Thermodynamic Modeling of Hydrogen Storage Capacity in Mg-Na Alloys
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 NaMgH3 hydride 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.
The Na–H system: from first-principles calculations to thermodynamic modeling
Abstract The Na–H system thermodynamic properties were assessed using Gibbs free energy model parameters obtained from best fit optimizations to combined experimental and first-principles predicted data. The first-principles finite temperature thermodynamic property predictions, based upon density functional theory ground state minimizations and direct method lattice dynamics, were used to supplement the Na–H dataset wherever experimental information was unavailable or unattainable. The predictions proved to be important for extending the evaluation of the heat capacity of the stable NaH phase to cover the complete 0 – 2000 K temperature range. The predicted thermodynamic properties of the hypothetical NaH3 end-member representing complete interstitial H substitution in solid body-centered cubic Na, provided a physical basis for modeling H dissolution in the Na lattice. The modeling also showed satisfactory agreement with experimental measurements of NaH enthalpies of formation, NaH decomposition pressures, and H solubility in liquid Na.
The honesty of thinking : reflections on critical thinking in Nietzsche's middle period and the later Heidegger
This dissertation engages with contemporary interpretations of Nietzsche and Heidegger on the issue of self-knowing with respect to the notions of honesty and authenticity. Accounting for the two philosophers' developing conceptions of these notions allows a response to interpreters who conceive the activity of self-knowing as a primarily personal problem. The alternative accounts proposed take as a point of departure transitional texts that reveal both thinkers to be engaged in processes of revision. The reading of honesty in Chapters 1 and 2 revolves around Nietzsche's groundwork on prejudice in Morgenrothe (1880-81), where he first problematizes the moral-historical forces entailed in actuating the 'will to truth'. The reading of authenticity in Chapters 3 and 4 revolves around Heidegger's lectures on what motivates one's thinking in Was heist Denken? (1951-52). The lectures call into question his previous formal suppositions on what calls forth one's 'will-to-have-a-conscience', in an interpretation of Parmenides on the issue of thought's linguistic determination, discussed further in the context of Unterwegs zur Sprache (1950-59). Chapter 5 shows how Heidegger's confrontation with Nietzsche contributed to his ongoing revisions to the notion of authenticity, and to the attending conceptions of critique and its authority. Particular attention is given to the specific purposes to which distinct Nietzschean foils are put near the confrontation's beginning--in Heidegger's lectures on Nietzsche's second Unzeitgemasse Betrachtung (1938), and in the monograph entitled Besinnung (1939) which they prepare--and near its end, in the interpretation of Also Sprach Zarathustra (1883-85) presented in the first half of Was heist Denken? Chapter 6 recapitulates the developments traced from the vantage point of the retrospective texts Die Zollikoner Seminare (1959-72) and the fifth Book of Die frohliche Wissenschaft (1887). Closing remarks are made in relation to recent empirical research on the socio-environmental structures involved in determining self-identity.