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Thermodynamics of Cr2O3, FeCr2O4, ZnCr2O4 and CoCr2O4

Description: High temperature heat capacity measurements were obtained for Cr{sub 2}O{sub 3}, FeCr{sub 2}O{sub 4}, ZnCr{sub 2}O{sub 4} and CoCr{sub 2}O{sub 4} using a differential scanning calorimeter. These data were combined with previously-available, overlapping heat capacity data at temperatures up to 400 K and fitted to 5-parameter Maier-Kelley C{sub p}(T) equations. Expressions for molar entropy were then derived by suitable integration of the Maier-Kelley equations in combination with recent S{sup o}(298) evaluations. Finally, a database of high temperature equilibrium measurements on the formation of these oxides was constructed and critically evaluated. Gibbs energies of Cr{sub 2}O{sub 3}, FeCr{sub 2}O{sub 4} and CoCr{sub 2}O{sub 4} were referenced by averaging the most reliable results at reference temperatures of 1100, 1400 and 1373 K, respectively, while Gibbs energies for ZnCr{sub 2}O{sub 4} were referenced to the results of Jacob [Thermochim. Acta 15 (1976) 79-87] at 1100 K. Thermodynamic extrapolations from the high temperature reference points to 298.15 K by application of the heat capacity correlations gave {Delta}{sub f}G{sup o}(298) = -1049.96, -1339.40, -1428.35 and -1326.75 kJ mol{sup -1} for Cr{sub 2}O{sub 3}, FeCr{sub 2}O{sub 4}, ZnCr{sub 2}O{sub 4} and CoCr{sub 2}O{sub 4}, respectively.
Date: January 9, 2007
Creator: Ziemniak SE, Anovitz LM, Castelli RA, Porter WD
Partner: UNT Libraries Government Documents Department

Multiple ordered phases in the filled skutterudite compound PrOs4As12

Description: Magnetization, specific heat, and electrical resistivity measurements were made on single crystals of the filled skutterudite compound PrOs{sub 4}As{sub 12}. Specific heat measurements indicate an electronic specific heat coefficient {gamma} {approx} 50-200 mJ/mol K{sup 2} at temperatures 10 K {le} T {le} 18 K, and {approx} 1 J/mol K{sup 2} for t {le} 1.6 K. Magnetization, specific heat, and electrical resistivity measurements reveal the presence of two, or possibly three, ordered phases at temperatures below {approx} 2.3 K and in fields below {approx} 3 T. The low temperature phase displays antiferromagnetic characteristics, while the nature of the ordering in the other phase(s) has yet to be determined.
Date: March 20, 2006
Creator: Yuhasz, W M; Butch, N P; Sayles, T A; Ho, P; Jeffries, J R; Yanagisawa, T et al.
Partner: UNT Libraries Government Documents Department


Description: This paper reports a set of modeling studies that were undertaken to acquire a more detailed knowledge of combustion inhibition mechanisms. Mixtures of H{sub 2}/O{sub 2}/Ar reacting in the idealized perfectly stirred reactor were investigated. Three H{sub 2}/O{sub 2} kinetic mechanisms were considered, differing from one another by the number of HO{sub 2} reactions included. Two physical inhibitors, Ar and N{sub 2}, and one chemical inhibitor, HBr, were investigated. Additional parameters considered were pressure, equivalence ratio, inhibitor concentration and rate coefficient variation. The most effective inhibitor was HBr which acted chemically and caused substantial reduction in radical concentrations in the mixtures considered. The molecules Ar and N{sub 2} acted as physical diluents with N{sub 2}, the more effective of the two due to its larger heat capacity.
Date: May 1, 1980
Creator: Brown, Nancy J. & Schefer, Robert W.
Partner: UNT Libraries Government Documents Department

Disorder and size effects on Kondo interactions and magneticcorrelations in CePt2 nanoscrystals

Description: The evolution of the Kondo effect and magnetic correlations with size reduction in CePt{sub 2} nanoparticles (3.1-26 nm) is studied by analysis of the temperature-dependent specific heat and magnetic susceptibility. The antiferromagnetic correlations diminish with size reduction. The Kondo effect predominates at small particle size with trivalent, small Kondo temperature (T{sub K}) magnetic regions coexisting with strongly mixed valent, large T{sub K} nonmagnetic regions. We discuss the role of structural disorder, background density of states and the electronic quantum size effect on the results.
Date: December 12, 2006
Creator: Chen, Y.Y.; Huang, P.H.; Ou, M.N.; Wang, C.R.; Yao, Y.D.; Lee,T.K. et al.
Partner: UNT Libraries Government Documents Department

Is U3Ni3Sn4 best described as near a quantum critical point?

Description: Although most known non-Fermi liquid (NFL) materials are structurally or chemically disordered, the role of this disorder remains unclear. In particular, very few systems have been discovered that may be stoichiometric and well ordered. To test whether U{sub 3}Ni{sub 3}Sn{sub 4} belongs in this latter class, we present measurements of the x-ray absorption fine structure (XAFS) of polycrystalline and single-crystal U{sub 3}Ni{sub 3}Sn{sub 4} samples that are consistent with no measurable local atomic disorder. We also present temperature-dependent specific heat data in applied magnetic fields as high as 8 T that show features that are inconsistent with the antiferromagnetic Griffiths' phase model, but do support the conclusion that a Fermi liquid/NFL crossover temperature increases with applied field. These results are inconsistent with theoretical explanations that require strong disorder effects, but do support the view that U{sub 3}Ni{sub 3}Sn{sub 4} is a stoichoiometric, ordered material that exhibits NFL behavior, and is best described as being near an antiferromagnetic quantum critical point.
Date: April 8, 2003
Creator: Booth, C. H.; Shlyk, L.; Nenkov, K.; Huber, J. G. & De Long, L. E.
Partner: UNT Libraries Government Documents Department

Phenomenological two-gap model for the specific heat of MgB2

Description: The authors show that the specific heat of the superconductor MgB{sub 2} in zero field, for which significant non-BCS features have been reported, can be fitted, essentially within experimental error, over the entire range of temperature to T{sub c} by a phenomenological two-gap model. The resulting gap parameters agree with previous determinations from band-structure calculations, and from various spectroscopic experiments. The determination from specific heat, a bulk property, shows that the presence of two superconducting gaps in MgB{sub 2} is a volume effect.
Date: June 22, 2001
Creator: Bouquet, F.; Wang, Y.; Fisher, R.A.; Hinks, D.G.; Jorgensen, J.D.; Junod, A. et al.
Partner: UNT Libraries Government Documents Department

Measurement of Specific Heat Capacity Using Differential Scanning Calorimeter

Description: This document describes the process used at the Idaho National Laboratory’s (INL) High Temperature Test Laboratory (HTTL) for measuring specific heat capacity using a differential scanning calorimeter (DSC). The document is divided into four sections: Approach, in which the technique is described; Setup, in which the physical system is described; Procedure, in which the testing steps are listed and detailed; and Example Test, in which a typical test is outlined following the steps listed in the Procedure section. Example data, results, photos, and curves are provided throughout the document to assist other users of this system.
Date: November 1, 2008
Creator: Daw, J. E.
Partner: UNT Libraries Government Documents Department

Energetics of Nanomaterials

Description: This project, "Energetics of Nanomaterials," represents a three-year collaboration among Alexandra Navrotsky (UC Davis), Brian Woodfield and Juliana Boerio-Goates (BYU), and Frances Hellman (UC Berkeley). It's purpose has been to explore the differences between bulk materials, nanoparticles, and thin films in term of their thermodynamic properties, with an emphasis on heat capaacities and entropies, as well as enthalpies. the three groups have brought very different expertise and capabilities to the project. Navrotsky is a solid-state chemist and geochemist, with a unique Thermochemistry Facility emphasizing enthalpy of formation measurements by high temperature oxide melt and room temperatue acid solution calorimetry. Boerio-Goates and Woodfield are calorimetry. Hellman is a physicist with expertise in magnetism and heat capacity measurements using microscale "detector on a chip" calorimetric technology that she pioneered. The overarching question of our work is "How does the free energy play out in nanoparticles?", or "How do differences in free energy affect overall nanoparticle behavior?" Because the free energy represents the temperature-dependent balance between the enthalpy of a system and its entropy, there are two separate, but related, components to the experimental investigations: Solution calorimetric measurements provide the energetics and two types of heat capacity measurements the entropy. We use materials that are well characterized in other ways (structurally, magnetically, and chemically), and samples are shared across the collaboration.
Date: January 28, 2005
Creator: Navrotsky, Alexandra; Woodfield, Brian; Boerio-Goates, Juliana & Hellman, Frances
Partner: UNT Libraries Government Documents Department

Lattice vibrations in noncrystalline solids

Description: The specific heat of noncrystalline solids differs from that predicted by the Debye model by amounts much larger than is known for crystalline solids. This deviation is most pronounced at temperatures below 1 deg K. Near 0.1 deg K. the experimental specific heat approaches a linear temperature dependence and is up to 30 times larger than predicted by the Debye model. This paper describes Brillouin scattering experiments, and also measurements of the thermal conductivity in thin glass fibers. This work is aimed at elucidating the nature of the excitations responsible for this large specific heat. It is concluded that Debye phonons have sufficiently long lifetimes to be considered as good normal modes in noncrystalline solids and also that these phonons are the main carriers of heat at low temperatures. (11 figures. 29 references) (auth)
Date: August 1, 1973
Creator: Pohl, R.O.; Love, W.F. & Stephens, R.B.
Partner: UNT Libraries Government Documents Department


Description: The thermodynamic properties for the saturated and superheated phases of sodium are presented in tabular form and as a Mollier diagram. The density, thermal conductivity, viscosity, specific heat, and surface tension of the metal are given by tables and charts. The methods used in determlning the properties are discussed. (auth)
Date: October 1, 1960
Creator: Dunning, E.L.
Partner: UNT Libraries Government Documents Department

Laser-Material Interaction Studies Utilizing the Solid-State Heat Capacity Laser

Description: A variety of laser-material interaction experiments have been conducted at Lawrence Livermore National Laboratory (LLNL) utilizing the solid-state heat capacity laser (SSHCL). For these series of experiments, laser output power is 25kW, on-target laser spot sizes of up to 16 cm by 16 cm square, with air speeds of approximately 100 meters per second flowing across the laser-target interaction surface as shown in Figure 1. The empirical results obtained are used to validate our simulation models.
Date: April 19, 2007
Creator: Yamamoto, R.; Parker, J.; Boley, C.; Cutter, K.; Fochs, S. & Rubenchik, A.
Partner: UNT Libraries Government Documents Department

Evaluating Fenestration Products for Zero-Energy Buildings: Issuesfor Discussion

Description: Computer modeling to determine fenestration product energy properties (U-factor, SHGC, VT) has emerged as the most cost-effective and accurate means to quantify them. Fenestration product simulation tools have been effective in increasing the use of low-e coatings and gas fills in insulating glass and in the widespread use of insulating frame designs and materials. However, for more efficient fenestration products (low heat loss products, dynamic products, products with non-specular optical characteristics, light re-directing products) to achieve widespread use, fenestration modeling software needs to be improved. This paper addresses the following questions: (1) Are the current properties (U, SHGC, VT) calculated sufficient to compare and distinguish between windows suitable for Zero Energy Buildings and conventional window products? If not, what data on the thermal and optical performance, on comfort, and on peak demand of windows is needed. (2) Are the algorithms in the tools sufficient to model the thermal and optical processes? Are specific heat transfer and optical effects not accounted for? Is the existing level of accuracy enough to distinguish between products designed for Zero Energy Buildings? Is the current input data adequate?
Date: July 25, 2006
Creator: Arasteh, Dariush; Curcija, Charlie; Huang, Joe; Huizenga,Charlie & Kohler, Christian
Partner: UNT Libraries Government Documents Department

Dynamic heat capacity of the east model and of a bead-spring polymer model.

Description: In this report we have presented a brief review of the glass transition and one means of characterizing glassy materials: linear and nonlinear thermodynamic oscillatory experiments to extract the dynamic heat capacity. We have applied these methods to the east model (a variation of the Ising model for glass forming systems) and a simple polymeric system via molecular dynamics simulation, and our results match what is seen in experiment. For the east model, since the dynamics are so simple, a mathematical model is developed that matches the simulated dynamics. For the polymeric system, since the system is a simulation, we can instantaneously 'quench' the system - removing all vibrational energy - to separate the vibrational dynamics from dynamics associated with particle rearrangements. This shows that the long-time glassy dynamics are due entirely to the particle rearrangements, i.e. basin jumping on the potential energy landscape. Finally, we present an extension of linear dynamic heat capacity to the nonlinear regime.
Date: October 1, 2011
Creator: McCoy, John Dwane (New Mexico Institute of Mining and Technology, Socorro, NM); Brown, Jonathan R. (New Mexico Institute of Mining and Technology, Socorro, NM) & Adolf, Douglas Brian
Partner: UNT Libraries Government Documents Department

Fast thermometry for superconducting rf cavity testing

Description: Fast readout of strategically placed low heat capacity thermometry can provide valuable information of Superconducting RF (SRF) cavity performance. Such a system has proven very effective for the development and testing of new cavity designs. Recently, several resistance temperature detectors (RTDs) were installed in key regions of interest on a new 9 cell 3.9 GHz SRF cavity with integrated HOM design at FNAL. A data acquisition system was developed to read out these sensors with enough time and temperature resolution to measure temperature changes on the cavity due to heat generated from multipacting or quenching within power pulses. The design and performance of the fast thermometry system will be discussed along with results from tests of the 9 cell 3.9GHz SRF cavity.
Date: June 1, 2007
Creator: Orris, Darryl; Bellantoni, Leo; Carcagno, Ruben H.; Edwards, Helen; Harms, Elvin Robert; Khabiboulline, Timergali N. et al.
Partner: UNT Libraries Government Documents Department

Modeling Antimortar Lethality by a Solid-State Heat-Capacity Laser

Description: We have studied the use of a solid-state heat-capacity laser (SSHCL) in mortar defense. This type of laser, as built at LLNL, produces high-energy pulses with a wavelength of about 1 {micro}m and a pulse repetition rate of 200 Hz. Currently, the average power is about 26 kW. Our model of target interactions includes optical absorption, two-dimensional heat transport in the metal casing and explosive, melting, wind effects (cooling and melt removal), high-explosive reactions, and mortar rotation. The simulations continue until HE initiation is reached. We first calculate the initiation time for a range of powers on target and spot sizes. Then we consider an engagement geometry in which a mortar is fired at an asset defended by a 100-kW SSHCL. Propagation effects such as diffraction, turbulent broadening, scattering, and absorption are calculated for points on the trajectory, by means of a validated model. We obtain kill times and fluences, as functions of the rotation rate. These appear quite feasible.
Date: February 15, 2005
Creator: Boley, C D & Rubenchik, A M
Partner: UNT Libraries Government Documents Department

Transparent Laser Ceramics at Lawrence Livermore National Laboratory (LLNL)

Description: LLNL has been using the largest transparent laser ceramics for the last two years in the solid-state heat capacity laser (SSHCL). The lab is very interested in extending the use of transparent ceramics to other laser applications. In this talk we will discuss work at the laboratory aimed at better understanding the sintering and the criteria needed for good ceramic transparency, the application of transparent ceramics in the SSHCL laser and possible new applications of tailored ceramics.
Date: June 28, 2007
Creator: Soules, T
Partner: UNT Libraries Government Documents Department

CeMIn[sub 5](M=Co,Ir,Rh) heavy fermion superconductors and the utility of high magnetic field.

Description: We review the properties of the recently discovered CeMIn5 (M=Co, Ir, Rh) heavy fermion superconductors and discuss the present state of our understanding of these materials. A particular focus is the role that magnetic fields have played in elucidating the properties of these materials. Specifically, we discuss quantum oscillation measurements on CeMIn5, the influence of applied field on the linear coefficient of specific heat, {gamma}, and the nature of the HT phase diagrams in both the normal and superconducting states of these materials.
Date: January 1, 2001
Creator: Sarrao, John L.,
Partner: UNT Libraries Government Documents Department

Laser Systems for Orbital Debris Removal

Description: The use of a ground based laser for space debris cleaning was investigated by the ORION project in 1996. Since that study the greatest technological advance in the development of high energy pulsed laser systems has taken place within the NIF project at LLNL. The proposed next laser system to follow the NIF at LLNL will be a high rep rate version of the NIF based on diode-pumping rather than flashlamp excitation; the so called 'LIFE' laser system. Because a single 'LIFE' beamline could be built up in a few year time frame, and has performance characteristics relevant to the space debris clearing problem, such a beamline could enable a near term demonstration of space debris cleaning. Moreover, the specifics of debris cleaning make it possible to simplify the LIFE laser beyond what is required for a fusion drive laser, and so substantially reduce its cost. Starting with the requirements for laser intensity on the target, and then considering beam delivery, we will flow back the laser requirements needed for space debris cleaning. Using these derived requirements we will then optimize the pulse duration, the operational regime, and the output pulse energy of the laser with a focus of simplifying its overall design. Anticipated simplifications include operation in the heat capacity regime, eliminating cooling requirements on the laser gain slabs, and relaxing B-integral and birefrigence requirements.
Date: February 5, 2010
Creator: Rubenchik, A M; Barty, C P; Beach, R J; Erlandson, A C & Caird, J A
Partner: UNT Libraries Government Documents Department

Magnetism and superconductivity of uranium and intermetallic compounds

Description: Heat capacity, resistivity, and phonon density of states have been measured on uranium and reported already. Many of the results are on single crystals of purity that has been unavailable before. Some intermetallic compounds have been measured that are in the class of so-called heavy-fermion materials. We present here the latest results along with a discussion of the occurrence of superconductivity or magnetism in these materials.
Date: January 1, 2001
Creator: Cooley, J. C. (Jason C.); Gay, E. C. (Eddie C.); Hanrahan, R. J. (Robert J.); Hults, W. L. (William L.); Lashley, J. C. (Jason C.); Manley, M. E. (Michael E.) et al.
Partner: UNT Libraries Government Documents Department