THERMAL STABILITY AND KINETICS OF HYDROGEN DESORPTION FROM THE HYDRIDE PHASE OF THE MgH2 OF A MECHANICAL ALLOY OF MAGNESI-UM WITH Si, Ti, Fe

• Дата: 2019
• Автори: Ershova, O., Solonin, Yu., Dobrovolsky, V., Koval, O.
• Формат: Стаття
• Мова: Ukrainian
• Опубліковано: Institute of Renewable Energy National Academy of Sciences of Ukraine 2019
• Теми: mechanical alloy; microstructure; thermodesorption spectroscopy; hydrogen-sorption properties; thermal stability; kinetics of hydro-gen desorption.; механічний сплав; мікроструктура; термодесорбційна спектроскопія; воденьсорбційні властивості; термічна стійкість; кінетика десорбції водню.
• Онлайн доступ: https://ve.org.ua/index.php/journal/article/view/187
• Назва журналу: Vidnovluvana energetika

Despite much attention of scientists paid to magnesium hydride, methods of its obtaining and properties investigation, the latter still has not found wide applications as a hydrogen material-accumulator for automotive industry because of the difficulty of two major drawbacks: high temperature (300 0C at 0,1MPa H2) and its slow dissociation kinetics. In this work, with the aim of lowering the temperature, improvement the kinetics of the decomposition of stoichiometric MgH2 hydride the possibility of its complex doping by Si, Ti, Fe using the method of reactive mechanochemical alloying (RMA) has been investigated. Mechanical alloy (MA) Mg + 10 % wt. Si + 2 % wt. Ti + 2 % wt. Fe have been synthesized and its phase composition, microstructure, hydrogen-sorption properties, thermal stability and hydrogen desorption kinetics have been investigated employing the X-ray diffraction (XRD), scanning electron microscopy (SEM) and thermodesorption spectroscopy (TDS) methods. To evaluate the influence of complex alloying by Ti, Fe, Si on decomposition temperature and thermal stability of MgH2 phase hydrogen desorption isobars have been obtained at the first heating after RМA synthesis of МA samples and after the next cyclic hydrogenation from gas phase. All isobars were obtained at hydrogen pressure in the reactor  0.1 MPa and sample heating rate of 3 o/min.  They were used to determine both the hydrogen desorption beginning temperature (Тbeg.) from hydride phase MgH2 of МA and temperature Tmax, that corresponds to the maximum speed of hydrogen release. The kinetic curves of hydrogen desorption  from mechanical alloy-composite has been obtained at the constant hydrogen pressure of 0,1 MPa in the reactor and temperature 310 and 330 0C. They were used to determine both the hydrogen time release of half of hydrogen quantity (τ1/2) and total hydrogen quantity release (τt) for MA. It is found that Si, Ti, Fe additives to magnesium significantly improve hydrogen desorption kinetics from MgH2 hydride phase of obtained MAs. However, the effect of thermodynamic stability reducing of MgH2 hydride phase as a result of its complex doping was not observed. The developed materials allow their use at stationary application conditions. Ref. 23, tab. 2, fig. 7.