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A M Baruzzi - One of the best experts on this subject based on the ideXlab platform.
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Alkaline Earth Cation transfer assisted by monensin across the water 1 2 dichloroethane interface in the presence of alkali Cations
Journal of Electroanalytical Chemistry, 2002Co-Authors: S A Dassie, A M BaruzziAbstract:Abstract The electrochemical transfer of Alkaline-Earth Cations (Me2+) assisted by monensin (HX) across the water ∣ 1,2-dichloroethane (DCE) in the presence of alkali Cations (M+) is reported. A shift in the peak potential for Ba2+ transfer and an increase in ΔEp from 0.030 to 0.060 V are the principal effects produced by the presence of M+. These findings depend on pH and the relative concentrations of both Cations. The following chemical exchange reaction M(w)++HX(c)+H2O⇄MX(o)+H3O+ coupled to the electrochemical transfer of Ba2+ accounts for ΔEp=0.060 V of the peak observed as a consequence of the net charge transfer of +1 at the interface. These results are in agreement with the hyper-Nernstian slope of 60 mV found for Ca2+ and Ba2+ ion selective electrodes based on antibiotics with carboxylic groups at intermediate pH values. A theoretical equation for the dependence of Δowφ1/2 for Me2+ with pH and M+ activity was developed.
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comparative analysis of alkali and Alkaline Earth Cation transfer assisted by monensin across the water 1 2 dichloroethane interface
Journal of Electroanalytical Chemistry, 2000Co-Authors: S A Dassie, A M BaruzziAbstract:Abstract In the first part of this paper the electrochemical transfer of alkali Cations (M+) assisted by monensin (HX) across the water ∣ 1,2-dichloroethane (DCE) interface at pH 9 the current is voltammetrically negligible. An equation for the dependence of Δowφ1/2 on pH and Na+ concentration is developed. In the second part of the paper the transfer of Alkaline Earth Cations assisted by the same ionophore is studied. The electrochemical reactions (Me(w)2++HX(o)⇄MeHX2+(o)) and (Me(w)2++X−(o)⇄MeX+(o)) are responsible for the peaks observed at pH 9.0, respectively. As expected, in both cases ΔEp=0.030 V while at intermediate pH the electrochemical exchange reaction (Me2+(w)+HX(o)⇄MeX+(o)+H+(w)) is proposed. The net charge transfer of +1 at the interface accounts for ΔEp=0.060 V for the peak observed ΔEp in agreement with the hyper-Nernstian slope of 60 mV found for Ca2+ and Ba2+ ISE based on antibiotics with carboxylic groups at intermediate pH values. The higher selectivity for Ba2+ and the tendency in selectivity at Alkaline pH found in the ISEs are also observed and thus explained according to the mechanism proposed.
Nicolas F Richet - One of the best experts on this subject based on the ideXlab platform.
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boson peak of alkali and Alkaline Earth silicate glasses influence of the nature and size of the network modifying Cation
Journal of Chemical Physics, 2012Co-Authors: Nicolas F RichetAbstract:The influence of the size of the Alkaline Earth Cation on the boson peak of binary metasilicate glasses, MSiO3 (M = Mg, Ca, Sr, Ba), has been investigated from vibrational densities of states determined by inversion of low-temperature heat capacities. As given both by Cp/T 3 and g(ω)/ω2, the intensity of the boson peak undergoes a 7-fold increase from Mg to Ba, whereas its temperature and frequency correlatively decrease from 18 to 10 K and from 100 to 20 cm−1, respectively. The boson peak results from a combination of librations of SiO4 tetrahedra and localized vibrations of network-modifying Cations with non-bridging oxygens whose contribution increases markedly with the ionic radius of the Alkaline Earth. As a function of ionic radii, the intensity for Sr and Ba varies in the same way as previously found for alkali metasilicate glasses. The localized vibrations involving alkali and heavy Alkaline Earth Cations appear to be insensitive to the overall glass structure. Although the new data are coherent w...
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boson peak of alkali and Alkaline Earth silicate glasses influence of the nature and size of the network modifying Cation
Journal of Chemical Physics, 2012Co-Authors: Nicolas F RichetAbstract:The influence of the size of the Alkaline Earth Cation on the boson peak of binary metasilicate glasses, MSiO3 (M = Mg, Ca, Sr, Ba), has been investigated from vibrational densities of states determined by inversion of low-temperature heat capacities. As given both by Cp/T 3 and g(ω)/ω2, the intensity of the boson peak undergoes a 7-fold increase from Mg to Ba, whereas its temperature and frequency correlatively decrease from 18 to 10 K and from 100 to 20 cm−1, respectively. The boson peak results from a combination of librations of SiO4 tetrahedra and localized vibrations of network-modifying Cations with non-bridging oxygens whose contribution increases markedly with the ionic radius of the Alkaline Earth. As a function of ionic radii, the intensity for Sr and Ba varies in the same way as previously found for alkali metasilicate glasses. The localized vibrations involving alkali and heavy Alkaline Earth Cations appear to be insensitive to the overall glass structure. Although the new data are coherent with an almost linear relationship between the temperature of the boson peak and transverse sound velocity, pure SiO2 and SiO2-rich glasses make marked exceptions to this trend because of the weak transverse character of SiO4 librations. Finally, the universality of the calorimetric boson peak is again borne out because all data for silicate glasses collapse on the same master curve when plotted in a reduced form (CP/T 3)/(CP/T 3)b vs. T/Tb.
S A Dassie - One of the best experts on this subject based on the ideXlab platform.
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Alkaline Earth Cation transfer assisted by monensin across the water 1 2 dichloroethane interface in the presence of alkali Cations
Journal of Electroanalytical Chemistry, 2002Co-Authors: S A Dassie, A M BaruzziAbstract:Abstract The electrochemical transfer of Alkaline-Earth Cations (Me2+) assisted by monensin (HX) across the water ∣ 1,2-dichloroethane (DCE) in the presence of alkali Cations (M+) is reported. A shift in the peak potential for Ba2+ transfer and an increase in ΔEp from 0.030 to 0.060 V are the principal effects produced by the presence of M+. These findings depend on pH and the relative concentrations of both Cations. The following chemical exchange reaction M(w)++HX(c)+H2O⇄MX(o)+H3O+ coupled to the electrochemical transfer of Ba2+ accounts for ΔEp=0.060 V of the peak observed as a consequence of the net charge transfer of +1 at the interface. These results are in agreement with the hyper-Nernstian slope of 60 mV found for Ca2+ and Ba2+ ion selective electrodes based on antibiotics with carboxylic groups at intermediate pH values. A theoretical equation for the dependence of Δowφ1/2 for Me2+ with pH and M+ activity was developed.
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comparative analysis of alkali and Alkaline Earth Cation transfer assisted by monensin across the water 1 2 dichloroethane interface
Journal of Electroanalytical Chemistry, 2000Co-Authors: S A Dassie, A M BaruzziAbstract:Abstract In the first part of this paper the electrochemical transfer of alkali Cations (M+) assisted by monensin (HX) across the water ∣ 1,2-dichloroethane (DCE) interface at pH 9 the current is voltammetrically negligible. An equation for the dependence of Δowφ1/2 on pH and Na+ concentration is developed. In the second part of the paper the transfer of Alkaline Earth Cations assisted by the same ionophore is studied. The electrochemical reactions (Me(w)2++HX(o)⇄MeHX2+(o)) and (Me(w)2++X−(o)⇄MeX+(o)) are responsible for the peaks observed at pH 9.0, respectively. As expected, in both cases ΔEp=0.030 V while at intermediate pH the electrochemical exchange reaction (Me2+(w)+HX(o)⇄MeX+(o)+H+(w)) is proposed. The net charge transfer of +1 at the interface accounts for ΔEp=0.060 V for the peak observed ΔEp in agreement with the hyper-Nernstian slope of 60 mV found for Ca2+ and Ba2+ ISE based on antibiotics with carboxylic groups at intermediate pH values. The higher selectivity for Ba2+ and the tendency in selectivity at Alkaline pH found in the ISEs are also observed and thus explained according to the mechanism proposed.
Joachim Mayer - One of the best experts on this subject based on the ideXlab platform.
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functional properties of la0 99x0 01nb0 99al0 01o4 δ and la0 99x0 01nb0 99ti0 01o4 δ proton conductors where x is an Alkaline Earth Cation
Journal of The European Ceramic Society, 2015Co-Authors: Mariya E Ivanova, Wilhelm A Meulenberg, Justinas Palisaitis, Doris Sebold, Cecilia Solis, Mirko Ziegner, Jose M Serra, Joachim MayerAbstract:Lanthanum niobates with general formulas of La0.99X0.01Nb0.99Al0.01O4−δ and La0.99X0.01Nb0.99Ti0.01O4−δ (X = Mg, Ca, Sr or Ba) were synthesized via the conventional solid state reaction. Specimens with relative density above 96% were produced after sintering. Structural and phase composition studies revealed predominant monoclinic Fergusonite structure for the majority of samples. SEM and TEM studies elucidated the effect of the used dopant combinations on grain growth, micro-crack formation and secondary phase formation. Results from microstructural study were correlated to the grain interior and grain boundary conductivities for selected samples (La0.99Sr0.01Nb0.99Al0.01O4−δ and La0.99Sr0.01Nb0.99Ti0.01O4−δ). The majority of co-doped niobates exhibited appreciable protonic conductivity under humid atmospheres at intermediate temperatures. Sr- or Ca-doped compounds displayed the highest total conductivities with values for LSNA equal to 6 × 10−4 S/cm and 3 × 10−4 S/cm in wet air and in wet 4% H2–Ar (900 °C), respectively. Additionally, thermal expansion was studied to complete functional characterization of co-doped LaNbO4.
Alexandra Navrotsky - One of the best experts on this subject based on the ideXlab platform.
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Thermodynamic study of alkali and Alkaline-Earth Cation-exchanged natrolites
Microporous and Mesoporous Materials, 2013Co-Authors: Lili Wu, Alexandra NavrotskyAbstract:Abstract A series of synthetic natrolites with different non-framework Cations (Li-NAT, Na-NAT, K-NAT, Rb-NAT, Cs-NAT, Ca-NAT, Sr-NAT and Pb-NAT) are investigated by high temperature oxide melt solution calorimetry. The formation enthalpy from the component oxides (Δ H f,ox ) becomes less exothermic with increasing ionic potential ( Z / r ) of the Cations. The dehydration behavior of NATs is examined using TG–DSC. The strength of water binding decreases with increasing Cation size. Similar to the trend seen in anhydrous zeolites, a linear dependence of Δ H f,ox on Al/(Al + Si) ratio for hydrous zeolites is established.
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enthalpy of formation and dehydration of Alkaline Earth Cation exchanged zeolite beta
Microporous and Mesoporous Materials, 2008Co-Authors: Pingping Sun, Alexandra NavrotskyAbstract:Abstract Cationic variants of zeolite beta (Mg-BEA 14, Ca-BEA 14, Sr-BEA 14, Ba-BEA 14, Mg-BEA 4 and Ca-BEA 4) were achieved by alumination and ion exchange processes, and characterized by XRD, NMR and TG–DSC. Mg-BEA 14/Ca-BEA 14, Sr-BEA 14/Ba-BEA 14, and Mg-BEA 4/Ca-BEA 4 have distinct thermal behavior. The low silica zeolites Mg-BEA 4 and Ca-BEA 4 were observed to have octahedral Al atoms and less crystallinity compared with high silica Mg-BEA 14 and Ca-BEA 14. High temperature oxide melt solution calorimetry determined the dehydration enthalpy and the formation enthalpy from the constituent oxides. For Alkaline Earth zeolite beta with the same Si/Al ratio, both the integral dehydration enthalpy and formation enthalpy from oxides becomes more endothermic with increasing average ionic potential. Mg-BEA 4 and Ca-BEA 4 have very endothermic formation enthalpies, in both dehydrated and hydrated forms, indicating a likely thermodynamic barrier to their direct synthesis, despite the natural occurrence of their analog, tschernichite.