scholarly journals Thermodynamic Modeling of Hydrogen Storage Capacity in Mg-Na Alloys

2014 ◽  
Vol 2014 ◽  
pp. 1-16 ◽  
Author(s):  
S. Abdessameud ◽  
M. Mezbahul-Islam ◽  
M. Medraj
Keyword(s):  
Hydrogen Storage ◽  
Thermodynamic Modeling ◽  
Binary Systems ◽  
Equilibrium Diagram ◽  
Thermodynamic Description ◽  
System A ◽  
Different Temperatures ◽  
Catalytic Role ◽  
Temperature Equilibrium ◽  
First Time

Thermodynamic modeling of the H-Mg-Na system is performed for the first time in this work in order to understand the phase relationships in this system. A new thermodynamic description of the stable NaMgH3hydride is performed and the thermodynamic models for the H-Mg, Mg-Na, and H-Na systems are reassessed using the modified quasichemical model for the liquid phase. The thermodynamic properties of the ternary system are estimated from the models of the binary systems and the ternary compound using CALPHAD technique. The constructed database is successfully used to reproduce the pressure-composition isotherms for MgH2 + 10 wt.% NaH mixtures. Also, the pressure-temperature equilibrium diagram and reaction paths for the same composition are predicted at different temperatures and pressures. Even though it is proved that H-Mg-Na does not meet the DOE hydrogen storage requirements for onboard applications, the best working temperatures and pressures to benefit from its full catalytic role are given. Also, the present database can be used for thermodynamic assessments of higher order systems.

scholarly journals Thermodynamic description of the C-Ge and C-Mg systems

2010 ◽  
Vol 46 (1) ◽  
pp. 97-103 ◽  
Author(s):  
B. Hu ◽  
Y. Du ◽  
H. Xu ◽  
W. Sun ◽  
W.W. Zhang ◽  
...  
Keyword(s):  
Thermodynamic Parameters ◽  
Enthalpy Of Formation ◽  
Thermodynamic Modeling ◽  
First Principles ◽  
Thermodynamic Description ◽  
Calphad Method ◽  
Thermodynamic Calculations ◽  
First Principles Calculation ◽  
System A ◽  
The Enthalpy Of Formation

The thermodynamic modeling for the C-Ge and C-Mg systems is performed by the CALPHAD method. The enthalpy of formation for Mg2C3, the experimental value of which is not available in the literature, is obtained via first-principles calculation to refine the thermodynamic modeling of the C-Mg system. A comparison of the thermodynamic calculations with the available literature data shows that the presently obtained two sets of thermodynamic parameters for the C-Ge and C-Mg systems can well describe the these two systems.

scholarly journals THERMODYNAMIC MODELING OF OXIDE MELTS OF CaO - Al2O3 - SiO2 SYSTEMS

2019 ◽  
Vol 63 (1) ◽  
pp. 45-50
Author(s):  
Svetlana E. Pratskova ◽  
Vladimir A. Burmistrov ◽  
Anna A. Starikova
Keyword(s):  
Phase Diagrams ◽  
Thermodynamic Modeling ◽  
Binary Systems ◽  
Thermodynamic Description ◽  
Ternary Systems ◽  
Oxide Melt ◽  
State Diagrams ◽  
Gibbs Energies ◽  
Metallurgical Slags ◽  
Oxide Melts

Oxide melts of the CaO – Al2O3 – SiO2 system are the basis of metallurgical slags. Therefore, the thermodynamic properties of this system have been repeatedly studied experimentally, and attempts have been made to describe them theoretically. Thermodynamic modeling of the state diagrams of the CaO – Al2O3, CaO – SiO2, Al2O3 – SiO2 binary systems, as well as the CaO – Al2O3 – SiO2 ternary system was performed. In the course of the work, expressions for the thermodynamic description of the activities of the components of the oxide melt of this system are derived. For the calculation, a generalized theory of regular ionic solutions was used. The energy parameters of the theory are determined, depending on the temperature and composition of the solution, using experimental data on the heat and melting point of oxides of calcium, aluminum and silicon. According to the results of the simulation, the coordinates of the points of nonvariant transformations in the phase diagrams of the binary and ternary systems under study are determined. The obtained results on thermodynamic modeling of the coordinates of the liquidus lines of the phase diagrams of the CaO – Al2O3, CaO – SiO2, Al2O3 – SiO2 binary systems were compared with the literature data for the studied systems. The calculated diagrams are in good agreement with the experimental ones, which indicates the applicability of the chosen system for the description of such oxide melts. The modeling technique used in this work allowed to estimate the Gibbs energies of formation of silicates and calcium aluminum silicates to be 3Al2O3∙2SiO2, 3CaO∙SiO2, 2CaO∙SiO2, 3CaO∙2SiO2, CaO∙SiO2, CaO∙Al2O3∙2SiO2, 2CaO∙Al2O3∙SiO2 on the base of obtained aquations for of activities of the components and calculated parameters of the theory. The calculated diagrams will allow to determine the nature of the interaction between the components of the system, the conditions of formation, the composition and properties of the compounds formed, without isolating them from the system.

Rhythmic Prose in Imperial Greek Literature

2018 ◽  
Author(s):  
G. O. Hutchinson
Keyword(s):  
The Novel ◽  
Greek Literature ◽  
System A ◽  
First Time

The chapter looks at the division between poetry and prose in ancient and other literatures, and shows the importance of rhythmic patterning in ancient prose. The development of rhythmic prose in Greek and Latin is sketched, the system explained and illustrated (from Latin). It is firmly established, for the first time, which of the main Greek non-Christian authors 31 BC–AD 300 write rhythmically. The method takes a substantial sample of random sentence-endings (usually 400) from each of a large number of Imperial authors; it compares that sample with one sample of the same size (400) drawn randomly from a range of authors earlier than the invention of this rhythmic system. A particular sort of X2-test is applied. Many Imperial authors, it emerges, write rhythmically; many do not. The genres most likely to offer rhythmic writing are, unexpectedly, narrative: historiography and the novel.

scholarly journals NEA rotations and binaries

2006 ◽  
Vol 2 (S236) ◽  
pp. 167-176 ◽  
Author(s):  
Petr Pravec ◽  
A. W. Harris ◽  
B. D. Warner
Keyword(s):  
Binary Systems ◽  
Principal Axis ◽  
Spin Distribution ◽  
Rotation Periods ◽  
System A ◽  
Binary Formation ◽  
Basic Spin ◽  
Axis Rotation ◽  
Near Earth Asteroids ◽  
Abundant Population

AbstractOf the nearly 3900 near-Earth asteroids (NEAs) known as of June 2006, 325 have estimated rotation periods, with most of those determined by lightcurve analysis led by a few dedicated programs. NEAs with diameters down to 10 meters have been sampled. Observed spin distribution shows a major changing point around diameter of 200 meters. Larger NEAs show a barrier against spins faster than 11 d−1 (period about 2.2 h) that shifts to slower rates (longer periods) with increasing lightcurve amplitude (i.e., with increasing equatorial elongation). The spin barrier is interpreted as a critical spin rate for bodies in a gravity regime; NEAs larger than 200 meters are predominantly bodies with tensile strength too low to withstand a centrifugal acceleration for rotation faster than the critical spin rate. The cohesionless spin barrier disappears at sizes less than 200 meters where most objects rotate too fast to be held together by self-gravitation only, so a cohesion is implied in the smaller NEAs.The distribution of NEA spin rates in the cohesionless size range (D0.2 km) is highly non-Maxwellian, suggesting that mechanisms other than just collisions have been at work. There is a pile up just in front of the barrier, at periods 2–3 h. It may be related to a spin up mechanism crowding asteroids to the barrier. An excess of slow rotators is observed at periods longer than 30 hours. A spin-down mechanism has no obvious lower limit on spin rate; periods as long as tens of days have been observed.Most NEAs appear to be in their basic spin states with rotation around principal axis with maximum moment of inertia. Tumbling objects (i.e., bodies in excited, non-principal axis rotation) are present and actually predominate among slow rotators with estimated damping timescales longer than the age of the solar system. A few tumblers observed among fast rotating coherent objects appear to be either more rigid or younger than the larger (cohesionless) tumblers.An abundant population of binary systems has been found among NEAs. The fraction of binaries among NEAs larger than 0.3 km has been estimated to be 15 ± 4%. Primaries of binary systems concentrate at fast spin rates (periods 2–3 h) and low amplitudes, i.e., they lie just below the cohesionless spin barrier. The total angular momentum content in binary systems suggests that they formed from parent bodies spinning at the critical rate. The fact that a very similar population of binaries has been found among small main belt asteroids suggests a binary formation mechanism that may not be related to close encounters with the terrestrial planets.

Critical evaluation and thermodynamic modeling of the Ag-X (X=Mn, Y, Sr) binary systems

2021 ◽  
Vol 136 ◽  
pp. 107260
Author(s):  
Jian Wang ◽  
Zhang Zhang ◽  
In-Ho Jung ◽  
Wei-Feng Rao
Keyword(s):  
Thermodynamic Modeling ◽  
Binary Systems ◽  
Critical Evaluation

scholarly journals Ultrasonic study of molecular interactions in binary mixtures of methyl methacrylate(MMA) with toluene and dimethylacetamide at 318 K

2016 ◽  
Vol 4 (1) ◽  
pp. 1
Author(s):  
R.G. Indhumathi
Keyword(s):  
Methyl Methacrylate ◽  
Binary Systems ◽  
Adiabatic Compressibility ◽  
Acoustical Parameters ◽  
Binary Solutions ◽  
Intermolecular Free Length ◽  
Wada’S Constant ◽  
Ultrasonic Measurements ◽  
Rao’S Constant ◽  
First Time

<p>The ultrasonic velocity, density and viscosity at 318K have been measured in the binary systems of Methyl methacrylate + Toluene and Methyl methacrylate + Dimethylacetamide. In this work an attempt has been made for the first time to investigate the behavior of binary solutions of Methylmethacrylate(MMA) in Toluene and Dimethylacetamide(DMAC) with regard to acoustical parameters such as adiabatic compressibility(β), intermolecular free length(l<sub>f</sub>), free volume(V<sub>f</sub>), Rao’s constant(R), Wada’s constant(W) and specific acoustical impedance(Z) from ultrasonic measurements at 318 K were calculated. The results are interpreted in terms of molecular interaction between the components of mixtures.</p>

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