The Experts below are selected from a list of 1845 Experts worldwide ranked by ideXlab platform
Laura Gagliardi - One of the best experts on this subject based on the ideXlab platform.
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Thorium and Uranium Carbide Cluster Cations in the Gas Phase: Similarities and Differences between Thorium and Uranium
2016Co-Authors: Claúdia C. L. Pereira, Ana F. Lucena, John K. Gibson, Lester Andrews, Laura GagliardiAbstract:ABSTRACT: Laser ionization of AnC4 alloys (An = Th, U) yielded gas-phase molecular thorium and Uranium Carbide cluster cations of composition AnmCn +, with m = 1, n = 2−14, and m = 2, n = 3−18, as detected by Fourier transform ion-cyclotron-resonance mass spectrometry. In the case of thorium, ThmCn + cluster ions with m = 3−13 and n = 5−30 were also produced, with an intriguing high intensity of Th13Cn + cations. The AnC13 + ions also exhibited an unexpectedly high abundance, in contrast to the gradual decrease in the intensity of other AnCn + ions with increasing values of n. High abundances of AnC2 + and AnC4 + ions are consistent with enhanced stability due to strong metal−C2 bonds. Amon
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thorium and Uranium Carbide cluster cations in the gas phase similarities and differences between thorium and Uranium
Inorganic Chemistry, 2013Co-Authors: Claúdia C. L. Pereira, Ana F. Lucena, John K. Gibson, Lester Andrews, Remi Maurice, A P Goncalves, Joaquim Marcalo, Laura GagliardiAbstract:Laser ionization of AnC4 alloys (An = Th, U) yielded gas-phase molecular thorium and Uranium Carbide cluster cations of composition An(m)C(n)(+), with m = 1, n = 2-14, and m = 2, n = 3-18, as detected by Fourier transform ion-cyclotron-resonance mass spectrometry. In the case of thorium, Th(m)C(n)(+) cluster ions with m = 3-13 and n = 5-30 were also produced, with an intriguing high intensity of Th13C(n)(+) cations. The AnC13(+) ions also exhibited an unexpectedly high abundance, in contrast to the gradual decrease in the intensity of other AnC(n)(+) ions with increasing values of n. High abundances of AnC2(+) and AnC4(+) ions are consistent with enhanced stability due to strong metal-C2 bonds. Among the most abundant bimetallic ions was Th2C3(+) for thorium; in contrast, U2C4(+) was the most intense bimetallic for Uranium, with essentially no U2C3(+) appearing. Density functional theory computations were performed to illuminate this distinction between thorium and Uranium. The computational results revealed structural and energetic disparities for the An2C3(+) and An2C4(+) cluster ions, which elucidate the observed differing abundances of the bimetallic Carbide ions. Particularly noteworthy is that the Th atoms are essentially equivalent in Th2C3(+), whereas there is a large asymmetry between the U atoms in U2C3(+).
Müşerref Önal - One of the best experts on this subject based on the ideXlab platform.
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Application of diffusion and transition state theories on the carburizing of steel AISI 316 by annealing in Uranium Carbide powder.
Heliyon, 2019Co-Authors: Yüksel Sarıkaya, Müşerref Önal, Abdullah Devrim PekdemirAbstract:Abstract The steel specimens were tempered in contact with Uranium Carbide powder by sodium bonding at 500, 600, 700, and 800 °C for 1000h. Carburizing zone of the specimens was determined by measuring of microhardness which is taken as a kinetic variable instead of the corresponding carbon content. Arrhenius equation was determined for the diffusion of carbon atoms in the steel by using the solution of Fick's second law. Temperature dependency of the activation enthalpy, Gibbs energy, and entropy was calculated from the transition state theory by an assumption that the carburizing occurs over an activated complex. Kinetic and thermodynamic for formation an activated complex were discussed depending on the obtained numerical values.
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High temperature carburizing of a stainless steel with Uranium Carbide
Journal of Alloys and Compounds, 2012Co-Authors: Yüksel Sarıkaya, Müşerref ÖnalAbstract:Abstract Diffusion theory (DT) and activated complex theory (ACT) were applied to the carburizing process of austenitic stainless steel 1.4988 with Uranium Carbide by sodium bonding at 773, 873, 973 and 1073 K for 1000 h. Microhardness profiles of the carburized steel specimens were obtained. Diffusion coefficient (D) of carbon atoms into the steel were calculated for each temperature by using the microhardness values instead of the carbon concentrations in the approximate solution of the second Fick’s equation. Arrhenius equation for the carburizing process was found as: D = 2.6 × 10−11 exp (−66753/RT) in m2 s−1. Equilibrium constant (K#) and enthalpy of activation (ΔH#) for the formation of an activated complex calculated for each temperature from the Eyring equation using the diffusion coefficient instead of the reaction rate constant. Temperature dependence of the ΔH# and change in heat capacities ( Δ C p # ) by the carburizing were graphically determined as: ΔH# = 66741 − 8.3T in J mol−1 and Δ C p # = 8.3 J K−1 mol−1. Temperature dependence of lnK#, Gibbs energy of activation (ΔG#) and entropy of activation (ΔS#) were found respectively as follows: lnK# = −66741/RT = (8.3/R)lnT −48.3, ΔG# = 66741 + 8.3T lnT + 48.3 RT in J mol−1, and ΔS# = −409.9−8.3 lnT in J K−1 mol−1. Based on these results, formation, size, and composition of the activated complex were discussed.
B. Fourest - One of the best experts on this subject based on the ideXlab platform.
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Simultaneous determination of Uranium Carbide dissolution products by capillary zone electrophoresis.
Journal of chromatography. A, 2009Co-Authors: Vladimir Sladkov, B. FourestAbstract:Abstract Separation and simultaneous determination of a number of organic acid anions (oxalate, mellitate, trimellitate and benzoate) and U(VI) with direct UV detection is developed for analysis of Uranium Carbide (UC) dissolution products by capillary zone electrophoresis (CZE). Reverse polarity mode is used. It is found that complex formation of U(VI) with carbonate, used as a carrier electrolyte, allows U(VI) to be determined, as negatively charged species, in a single run with organic acid anions. Some parameters such as pH value, composition of electrolyte and detection wavelength are optimized. Under the chosen conditions (carbonate buffer (ionic strength of 100 mM), pH 9.8, 0.15 mM tetradecyltrimethylammonium bromide (TTAB)) a complete separation is achieved. Calibration plots are linear in two ranges of concentration for U(VI) (∼1 × 10 −5 to 1 × 10 −3 ), mellitate and trimellitate (∼5 × 10 −6 to 5 × 10 −4 ), and about one range (∼1 × 10 −4 to 5 × 10 −3 ) for oxalate and benzoate. Accuracy of the procedure is checked by the “added-found” method in standard mixture solutions. Relative standard deviation is within the range of 2–10% and the recovery is in the range of 90–110%. This method is applied for the analysis of real UC dissolution samples.
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Simultaneous determination of Uranium Carbide dissolution products by capillary zone electrophoresis
Journal of Chromatography A, 2009Co-Authors: Vladimir Sladkov, B. FourestAbstract:Separation and simultaneous determination of a number of organic acid anions (oxalate, mellitate, trimellitate and benzoate) and U(VI) with direct UV detection is developed for analysis of Uranium Carbide (UC) dissolution products by capillary zone electrophoresis (CZE). Reverse polarity mode is used. It is found that complex formation of U(VI) with carbonate, used as a carrier electrolyte, allows U(VI) to be determined, as negatively charged species, in a single run with organic acid anions. Some parameters such as pH value, composition of electrolyte and detection wavelength are optimized. Under the chosen conditions (carbonate buffer (ionic strength of 100 mM), pH 9.8, 0.15 mM tetradecyltrimethylammonium bromide (TTAB)) a complete separation is achieved. Calibration plots are linear in two ranges of concentration for U(VI) (not, vert, similar1 × 10−5 to 1 × 10−3), mellitate and trimellitate (not, vert, similar5 × 10−6 to 5 × 10−4), and about one range (not, vert, similar1 × 10−4 to 5 × 10−3) for oxalate and benzoate. Accuracy of the procedure is checked by the “added-found” method in standard mixture solutions. Relative standard deviation is within the range of 2-10% and the recovery is in the range of 90-110%. This method is applied for the analysis of real UC dissolution samples.
Claúdia C. L. Pereira - One of the best experts on this subject based on the ideXlab platform.
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Thorium and Uranium Carbide Cluster Cations in the Gas Phase: Similarities and Differences between Thorium and Uranium
2016Co-Authors: Claúdia C. L. Pereira, Ana F. Lucena, John K. Gibson, Lester Andrews, Laura GagliardiAbstract:ABSTRACT: Laser ionization of AnC4 alloys (An = Th, U) yielded gas-phase molecular thorium and Uranium Carbide cluster cations of composition AnmCn +, with m = 1, n = 2−14, and m = 2, n = 3−18, as detected by Fourier transform ion-cyclotron-resonance mass spectrometry. In the case of thorium, ThmCn + cluster ions with m = 3−13 and n = 5−30 were also produced, with an intriguing high intensity of Th13Cn + cations. The AnC13 + ions also exhibited an unexpectedly high abundance, in contrast to the gradual decrease in the intensity of other AnCn + ions with increasing values of n. High abundances of AnC2 + and AnC4 + ions are consistent with enhanced stability due to strong metal−C2 bonds. Amon
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thorium and Uranium Carbide cluster cations in the gas phase similarities and differences between thorium and Uranium
Inorganic Chemistry, 2013Co-Authors: Claúdia C. L. Pereira, Ana F. Lucena, John K. Gibson, Lester Andrews, Remi Maurice, A P Goncalves, Joaquim Marcalo, Laura GagliardiAbstract:Laser ionization of AnC4 alloys (An = Th, U) yielded gas-phase molecular thorium and Uranium Carbide cluster cations of composition An(m)C(n)(+), with m = 1, n = 2-14, and m = 2, n = 3-18, as detected by Fourier transform ion-cyclotron-resonance mass spectrometry. In the case of thorium, Th(m)C(n)(+) cluster ions with m = 3-13 and n = 5-30 were also produced, with an intriguing high intensity of Th13C(n)(+) cations. The AnC13(+) ions also exhibited an unexpectedly high abundance, in contrast to the gradual decrease in the intensity of other AnC(n)(+) ions with increasing values of n. High abundances of AnC2(+) and AnC4(+) ions are consistent with enhanced stability due to strong metal-C2 bonds. Among the most abundant bimetallic ions was Th2C3(+) for thorium; in contrast, U2C4(+) was the most intense bimetallic for Uranium, with essentially no U2C3(+) appearing. Density functional theory computations were performed to illuminate this distinction between thorium and Uranium. The computational results revealed structural and energetic disparities for the An2C3(+) and An2C4(+) cluster ions, which elucidate the observed differing abundances of the bimetallic Carbide ions. Particularly noteworthy is that the Th atoms are essentially equivalent in Th2C3(+), whereas there is a large asymmetry between the U atoms in U2C3(+).
Yüksel Sarıkaya - One of the best experts on this subject based on the ideXlab platform.
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Application of diffusion and transition state theories on the carburizing of steel AISI 316 by annealing in Uranium Carbide powder.
Heliyon, 2019Co-Authors: Yüksel Sarıkaya, Müşerref Önal, Abdullah Devrim PekdemirAbstract:Abstract The steel specimens were tempered in contact with Uranium Carbide powder by sodium bonding at 500, 600, 700, and 800 °C for 1000h. Carburizing zone of the specimens was determined by measuring of microhardness which is taken as a kinetic variable instead of the corresponding carbon content. Arrhenius equation was determined for the diffusion of carbon atoms in the steel by using the solution of Fick's second law. Temperature dependency of the activation enthalpy, Gibbs energy, and entropy was calculated from the transition state theory by an assumption that the carburizing occurs over an activated complex. Kinetic and thermodynamic for formation an activated complex were discussed depending on the obtained numerical values.
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High temperature carburizing of a stainless steel with Uranium Carbide
Journal of Alloys and Compounds, 2012Co-Authors: Yüksel Sarıkaya, Müşerref ÖnalAbstract:Abstract Diffusion theory (DT) and activated complex theory (ACT) were applied to the carburizing process of austenitic stainless steel 1.4988 with Uranium Carbide by sodium bonding at 773, 873, 973 and 1073 K for 1000 h. Microhardness profiles of the carburized steel specimens were obtained. Diffusion coefficient (D) of carbon atoms into the steel were calculated for each temperature by using the microhardness values instead of the carbon concentrations in the approximate solution of the second Fick’s equation. Arrhenius equation for the carburizing process was found as: D = 2.6 × 10−11 exp (−66753/RT) in m2 s−1. Equilibrium constant (K#) and enthalpy of activation (ΔH#) for the formation of an activated complex calculated for each temperature from the Eyring equation using the diffusion coefficient instead of the reaction rate constant. Temperature dependence of the ΔH# and change in heat capacities ( Δ C p # ) by the carburizing were graphically determined as: ΔH# = 66741 − 8.3T in J mol−1 and Δ C p # = 8.3 J K−1 mol−1. Temperature dependence of lnK#, Gibbs energy of activation (ΔG#) and entropy of activation (ΔS#) were found respectively as follows: lnK# = −66741/RT = (8.3/R)lnT −48.3, ΔG# = 66741 + 8.3T lnT + 48.3 RT in J mol−1, and ΔS# = −409.9−8.3 lnT in J K−1 mol−1. Based on these results, formation, size, and composition of the activated complex were discussed.
