bluuebunny/crossref_metadata_2025_split huggingface dataset:
Research on a Crystalline Oxide Film on Ti-Ta Alloy By Anodic Oxidation and Hydrothermal Treatment
Authors: Ou Shih-Fu , Ou Keng-Liang 
Published: February 2020

Ti-Ta alloys, having low Young’s modulus and high corrosion resistance1, are expected to be candidates for dental and orthopaedic implants. However, for implant applications, the surface properties of Ti-Ta alloys are needed to be more bioacitve. Anodic oxidation is an efficient surface treatment to modify Ti surfaces because it changes the chemical and physical characteristics of Ti surfaces. According to the report by Sul et al.2, an anodically oxidized Ti implant shows a strong response to bone because it surface incorporates P. Therefore, in this study, we attempt to fabricate a P-rich oxide on Ti-Ta alloys by anodic oxidation and hydrothermal treatment.
In this study, Ti-50Ta plates (ϕ10×1 mm) were abraded to grade 800 silicon carbon paper. Then, the abraded samples were washed with acetone for 5 min followed by ethanol for 3 min in an ultrasonic cleaner, and finally dried at room temperature. Anodic oxidation of Ti-50Ta samples were performed in 30% phosphate acid solution. A high-density graphite plate was used as the cathode. The Ti-50Ta samples were galvanostatically anodized at a constant current density of 50 mA/cm2 up to 300 V for 2 min using a direct current power supply. After anodic oxidation, the samples were washed with distilled water and the dries at room temperature. The anodically oxidized samples were hydrothermally treated in a 500 ml Teflon autoclave containing 50% distilled water as a reaction reagent. The samples were treated at 200 ℃ for 6 h.
Results show that after anodic oxidation, an oxide film with rough surface formed on a Ti-50Ta plate. A typical morphology, craters on the surface of oxide film, was observed and it is attributed to sparking occur on the surface. After hydrothermal treatment, crystals with size of ~100 nm formed on the anodic oxide film were observed in Fig. 1. These nano-crystals were suggested as P-O compounds. Sul et al. demonstrated that P-incorporated anodically treated films on Ti implants imparted much stronger bonding with bones than mechanically turned Ti implants. Consequently, this P-rich surface on Ti-Ta alloy is expected to possess a good biological ability.
References
1. D. Mareci, R. Chelariu, D.-M. Gordin, G. Ungureanu, T. Gloriant, Comparative corrosion study of Ti–Ta alloys for dental applications. Acta Biomaterial 2009; 5:3625-3639.
2. Y.T. Sul, C.B. Johansson, Y. Kang, D.G. Jeon, T. Albrektsson, Bone reactions to oxidized titanium implants with electrochemical anion sulphuric acid and phosphoric acid incorporation. Clinical Implant Dentistry and Related Research 2002;4(2):78-87.
Palladium Nanodendrites for Electrocatalytic Applications
Authors: Chetty Raghuram , Maniam Kranthi Kumar , Muthukumar Volga 
Published: February 2020

Polymer electrolyte membrane fuel cells (PEMFC) are attractive energy conversion devices for portable applications and electric vehicles owing to their high efficiency, high power density and low operating temperature. However, the high price and the limited resources of platinum catalysts are among the main challenges hindering their further commercialization. As palladium (Pd) possesses a similar valence electronic configuration to platinum and also has high methanol-tolerant ability, researchers have devoted to develop palladium-based catalysts as a promising alternative to platinum. A number of wet-chemical routes have been developed to produce Pd nanostructures to improve the catalytic activity and selectivity. However, they have been limited due to the use of organic surfactants, polymeric stabilizers at elevated temperature or template techniques relying on the use of nanometer-sized pores as structure-directing agents, which are technically complicated, due to the requirements for template removal to obtain pure products.
In this work, Pd dendrites were prepared by electrochemical deposition directly on carbon-based substrates, which are widely used as support material in fuel cells. Electrodeposition of Pd was carried out on an electrochemically activated carbon black substrate using potentiostatic and cyclic voltammetric techniques. Comparison was also made with Pt dendritesprepared by the electrochemical deposition. The effects of electrochemical activation, deposition potential, time, precursor concentration and carbon loading were studied in relation to the morphology and development of the nanostructures. The results indicated that controlled insertion of defects on the carbon black during electrochemical activation favored a good metal-support interaction and improved the hydrophilicity of the surface, resulting in a dendritic morphology with enhanced catalytic activity towards oxidation and reduction reactions in fuel cells.
Modeling ORR/Oxide Formation and Pt Dissolution - from Liquid Electrolyte to Polymer Electrolyte Systems: Issues and Approaches
Authors: Jayasankar Barathram , Karan Kunal , Harvey David 
Published: February 2020

Recently, we presented an extension of Wang’s multi-step oxygen reduction reaction (ORR) kinetic model [1] to account for sub-surface oxide formation. Our model adequately captures three distinct oxygen electrochemistry on Pt features: ORR kinetics, oxide formation and reduction during cyclic voltammetry, and logarithmic oxide growth – and was extended to Pt dissolution [2]. Experimental data on oxygen electrochemistry on Pt and Pt dissolution are largely available for liquid electrolyte systems. Extension of the aforementioned model to fuel cell electrodes offers some challenges. The kinetic model depends on proton and water concentrations. In a liquid electrolyte system, similar to the ex-situ systems that comprise of dilute acid electrolytes to study ORR and cyclic voltammetry, the respective concentrations can be calculated in a straightforward manner. However in an actual fuel cell catalyst layer, where the liquid water is present is not clear. The concentration of liquid water can be treated to be that of the pure water but for Pt dissolution modeling, one needs to know the volume of the water pool surrounding the Pt crystal. The pH or proton concentration poses another challenge. The proton conductivity of ionomer is known to be RH dependent. However, the local proton concentration is not known and is expected to be function of local liquid water content. This is turn is expected to be a function of material composition, catalyst layer structure, RH, and operating current. This is illustrated by the trends shown in Figure 2 that highlight the effect of RH on cyclic voltammetry [3]. Furthermore these issues have a bearing on the ability to calculate platinum ion concentration within the catalyst layer in degradation studies.
This presentation will discuss these important issues and some of the approaches we are taking to address the challenges.

References

[1] J.X. Wang, J. Zhang and R.R. Adzic J. Phys. Chem.A, 2007, 111 (49), 12702–12710.
[2} Jayasankar, Barathram, Kunal Karan, and David Harvey. "Platinum degradation model in the presence of oxygen." Meeting Abstracts. No. 15. The Electrochemical Society, 2013.
[3] Ruichun Jiang, H. Russell Kunz, James M. Fenton. “Investigation of membrane property and fuel cell behavior with sulfonated poly (ether ether ketone) electrolyte: Temperature and relative humidity effects”. Journal of power sources 150 (2005) 120-128
INVITED TALK - Chemical Durability of SOFCs
Authors: Sasaki Kazunari , Hanasaki Masahiro , Nishimura Takashi , Hosoi Takami , Daio Takeshi , Tachikawa Yuya , Shiratori Yusuke , Taniguchi Shunsuke 
Published: February 2020

Introduction

Solid oxide fuel cell (SOFC) is the promising type of fuel cells with e.g. high electric efficiency and fuel flexibility. Durability and reliability are the most important technological issues on such an early commercialization stage. In our research group, we are focusing on the chemical degradation of SOFCs, determining the lifetime of SOFCs operating at high temperatures using various kinds of practical fuels. In this paper, various extrinsic and intrinsic degradation phenomena are systematically classified and their degradation mechanisms are discussed [1-3].

Extrinsic chemical degradation phenomena

While the advantage of SOFCs is their fuel flexibility, impurity species can often flow into the SOFC system, causing degradation phenomena. Due to their high operational temperatures, species with a high vapor pressure can also evaporate and flow into the SOFC stacks from system components. In addition, the use of low-purity raw materials could cause impurity poisoning by the contaminants in such raw materials. Possible extrinsic degradation phenomena are summarized in Fig. 1, including mechanisms associated with surface adsorption/desorption in the case of sulfur at a relatively low concentration, but associated with accumulation and reaction product formation for other impurities.

Intrinsic chemical degradation phenomena

External impurities can be, in principle, removed by using a getter as a desulfurization reactor or by using fuels with better purity. However, chemical degradation associated with diffusion from neighboring components may become important in long-term operation. As compiled in Fig. 2, various intrinsic degradation phenomena have been revealed by evaluating SOFC samples after long-term tests beyond one thousand or several thousand hours. Future perspectives are also presented including the importance of long-term / cycle testing followed by detailed microstructural analysis.

Acknowledgements: We thank for the financial support by METI to establish Next-Generation Fuel Cell Research Center. Financial supported by the NEDO SOFC project is gratefully acknowledged.

References

[1] K. Sasaki et al., J. Power Sources, 196[22], 9130 (2011).
[2] K. Sasaki et al., J. Electrochem. Soc., 153 [11], A2023 (2006).
[3] K. Sasaki et al., ECS Trans., 57 [1], 315 (2013).
New Electrode of La0.75Sr0.25Mn0.5Cr0.5-XCuxO3-δ (x=0, 0.05, 0.10, 0.20) for Symmetric Solid Oxide Fuel Cell
Authors: Lu Jun , Yin Jiewei , Sun Lin , Lv Weiming , Yin Yimei , Ma Zi-Feng 
Published: February 2020

Abstract:

New perovskite oxides La0.75Sr0.25Mn0.5Cr0.5-x
Cu
x
O3-δ (LSMCr0.5-x
Cu
x
,
x=0, 0.05, 0.10, 0.20) have been developed as both cathode and anode for symmetric single solid oxide fuel cells (SOFCs). The as-prepared LSMCr0.5-x
Cu
x
powders are rhombohedral perovskite phase, and their properties are remarkably affected by Cu content (x). For example, the particle sizes and electrical conductivities of LSMCr0.5-x
Cu
x
increase with x both in air and in 5% H2-Ar atmosphere. Their p-type conductivity shows lower values under 5% H2-Ar reducing atmosphere than in air due to the decrease of the ratio of Mn4+/Mn3+ cation pairs through the reduction of Mn4+. Among of the oxides, LSMCr0.45Cu0.05 shows the best anodic and cathodic performance in symmetrical half cells. The maximum power density of a LSMCr0.45Cu0.05 / ScSZ / LSMCr0.45Cu0.05 symmetric single SOFC reaches as high as 451.2 mW·cm-2 in wet H2 as fuel at 900 oC.

Keywords

: solid oxide fuel cell; symmetric cell; LSCM; Cu substitution

Acknowledgements:

This research was financially supported by the Natural Science Foundation of China (21173147), 973 Program of China (2014CB239700). Thanks were also given to the support of National Key Laboratory of Metallic Matrix Composite Material.
*Corresponding author. Tel.: +86 21 34206255; Fax: +86 21 54741297.
E-mail address: yimei@sjtu.edu.cn (Y.-M. Yin).
New Approach of Data Mining from the Complex Impedance Plane: Parameters You Have Always Wanted to Have
Authors: Macak Jan M. , Patil Deepak , Fraenkl Max , Zima Vitezslav , Shimakawa Koichi , Wagner Tomas 
Published: February 2020

Conventional analysis of data recorded using the Electrochemical Impedance Spectroscopy (EIS) is a relatively simple procedure from the mathematical point of view. It involves an elucidation of electrode processes to derive their characteristic parameters. Another advantage is that it represents a quick visualization tool being still a very sensitive technique [1,2]. However, it has a number of disadvantages too. Often, the interpretation of EIS data using equivalent circuits is quite difficult due to a tedious search for a good fitting correlation. Moreover, results do not give information about number of moving ions (cations or anions), hopping time etc. Knowledge and consideration of these parameters would be very helpful in many electrochemistry-related fields, such as for instance in the development of solid state batteries and in the semiconductor field.
Being unhappy with these drawbacks and limitations of the conventional data analysis method, we recently developed a new approach [4] in which the Z
1 - Z
2 complex impedance plane (where Z
1 and Z
2are the real and imaginary parts of the impedance of materials) has been analyzed, based on Dyre’s random-walk theory. Through this approach we have obtained from EIS data (that are measured anyway), a new set of physical parameters, yet unseen and unmined:
i) the diffusion coefficient D and
ii) the number of moving ions N
ions,

both parameters further distinguishable in the bulk region of the sample as well as at the interface.
The presentation will explain in detail our recently developed approach that has the potential to find a widespread use in various electrochemical fields, such as in batteries, solar cells, fuel cells and semiconductor industry in general. The presentation will show, how helpful this approach can be to understand the electrode polarization as well as the ionic transport mechanism in various conductors. In particular, we will discuss in detail recent results achieved on various materials, including selected ionic conductors [3-5], silicons and titanium dioxides [6].
Literature:

D. D. Macdonald, Transient Techniques in Electrochemistry, Springer US, 1977.

E. Barsoukov, J. R. Macdonald, Impedance Spectroscopy Theory, Experiment, and Application, Second Ed., John Wiley and Sons, New Jersey, 2005

S. Stehlik, J. Orava, T. Kohoutek, T. Wagner, M. Frumar, V. Zima, T. Hara, Y. Matsui, K. Ueda, M. Pumera, J. of Solid State Chem. 183 (2010) 144.

S. Stehlik, K. Shimakawa, T. Wagner and M. Frumar, J. Phys. D: Appl. Phys. 45(2012) 205304.

D.S. Patik, K. Shimakawa, V. Zima, J. Macak, and T. Wagner, J. Appl. Phys. 113 (2013) 143705.

T.Wagner et al., Ms in preparation.
Degradation Behavior of PTB7/PC71bm and P3HT/PC71bm Organic Solar Cells with a TiOx Interlayer
Authors: Abdel-Fattah Tarek M , Younes Enas m , Namkoong Gon , El-Maghraby Mohamed , Elsayed Adly , Abo Elazm A. H. 
Published: February 2020

Recently, the performance of organic solar cells has dramatically improved by incorporating a functional interfacial layer between active layer and metal electrode, forming bulk heterojunction (BHJ). Many interfacial materials, such as metal oxides, self-assembled monolayers (SAMs) and conjugated polyelectrolytes (CPEs), have successfully enhanced energy conversion efficiency of solar cells [4]. Among these interlayers, titanium oxide (TiOx) was used for an optical spacer as well as a hole blocking layer which led to an increase in the power conversion efficiency (PCE). In addition TiOx is known to improve the stability of the organic solar cell devices [5].
In this study, the organic photovoltaic with bulk heterojunction (BHJ), thieno(3,4-b)-thiophene/ benzodithiophene copolymer and (6,6)-phenyl C71 butyric acid methyl ester (PTB7/PC71BM) treated with titanium oxide (TiOx) interlayer was fabricated and compared with the stability of organic solar cells based on poly (3- hexylthiophene) and [6,6]-phenylC71 butyric acid methyl ester (P3HT/PC71BM) with TiOx interlayer. TiOx was prepared by sol-gel chemistry method. The crystalline structure of TiOx was described by X-ray diffraction (XRD) while the absorption spectrum, and surface morphology of the BHJ were studied by UV-Vis spectroscopy and atomic force microscopy (AFM) respectively.
Organic solar cells were fabricated by spin-coating PEDOT:PSS layer on the top of ITO glass substrate. After annealing, the substrates were then transferred into a nitrogen filled glove box for spin-casting photoactive layers. Then TiOx layer was spin coated in air. Subsequently, aluminum (Al) electrode was deposited, producing the devices active area of ~ 10 mm2. Finally after Al deposition, the P3HT/PC71BM device was subjected to annealing treatment in glove box.
The electrical properties of the resultant devices were investigated by measuring the current density–voltage (J–V). Also the normalized efficiency of both devices as a function of time has been measured and stability was analyzed in terms of optical, structural and morphological degradation.

References

[1]K.-D. Kim, D. C. Lim, H. O. Seo, J. Y. Lee, B. Y. Seo, D. J. Lee, Y. Song, S. Cho, J.-H. Lim, Y. D. Kim, Applied Surface Science, 279, 2013, 380– 383.
[2] W. Zhang, B. Zhao, Z. He, X. Zhao, H. Wang, S. Yang, H. Wu and Y. Cao, Energy Environ. Sci., 6, 2013, 1956–1964.
[3] Y.-M. Chang and C.-Y. Leu, J. Mater. Chem. A, 1, 2013, 6446–6451.
[4] H. Zhou, Y. Zhang, J. Seifter , S. D. Collins, C. Luo, G. C. Bazan, T.-Q. Nguyen , and A. J. Heeger, Adv. Mater, 25, 2013, 1646–1652.
[5] S. H. Park, A. Roy, S. Beaupre, S. Cho, N. Coates, J. S. Moon, D. Moses, M. Leclerc, K. Lee and A. J. Heeger, Nature Photonics, 3, 2009, 297-303.
Visible Light Driven Decomposition of Organic Compounds By Two Different Cocatalysts
Authors: Jeevagan Arockiam John , Tsuda Takashi , Saravanan Govindachetty , Gunji Takao , Hashimoto Masanari , Kaneko Shingo , Miyauchi Masahiro , Matsumoto Futoshi 
Published: February 2020

1.
Introduction

Photocatalytic decomposition of organic pollutants is one of the promising method for environmental purification. Most of the researchers focused on efficient decomposition of environmental organic contaminants under visible light irradiation or indoor fluorescent light.1 Oxide-supported metal catalysts are widely acknowledged as important catalysts that are related to versatile key in photochromism, chemical sensing and photocatalytic activity. Tungsten trioxide (WO3) acts as a ideal visible light photocatalyst owing to its small band gap energy (2.4-2.8 eV) and high oxidation power of vanlence band holes. But, WO3 exhibits low photocatalytic activity due its high recombination rate of photoexcited electrons and holes. In order to suppress the recombination of photoexcited carriers and significantly increase the photocatalytic efficiency, most research has focused to prepare WO3 doping constituent or WO3 composites.2,3 In the present study, we have synthesized PtPb/WO3 and PtAu/WO3 alloy catalysts, demonstrated to exhibit the efficiency for the decompostion of organic pollutants under visible light irradiation.

2.
Experimental

A simple one-pot synthesis approach to obtain WO3 supported PtAu catalyst is as follows. In the synthesis, 0.5 g of WO3was suspended in 15 mL of anhyrous methanol for 15 min in a two neck round bottom flask. Pt (0.0075 g) and Au (0.0045 g) precursors were dissolved in 15 mL anhydrous methanol in the shielded vial uder Ar atmosphere and transferred to the suspensions. Then, the solution was stirred for 30 min to yield homogeneous color soluion. Required amount of NaBH4 in mehtanol was injected into the suspensions. The product were washed and centrifuged with anhydrous methanol for three times and dried under vacuum. Similar procedure was followed to synthesis the PtPb/WO3 catalyst.

3. Results and Discussion

Figure 1 shows the TEM images of (a) Pt/WO3 (b) PtPb/WO3 and (c) PtAu/WO3 photocatalysts. Pt and PtPb and PtAu NPs are showed monodispersity and homogeneity on the WO3 supports. The average particle size of the three catalysts can be ranked as PtPb/WO3~PtAu/WO3 > Pt/WO3. The TEM results show that the addition of Pb and Au increases the size of NPs. Figure 2 depicts that the CO2 formation profile over different photocatalysts under visible light irradiation time. PtPb/WO3 photocatalyst (1 wt %) shows the higher rate of CO2formation over other photocatalysts. The details about the characterization and photocatalytic activity of catalysts would be discussed in the presentation.

4. References

1. M.R. Hoffmann, S.T. Martin, W. Choi and D.W. Bahnemann, Chem. Rev., 95, 69, (1995).
2. R. Abe, H. Takami, N. Murakami and B. Otani, J. Am. Chem. Soc., 130, 7780, (2008).
3. M. Miyauchi, Phys. Chem. Chem. Phys., 10, 6258, (2008).
Low Temperature PEM Degradation: Failure Modes & Mitigation Strategies
Authors: Gittleman Craig S , Coms Frank D. , Lai Yeh-Hung 
Published: February 2020

There are three critical membrane degradation mechanisms that can lead to failure of polymer electrolyte fuel cell systems: chemical degradation, mechanical degradation, and membrane shorting. This talk will focus on the individual failure modes; with attention dedicated to describing the fundamental model-based mechanistic understandings, appropriate accelerated stress tests that enable rapid screening and relevant in-situ diagnostics to track membrane health during fuel cell operation, as well as discussions of effective mitigation strategies to prevent or minimize the risk of failure caused by the specific modes of membrane degradation. The effect of simultaneous chemical and mechanical degradation will also be discussed.
Both chemical and mechanical degradation of perfluorosulfonic acid (PFSA) membranes have been extensively studied, and effective mitigation strategies have been developed that can significantly extend PFSA proton exchange membrane (PEM) lifetimes. Accelerated stress tests (ASTs) have been developed that can be used to screen various membrane types and mitigation strategies, and effective in-situ diagnostics have been developed to track degradation of PFSA membranes during fuel cell operation. The failures observed in these accelerated tests as seen by postmortem analysis mimic the failures of PFSA membranes in field tests. Durability of PFSA membranes will be discussed and an overview of the degradation of alternate PEM chemistries, such as hydrocarbon membranes, will also be provided. Insight into the degradation of these materials is limited because there is hardly any field data which can be used to determine the root causes of failure and validate that the ASTs are accelerating the relevant stressors and, also, because appropriate diagnostics, such as those used for PFSA membrane systems, have not been developed.
This talk will also address shorting of PEMs in fuel cell systems. Shorting is a two step process during which soft shorts are created by penetration of conductive materials though the thickness of the membrane. Soft shorts become hard shorts when there is a voltage excursion that leads to high local temperatures and subsequent thermal decay of the PEM. These hard shorts are the severe events that lead to fuel cell stack failure. Results and analysis suggest that the PEM type is not the limiting factor in preventing membrane shorting, and that mitigation is best achieved by a combination of design and operating strategies.