Globally valid relations converting magnitudes of intermediate and deep-focus earthquakes to MW

Μία βασική διεργασία κατά τη σύνταξη ομογενών και πλήρων καταλόγων σεισμικότητας είναι η διεξοδική διερεύνηση των δυνητικά εύρωστων σχέσεων που συνδέουν μεταξύ τους κλίμακες διαφορετικών μεγεθών. Η συντριπτική πλειονότητα των ήδη δημοσιευμένων σχέσεων αφορά ως επί το πλείστον δεδομένα επιφανειακών σεισμών με εστιακά βάθη μέχρι και τα 60-70 χιλιόμετρα. Στην παρούσα εργασία, διαφορετικές κλίμακες μεγέθους προερχόμενες από 66 κέντρα σε παγκόσμια κλίμακα, σε συνδυασμό με ήδη δημοσιευμένους καταλόγους, εξετάζονται για σεισμούς με εστιακά βάθη  61-700 χιλιομέτρων. Εφαρμόζοντας ανάλυση ελαχίστων τετραγώνων προέκυψαν 12 νέες αξιόπιστες σχέσεις βαθμονόμησης που συνδέουν τις αντίστοιχες κλίμακες μεγεθών με το μέγεθος σεισμικής ροπής. Μεταξύ άλλω ελέγχθηκαν οι κλίμακες  χωρικού (mb) και επιφανειακού μεγέθους (Ms) που ανακοινώνονται από Διεθνή (ISC, NEIC και IDC) και εθνικά κέντρα ( MOS από Μόσχα,  BJI από Πεκίνο,  DJA από Τζακάρτα) καθώς και το μέγεθος που υπολογίζεται από το JMA (Ιαπωνία). Από τα παραπάνω αποτελέσματα προκύπτουν σημαντικές παρατηρήσεις σχετικά με την συμπεριφορά ορισμένων από τις κλίμακες μεγέθους. Αξιοσημείωτη είναι η διαφοροποίηση που παρατηρείται ως προς τους ενδιαμέσου και τους μεγάλου βάθους σεισμούς για το χωρικό μέγεθος mb του IDC. Επιπλέον, η σύγκριση του μεγέθους σεισμικής ροπής του NIED με τα αντίστοιχα μεγέθη από GCMT και NEIC αναδεικνύει ένα εμφανώς κατώτερο επίπεδο "κορεσμού" προσδιοριζόμενο περίπου στη τιμή 5.0An essential step in the compilation of homogeneous and complete earthquake catalogs is the thorough investigation of potentially robust relations between different magnitude scales. The vast majority of already published relations usually concerns shallow-focus earthquake data with depths up to 60-70 km. In the present study, several magnitude scales reported by 66 world-wide data providers in conjunction with published catalogs are examined within the depth range of 61-700 km, by applying least-squares regression analysis. Among other widely used scales, as body wave (mb, mB) and surface wave (Ms) magnitudes cited by International Centers (i.e. ISC, NEIC and IDC), the behavior of relevant magnitude scales determined by MOS (Moscow, Russia), BJI (Beijing, China), DJA (Djakarta, Indonesia) and the Japanese magnitude calculated by JMA, is also examined. By this way, robust calibrating relationships of 12 magnitude scales to the moment magnitudes provided by GCMT, NEIC and JMA are defined. From the obtained results important observations on the behavior of certain magnitude scales were made. Thus, a remarkable variation of mb scale cited by IDC could be noted for intermediate and deep focus events. Furthermore, a comparison with the Mw of NIED revealed an apparent lower “saturation” level around 5.0 below which the moment magnitude values published by GCMT and NEIC, are systematically overestimated

Globally valid relations converting magnitudes of intermediate and deep-focus earthquakes to MW

Μία βασική διεργασία κατά τη σύνταξη ομογενών και πλήρων καταλόγων σεισμικότητας είναι η διεξοδική διερεύνηση των δυνητικά εύρωστων σχέσεων που συνδέουν μεταξύ τους κλίμακες διαφορετικών μεγεθών. Η συντριπτική πλειονότητα των ήδη δημοσιευμένων σχέσεων αφορά ως επί το πλείστον δεδομένα επιφανειακών σεισμών με εστιακά βάθη μέχρι και τα 60-70 χιλιόμετρα. Στην παρούσα εργασία, διαφορετικές κλίμακες μεγέθους προερχόμενες από 66 κέντρα σε παγκόσμια κλίμακα, σε συνδυασμό με ήδη δημοσιευμένους καταλόγους, εξετάζονται για σεισμούς με εστιακά βάθη  61-700 χιλιομέτρων. Εφαρμόζοντας ανάλυση ελαχίστων τετραγώνων προέκυψαν 12 νέες αξιόπιστες σχέσεις βαθμονόμησης που συνδέουν τις αντίστοιχες κλίμακες μεγεθών με το μέγεθος σεισμικής ροπής. Μεταξύ άλλω ελέγχθηκαν οι κλίμακες  χωρικού (mb) και επιφανειακού μεγέθους (Ms) που ανακοινώνονται από Διεθνή (ISC, NEIC και IDC) και εθνικά κέντρα ( MOS από Μόσχα,  BJI από Πεκίνο,  DJA από Τζακάρτα) καθώς και το μέγεθος που υπολογίζεται από το JMA (Ιαπωνία). Από τα παραπάνω αποτελέσματα προκύπτουν σημαντικές παρατηρήσεις σχετικά με την συμπεριφορά ορισμένων από τις κλίμακες μεγέθους. Αξιοσημείωτη είναι η διαφοροποίηση που παρατηρείται ως προς τους ενδιαμέσου και τους μεγάλου βάθους σεισμούς για το χωρικό μέγεθος mb του IDC. Επιπλέον, η σύγκριση του μεγέθους σεισμικής ροπής του NIED με τα αντίστοιχα μεγέθη από GCMT και NEIC αναδεικνύει ένα εμφανώς κατώτερο επίπεδο "κορεσμού" προσδιοριζόμενο περίπου στη τιμή 5.0An essential step in the compilation of homogeneous and complete earthquake catalogs is the thorough investigation of potentially robust relations between different magnitude scales. The vast majority of already published relations usually concerns shallow-focus earthquake data with depths up to 60-70 km. In the present study, several magnitude scales reported by 66 world-wide data providers in conjunction with published catalogs are examined within the depth range of 61-700 km, by applying least-squares regression analysis. Among other widely used scales, as body wave (mb, mB) and surface wave (Ms) magnitudes cited by International Centers (i.e. ISC, NEIC and IDC), the behavior of relevant magnitude scales determined by MOS (Moscow, Russia), BJI (Beijing, China), DJA (Djakarta, Indonesia) and the Japanese magnitude calculated by JMA, is also examined. By this way, robust calibrating relationships of 12 magnitude scales to the moment magnitudes provided by GCMT, NEIC and JMA are defined. From the obtained results important observations on the behavior of certain magnitude scales were made. Thus, a remarkable variation of mb scale cited by IDC could be noted for intermediate and deep focus events. Furthermore, a comparison with the Mw of NIED revealed an apparent lower “saturation” level around 5.0 below which the moment magnitude values published by GCMT and NEIC, are systematically overestimated

Plasma Driven Exsolution for Nanoscale Functionalization of Perovskite Oxides

Perovskite oxides with dispersed nanoparticles on their surface are considered instrumental in energy conversion and catalytic processes. Redox exsolution is an alternative method to the conventional deposition techniques for directly growing well-dispersed and anchored nanoarchitectures from the oxide support through thermochemical or electrochemical reduction. Herein, a new method for such nanoparticle nucleation through the exposure of the host perovskite to plasma is shown. The applicability of this new method is demonstrated by performing catalytic tests for CO2 hydrogenation over Ni exsolved nanoparticles prepared by either plasma or conventional H2 reduction. Compared to the conventional thermochemical H2 reduction, there are plasma conditions that lead to the exsolution of a more than ten times higher Ni amount from a lanthanum titanate perovskite, which is similar to the reported values of the electrochemical method. Unlike the electrochemical method, however, plasma does not require the integration of the material in an electrochemical cell, and is thus applicable to a wide range of microstructures and physical forms. Additionally, when N2 plasma is employed, the nitrogen species are stripping out oxygen from the perovskite lattice, generating a key chemical intermediate, such as NO, rendering this technology even more appealing.</p

Towards a new step-forward in the Electrochemical Promotion of Catalysis: Development of highly stable Ni nanoparticles by exsolution

SSCI-VIDE+CARE+MCX:IKL:PVE:ACVInternational audienceCatalytic reactions may be promoted in a controlled and reversible manner in electrochemical devices via electrochemical promotion of catalysis (EPOC) [1]. This phenomenon is based on the modification of the local electronic density of the surface of a catalyst coated on a dense electrolyte via the supply of O2- anion. The latter impact the catalytic performances of the catalyst behaving as electronic promoters. So far, the main technological issue of EPOC is related to the use of continuous metallic coatings interfaced on dense solid electrolyte supports. On account of that, the metallic dispersion of the catalyst/electrodes, and therefore their catalytic activity, are usually far lower than that of commercially available dispersed catalysts. Hence, one of the main challenges of the EPOC phenomenon is to combine dispersed catalysts at the nanometric scale with the concept of electrochemical activation via EPOC. In this sense, within the last decade, a powerful phenomena known as exsolution has been identified as a versatile tool allowing a control of the reactivity and durability of metallic particle [2]. Upon the use of ABO3 perovskite materials, certain metals can be inserted within the lattice on the B sites under oxidizing conditions. Upon reductive thermal treatment, the aforementioned metal exsolves, allowing the in situ growth of metallic nanoparticles. Fine tuning of the experimental condition allows the formation of well anchored and well distributed nanoparticles. The non-stoichiometry of the perovskite (i.e. A site deficiency) appears as one of the key parameter driving the exsolution of metal cations to its surface [2]. Recent progress have shown that the exsolution process can be driven electrochemically in fuel cell type devices.The aim of this work is to prove, for the very first time, that stable and well dispersed metallic nanoparticles on the surface of a perovskite may be obtained via exsolution and their activity could be enhanced via EPOC. The perovskite chosen was a A site deficient lanthanum calcium titanate (LCT) doped with 6 % of nickel on the B site (i.e. La0.43Ca0.37Ni0.06Ti0.94O3-δ; LCNT6). It was prepared via a citrate sol-gel synthesis [3] with a calcination temperature of 1200 °C leading to a specific surface area of 7 m2·g-1. A reduction was then performed in 5% H2 (i.e. 900 °C, 2 h) in order to exsolve Ni from LCT lattice. The material was then tested for CO oxidation allowing to probe its catalytic performance (see Figure 1). One can observe that the reductive treatment clearly enhanced the catalytic activity of LCNT6. Moreover, in order to study the stability of the Ni nanoparticles formed via exsolution, a hydrothermal treatment was applied (i.e. 900 °C, 24 h, 10% H2O) followed by a subsequent reduction (i.e. 900 °C, 2 h, 5% H2). As observed in Figure 1, the activity of LCNT6 was not affected by this treatment suggesting the good thermal stability of Ni particles regarding aggregation. To further study the stability of the exsolved nanoparticles aging in presence of water and oxygen was performed (i.e. 900 °C, 24 h, 10% H2O, 20% O2) followed by a reduction (i.e. 900 °C, 2 h, 5% H2). The performance of LCNT6 is not affected either by a hydrothermal treatment in presence of oxygen which proves Ni nanoparticles formed via exsolution to possess very good stability properties. Following the successful formation of stable Ni particles via exsolution on the surface of LCT, electrochemical promotion of catalysis was investigated on this material for CO oxidation. [1] P. Vernoux et al., Chem. Rev., 113, 8192 (2013)[2] D. Neagu et al., Nature Chemistry 5, 916 (2013)[3] N.K.Monteiro et al., International Journal of Hydrogen Energy, 37, 9816, (2012

Triode operation for enhancing the performance of H2S-poisoned SOFCs operated under CH4-H2O mixtures

SSCI-VIDE+CARE+FSA:MTS:CZA:ABO:PVEInternational audienc

Towards a new step-forward in the Electrochemical Promotion of Catalysis: Development of highly stable Ni nanoparticles by exsolution

SSCI-VIDE+CARE+MCX:IKL:PVE:ACVInternational audienceCatalytic reactions may be promoted in a controlled and reversible manner in electrochemical devices via electrochemical promotion of catalysis (EPOC) [1]. This phenomenon is based on the modification of the local electronic density of the surface of a catalyst coated on a dense electrolyte via the supply of O2- anion. The latter impact the catalytic performances of the catalyst behaving as electronic promoters. So far, the main technological issue of EPOC is related to the use of continuous metallic coatings interfaced on dense solid electrolyte supports. On account of that, the metallic dispersion of the catalyst/electrodes, and therefore their catalytic activity, are usually far lower than that of commercially available dispersed catalysts. Hence, one of the main challenges of the EPOC phenomenon is to combine dispersed catalysts at the nanometric scale with the concept of electrochemical activation via EPOC. In this sense, within the last decade, a powerful phenomena known as exsolution has been identified as a versatile tool allowing a control of the reactivity and durability of metallic particle [2]. Upon the use of ABO3 perovskite materials, certain metals can be inserted within the lattice on the B sites under oxidizing conditions. Upon reductive thermal treatment, the aforementioned metal exsolves, allowing the in situ growth of metallic nanoparticles. Fine tuning of the experimental condition allows the formation of well anchored and well distributed nanoparticles. The non-stoichiometry of the perovskite (i.e. A site deficiency) appears as one of the key parameter driving the exsolution of metal cations to its surface [2]. Recent progress have shown that the exsolution process can be driven electrochemically in fuel cell type devices.The aim of this work is to prove, for the very first time, that stable and well dispersed metallic nanoparticles on the surface of a perovskite may be obtained via exsolution and their activity could be enhanced via EPOC. The perovskite chosen was a A site deficient lanthanum calcium titanate (LCT) doped with 6 % of nickel on the B site (i.e. La0.43Ca0.37Ni0.06Ti0.94O3-δ; LCNT6). It was prepared via a citrate sol-gel synthesis [3] with a calcination temperature of 1200 °C leading to a specific surface area of 7 m2·g-1. A reduction was then performed in 5% H2 (i.e. 900 °C, 2 h) in order to exsolve Ni from LCT lattice. The material was then tested for CO oxidation allowing to probe its catalytic performance (see Figure 1). One can observe that the reductive treatment clearly enhanced the catalytic activity of LCNT6. Moreover, in order to study the stability of the Ni nanoparticles formed via exsolution, a hydrothermal treatment was applied (i.e. 900 °C, 24 h, 10% H2O) followed by a subsequent reduction (i.e. 900 °C, 2 h, 5% H2). As observed in Figure 1, the activity of LCNT6 was not affected by this treatment suggesting the good thermal stability of Ni particles regarding aggregation. To further study the stability of the exsolved nanoparticles aging in presence of water and oxygen was performed (i.e. 900 °C, 24 h, 10% H2O, 20% O2) followed by a reduction (i.e. 900 °C, 2 h, 5% H2). The performance of LCNT6 is not affected either by a hydrothermal treatment in presence of oxygen which proves Ni nanoparticles formed via exsolution to possess very good stability properties. Following the successful formation of stable Ni particles via exsolution on the surface of LCT, electrochemical promotion of catalysis was investigated on this material for CO oxidation. [1] P. Vernoux et al., Chem. Rev., 113, 8192 (2013)[2] D. Neagu et al., Nature Chemistry 5, 916 (2013)[3] N.K.Monteiro et al., International Journal of Hydrogen Energy, 37, 9816, (2012

Novel anode materials and triode operation: Two approaches for improving the performance of SOFCs supplied with H2S containing-methane

International @ AIR+ABO:LRE:PVE:MTSInternational audienceSolid oxide fuel cells have the flexibility, due to their high operating temperature, to use natural gas directly as the fuel in the anodic compartment. A typical problem in this process is the significant degradation in cell voltage and in the catalytic direct internal reforming activity due to H2S poisoning, which is present in natural gas [1]. The aim of this study is to enhance the sulphur tolerance of SOFCs operated under 2%CH4-5%H2O in presence of 1-10 ppm H2S at 800-900oC. The first aim of this study is the development of novel modified Ni/GDC anodes with improved sulphur tolerance during catalytic CH4 reforming. The second approach entails the use of triode operation in order to enhance the SOFC performance

Triode Operation for Enhancing the Performance of H2S-PoisonedSOFCs for CH4 Steam Reforming

SSCI-VIDE+CARE+ABO:LRE:PVEInternational audiencePerformances of Solid Oxide Fuel Cells (SOFCs) were investigated in triode operation mode under methane steam reforming in presence of H2S. Both the catalytic performances for methane steam reforming and the electrochemical properties of the anode are drastically dropped by the presence of H2S impurities introduced through the use of fuels such as natural gas. Indeed, typically 1-30 ppm H2S content can be observed in natural gas. Conventional Ni-based cermet anode exhibit strong deactivation when exposed to few ppm H2S. This loss is generally attributed to sulfur adsorption on Ni active sites.Triode operation is a novel approach for enhancing the performances of fuel cells and electrolysers. This concept is based on the introduction of a third electrode (auxiliary electrode) in addition to the conventional anode and cathode. This auxiliary electrode is located at the cathode side, as shown in the following figure: Electrodes were deposited by screen printing of commercial powders (Marion Technologies) on YSZ discs (Dynamic Ceramic, 8% mol Y2O3-ZrO2) with diameter of 20 mm and 1.6 mm thickness. The anode electrode was a Ni/GDC film of 40 µm thickness and a surface area of 1.76 cm2 and was sintered at 1250°C for 2 hours. The cathode and the auxiliary electrodes were composed of LSM oxides (La0.65Sr0.35MnO3 - fuel Cell Materials, LSM35) mixed with YSZ (Tosoh). The cathode was a ring shaped electrode at the periphery of 0.93 cm2 surface area, and the auxiliary was a circular dot electrode of 0.31 cm2 surface area at the center of the cathode but separated from the cathode. They were sintered at 1150°C for 2 hours.To study the performances of the bottom cells, we have used a test rig (ProboStat, NorECs, Netherland). The sealing between the anodic and cathodic compartments was ensured by a gold ring which was annealed at 1040°C for 4 days under air. For current collection, Pt meshes were used for cathode and auxiliary while Ti mesh, catalytically inactive,was used for anode. Prior to the experiments, the catalysts were reduced under pure H2 at 900oC for 2 hours. The effect of the addition of H2S in the reaction mixture has been investigated (1 ppm of H2S/He, 2%CH4/He â Air Liquide, 5% H2O added with a thermostated water saturator regulated at 33 °C) under 200cc/min flow while cathode and auxiliary were exposed under synthetic air (Linde 99,995%). The products of the reaction were analyzed by using a Hiden Analytical HPR20 quadripole mass spectrometer.H2S poisoning was followed in open circuit mode, in fuel cell mode and in triode operation mode at 900°C. Triode operation cannot avoid or limit the catalytic degradation of the SOFC cell exposed to 1 ppm H2S but can maintain higher anodic electrochemical performances. This confirms that active sites for catalytic conversion (methane steam reforming) and those for electrochemical oxidation of hydrogen are not the same. The cell performances loss is mainly attributed to the degradation of the catalytic activity, then decreasing the concentration of electroactive species, i.e. hydrogen. Triode operation can slightly compensate the deactivation of the catalytic sites most probably with a local production of H2, from H2O electrolysis. Some specific triode operations can be found to achieve a thermodynamic efficiency close to the unity to avoid any energy overconsumption.Acknowledgements: this work was financed by the EU 7th Framework Program, Fuel Cells and Hydrogen Joint Technology Initiative, under the frame of the T-CELL project (grant agreement 298300)