Master of Science (MS), Ohio University, 2007, Mechanical Engineering (Engineering)

Use of hydrogen as an automotive fuel has been successfully demonstrated for the use but they are not ready for consumers yet. One of the major problems associated with the use of hydrogen as an automotive fuel is the storage of hydrogen on-board. Hydrostatic Pressure Retainment (HPR) is an innovative gaseous storage concept which consists of a number of small hollow spherical bubbles arranged within a solid mass similar to a sponge-like structure. These spherical bubbles or the inner-matrix can be arranged in similar fashion as the three basic packing structures of crystalline metals: Simple Cubic (SC), Body Centered Cubic (BCC) and Face Centered Cubic (FCC). In a HPR vessel, suitable configuration for the inner-matrix and feasibility study of different materials is a crucial design step. This thesis investigates the feasibility of different materials for inner-matrix using an ideal BCC microstructure and also achieves one of the milestones of the HPR research by finding and analytically supporting the suitable configuration for the HPR inner-matrix, using Finite Element Analysis.

Committee: Hajrudin Pasic (Advisor) Subjects:

Master of Science in Renewable and Clean Energy Engineering (MSRCE), Wright State University, 2023, Renewable and Clean Energy

In the past several years, the energy sector has experienced a rapid increase in renewable energy installations due to declining capital costs for wind turbines, solar panels, and batteries. Wind and solar electricity generation are intermittent in nature which must be considered in an economic analysis if a fair comparison is to be made between electricity supplied from renewables and electricity purchased from the grid. Energy storage reduces curtailment of wind and solar and minimizes electricity purchases from the grid by storing excess electricity and deploying the energy at times when demand exceeds the renewable energy supply. The objective of this work is to study the generation of electric power with wind turbines and solar panels coupled to either battery energy storage or hydrogen energy storage. So that logical conclusions can be drawn on the economic effectiveness of battery and hydrogen energy storage, four scenarios are analyzed: 1) purchasing all required electricity from the grid, 2) generating electricity with a combined wind and solar farm without energy storage, 3) generating electricity with a combined wind and solar farm with battery energy storage, and 4) generating electricity with a combined wind and solar farm with hydrogen energy storage. All four of these scenarios purchase electricity from the grid to meet demand that is not met by the renewable energy power plant. All scenarios are compared based on the lowest net present cost of supplying the specified electrical loads to serve 25,000 homes in Rio Vista, California over 25 years of operation. The detailed economics and electric power production of both wind and solar combined with energy storage for any size of wind facility, solar facility, battery facility, and hydrogen facility are analyzed with a MATLAB computer program developed for this work. The program contains technical and economic models of each of these systems working in different combinations. Current equipment c (open full item for complete abstract)

Committee: James Menart Ph.D. (Advisor); Hong Huang Ph.D. (Committee Member); Mitch Wolff Ph.D. (Committee Member) Subjects: Alternative Energy; Energy; Engineering

Doctor of Philosophy, University of Akron, 2023, Chemical Engineering

Sustainable development becomes an important topic due to the escalating energy shortage and environmental change. Governments around the world have taken various steps and implemented several initiatives in addressing pressing environmental issues. Green technology and innovations have been largely promoted not only in cutting-edge research but also in industry and manufacturing sectors. Among those sustainable practices, methane conversion, hydrogen storage, and fuel cell play crucial roles that promote energy efficiency and contribute to a circular economy. The dissertation aims to understand the chemical aspects in these three fields for sustainable development. For example, (1) methane, as a potent greenhouse gas, significantly contributes to global warming. By converting methane into value-added chemicals under mild conditions, sustainable development benefits can be achieved. (2) Hydrogen as green energy is an important research topic but has great challenges in its storage with hydrogen's low density. Efficient hydrogen storage technologies are required to enable the efficient utilization of hydrogen. (3) Fuel cells offer a clean and efficient alternative to traditional energy conversion technologies, which convert the chemical energy of a fuel directly into electricity through an electrochemical reaction. A new concept of a regenerative fuel cell is being discussed that has the ability to convert electricity back to chemical energy. These sustainable practices: methane conversion, hydrogen storage, and regenerative fuel cell, drive technological innovation and opportunities in catalyst materials, new energy, and electrochemistry.

Committee: Zhenmeng Peng (Advisor); Qixin Zhou (Committee Member); George Chase (Committee Member); Chrys Wesdemiotis (Committee Member); Toshikazu Miyoshi (Committee Member) Subjects: Chemical Engineering; Chemistry; Computer Engineering; Environmental Engineering

Master of Science in Chemistry, Youngstown State University, 2019, Department of Chemistry

Solid state hydrogen storage is seen as the ultimate answer in realizing the hydrogen economy and minimizing our overdependence on nonrenewable fossil fuels. The use of fossil fuels has contributed negatively towards climate change, leading to a lot of future uncertainties. Alkali metal borohydrides, especially lithium borohydride, with desirable H2 storage properties such dry air stability and high gravimetric and volumetric storage densities of 18.5 wt% and 121 kg/m3, respectively, are proving to be some of the most important solid state hydrogen storage materials. However, their current cost of production is very high considering that most borohydrides are synthesized from sodium borohydride, which in turn is made from sodium hydride, NaH, and trimethyl borate, B(OCH3)3. NaH, which is a product of an energetic process, namely hydrogenation following electrodeposition of the metal from a molten salt, acts as the source of H- required for the formation of the borohydride ion. In this work, electrochemical transfer of H- from a Pd foil, which is considered less energetic than NaH, was investigated. Hydrogen gas at a pressure of about 1 atm was passed through the Pd foil, which was used as the working electrode in an electrochemical cell containing 0.1 M LiClO4 and 4.4 M B(OCH3)3 in CH3CN as the electrolyte. Using a potentiostat, a voltammetric experiment with 3 cycles at 50 mV/s was performed with and without hydrogen application. A potentiostatic experiment was conducted by holding the Pd foil at -2.75 V vs Ag/AgClO4 and run for 10.6 hours. Analysis of a portion of the electrolyte using IR and NMR spectrometry showed the presence of borohydride. A two compartment cell with Nafion as the separator of the electrode reagents was used to increase the yield.

Committee: Clovis Linkous PhD (Advisor); Sherri Lovelace-Cameron PhD (Committee Member); Timothy Wagner PhD (Committee Member) Subjects: Chemistry; Energy; Materials Science

Master of Science (MS), Wright State University, 2012, Chemistry

Computational modeling using classical grand canonical Monte Carlo simulations and first-principles calculations were carried out to study the adsorption of molecular hydrogen on nanoporous carbon modeled by the slit- pore geometry. It has previously been shown that hydrogen adsorption on pristine porous carbon has dependence on pore size and that an optimum pore size, which exhibits the maximum mass uptake, exists. There have been suggestions that doping graphitic nanocarbon structures with Pd enhances their adsorption capacity. The pore-size dependence of this change in adsorption brought about by Pd and the conditions at which improvement in adsorption can occur have not been extensively addressed to date. In this work, we perform computational modeling to examine hydrogen adsorption on pristine carbon and Pd-doped carbon nanopores. First-principles calculations were used to generate minimized configurations of the sorbent system while grand canonical Monte Carlo simulations modeled the finite temperature and pressure adsorption of hydrogen. We perform simulations at 298 K and pressures of 0.01 MPa, 1 MPa, and 5 MPa for systems with Pd to C ratios of 1:32, 1:18 and 1:8. Among the systems examined, pristine carbon at 5 MPa exhibited the highest mass uptake at 4.2 wt % adsorption capacity. This is consistent with the expectation that as the gas reservoir pressure increases, the adsorption capacity also increases. The presence of Pd resulted to enhancement in adsorption only at 0.01 MPa, the lowest pressure investigated. For the maximum adsorption of 4.2 wt% at 5 MPa, the heat of adsorption was calculated to be 8 kJ/mol. The target heat of adsorption value for hydrogen storage materials is 25 kJ/mol, and this was achieved for the 1:8 Pd:C ratio at a pore size of 6 Angstroms, but the system showed a lower adsorption capacity of 1.5 wt%.

Committee: Rachel Aga PhD (Advisor); Paul Seybold PhD (Committee Member); Ioana Sizemore PhD (Committee Member) Subjects: Physical Chemistry

Master of Science in Engineering (MSEgr), Wright State University, 2010, Renewable and Clean Energy

The energies and temperature-dependent dynamics of hydrogen and lithium chemisorption on a silicon nanosheet, called silicene, were studied using density functional theory and molecular-dynamics (MD) simulations. Silicene has a buckled honeycomb structure, and has been fabricated as suspended monolayer sheets and nanoribbons in recent experiments. We calculated the adsorption energies of hydrogen and lithium on silicene for different adsorption ratios between 3.1% and 100%. The studies will clarify the characteristics of these novel and promising nanomaterials, and pave the way for their applications. For Hydrogen, the adsorption energy had a maximum of 3.01 eV/H for complete hydrogenation, and decreased by 24.5 % to 2.27 eV/H for single atom adsorption on a 32-silicon-atom supercell. It was determined that the preferred hydrogen adsorption patterns were clusters. Molecular dynamics simulations revealed the stability of adsorption configurations at 300K. The electronic structure of these stable configurations could be modified and controlled through partial and complete hydrogenations, and a transformation from zero-gap semiconductor to insulator was observed. For lithium on silicene, the adsorption energy had a maximum of 2.23 eV/Li for 50% lithiation and decreased by 29.6% to 1.57 eV/Li for 100% lithiation. For partial Lithium adsorptions up to 50%, the preferred adsorption sites were hollow sites on top of silicon hexagons. This preference changed as more lithium atoms were introduced. At a 100 % adsorption ratio, the lithium atoms adsorbed to sites directly above or below the silicon atoms. Unlike hydrogenated silicene, the band structure of each partially lithiated structure was shown to be that of a metal. Combining hydrogen and lithium adsorptions, it was shown that silicene-Li nanocompounds can be considered for hydrogen storage.

Committee: Amir Farajian PhD (Advisor); Amer Maher PhD (Committee Member); Daniel Young PhD (Committee Member) Subjects: Materials Science

Master of Science, The Ohio State University, 2010, Chemistry

A number of methods and materials have been synthesized for use as hydrogen storage materials. However, to date, none of the materials are capable of being used as a sustainable fuel source as a result of poor recyclability. Therefore, new materials need to be synthesized and evaluated in order to obtain the goal of creating a hydrogen fuel economy. Furthermore, some possible hydrogen storage candidates have been ignored as a result of poor and laborious syntheses. Finding new synthetic routes to these materials opens exploration of their effectiveness as a hydrogen source. The reaction of lithium aluminum hydride with ammonia borane has been investigated in varying ratios. Evaluation of the hydrogen released, proton and boron-11 NMR spectroscopy, and infrared spectroscopy indicate the formation of a compound of composition LiAl(NHBH3)H2 in the equimolar reaction of lithium aluminum hydride and ammonia borane followed by subsequent addition of amidotrihydroborate to this material with the presence of additional ammonia borane to form LiAl(NHBH3)(NH2BH3)H and LiAl(NHBH3)(NH2BH3)2. It was unclear whether the reaction in a ratio of 1:4 lithium aluminum hydride to ammonia borane produced LiAl(NH2BH3)4 or if the product was identical to that of the reaction in a 1:3 ratio. All of the compounds made retain a high gravimetric capacity of hydrogen. Solvent-free sodium octahydrotriborate was synthesized via a new method en route to ammonia triborane. Tetrahydrofuran borane complex solution was stirred with an amalgamation of sodium and mercury to produce the solvent coordinated sodium octahydrotriborate and sodium borohydride. The product was separated by extraction with ethyl ether and heating to remove coordinated solvent. Average yield of the final product was approximately 60%. A literature method for synthesizing ammonia triborane was refined, removing the need for multiple cooling steps and for the use of column chromatography to purify the product. The reaction of (open full item for complete abstract)

Committee: Sheldon Shore Ph.D. (Advisor); James Cowan Ph.D. (Committee Member) Subjects: Chemistry

Doctor of Philosophy, The Ohio State University, 2009, Chemistry

PART I Water-free rare earth(III) hexacyanoferrate(III) complexes, {Ln(DMF)6(µ-CN)2Fe(CN)4}∞ (DMF= N,N-dimethylformamide; Ln= rare earths excluding Pm), were synthesized in dry DMF through the metathesis reactions of [(18-crown-6)K]3Fe(CN)6 with LnX3(DMF)n (X= Cl or NO3). Anhydrous DMF solutions of LnX3(DMF)n were prepared at room temperature from LnCl3 or LnX3*nH2O under a dynamic vacuum. Compounds were characterized by IR, X-ray powder diffraction, elemental analysis, and single crystal X-ray diffraction. Infrared spectra reveal that a monotonic, linear relationship exists between the ionic radius of the Ln and the νμ-CN stretching frequency. X-ray powder diffraction data are in agreement with powder patterns calculated from single crystal X-ray diffraction results indicating that each compound consists of one pure crystalline phase. This agreement is a useful alternative for bulk sample confirmation when elemental analyses are difficult to obtain. Eight-coordinate Ln(III) metal centers are observed for all structures. Trans-cyanide units of [Fe(CN)6]3- form isocyanide linkages with Ln(III) resulting in one-dimensional polymeric chains. Rare earth(III) tetracyanometalate(II) complexes [Ln(DMF)n]2[M(CN)4]3 (M= Ni, Pd, Pt) have been synthesized and structurally characterized. The assumption that only the size (identity) of rare earth element dictates the observed structure type has been proven false. The coordination number of the rare earth metal (n= 5 or 6) was found to depend on the identity of the group-10 metals as well as the identity of the rare earth metal. Complexes [LnX(DMF)n][M(CN)4] (where X= Cl or NO3) with a Ln:M ratio of 1:1 have been synthesized and structurally characterized. The anion [Pt(CN)4]2- was not able to replace the nitrate ligand of [Ce(NO3)(DMF)5][Pt(CN)4]; however, the anion [Pt(CN)4]2- was able to replace the chloride ligand to produce [Ce(DMF)5]2[Pt(CN)4]3. PART II An investigation into the coordination chemistry of the amidot (open full item for complete abstract)

Committee: Sheldon Shore PhD (Advisor); Claudia Turro PhD (Committee Member); Patrick Woodward PhD (Committee Member) Subjects: Chemistry

Master of Science (MS), Ohio University, 2006, Mechanical Engineering (Engineering)

Studies have proven hydrogen gas as a highly efficient, renewable and alternative energy source and it is expected to serve as a common fuel for all mobile and stationary applications. However, currently the on-board storage difficulties prevent the practical usage of hydrogen in automotive applications. A more efficient and innovative method of hydrogen storage for automotive fuel cell application is to compress hydrogen in minute hollow spherical bubbles incorporating the Hydrostatic Pressure Retainment (HPR) technology. In a HPR vessel, the material properties and the inner matrix structure are two critical design parameters that determine the hydrogen mass efficiency. The focus of this study is devoted to investigating the performance characteristics of one configuration; spherically shaped bubbles homogenously arranged in a simple cubic inner matrix packing structure for a HPR vessel, using Finite Element Analysis.

Committee: Hajrudin Pasic (Advisor) Subjects: Engineering, Mechanical

Master of Science (MS), Ohio University, 2006, Mechanical Engineering (Engineering)

One of the major hurdles to be traversed before a Hydrogen Economy becomes practical, and therefore abundant, is the problem of its storage. An ideal HPR pressure vessel exhibits uniformly sized, spherical cells arranged in a homogeneous fashion. An ideal HPR pressure vessel is probably a feasible option for the automotive industry. Although the ideal microstructure may be sound, the structural integrity of the actual microstructure of polymeric foams was examined. Various polymeric foam samples were obtained and examined via the use of Scanning Electron Microscopy (SEM) imaging and X-ray computed Micro-Tomography (micro-CT). The mechanical behavior of such foams under internal pressure was simulated and analyzed using Finite Element Analysis (FEA). While neither the H130 nor the DF-630A foam structures proved adequate to compete with other current hydrogen storage methods, this work has developed an effective methodology for the examination of polymeric foam for HPR application.

Committee: Bhavin Mehta (Advisor) Subjects: Engineering, Mechanical

Master of Science (MS), Ohio University, 2004, Mechanical Engineering (Engineering)

There is a great deal of attention being concentrated on reducing the weight of pressure vessels and fuel/oxidizer tanks (tankage) by 10% to 20%. Most efforts are focused at the use of new lighter weight high strength materials to achieve this goal. This author proposes another approach called Hydrostatic Pressure Retainment™ (HPR™) which has the potential of reducing tank weights by nearly 40% while simultaneously increasing safety and design versatility. HPR™ is an original invention of the author and his advisor, and represents a truly novel approach to light weight pressure vessel design. Described herein are the initial steps towards development of this new technology.

Committee: Bhavin Mehta (Advisor) Subjects: Engineering, Mechanical

BA, Oberlin College, 2009, Physics and Astronomy

In this thesis we examine the hydrogen storage properties of four different materials. Because of the global climate crisis and the growing realization that petroleum resources are limited, there has been a strong push to find alternative means of energy storage. At the forefront of this push is the hydrogen economy, the idea that hydrogen gas is a bountiful, clean, alternative means of energy storage. One step towards realizing the hydrogen economy is finding a practical means of hydrogen storage. The conventional methods of hydrogen storage are in high-pressure gas cylinders or as a liquid. Both of these methods are impractical for energy storage purposes. The gas cylinders are very massive and so hold little hydrogen for their weight; and hydrogen only liquefies at -251.9° C (-421.4° F), which imposes impractical limitations on its use. The most promising alternative storage option is finding a material that traps a large quantity of hydrogen at room temperature and atmospheric pressure. At the current time, there is no known material that is a practical option for hydrogen storage. In this thesis we use infrared spectroscopy to investigate the behavior of the hydrogen inside the material and the interaction between the trapped hydrogen and the material . By refining our understanding of this interaction, we can predict what might make good storage materials. Currently, theoretical models are unable to predict energies that are correct within 25%. We successfully explain the observed behavior of the trapped hydrogen in the four materials. Our investigation also provides a wealth of data that can be used to calibrate theoretical models. These results will help guide us towards new materials that have greater potential to be viable storage alternatives.

Committee: Stephen FitzGerald PhD (Advisor) Subjects: Chemistry; Materials Science; Physics

Doctor of Philosophy, Miami University, 2008, Chemistry and Biochemistry

Porous metal-organic frameworks (MOFs) represent a new type of functional materials and have been found to exhibit great potential in various applications such as catalysis, magnetism, gas storage/separation etc. This dissertation details the investigation of porous MOFs for gas adsorption applications, including hydrogen storage, methane storage, and selective gas adsorption. The first section evaluates porous MOFs as promising candidates for hydrogen storage application. It discusses various strategies to improve hydrogen uptakes in porous MOFs, which includes mimicking hemoglobin to create entatic metal centers in PCN-9 resulting in a high hydrogen heat of adsorption of 10.1 kJ/mol, functionalizing the organic ligand with fused aromatic rings to achieve high hydrogen adsorption capacity of 2.7 wt% in PCN-14 at 77 K and 1 bar, and utilizing catenation to generate PCN-6 with a hydrogen uptake of 9.5 wt% (absolute, at 77 K and 50 bar) as well as a surface area of 3800 m2/g in. The second section discusses methane storage applications of porous MOFs. Constructed from a pre-designed ligand, the porous MOF, PCN-14 exhibits the highest methane uptake capacity among currently reported materials with a value of 230 v/v (absolute, at ambient temperature and 35 bar), which is 28% higher than the US DOE target (180 v/v) for methane storage. The third section addresses microporous MOFs as molecular sieves for selective gas adsorption application. Increasing the bulkiness of the struts and introducing coordinatively linked interpenetration restrict the pore sizes of PCN-13 and PCN-17 respectively to scelectively adsorb oxygen and hydrogen over nitrogen and carbon monoxide. Based on some amphiphilic ligands, a series of mesh-adjustable molecular sieves, whose pore sizes can be continuously tuned from 2.9 to 5.0 angstrom, have been designed for various gas separation applications.

Committee: Hongcai Zhou PhD (Advisor); Michael Crowder PhD (Committee Chair); Benjamin Gung PhD (Committee Member); André Sommer PhD (Committee Member); Qingshun Li PhD (Committee Member) Subjects: Chemistry

Doctor of Engineering, Cleveland State University, 2008, Fenn College of Engineering

Searching for new energy sources is highly desirable for the next generations when rapidly changing factors are considered such as population, increasing pollution and exhaustion of fossil fuels. Hence, there is a need for clean, safe and efficient energy carriers or forms of energy that can be transported to the end user. One of these energy carriers is electricity which has been used widely and can be produced from various sources. However, its production from fossil fuels contributes to pollution. On the other hand hydrogen, due to its abundance, light weight, low mass density, high energy density and non-polluting nature attract many researchers' attention to be used as an energy carrier so that the dependence on fossil fuels would be minimized which are responsible for global warming due to harmful emissions to the atmosphere. In addition, hydrogen can be converted to other forms of energy more efficiently through catalytic combustion, electrochemical conversion, etc. However, hydrogen must be handled extremely carefully due to its physico-chemical properties. Its on-board storage is a major challenge because of its high explosiveness and the high cost of the storage process. There are many factors that need to be considered when deciding upon the storage method and the most important ones are safety, gravimetric and volumetric capacities, cost, environmental friendliness, reversibility and release rate.This work is dedicated to study the hydrogen uptake behavior of nanostructured palladium constructed through template-assisted electrochemical deposition process. Hydrogen sorption experiments were conducted using a custom-made volumetric system. Nickel was used as the test metal to tune the electrochemical deposition process before conducting the experiments with palladium. Growth mechanism of the nanostructured metals in various substrates was investigated. Conditions for growing nano-scaled palladium were optimized and the hydrogen sorption experiments were c (open full item for complete abstract)

Committee: Orhan Talu Ph.D. (Advisor); Surendra Tewari Ph.D. (Committee Member); D.B. Shah Ph.D. (Committee Member); Nolan Holland Ph.D. (Committee Member); Petru Fodor Ph.D (Committee Member) Subjects: Chemical Engineering

Doctor of Philosophy, Case Western Reserve University, 2004, Materials Science and Engineering

Micro-fabricated PEM fuel cells and other micro-power systems are being developed to provide on-board electrical power source for MEMS systems. The development of these micro-power systems needs a hydrogen source that has high volume density, fast hydriding/de-hydriding kinetics and can be easily activated under atmosphere pressure at room temperature. In this investigation, the effects of palladium on the hydrogen storage properties of LaNi4.7Al0.3, CaNi5 and Mg2.4Ni were studied. It is found that mechanical grinding these alloys with palladium can lower the activation pressures to sub-atmosphere at room temperature and significantly increase hydriding/de-hydriding kinetics; the activation durability of these alloys in air is also greatly extended to more than 2 years. The hydride ink making process, in which polymer binders are added to the 10wt% palladium modified alloy, slightly decreases the storage capacity, but the alloy is still active under atmospheric pressure at room temperature. The cyclic hydriding/dehydriding stabilities of palladium modified alloys under pure and humidified hydrogen were studied. After 5000 cycles under pure hydrogen, the storage capacities of 10wt% palladium modified LaNi4.7Al0.3 and CaNi5 decrease 14-20% and 30-35% respectively. For test under hydrogen with 75% relative humidity, the storage capacity of 10wt% palladium modified LaNi4.7Al0.3 decreases 60% after 3000 cycles. The degradation of LaNi4.7Al0.3 is mainly due to the oxidation caused by air exposures during the test or water vapor in the hydrogen; for CaNi5, disproportionation of CaNi5 is the main reason. The mechanism of palladium on the activation and hydriding/de-hydriding of the alloys can be explained by hydrogen spillover and reverse hydrogen spillover. When inks made with 10wt% palladium modified LaNi4.7Al0.3 and CaNi5 were used as the hydrogen source for PEM fuel cell, the maximum currents they can provide exceed the requirement for the micro-fabricated PEM fuel cell (open full item for complete abstract)

Committee: Joe Payer (Advisor) Subjects: Engineering, Materials Science

Doctor of Philosophy, The Ohio State University, 2013, Materials Science and Engineering

Hydrogen storage was identified by the US Department of Energy as a “grand challenge” for the implementation of hydrogen-powered fuel cell vehicles for reduced CO2 emissions from transportation vehicles. None of the hydrogen storage options currently developed can satisfy the high gravimetric, volumetric and system design requirements. Intermetallic compounds with Laves structures in the formula of AB2 have long been known to store hydrogen in their interstitial sites to serve as reversible hydrogen storage materials (A and B are metallic elements). They have the potential to be hydrided to a maximum of ~ AB2H6 due to the impeding H-H interactions at neighboring interstitial sites. To achieve the highest weight percent of hydrogen storage in AB2H6, the lowest combined atomic weight of AB2 is required. The CaLi2 compound is the lightest known Laves phase, but it could not maintain its Laves structure when it was hydrided. Existing work of Akiba's group showed that a ternary Laves phase CaLi1.8Mg0.2 could be hydrided to form a hydrogenated Laves phase, but the absorbed hydrogen could not be released for reversible storage. Substitutions (Ca,X)Li1.8Mg0.2 are explored in the present study to see whether heavier elements [X = Sr, Ba and Ce] in small quantities can make the lightweight Laves compounds reversibly store hydrogen. Induction melting was successful in obtaining the desired Laves phases. The base system, CaLi1.8Mg0.2, formed a single phase, consistent with the literature result. Both Ca0.9Ba0.1Li1.8Mg0.2 and Ca0.9Ce0.1Li1.8Mg0.2 also formed a single-phase C14 Laves, whereas both Ca0.9Sr0.1Li1.8Mg0.2 and Ca0.8Sr0.2Li1.8Mg0.2 formed two seperature Laves phases with the same crystal structure, indicating a phase separation. The Ca0.8Ba0.2Li1.8Mg0.2 composition completely lost the Laves-phase structure, forming CaLi2, CaMg2, BaLi4 and Ca. All compounds tested at temperatures from 25 ¿¿C to 150 ¿¿C show the characteristic “plateau” behavior in the pressure-composit (open full item for complete abstract)

Committee: Ji-Cheng Zhao PhD (Advisor); John Morral PhD (Committee Member); Yogeshwar Sahai PhD (Committee Member) Subjects: Materials Science