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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

Final technical report for contract year November 9, 1947 to November 9, 1948

Description: Report describing processes to prepare metallic calcium of a very high purity. Report details promising methods for electrolyte purification. Methods of chemical analysis for nitrogen are also improved upon and spectrochemical methods and standards established for twelve other specified elements.
Date: 1948
Creator: Brown, H. & Woodberry, P.
Partner: UNT Libraries Government Documents Department

Uranium Hydride : A Survey

Description: The following report discusses the results of a survey that was initiated to ascertain the availability of uranium hydride in tonnage quantities.
Date: April 10, 1950
Creator: Kitzes, A. S.
Partner: UNT Libraries Government Documents Department

The X-ray Investigation of the Uranium Hydrogen System: The Structure of UH₃

Description: From abstract: "The uranium-hydrogen system has been examined by X-ray diffraction. This study has revealed one cubic hydride (UH3). Since the structure of the hydride is unrelated to the structures of any of the metal and the hydride has a definite composition, it is not an interstitial solid solution but a true compound."
Date: 1948
Creator: Rundle, R. E.; Wilson, A. S. & McDonald, R. A.
Partner: UNT Libraries Government Documents Department

Delta-Phase Zirconium Hydride as a Solid Moderator

Description: Abstract: "In a study of the preparation and properties of delta-phase zirconium hydride it was found that large, sound bodies of the hydride can be prepared by direct combination of the elements if the rate of the reaction is retarded by limiting the supply of available hydrogen. Specimens up to 1-in. diameter were prepared using this technique. Because delta phase zirconium hydride does not readily form eutectics with iron-and nickel-base alloys below 1800 F these materials may be utilized for clodding the hydride. Delta-phase zirconium hydride is unaffected by exposure to liquid NaK or to nitrogen gas at temperatures below 1000 F. The hot hardness of delta-phase zirconium hydrid is about 130 kg per mm-2 at room temperature and 40 kg per mm-2 at 1500 F. The mean coefficient of thermal expansion (68 to 1337 F) is 6.5 x 10^-6 per deg F. The thermal conductivity varies from 5.7 Btu/(ft)(hr)(F) at 300 F to 5.1 Btu/(ft)(hr)(F) at 1300 F."
Date: December 18, 1957
Creator: Vetrano, James B.
Partner: UNT Libraries Government Documents Department

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

Preparation and Physical Properties of Uranium Hydride

Description: Report discussing the preparation of uranium hydride and its properties such as density, crystal structure, and number of atoms per unit cell. From abstract: "The pressure-composition isotherm as well as other data indicates that uranium hydride is a true compound."
Date: 1948
Creator: Spedding, F. H.; Newton, A. S.; John, I. B.; Johnson, O.; Daane, A.; Nottorf, R. W. et al.
Partner: UNT Libraries Government Documents Department

Evaluation of Zirconium Hydride as Moderator in Integral, Boiling Water-Superheat Reactors

Description: This report summarizes the results and conclusions of a study made to evaluate the merits of using zirconium hydride as a solid moderator in an integral boiling water-nuclear superheat reactor of the pressure vessel type.
Date: March 1, 1962
Creator: Gylfe, J. D.; Rood, H.; Greenleaf, J.; Balkwill, K.; Prem, L. & Goldfisher, L.
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

The Cladding of Delta-Phase Zirconium Hydride

Description: Abstract: A study has been made of the cladding of solid and powdered delta-phase zirconium hydride is both red and flat shapes with stainless steel. The program included investigations of metallurgical bonding, both with and without the sore of metallic barrier materials. Types 304 and 347 stainless steel were used for cladding material. The intermediate barrier-layer materials used were niobium, molybdenum, a combination of copper and molybdenum, and a combination of copper and niobium. The pressure-bonding techniques, involving the use of gas pressure at elevated temperatures, was employed in this study. Variable times and temperatures with a constant pressure of 10,000 poi were utilized by produce bonding. In this study, the best results were archived is cladding delta-phase zirconium hydride directly with Types 304 or 347 stainless steel. Good bonds were obtained by pressure bonding at 1600 F for 3 or 4 hr subsequent to pressure bonding at 1900 F for 1 to 2 hr at a pressure of 10,000 poi. Partial bonding was achieved between niobium and zirconium hydride and molybdeum and girconium hydride.
Date: December 27, 1957
Creator: Paprocki, Stan J.; Hodge, Edwin S. & Boyer, Charles B.
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