bluuebunny/crossref_metadata_2025 huggingface dataset:
Three-Dimensional Amorphous TiO2 Thin-Film Electrodes Deposited on Micro-Pillars By Spatial Atomic Layer Deposition for Li+-Ion Batteries
Authors: Moitzheim Sébastien , Balder Elisabeth , Poodt Paul , Unnikrishnan Sandeep , Vereecken Philippe M
Published: February 2020

A promising route to improve Li+-ion batteries in terms of capacity and rate-performance, is the development of all solid-state three-dimensional (3D) thin-film Li+-ion batteries. For this, the use of amorphous TiO2 (am-TiO2) as a 3D thin-film electrode was investigated. Using spatial atomic layer deposition (s-ALD), ~100 nm thick am-TiO2 films were deposited on high aspect ratio silicon micro-pillars. Due to the self-limiting nature of atomic layer deposition, high quality, uniform and conformal films can be deposited even on 3D structures. Spatial ALD is a fast and upscaleable technique which can significantly lower the cost above conventional ALD. The role of the am-TiO2 s-ALD deposition parameters were investigated for optimal conformal coating. With the optimized process, the thickness variation was at most ~20% for layers deposited on an aspect ratio of 25. Furthermore, the am-TiO2 layers using our process are shown to have a very high capacity and rate-performance, far above that for traditional anatase TiO2 thin-films. At a rate of 1C, near theoretical lithium insertion/extraction (i.e. Li1TiO2) is achieved of ~1150 mAh /cm3. Increasing the rate to 20C (theoretical charging in 3 minutes), results in a capacity of ~890 mAh/cm3, which is still above the average capacity of anatase TiO2 of 769 mAh/cm3 (i.e. Li0.6TiO2), which can typically only be achieved for slow C-rates (C-rate << 1C). This report shows for the first time the use of s-ALD to deposit am-TiO2 thin-films on 3D structures with ultra-fast lithium-ion insertion/extraction capabilities.

Figure 1
HE3DA
Authors: Prochazka Jan
Published: February 2020

The HE3DA®concept of several millimeters thick electrodes (3D) gives the battery incomparable safety and brings a number of new technical attributes, which are not achievable by the existing thin film technology (2D).

Recently patented internal cooling system radically shrinks the battery pack size and extends the battery life.

The safe and robust construction with multifunctional frames, easy degassing, low internal resistance and electrolyte regeneration make this new lithium accumulator technology ideal for high capacity batteries and large energy storage modules.

The HE3DA® battery is based on fast Li+ diffusion into nanomaterials, special inorganic separators and several millimeters thick electrodes.

This fully inorganic battery does not contain any organic melting parts, demonstrates a very low internal resistance, allows easy degassing and shows a number of other advantages that are not possible to utilize by the conventional 2D technologies. HE3DA® battery technology provides an inherited safety to the batteries, enabling construction of very large cells on MWh level and modules on hundreds of MWh scale.  

The performance of a small module of HE3DA® battery with photovoltaic panels will be demonstrated.
Aqueous Electrolyte Polyionic Batteries for Scaled Stationary Energy Storage
Authors: Whitacre Jay
Published: February 2020

This presentation will cover the scaling and implementation of large-scale energy storage electrochemical batteries that use largely unexplored electrode interactions that exploit muti-cation interactions simultaneously, and have a high electrode mass to electrolyte mass ratio. The core (anode-limited) electrochemical couple uses a configuration wherein the active anode material consists of a blend of NaTi2(PO4)3 and activated carbon and the cathode is Li-inserted cubic spinel l-MnO2, and the electrolyte is a blend of Li+ and Na+ and hydrogen cation species (at some states of charge) solvated in an aqueous electrolyte with SO4
- and OH-(at some states of charge) as the countering anions. The basic function of the battery will be discussed, and comparisons between small bench top cells and fully scaled product-level devices will be drawn. Data will be presented showing that large scale industrially packaged batteries with over 3000 Wh in capacity have be produced and qualified. Further data will show that packs of these batteries in the multi-kWh range have been effectively implemented in field-testing around the world. These applications include support for both smaller off-grid applications with bus voltages in the in the 20 to 100 V range, as well as, grid compatible systems with bus voltages in excess of 1000 V.

Key topics to be addressed include: (0) a description of the core electrochemical technology, including Na/Li displacement reactions in the anode, (1) a novel charge cutoff methodology that optimizes lifetime and function, (2) lifetime performance of this system through a range of temperatures, and (3) data from field tests in relevant applications showing the performance of our batteries under application specific load profiles.
Improved Performance of Ti/Mn Redox Flow Battery By Thermally Treated Carbon Paper Electrodes
Authors: Dong Yong-Rong , Kaku Hirokazu , Hanafusa Kei , Moriuchi Kiyoaki , Shigematsu Toshio
Published: February 2020

Nowadays, with the fast growing of fluctuating renewable energy like wind and solar, the rechargeable battery technologies have attracted much attention. Redox Flow Batteries (RFBs) offer the independent design of power and energy, which can provide capacity ranging from a few milliseconds to hours. The unique design flexibility and scalability enable RFBs to meet multiple applications simultaneously, such as frequency regulation, peak cut, surplus energy storage and etc. RFBs consist of tanks of electrolyte that storage chemical energy and electrochemical cells that reversibly convert chemical energy to electricity. Various RFBs have been developed, and they can be classified into two types according to the electrolyte: aqueous and non-aqueous RFBs. Among various aqueous RFBs, all vanadium RFBs are the most mature technology and have been used in practical applications.

We reported a Ti(IV) and Mn(II) mixed aqueous electrolyte which is applied for a Ti/Mn RFB[1]. The aqueous Ti-Mn RFB shows a high energy density of 23.5kWh/m3, and provides a low-cost option. However, the current density (50mA/cm2) remained low and need to be improved. The low activity of carbon electrodes leads to the low power density. In order to improve the power density, this work investigates the effect of thermal treatment of carbon papers for both positive and negative electrodes. Through the heat treatment in the air atmosphere, the surface area of the electrode is greatly increased, and the performance is improved at a high current density of more than 100mA/cm2.

Acknowledgments

This work is financially supported by Ministry of Economy, Trade and Industry (METI). This work is technically supported by The National Institute of Advanced Industrial Science and Technology (AIST).

References

[1] Y.-R. Dong et al. ECS Trans., 69(18), 59 (2015).
Solid Dispersion Flow Battery Particle Synthesis and Electrochemical Characterization
Authors: Koenig Gary
Published: February 2020

Flow batteries have a number of advantages as an energy storage system, including the ability to decouple the power and energy of the battery. The electroactive material within traditional flow batteries consists of transition metals dissolved in aqueous acidic electrolytes, however, recently there have been reports of using solid particles as the electroactive material. The advantages of solid particles are that by starting with a solid the solubility of the electroactive species is no longer a limiting factor with regards to energy density and the energy density of the flow battery electrolyte can be increased substantially. In addition, by using organic solvents and lithium-ion battery active materials as the solid particles in the flow battery the energy density of the system can be further improved. A challenge in these so-called semisolid flow batteries is that most have carbon additives that form interconnected electrode structures. The carbon addition significantly increases the viscosity of the electrolyte, which results in additional net energy lost to pumping the electrolyte through the system as well as higher power pumps required to achieve equivalent volumetric flow rates through the channels.

Our research group has been investigating flow batteries that rely on solid electroactive materials. However, within our solid dispersion flow battery system the electrochemical reactions are the consequence of collisions with the current collector. The coupling between electrochemical and rheological properties within this flow battery are highly sensitive to both the fluid flow through the channel and the electrochemically active particle morphology and loading within the electrolyte. Thus, this system requires understanding of the electrochemical properties as a function of both particle loading, particle interactions with the current collector, and the flow geometry that the electrolyte traverses through.

In this talk, we will describe recent work within our group to design scalable processes to synthesize particles that form stable dispersions within the solid dispersion flow battery geometry. The synthesis route consists of sacrificial precursor components that results in loosely connected agglomerate structures that are easily separated to form small, dispersible lithium-ion battery active material particles. We will discuss recent efforts to characterize these lithium-ion battery particles within solid-dispersion flow battery systems and experiments to understand the electrochemical and rheological properties and their coupling within flow batteries comprised of dispersed solid particles. Limitations with regards to power capability and the role of the current collectors within this system will also be discussed.
Photo-Potential Property of TiO2 Electrode Prepared By the Screen Printing Method
Authors: Watanabe Fumi , Motoda Shinichi , Morita Motoaki
Published: February 2020

We have been investigating the marine microbial fuel cell(MFC) composed of biofilm covered stainless steel cathode and TiO2 coated stainless steel anode in seawater. It is necessary to improve the properties of anode electrode for increase the power density of MFC. The purpose of this study is to improve the photo-potential characteristics of TiO2 anode. In the present work, we focused on the film formation method of TiO2 for the improvement of photo-potential properties by introducing screen printing method with the annealing into the coating process of TiO2 film.

The electrode was stainless steel Type 329J4L (40mm in square, 1mm thickness) coated by TiO2 film. Titanium dioxide film was composed of two layers formed by repetition of film forming process with two methods of squeegee printing and screen printing. Sintering condition of first layer took 60 minutes at 150°C and took 30 minutes at 550°C for second layer. The composition of TiO2 paste was as follows, TiO2(anatase):16, alcohols:17 and H2O:67 in mass.%. After film formation, electrodes were annealed with changing heat treatment temperatures. Annealing temperatures were 100°C, 150°C and 200°C, cooling method was air cooling. TiO2 electrodes were immersed in the 1 liter artificial seawater as an electrolyte and photo-potential was measured using the potentiostat with saturated calomel electrode(SCE) as a reference electrode. The light source irradiated was 150W Xenon lamp which was calibrated 250nm to 800nm and quantity of light was 10.5mW/cm2on the electrodes surface.

We measured photo-potentials three times under the light irradiation for each electrode. Steady photo-potentials of electrode manufactured by the squeegee method were -548mV(vs.SCE) at the experiment of first run, -510mV(vs.SCE) at the second and -515mV(vs.SCE) at the third. The increase of photo-potential occurred was considered by the substrate corrosion resulted from small cracks of TiO2 film during the sintering. On the other hand, steady photo-potentials of the electrode manufactured by the screen printing method were -517mV(vs.SCE) at the experiment of first run, -518mV(vs.SCE) at the second and -517mV(vs.SCE) at the third. It was considered that uniformly formed film by the screen printing improved the durability of film. From the results, the durability of electrodes improved reproducibility of repetition by the introducing the screen printing method. It was considered that corrosion which affects the photo-catalytic reaction of TiO2, was suppressed by forming the uniform film due to the screen printing method.

We investigated also the effect of annealing process to the electrode which was coated TiO2 film by the screen printing method. Photo-potentials of electrodes were -557mV(vs.SCE) at annealing temperature of 100°C , -589mV(vs.SCE) at 150°C and -593mV(vs.SCE) at 200°C. It is considered that the increase of the oxygen defect by the annealing process improved the semiconductor intrinsic properties of the TiO2 film.
Electrochemical Intercalation of Bis(trifluoromethanesulfonyl)Imide (TFSI) Anion into Graphitic Carbon from Organic Electrolyte and Application for Dual Carbon Battery
Authors: Kurihara Takuya , Fukuda Taro , Ida Shintaro , Ishihara Tatsumi
Published: February 2020

Li-ion batteries (LIB) are now widely used in various areas such as electric vehicle (EV) or mobile phone. However, there are some issues of LIB like high-cost, safety, and energy density. Therefore, battery that has higher energy density and high power density is strongly required. Dual carbon battery (DCB), which consists of graphitic carbon for both positive and negative electrodes, is attracting much interest because of superior rate property, low cost, and high discharge potential. In this battery, for charge process, Li ions intercalate into anodic graphite, and counter anions in electrolyte also intercalate into cathodic graphite, and for discharge process, de-intercalation is occurred in both electrodes. Therefore, charge and discharge scheme is similar with that of capacitor, however, by using intercalation reaction, much higher energy storage capacity is expected. In our previous study, we investigated dual carbon battery using LiPF6 and demonstrated that discharge is observed at potential from 4.0 to 5V with 90mAh/g-carbon on the full cell and by using the high concentration electrolyte of 3 M LiPF6 in DMC, energy density is also much increased. Since it is reported that intercalation potential increases with increasing ionic size of anion, we investigated electrochemical intercalation property of bis(trifluoromethanesulfonyl) imide (TFSI) anion in this study. Effects of electrolyte on intercalation of TFSI anion into graphitic carbon was investigated and it was found that intercalation of TFSI anion was observed in propylene carbonate (PC) based electrolyte at room temperature. Among the electrolytes examined, the largest intercalation capacity was achieved in PC-EMC(1:1). By using 3MLiTFSI/PC-EMC (1:1), discharge capacity of 110mAh/g was stably sustained over 50 cycles, however, coulombic efficiency is around 90%. Further detail study was performed on intercalated structure of TFSI anion. Comparing with PF6 anion, intercalation potential is almost the same, however, the capacity is larger (90 mAh/g for PF6, and 110 mAh/g for TFSI). Therefore, it was found that the intercalation of TFSI anion is also usable for cathodic reaction in dual carbon battery. Stage structure of intercalated TFSI- is also studied by using in-situ XRD and it was confirmed that the distance of (002) plane of graphitic carbon was expanded by increasing potential suggesting that electrochemical intercalation of TFSI anion is occurred. From the distance of (002) plane, stage 1 structure seems to be observed at 5.2V with 0.79 nm distance which is little larger than that of PF6- (0.77nm). Although expansion of electrode is little larger, TFSI anion is also promising anion for dual carbon battery from high potential plateau (5V) and large capacity (110mAh/g).
Density Functional Theory Modeling of Boron-Doped Graphene Flakes for Electrochemical Storage Applications
Authors: Zhu Yuntong , Kim Ki Chul , Jang Seung Soon
Published: February 2020

In recent years, electrochemical energy storage devices such as lithium ion batteries and lithium sulfur batteries have been intensively developed to meet the increasing demand for portable electronic devices and electric vehicles. Despite such considerable efforts, the performance of the batteries is still limited by the cell voltage drop which is observed during the charging/discharging cycles. Therefore, a suitable methodology need to be systematically developed to design promising cathode material candidates with high redox potentials and thereby inherently maximize the cell voltage. Well-designed materials should be able to not only have the high onset redox potentials but also sustain the high redox potentials without significant voltage drops during the discharging process. In this work, a series of boron-doped graphene materials with various boron concentrations and distributions are designed and investigated using density functional theory modeling. It is stressed in this work that the redox and electronic properties can be tailored by the boron atoms doped on the graphene flakes. This provides better understanding of the redox property of the boron-doped graphene flakes and offers valuable information for the high-performance material design in electrochemical energy storage devices.
Effects of Additives on the Stability of Positive Electrolytes for All-Vanadium Redox Flow Battery
Authors: Park Se-Kook , Jin Chang-Soo , Yeon Sun-Hwa , Shin Kyoung-Hee , Lee Bum suk
Published: February 2020

The all- Vanadium redox flow battery (VRFB) is a promising technology for large-scale electrical energy storage systems[1, 2]. VRFB is an electrochemical system using reactions of two redox couples of V2+/V3+ in a negative half-cell and VO2+/VO2
+ in a positive half-cell to perform a reversible conversion between electrical energy and chemical energy. However, poor stability of the electrolytes, especially the positive electrolyte, greatly limits the concentration of redox couples in the electrolyte solution, which significantly affects the performance of VRFBs[3, 4].

In order to achieve high electrolyte performance, a sodium pyrophosphate dibasic (SPD) introduced as an inorganic additive in positive electrolyte VO2
+ for VRFBs. And its effects on long-term stability and electrochemical performances were investigated, through UV-vis spectrophotometry, cyclic voltammetry, and through the performance of a charge/discharge test.

[1] A. Parasuraman, T.M. Lim, C. Menictas, M. Skyllas-Kazacos, Review of material research and development for vanadium redox flow battery applications, Electrochimica Acta, 101 (2013) 27-40.

[2] A.Z. Weber, M.M. Mench, J.P. Meyers, P.N. Ross, J.T. Gostick, Q. Liu, Redox flow batteries: a review, Journal of Applied Electrochemistry, 41 (2011) 1137-1164.

[3] J. Zhang, L. Li, Z. Nie, B. Chen, M. Vijayakumar, S. Kim, W. Wang, B. Schwenzer, J. Liu, Z. Yang, Effects of additives on the stability of electrolytes for all-vanadium redox flow batteries, Journal of Applied Electrochemistry, 41 (2011) 1215-1221.

[4] S.-K. Park, J. Shim, J.H. Yang, C.-S. Jin, B.S. Lee, Y.-S. Lee, K.-H. Shin, J.-D. Jeon, Effect of inorganic additive sodium pyrophosphate tetrabasic on positive electrolytes for a vanadium redox flow battery, Electrochimica Acta, 121 (2014) 321-327.
Indirect Fuel Cell Based on a Redox-Flow Battery Toward the Reduction of Platinum Usage
Authors: Siroma Zyun , Maruyama Jun , Yamazaki Shin-ichi , Ioroi Tsutomu
Published: February 2020

An indirect fuel cell [1-3], which is composed of a redox-flow battery (RFB) and a chemical reactor to regenerate (oxidize) the catholyte by oxygen and another reactor to regenerate (reduce) the anolyte by a fuel, is constructed as an alternative to a PEFC. We have already proposed a new design for the RFB [4] for our indirect fuel cell, which has a gas phase of hydrogen to separate the catholyte and anolyte to eliminate the crossover of ionic species. In this work, to clarify the possibility to use an indirect fuel cell to reduce the usage of noble-metal catalysts, a non-noble-metal catalyst and a mixture of two molecular catalysts were used in the catholyte and anolyte regenerators, respectively. In the catholyte regenerator, a carbonized hemoglobin powder was used as a solid catalyst. This material has been proved to be effective as an electrocatalyst for oxygen reduction reaction (ORR) in a PEFC [5]. In this work, it was used after immobilization on a polymer sheet support. In the anolyte regenerator, a rhodium complex was used for hydrogen oxidation and another rhodium complex for carbon monoxide oxidation. Although these two complexes contain a noble metal, they are soluble in the electrolyte and used as homogeneous catalysts. Since the active site of such a complex molecular catalyst is a single metal atom, the usage of metal can be reduced compared with a metallic platinum catalyst.

This work demonstrates a steady-state operation of the above-mentioned indirect fuel cell by feeding of oxygen and CO-containing hydrogen to the catholyte and anolyte regenerators, respectively.

This work was supported by JSPS KAKENHI Grant Number 25289363.

[1] A.M. Posner, Fuel, 34 (1955) 330.

[2] S. Ashimura, Y. Miyake, Denki Kagaku, 31 (1963) 598.

[3] D.-G. Oei, J. Appl. Electrochem. 12 (1982) 41.

[4] Z. Siroma, S. Yamazaki, N. Fujiwara, M. Asahi, T. Nagai, T. Ioroi, J. Power Sources, 242 (2013) 106.

[5] J. Maruyama, I. Abe, Chem. Mater., 18 (2006) 1303.
Effects of Applied Strain and Sensitization on SCC Behavior of 304 Stainless Steel in Atmospheric Corrosion Environments
Authors: Tada Eiji , Nakao Kazuki , Yamada Shinji , Nishikata Atsushi
Published: February 2020

Austenitic stainless steels have relatively good corrosion resistance due to the formation of a Cr-rich passive film. However, in atmospheric corrosion environments near seashore, austenitic stainless steels can suffer from localized attacks such as pitting corrosion and crevice corrosion. This is due to the formation of thin water layers containing high concentration of chloride ions on the stainless steels. In addition, when the steels are subjected to tensile stress or deformation, stress corrosion cracking (SCC) can occur from pits. Since it is well-know that sensitization can enhance SCC susceptibility of austenitic stainless steels, it is needed to clarify the effect of deformation and sensitization on the SCC of the steels in atmospheric corrosion environments. In this study, crack initiation and propagation behavior of sensitized 304 stainless steels was investigated under a MgCl2 solution droplet. The experimental results demonstrated that cracks were initiated from pits by applying plastic deformation. It was confirmed that hydrogen evolution was observed during propagation of the cracks. In the presentation, SCC mechanism of sensitized 304 stainless steels in atmospheric corrosion environments will be discussed.
Recovery of the Pitting Corrosion Resistance for a Sensitized Duplex Stainless Steel Using Interstitial Hardening
Authors: Tailleart Nicole R , Martin Farrel J , Rayne Roy , Bayles Robert , Rubinoff Aron , Levenberry Leroy , Natishan Paul M.
Published: February 2020

A cast duplex stainless steel, alloy 2205, a mix of ferrite and austenite, was heat-treated at 845 oC for 1 and 5 hours. These heat treatments resulted in the formation of additional phases, e.g. sigma and chi, which depleted the surrounding grains of passivity promoting alloying elements such as Cr, causing alloy sensitization and a corresponding decrease in the pitting resistance. A low temperature gas-phase interstitial hardening (IH) surface modification process was used to surface alloy sensitized samples. Anodic polarization curves showed that after receiving the IH treatment, the pitting resistance, determined by the pitting potential, of sensitized samples was restored to values of the as-cast material.
Investigation of Structural Change of Rust Layer of Steels during Wet and Dry Cycles By Synchrotron Radiation and Neutron Beams
Authors: Nakayama Takenori
Published: February 2020

The authors carried out in-situ inspection of the very early stage of rust formation for iron under wet/dry cycle by SR-XRD at SPring-8. The result seems to agree with the electrochemical redox model proposed by U. R. Evans, which states that, in wet processes, FeOOH is reduced into Fe3O4 by cathodic reduction, which acts as an oxidant to promote the corrosion of iron, while, in dry processes, Fe3O4 is oxidized by air into FeOOH: these processes are repeated, promoting atmospheric corrosion. The small angle neutron scattering experiments at J-PARC also showed that fine particles a few nanometers in size were yielded during the wet → dry period, but they disappeared during the dry → wet period.
Effect of Metal Cations in Fresh Water on Surface Film Structure and Initial Corrosion of Mild Steel
Authors: Otani Kyohei , Sakairi Masatoshi
Published: February 2020

Corrosion of steel in fresh water is a serious problem in circulative cooling systems, water supply systems and water storage tanks, therefore many researchers have reported the corrosion of steel in fresh water.1 The initial corrosion behavior of steel has been discussed on the basis of oxide films, and the films are generally destroyed by chloride ions.2 On the other hand, Kato et al. investigated the corrosion behaviour of mild steel by focusing on the effects of metal cations, and they found that some cations show corrosion inhibiting ability.3 However, there have been a few study in which the quantitative effects of metal cations on corrosion of steel in fresh water, and the effect of metal cations in solution to the oxide films has not been clarified.

The authors focused on “hardness of cations, X” to explain the different effect of metal cations on oxide films of mild steel. X is an indicator of the basis of HSAB concept,4 and the value means that tendency of the incorporation between the metal cations and oxygen atoms in the passive films. Therefore, it is expected that the effect of metal cations in solution to the oxide film and the corrosion of mild steel would be explained by using X.

The effects of metal cations on the oxide films and corrosion of mild steel in model fresh water were investigated by immersion tests with surface analysis of X-ray photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy (EIS). Five different salt solutions, NaCl (Nasol), MgCl2 (Mgsol), ZnCl2 (Znsol), AlCl3 (Alsol), and ZrCl2O (Zrsol), were used as model fresh water, and the concentration of chloride ions in each solutions was the same. Analysis of XPS showed that metal cations that have large hardness of cations, X, were incorporated with passive films, and then the hydroxides of metal cations were formed on the mild steel. The EIS and immersion results showed that the initial corrosion resistance of mild steel increased with increase in X except for the specimens immersed in Mgsol and Zrsol.

Reference

1. R. E. Melchers, Corros. Sci., 48 ,4174 (2006).

2. H. J. Engell, Eletrochimica Acta, 22, 987 (1977).

3. M. Kato, Boshoku Gijutsu, 31, 27 (1982).

4. M. Misono, E. Ochiai, Y. Saito, Y. Yoneda, J. Inorg. Nucl. Chem., 29, 2658 (1967).
(Invited) Fabrication of Highly Ordered Anodic Porous Alumina and Its Applications to Functional Nanodevices
Authors: Masuda Hideki , Yanagishita Takashi , Kondo Toshiaki
Published: February 2020

The anodic porous alumina, which is formed by anodization of Al in an acidic electrolyte, has attracted much interest as the starting materials for various types of functional nanodevices due to its unique geometrical structures.1) It has been reported that long-range-ordered anodic porous alumina with an ideally ordered hole arrangement can be obtained under appropriate anodization conditions.2-4) Such ordered structures are useful for the preparation of the functional nanodevices, which require the ordered nano- structures. The control of hole intervals and hole sizes of anodic porous alumina while retaining the long-range ordered hole arrangement is very important for expanding the application fields of the anodic porous alumina. As an example of the expansion of the range of the hole intervals and hole sizes with long-range ordered hole arrangement, we have shown the formation of long-range-ordered anodic porous alumina with reduced hole intervals and hole sizes. In this process, highly ordered anodic porous alumina with reduced hole interval of ~25 nm can be obtained by the appropriate anodizing condition5,6). In the present report, the formation of the highly ordered anodic porous alumina with various hole intervals and hole sizes will be presented. In addition, the template synthesis of the ordered nanostructures with reduced dimensions will be also reported.

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

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

3. H. Masuda, F. Hasegawa, and S. Ono, J. Electrochem. Soc., 144,L127 (1997).

4. H. Masuda, K. Yada, and A. Osaka, Jpn. J. Appl. Phys., 37, L1340 (1998).

5. H. Masuda, M. Nagae, T. Morikawa, and K. Nishio, Jpn. J. Appl. Phys., 45, L406 (2006).

6. H. Masuda, K. Takenaka, T. Ishi, and K. Nishio, Jpn. J. Appl. Phys., 43, L1165 (2006).
The Effect of Thermal Hydrogenation Processing on the Nano-Size Grain Refinement and Oxide Layer Fomation of Ti-6Al-4V Alloy
Authors: Wang Le-Min , Tsai Chih-Jen
Published: February 2020

Our earlier works have shown that the better corrosion resistance of Ti-6Al-4V alloy can be achieved by applying a post-THP annealing treatment associated with a controlled oxidation reaction which can produce ﬁner oxide particles and almost seal the oxygen diffusion paths leading to the formation of a much thinner (0.56 μm), but denser oxide layer than has been indicated in the literature [1,2].

This study aims to investigate the effect of common industrial heat treatments on the mechanical properties and corrosion resistance of Ti-6Al-4V alloy following thermal hydrogenation processing (THP) plus related heat treatments under variant hydrogen loadings. The correlation among the microstructural characteristics in matrix, the oxide layer structure on the surface, and the corresponding properties of the samples after related treatments was analyzed. The phase transformation, microstructural evolution, the formation of intermetallic compounds, oxide layer and the possible mechanism of grain refinement into nano-size scale were also discussed by using HRTEM under variant hydrogen loadings.

Keywords：Ti-6Al-4V alloy, Thermal hydrogenation processing, Heat treatment, Microstructure, Oxide layer, , Corrosion resistance, HRTEM.

References

[1]Tsai, C. J. and Wang, L. M., “The Effect of Thermal Hydrogenation Processing on the Oxide Layer Formation of Ti-6Al-4V Alloy,” Journal of the Electrochemical Society, Vol. 160, pp. C560-C568, 2013.

[2] Tsai, C. J., Yu, S. S., Wang, L. M., and Shen, C. C., “The Effect of Thermal Hydrogenation Processing on the Oxide Layer Formation of Ti-6Al-4V Alloy,” ECS Transactions, Vol. 50(30), pp. 79-90, 2013.

Figure 1
(Invited) Surface Modification and Coating of Biodegradable Magnesium
Authors: Virtanen Sannakaisa
Published: February 2020

The possible use Mg alloys in biodegradable biomedical devices has found tremendously increasing research interest in recent years. For successful applications, the degradation behavior needs to be optimized. Therefore, a large amount of research has been carried out to control the corrosion rate, either by alloying or by surface modification. There is still need for optimization and further development of biocompatible, biofunctional and biodegradable coatings for Mg alloys. The presentation discusses some recent developments in biocompatible surface modification and coating of Mg. On one hand side, different types of conversion coatings have been studied that may either function as a pre-treatment for subsequent coating steps or even offer sufficient short-term corrosion protection as such. On the other side, preparation and properties of various biocompatible polymer coatings on Mg will be presented.
Multifunctional Titanium Dioxide Nanotubes for Biomedical Applications
Authors: Shokuhfar Tolou
Published: February 2020

Engineered-nanotubular structures offer exciting progress toward the design of multifunctional medical implants. Using facile electrochemical technique based on low cost electrode materials, we have been able to fabricate three-dimensional high quality self-aligned nanotubes on the surface of arbitrary geometries. We have observed that the fabrication of TiO2 nanotubes with elastic modulus close to actual bone promotes osteoblast growth. In addition TiO2 nanotubes could be considered a suitable alternative route for the development of drug-eluting antimicrobial implants due to the fact that these nanostructures are not an added coating but rather are rooted in the implants and will not delaminate from the surface. Such drug-eluting implants can prevent unnecessary side effects caused by oral administration of drugs, increase drug efficiency, and prevent infection related implant complications and failures. The PI would like to acknowledge the funding from NSF CAREER as well financial support from NSF-Major Research Instrumentation, Pacific Northwest National Laboratories, North Carolina Nonwoven Institute, Chicago Biomedical Consorsium, and USG company.
Dissociation Oxygen Partial Pressure of CaPd3O4 from 1023 to 1328 K
Authors: Kawamura Kenichi , Yuasa Yasunori
Published: February 2020

Introduction

The high level radioactive wastes in spent fuels are immobilized in borosilicate glass. The spent fuels is mixed with borosilicate glass and the mixture is heated by joule heat directly supplied by electrical current. The oxides of platinum group metals (Rh, Pd or Ru) exist in the spent fuels. Since the oxides are easily reduced resulting in low resistivity, their thermodynamic properties are indispensable to establish the immobilizing process. The object of this study is to make clear the dissociation oxygen pressure over the Pd-CaO-CaPd3O4 coexistence by using the electrochemical cell.

Experimental

The dissociation of CaPd3O4 is represented by

2CaPd3O4 → 2CaO + 6Pd + 3O2 (1).

Equilibrium oxygen partial pressures of the above reaction were measured by oxygen concentration cells using CaO stabilized ZrO2 solid electrolyte.

The cell is described as

Pt, CaO, CaPd3O4, Pd, O2(sample) |CSZ| O2(air), Pt.

Electromotive force (emf) of the cell from 1023 to 1328 K was measured by a digital volt meter with impedance of 109 Ω.

Results and discussion

The equilibrium value was adopted from an average of emfs for last 30 s when the changes in the emfs were within 1 mV par 30 ks. The least squares fits give the emf's of the cell in the following expression.

E/V = 0.6781 − (5.177x10-4) T

From the obtained emf values, the equilibrium oxygen partial pressures of Pd-CaO-CaPd3O4 coexistence is represented by

log p(O2)/bar = 51.8 - 72.6x103/T.

Therefore, the dissociation oxygen partial pressure is higher than atmospheric oxygen partial pressure above 1310 K.

From the obtained equilibrium oxygen partial pressure, the standard Gibbs energy change of the reaction (1) is represented by

∆G
0(1) / kJ mol-1 = -262.0 + 0.1871 T.

Using the reported values of the standard Gibbs energy of formation of CaO, we obtained the standard Gibbs energy of formation of CaPd3O4 as follows.

Δf
G
0(CaPd3O4) / kJ mol-1 = -1034 + 0.3904T.
Improvement of Oxidation Behavior in Cr(N,O) By Increasing the Oxygen Content
Authors: Suematsu Hisayuki , Suzuki Kazuma , Suzuki Tsuneo , Nakayama Tadachika , Niihara Koichi
Published: February 2020

Chromium oxynitride(Cr(N,O)) thin films have been developed by controlling the oxygen partial pressure during the deposition 1). The Cr(N,O) thin films show superior properties not only the hardness but also the oxidation behavior than those of CrN, which are suitable for machining tool applications. However, the reason of the oxidation improvement was not known because of the presence of grain boundaries. Recently, we have succeeded in preparation of epitaxially grown Cr(N,O) on MgO and other single crystal substrates to reduce the density of grain boundaries2). In this work, oxidation behavior of the epitaxially grown Cr(N,O) thin films was investigated from crosssectional transmission electron microscope (TEM) observations.

Thin films of Cr(N,O) were epitaxially grown by a pulsed laser deposition method. In the deposition chamber, oxygen gas with a partial pressure of 2x10-5Pa and N radicals from an RF radical source were introduced. A plate of Cr was rotated in the deposition chamber was irradiated by a Nd:YAG pulsed laser with a wavelength of 355 nm. Thin films were deposited on MgO (100) single crystal substrates kept at 973 K in the deposition chamber. After the deposition, oxidation tests were carried out in a furnace at 673-1173 K in air for one hour. After the oxidation tests, powder X-ray diffraction (XRD), crosssectional TEM and electron energy loss spectroscopy (EELS) observations/analyses were conducted for precise phase, microstructure and composition analysis.

From the XRD and TEM analyses, the as-deposited thin films were of epitaxially grown Cr(N,O) on the substrates. After the oxidation tests, from XRD patterns, peaks for Cr2O3were seen from samples heated above 873 K. On the other hand, peaks for Cr(N,O) remained up to 1073 K. From TEM and EELS analyses of the sample heated at 1073K, on the existing Cr(N,O) epitaxially grown thin film, a polycrystalline oxide layer was covering. It was found that the oxide layer works as an oxygen diffusion barrier from the surface.

References

1) T. Suzuki, J. Inoue, H. Saito, M. Hirai, H. Suematsu, W. Jiang, and K. Yatsui, Thin Solid Films 515, 2161 (2006).

2) K. Suzuki, T. Endo, A. Sato, T. Suzuki, T. Nakayama, H. Suematsu, and K. Niihara, Mater. Trans. 54, 1957 (2013).
Kinetics and Microstructure of Sulfonitriding of Die-Steels
Authors: Nanko Makoto , Horie Kazuya , Nakagane Ryosuke , Kadowaki Satoru , Kuwabara Yoshihiro
Published: February 2020

Sulfonitriding is one of the surface treatments of die made of steels for forging and casting. In this surface treatment, annealing under NH3 and H2S containing atmosphere provides the formation of top sulfide layer on the nitrided zone. The surface sulfide zone has anti-seizure and lubrication effects during forging and casting processes. In this study, microstructure development and its kinetics in sulfonitriding of die-steels.

Commercial die-steels, JIS-SKT4 and JIS-SKD61, were used. Those steels were annealed under gas-mixture of N2 and H2S at 520°C for 0.5 h and NH3for 2.5 h. Microstructure of the samples was observed by using scanning electron microscopy (SEM) and electron probe micro-analyzer (EPMA). Phase identification of the samples was conducted with X-ray diffraction (XRD). Chemical profile from the surface was obtained by using glow discharge spectroscopy (GDS).

A thin continuous layer with 2 -3 μm in thickness was developed on the surface of die-steels. XRD revealed the formation of FeS after sulfonitriding process. The FeS layer was so dense without significant pore network. Results of GDS and EPMA shows that the surface FeS layer include nitrogen and Cr. Inner nitrided zone consisted of mainly Fe3N. Repeating the sulfonitriding process, thickness of the top FeS layer and Fe3N zone increase parabolically. As a result of the marker experiments with Al2O3 particles, top FeS layer was developed by the outward diffusion of Fe and Fe3N zone was grown with inward diffusion of N. Because open pore network in the top FeS layer was not observed, inward diffuses of nitrogen passing through the top FeS layer occurs during sulfonitriding process.
High Temperature Corrosion of High Strength Materials for Boiler Applications in the Temperature Range from 550 C to 750 C
Authors: Singheiser Lorenz , Zurek Joanna , Huczkowski Pawel , Müller Michael , Quadakkers Joe
Published: February 2020

Since more than 10 years boiler concepts up to 750 °C using ferritic-martensitic and austenitic steels as well as nickel base alloys above 650 °C have been developed to increase power plant efficiency and to reduce CO2- emissions by post combustion as well as oxyfuel processes.

The paper summarizes the influence of temperature and Cr- concentration on the steam oxidation behavior of ferritic martensitic steels as well as of austenitic steels and their limits for long-term high temperature applications, which are mainly determined in conventional boiler applications by steam oxidation. For temperatures well above 650 °C nickel base alloys have to be used, which have good steam oxidation resistance, if Cr- contents are high enough. At temperatures above 670 °C nickel base alloys are prone to type II hot corrosion on the fireside of superheaters, if deposits with high NaSO4 and sulfur content are formed as a consequence of Na- and sulfur rich coal combustion. The maximum of hot corrosion attack is at 750 °C, in good agreement with similar results obtained from gas turbine experience. The susceptibility to hot corrosion can be calculated using Calphad based simulation, if coal composition and combustion conditions are known.

Oxyfuel processes exhibit high CO2- concentrations between 60 to 70 % and approx. 30 % H2O. Due to recirculation of dust free exhaust gas to increase heat transfer within the boiler and superheater, impurities like SO2, NOX and HCl may result in increased oxidation and sulfidation rate. The high CO2- content result in extended internal carburization of ferritic martensitic steels, if water vapor contents are low. With increasing water vapor content, carburization rate decreases due to reduced carbon activity according to the water gas shift reaction. Formation of chromia scales on austenitic steels as well as nickel base alloys prevents carbon uptake in the base alloys. The higher SO2- contents in the oxyfuel flue gas power plants do not significantly accelerate corrosion rates of ferritic martensitic steels at temperatures below 600 °C, which are currently considered for oxyfuel power plants.
Environmental Degradation of Au-Nanoparticle Incorporated Oxides By Reactive Evaporation of AuH(g)
Authors: Holcomb Gordon R , Tylczak Joseph , Baltrus John P , Ohodnicki Paul R
Published: February 2020

Au-nanoparticle incorporated metal oxide based sensing layers show significant promise for high temperature remote optical sensing applications at temperatures approaching 800°C—or higher depending upon the base oxide material. Simultaneous measurements of temperature and gas composition are possible. Simplified specimens of Au-nanoparticles on SiO2 substrates were exposed to N2 and N2-H2 environments for one week at 700 to 800°C. Loss of Au, as measured by X-ray Photoelectron Spectroscopy (XPS), was detected after exposure in N2-H2 environments with both low (1%) and significant (29%) amounts of H2, and not detected after exposure in pure N2. Thermodynamic and kinetic calculations were made of reactive evaporation reactions of Au to form AuH(g), which were consistent with the observed results.
A Study of High Temperature Stability of Zirconia Surface in Pressurized Water with High Resolution X-Ray Reflectivity
Authors: Hou Binyang , Park Changyong , Kim Seunghyun , Kim Taeho , Kim Ji Hyun , Kim Jongjin , Hong Seungbum , Bahn Chibum
Published: February 2020

Metals and metal-alloys under hydrothermal conditions undergo accelerated corrosion and degradation which is detrimental to the integrity and safety of many industrial operations. Owing to their low thermal neutron cross-section, reasonable mechanical properties, and adequate corrosion resistance in high temperature water, zirconium alloys have been used as nuclear power plant fuel cladding materials. The presence of a passive oxide layer on the zirconium surface acts as a barrier to mitigate further corrosion of the metal, which plays a key role in sustaining the integrity of cladding. However, the continuous growth of zirconia on the alloy surface limits the life span of the cladding material and therefore reduces the burn-up efficiency of the nuclear fuel and also introduces potential safety risks. Despite the factor that there exists numerous studies on the mechanisms of in-reactor corrosion of zirconium alloys, the very initial stage of the degradation mechanism still remains unclear. With development of a hydrothermal cell dedicated for in-situ synchrotron X-ray reflectivity measurement of oxide-water interface, we successfully measured the interfacial structure at yttria-stabilized zirconia, or YSZ, (111) surface for a series of temperatures ranging from room temperature up to 360 ºC in pressurized water condition of ~20 MPa. As the temperature increases, small changes in the X-ray reflectivity are observed which is presumably attributed to atomic level modification of the interfacial structure. With increasing duration time for hydrothermal reaction at higher temperatures above 340 ºC, the change in the X-ray reflectivity patterns becomes distinct and a layered structure in addition to the ambient hydration structure could be qualitatively deduced from the measured X-ray reflectivity data. Interestingly, however, when the temperature goes back to 50 ºC, the ambient hydration structure was recovered although it was not perfectly reversible but qualitatively similar. The quantitative analysis of the X-ray patterns at different temperatures and hydrothermal reaction time will provide valuable information on the interfacial hydration structure and processes from the molecular level insight.
Effect of H2O on Corrosion of Ni in Molten Eutectic LiCl-KCl
Authors: Horvath David , Simpson Michael Forrest
Published: February 2020

In the absence of water and oxygen, it is known that molten chloride salts are relatively non-corrosive to a wide range of metals. Corrosion rates are expected to increase when water is present, however. To understand the threshold at which very small concentrations of water can cause corrosion of metals such as nickel and iron, a series of electrochemical measurements were made in molten eutectic LiCl-KCl and LiCl-KCl-UCl3. The presence of UCl3 is relevant for the use of this electrolyte in nuclear fuel electrorefining systems. Such systems are normally operated in inert atmosphere glove boxes or hot cells, where water concentration ranges from 1 to 50 ppm. In this study, argon gas containing up to 900 ppm H2O was bubbled into molten LiCl-KCl or LiCl-KCl-UCl3. Either a nickel or iron rod was inserted into the salt along with a Ag/AgCl reference electrode encased in a close-ended ceramic tube. The open circuit potential (OCP) was measured between the metal rod and the reference electrode as the gaseous Ar+H2O was bubbled into the salt. The temperature was held constant at 773 K. This is expected to result in formation of HCl, which will corrode the metal and cause a metal chloride to form and partition into the salt phase. Based on the Nernst Equation, this should cause a positive rise in the OCP. Based on changing OCP as a function of time, the rates of corrosion were compared for different concentrations of H2O in the gas stream. Cyclic voltammetry scans and samples of the salt were taken to verify the concentration of nickel and iron chloride in the salt at the end of each experiment. Noticeable corrosion was achieved in a time frame of 4 hours with water concentration as low as 120 ppm. This result demonstrates the importance of achieving a very high level of dryness in the salt prior to heating and melting it. Water concentration in the contacting atmosphere should also be well below 100 ppm to ensure long-term stability of the steels and similar metal alloys in molten LiCl-KCl or LiCl-KCl-UCl3. Implications and strategies for long term operation of electrorefiners using LiCl-KCl will be discussed.