Design of Multicomponent Alloys with Single C14 Laves Phase for Hydrogen Storage assisted by Computational Thermodynamic

Design methods with predictive properties modelling are paramount tools to explore the vast compositional field of multicomponent alloys. The applicability of an alloy as a hydrogen storage media is governed by its pressure-composition-temperature (PCT) diagram. Therefore, the prediction of PCT diagrams for multicomponent alloys is fundamental to design alloys with optimized properties for hydrogen storage applications. In this work, a strategy to design single C14-type Laves phase multicomponent alloys for hydrogen storage assisted by computational thermodynamic is presented. Since electronic and geometrical factors play an important role in the formation and stability of multicomponent Laves phase, valence electron concentration (VEC), atomic radius ratio (r_A/r_B), and atomic size mismatch (δ) are initially considered to screen a high number of compositions and find alloy systems prone to form Laves phase structure. Then, CALPHAD method was employed to find 142 alloys of the (Ti, Zr or Nb)(Cr, Mn, Fe, Co, Ni, Cu, or Zn)2 system predicted to crystallize as single C14 Laves phase structure. In addition, we present a thermodynamic model to calculate PCT diagrams of C14 Laves phase alloys based solely on the alloy’s composition. In this work, the entropy and enthalpy of hydrogen solution in the C14 Laves phase were modelled considering that hydrogen solid solution occurs only at the A2B2-type interstitial sites of the C14 Laves phase structure. Experimental pressure-composition-isotherm (PCI) diagrams of six C14 Laves phase alloys were compared against the calculated ones resulting in a good prediction capability. Therefore, the room temperature PCI diagrams of 142 single C14 Laves phase multicomponent alloys were calculated. The results show that single C14 Laves phase multicomponent alloys within a wide range of equilibrium pressure at room temperature can be obtained, being promising candidates for different hydrogen storage applications, such as room temperature tanks, hybrid tanks and Ni-metal hydrides batteries.

The EDGE-CALIFA Survey: The Resolved Star Formation Efficiency and Local Physical Conditions

We measure the star formation rate (SFR) per unit gas mass and the star formation efficiency (SFEgas for total gas, SFEmol for the molecular gas) in 81 nearby galaxies selected from the EDGE-CALIFA survey, using 12CO (J = 1–0) and optical IFU data. For this analysis we stack CO spectra coherently by using the velocities of Hα detections to detect fainter CO emission out to galactocentric radii r gal ∼ 1.2r 25 (∼3R e) and include the effects of metallicity and high surface densities in the CO-to-H2 conversion. We determine the scale lengths for the molecular and stellar components, finding a close to 1:1 relation between them. This result indicates that CO emission and star formation activity are closely related. We examine the radial dependence of SFEgas on physical parameters such as galactocentric radius, stellar surface density Σ⋆, dynamical equilibrium pressure P DE, orbital timescale τ orb, and the Toomre Q stability parameter (including star and gas Q star+gas). We observe a generally smooth, continuous exponential decline in the SFEgas with r gal. The SFEgas dependence on most of the physical quantities appears to be well described by a power law. Our results also show a flattening in the SFEgas–τ orb relation at log [ τ orb ] ∼ 7.9 – 8.1 and a morphological dependence of the SFEgas per orbital time, which may reflect star formation quenching due to the presence of a bulge component. We do not find a clear correlation between SFEgas and Q star+gas.

Experimental Study on Desorption Characteristics of Anthracite in Positive Pressure Environments

In order to investigate the desorption characteristics of methane adsorption in coal under positive pressure conditions, methane adsorption and successive desorption experiments of anthracite coal under positive pressure conditions were conducted on the developed experimental equipment, and the experimental data were analyzed. In the process of desorption of coal samples with the same adsorption equilibrium pressure and the same pressure drop gradient, the phase desorption rate decreased with the increase of pressure, and the positive pressure environment had a significant inhibitory effect on the desorption of methane in coal.

Design of internal heat transport intensifier for metal hydride storage tank

The present article deals with potential improvement of heat removal from the centre of a metal hydride tank towards the tank’s periphery while using passive heat transfer modules. Passive cooling elements are used in order to improve heat removal from the centre of a tank towards its peripheral parts. This increases the homogeneity of the thermal field in a tank’s cross-section, which is perpendicular to the longitudinal axis. Moreover, the use of such elements improves the kinetics of hydrogen absorption into an alloy, in particular by prolonging the time to an equilibrium temperature of the alloy for a particular equilibrium pressure, which may shorten the time to a tank being 100% filled with hydrogen. The article describes four different designs of internal heat transfer intensifiers, which are aimed at improving the thermal field distribution inside the tank and their theoretical impact on the thermal field, which was examined using Ansys CFX software.

Study on Hydrate Phase Equilibrium Diagram of Methane Containing System Based on Thermodynamic Model

Natural gas hydrate is a potential energy source in the future, which widely occurs in nature and industrial activities, and its formation and decomposition are identified by phase equilibrium. The calculation of multicomponent gas phase equilibrium is more complex than that of single component gas, which depends on the accurate model characterized by enthalpy and free energy. Based on the Kvamme-Tanaka statistical thermodynamic model, theoretical and experimental methods were used to predict and verify the phase equilibrium of pure methane hydrate and carbon dioxide hydrate in the temperature range of 273.17–289.05 K. The phase equilibrium curves of methane-containing gases such as CH4+CO2,CH4+C2H6,CH4+H2S and CH4+CO2+H2S under different mole fractions were drawn and analyzed, and the decomposition or formation enthalpy and free energy of hydrate were calculated. The results show that, the phase equilibrium curves of the methane containing systems is mainly related to the guest molecule type and the composition of gas. The evolution law of phase equilibrium pressure of different gases varies with composition and temperature, and the phase splitting of CO2 at the quadruple point affects the phase equilibrium conditions. Due to the consideration of the interaction between the motion of guest molecules and the vibration of crystal lattice, the model exhibits a good performance, which is quantified in terms of mean square error (MSE) with respect to the experimental data. The magnitudes of MSE percent are respectively 1.2, 4.8, 15.12 and 9.20 MPa2 for CH4+CO2, CH4+C2H6, CH4+H2S and CH4+CO2+H2S systems, and the values are as low as 3.57 and 1.32 MPa2 for pure methane and carbon dioxide, respectively. This study provides engineers and researchers who want to consult the diagrams at any time with some new and accurate experimental data, calculated results and phase equilibrium curves. The research results are of great significance to the development and utilization of gas hydrate and the flow safety prediction of gas gathering and transportation.

Ricci cosmology in light of astronomical data

Recently, a new cosmological framework, dubbed Ricci cosmology, has been proposed. Such a framework has emerged from the study of relativistic dynamics of fluids out of equilibrium in a curved background and is characterised by the presence of deviations from the equilibrium pressure in the energy–momentum tensor which are due to linear terms in the Ricci scalar and the Ricci tensor. The coefficients in front of such terms are called the second order transport coefficients and they parametrise the fluid response to the pressure terms arising from the spacetime curvature. Under the preliminary assumption that the second order transport coefficients are constant, we find the simplest solution of Ricci cosmology in which the presence of pressure terms causes a departure from the perfect fluid redshift scaling for matter components filling the Universe. In order to test the viability of this solution, we make four different ansätze on the transport coefficients, giving rise to four different cases of our model. On the physical ground of the second law of thermodynamics for fluids with non-equilibrium pressure, we find some theoretical bounds (priors) on the parameters of the models. Our main concern is then the check of each of the case against the standard set of cosmological data in order to obtain the observational bounds on the second order transport coefficients. We find those bounds also realising that Ricci cosmology model is compatible with $$\Lambda $$ Λ CDM cosmology for all the ansätze.

Promising Isotope Effect in Pd77Ag23 for Hydrogen Separation

Pd–Ag alloys are largely used as hydrogen separation membranes and, as a consequence, the Pd–Ag–H system has been intensively studied. On the contrary, fewer information is available for the Pd–Ag–D system; thus, the aim of this work is to improve the knowledge of the isotope effect on the commercial Pd77Ag23 alloy, especially for temperature above 200 °C. In particular, deuterium absorption measurements are carried out in the Pd77Ag23 alloy in the temperature range between 79 and 400 °C and in the pressure range between 10−2 and 16 bar. In this exploited pressure (p) and composition (c) range, above 300 °C the pc isotherms display the typical shape of materials where only a solid solution of deuterium is present while at lower temperatures these curves seem to be better described by the coexistence of a solid solution and a deuteride in a large composition range. The obtained results are compared and discussed with the ones previously measured with the lightest hydrogen isotope. Such a comparison shows that the Pd77Ag23 alloy exhibits a clear inverse isotope effect, as the equilibrium pressure of the Pd–Ag–D system is higher than in Pd–Ag–H by a factor of ≈2 and the solubility of deuterium is about one half of that of hydrogen. In addition, the absorption measurements were used to assess the deuteration enthalpy that below 300 °C is ΔHdeut = 31.9 ± 0.3 kJ/mol, while for temperatures higher than 300 °C, ΔHdeut increases to 43 ± 1 kJ/mol. Additionally, in this case a comparison with the lighter isotope is given and both deuteration enthalpy values result lower than those reported for hydrogenation. The results described in this paper are of practical interest for applications operating above 200 °C, such as membranes or packing column, in which Pd77Ag23 has to interact with a gas stream containing both hydrogen isotopes.

A metafluid with multistable density and internal energy states

The efficiency, operation range, and environmental safety of energy and refrigeration cycles are determined by the thermodynamic properties of available fluids. We here suggest combining gas, liquid and multistable elastic capsules to create an artificial fluid with a multitude of stable states. We study, theoretically and experimentally, the suspension’s internal energy, equilibrium pressure-density relations and their stability for both adiabatic and isothermal processes. We show that the elastic multistability of the capsules endows the fluid with multistable thermodynamic properties, including the ability of capturing and storing energy at standard atmospheric conditions, not found in naturally available fluids.