of 2D systems plays an important role for the effective bandgap of the FET, an aspect that I will discuss in greater detail in my talk. Multi-layer TMDs and BP are also particular in that the hybridization between layers is weak due to the fact that van der Waals interaction – rather than covalent or ionic bonds – is the “glue” between layers, making the system highly anisotropic for charge transport. In fact, this anisotropy is considered to be the key for the formation of so-called “atomically abrupt” p-n junctions, in particular in heterostructures from 2D materials. In my talk, I will discuss in how far lateral and vertical transport is rather entangled in many device geometries and will offer an alternative interpretation – other than an abrupt p-n junction – for transport data that show high current rectification ratios in vertical 2D heterostructures. Last, I will discuss a model to describe transport across multi-layer 2D structures that allows extracting the vertical transport mass in MoS2 and WSe2.
Encoding Polymers with Information. A Supramolecular Porphyrin Approach
Authors: Nolte Roeland , Elemans Johannes
Published: February 2020

The amount of information trafficking internet nowadays is enormous and will increase further in the near future. It can be expected that in the next decennia the current technologies to store and process data will no longer suffice and that other strategies to handle information will have to be developed. One approach is to explore chemical routes, which nature has also followed during evolution: our brain can store and handle very large amounts of data and process them in a way silicon-based computers cannot do. Although brain-like chemical computers are still far beyond reach, it is of interest to explore how atom and molecule-based systems that can write, read, and store information might be designed and constructed.

In this lecture I will discuss our efforts to develop a new technology to write, store, and read information, i.e. on a single polymer chain with the help of “molecular machines” that are inspired by the hypothetical device (Turing machine) proposed by the British mathematician Alan Turing in 1936 as the general basis for the operation of a computer. We are following two approaches. In the first one we try to construct molecular machines based on clamp-shaped proteins, modified with porphyrin catalysts, that can bind to DNA and move along it while modifying the DNA chain in a controlled fashion. In the second approach we use synthetic machines that are derived from chiral porphyrin cages, which bind to synthetic polymers (e.g. polybutadiene) and glide along it while encoding it with chiral epoxide functions, i.e. (R,R)-epoxide (symbol 0) and (S,S)-epoxide (symbol 1). This encoding process, which is in progress, will be controlled by light.
Chirality Sensing, Halochromism and Solvatochromism in a Conjugated Calix[4]Pyrrole
Authors: Hill Jonathan P. , Labuta Jan , Březiná Vaclav , Ishihara Shinsuke , Hanykova Lenka , Ariga Katsuhiko
Published: February 2020

The conjugated calix[4]pyrrole tetrakis(3,5-di-t-butyl-4-oxocyclohexadien-2,5-yl)porphyrinogen (OxP) is a highly coloured macrocycle with excellent potential as a sensing element in various applications. The first of these is chiral sensing where guest binding at the macrocyclic NH groups allows for estimation of enantiomeric excesses in non-racemic mixtures of chiral analytes. This feature is permitted by the relatively weak binding of the guest resulting in its rapid exchange so that the molecule essentially acts as a probe of average solution chirality. Chirality sensing in OxP is complicated by tautomeric processes when an acid analyte is used. This has allowed us also to develop an acidity sensor for use in non-polar media. More recently, we have designed a series of OxP type molecules that undergo modulation of halochromic (sensitivity to acid) properties and the development of colour scales based on the blocking of OxP binding sites and involving allied protic tautomerization of the OxP chromophore. We will discuss the sensing properties of OxP in relation to chirality, tautomeric processes and the complicating factor of solvatochromism.
Coordination and Electronic Structures of Short-Lived Intermediate of Heme-Containing NO Reductases
Authors: Shiro Yoshitsugu
Published: February 2020

Nitric oxide reductases (NOR) are heme-containing enzymes, which are involved in fungal or bacterial denitrification, and reduce nitric oxide (NO) to nitrous oxide (N2O) fro detoxification. Fungal NOR is a water-soluble and cytochrome P450 type enzyme, while bacterial NOR is a membrane-integrated enzyme containing a heme/non-heme iron binuclear center as its active site. In both enyzmes, short-lived intermediates are appeared during the NO reduction reaction. For characterizing the coordination and electronic structures of the intermediates, we applied time-resolved IR spectroscopic and crystallographic techniques. The information obtained from these experiments will help us to understand the molecular mechanism of the NO reduction catalyzed by two different NOR enzymes.
Photoinduced Energy and Electron Transfer in Bacterichlorins
Authors: Arnaut Luis
Published: February 2020

Bacteriochlorins are characterized by intense near-infrared absorption bands (700-800 nm), which are of interest for diverse applications such as photodynamic therapy (PDT) of diseased tissues or dyes in solar cells. Although naturally-occurring bacteriochlorin derivatives are labile and this limits their applications, we synthesized photostable bacteriochlorins that can endure many cycles of photoinduced energy and electron transfer reactions without photodecomposition. The factors contributing to this photostability are discussed. In particular, it is shown that bacteriochlorins are prone to oxidation but this can be prevented by introducing electron-withdrawing substituents in the phenyl groups of tetraphenylbacteriochlorins. The oxidation potentials of tetraphenylbacteriochlorins increase when such substituents are present, and it is shown that in a series of structurally-related bacteriochlorins, chlorins and porphyrins, the photodecompositing quantum yields decrease as the oxidation potentials increase. The control of the oxidation potential is also relevant to determine the propensity of these photosensitizers to undergo energy or electron transfer to molecular oxygen.

Efficient energy transfer (Type II process) and electron transfer (Type I process) to molecular oxygen, with the consequent formation of reactive oxygen species, is critical to the success of PDT of solid tumors. We tuned the properties of tetraphenylbacteriochlorins to optimize a photosensitizer for PDT of cancer. The optimized photosensitizer, named redaporfin, proved very effective in the treatment of tumors implanted in animal models and is now in clinical trials for advanced head and neck cancer

References

Pucelik, R. Paczyński, G. Dubin, M. M. Pereira, L. G. Arnaut, J. M. Dąbrowski, Plos ONE, 12 (2017) e0185984

Pucelik, L. G. Arnaut, G. Stochel, J. M. Dąbrowski, ACS Appl. Mater. Interfaces, 8 (2016) 22039-22055

Tão, J. R. S. Campos, L. C. Gomes-da-Silva, F. A. Schaberle, J. M. Dabrowski, L. G. Arnaut, ChemBioChem, 17 (2016) 836-842.

M. Dabrowski, L. G. Arnaut, Photochem. Photobiol. Sc., 14 (2015) 1765-1780.

B. Rocha, L. C. Gomes-da-Silva, J. M. Dabrowski, L. G. Arnaut, Eur. J. Cancer, 51 (2015) 1822-1830.

Saavedra, L. B. Rocha, J. M. Dąbrowski, L. G. Arnaut, ChemMedChem, 9 (2014) 390-398.

G. Arnaut, M. M. Pereira, J. M. Dabrowski,* E. F. F. Silva, F. A. Schaberle, A. R. Abreu, L. B. Rocha, M. M. Barsan, K. Urbanska, G. Stochel, C. M. A. Brett, Chem. Eur. J., 20 (2014) 5346-5357.
C-H Insertions by Iron Porphyrin Carbene: Basic Mechanism and Origin of Substrate Selectivity
Authors: Khade Rahul , Zhang Yong
Published: February 2020

Recent experimental reports of heme carbene C-H insertions show promising results for sustainable chemistry due to good yield and selectivity, low cost of iron, and low/no toxicity of hemes. But mechanistic details are mostly unknown. Despite structural similarity and isoelectronic nature between heme carbene and FeIV=O intermediate, our quantum chemical studies with detailed geometric and electronic information for the first time reveals an FeII-based, concerted, hydride transfer mechanism, different from the FeIV-based stepwise hydrogen atom transfer mechanism for C-H functionalization by native heme enzymes. A trend of broad range experimental C-H insertion yields (0-88%) of five different C-H bonds including mostly non-functionalized ones was well reproduced. Results suggest that the substrate selectivity originate from the hydride formation capability. The predicted kinetic isotope effects were also in excellent agreement with experiment. Useful geometry, charge, and energy parameters well correlated with barriers were reported. Results provide the first theoretical evidence that carbene formation is the overall rate-limiting step and suggest a key role of the formation of strong electrophilic heme carbene in developing heme-based C-H insertion catalysts and biocatalysts.
Surprising Substituent Effect in Corroles on the Electrochemical Activation of Oxygen Reduction
Authors: Elbaz Lior , Levy Naomi
Published: February 2020

Following our methodological study on the parameters affecting the oxygen reduction reaction (ORR) electrocatalytic activity of metallo-corroles, four different β-pyrrole-substituted cobalt(III) corroles were synthesized and studied as electrocatalysts for ORR. In this work, the influence of substituting the hydrogen to halogen atoms on the b-position on the Co-corrole was investigated by both computational and experimental methods. When comparing the catalytic activity of these corroles when adsorbed on GC electrode, it appears that their catalytic ORR performance is in the following order: Co-Br8>Co-Cl8~CoH8>Co-F8. While the effect of the halides could be explained by a combination of π-donating and σ-withdrawing abilities, the advantage of not having halides on the b-pyrrole positions appears preferable. The results disclose high dependence of the corrole’s performance on its substituents, but once adsorbed on high surface area carbon, this effect vanishes, resulting in a better catalytic performance than most well-defined molecular electrocatalysts for this reaction.
The Design of Highly Efficient Non-Precious Metal Catalysts for Oxygen Reduction, Oxygen Evolution and CO2 fixation/Reduction
Authors: Schoefberger Wolfgang
Published: February 2020

Selective catalysts are urgently needed for the oxygen evolution reaction (OER), the oxygen reduction reaction (ORR) and CO2 fixation/reduction reactions (CO2RR) in order to replace fossil fuels with renewable fuels. To date, noble metals and precious metal catalysts have achieved the best performance in energy yield and Faradaic efficiency, and have recently reached impressive electrical-to-chemical power conversion efficiencies. However, the scarcity of precious metals makes the search for scalable, non-precious or even metal-free catalysts for the above mentioned reactions all the more important. During the lecture, I will discuss our synthesis efforts to develop functional materials based on metal corrole systems or polymeric materials and subsequently show their application as catalysts for OER/ORRs [1] and CO2RR [2-4].

[1] Schöfberger et al., Angew. Chem. Int. Ed. 2016, 55, 7, 2350–2355 and Angew. Chem. 2016, 128 (7), 2396–2401. [2] Tiffner et al., Chem. Asian J., 2017, 12 (10), 1048–1051. [3] Coskun et al., Sci. Adv. 2017; 3:e1700686. [4] Tebi et al., ACS Nano, 2017, 11 (3), 3383–3391.

Figure 1
Electrochemistry and Spectroelectrochemistry of Cobalt Bis(phenolate)Dipyrrins
Authors: Kadish Karl M , Shan Wenqian , Pacquelet Sandrine , Chang Yi , Desbois Nicolas , Gros Claude
Published: February 2020

Three cobalt bis(phenolate)dipyrrins with different meso-tetraaryl groups were synthesized and characterized by UV−visible spectroscopy, 1H NMR spectroscopy and mass spectrometry in nonaqueous media. The structures of the investigated compounds are shown in Chart 1. The redox potentials for each electrode reaction of the above compounds were measured by cyclic voltammetry in CH2Cl2, PhCN, DMSO and pyridine containing 0.1 M TBAP and the spectra of the electroreduced and electroxidized species were obtained by thin-layer UV-visible spectroelectrochemistry under the same solution conditions. The electrochemical and spectroelectrochemical data were then analyzed as a function of the metal oxidation state, solvent properties, meso-substituents and non-innocence (or innocence) of the dipyrrin ligand. The axial ligand binding properties with the solvent (e.g. PhCN, DMSO or pyridine) and other small molecules (e.g. CO or NH3) were investigated and comparisons were made with related four-, five- and six-coordinate cobalt corroles under the same solution conditions. An X-ray crystal structure for the F5Ph derivative, compound 1, with two axial NH3 ligands is also presented.

Figure 1
Non-Planar Pyrrole-Fused Azacoronenes with Various Redox States
Authors: Takase Masayoshi
Published: February 2020

Heteroatom-containg polycyclic hydrocarbons have attracted a great deal of attention from materials science, since such heteroatoms can tune the electronic nature without modifying the structure. Given these expectations, we have reported a novel nitrogen-containing π-system, i.e. hexapyrrolohexaazacoronene and its derivaticves. To further understand the structure–property relationship, we have newly designed and synthesized pyrrole-fused azacoronenes with curved structure. In the presentation, we will report on the synthesis, crystal structures, and optical and electronic properties in neutral and oxidized states.
Synthesis and Properties of Zn Tetraphenylporphyrin Model Compounds for Solar Energy Conversion
Authors: Galoppini Elena
Published: February 2020

Over the past two decades molecular design has played an important role to control, at the molecular level, the properties of the interface between nanostructured metal oxide semiconductors (particularly TiO2 and ZnO) and chromophoric compounds, especially porphyrin derivatives, as these are efficient dyes for dye sensitized solar cells and effective photocatalysts. The ultimate objective is develop hybrid organic-inorganic systems that are efficient for solar energy conversion, but an important aspect of this research is the ability gain a fundamental understanding of charge transfer processes at these important interfaces. The presentation will address several aspect of porphyrin design that our group, in collaboration with others, has focused on and, in particular, our recent progress in the influence of interfacial dipoles built in the porphyrin framework.
Tuning Optoelectronic Properties of Ionic Porphyrin Semiconductors
Authors: Mazur Ursula , Hipps K W
Published: February 2020

The effect of selective metallation of free-base ionic porphyrin tectons on the structural, electronic, and optical properties of their crystalline self-assemblies is presented. Rod-like crystals were prepared by combining meso-tetra(N-methyl-pyridyl)porphyrin, H2TMPyP, and meso-tetra(4-sulfonatophenyl)porphyrin, H2TSPP, with either a nickel or copper ion contained in one of the synthons. These materials were characterized by optical microscopy, X-ray diffraction methods, thermogravimetric analysis, diffuse reflectance UV-visible and luminescence spectroscopies, and conductivity and photoconductivity measurements. All the porphyrin assemblies formed monoclinic P21/C crystals with pseudo-hexagonal cross sections. Thermogravimetric experiments indicate that water molecules associated with crystals desorb at two different rates. In addition, the temperature dependent XRD showed that the dehydration of the porphyrin solids causes modification in the crystals which is completely reversible (i.e., crystals return to their original structural geometry upon rehydration). All the metallated porphyrin crystals exhibit dark conductivity at moderately high temperatures and become more conducting upon photoexciation. The primary charge carriers in these solids upon photoexcitation are electrons and the charge recombination mechanism follows monomolecular kinetics. Quantum mechanical calculations provide the electronic band structure, the density of states and explain the experimental prompt photoconductivity measurements of the porphyrin self-assemblies.
Novel Corroles for Chemical Sensor Applications
Authors: Paolesse Roberto , Nardis Sara , Mandoj Federica , Stefanelli Manuela , Di Natale Corrado
Published: February 2020

In the last few years corrole has been one of the protagonist of the porphyrinoid scenario, due to the impressive number of researches devoted to investigate the chemistry of such a macrocycle.

The refinement of simple synthetic routes for the preparation of meso-substituted corroles made this macrocycle easily available to researchers, before hampered by the multi-step preparation necessary to obtain this contracted porphyrin.

Although this synthetic availability contributed to the corrole popularity, it is for sure the peculiarity of the chemistry of such a macrocycle that justified the impressive increase in researches related to corroles. This peculiarity is characterized by the non-innocent character as ligand, which from one side makes its behavior particularly intriguing and challenging for the electronic structure characterization, and from the other side makes its metal derivatives interesting for catalytic applications. To further enrich this scenario, it is important to study different synthetic routes devoted to the modification of the corrole ring, by the introduction of peripheral substituents. In this way it is possible to modulate the characteristics of the corrole ligand and consequently its metal derivatives.

In the present work we summarize our recent achievements in the preparation of novel corrole derivatives for chemical sensors development.
Composites of Carbon Nanotubes and Graphene for Energy Conversion and Wearable Sensing
Authors: Ouyang Jianyong
Published: February 2020

Composites of carbon nanotubes and graphene can give rise to superior function arising from the synergistic effects of the two components. Here, I will present some of our works in investigating the application of carbon nanotube/graphene composites in dye-sensitized solar cells and wearable sensors. The carbon nanotube/grpahene composites prepared by gel coating can effectively catalyze the regeneration of the redox species of dye-sensitized solar cells. They can give rise to a photovoltaic efficiency higher than that with carbon nanotubes, graphene or Pt as the counter electrode. Moreover, we prepare hybrid carbon nanotube/graphene on fibrics. They are sensitive to strain and can be used as washable wearable sensors.
Assessing the Importance of Crease Parameters and Infiltration in Creating Miura-Ori Tungsten Carbide Parts
Authors: Patterson Jenna , Sterckx Peter , Islam Monsur , Martinez-Duarte Rodrigo
Published: February 2020

The combination of the structure of origami folding geometries and the strength of carbides has the potential to create strong yet flexible low density parts. For the structure aspect, the Miura-ori origami geometry is able to fold compactly or unfold into a panel, allowing it to deform as loads are applied. Tungsten carbide is chosen as the potential carbide due to its extreme hardness and relatively high Young’s modulus of 530-700 GPa. Previous work by our group showed how the heat treatment of a Miura-ori geometry, made with cellulosic paper infiltrated with a tungsten precursor, yielded a rigid Miura-ori tungsten carbide structure. Here, we focus on studying the effect of crease geometries and materials as it relates to the specific strength of the Miura-ori carbide structure.

The crease geometry is a function of the cutter plotter’s inputs, specifically including creasing force, crease width, and the number of passes over each crease. These variables are varied using the Taguchi design of experiment in order to determine the optimal crease geometry that will yield the highest Young’s modulus. The main challenge has been to crease the paper without it ripping, as this sometimes occurs when the force is high and the line thickness is small. After creasing, the structures are folded and then carbonized (Fig. 1). The carbonized Miura-ori structure is then load tested to determine the Young’s modulus and, knowing the dimensions of the part, the specific strength.

To determine how the tungsten carbide affects the strength of the material, an inkjet printer deposits an ammonium metatungstate [AMT] solution onto the paper after it is creased. When the structure is carbonized, the AMT decomposes and forms tungsten carbide in the presence of the carbon in the paper. This process yields a Miura-ori structure that is at least partially tungsten carbide. Different concentrations of AMT solution should yield greater percent tungsten carbide in the carbonized part, which is something that will be explored in the future.

Ongoing work is on characterizing the effect of processing on the mechanical properties of the carbon structures. To this end, the carbonized parts are load tested to determine their Young’s modulus and the specific strength. These explorations into the part’s physical geometry and composition will allow for optimization of the structure’s strength through physical and chemical optimization.

References

Schenk, M., & Guest, S. (2013). Geometry of Miura-folded metamaterials. Proceedings of the National Academy of Sciences of the United States of America,
110(9), 3276-3281.

Figure 1
Electrochemical Corrosion Behavior of Ti-6Al-4V Alloy Using Akermanite As a Bioceramic Coating
Authors: Rabiei Baboukani Amin , Saatchi Ahmad , Wang Chunlei
Published: February 2020

In recent years, ceramic material Akermanite (Ca2­Mg­Si2O7) by the ability to connective and link with the hard tissue of the body, In the recovery, treatment and orthopedics of bone and implants coated body has been considered. The purpose of this research was manufacture, preparation and evaluation and characterized of Akermanite nanoparticles and applied this coating on titanium alloy substrate (Ti-6Al-4V) with sol-gel method. Akermanite nanoparticles were prepared by sol-gel method and its structure was determined by X-ray diffraction test. To study the morphology and particle size of Akermanite, transmission electron microscopy (TEM) was used. The morphology and microstructure surface of coating were evaluated by scanning electron microscopy (SEM). Bioactivity of coating was evaluated in body simulation solutions (SBF). Polarization and electrochemical impedance electrochemical test in two different physiological solution was performed in order to compare the corrosion behavior of coated and uncoated titanium samples. Transmission electron microscopy was confirmed powder sizes below 100­nm. According to the Tofel and Linear polarization tests, in the presence of coating in physiological solution compared to Ringer's solution, corrosion current density decreased and corrosion potential shifted to the more noble values and corrosion resistance of the alloy increased. Based on the results obtained by the impedance test, in the presence of Akermanite coating in physiological solution, charge transfer resistance increased and double-layer capacity decreased, which shows improvement in corrosion resistance. According to the corrosion tests, Akermanite coating created on the surface of titanium alloy, has created higher corrosion resistance in physiological solution, compared to Ringer's solution. According to the results of bioactivity test and scanning electron microscopy (SEM), hydroxyapatite is formed on the surface of alloy. The results showed that Akermanite bioceramic coating applied by the sol-gel method, reduced the release of metal ions and improve the biocompatibility of metal implants and also, promote their potential ability to the growth of bone and connective with it.
Depassivation of Steel Rebar in Concrete Investigated By Electrochemical Impedance
Authors: Itagaki Masayuki , Okamoto Tatsuki , Watanabe Shuhei , Tokieda Hiroyuki , Hoshi Yoshinao , Shitanda Isao , Kato Yoshitaka
Published: February 2020

The degradation of concrete and the corrosion of steel-reinforcing bar are serious problem in infrastructures. The electrochemical measurements are useful to evaluate the stability of passive film formed on steel rebar in concrete, which are mainly measurements of corrosion potential [1] and polarization curve. Dawson et al. [2] applied an electrochemical impedance spectroscopy (EIS) to the investigation of rebar corrosion in concrete because the charge transfer resistance at rebar/concrete interface can be determined from the impedance spectrum. Recently, the authors developed an electrode in Fig. 1 as a sensor probe to monitor concrete degradation and rebar corrosion. A couple of electrodes, which were made of same material as steel rebar, can be embedded in concrete structure and complex impedance can be measured continuously on the basis of two-electrode method.

The authors’ group has performed the following three types of impedance measurements in order to prove the of the developed sensor probe.

(1) Impedance between two electrodes in aqueous solution that simulates the water quality of transition zone (laboratory test).

(2) Impedance between two electrodes embedded in the concrete which was fabricated in the laboratory.

(3) Field test at bridge pier of the highway in coastal marine environment.

It is well known that the rebar corrosion in concrete is strongly influenced by the conditions of cover concrete. Thin water layer is formed at rebar/concrete interface due to water absorption in the concrete. The concrete is good health status and the passive film is formed on steel rebar when the pH of water layer on steel rebar is sufficiently high. The breakdown of passive film occurs by neutralization and enriched chloride ions in the water layer with the degradation of concrete. In this presentation, the authors investigate the critical values of pH and chloride concentration to maintain the passive film on steel rebar and discuss the depassivation mechanisms by the measurements of electrochemical impedance with the developed sensor probe.

References:

[1] ASTM C 876-91 (Reapproved 1999): Standard Test Method for Half-Cell Potentials of Uncoated Reinforcing Steel in Concrete, Annual Book of ASTM standards, Vol. 03.02, pp. 457-462, 1999.

[2] J. L. Dawson, L. M. Callow, K. Hladky and J. A. Richardson, Corrosion/78, No-125 (1978).

Figure 1
Anodic Polarization Behavior of Zn in Aqueous MgCl2 Solutions
Authors: Tsurumaki Yumiko , Tada Eiji , Ooi Azusa , Nishikata Atsushi
Published: February 2020

Zn-coated steels have been widely used in various engineering fields such as automobiles and construction since they have excellent corrosion resistance in mild atmospheric corrosion environments. In order to improve the corrosion resistance of the coated steels, Zn-alloy coatings containing Mg have been newly developed and they have shown superior corrosion resistance compared with Zn coatings. However, Mg should dissolve into aqueous solutions preferentially in the early stage of immersion because of one of the active metallic elements. Therefore, it is considered that better corrosion resistance of Zn-alloy coatings containing Mg is related to the presence of Mg2+ ions in corrosion media. However, the effect of Mg2+ on the improvement of corrosion resistance of Zn and Zn-alloy coatings is still unclear. In this study, the effect of Mg2+ on the anodic polarization behavior of Zn is investigated by polarization measurements.

The sample used in this study was Zn plate (99.7%, Goodfellow) and it was ground down to JIS#2000 grit with SiC abrasive papers. Then the sample was degreased in EtOH ultrasonically and then dried in air. The test solutions was aqueous solutions of MgCl2 of various concentrations ranging from 0.05 M to 1 M. Some of the test solutions were deaerated by Ar bubbling at least for 20 h. Anodic polarization curves for Zn were measured at a sweep rate of 0.5 mV/s.

Anodic polarization curves for Zn was measured both in aerated and deaerated MgCl2 solutions. For the measurements in deaerated solutions, cathodic polarization treatment for reduction of air-formed films on Zn was done in NaCl solutions without Mg2+ ions. It was found from the results of anodic polarization curves for Zn in aerated MgCl2 solutions that anodic dissolution was enhanced with increasing concentration of MgCl2 and that Tafel slopes of the curves were relatively small in the order of tens of mV/dec independent of MgCl2 concentration. On the other hand, anodic polarization behaviors of Zn in deaerated MgCl2 solution were almost the same with Tafel slopes of 40 mV/dec independent of MgCl2 concentration. These results suggests that surface film formed on Zn in aerated solutions is related to anodic polarization behavior in MgCl2 solutions and that Mg2+ ions improve anti-corrosion performance of the film.
A pH Sensing Channel Flow Double Electrode to Investigate Anodic Dissolution of Mg and Mg Alloys with Real-Time Surface Observation
Authors: Hoshi Yoshinao , Miyazawa Kei , Shitanda Isao , Itagaki Masayuki
Published: February 2020

Magnesium (Mg) is an attractive material for a transportation industry because it has low density and good mechanical properties. However, a high reactivity of Mg in an aqueous solution limits its wider usage in the industry. It was reported that the rate of hydrogen evolution reaction on Mg is increased with noble potential from the open circuit potential. This phenomenon is termed the Negative Difference Effect (NDE) 1-5.

In order to investigate the anodic dissolution of Mg, we developed a pH sensing channel flow double electrode (CFDE). The CFDE is one of the hydrodynamic method for analysis of anodic dissolution of metals and alloys 6-10. In this method, the metallic ions dissolved from the working electrode (WE) can be detected by arranging a detecting electrode (DE) downstream of the WE. In the present study, the Mg and tungsten (W) were used as the WE and DE. Because the hydroxide ions generated due to the anodic dissolution of Mg flow to the W, pH can be estimated from the measurement of the open circuit potential of W. In addition, a video recording of Mg surface was performed during measurement in the developed system 10. The hydrogen evolution of Mg during anodic dissolution was discussed with results of pH changes and an in-situ surface observation.

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Oxidation Characteristics of Nano-Oxide Dispersed Ferritic Stainless Steel Alloys for Solid Oxide Fuel Cell Interconnects
Authors: Mehran Muhammad Taqi , Song Rak-Hyun , Lim Tak-Hyoung , Lee Seung-Bok , Hong Jong-Eun
Published: February 2020

Ferritic stainless steel based metallic interconnects for intermediate temperature solid oxide fuel cells (SOFC) show performance degradation due to the continuous growth of chromia scale. Modification of stainless steel alloy is considered to be one of the viable options to utilize ferritic stainless steel for long-term application in SOFC as interconnect. In this study, we developed the nano-oxide dispersed alloys of ferritic stainless steel SUS430 and studied the oxidation properties at 800 °C in oxidizing conditions. Nano-oxides of CeO2, La2O3, Y2O3, and LaCrO3 were dispersed in commercial SUS430 by high-energy ball milling and the specimen were fabricated by uniaxial and isostatic pressing and sintering in H2 at 1400 °C. The sintered samples were tested for oxidation properties and long-term area specific resistance (ASR) in the air at 800 °C for 1000h and post-test SEM and XRD analysis was performed to analyze the oxide scale. It was found that the addition of up to 3wt. % nano-CeO2 is the most beneficial among the added nano-oxides in order to improve the oxidation properties of SUS430 due to the reduced thickness of the chromia scale, and improved adhesion of the oxide scale and the alloy substrate.
EBSD Study of 55 Wt.% Al-Zn Coating and Corrosion Behavior Effected by Austenitization Heat Treatment
Authors: Chang Jun-Kai , Yang Tzu-Chin , Lin Chao-Sung
Published: February 2020

Reduction of CO2 emission and enhancement of fuel efficiency are an important environmental issue and the design trend of vehicle structures. Hot stamping process has been employed to for advanced high-strength steel (AHSS) parts for the automobile components. Several coating systems, such Al-Si, Zn, and Zn-Al, on the AHSS for the hot stamping process have been reported. The microstructural evolution during austenitization differs in the type of the coating, which is mainly characterized using the SEM and TEM, as well as the EDS.

Electron back-scattering diffraction (EBSD) is a kind of the crystal identification technologies. Due to the difference in the crystal orientation of phases, the phase mapping is power for detailing large-scale microstructural evolution. In this study, the EBSD was employed to identify the phase evolution of a 55 wt.% Al-Zn coated steel during different heat treatments. The result showed that the Fe2Al5 was the major phase formed at 800℃ for 5 min and no Fe-Zn IMCs was found in the coating. As the temperature of the heat treatment was increased to 900℃, the FeAl phase formed on the top of the coating and gradually became the major constituent of the coating. Moreover, the Zn did not react with the FeAl phase and gathered on the top of the coating to form the Zn-oxide. The result of pole figure indicates that the texture orientation of the FeAl phase had changed; however, the orientation change of the Fe2Al5 phase was not obvious and showed preferred orientation. Finally, the chemical stripping results show that the potential of the coating was active than the steel substrate and the potential gap between the coating and steel substrate was approximately 500 mV, which is closed to the result of Zn-coated steel without heat treatment.

Key words: 55 wt.%Al-Zn coating, EBSD, austenitization heat treatment, Fe-Al IMCs, chemical stripping

Figure 1
Electrodeposition of Pure Phase Snsb As Anode Material for Lithium- and Sodium- Ion Batteries
Authors: Ma Jeffrey , Prieto Amy L.
Published: February 2020

Commercial industries currently utilize graphite as the primary lithium anode material for secondary batteries. Graphite’s gravimetric capacity, however, has already been fully utilized and materials with higher capacities are more desirable for the advancement of next generation applications, such as electric vehicles. Of these materials, intermetallic alloys such as SnSb are of interest due to their ability to store multiple alkali metals per metal center, resulting in higher gravimetric and volumetric capacities. Electrodeposition is a promising method to produce these alloy anodes, as it can control the particle morphology, size, thickness, composition, and is easily scalable to larger productions. In this work, we have successfully synthesized pure SnSb by electrodeposition which, based on the authors’ knowledge, is the first occurrence to date. The synthesis is carefully analyzed through tools and techniques such as cyclic voltammetry, scanning electron microscopy, and x-ray diffraction. Electrochemical testing of the electrodeposited SnSb samples showed promising performance of the material, with long cycle life and high rate capabilities as both lithium- and sodium- ion battery anodes. It is also found that purity of the material has an evident impact on the electrochemical performance of the electrode, in which control of the purity is important to the material’s cycling lifetime.
Electrochemical Liquid Liquid Solid Growth of Group IV Nanowires and Microwires for Recharge Battery Anode Applications
Authors: Maldonado Stephen
Published: February 2020

This presentation will describe our latest efforts in the synthesis of nanostructured Group IV semiconductor nanowires by the electrochemical liquid-liquid-solid (ec-LLS) process for preparing rechargeable battery anode materials. Briefly, we have developed a hybrid electrodeposition strategy that mimics high temperature, chemical vapor phase nanowire growth but at low temperatures with reactants dissolved in an electrolyte. The key concept is the use of a liquid metal electrode that also serves as a seed for the crystal growth of electrodeposited Group IV semiconductors. We will first show the basic generality of the ec-LLS process in terms of material, employed substrate, electrolyte composition, and applied electrochemical waveform. Then we will discuss details of battery electrode preparation by ec-LLS and the resultant cycling performance under various treatments. We will specifically show the influence of the liquid metal seed used in ec-LLS on the cycling properties of Ge nanowires and microwires for Li+
insertion/de-insertion. Electrochemical response patterns, ex-situ electron microscopy, atom probe tomography, and X-ray diffraction patterns indicate that certain metal impurities significantly extend cyclability of Ge microwires due to an 'atomic' binder effect imparted by metal impurities incurred by the ec-LLS process.
Electrodeposition of Adherent MnO2 Films with Optimized Current Collector Interface for 3D Li-Ion Electrodes
Authors: Vereecken Philippe M. , Timmermans Marina Y. , Mattelaer Felix , Labyedh Nouha , Zankowski Stanislaw Piotr , Detavernier Christophe
Published: February 2020

Three-dimensional (3D) architectures for high-performance energy storage devices has been the subject of ongoing investigations targeting their integration in autonomous microelectronic systems. In this paper we present a route toward the realization of high capacity LiMn2O4 (LMO) cathode films for 3D thin-film lithium-ion batteries. One of the critical steps in the process is the electrodeposition of MnO2 coatings also known as electrolytic manganese dioxide (EMD) films. The main challenges of depositing thick enough EMD films directly on the current collector often lay in achieving a good film adhesion and preventing oxidation of non-noble current collectors such as TiN and Ni. Indeed, whereas EMD is typically used as powder for primary MnO2 based batteries and thus delamination from the current collector is desired, well adherent films are required for 3D thin-film batteries. To improve the adhesion of the EMD films we modify the surface of the current collector by means of nanometer thin seed layer coatings, which also prevent the oxidation of the underlying current collector substrate during the anodic deposition process. As a result, submicron to micron thick EMD films with good adhesion were deposited on various current collectors. The acidity of the electrolyte solutions was adjusted depending on the type of the surface coating or current collector used. The mechanism of the EMD film growth and morphology on different substrates will be discussed. Compatibility of the proposed current collector interface modification for the electrodeposition of conformal thick EMD films on high-aspect ratio microstructures was demonstrated. Finally, conversion of the EMD to LMO films is shown at low enough temperatures to be compatible with the underlying substrates. The functionality and high rate performance of the 3D LMO electrodes in Li-ion cell is demonstrated.

Figure: Electrolytic manganese dioxide (EMD) films coated conformally on high aspect ratio pillar arrays for 3D thin-film batteries.

Figure 1
(Invited) Thin Film Processing for Innovative Solid State Lithium Batteries
Authors: Oukassi Sami , Porthault Hélène , Martin Steve , Bedjaoui Messaoud , Salot Raphaël
Published: February 2020

With the emergence of novel multifunctional internet of things and wearable electronic devices, the development of high performance energy storage devices is becoming increasingly important. Thin film solid state lithium batteries (TFBs) are known to be one of the most promising candidates to meet these applications’ demands.

In this context, it is expected that conformal deposition of additively patterned TFB layers would provide opportunities to enhance the device performance and widen the scope of possible form factor and integration schemes. Several options have been explored by our group, including key enabling technologies such as electrochemical deposition, vapor and atomic layer deposition as well as a combination thereof. Here we will discuss our efforts to develop advanced TFB architectures based on these approaches.