Jalaal Hayes, PhD

This publication serves as an inspirational story as well as a roadmap to show you how you can GROW UP and be GREAT as well. From the author's perspective, the word GREAT serves as an acronym: Giving, Receiving, Expecting, Achieving, and Teaching. The five words serve as checkpoints that you will be learning and applying throughout the book as well as in life.

Abstract: In this study, the effects of several alkali metal hydride dopants on the thermodynamics and kinetics of the 2LiNH2/MgH2 system were determined. The results showed that the stabilities of the doped 2LiNH2/MgH2 system are in the order: KH < RbH < CsH. Kinetics measurements showed that the absorption and desorption rates are in the order: RbH > KH > CsH, with absorption rates being about twice as fast as desorption from the corresponding materials. As expected, the… Show more

Abstract: In this study, the effects of several alkali metal hydride dopants on the thermodynamics and kinetics of the 2LiNH2/MgH2 system were determined. The results showed that the stabilities of the doped 2LiNH2/MgH2 system are in the order: KH < RbH < CsH. Kinetics measurements showed that the absorption and desorption rates are in the order: RbH > KH > CsH, with absorption rates being about twice as fast as desorption from the corresponding materials. As expected, the activation energies for the reactions were in the order: RbH < KH < CsH with the activation energies for absorption being less than that for the corresponding desorption reaction. Modeling studies revealed that desorption reactions are controlled by diffusion during the entire process. However, for absorption reactions the rate-controlling process changed during the course of the reactions. The rate-controlling process in the first 70% of the absorption reactions was reaction at the phase boundary whereas diffusion controlled the rate in the latter stages.
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Abstract: In this study, the effectiveness of several alkali metal hydrides (KH, RbH and CsH) for
improving the hydrogen desorption properties of a 2LiNH2/MgH2 mixture was studied.
Results showed that the relative effectiveness of these additives in decreasing the
hydrogen desorption temperature, lowering the activation energy and increasing desorption
rates from the mixtures is in the order: RbH > KH > CsH > Un-catalyzed. Modeling
studies showed that diffusion through a… Show more

Abstract: In this study, the effectiveness of several alkali metal hydrides (KH, RbH and CsH) for
improving the hydrogen desorption properties of a 2LiNH2/MgH2 mixture was studied.
Results showed that the relative effectiveness of these additives in decreasing the
hydrogen desorption temperature, lowering the activation energy and increasing desorption
rates from the mixtures is in the order: RbH > KH > CsH > Un-catalyzed. Modeling
studies showed that diffusion through a Li2Mg(NH)2 product layer is the rate-controlling
process. It is believed that the alkali elements: K, Rb and Cs partially replace the Li in
the product layer. This may have an inductive effect in which the N-H bond is weakened
thus leading to lower desorption enthalpies. The lattice expansion caused by substitution
of the larger alkali elements for Li may also allow for faster diffusion and increased
desorption rates. Show less

Abstract: In this study, thermodynamic and kinetic properties of RbH doped 2LiNH2/MgH2 were
measured and compared for hydrogen absorption and desorption. Pressure-composition-temperature isotherms were obtained in the 150-180 oC temperature range and were used to
construct van’t Hoff plots. The results showed that the absorption enthalpy, 39.7 kJ mol-1, was
less than the desorption enthalpy, 43 kJ mol-1. Kinetics measurements, done at 160 oC using
constant pressure thermodynamic… Show more

Abstract: In this study, thermodynamic and kinetic properties of RbH doped 2LiNH2/MgH2 were
measured and compared for hydrogen absorption and desorption. Pressure-composition-temperature isotherms were obtained in the 150-180 oC temperature range and were used to
construct van’t Hoff plots. The results showed that the absorption enthalpy, 39.7 kJ mol-1, was
less than the desorption enthalpy, 43 kJ mol-1. Kinetics measurements, done at 160 oC using
constant pressure thermodynamic driving forces, show that under the same conditions,
absorption is approximately twice as fast as desorption. Modeling studies, based on a shrinking
core model, show that diffusion is the rate-limiting process for both absorption and desorption.
Cycling studies were also done to determine if any changes would occur in the sample upon
repeated hydriding/dehydriding at 200oC. It was found that the amount of hysteresis increased
and there was also about a 30% decrease in the hydrogen capacity after 70 cycles. Show less

Abstract:The 2LiNH2/MgH2 system has been identified as an attractive system for hydrogen storage, but suitable catalysts are needed to reduce the hydrogen desorption temperature and improve the rates of reaction. One of the most effective catalysts for lowering the desorption temperature and improving the desorption rate from this system has been KH. In this work a new catalytic additive, rubidium hydride (RbH), was synthesized, and its effects on hydrogen desorption from the 2LiNH2/MgH2 system… Show more

Abstract:The 2LiNH2/MgH2 system has been identified as an attractive system for hydrogen storage, but suitable catalysts are needed to reduce the hydrogen desorption temperature and improve the rates of reaction. One of the most effective catalysts for lowering the desorption temperature and improving the desorption rate from this system has been KH. In this work a new catalytic additive, rubidium hydride (RbH), was synthesized, and its effects on hydrogen desorption from the 2LiNH2/MgH2 system were studied and compared to those of KH. Temperature-programmed desorption measurements showed that the addition of approximately 3 mol % RbH lowered the desorption temperature of the system by 94 °C, which is somewhat better than KH. Desorption enthalpies for the catalyzed samples were found to be approximately 42 kJ/mol, which is significantly lower than the 65 kJ/mol that was found for the uncatalyzed mixture. The hydrogen desorption rate of the RbH-doped sample was found to be approximately twice as fast as the KH-doped sample and about 60 times faster than the uncatalyzed sample, making RbH one of the best catalytic additives to date for the 2LiNH2/MgH2 system. Modeling studies were done using two approaches, and both indicated that diffusion controlled the rate of hydrogen desorption from 2LiNH2/MgH2 in the two-phase plateau region. Show less