bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) The Regioselectivity of the Diels-Alder and Bingel-Hirsch Additions to La@C2v
-C82
Authors: Solà Miquel , Martínez Juan Pablo , Garcia-Borràs Marc , Swart Marcel , Poater Jordi , Bickelhaupt F. Matthias , Luis Josep Maria , Osuna Sílvia
Published: February 2020

Two of the most important reactions in fullerene chemistry are the Diels-Alder and the Bingel-Hirsch additions. In this work, we have quantum chemically explored all possible mechanistic pathways of the Diels-Alder cycloaddition of (1,2,3,4,5-pentamethyl)cyclopentadiene and the Bingel-Hirsch addition of dimethyl bromomalonate to La@C2v
-C82 using dispersion-corrected DFT. La@C2v
-C82 has 24 nonequivalent carbon atoms and 35 different bonds (see Figure 1). Our calculations show that the Diels-Alder reaction to La@C2v
-C82 is very regioselective and occurs exclusively on bond o [1]. On the other hand, La@C2v
-C82 is not particularly regioselective under Bingel-Hirsch conditions. Still, from the obtained results one can make a tentative assignment of the products experimentally observed [2]. According to our calculations [3], the observed fulleroid adduct results from the attack to bond 19 and the singly-bonded derivatives correspond to the C2, C19, C21, and C23 initial attacks. However, other possibilities cannot be ruled out completely.

 

References

1. M. Garcia-Borràs, J. M. Luis, M. Swart, M. Solà, Chem. Eur. J.
2013, 19
, 4468–4479.

2. L. Feng, T. Wakahara, T. Nakahodo, T. Tsuchiya, Q. Piao, Y. Maeda, Y. Lian, T. Akasaka, E. Horn, K. Yoza, T. Kato, N. Mizorogi, S. Nagase, Chem. Eur. J.
2006, 12, 5578–5586.

3. J. P. Martínez, M. Garcia-Borràs, S. Osuna, J. Poater, F. M. Bickelhaupt, M. Solà, submitted for publication.

Figure 1
(Invited) New Endohedral Fullerene Compounds and Derivatives
Authors: Echegoyen Luis
Published: February 2020

We continue to work with uranium-based endohedral fullerenes and have identified several different families of compounds; some incorporate single uranium atoms encapsulated in different sized carbon cages, others incorporate two uranium atoms in variable sized cages and still other families contain odd numbers of carbons atoms, indicative of possible uranium carbides. Several of these new coompounds are being isolated and characterized and the most recent results will be presented.

We are also working with mixed metallic sulfides, including Dy as one of the encapsulated metals, and have managed to purify some of these. The most recent results at the time of the symposium will be presented and discussed.

Finally, functionalization of endohedral fullerenes continues to be a major component of our research efforts, mainly focused on bis-functionalization, and especially interested in the interplay between endohedral cluster nature and structure and exohedral derivatization. We are also exploring tris-functionalization and will present the most recent results at the symposium.
(Invited) Stabilization of Giant Fullerene Cages By Encapsulation of Large Metallic Clusters
Authors: Lu Xing
Published: February 2020

Giant tubular fullerenes are prototypes of finite-length end-capped carbon nanotubes (CNTs) which can be accurately characterized by single-crystal X-ray diffraction. We present here the synthesis, isolation and characterization of several novel tubular fullerene cages stabilized by the encapsulation of a large and streched La2C2 cluster, namely, La2C2@C92-C104. The La2C2 cluster no longer has butterfly configuration in large cages such as (450)-C100, Cs(574)-C102 and D3d(822)-C104 , butit adopts a twisted and nearly planar geometry, which is obviously dependent on the cage symmetry. The strong metal-cage interactions are proved to be responsible for the stabilization of these giant fullerene cages. Furthermore, the analysis of the transformation processes from  large cages to the smaller ones provides crystallographic evidences for the formation mechanism of ideal CNTs from defective ones at the atomic level as probed with single-crystal crystallography, which is instructive to future works of the selective synthesis of ideal CNTs with identical diameter and chirality.
Electrochemical Sodium-Ion Intercalation Reaction at Graphite Electrodes
Authors: Kondo Yasuyuki , Fukutsuka Tomokazu , Miyazaki Kohei , Abe Takeshi
Published: February 2020

Introduction

 Sodium-ion batteries (SIBs) are widely focused on as post lithium-ion batteries (LIBs) from the view of element strategy[1]. Hard carbon electrode is often used as the negative electrode of sodium-ion battery. This is because the graphite electrodes show negligible reversible capacity different from LIBs. Graphite is cheaper and has higher density than hard carbon, and therefore, graphite negative electrode for SIBs should be quite attractive. However, it is well-known that sodium-ion insertion at graphite electrode is very difficult although the reason has not been clarified yet. In this study, the sodium-ion intercalation reaction at graphite electrodes in organic electrolyte solutions was investigated to understand the sodium-intercalation mechanism.

 

Expetimental

 Electrochemical measurements were carried out using a three-electrode cell. Working electrode was graphite composite electrode (natural graphite and graphitized carbon nanosphere[2] (GCNS)). Reference electrode was Ag/Ag+ electrode and counter electrode was natural graphite composite electrode. The electrolyte solution was 0.9 mol kg-
1 sodium bis(fluorosulfonyl)amide (NaFSA)/ethylene carbonate (EC) + dimethyl carbonate (DMC) (1:1 by vol.). Cyclic voltammetry and charge-discharge measurements were carried out. To characterize the sodium intercalated graphite, Raman spectroscopy and X-ray diffraction (XRD) measurement were used.

 

Results

 Figure 1 shows cyclic voltammograms of natural graphite composite electrode in 0.9 mol kg-
1 NaFSA/EC+DMC(1:1 by vol.). Reversible sodium-ion intercalation was not indicated. In charge-discharge curves, large irreversible capacity was observed at the 1st cycle. Reversible capacity was around 5 mAh g-
1. Thus, a small amount of reversible sodium-ion intercalation into graphite was indicated. The XRD patterns for graphite electrodes held at -3.03 V vs. Fc/Fc+ during from 1day to 7 days didn’t change compared with the XRD pattern for pristine graphite electrode. Figure 2 shows Raman spectra of the graphite electrode held at -3.03 V vs. Fc/Fc+. After 1day, G-band around 1580 cm-
1 was split and a new band around 1600 cm-
1 derived from intercalated species[3] appeared. The ratio of band intensity indicated the formation of stage-5 sodium graphite intercalation compound (Na-GIC). The intensity of the new band increased with increasing potential holding time, and the formation of lower stage Na-GIC was indicated. Therefore, the formation of Na-GIC was limited on the surface region of graphite. It suggests that the diffusion of sodium-ion in graphite is very slow.

In the meeting, the results for GCNS will be reported.

 

Acknowledgement

This work was partially supported by ESICB, Kyoto University.

 

Reference

S. Komaba et al., Adv. Funct. Mater., 21 (2011) 3859.

N. Yoshizawa et al., Mater. Chem. Phys., 121 (2010) 419.

M. S. Dresselhaus and G. Dresselhaus., Adv. Phys.,
51 (2002) 1.

Figure 1
In Operando Structural and Acoustic Analysis of Lithium-Ion Batteries
Authors: Hsieh Andrew , Davies Greg , Wang Michael , Steingart Daniel A
Published: February 2020

Previously, we presented proof-of-concept results that demonstrated the promise of electrochemical-acoustic analysis as a scaleable method for in operando battery diagnostics. This technique is based on the redistribution of mass (density) and rearrangement of chemical bonds (modulus) that are fundamental to the operation of all closed, fixed-volume batteries. Using standard ultrasonic non-destructive testing hardware, we showed that for all closed batteries, each cell type (i.e., each chemistry and construction combination) has a unique acoustic fingerprint during cycling. These fingerprints display strong correlations between the acoustic properties of batteries and their state of charge (SOC). Here, we report on results gathered at beam line 6-BM-A at the Advanced Photon Source at Argonne National Laboratory. Simultaneous energy-dispersive x-Ray diffraction (EDXRD) and acoustic analysis measurements were made on several common types of commercial lithium-ion batteries, including LCO, LFP, and NCA. By comparing the in operando structural and acoustic data, we examine and discuss the physical underpinnings of these robust electrochemical-acoustic correlations.
Rechargeability of Manganese Dioxide-Zinc Batteries
Authors: Bonakdarpour Arman , Mehta Sean , Afonso Greg , Wilkinson David P.
Published: February 2020

Primary alkaline batteries use electrolytic manganese dioxide (EMD) as the cathode and zinc as the anode and have been in commercial use for several decades. This chemistry is of great interest because the materials used are inexpensive, environmental friendly, and abundant. In addition, alkaline chemistry offers a better energy density and shelf life than some other aqueous batteries such as lead-acid technology. Rechargeability of EMD, however, is challenging and commercial rechargeable batteries based on this electrochemistry have faced limited success due to the limitation of cycling performance. We have investigated the causes of cycling failures using flatplate-type cathode (MnO2) and anode (Zinc) electrodes which are amenable to large scale production. Electrochemical and physiochemical characterizations were performed and will be presented.

Flatplate-type electrodes were prepared by producing paste-like mixtures of cathode and anode materials and applying them onto expanded Ni (cathode) and expanded brass (anode) current collectors. The cathode mixture contained EMD, graphite, additives, SBR binder and CMC gelling agent. Anode mixtures were prepared from zinc, zinc oxide, hydrogen inhibitors, teflon binder and carbapol gelling agent. The alkaline electrolyte (9M) was prepared from DI-water and KOH salt. All the cell hardware used was developed in-house. For the cathode electrode, a number of chemical additives such as BaSO4, Sr(OH)2·8H2O, Ca(OH)2, and Bi2O3were investigated at 5 wt. %.

Deep discharge cycling (to 1.1 V) reduces the initial specific capacity of 250 mAh g-1 by 50% after 20 cycles. The specific capacity reduces, although at a slower rate, to about 50 mAh g-1 after 100 cycles. Additives such as BaSO4show marginal improvement in the earlier cycles (cycles 10-50), but beyond cycle 50 no noticeable effect was observed. Deeper cycling can be combined with shallow depths of discharge (1.4 – 1.45 V) to extend the cycle life-time of the batteries. Figure 1 shows the cycling performance of RAM cells for combined deep/shallow depths of discharge at C/2 and C/10 rates.

Post-cycling XRD analysis of the cathode electrode shows formation of a todorokite-like phase which could limit the cycling performance. Impedance studies show a rapid increase in the charge transfer resistance, indicating that formation of surface inactive phases also play a role in reducing the capacity upon cycling.

Figure 1
Elevated Temperature Lithium Rechargeable Batteries: Motivation and Challenges
Authors: Addison Dan , Giordani Vincent , Uddin Jasim , Tan Hongjin , Chase Gregory V
Published: February 2020

During the last three decades, research and development in lithium-based rechargeable batteries has primarily focused on cells that are designed to operate at or near ambient temperature. The most successful technology in the field, namely Li-ion cells with intercalation electrodes and organic electrolyte, has enabled the wireless device industry, but it is not ideally suited for long-range, light-duty vehicles, particularly with respect to cost, capacity and abuse tolerance. Alternative electrodes, cell chemistries, and electrolyte materials under development continue to target operation at or near ambient temperature.

This presentation describes research and development at Liox Power, Inc. into high energy lithium rechargeable batteries that operate in the 80 °C to 200 °C temperature range. Specific motivations and challenges will be provided, particularly vis à vis new electrolyte materials, lithium metal electrodes and high energy positive electrode materials. Improvements in properties at elevated temperature expected from Arrhenius behavior will be noted, but we particularly focus on identification of physical phenomena (e.g. phase behavior) that may be uniquely accessed in this temperature range. Results demonstrating substantial improvements in key figures of merit that currently limit advanced rechargeable lithium battery chemistries will be provided.
Countering Degradation of Carbon Felt Electrodes in All-Vanadium Redox Flow Batteries (VRFB)
Authors: Derr Igor , Roth Christina
Published: February 2020

Carbon felt electrodes are used as electrode material in VRFB. The main reasons to use carbon felt electrodes are their corrosion resistance in acidic electrolyte, high overpotential towards hydrogen evolution reaction and low material costs.

Different origins of degradation can be related to dynamic cycling conditions or to possible side reactions. Chemical degradation or aging on the other hand can be caused by simple contact with the electrolyte. The static aging and the dynamic degradation of heat-treated carbon felt electrodes in all-Vanadium redox flow battery systems were investigated by different electrochemical and analytical methods. Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) were used to determine the performance loss of the carbon-based electrodes. Different characterization methods, such as scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), were applied to study cause and effects of material’s degradation.

Chemical aging was found to take place during the first 6 days of mere contact with the electrolyte (1.6 M V3+/4+, 2 M H2SO4, 0.05 M H3PO4). Both, the charge transfer resistance and the diffusion resistance increased with time. Electrochemical degradation was observed for 50 charge and discharge cycles of a 10 cm2 cell with flow-through design and 100 mL of electrolyte. The half-cell potentials shifted towards more negative potentials with an increasing amount of cycles. Chemical aging and electrochemical degradation have a strong impact on the negative half-cell. XPS and SEM reveal that the main reason for the observed performance loss is a decrease of electrochemically active surface area (ECSA) due to the oxidation of the carbon felt to CO and CO2.

The durability of the electrodes was increased by introducing bismuth coated electrodes in the negative half-cell. Bismuth was deposited on the carbon felt with a pulse deposition protocol out of an aqueous solution. Charge and discharge experiments exhibited a more stable performance compared to pure carbon felt electrodes. The half-cell potentials remained constant during cycling but the overall cell resistance was higher, because the electrical conductivity of bismuth is lower compared to graphitic carbon.
Non-Aqueous Redox Flow Batteries Based on Polyoxometalates
Authors: Chen Jee-Jay James , Barteau Mark Alan
Published: February 2020

Renewable energy generation around the world continues to see dramatic growth. According to a recent U.S. Energy Information Administration (EIA) report, 13% of US energy demand in 2013 was met by renewables and the amount is still increasing. Large scale energy storage systems promise to increase the effectiveness of renewable energy sources. Redox Flow Batteries (RFB) represent a highly scalable approach. Traditional RFBs are mostly aqueous which limits their operating voltage range due to water splitting. Non-aqueous systems offer a larger voltage window. Polyoxometalates (POMs), which exhibit versatile redox properties and multiple electron transfers were used as the active species in non-aqueous RFBs. POMs generally contain group 5 or group 6 transition metals linked by oxygen atoms and centered around a heteratom. Common POMs are of the Keggin type ([XM12O40]q−, where X = P, Si, Ge, etc., and M = Mo, W, V, etc. ) or Wells-Dawson type ([X2M18O62]q-).  The redox properties of POMs can be altered by exchanging the framework metal atoms or the central heteroatom very easily.

Li3PMo12O40, Li4PMo11VO40 and Li6P2W18O62 were tested in acetonitrile and the lithium was chosen as the counter-cation in order to avoid H2 generation. Owing to limitations on the transport rate of Li+ through conventional proton-exchange membranes such as Nafion, an aramid nano-fiber (ANF) membrane was utilized for charge-discharge experiments. The low permeability of ANF prevents the POM crossover, with less than 1% crossover observed after one week. Greater than 85% coulombic efficiency was observed for symmetric cells containing the POMs above, with good reversibility and stability.  Both symmetric and asymmetric cells (different POMs utilized for the anolyte and catholyte) were tested. Asymmetric POM-based RFBs hold promise for increasing the voltage window and overall energy density.
Parametrization and Validation of a Vanadium-Redox-Flow Cell Model
Authors: Kleinsteinberg Björn , Çerçi Ayşen , Sauer Dirk Uwe
Published: February 2020

Performance improvement of electrochemical energy storage systems is a continuous process. Every application has its unique requirement profiles. In the field of stationary energy storage the cyclability is an important feature, flow batteries are beneficial for applications with high numbers of cycles. This study focuses on Vanadium-Redox-Flow Batteries (VRFB) to improve an existing cell design. Production of prototypes is expensive, but with a good model optimized geometries can be predicted. A key task is the precise validation of the model to minimize the errors. In this study a model of a VRFB is developed in COMSOL Multiphysics and it is evaluated with measurements on the cell itself.

The model is based on a laboratory cell. It consists of graphite felts as electrodes, separated by an ion exchange membrane and the cupper current collectors are protected from the corrosive electrolyte by bipolar plates. The electrodes are in rectangular shape and squeezed to about 80% of their thickness. The porosity of the electrodes and the specific area were determined with optical measurement methods with a visual light microscope and image processing. The diffusion coefficients inside the electrodes were determined with electrochemical impedance spectroscopy. The diffusion coefficients were determined at different state of charge (SOC) to evaluate the difference in ion transport. The SOC was determined in two different ways, with UV-VIS spectroscopy, measuring the amount of Vanadium species in the electrolyte additionally to potential measurement on cell level before taking the sample. In addition to the data sheet information the commercial vanadium electrolyte was investigated with ICP-OES and the amount of vanadium and sulfuric acid was determined more precisely.  

The model of the cell is a 2D implementation using the here determined parameters of geometry and kinetics of the active material inside the cell. For future purposes it is modeled as the 3D problem, accepting the additional computing time, to increase the precision of the model. The model includes the porous electrodes, the membrane and the bi-polar plates. These are all active parts of a VRFB and the bi-polar plates are included as they might have an effect of the electrochemical reactions too.

The evaluation shows that the model does represent the measured potentials the selected SOCs very well. With the confirmation of the evaluation, it is possible to withdraw information from the inside of the cell which is not accessible otherwise.

The model will be used to determine optimization potentials to simulate them before starting the cost intensive and time consuming prototyping. Another option of this model is its extension towards aging effects of the components inside the cell to give life time predictions for the application.

Figure 1
Bifunctional MnO
x
@Metal-Oxide Core-Shell Structure As Highly Efficient and Durable Oxygen Catalysts
Authors: Cheng Yi , Dou Shou , Saunders Martin , Zhang Jin , Wang Shuangyin , Jiang San Ping
Published: February 2020

It is highly desirable but very challenging to develop bifunctional catalysts for reversible oxygen reduction and evolution reactions (ORR & OER) with high activity and durability. Here a new bifunctional oxygen catalyst based on a core-shell structure of ultrafine metal oxide nanoparticles (NPs) such as NiO, FeO or NiFeO embedded in amorphous MnO
x
, MnO
x
@metal-oxide, has been developed. The best performance was obtained on MnO
x
@NiFeO, exhibiting a potential gap, △E, of 0.798 V to achieve a current of 3 mA cm-2 for ORR and 5 mA cm-2 for OER in 0.1 M KOH solution, better than the 0.924 V and 1.031 V obtained for Ir/C and Pt/C catalysts. Most importantly, MnO
x
@NiFeO shows superior stability, achieving △E of 0.881 V after 300 cycles, significantly better than the 1.093 V obtained for state-of-the-art Ir-Pt/C oxygen catalysts. The high activity and stability of the MnO
x
@NiFeO oxygen catalyst was also demonstrated in a Zn-air battery. The superiority of the MnO
x
@NiFeO oxygen catalyst can be attributed to the excellent ORR activity of the MnO
x
shell enhanced by the synergistic effect between NiFeO and MnO
x
that weakens the adsorption energy of MnO
x
for oxygen species, and the high OER activity of the NiFeO core, and the outstanding structural confinement of the amorphous MnO
x
shell.

Figure 1
Composite Nafion-Functionalized PDMS Electrospun Fibers for Direct Methanol Fuel Cells
Authors: Li Yunxi , Mason George , Hoorfar Mina
Published: February 2020

Direct methanol fuel cells (DMF) have received great attention as a promising portable device due to its high power density, low overall emission and longtime power supply. As the key component of the DMFC system, proton exchange membranes (PEM) are extensively studied since the conception of of proton electrolyte membrane fuel cells in early 1960s. An efficient membrane essentially provides two main functionalities: (1) physically separating the anode from the cathode, and (2) providing proton pathways for inter-electrode proton transport. Nafion is the most widely used PEMs due to its high proton conductivity. Water is of an important element during proton transfer mechanism; however it causes membrane swelling, resulting in serious methanol permeation. To overcome swelling and excessive methanol crossover, a novel PDMS reinforced Nafion membrane is developed in this paper. PDMS has good liquidity before crosslinking due to its flexible molecular structure. Its hydrophobicity also effectively limits membrane swelling in a high relative humidity environment. In this study, Nafion solution is electrospun into mats and the morphological structures are observed via a scanning electron microscopy. Different ratios of Nafion are also mechanically dispersed into PDMS and mixture is successfully infiltrated into the void space among fibers to improve the connectivity of proton transport. The performances of different fabricated composite membranes are compared against a simple Nafion membrane in terms of water swelling and uptake, and the fuel cell performance.
Cycle and Calendar Aging Study of Lithium-Ion Batteries Under Various Vehicle-to-Grid Scenarios
Authors: Devie Arnaud , Dubarry Matthieu
Published: February 2020

Battery degradation is extremely sensitive to usage and chemistry. Some batteries may be markedly sensitive to temperature, to state of charge, to both, or to some other factors. This raises concerns over battery durability in the rollout of electric vehicles (EVs) in hot climate. Additionally, with the integration of more and more intermittent renewable energy power plants on the grid, there is a push to use EV batteries as energy storage systems which may stress the batteries even more. In most studies on the techno-economical impact of EVs on the grid, the battery is often viewed as a black box and therefore there is no real understanding on the actual long term impact of climate and/or vehicle-to-grid (V2G) and grid-to-vehicle (G2V) charging profiles on batteries. This work aims at assessing such impact.

Daily vehicle usage can be broken down into driving, charging and idling periods. In most cases, car batteries spend most of their time idling and it is therefore essential to understand the degradation associated with time, temperature and state of charge on top of the impact of the duty cycles. Herein, we studied the impact of driving on the cell degradation with or without V2G and G2V episodes by looking at both the calendar-induced and cycling-induced degradation. All the data was analyzed using HNEI’s unique diagnosis and prognosis tools [1-3] to forecast the degradation over the battery warranty period and beyond.

This research supports the goals of the Electric Vehicle Transportation Center.

 [1] M. Dubarry, C. Truchot and B.Y. Liaw, J. Power Sources 219 (2012) 204-216

 [2] M. Dubarry, A. Devie and B.Y. Liaw, J. Energy Power Sources 1(5) (2014) 242-249

 [3] https://www.soest.hawaii.edu/HNEI/alawa/
Antimony Sulphide As an Anode Material for Lithium and Sodium Ion Batteries
Authors: Lee Hyukjae , Park Chang-Yong
Published: February 2020

Antimony sulphide (Sb2S3) has been chosen as promising electrode material for lithium and sodium ion batteries due to the high theoretical capacity. In this study, we report on the lithium and sodium electrochemical behaviors of Sb2S3 anode materials with different sizes and morphologies obtained from various routes. Four different types of Sb2S3 samples are evaluated : two commercially obtained bulk crystalline Sb2S3 powders and homemade Sb2S3 powders prepared via mechanical ball milling and hydrothermal technique. For Li-ion batteries, even bulk Sb2S3 shows decent cycling stability and high capacity (more than 500 mAh/g up to 100 cycles) when a proper additive is used. On the other hand, for Na-ion batteries, bulk Sb2S3 results in very poor cycling performance (~ 50 mAh/g at 50 cycles) and rate capability, so that the morphological modification is required to employ as an electrode. The binder and electrolyte additives are proven to be important for both Li- and Na ion batteries. Especially for Na-ion battery, the proper combination of binder and additive is critical to sustain capacity with cycling.
Effect of Chloride Anion on Anodic Dissolution of Aluminum in 4 M NaOH Solution
Authors: Lee Hyeok Jae , Park In Jun , Choi Seok Ryul , Kim Jung Gu
Published: February 2020

Aluminum air battery is a chemical cell that provides theoretical high energy density. However the anodic dissolution rate of aluminum in 4 M NaOH solution is limited by the film formed on aluminum surface. Electrochemical measurements and scanning electron microscope (SEM) images after electrostatic polarization were used to analyze the surface structure, ionic reactions, and anodic dissolution of aluminum in 4 M NaOH. The anodic dissolution is mainly affected by aluminum oxide layer. Chloride anion suppresses the anodic dissolution below the breakdown potential. However, over the breakdown potential, chloride anion breaks down the oxide layer, and accelerates the anodic dissolution of aluminum.
Improvement of Electrochemical Property of Molecular Cluster Ion Cathode Material for Lithium Battery
Authors: Sonoyama Noriyuki , Tsukada Tetsuya , Ni Erfu
Published: February 2020

Polyoxometalates (POM) are very famous cluster ions that can be synthesized self-assembly formation in the solution. These cluster ions behave as independent molecules and show reversible redox activity in the solution. These molecular cluster ions are expected to show different property from the usual cathode materials for lithium ion battery those are the bulk continuum ionic crystals.[1-3] In this paper, we have synthesized Anderson-type POM Na3[AlMo6O24H6] (Fig.1 ) and examined its electrochemical property as cathode materials for lithium battery. In Anderson-type POM, all [MoO6] share the edge with hetero ion [AlO6]. This covalent bond of [MoO6] with unreactive hetero ion would stabilize the structure of the reduced POM.

Anderson-type POMs were synthesized according to the reported method. [4] Obtained samples were mixed with acetylene black with the weight ratio of 1:2 using ball mill. The charge-discharge test and AC-impedance spectra measurements are performed using the coin cells at 25ºC. Lithium metal was used as anode and 1M solution of LiPF6in EC:DEC (3:7 v/v%) was used as the electrolyte. After the charge-discharge measurements, ex-situ XRD and Raman measurements were carried out under Ar atmosphere again.

NMR, FT-IR and Raman spectra of obtained samples agreed with those for reported Anderson-type POM. In Fig. 1, the discharge-charge curves for Na3AlMo6O24H6 were shown. Na3AlMo6O24H6 mixed by ball mill show large capacity over 420 mAh/g. In Fig.2, cycle stability of Na3AlMo6O24H6 was shown. The cycle stability of Na3AlMo6O24H6 was higher than the most representative POM K3PMo12O40 with Keggin type structure. 90% of the initial discharge capacity for Anderson-type POM was retained after 50 cycles, whereas that for KPM decreased steeply in the first 10 cycles.  This result suggests Anderson type POM has higher stability than Keggin type POM.

In the presentation, methods for further improvement of the electrochemical property of POM will be explained.

 [1] N. Sonoyama et al, J. Power Sources, 196 (2011) 6822.

[2] S. Uematsu et al, , J. Power Sources, J. Power Sources, 217, (2012)13.

[3] E. Ni et al. J Nanopart Res, 15(2013) 1732.

[4] Kenji Nomiya et al. Polyhedron, (1987) 213.

Figure 1
Anodizing of MgZn2 Phase in Sulfuric Acid: Mechanism of O2- Diffusion in Mixed (Mg,Zn)O at High Voltage
Authors: Rocca Emmanuel , Tardelli Joffrey
Published: February 2020

The η-MgZn2 phase is an important intermetallic phase present in some galvanized coatings on steel, but also is present as strengthening phase in many aluminum alloys belonging to the 7XXX series. The objective of this work is to characterize the electrochemical behavior of MgZn2 phase in the classical electrolyte of aluminum anodizing, H2SO4 2 M.

Firstly, bulk phase was synthesized by melting pure zinc and magnesium at 700 °C during 1 hour in a furnace under argon flux and then the sample was annealed at 400 °C during 12 hours. As expected by the E-pH diagram of zinc and magnesium, the MgZn2 phase undergoes a rapid dissolution in sulfuric acid medium at open-circuit potential. The surface analyses show a classical morphology of metallic dissolution.

At high voltage (between 3V to 30 V), the dissolution of MgZn2 phase is greatly reduced and the electrochemical measurements reveal the presence of a passivation plateau. Even though the passive current density remains relatively high (around 20 mA cm-2 at 10 V), the formation of a thin layer of oxide on surface was observed by microscopic analysis on surface and metallographic cross-sections (FEG-SEM). X-ray diffraction at grazing incidence and X-ray photoelectron spectroscopy allowed us to determine the overall composition of the oxide, MgxZn1-xO.

The growth kinetic of oxide was characterized versus the voltage and the anodizing time by in-situ electrochemical impedance spectroscopy measurements at high voltage.

At low voltage (< 5 V), the growth of the anodized layer is governed the diffusion of O2- in the solid state under the electric field. Nevertheless, the growth rate is low because the apparent diffusion coefficient, determined by EIS, is low in this voltage range and the oxide dissolution is important in the electrolyte.At high voltage (> 10 V), the in-situ EIS measurements show a blocking behavior of the electrode. The growth rate is managed by the metal/oxide interface and the growth rate of oxide layer remains low in acid sulfuric medium.

 In-situ electrochemical impedance constitutes an important tool to determine the conditions of anodizing and the useful anodizing range of most of metallic materials.
(Corrosion Division H. H. Uhlig Award) Electrochemical Modeling of Intergranular Corrosion and Stress-Corrosion Cracking in AA5083-H131
Authors: Kelly Robert G.
Published: February 2020

Al-Mg alloys containing more than 3 wt. % Mg exposed to temperatures as low as 50oC for long periods of time can form b-phase (Al3Mg2) that will precipitate via heterogeneous nucleation and growth, leading to sensitization, and susceptibility to intergranular attack. The grain boundary precipitation of β-phase is dependent on Mg content, temperature, exposure time, and grain boundary characteristics, and is often practically characterized by degree of sensitization (DoS) defined by ASTM G-67, but more scientifically by β- phase grain boundary coverage.  The presence of the b-phase renders the material susceptible to both intergranular corrosion (IGC) and intergranular stress-corrosion cracking (IGSCC). IGC and IGSCC penetration depend on DoS, but more directly β-phase coverage, grain orientation, temper and critically on electrochemical potential in NaCl solution. An aggressive fissure chemistry must be maintained to sustain IGC/IGSCC growth, and this maintenance depends on the dissolution properties of both α and β phases. Threshold potentials are observed for IGC in NaCl solution. The origins of both the threshold and potential dependency of IGC and IGSCC growth rates in Al-Mg alloys will be discussed in terms of the coverage of β on the grain boundaries and the electrochemical properties of the alloy phases.
Preparation of Niobium Pentoxide Nanotube Powders By a Facile Electrochemical Anodization
Authors: Liu Xiaolin , Lin Jia
Published: February 2020

Niobium pentoxide (Nb2O5) nanostructures are promising candidate for various applications including solar cells, sensors, supercapacitors, photocatalysis, and electrochromic coatings, etc. And the morphologies, crystal structures, and surface areas of Nb2O5 nanostructures greatly affect their devices performances. The electrochemical anodization is a versatile and facile method to fabricate various metal oxide nanostructures, for example, TiO2, Al2O3, WO3, Nb2O5, and Ta2O5. The usual form of obtained anodic metal oxides is thin oxide film attached on metal substrates with nanotube, nanopore or nanochannel structures. Here we report on the fabrication of Nb2O5 nanotube powders by a direct electrochemical anodization method. By simply adjusting the anodization conditions, such as applied voltage, electrolyte composition, and bath temperature, the anodically formed Nb2O5 nanostructures can be spontaneously and continuously released into the anodization electrolyte during the reaction process. After washing and centrifugation, porous powders can be obtained. Under the optimized conditions, the highly porous Nb2O5 powder with nanotube morphology can be obtained, which can provide a very high specific surface area and can be used for various applications. By coating the Nb2O5 nanotube powders onto transparent conducting glasses, the oxide films can be used as the photoanodes for dye-sensitized solar cells with the front-side illumination configuration, leading to a high light harvesting efficiency. The nanotube powders can also be used as an efficient photocatalyst to decompose organic contaminant, with a high decomposition efficiency. The rapid and continuous electrochemical anodization to the formation of Nb2O5 nanotube powders is a promising method for mass production of functional Nb2O5 nanostructures for various applications.
Anodizing of Aluminum in Etidronic Acid Solution
Authors: Kikuchi Tatsuya , Takenaga Akimasa , Nishinaga Osamu , Natsui Shungo , Suzuki Ryosuke O.
Published: February 2020

Introduction

Anodizing of aluminum under appropriate conditions allows the formation of self-ordered porous alumina (porous type oxide film). Ordered porous alumina with large-scale cell sizes and pores is required for expanding the application field in nanotechnology. In the present investigation, we demonstrated anodizing at various conditions in a new electrolyte, etidronic acid, for large-scale ordered porous alumina.

Experimental

High-purity aluminum plates (99.999 wt%) were ultrasonically degreased and electropolished. The electropolished specimens were immersed in 0.2-4.2 M etidronic acid solutions at 288-323 K and then anodized at a constant cell voltage of 145-310 V for up to 24 h. After anodizing, the anodic oxide was selectively dissolved in a 0.2 M CrO3/0.51 M H3PO4 solution at 353 K to expose the aluminum substrate, and then two-step anodizing was carried out for the formation of highly ordered porous alumina. The specimens were examined by field emission scanning electron microscopy (FE-SEM) and image-aberration-corrected scanning transmission electron microscopy (STEM).

Results

Etidronic acid anodizing at 165-270 V and the appropriate temperature caused the self-ordering of porous alumina measuring 400-670 nm in cell diameter. Figure 1 shows an ordered aluminum dimple array fabricated in a 0.2 M etidronic acid solution at 298 K and 260 V for 24 h, and an ideal dimple array was successfully fabricated via etidronic acid anodizing. Ordered porous alumina through the vertical cross-section could be fabricated via two-step etidronic acid anodizing. Phosphorus-free oxide cell boundaries with a honeycomb configuration were measured by STEM-energy dispersive X-ray spectrometry (EDS).

Figure 1. An SEM image of the aluminum dimple array fabricated via 0.2 M etidronic acid anodizing at 260 V for 24 h.

Figure 1
Quantifying the Role of Transition Metal (Re)Plating in the Cathodic Activation of Corroding Magnesium
Authors: Michailidou Emmanouela , McMurray Hamilton Neil , Williams Geraint
Published: February 2020

Magnesium (Mg) and magnesium-based alloys as biodegradable implants form a distinct pole of attraction for the scientific world due to their advantages over conventional biodegradable metallic materials. Regardless, though, of the promising properties that magnesium offers, its extensive use in vivo is restricted with the main limiting factor to be its high rate of degradation. This paper examines the effect that the transition metals, which have been intentionally or unintentionally added as traces within the metal bulk composition, have on the corrosion properties of commercially high purity magnesium. Furthermore, a series of experiments provide an indication regarding the ability of the selected transition metals to accelerate corrosion through the process of (re)plating aiming to gain an insight on the Mg corrosion activation described in recent publications. Consequently, the current research presents the kinetics involved behind the role of the transition metals in the cathodic activation of corroding magnesium.

During the experimental procedure, high purity magnesium samples containing <80ppm Fe were used, while the kinetics of the effect of Fe2+, Cu2+, Zn2+ and Mn2+ transition metal ions were studied as these are the most common traces of addition alloying or impurities found within the bulk composition of magnesium and magnesium alloys. The transition metals were either added into a corrosive electrolyte of 5% aqueous NaCl at near neutral pH at concentrations ranging from 10-6M to 8·10-3M or they were injected in solid form directly on the immediate vicinity of the corroding surface at a weight range of 5mg to 50mg. Following this step was the volumetrically recording of the evolution of hydrogen gas over a constant period of time in order to follow the kinetics of magnesium corrosion.

The results indicate that the presence of transition metal ions within the solution leads to transition metal (re)plating and to an increase of the magnesium corrosion rate. Furthermore, by systematically varying the transition metal ion concentration it was possible to determine the relative efficiencies of the selected metal cations. During the experiment, it was also observed that the metal (re)plating process and the efficiency of the cathodic activation were limited by the formation of insoluble transition metal (hydr)oxide precipitates and the time-dependent hydrolysis. It was possible, though, to minimize the negative effect of hydrolysis by introducing the metal cations directly on the magnesium surface as it may be assumed then that both the diffusion path length and the time period during which hydrolysis can initiate are shorter.
(Invited) In-Situ Detection of Breakaway of Fe-17% Stainless Steel in Water Vapor Containing Air By Synchrotron Radiation X-Ray Diffraction
Authors: Saeki Isao
Published: February 2020

Stainless steels containing more than 16 mass% of Cr show slow oxidation after protective Cr2O3 film has covered the surface at high temperature. For longer exposure, however, oxidation accelerates after non-protective Fe oxide formed. It is important to explain the cause of the transition from protective to non-protective oxidation. Mainly two models have been proposed: mechanical failure and chemical failure of Cr2O3. Objective of this study is to make clear which mechanism is predominant for such a transition on a Fe-17% stainless steel (SS430). Because the transition occurs suddenly at high temperature, no experimental study has made so far. In this study, an in-situ measurement of oxide crystal structure on SS430 stainless steel was carried out at 1373 K using an intense synchrotron X-ray source and the following results were obtained. The surface of the steel was initially covered with Cr2O3, which was then converted to FeCr2O4, and finally Fe3O4 and Fe2O3 formed on SS430 stainless steel. These results indicated that the transition on SS430 stainless steel is due to the chemical failure, in which Cr depletion beneath Cr2O3 layer and the subsequent ionization of Fe took place. Mechanical failure of Cr2O3 can not explain the transition.
Does Hydrogen Affect Oxygen Permeability in Alloys?
Authors: Shemet Vladimir
Published: February 2020

Water vapour and/or steam are well known to accelerate breakaway oxidation of chromia-forming alloys. Some authors have proposed that hydrogen promotes internal oxidation of chromium, resulting in breakaway oxidation. We tested this hypothesis by directly measuring oxygen permeability after oxidation in high pO2
pO2 atmospheres containing water vapour. Palladium with 1 wt% chromium alloy was oxidized in dry and wet Ar-1%O2 at 850 °C. The internal oxidation in all cases obeyed parabolic kinetics. The oxygen permeability deduced from Wagner's diffusion model showed small differences in the internal oxidation of the Pd-1Cr alloy in these gases. We conclude that hydrogen has no influence on oxygen permeability in chromium-containing alloys.
Synthesis, Processing, and Properties of Multi-Phase Metal-Ceramics in the Ta-Hf-C System
Authors: Opeka Mark Matthew , Zaykoski James A.
Published: February 2020

Multi-phase materials in the Ta-Hf-C system were investigated to identify the properties of ceramic-metal (“cermet”) compositions. Eight two- and three-phase ceramics on the Ta2C-HfC, Ta2C-“TaHf”, and Ta-HfC composition lines were prepared from the elemental powders by hot-pressing at 2000°C. They were characterized for phase composition with XRD, microstructure using SEM, four point flexural strength, Vickers hardness, and oxidation testing in air at 600 -1500°C. Two-phase compositions with metal and monocarbide solid solutions exhibited the highest strengths of approximately 800 MPa yet showed the lowest Vickers hardness of 3.5 GPa. The only single phase ceramic investigated, Ta2C, exhibited a very low strength of 114 MPa yet a very high hardness of 15.9 GPa. Other compositions exhibited strength and hardness values within these ranges. Despite the presence of the metal phases, no plasticity was observed in the flexural testing at room temperature. All compositions had good oxidation resistance up to 1000C. The Hf-rich compositions exhibited modest oxidation resistance up to nearly 1500°C, while the Ta-rich ceramics behaved much more poorly and oxidized rapidly above 1000°C.
High-Temperature Reactions of Cesium Molybdate on 304 Stainless Steel
Authors: Do Thi-Mai-Dung , Sujatanond Supamard , Ogawa Toru
Published: February 2020

During a severe accident in a Boiling Water Reactor (BWR), cesium is one of fission products that could be released from nuclear fuel to the reactor vessel and to deposit on the reactor coolant system that is made of stainless steel (SUS). Recently, it has been informed that the released form of cesium is predominantly cesium molybdate. (Cs2MoO4). Under vapor pressure, at high temperature, the deposition of Cs2MoO4 on the surface of oxide SUS could cause some chemical reactions. However, the type of reactions as well as the thermodynamics have not been confimed yet. The aim of this work is to clarify the possible reactions of Cs2MoO4 on the SUS surface at high temperatures. Cs2MoO4 powder was placed in a platinum boat and heated at 1573 K. Either SUS304 or platinum plates were placed downstream at different distances corresponding to temperatures ranging from 1554 to 547 K. The carrier gas was pure argon or argon saturated with steam at 70°C. The flow rate is 100 ml/min. The deposits on SUS304 and platinum plates were examined by X-Ray diffraction equipment (XRD), the micro-Raman spectroscopy and the electron probe micro analyzer (EPMA). The exit gas was passed through the (1%wt HNO3 + H2O) solution. The solution was analyzed by inductively coupled plasma mass spectroscopy (ICP-MS). In dry argon, the obtained deposits on Pt were Cs2MoO4. But on SUS304, the deposits were mainly Mo metal at ~1500 K, then Cs2MoO4 and Cs2Mo2O7 at ~1220K. At further downstream, the deposit were mainly Cs2MoO4. In Ar+steam, on Pt surface, at temperature higher than 1500 K, the deposit could not be obtained, this was probably due to the Cs2MoO4 prefered to stay in gas phase at this stage, but at the temperature below 1200 K, which is close to the melting point (1213 K) of Cs2MoO4, the deposits were predominantly Cs2MoO4. On the surface of SUS304 in Ar+steam, various reactions happened, depending on the temperature. The reaction became even complicated due to the vaporization of CrO2(OH)2. Molybdenum-containing species were found at higher temperatures. But there was no sign of cesium-containing species in SUS304, except for those found on the plates at the low temperatures below ~730 K, where Cs was found as Cs2MoO4.
"Drop-n-Catch" Approach to Calorimetry of Laser Heated Levitated Alumina and Yttria Above 2000 °C
Authors: Kapush Denys , Ushakov Sergey V. , Navrotsky Alexandra
Published: February 2020

Design and processing of ultra-high-temperature materials (aerospace and nuclear applications) demand detailed understanding of thermodynamic properties of their constituents. Nevertheless there is a lack of experimental thermodynamic data above 2000 °C. Even for La2O3, Y2O3, HfO2, and ZrO2binary oxides, high temperature data are often missing and evaluated with a number of assumptions. Among the rare earth oxides, fusion enthalpy data are largely missing.

A recently modified commercial Setaram Setsys DTA instrument working up to 2500 °C allows observation of phase transitions but the lack of reliable enthalpy standards above the melting temperature of Al2O3 (2054 °C) has posed a major problem caused by the absence of reliable sensitivity calibration in the 2100–2500 oC range.

A newly designed "drop-n-catch" (DnC) calorimeter utilizing laser heated levitated samples significantly complement thermal analysis above 2000 °C and makes it possible to measure enthalpies of phase transitions and fusion in variable atmospheres at temperatures limited by the sample only.

Enthalpy increments measured on DnC experiments give the fusion enthalpy in Al2O3 as 117 ± 10 kJ/mol, compared to 120 kJ/mol from FactSage database. The sum  of premelting phase transition (cubic-to-hexagonal) and fusion enthalpies in Y2O3 has been estimated as ~ 155 kJ/mol. These first results open the door to measurements previously inaccessible in terms of temperature range, controllable atmosphere, and lack of sample-container interactions. The instrument and future directions will be discussed.