New magnesium intermetallic compounds are promising, reliable, reversible hydrogen accumulators

Abstract

The proposed work considers: hydrogen sorption properties of systems of magnesium intermetallic compounds with a complex cubic structure C15b, as promising, reliable, reversible hydrogen accumulators. Considered thermal processes. A statistical theory is proposed for the cubic structure C15b of composition MgRT4Hx, where R = Ce, La, Nd, Pr, Y; T = Co, Ni; 0 ≤ x ≤ 6 at phase transitions in the process of hydrogenation, taking into account pressure. The concentration dependences of the maximum values of the order parameter and a priori probabilities are established. Hydrogen solubility isopleths and isotherms are calculated and considered, and a graphical concentration dependence of the hydrogen atom ordering temperature in MgCeCo4-type crystals is created. The order-disorder transition is considered with allowance for temperature, and the process of absorption-desorption of hydrogen by the C15b structure is also studied. The equation of thermodynamic equilibrium with the calculation of free energy is derived. And also considered the graphical dependence of the value of the order parameter on temperature and pressure. The temperature dependence of hydrogen solubility in the α, β phases for the MgCeCo4 crystal is considered. The configurational heat capacity of a crystal of the MgSnCu4Hx type structure has been studied, taking into account the temperature and the order parameter. A graph of hydrogen absorption-desorption of the MgCeCo4Hx crystal has been constructed. A comparative analysis of the experimental and practical results of the absorption-desorption of hydrogen by the working fluid of the composition MgRT4Hx has been carried out.