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Wei-e Wang - One of the best experts on this subject based on the ideXlab platform.

  • characterization of the vanadium nitrogen system with nitrogen pressure isobars
    Journal of Alloys and Compounds, 2000
    Co-Authors: Wei-e Wang, Hyun Seon Hong
    Abstract:

    Abstract The partial thermodynamic functions of the V–N system from V to VN over the temperature range 1000 to 2100 K have been investigated. The discrepancies among the pressure–composition–temperature (p–C–T) relationships in the δ-VN single-phase region have been resolved. The p–C–T relationships for other phases, where no data were available from the literature, have been established by applying the appropriate thermodynamic constraints and a modified form of Sieverts Law. The results are presented as the nitrogen isobars superimposed on the phase diagram.

  • Characterization of the vanadium–nitrogen system with nitrogen pressure isobars
    Journal of Alloys and Compounds, 2000
    Co-Authors: Wei-e Wang, Yeon Soo Kim, Hyun Seon Hong
    Abstract:

    Abstract The partial thermodynamic functions of the V–N system from V to VN over the temperature range 1000 to 2100 K have been investigated. The discrepancies among the pressure–composition–temperature (p–C–T) relationships in the δ-VN single-phase region have been resolved. The p–C–T relationships for other phases, where no data were available from the literature, have been established by applying the appropriate thermodynamic constraints and a modified form of Sieverts Law. The results are presented as the nitrogen isobars superimposed on the phase diagram.

  • Characterization of the U–UO2 phase diagram with oxygen isobars at high temperatures
    Journal of Alloys and Compounds, 1999
    Co-Authors: Wei-e Wang
    Abstract:

    Abstract Thermodynamic constraints, together with Sieverts Law assumption, are used to construct the equilibrium molecular oxygen pressure–composition–temperature ( p (O 2 )–C–T) spectrum over the U–UO 2 system from 2300 K to 3100 K even at regions where no direct measurements of p O 2 are available. The ensemble of the results is presented as the oxygen isobars superimposed on the phase diagram.

  • Thermodynamics of the UO and Zr-systems and application to analysis of fuel liquefaction during severe accidents in light water reactors
    Journal of Nuclear Materials, 1997
    Co-Authors: Donald R. Olander, Wei-e Wang
    Abstract:

    Severe accident modeling requires knowledge of the heat effects accompanying simultaneous dissolution of UO2 and fusion of Zircaloy to form the UZrO melt. Estimation of the enthalpy changes must rely chiefly on data from the UO and ZrO binary systems. The partial molar enthalpies of oxygen in the pure liquid metals are determined by application of Sieverts' Law. The Sieverts' Law constant is obtained by deriving the complete relationship between the oxygen pressure, the OM of the solid or liquid phase and temperature from the pure metal M to the dioxide MO2. This assessment utilizes pressure p, over the entire composition range. Once the p-C-T relatnonship has been established, the enthalpy changes on dissolving UO2 and αZr(O) into the UZrO melt are computed. The heat effects of fuel/cladding dissolution in a severe accident are applied in a liquefaction model based on kinetic control by the available heat from fission product decay. In addition to the portion of the decay heat reaching the inner cladding surface, the rate of melting of the cladding depends on heat flow to its outer surface from steam oxidation or radiation from other parts of the core. Depending on the relative importance of these two heat inputs to the cladding, time to melting is from 100 to 400 s and the fraction of the fuel dissolved varies from 5 to 20%.

  • Thermodynamic evaluation of the titanium-hydrogen system
    Journal of Alloys and Compounds, 1996
    Co-Authors: Wei-e Wang
    Abstract:

    Abstract Thermodynamic constraints, together with a modified form of Sieverts Law, are used to evaluate the partial and integral thermodynamic functions of the TiH system from 400 to 1010 K. Satisfactory pCT relationships for each phase have been developed, even in regions where no data are available. The results are presented as hydrogen isobars superimposed on the phase diagram. The discrepancies in the Sieverts Law constant for αTi and the standard free energy of formation of TiH2 have been resolved.

Masanobu Miyake - One of the best experts on this subject based on the ideXlab platform.

  • HYDROGEN SOLUBILITY IN ZIRCONIUM ALLOYS
    Journal of Alloys and Compounds, 1995
    Co-Authors: Shusuke Yamanaka, K. Higuchi, Masanobu Miyake
    Abstract:

    Abstract The zirconium alloys employed in this study were Zircaloy-2 (1.47 wt.% Sn, 0.14 wt.% Fe, 0.11 wt.% Cr, 0.05 wt.% Ni), Zircaloy-4 (1.52 wt.% Sn, 0.21 wt.% Fe, 0.11 wt.% Cr) and Zr-1wt.% Nb. The hydrogen solubilities in these alloys were measured in the temperature range 600–1050°C at a hydrogen pressure below 100 Pa. The hydrogen solubilities for all the alloys obeyed Sieverts' Law in both the α phase (h.c.p.) and β phase (b.c.c.) regions. In the α phase region (below 850 °C) Zircaloy-4 had the largest solubility among the alloys and pure zirconium. The enthalpies of solution for the alloys were higher than that for pure zirconium. In the β phase region (above 950 °C) the hydrogen solubilities in the alloys were smaller than that in pure zirconium. The enthalpies of solution for the alloys were appreciably higher than that for pure zirconium. The partial thermodynamic functions of hydrogen in the zirconium alloys were derived from the experimental data sets.

  • Influence of interstitial oxygen on hydrogen solubility in vanadium
    Journal of Alloys and Compounds, 1995
    Co-Authors: Shusuke Yamanaka, Y. Kashiwara, Masanobu Miyake
    Abstract:

    Abstract Measurement of hydrogen solubility was performed in the temperature range 500–800 °C at a hydrogen pressure below 10 4 using a modified Sieverts ultrahigh vacuum apparatus. The vanadium-oxygen alloys employed in the present study had [O]/[V] atomic ratios from 0.010 to 0.044 and showed a homogeneous b.c.c. phase. All the hydrogen solubility data for the vanadium oxygen alloys followed the Sieverts' Law. At lower temperatures (below 600 °C), the hydrogen solubility decreased with increasing oxygen content of alloy. At higher temperatures (above 600 °C), the hydrogen solubility first increased slightly and then decreased with increasing oxygen content. The variation in enthalpy of solution of hydrogen with the oxygen content indicated a pronounced maximum at an [O]/[V] atom ratio of 0.01. Partial molar quantities of hydrogen were derived by applying a solution model to the experimental solubility data. Both partial molar enthalpy and partial molar excess entropy first increased and passed through maximum. The changes in the quantities with the oxygen content are discussed in terms of sums over vibrational, lattice dilatational and configurational contributions.

  • Thermodynamic analysis of hydrogen solubility in graphite
    Journal of Nuclear Materials, 1993
    Co-Authors: Yoshirou Shirasu, Shinsuke Yamanaka, Masanobu Miyake
    Abstract:

    Abstract The hydrogen solubility in isotropic graphites ISO 880U and EK 98 has been measured in the temperature range of 700–1000°C at pressures below 2 × 10 4 Pa . The solubility data obtained closely obeyed Sieverts' Law. The hydrogen solubility and the enthalpy of solution for ISO 880U and EK 98 graphites were compared with those for isotropic graphites IG 110U and POCO AXF-5Q. The hydrogen solubility in a highly oriented pyrolytic graphite PGCCL has also been measured at 1000°C. It was an order of magnitude lower than that in isotropic graphites. Partial thermodynamic functions of hydrogen in isotropic graphites were obtained by a dilute solution model and discussed.

  • Effect of interstitial oxygen on hydrogen solubility in titanium, zirconium and hafnium
    Journal of The Less Common Metals, 1993
    Co-Authors: Shinsuke Yamanaka, Hidenori Ogawa, Masanobu Miyake
    Abstract:

    Abstract Measurements of hydrogen solubility in HfO alloys with oxygen contents of 0.048–0.188 O/Hf were performed at temperatures of 600–850 °C and an H2 pressure below 100 Pa using a constant-volume method. All the hydrogen solubility data for the HfO alloys closely followed Sieverts' Law. The hydrogen solubility decreased with oxygen content. The enthalpy of solution for hydrogen was lower for the HfO alloy than for pure hafnium. These trends in solubility and enthalpy of solution for the HfO alloy were more similar to those for TiO than ZrO alloys. Partial thermodynamic quantities for hydrogen in the HfOH ternary system were estimated and compared with previous results for TiOH and ZrOH ternary systems. The change in hydrogen solubility due to interstitial oxygen was inferred from the analysis to be attributable to a net result of the decreases in partial molar enthalpy and excess entropy of hydrogen.

  • Hydrogen solubility in boron carbide
    Journal of Alloys and Compounds, 1992
    Co-Authors: Yoshirou Shirasu, Shinsuke Yamanaka, Masanobu Miyake
    Abstract:

    Abstract Solubility measurements have been performed for hydrogen in B 4 C in the temperature range 700–1000 °C at a hydrogen pressure below 10 5 Pa. The solubility data closely obeyed Sieverts' Law. A negative enthalpy of solution was obtained. A dilute solution model was proposed for the hydrogen solubility in B 4 C on the assumption that hydrogen atoms are dissolved in interstitial sites in B 4 C. The partial molar enthalpy and entropy of hydrogen in B 4 C were estimated from the thermodynamic analysis.

Enrico Drioli - One of the best experts on this subject based on the ideXlab platform.

  • Sieverts Law pressure exponent for hydrogen permeation through pd based membranes coupled influence of non ideal diffusion and multicomponent external mass transfer
    International Journal of Hydrogen Energy, 2013
    Co-Authors: Alessio Caravella, Enrico Drioli, Shigeki Hara, Giuseppe Barbieri
    Abstract:

    Abstract This paper focuses on the suitability of using a Sieverts-type empirical Law to describe hydrogen permeation through Pd-based membranes in the presence of both concentration-dependent hydrogen transport through the selective layer – referred to as “non-ideal” behaviour – and external mass transfer resistance. In particular, the functionality of the pressure exponent with temperature, pressure and membrane thickness is provided, showing that the Sieverts-type empirical Law can be used to incorporate the external mass transfer influence just up to a moderate external resistance. The explanation for this fact is recognised in the inadequacy of the Sieverts-type empirical Law to describe the behaviour of the flux limited by external resistance for a sufficiently large permeation driving force. The methodology described in this paper is effective also when the permeation-determining steps cannot be established, helping researchers to a correct interpretation of permeation tests in the presence of severe mass transfer resistance.

  • Sieverts Law empirical exponent for Pd-based membranes: critical analysis in pure H2 permeation.
    The journal of physical chemistry. B, 2010
    Co-Authors: Alessio Caravella, Francesco Scura, Giuseppe Barbieri, Enrico Drioli
    Abstract:

    In this paper, the physical meaning of the Sieverts-type driving force exponent n is analyzed for hydrogen permeation through Pd-based membranes by considering a complex model involving several elementary permeation steps (adsorption on the membrane surface on the feed side, desorption from the surface on the permeate side, diffusion through the metal lattice, and the two transition phenomena surface-to-bulk and bulk-to-surface). First, the characteristic driving force of each step is evaluated, showing that adsorption and desorption singularly considered and the adsorption and desorption considered at the same time are characterized by driving forces depending on the ratio of feed and permeate hydrogen pressure. On the contrary, the diffusion step is found to present a driving force that is composed of two terms, one which corresponds to the original Sieverts Law (with an exponent of 0.5) and the other which is the product of the pressure difference and a temperature-dependent factor. Then, the characteristic n is evaluated by applying the multistep model to two different membranes from the literature in several cases, (a) considering each permeation step as the only limiting one and (b) considering the overall effect of all steps. The results of the analysis show that for a low temperature and thin membrane thickness, the effect of the surface phenomena is, in general, a decrease of the overall exponent n toward values lower than 0.5, even though, under particular operating conditions, the n theoretical value of the surface phenomena is equal to unity. At a higher temperature and thickness (diffusion-controlled permeation), n tends to 0.5, even though the rapidity of this tendency depends strictly on the membrane diffusional parameters. In this frame, the expression developed for the diffusion step provides a theoretical reason why n values higher than 0.5 are found even for thick membranes and high temperature, where diffusion is the only rate-determining step.

  • Sieverts Law empirical exponent for pd based membranes critical analysis in pure h2 permeation
    Journal of Physical Chemistry B, 2010
    Co-Authors: Alessio Caravella, Francesco Scura, Giuseppe Barbieri, Enrico Drioli
    Abstract:

    In this paper, the physical meaning of the Sieverts-type driving force exponent n is analyzed for hydrogen permeation through Pd-based membranes by considering a complex model involving several elementary permeation steps (adsorption on the membrane surface on the feed side, desorption from the surface on the permeate side, diffusion through the metal lattice, and the two transition phenomena surface-to-bulk and bulk-to-surface). First, the characteristic driving force of each step is evaluated, showing that adsorption and desorption singularly considered and the adsorption and desorption considered at the same time are characterized by driving forces depending on the ratio of feed and permeate hydrogen pressure. On the contrary, the diffusion step is found to present a driving force that is composed of two terms, one which corresponds to the original Sieverts Law (with an exponent of 0.5) and the other which is the product of the pressure difference and a temperature-dependent factor. Then, the character...

Alessio Caravella - One of the best experts on this subject based on the ideXlab platform.

  • Sieverts Law pressure exponent for hydrogen permeation through pd based membranes coupled influence of non ideal diffusion and multicomponent external mass transfer
    International Journal of Hydrogen Energy, 2013
    Co-Authors: Alessio Caravella, Enrico Drioli, Shigeki Hara, Giuseppe Barbieri
    Abstract:

    Abstract This paper focuses on the suitability of using a Sieverts-type empirical Law to describe hydrogen permeation through Pd-based membranes in the presence of both concentration-dependent hydrogen transport through the selective layer – referred to as “non-ideal” behaviour – and external mass transfer resistance. In particular, the functionality of the pressure exponent with temperature, pressure and membrane thickness is provided, showing that the Sieverts-type empirical Law can be used to incorporate the external mass transfer influence just up to a moderate external resistance. The explanation for this fact is recognised in the inadequacy of the Sieverts-type empirical Law to describe the behaviour of the flux limited by external resistance for a sufficiently large permeation driving force. The methodology described in this paper is effective also when the permeation-determining steps cannot be established, helping researchers to a correct interpretation of permeation tests in the presence of severe mass transfer resistance.

  • Sieverts Law empirical exponent for Pd-based membranes: critical analysis in pure H2 permeation.
    The journal of physical chemistry. B, 2010
    Co-Authors: Alessio Caravella, Francesco Scura, Giuseppe Barbieri, Enrico Drioli
    Abstract:

    In this paper, the physical meaning of the Sieverts-type driving force exponent n is analyzed for hydrogen permeation through Pd-based membranes by considering a complex model involving several elementary permeation steps (adsorption on the membrane surface on the feed side, desorption from the surface on the permeate side, diffusion through the metal lattice, and the two transition phenomena surface-to-bulk and bulk-to-surface). First, the characteristic driving force of each step is evaluated, showing that adsorption and desorption singularly considered and the adsorption and desorption considered at the same time are characterized by driving forces depending on the ratio of feed and permeate hydrogen pressure. On the contrary, the diffusion step is found to present a driving force that is composed of two terms, one which corresponds to the original Sieverts Law (with an exponent of 0.5) and the other which is the product of the pressure difference and a temperature-dependent factor. Then, the characteristic n is evaluated by applying the multistep model to two different membranes from the literature in several cases, (a) considering each permeation step as the only limiting one and (b) considering the overall effect of all steps. The results of the analysis show that for a low temperature and thin membrane thickness, the effect of the surface phenomena is, in general, a decrease of the overall exponent n toward values lower than 0.5, even though, under particular operating conditions, the n theoretical value of the surface phenomena is equal to unity. At a higher temperature and thickness (diffusion-controlled permeation), n tends to 0.5, even though the rapidity of this tendency depends strictly on the membrane diffusional parameters. In this frame, the expression developed for the diffusion step provides a theoretical reason why n values higher than 0.5 are found even for thick membranes and high temperature, where diffusion is the only rate-determining step.

  • Sieverts Law empirical exponent for pd based membranes critical analysis in pure h2 permeation
    Journal of Physical Chemistry B, 2010
    Co-Authors: Alessio Caravella, Francesco Scura, Giuseppe Barbieri, Enrico Drioli
    Abstract:

    In this paper, the physical meaning of the Sieverts-type driving force exponent n is analyzed for hydrogen permeation through Pd-based membranes by considering a complex model involving several elementary permeation steps (adsorption on the membrane surface on the feed side, desorption from the surface on the permeate side, diffusion through the metal lattice, and the two transition phenomena surface-to-bulk and bulk-to-surface). First, the characteristic driving force of each step is evaluated, showing that adsorption and desorption singularly considered and the adsorption and desorption considered at the same time are characterized by driving forces depending on the ratio of feed and permeate hydrogen pressure. On the contrary, the diffusion step is found to present a driving force that is composed of two terms, one which corresponds to the original Sieverts Law (with an exponent of 0.5) and the other which is the product of the pressure difference and a temperature-dependent factor. Then, the character...

Giuseppe Barbieri - One of the best experts on this subject based on the ideXlab platform.

  • Sieverts Law pressure exponent for hydrogen permeation through pd based membranes coupled influence of non ideal diffusion and multicomponent external mass transfer
    International Journal of Hydrogen Energy, 2013
    Co-Authors: Alessio Caravella, Enrico Drioli, Shigeki Hara, Giuseppe Barbieri
    Abstract:

    Abstract This paper focuses on the suitability of using a Sieverts-type empirical Law to describe hydrogen permeation through Pd-based membranes in the presence of both concentration-dependent hydrogen transport through the selective layer – referred to as “non-ideal” behaviour – and external mass transfer resistance. In particular, the functionality of the pressure exponent with temperature, pressure and membrane thickness is provided, showing that the Sieverts-type empirical Law can be used to incorporate the external mass transfer influence just up to a moderate external resistance. The explanation for this fact is recognised in the inadequacy of the Sieverts-type empirical Law to describe the behaviour of the flux limited by external resistance for a sufficiently large permeation driving force. The methodology described in this paper is effective also when the permeation-determining steps cannot be established, helping researchers to a correct interpretation of permeation tests in the presence of severe mass transfer resistance.

  • Sieverts Law empirical exponent for Pd-based membranes: critical analysis in pure H2 permeation.
    The journal of physical chemistry. B, 2010
    Co-Authors: Alessio Caravella, Francesco Scura, Giuseppe Barbieri, Enrico Drioli
    Abstract:

    In this paper, the physical meaning of the Sieverts-type driving force exponent n is analyzed for hydrogen permeation through Pd-based membranes by considering a complex model involving several elementary permeation steps (adsorption on the membrane surface on the feed side, desorption from the surface on the permeate side, diffusion through the metal lattice, and the two transition phenomena surface-to-bulk and bulk-to-surface). First, the characteristic driving force of each step is evaluated, showing that adsorption and desorption singularly considered and the adsorption and desorption considered at the same time are characterized by driving forces depending on the ratio of feed and permeate hydrogen pressure. On the contrary, the diffusion step is found to present a driving force that is composed of two terms, one which corresponds to the original Sieverts Law (with an exponent of 0.5) and the other which is the product of the pressure difference and a temperature-dependent factor. Then, the characteristic n is evaluated by applying the multistep model to two different membranes from the literature in several cases, (a) considering each permeation step as the only limiting one and (b) considering the overall effect of all steps. The results of the analysis show that for a low temperature and thin membrane thickness, the effect of the surface phenomena is, in general, a decrease of the overall exponent n toward values lower than 0.5, even though, under particular operating conditions, the n theoretical value of the surface phenomena is equal to unity. At a higher temperature and thickness (diffusion-controlled permeation), n tends to 0.5, even though the rapidity of this tendency depends strictly on the membrane diffusional parameters. In this frame, the expression developed for the diffusion step provides a theoretical reason why n values higher than 0.5 are found even for thick membranes and high temperature, where diffusion is the only rate-determining step.

  • Sieverts Law empirical exponent for pd based membranes critical analysis in pure h2 permeation
    Journal of Physical Chemistry B, 2010
    Co-Authors: Alessio Caravella, Francesco Scura, Giuseppe Barbieri, Enrico Drioli
    Abstract:

    In this paper, the physical meaning of the Sieverts-type driving force exponent n is analyzed for hydrogen permeation through Pd-based membranes by considering a complex model involving several elementary permeation steps (adsorption on the membrane surface on the feed side, desorption from the surface on the permeate side, diffusion through the metal lattice, and the two transition phenomena surface-to-bulk and bulk-to-surface). First, the characteristic driving force of each step is evaluated, showing that adsorption and desorption singularly considered and the adsorption and desorption considered at the same time are characterized by driving forces depending on the ratio of feed and permeate hydrogen pressure. On the contrary, the diffusion step is found to present a driving force that is composed of two terms, one which corresponds to the original Sieverts Law (with an exponent of 0.5) and the other which is the product of the pressure difference and a temperature-dependent factor. Then, the character...