Materials Transactions Research Articles

Synthesis and Characterization of Electrocatalysts for the Hydrogen Evolution and Hydrogen Oxidation Reactions in Alkaline Environment

The development of catalysts for the electrochemical processes of hydrogen systems (e.g. fuel cells and electrolyzer systems) continues to be a significant area of research for renewable energy technologies. One significant challenge has been the development of hydrogen catalysts that can be utilized in alkaline environments as the kinetics of hydrogen reactions decrease by two orders of magnitude in alkaline environments compared to acidic[1,2]. Chemical vapor deposition (CVD) is a conventional tool used in the synthesis of such catalysts[3,4]. This presentation discusses the extending work being done using a variant CVD process known as “Poor Man’s” CVD (PMCVD), to further its impact in electrochemical catalyst application[5]. PMCVD is utilizes an inexpensive vacuum oven to sublime commercially available metal-organic precursors; lowering synthesis cost while providing increased control of particle size and distribution. This work describes the work done to assess the PMCVD mechanisms as well as its use to develop catalysts for the hydrogen oxidation reaction (HOR) and hydrogen evolution reaction (HER) in alkaline environments. Preliminary studies have shown that PMCVD can develop catalysts with highly dispersed nanoparticles on various supports. As depicted in Figure 1, PMCVD synthesized Pt/C and PtRu/C catalysts have shown to have improved kinetics over commercial developed catalysts exhibiting approximately a 40% and 45% increase in average exchange current densities respectively when compared to Tanaka Kikinzoku catalysts of the same loading. An extended function of the PMVCD process is the ability to synthesize alloyed catalysts in a single deposition process. By understanding the parametric effects of temperature and pressure on the deposition process with respect to particle size and distribution, we can optimize the PMCVD process to develop highly active catalysts that can be used in alkaline hydrogen systems. [1] Durst, J. et al. New insights into the electrochemical hydrogen oxidation and evolution reaction mechanism. Energ. Environ. Sci. 7, 2255–2260 (2014). [2]Sheng, W. et al. Hydrogen Oxidation and Evolution Reaction Kinetics on Platinum: Acid vs Alkaline Electrolytes. . Electrochem. Soc. 2010 volume 157, issue 11, B1529-B1536 [3] Garcia, Vargas, et al. “Chemical Vapor Deposition of Iridium, platinum, Rhodium, and Palladium.” Materials Transactions, Vol. 44, No. 9 (2003) pp. 1717-1728 [4] Serp, Philppe, et. al. “Chemical Vapor Deposition Methods for the Controlled Preparation of Supported Catalytic Materials.” Chem. Rev. 2002, 102, 3085−3128 [5] Papandrew, A. et al. Advanced Electrodes for Solid Acid Fuel Cells by Platinum Deposition on CsH2PO4. Chem. Mater. 2011, 23, 7, 1659-1667 Figure 1

The mechanics of High Pressure Compressive Shearing with application to ARMCO® steel

In High Pressure Shearing (HPS) a flat sample is subjected to large shear strain by displacing one of its flat surfaces with respect to the other under high compressive force. The process is driven by non-sliding friction provided by the large compressive stress. The HPS process was first proposed by Fujioka and Horita [Materials transactions, 50 (2009) 930–933], and was applied to aluminum strips; upscaling was also developed. In the present work we introduce a modified version of HPS where the compression strain is relevant, so the new process is called High Pressure Compressive Shearing (HPCS). In HPCS, the experiments are conducted similarly to HPS but with the addition of a confining-pressure and more compression strain to increase the shear strain. This paper presents the mechanical analysis of stress and strain states during HPCS and demonstrates in situ measurements of stress-strain relations in ARMCO® steel subject to HPCS at room temperature up to an equivalent strain of 33.3. The strain hardening characteristics, the texture and the microstructure were analyzed. It has been shown that compression during HPCS results in a non-hydrostatic stress state and that ultimate steady state of grain fragmentation can be readily reached by HPCS.

High Temperature Oxidation Resistance of Cr Coatings on 22MnB5 Steel Electroplated in Trivalent Cr Baths

22MnB5 steel is one kind of advanced high-strength steels commonly used for vehicles to enhance passengers’ safety and reduce carbon dioxide emission[1]. However, 22MnB5 steel is vulnerable to high-temperature oxidation and a protective coating is essential to inhibit oxidation during hot stamping process. For example, hot-dip Al-10 wt % Si coating has been extensively applied on press hardening steel although it does not provide sacrificial protection on the steel parts[2]. In contrast, hot-dip Zn coating, which confers sacrificial protection, tends to suffer oxidation and liquid metal embrittlement during hot stamping[3, 4]. This study investigated the structure and properties of Cr coatings on 22MnB5 steel electroplated in a trivalent Cr (Cr(III)) bath. The DC electroplating was conducted in a chloride-based Cr(III) electrolyte with and without the addition of sulfur-containing organic compounds. The morphology, microstructure, and composition of the Cr coating were characterized using scanning electron microscope (SEM), X-ray diffraction (XRD), and electron dispersive spectroscopy (EDS). The thickness of the deposit before and after high-temperature heat treatment (900℃ for 5 min in air) was measured using cross-sectional SEM. Experimental results show that the sulfur-containing organic compound in the electrolyte reduces the carbon content and increases the sulfur content of the Cr coating, which, in turn, reduces the residual stress of the coating. As a result, a crack-free Cr coating can be obtained in the electrolyte with the organic additive. In contrast, many cracks develop on the Cr coating plated in the electrolyte without the organic additive. After the heat treatment at 900℃ for 5 min, extensive oxidation was observed on the crack-free Cr coating, but not on the Cr coating with cracks. It is likely that the presence of sulfur in Cr coating deteriorates the oxidation resistance. Crack openings of the Cr coating free of sulfur are filled with compact oxides after 900℃heat treatment for 5 min. The steel substrate with a Cr overlay remains intact, indicating the Cr coating prevents the steel substrate from oxidation at 900℃.Finally, a 2-mm-thick Cr coating can be electroplated in the Cr(III) bath without the organic additive at a current density of 10 A/dm2and a plating time of 1 min and effectively protects the 22MnB5 steel from high-temperature oxidation. Reference [1] H. Karbasian, A.E. Tekkaya, Journal of Materials Processing Technology, 210 (2010) 2103-2118. [2] D.W. Fan, H.S. Kim, J.-K. Oh, K.-G. Chin, ISIJ international, 50 (2010) 561-568. [3] C.W. Lee, D.W. Fan, I.R. Sohn, S.-J. Lee, B.C. De Cooman, Metallurgical and Materials Transactions A, 43 (2012) 5122-5127. [4] M. Razmpoosh, A. Macwan, E. Biro, D. Chen, Y. Peng, F. Goodwin, Y. Zhou, Materials & Design, (2018).

Development of an Inert Anode for the Electrolytic Reduction of Cerium Oxide

Since the early 2000s, when the Fray-Farthing-Chen (FFC, direct mechanism) and the Ono-Suzuki (OS, indirect mechanism) processes for the reduction of titanium oxide were elucidated, several additional metal oxides (ZrO2, Ta2O5, Cr2O3, and Nb2O5) have been reported to electrolytically reduce to their metallic state in molten CaCl2-CaO.1-3 In our hands, the electrolytic reduction of cerium oxide has resulted in mixed degrees of success due to side reactions within the molten salt. Cyclic voltammetry (CV) was performed in order to identify the products of these side reactions, and resulted in greater understanding of the system; based on CV results, parameters were refined, resulting in an improved production of Ce0. When Ce0 was successfully produced by electrolytic oxide reduction, a large amount of passed charge was required due to various inefficiencies of the process, requiring further optimization. Anode material has been identified as a possible source of inefficiency, as it degrades throughout an experiment. Currently, pyrolytic graphite is used as the anode, which leads to carbon dissolution and contamination of the salt bath. As such, the goal of this study is to identify an inert anode material and operational parameters to ensure greater yields of metallic product. References Chen, G. Z., Fray, D. J. & Farthing, T. W. Direct electrochemical reduction of titanium dioxide to titanium in molten calcium chloride. Nature 407, 361-364 (2000).Claux, B., Serp, J. & Fouletier, J. Electrochemical reduction of cerium oxide into metal. Electrochimica Acta 56, 2771-2780, (2011).Suzuki, R. O., Ono, K. & Teranuma, K. Calciothermic reduction of titanium oxide and insitu electrolysis in molten CaCl2. Metallurgical and Materials Transactions B 34, 287-295, (2003). LA-UR-18-22498

Electrolytic Reduction of Cerium Oxide

Since the early 2000s, when the Fray-Farthing-Chen (FFC, direct reduction) and the Ono-Suzuki (OS, indirect reduction) processes on titanium oxide were elucidated, several additional metal oxides (Zr, Ta, Cr, and Nb) have been reported to electrolytically reduce to their metallic state in molten CaCl2-CaO.1-3 However, the electrolytic reduction of cerium oxide has resulted in mixed degrees of success. As such, the goal of this study is to identify side reactions that occur that are parasitic to the overall reaction of producing cerium metal and correlate that to the composition of the salt. Previous reports indicate that the reaction pathway from CeO2 to Ce0 is not direct and includes side reactions that result in the formation of Ce2O3, CeOCl and CeCl3.3-5 Our efforts to use cyclic voltammetry to identify side reactions, which allowed for the determination of approximate concentrations of side reaction products as well as Ce0 produced as a result of electrolysis, will be presented. Acknowledgements For financial support of this work, we acknowledge the U.S. Department of Energy through the LANL LDRD Program (Mission Foundations Research Project #20170558ER). References 1 Chen, G. Z., Fray, D. J. & Farthing, T. W. Direct electrochemical reduction of titanium dioxide to titanium in molten calcium chloride. Nature 407, 361-364 (2000). 2 Suzuki, R. O., Ono, K. & Teranuma, K. Calciothermic reduction of titanium oxide and in-situ electrolysis in molten CaCl2. Metallurgical and Materials Transactions B 34, 287-295, (2003). 3 Claux, B., Serp, J. & Fouletier, J. Electrochemical reduction of cerium oxide into metal. Electrochimica Acta 56, 2771-2780, (2011). 4 Zhao, B. et al. Direct electrolytic preparation of cerium/nickel hydrogen storage alloy powder in molten salt. Journal of Alloys and Compounds 468, 379-385, (2009). 5 Castrillejo, Y., Bermejo, M. R., Pardo, R. & Martı́nez, A. M. Use of electrochemical techniques for the study of solubilization processes of cerium–oxide compounds and recovery of the metal from molten chlorides. Journal of Electroanalytical Chemistry 522, 124-140, (2002).

Ni-Al-Ti Ohmic Contacts on 1 x 1020 cm-3 Al+ Ion Implanted 4H-SiC

The Al-Ti based alloys give ohmic contacts on p-type 4H-SiC with reasonably low specific contact resistance (≤ 10-4­ Ωcm2). Unfortunately during alloying the deposited metals go through a liquid phase [1] and contact areas lose their form. Moreover, during cooling the Al in excess segregates in Al droplets on the top of the contact surface. All that produces ohmic contacts that have not an homogeneous interface with the semiconductor and limits the minimum distance between adjacent contact areas. In previous studies it has been shown that a thin layer of metal with high melting temperature like Ni can be used as a cap on the top of the deposited Al-Ti layer for reducing or avoiding the enlargement of the melted Al-Ti film during alloying, depending on the combination of the Ni, Al and Ti thin film thicknesses [2,3]. In the same studies it was shown that it exists an optimum Ni : Al : Ti thicknesses ratios to preserve the contact form and with optically homogenous and shiny contact surfaces with specific contact resistance values in the low 10-4 Ωcm2 decade at room temperature for p-type resistivity in the range 0.1-1 Ωcm [3]. This study will focus on the electrical performence of these optimal contacts above room temperature. 4° off-axis <0001> n-type 4H-SiC homo-epitaxial specimens with a 200 nm p-type layer at the top surface have been used for this study. The p-type resistivity of these layers varied in the range 10-2 – 101Ωcm. Ni(50nm)/Al(40nm)/Ti(20nm) were evaporated on the surface of these samples and circular TLM devices (TLM-C) were obtained by the lift-off technology. The intra pad-distances of these devices was in the range 4 – 49 μm, and the internal-pad-radius in the range 51 – 508 μm. After lift-off the specimens were alloyed at 1000°C for 2 min in vacuum. The preservation of the pads form factor and of a mirror like contact surfaces after alloying [3] were verified by optical inspection. The ohmic behavior of the alloyed contact was tested by current-voltage (I-V) measurements in the temperature range 300-560 K. The specific ohmic resistance rc and transfer length LTwere obtained from the I-V resistance values of TLM devices versus intra-pads distance for constant internal-pad radius [4]. As a cross check, the so obtained values were verified to be good for fitting the TLM resistance data obtained from the I-V measurements of devices versus variable internal-pad radius and constant intra-pads distance [4]. The main result of this study is that, for temperatures in the range 300-560 K, the specific contact resistance of the studied contacts is in the range 2 – 4 × 10 -4 Ωcm2 over three decades of p-type material resistivity, i.e. 10-2 – 101 Ωcm, that corresponds to a range of 103- 6×104 Ωsq sheet resistance values, taking into account the thickness of the p-type layer. Reasons for such a perfomance will be discussed. [1] Susumu Tsukimoto, Kazuhiro Ito, Zhongchang Wang, Mitsuhiro Saito,Yuichi Ikuhara, Masanori Murakami, Materials Transactions 50(5), 1071-1075 (2009). [2] P. Fedeli, M. Puzzanghera, F. Moscatelli, R. A. Minamisawa, G. Alfieri, U. Grossner, R. Nipoti, Mater. Sci. Forum 897, 391-394 (2017). [3] R. Nipoti, M. Puzzanghera, M.C. Canino, P. Fedeli, G. Sozzi, submitted to ICSCRM2017, Washington, DC, Sept. 17-22, 2017 [4] D. K. Schroder, Semiconductor Material and Device Characterization, 3rd Edition, 2006, Wiley-IEEE Press.

Electrochemical Reduction of Molybdenium Compounds to Form Molybdenium Powder

Molybdenum (Mo) is a refractory metal and mostly used as an alloying agent in cast iron, steels and superalloys to enhance hardenability, strength, toughness and corrosion resistance. It also finds other uses either in the form of a pure metal or an element in, for example, lubricants and catalysts. Traditional metal production methods are not suitable for molybdenum because pure molybdenum has very high melting point and has a tendency to get oxidized at low temperatures. Hydrogen reduction of molybdenum oxide is a very common way for Mo production but, it has two stages during process. At the second stage, the reduction process needs very high temperatures, therefore, high energy consumption and special equipment requirement is essential. FFC Cambridge process [1] based on electrochemical reduction of solid compounds was considered as an alternative way to produce molybdenum at relatively low temperatures. Similar to reduction of WO3 [2], loss of molybdenum as molybdenum oxychloride from MoO3 in CaCl2 containing molten salts is inevitable [3]. MoS2 powder pressed and sintered at 400oC to form pellets were used as starting material for electrochemical formation of pure Mo in molten CaCl2-NaCl salt mixture under argon gas at 800oC. A constant voltage in the range 1 to 3.0V was applied between MoS2 cathode and graphite anode. When the process was terminated at a prescribed time, the cathode was removed from the molten salt, cooled in argon, washed with water in air to dissolve the solidified salt, and then dried at about 100oC in vacuum before further analysis employing XRD, SEM and EDS. [1] G.Z. Chen, D. J. Fray, T. W. Farthing, Direct Electrochemical Reduction of Titanium Dioxide to Titanium in Molten Calcium Chloride, Nature, 407 (2000), 361-364. [2] M. Erdoğan, İ. Karakaya, Electrochemical Reduction of Tungsten Compounds to Produce Tungsten Powder, Metallurgical and Materials Transactions B, 41B (2010), 798-804. [3] W.T. Thompson, C.W. Bale, and A.D. Pelton: Facility for the Analysis of Chemical Thermodynamics (FACT), McGill University Montreal, Royal Military College of Canada in Kingston, E´cole Polytechnique, Montreal, Canada, 1985.

Silane-Based Coating on Hot-Dip Zn Steel Sheets for Hot Stamping

Advanced high strength steels have been widely used in the automobile structures to enhance passengers’ safety [1]. Hot stamping process is recently applied and the strength of press hardening steels is elevated via martensitic phase transformation [2; 3]. Nevertheless, the oxidation and decarburization generally occur during the heat treatment prior to stamping[4], which in turn deteriorate the properties of steels [5]. Hot-dip galvanizing has been applied in steel industries due to its effectiveness to produce a Zn coating with both barrier and cathodic protections again corrosion [6]. Recently, hot-dip galvanized coatings have been studied to evaluate the protection on steels during hot stamping and the corrosion resistance of the resultant coating after hot stamping. The critical issues of the galvanized steels for hot stamping are oxidation and liquid metal embrittlement [7; 8]. The former deteriorates the resistance spot weldability and paintability, whereas the later has a negative effect on formability [9]. Silane, a kind of Si-based coating on light metals, has been used in galvanized steels to offer barrier protection against corrosion [10]. In this study, silane coating was applied on galvanized (GI) and galvannealed (GA) steels to elevate the practicability for the hot stamping application. The GI and GA steel sheets were received from China Steel Co., Taiwan, with coating thickness of approximately 10µm. Silane coating film was formed by a laboratory rolling method. The treating solution was prepared by mixing tetraethyl orthosilicate (TEOS), acidified water (pH= 1.0, adjusted by HNO3), γ-glycidoxypropyltrimethoxysilane (GPTMS), followed by stirring for 2 h at room temperature. The GI and GA steel sheets with and without the silane coating were isothermally held at 900℃ under the atmosphere for 5 min to simulate austenitization prior to hot stamping. XRD, SEM, TEM, and XPS were employed to characterize the surface microstructure of the various steels. Corrosion behaviors were tested by electrochemical stripping and potentiodynamic polarization measurements. The GI steel displayed a gray color after austenitization. In contrast, the GI steel with the silane coating still exhibited a metallic color, suggesting the silane coating is effective in preventing the GI steel from oxidation at 900℃ (Fig(a)). This is consistent with the XRD pattern showing the absence of the peaks resulting from ZnO for the GI steel with the silane coating (Fig.(b)). However, the silane coating offered a less degree of protection on the GA steel. The cross section of the silane-coated GI and (b) GA steels was further characterized by the SEM. Zn oxides were readily observed on the GA steel; conversely, Zn oxide scale was hardly observed on the GI steel. After austenitization, the silane-coated GI coating transformed to a mixture of Γ phase and Zn saturated α-Fe, which retained the cathodic protection over the steel substrate. However, the alloy layer of the silane-coated GA steel was solely composed of Zn saturated α-Fe and the cathodic protection was largely reduced after austenitization. Reference [1] R. Kuziak, R. Kawalla, S. Waengler, Archives of civil and mechanical engineering 8 (2008) 103-117.[2] D.W. Fan, H.S. Kim, B.C. De Cooman, Steel Research International 80 (2009) 241-248.[3] H. Karbasian, A.E. Tekkaya, Journal of Materials Processing Technology 210 (2010) 2103-2118.[4] D.W. Fan, B.C. De Cooman, steel research international 83 (2012) 412-433.[5] L. Dosdat, J. Petitjean, T. Vietoris, O. Clauzeau, steel research international 82 (2011) 726-733.[6] A. Marder, Progress in materials science 45 (2000) 191-271.[7] C.W. Lee, D.W. Fan, I.R. Sohn, S.-J. Lee, B.C. De Cooman, Metallurgical and Materials Transactions A 43 (2012) 5122-5127.[8] R. Autengruber, G. Luckeneder, S. Kolnberger, J. Faderl, A.W. Hassel, steel research international 83 (2012) 1005-1011.[9] C.-W. Ji, I. Jo, H. Lee, I.-D. Choi, Y. Do Kim, Y.-D. Park, Journal of Mechanical Science and Technology 28 (2014) 4761-4769.[10] R. Figueira, C.J. Silva, E. Pereira, Journal of Coatings Technology and Research 12 (2015) 1-35. Figure 1

Electrochemical Kinetics during Production of Liquid Iron at 1550 C Via Molten Oxide Electrolysis

Molten oxide electrolysis is a potentially new route to lower CO2 emissions in steel industry. The concept, pioneered by researchers of the M.I.T.[1], enables the use of renewable energies for electrolytic production of molten iron. The challenges of this procedure are elevated temperatures above 1550°C, the choice of suitable electrode materials and the up-scaling of the laboratory cells to pre-industrial dimensions. The general electrochemical reactions at 1600°C at the electrodes are: 2Fe2+ +4e-→ 2Fe (Cathode) 2O2- → O2 + 4e-(Anode) Choice of electrolyte composition has to be done following the premise of a maximum in faradaic efficiency, which is highly dependent on the ratio between the ferrous and ferric iron in the slag. If the inherent ferric proportion is high, the production of liquid iron can be disturbed by two different processes. At low iron concentration in the melt, ferric iron is reduced at the cathode and subsequently migrates towards the anode, where it is reoxidized. At iron concentrations above 20 wt%, onset of electron charge hopping between the two species is likely to occur [2]. One possibility to avoid both scenarios is the utilization of a silica based composition, in which ferric iron is unstable.According to these requirements, a device to conduct molten oxide electrolysis in laboratory scale was built, comprising an electrolyte based on an alumina-silicate composition on which current is applied through 2 Pt wire-electrodes at 1550°C. After slow cooling of the cell, the produced metal is obtained as a small sphere at the cathode at the bottom of the cell (Figure 1). The maximum weight of the deposit produced so far is 500 mg with an experimental duration exceeding 11 hrs. Recovered metal shows a high purity, suggesting a high selectivity of the electrochemical process. Depending on the imposed potential, stable current signals of up to 150 mA were achieved. Faradaic current efficiency lies between 70-80 % for considering the Mol O2 produced at the anode during electrolysis. Ongoing research in ArcelorMittal is dedicated to the characterization of the electrolyte voltammetric assessments (Figure 2). Reduction potentials of ferrous iron and silica in the experimental setup were determined to 0.98 and 1.6 V respectively. Furthermore the currently used electrolyte exhibits a current limitation in correlation with the total content of iron oxide in the melt. Behavior of this limitation implies that the addition of iron oxide has a strong impact on transport properties of the melt. To validate this hypothesis additional 2-electrode configurations have been designed (Figure 3). In these designs a large surface of one of the electrodes allows the study of the kinetic overpotential of the other. Experiments performed so far indicate the presence of a process rate limitation at the cathode for low iron concentrations. Electrochemical results are complemented with thermodynamic calculations assisted by thermochemical software [3] [1] Sadoway D, Kheptal D, Ducret A. (2004) TMS Charlotte [2] Barati M. and Coley K.S. (2007) Metallurgical and Materials Transactions B, pp. 51-60 [3] Gatellier C., Gaye H., Lehmann J., Zbaczyniak Y. (1992) CIT Revue de Métallurgie, pp. 887-888 Figure 1

Search for Spinel Type Cathode Materials of Magnesium Secondary Battery By First-Principles Calculation and the Battery Properties, Crystal and Electronic Structure of Cathode Material

INTRODUCTION Currently, the cathode materials of the high-capacity lithium ion battery have been developed. However it is difficult to be tremendous capacity improvement. Therefore divalent magnesium ions have been noted. Due to approximately the same ionic radius of Mg2+ as the Li+, the theoretical capacity of magnesium per volume is higher than lithium, so that magnesium secondary batteries are expected as a next-generation battery. The charge-discharge test of the positive electrode material, such as MgCo2O4, was performed. Although the stable crystal structure and diffusion mechanism of Mg ions is not clear. In this study, the electrochemical evaluation and the crystal structure analysis of the MgCo2O4 and Li2-xCo2O4 were performed and the crystal structure determined by Rietveld analysis. Moreover, the first-principles calculation for MgCo2O4 evaluated the electronic structure especially in the M-O bond. The purpose of this study was to resolve the relationship between the phase stability and Mg/Co mixing in the crystal structure. EXPERIMENTAL MgCo2O4(MCO) was synthesized by reverse co-precipitation method2). Li2Co2O4 was synthesized by solid-state reaction which was chemically delithiated by using the Na2S2O8. The resulting materials were identified by XRD and determined by ICP for the composition of the metals. The charge/discharge test (HS cells : 3.5~0 V vs. Mg/Mg2+; three electrode cells : 0.345 - -0.855V vs. Ag/Ag+, the negative electrode metal Mg or Mg alloy (AZ31), reference electrode : Ag, separator : polypropylene or glass fiber filter, electrolyte : 0.5M-Mg(N(SO2CF3)2)2/CH3CN or Triglyme). These samples were performed by synchrotron X-ray diffraction (BL02B2, SPring-8). It was also investigated for the valence state of Co by XAFS (BL01B1, SPring-8). In addition, the first-principles calculations were performed for the three types of structure models that extends the unit cell of the MCO(VASP-code in 2 × 2 × 1 cell) and were evaluated for binding and the structural stability. RESULTS AND DISCUSSION The XRD for MCO and Li2Co2O4 showed that all of the diffraction peaks were attributed to the spinel structure (S.G.Fd-3m). The Rietveld analysis for the synchrotron X-ray diffraction data showed that Mg and Co in MCO were almost disorderly distributed and cation mixing. Chemically delithitated Li2Co2O4 sample, i.e. Li2-xCo2O4, was synthesized. From the results of charge-discharge test of MCO and Li2-xCo2O4 (counter Mg), the overvoltage of Li2-xCo2O4 was lower than that of MCO, since diffusion path of Mg could be secured by the regular arrangement of Mg/Co. As a result of the charge / discharge test of MCO using three-electrodes cell, we found a plateau of about 2.6 V (Mg/Mg2+) at the discharge (Fig.1). We also investigated the phase stability, Mg/Co mixing, and electronic structure of MCO by first-principles calculations. It was found that the model where the Mg occupied at only 8a site and Co occupied 16d site was stable arrangement. The electron densities between Co-O for all models exhibited higher than those of Mg-O and it means high covalency of Co-O. Therefore, the Mg of the 8a site became weak bond to oxygen to deintercalate. By Mg/Co mixing, the diffusion path of Mg would be inhibited by strong covalent bonds of Co-O. Then, MCO showed larger overvoltage than less mixing of Li2-xCo2O4. It was performed by help of ALCA-SPRING and shows thanks to the members concerned. References 1) N. Kamioka, T. Ichitubo, T. Uda, S. Imashuku, Y. Taninuchi and E. Matsubara, Materials Transactions, 49, 4, pp.824-828 (2008). 2) S.Yagi et al., Jpn. J. Appl. Phys., 52, 025501(2013). Figure 1

Tresa Pollock Looks to the Future of Metallurgical and Materials Transactions

Tresa Pollock Looks to the Future of Metallurgical and Materials Transactions

Jeremy Busby Joins Editorial Team for Metallurgical and Materials Transactions E

Jeremy Busby Joins Editorial Team for Metallurgical and Materials Transactions E

Metallurgical and Materials Transactions Announces Incoming Principal Editor; JOM Best Paper Awards

Metallurgical and Materials Transactions Announces Incoming Principal Editor; JOM Best Paper Awards

Thin Oxide Film Reduction Via the Polyol Method: An Electrochemical Study of a Polyol Reduction Process

Polyols are non-aqueous hydrogen bonded liquids, analogous to alcohols, which have the ability to dissolve both organic and inorganic solids. Polyol synthesis [1] has been widely employed for the preparation of metallic nanoparticles using the temperature-dependent reducing ability of polyols in the presence/absence of capping agents, such as polyvinylpyrrolidone (PVP). In a typical polyol synthesis process, ethylene glycol (EG) is used as a solvent to dissolve metal precursors and as a mild reducing agent. By heating the mixture, the reducing power of the EG increases and ultimately reduces the metal precursors, forming metal nanoparticles with narrow-size distribution. In a modified-polyol method [2], an external reducing agent that is stronger than EG is used. This is usually practiced when the metal precursor can’t be reduced by the ethylene glycol alone. In a polyol or a modified polyol method, the metal precursor can be oxides, hydroxides, nitrates, and acetates that are either dissolved or suspended in the solvent. In case of oxide or hydroxide precursors, they have to be at least slightly soluble in EG at high temperature, otherwise, the addition of an acid is needed. In the work we are presenting here, we are investigating the possibility of using a (modified-)polyol method to reduce thin oxide films of solid surfaces and surface oxide of bulk oxide materials. We investigated the reduction of Sn oxide thin film [3] on a Sn metal substrate as well as the surface reduction of Sn oxide particles to produce meta-stable SnO2@Sn particles that spontaneously form stable SnO2@SnO particles once in contact with air. The reduction of the Sn oxide thin film on a Sn metal substrate was indicated by the sudden change in the Sn electrode potential when measured vs. a reference electrode (Ag/AgCl). Fig. 1 shows a typical OCP (open circuit potential) measured during heating and cooling cycles of hydrazine-containing ethylene glycol. The sudden change of the OCP at ~110°C is attributed to the reduction of the Sn oxide film as the interface changes from SnO2/EG to Sn/EG. More details about the origin of this OCP change will be provided in the presentation with the help of information obtained from quartz crystal microbalance (QCM) and/or impedance spectroscopy (EIS). The surface reduction of bulk Sn oxide in the form of SnO2 particles (50-100 nm) was also investigated. It was found that NaBH4 can reduce the surface oxide resulting in surface SnO. Raman spectroscopy showed that a very small amount of SnO was formed, which is reasonable if it was a surface oxide. Auger and XPS analyses did not show any SnO formation on the surface. The two pieces of information together suggest that SnO has formed on top of the SnO2, but due to the exposure to the atmosphere, the SnO on the top surface oxidized to SnO2 and therefore protected the remaining SnO underneath it and so it was detectable by the Raman and only SnO2 was found on the outermost surface. Further details and supporting results about the oxide reduction in both cases will be provided in the presentation. Acknowledgements The research leading to these results has received funding from the European Community's Seventh Framework Programme (FP7/2013-2016) for the Fuel Cell and Hydrogen Joint Technology Initiative under grant agreement CATAPULT n°.325268. Special thanks to Sebastian Schwaminger for the assistance with XPS and Raman analyses, Katia Rodewald for the superb SEM pictures and analyses and Marianne Hanzlik for the TEM analysis.

An Experimental Evaluation of the Gerdemann–Jablonski Compaction Equation

This paper reports on an attempt to independently evaluate the validity and applicability of a new compaction equation recently presented by Gerdemann and Jablonski [Metallurgical and Materials Transactions A, 42 (2011) 1325–1333] using experimental data. Furthermore, the rationality of Gerdemann and Jablonski’s interpretation of the equation parameters is examined. The results are discussed in terms of the comparative evaluation of four different titanium powders (sponge Ti, CP TiH2, Grade 2 CP Ti, and TiH2-SS316L nanocomposite blend prepared by high energy milling) cold pressed in die to compaction pressures of up to 1300 MPa.

ASM News for October 2013

Abstract News about ASM members, chapters, events, awards, conferences, affiliates, and other society activities. Topics include: ASM Materials Education Foundation 2013 Scholarship Winners; Jacquet-Lucas Award for Excellence in Metallography; Fashion Forward Micrograph; New Micrograph Tie and Scarf; Zinkle, Seetharaman Named Editors for Metallurgical and Materials Transactions; and Emerging Professionals: Engaging Young Professionals in Your Local Chapter.

Foreword

We are pleased to present in this issue of Metallurgical and Materials Transactions B selected papers from the 15th International Conference on Advances in Materials and Processing Technologies (AMPT2012) held in Wollongong, Australia, 23 to 26 September 2012. This year, the conference program covered over 450 papers in 72 technical sessions and 100 poster presentations with a broad range of topics such as materials, deformation processing, materials removal process, processing of new and advanced materials, welding and joining, surface engineering and other related processes. The conference has been a highlight in the 2012 Calendar on Materials and Processing Technologies.

Discussion of Six Papers From May 2013 Issue

The May 2013 issue of Metallurgical and Materials Transactions A is a typical issue, containing a number of papers, all of which would be explicable assuming the near-universality of the presence of oxide bifilms in metals as a result of the entrainment of the surface oxide film during pouring. The unbonded interface between the necessarily doubled-over surface film, often only a few nanometers thick, and often occurring at grain boundaries, appears to be the cause of grain boundary failures and the initiation of cracks. The precipitation of second phases on the outer surfaces of the bifilm, in good atomic contact with the matrix, explains the apparent brittleness of many intermetallics and second phases. The number of papers from the May issue of MMTA illustrates the ubiquitous presence of bifilms, up to now almost unknown, and their central importance in physical metallurgy, and their possible control, in turn, by up-to-date process metallurgy.

Effect of Grain Boundary Structure on Misorientation Change of Pure Copper Bicrystals Pressed by One-Pass Equal-Channel Angular Pressing

Following a previous paper, (Materials Transactions, Vol. 53 (2012), p. 1858), which reports on the dynamic misorientation change absorbed by the grain boundaries themselves during one-pass equal-channel angular pressing (ECAP), the effect of grain boundary structure on the misorientation change during ECAP was examined as the next step. Two bicrystals with a ­3{111} grain boundary and a random one were subjected to ECAP for one pass, and compared. Both the bicrystals were designed to have a similar slip pattern where slip activity was concentrated on one slip plane. Direct evidence of misorientation changes absorbed by grain boundary themselves was obtained again, and its marked dependency on grain boundary structure became evident. Namely, in ­3 grain boundary, misorientation was partially carried by the grain interior in its vicinity, which stems from the dislocation accumulation. On the other hand, in the random grain boundary, most of the misorientation was carried by the boundary itself. These differences are discussed in terms of the capability as a sink of lattice dislocations during severe plastic deformation. [doi:10.2320/matertrans.M2013076]

Reminiscences About a Chemistry Nobel Prize Won with Metallurgy: Comments on D. Shechtman and I. A. Blech; Metall. Trans. A, 1985, vol. 16A, pp. 1005–12

A paper, ‘‘The Microstructure of Rapidly Solidified Al6Mn,’’ [1] was submitted for publication in October 1984 by D. Shechtman and I. Blech to the Metallurgical Transactions A (now Metallurgical and Materials Transactions) after having been rejected by The Journal of Applied Physics (JAP) in the summer of 1984. A second paper, ‘‘Metallic Phase with Long-Range Orientational Order and No Translational Symmetry,’’ was submitted within a week by Dan Shechtman and coworkers to the Physical Review Letters (PRL). Both papers announced the creation by rapid solidification, at the National Bureau of Standards (NBS)—now the National Institute of Standards and Technology (NIST)— of a sharply diffracting metallic Al-Mn solid phase that, because of its icosahedral symmetry, could not be periodic. In 2011, Dan Shechtman was awarded the Nobel Prize in Chemistry for this discovery. The Award cites him for ‘‘changing the way chemists looked at the solid state.’’ We, the three co-authors of these papers, are pleased to have been invited by the editor of Metallurgical and Materials Transactions to recount our participation in this work and to summarize its significance. The two papers differ in several ways. The Physical Review Letters paper was confined to the compelling case made by the NBS experiments alone that challenged several prevailing paradigms of crystallography. The Metallurgical Transactions A paper had, in addition, a model created by Ilan Blech, then at the Technion, demonstrating that an icosahedral electron diffraction pattern could result from a special sort of an icosahedral glass in which the translational symmetry is broken while retaining icosahedral orientational symmetry. This model was referred to, but left out of the Physical Review Letters, for three main reasons: (1) The experimental case by itself was strong and sufficient to force a change in thinking, (2) the model was open to criticism and might distract attention from the experiments, and (3) Physical Review Letters has a page limitation. According to the then-prevailing crystallographic theories, crystals with icosahedral symmetry could not exist. Within a short time of publication, the existence of many others with forbidden symmetries were reported. Their undeniable existence and properties formed a classic example of the truism that experiments are unsurpassed at disproving theories. Nothing else was needed to force a change in the prevailing theories. The discovery challenged two basic principles of crystallography. In the late 1700s, Rene Just Hauy postulated that all crystals were made up of clusters of atoms repeated periodically in three dimensions. The severe restrictions that periodicity places on crystals became a cornerstone of crystallography. In the 19th century, it was established that only 1-, 2-, 3-, 4-, and 6-fold rotation axes, only 14 Bravais lattices, 32 point groups, 51 crystal forms, and 230 space groups can be consistent with periodicity. Throughout the 19th century, all measured properties and external forms had been consistent with these restrictions. In 1912, the diffraction of X-rays by crystals brilliantly confirmed both that X-rays were short wavelength light and that crystals were periodic. The point group symmetries of the diffraction patterns, which are the same as those of the objects, also conformed to what was allowed by Hauy’s postulate. With no exceptions reported in almost 200 years, periodicity became the definition of a crystal and an axiom or a law of crystallography. Diffraction from periodic objects results in sharp spots arrayed on a reciprocal lattice. The converse, that sharp diffraction spots could only come from a periodic object, was a widely accepted fallacy. By the definition of quasiperiodicity, the diffraction from quasiperiodic objects is sharp. Quasiperiodic objects have no lattice, and their diffraction spots will not form a reciprocal lattice. Because of the 5-fold axis, a frequent ratio of spacing of spots in Figures 2 and 6* is the golden mean, ILAN A. BLECH, 25551 Burke Lane, Los Altos Hills, CA 94022. JOHN W. CAHN, Affiliate Professor, UW Physics, Senior Fellow Emeritus, is with the National Institute of Standards & Technology, Gaithersburg, MD 20899. Contact e-mail: jwcahn@gmail.com DENIS GRATIAS, Research Director, is with the Laboratoire d’Etudes des Microstructures CNRS ONERA, 92322 Châtillon, France. Article published online July 31, 2012 *Figure numbers refer to figures in the Metallurgical Transactions A paper.