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Kinetic Studies of the Reactions of Alkyl and Silyl Hydrides

Description: The Kinetics of the reactions involving alkyl and silyl hydrides were studied by the flash photolysis / resonance fluorescence technique. The reactions of alkyl radicals (R = C₂H₅, i-C₃H₇, t-C₄H₉) with HBr have been studied at room temperature and the rate constants obtained (units are in cm³ s^-1 ) are: k₃.₃ = (7.01 ± 0.15) x 10^-12, k₃.₂ = (1.25 ± 0.06) x 10^-11, k₃.₁ = (2.67 ± 0.13) x 10^-11 These results, combined with previously determined reverse rate constants and other kinetic information, yield bond dissociation enthalpies (units in kJ mol^-1) at 298 K : primary C-H in C₂H₅-H (423.6 ± 2), secondary C-H in i-C₃H₇-H (409.9 ± 2), tertiary C-H in t-C₄H₉-H (405.1 ± 2). These rate constants and bond energies are in good agreement with previous results.
Date: August 1996
Creator: Yuan, Jessie (Jessie Win-Jae)
Partner: UNT Libraries


Description: Mixtures of light-weight elements and hydrides were investigated to increase the understanding of the chemical reactions that take place between various materials. This report details investigations we have made into mixtures that include NaAlH{sub 4}, LiAlH{sub 4}, MgH{sub 2}, Mg{sub 2}NiH{sub 4}, alkali(ne) hydrides, and early third row transition metals (V, Cr, Mn). Experimental parameters such as stoichiometry, heat from ball milling versus hand milling, and varying the temperature of high pressure molten state processing were studied to examine the effects of these parameters on the reactions of the complex metal hydrides.
Date: June 7, 2007
Creator: Berseth, P; Ragaiy Zidan, R; Donald Anton, D; Kirk Shanahan, K & Ashley Stowe, A
Partner: UNT Libraries Government Documents Department

NMR Study of n-Propyllithium Aggregates

Description: A variable temperature 1H, 13C, and 6Li NMR study of n-propyl-6Li-lithium showed five different aggregates, similar to that in the literature as (RLi)n, n= 6, 8, 9, 9, 9. There were also a number of additional new species, identified as lithium hydride containing aggregates. Unexpectedly, a series of 13C{1H} 1-D NMR experiments with selective 6Li decoupling showed evidence for 13C-6Li spin-spin coupling between the previously reported (RLi)n aggregates and various hydride species.
Date: December 2002
Creator: Davis, James W.
Partner: UNT Libraries

First-Principles Modeling of Hydrogen Storage in Metal Hydride Systems

Description: The objective of this project is to complement experimental efforts of MHoCE partners by using state-of-the-art theory and modeling to study the structure, thermodynamics, and kinetics of hydrogen storage materials. Specific goals include prediction of the heats of formation and other thermodynamic properties of alloys from first principles methods, identification of new alloys that can be tested experimentally, calculation of surface and energetic properties of nanoparticles, and calculation of kinetics involved with hydrogenation and dehydrogenation processes. Discovery of new metal hydrides with enhanced properties compared with existing materials is a critical need for the Metal Hydride Center of Excellence. New materials discovery can be aided by the use of first principles (ab initio) computational modeling in two ways: (1) The properties, including mechanisms, of existing materials can be better elucidated through a combined modeling/experimental approach. (2) The thermodynamic properties of novel materials that have not been made can, in many cases, be quickly screened with ab initio methods. We have used state-of-the-art computational techniques to explore millions of possible reaction conditions consisting of different element spaces, compositions, and temperatures. We have identified potentially promising single- and multi-step reactions that can be explored experimentally.
Date: May 20, 2011
Creator: Johnson, J. Karl
Partner: UNT Libraries Government Documents Department

Electrochemical and in situ neutron diffraction investigations of La-Ni-Al-H alloys

Description: Li/metal hydride batteries are a strong contender to replace Ni/Cd batteries. Since the role of alloying components is not yet understood, a combination of electrochemical and neutron diffraction techniques has been designed to investigate metal hydrides. In this work, several Al-substituted LaNi{sub 5} alloys were investigated for their specific capacity (measured by mAh/La and symbolized by x in LaNi{sub 5-y}Al{sub y}H{sub x}), impedance, and cycling stability. Neutron diffraction was used to study the electrochemically induced phase transformation and structure change during charge/discharge.
Date: May 1, 1996
Creator: Peng, W.; Redey, L.; Vissers, D.R.; Myles, K.M.; Carpenter, J.; Richardson et al.
Partner: UNT Libraries Government Documents Department

HYCSOS : A Chemical Heat Pump and Energy Conversion System Based on Metal Hydrides

Description: The current status of the HYCSOS chemical heat pump and energy conversion system based on metal hydrides is described. Heat transfer fluid loops were insulated and modified for isothermal operation. Software development for HYCSOS manual mode operation was completed. Routines to handle data acquisition, logging, compression, correction and plotting, using a Tektronix Graphics system with flexible disk data storage, provide a rapid and versatile means of presenting HYCSOS data for analysis. Advanced concept heat exchangers to improve the heat transfer of the hydride bed with the heat transfer fluid are discussed. Preliminary tests made with a LaNi5 loaded aluminum foam test unit showed that heat transfer properties are very markedly improved. Thermodynamic expressions are applied to the selection of alloys for use in HYCSOS. The substitution of aluminum for nickel in AB5 type alloys is shown to reduce hysteresis and permits the use of potentially lower cost materials with added flexibility for the optimization of engineering design and performance characteristics of the hydride heat pump system. Transient thermal measurements on hydride beds of CaNi5 and LaNi5 show no deterioration with cycling. Relatively slow heat transfer between the hydride beds and heat transfer fluid in the coiled tube heat exchangers is indicated by temperature lag of the bed and heat transfer fluid. Improved heat transfer is anticipated with aluminum foam heat exchangers.
Date: April 1979
Creator: Sheft, Irving; Gruen, Dieter M. & Lamich, George
Partner: UNT Libraries Government Documents Department


Description: >The excitation by nuclear collisions of the acoustic modes of a metal hydride crystal was investigated, using a model of the crystal based on experiments on ZrH/sub 2/, but slightly more general. It is found that these modes contribute little tc neutron moderation in ZrH/sub 2/. In the course of the discussion, a generalized form of the Wilkins equation, which determines the spectrum of neutrons thermalizing in a heavy moderator, is developed, applicable when the scattering cross section varies with energy. (auth)
Date: December 1, 1959
Creator: Vaughan, E.U.
Partner: UNT Libraries Government Documents Department

Tritium transport vessel using depleted uranium

Description: A tritium transport vessel using depleted uranium was tested in the laboratory using deuterium and protium. The vessel contains 0.5 kg of depleted uranium and can hold up to 18 grams of tritium. The conditions for activation, tritium loading and tritium unloading were defined. The safety aspects that included air-ingress, tritium diffusion, temperature and pressure potentials were evaluated.
Date: January 1995
Creator: Heung, L. K.
Partner: UNT Libraries Government Documents Department

Complex Hydrides for Hydrogen Storage

Description: This report describes research into the use of complex hydrides for hydrogen storage. The synthesis of a number of alanates, (AIH4) compounds, was investigated. Both wet chemical and mechano-chemical methods were studied.
Date: March 10, 2003
Creator: Slattery, Darlene & Hampton, Michael
Partner: UNT Libraries Government Documents Department

Energetics Inc

Description: This report includes thirteen site-visit-based analyses or assessments of hydrogen R&D projects as well as four analyses of hydrogen process scenarios. The latter include the use of hydrogen/bromine electricity storage, hydrogen as a bus fuel, low-rank coal as thermal source to regenerate hydrides, and sodium hydride on-board storage.
Date: July 1, 2003
Creator: Inc, Energetics
Partner: UNT Libraries Government Documents Department


Description: This paper reports the results in the effort to destabilize lithium borohydride for reversible hydrogen storage. A number of metals, metal hydrides, metal chlorides and complex hydrides were selected and evaluated as the destabilization agents for reducing dehydriding temperature and generating dehydriding-rehydriding reversibility. It is found that some additives are effective. The Raman spectroscopic analysis shows the change of B-H binding nature.
Date: May 10, 2006
Creator: Au, Ming
Partner: UNT Libraries Government Documents Department

Final report for the DOE Metal Hydride Center of Excellence.

Description: This report summarizes the R&D activities within the U.S. Department of Energy Metal Hydride Center of Excellence (MHCoE) from March 2005 to June 2010. The purpose of the MHCoE has been to conduct highly collaborative and multi-disciplinary applied R&D to develop new reversible hydrogen storage materials that meet or exceed DOE 2010 and 2015 system goals for hydrogen storage materials. The MHCoE combines three broad areas: mechanisms and modeling (which provide a theoretically driven basis for pursuing new materials), materials development (in which new materials are synthesized and characterized) and system design and engineering (which allow these new materials to be realized as practical automotive hydrogen storage systems). This Final Report summarizes the organization and execution of the 5-year research program to develop practical hydrogen storage materials for light duty vehicles. Major results from the MHCoE are summarized, along with suggestions for future research areas.
Date: January 1, 2012
Creator: Keller, Jay O. & Klebanoff, Leonard E.
Partner: UNT Libraries Government Documents Department

Q disease on 350-MHZ superconducting spoke cavities

Description: Q disease, i.e., an increase of RF surface resistance due to hydride precipitation, has been investigated with 350-MHz spoke cavities. This phenomenon was studied extensively in early 1990s with cavities at frequencies >1 GHz. This is possibly due to the fact that the lower-frequency cavities were believed to show insignificant effect. However, early 500-MHz KEK elliptical cavities and JAERI 130-MHz quarter wave resonators have shown significant Q degradation, suggesting that this disease can be a serious problem with lower-frequency cavities as well. Since there were no quantitative data with 350-MHz cavities, we decided to measure our two spoke cavities. Our spoke cavities were made of RRR{approx}250 niobium and were chemically polished {approx}150 microns. A few series of systematic tests have shown that our spoke cavities do not show any Q{sub 0} degradation up to {approx}24 hours of holding the cavity at 100 K. However it starts showing degradation if it is held for a longer time and the additional loss due to the Q disease increases linearly. It was also found that our spoke cavity recovers from Q disease if it is warmed up to 150 K or higher for 12 hours.
Date: January 1, 2003
Creator: Tajima, T. (Tsuyoshi); Edwards, R. L. (Randall L.); Krawczyk, F. L. (Frank L.); Liu, Jianfei; Schrage, D. L. (Dale L.) & Shapiro, A. H. (Alan H.)
Partner: UNT Libraries Government Documents Department


Description: Aluminum hydride is a covalent, binary hydride that has been known for more than 60 years and is an attractive medium for on-board automotive hydrogen storage, since it contains 10.1% by wt. hydrogen with a density of 1.48 g/ml. There are at least 7 non-solvated AlH{sub 3} phases, namely {alpha}, {alpha}{prime}, {beta}, {gamma}, {var_epsilon} and {zeta}. The properties of {alpha}-AlH{sub 3}, obtained from the Dow Chemical Co. in 1980, have been previously reported. Here we present a description of the thermodynamic and kinetic properties of freshly prepared {alpha}, {beta} and {gamma} phases of AlH{sub 3}. In all cases the decomposition kinetics are appreciable below 100 C and all will meet the DOE 2010 gravimetric and volumetric vehicular system targets (6 wt% H{sub 2} and 0.045 kg/L). However, further research will be required to develop an efficient and economical process to regenerate AlH{sub 3} from the spent Al powder.
Date: November 27, 2006
Partner: UNT Libraries Government Documents Department


Description: Thorium forms a tetragonal lower hydride of composition ThH{sub 2}. The hydrides ThH{sub 2}, ThD{sub 2} and ZrD{sub 2} have been studied by neutron diffraction in order that hydrogen positions could be determined. The hydrides are isomorphous, and have a deformed fluorite structure. Metal-hydrogen distances in thorium hydride are unusually large, as in UH{sub 3}. Thorium and zirconium scattering amplitudes and a revised scattering amplitude for deuterium are reported.
Date: April 20, 1951
Creator: Rundle, R.E.; Shull, C.G. & Wollan, E.O.
Partner: UNT Libraries Government Documents Department

Integrated Advanced Energy Systems Research at IIT

Description: This report consists of Two research projects; Sustainable Buildings and Hydrogen Storage. Sustainable Building Part includes: Wind and the self powered built environment by professor P. Land and his research group and experimental and computational works by professor D. Rempfer and his research group. Hydrogen Storage part includes: Hydrogen Storage Using Mg-Mixed Metal Hydrides by professor H. Arastoopour and his research team and Carbon Nanostructure as Hydrogen Storage Material by professor J. Prakash and his research team.
Date: September 30, 2010
Creator: Arastoopour, Hamid
Partner: UNT Libraries Government Documents Department

Thermodynamics of coherent open systems with applications to hydrides: The physical origin of hysteresis in absorption-desorption isotherms. [Final report]

Description: Purpose was to study the physical origin of a strong hysteresis on the pressure-composition isotherms of metal hydrides (plateau pressure during hydrogen absorption is several times higher than during reverse desorption). The research ended up studying the behavior of open coherent systems and the thermodynamics of an elastically coherent two-phase open system consisting of an interstitial solid solution in equilibrium with a gas reservoir of solute atoms.
Date: December 31, 1994
Creator: Khachaturyan, A. & Schwarz, R.
Partner: UNT Libraries Government Documents Department