NASA Astrophysics Data System (ADS)
Zhu, Zun-Lue; Fu, Hong-Zhi; Sun, Jin-Feng; Liu, Yu-Fang; Shi, De-Heng; Xu, Guo-Liang
2009-08-01
The first-principles plane-wave pseudopotential method using the generalized gradient approximation within the framework of density functional theory is applied to anaylse the equilibrium lattice parameters, six independent elastic constants, bulk moduli, thermal expansions and heat capacities of MoSi2. The quasi-harmonic Debye model, using a set of total energy versus cell volume obtained with the plane-wave pseudopotential method, is applied to the study of the elastic properties, thermodynamic properties and vibrational effects. The calculated zero pressure elastic constants are in overall good agreement with the experimental data. The calculated heat capacities and the thermal expansions agree well with the observed values under ambient conditions and those calculated by others. The results show that the temperature has hardly any effect under high pressure.
NASA Astrophysics Data System (ADS)
Wentzcovitch, R. M.; Wu, Z.; Cococcioni, M.; Umemoto, K.
2012-12-01
First principles calculations in mineral physics have contributed decisively to understanding numerous mineral properties of interest in geophysics. Thermal elasticity is the essential property that allows for direct insights into the origin of seismic observables such as velocity discontinuities, gradients, anisotropies, and heterogeneities. Earth materials are challenging to calculations because they contain iron, a strongly correlated element that may undergo spin crossover under pressure, hydrogen, that even in very small amounts can produce can produce anelastic effects, and phases that are stabilized only by anharmonic fluctuations, e.g., CaSiO3-perovskite. I will describe recent progress in methodology that is enabling calculations of thermal elastic properties with unprecedented easiness. I will exemplify its power on iron bearing phases including some undergoing spin crossovers, and provide an updated view of lower mantle velocities.
Optical, elastic and thermal properties of ZB-AlN semiconductor from first-principle calculations
NASA Astrophysics Data System (ADS)
Kumar, V.; Singh, Bhanu P.; Chandra, Satish
2016-12-01
The optical, elastic and thermal properties of zincblende aluminium nitride have been studied. The refractive index, absorption coefficient, reflectivity, dielectric constant, extinction coefficient, and energy-loss spectrum have been calculated using the pseudo-potential method under density functional theory at different pressures. The heat capacity, Debye temperature and phonon frequencies have been calculated using CASTEP code at 0 GPa. The elastic stiffness constants, bulk modulus, Young's modulus, shear modulus and pressure derivatives of elastic constants have also been calculated. The calculated results are compared with the available experimental and theoretical data. Reasonably good agreement has been found between them.
Optical, elastic and thermal properties of ZB-AlN semiconductor from first-principle calculations
NASA Astrophysics Data System (ADS)
Kumar, V.; Singh, Bhanu P.; Chandra, Satish
2017-04-01
The optical, elastic and thermal properties of zincblende aluminium nitride have been studied. The refractive index, absorption coefficient, reflectivity, dielectric constant, extinction coefficient, and energy-loss spectrum have been calculated using the pseudo-potential method under density functional theory at different pressures. The heat capacity, Debye temperature and phonon frequencies have been calculated using CASTEP code at 0 GPa. The elastic stiffness constants, bulk modulus, Young's modulus, shear modulus and pressure derivatives of elastic constants have also been calculated. The calculated results are compared with the available experimental and theoretical data. Reasonably good agreement has been found between them.
Calculated transport properties of CdO: thermal conductivity and thermoelectric power factor
Lindsay, Lucas R.; Parker, David S.
2015-10-01
We present first principles calculations of the thermal and electronic transport properties of the oxide semiconductor CdO. In particular, we find from theory that the accepted thermal conductivity κ value of 0.7 Wm-1K-1 is approximately one order of magnitude too small; our calculations of κ of CdO are in good agreement with recent measurements. We also find that alloying of MgO with CdO is an effective means to reduce the lattice contribution to κ, despite MgO having a much larger thermal conductivity. We further consider the electronic structure of CdO in relation to thermoelectric performance, finding that large thermoelectric powermore » factors may occur if the material can be heavily doped p-type. This work develops insight into the nature of thermal and electronic transport in an important oxide semiconductor.« less
Calculated transport properties of CdO: thermal conductivity and thermoelectric power factor
Lindsay, Lucas R.; Parker, David S.
2015-10-01
We present first principles calculations of the thermal and electronic transport properties of the oxide semiconductor CdO. In particular, we find from theory that the accepted thermal conductivity κ value of 0.7 Wm^{-1}K^{-1} is approximately one order of magnitude too small; our calculations of κ of CdO are in good agreement with recent measurements. We also find that alloying of MgO with CdO is an effective means to reduce the lattice contribution to κ, despite MgO having a much larger thermal conductivity. We further consider the electronic structure of CdO in relation to thermoelectric performance, finding that large thermoelectric power factors may occur if the material can be heavily doped p-type. This work develops insight into the nature of thermal and electronic transport in an important oxide semiconductor.
NASA Astrophysics Data System (ADS)
Bock, Steffen; Bich, Eckard; Vogel, Eckhard; Dickinson, Alan S.; Vesovic, Velisa
2004-05-01
The transport properties of pure carbon dioxide have been calculated from the intermolecular potential using the classical trajectory method. Results are reported in the dilute-gas limit for thermal conductivity and thermomagnetic coefficients for temperatures ranging from 200 K to 1000 K. Three recent carbon dioxide potential energy hypersurfaces have been investigated. Since thermal conductivity is influenced by vibrational degrees of freedom, not included in the rigid-rotor classical trajectory calculation, a correction for vibration has also been employed. The calculations indicate that the second-order thermal conductivity corrections due to the angular momentum polarization (<2%) and velocity polarization (<1%) are both small. Thermal conductivity values calculated using the potential energy hypersurface by Bukowski et al. (1999) are in good agreement with the available experimental data. They underestimate the best experimental data at room temperature by 1% and in the range up to 470 K by 1%-3%, depending on the data source. Outside this range the calculated values, we believe, may be more reliable than the currently available experimental data. Our results are consistent with measurements of the thermomagnetic effect at 300 K only when the vibrational degrees of freedom are considered fully. This excellent agreement for these properties indicates that particularly the potential surface of Bukowski et al. provides a realistic description of the anisotropy of the surface.
Elastic and Thermal Properties of Silicon Compounds from First-Principles Calculations
NASA Astrophysics Data System (ADS)
Hou, Haijun; Zhu, H. J.; Cheng, W. H.; Xie, L. H.
2016-07-01
The structural and elastic properties of V-Si (V3Si, VSi2, V5Si3, and V6Si5) compounds are studied by using first-principles method. The calculated equilibrium lattice parameters and formation enthalpy are in good agreement with the available experimental data and other theoretical results. The calculated results indicate that the V-Si compounds are mechanically stable. Elastic properties including bulk modulus, shear modulus, Young's modulus, and Poisson's ratio are also obtained. The elastic anisotropies of V-Si compounds are investigated via the three-dimensional (3D) figures of directional dependences of reciprocals of Young's modulus. Finally, based on the quasi-harmonic Debye model, the internal energy, Helmholtz free energy, entropy, heat capacity, thermal expansion coefficient, Grüneisen parameter, and Debye temperature of V-Si compounds have been calculated.
Lattice EFT calculation of thermal properties of low-density neutron matter
NASA Astrophysics Data System (ADS)
Abe, T.; Seki, R.
2011-09-01
Thermal properties of low-density neutron matter are investigated by lattice calculation with nuclear effective field theory without pions up to the next-to-leading order. The 1S0 pairing gap is extracted near zero temperature at low densities. We find that the pairing gap is smaller than the BCS approximation with the conventional NN potentials, but not as small as those by various many-body calculations beyond BCS approximation. Our result is consistent with the recent Green's Function Monte Carlo calculation within the statistical errors. The critical temperature of the normal-to-superfluid phase transition and the pairing temperature scale are also extracted at low densities, and the phase diagram is given. We find that the physics of low-density neutron matter is clearly identified as being BCS-BEC crossover.
NASA Astrophysics Data System (ADS)
Vila, F. D.; Rehr, J. J.
Effects of thermal vibrations are essential to obtain a more complete understanding of the properties of complex materials. For example, they are important in the analysis and simulation of x-ray absorption spectra (XAS). In previous work we introduced an ab initio approach for a variety of vibrational effects, such as crystallographic and XAS Debye-Waller factors, Debye and Einstein temperatures, and thermal expansion coefficients. This approach uses theoretical dynamical matrices from which the locally-projected vibrational densities of states are obtained using a Lanczos recursion algorithm. In this talk I present recent improvements to our implementation, which permit simulations of more complex materials with up to two orders of magnitude larger simulation cells. The method takes advantage of parallelization in calculations of the dynamical matrix with VASP. To illustrate these capabilities we discuss two problems of considerable interest: negative thermal expansion in ZrW2O8; and local inhomogeneities in the elastic properties of supported metal nanoparticles. Both cases highlight the importance of a local treatment of vibrational properties. Supported by DOE Grant DE-FG02-03ER15476, with computer support from DOE-NERSC.
Chang, Hsi-Hung; Hwang, Chi-Chuan; Shen, Yue-Ling
2011-06-01
Thermomechanical vibration of ultrathin, self-supported copper films due to thermal fluctuations is studied via the molecular dynamics simulation at room temperature. The elastodynamic theory with pre-stress is adopted to extract the physical properties of the films by comparing with the molecular dynamics data. The edge-clamped circular films consist of several atomic layers of fcc copper with the [100] direction normal to the film surface. From the time-history trajectories of atoms and their Fourier frequency spectrums, it was found that the fundamental resonant frequency non-monotonically varies with the film thickness due to the existence of residual stress in the film. Multiple resonant modes are adopted for modulus calculation and residual stress determination. The value of Young's modulus increases with increasing thickness of the film and the residual stress decreases with increasing thickness. Thicker films exhibit less residual stress, indicating the equilibrium distance between copper atoms changes with the film thickness.
NASA Technical Reports Server (NTRS)
Cleghorn, T. F.
1994-01-01
MIPROPS is a set of programs which gives the thermophysical and transport properties of selected fluids. Although these programs are written in FORTRAN 77 for implementation on microcomputers, they are direct translations of interactive FORTRAN IV programs which were originally developed for large mainframes. MIPROPS calculates the properties of fluids in both the liquid and vapor states over a wide range of temperatures and pressures. The fluids included are: helium, parahydrogen, nitrogen, oxygen, argon, nitrogen trifluoride, methane, ethylene, ethane, propane, and iso- and normal butane. All of the programs except for the helium program utilize the same mathematical model of the equation of state. A separate program was necessary for helium, as the model for the helium thermodynamic surface is of a different form. The input variables are any two of pressure, density, or temperature for the single phase regions, and either pressure or temperature for the saturated liquid or vapor states. The output is pressure, density, temperature, internal energy, enthalpy, entropy, specific heat capacities, and speed of sound. In addition, viscosity, thermal conductivity, and dielectric constants are calculated for most of the fluids. The user can select either a single point or a table of output values for a specified temperature range, and can display the data either in engineering or metric units. This machine independent FORTRAN 77 program was implemented on an IBM PC XT with an MS-DOS 3.21 operating system. It has a memory requirement of approximately 100K. The program was developed in 1986.
NASA Technical Reports Server (NTRS)
Cleghorn, T. F.
1994-01-01
MIPROPS is a set of programs which gives the thermophysical and transport properties of selected fluids. Although these programs are written in FORTRAN 77 for implementation on microcomputers, they are direct translations of interactive FORTRAN IV programs which were originally developed for large mainframes. MIPROPS calculates the properties of fluids in both the liquid and vapor states over a wide range of temperatures and pressures. The fluids included are: helium, parahydrogen, nitrogen, oxygen, argon, nitrogen trifluoride, methane, ethylene, ethane, propane, and iso- and normal butane. All of the programs except for the helium program utilize the same mathematical model of the equation of state. A separate program was necessary for helium, as the model for the helium thermodynamic surface is of a different form. The input variables are any two of pressure, density, or temperature for the single phase regions, and either pressure or temperature for the saturated liquid or vapor states. The output is pressure, density, temperature, internal energy, enthalpy, entropy, specific heat capacities, and speed of sound. In addition, viscosity, thermal conductivity, and dielectric constants are calculated for most of the fluids. The user can select either a single point or a table of output values for a specified temperature range, and can display the data either in engineering or metric units. This machine independent FORTRAN 77 program was implemented on an IBM PC XT with an MS-DOS 3.21 operating system. It has a memory requirement of approximately 100K. The program was developed in 1986.
NASA Astrophysics Data System (ADS)
Mebrouki, M.; Ouahrani, T.; Çiftci, Y. Öztekin
2016-07-01
Using a toolkit of theoretical techniques comprising ab initio density functional theory calculations and quasiharmonic approximation, we investigate temperature dependence of dynamical properties of BaVO_3 perovskite. This interest is triggered by the fact that, recently, it was possible to synthesize a BaVO_3 perovskite, in a cubic phase, at high pressure and temperature. First-principle calculations are achieved thanks to recent development in numerical facilities, especially phonon dispersion curves which are then fully obtained. Elastic constants of the compound are dependent on temperature due to the inevitable anharmonic effects in solids. We show that at low temperature, the full account of the thermal effects incorporating the phonon densities and Sommerfeld model is more appropriate to calculate the thermal properties of a metal.
Calculated elastic and thermal properties of MGO at high pressures and temperatures
NASA Astrophysics Data System (ADS)
Isaak, Donald G.; Cohen, Ronald E.; Mehl, Michael J.
1990-05-01
Using the potential-induced breathing model, we calculate the pressure and temperature dependence of the thermoelastic properties of MgO. These calculations represent the first attempt to obtain a consistent set of thermodynamic elastic moduli for an oxide from an ab initio model over a wide range of pressure and temperature. By assuming the quasi-harmonic approximation for the free energies, we find excellent agreement between the temperature dependence of calculated elastic moduli and those obtained from experiments. Comparison of the calculated athermal and isothermal elastic moduli shows approximations using athermal values to be unreliable at high temperature. The elastic moduli for MgO are presented for pressures and temperatures appropriate for the lower mantle, a regime in which elastic moduli cannot be obtained by direct measurement.
Tight binding calculations of vibrational and thermal properties of amorphous silicon
NASA Astrophysics Data System (ADS)
Mehl, Michael; Feldman, Joseph; Papaconstantopoulos, Dimitris; Bernstein, Noam
2006-03-01
By displacing atoms by different amounts and computing atomic forces within the NRL tight binding method we obtain all second order (harmonic) and some third order (anharmonic) coupling constants of a 1000 atom TB-relaxed Wooten CRN model of amorphous silicon. The harmonic force constant results allow us to study various properties including vibrational density of states, dynamic structure factors, specific heat and thermal conductivity within Kubo theory. We shall present results of these applications and compare to experiment and previous work based on the Stillinger Weber potential.
NASA Astrophysics Data System (ADS)
Tsuchiya, Yooko; Yoshii, Noriyuki; Iwatsubo, Tetsushiro
2004-08-01
Since heat storage technology contributes greatly to the effective use of energy, we are attempting to develop latent heat storage materials. If computer simulations enable the estimation of material properties prior to experiments, they will provide us with very effective tools for the development of new materials. We use molecular dynamics calculations to predict the melting points and latent heats of fusion, which are crucial thermal properties for evaluating the suitability of heat-storage materials. As the object of calculation, poly(vinyl alcohol) (PVA) was chosen, because polymer materials are effective in that they can be made to cover all temperature ranges by changing the molecular weight. The melting points were determined from the volume change, and the latent heats of fusion were determined from the internal energy. As for these calculations, it was ascertained that these thermal properties were suitable values in comparison with the results of actual calorimetry. From the comparative calculation of the polymer consistent force field (PCFF) and optimized potentials for liquid simulations (OPLS) force field, it was shown that the intermolecular potential could be simplified. Moreover, the stability of the structural isomer of PVA and the state of the hydrogen bond were evaluated, because a strong intermolecular bond leads to structural stability and a high melting temperature.
NASA Astrophysics Data System (ADS)
Nagabalasubramanian, P. B.; Periandy, S.; Karabacak, Mehmet; Govindarajan, M.
2015-06-01
The solid phase FT-IR and FT-Raman spectra of 4-vinylcyclohexene (abbreviated as 4-VCH) have been recorded in the region 4000-100 cm-1. The optimized molecular geometry and vibrational frequencies of the fundamental modes of 4-VCH have been precisely assigned and analyzed with the aid of structure optimizations and normal coordinate force field calculations based on density functional theory (DFT) method at 6-311++G(d,p) level basis set. The theoretical frequencies were properly scaled and compared with experimentally obtained FT-IR and FT-Raman spectra. Also, the effect due the substitution of vinyl group on the ring vibrational frequencies was analyzed and a detailed interpretation of the vibrational spectra of this compound has been made on the basis of the calculated total energy distribution (TED). The time dependent DFT (TD-DFT) method was employed to predict its electronic properties, such as electronic transitions by UV-Visible analysis, HOMO and LUMO energies, molecular electrostatic potential (MEP) and various global reactivity and selectivity descriptors (chemical hardness, chemical potential, softness, electrophilicity index). Stability of the molecule arising from hyper conjugative interaction, charge delocalization has been analyzed using natural bond orbital (NBO) analysis. Atomic charges obtained by Mulliken population analysis and NBO analysis are compared. Thermodynamic properties (heat capacity, entropy and enthalpy) of the title compound at different temperatures are also calculated.
NASA Astrophysics Data System (ADS)
Hamioud, L.; Boumaza, A.; Touam, S.; Meradji, H.; Ghemid, S.; El Haj Hassan, F.; Khenata, R.; Omran, S. Bin
2016-06-01
The present paper aims to study the structural, electronic, optical and thermal properties of the boron nitride (BN) and BAs bulk materials as well as the BNxAs1-x ternary alloys by employing the full-potential-linearised augmented plane wave method within the density functional theory. The structural properties are determined using the Wu-Cohen generalised gradient approximation that is based on the optimisation of the total energy. For band structure calculations, both the Wu-Cohen generalised gradient approximation and the modified Becke-Johnson of the exchange-correlation energy and potential, respectively, are used. We investigated the effect of composition on the lattice constants, bulk modulus and band gap. Deviations of the lattice constants and the bulk modulus from the Vegard's law and the linear concentration dependence, respectively, were observed for the alloys where this result allows us to explain some specific behaviours in the electronic properties of the alloys. For the optical properties, the calculated refractive indices and the optical dielectric constants were found to vary nonlinearly with the N composition. Finally, the thermal effect on some of the macroscopic properties was predicted using the quasi-harmonic Debye model in which the lattice vibrations are taken into account.
Roger M. Rowell
2005-01-01
The traditional question at the start of a class on thermal properties of wood is, âDoes wood burn?â The students have all been warmed in front of a wood-burning fire before, so they are sure the answer is yesâbut since the professor asked the question, there must be some hidden trick to the obvious answer. Going with their experience, their answer is âyes, wood burns...
NASA Astrophysics Data System (ADS)
Kurban, Mustafa; Erkoç, Şakir
2017-04-01
Surface and core formation, thermal and electronic properties of ternary cubic CdZnTe clusters are investigated by using classical molecular dynamics (MD) simulations and density functional theory (DFT) calculations. In this work, MD simulations of the CdZnTe clusters are performed by means of LAMMPS by using bond order potential (BOP). MD simulations are carried out at different temperatures to study the segregation phenomena of Cd, Zn and Te atoms, and deviation of clusters and heat capacity. After that, using optimized geometries obtained, excess charge on atoms, dipole moments, highest occupied molecular orbitals, lowest unoccupied molecular orbitals, HOMO-LUMO gaps (Eg) , total energies, spin density and the density of states (DOS) have been calculated with DFT. Simulation results such as heat capacity and segregation formation are compared with experimental bulk and theoretical results.
NASA Astrophysics Data System (ADS)
Chelli, S.; Meradji, H.; Amara Korba, S.; Ghemid, S.; El Haj Hassan, F.
2014-12-01
The structural, electronic thermodynamic and thermal properties of BaxSr1-xTe ternary mixed crystals have been studied using the ab initio full-potential linearized augmented plane wave (FP-LAPW) method within density functional theory (DFT). In this approach, the Perdew-Burke-Ernzerhof-generalized gradient approximation (PBE-GGA) was used for the exchange-correlation potential. Moreover, the recently proposed modified Becke Johnson (mBJ) potential approximation, which successfully corrects the band-gap problem was also used for band structure calculations. The ground-state properties are determined for the cubic bulk materials BaTe, SrTe and their mixed crystals at various concentrations (x = 0.25, 0.5 and 0.75). The effect of composition on lattice constant, bulk modulus and band gap was analyzed. Deviation of the lattice constant from Vegard's law and the bulk modulus from linear concentration dependence (LCD) were observed for the ternary BaxSr1-xTe alloys. The microscopic origins of the gap bowing were explained by using the approach of Zunger and co-workers. On the other hand, the thermodynamic stability of these alloys was investigated by calculating the excess enthalpy of mixing, ΔHm as well as the phase diagram. It was shown that these alloys are stable at high temperature. Thermal effects on some macroscopic properties of BaxSr1-xTe alloys were investigated using the quasi-harmonic Debye model, in which the phononic effects are considered.
Erba, Alessandro; Maul, Jefferson; Civalleri, Bartolomeo
2016-01-31
An ab initio quantum-mechanical theoretical framework is presented to compute the thermal properties of molecular crystals. The present strategy combines dispersion-corrected density-functional-theory (DFT-D), harmonic phonon dispersion, quasi-harmonic approximation to the lattice dynamics for thermal expansion and thermodynamic functions, and quasi-static approximation for anisotropic thermo-elasticity. The proposed scheme is shown to reliably describe thermal properties of the urea molecular crystal by a thorough comparison with experimental data.
First-principle calculation on mechanical and thermal properties of B2-NiSc with point defects
NASA Astrophysics Data System (ADS)
Yuan, Zhipeng; Cui, Hongbao; Guo, Xuefeng
2017-01-01
Using the first-principles plane-wave pseudo-potential method based on density functional theory, the effect of vacancy and anti-position defect on the mechanical and thermal properties of B2-NiSc intermetallics were discussed in detail. Several parameters, such as the shear modulus, bulk modulus, modulus of elasticity, C 11–C 11, the Debye temperature and Poisson's ratio, have been calculated to evaluate the effect of vacancy and anti-position defect on the hardness, ductility and thermal properties of B2-NiSc intermetallics. The results show that VNi, ScNi, VSc and NiSc the four point defects all make the crystal hardness decrease and improve plasticity of B2-NiSc intermetallics. The entropy, enthalpy and free energy of VNi, ScNi, VSc and NiSc are monotonously changed as temperature changes. From the perspective of free energy, NiSc is the most stable, while ScNi is the most unstable. Debye temperature of NiSc intermetallics with four different point defects shows VNi, ScNi, VSc and NiSc the four point defects all reduce the stability of B2-NiSc intermetallics. Project supported by the National Natural Science Foundation of China (Nos. 51301063, 51571086) and the Talent Introduction Foundation of Henan Polytechnic University (No. Y-2009).
PHYSICOCHEMICAL PROPERTY CALCULATIONS
Computer models have been developed to estimate a wide range of physical-chemical properties from molecular structure. The SPARC modeling system approaches calculations as site specific reactions (pKa, hydrolysis, hydration) and `whole molecule' properties (vapor pressure, boilin...
PHYSICOCHEMICAL PROPERTY CALCULATIONS
Computer models have been developed to estimate a wide range of physical-chemical properties from molecular structure. The SPARC modeling system approaches calculations as site specific reactions (pKa, hydrolysis, hydration) and `whole molecule' properties (vapor pressure, boilin...
Abe, T.; Seki, R.
2009-05-15
Thermal properties of low-density neutron matter are investigated by determinantal quantum Monte Carlo lattice calculations on 3+1 dimensional cubic lattices. Nuclear effective field theory (EFT) is applied using the pionless single- and two-parameter neutron-neutron interactions, determined from the {sup 1}S{sub 0} scattering length and effective range. The determination of the interactions and the calculations of neutron matter are carried out consistently by applying EFT power counting rules. The thermodynamic limit is taken by the method of finite-size scaling, and the continuum limit is examined in the vanishing lattice filling limit. The {sup 1}S{sub 0} pairing gap at T{approx_equal}0 is computed directly from the off-diagonal long-range order of the spin pair-pair correlation function and is found to be approximately 30% smaller than BCS calculations with the conventional nucleon-nucleon potentials. The critical temperature T{sub c} of the normal-to-superfluid phase transition and the pairing temperature scale T* are determined, and the temperature-density phase diagram is constructed. The physics of low-density neutron matter is clearly identified as being a BCS-Bose-Einstein condensation crossover.
NASA Technical Reports Server (NTRS)
Wanser, K. H.
1981-01-01
Silicon has interesting harmonic and anharmonic properties such as the low lying transverse acoustic modes at the X and L points of the Brillouin zone, negative Gruneisen parameters, negative thermal expansion and anomalous acoustic attenuation. In an attempt to understand these properties, a lattice dynamical model employing long range, nonlocal, dipole-dipole interactions was developed. Analytic expression for the Gruneisen parameters of several modes are presented. These expressions explain how the negative Gruneisen parameters arise. This model is applied to the calculation of the thermal expansion of silicon from 5K to 1700K. The thermoelastic contribution to the acoustic attenuation of silicon is computed from 1 to 300 K. Strong attenuation anomalies associated with negative thermal expansion are found in the vicinity of 17K and 125K.
NASA Astrophysics Data System (ADS)
Boumaza, A.; Ghemid, S.; Chouahda, Z.; Meradji, H.; El Haj Hassan, F.
2012-09-01
The structural, electronic, elastic, thermal and thermodynamic properties of Zn1-xBexTe semiconductor alloys have been investigated using the full-potential linearized augmented plane wave method within density functional theory. We use both the Wu-Cohen and the Engel-Vosko generalized gradient approximations of the exchange-correlation energy that are based on the optimization of the total energy and the corresponding potential, respectively. The ground state properties such as lattice constants, bulk modulus and elastic constants are in good agreement with numerous experimental and theoretical data. The calculated band structures show that the band gap undergoes a direct to indirect transition at a given concentration. A regular-solution model is used to investigate the thermodynamic stability of the alloy that mainly indicates a phase miscibility gap. In addition, the quasi-harmonic Debye model is applied to determine the thermal properties of the alloy.
NASA Astrophysics Data System (ADS)
Ben hassen, C.; Boujelbene, M.; Bahri, M.; Zouari, N.; Mhiri, T.
2014-09-01
The present paper undertakes the study of a new hybrid compound [2-CH3C6H4NH3]2SeO4 characterized by the X-ray diffraction, IR, DFT calculation, TG-DTA, DSC and electrical conductivity. This new organic-inorganic hybrid compound crystallizes in the monoclinic system with P21/c space group and the following parameters a = 14.821 (5) Å; b = 16.245 (5) Å; c = 6.713 (5) Å; ß = 102.844 (5)°, Z = 4 and V = 1575.8 (14) Å3. The atomic arrangement can be described as isolated tetrahedral SeO42- connected with the organic groups by means of Nsbnd H⋯O hydrogen bonds to form infinite sinusoidal chains in the c-direction. BHHLYP/6-311g** method was used to determine the harmonic frequencies for two optimized cluster structures. The calculated modes were animated using the Molden graphical package to give tentative assignments of the observed IR spectra. Thermal analysis of the title compound does not indicate the occurrence of a phase transition in the temperature range of 300-650 K. Dielectric study of this compound has been measured, in order to determine the conductivity. The conductivity relaxation parameters associated with some H+ conduction have been determined from an analysis of the M″/M″max spectrum measured in a wide temperature range.
NASA Astrophysics Data System (ADS)
Łuszczak, Katarzyna; Persano, Cristina; Braun, Jean; Stuart, Finlay
2016-04-01
Low temperature thermochronometers are mainly used to decipher crustal denudation histories. However, these methods provide cooling paths that can be confidently translated into denudation rates only if the geothermal gradient at the time of cooling is known. As past geothermal gradients cannot be directly measured, they can be sometimes estimated from the thermochronometric data, when borehole data or vertical profiles are available. In all the other cases, our knowledge of the spatial and temporal variation of the geothermal gradient is limited. It is common practice in many thermochronometric studies to calculate the amounts and rates of denudation through time assuming a constant, average present-day value for the geothermal gradient. In this study, using 1D and 3D (Pecube) models, we have investigated the impact of crustal heat production and thermal conductivity (κ) on the estimated values of denudation, taking central west Britain as our case study. In this region, the apatite fission track (AFT) ages describe a characteristic U-shape pattern with early Cenozoic ages in the English Lake District and older, up to 200 Ma ages northwards in S Scotland, and southwards in N Wales. This pattern, which could be referred to a difficult to justify localized, differential denudation, can actually be best explained as an effect of the spatially variable heat production. The insulating effect of low thermal conductivity Upper Mesozoic sedimentary rocks, composed largely by chalk, increases the palaeogeothermal gradient and reduces the amounts of denudation, especially in the Lake District, where a heat productive granite batholith increases the local heat flow. The observed AFT age pattern may be, therefore, explained without any significant variation of early Cenozoic denudation across central west Britain. If the thermal proprieties of the crust are not taken into account, denudation in the Lake District will be overestimated by a factor of 1.5-2.0 and the mechanisms
NASA Astrophysics Data System (ADS)
Ness, H.; Stella, L.; Lorenz, C. D.; Kantorovich, L.
2017-04-01
We use a generalised Langevin equation scheme to study the thermal transport of low dimensional systems. In this approach, the central classical region is connected to two realistic thermal baths kept at two different temperatures [H. Ness et al., Phys. Rev. B 93, 174303 (2016)]. We consider model Al systems, i.e., one-dimensional atomic chains connected to three-dimensional baths. The thermal transport properties are studied as a function of the chain length N and the temperature difference Δ T between the baths. We calculate the transport properties both in the linear response regime and in the non-linear regime. Two different laws are obtained for the linear conductance versus the length of the chains. For large temperatures (T ≳500 K) and temperature differences (Δ T ≳500 K), the chains, with N >18 atoms, present a diffusive transport regime with the presence of a temperature gradient across the system. For lower temperatures (T ≲500 K) and temperature differences (Δ T ≲400 K), a regime similar to the ballistic regime is observed. Such a ballistic-like regime is also obtained for shorter chains (N ≤15 ). Our detailed analysis suggests that the behaviour at higher temperatures and temperature differences is mainly due to anharmonic effects within the long chains.
Ness, H; Stella, L; Lorenz, C D; Kantorovich, L
2017-04-28
We use a generalised Langevin equation scheme to study the thermal transport of low dimensional systems. In this approach, the central classical region is connected to two realistic thermal baths kept at two different temperatures [H. Ness et al., Phys. Rev. B 93, 174303 (2016)]. We consider model Al systems, i.e., one-dimensional atomic chains connected to three-dimensional baths. The thermal transport properties are studied as a function of the chain length N and the temperature difference ΔT between the baths. We calculate the transport properties both in the linear response regime and in the non-linear regime. Two different laws are obtained for the linear conductance versus the length of the chains. For large temperatures (T≳500 K) and temperature differences (ΔT≳500 K), the chains, with N>18 atoms, present a diffusive transport regime with the presence of a temperature gradient across the system. For lower temperatures (T≲500 K) and temperature differences (ΔT≲400 K), a regime similar to the ballistic regime is observed. Such a ballistic-like regime is also obtained for shorter chains (N≤15). Our detailed analysis suggests that the behaviour at higher temperatures and temperature differences is mainly due to anharmonic effects within the long chains.
NASA Astrophysics Data System (ADS)
Habershon, Scott
2013-09-01
We introduce a new approach for calculating quantum time-correlation functions and time-dependent expectation values in many-body thermal systems; both electronically adiabatic and non-adiabatic cases can be treated. Our approach uses a path integral simulation to sample an initial thermal density matrix; subsequent evolution of this density matrix is equivalent to solution of the time-dependent Schrödinger equation, which we perform using a linear expansion of Gaussian wavepacket basis functions which evolve according to simple classical-like trajectories. Overall, this methodology represents a formally exact approach for calculating time-dependent quantum properties; by introducing approximations into both the imaginary-time and real-time propagations, this approach can be adapted for complex many-particle systems interacting through arbitrary potentials. We demonstrate this method for the spin Boson model, where we find good agreement with numerically exact calculations. We also discuss future directions of improvement for our approach with a view to improving accuracy and efficiency.
Thermal radiative properties: Coatings.
NASA Technical Reports Server (NTRS)
Touloukian, Y. S.; Dewitt, D. P.; Hernicz, R. S.
1972-01-01
This volume consists, for the most part, of a presentation of numerical data compiled over the years in a most comprehensive manner on coatings for all applications, in particular, thermal control. After a moderately detailed discussion of the theoretical nature of the thermal radiative properties of coatings, together with an overview of predictive procedures and recognized experimental techniques, extensive numerical data on the thermal radiative properties of pigmented, contact, and conversion coatings are presented. These data cover metallic and nonmetallic pigmented coatings, enamels, metallic and nonmetallic contact coatings, antireflection coatings, resin coatings, metallic black coatings, and anodized and oxidized conversion coatings.
Thermal Properties Measurement Report
Carmack, Jon; Braase, Lori; Papesch, Cynthia; Hurley, David; Tonks, Michael; Zhang, Yongfeng; Gofryk, Krzysztof; Harp, Jason; Fielding, Randy; Knight, Collin; Meyer, Mitch
2015-08-01
The Thermal Properties Measurement Report summarizes the research, development, installation, and initial use of significant experimental thermal property characterization capabilities at the INL in FY 2015. These new capabilities were used to characterize a U_{3}Si_{2} (candidate Accident Tolerant) fuel sample fabricated at the INL. The ability to perform measurements at various length scales is important and provides additional data that is not currently in the literature. However, the real value of the data will be in accomplishing a phenomenological understanding of the thermal conductivity in fuels and the ties to predictive modeling. Thus, the MARMOT advanced modeling and simulation capability was utilized to illustrate how the microstructural data can be modeled and compared with bulk characterization data. A scientific method was established for thermal property measurement capability on irradiated nuclear fuel samples, which will be installed in the Irradiated Material Characterization Laboratory (IMCL).
Thermal properties of nanofluids.
Philip, John; Shima, P D
2012-11-15
Colloidal suspensions of fine nanomaterials in the size range of 1-100 nm in carrier fluids are known as nanofluids. For the last one decade, nanofluids have been a topic of intense research due to their enhanced thermal properties and possible heat transfer applications. Miniaturization and increased operating speeds of gadgets warranted the need for new and innovative cooling concepts for better performance. The low thermal conductivity of conventional heat transfer fluid has been a serious impediment for improving the performance and compactness of engineering equipments. Initial studies on thermal conductivity of suspensions with micrometer-sized particles encountered problems of rapid settling of particles, clogging of flow channels and increased pressure drop in the fluid. These problems are resolved by using dispersions of fine nanometer-sized particles. Despite numerous experimental and theoretical studies, it is still unclear whether the thermal conductivity enhancement in nanofluids is anomalous or within the predictions of effective medium theory. Further, many reports on thermal conductivity of nanofluids are conflicting due to the complex issues associated with the surface chemistry of nanofluids. This review provides an overview of recent advances in the field of nanofluids, especially the important material properties that affect the thermal properties of nanofluids and novel approaches to achieve extremely high thermal conductivities. The background information is also provided for beginners to better understand the subject.
NASA Astrophysics Data System (ADS)
Guezlane, M.; Baaziz, H.; El Haj Hassan, F.; Charifi, Z.; Djaballah, Y.
2016-09-01
Density functional theory (DFT) based on the full-potential linearized augmented plane wave (FP-LAPW) method is used to investigate the structural, electronic, magnetic and thermal properties of Co2CrxFe1-xX (X=Al, Si) full Heusler alloys, with L21 structure. The structural properties and spin magnetic moments are investigated by the generalized gradient approximations (GGA) minimizing the total energy. For band structure calculations, GGA, the Engel-Vosko generalized gradient approximation (EVGGA) and modified Becke-Johnson (mBJ) schemes are used. Results of density of states (DOS) and band structures show that these alloys are half-metallic ferromagnets (HMFS). A regular-solution model has been used to investigate the thermodynamic stability of the compounds Co2CrxFe1-xX that indicates a phase miscibility gap. The thermal effects using the quasi-harmonic Debye model are investigated within the lattice vibrations. The temperature and pressure effects on the heat capacities, Debye temperatures and entropy are determined from the non-equilibrium Gibbs functions.
NASA Astrophysics Data System (ADS)
Drablia, S.; Boukhris, N.; Boulechfar, R.; Meradji, H.; Ghemid, S.; Ahmed, R.; Omran, S. Bin; El Haj Hassan, F.; Khenata, R.
2017-10-01
The alkaline earth metal chalcogenides are being intensively investigated because of their advanced technological applications, for example in photoluminescent devices. In this study, the structural, electronic, thermodynamic and thermal properties of the BaSe1‑x Te x alloys at alloying composition x = 0, 0.25, 0.50, 0.75 and 1 are investigated. The full potential linearized augmented plane wave plus local orbital method designed within the density functional theory was used to perform the total energy calculations. In this research work the effect of the composition on the results of the parameters and bulk modulus as well as on the band gap energy is analyzed. From our results, we found a deviation of the obtained results for the lattice constants from Vegard’s law as well as a deviation of the value of the bulk modulus from the linear concentration dependence. We also carried out a microscopic analysis of the origin of the band gap energy bowing parameter. Furthermore, the thermodynamic stability of the considered alloys was explored through the measurement of the miscibility critical temperature. The quasi-harmonic Debye model, as implemented in the Gibbs code, was used to predict the thermal properties of the BaSe1‑x Te x alloys, and these investigations comprise our first theoretical predictions concerning the BaSe1‑x Te x alloys.
LMR thermal hydraulics calculations in the US
Dunn, F.E.; Malloy, D.J.; Mohr, D.
1987-04-27
A wide range of thermal hydraulics computer codes have been developed by various organizations in the US. These codes cover an extensive range of purposes from within-assembly-wise pin temperature calculations to plant wide transient analysis. The codes are used for static analysis, for analysis of protected anticipated transients, and for analysis of a wide range of unprotected transients for the more recent inherently safe LMR designs. Some of these codes are plant-specific codes with properties of a specific plant built into them. Other codes are more general and can be applied to a number of plants or designs. These codes, and the purposes for which they have been used, are described.
NASA Astrophysics Data System (ADS)
Zhou, Bo; Su, Qing; He, De-Yan
2009-11-01
Using a first-principles approach based on density functional theory, this paper studies the electronic and dynamical properties of β-V2O5. A smaller band gap and much wider split-off bands have been observed in comparison with α-V2O5. The Raman- and infrared-active modes at the Γ point of the Brillouin zone are evaluated with LO/TO splitting, where the symbol denotes the longitudinal and transverse optical model. The nonresonant Raman spectrum of a β-V2O5 powder sample is also computed, providing benchmark theoretical results for the assignment of the experimental spectrum. The computed spectrum agrees with the available experimental data very well. This calculation helps to gain a better understanding of the transition from α- to β-V2O5.
NASA Astrophysics Data System (ADS)
Yang, Kuo; Zhang, Ji-Ping
2009-05-01
With the strong-field scheme and trigonal bases, the complete d3 energy matrix in a trigonally distorted cubic-field has been constructed. By diagonalizing this matrix, the energy spectrum of YGG:Cr3+ at normal pressure and low temperature has been calculated. The g factor of the ground-state has been evaluated in terms of the energy spectrum. At the same time, by using the wavefunctions obtained from diagonalizing the complete d3 energy matrix and Thermal Shifts theory, we calculate the thermal shifts of the sharp lines of YGG:Cr3+ and determine the relevant parameters. The calculated results are all in good agreement with the optical-spectrum and EPR experimental data. It is demonstrated that the obtained wavefunctions and the values of parameters are reasonable.
NASA Technical Reports Server (NTRS)
Gupta, Roop N.; Yos, Jerrold M.; Thompson, Richard A.
1989-01-01
Reaction rate coefficients and thermodynamic and transport properties are provided for the 11-species air model which can be used for analyzing flows in chemical and thermal nonequilibrium. Such flows will likely occur around currently planned and future hypersonic vehicles. Guidelines for determining the state of the surrounding environment are provided. Approximate and more exact formulas are provided for computing the properties of partially ionized air mixtures in such environments.
Thermal Properties of Damocloids
NASA Astrophysics Data System (ADS)
Jewitt, David; Fernandez, Yanga
2005-06-01
We propose to detect the thermal emission from 16 Damocloids. These are apparent asteroids on high-inclination and high-eccentricity orbits that are the dormant or extinct analogs to the Halley-Family (HF) and Long-Period (LP) comets. As such the Damocloids provide a way to study the physical properties of these cometary nuclei by proxy. Normally a HF or LP comet is active to very large heliocentric distances, thus making study of its nucleus problematic. So far we know fundamental properties of only a handful of these comets. Our primary goal is to sample the albedo and size distribution of the Damocloids by using complimentary visible-wavelength observations in concert with the proposed mid-IR program here. By sampling a large fraction of the entire known population of Damocloids, we will be able to make comparisons with the physical properties of both active and extinct Jupiter-family comets. We will look for differences that could be caused by the different evolutionary histories suffered by the two classes of comets. In addition we will search for indications of current and historical cometary activity. Deviations of the object's profile from a point source would indicate remnant low-level outgassing and dust ejection, while dust trails would suggest activity in the near past. Our program represents a first step in exploring this class of objects in the context of Solar System evolution.
Thermal properties of heterogeneous grains
NASA Technical Reports Server (NTRS)
Lien, David J.
1988-01-01
Cometary dust is not spherical nor homogeneous, yet these are the assumptions used to model its thermal, optical, and dynamical properties. To better understand the effects of heterogeneity on the thermal and optical properties of dust grains, the effective dielectric constant for an admixture of magnetite and a silicate were calculated using two different effective medium theories: the Maxwell-Garnett theory and the Bruggeman theory. In concept, the MG theory describes the effective dielectric constant of a matrix material into which is embedded a large number of very small inclusions of a second material. The Bruggeman theory describes the dielectric constant of a well mixed aggregate of two or more types of materials. Both theories assume that the individual particles are much smaller than the wavelength of the incident radiation. The refractivity for a heterogeneous grain using the MG theory is very similar to the refractivity of the matrix material, even for large volume fractions of the inclusion. The equilibrium grain temperature for spherical particles sized from .001 to 100 microns in radius at 1 astronomical unit from the sun was calculated. Further explanation is given.
NASA Technical Reports Server (NTRS)
Gupta, Roop N.; Yos, Jerrold M.; Thompson, Richard A.; Lee, Kam-Pui
1990-01-01
Reaction rate coefficients and thermodynamic and transport properties are reviewed and supplemented for the 11-species air model which can be used for analyzing flows in chemical and thermal nonequilibrium up to temperatures of 3000 K. Such flows will likely occur around currently planned and future hypersonic vehicles. Guidelines for determining the state of the surrounding environment are provided. Curve fits are given for the various species properties for their efficient computation in flowfield codes. Approximate and more exact formulas are provided for computing the properties of partially ionized air mixtures in a high energy environment. Limitations of the approximate mixing laws are discussed for a mixture of ionized species. An electron number-density correction for the transport properties of the charged species is obtained. This correction has been generally ignored in the literature.
1979-11-23
electrical energy. The theory involved in computing the thermal resistivity using the thermal needle method is presented in Appendix C. i The thermal...thermal needle , consist- ing of a stainless steel hypodermic tubing which contains iOR NATIONAL. ,NO. FN-TR-29 23 a heater element and a thermocouple...22 3.1 Thermal Needle ...................................... 22 3.2 Test Procedure ...................................... 23 3.3 Results
NASA Astrophysics Data System (ADS)
Dai, Xian-Qi; Zhao, Jian-Hua; Sun, Yong-Can; Wei, Shu-Yi; Wei, Guo-Hong
2010-09-01
The atomic and electronic structures of Tl and In on Si(111) surfaces are investigated using the first-principles total energy calculations. Total energy optimizations show that the energetically favored structure is 1/3 ML Tl adsorbed at the T4 sites on Si(111) surfaces. The adsorption energy difference of one Tl adatom between (√3 × √3) and (1 × 1) is less than that of each In adatom. The DOS indicates that Tl 6p and Si 3p electrons play a very important role in the formation of the surface states. It is concluded that the bonding of Tl adatoms on Si(111) surfaces is mainly polar covalent, which is weaker than that of In on Si(111). So Tl atom is more easy to be migrated than In atom in the same external electric field and the structures of Tl on Si(111) is prone to switch between (√3 × √3) and (1 × 1).
Thermal Properties of oil sand
NASA Astrophysics Data System (ADS)
LEE, Y.; Lee, H.; Kwon, Y.; Kim, J.
2013-12-01
Thermal recovery methods such as Cyclic Steam Injection or Steam Assisted Gravity Drainage (SAGD) are the effective methods for producing heavy oil or bitumen. In any thermal recovery methods, thermal properties (e.g., thermal conductivity, thermal diffusivity, and volumetric heat capacity) are closely related to the formation and expansion of steam chamber within a reservoir, which is key factors to control efficiency of thermal recovery. However, thermal properties of heavy oil or bitumen have not been well-studied despite their importance in thermal recovery methods. We measured thermal conductivity, thermal diffusivity, and volumetric heat capacity of 43 oil sand samples from Athabasca, Canada, using a transient thermal property measurement instrument. Thermal conductivity of 43 oil sand samples varies from 0.74 W/mK to 1.57 W/mK with the mean thermal conductivity of 1.09 W/mK. The mean thermal diffusivity is 5.7×10-7 m2/s with the minimum value of 4.2×10-7 m2/s and the maximum value of 8.0×10-7 m2/s. Volumetric heat capacity varies from 1.5×106 J/m3K to 2.11×106 J/m3K with the mean volumetric heat capacity of 1.91×106 J/m3K. In addition, physical and chemical properties (e.g., bitumen content, electric resistivity, porosity, gamma ray and so on) of oil sand samples have been measured by geophysical logging and in the laboratory. We are now proceeding to investigate the relationship between thermal properties and physical/chemical properties of oil sand.
The calculation of thermophysical properties of nickel plasma
Apfelbaum, E. M.
2015-09-15
The thermophysical properties of Nickel plasma have been calculated for the temperatures 10–60 kK and densities less than 1 g/cm{sup 3}. These properties are the pressure, internal energy, heat capacity, and the electronic transport coefficients (electrical conductivity, thermal conductivity, and thermal power). The thermodynamic values have been calculated by means of the chemical model, which also allows one to obtain the ionic composition of considered plasma. The composition has been used to calculate the electronic transport coefficients within the relaxation time approximation. The results of the present investigation have been compared with the calculations of other researchers and available data of measurements.
Lattice thermal conductivity of borophene from first principle calculation
Xiao, Huaping; Cao, Wei; Ouyang, Tao; Guo, Sumei; He, Chaoyu; Zhong, Jianxin
2017-01-01
The phonon transport property is a foundation of understanding a material and predicting the potential application in mirco/nano devices. In this paper, the thermal transport property of borophene is investigated by combining first-principle calculations and phonon Boltzmann transport equation. At room temperature, the lattice thermal conductivity of borophene is found to be about 14.34 W/mK (error is about 3%), which is much smaller than that of graphene (about 3500 W/mK). The contributions from different phonon modes are qualified, and some phonon modes with high frequency abnormally play critical role on the thermal transport of borophene. This is quite different from the traditional understanding that thermal transport is usually largely contributed by the low frequency acoustic phonon modes for most of suspended 2D materials. Detailed analysis further reveals that the scattering between the out-of-plane flexural acoustic mode (FA) and other modes likes FA + FA/TA/LA/OP ↔ TA/LA/OP is the predominant phonon process channel. Finally the vibrational characteristic of some typical phonon modes and mean free path distribution of different phonon modes are also presented in this work. Our results shed light on the fundamental phonon transport properties of borophene, and foreshow the potential application for thermal management community. PMID:28374853
Lattice thermal conductivity of borophene from first principle calculation
NASA Astrophysics Data System (ADS)
Xiao, Huaping; Cao, Wei; Ouyang, Tao; Guo, Sumei; He, Chaoyu; Zhong, Jianxin
2017-04-01
The phonon transport property is a foundation of understanding a material and predicting the potential application in mirco/nano devices. In this paper, the thermal transport property of borophene is investigated by combining first-principle calculations and phonon Boltzmann transport equation. At room temperature, the lattice thermal conductivity of borophene is found to be about 14.34 W/mK (error is about 3%), which is much smaller than that of graphene (about 3500 W/mK). The contributions from different phonon modes are qualified, and some phonon modes with high frequency abnormally play critical role on the thermal transport of borophene. This is quite different from the traditional understanding that thermal transport is usually largely contributed by the low frequency acoustic phonon modes for most of suspended 2D materials. Detailed analysis further reveals that the scattering between the out-of-plane flexural acoustic mode (FA) and other modes likes FA + FA/TA/LA/OP ↔ TA/LA/OP is the predominant phonon process channel. Finally the vibrational characteristic of some typical phonon modes and mean free path distribution of different phonon modes are also presented in this work. Our results shed light on the fundamental phonon transport properties of borophene, and foreshow the potential application for thermal management community.
NASA Astrophysics Data System (ADS)
Sun, Liang; Gao, Yimin; Yoshida, Katsumi; Yano, Toyohiko; Li, Yefei; Liu, Yangzhen
2017-01-01
Structural, electronic, elastic and thermal properties of Al4Si2C5 under constant pressure were investigated by using first-principles theory. The total volume of the cell decreased by almost 15.7% under 40 GPa which is smaller than that of Al4SiC4 (16%), while the linear compressibility along a- or b-axis direction showed better anti-deformation behavior than that of along c-axis direction. The peak heights of total density of state (TDOS) and partial density of state (PDOS) curves of Al4Si2C5 are slightly lowered with forced high pressure. Meanwhile, the mechanical properties of Al4Si2C5-like elastic constants and elastic moduli accelerate with the pressure increasing from 0 GPa to 40 GPa; the thermal expansion coefficient α increases rapidly at lower temperature and this tendency gradually approaches a linear increase when the temperature is above 1000 K. At particular temperature, α decreases continuously with the pressure accelerating. Heat capacity at constant volume (CV) with pressure was also evaluated, the results displayed that CV is sensitive with the temperature rather than the pressure. The elastic anisotropy and Debye temperature with pressure were successfully obtained and discussed.
REACTOR GROUT THERMAL PROPERTIES
Steimke, J.; Qureshi, Z.; Restivo, M.; Guerrero, H.
2011-01-28
Savannah River Site has five dormant nuclear production reactors. Long term disposition will require filling some reactor buildings with grout up to ground level. Portland cement based grout will be used to fill the buildings with the exception of some reactor tanks. Some reactor tanks contain significant quantities of aluminum which could react with Portland cement based grout to form hydrogen. Hydrogen production is a safety concern and gas generation could also compromise the structural integrity of the grout pour. Therefore, it was necessary to develop a non-Portland cement grout to fill reactors that contain significant quantities of aluminum. Grouts generate heat when they set, so the potential exists for large temperature increases in a large pour, which could compromise the integrity of the pour. The primary purpose of the testing reported here was to measure heat of hydration, specific heat, thermal conductivity and density of various reactor grouts under consideration so that these properties could be used to model transient heat transfer for different pouring strategies. A secondary purpose was to make qualitative judgments of grout pourability and hardened strength. Some reactor grout formulations were unacceptable because they generated too much heat, or started setting too fast, or required too long to harden or were too weak. The formulation called 102H had the best combination of characteristics. It is a Calcium Alumino-Sulfate grout that contains Ciment Fondu (calcium aluminate cement), Plaster of Paris (calcium sulfate hemihydrate), sand, Class F fly ash, boric acid and small quantities of additives. This composition afforded about ten hours of working time. Heat release began at 12 hours and was complete by 24 hours. The adiabatic temperature rise was 54 C which was within specification. The final product was hard and displayed no visible segregation. The density and maximum particle size were within specification.
Lattice thermal conductivity evaluated using elastic properties
NASA Astrophysics Data System (ADS)
Jia, Tiantian; Chen, Gang; Zhang, Yongsheng
2017-04-01
Lattice thermal conductivity is one of the most important thermoelectric parameters in determining the energy conversion efficiency of thermoelectric materials. However, the lattice thermal conductivity evaluation requires time-consuming first-principles (quasi)phonon calculations, which limits seeking high-performance thermoelectric materials through high-throughput computations. Here, we establish a methodology to determine the Debye temperature Θ , Grüneisen parameter γ , and lattice thermal conductivity κ using computationally feasible elastic properties (the bulk and shear moduli). For 39 compounds with three different prototypes (the cubic isotropic rocksalt and zinc blende, and the noncubic anisotropic wurtzite), the theoretically calculated Θ ,γ , and κ are in reasonable agreement with those determined using (quasi)harmonic phonon calculations or experimental measurements. Our results show that the methodology is an efficient tool to predict the anharmonicity and the lattice thermal conductivity.
Vesta surface thermal properties map
Capria, Maria Teresa; Tosi, F.; De Santis, Maria Cristina; Capaccioni, F.; Ammannito, E.; Frigeri, A.; Zambon, F; Fonte, S.; Palomba, E.; Turrini, D.; Titus, T.N.; Schroder, S.E.; Toplis, M.J.; Liu, J.Y.; Combe, J.-P.; Raymond, C.A.; Russell, C.T.
2014-01-01
The first ever regional thermal properties map of Vesta has been derived from the temperatures retrieved by infrared data by the mission Dawn. The low average value of thermal inertia, 30 ± 10 J m−2 s−0.5 K−1, indicates a surface covered by a fine regolith. A range of thermal inertia values suggesting terrains with different physical properties has been determined. The lower thermal inertia of the regions north of the equator suggests that they are covered by an older, more processed surface. A few specific areas have higher than average thermal inertia values, indicative of a more compact material. The highest thermal inertia value has been determined on the Marcia crater, known for its pitted terrain and the presence of hydroxyl in the ejecta. Our results suggest that this type of terrain can be the result of soil compaction following the degassing of a local subsurface reservoir of volatiles.
NASA Astrophysics Data System (ADS)
Tang, Chun-Mei; Deng, Kai-Ming; Chen, Xuan; Xiao, Chuan-Yun; Liu, Yu-Zhen; Li, Qun-Xiang
2009-07-01
The structural and electronic properties of the 0.5 ML-terminated allyl mercaptan (ALM)/Si(100)-(2 × 1) surface are studied using the density functional method. The calculated absorption energy of the ALM molecule on the 0.5 ML-terminated ALM/Si(100)-(2 × 1) surface is 3.36 eV, implying that adsorption is strongly favorable. The electronic structure calculations show that the ALM/Si(100)-(2 × 1), the clean Si(100)-(2 × 1), and the fully-terminated H/Si(100)-(2 × 1) surfaces have the nature of an indirect band gap semiconductor. The highest occupied molecular orbital is dominated by the ALM, confirming the mechanism proposed by Hossain for its chain reaction.
NASA Astrophysics Data System (ADS)
Hiadsi, S.; Bouafia, H.; Sahli, B.; Abidri, B.; Bouaza, A.; Akriche, A.
2016-08-01
This study presents a theoretical prediction of the structural, mechanical, electronic and thermal properties of the zinc-based Perovskites (AgZnF3 and KZnF3) within the framework of Density Functional Theory (DFT) using All-electron self consistent Full Potential Augmented Plane Waves plus local orbital FP-(L)APW + lo method. To make our work comparable and reliable, several functional were used for the exchange-correlation potential. Also, this study intends to provide a basis and an improvement for updating either the values already predicted by other previous work (by using obsolete functional) or to predict them for the first time. GGA-PBE and GGA-PBEsol were used to predict the structural properties of AgZnF3 and KZnF3 Perovskites such as lattice parameter, bulk modulus and its pressure derivative and the cohesive energy. For these properties, the found values are in very good agreement; also those found by GGA-PBEsol are closer to other available previous and experimental results. The electronic properties of these materials are investigated and compared to provide a consolidated prediction by using the modified Becke Johnson potential TB-mBJ with other functional; the values found by this potential are closer to the available proven results and show that these materials exhibit an indirect gap from R to Γ point. The charge densities plot for [110] direction and QTAIM (Quantum Theory of Atoms in Molecules) theory indicate that ionic character is predominate for (K, Ag, Zn)sbnd F bonds. Finally, the effect of temperature and pressure on the unit cell volume, the heat capacity CV and entropy were studied using the quasi-harmonic Debye model.
Calculation of thermophysical properties of sodium. [LMFBR
Fink, J.K.; Leibowitz, L.
1981-01-01
The thermodynamic properties of sodium previously recommended by Padilla have been updated. As much as possible, the approach described by Padilla has been used. For sodium in the states of saturated liquid and vapor, subcooled liquid and superheated vapor, the following thermodynamic properties were determined: enthalpy, heat capacity (constant pressure and constant volume), pressure, density, thermal-expansion coefficient, and compressibility (adiabatic and isothermal). In addition to the above properties, thermodynamic properties including heat of fusion, heat of vaporization, surface tension, speed of sound and transport properties of themal conductivity, thermal diffusivity, emissivity, and viscosity were determined for saturated sodium.
Program calculation of thermodynamic properties
NASA Astrophysics Data System (ADS)
Gill, Walter; Filho, Fernando Fachini; Ribeirodeoliveira, Ronaldo
1986-12-01
The determination of the thermodynamic properties are examined through the basic equations such as: state equation (Beattie-Bridgeman Form), saturation pressure equation, specific heat constant pressure or constant volume equation, and specific volume or density of liquid equation.
Zhang, J; Liu, H J; Cheng, L; Wei, J; Liang, J H; Fan, D D; Jiang, P H; Shi, J
2017-07-04
Phosphorene has attracted tremendous interest recently due to its intriguing electronic properties. However, the thermal transport properties of phosphorene, especially for its allotropes, are still not well-understood. In this work, we calculate the thermal conductivities of five phosphorene allotropes (α-, β-, γ-, δ- and ζ-phase) by using phonon Boltzmann transport theory combined with first-principles calculations. It is found that the α-phosphorene exhibits considerable anisotropic thermal transport, while it is less obvious in the other four phosphorene allotropes. The highest thermal conductivity is found in the β-phosphorene, followed by the δ-, γ- and ζ-phase. The much lower thermal conductivity of the ζ-phase can be attributed to its relatively complex atomic configuration. It is expected that the rich thermal transport properties of phosphorene allotropes can have potential applications in the thermoelectrics and thermal management.
The calculations of thermophysical properties of molybdenum plasma
NASA Astrophysics Data System (ADS)
Apfelbaum, E. M.
2017-05-01
The thermophysical properties (pressure, internal energy, conductivity, thermal conductivity, and thermal power) of molybdenum plasma at temperatures 10-60 kK and densities less than 2 g/cm3 have been calculated. The corresponding model has been developed on the basis of the chemical approach and relaxation time approximation. The approximations used in our model are valid under these conditions. A comparison with available experimental data on conductivity has shown good agreement in this area.
Calculating Theromodynamic And Transport Properties Of Fluids
NASA Technical Reports Server (NTRS)
Proctor, Margaret P.; Klem, Mark D.
1987-01-01
Computer program incorporates van der Waals equation and correction tables. FLUID program developed to calculate thermodynamic and transport properties of pure fluids in both liquid and gas phases. Properties calculated by use of simple gas model, empirical corrections, and efficient numerical interpolation scheme. Produces results that agree very well with measured values. Much faster than older, more complex programs developed for same purpose.
Computer program for calculating water and steam properties
NASA Technical Reports Server (NTRS)
Hendricks, R. C.; Peller, I. C.; Baron, A. K.
1975-01-01
Computer subprogram calculates thermodynamic and transport properties of water and steam. Program accepts any two of pressure, temperature, and density as input conditions. Pressure and either entropy or enthalpy are also allowable input variables. Output includes any combination of temperature, density, pressure, entropy, enthalpy, specific heats, sonic velocity, viscosity, thermal conductivity, surface tension, and the Laplace constant.
Thermal properties of fluorinated graphene
NASA Astrophysics Data System (ADS)
Singh, Sandeep Kumar; Srinivasan, S. Goverapet; Neek-Amal, M.; Costamagna, S.; van Duin, Adri C. T.; Peeters, F. M.
2013-03-01
Large-scale atomistic simulations using the reactive force field approach are implemented to investigate the thermomechanical properties of fluorinated graphene (FG). A set of parameters for the reactive force field potential optimized to reproduce key quantum mechanical properties of relevant carbon-fluorine cluster systems are presented. Molecular dynamics simulations are used to investigate the thermal rippling behavior of FG and its mechanical properties and compare them with graphene, graphane and a sheet of boron nitride. The mean square value of the height fluctuations
The hydrogenation-dependent thermal expansion properties of hydrogenated graphene
NASA Astrophysics Data System (ADS)
He, Haiyan; Pan, Bicai
2014-02-01
Thermal expansion properties of hydrogenated graphene are investigated by performing the first-principles calculations. We find that both fully hydrogenated graphene (graphane) and half hydrogenated graphene (graphone) exhibit negative thermal expansion properties at low temperatures. Their thermal expansion behaviors display the hydrogenation-dependent features: hydrogenated graphene with boat-like structures possess better negative thermal expansion properties than those with chair-like structures. In particular, the graphane with boat-like structure shows giant negative thermal expansion, with thermal expansion coefficient of about -4.1 × 10-5 K-1. Such different thermal behaviors are ascribed to different vibrational features, and the typical modes contributing to the negative thermal properties of the systems are addressed. Our results will be of importance for both fundamental understanding and the application of this family in nanodevices in the future.
Properties of air-aluminum thermal plasmas
NASA Astrophysics Data System (ADS)
Cressault, Y.; Gleizes, A.; Riquel, G.
2012-07-01
We present the calculation and the main results of the properties of air-aluminum thermal plasmas, useful for complete modelling of arc systems involving aluminum contacts. The properties are calculated assuming thermal equilibrium and correspond to the equilibrium composition, thermodynamic functions, transport coefficients including diffusion coefficients and net emission coefficient representing the divergence of the radiative flux in the hottest plasma regions. The calculation is developed in the temperature range between 2000 and 30 000 K, for a pressure range from 0.1 to 1 bar and for several metal mass proportions. As in the case of other metals, the presence of aluminum vapours has a strong influence on three properties at intermediate temperatures: the electron number density, the electrical conductivity and the net emission coefficient. Some comparisons with other metal vapour (Cu, Fe and Ag) properties are made and show the original behaviour for Al-containing mixtures: mass density at high temperatures is low due to the low Al atomic mass; high electrical conductivity at T < 10 000 K due to low ionization potential (around 2 V less for Al than for the other metals); very strong self-absorption of ionized aluminum lines, leading to a net emission coefficient lower than that of pure air when T > 10 000 K, in contrast to copper or iron radiation.
Thermal properties of time machines
NASA Astrophysics Data System (ADS)
González-Díaz, Pedro F.
2012-05-01
Connections between universes through tunneling space-times could make the multiverse a physical entity able to be observed from our own single universe. In this paper we first study the thermal properties of the static Klein-bottle holes and then consider one of the potentially observable effects from wormholes, ringholes, and nonorientable tunnelings when they are converted into time machines connecting other universes with ours own, that is a randomly varying in space and time thermal radiation which, with an unpredictable cadence, randomly manifested to a far observer as a short, occasional pulse with very high intensity and fluence which would be made of black body phantom or ordinary radiation. We discuss the odds for these bursts of thermal radiation to be eventually observable.
Calculating Thermophysical Properties Of 12 Fluids
NASA Technical Reports Server (NTRS)
Cleghorn, T. F.; Mccarty, R. D.
1991-01-01
MIPROPS is set of computer programs giving thermophysical and transport properties of selected fluids. Calculates properties of fluids in both liquid and vapor states over wide range of temperatures and pressures. Fluids included: helium, hydrogen, nitrogen, oxygen, argon, nitrogen trifluoride, methane, ethylene, ethane, propane, isobutane, and normal butane. All programs except helium program incorporate same equation of state. Written in FORTRAN 77.
Method for measuring thermal properties using a long-wavelength infrared thermal image
Walker, Charles L.; Costin, Laurence S.; Smith, Jody L.; Moya, Mary M.; Mercier, Jeffrey A.
2007-01-30
A method for estimating the thermal properties of surface materials using long-wavelength thermal imagery by exploiting the differential heating histories of ground points in the vicinity of shadows. The use of differential heating histories of different ground points of the same surface material allows the use of a single image acquisition step to provide the necessary variation in measured parameters for calculation of the thermal properties of surface materials.
Thermal radiation properties of PTFE plasma
NASA Astrophysics Data System (ADS)
Liu, Xiangyang; Wang, Siyu; Zhou, Yang; Wu, Zhiwen; Xie, Kan; Wang, Ningfei
2017-06-01
To illuminate the thermal transfer mechanism of devices adopting polytetrafluoroethylene (PTFE) as ablation materials, the thermal radiation properties of PTFE plasma are calculated and discussed based on local thermodynamic equilibrium (LTE) and optical thin assumptions. It is clarified that line radiation is the dominant mechanism of PTFE plasma. The emission coefficient shows an opposite trend for both wavelength regions divided by 550 nm at a temperature above 15 000 K. The emission coefficient increases with increasing temperature and pressure. Furthermore, it has a good log linear relation with pressure. Equivalent emissivity varies complexly with temperature, and has a critical point between 20 000 K to 25 000 K. The equivalent cross points of the average ionic valence and radiation property are about 10 000 K and 15 000 K for fully single ionization.
Burnham, A K; Weese, R K; Wang, R; Kwok, Q M; Jones, D G
2005-03-30
Much effort has been devoted to an ongoing search for more powerful, safer and environmentally friendly explosives. Since it was developed in the late 1990s, 1,1-diamino-2,2-dinitroethene (FOX-7), with lower sensitivity and comparable performance to RDX, has received increasing interest. Preliminary results on the physical and chemical characterization of FOX-7 have shown that it possesses good thermal and chemical stability. It is expected that FOX-7 will be a new important explosive ingredient in high performance, insensitive munition (IM) explosives. One of the major focuses in research on this novel energetic material is a study of its thermal properties. Oestmark et al have reported that DSC curves exhibit two minor endothermic peaks as well as two major exothermic peaks. Two endothermic peaks at {approx}116 and {approx}158 C suggest the presence of two solid-solid phase transitions. A third phase change below 100 C has also been reported based on a X-ray powder diffraction (XPD) study. The shapes, areas and observed temperatures of the two decomposition peaks at {approx}235 C and {approx}280 C vary with different batches and sources of the sample, and occasionally these two peaks are merged into one. The factors leading to this variation and a more complete investigation are in progress. Our laboratories have been interested in the thermal properties of energetic materials characterized by means of various thermal analysis techniques. This paper will present our results for the thermal behavior of FOX-7 including the phase changes, decomposition, kinetic analysis and the decomposition products using DSC, TG, ARC (Accelerating Rate Calorimetry), HFC (Heat Flow Calorimetry) and simultaneous TGDTA-FTIR (Fourier Transform Infrared Spectroscopy) Spectroscopy-MS (Mass) measurements.
Direct-Semidirect Thermal Neutron Capture Calculations
Arbanas, G; Dietrich, F S; Kerman, A K
2005-12-20
A method for computing direct-semidirect (DSD) neutron radiative capture is presented and applied to thermal neutron capture on {sup 19}F, {sup 27}Al, {sup 28,29.30}Si, {sup 35,37}Cl, {sup 39,41}K, {sup 56}Fe, and {sup 238}U, in support of data evaluation effort at the O.R.N.L. The DSD method includes both direct and semidirect capture; the latter is a core-polarization term in which the giant dipole resonance is formed. We study the effects of a commonly used ''density'' approximation to the EM operator and find it to be unsatisfactory for the nuclei considered here. We also study the magnitude of semidirect capture relative to the pure direct capture. Furthermore, we compare our results with those obtained from another direct capture code (Tedca [17]). We also compare our results with those obtained from analytical expression for external capture derived by Lane and Lynn [3], and its extension to include internal capture [7]. To estimate the effect of nuclear deformation on direct capture, we computed direct thermal capture on {sup 238}U with and without imposition of spherical symmetry. Direct capture for a spherically symmetric {sup 238}U was approximately 6 mb, while a quadrupole deformation of 0.215 on the shape of {sup 238}U lowers this cross section down to approximately 2 mb. This result suggests that effects of nuclear deformation on direct capture warrant a further study. We also find out that contribution to the direct capture on {sup 238}U from the nuclear interior significantly cancels that coming from the exterior region, and hence both contributions must be taken into account. We reproduced a well known discrepancy between the computed and observed branching ratios in {sup 56}Fe(n,{gamma}). This will lead us to revisit the concept of doorway states in the particle-hole model.
Thermal property microscopy with frequency domain thermoreflectance.
Yang, Jia; Maragliano, Carlo; Schmidt, Aaron J
2013-10-01
A thermal property microscopy technique based on frequency domain thermoreflectance (FDTR) is presented. In FDTR, a periodically modulated laser locally heats a sample while a second probe beam monitors the surface reflectivity, which is related to the thermal properties of the sample with an analytical model. Here, we extend FDTR into an imaging technique capable of producing micrometer-scale maps of several thermophysical properties simultaneously. Thermal phase images are recorded at multiple frequencies chosen for maximum sensitivity to thermal properties of interest according to a thermal model of the sample. The phase versus frequency curves are then fit point-by-point to obtain quantitative thermal property images of various combinations of thermal properties in multilayer samples, including the in-plane and cross-plane thermal conductivities, heat capacity, thermal interface conductance, and film thickness. An FDTR microscope based on two continuous-wave lasers is described, and a sensitivity analysis of the technique to different thermal properties is carried out. As a demonstration, we image ~3 nm of patterned titanium under 100 nm of gold on a silicon substrate, and simultaneously create maps of the thermal interface conductance and substrate thermal conductivity. Results confirm the potential of our technique for imaging and quantifying thermal properties of buried layers, indicating its utility for mapping thermal properties in integrated circuits.
NASA Technical Reports Server (NTRS)
Hendricks, R. C.; Baron, A. K.; Peller, I. C.
1975-01-01
A FORTRAN IV subprogram called GASP is discussed which calculates the thermodynamic and transport properties for 10 pure fluids: parahydrogen, helium, neon, methane, nitrogen, carbon monoxide, oxygen, fluorine, argon, and carbon dioxide. The pressure range is generally from 0.1 to 400 atmospheres (to 100 atm for helium and to 1000 atm for hydrogen). The temperature ranges are from the triple point to 300 K for neon; to 500 K for carbon monoxide, oxygen, and fluorine; to 600 K for methane and nitrogen; to 1000 K for argon and carbon dioxide; to 2000 K for hydrogen; and from 6 to 500 K for helium. GASP accepts any two of pressure, temperature and density as input conditions along with pressure, and either entropy or enthalpy. The properties available in any combination as output include temperature, density, pressure, entropy, enthalpy, specific heats, sonic velocity, viscosity, thermal conductivity, and surface tension. The subprogram design is modular so that the user can choose only those subroutines necessary to the calculations.
NASA Astrophysics Data System (ADS)
Jan, C.; Cressault, Y.; Gleizes, A.; Bousoltane, K.
2014-01-01
Radiative transfer is a key point for accurate simulations of arcs in high voltage circuit breakers where the plasma is mainly composed, at high current, of a mixture of SF6 and PTFE vapours (C2F4 and decomposition products). Assuming local thermodynamic equilibrium, we have built a database of absorption coefficients over almost 300 000 spectral points, for a pressure range between 1 and 100 bar, temperatures from 300 to 50 000 K, and proportions from pure SF6 to pure C2F4. From these data, we have calculated the mean absorption coefficients (MAC) by considering several definitions of the mean coefficient and several spectral ranges or intervals. The choice between the various definitions was operated using a one dimensional radiative transfer model with imposed temperature profiles. The results showed that a combination of a normal average over the molecular continuum at low temperature, with a mixed definition of Planck average at high temperature gives the most accurate results. The optimization of the number of intervals for the definition of the MAC database was performed and showed that the accuracy on the radiative flux and on the divergence of the flux depends on the temperature profile. A good compromise is obtained with five or seven intervals.
Thermodynamic Properties of Rutile (TiO2) Within the Phonon Calculations
NASA Astrophysics Data System (ADS)
Kangarlou, Haleh; Abdollahi, Arash
2016-11-01
Full phonon calculations have been performed to estimate the thermal properties of rutile (titanium dioxide). Calculations have been carried out using the pseudo-potential method within the local density approximation. Thermodynamic properties including the thermal expansion, thermal expansion coefficient, heat capacity and entropy were calculated as a function of temperature in the framework of quasi-harmonic approximation. Also, to compare the results with the results of other approaches, we apply Debye-Slater and Debye-Gruneisen approaches with the same parameters for electronic calculations. It is found that the phonon calculations provide more accurate estimates in comparison with the other two models.
Thermal conductance of one-dimensional materials calculated with typical lattice models
NASA Astrophysics Data System (ADS)
Zhang, Chunyi; Kang, Wei; Wang, Jianxiang
2016-11-01
We show through calculations on typical lattice models that thermal conductance σ can well describe the near-equilibrium thermal transport property of one-dimensional materials of finite length, which presents a situation often met in the application of nanoscale devices. The σ generally contains contributions from the material itself and those from the thermal reservoirs. The intrinsic σ of the material, i.e., the one with the fewest external influences, can be efficiently calculated with the help of the "blackbody"-like nonreflective thermal reservoir, either through the nonequilibrium method or through the Green-Kubo-type formula. σ thus calculated would be helpful to guide the design of thermal management and heat control in nanoscale devices.
Calculation of tin atomic data and plasma properties.
Morozov, V.; Tolkach, V.; Hassanein, A.
2005-08-26
This report reviews the major methods and techniques we use in generating basic atomic and plasma properties relevant to extreme ultraviolet (EUV) lithography applications. The basis of the work is the calculation of the atomic energy levels, transitions probabilities, and other atomic data by various methods, which differ in accuracy, completeness, and complication. Later on, we calculate the populations of atomic levels and ion states in plasmas by means of the collision-radiation equilibrium (CRE) model. The results of the CRE model are used as input to the thermodynamic functions, such as pressure and temperature from the internal energy and density (equation of state), electric resistance, thermal conduction, and other plasma properties. In addition, optical coefficients, such as emission and absorption coefficients, are generated to resolve a radiation transport equation (RTE). The capabilities of our approach are demonstrated by generating the required atomic and plasma properties for tin ions and plasma within the EUV region near 13.5 nm.
NASA Technical Reports Server (NTRS)
Gordon, S.; Mcbride, B.; Zeleznik, F. J.
1984-01-01
An addition to the computer program of NASA SP-273 is given that permits transport property calculations for the gaseous phase. Approximate mixture formulas are used to obtain viscosity and frozen thermal conductivity. Reaction thermal conductivity is obtained by the same method as in NASA TN D-7056. Transport properties for 154 gaseous species were selected for use with the program.
NASA Astrophysics Data System (ADS)
Gordon, S.; McBride, B.; Zeleznik, F. J.
1984-10-01
An addition to the computer program of NASA SP-273 is given that permits transport property calculations for the gaseous phase. Approximate mixture formulas are used to obtain viscosity and frozen thermal conductivity. Reaction thermal conductivity is obtained by the same method as in NASA TN D-7056. Transport properties for 154 gaseous species were selected for use with the program.
Point kinetics calculations with fully coupled thermal fluids reactivity feedback
Zhang, H.; Zou, L.; Andrs, D.; Zhao, H.; Martineau, R.
2013-07-01
The point kinetics model has been widely used in the analysis of the transient behavior of a nuclear reactor. In the traditional nuclear reactor system safety analysis codes such as RELAP5, the reactivity feedback effects are calculated in a loosely coupled fashion through operator splitting approach. This paper discusses the point kinetics calculations with the fully coupled thermal fluids and fuel temperature feedback implemented into the RELAP-7 code currently being developed with the MOOSE framework. (authors)
Refinement of thermal imager minimum resolvable temperature difference calculating method
NASA Astrophysics Data System (ADS)
Kolobrodov, V. G.; Mykytenko, V. I.
2015-11-01
Calculating methods, which accurately predict minimum resolvable temperature difference (MRTD), are of significant interest for many years. The article deals with improvement the accuracy of determining the thermal imaging system MRTD by elaboration the visual perception model. We suggest MRTD calculating algorithm, which is based on a reliable approximation of the human visual system modulation transfer function (MTF) proposed by N. Nill. There was obtained a new expression for the bandwidth evaluation, which is independent of angular size of the Foucault bar target.
Benchmark calculations of thermal reaction rates. I - Quantal scattering theory
NASA Technical Reports Server (NTRS)
Chatfield, David C.; Truhlar, Donald G.; Schwenke, David W.
1991-01-01
The thermal rate coefficient for the prototype reaction H + H2 yields H2 + H with zero total angular momentum is calculated by summing, averaging, and numerically integrating state-to-state reaction probabilities calculated by time-independent quantum-mechanical scattering theory. The results are very carefully converged with respect to all numerical parameters in order to provide high-precision benchmark results for confirming the accuracy of new methods and testing their efficiency.
A Method for Calculating Viscosity and Thermal Conductivity of a Helium-Xenon Gas Mixture
NASA Technical Reports Server (NTRS)
Johnson, Paul K.
2006-01-01
A method for calculating viscosity and thermal conductivity of a helium-xenon (He-Xe) gas mixture was employed, and results were compared to AiResearch (part of Honeywell) analytical data. The method of choice was that presented by Hirschfelder with Singh's third-order correction factor applied to thermal conductivity. Values for viscosity and thermal conductivity were calculated over a temperature range of 400 to 1200 K for He-Xe gas mixture molecular weights of 20.183, 39.94, and 83.8 kg/kmol. First-order values for both transport properties were in good agreement with AiResearch analytical data. Third-order-corrected thermal conductivity values were all greater than AiResearch data, but were considered to be a better approximation of thermal conductivity because higher-order effects of mass and temperature were taken into consideration. Viscosity, conductivity, and Prandtl number were then compared to experimental data presented by Taylor.
Thermal properties of methyltrimethoxysilane aerogel thin films
NASA Astrophysics Data System (ADS)
Acquaroli, Leandro N.; Newby, Pascal; Santato, Clara; Peter, Yves-Alain
2016-10-01
Aerogels are light and porous solids whose properties, largely determined by their nanostructure, are useful in a wide range of applications, e.g., thermal insulation. In this work, as-deposited and thermally treated air-filled silica aerogel thin films synthesized using the sol-gel method were studied for their thermal properties using the 3-omega technique, at ambient conditions. The thermal conductivity and diffusivity were found to increase as the porosity of the aerogel decreased. Thermally treated films show a clear reduction in thermal conductivity compared with that of as-deposited films, likely due to an increase of porosity. The smallest thermal conductivity and diffusivity found for our aerogels were 0.019 W m-1 K-1 and 9.8 × 10-9 m2 s-1. A model was used to identify the components (solid, gaseous and radiative) of the total thermal conductivity of the aerogel.
Thermal Properties of Bazhen fm. Sediments from Thermal Core Logging
NASA Astrophysics Data System (ADS)
Spasennykh, Mikhail; Popov, Evgeny; Popov, Yury; Chekhonin, Evgeny; Romushkevich, Raisa; Zagranovskaya, Dzhuliya; Belenkaya, Irina; Zhukov, Vladislav; Karpov, Igor; Saveliev, Egor; Gabova, Anastasia
2016-04-01
The Bazhen formation (B. fm.) is the hugest self-contained source-and-reservoir continuous petroleum system covering by more than 1 mln. km2 (West Siberia, Russia). High lithological differentiation in Bazhen deposits dominated by silicic shales and carbonates accompanied by extremely high total organic carbon values (of up to 35%), pyrite content and brittle mineralogical composition deteriorate standard thermal properties assessment for low permeable rocks. Reliable information of unconventional system thermal characteristics is the necessary part of works such as modelling of different processes in reservoir under thermal EOR for accessing their efficiency, developing and optimizing design of the oil recovery methods, interpretation of the well temperature logging data and for the basin petroleum modelling. A unique set of data including thermal conductivity, thermal diffusivity, volumetric heat capacity, thermal anisotropy for the B.fm. rocks was obtained from thermal core logging (high resolution continuous thermal profiling) on more than 4680 core samples (2000 of B.fm. samples are among) along seven wells for four oil fields. Some systematic peculiarities of the relation between thermal properties of the B.fm. rocks and their mineralogical composition, structural and texture properties were obtained. The high-resolution data are processed jointly with the standard petrophysical logging that allowed us to provide better separation of the formation. The research work was done with financial support of the Russian Ministry of Education and Science (unique identification number RFMEFI58114X0008).
Thermal properties of defective fullerene
NASA Astrophysics Data System (ADS)
Li, Jian; Zheng, Dong-Qin; Zhong, Wei-Rong
2016-09-01
We have investigated the thermal conductivity of defective fullerene (C60) by using the nonequilibrium molecular dynamics (MD) method. It is found that the thermal conductivity of C60 with one defect is lower than the thermal conductivity of perfect C60. However, double defects in C60 have either positive or negative influence on the thermal conductivity, which depends on the positions of the defects. The phonon spectra of perfect and defective C60 are also provided to give corresponding supports. Our results can be extended to long C60 chains, which is helpful for the thermal management of C60.
Thermal Properties of Whispering Gallery Mode Resonators
2014-12-22
F01m 298 (Rev 8/98) Prescribed by ANSI Std. Z39.18 ABSTRACT Number of Papers published in peer-reviewed journals: Thermal Properties of Whispering...Gallery Mode Resonators Report Title In this project, we studied the thermal properties of ultra-high-quality whispering-gallery-mode microtoroid...resonators. More specifically, we measured the thermal relaxation time of the resonator to estimate the response time of the resonator based infrared (IR
Thermal conductivity calculations of crystalline quartz from the BKS potential
NASA Astrophysics Data System (ADS)
Yoon, Young-Gui; Car, Roberto; Srolovitz, David J.; Scandolo, Sandro
2003-03-01
We present thermal conductivity calculations from the classical BKS potential[1]. Following a velocity rescaling method for a constant heat flux proposed by P. Jund and R. Jullien[2], thermal conductivity as a heat flux to temperature gradient ratio is directly calculated in periodic simulation cells. Our calculations in a wide temperature range at which crystalline quartz exists are consistent with the experimental trend[3]. The conductivity decreases with temperature in the alpha-quartz regime, and increases after the phase transition to beta-quartz. The temperature dependence is rather small in the beta-quartz regime. [1] B. W. H. van Beest, G. J. Kramer, and R. A. van Santen, Phy. Rev. Lett. 64, 1995 (1990). [2] P. Jund, and R. Jullien, Phy. Rev. B 59, 13707 (1999). [3] H. Kanamori, N. Fujii, and H. Mizutani, J. Geophys. Res. 73, 595 (1968).
Anisotropic intrinsic lattice thermal conductivity of borophane from first-principles calculations.
Liu, Gang; Wang, Haifeng; Gao, Yan; Zhou, Jian; Wang, Hui
2017-01-25
Borophene (boron sheet) as a new type of two-dimensional (2D) material was grown successfully recently. Unfortunately, the structural stability of freestanding borophene is still an open issue. Theoretical research has found that full hydrogenation can remove such instability, and the product is called borophane. In this paper, using first-principles calculations we investigate the lattice dynamics and thermal transport properties of borophane. The intrinsic lattice thermal conductivity and the relaxation time of borophane are investigated by solving the phonon Boltzmann transport equation (BTE) based on first-principles calculations. We find that the intrinsic lattice thermal conductivity of borophane is anisotropic, as the higher value (along the zigzag direction) is about two times of the lower one (along the armchair direction). The contributions of phonon branches to the lattice thermal conductivities along different directions are evaluated. It is found that both the anisotropy of thermal conductivity and the different phonon branches which dominate the thermal transport along different directions are decided by the group velocity and the relaxation time of phonons with very low frequency. In addition, the size dependence of thermal conductivity is investigated using cumulative thermal conductivity. The underlying physical mechanisms of these unique properties are also discussed in this paper.
Recommended radiative property data for Venusian entry calculations
NASA Technical Reports Server (NTRS)
Jones, J. J.; Boughner, R. E.; Haggard, K. V.; Nealy, J. E.; Schryer, D. R.; Zoby, E. V.
1974-01-01
A compilation of experimental and calculated data on the radiative properties species important in Venusian entry is presented. Molecular band systems, atomic lines, free-bound, and free-free continua are considered for the principal radiating species of shock heated carbon dioxide. A limited amount of data pertinent to the species in the ablation layer is also included. The assumption is made that the Venus atmosphere so closely approximates pure CO2 that the inviscid layer radiation is due almost entirely to thermally excited CO2. The only exception is the inclusion of data on the Violet band system of CN. Recommendations are made as to best property values for radiative heating calculations. A review of the basic equations and the relationships of the various emission-absorption gas porperties is also included.
Identifying and bounding uncertainties in nuclear reactor thermal power calculations
Phillips, J.; Hauser, E.; Estrada, H.
2012-07-01
Determination of the thermal power generated in the reactor core of a nuclear power plant is a critical element in the safe and economic operation of the plant. Direct measurement of the reactor core thermal power is made using neutron flux instrumentation; however, this instrumentation requires frequent calibration due to changes in the measured flux caused by fuel burn-up, flux pattern changes, and instrumentation drift. To calibrate the nuclear instruments, steam plant calorimetry, a process of performing a heat balance around the nuclear steam supply system, is used. There are four basic elements involved in the calculation of thermal power based on steam plant calorimetry: The mass flow of the feedwater from the power conversion system, the specific enthalpy of that feedwater, the specific enthalpy of the steam delivered to the power conversion system, and other cycle gains and losses. Of these elements, the accuracy of the feedwater mass flow and the feedwater enthalpy, as determined from its temperature and pressure, are typically the largest contributors to the calorimetric calculation uncertainty. Historically, plants have been required to include a margin of 2% in the calculation of the reactor thermal power for the licensed maximum plant output to account for instrumentation uncertainty. The margin is intended to ensure a cushion between operating power and the power for which safety analyses are performed. Use of approved chordal ultrasonic transit-time technology to make the feedwater flow and temperature measurements (in place of traditional differential-pressure- based instruments and resistance temperature detectors [RTDs]) allows for nuclear plant thermal power calculations accurate to 0.3%-0.4% of plant rated power. This improvement in measurement accuracy has allowed many plant operators in the U.S. and around the world to increase plant power output through Measurement Uncertainty Recapture (MUR) up-rates of up to 1.7% of rated power, while also
NASA Technical Reports Server (NTRS)
Jenkins, J. M.; Taylor, A. H.; Sakata, I. F.
1985-01-01
A hybrid spar of titanium with an integrally brazed composite, consisting of an aluminum matrix reinforced with boron-carbide-coated fibers, was heated in an oven and the resulting thermal stresses were measured. Uniform heating of the spar in an oven resulted in thermal stresses arising from the effects of dissimilar materials and anisotropy of the metal matrix composite. Thermal stresses were calculated from a finite element structural model using anisotropic material properties deduced from constituent properties and rules of mixtures. Comparisons of calculated thermal stresses with measured thermal stresses on the spar are presented. It was shown that failure to account for anisotropy in the metal matrix composite elements would result in large errors in correlating measured and calculated thermal stresses. It was concluded that very strong material characterization efforts are required to predict accurate thermal stresses in anisotropic composite structures.
QSPR modeling of thermal stability of nitroaromatic compounds: DFT vs. AM1 calculated descriptors.
Fayet, Guillaume; Rotureau, Patricia; Joubert, Laurent; Adamo, Carlo
2010-04-01
The quantitative structure-property relationship (QSPR) methodology was applied to predict the decomposition enthalpies of 22 nitroaromatic compounds, used as indicators of thermal stability. An extended series of descriptors (constitutional, topological, geometrical charge related and quantum chemical) was calculated at two different levels of theory: density functional theory (DFT) and semi-empirical AM1 approaches. Reliable models have been developed for each level, leading to similar correlations between calculated and experimental data (R(2) > 0.98). Hence, both of them can be employed as screening tools for the prediction of thermal stability of nitroaromatic compounds. If using the AM1 model presents the advantage to be less time consuming, DFT allows the calculation of more accurate molecular quantum properties, e.g., conceptual DFT descriptors. In this study, our best QSPR model is based on such descriptors, providing more chemical comprehensive relationships with decomposition reactivity, a particularly complex property for the specific class of nitroaromatic compounds.
Properties of samarium nitride: First principle calculations
Aynyas, Mahendra; Panwar, Y. S.; Pataiya, J.; Makode, C.; Sanyal, Sankar P.
2016-05-06
The tight binding linear muffin-tin-orbital (TB-LMTO) method within the local density approximation (LDA has been used to calculate structural and electronic properties of samarium nitride at ambient and high pressure. As a function of volume, the total energy is evaluated. The phase transition pressure for this compound was found to be 6.0 GPa and it is transform from NaCl to CsCl-type structure. Apart from this, the lattice parameter (a{sub 0}), bulk modulus (B{sub 0}), band structure (BS) and density of states (DOS) are calculated. From energy band diagram we observed metallic behaviour in SmN compound. The values of equilibrium lattice constants and bulk modulus are agreed well with the available data.
Shale: Measurement of thermal properties
Gilliam, T.M.; Morgan, I.L.
1987-07-01
Thermal conductivity and heat capacity measurements were made on samples of Devonian shale, Pierre shale, and oil shale from the Green River Formation. Thermal expansion measurements were made on selected samples of Devonian shale. Measurements were obtained over the temperature range of ambient to 473 K. Average values for thermal conductivity and heat capacity for the samples studied were within two standard deviations of all data over this temperature range. 15 refs., 12 figs., 4 tabs.
Ab initio theory of thermal properties of germanane
NASA Astrophysics Data System (ADS)
Heine, Matthew; Lindsay, Lucas; Carrete, Jesús; Mingo, Natalio; Hellman, Olle; Broido, David
Germanane(GeH) is a germanium based hydrogen-terminated multi-layered graphane analogue semiconductor, which may be a promising thermoelectric due to its high electron mobility and the capability to tune its transport properties. We have performed first principles calculations of the thermal properties of germanane. Harmonic and anharmonic interatomic force constants are calculated within the framework of density functional theory, from which phonon dispersions, specific heat, thermal expansion are obtained. The phonon Boltzmann equation is solved to obtain the lattice thermal conductivity. The disparity in constituent masses in GeH gives phonon modes that are distinctly Ge or H in character and causes the specific heat not to saturate until much higher temperatures than in bulk Ge. Weak interlayer bonding and strong phonon-phonon scattering result in highly anisotropic and quite low intrinsic lattice thermal conductivity compared to Ge.
Numerical calculation of thermal effect on cavitation in cryogenic fluids
NASA Astrophysics Data System (ADS)
Shi, Suguo; Wang, Guoyu
2012-11-01
A key design issue related to the turbopump of the rocket engine is that cavitation occurs in cryogenic fluids when the fluid pressure is lower than the vapor pressure at a local thermodynamic state. Cavitation in cryogenic fluids generates substantial thermal effects and strong variations in fluid properties, which in turn alter the cavity characteristics. To date, fewer investigate the thermal effect on cavitation in cryogenic fluids clearly by the numerical methods due to the difficulty of the heat transfer in the phase change process. In order to study the thermal effect on cavitation in cryogenic fluid, computations are conducted around a 2D quarter caliber hydrofoil in liquid nitrogen and hydrogen respectively by implementing modified Merkle cavitation model, which accounts for the energy balance and variable thermodynamic properties of the fluid. The numerical results show that with the thermal effect, the vapour content in constant location decreases, the cavity becomes more porous and the interface becomes less distinct which shows increased spreading while getting shorter in length. In the cavity region, the temperature around the cavity depresses due to absorb the evaporation latent heat and the saturation pressure drops. When the vapour volume fraction is higher, the temperature depression and pressure depression becomes larger. It is also observed that a slight temperature rise is found above the reference fluid temperature at the cavity rear end attributed to the release of latent heat during the condensation process. When the fluid is operating close to its critical temperature, thermal effects on cavitation are more obviously in both the liquid nitrogen and hydrogen. The thermal effect on cavitation in liquid hydrogen is more distinctly compared with that in liquid nitrogen due to the density ratio, vapour pressure and other variable properties of the fluid. The investigation provides aid for the design of the cryogenic pump of the liquid rocket.
Thermal inertia properties of autoclaved aerated concrete
Ropelewski, L.; Neufeld, R.D.
1999-08-01
Autoclaved aerated concrete (AAC) is a lightweight, porous concrete with advanced thermal properties. AAC is unique among construction materials in combining excellent thermal resistance and thermal inertia. Generally, low-density construction materials do not provide good thermal inertia, while heavier ones commonly have poor thermal resistance. Five different 10.2 cm (4 in.) AAC samples made from US electric utility fly ash as the silica source, along with three 10.2 cm (4 in.) conventional building material specimens, were tested for thermal inertia properties. Three primary issues addressed by these experiments were: (1) to develop and compare AAC thermal inertia to conventional building materials; (2) to document differences in thermal inertia characteristics of the AAC blocks produced by the various utilities; and (3) to determine if a periodic heat flow model using the thermal inertia approach adequately predicts the observed thermal inertia parameters of a material. A theoretical periodic heat flow model in the literature for thermal inertia did an adequate job of predicting the observed thermal inertia parameters for the AAC and conventional construction samples.
Differential pressure corrections calculated for a tank thermal expansion experiment
Jones, F.E.
1993-12-31
The data from a tank thermal expansion experiment were treated by applying corrections to bubbler tube differential pressure measurements at the initial temperature. The tank had a capacity of 3.55 m{sup 3} and an internal height of 8.70 m. Water was used as the experimental fluid and the masses of water for the 4 experimental runs were 911.1, 1497.3, 876.98, and 2048.3 kg. Initial temperature ranged from 13.5 to 37.6 C; maximum temperatures ranged from 54.7 to 70.4 C. Four corrections were calculated for each temperature to obtain the correction to calculate the differential pressure for each successive temperature. The calculated differential pressure was compared to the measured differential pressure. The agreement between calculated and measured differential pressure was excellent.
NASA Astrophysics Data System (ADS)
Guo, Xingye; Lu, Zhe; Jung, Yeon-Gil; Li, Li; Knapp, James; Zhang, Jing
2016-06-01
Lanthanum zirconate (La2Zr2O7) coatings are newly proposed thermal barrier coating (TBC) systems which exhibit lower thermal conductivity and potentially higher thermal stability compared to other traditional thermal barrier systems. In this work, La2Zr2O7 and 8 wt pct yttria stabilized zirconia (8YSZ) single-layer and double-layer TBC systems were deposited using the air plasma spray technique. Thermal properties of the coatings were measured. Furnace heat treatment and jet engine thermal shock tests were implemented to evaluate coating performance during thermal cycling. The measured average thermal conductivity of porous La2Zr2O7 coating ranged from 0.59 to 0.68 W/m/K in the temperature range of 297 K to 1172 K (24 °C to 899 °C), which was approximately 25 pct lower than that of porous 8YSZ (0.84 to 0.87 W/m/K) in the same temperature range. The coefficients of thermal expansion values of La2Zr2O7 were approximately 9 to 10 × 10-6/K from 400 K to 1600 K (127 °C to 1327 °C), which were about 10 pct lower than those of porous 8YSZ. The double-layer coating system consisting of the porous 8YSZ and La2Zr2O7 layers had better thermal shock resistance and thermal cycling performance than those of single-layer La2Zr2O7 coating and double-layer coating with dense 8YSZ and La2Zr2O7 coatings. This study suggests that porous 8YSZ coating can be employed as a buffer layer in La2Zr2O7-based TBC systems to improve the overall coating durability during service.
Determination of Thermal Properties of Composting Bulking Materials
USDA-ARS?s Scientific Manuscript database
Thermal properties of compost bulking materials affect temperature and biodegradation during the composting process. Well determined thermal properties of compost feedstocks will therefore contribute to practical thermodynamic approaches. Thermal conductivity, thermal diffusivity, and volumetric hea...
Thermal diffusion calculations for the ionosphere of Venus
NASA Technical Reports Server (NTRS)
Nakada, M. P.; Sullivan, E. C.
1980-01-01
Simplified multicomponent diffusion calculations are made for the ionosphere of Venus. Large differences in temperature between electrons and ions and appreciable temperature gradients that are near those of recent measurements are used. Compositions for which binary thermal diffusion coefficients for ions are the same as multi-ion ones are examined as well as those that are quite different. An attempt to combine binary coefficients to give multi-ions ones has not been particularly successful.
Thermal calculations pertaining to experiments in the Yucca Mountain Exploratory Shaft
Montan, D.N.
1986-03-01
A series of thermal calculations have been presented that appear to satisfy the needs for design of the Yucca Mountain Exploratory Shaft Tests. The accuracy of the modeling and calculational techniques employed probably exceeds the accuracy of the thermal properties used. The rather close agreement between simple analytical methods (the PLUS Family) and much more complex methods (TRUMP) suggest that the PLUS Family might be appropriate during final design to model, in a single calculation, the entire test array and sequence. Before doing further calculations it is recommended that all available thermal property information be critically evaluated to determine "best" values to be used for conductivity and saturation. Another possibility is to design one or more of the test sequences to approximately duplicate the early phase of Heater Test 1. In that experiment an unplanned power outage for about two days that occurred a week into the experiment gave extremely useful data from which to determine the conductivity and diffusivity. In any case we urge that adequate, properly calibrated instrumentation with data output available on a quasi-real time basis be installed. This would allow us to take advantage of significant power changes (planned or not) and also help "steer" the tests to desired temperatures. Finally, it should be kept in mind that the calculations presented here are strictly thermal. No hydrothermal effects due to liquid and vapor pressures have been considered.
Thermal properties of alkali-activated aluminosilicates
NASA Astrophysics Data System (ADS)
Florian, Pavel; Valentova, Katerina; Fiala, Lukas; Zmeskal, Oldrich
2017-07-01
The paper is focused on measurements and evaluation of thermal properties of alkali-activated aluminosilicates (AAA) with various carbon admixtures. Such composites consisting of blast-furnace slag, quartz sand, water glass as alkali activator and small amount of electrically conductive carbon admixture exhibit better electric and thermal properties than the reference material. Such enhancement opens up new practical applications, such as designing of snow-melting, de-icing or self-sensing systems that do not need any external sensors to detect current condition of building material. Thermal properties of the studied materials were measured by the step-wise transient method and mutually compared.
Thermal properties of UO2 single crystal
NASA Astrophysics Data System (ADS)
Gofryk, K.; Du, S.; Andersson, A. D.; Stanek, C. R.; Schulze, R.; Safarik, D.; Mihaila, B.; Lashley, J. C.; Smith, J. L.
2013-03-01
For decades UO2 has been the most widely studied actinide oxide because of its technological importance as fuel material for nuclear reactors. Therefore there is a large interest in understanding its thermal, transport and thermodynamic properties. We present recent experimental results for the thermal conductivity and thermal expansion of high quality UO2 single crystal, obtained for different crystallographic directions, and compare with results of molecular dynamics simulations. We will discuss the implications of this study.
Thermal to electricity conversion using thermal magnetic properties
West, Phillip B [Idaho Falls, ID; Svoboda, John [Idaho Falls, ID
2010-04-27
A system for the generation of Electricity from Thermal Energy using the thermal magnetic properties of a Ferromagnetic, Electrically Conductive Material (FECM) in one or more Magnetic Fields. A FECM is exposed to one or more Magnetic Fields. Thermal Energy is applied to a portion of the FECM heating the FECM above its Curie Point. The FECM, now partially paramagnetic, moves under the force of the one or more Magnetic Fields. The movement of the FECM induces an electrical current through the FECM, generating Electricity.
Differential pressure corrections calculated for a tank thermal expansion experiment
Jones, F.E.; Crawford, J.M.
1997-12-31
The data from a tank thermal expansion experiment were treated by applying corrections to bubble tube differential pressure measurements at an initial temperature. The tank had a capacity of 3.55 m{sup 3} and an internal height of about 0.90 m. Water was used as the experimental fluid for four runs. Minimum temperature for the runs ranged from 13.5 C to 37.6 C; maximum temperatures ranged from 48.6 C to 70.4 C. For each run, using an equation appropriate for the ANSI N15.19 tank volume calibration standard, differential pressure was calculated at various temperatures from measured differential pressure at an initial temperature. The calculated differential pressure was compared to the measured differential pressure. The agreement between calculated and measured differential pressure was excellent.
Equations for calculating the properties of dissociated steam
NASA Astrophysics Data System (ADS)
Aminov, R. Z.; Gudym, A. A.
2017-08-01
The equations of state for dissociated steam have been developed in the temperature and pressure ranges of 1250-2300 K and 0.01-10.00 MPa for calculating thermodynamic processes in thermal power units operating on high-temperature steam. These equations are based on the property tables for dissociated steam derived at a reference temperature of 0 K. It is assumed that the initial substance is steam, the dissociation of which—in accordance with the most likely chemical reactions—results in formation of molecules of hydrogen, oxygen, steam, hydroxyl, and atoms of oxygen and hydrogen. Differential thermodynamic correlations, considering a change in the chemical potential and the composition of the mixture, during the steam dissociation are used. A reference temperature of 0.01°C used in the calculation of parameters of nondissociated steam has been adopted to predict processes in thermal power units without matching the reference temperatures and to account for transformation of dissociated steam into its usual form for which there is the international system of equations with the water triple point of 0.01°C taken as the reference. In the investigated region, the deviation of dissociated steam properties from those of nondissociated steam, which increases with decreasing the pressure or increasing the temperature, was determined. For a pressure of 0.02 MPa and a temperature of 2200 K, these deviations are 512 kJ/kg for the enthalpy, 0.2574 kJ/(kg K) for the entropy, and 3.431 kJ/(kg K) for the heat capacity at constant pressure. The maximum deviation of the dissociated steam properties calculated by the developed equations from the handbook values that these equations are based on does not exceed 0.03-0.05%.
Thermal properties of ethylene glycol aqueous solutions.
Baudot, A; Odagescu, V
2004-06-01
Preventing ice crystallization by transforming liquids into an amorphous state, vitrification can be considered as the most suitable technique allowing complex tissues, and organs cryopreservation. This process requires the use of rapid cooling rates in the presence of cryoprotective solutions highly concentrated in antifreeze compounds, such as polyalcohols. Many of them have already been intensively studied. Their glass forming tendency and the stability of their amorphous state would make vitrification a reality if their biological toxicity did not reduce their usable concentrations often below the concentrations necessary to vitrify organs under achievable thermal conditions. Fortunately, it has been shown that mixtures of cryoprotectants tend to reduce the global toxicity of cryoprotective solutions and various efficient combinations have been proposed containing ethanediol. This work reports on the thermal properties of aqueous solutions with 40, 43, 45, 48, and 50% (w/w) of this compound measured by differential scanning calorimetry. The glass forming tendency and the stability of the amorphous state are evaluated as a function of concentration. They are given by the critical cooling rates v(ccr)above which ice crystallization is avoided, and the critical warming rates v(cwr) necessary to prevent ice crystallization in the supercooled liquid state during rewarming. Those critical rates are calculated using the same semi-empirical model as previously. This work shows a strong decrease of averaged critical cooling and warming rates when ethanediol concentration increases, V(ccr) and V(cwr) = 1.08 x 10 (10) K/min for 40% (w/w) whereas V(ccr) = 11 and V(cwr) = 853 K/min for 50% (w/w). Those results are compared with the corresponding properties of other dialcohols obtained by the same method. Ethylene glycol efficiency is between those of 1,2-propanediol and 1,3-propanediol.
Thermal characterization and properties of a copper-diamond composite
Yang, Pin; Chavez, Thomas P.; DiAntonio, Christopher Brian; Coker, Eric Nicholas
2014-09-01
The thermal properties of a commercial copper-diamond composite were measured from below -50°C to above 200°C. The results of thermal expansion, heat capacity, and thermal diffusivity were reported. These data were used to calculate the thermal conductivity of the composite as a function of temperature in the thickness direction. These results are compared with estimated values based on a simple mixing rule and the temperature dependence of these physical properties is represented by curve fitting equations. These fitting equations can be used for thermal modeling of practical devices/systems at their operation temperatures. The results of the mixing rule showed a consistent correlation between the amount of copper and diamond in the composite, based on density, thermal expansion, and heat capacity measurements. However, there was a disparity between measured and estimated thermal diffusivity and thermal conductivity. These discrepancies can be caused by many intrinsic material issues such as lattice defects and impurities, but the dominant factor is attributed to the large uncertainty of the interfacial thermal conductance between diamond and copper.
Thermal neutron scattering law calculations using ab initio molecular dynamics
NASA Astrophysics Data System (ADS)
Wormald, Jonathan; Hawari, Ayman I.
2017-09-01
In recent years, methods for the calculation of the thermal scattering law (i.e. S(α,β), where α and β are dimensionless momentum and energy transfer variables, respectively) were developed based on ab initio lattice dynamics (AILD) and/or classical molecular dynamics (CMD). While these methods are now mature and efficient, further advancement in the application of such atomistic techniques is possible using ab initio molecular dynamics (AIMD) methods. In this case, temperature effects are inherently included in the calculation, e.g. phonon density of states (DOS), while using ab initio force fields that eliminate the need for parameterized semi-empirical force fields. In this work, AIMD simulations were performed to predict the phonon spectra as a function of temperature for beryllium and graphite, which are representative nuclear reactor moderator and reflector materials. Subsequently, the calculated phonon spectra were utilized to predict S(α,β) using the LEAPR module of the NJOY code. The AIMD models of beryllium and graphite were 5 × 5 × 5 crystal unit cells (250 atoms and 500 atoms respectively). Electronic structure calculations for the prediction of Hellman-Feynman forces were performed using density functional theory with a GGA exchange correlation functional and corresponding core electron pseudopotentials. AIMD simulations of 1000-10,000 time-steps were performed with the canonical ensemble (NVT thermostat) for several temperatures between 300 K and 900 K. The phonon DOS were calculated as the power spectrum of the AIMD predicted velocity autocorrelation functions. The resulting AIMD phonon DOS and corresponding inelastic thermal neutron scattering cross sections at 300 K, where anharmonic effects are expected to be small, were found to be in reasonable agreement with the results generated using traditional AILD. This illustrated the validity of the AIMD approach. However, since the impact of the temperature on the phonon DOS (e.g. broadening of
Sumi, Chikayoshi; Yanagimura, Hiroyuki
2007-05-21
We report robust noninvasive techniques for reconstructing the thermal properties of living tissues, such as thermal conductivity, thermal capacity and thermal diffusivity, for the diagnosis, monitoring and planning of thermal treatments. Internal temperature distributions can be measured using ultrasonic imaging or magnetic resonance imaging. Provided that the reference thermal properties are given in the region of interest as initial conditions, by solving bioheat transfer equations as simultaneous first-order partial differential equations having temperature distributions as inhomogeneous coefficients, we can determine thermal property distributions. A novel regularized numerical solution is also presented to realize useful, unique, stable reconstructions of the thermal property distributions. To verify the feasibility of the numerical solution, simulations and ultrasonic phantom experiments are conducted. The reconstruction of perfusion by blood flow and thermal source/sink by this approach is also addressed.
Thermal properties of lithium sulphate
NASA Astrophysics Data System (ADS)
Suleiman, B. M.; Gustavsson, M.; Karawacki, E.; Lundén, A.
1997-09-01
The thermal conductivity and diffusivity of lithium sulphate have been measured simultaneously, using the transient plane source technique over the temperature range 300 - 900 K. The thermal conductivity decreases slowly up to about 640 K, whereupon a distinct rise occurs, indicating the onset of a pre-transitional behaviour, which causes a continuous growth of the conductivity up to the structural phase transition at 851 K, whereupon a very sharp increase occurs. A similar behaviour has been observed for the thermal diffusivity, for which a very sharp dip occurs at the transition point due to the exceptionally large transition enthalpy. The pre-transitional behaviour of heat transport is associated with the librational disorder of the sulphate anions known from Raman scattering studies of both phases (and neutron scattering from the cubic phase), whereas the translational disorder of lithium cations is of hardly any importance. It is thus possible to link the `paddle-wheel' concept of ion migration in the cubic phase to the enhancement of heat transport observed in the `pre-transition' region, as well as to the large difference in heat-transport rates between the monoclinic and cubic phases.
NASA Technical Reports Server (NTRS)
Haskins, Justin; Kinaci, Alper; Sevik, Cem; Cagin, Tahir
2012-01-01
It is widely known that graphene and many of its derivative nanostructures have exceedingly high reported thermal conductivities (up to 4000 W/mK at 300 K). Such attractive thermal properties beg the use of these structures in practical devices; however, to implement these materials while preserving transport quality, the influence of structure on thermal conductivity should be thoroughly understood. For graphene nanostructures, having average phonon mean free paths on the order of one micron, a primary concern is how size influences the potential for heat conduction. To investigate this, we employ a novel technique to evaluate the lattice thermal conductivity from the Green-Kubo relations and equilibrium molecular dynamics in systems where phonon-boundary scattering dominates heat flow. Specifically, the thermal conductivities of graphene nanoribbons and carbon nanotubes are calculated in sizes up to 3 microns, and the relative influence of boundary scattering on thermal transport is determined to be dominant at sizes less than 1 micron, after which the thermal transport largely depends on the quality of the nanostructure interface. The method is also extended to carbon nanostructures (fullerenes) where phonon confinement, as opposed to boundary scattering, dominates, and general trends related to the influence of curvature on thermal transport in these materials are discussed.
Thermal Properties of Structural Materials Used in LWR Vessels
J. E. Daw; J. L. Rempe; D. L. Knudson
2011-01-01
High temperature material property data for structural materials used in existing Light Water Reactors (LWRs) are limited. Often, extrapolated values recommended in the literature differ significantly. To reduce uncertainties in predictions relying upon extrapolated data for LWR vessel and penetration materials, high temperature tests were completed on SA533 Grade B, Class 1 (SA533B1) low alloy steel, Stainless Steel 304 (SS304), and Inconel 600 using material property measurement systems available in the High Temperature Test Laboratory (HTTL) at the Idaho National Laboratory (INL). Properties measured include thermal expansion, specific heat capacity, and thermal diffusivity for temperatures up to 1200 °C. From these results, thermal conductivity and density were calculated. Results show that, in some cases, previously recommended values for these materials differ significantly from measured values at high temperatures.
Thermal Properties of Lignocellulose Pellets
NASA Astrophysics Data System (ADS)
Wachter, Igor; Hirle, Siegfried; Balog, Karol
2017-06-01
This article deals with the characterization of biomass pellets using Differential Scanning Calorimetry. We used three types of industrially produced and commercially available pellets as samples: wood pellets containing grass, wood pellet containing bark and wood pellets without bark. Each of the samples were examined using the DSC method. Based on the measurements in atmosphere of air and nitrogen temperature, the changes caused by thermal degradation of various kinds of test fuels were observed. Subsequently, limits of exothermic processes, reaction enthalpy changes and the temperature at which exothermic reactions reached peaks were determined.
Huang, Jianhua
2012-07-01
There are three methods for calculating thermal insulation of clothing measured with a thermal manikin, i.e. the global method, the serial method, and the parallel method. Under the condition of homogeneous clothing insulation, these three methods yield the same insulation values. If the local heat flux is uniform over the manikin body, the global and serial methods provide the same insulation value. In most cases, the serial method gives a higher insulation value than the global method. There is a possibility that the insulation value from the serial method is lower than the value from the global method. The serial method always gives higher insulation value than the parallel method. The insulation value from the parallel method is higher or lower than the value from the global method, depending on the relationship between the heat loss distribution and the surface temperatures. Under the circumstance of uniform surface temperature distribution over the manikin body, the global and parallel methods give the same insulation value. If the constant surface temperature mode is used in the manikin test, the parallel method can be used to calculate the thermal insulation of clothing. If the constant heat flux mode is used in the manikin test, the serial method can be used to calculate the thermal insulation of clothing. The global method should be used for calculating thermal insulation of clothing for all manikin control modes, especially for thermal comfort regulation mode. The global method should be chosen by clothing manufacturers for labelling their products. The serial and parallel methods provide more information with respect to the different parts of clothing.
StreamThermal: A software package for calculating thermal metrics from stream temperature data
Tsang, Yin-Phan; Infante, Dana M.; Stewart, Jana S.; Wang, Lizhu; Tingly, Ralph; Thornbrugh, Darren; Cooper, Arthur; Wesley, Daniel
2016-01-01
Improving quality and better availability of continuous stream temperature data allows natural resource managers, particularly in fisheries, to understand associations between different characteristics of stream thermal regimes and stream fishes. However, there is no convenient tool to efficiently characterize multiple metrics reflecting stream thermal regimes with the increasing amount of data. This article describes a software program packaged as a library in R to facilitate this process. With this freely-available package, users will be able to quickly summarize metrics that describe five categories of stream thermal regimes: magnitude, variability, frequency, timing, and rate of change. The installation and usage instruction of this package, the definition of calculated thermal metrics, as well as the output format from the package are described, along with an application showing the utility for multiple metrics. We believe this package can be widely utilized by interested stakeholders and greatly assist more studies in fisheries.
Variable thermal properties and thermal relaxation time in hyperbolic heat conduction
NASA Technical Reports Server (NTRS)
Glass, David E.; Mcrae, D. Scott
1989-01-01
Numerical solutions were obtained for a finite slab with an applied surface heat flux at one boundary using both the hyperbolic (MacCormack's method) and parabolic (Crank-Nicolson method) heat conduction equations. The effects on the temperature distributions of varying density, specific heat, and thermal relaxation time were calculated. Each of these properties had an effect on the thermal front velocity (in the hyperbolic solution) as well as the temperatures in the medium. In the hyperbolic solutions, as the density or specific heat decreased with temperature, both the temperatures within the medium and the thermal front velocity increased. The value taken for the thermal relaxation time was found to determine the 'hyperbolicity' of the heat conduction model. The use of a time dependent relaxation time allowed for solutions where the thermal energy propagated as a high temperature wave initially, but approached a diffusion process more rapidly than was possible with a constant large relaxation time.
Some Properties of Generalized Hypergeometric Thermal Coherent States
NASA Astrophysics Data System (ADS)
Popov, Dusan
2006-06-01
The generalized hypergeometric coherent states (GHCSs) have been introduced by Appl and Schiller [1] In the present paper we have extended some considerations about GHCSs to the mixed (thermal) states and applied, particularly, to the case of pseudoharmonic oscillator (PHO). The Husimi's Q distribution function and the diagonal P - distribution function, in the GHCSs representation, have been deduced for these mixed states. The obtained distribution functions were used to calculate thermal averages and to examine some nonclassical properties of the generalized hypergeometric thermal coherent states (GHTCSs), particularly for the PHO. We have also defined and calculated the thermal analogue of the Mandel parameter and the thermal analogue of the second-order correlation function. By particularizing the parameters p and q of the hypergeometric functions, we recover the usual Barut-Girardello coherent states and their main properties for the PHO from our previous paper [9] All calculations are performed in terms of the Meijer's G-functions [2], which are related to the hypergeometric functions. This manner provides an elegance and uniformity of the obtained results and so the GHCSs become a new field of application for these functions. Moreover, this mathematical approach can be used also for other kind of coherent states (e.g. Klauder-Perelomov, Gazeau-Klauder or nonlinear coherent states ([10] [12]).
Martínez, G M; Rennó, N; Fischer, E; Borlina, C S; Hallet, B; de la Torre Juárez, M; Vasavada, A R; Ramos, M; Hamilton, V; Gomez-Elvira, J; Haberle, R M
2014-08-01
The analysis of the surface energy budget (SEB) yields insights into soil-atmosphere interactions and local climates, while the analysis of the thermal inertia (I) of shallow subsurfaces provides context for evaluating geological features. Mars orbital data have been used to determine thermal inertias at horizontal scales of ∼10(4) m(2) to ∼10(7) m(2). Here we use measurements of ground temperature and atmospheric variables by Curiosity to calculate thermal inertias at Gale Crater at horizontal scales of ∼10(2) m(2). We analyze three sols representing distinct environmental conditions and soil properties, sol 82 at Rocknest (RCK), sol 112 at Point Lake (PL), and sol 139 at Yellowknife Bay (YKB). Our results indicate that the largest thermal inertia I = 452 J m(-2) K(-1) s(-1/2) (SI units used throughout this article) is found at YKB followed by PL with I = 306 and RCK with I = 295. These values are consistent with the expected thermal inertias for the types of terrain imaged by Mastcam and with previous satellite estimations at Gale Crater. We also calculate the SEB using data from measurements by Curiosity's Rover Environmental Monitoring Station and dust opacity values derived from measurements by Mastcam. The knowledge of the SEB and thermal inertia has the potential to enhance our understanding of the climate, the geology, and the habitability of Mars.
Martínez, G M; Rennó, N; Fischer, E; Borlina, C S; Hallet, B; de la Torre Juárez, M; Vasavada, A R; Ramos, M; Hamilton, V; Gomez-Elvira, J; Haberle, R M
2014-01-01
The analysis of the surface energy budget (SEB) yields insights into soil-atmosphere interactions and local climates, while the analysis of the thermal inertia (I) of shallow subsurfaces provides context for evaluating geological features. Mars orbital data have been used to determine thermal inertias at horizontal scales of ∼104 m2 to ∼107 m2. Here we use measurements of ground temperature and atmospheric variables by Curiosity to calculate thermal inertias at Gale Crater at horizontal scales of ∼102 m2. We analyze three sols representing distinct environmental conditions and soil properties, sol 82 at Rocknest (RCK), sol 112 at Point Lake (PL), and sol 139 at Yellowknife Bay (YKB). Our results indicate that the largest thermal inertia I = 452 J m−2 K−1 s−1/2 (SI units used throughout this article) is found at YKB followed by PL with I = 306 and RCK with I = 295. These values are consistent with the expected thermal inertias for the types of terrain imaged by Mastcam and with previous satellite estimations at Gale Crater. We also calculate the SEB using data from measurements by Curiosity's Rover Environmental Monitoring Station and dust opacity values derived from measurements by Mastcam. The knowledge of the SEB and thermal inertia has the potential to enhance our understanding of the climate, the geology, and the habitability of Mars. PMID:26213666
Thermal properties of polymers below 4 K.
NASA Technical Reports Server (NTRS)
Salinger, G. L.
1972-01-01
Obtained measurement data on the Debye contribution to the specific heat, the specific heat, and the thermal conductivity in polymers below 4 deg K are discussed. The results obtained suggest that impurities are responsible for the apparent thermal properties of polymers and glasses at low temperatures. In order to determine the intrinsic behavior of amorphous solids, measurements must be made at temperatures low enough to freeze out the local modes.
Thermal radiative properties: Nonmetallic solids.
NASA Technical Reports Server (NTRS)
Touloukian, Y. S.; Dewitt, D. P.
1972-01-01
The volume consists of a text on theory, estimation, and measurement, together with its bibliography, the main body of numerical data and its references, and the material index. The text material assumes a role complementary to the main body of numerical data. The physics and basic concepts of thermal radiation are discussed in detail, focusing attention on treatment of nonmetallic materials: theory, estimation, and methods of measurement. Numerical data is presented in a comprehensive manner. The scope of coverage includes the nonmetallic elements and their compounds, intermetallics, polymers, glasses, and minerals. Analyzed data graphs provide an evaluative review of the data. All data have been obtained from their original sources, and each data set is so referenced.
Thermal expansion properties of composite materials
NASA Technical Reports Server (NTRS)
Johnson, R. R.; Kural, M. H.; Mackey, G. B.
1981-01-01
Thermal expansion data for several composite materials, including generic epoxy resins, various graphite, boron, and glass fibers, and unidirectional and woven fabric composites in an epoxy matrix, were compiled. A discussion of the design, material, environmental, and fabrication properties affecting thermal expansion behavior is presented. Test methods and their accuracy are discussed. Analytical approaches to predict laminate coefficients of thermal expansion (CTE) based on lamination theory and micromechanics are also included. A discussion is included of methods of tuning a laminate to obtain a near-zero CTE for space applications.
Thermal properties of three Fermi pulsars
NASA Astrophysics Data System (ADS)
Danilenko, A.; Karpova, A.; Kirichenko, A.; Shibanov, Y.; Shternin, P.; Zharikov, S.; Zyuzin, D.
2014-07-01
We analysed thermal properties of the Fermi pulsars J0357+3205, J1741-2054, and J0633+0632 using data from the XMM-Newton and Chandra archives. The X-ray spectra of all three pulsars can be fitted by sum of thermal and power-law components. For J1741-2054, the thermal component is best described by a blackbody model whose normalization suggests that the thermal emission comes from the bulk of the neutron star surface. The effective temperature of 60 eV, which is rather large for a pulsar as old as J1741-2054, makes it similar to the well-studied pulsar B1055-52, one of ``the three musketeers''. The thermal components of PSRs J0357+3205 and J0633+0632 can be equally well described by blackbody or the hydrogen atmosphere models. In the former case the normalizations suggest hot polar cap as thermal emission origin and only upper limits on the neutron stars surface temperatures can be computed. For the hydrogen atmosphere models, the normalizations are in agreement with emission coming from a substantial part of neutron star surface. Thermal properties of the pulsars are confronted with similar data on other isolated neutron stars and predictions of the neutron star cooling theory.
High-Fidelity Coupled Monte-Carlo/Thermal-Hydraulics Calculations
NASA Astrophysics Data System (ADS)
Ivanov, Aleksandar; Sanchez, Victor; Ivanov, Kostadin
2014-06-01
Monte Carlo methods have been used as reference reactor physics calculation tools worldwide. The advance in computer technology allows the calculation of detailed flux distributions in both space and energy. In most of the cases however, those calculations are done under the assumption of homogeneous material density and temperature distributions. The aim of this work is to develop a consistent methodology for providing realistic three-dimensional thermal-hydraulic distributions by coupling the in-house developed sub-channel code SUBCHANFLOW with the standard Monte-Carlo transport code MCNP. In addition to the innovative technique of on-the fly material definition, a flux-based weight-window technique has been introduced to improve both the magnitude and the distribution of the relative errors. Finally, a coupled code system for the simulation of steady-state reactor physics problems has been developed. Besides the problem of effective feedback data interchange between the codes, the treatment of temperature dependence of the continuous energy nuclear data has been investigated.
Thermal properties for the thermal-hydraulics analyses of the BR2 maximum nominal heat flux.
Dionne, B.; Kim, Y. S.; Hofman, G. L.
2011-05-23
This memo describes the assumptions and references used in determining the thermal properties for the various materials used in the BR2 HEU (93% enriched in {sup 235}U) to LEU (19.75% enriched in {sup 235}U) conversion feasibility analysis. More specifically, this memo focuses on the materials contained within the pressure vessel (PV), i.e., the materials that are most relevant to the study of impact of the change of fuel from HEU to LEU. This section is regrouping all of the thermal property tables. Section 2 provides a summary of the thermal properties in form of tables while the following sections present the justification of these values. Section 3 presents a brief background on the approach used to evaluate the thermal properties of the dispersion fuel meat and specific heat capacity. Sections 4 to 7 discuss the material properties for the following materials: (i) aluminum, (ii) dispersion fuel meat (UAlx-Al and U-7Mo-Al), (iii) beryllium, and (iv) stainless steel. Section 8 discusses the impact of irradiation on material properties. Section 9 summarizes the material properties for typical operating temperatures. Appendix A elaborates on how to calculate dispersed phase's volume fraction. Appendix B shows the evolution of the BR2 maximum heat flux with burnup.
NASA Astrophysics Data System (ADS)
Khatun, Ayesha
The thermal properties of the sidewall lining materials are capturing attention since the last two decades. Good prediction of the dynamic thermal behaviour of Hall Heroult cells, including precise estimation of energy losses and location of the side ledge formed by the solidification of electrolytic bath, is made possible when the sidelining materials are well characterized in function of temperature. The present work aim at measuring the thermal diffusivity, heat capacity and thermal conductivity of silicon carbide (SiC), graphitic and graphitized carbon materials and cryolite (Na3AlF 6) based on transient characterization techniques. The thermal diffusivity and the heat capacity are measured by using state-of-the-art transient laser flash analyzer and differential scanning calorimeter respectively. The thermal conductivity is calculated by assuming a constant density. The range of precision error for each thermal property is also calculated for a finite number of data sets. Empirical correlation has been drawn for each of the properties to describe the relation with temperature in mathematical terms. Thermal characterization of the latent heat evolved during the melting of ledge is also carried out. Finally, based on the calculations conducted with a 2-D numerical model, the effect of the precision errors of temperature varying thermal properties of the sidewall materials and ledge on the dynamic behaviour of a laboratory scale phase change reactor is also presented. The results, so obtained, encourage further studies on the thermal properties of materials used in the aluminium reduction cell to find out the thermal environment inside the cell, heat loss estimation and effect of the additives on the location of ledge. Key words: Thermal conductivity, thermal diffusivity, heat capacity, temperature varying properties, precision error, phase change profile, latent heat.
Modeling thermal properties of plutonium mononitride
NASA Astrophysics Data System (ADS)
Yu, H. L.; Huang, H.; Li, G.; Li, H. B.; Meng, D. Q.
2015-06-01
The thermal properties of plutonium mononitride (PuN) were investigated by molecular dynamics method. The interatomic potentials of PuN were fitted by using Chen-Möbius multiple lattice inversion technique. Based on these interatomic potentials, the lattice constant, bulk modulus, compressibility, cohesive energy and heat capacity of PuN were obtained and the results are well consistent with experimental data and previous reports. It indicates that the potentials we build in this study are effective for studying thermal properties of PuN.
Thermal and thermoelectric properties of graphene.
Xu, Yong; Li, Zuanyi; Duan, Wenhui
2014-06-12
The subject of thermal transport at the mesoscopic scale and in low-dimensional systems is interesting for both fundamental research and practical applications. As the first example of truly two-dimensional materials, graphene has exceptionally high thermal conductivity, and thus provides an ideal platform for the research. Here we review recent studies on thermal and thermoelectric properties of graphene, with an emphasis on experimental progresses. A general physical picture based on the Landauer transport formalism is introduced to understand underlying mechanisms. We show that the superior thermal conductivity of graphene is contributed not only by large ballistic thermal conductance but also by very long phonon mean free path (MFP). The long phonon MFP, explained by the low-dimensional nature and high sample purity of graphene, results in important isotope effects and size effects on thermal conduction. In terms of various scattering mechanisms in graphene, several approaches are suggested to control thermal conductivity. Among them, introducing rough boundaries and weakly-coupled interfaces are promising ways to suppress thermal conduction effectively. We also discuss the Seebeck effect of graphene. Graphene itself might not be a good thermoelectric material. However, the concepts developed by graphene research might be applied to improve thermoelectric performance of other materials.
THERMAL: A routine designed to calculate neutron thermal scattering. Revision 1
Cullen, D.E.
1995-09-19
THERMAL is designed to calculate neutron thermal scattering that is elastic and isotropic in the center of mass system. At low energy thermal motion will be included. At high energies the target nuclei are assumed to be stationary. The point of transition between low and high energies has been defined to insure a smooth transition. It is assumed that at low energy the elastic cross section is constant in the relative system. At high energy the cross section can be of any form. You can use this routine for all energies where the elastic scattering is isotropic in the center of mass system. In most materials this will be a fairly high energy, e.g., the keV energy range. The THERMAL method is simple, clean, easy to understand, and most important very efficient; on a SUN SPARC-10 workstation, at low energies with thermal scattering it can do almost 6 million scatters a minute and at high energy over 13 million. Warning: This version of THERMAL completely supersedes the original version described in the same report number, dated February 24, 1995. The method used in the original code is incorrect, as explained in this report.
Microscopic calculation of thermally induced spin-transfer torques
NASA Astrophysics Data System (ADS)
Kohno, Hiroshi; Hiraoka, Yuuki; Hatami, Moosa; Bauer, Gerrit E. W.
2016-09-01
Spin-transfer torques, both reactive and dissipative, induced by temperature gradients in conducting ferromagnets are calculated microscopically for smooth magnetization textures. Temperature gradients are treated à la Luttinger by introducing a fictitious gravitational field that couples to the energy density. The thermal torque coefficients obtained by the Kubo formula contain unphysical terms that diverge towards zero temperature. Such terms are caused by equilibrium components and should be subtracted before applying the Einstein-Luttinger relation. Only by following this procedure a familiar Mott-like formula is obtained for the dissipative spin-transfer torque. The result indicates that a fictitious field that couples to the entropy rather than energy would solve the issue from the outset.
Calculation and application of combined diffusion coefficients in thermal plasmas
NASA Astrophysics Data System (ADS)
Murphy, Anthony B.
2014-03-01
The combined diffusion coefficient method is widely used to treat the mixing and demixing of different plasma gases and vapours in thermal plasmas, such as welding arcs and plasma jets. It greatly simplifies the treatment of diffusion for many gas mixtures without sacrificing accuracy. Here, three subjects that are important in the implementation of the combined diffusion coefficient method are considered. First, it is shown that different expressions for the combined diffusion coefficients, arising from different definitions for the stoichiometric coefficients that assign the electrons to the two gases, are equivalent. Second, an approach is presented for calculating certain partial differential terms in the combined temperature and pressure diffusion coefficients that can cause difficulties. Finally, a method for applying the combined diffusion coefficients in computational models, which typically require diffusion to be expressed in terms of mass fraction gradients, is given.
Calculation and application of combined diffusion coefficients in thermal plasmas.
Murphy, Anthony B
2014-03-07
The combined diffusion coefficient method is widely used to treat the mixing and demixing of different plasma gases and vapours in thermal plasmas, such as welding arcs and plasma jets. It greatly simplifies the treatment of diffusion for many gas mixtures without sacrificing accuracy. Here, three subjects that are important in the implementation of the combined diffusion coefficient method are considered. First, it is shown that different expressions for the combined diffusion coefficients, arising from different definitions for the stoichiometric coefficients that assign the electrons to the two gases, are equivalent. Second, an approach is presented for calculating certain partial differential terms in the combined temperature and pressure diffusion coefficients that can cause difficulties. Finally, a method for applying the combined diffusion coefficients in computational models, which typically require diffusion to be expressed in terms of mass fraction gradients, is given.
Effect of molecular models on viscosity and thermal conductivity calculations
NASA Astrophysics Data System (ADS)
Weaver, Andrew B.; Alexeenko, Alina A.
2014-12-01
The effect of molecular models on viscosity and thermal conductivity calculations is investigated. The Direct Simulation Monte Carlo (DSMC) method for rarefied gas flows is used to simulate Couette and Fourier flows as a means of obtaining the transport coefficients. Experimental measurements for argon (Ar) provide a baseline for comparison over a wide temperature range of 100-1,500 K. The variable hard sphere (VHS), variable soft sphere (VSS), and Lennard-Jones (L-J) molecular models have been implemented into a parallel version of Bird's one-dimensional DSMC code, DSMC1, and the model parameters have been recalibrated to the current experimental data set. While the VHS and VSS models only consider the short-range, repulsive forces, the L-J model also includes constributions from the long-range, dispersion forces. Theoretical results for viscosity and thermal conductivity indicate the L-J model is more accurate than the VSS model; with maximum errors of 1.4% and 3.0% in the range 300-1,500 K for L-J and VSS models, respectively. The range of validity of the VSS model is extended to 1,650 K through appropriate choices for the model parameters.
Monte Carlo calculations of elementary particle properties
NASA Technical Reports Server (NTRS)
Guralnik, G. S.; Warnock, T.; Zemach, C.
1984-01-01
The object of this project is to calculate the masses of the elementary particles. This ambitious goal apparently is not possible using analytic methods or known approximation methods. However, it is probable that the power of a modern super computer will make at least part of the low lying mass spectrum accessible through direct numerical computation. Initial attempts by several groups at calculating this spectrum on small lattices of space time points have been very promising. Using new methods and super computers considerable progress has been made towards evaluating the mass spectrum on comparatively large lattices. Only more time and faster machines with increased storage will allow calculations of systems with guaranteed minimal boundary effects. The ideas that currently go into this calculation are outlined.
Calculation of Hugoniot values from atomic properties
Walker, F.E.; Walker, F.G.; Walker, J.B.
1986-01-01
A relatively simple equation is presented for use in calculating the Hugoniot values of any condensed element from its atomic weight, atomic radius, and density. Calculations from the equation are compared with data for many elements, and a discussion of the development and utility of the equation is included. The equation also appears to be useful for the gaseous elements when they are in condensed phases. 19 refs., 12 figs., 9 tabs.
Coefficients for calculating thermodynamic and transport properties of individual species
NASA Technical Reports Server (NTRS)
Mcbride, Bonnie J.; Gordon, Sanford; Reno, Martin A.
1993-01-01
Libraries of thermodynamic data and transport properties are given for individual species in the form of least-squares coefficients. Values of C(sup 0)(sub p)(T), H(sup 0)(T), and S(sup 0)(T) are available for 1130 solid, liquid, and gaseous species. Viscosity and thermal conductivity data are given for 155 gases. The original C(sup 0)(sub p)(T) values were fit to a fourth-order polynomial with integration constants for H(sup 0)(T) and S(sup 0)(T). For each species the integration constant for H(sup 0)(T) includes the heat of formation. Transport properties have a different functional form. The temperature range for most of the data is 300 to 5000 K, although some of the newer thermodynamic data have a range of 200 to 6000 K. Because the species are mainly possible products of reaction, the data are useful for chemical equilibrium and kinetics computer codes. Much of the data has been distributed for several years with the NASA Lewis equilibrium program CET89. The thermodynamic properties of the reference elements were updated along with about 175 species that involve the elements carbon, hydrogen, oxygen, and nitrogen. These sets of data will be distributed with the NASA Lewis personal computer program for calculating chemical equilibria, CETPC.
Thermal Properties for the Thermal-Hydraulics Analyses of the BR2 Maximum Nominal Heat Flux
Dionne, B.; Bergeron, A.; Licht, J. R.; Kim, Y. S.; Hofman, G. L.
2015-02-01
This memo describes the assumptions and references used in determining the thermal properties for the various materials used in the BR2 HEU (93% enriched in ^{235}U) to LEU (19.75% enriched in ^{235}U) conversion feasibility analysis. More specifically, this memo focuses on the materials contained within the pressure vessel (PV), i.e., the materials that are most relevant to the study of impact of the change of fuel from HEU to LEU. Section 2 provides a summary of the thermal properties in the form of tables while the following sections and appendices present the justification of these values. Section 3 presents a brief background on the approach used to evaluate the thermal properties of the dispersion fuel meat and specific heat capacity. Sections 4 to 7 discuss the material properties for the following materials: i) aluminum, ii) dispersion fuel meat (UAlx-Al and U-7Mo-Al), iii) beryllium, and iv) stainless steel. Section 8 discusses the impact of irradiation on material properties. Section 9 summarizes the material properties for typical operating temperatures. Appendix A elaborates on how to calculate dispersed phase’s volume fraction. Appendix B provides a revised methodology for determining the thermal conductivity as a function of burnup for HEU and LEU.
Native Cellulose: Structure, Characterization and Thermal Properties
Poletto, Matheus; Ornaghi Júnior, Heitor L.; Zattera, Ademir J.
2014-01-01
In this work, the relationship between cellulose crystallinity, the influence of extractive content on lignocellulosic fiber degradation, the correlation between chemical composition and the physical properties of ten types of natural fibers were investigated by FTIR spectroscopy, X-ray diffraction and thermogravimetry techniques. The results showed that higher extractive contents associated with lower crystallinity and lower cellulose crystallite size can accelerate the degradation process and reduce the thermal stability of the lignocellulosic fibers studied. On the other hand, the thermal decomposition of natural fibers is shifted to higher temperatures with increasing the cellulose crystallinity and crystallite size. These results indicated that the cellulose crystallite size affects the thermal degradation temperature of natural fibers. This study showed that through the methods used, previous information about the structure and properties of lignocellulosic fibers can be obtained before use in composite formulations. PMID:28788179
Measurement of directional thermal properties of biomaterials.
Bhavaraju, N C; Cao, H; Yuan, D Y; Valvano, J W; Webster, J G
2001-02-01
This paper presents an experimental technique to measure the directional thermal conductivity and thermal diffusivity of materials. A heated thermistor heats the sample and a sensing thermistor placed about 2.5 mm away measures the temperature rise due the heating pulse at the heated thermistor. An empirical relation between the power delivered by the first thermistor and the temperature rise recorded by the sensing thermistor is used to measure the thermal conductivity of the material along the line joining the thermistors. Diffusivity of the material is determined from the delay between the power pulse in the heated thermistor and the temperature pulse at the sensing thermistor. Signal processing was done to eliminate errors in the measurement due to change of base line temperature. Uncertainty of the measurement technique was found to be 5% when tested in media of known thermal properties. The thermal conductivity and thermal diffusivity of swine left ventricle in normal and ablated conditions were measured using this technique. The thermal conductivity of the tissue dropped significantly from 0.61 to 0.50 W.m(-1).K(-1) after ablation while the diffusivity dropped from 2.1 x 10(-7) to 1.7 x 10(-7)m2.s(-1).
Optimization of Norbornadiene Compounds for Solar Thermal Storage by First-Principles Calculations.
Kuisma, Mikael; Lundin, Angelica; Moth-Poulsen, Kasper; Hyldgaard, Per; Erhart, Paul
2016-07-21
Molecular photoswitches capable of storing solar energy are interesting candidates for future renewable energy applications. Here, using quantum mechanical calculations, we carry out a systematic screening of crucial optical (solar spectrum match) and thermal (storage energy density) properties of 64 such compounds based on the norbornadiene-quadricyclane system. Whereas a substantial number of these molecules reach the theoretical maximum solar power conversion efficiency, this requires a strong red-shift of the absorption spectrum, which causes undesirable absorption by the photoisomer as well as reduced thermal stability. These compounds typically also have a large molecular mass, leading to low storage densities. By contrast, single-substituted systems achieve a good compromise between efficiency and storage density, while avoiding competing absorption by the photo-isomer. This establishes guiding principles for the future development of molecular solar thermal storage systems. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Novel thermal properties of nanostructured materials.
Eastman, J. A.
1999-01-13
A new class of heat transfer fluids, termed nanofluids, has been developed by suspending nanocrystalline particles in liquids. Due to the orders-of-magnitude larger thermal conductivities of solids compared to those of liquids such as water, significantly enhanced thermal properties are obtained with nanofluids. For example, an approximately 20% improvement in effective thermal conductivity is observed when 5 vol.% CuO nanoparticles are added to water. Even more importantly, the heat transfer coefficient of water under dynamic flow conditions is increased more than 15% with the addition of less than 1 vol.% CuO particles. The use of nanofluids could impact many industrial sectors, including transportation, energy supply and production, electronics, textiles, and paper production by, for example, decreasing pumping power needs or reducing heat exchanger sizes. In contrast to the enhancement in effective thermal transport rates that is obtained when nanoparticles are suspended in fluids, nanocrystalline coatings are expected to exhibit reduced thermal conductivities compared to coarse-grained coatings. Reduced thermal conductivities are predicted to arise because of a reduction in the mean free path of phonons due to presence of grain boundaries. This behavior, combined with improved mechanical properties, makes nanostructured zirconia coatings excellent candidates for future applications as thermal barriers. Yttria-stabilized zirconia (YSZ) thin films are being produced by metal-organic chemical vapor deposition techniques. Preliminary results have indicated that the thermal conductivity is reduced by approximately a factor-of-two at room temperature in 10 nm grain-sized YSZ compared to coarse-grained or single crystal YSZ.
Calculated fission properties of the heaviest elements
Moeller, P.; Nix, J.R.; Swiatecki, W.J.
1986-09-01
A quantitative calculation is presented that shows where high-kinetic-energy symmetric fission occurs and why it is associated with a sudden and large decrease in fission half-lives. The study is based on calculations of potential-energy surfaces in the macroscopic-microscopic model and a semi-empirical model for the nuclear inertia. For the macroscopic part a Yukawa-plus-exponential model is used and for the microscopic part a folded-Yukawa single-particle potential is used. The three-quadratic-surface parameterization generates shapes for which the potential-energy surfaces are calculated. The use of this parameterization and the use of the finite-range macroscopic model allows for the study of two touching spheres and similar shapes. The results of the calculations in terms of potential-energy surfaces and fission half-lives are presented for heavy even nuclei. The surfaces are displayed in the form of contour diagrams as functions of two moments of the shape. 53 refs., 15 figs., 1 tab.
Thermal properties of food and pharmaceutical powders
NASA Astrophysics Data System (ADS)
Abiad, Mohamad Ghassan
Foods and pharmaceuticals are complex systems usually exposed to various environmental conditions during processing and thus storage, stability, functionality and quality are key attributes that deserve careful attention. The quality and stability of foods and pharmaceuticals are mainly affected by environmental conditions such as temperature, humidity, time, and processing conditions (e.g. shear, pressure) under which they may undergo physical and/or chemical transformations. Glass transition as well as other thermal properties is a key to understand how external conditions affect physical changes of such materials. Development of new materials and understanding the physico-chemical behavior of existing ones require a scientific foundation that translates into safe and high quality foods, improved quality of pharmaceuticals and nutraceuticals with lower risk to patients and functional efficacy of polymers used in food and medicinal products. This research provides an overview of the glass transition and other thermal properties and introduces novel methods developed to characterize such properties.
Heuze, F.E.
1983-03-01
An attempt to model the complex thermal and mechanical phenomena occurring in the disposal of high-level nuclear wastes in rock at high power loading is described. Such processes include melting of the rock, convection of the molten material, and very high stressing of the rock mass, leading to new fracturing. Because of the phase changes and the wide temperature ranges considered, realistic models must provide for coupling of the thermal and mechanical calculations, for large deformations, and for steady-state temperature-depenent creep of the rock mass. Explicit representation of convection would be desirable, as would the ability to show fracture development and migration of fluids in cracks. Enhancements to SNAGRE consisted of: array modifications to accommodate complex variations of thermal and mechanical properties with temperature; introduction of the ability of calculate thermally induced stresses; improved management of the minimum time step and minimum temperature step to increase code efficiency; introduction of a variable heat-generation algorithm to accommodate heat decay of the nuclear materials; streamlining of the code by general editing and extensive deletion of coding used in mesh generation; and updating of the program users' manual. The enhanced LLNL version of the code was renamed LSANGRE. Phase changes were handled by introducing sharp variations in the specific heat of the rock in a narrow range about the melting point. The accuracy of this procedure was tested successfully on a melting slab problem. LSANGRE replicated the results of both the analytical solution and calculations with the finite difference TRUMP code. Following enhancement and verification, a purely thermal calculation was carried to 105 years. It went beyond the extent of maximum melt and into the beginning of the cooling phase.
Measurement of textile materials thermal properties
NASA Astrophysics Data System (ADS)
Fournier, M.; Duvaut, T.; Chirtoc, M.; Bachmann, J. M.
2008-01-01
The determination of thermal properties of textile materials is difficult and subject to errors. Here we used two experimental methods. A PhotoPyroElectric method (Front PPE configuration with a modulated heat flow imposed on the surface of the sensor) and a commercial device (Alambeta) based the hot plate method. Two theorical approaches for the latter device were used. We tested the two methods on different textile materials (cotton, modal, wool and spacer). We observe good agreement between thermal conductivities measured with the two methods.
Effect of element density on the NASTRAN calculated mechanical and thermal stresses of a spar
NASA Technical Reports Server (NTRS)
Jenkins, J. M.
1979-01-01
A NASTRAN model of a spar was examined to determine the sensitivity of calculated axial thermal stresses and bending stresses to changes in element density of the model. The thermal stresses calculated with three different element densities resulted in drastically differing values. The position of the constraint also significantly affected the value of the calculated thermal stresses. Mechanical stresses calculated from an applied loading were insensitive to element density.
Thermal conductivity of wurtzite and zinc blende cubic phases of BeO from ab initio calculations
NASA Astrophysics Data System (ADS)
Malakkal, Linu; Szpunar, Barbara; Siripurapu, Ravi Kiran; Zuniga, Juan Carlos; Szpunar, Jerzy A.
2017-03-01
The structural, mechanical, thermal and thermodynamic properties of Beryllium oxide (BeO) in the zinc blende (ZB) and wurtzite (WZ) form have been calculated using the density functional theory (DFT) in the general gradient approximation (GGA). The ground state structural and elastic properties of wurtzite BeO (w-BeO) is calculated using the new GGA ultrasoft pseudopotentials for solids (pbesol); the simulated results have shown excellent agreement with the experiments. The thermodynamic properties are studied using quasi-harmonic approximation (QHA), and the predicted properties agree well for the WZ phase for which the experimental data are available, while for ZB phase it remains to be validated with future experiments. Both Boltzmann transport equation (BTE) and Slack model were used to calculate the lattice thermal conductivity of wurtzite BeO (w-BeO). Furthermore, the thermal conductivity along the crystallographic 'a' and 'c' axis of wurtzite BeO is investigated using BTE. Our calculation of w-BeO agrees well with the available experimental measurements. Apart from these studies on w-BeO, we have also compared the mechanical, structural and phonon dispersions of z-BeO with previously reported theoretical studies. Additionally we report the volume thermal expansion and the heat capacity at constant pressure of z-BeO for the first time and the bulk thermal conductivity of zinc blende BeO (z-BeO) using BTE.
Heat Transfer Principles in Thermal Calculation of Structures in Fire.
Zhang, Chao; Usmani, Asif
2015-11-01
Structural fire engineering (SFE) is a relatively new interdisciplinary subject, which requires a comprehensive knowledge of heat transfer, fire dynamics and structural analysis. It is predominantly the community of structural engineers who currently carry out most of the structural fire engineering research and design work. The structural engineering curriculum in universities and colleges do not usually include courses in heat transfer and fire dynamics. In some institutions of higher education, there are graduate courses for fire resistant design which focus on the design approaches in codes. As a result, structural engineers who are responsible for structural fire safety and are competent to do their jobs by following the rules specified in prescriptive codes may find it difficult to move toward performance-based fire safety design which requires a deep understanding of both fire and heat. Fire safety engineers, on the other hand, are usually focused on fire development and smoke control, and may not be familiar with the heat transfer principles used in structural fire analysis, or structural failure analysis. This paper discusses the fundamental heat transfer principles in thermal calculation of structures in fire, which might serve as an educational guide for students, engineers and researchers. Insights on problems which are commonly ignored in performance based fire safety design are also presented.
Tables for simplifying calculations of activities produced by thermal neutrons
Senftle, F.E.; Champion, W.R.
1954-01-01
The method of calculation described is useful for the types of work of which examples are given. It is also useful in making rapid comparison of the activities that might be expected from several different elements. For instance, suppose it is desired to know which of the three elements, cobalt, nickel, or vanadium is, under similar conditions, activated to the greatest extent by thermal neutrons. If reference is made to a cross-section table only, the values may be misleading unless properly interpreted by a suitable comparison of half-lives and abundances. In this table all the variables have been combined and the desired information can be obtained directly from the values of A 3??, the activity produced per gram per second of irradiation, under the stated conditions. Hence, it is easily seen that, under similar circumstances of irradiation, vanadium is most easily activated even though the cross section of one of the cobalt isotopes is nearly five times that of vanadium and the cross section of one of the nickel isotopes is three times that of vanadium. ?? 1954 Societa?? Italiana di Fisica.
Heat Transfer Principles in Thermal Calculation of Structures in Fire
Zhang, Chao; Usmani, Asif
2016-01-01
Structural fire engineering (SFE) is a relatively new interdisciplinary subject, which requires a comprehensive knowledge of heat transfer, fire dynamics and structural analysis. It is predominantly the community of structural engineers who currently carry out most of the structural fire engineering research and design work. The structural engineering curriculum in universities and colleges do not usually include courses in heat transfer and fire dynamics. In some institutions of higher education, there are graduate courses for fire resistant design which focus on the design approaches in codes. As a result, structural engineers who are responsible for structural fire safety and are competent to do their jobs by following the rules specified in prescriptive codes may find it difficult to move toward performance-based fire safety design which requires a deep understanding of both fire and heat. Fire safety engineers, on the other hand, are usually focused on fire development and smoke control, and may not be familiar with the heat transfer principles used in structural fire analysis, or structural failure analysis. This paper discusses the fundamental heat transfer principles in thermal calculation of structures in fire, which might serve as an educational guide for students, engineers and researchers. Insights on problems which are commonly ignored in performance based fire safety design are also presented. PMID:26783379
Three-dimensional surface grid generation for calculation of thermal radiation shape factors
NASA Technical Reports Server (NTRS)
Aly, Hany M.
1992-01-01
A technique is described to generate three dimensional surface grids suitable for calculating shape factors for thermal radiative heat transfer. The surface under consideration is approximated by finite triangular elements generated in a special manner. The grid is generated by dividing the surface into a two dimensional array of nodes. Each node is defined by its coordinates. Each set of four adjacent nodes is used to construct two triangular elements. Each triangular element is characterized by the vector representation of its vertices. Vector algebra is used to calculate all desired geometric properties of grid elements. The properties are used to determine the shape factor between the element and an area element in space. The grid generation can be graphically displayed using any software with three dimensional features. DISSPLA was used to view the grids.
Thermal properties of methane gas hydrates
Waite, William F.
2007-01-01
Gas hydrates are crystalline solids in which molecules of a “guest” species occupy and stabilize cages formed by water molecules. Similar to ice in appearance (fig. 1), gas hydrates are stable at high pressures and temperatures above freezing (0°C). Methane is the most common naturally occurring hydrate guest species. Methane hydrates, also called simply “gas hydrates,” are extremely concentrated stores of methane and are found in shallow permafrost and continental margin sediments worldwide. Brought to sea-level conditions, methane hydrate breaks down and releases up to 160 times its own volume in methane gas. The methane stored in gas hydrates is of interest and concern to policy makers as a potential alternative energy resource and as a potent greenhouse gas that could be released from sediments to the atmosphere and ocean during global warming. In continental margin settings, methane release from gas hydrates also is a potential geohazard and could cause submarine landslides that endanger offshore infrastructure. Gas hydrate stability is sensitive to temperature changes. To understand methane release from gas hydrate, the U.S. Geological Survey (USGS) conducted a laboratory investigation of pure methane hydrate thermal properties at conditions relevant to accumulations of naturally occurring methane hydrate. Prior to this work, thermal properties for gas hydrates generally were measured on analog systems such as ice and non-methane hydrates or at temperatures below freezing; these conditions limit direct comparisons to methane hydrates in marine and permafrost sediment. Three thermal properties, defined succinctly by Briaud and Chaouch (1997), are estimated from the experiments described here: - Thermal conductivity, λ: if λ is high, heat travels easily through the material. - Thermal diffusivity, κ: if κ is high, it takes little time for the temperature to rise in the material. - Specific heat, cp: if cp is high, it takes a great deal of heat to
Acoustic and thermal properties of tissue
NASA Astrophysics Data System (ADS)
Retat, L.; Rivens, I.; ter Haar, G. R.
2012-10-01
Differences in ultrasound (US) and thermal properties of abdominal soft tissues may affect the delivery of thermal therapies such as high intensity focused ultrasound and may provide a basis for US monitoring of such therapies. 21 rat livers were obtained, within one hour of surgical removal. For a single liver, 3 lobes were selected and each treated in one of 3 ways: maintained at room temperature, water bath heated to 50°C ± 1°C for 10 ± 0.5 minutes, or water bath heated to 60°C ± 1°C for 10 ± 0.6 minutes. The attenuation coefficient, speed of sound and thermal conductivity of fresh rat liver was measured. The attenuation coefficients and speed of sound were measured using the finite-amplitude insertion-substitution (FAIS) method. For each rat liver, the control and treated lobes were scanned using a pair of weakly focused 2.5 MHz Imasonic transducers over the range 1.8 to 3 MHz. The conductivity measurement apparatus was designed to provide one-dimensional heat flow through each specimen using a combination of insulation, heat source and heat sink. Using 35 MHz US images to determine the volume of air trapped in the system, the thermal conductivity was corrected using a simulation based on the Helmhotz bio-heat equation. The process of correlating these results with biological properties is discussed.
Post-test thermal calculations and data analyses for the Spent Fuel Test, Climax
Montan, D.N.; Patrick, W.C.
1986-06-01
After the Spent Fuel Test - Climax (SFT-C) was completed, additional calculations were performed using the best available (directly measured or inferred from measurements made during the test) input parameters, thermal properties, and power levels. This report documents those calculations and compares the results with measurements made during the three-year heating phase and six-month posttest cooling phase of the SFT-C. Three basic types of heat-transfer calculations include a combined two-dimensional/three-dimensional, infinite-length, finite-difference model; a fully three-dimensional, finite-length, finite-difference model; and a fully three-dimensional, finite-length, analytical solution. The finite-length model much more accurately reflects heat flow near the ends of the array and produces cooler temperatures everywhere than does its infinite-length counterpart. 14 refs., 144 figs., 4 tabs.
Adsorption properties of thermally sputtered calcein film
NASA Astrophysics Data System (ADS)
Kruglenko, I.; Burlachenko, J.; Kravchenko, S.; Savchenko, A.; Slabkovska, M.; Shirshov, Yu.
2014-05-01
High humidity environments are often found in such areas as biotechnology, food chemistry, plant physiology etc. The controlling of parameters of such ambiences is vitally important. Thermally deposited calcein films have extremely high adsorptivity at exposure to water vapor of high concentration. This feature makes calcein a promising material for humidity sensing applications. The aim of this work is to explain high sensitivity and selectivity of calcein film to high humidity. Quartz crystal microbalance sensor, AFM and ellipsometry were used for calcein film characterization and adsorption properties investigation. The proposed model takes into account both the molecular properties of calcein (the presence of several functional groups capable of forming hydrogen bonds, and their arrangement) and the features of structure of thermally deposited calcein film (film restructuring due to the switching of bonds "calcein-calcein" to "calcein-water" in the course of water adsorption).
Computation of Thermally Perfect Compressible Flow Properties
NASA Technical Reports Server (NTRS)
Witte, David W.; Tatum, Kenneth E.; Williams, S. Blake
1996-01-01
A set of compressible flow relations for a thermally perfect, calorically imperfect gas are derived for a value of c(sub p) (specific heat at constant pressure) expressed as a polynomial function of temperature and developed into a computer program, referred to as the Thermally Perfect Gas (TPG) code. The code is available free from the NASA Langley Software Server at URL http://www.larc.nasa.gov/LSS. The code produces tables of compressible flow properties similar to those found in NACA Report 1135. Unlike the NACA Report 1135 tables which are valid only in the calorically perfect temperature regime the TPG code results are also valid in the thermally perfect, calorically imperfect temperature regime, giving the TPG code a considerably larger range of temperature application. Accuracy of the TPG code in the calorically perfect and in the thermally perfect, calorically imperfect temperature regimes are verified by comparisons with the methods of NACA Report 1135. The advantages of the TPG code compared to the thermally perfect, calorically imperfect method of NACA Report 1135 are its applicability to any type of gas (monatomic, diatomic, triatomic, or polyatomic) or any specified mixture of gases, ease-of-use, and tabulated results.
Thermal properties of an erythritol derivative
NASA Astrophysics Data System (ADS)
Trhlikova, Lucie; Prikryl, Radek; Zmeskal, Oldrich
2016-06-01
Erythritol (C4H10O4) is a sugar alcohol (or polyol) that is commonly used in the food industry. Its molar mass is 122.12 g.mol-1 and mass density 1450 kg.m-3. Erythritol, an odorless crystalline powder, can also be characterized by other physical parameters like melting temperature (121 °C) and boiling temperature (329 °C). The substance can be used for the accumulation of energy in heat exchangers based on various oils or water. The PlusICE A118 product manufactured by the PCM Products Ltd. company (melting temperature Θ = 118 °C, specific heat capacity cp = 2.70 kJ.K-1.kg-1, mass density 1450 kg.m-3, latent heat capacity 340 kJ.kg-1, volumetric heat capacity 493 MJ.m-3) is based on an erythritol-type medium. Thermal properties of the PlusICE A118 product in both solid and liquid phase were investigated for this purpose in terms of potential applications. Temperature dependences of its thermal parameters (thermal diffusivity, thermal conductivity, and specific heat) were determined using a transient (step-wise) method. A fractal model of heat transport was used for determination of the above thermal parameters. This model is independent of geometry and type of sample heating. Moreover, it also considers heat losses. The experiment confirmed the formerly declared value of phase change temperature, about 120 °C.
Computer code for determination of thermally perfect gas properties
NASA Technical Reports Server (NTRS)
Witte, David W.; Tatum, Kenneth E.
1994-01-01
A set of one-dimensional compressible flow relations for a thermally perfect, calorically imperfect gas is derived for the specific heat c(sub p), expressed as a polynomial function of temperature, and developed into the thermally perfect gas (TPG) computer code. The code produces tables of compressible flow properties similar to those of NACA Rep. 1135. Unlike the tables of NACA Rep. 1135 which are valid only in the calorically perfect temperature regime, the TPG code results are also valid in the thermally perfect calorically imperfect temperature regime which considerably extends the range of temperature application. Accuracy of the TPG code in the calorically perfect temperature regime is verified by comparisons with the tables of NACA Rep. 1135. In the thermally perfect, calorically imperfect temperature regime, the TPG code is validated by comparisons with results obtained from the method of NACA Rep. 1135 for calculating the thermally perfect calorically imperfect compressible flow properties. The temperature limits for application of the TPG code are also examined. The advantage of the TPG code is its applicability to any type of gas (monatomic, diatomic, triatomic, or polyatomic) or any specified mixture thereof, whereas the method of NACA Rep. 1135 is restricted to only diatomic gases.
Zhang, Tianbiao; Zhao, Ying; Tong, Zhaoxue; Guan, Yifu
2016-01-01
Mechanical properties, as the inherent characteristics of cells, play a critical role in many essential physiological processes, including cell differentiation, migration, and growth. The mechanical properties of cells are one of the criteria that help to determine whether the tissue contains lesions at the single cell level, and it is very important for the early prevention and accurate diagnosis of diseases. Atomic force microscopy (AFM) makes it possible to measure the mechanical properties at single cell level in physiological state. This paper presents a novel method to calculate the mechanical properties of cancer cells more accurately through Atomic force microscopy. A new induced equation of Hertz's model, called differential Hertz's model, has been proposed to calculate the mechanical properties of cancer cells. Moreover, the substrate effect has also been effectively reduced through comparing the calculated mechanical properties of cell at different cell surface areas. The results indicate that the method utilized to calculate the mechanical properties of cells can effectively eliminate the errors in calculation, caused by the thermal drift of AFM system and the substrate effect, and thus improve the calculation accuracy. The mechanical properties calculated by our method in this study are closer to the actual value. Thus, this method shows potential for use in establishing a standard library of Young's modulus.
WASP: A flexible FORTRAN 4 computer code for calculating water and steam properties
NASA Technical Reports Server (NTRS)
Hendricks, R. C.; Peller, I. C.; Baron, A. K.
1973-01-01
A FORTRAN 4 subprogram, WASP, was developed to calculate the thermodynamic and transport properties of water and steam. The temperature range is from the triple point to 1750 K, and the pressure range is from 0.1 to 100 MN/m2 (1 to 1000 bars) for the thermodynamic properties and to 50 MN/m2 (500 bars) for thermal conductivity and to 80 MN/m2 (800 bars) for viscosity. WASP accepts any two of pressure, temperature, and density as input conditions. In addition, pressure and either entropy or enthalpy are also allowable input variables. This flexibility is especially useful in cycle analysis. The properties available in any combination as output include temperature, density, pressure, entropy, enthalpy, specific heats, sonic velocity, viscosity, thermal conductivity, surface tension, and the Laplace constant. The subroutine structure is modular so that the user can choose only those subroutines necessary to his calculations. Metastable calculations can also be made by using WASP.
Tabulated In-Drift Geometric and Thermal Properties Used In Drift-Scale Models for TSPA-SR
N.D. Francis
2000-06-16
The objective of this calculation is to provide in-drift physical properties required by the drift-scale models (both two- and three-dimensional) used in total system performance assessments (TSPA). The physical properties include waste package geometry, waste package thermal properties, emplacement drift geometry including backfill and invert geometry and properties (both thermal and hydrologic), drip shield geometry and thermal properties, all tabulated in a single source.
First-principles calculations on thermodynamic properties of BaTiO3 rhombohedral phase.
Bandura, Andrei V; Evarestov, Robert A
2012-07-05
The calculations based on the linear combination of atomic orbitals have been performed for the low-temperature phase of BaTiO(3) crystal. Structural and electronic properties, as well as phonon frequencies were obtained using hybrid PBE0 exchange-correlation functional. The calculated frequencies and total energies at different volumes have been used to determine the equation of state and thermal contribution to the Helmholtz free energy within the quasiharmonic approximation. For the first time, the bulk modulus, volume thermal expansion coefficient, heat capacity, and Grüneisen parameters in BaTiO(3) rhombohedral phase have been estimated at zero pressure and temperatures form 0 to 200 K, based on the results of first-principles calculations. Empirical equation has been proposed to reproduce the temperature dependence of the calculated quantities. The agreement between the theoretical and experimental thermodynamic properties was found to be satisfactory. Copyright © 2012 Wiley Periodicals, Inc.
NASA Astrophysics Data System (ADS)
Viswanathan, E.; Sundareswari, M.; Jayalakshmi, D. S.; Manjula, M.; Krishnaveni, S.
2017-09-01
First principles calculations are carried out in order to analyze the structural, electronic, mechanical, thermal and optical properties of BP and BAs compounds by ternary alloying with nitrogen namely B(P,As)1-xNx (x = 0.25, 0.5, 0.75) alloys at ambient condition. Thereby we report the mechanical and thermal properties of B(P,As)1-xNx (x = 0.25, 0.5, 0.75) alloys namely bulk modulus, shear modulus, Young's modulus, hardness, ductile-brittle nature, elastic wave velocity, Debye temperature, melting point, etc.; optical properties of B(P)1-xNx (x = 0.25, 0.5, 0.75) and B(As)1-xNx (x = 0.25, 0.75) alloys namely the dielectric function of real and imaginary part, refractive index, extinction coefficient and reflectivity and the hardness profile of the parent compounds BP and BAs under compression. The charge density plot, density of states histograms and band structures are plotted and discussed for all the ternary alloys of the present study. The calculated results agree very well with the available literature. Analysis of the present study reveals that the ternary alloy combinations namely BP.25N.75 and BAs.25N.75 could be superhard materials; hardness of BP and BAs increases with compression.
Crystal dynamics and thermal properties of neptunium dioxide
NASA Astrophysics Data System (ADS)
Maldonado, P.; Paolasini, L.; Oppeneer, P. M.; Forrest, T. R.; Prodi, A.; Magnani, N.; Bosak, A.; Lander, G. H.; Caciuffo, R.
2016-04-01
We report an experimental and theoretical investigation of the lattice dynamics and thermal properties of the actinide dioxide NpO2. The energy-wave-vector dispersion relation for normal modes of vibration propagating along the [001 ] , [110 ] , and [111 ] high-symmetry lines in NpO2 at room temperature has been determined by measuring the coherent one-phonon scattering of x rays from an ˜1.2 -mg single-crystal specimen, the largest available single crystal for this compound. The results are compared against ab initio phonon dispersions computed within the first-principles density functional theory in the generalized gradient approximation plus Hubbard U correlation (GGA+U ) approach, taking into account third-order anharmonicity effects in the quasiharmonic approximation. Good agreement with the experiment is obtained for calculations with an on-site Coulomb parameter U =4 eV and Hund's exchange J =0.6 eV in line with previous electronic structure calculations. We further compute the thermal expansion, heat capacity, thermal conductivity, phonon linewidth, and thermal phonon softening, and compare with available experiments. The theoretical and measured heat capacities are in close agreement with another. About 27% of the calculated thermal conductivity is due to phonons with energy higher than 25 meV (˜6 THz ), suggesting an important role of high-energy optical phonons in the heat transport. The simulated thermal expansion reproduces well the experimental data up to about 1000 K, indicating a failure of the quasiharmonic approximation above this limit.
Determining the Thermal Properties of Space Lubricants
NASA Technical Reports Server (NTRS)
Maldonado, Christina M.
2004-01-01
Many mechanisms used in spacecrafts, such as satellites or the space shuttle, employ ball bearings or gears that need to be lubricated. Normally this is not a problem, but in outer space the regular lubricants that are used on Earth will not function properly. Regular lubricants will quickly vaporize in the near vacuum of space. A unique liquid called a perfluoropolyalkylether (PFPE) has an extremely low vapor pressure, around l0(exp -10) torr at 20 C, and has been used in numerous satellites and is currently used in the space shuttle. Many people refer to the PFPEs as "liquid Teflon". PFPE lubricants however, have a number of problems with them. Lubricants need many soluble additives, especially boundary and anti-wear additives, in them to function properly. All the regular known boundary additives are insoluble in PFPEs and so PFPEs lubricate poorly under highly loaded conditions leading to many malfunctioning ball bearings and gears. JAXA, the Japanese Space Agency, is designing and building a centrifuge rotor to be installed in the International Space Station. The centrifuge rotor is part of a biology lab module. They have selected a PFPE lubricant to lubricate the rotor s ball bearings and NASA bearing experts feel this is not a wise choice. An assessment of the centrifuge rotor design is being conducted by NASA and part of the assessment entails knowing the physical and thermal properties of the PFPE lubricant. One important property, the thermal diffusivity, is not known. An experimental apparatus was set up in order to measure the thermal diffusivity of the PFPE. The apparatus consists of a constant temperature heat source, cylindrical Pyrex glassware, a thermal couple and digital thermometer. The apparatus was tested and calibrated using water since the thermal diffusivity of water is known.
Experimental methods of determining thermal properties of granite
USDA-ARS?s Scientific Manuscript database
Determination of thermal properties of granite using the block method is discussed and compared with other methods. Problems that limit the accuracy of contact method in determining thermal properties of porous media are evaluated. Thermal properties of granite is determined in the laboratory with a...
Thermal and magnetic properties of manganese oxides
NASA Astrophysics Data System (ADS)
Smolyaninova, Vera Nikolaevna
This thesis reports a study of the thermal, magnetic and transport properties of perovskite manganese oxides A1-xBxMnO3 (A = La, Nd, and Pr; B = Ca, Ba, and Sr). The ferromagnetic (FM) metallic (low x) and the charge-ordered (CO) (high x) doping regimes were studied in order to better understand the complex behavior of these materials. In the metallic doping range the low temperature magnetization was found to be in agreement with the Bloch law for ferromagnetic spin waves, and the spin-wave stiffness was determined. Important parameters such as the Debye temperature and the effective mass of the charge carriers were determined from low temperature specific heat experiments. The effective mass of the charge carriers was found to be 2--4 times heavier than the mass obtained from band structure calculations suggesting an important role of electron-phonon interactions in these materials. In order to better understand the nature of the metal-insulator transition at the ferromagnetic TC the resistivity and magnetization of epitaxial thin films of La0.67Ca 0.33MnO3 and Nd0.7Sr0.3MnO3 were studied. It was found that the behavior of the resistivity and magnetization near TC is inconsistent with Anderson localization as proposed by several theories. Various compositions of charge-ordered La1-xCaxMnO3 and Pr1-xCa1-xMnO 3 were studied to better understand the CO transition and its ground state. From powder neutron diffraction measurements we found that the CO antiferromagnetic (AFM) and ferromagnetic metallic phases coexist at low temperatures. Charge ordered Pr1-xCaxMnO3 and La1-xCax MnO3 (x ≈ 0.5) were found to have an anomalous excess specific heat ( C') at low temperatures (T < 20 K). This C' contribution has a temperature dependence consistent with non-magnetic excitations with a dispersion relation e = Delta' + Bq2. Surprisingly, it was found that a magnetic field sufficient to induce the transition from the insulating CO (and AFM) state to the metallic FM state is
Computation of Thermally Perfect Properties of Oblique Shock Waves
NASA Technical Reports Server (NTRS)
Tatum, Kenneth E.
1996-01-01
A set of compressible flow relations describing flow properties across oblique shock waves, derived for a thermally perfect, calorically imperfect gas, is applied within the existing thermally perfect gas (TPG) computer code. The relations are based upon a value of cp expressed as a polynomial function of temperature. The updated code produces tables of compressible flow properties of oblique shock waves, as well as the original properties of normal shock waves and basic isentropic flow, in a format similar to the tables for normal shock waves found in NACA Rep. 1135. The code results are validated in both the calorically perfect and the calorically imperfect, thermally perfect temperature regimes through comparisons with the theoretical methods of NACA Rep. 1135, and with a state-of-the-art computational fluid dynamics code. The advantages of the TPG code for oblique shock wave calculations, as well as for the properties of isentropic flow and normal shock waves, are its ease of use, and its applicability to any type of gas (monatomic, diatomic, triatomic, polyatomic, or any specified mixture thereof).
Computation of Thermally Perfect Oblique Shock Wave Properties
NASA Technical Reports Server (NTRS)
Tatum, Kenneth E.
1997-01-01
A set of compressible flow relations describing flow properties across oblique shock waves, derived for a thermally perfect, calorically imperfect gas, is applied within the existing thermally perfect gas (TPG) computer code. The relations are based upon the specific heat expressed as a polynomial function of temperature. The updated code produces tables of compressible flow properties of oblique shock waves, as well as the original properties of normal shock waves and basic isentropic flow, in a format similar to the tables for normal shock waves found in NACA Rep. 1135. The code results are validated in both the calorically perfect and the calorically imperfect, thermally perfect temperature regimes through comparisons with the theoretical methods of NACA Rep. 1135. The advantages of the TPG code for oblique shock wave calculations, as well as for the properties of isentropic flow and normal shock waves, are its ease of use and its applicability to any type of gas (monatomic, diatomic, triatomic, polyatomic, or any specified mixture thereof).
Biodegradable compounds: Rheological, mechanical and thermal properties
NASA Astrophysics Data System (ADS)
Nobile, Maria Rossella; Lucia, G.; Santella, M.; Malinconico, M.; Cerruti, P.; Pantani, R.
2015-12-01
Recently great attention from industry has been focused on biodegradable polyesters derived from renewable resources. In particular, PLA has attracted great interest due to its high strength and high modulus and a good biocompatibility, however its brittleness and low heat distortion temperature (HDT) restrict its wide application. On the other hand, Poly(butylene succinate) (PBS) is a biodegradable polymer with a low tensile modulus but characterized by a high flexibility, excellent impact strength, good thermal and chemical resistance. In this work the two aliphatic biodegradable polyesters PBS and PLA were selected with the aim to obtain a biodegradable material for the industry of plastic cups and plates. PBS was also blended with a thermoplastic starch. Talc was also added to the compounds because of its low cost and its effectiveness in increasing the modulus and the HDT of polymers. The compounds were obtained by melt compounding in a single screw extruder and the rheological, mechanical and thermal properties were investigated. The properties of the two compounds were compared and it was found that the values of the tensile modulus and elongation at break measured for the PBS/PLA/Talc compound make it interesting for the production of disposable plates and cups. In terms of thermal resistance the compounds have HDTs high enough to contain hot food or beverages. The PLA/PBS/Talc compound can be, then, considered as biodegradable substitute for polystyrene for the production of disposable plates and cups for hot food and beverages.
NASA Astrophysics Data System (ADS)
Wang, Hsin; Porter, Wallace D.; Böttner, Harald; König, Jan; Chen, Lidong; Bai, Shengqiang; Tritt, Terry M.; Mayolet, Alex; Senawiratne, Jayantha; Smith, Charlene; Harris, Fred; Gilbert, Patricia; Sharp, Jeff; Lo, Jason; Kleinke, Holger; Kiss, Laszlo
2013-06-01
For bulk thermoelectrics, improvement of the figure of merit ZT to above 2 from the current values of 1.0 to 1.5 would enhance their competitiveness with alternative technologies. In recent years, the most significant improvements in ZT have mainly been due to successful reduction of thermal conductivity. However, thermal conductivity is difficult to measure directly at high temperatures. Combined measurements of thermal diffusivity, specific heat, and mass density are a widely used alternative to direct measurement of thermal conductivity. In this work, thermal conductivity is shown to be the factor in the calculation of ZT with the greatest measurement uncertainty. The International Energy Agency (IEA) group, under the implementing agreement for Advanced Materials for Transportation (AMT), has conducted two international round-robins since 2009. This paper, part II of our report on the international round-robin testing of transport properties of bulk bismuth telluride, focuses on thermal diffusivity, specific heat, and thermal conductivity measurements.
Nanofluid enhancement of mineral oil and thermal properties instrument design
NASA Astrophysics Data System (ADS)
Wilborn, Eli
thermal conductivities of various fluids. The second design calculated a thermal conductivity of water to be 0.59W/m2 c', while the commonly accepted value is 0.58W/ m2c', which is well within a tolerable range of error to accept this value as accurate at the experimental conditions. This heat transfer cell also calculated the thermal conductivity value for AMSOIL synthetic motor oil to be 0.12W/m2 c and 0.10W/m2c for mineral oil, both of these values are within the expected ranges of thermal conductivity for oils. The second goal of applying the heat transfer enhancement properties of a nanofluid to a transformer cooling application proved to be futile for Copper Oxide(40nm) and Carbon coated Copper nanoparticles(25nm) in mineral oil. All of the attempted nanofluids fell out of suspension within a timeframe of a day, and in a transformer cell where natural convection is the only means of flow available that contributes to keeping the nanoparticles suspended, there is not enough flow to keep the nanoparticles from falling out of suspension. That is why unless the transformer industry moves towards another coolant besides mineral oil, heat transfer enhancement using Copper Oxide (40nm) or Carbon Coated nanoparticles (25nm) in a mineral oil nanofluid is not a viable option.
A novel approach to calculate thermal expansion of graphene: Molecular dynamics study
NASA Astrophysics Data System (ADS)
Ghasemi, Hamid; Rajabpour, Ali
2017-05-01
High surface-to-volume ratio is one of the extraordinary physical parameters of graphene which plays a crucial role in its electronic, thermal, mechanical and chemical behavior. Despite a lot of continuing theoretical and experimental researches, there are properties of graphene which are not fully understood and known. One of these properties is the thermal expansion coefficient (TEC) of graphene which shows a quite different behavior from what is expected for ordinary materials and has been reported to have a negative value for a wide range of temperatures. All previous researchers have calculated the TEC of graphene by considering its projected size which decreases when the temperature increases. In this paper, a novel method has been used to report the TEC of graphene based on the calculation of its real surface area using molecular dynamics simulations. Our results make clear how much the real surface area of graphene varies with respect to the temperature which is applicable in designing graphene-based nanodevices.
Alon, Leeor; Sodickson, Daniel K.; Deniz, Cem M.
2017-01-01
Deposition of radiofrequency (RF) energy can be quantified via electric field or temperature change measurements. Magnetic resonance imaging has been used as a tool to measure three dimensional small temperature changes associated with RF radiation exposure. When duration of RF exposure is long, conversion from temperature change to specific absorption rate (SAR) is nontrivial due to prominent heat-diffusion and conduction effects. In this work, we demonstrated a method for calculation of SAR via an inversion of the heat equation including heat-diffusion and conduction effects. This method utilizes high-resolution three dimensional magnetic resonance temperature images and measured thermal properties of the phantom to achieve accurate calculation of SAR. Accuracy of the proposed method was analyzed with respect to operating frequency of a dipole antenna and parameters used in heat equation inversion. PMID:27490064
Alon, Leeor; Sodickson, Daniel K; Deniz, Cem M
2016-10-01
Deposition of radiofrequency (RF) energy can be quantified via electric field or temperature change measurements. Magnetic resonance imaging has been used as a tool to measure three dimensional small temperature changes associated with RF radiation exposure. When duration of RF exposure is long, conversion from temperature change to specific absorption rate (SAR) is nontrivial due to prominent heat-diffusion and conduction effects. In this work, we demonstrated a method for calculation of SAR via an inversion of the heat equation including heat-diffusion and conduction effects. This method utilizes high-resolution three dimensional magnetic resonance temperature images and measured thermal properties of the phantom to achieve accurate calculation of SAR. Accuracy of the proposed method was analyzed with respect to operating frequency of a dipole antenna and parameters used in heat equation inversion. Bioelectromagnetics. 37:493-503, 2016. © 2016 Wiley Periodicals, Inc.
40 CFR 80.66 - Calculation of reformulated gasoline properties.
Code of Federal Regulations, 2012 CFR
2012-07-01
... 40 Protection of Environment 17 2012-07-01 2012-07-01 false Calculation of reformulated gasoline... PROGRAMS (CONTINUED) REGULATION OF FUELS AND FUEL ADDITIVES Reformulated Gasoline § 80.66 Calculation of reformulated gasoline properties. (a) All volume measurements required by these regulations shall be...
40 CFR 80.66 - Calculation of reformulated gasoline properties.
Code of Federal Regulations, 2014 CFR
2014-07-01
... 40 Protection of Environment 17 2014-07-01 2014-07-01 false Calculation of reformulated gasoline... PROGRAMS (CONTINUED) REGULATION OF FUELS AND FUEL ADDITIVES Reformulated Gasoline § 80.66 Calculation of reformulated gasoline properties. (a) All volume measurements required by these regulations shall be...
40 CFR 80.66 - Calculation of reformulated gasoline properties.
Code of Federal Regulations, 2013 CFR
2013-07-01
... 40 Protection of Environment 17 2013-07-01 2013-07-01 false Calculation of reformulated gasoline... PROGRAMS (CONTINUED) REGULATION OF FUELS AND FUEL ADDITIVES Reformulated Gasoline § 80.66 Calculation of reformulated gasoline properties. (a) All volume measurements required by these regulations shall be...
Meng-Lund, Helena; Friis, Natascha; van de Weert, Marco; Rantanen, Jukka; Poso, Antti; Grohganz, Holger; Jorgensen, Lene
2017-05-15
A quantitative structure-property relationship (QSPR) between protein stability and the physicochemical properties of excipients was investigated to enable a more rational choice of stabilizing excipients than prior knowledge. The thermal transition temperature and aggregation time were determined for lysozyme in combination with 13 different amino acids using high throughput fluorescence spectroscopy and kinetic static light scattering measurements. On the theoretical side, around 200 2D and 3D molecular descriptors were calculated based on the amino acids' chemical structure. Multivariate data analysis was applied to correlate the descriptors with the experimental results. It was possible to identify descriptors, i.e. amino acids properties, with a positive influence on either transition temperature or aggregation onset time, or both. A high number of hydrogen bond acceptor moieties was the most prominent stabilizing factor for both responses, whereas hydrophilic surface properties and high molecular mass density mostly had a positive influence on the unfolding temperature. A high partition coefficient (logP(o/w)) was identified as the most prominent destabilizing factor for both responses. The QSPR shows good correlation between calculated molecular descriptors and the measured stabilizing effect of amino acids on lysozyme. Copyright © 2017 Elsevier B.V. All rights reserved.
Measurement of Thermal Radiation Properties of Solids
NASA Technical Reports Server (NTRS)
Richmond, J. C. (Editor)
1963-01-01
The overall objectives of the Symposium were to afford (1) an opportunity for workers in the field to describe the equipment and procedures currently in use for measuring thermal radiation properties of solids, (2) an opportunity for constructive criticism of the material presented, and (3) an open forum for discussion of mutual problems. It was also the hope of the sponsors that the published proceedings of the Symposium would serve as a valuable reference on measurement techniques for evaluating thermal radiation properties of solids, partic.ularly for those with limited experience in the field. Because of the strong dependence of emitted flux upon temperature, the program committee thought it advisable to devote the first session to a discussion of the problems of temperature measurement. All of the papers in Session I were presented at the request of and upon topics suggested by the Committee. Because of time and space limitations, it, was impossible to consider all temperature measurement problems that might arise--the objective was rather to call to the attention of the reader some of the problems that might be encountered, and to provide references that might provide solutions.
Thermal and rheological properties of breadfruit starch.
Wang, Xueyu; Chen, Ling; Li, Xiaoxi; Xie, Fengwei; Liu, Hongshen; Yu, Long
2011-01-01
The thermal and rheological properties of breadfruit starch were studied using DSC and 2 different rheometers. It was found that the gelatinization temperature of starch with excess moisture content (>70%) was at approximately 75 °C. A new endotherm was detected at about 173 °C when the moisture content was lower than required for full gelatinization of the starch. A detailed examination revealed that this endotherm represented the melting of amylose-lipid complexes. Breadfruit starch paste exhibited shear-thinning fluid characteristics, and good thermal and pH stability. The setback viscosity of the breadfruit starch was lower than that of potato and corn starches. The rheological properties of the breadfruit starch paste was well described by the Herschel-Bulkley model at a shear rate of 0 to 100 s(-1), where R(2) is greater than 0.95, and it behaved like a yield-pseudoplastic fluid. Both the storage modulus and loss modulus of the paste initially increased sharply, then dropped after reaching the gelatinization peak. Breadfruit starch gel showed both flexibility and viscosity. Suspension with 6% starch content exhibited very weak gel rigidity; however, this increased significantly at starch contents above 20%.
Thermal protection materials: Thermophysical property data
NASA Technical Reports Server (NTRS)
Williams, S. D.; Curry, Donald M.
1992-01-01
This publication presents a thermophysical property survey on materials that could potentially be used for future spacecraft thermal protection systems (TPS). This includes data that was reported in the 1960's as well as more current information reported through the 1980's. An attempt was made to cite the manufacturers as well as the data source in the bibliography. This volume represents an attempt to provide in a single source a complete set of thermophysical data on a large variety of materials used in spacecraft TPS analysis. The property data is divided into two categories: ablative and reusable. The ablative materials have been compiled into twelve categories that are descriptive of the material composition. An attempt was made to define the Arrhenius equation for each material although this data may not be available for some materials. In a similar manner, char data may not be available for some of the ablative materials. The reusable materials have been divided into three basic categories: thermal protection materials (such as insulators), adhesives, and structural materials.
Thermal properties of hemp fibre non-woven materials
NASA Astrophysics Data System (ADS)
Freivalde, Liga; Kukle, Silvija; Russell, Stephen
2013-12-01
This review considers the thermal properties analysis of hemp fiber non-woven materials made by three different manufacturing technologies - thermal bonding, needle-punching and hydro-entanglement. For non-wovens development two hemp fibers cultivars grown in Latvia were used - Purini and Bialobrzeskie. Thermal resistance, conductivity and the effects of several parameters on thermal performance are revised.
Calculating nonlocal optical properties of structures with arbitrary shape.
McMahon, J. M.; Gray, S. K.; Schatz, G. C.; Northwestern Univ.
2010-07-16
In a recent Letter [J. M. McMahon, S. K. Gray, and G. C. Schatz, Phys. Rev. Lett. 103, 097403 (2009)], we outlined a computational method to calculate the optical properties of structures with a spatially nonlocal dielectric function. In this paper, we detail the full method and verify it against analytical results for cylindrical nanowires. Then, as examples of our method, we calculate the optical properties of Au nanostructures in one, two, and three dimensions. We first calculate the transmission, reflection, and absorption spectra of thin films. Because of their simplicity, these systems demonstrate clearly the longitudinal (or volume) plasmons characteristic of nonlocal effects, which result in anomalous absorption and plasmon blueshifting. We then study the optical properties of spherical nanoparticles, which also exhibit such nonlocal effects. Finally, we compare the maximum and average electric field enhancements around nanowires of various shapes to local theory predictions. We demonstrate that when nonlocal effects are included, significant decreases in such properties can occur.
Verification Of Energy Balance In The Ansys V5.4 Thermal Calculations
H. Marr; M.J. Anderson
2001-02-08
The objective of this calculation is to verify the energy balance of the thermal calculations analyzed by ANSYS Version (V) 5.4 solver (see Section 4). The scope of this calculation is limited to calculating the energy balance of a two-dimensional repository thermal representation using the temperatures obtained from ANSYS V5.4. The procedure, AP-3.124, Calculations (Ref. 3), and the Technical Work Plan for: Waste Package Design Description for LA (Ref. 2) are used to develop this calculation. The associated activity is the development of engineering evaluations to support the Licensing Application design activities.
Ab initio study of the thermodynamic properties and the phonon calculations of Zircon and Reidite
NASA Astrophysics Data System (ADS)
Chaudhari, Mrunalkumar; Du, Jincheng
2011-03-01
Zircon and Reidite are the polymorphs of Zirconium Silicate which find its importance geologically, because of its natural hosting to various radioactive elements in the crust of the earth. High permittivity also makes it a promising material for the gate dielectric material in metal-oxide semiconductors. Knowledge of the thermodynamic properties and the phonon based calculations is very critical to understand the high temperature and high pressure properties in order to consider its application as an effective natural storage for the radioactive wastes. These properties are thoroughly studied both computationally and experimentally for zircon, while significantly less attention was paid to reidite in the literature. The thermodynamic properties and phonon calculations of Zircon and Reidite were studied using ab initio based periodic density-functional theory (DFT) based calculations using the generalized gradient approximation (GGA). Various properties such as free energy, internal energy, entropy, heat capacity and thermal displacement as a function of temperature is calculated using the PHONON software. Various phonon based density of states and dispersion curves are calculated and compared with the experimental data. No first principles based computational results were reported up to now. Calculated bulk properties agree very well with the experimental data in the literature.
Ballistic phonon thermal conductance in graphene nano-ribbon: First-principles calculations
Nakamura, Jun; Tomita, Hiroki
2013-12-04
Ballistic phonon thermal conductances for graphene nanoribbons are investigated using first-principles calculations with the density functional perturbation theory and the Landauer theory. The phonon thermal conductance per unit width for GNR is larger than that for graphene and increases with decreasing ribbon width. The normalized thermal conductances with regard to a thermal quantum for GNRs are higher than those for the single-walled carbon nanotube that have circumferential lengths corresponding to the width of GNR.
Fayet, Guillaume; Rotureau, Patricia; Joubert, Laurent; Adamo, Carlo
2009-11-15
This work presents a new approach to predict thermal stability of nitroaromatic compounds based on quantum chemical calculations and on quantitative structure-property relationship (QSPR) methods. The data set consists of 22 nitroaromatic compounds of known decomposition enthalpy (taken as a macroscopic property related to explosibility) obtained from differential scanning calorimetry. Geometric, electronic and energetic descriptors have been selected and computed using density functional theory (DFT) calculation to describe the 22 molecules. First approach consisted in looking at their linear correlations with the experimental decomposition enthalpy. Molecular weight, electrophilicity index, electron affinity and oxygen balance appeared as the most correlated descriptors (respectively R(2)=0.76, 0.75, 0.71 and 0.64). Then multilinear regression was computed with these descriptors. The obtained model is a six-parameter equation containing descriptors all issued from quantum chemical calculations. The prediction is satisfactory with a correlation coefficient R(2) of 0.91 and a predictivity coefficient R(cv)(2) of 0.84 using a cross validation method.
Temperature-dependent thermal properties of supported MoS2 monolayers.
Taube, Andrzej; Judek, Jarosław; Łapińska, Anna; Zdrojek, Mariusz
2015-03-11
Thermal properties can substantially affect the operation of various electronics and optoelectronics devices based on two-dimensional materials. In this work, we describe our investigation of temperature-dependent thermal conductivity and interfacial thermal conductance of molybdenum disulfide monolayers supported on SiO2/Si substrates, using Raman spectroscopy. We observed that the calculated thermal conductivity (κ) and interfacial thermal conductance (g) decreased with increasing temperature from 62.2 W m(-1) K(-1) and 1.94 MW m(-2) K(-1) at 300 K to 7.45 W m(-1) K(-1) and 1.25 MW m(-2) K(-1) at 450 K, respectively.
Semiconductor nanowires: Controlled growth and thermal properties
NASA Astrophysics Data System (ADS)
Wu, Yiying
This dissertation presents an experimental study of the controlled growth of semiconductor nanowires and their thermophysical properties. The synthesis of nanowires was based on the well-known Vapor-Liquid-Solid (VLS) mechanism in which the growth of nanowire is initiated by a nanosized liquid droplet. The prepared nanowires are single-crystalline with certain preferred growth direction. Nanowires with different compositions have been synthesized, including Si, Ge, boron and MgB2. The control of nanowire composition, diameter and orientation has also been achieved. In addition, a Pulsed Laser Ablation-Chemical Vapor Deposition (PLA-CVD) hybrid process was developed to synthesize Si/SiGe longitudinally superlattice nanowires. The thermal conductivity of individual pure Si nanowire and Si/SiGe nanowire was measured using a microfabricated suspended device over a temperature range of 20--320 K. The thermal conductivities of individual 22, 37, 56, and 115 nm diameter single crystalline intrinsic Si nanowires were much lower than the bulk value due to the strong phonon boundary scattering. Except for the 22 nm diameter nanowire, theoretical predictions using a modified Callaway model fit the experimental data very well. The data for the 22 nm diameter wire suggest that changes in phonon dispersion due to confinement can cause additional thermal conductivity reduction. The Si/SiGe superlattice nanowires with diameters of 83 run and 58 nm were also measured. Their thermal conductivities are smaller than pure Si nanowire with similar diameter, as well as Si/SiGe superlattice thin film with comparable period. Both the alloying scattering and the boundary scattering are believed to contribute to this reduction. Size dependent melting-recrystallization study of the carbon-sheathed semiconductor Ge nanowires was carried out in in-situ high temperature transmission electron microscope (TEM). Significant depression in melting temperature with decreasing size of the nanowires as
Attia, Ali Kamal; Souaya, Eglal R; Soliman, Ethar A
2015-11-01
Thermal analysis techniques have been used to study the thermal behavior of dapoxetine and vardenafil hydrochlorides and confirmed using semi-empirical molecular orbital calculations. Thermogravimetric analysis, derivative thermogravimetry, differential thermal analysis and differential scanning calorimetry were used to determine the thermal behavior and purity of the drugs under investigation. Thermodynamic parameters such as activation energy, enthalpy, entropy and Gibbs free energy were calculated. Thermal behavior of DAP and VAR were confirmed using by semi-empirical molecular orbital calculations. The purity values were found to be 99.97% and 99.95% for dapoxetine and vardenafil hydrochlorides, respectively. The purity of dapoxetine and vardenafil hydrochlorides is similar to that found by reported methods according to DSC data. Thermal analysis justifies its application in quality control of pharmaceutical compounds due to its simplicity, sensitivity and low operational costs.
Thermal properties of silicon nitride beams below one Kelvin.
Wang, G.; Yefremenko, V.; Novosad, V.; Datesman, A.; Pearson, J.; Divan, R.; Chang, C. L.; Bleem, L.; Crites, A. T.; Mehl, J.; Natoli, T.; McMahon, J.; Sayre, J.; Ruhl, J.; Meyer, S. S.; Carlstrom, J. E.
2011-06-01
We have investigated thermal properties of 1 {micro}m thick silicon nitride beams of different lateral dimensions. We measured the thermal conductance by simultaneously employing a TES both as a heater and as a sensor. Based upon these measurements, we calculate the thermal conductivity of the beams. We utilize a boundary limited phonon transport model and assume a temperature independent phonon mean free path. We find that the thermal conductivity is determined by the fraction of diffusive reflection at surface. The following results are obtained from 0.30 K to 0.55 K: the volume heat capacity is 0.082T+0.502T{sup 3} J/m{sup 3}-K . The width dependent phonon mean free path is 6.58 {micro}m, 9.80 {micro}m and 11.55 {micro}m for 10 {micro}m, 20 {micro}m and 30 {micro}m beams respectively at a 29% surface diffusive reflection.
Thermal and elastic properties of solid neon
NASA Astrophysics Data System (ADS)
Acocella, Dominic; Horton, George K.; Cowley, E. Roger
2000-04-01
We apply the improved effective potential Monte Carlo (IEP) and the improved self-consistent (ISC) theories to study the thermal and elastic properties of natural solid Ne. As a first orientation, we use the (12-6) Lennard-Jones (LJ) potential for first-neighbor forces only. The two parameters in the potential are determined from the 0 K lattice spacing and the sublimation energy of the crystal. We also create a realistic interatomic potential for the Ne dimer based on our study of the existing literature. When supplemented by many-body contributions, this potential is also used with ISC and IEP. The results are then compared with the experimental data in the literature. We conclude that our realistic potential which we regard as the best currently available is not significantly superior in accounting for the experimental data to the LJ potential, though both give a decent account of the experimental data.
Determination of Viral Capsid Elastic Properties from Equilibrium Thermal Fluctuations
NASA Astrophysics Data System (ADS)
May, Eric R.; Brooks, Charles L., III
2011-05-01
We apply two-dimensional elasticity theory to viral capsids to develop a framework for calculating elastic properties of viruses from equilibrium thermal fluctuations of the capsid surface in molecular dynamics and elastic network model trajectories. We show that the magnitudes of the long wavelength modes of motion available in a simulation with all atomic degrees of freedom are recapitulated by an elastic network model. For the mode spectra to match, the elastic network model must be scaled appropriately by a factor which can be determined from an icosahedrally constrained all-atom simulation. With this method we calculate the two-dimensional Young’s modulus Y, bending modulus κ, and Föppl-von Kármán number γ, for the T=1 mutant of the Sesbania mosaic virus. The values determined are in the range of previous theoretical estimates.
Interactive calculations of thermodynamics properties of minerals in VLab
NASA Astrophysics Data System (ADS)
Kelly, N.; da Silveira, P. R.; Wentzcovitch, R. M.
2009-12-01
We have developed a page within the VLab web site from which calculations of thermodynamics properties of minerals can be performed interactively. Previously published first principles calculations based on qhasiharmonic theory by our group have produced pressure dependent vibrational density of states (VDOSs). These calculations were costly and the essential information they produced, the VDOSs, are now stored on a database. They can be used to regenerate published results or calculate thermodynamics properties using specific user entered information (pressure and temperature range and grids, equation of state type, etc). Results are presented in numerical or graphics format (Gnuplot 4.2.2) that are interactively customized and downloadable. All codes behind the Web container are written in Java.
NASA Astrophysics Data System (ADS)
Kaplun, Alexander; Meshalkin, Arkadiy
2014-08-01
The new simple semi empirical equation of state for description of P-ρ-T data of "normal" substances was specified. New equation of state has 10 individual adjustable coefficients and it describes thermal properties of gas, liquid and fluid in the main with the accuracy within the error of experimental data, except of critical region. The caloric properties and the speed of sound of argon, nitrogen and carbon dioxide were calculated with the help of known thermodynamic equations and in general divergences between calculated and tabular caloric data do not exceed the experimental error. New equation can be used for engineering calculations at the deficit of experimental data, especially on the caloric properties of substances.
239Pu Resonance Evaluation for Thermal Benchmark System Calculations
Leal, Luiz C; Noguere, G; De Saint Jean, C; Kahler, A.
2013-01-01
Analyses of thermal plutonium solution critical benchmark systems have indicated a deciency in the 239Pu resonance evaluation. To investigate possible solutions to this issue, the Organisation for Economic Co-operation and Development (OECD) Nuclear Energy Agency (NEA) Working Party for Evaluation Cooperation (WPEC) established Subgroup 34 to focus on the reevaluation of the 239Pu resolved resonance parameters. In addition, the impacts of the prompt neutron multiplication (nubar) and the prompt neutron ssion spectrum (PFNS) have been investigated. The objective of this paper is to present the results of the 239Pu resolved resonance evaluation eort.
239Pu Resonance Evaluation for Thermal Benchmark System Calculations
NASA Astrophysics Data System (ADS)
Leal, L. C.; Noguere, G.; de Saint Jean, C.; Kahler, A. C.
2014-04-01
Analyses of thermal plutonium solution critical benchmark systems have indicated a deficiency in the 239Pu resonance evaluation. To investigate possible solutions to this issue, the Organisation for Economic Co-operation and Development (OECD) Nuclear Energy Agency (NEA) Working Party for Evaluation Cooperation (WPEC) established Subgroup 34 to focus on the reevaluation of the 239Pu resolved resonance parameters. In addition, the impacts of the prompt neutron multiplicity (νbar) and the prompt neutron fission spectrum (PFNS) have been investigated. The objective of this paper is to present the results of the 239Pu resolved resonance evaluation effort.
NASA Astrophysics Data System (ADS)
Irwanto, Dwi; Setiadipura, Topan; Pramutadi, Asril
2017-07-01
There are two type of High Temperature Gas Reactor (HTGR), prismatic and pebble bed. Pebble Bed type has unique configuration because the fuels are randomly distributed inside the reactor core. In term of safety features, Pebble Bed Reactor (PBR) is one of the most promising reactor type in avoiding severe nuclear accidents. In order to analyze heat transfer and safety of this reactor type, a computer code is now under development. As a first step, calculation method proposed by Stroh [1] is adopted. An approach has been made to treat randomly distributed pebble balls contains fissile material inside the reactor core as a porous medium. Helium gas act as coolant on the reactor system are carrying heat flowing in the area between the pebble balls. Several parameters and constants are taken into account in the new developed code. Progress of the development of the code especially comparison of several thermal conductivity constants for a certain PBR-case are reported in the present study.
Substructure Versus Property-Level Dispersed Modes Calculation
NASA Technical Reports Server (NTRS)
Stewart, Eric C.; Peck, Jeff A.; Bush, T. Jason; Fulcher, Clay W.
2016-01-01
This paper calculates the effect of perturbed finite element mass and stiffness values on the eigenvectors and eigenvalues of the finite element model. The structure is perturbed in two ways: at the "subelement" level and at the material property level. In the subelement eigenvalue uncertainty analysis the mass and stiffness of each subelement is perturbed by a factor before being assembled into the global matrices. In the property-level eigenvalue uncertainty analysis all material density and stiffness parameters of the structure are perturbed modified prior to the eigenvalue analysis. The eigenvalue and eigenvector dispersions of each analysis (subelement and property-level) are also calculated using an analytical sensitivity approximation. Two structural models are used to compare these methods: a cantilevered beam model, and a model of the Space Launch System. For each structural model it is shown how well the analytical sensitivity modes approximate the exact modes when the uncertainties are applied at the subelement level and at the property level.
THERMAL STRESS CALCULATIONS FOR HEATPIPE-COOLED REACTOR POWER SYSTEMS.
Kapernick, R. J.; Guffee, R. M.
2001-01-01
A heatpipe-cooled fast reactor concept has been under development at Los Alamos National Laboratory for the past several years, to be used as a power source for nuclear electric propulsion (NEP) or as a planetary surface power system. The reactor core consists of an array of modules that are held together by a core lateral restraint system. Each module comprises a single heatpipe surrounded by 3-6 clad fuel pins. As part of the design development and performance assessment activities for these reactors, specialized methods and models have been developed to perform thermal and stress analyses of the core modules. The methods have been automated so that trade studies can be readily performed, looking at design options such as module size, heatpipe and clad thickness, use of sleeves to contain the fuel, material type, etc. This paper describes the methods and models that have been developed, and presents thermal and stress analysis results for a Mars surface power system and a NEP power source.
Composition, structure and properties of sediment thermal springs of Kamchatka
NASA Astrophysics Data System (ADS)
Shanina, Violetta; Smolyakov, Pavel; Parfenov, Oleg
2016-04-01
associated with the rise of mixed solutions, formed at the boundary of secondary boil through faults to the surface thermal boiler (Bortnikova et al., 2009). Calculated flow index and plasticity, shows the classification in accordance with GOST 25100-2011. From these figures it is clear that all the sediments are sandy loam and are in a fluid state. A clear relationship between temperature, pH and particle size distribution of sediment thermal springs can not be traced, great importance is the geological evolution of the volcanic activity, hydrogeological conditions and the time factor. Therefore, samples with a currently active Mutnovsky volcano - sandy loam, sediments of the thermal springs Koshelevo fields are often to loams. The bottom sediments of thermal springs from the territory of the Lower Koshelevo thermal field in a natural occurrence in a state of higher yield strength, so they are an unstable surface, which may cause landslides. The bottom sediments of thermal springs are low explored subject of engineering geology, it is important to examine their properties to simulate the conditions of formation and the development of dangerous processes.
Calculation of the transport and relaxation properties of dilute water vapor
NASA Astrophysics Data System (ADS)
Hellmann, Robert; Bich, Eckard; Vogel, Eckhard; Dickinson, Alan S.; Vesovic, Velisa
2009-07-01
Transport properties of dilute water vapor have been calculated in the rigid-rotor approximation using four different potential energy hypersurfaces and the classical-trajectory method. Results are reported for shear viscosity, self-diffusion, thermal conductivity, and volume viscosity in the dilute-gas limit for the temperature range of 250-2500 K. Of these four surfaces the CC-pol surface of Bukowski et al. [J. Chem. Phys. 128, 094314 (2008)] is in best accord with the available measurements. Very good agreement is found with the most accurate results for viscosity in the whole temperature range of the experiments. For thermal conductivity the deviations of the calculated values from the experimental data increase systematically with increasing temperature to around 5% at 1100 K. For both self-diffusion and volume viscosity, the much more limited number of available measurements are generally consistent with the calculated values, apart from the lower temperature isotopically labeled diffusion measurements.
Severin, Jonathan; Jund, Philippe
2017-02-07
In this work, we aim to study the thermal properties of materials using classical molecular dynamics simulations and specialized numerical methods. We focus primarily on the thermal conductivity κ using non-equilibrium molecular dynamics (NEMD) to study the response of a crystalline solid, namely hematite (α-Fe2O3), to an imposed heat flux as is the case in real life applications. We present a methodology for the calculation of κ as well as an adapted potential for hematite. Taking into account the size of the simulation box, we show that not only the longitudinal size (in the direction of the heat flux) but also the transverse size plays a role in the determination of κ and should be converged properly in order to have reliable results. Moreover we propose a comparison of thermal conductivity calculations in two different crystallographic directions to highlight the spatial anisotropy and we investigate the non-linear temperature behavior typically observed in NEMD methods.
NASA Astrophysics Data System (ADS)
Severin, Jonathan; Jund, Philippe
2017-02-01
In this work, we aim to study the thermal properties of materials using classical molecular dynamics simulations and specialized numerical methods. We focus primarily on the thermal conductivity κ using non-equilibrium molecular dynamics (NEMD) to study the response of a crystalline solid, namely hematite (α -Fe2O3 ), to an imposed heat flux as is the case in real life applications. We present a methodology for the calculation of κ as well as an adapted potential for hematite. Taking into account the size of the simulation box, we show that not only the longitudinal size (in the direction of the heat flux) but also the transverse size plays a role in the determination of κ and should be converged properly in order to have reliable results. Moreover we propose a comparison of thermal conductivity calculations in two different crystallographic directions to highlight the spatial anisotropy and we investigate the non-linear temperature behavior typically observed in NEMD methods.
Studies of thermal transport properties using molecular dynamics simulation techniques
NASA Astrophysics Data System (ADS)
Ratanapisit, Juraivan
The purpose of this research has been to investigate the transport properties of fluids using novel techniques in molecular dynamics simulations: symplectic integration algorithms for equations of motion, Baranyai's thermostatted fluid wall algorithm, and Rapaport's algorithm for hard chain fluids. In the symplectic integration study, an extensive series of equilibrium molecular dynamic simulations have been performed to investigate the accuracy, stability and efficiency of second order explicit symplectic integrators: position Verlet, velocity Verlet, and the McLauchlan-Atela algorithms. To our knowledge, previous studies of the symplectic integrators have only looked at the thermodynamic energy using a simple model fluid. Our work presents realistic but perhaps the simplest simulations possible to test the effect of the integrators on the three main transport properties. Our results suggest that if an algorithm fails to adequately conserve energy, it will also show significant uncertainties in transport property calculations. A large portion of the simulation study focused on a new algorithm for thermal conductivity based on Baranyai's fluid wall method. This algorithm is stable enough to perform simulations even using large time steps and provides reasonable values and uncertainties for the thermal conductivity. The investigation was conducted using two different thermostat algorithms: the Gaussian and Nosé-Hoover thermostats. The final part of this research focused on the viscosity of hard chain fluids. This study was initiated with an investigation of the equilibrium molecular dynamic simulations of pure hard-sphere molecules. The natural extension of that work was to hard chain fluids. (Abstract shortened by UMI.)
The spacing calculator software—A Visual Basic program to calculate spatial properties of lineaments
NASA Astrophysics Data System (ADS)
Ekneligoda, Thushan C.; Henkel, Herbert
2006-05-01
A software tool is presented which calculates the spatial properties azimuth, length, spacing, and frequency of lineaments that are defined by their starting and ending co-ordinates in a two-dimensional (2-D) planar co-ordinate system. A simple graphical interface with five display windows creates a user-friendly interactive environment. All lineaments are considered in the calculations, and no secondary sampling grid is needed for the elaboration of the spatial properties. Several rule-based decisions are made to determine the nearest lineament in the spacing calculation. As a default procedure, the programme defines a window that depends on the mode value of the length distribution of the lineaments in a study area. This makes the results more consistent, compared to the manual method of spacing calculation. Histograms are provided to illustrate and elaborate the distribution of the azimuth, length and spacing. The core of the tool is the spacing calculation between neighbouring parallel lineaments, which gives direct information about the variation of block sizes in a given category of structures. The 2-D lineament frequency is calculated for the actual area that is occupied by the lineaments.
Thermal Stress Calculations for Heatpipe-Cooled Reactor Power Systems
NASA Astrophysics Data System (ADS)
Kapernick, Richard J.; Guffee, Ray M.
2003-01-01
A heatpipe-cooled fast reactor concept has been under development at Los Alamos National Laboratory for the past several years, to be used as a power source for nuclear electric propulsion (NEP) or as a planetary surface power system. The reactor core consists of an array of modules that are held together by a core lateral restraint system. Each module includes a single heatpipe surrounded by 3-6 clad fuel pins. As part of this development effort, a partial array of a candidate heatpipe-cooled reactor is to be tested in the SAFE-100 experimental program at the Marshall Space Flight Center. The partial array comprises 19 3-pin modules, which are powered by resistance heaters. This paper describes the analyses that were performed in support of this test program, to assess thermal and structural performance and to specify the test conditions needed to simulate reactor operating conditions.
First principles calculations of thermodynamical properties of cage-like silicon clathrate materials
NASA Astrophysics Data System (ADS)
Jack, Deslippe; Dong, Jianjun
2003-03-01
Si, Ge, and Sn based clathrate materials are potential high ZT thermoelectric materials due to their electron-crystal-phon-glass properties. Recently, the synthesis of guest-free type-II Si clathrate (Si136) was reported. The pristine (guest-free) Si and Ge clathrate can be viewed as "negative-pressure" phases, which might exist metastably at ambient conditions. In this talk, we will report our recent calculations of the thermodynamic properties of silicon type-I and -II Clathrate phases, as well as the ground state Si diamond phase. Statistical quasi-harmonic theory is used in conjunction with first-principles static bonding energy and dynamic phonon spectrum calculations to obtain free energies of the lattices. At zero temperature, the transition pressures of diamond-to-clathrate-I and diamond-to-clathrates-II transitions are predicted to be -46.9 kbar and -38.9 kbar respectively, while the Clapeyron slopes (dP/dT) of the two transitions at 300K are 8.64 bar/K and 7.38 bar/K respectively. Thermal properties of the Si materials, such as (linear) thermal expansion coefficients, Gruneisen parameters, heat capacities, and thermal bulk moduli etc. are also calculated. We find good agreement with experiment in the Si diamond phase. The results of the Si clathrates are discussed in comparison to those of the Si diamond, as well as available data of metal-encapsulated Si-based clathrate compounds (such as Na8Si46).
Guo, Yaguang; Zhang, Shunhong; Zhao, Tianshan; Wang, Qian
2016-05-19
Mechanical cleavage, chemical intercalation and chemical vapor deposition are the main methods that are currently used to synthesize nanosheets or monolayers. Here, we propose a new strategy, thermal exfoliation for the fabrication of silica monolayers. Using a variety of state-of-the-art theoretical calculations we show that a stoichiometric single-layer silica with a tetragonal lattice, T-silica, can be thermally exfoliated from the stishovite phase in a clean environment at room temperature. The resulting single-layer silica is dynamically, thermally, and mechanically stable with exceptional properties, including a large band gap of 7.2 eV, an unusual negative Poisson's ratio, a giant Stark effect, and a high breakdown voltage. Moreover, other analogous structures like single-layer GeO2 can also be obtained by thermal exfoliation of its bulk phase. Our findings are expected to motivate experimental efforts on developing new techniques for the synthesis of monolayer materials.
Thermal properties of PZT95/5(1.8Nb) and PSZT ceramics.
DiAntonio, Christopher Brian; Rae, David F.; Corelis, David J.; Yang, Pin; Burns, George Robert
2006-11-01
Thermal properties of niobium-modified PZT95/5(1.8Nb) and PSZT ceramics used for the ferroelectric power supply have been studied from -100 C to 375 C. Within this temperature range, these materials exhibit ferroelectric-ferroelectric and ferroelectric-paraelectric phase transformations. The thermal expansion coefficient, heat capacity, and thermal diffusivity of different phases were measured. Thermal conductivity and Grueneisen constant were calculated at several selected temperatures between -60 C and 100 C. Results show that thermal properties of these two solid solutions are very similar. Phase transformations in these ceramics possess first order transformation characteristics including thermal hysteresis, transformational strain, and enthalpy change. The thermal strain in the high temperature rhombohedral phase region is extremely anisotropic. The heat capacity for both materials approaches to 3R (or 5.938 cal/(g-mole*K)) near room temperature. The thermal diffusivity and the thermal conductivity are quite low in comparison to common oxide ceramics, and are comparable to amorphous silicate glass. Furthermore, the thermal conductivity of these materials between -60 C and 100 C becomes independent of temperature and is sensitive to the structural phase transformation. These phenomena suggest that the phonon mean free path governing the thermal conductivity in this temperature range is limited by the lattice dimensions, which is in good agreement with calculated values. Effects of small compositional changes and density/porosity variations in these ceramics on their thermal properties are also discussed. The implications of these transformation characteristics and unusual thermal properties are important in guiding processing and handling procedures for these materials.
Thermal Properties of G-348 Graphite
McEligot, Donald; Swank, W. David; Cottle, David L.; Valentin, Francisco I.
2016-05-01
Fundamental measurements have been obtained in the INL Graphite Characterization Laboratory to deduce the temperature dependence of thermal conductivity for G-348 isotropic graphite, which has been used by City College of New York in thermal experiments related to gas-cooled nuclear reactors. Measurements of thermal diffusivity, mass, volume and thermal expansion were converted to thermal conductivity in accordance with ASTM Standard Practice C781-08. Data are tabulated and a preliminary correlation for the thermal conductivity is presented as a function of temperature from laboratory temperature to 1000C.
Calculation of petrophysical properties for Mishrif carbonate reservoir
NASA Astrophysics Data System (ADS)
Kadhim, Fadhil Sarhan; Samsuri, Ariffin; Idris, Ahmad Kamal
2014-10-01
The accurate calculations of petrophysical properties in carbonate reservoirs are the most challenging aspects of well log analysis. Many equations have been developed over the years based on known physical principles or on empirically derived relationships, which are used to calculate carbonate rock petrophysical properties. Carbonate reservoirs in the Middle East are very heterogeneous in terms of rock types. Therefore the reservoir should be split into layers on the basis of the dominant rock type in order to define average values and trends of petrophysical parameters in the reservoir rock. The saturation exponent (n) and cementation exponent (m) are calculated from well log data using Pickett method. The study made across the Mishrif carbonate formation, which is the shallowest formation of the hydrocarbon bearing zone in the NS oil field in the Middle East. Results show that the average formation water resistivity (Rw= 0.0243), average mud filtrate resistivity (Rmf= 0.199), Irreducible Water Saturation (Swi=0. 18), and Archie's parameters (m=1. 78, n= 2, and a=1). While porosity, true resistivity, and water saturation values with depth of formation were calculated by using Interactive Petrophysics software (IP V3.5, 2008). The computer process interpretation (CPI) illustrates that the shale member splits the Mishrif formation into two parts; Upper and Lower Mishrif. This study is a step to investigate petrophysical properties, which used to calculate water saturation that should use to estimate original oil in place and detected the perforation zones.
Microcomputer Calculation of Thermodynamic Properties from Molecular Parameters of Gases.
ERIC Educational Resources Information Center
Venugopalan, Mundiyath
1990-01-01
Described in this article is a problem-solving activity which integrates the application of microcomputers with the learning of physical chemistry. Students use the program with spectroscopic data to calculate the thermodynamic properties and compare them with the values from the thermochemical tables. (Author/KR)
NASA Astrophysics Data System (ADS)
Guo, Yaguang; Zhang, Shunhong; Zhao, Tianshan; Wang, Qian
2016-05-01
Mechanical cleavage, chemical intercalation and chemical vapor deposition are the main methods that are currently used to synthesize nanosheets or monolayers. Here, we propose a new strategy, thermal exfoliation for the fabrication of silica monolayers. Using a variety of state-of-the-art theoretical calculations we show that a stoichiometric single-layer silica with a tetragonal lattice, T-silica, can be thermally exfoliated from the stishovite phase in a clean environment at room temperature. The resulting single-layer silica is dynamically, thermally, and mechanically stable with exceptional properties, including a large band gap of 7.2 eV, an unusual negative Poisson's ratio, a giant Stark effect, and a high breakdown voltage. Moreover, other analogous structures like single-layer GeO2 can also be obtained by thermal exfoliation of its bulk phase. Our findings are expected to motivate experimental efforts on developing new techniques for the synthesis of monolayer materials.Mechanical cleavage, chemical intercalation and chemical vapor deposition are the main methods that are currently used to synthesize nanosheets or monolayers. Here, we propose a new strategy, thermal exfoliation for the fabrication of silica monolayers. Using a variety of state-of-the-art theoretical calculations we show that a stoichiometric single-layer silica with a tetragonal lattice, T-silica, can be thermally exfoliated from the stishovite phase in a clean environment at room temperature. The resulting single-layer silica is dynamically, thermally, and mechanically stable with exceptional properties, including a large band gap of 7.2 eV, an unusual negative Poisson's ratio, a giant Stark effect, and a high breakdown voltage. Moreover, other analogous structures like single-layer GeO2 can also be obtained by thermal exfoliation of its bulk phase. Our findings are expected to motivate experimental efforts on developing new techniques for the synthesis of monolayer materials. Electronic
Using electron microscopy to calculate optical properties of biological samples.
Wu, Wenli; Radosevich, Andrew J; Eshein, Adam; Nguyen, The-Quyen; Yi, Ji; Cherkezyan, Lusik; Roy, Hemant K; Szleifer, Igal; Backman, Vadim
2016-11-01
The microscopic structural origins of optical properties in biological media are still not fully understood. Better understanding these origins can serve to improve the utility of existing techniques and facilitate the discovery of other novel techniques. We propose a novel analysis technique using electron microscopy (EM) to calculate optical properties of specific biological structures. This method is demonstrated with images of human epithelial colon cell nuclei. The spectrum of anisotropy factor g, the phase function and the shape factor D of the nuclei are calculated. The results show strong agreement with an independent study. This method provides a new way to extract the true phase function of biological samples and provides an independent validation for optical property measurement techniques.
Using electron microscopy to calculate optical properties of biological samples
Wu, Wenli; Radosevich, Andrew J.; Eshein, Adam; Nguyen, The-Quyen; Yi, Ji; Cherkezyan, Lusik; Roy, Hemant K.; Szleifer, Igal; Backman, Vadim
2016-01-01
The microscopic structural origins of optical properties in biological media are still not fully understood. Better understanding these origins can serve to improve the utility of existing techniques and facilitate the discovery of other novel techniques. We propose a novel analysis technique using electron microscopy (EM) to calculate optical properties of specific biological structures. This method is demonstrated with images of human epithelial colon cell nuclei. The spectrum of anisotropy factor g, the phase function and the shape factor D of the nuclei are calculated. The results show strong agreement with an independent study. This method provides a new way to extract the true phase function of biological samples and provides an independent validation for optical property measurement techniques. PMID:27896013
Optimal experimental designs for the estimation of thermal properties of composite materials
NASA Technical Reports Server (NTRS)
Scott, Elaine P.; Moncman, Deborah A.
1994-01-01
Reliable estimation of thermal properties is extremely important in the utilization of new advanced materials, such as composite materials. The accuracy of these estimates can be increased if the experiments are designed carefully. The objectives of this study are to design optimal experiments to be used in the prediction of these thermal properties and to then utilize these designs in the development of an estimation procedure to determine the effective thermal properties (thermal conductivity and volumetric heat capacity). The experiments were optimized by choosing experimental parameters that maximize the temperature derivatives with respect to all of the unknown thermal properties. This procedure has the effect of minimizing the confidence intervals of the resulting thermal property estimates. Both one-dimensional and two-dimensional experimental designs were optimized. A heat flux boundary condition is required in both analyses for the simultaneous estimation of the thermal properties. For the one-dimensional experiment, the parameters optimized were the heating time of the applied heat flux, the temperature sensor location, and the experimental time. In addition to these parameters, the optimal location of the heat flux was also determined for the two-dimensional experiments. Utilizing the optimal one-dimensional experiment, the effective thermal conductivity perpendicular to the fibers and the effective volumetric heat capacity were then estimated for an IM7-Bismaleimide composite material. The estimation procedure used is based on the minimization of a least squares function which incorporates both calculated and measured temperatures and allows for the parameters to be estimated simultaneously.
NASA Astrophysics Data System (ADS)
Landerville, Aaron; Oleynik, Ivan
2015-06-01
Dispersion Corrected Density Functional Theory (DFT+vdW) calculations are performed to predict vibrational and thermal properties of the bulk energetic materials (EMs) β-octahydrocyclotetramethylene-tetranitramine (β-HMX) and triaminotrinitrobenzene (TATB). DFT+vdW calculations of optimized unit cells along the hydrostatic equation of state are followed by frozen-phonon calculations of their respective vibration spectra. These are then used under the quasi-harmonic approximation to obtain zero-point and thermal free energy contributions to the pressure, resulting in PVT equations of state for each material that is in excellent agreement with experiment. Further, heat capacities, thermal expansion coefficients, and Gruneissen parameters as functions of temperature are calculated and compared with experiment. The vibrational properties, including phonon densities of states and pressure dependencies of individual modes, are also analyzed and compared with experiment.
Consiglio, Anthony; Tian, Zhiting
2016-11-10
The wide bandgap semiconductor, ZnO, has gained interest recently as a promising option for use in power electronics such as thermoelectric and piezoelectric generators, as well as optoelectronic devices. Though much work has been done to improve its electronic properties, relatively little is known of its thermal transport properties with large variations in measured thermal conductivity. In this study, we examine the effects of a Hubbard corrected energy functional on the lattice thermal conductivity of wurtzite ZnO calculated using density functional theory and an iterative solution to the Boltzmann transport equation. Showing good agreement with existing experimental measurements, and with a detailed analysis of the mode-dependence and phonon properties, the results from this study highlight the importance of the Hubbard correction in calculations of thermal transport properties of materials with strongly correlated electron systems.
NASA Astrophysics Data System (ADS)
Consiglio, Anthony; Tian, Zhiting
2016-11-01
The wide bandgap semiconductor, ZnO, has gained interest recently as a promising option for use in power electronics such as thermoelectric and piezoelectric generators, as well as optoelectronic devices. Though much work has been done to improve its electronic properties, relatively little is known of its thermal transport properties with large variations in measured thermal conductivity. In this study, we examine the effects of a Hubbard corrected energy functional on the lattice thermal conductivity of wurtzite ZnO calculated using density functional theory and an iterative solution to the Boltzmann transport equation. Showing good agreement with existing experimental measurements, and with a detailed analysis of the mode-dependence and phonon properties, the results from this study highlight the importance of the Hubbard correction in calculations of thermal transport properties of materials with strongly correlated electron systems.
Consiglio, Anthony; Tian, Zhiting
2016-01-01
The wide bandgap semiconductor, ZnO, has gained interest recently as a promising option for use in power electronics such as thermoelectric and piezoelectric generators, as well as optoelectronic devices. Though much work has been done to improve its electronic properties, relatively little is known of its thermal transport properties with large variations in measured thermal conductivity. In this study, we examine the effects of a Hubbard corrected energy functional on the lattice thermal conductivity of wurtzite ZnO calculated using density functional theory and an iterative solution to the Boltzmann transport equation. Showing good agreement with existing experimental measurements, and with a detailed analysis of the mode-dependence and phonon properties, the results from this study highlight the importance of the Hubbard correction in calculations of thermal transport properties of materials with strongly correlated electron systems. PMID:27830737
Thermal Property Measurements of Critical Materials for SPICA Payload Module
NASA Astrophysics Data System (ADS)
Shinozaki, Keisuke; Mizutani, Tadahito; Fujii, Takenori; Onaka, Takashi; Nakagawa, Takao; Sugita, Hiroyuki
The Space Infrared Telescope for Cosmology and Astrophysics (SPICA) is a pre-project of JAXA in collaboration with ESA to be launched around 2025. The 3m-class infrared telescope must be below 6K, based on scientific requirements, and features effective radiant cooling into deep space at L2 point combined with a mechanical cooler system in order to cool scientific instruments as well as the telescope. The thermal design of the SPICA payload module must involve researching and measuring the thermophysical properties of materials in order to achieve a highly reliable cooling chain. Accordingly, all critical materials, particularly FRPs were determined and their thermal properties (thermal conductivity, specific heat, and thermal expansion) measured. Subsequently, the measured values were compared with those in literature and included in a thermal model analysis. This paper introduces details of these thermal properties measurements, comparisons with values in literature, and a thermal model analysis of the SPICA payload module.
Galileo probe forebody thermal protection - Benchmark heating environment calculations
NASA Technical Reports Server (NTRS)
Balakrishnan, A.; Nicolet, W. E.
1981-01-01
Solutions are presented for the aerothermal heating environment for the forebody heatshield of candidate Galileo probe. Entry into both the nominal and cool-heavy model atmospheres were considered. Solutions were obtained for the candidate heavy probe with a weight of 310 kg and a lighter probe with a weight of 290 kg. In the flowfield analysis, a finite difference procedure was employed to obtain benchmark predictions of pressure, radiative and convective heating rates, and the steady-state wall blowing rates. Calculated heating rates for entry into the cool-heavy model atmosphere were about 60 percent higher than those predicted for the entry into the nominal atmosphere. The total mass lost for entry into the cool-heavy model atmosphere was about 146 kg and the mass lost for entry into the nominal model atmosphere was about 101 kg.
Thermal equivalence of DNA duplexes without calculation of melting temperature
NASA Astrophysics Data System (ADS)
Weber, Gerald; Haslam, Niall; Whiteford, Nava; Prügel-Bennett, Adam; Essex, Jonathan W.; Neylon, Cameron
2006-01-01
The common key to nearly all processes involving DNA is the hybridization and melting of the double helix: from transmission of genetic information and RNA transcription, to polymerase chain reaction and DNA microarray analysis, DNA mechanical nanodevices and DNA computing. Selecting DNA sequences with similar melting temperatures is essential for many applications in biotechnology. We show that instead of calculating these temperatures, a single parameter can be derived from a statistical-mechanics model that conveniently represents the thermodynamic equivalence of DNA sequences. This parameter is shown to order experimental melting temperatures correctly, is much more readily obtained than the melting temperature, and is easier to handle than the numerous parameters of empirical regression models.
Electronic and thermal properties of Biphenyl molecules
NASA Astrophysics Data System (ADS)
Medina, F. G.; Ojeda, J. H.; Duque, C. A.; Laroze, D.
2015-11-01
Transport properties of a single Biphenyl molecule coupled to two contacts are studied. We characterise this system by a tight-binding Hamiltonian. Based on the non-equilibrium Green's functions technique with a Landauer-Büttiker formalism the transmission probability, current and thermoelectrical power are obtained. We show that the Biphenyl molecule may have semiconductor behavior for certain values of the electrode-molecule-electrode junctions and different values of the angle between the two rings of the molecule. In addition, the density of states (DOS) is calculated to compare the bandwidths with the profile of the transmission probability. DOS allows us to explain the asymmetric shape with respect to the molecule's Fermi energy.
Computer Programs for Calculating the Isentropic Flow Properties for Mixtures of R-134a and Air
NASA Technical Reports Server (NTRS)
Kvaternik, Raymond G.
2000-01-01
Three computer programs for calculating the isentropic flow properties of R-134a/air mixtures which were developed in support of the heavy gas conversion of the Langley Transonic Dynamics Tunnel (TDT) from dichlorodifluoromethane (R-12) to 1,1,1,2 tetrafluoroethane (R-134a) are described. The first program calculates the Mach number and the corresponding flow properties when the total temperature, total pressure, static pressure, and mole fraction of R-134a in the mixture are given. The second program calculates tables of isentropic flow properties for a specified set of free-stream Mach numbers given the total pressure, total temperature, and mole fraction of R-134a. Real-gas effects are accounted for in these programs by treating the gases comprising the mixture as both thermally and calorically imperfect. The third program is a specialized version of the first program in which the gases are thermally perfect. It was written to provide a simpler computational alternative to the first program in those cases where real-gas effects are not important. The theory and computational procedures underlying the programs are summarized, the equations used to compute the flow quantities of interest are given, and sample calculated results that encompass the operating conditions of the TDT are shown.
Thermal properties of {sup 40}Ca and {sup 90}Zr
Hasan, M.A.; Vary, J.P.; Hasan, M.A.; Vary, J.P.
1998-11-01
We evaluate the thermal properties of {sup 40}Ca and {sup 90}Zr with two different effective Hamiltonians in a mean-field approach. Observed differences in the results are traced to the dependence of thermal properties on the shell gap near the Fermi surface which varies with the choice of Hamiltonian. {copyright} {ital 1998} {ital The American Physical Society}
Impacts of doping on thermal and thermoelectric properties of nanomaterials.
Zhang, Gang; Li, Baowen
2010-07-01
Thermal transport in nanoscale structures has attracted an increasing interest in the last two decades. On the one hand, the low dimensional nanostructured materials are platforms for testing novel phonon transport theories. On the other hand, nanomaterials are promising candidates for nanoscale on-chip coolers. This review is focused on the thermal conductance, thermoelectric property, and impacts of doping on these properties.
Thermal Coatings Seminar Series Training Part 1: Properties of Thermal Coatings
NASA Technical Reports Server (NTRS)
Triolo, Jack
2015-01-01
This course will present an overview of a variety of thermal coatings-related topics, including: coating types and availability, thermal properties measurements, environmental testing (lab and in-flight), environmental impacts, contamination impacts, contamination liabilities, determination of BOLEOL values, and what does specularity mean to the thermal engineer.
Adjustment of Sensor Locations During Thermal Property Parameter Estimation
NASA Technical Reports Server (NTRS)
Milos, Frank S.; Marschall, Jochen; Rasky, Daniel J. (Technical Monitor)
1996-01-01
The temperature dependent thermal properties of a material may be evaluated from transient temperature histories using nonlinear parameter estimation techniques. The usual approach is to minimize the sum of the squared errors between measured and calculated temperatures at specific locations in the body. Temperature measurements are usually made with thermocouples and it is customary to take thermocouple locations as known and fixed during parameter estimation computations. In fact, thermocouple locations are never known exactly. Location errors on the order of the thermocouple wire diameter are intrinsic to most common instrumentation procedures (e.g., inserting a thermocouple into a drilled hole) and additional errors can be expected for delicate materials, difficult installations, large thermocouple beads, etc.. Thermocouple location errors are especially significant when estimating thermal properties of low diffusively materials which can sustain large temperature gradients during testing. In the present work, a parameter estimation formulation is presented which allows for the direct inclusion of thermocouple positions into the primary parameter estimation procedure. It is straightforward to set bounds on thermocouple locations which exclude non-physical locations and are consistent with installation tolerances. Furthermore, bounds may be tightened to an extent consistent with any independent verification of thermocouple location, such as x-raying, and so the procedure is entirely consonant with experimental information. A mathematical outline of the procedure is given and its implementation is illustrated through numerical examples characteristic of light-weight, high-temperature ceramic insulation during transient heating. The efficacy and the errors associated with the procedure are discussed.
Thermodynamic and mechanical properties of TiC from ab initio calculation
Dang, D. Y.; Fan, J. L.; Gong, H. R.
2014-07-21
The temperature-dependent thermodynamic and mechanical properties of TiC are systematically investigated by means of a combination of density-functional theory, quasi-harmonic approximation, and thermal electronic excitation. It is found that the quasi-harmonic Debye model should be pertinent to reflect thermodynamic properties of TiC, and the elastic properties of TiC decease almost linearly with the increase of temperature. Calculations also reveal that TiC possesses a pronounced directional pseudogap across the Fermi level, mainly due to the strong hybridization of Ti 3d and C 2p states. Moreover, the strong covalent bonding of TiC would be enhanced (reduced) with the decrease (increase) of temperature, while the change of volume (temperature) should have negligible effect on density of states at the Fermi level. The calculated results agree well with experimental observations in the literature.
Internet calculations of thermodynamic properties of substances: Some problems and results
NASA Astrophysics Data System (ADS)
Ustyuzhanin, E. E.; Ochkov, V. F.; Shishakov, V. V.; Rykov, S. V.
2016-11-01
Internet resources (databases, web sites and others) on thermodynamic properties R = (p,T,s,...) of technologically important substances are analyzed. These databases put online by a number of organizations (the Joint Institute for High Temperatures of the Russian Academy of Sciences, Standartinform, the National Institute of Standards and Technology USA, the Institute for Thermal Physics of the Siberian Branch of the Russian Academy of Sciences, etc) are investigated. Software codes are elaborated in the work in forms of “client functions” those have such characteristics: (i) they are placed on a remote server, (ii) they serve as open interactive Internet resources. A client can use them for a calculation of R properties of substances. “Complex client functions” are considered. They are focused on sharing (i) software codes elaborated to design of power plants (PP) and (ii) client functions those can calculate R properties of working fluids for PP.
Thermal-optical properties of Fluorel L-3203-6 and 1059
NASA Technical Reports Server (NTRS)
French, B.
1972-01-01
Fluorel L-3203-6 and 1059 and four Fluorel derivatives were irradiated monochromatically and hemispherically with electromagnetic energy in the solar- and infrared-wavelength range to determine the thermal-optical properties that are required for engineering analysis. The thermal-optical properties were measured and analyzed, and the resulting data were tabulated for convenient engineering use. The results prove that the electromagnetic-energy distribution and the measured reflectance and transmittance of materials can be used to calculate several mean values, which are the total and hemispherical thermal-optical properties. The test results also illustrate that Fluorel effectively absorbs energy in the solar- and infrared-wavelength range. In addition, the results demonstrate that fabrication alters the thermal-optical properties of Fluorel.
First principles calculation of thermo-mechanical properties of thoria using Quantum ESPRESSO
NASA Astrophysics Data System (ADS)
Malakkal, Linu; Szpunar, Barbara; Zuniga, Juan Carlos; Siripurapu, Ravi Kiran; Szpunar, Jerzy A.
2016-05-01
In this work, we have used Quantum ESPRESSO (QE), an open source first principles code, based on density-functional theory, plane waves, and pseudopotentials, along with quasi-harmonic approximation (QHA) to calculate the thermo-mechanical properties of thorium dioxide (ThO2). Using Python programming language, our group developed qe-nipy-advanced, an interface to QE, which can evaluate the structural and thermo-mechanical properties of materials. We predicted the phonon contribution to thermal conductivity (kL) using the Slack model. We performed the calculations within local density approximation (LDA) and generalized gradient approximation (GGA) with the recently proposed version for solids (PBEsol). We employed a Monkhorst-Pack 5 × 5 × 5 k-points mesh in reciprocal space with a plane wave cut-off energy of 150 Ry to obtain the convergence of the structure. We calculated the dynamical matrices of the lattice on a 4 × 4 × 4 mesh. We have predicted the heat capacity, thermal expansion and the phonon contribution to thermal conductivity, as a function of temperature up to 1400K, and compared them with the previous work and known experimental results.
NASA Astrophysics Data System (ADS)
Birtok-Bǎneasǎ, Corneliu; RaÅ£iu, Sorin Aurel; HepuÅ£, Teodor
2017-07-01
This paper presents a method for reduce thermal losses in the intake system of an internal combustion engine, whit improvement of airflow and thermal protection. The method consists in insulating the intake with a new kind of material. The present paper focuses on calculation of thermal conductivity for a new material developed by the authors, using the heat flux plate method. This experimental method consists in placing the sample of the new material in a calorimetric chamber and heating from underside. As the heat flux which passes through the sample material is constant and knowing the values of the temperatures for the both sides of sample, the sample material thermal conductivity is determined.
Gopakumar, Abhijith M; Gupta, M K; Mittal, R; Rols, S; Chaplot, S L
2017-05-17
We investigate the detailed lattice dynamics of copper halides, CuX (X = Cl, Br, and I), using neutron inelastic scattering measurements and ab initio calculations aimed at a comparative study of their thermal expansion behavior. We identify the low energy phonons which soften with pressure and are responsible for negative thermal expansion. The eigenvector analysis of these modes suggests that softening of the transverse-acoustic modes would lead to NTE in these compounds. The calculations are in very good agreement with our measurements of phonon spectra and thermal expansion behavior as reported in the literature. Our calculations at high pressure further reveal that a large difference in negative thermal expansion behavior in these compounds is associated with the difference in the unit cell volume.
Thermoelectric Properties of Half-Heusler Heterostructures from Ab Initio Calculations
NASA Astrophysics Data System (ADS)
Fiedler, Gregor; Kratzer, Peter
2016-03-01
Semiconducting half-Heusler alloys have recently emerged as a class of thermoelectric materials with outstanding performance in the medium- to high-temperature range. Heterostructures promise a further reduction of thermal conductivity as a result of phonon scattering at interfaces. Here, both the electronic and phononic spectra of half-Heusler compounds based on Ti, Zr, and Hf are calculated using density functional theory. With this input, thermoelectric properties are obtained, and the thermal conductivity of a heterostructure superlattice is estimated by extending the diffuse mismatch model of interface conductance. We find that a high power factor σ S^2 can be retained in a short-period superlattice, while thermal conductivity is reduced compared to that in single-phase half-Heusler crystals.
NASA Astrophysics Data System (ADS)
Landry, E. S.; McGaughey, A. J. H.
2009-10-01
The accuracies of two theoretical expressions for thermal boundary resistance are assessed by comparing their predictions to independent predictions from molecular dynamics (MD) simulations. In one expression (RE) , the phonon distributions are assumed to follow the equilibrium, Bose-Einstein distribution, while in the other expression (RNE) , the phonons are assumed to have nonequilibrium, but bulk-like distributions. The phonon properties are obtained using lattice dynamics-based methods, which assume that the phonon interface scattering is specular and elastic. We consider (i) a symmetrically strained Si/Ge interface, and (ii) a series of interfaces between Si and “heavy-Si,” which differs from Si only in mass. All of the interfaces are perfect, justifying the assumption of specular scattering. The MD-predicted Si/Ge thermal boundary resistance is temperature independent and equal to 3.1×10-9m2-K/W below a temperature of ˜500K , indicating that the phonon scattering is elastic, as required for the validity of the theoretical calculations. At higher-temperatures, the MD-predicted Si/Ge thermal boundary resistance decreases with increasing temperature, a trend we attribute to inelastic scattering. For the Si/Ge interface and the Si/heavy-Si interfaces with mass ratios greater than two, RE is in good agreement with the corresponding MD-predicted values at temperatures where the interface scattering is elastic. When applied to a system containing no interface, RE is erroneously nonzero due to the assumption of equilibrium phonon distributions on either side of the interface. While RNE is zero for a system containing no interface, it is 40%-60% less than the corresponding MD-predicted values for the Si/Ge interface and the Si/heavy-Si interfaces at temperatures where the interface scattering is elastic. This inaccuracy is attributed to the assumption of bulk-like phonon distributions on either side of the interface.
Study of the thermal stability of studtite by in situ Raman spectroscopy and DFT calculations
NASA Astrophysics Data System (ADS)
Colmenero, Francisco; Bonales, Laura J.; Cobos, Joaquín; Timón, Vicente
2017-03-01
The design of a safe spent nuclear fuel repository requires the knowledge of the stability of the secondary phases which precipitate when water reaches the fuel surface. Studtite is recognized as one of the secondary phases that play a key-role in the mobilization of the radionuclides contained in the spent fuel. Thereby, it has been identified as a product formed under oxidation conditions at the surface of the fuel, and recently found as a corrosion product in the Fukushima-Daiichi nuclear plant accident. Thermal stability is one of the properties that should be determined due to the high temperature of the fuel. In this work we report a detailed analysis of the structure and thermal stability of studtite. The structure has been studied both by experimental techniques (SEM, TGA, XRD and Raman spectroscopy) and theoretical DFT electronic structure and spectroscopic calculations. The comparison of the results allows us to perform for the first time the Raman bands assignment of the whole spectrum. The thermal stability of studtite has been analyzed by in situ Raman spectroscopy, with the aim of studying the effect of the heating rate and the presence of water. For this purpose, a new cell has been designed. The results show that studtite is stable under dry conditions only at temperatures below 30 °C, in contrast with the higher temperatures published up to date ( 130 °C). Opposite behaviour has been found when studtite is in contact with water; under these conditions studtite is stable up to 90 °C, what is consistent with the encounter of this phase after the Fukushima-Daiichi accident.
Study of the thermal stability of studtite by in situ Raman spectroscopy and DFT calculations.
Colmenero, Francisco; Bonales, Laura J; Cobos, Joaquín; Timón, Vicente
2017-03-05
The design of a safe spent nuclear fuel repository requires the knowledge of the stability of the secondary phases which precipitate when water reaches the fuel surface. Studtite is recognized as one of the secondary phases that play a key-role in the mobilization of the radionuclides contained in the spent fuel. Thereby, it has been identified as a product formed under oxidation conditions at the surface of the fuel, and recently found as a corrosion product in the Fukushima-Daiichi nuclear plant accident. Thermal stability is one of the properties that should be determined due to the high temperature of the fuel. In this work we report a detailed analysis of the structure and thermal stability of studtite. The structure has been studied both by experimental techniques (SEM, TGA, XRD and Raman spectroscopy) and theoretical DFT electronic structure and spectroscopic calculations. The comparison of the results allows us to perform for the first time the Raman bands assignment of the whole spectrum. The thermal stability of studtite has been analyzed by in situ Raman spectroscopy, with the aim of studying the effect of the heating rate and the presence of water. For this purpose, a new cell has been designed. The results show that studtite is stable under dry conditions only at temperatures below 30°C, in contrast with the higher temperatures published up to date (~130°C). Opposite behaviour has been found when studtite is in contact with water; under these conditions studtite is stable up to 90°C, what is consistent with the encounter of this phase after the Fukushima-Daiichi accident.
Predicting the properties of the lead alloys from DFT calculations
Buimaga-Iarinca, L. Calborean, A.
2015-12-23
We provide qualitative results for the physical properties of the lead alloys at atomic scale by using DFT calculations. Our approach is based on the two assumptions: (i) the geometric structure of lead atoms provides a matrix where the alloying elements can take their positions in the structure as substitutions and (ii) there is a small probability of a direct interaction between the alloying elements, thus the interactions of each alloying element may be approximated by the interactions to the lead matrix. DFT calculations are used to investigate the interaction between several types of impurities and the lead matrix for low concentrations of the alloying element. We report results such as the enthalpy of formation, charge transfer and mechanical stress induced by the impurities in the lead matrix; these results can be used as qualitative guide in tuning the physico-chemical properties of the lead alloys.
AUTOSTRUCTURE: General program for calculation of atomic and ionic properties
NASA Astrophysics Data System (ADS)
Badnell, Nigel R.
2016-12-01
AUTOSTRUCTURE calculates atomic and ionic energy levels, radiative rates, autoionization rates, photoionization cross sections, plane-wave Born and distorted-wave excitation cross sections in LS- and intermediate-coupling using non- or (kappa-averaged) relativistic wavefunctions. These can then be further processed to form Auger yields, fluorescence yields, partial and total dielectronic and radiative recombination cross sections and rate coefficients, photoabsorption cross sections, and monochromatic opacities, among other properties.
Influence of saturation properties on shell-model calculations
NASA Astrophysics Data System (ADS)
Abzouzi, A.; Caurier, E.; Zuker, A. P.
1991-03-01
It is shown that the nuclear Hamiltonian scrH separates rigorously into a monopole field scrHm and a multipole part scrHm. scrHm is entirely responsible for saturation properties and can be treated phenomenologically with few parameters. When realistic interactions are used for scrHM in regions from the p shell to the N=82 isotones, shell-model calculations yield excellent spectroscopy and demand nuclear radii very close to the observed ones.
Thermal properties of freezing bound water restrained by polysaccharides.
Hatakeyama, Tatsuko; Tanaka, Masaru; Hatakeyama, Hyoe
2010-01-01
This review focuses on the thermal properties of bound water restrained by various kinds of polysaccharides and several synthetic polymers. The characteristic features of freezing bound water which is closely related with biocompatibility of polymers are summarized based on results obtained by differential scanning calorimetry. Glass transition, cold crystallization and melting of water-polysaccharide systems were observed. Three kinds of water, non-freezing, freezing bound and free water, were quantified from the enthalpy of melting of water in the system. Freezing bound water restrained by polysaccharides is in a metastable state. The equilibrium melting temperature of freezing bound water is lower than 0°C and the temperature decreases with decreasing water content. Nucleation and growth rate of freezing bound water were calculated from isothermal crystallization and the values were compared with those of free water.
Cavern/Vault Disposal Concepts and Thermal Calculations for Direct Disposal of 37-PWR Size DPCs
Hardin, Ernest; Hadgu, Teklu; Clayton, Daniel James
2015-03-01
This report provides two sets of calculations not presented in previous reports on the technical feasibility of spent nuclear fuel (SNF) disposal directly in dual-purpose canisters (DPCs): 1) thermal calculations for reference disposal concepts using larger 37-PWR size DPC-based waste packages, and 2) analysis and thermal calculations for underground vault-type storage and eventual disposal of DPCs. The reader is referred to the earlier reports (Hardin et al. 2011, 2012, 2013; Hardin and Voegele 2013) for contextual information on DPC direct disposal alternatives.
Calculated optical properties of thorium, protactinium, and uranium metals
Gasche, T.; Brooks, M.S.; Johansson, B.
1996-07-01
We report self-consistent energy band calculations using the linear muffin-tin orbital method and the local-spin-density approximation to exchange and correlation in density-functional theory for the light actinide metals Th, Pa, and U. The optical properties have been calculated and compared with measurements, where possible. The dependence of the optical response functions upon crystal structure was found to be surprisingly large and the dependence upon spin-orbit coupling, less so. Where it was possible to make comparison, agreement with experiment was obtained for the maxima of the optical spectra, the exception being a feature in the optical conductivity at 10 eV measured in both Th and U but not obtained in the calculations. {copyright} {ital 1996 The American Physical Society.}
Mechanical properties of thermal protection system materials.
Hardy, Robert Douglas; Bronowski, David R.; Lee, Moo Yul; Hofer, John H.
2005-06-01
An experimental study was conducted to measure the mechanical properties of the Thermal Protection System (TPS) materials used for the Space Shuttle. Three types of TPS materials (LI-900, LI-2200, and FRCI-12) were tested in 'in-plane' and 'out-of-plane' orientations. Four types of quasi-static mechanical tests (uniaxial tension, uniaxial compression, uniaxial strain, and shear) were performed under low (10{sup -4} to 10{sup -3}/s) and intermediate (1 to 10/s) strain rate conditions. In addition, split Hopkinson pressure bar tests were conducted to obtain the strength of the materials under a relatively higher strain rate ({approx}10{sup 2} to 10{sup 3}/s) condition. In general, TPS materials have higher strength and higher Young's modulus when tested in 'in-plane' than in 'through-the-thickness' orientation under compressive (unconfined and confined) and tensile stress conditions. In both stress conditions, the strength of the material increases as the strain rate increases. The rate of increase in LI-900 is relatively small compared to those for the other two TPS materials tested in this study. But, the Young's modulus appears to be insensitive to the different strain rates applied. The FRCI-12 material, designed to replace the heavier LI-2200, showed higher strengths under tensile and shear stress conditions. But, under a compressive stress condition, LI-2200 showed higher strength than FRCI-12. As far as the modulus is concerned, LI-2200 has higher Young's modulus both in compression and in tension. The shear modulus of FRCI-12 and LI-2200 fell in the same range.
Thermal properties of rocks of the borehole Yaxcopoil-1 (Impact Crater Chicxulub, Mexico)
NASA Astrophysics Data System (ADS)
Popov, Yu.; Romushkevich, R.; Korobkov, D.; Mayr, S.; Bayuk, I.; Burkhardt, H.; Wilhelm, H.
2011-02-01
The results of thermal property measurements on cores from the scientific well Yaxcopoil-1 (1511 m in depth) drilled in the Chicxulub impact structure (Mexico) are described. The thermal conductivity, thermal diffusivity, volumetric heat capacity, thermal anisotropy coefficient, thermal heterogeneity factor, and, in addition, porosity and density were measured on 451 dry and water-saturated cores from the depth interval of 404-1511 m. The acoustic velocities were determined on a subgroup of representative samples. Significant vertical short- and long-scale variations of physical properties related to the grade of shock-thermal metamorphism and correlations between thermal and other physical properties are established. Rocks of the post-impact and impact complexes differ significantly in heterogeneity demonstrating that the impact complex has larger micro- heterogeneity on sample scale. The pre-impact rocks differ essentially from the impact and post-impact rocks in the thermal conductivity, thermal diffusivity, density and porosity. The thermal anisotropy of rocks of all structural-lithological complexes is very low (K = 1.02 … 1.08), which is similar to the situation in the Puchezh-Katunk and Ries impact structures. Correlations are established between the thermal conductivity and elastic wave velocities measured in laboratory. For limestone-calcarenites, the thermal conductivity (λ) can be calculated from the compressional wave velocity (Vp) using the formula λ= 0.346 Vp + 0.844, and for dolomite-anhydrites this relation has the form λ= 0.998 Vp + 1.163 [for λ in W (m K)-1 and Vp in km s-1]. These correlations are used for downscaling of the sonic velocities to the decimetre scale. The effective medium theory is applied to invert the matrix thermal conductivity and pore/crack geometry from the thermal conductivity measured on the studied samples. Representative experimental data on the thermal properties for all lithological groups encountered by the
Thermal properties of nonstoichiometry uranium dioxide
NASA Astrophysics Data System (ADS)
Kavazauri, R.; Pokrovskiy, S. A.; Baranov, V. G.; Tenishev, A. V.
2016-04-01
In this paper, was developed a method of oxidation pure uranium dioxide to a predetermined deviation from the stoichiometry. Oxidation was carried out using the thermogravimetric method on NETZSCH STA 409 CD with a solid electrolyte galvanic cell for controlling the oxygen potential of the environment. 4 samples uranium oxide were obtained with a different ratio of oxygen-to-metal: O / U = 2.002, O / U = 2.005, O / U = 2.015, O / U = 2.033. For the obtained samples were determined basic thermal characteristics of the heat capacity, thermal diffusivity, thermal conductivity. The error of heat capacity determination is equal to 5%. Thermal diffusivity and thermal conductivity of the samples decreased with increasing deviation from stoichiometry. For the sample with O / M = 2.033, difference of both values with those of stoichiometric uranium dioxide is close to 50%.
Synthesis and thermal properties of new bionanofluids containing gold nanoparticles
NASA Astrophysics Data System (ADS)
Jiménez-Pérez, J. L.; López Gamboa, G.; Gutiérrez Fuentes, R.; Sánchez Ramírez, J. F.; Correa Pacheco, Z. N.; López-y-López, V. E.; Tepech-Carrillo, L.
2016-10-01
New bionanofluids containing Au nanoparticles with different concentrations were prepared by chemical reduction method. The nanoparticles were mixed with biodiesel from soybean prepared using alkaline catalysts. Thermal properties of biodiesel containing Au nanoparticles with different volume percentage concentrations were measured by mismatched dual-beam mode thermal lens technique in order to measure the effect of the presence of nanoparticles ( φ = 13.3 nm) on the bionanofluids thermal diffusivity. The characteristic time constant of the transient thermal lens was estimated by fitting the experimental data to the theoretical expression for transient thermal lens. The thermal diffusivity of the bionanofluids (biodiesel containing Au nanoparticles) seems to be strongly dependent on the presence of nanoparticles. It was observed an increase in the thermal diffusivity when volume percentage of nanoparticles increased. A possible explanation for such high thermal diffusivity of the biodiesel with Au nanoparticles is given. UV-Vis spectroscopy and TEM microscopy techniques were used to characterize the bionanofluids.
Kan, An-Kang; Cao, Dan; Zhang, Xue-Lai
2015-04-01
Accurately predicting the effective thermal conductivity of the fibrous materials is highly desirable but remains to be a challenging work. In this paper, the microstructure of the porous fiber materials is analyzed, approximated and modeled on basis of the statistical self-similarity of fractal theory. A fractal model is presented to accurately calculate the effective thermal conductivity of fibrous porous materials. Taking the two-phase heat transfer effect into account, the existing statistical microscopic geometrical characteristics are analyzed and the Hertzian Contact solution is introduced to calculate the thermal resistance of contact points. Using the fractal method, the impacts of various factors, including the porosity, fiber orientation, fractal diameter and dimension, rarified air pressure, bulk thermal conductivity coefficient, thickness and environment condition, on the effective thermal conductivity, are analyzed. The calculation results show that the fiber orientation angle caused the material effective thermal conductivity to be anisotropic, and normal distribution is introduced into the mathematic function. The effective thermal conductivity of fibrous material increases with the fiber fractal diameter, fractal dimension and rarefied air pressure within the materials, but decreases with the increase of vacancy porosity.
Membrane protein properties revealed through data-rich electrostatics calculations
Guerriero, Christopher J.; Brodsky, Jeffrey L.; Grabe, Michael
2015-01-01
SUMMARY The electrostatic properties of membrane proteins often reveal many of their key biophysical characteristics, such as ion channel selectivity and the stability of charged membrane-spanning segments. The Poisson-Boltzmann (PB) equation is the gold standard for calculating protein electrostatics, and the software APBSmem enables the solution of the PB equation in the presence of a membrane. Here, we describe significant advances to APBSmem including: full automation of system setup, per-residue energy decomposition, incorporation of PDB2PQR, calculation of membrane induced pKa shifts, calculation of non-polar energies, and command-line scripting for large scale calculations. We highlight these new features with calculations carried out on a number of membrane proteins, including the recently solved structure of the ion channel TRPV1 and a large survey of 1,614 membrane proteins of known structure. This survey provides a comprehensive list of residues with large electrostatic penalties for being embedded in the membrane potentially revealing interesting functional information. PMID:26118532
Membrane Protein Properties Revealed through Data-Rich Electrostatics Calculations.
Marcoline, Frank V; Bethel, Neville; Guerriero, Christopher J; Brodsky, Jeffrey L; Grabe, Michael
2015-08-04
The electrostatic properties of membrane proteins often reveal many of their key biophysical characteristics, such as ion channel selectivity and the stability of charged membrane-spanning segments. The Poisson-Boltzmann (PB) equation is the gold standard for calculating protein electrostatics, and the software APBSmem enables the solution of the PB equation in the presence of a membrane. Here, we describe significant advances to APBSmem, including full automation of system setup, per-residue energy decomposition, incorporation of PDB2PQR, calculation of membrane-induced pKa shifts, calculation of non-polar energies, and command-line scripting for large-scale calculations. We highlight these new features with calculations carried out on a number of membrane proteins, including the recently solved structure of the ion channel TRPV1 and a large survey of 1,614 membrane proteins of known structure. This survey provides a comprehensive list of residues with large electrostatic penalties for being embedded in the membrane, potentially revealing interesting functional information. Copyright © 2015 Elsevier Ltd. All rights reserved.
Measurement of Thermal Properties of Biosourced Building Materials
NASA Astrophysics Data System (ADS)
Pierre, Thomas; Colinart, Thibaut; Glouannec, Patrick
2014-10-01
This paper presents both experimental and theoretical works concerning the evaluation of the thermal conductivity and thermal diffusivity of hemp concrete. Experimental measurements of thermal properties are performed using a hot-strip technique for temperatures ranging from 3 to 30 and relative humidities ranging from 0 % to 95 %, thus creating a large database for this material. These experimental thermal conductivities are then compared with the results from the Krischer theoretical predictive model. The comparison shows good agreement, and a predictive analytical relation between the hemp concrete thermal conductivity, temperature, and relative humidity is determined.
Calculations and curve fits of thermodynamic and transport properties for equilibrium air to 30000 K
NASA Technical Reports Server (NTRS)
Gupta, Roop N.; Lee, Kam-Pui; Thompson, Richard A.; Yos, Jerrold M.
1991-01-01
A self-consistent set of equilibrium air values were computed for enthalpy, total specific heat at constant pressure, compressibility factor, viscosity, total thermal conductivity, and total Prandtl number from 500 to 30,000 K over a range of 10(exp -4) atm to 10(exp 2) atm. The mixture values are calculated from the transport and thermodynamic properties of the individual species provided in a recent study by the authors. The concentrations of the individual species, required in the mixture relations, are obtained from a free energy minimization calculation procedure. Present calculations are based on an 11-species air model. For pressures less than 10(exp -2) atm and temperatures of about 15,000 K and greater, the concentrations of N(++) and O(++) become important, and consequently, they are included in the calculations determining the various properties. The computed properties are curve fitted as a function of temperature at a constant value of pressure. These curve fits reproduce the computed values within 5 percent for the entire temperature range considered here at specific pressures and provide an efficient means for computing the flowfield properties of equilibrium air, provided the elemental composition remains constant at 0.24 for oxygen and 0.76 for nitrogen by mass.
NASA Astrophysics Data System (ADS)
Chen, C. Z.; Wen, N. Y.; Chen, H. J.; Li, Y.; Cai, C. B.
2017-02-01
Tungsten (W)-doped SnO2 is investigated by first-principle calculations, with a view to understand the effect of doping on the lattice structure, thermal stability, conductivity, and optical transparency. Due to the slight difference in ionic radius as well as high thermal and chemical compatibility between the native element and the heterogeneous dopant, the doped system changes a little with different deviations in the lattice constant from Vegard's law, and good thermal stability is observed as the doping level reaches x = 0.125 in Sn1- x W x O2 compounds. Nevertheless, the large disparities in electron configuration and electronegativity between W and Sn atoms will dramatically modify the electronic structure and charge distribution of W-doped SnO2, leading to a remarkable enhancement of conductivity, electron excitation in the low energy region, and the consequent optical properties, while the visible transparency of Sn1 -x W x O2 is still preserved. Particularly, it is found that the optimal photoelectric properties of W-doped SnO2 may be achieved at x = 0.03. These observations are consistent with the experimental results available on the structural, thermal, electronic, and optical properties of Sn1- x W x O2, thus presenting a practical way of tailoring the physical behaviors of SnO2 through the doping technique.
Anisotropic thermal transport property of defect-free GaN
Ju, Wenjing; Zhou, Zhongyuan E-mail: zywei@seu.edu.cn; Wei, Zhiyong E-mail: zywei@seu.edu.cn
2016-06-15
Non-equilibrium molecular dynamics (MD) simulation is performed to calculate the thermal conductivity of defect-free GaN along three high-symmetry directions. It is found that the thermal conductivity along [001] direction is about 25% higher than that along [100] or [120] direction. The calculated phonon dispersion relation and iso-energy surface from lattice dynamics show that the difference of the sound speeds among the three high-symmetry directions is quite small for the same mode. However, the variation of phonon irradiation with direction is qualitatively consistent with that of the calculated thermal conductivity. Our results indicate that the anisotropic thermal conductivity may partly result from the phonons in the low-symmetry region of the first Brillouin zone due to phonon focus effects, even though the elastic properties along the three high-symmetry directions are nearly isotropic. Thus, the phonon irradiation is able to better describe the property of thermal conductivity as compared to the commonly used phonon dispersion relation. The present investigations uncover the physical origin of the anisotropic thermal conductivity in defect-free GaN, which would provide an important guide for optimizing the thermal management of GaN-based device.
NASA Astrophysics Data System (ADS)
Landerville, Aaron C.; Oleynik, Ivan I.
2017-01-01
Dispersion Corrected Density Functional Theory (DFT+vdW) calculations are performed to predict vibrational and thermal properties of the bulk energetic materials (EMs) β-octahydrocyclotetramethylene-tetranitramine (β-HMX) and triaminotrinitrobenzene (TATB). DFT+vdW calculations of pressure-dependent crystal structure and the hydrostatic equation of state are followed by frozen-phonon calculations of their respective vibration spectra at each pressure. These are then used under the quasi-harmonic approximation to obtain zero-point and thermal free energy contributions to the pressure, resulting in pressure-volume-temperature (PVT) EOS for each material that are in excellent agreement with experiment. Heat capacities, and coefficients of thermal expansion as functions of temperature are also calculated and compared with experiment.
Electronic, thermal and mechanical properties of carbon nanotubes.
Dresselhaus, M S; Dresselhaus, G; Charlier, J C; Hernández, E
2004-10-15
A review of the electronic, thermal and mechanical properties of nanotubes is presented, with particular reference to properties that differ from those of the bulk counterparts and to potential applications that might result from the special structure and properties of nanotubes. Both experimental and theoretical aspects of these topics are reviewed.
Thermal Properties of Degenerate Relativistic Quantum Gases
NASA Astrophysics Data System (ADS)
Homorodean, Laurean
We present the concentration-temperature phase diagram, characteristic functions, thermal equation of state and heat capacity at constant volume for degenerate ideal gases of relativistic fermions and bosons. The nonrelativistic and ultrarelativistic limits of these laws are also discussed.
Deformation and Thermal Properties of Energetic Materials.
1980-12-01
decomposition of PETN/polymer samples 5 (b) Thermal decomposition of PETN/ Benzoyl peroxide samples ......... 6 (c) Effect of ultra-violet light on... Benzoyl peroxide samples The results of the preceeding section show that the additives tested have very little effect on the thermal decomposition of PETN...nitrate. In order to test this hypothesis, mixtures of benzoyl peroxide and PETN were used in a series of TG experiments. Benzoyl peroxide is an
Thermal Properties of Methane Hydrate by Experiment and Modeling and Impacts on Technology
Warzinski, R.P.; Gamwo, I.K.; Rosenbaum, E.M.; Jiang, Hao; Jordan, K.D.; English, N.J.; Shaw, D.W.
2008-07-01
Thermal properties of pure methane hydrate, under conditions similar to naturally occurring hydrate-bearing sediments being considered for potential production, have been determined both by a new experimental technique and by advanced molecular dynamics simulation (MDS). A novel single-sided, Transient Plane Source (TPS) technique has been developed and used to measure thermal conductivity and thermal diffusivity values of low-porosity methane hydrate formed in the laboratory. The experimental thermal conductivity data are closely matched by results from an equilibrium MDS method using in-plane polarization of the water molecules. MDS was also performed using a non-equilibrium model with a fully polarizable force field for water. The calculated thermal conductivity values from this latter approach were similar to the experimental data. The impact of thermal conductivity on gas production from a hydrate-bearing reservoir was also evaluated using the Tough+/Hydrate reservoir simulator.
Investigation of thermal properties of raw materials of asphalt mixtures
NASA Astrophysics Data System (ADS)
Géber, R.; Simon, A.; Kocserha, I.
2017-02-01
Asphalt mixtures are composite materials, which are made of different grades of mineral aggregates and bitumen. During the mixing process mineral materials were blended with bitumen at relatively high temperature (∼200 °C). As the binding process come off in these higher temperature range, thermal properties of asphaltic materials are important. The aim of this project is to reveal the thermal properties of raw materials. During our research two types of mineral aggregates were tested (limestone and dolomite) by different methods. Differential thermal analysis, thermal expansion and thermal conductivity were investigated at technologically important temperatures. The results showed that the structure of mineral materials did not change at elevated temperatures, expansion of samples was neglible, while thermal conductivity changed by temperature.
Effects of nanosized constriction on thermal transport properties of graphene
2014-01-01
Thermal transport properties of graphene with nanosized constrictions are investigated using nonequilibrium molecular dynamics simulations. The results show that the nanosized constrictions have a significant influence on the thermal transport properties of graphene. The thermal resistance of the nanosized constrictions is on the order of 107 to 109 K/W at 150 K, which reduces the thermal conductivity by 7.7% to 90.4%. It is also found that the constriction resistance is inversely proportional to the width of the constriction and independent of the heat current. Moreover, we developed an analytical model for the ballistic thermal resistance of the nanosized constrictions in two-dimensional nanosystems. The theoretical prediction agrees well with the simulation results in this paper, which suggests that the thermal transport across the nanosized constrictions in two-dimensional nanosystems is ballistic in nature. PACS 65.80.CK; 61.48.Gh; 63.20.kp; 31.15.xv PMID:25232292
Novel applications exploiting the thermal properties of nanostructured materials.
Eastman, J. A.
1998-11-20
A new class of heat transfer fluids, termed nanofluids, has been developed by suspending nanocrystalline particles in liquids. Due to the orders-of-magnitude larger thermal conductivities of solids compared to those of liquids such as water, significantly enhanced thermal properties are obtained with nanofluids. The use of nanofluids could impact many industrial sectors, including transportation, energy supply and production, electronics, textiles, and paper production by, for example, decreasing pumping power needs or reducing heat exchanger sizes. In contrast to the enhancement in effective thermal transport rates that is obtained when nanoparticles are suspended in fluids, nanocrystalline coatings are expected to exhibit reduced thermal conductivities compared to coarse-grained coatings. Reduced thermal conductivities are predicted to arise because of a reduction in the mean free path of phonons due to presence of grain boundaries. This behavior, combined with improved mechanical properties, makes nanostructured zirconia coatings excellent candidates for future applications as thermal barriers.
Cassini CAPS Measurements of Thermal Ion Properties: An Update
NASA Astrophysics Data System (ADS)
Wilson, R. J.; Bagenal, F.; Delamere, P. A.
2010-12-01
Since the Wilson et al. [2008] paper on thermal ion properties in Saturn's inner equatorial magnetosphere there have been several advances in forward model techniques and instrument knowledge. These include: a) Improved CAPS (SNG) calibration values since 2008. While the previous fits to data are still valid, this efficiency adjustment has the effect of reducing the density values calculated from that fit. Compared to the previous calibration values, nOH+ and nH+ are ≈30% and ≈9% lower respectively. b) Robust error analysis on the forward model process to produce standard deviations for the fitted parameters. This also shows the expected dependences between various fitted parameters, such as Vφ and OH+ T⊥, inherent in the model. c) Utilization of real magnetic field data to forward model T⊥ and T\\par. Previously assumed magnetic field was in the -z direction. In addition, these improvements allow us to remove the constraint that Vz = 0, and the use of real magnetic field data allows us to analyze data farther from the equator. References Wilson, R. J., R. L. Tokar, M. G. Henderson, T. W. Hill, M. F. Thomsen, and D. H. Pontius (2008), Cassini plasma spectrometer thermal ion measurements in Saturn's inner magnetosphere,
Thermal properties of corn gluten meal and its proteic components.
Di Gioia, L; Cuq, B; Guilbert, S
1999-05-01
Thermal properties of corn gluten meal (CGM) and of its extracted proteic components (zein and glutelin) at 0% moisture content, is studied by dynamic mechanical thermal analysis (DMTA) and modulated differential scanning calorimetry (MDSC). The glass transition temperature (Tg) on first heating, is measured at 176 and 174 degrees C, respectively, for hot-air-dried and native CGM. For zein and glutelin isolated fractions, the measured Tg values are 164 and 209 degrees C, respectively. The calculated Tg from using Matveev's method (Matveev YI. Spec Publ R Soc Chem 1995;156;552) is in good agreement with experimental data for zein, a well defined protein. MDSC allows the measurement of change in heat capacity at Tg (deltaCp) with a single heating scan, avoiding sample alteration, and deltaCp values are 0.365 J/g per K for zein and 0.184 J/g per K for glutelin. The differences observed in Tg, relaxation temperatures, deltaCp and tan delta peak height are related to differences in the structure of the proteins, through the cross-linkages and hydrogen or van der Waals interactions. Experimental data from DMTA and MDSC, and the Couchman-Karasz thermodynamic approach indicate that CGM behaves as a miscible blend of its components, with high non-polar interactions between zein and glutelin proteins.
Mechanical and Thermal Properties of Praseodymium Monopnictides: AN Ultrasonic Study
NASA Astrophysics Data System (ADS)
Bhalla, Vyoma; Kumar, Raj; Tripathy, Chinmayee; Singh, Devraj
2013-09-01
We have computed ultrasonic attenuation, acoustic coupling constants and ultrasonic velocities of praseodymium monopnictides PrX(X: N, P, As, Sb and Bi) along the <100>, <110>, <111> in the temperature range 100-500 K using higher order elastic constants. The higher order elastic constants are evaluated using Coulomb and Born-Mayer potential with two basic parameters viz. nearest-neighbor distance and hardness parameter in the temperature range of 0-500 K. Several other mechanical and thermal parameters like bulk modulus, shear modulus, Young's modulus, Poisson ratio, anisotropic ratio, tetragonal moduli, Breazeale's nonlinearity parameter and Debye temperature are also calculated. In the present study, the fracture/toughness (B/G) ratio is less than 1.75 which implies that PrX compounds are brittle in nature at room temperature. The chosen material fulfilled Born criterion of mechanical stability. We also found the deviation of Cauchy's relation at higher temperatures. PrN is most stable material as it has highest valued higher order elastic constants as well as the ultrasonic velocity. Further, the lattice thermal conductivity using modified approach of Slack and Berman is determined at room temperature. The ultrasonic attenuation due to phonon-phonon interaction and thermoelastic relaxation mechanisms have been computed using modified Mason's approach. The results with other well-known physical properties are useful for industrial applications.
Variations in thermal properties of diamond under isothermal compression
NASA Astrophysics Data System (ADS)
Magomedov, M. N.
2017-05-01
State equation P( V/ V 0, T) and baric dependences of thermal properties of diamond have been obtained without any fitting parameters from the interatomic pair Mie-Lennard-Jones potential and the Einstein model of a crystal. Calculations have been performed along two isotherms (at T = 300 and 3000 K) up to P = 10000 kbar = 1000 GPa, i.e., to a relative volume of V/ V 0 = 0.5. The baric dependences have been obtained for the following characteristics: isothermal elastic modulus B T and B'( P), isochoric heat capacity C v and C v ' ( P), isobaric heat capacity C p ; thermal expansion coefficient α p and α p ' (P); and specific surface energy σ, as well as its derivatives σ'( P) and σ'( T). It is shown that for P → ∞, functions B T ( P) and σ( P) vary linearly, functions B'( P), α p ( P), C v ( P), C p ( P) and σ'( P) tend to constants, while functions α p '( P), C v '( P), and difference C p ( P)- C v ( P) tend to zero. Good agreement with experimental data has been demonstrated.
Vitruk, S.G.; Korsun, A.S.; Ushakov, P.A.
1995-09-01
The multilevel mathematical model of neutron thermal hydrodynamic processes in a passive safety core without assemblies duct walls and appropriate computer code SKETCH, consisted of thermal hydrodynamic module THEHYCO-3DT and neutron one, are described. A new effective discretization technique for energy, momentum and mass conservation equations is applied in hexagonal - z geometry. The model adequacy and applicability are presented. The results of the calculations show that the model and the computer code could be used in conceptual design of advanced reactors.
Unified expression for the calculation of thermal conductivity in the canonical ensemble
NASA Astrophysics Data System (ADS)
Chialvo, Ariel A.; Cummings, Peter T.
A proof of the theoretical equivalence between the E. Helfand, 1960, Phys. Rev., 119, 1 and the D. McQuarrie, 1976, Statistical Mechanics (Harper & Row), Chap. 21 equations for the calculation of thermal conductivity via the Einsteintype relations is presented here. Some theoretical implications of that equivalence are also discussed, such as the unification of the thermal conductivity expressions into one similar to that given for linear transport coefficients by F. C. Andrews, 1967, J. Chem. Phys., 47, 3161.
Thermal properties of graphite oxide, thermally reduced graphene and chemically reduced graphene
NASA Astrophysics Data System (ADS)
Jankovský, Ondřej; Sedmidubský, David; Lojka, Michal; Sofer, Zdeněk
2017-07-01
We compared thermal behavior and other properties of graphite oxide, thermally reduced graphene and chemically reduced graphene. Graphite was oxidized according to the Hofmann method using potassium chlorate as oxidizing agent in strongly acidic environment. In the next step, the formed graphite oxide was chemically or thermally reduced yielding graphene. The mechanism of thermal reduction was studied using STA-MS. Graphite oxide and both thermally and chemically reduced graphenes were analysed by SEM, EDS, elemental combustion analysis, XPS, Raman spectroscopy, XRD and BET. These findings will help for the large scale production of graphene with appropriate chemical composition.
Cao, Bing-Yang; Li, Yuan-Wei
2010-07-14
A uniform source-and-sink (USS) scheme, which combines features of the reverse [F. Müller-Plathe, J. Chem. Phys. 106, 6082 (1997)] and improved relaxation [B. Y. Cao, J. Chem. Phys. 129, 074106 (2008)] methods, is developed to calculate the thermal conductivity by nonequilibrium molecular dynamics (NEMD). The uniform internal heat source and sink are realized by exchanging the velocity vectors of individual atoms in the right half and left half systems, and produce a periodically quadratic temperature profile throughout the system. The thermal conductivity can be easily extracted from the mean temperatures of the right and left half systems rather than by fitting the temperature profiles. In particular, this scheme greatly increases the relaxation of the exited localized phonon modes which often worsen the calculation accuracy and efficiency in most other NEMD methods. The calculation of the thermal conductivities of solid argon shows that the simple USS scheme gives accurate results with fast convergence.
NASA Astrophysics Data System (ADS)
Cao, Bing-Yang; Li, Yuan-Wei
2010-07-01
A uniform source-and-sink (USS) scheme, which combines features of the reverse [F. Müller-Plathe, J. Chem. Phys. 106, 6082 (1997)] and improved relaxation [B. Y. Cao, J. Chem. Phys. 129, 074106 (2008)] methods, is developed to calculate the thermal conductivity by nonequilibrium molecular dynamics (NEMD). The uniform internal heat source and sink are realized by exchanging the velocity vectors of individual atoms in the right half and left half systems, and produce a periodically quadratic temperature profile throughout the system. The thermal conductivity can be easily extracted from the mean temperatures of the right and left half systems rather than by fitting the temperature profiles. In particular, this scheme greatly increases the relaxation of the exited localized phonon modes which often worsen the calculation accuracy and efficiency in most other NEMD methods. The calculation of the thermal conductivities of solid argon shows that the simple USS scheme gives accurate results with fast convergence.
Non-Equilibrium Properties from Equilibrium Free Energy Calculations
NASA Technical Reports Server (NTRS)
Pohorille, Andrew; Wilson, Michael A.
2012-01-01
Calculating free energy in computer simulations is of central importance in statistical mechanics of condensed media and its applications to chemistry and biology not only because it is the most comprehensive and informative quantity that characterizes the eqUilibrium state, but also because it often provides an efficient route to access dynamic and kinetic properties of a system. Most of applications of equilibrium free energy calculations to non-equilibrium processes rely on a description in which a molecule or an ion diffuses in the potential of mean force. In general case this description is a simplification, but it might be satisfactorily accurate in many instances of practical interest. This hypothesis has been tested in the example of the electrodiffusion equation . Conductance of model ion channels has been calculated directly through counting the number of ion crossing events observed during long molecular dynamics simulations and has been compared with the conductance obtained from solving the generalized Nernst-Plank equation. It has been shown that under relatively modest conditions the agreement between these two approaches is excellent, thus demonstrating the assumptions underlying the diffusion equation are fulfilled. Under these conditions the electrodiffusion equation provides an efficient approach to calculating the full voltage-current dependence routinely measured in electrophysiological experiments.
Thermophysical Properties of Polymer Materials with High Thermal Conductivity
NASA Astrophysics Data System (ADS)
Lebedev, S. M.; Gefle, O. S.; Dneprovskii, S. N.; Amitov, E. T.
2015-06-01
Results of studies on the main thermophysical properties of new thermally conductive polymer materials are presented. It is shown that modification of polymer dielectrics by micron-sized fillers allows thermally conductive materials with thermal conductivity not less than 2 W/(m K) to be produced, which makes it possible to use such materials as cooling elements of various electrical engineering and semiconductor equipment and devices.
Thermal properties of epoxy composites filled with boric acid
NASA Astrophysics Data System (ADS)
Visakh, P. M.; Nazarenko, O. B.; Amelkovich, Yu A.; Melnikova, T. V.
2015-04-01
The thermal properties of epoxy composites filled with boric acid fine powder at different percentage were studied. Epoxy composites were prepared using epoxy resin ED-20, boric acid as flame-retardant filler, hexamethylenediamine as a curing agent. The prepared samples and starting materials were examined using methods of thermal analysis, scanning electron microscopy and infrared spectroscopy. It was found that the incorporation of boric acid fine powder enhances the thermal stability of epoxy composites.
Thermal state of SNPS Topaz'' units: Calculation basing and experimental confirmation
Bogush, I.P.; Bushinsky, A.V.; Galkin, A.Y.; Serbin, V.I.; Zhabotinsky, E.E. )
1991-01-01
The ensuring thermal state parameters of thermionic space nuclear power system (SNPS) units in required limits on all operating regimes is a factor which determines SNPSs lifetime. The requirements to unit thermal state are distinguished to a marked degree, and both the corresponding units arragement in SNPS power generating module and the use of definite control algorithms, special thermal regulation and protection are neccessary for its provision. The computer codes which permit to define the thermal transient performances of liquid metal loop and main units had been elaborated for calculation basis of required SNPS Topaz'' unit thermal state. The conformity of these parameters to a given requirements are confirmed by results of autonomous unit tests, tests of mock-ups, power tests of ground SNPS prototypes and flight tests of two SNPS Topaz''.
Bogoliubov-normal interaction and calculation of thermal conductivity of superfluid A1-3He
NASA Astrophysics Data System (ADS)
Afzali, R.; Ebrahimian, N.
2006-09-01
The diffusive thermal conductivity tensor of the A 1-phase of superfluid 3He at low temperatures and melting pressure are calculated by s-p approximation, by using the Boltzmann equation approach. We obtain that the elements of the diffusive thermal conductivities, Kxx, Kyy, and Kzz, are proportional to T -1. Then we compare the results of this paper and our results of thermal conductivity based on Pfitzner procedure. Temperature dependence of both results is equal but numerical coefficients of them are little different. Also we show that Boguliubov-normal interaction is important in comparison to other interactions.
Techniques for achieving thermal equilibrium in molecular dynamics calculations for solids
NASA Astrophysics Data System (ADS)
Wu, Ernest Yue; Friauf, Robert J.
1990-06-01
We develop techniques for achieving thermal equilibrium in molecular dynamics calculations for solids. Atoms in a Lennard-Jones solid are initially given random velocities and displacements from their equilibrium positions with suitably scaled Maxwellian distributions. A quantitative criterion for thermal equilibrium of the solid is established by using the equipartition of energy theorem. At high temperatures, thermal expansion is studied, and we introduce a method for adjusting the lattice parameter to ensure zero external pressure. The results of molecular dynamics simulations show agreement with experimental data for rare gas and ionic crystals.
Thermal properties of organic and modified inorganic aerogels
Pekala, R.W.; Hrubesh, L.W.
1992-08-01
Aerogels are open-cell foams that have already been shown to be among the best thermal insulating solid materials known. Improvements in the thermal insulating properties of aerogels are possible by synthesizing new organic varieties, by using additives within existing aerogel matrix, and by optimizing their nanostructures. We discuss these approaches and give some examples of aerogels which demonstrate the improvements.
Water absorbance and thermal properties of sulfated wheat gluten films
USDA-ARS?s Scientific Manuscript database
Wheat gluten films of varying thicknesses formed at 30C to 70C were treated with cold sulfuric acid to produce sulfated gluten films. Chemical, thermal, thermal stability, and water uptake properties were characterized for neat and sulfated films. The sulfated gluten films were able ...
Laboratory measurements of gravel thermal properties. A methodology proposal
NASA Astrophysics Data System (ADS)
Cultrera, Matteo; Peron, Fabio; Bison, Paolo; Dalla Santa, Giorgia; Bertermann, David; Muller, Johannes; Bernardi, Adriana; Galgaro, Antonio
2017-04-01
Gravel thermal properties measurements at laboratory level is quite challenging due to several technical and logistic issues, mainly connected to the sediment sizes and the variability of their mineralogical composition. The direct measurement of gravel thermal properties usually are not able to involve a representative volume of geological material, consequently the thermal measurements performed produce much dispersed results and not consistent due to the large interstitial voids and the poor physical contact with the measuring sensors. With the aim of directly provide the measurement of the gravel thermal properties, a new methodology has been developed and some results are already available on several gravel deposits samples around Europe. Indeed, a single guarded hot plate Taurus Instruments TLP 800 measured the gravel thermal properties. Some instrumental adjustments were necessary to adapt the measuring devices and to finalize the thermal measurements on gravels at the IUAV FISTEC laboratory (Environmental Technical Physics Laboratory of Venice University). This device usually provides thermal measurements according to ISO 8302, ASTM C177, EN 1946-2, EN 12664, EN 12667 and EN 12939 for building materials. A preliminary calibration has been performed comparing the outcomes obtained with the single guarded hot plate with a needle probe of a portable thermal conductivity meter (ISOMET). Standard sand (ISO 67:2009) is used as reference material. This study is provided under the Cheap-GSHPs project that has received funding from the European Union's Horizon 2020 research and innovation program under grant agreement no. 657982
Simultaneous Measurements of Thermal Properties of Individual Carbon Fibers
NASA Astrophysics Data System (ADS)
Wang, Jianli; Song, Bai; Zhang, Xing; Song, Yang; Wu, Gangping
2011-05-01
Combining the steady-state and quasi-steady-state T type probes, the longitudinal thermal conductivity and thermal effusivity of individual mesophase pitch-based carbon fiber heat treated at 2800 °C and 1000 °C have been measured from 100 K to 300 K. The present method allows simultaneous measurements of thermal properties using the same instrument, by simply changing the applied direct current to alternating current. The specific heat is found to decrease with increasing heat-treatment temperature and to approach the value of graphite. The highly graphitized carbon fiber has a maximum thermal conductivity of 410 W · m-1 · K-1 at about 250 K, and its thermal diffusivity decreases with increasing temperature. Comparatively, the thermal conductivity of the fiber heat treated at 1000 °C is much smaller, with the peak shifting to high temperature due to a large defect density, and its thermal diffusivity is nearly temperature independent.
Calculation evaluation of multiplying properties of LWR with thorium fuel
NASA Astrophysics Data System (ADS)
Shamanin, I. V.; Grachev, V. M.; Knyshev, V. V.; Bedenko, S. V.; Novikova, N. G.
2017-01-01
The results of multiplying properties design research of the unit cell and LWR fuel assembly with the high temperature gas-cooled thorium reactor fuel pellet are presented in the work. The calculation evaluation showed the possibility of using thorium in LWR effectively. In this case the amount of fissile isotope is 2.45 times smaller in comparison with the standard loading of LWR. The research and numerical experiments were carried out using the verified accounting code of the program MCU5, modern libraries of evaluated nuclear data and multigroup approximations.
High-accuracy coupled cluster calculations of atomic properties
NASA Astrophysics Data System (ADS)
Borschevsky, A.; Yakobi, H.; Eliav, E.; Kaldor, U.
2015-01-01
The four-component Fock-space coupled cluster and intermediate Hamiltonian methods are implemented to evaluate atomic properties. The latter include the spectra of nobelium and lawrencium (elements 102 and 103) in the range 20000-30000 cm-1, the polarizabilities of elements 112-114 and 118, required for estimating their adsorption enthalpies on surfaces used to separate them in accelerators, and the nuclear quadrupole moments of some heavy atoms. The calculations on superheavy elements are supported by the very good agreement with experiment obtained for the lighter homologues.
High-accuracy coupled cluster calculations of atomic properties
Borschevsky, A.; Yakobi, H.; Eliav, E.; Kaldor, U.
2015-01-22
The four-component Fock-space coupled cluster and intermediate Hamiltonian methods are implemented to evaluate atomic properties. The latter include the spectra of nobelium and lawrencium (elements 102 and 103) in the range 20000-30000 cm{sup −1}, the polarizabilities of elements 112-114 and 118, required for estimating their adsorption enthalpies on surfaces used to separate them in accelerators, and the nuclear quadrupole moments of some heavy atoms. The calculations on superheavy elements are supported by the very good agreement with experiment obtained for the lighter homologues.
NASA Astrophysics Data System (ADS)
Todd, B.; Stackhouse, S.; Walker, A.; Mound, J. E.
2016-12-01
Thermal conductivity is a key parameter for Earth models involving heat flow across the core-mantle boundary. It is not currently possible to measure the thermal conductivity of minerals at lower mantle temperatures, meaning that lower temperature experimental values must be extrapolated, introducing considerable uncertainty. Furthermore, the effect of impurities, such as Fe and Al, is poorly constrained. In view of this, we use two complementary theoretical methods to determine the lattice thermal conductivity of (Fe,Mg)SiO3 bridgmanite, with varying concentration and distribution of Fe impurities. First, we utilise the direct method (non-equilibrium molecular dynamics), which allows thermal conductivity to be calculated, via Fourier's law, from the ratio of an imposed heat-flux and induced thermal gradient. Second, equilibrium molecular dynamics is employed to measure the time-dependence of instantaneous heat-flux variations, which are related to thermal conductivity via the Green-Kubo equation. We find that both methods have finite-size effects, which must be resolved before considering the important issue of impurity content. These effects are assessed using interatomic potentials, in order to reach the requisite large simulation sizes (up to approximately 60,000 atoms) on a reasonable timescale. Our work provides a systematic study of the effects to consider when calculating the thermal conductivity of minerals at lower mantle conditions.
NASA Glenn Coefficients for Calculating Thermodynamic Properties of Individual Species
NASA Technical Reports Server (NTRS)
McBride, Bonnie J.; Zehe, Michael J.; Gordon, Sanford
2002-01-01
This report documents the library of thermodynamic data used with the NASA Glenn computer program CEA (Chemical Equilibrium with Applications). This library, containing data for over 2000 solid, liquid, and gaseous chemical species for temperatures ranging from 200 to 20,000 K, is available for use with other computer codes as well. The data are expressed as least-squares coefficients to a seven-term functional form for C((sup o)(sub p)) (T) / R with integration constants for H (sup o) (T) / RT and S(sup o) (T) / R. The NASA Glenn computer program PAC (Properties and Coefficients) was used to calculate thermodynamic functions and to generate the least-squares coefficients. PAC input was taken from a variety of sources. A complete listing of the database is given along with a summary of thermodynamic properties at 0 and 298.15 K.
Insights into Asteroid Thermal Properties from Lunar Eclipse Observations
NASA Astrophysics Data System (ADS)
Hayne, Paul; Lucey, Paul G.; Paige, David A.
2015-08-01
Surface temperatures on airless planetary bodies are controlled primarily by insolation and the thermophysical properties of the subsurface layer probed by the diurnal and seasonal thermal waves. Observations of asteroid thermal emission are used to constrain the physical structure of this surface layer. However, the thermal skin depth probed by this technique depends on rotation period, and the derived thermal inertia is a weighted average over a finite depth, which varies from one asteroid to another. If the properties of the surface layer are depth-dependent, then physically identical bodies with different rotation periods will have different apparent thermal inertia values. The Moon provides an opportunity to investigate this phenomenon, using thermal infrared emission curves on both the diurnal and eclipse timescales.We used multi-spectral thermal infrared observations of the Moon from two instruments: The Maui Space Surveillance System’s Longwave-IR (LWIR) imager, and the Lunar Reconnaissance Orbiter’s Diviner Lunar Radiometer. Diviner’s near-complete characterization of the lunar diurnal temperature cycles are used to constrain the properties of the uppermost √κt ~ 30 cm, where κ is thermal diffusivity and t is the rotation period. Eclipse cooling data from both LWIR and Diviner reveal the properties of the uppermost ~ 1 cm. Here, we focus on results from the October, 2014, and April, 2015 total lunar eclipses.Using a 1-d thermal model with depth-dependent thermal properties, we fit both the diurnal and eclipse brightness temperature data. Results show that the regolith thermal inertia increases exponentially with depth, from ~10 J m-2 K-1 s-1/2 at the surface to ~90 J m-2 K-1 s-1/2 at > 30 cm depth. This range brackets values derived from thermal light curves of many asteroids. Surface thermal inertia values derived from eclipse data are ~25 - 50% lower than previous models based on diurnal temperatures alone, and are similar to the lower end of
Calculation of effective transport properties of partially saturated gas diffusion layers
NASA Astrophysics Data System (ADS)
Bednarek, Tomasz; Tsotridis, Georgios
2017-02-01
A large number of currently available Computational Fluid Dynamics numerical models of Polymer Electrolyte Membrane Fuel Cells (PEMFC) are based on the assumption that porous structures are mainly considered as thin and homogenous layers, hence the mass transport equations in structures such as Gas Diffusion Layers (GDL) are usually modelled according to the Darcy assumptions. Application of homogenous models implies that the effects of porous structures are taken into consideration via the effective transport properties of porosity, tortuosity, permeability (or flow resistance), diffusivity, electric and thermal conductivity. Therefore, reliable values of those effective properties of GDL play a significant role for PEMFC modelling when employing Computational Fluid Dynamics, since these parameters are required as input values for performing the numerical calculations. The objective of the current study is to calculate the effective transport properties of GDL, namely gas permeability, diffusivity and thermal conductivity, as a function of liquid water saturation by using the Lattice-Boltzmann approach. The study proposes a method of uniform water impregnation of the GDL based on the "Fine-Mist" assumption by taking into account the surface tension of water droplets and the actual shape of GDL pores.
NASA Astrophysics Data System (ADS)
Nemec, Patrik; Malcho, Milan; Kaduchová, Katarína
This work deal with evaluation of condenser temperature by experimental measurement, calculation and thermal visualization of cooling device working with a heat pipe technology. The referred device in the article is cooling device capable transfer high heat fluxes from electric elements to the surrounding. One from many things influenced the heat flux amount transferred from electronic elements through the cooling device to the surrounding is condenser construction, its capacity and option of heat removal. The work contain description, working principle and construction of cooling device. Experimental part describe the measuring method and mathematical calculation to condenser temperature evaluation of cooling device depending on the loaded heat of electronic components in range from 250 to 750 W. The mathematical calculation is based on physical phenomena of boiling, condensation and natural convection heat transfer. The results of experimental measurement and mathematical calculation are verified by thermal imagining of device condenser by IR camera.
A computer program to calculate radiation properties of reflector antennas
NASA Technical Reports Server (NTRS)
Agrawal, P. K.
1978-01-01
A computer program to calculate the radiation properties of the reflector antennas is presented. It can be used for paraboloidal, spherical, or ellipsoidal reflector surfaces and is easily modified to handle any surface that can be expressed analytically. The program is general enough to allow any arbitrary location and pointing angle for the feed antenna. The effect of blockage due to the feed horn is also included in the computations. The computer program is based upon the technique of tracing the rays from the feed antenna to the reflector to an aperture plane. The far field radiation properties are then calculated by performing a double integration over the field points in the aperture plane. To facilitate the computation of double intergral, the field points are first aligned along the equispaced straight lines in the aperture plane. The computation time is relatively insensitive to the absolute size of the aperture and even though no limits on the largest reflector size have been determined, the program was used for reflector diameters of 1000 wavelenghts.
NASA Astrophysics Data System (ADS)
Chi, Weiguang
The complex microstructures of thermally sprayed coatings are very sensitive to processing conditions and have a significant influence on the properties. The thermal transport property is a very important design parameter for thermally sprayed coatings. Despite considerable progress in this area, there is continued need to clarify the interrelationships among processing, microstructure and thermal transport properties. This has been enabled through continued advancements in processing science and control, enhancements in microstructural characterization and new methods of property characterization. The purpose of this research is to seek a successive pathway to prior efforts in understanding the effect of microstructural defects on the thermal transport property of thermally sprayed coatings. Relationship between microstructure and thermal conductivity is investigated for three sets of plasma sprayed yttria stabilized zirconia (YSZ) coating systems made using different morphology powders, different particle size distribution and controlled modification of particle states via plasma torch parameters. By integrating the results, maps of the thermal conductivity-porosity relationship have been established. Such maps highlight the role of splat thickness and interfaces in thermal conductivity. Furthermore, a new microstructural parameter termed "effective porosity" is proposed which considers the dominating role of interlamellar pores on through thickness thermal transport in thermally sprayed coatings. This effective porosity is rationalized based on the heat transport mechanism and enables better understanding of microstructure-thermal transport property correlation. An inverse linear model and a percolation model are established which can serve as predictive tools for understanding microstructure-thermal conductivity relationships. In addition, a systematic assessment of thermal conductivity anisotropy has been carried out for YSZ, Al2O 3 and several metallic
THERMAL PROPERTIES OF SECONDARY ORGANIC AEROSOLS
Volume concentrations of steady-state secondary organic aerosol (SOA) were measured in several hydrocarbon/NO_{x} irradiation experiments. These measurements were used to estimate the thermal behavior of the particles that may be formed in the atmosphere. These laborator...
THERMAL PROPERTIES OF SECONDARY ORGANIC AEROSOLS
Volume concentrations of steady-state secondary organic aerosol (SOA) were measured in several hydrocarbon/NO_{x} irradiation experiments. These measurements were used to estimate the thermal behavior of the particles that may be formed in the atmosphere. These laborator...
Thermal conductivity and other properties of cementitious grouts
Allan, M.
1998-08-01
The thermal conductivity and other properties cementitious grouts have been investigated in order to determine suitability of these materials for grouting vertical boreholes used with geothermal heat pumps. The roles of mix variables such as water/cement ratio, sand/cement ratio and superplasticizer dosage were measured. In addition to thermal conductivity, the cementitious grouts were also tested for bleeding, permeability, bond to HDPE pipe, shrinkage, coefficient of thermal expansion, exotherm, durability and environmental impact. This paper summarizes the results for selected grout mixes. Relatively high thermal conductivities were obtained and this leads to reduction in predicted bore length and installation costs. Improvements in shrinkage resistance and bonding were achieved.
THERMAL CONDUCTIVITY AND OTHER PROPERTIES OF CEMENTITIOUS GROUTS
ALLAN,M.
1998-05-01
The thermal conductivity and other properties cementitious grouts have been investigated in order to determine suitability of these materials for grouting vertical boreholes used with geothermal heat pumps. The roles of mix variables such as water/cement ratio, sand/cement ratio and superplasticizer dosage were measured. In addition to thermal conductivity, the cementitious grouts were also tested for bleeding, permeability, bond to HDPE pipe, shrinkage, coefficient of thermal expansion, exotherm, durability and environmental impact. This paper summarizes the results for selected grout mixes. Relatively high thermal conductivities were obtained and this leads to reduction in predicted bore length and installation costs. Improvements in shrinkage resistance and bonding were achieved.
Calculation of atomic structures and radiative properties of fusion plasmas
NASA Astrophysics Data System (ADS)
Jarrah, Walid; Pain, Jean-Christophe; Benredjem, Djamel
2017-03-01
The opacity is an important issue in the knowledge of the radiative properties of Inertial Confinement Fusion (ICF) and astrophysical plasmas. In this work we present the opacity of the mixture C+Si, composing the ablator of some ICF capsules. We have used Cowan's code to calculate the atomic structure of carbon and silicon. We also have developed a collisional-radiative model in order to obtain the opacity of the mixture. Line broadening, line shift and ionization potential depression are taken into account in the opacity profile. Comparisons to other calculations are carried out. NLTE and LTE opacity calculations show discrepancies mainly in the range 1900-2000 eV for the bound-bound contribution to the total opacity and in the range 50-350 eV for the bound-free contribution. We have also accounted for photoexcitation and photoionization processes. The corresponding rates are obtained by modeling the Hohlraum radiation by a Planckian distribution at a radiative temperature of 300 eV.
Use of thermal-inertia properties for material identification
NASA Technical Reports Server (NTRS)
Schieldge, J. P.; Kahle, A. B.; Alley, R. E.; Gillespie, A. R.
1980-01-01
It is noted that a knowledge of the thermal inertia of the earth's surface can be used in geologic mapping as a complement to surface reflectance data as provided by Landsat. Thermal inertia, which is a body property, cannot be determined directly but can be inferred from radiation temperature measurements made at various times in the diurnal heating cycle, combined with a model of the surface heating processes. A model of this type is developed and applied along with temperature measurements made in the field and by satellite to determine thermal properties of surface materials. An example from a test site in western Nevada is used to demonstrate the utility of this technique.
Review of thermal properties of graphite composite materials
NASA Technical Reports Server (NTRS)
Kourtides, D. A.
1987-01-01
Flammability, thermal, and selected mechanical properties of composites fabricated with epoxy and other thermally stable resin matrices are described. Properties which were measured included limiting-oxygen index, smoke evolution, thermal degradation products, total-heat release, heat-release rates, mass loss, flame spread, ignition resistance, thermogravimetric analysis, and selected mechanical properties. The properties of 8 different graphite composite panels fabricated using four different resin matrices and two types of graphite reinforcement are described. The resin matrices included: XU71775/H795, a blend of vinyl polystyryl pyridine and bismaleimide; H795, a bismaleimide; Cycom 6162, a phenolic; and PSP 6022M, a polystyryl pyridine. The graphite fiber used was AS-4 in the form of either tape or fabric. The properties of these composites were compared with epoxy composites. It was determined that the blend of vinyl polystyryl pyridine and bismaleimide (XU71775/H795) with the graphite tape was the optimum design giving the lowest heat release rate.
Review of thermal properties of graphite composite materials
Kourtides, D.A.
1987-12-01
Flammability, thermal, and selected mechanical properties of composites fabricated with epoxy and other thermally stable resin matrices are described. Properties which were measured included limiting-oxygen index, smoke evolution, thermal degradation products, total-heat release, heat-release rates, mass loss, flame spread, ignition resistance, thermogravimetric analysis, and selected mechanical properties. The properties of 8 different graphite composite panels fabricated using four different resin matrices and two types of graphite reinforcement are described. The resin matrices included: XU71775/H795, a blend of vinyl polystyryl pyridine and bismaleimide; H795, a bismaleimide; Cycom 6162, a phenolic; and PSP 6022M, a polystyryl pyridine. The graphite fiber used was AS-4 in the form of either tape or fabric. The properties of these composites were compared with epoxy composites. It was determined that the blend of vinyl polystyryl pyridine and bismaleimide (XU71775/H795) with the graphite tape was the optimum design giving the lowest heat release rate.
Measurement of thermal properties of white radish (R. raphanistrum) using easily constructed probes
Obot, Mfrekemfon Samuel; Li, Changcheng; Fang, Ting; Chen, Jinquan
2017-01-01
Thermal properties are necessary for the design and control of processes and storage facilities of food materials. This study proposes the measurement of thermal properties using easily constructed probes with specific heat capacity calculated, as opposed to the use of Differential Scanning Calorimeter (DSC) or other. These probes were constructed and used to measure thermal properties of white radish in the temperature range of 80–20°C and moisture content of 91–6.1% wb. Results showed thermal properties were within the range of 0.71–0.111 Wm-1 C-1 for thermal conductivity, 1.869×10−7–0.72×10−8 m2s-1 for thermal diffusivity and 4.316–1.977 kJ kg-1C-1for specific heat capacity. These results agree with reports for similar products studied using DSC and commercially available line heat source probes. Empirical models were developed for each property through linear multiple regressions. The data generated would be useful in modeling and control of its processing and equipment design. PMID:28288175
In situ thermally reduced graphene oxide/epoxy composites: thermal and mechanical properties
NASA Astrophysics Data System (ADS)
Olowojoba, Ganiu B.; Eslava, Salvador; Gutierrez, Eduardo S.; Kinloch, Anthony J.; Mattevi, Cecilia; Rocha, Victoria G.; Taylor, Ambrose C.
2016-10-01
Graphene has excellent mechanical, thermal, optical and electrical properties and this has made it a prime target for use as a filler material in the development of multifunctional polymeric composites. However, several challenges need to be overcome to take full advantage of the aforementioned properties of graphene. These include achieving good dispersion and interfacial properties between the graphene filler and the polymeric matrix. In the present work, we report the thermal and mechanical properties of reduced graphene oxide/epoxy composites prepared via a facile, scalable and commercially viable method. Electron micrographs of the composites demonstrate that the reduced graphene oxide (rGO) is well dispersed throughout the composite. Although no improvements in glass transition temperature, tensile strength and thermal stability in air of the composites were observed, good improvements in thermal conductivity (about 36 %), tensile and storage moduli (more than 13 %) were recorded with the addition of 2 wt% of rGO.
NASA Astrophysics Data System (ADS)
Sangeetha, V.; Govindarajan, M.; Kanagathara, N.; Gunasekaran, S.; Rajakumar, P. R.; Anbalagan, G.
2014-06-01
Single crystals of melaminium bis (hydrogen oxalate) (MOX) were grown by slow evaporation method. X-ray powder diffraction analysis indicates that MOX crystallizes in monoclinic system (space group C2/c) and the calculated lattice constants are a = 20.075 ± 0.123 Ǻ, b = 8.477 ± 0.045 Ǻ, c = 6.983 ± 0.015, α = γ 90° and β = 102.6 ± 0.33°. Thermal analysis confirms that MOX is thermally stable up to 250 °C. A detailed interpretation of the FT-IR, FT-Raman and NMR spectra were reported. The equilibrium geometry, bonding features, and harmonic vibrational frequencies have been investigated with the help of PM6, HF and DFT/B3LYP methods. The potential energy curve shows that MOX molecule has two stable structures and the computational results diagnose that Rot I is the most stable conformer. The 1H and 13C nuclear magnetic resonance (NMR) chemical shifts of the molecule were calculated by the Gauge-Invariant Atomic Orbital (GIAO) method. Stability of the molecule, arising from hyperconjugative interactions and charge delocalization, has been analyzed using Natural Bond Orbital (NBO) analysis. The electronic properties, such as HOMO and LUMO energies, were calculated by Time-Dependent DFT (TD-DFT) approach. To estimate chemical reactivity of the molecule, the molecular electrostatic potential (MEP) surface map is calculated for the optimized geometry of the molecule.
NASA Astrophysics Data System (ADS)
Valdes, Raymond
The characterization of thermal barrier coating (TBC) systems is increasingly important because they enable gas turbine engines to operate at high temperatures and efficiency. Phase of photothermal emission analysis (PopTea) has been developed to analyze the thermal behavior of the ceramic top-coat of TBCs, as a nondestructive and noncontact method for measuring thermal diffusivity and thermal conductivity. Most TBC allocations are on actively-cooled high temperature turbine blades, which makes it difficult to precisely model heat transfer in the metallic subsystem. This reduces the ability of rote thermal modeling to reflect the actual physical conditions of the system and can lead to higher uncertainty in measured thermal properties. This dissertation investigates fundamental issues underpinning robust thermal property measurements that are adaptive to non-specific, complex, and evolving system characteristics using the PopTea method. A generic and adaptive subsystem PopTea thermal model was developed to account for complex geometry beyond a well-defined coating and substrate system. Without a priori knowledge of the subsystem characteristics, two different measurement techniques were implemented using the subsystem model. In the first technique, the properties of the subsystem were resolved as part of the PopTea parameter estimation algorithm; and, the second technique independently resolved the subsystem properties using a differential "bare" subsystem. The confidence in thermal properties measured using the generic subsystem model is similar to that from a standard PopTea measurement on a "well-defined" TBC system. Non-systematic bias-error on experimental observations in PopTea measurements due to generic thermal model discrepancies was also mitigated using a regression-based sensitivity analysis. The sensitivity analysis reported measurement uncertainty and was developed into a data reduction method to filter out these "erroneous" observations. It was found
Thermal transport properties of complex oxides from first principles
NASA Astrophysics Data System (ADS)
Bhatti, Aqyan; Jain, Ankit; McGaughey, Alan; Benedek, Nicole
2015-03-01
Thermal transport properties of materials are key parameters in the design of many engineering devices. For this reason, it is highly desirable to be able to control or tailor the thermal properties of materials for specific applications. Complex oxides are attractive in this regard, due to their low and potentially highly tunable thermal conductivity. However, the theoretical description of the thermal transport properties of oxides presents a number of challenges compared to conventional semiconductors. For example, oxides tend to have complex crystal structures and the atoms interact through long-range electrostatic forces. In this talk, we use the example of PbTiO3 to discuss some of the challenges and opportunities associated with thermal transport predictions in complex oxides. For example, many oxides contain very low-lying optical branches, which may provide important acoustic-optical scattering channels. In addition, it is often possible to tune the frequencies of such optical modes with epitaxial strain. We also link the observed negative thermal expansion behavior of PbTiO3 to two zone-boundary modes with large, negative Grüneisen parameters and comment on the consequences of this finding for the thermal transport properties of this material.
Thermal transport properties of metal/MoS{sub 2} interfaces from first principles
Mao, Rui; Kong, Byoung Don; Kim, Ki Wook
2014-07-21
Thermal transport properties at the metal/MoS{sub 2} interfaces are analyzed by using an atomistic phonon transport model based on the Landauer formalism and first-principles calculations. The considered structures include chemisorbed Sc(0001)/MoS{sub 2} and Ru(0001)/MoS{sub 2}, physisorbed Au(111)/MoS{sub 2}, as well as Pd(111)/MoS{sub 2} with intermediate characteristics. Calculated results illustrate a distinctive dependence of thermal transfer on the details of interfacial microstructures. More specifically, the chemisorbed case with a stronger bonding exhibits a generally smaller interfacial thermal resistance than the physisorbed. Comparison between metal/MoS{sub 2} and metal/graphene systems suggests that metal/MoS{sub 2} is significantly more resistive. Further examination of lattice dynamics identifies the presence of multiple distinct atomic planes and bonding patterns at the interface as the key origins of the observed large thermal resistance.
NASA Astrophysics Data System (ADS)
Hamdi, Boualem; Hamdi, Safia
The chemical and physical properties of a Algerian diatomite were given before and after heat treatment and chemical with an aim of a use in the heat insulation of constructions. The preliminary results obtained showed that this material is extremely porous (porosity >70 %), characterized of a low density and a very low thermal conductivity. These promising properties support the use of this local material in the thermal insulation.
Thermal Properties of Polymethyl Methacrylate Composite Containing Copper Nanoparticles.
Yu, Wei; Xie, Huaqing; Xin, Sha; Yin, Junshan; Jiang, Yitong; Wang, Mingzhu
2015-04-01
Thermal functional Materials have wide applications in thermal management fields, and inserting highly thermal conductive materials is effective in enhancing thermal conductivity of matrix. In this paper, copper nanoparticles were selected as the additive to prepare polymethyl methacrylate (PMMA) based nanocomposite with enhanced thermal properties. Uniform copper nanoparticles with pure face-centered lattice were prepared by liquid phase reduction method. Then, they were added into PMMA/N, N-Dimethylmethanamide (DMF) solution according to the different mass fraction for uniform dispersion. After DMF was evaporated, Cu-PMMA nanocomposites were gained. The thermal analysis measurement results showed that the decomposition temperature of nanocomposites decreased gradually with the increasing particle loadings. The thermal conductivity of the Cu-PMMA nanocomposites rose with the increasing contents of copper nanoparticles. With a 20 vol.% addition, the thermal conductivity was up to 1.2 W/m · K, a 380.5% increase compared to the pure PMMA. The results demonstrate that copper nanoparticles have great potential in enhancing thermal transport properties of polymer.
Thermophysical Properties of Lithium Alloys for Thermal Batteries
NASA Astrophysics Data System (ADS)
Swift, Geoffrey A.
2011-10-01
Thermal batteries are electrochemical systems primarily used in defense applications. The long-term storage capability afforded by the electrically inert low-temperature properties of the electrolyte-separator enables the use of this technology for military purposes. The current state-of-the art for thermal batteries relies upon the Li/FeS2 couple for power generation with the anode typically an Li-Si or Li-Al alloy. Thermal modeling of these primary battery systems is crucial to allowing the predictive capability of thermal evolution both in terms of the battery lifetime and thermal profile for the proper design of internal insulation and the surrounding environment. However, thermophysical properties for the anode alloys are not available in the literature. Thermophysical measurements of the alloys used in thermal batteries are essential for thermal modeling and simulation. The laser-flash method was used to determine the specific heat, thermal diffusivity, and thermal conductivity for Li-Si and Li-Al alloys as a function of temperature.
Ab Initio Calculations and Measurements of Thermoelectric Properties of V2O5 Films
NASA Astrophysics Data System (ADS)
Chumakov, Yu.; Xiong, S.-Y.; Santos, J. R.; Ferreira, I.; Termentzidis, K.; Pokropivny, A.; Cortona, P.; Volz, S.
2013-07-01
Density functional theory and the Boltzmann transport equation were used to calculate the thermoelectric transport coefficients for bulk V2O5 and MV2O5 (M = Cr, Ti, Na, Li). The structural relaxation for the given compounds based on the ABINIT code was observed. The temperature dependences of the Seebeck coefficients as well as electrical and thermal electrical conductivities of all relaxed structures displayed anisotropic behavior. Electrooptical measurements of thermoelectric properties were carried out on V2O5 thin films obtained by thermal evaporation with different post-annealing treatments. A Seebeck coefficient of -148 μV/K at T = 300 K was obtained in the in-plane direction for V2O5 thin films with thickness less than 100 nm.
Muraleedharan, Murali Gopal; Sundaram, Dilip; Henry, Asegun; Yang, Vigor
2017-02-07
The presence of artificial correlations associated with Green-Kubo (GK) thermal conductivity calculations is investigated. The thermal conductivity of nano-suspensions is calculated by equilibrium molecular dynamics (EMD) simulations using GK relations. Calculations are first performed for a single alumina (Al2O3) nanoparticle dispersed in a water medium. For a particle size of 1 nm and volume fraction of 9%, results show enhancements as high as 235%, which is much higher than the Maxwell model predictions. When calculations are done with multiple suspended particles, no such anomalous enhancement is observed. This is because the vibrations in alumina crystal can act as low frequency perturbations, which can travel long distances through the surrounding water medium, characterized by higher vibration frequencies. As a result of the periodic boundaries, they re-enter the system resulting in a circular resonance of thermal fluctuations between the alumina particle and its own image, eventually leading to artificial correlations in the heat current autocorrelation function (HCACF), which when integrated yields abnormally high thermal conductivities. Adding more particles presents 'obstacles' with which the fluctuations interact and get dissipated, before they get fed back to the periodic image. A systematic study of the temporal evolution of HCACF indicates that the magnitude and oscillations of artificial correlations decrease substantially with increase in the number of suspended nanoparticles.
NASA Astrophysics Data System (ADS)
Gopal Muraleedharan, Murali; Srinivas Sundaram, Dilip; Henry, Asegun; Yang, Vigor
2017-04-01
The presence of artificial correlations associated with Green–Kubo (GK) thermal conductivity calculations is investigated. The thermal conductivity of nano-suspensions is calculated by equilibrium molecular dynamics (EMD) simulations using GK relations. Calculations are first performed for a single alumina (Al2O3) nanoparticle dispersed in a water medium. For a particle size of 1 nm and volume fraction of 9%, results show enhancements as high as 235%, which is much higher than the Maxwell model predictions. When calculations are done with multiple suspended particles, no such anomalous enhancement is observed. This is because the vibrations in alumina crystal can act as low frequency perturbations, which can travel long distances through the surrounding water medium, characterized by higher vibration frequencies. As a result of the periodic boundaries, they re-enter the system resulting in a circular resonance of thermal fluctuations between the alumina particle and its own image, eventually leading to artificial correlations in the heat current autocorrelation function (HCACF), which when integrated yields abnormally high thermal conductivities. Adding more particles presents ‘obstacles’ with which the fluctuations interact and get dissipated, before they get fed back to the periodic image. A systematic study of the temporal evolution of HCACF indicates that the magnitude and oscillations of artificial correlations decrease substantially with increase in the number of suspended nanoparticles.
Calculation of the Thermal Loading of the Cylinder-Piston Group of the Automobile Engine
NASA Astrophysics Data System (ADS)
Barchenko, F. B.; Bakulin, V. N.
2017-05-01
We propose a mathematical model for calculating thermal loods of parts of the cylinder-piston group of the automobile engine operating under unstable conditions in its complete life cycle. Methods have been described for calculating the boundary conditions to determine the thermal state of the parts of the cylinder-piston group of such an engine with the use of theoretical formulas, empirical and semiempirical relations, and tabulated data. In modeling, we calculated the work of all systems of the engine (pumps, pipelines, heat exchangers) influencing directly or indirectly the thermal state of its cylinder-piston group. The nonstationary thermal state was calculated once in the operating cycle of the engine with the use of the cycle-averaged values of the local heat transfer coefficients and the resulting temperature of the medium. The personal computer counting time for one time step of a transport diesel engine of typical design with a number of units of the order of 500 was 5 s.
A biharmonic relaxation method for calculating thermal stress in cooled irregular cylinders
NASA Technical Reports Server (NTRS)
Holms, Arthur G
1952-01-01
A numerical method was developed for calculating thermal stresses in irregular cylinders cooled by one or more internal passages. The use of relaxation methods and elementary methods of finite differences was found to give approximations to the correct values when compared with previously known solutions for concentric circular cylinders possessing symmetrical and asymmetrical temperature distributions.
Thermal properties of composite materials: a complex systems approximation
NASA Astrophysics Data System (ADS)
Carrillo, J. L.; Bonilla, Beatriz; Reyes, J. J.; Dossetti, Victor
We propose an effective media approximation to describe the thermal diffusivity of composite samples made of polyester resin and magnetite inclusions. By means of photoacoustic spectroscopy, the thermal diffusivity of the samples were experimentally measured. The volume fraction of the inclusions was systematically varied in order to study the changes in the effective thermal diffusivity of the composites. For some samples, a static magnetic field was applied during the polymerization process, resulting in anisotropic inclusion distributions. Our results show a significant difference in the thermal properties of the anisotropic samples, compared to the isotropic randomly distributed. We correlate some measures of the complexity of the inclusion structure with the observed thermal response through a multifractal analysis. In this way, we are able to describe, and at some extent predict, the behavior of the thermal diffusivity in terms of the lacunarity and other measures of the complexity of these samples Partial Financial Support by CONACyT México and VIEP-BUAP.
NASA Astrophysics Data System (ADS)
Kheyri, A.; Nourbakhsh, Z.
2016-09-01
The thermal properties of pure graphene and graphene-impurity (impurity = Fe, Co, Si, and Ge) sheets have been investigated at various pressures (0-7 GPa) and temperatures (0-900 K). Some basic thermodynamic quantities such as bulk modulus, coefficient of volume thermal expansion, heat capacities at constant pressure and constant volume of these sheets as a function of temperature and pressure are discussed. Furthermore, the effect of the impurity density and tensile strain on the thermodynamic properties of these sheets are investigated. All of these calculations are performed based on the density functional theory and full quasi harmonic approximation.
Thermal transmission at Si/Ge interface: ab initio lattice dynamics calculation
NASA Astrophysics Data System (ADS)
Alkurdi, A.; Merabia, S.
2017-01-01
We perform lattice dynamics calculations (LD) on silicon/germanium interfaces using ab initio interatomic force constants to predict the interfacial phonon transmission as a function of both phonon frequency and the transmission angle. We carry out a spectral and angular analysis to quantify the contribution of each phonon mode in a given scattering direction. The effect of the interaction range was studied at this interface by taking account of more or less atom layers across the interface. Moreover, we were able to predict the thermal boundary conductance (TBC) as a function of the transmission angle and temperature as well. Our results show that, the thermal energy transmission is highly anisotropic while thermal energy reflection is almost isotropic. In addition, we found that it seems there is a global critical angle of transmission beyond which almost no thermal energy is transmitted. This can be used to device high pass phonon filter via changing the orientation of the interface.
Pressure dependence of thermal transport properties
Hofmeister, Anne M.
2007-01-01
Pressure (P) derivatives of thermal conductivity (k) and thermal diffusivity (D) are important to geophysics but are difficult to measure accurately because minerals, being hard and partially transparent, likely incur systematic errors through thermal losses at interfaces and spurious radiative transfer. To evaluate accuracy, repeat experiments for olivine [(Mg0.9Fe0.1)2SiO4], quartz (SiO2), and NaCl are examined in detail: these and other data on electrical insulators are compared with theory. At ambient conditions, D is underestimated in proportion to the number of contacts. As temperature (T) increases, spurious radiative transfer more than offsets contact loss. Compression of pore space and contact losses affect pressure derivatives, but these seem independent of T. Accurate (±2%) values of D(T) at 1 atm are obtained with the contact-free, laser-flash method. Other optical techniques do not pinpoint D but provide useful pressure derivatives. Published data on ∂(lnk)/∂P at ambient conditions agree roughly with all available models, the simplest of which predicts ∂(lnk)/∂P ∼ ∂(lnKT)/∂P, where KT is the bulk modulus. However, derivatives verified by multiple measurements are reproduced accurately only by the damped harmonic oscillator model. An improved database is needed to refine this model and to confidently extrapolate these difficult measurements to geophysically relevant conditions. PMID:17299046
NASA Astrophysics Data System (ADS)
Zhang, Ping; Wang, Bao-Tian; Zhao, Xian-Geng
2010-10-01
Plutonium dioxide is of high technological importance in nuclear fuel cycle and is particularly crucial in long-term storage of Pu-based radioactive waste. Using first-principles density-functional theory, in this paper we systematically study the structural, electronic, mechanical, thermodynamic properties, and pressure-induced structural transition of PuO2 . To properly describe the strong correlation in Pu5f electrons, the local-density approximation (LDA)+U and the generalized gradient approximation+U theoretical formalisms have been employed. We optimize U parameter in calculating the total energy, lattice parameters, and bulk modulus at nonmagnetic, ferromagnetic, and antiferromagnetic configurations for both ground-state fluorite structure and high-pressure cotunnite structure. Best agreement with experiments is obtained by tuning the effective Hubbard parameter U at around 4 eV within LDA+U approach. After carefully testing the validity of the ground-state calculation, we further investigate the bonding nature, elastic constants, various moduli, Debye temperature, hardness, ideal tensile strength, and phonon dispersion for fluorite PuO2 . Some thermodynamic properties, e.g., Gibbs free energy, volume thermal expansion, and specific heat are also calculated. As for cotunnite phase, besides elastic constants, various moduli, and Debye temperature at 0 GPa, we have further presented our calculated electronic, structural, and magnetic properties for PuO2 under pressure up to 280 GPa. A metallic transition at around 133 GPa and an isostructural transition in pressure range of 75-133 GPa are predicted. Additionally, as an illustration on the valency trend and subsequent effect on the mechanical properties, the calculated results for other actinide metal dioxides ( ThO2 , UO2 , and NpO2 ) are also presented.
Thermal properties of {sup 4}He surfaces and interfaces
Clements, B.E.; Krotscheck, E. |; Tymczak, C.J.
1997-05-01
A first-principle quantum statistical mechanical theory is used to study the properties of thick liquid {sup 4}He films absorbed to the weakly binding substrates: Li, Na, and Cs. Values for the liquid-gas and solid-liquid surface energies are determined. By fitting, at long wavelengths, the film`s lowest energy mode with the standard expression for the ripplon energy, which depends on the liquid-gas surface energy, the authors obtain excellent agreement with the liquid-vacuum surface energy from recent experiments and also the one previously extracted from quantum liquid droplet calculations. The full spectrum of excitations for wave vectors less than 0.50 {Angstrom}{sup {minus}1} is calculated using a dynamical correlated basis function theory developed in earlier work, which includes multi-phonon scattering processes. Particle currents and transition densities are used to elucidate the nature of the excitations. At a coverage of 0.40 {Angstrom}{sup {minus}2}, the lowest mode shows no significant substrate dependence, and is recognized as being a ripplon propagating in the liquid film at the liquid-gas surface. A new effect is observed for the Cs substrate; the second lowest mode is qualitatively different than found on the other substrates and is identified as interfacial ripplon. In the other substrates the second mode is a volume mode altered somewhat by the high density inner liquid layers. The linewidths of these modes are also calculated. The dynamic excitations provide the input for the thermodynamic theory and the effects on the free energy, heat capacity, and thermal surface broadening of these films are studied as function of the nature of the excitations, the number of modes, and variations in the substrate potentials.
Effect of Moisture Content on Thermal Properties of Porous Building Materials
NASA Astrophysics Data System (ADS)
Kočí, Václav; Vejmelková, Eva; Čáchová, Monika; Koňáková, Dana; Keppert, Martin; Maděra, Jiří; Černý, Robert
2017-02-01
The thermal conductivity and specific heat capacity of characteristic types of porous building materials are determined in the whole range of moisture content from dry to fully water-saturated state. A transient pulse technique is used in the experiments, in order to avoid the influence of moisture transport on measured data. The investigated specimens include cement composites, ceramics, plasters, and thermal insulation boards. The effect of moisture-induced changes in thermal conductivity and specific heat capacity on the energy performance of selected building envelopes containing the studied materials is then analyzed using computational modeling of coupled heat and moisture transport. The results show an increased moisture content as a substantial negative factor affecting both thermal properties of materials and energy balance of envelopes, which underlines the necessity to use moisture-dependent thermal parameters of building materials in energy-related calculations.
Calculation of the radiative properties of photosynthetic microorganisms
NASA Astrophysics Data System (ADS)
Dauchet, Jérémi; Blanco, Stéphane; Cornet, Jean-François; Fournier, Richard
2015-08-01
A generic methodological chain for the predictive calculation of the light-scattering and absorption properties of photosynthetic microorganisms within the visible spectrum is presented here. This methodology has been developed in order to provide the radiative properties needed for the analysis of radiative transfer within photobioreactor processes, with a view to enable their optimization for large-scale sustainable production of chemicals for energy and chemistry. It gathers an electromagnetic model of light-particle interaction along with detailed and validated protocols for the determination of input parameters: morphological and structural characteristics of the studied microorganisms as well as their photosynthetic-pigment content. The microorganisms are described as homogeneous equivalent-particles whose shape and size distribution is characterized by image analysis. The imaginary part of their refractive index is obtained thanks to a new and quite extended database of the in vivo absorption spectra of photosynthetic pigments (that is made available to the reader). The real part of the refractive index is then calculated by using the singly subtractive Kramers-Krönig approximation, for which the anchor point is determined with the Bruggeman mixing rule, based on the volume fraction of the microorganism internal-structures and their refractive indices (extracted from a database). Afterwards, the radiative properties are estimated using the Schiff approximation for spheroidal or cylindrical particles, as a first step toward the description of the complexity and diversity of the shapes encountered within the microbial world. Finally, these predictive results are confronted to experimental normal-hemispherical transmittance spectra for validation. This entire procedure is implemented for Rhodospirillum rubrum, Arthrospira platensis and Chlamydomonas reinhardtii, each representative of the main three kinds of photosynthetic microorganisms, i.e. respectively
Micromechanics of intraply hybrid composites: Elastic and thermal properties
NASA Technical Reports Server (NTRS)
Chamis, C. C.; Sinclair, J. H.
1979-01-01
Composite micromechanics are used to derive equations for predicting the elastic and thermal properties of unidirectional intraply hybrid composites. The results predicted using these equations are compared with those predicted using approximate equations based on the rule of mixtures, linear laminate theory, finite element analysis and limited experimental data. The comparisons for three different intraply hybrids indicate that all four methods predict approximately the same elastic properties and are in good agreement with measured data. The micromechanics equations and linear laminate theory predict about the same values for thermal expansion coefficients. The micromechanics equations predict through-the-thickness properties which are in good agreement with the finite element results.
Determination of thermal properties of composting bulking materials.
Ahn, H K; Sauer, T J; Richard, T L; Glanville, T D
2009-09-01
Thermal properties of compost bulking materials affect temperature and biodegradation during the composting process. Well determined thermal properties of compost feedstocks will therefore contribute to practical thermodynamic approaches. Thermal conductivity, thermal diffusivity, and volumetric heat capacity of 12 compost bulking materials were determined in this study. Thermal properties were determined at varying bulk densities (1, 1.3, 1.7, 2.5, and 5 times uncompacted bulk density), particle sizes (ground and bulk), and water contents (0, 20, 50, 80% of water holding capacity and saturated condition). For the water content at 80% of water holding capacity, saw dust, soil compost blend, beef manure, and turkey litter showed the highest thermal conductivity (K) and volumetric heat capacity (C) (K: 0.12-0.81 W/m degrees C and C: 1.36-4.08 MJ/m(3) degrees C). Silage showed medium values at the same water content (K: 0.09-0.47 W/m degrees C and C: 0.93-3.09 MJ/m(3) degrees C). Wheat straw, oat straw, soybean straw, cornstalks, alfalfa hay, and wood shavings produced the lowest K and C values (K: 0.03-0.30 W/m degrees C and C: 0.26-3.45 MJ/m(3) degrees C). Thermal conductivity and volumetric heat capacity showed a linear relationship with moisture content and bulk density, while thermal diffusivity showed a nonlinear relationship. Since the water, air, and solid materials have their own specific thermal property values, thermal properties of compost bulking materials vary with the rate of those three components by changing water content, bulk density, and particle size. The degree of saturation was used to represent the interaction between volumes of water, air, and solids under the various combinations of moisture content, bulk density, and particle size. The first order regression models developed in this paper represent the relationship between degree of saturation and volumetric heat capacity (r=0.95-0.99) and thermal conductivity (r=0.84-0.99) well. Improved
OligoCalc: an online oligonucleotide properties calculator
Kibbe, Warren A.
2007-01-01
We developed OligoCalc as a web-accessible, client-based computational engine for reporting DNA and RNA single-stranded and double-stranded properties, including molecular weight, solution concentration, melting temperature, estimated absorbance coefficients, inter-molecular self-complementarity estimation and intra-molecular hairpin loop formation. OligoCalc has a familiar ‘calculator’ look and feel, making it readily understandable and usable. OligoCalc incorporates three common methods for calculating oligonucleotide-melting temperatures, including a nearest-neighbor thermodynamic model for melting temperature. Since it first came online in 1997, there have been more than 900 000 accesses of OligoCalc from nearly 200 000 distinct hosts, excluding search engines. OligoCalc is available at http://basic.northwestern.edu/biotools/OligoCalc.html, with links to the full source code, usage patterns and statistics at that link as well. PMID:17452344
Anisotropic thermal property of magnetically oriented carbon nanotube polymer composites
NASA Astrophysics Data System (ADS)
Li, Bin; Dong, Shuai; Wang, Caiping; Wang, Xiaojie; Fang, Jun
2016-04-01
This paper proposes a method for preparing multi-walled carbon nanotubea/polydimethylsiloxane (MWCNTs/PDMS) composites with enhanced thermal properties by using a high magnetic field (up to 10T). The MWCNT are oriented magnetically inside a silicone by in-situ polymerization method. The anisotropic structure would be expected to produce directional thermal conductivity. This study will provide a new approach to the development of anisotropic thermal-conductive polymer composites. Systematic studies with the preparation of silicone/graphene composites corresponding to their thermal and mechanical properties are carried out under various conditions: intensity of magnetic field, time, temperature, fillings. The effect of MWCNT/graphene content and preparation procedures on thermal conductivity of composites is investigated. Dynamic mechanical analysis (DMA) is used to reveal the mechanical properties of the composites in terms of the filling contents and magnetic field strength. The scanning electron microscope (SEM) is used to observe the micro-structure of the MWCNT composites. The alignment of MWCNTs in PDMS matrix is also studied by Raman spectroscopy. The thermal conductivity measurements show that the magnetically aligned CNT-composites feature high anisotropy in thermal conductivity.
Thermoelectric properties of rocksalt ZnO from first-principles calculations
Alvarado, Andrew; Attapattu, Jeevake; Zhang, Yi; ...
2015-10-22
Zinc oxide (ZnO) undergoes a pressure-induced structural transition from its normal ambient-pressure wurtzite (WZ) phase to a rocksalt (RS) phase around 10 GPa. A recent experiment shows that the high-pressure RS ZnO phase can be recovered and stabilized at ambient conditions, which raises exciting prospects of expanding the range of properties of ZnO. For a fundamental understanding of the RS ZnO phase, we have performed first-principles calculations to determine its electronic, phonon, and thermodynamic properties at high (20 GPa) and ambient (0 GPa) pressure. Furthermore, we have calculated its electrical and thermal transport properties, which allow an evaluation of itsmore » thermoelectric figure of merit ZT at different temperature and doping levels. Our calculations show that the ambient-pressure RS ZnO phase can reach ZT values of 0.25 to 0.3 under both n-type and p-type doping in a large temperature range of 400 K to 800 K, which is considerably lower than the temperature range of 1400 K to 1600 K where WZ ZnO reaches similar ZT values. Lastly, these results establish RS ZnO as a promising material for thermoelectric devices designed to operate at temperatures desirable for many heat recovery applications.« less
Thermoelectric properties of rocksalt ZnO from first-principles calculations
Alvarado, Andrew; Attapattu, Jeevake; Zhang, Yi; Chen, Changfeng
2015-10-28
Zinc oxide (ZnO) undergoes a pressure-induced structural transition from its normal ambient-pressure wurtzite (WZ) phase to a rocksalt (RS) phase around 10 GPa. A recent experiment shows that the high-pressure RS ZnO phase can be recovered and stabilized at ambient conditions, which raises exciting prospects of expanding the range of properties of ZnO. For a fundamental understanding of the RS ZnO phase, we have performed first-principles calculations to determine its electronic, phonon, and thermodynamic properties at high (20 GPa) and ambient (0 GPa) pressure. Furthermore, we have calculated its electrical and thermal transport properties, which allow an evaluation of its thermoelectric figure of merit ZT at different temperature and doping levels. Our calculations show that the ambient-pressure RS ZnO phase can reach ZT values of 0.25 to 0.3 under both n-type and p-type doping in a large temperature range of 400 K to 800 K, which is considerably lower than the temperature range of 1400 K to 1600 K where WZ ZnO reaches similar ZT values. These results establish RS ZnO as a promising material for thermoelectric devices designed to operate at temperatures desirable for many heat recovery applications.
Thermoelectric properties of rocksalt ZnO from first-principles calculations
Alvarado, Andrew; Attapattu, Jeevake; Zhang, Yi; Chen, Changfeng
2015-10-22
Zinc oxide (ZnO) undergoes a pressure-induced structural transition from its normal ambient-pressure wurtzite (WZ) phase to a rocksalt (RS) phase around 10 GPa. A recent experiment shows that the high-pressure RS ZnO phase can be recovered and stabilized at ambient conditions, which raises exciting prospects of expanding the range of properties of ZnO. For a fundamental understanding of the RS ZnO phase, we have performed first-principles calculations to determine its electronic, phonon, and thermodynamic properties at high (20 GPa) and ambient (0 GPa) pressure. Furthermore, we have calculated its electrical and thermal transport properties, which allow an evaluation of its thermoelectric figure of merit ZT at different temperature and doping levels. Our calculations show that the ambient-pressure RS ZnO phase can reach ZT values of 0.25 to 0.3 under both n-type and p-type doping in a large temperature range of 400 K to 800 K, which is considerably lower than the temperature range of 1400 K to 1600 K where WZ ZnO reaches similar ZT values. Lastly, these results establish RS ZnO as a promising material for thermoelectric devices designed to operate at temperatures desirable for many heat recovery applications.
Crystallite Size Effect on Thermal Conductive Properties of Nonwoven Nanocellulose Sheets.
Uetani, Kojiro; Okada, Takumi; Oyama, Hideko T
2015-07-13
The thermal conductive properties, including the thermal diffusivity and resultant thermal conductivity, of nonwoven nanocellulose sheets were investigated by separately measuring the thermal diffusivity of the sheets in the in-plane and thickness directions with a periodic heating method. The cross-sectional area (or width) of the cellulose crystallites was the main determinant of the thermal conductive properties. Thus, the results strongly indicate that there is a crystallite size effect on phonon conduction within the nanocellulose sheets. The results also indicated that there is a large interfacial thermal resistance between the nanocellulose surfaces. The phonon propagation velocity (i.e., the sound velocity) within the nanocellulose sheets was estimated to be ∼800 m/s based on the relationship between the thermal diffusivities and crystallite widths. The resulting in-plane thermal conductivity of the tunicate nanocellulose sheet was calculated to be ∼2.5 W/mK, markedly higher than other plastic films available for flexible electronic devices.
Effect of Silver Nanoparticles on the Thermal Properties of Sodium Acetate Trihydrate
NASA Astrophysics Data System (ADS)
Garay-Ramírez, B.; Cruz-Orea, A.; San Martín-Martínez, E.
2015-06-01
Sodium acetate trihydrate (SAT) is used as a phase change material (PCM) because of its high latent heat of fusion. Mixtures were prepared with SAT, a blend of the polymer sodium carboxymethil cellulose (CMC) and silica gel, silver nanoparticles (AgNPs), and anhydrous sodium sulfate to form a composite-PCM (c-PCM) based on SAT; the relative proportions of CMC/silica gel in the blend and AgNP content were varied according to a central composite experimental design. The thermal properties were determined for raw SAT, CMC, , and c-PCM samples. The thermal effusivity of samples was evaluated by the inverse photopyroelectric technique. The thermal diffusivity was obtained for samples by the open photoacoustic cell technique. The thermal conductivity was calculated from the obtained and values. To assess the thermal performance of the c-PCM compared to raw SAT, samples were studied through differential scanning calorimetry which served to determine the latent heat recovery ( LHR). Properties , and LHR were analyzed by response surface methodology and compared. The SAT-based c-PCM was found to be more thermally conductive than raw SAT. The best LHR with good thermal diffusivity and thermal conductivity was identified in the region of the central composite experimental design with medium-low AgNPs and higher proportions of CMC in the polymer blend.
Shao, Cheng; Bao, Hua
2016-01-01
The successful exfoliation of atomically-thin bismuth telluride (Bi2Te3) quintuple layer (QL) attracts tremendous research interest in this strongly anharmonic quasi-two-dimensional material. The thermal transport properties of this material are not well understood, especially the mode-wise properties and when it is coupled with a substrate. In this work, we have performed molecular dynamics simulations and normal mode analysis to study the mode-resolved thermal transport in freestanding and supported Bi2Te3 QL. The detailed mode-wise phonon properties are calculated and the accumulated thermal conductivities with respect to phonon mean free path (MFP) are constructed. It is shown that 60% of the thermal transport is contributed by phonons with MFP longer than 20 nm. Coupling with a-SiO2 substrate leads to about 60% reduction of thermal conductivity. Through varying the interfacial coupling strength and the atomic mass of substrate, we also find that phonon in Bi2Te3 QL is more strongly scattered by interfacial potential and its transport process is less affected by the dynamics of substrate. Our study provides an in-depth understanding of heat transport in Bi2Te3 QL and is helpful in further tailoring its thermal property through nanostructuring. PMID:27263656
Measurement of Thermal Properties of Saltstone
Steimke, J.L.; Fowley, M.D.
1998-05-01
Radioactive liquid effluent from the In Tank Precipitation Process is mixed with Portland cement, flyash and furnace alag to form Saltstone. The Saltstone is poured into vaults at Z Area for long term disposal. A transient heat transfer model of the Saltstone pouring process was previously written to determine whether the Saltstone temperature would exceed the Technical Specification Limit of 95 degrees C. The present work was performed to provide Saltstone density, heat capacity, heat of hydration and thermal conductivity for inclusion in the model.
First principles study on structural, lattice dynamical and thermal properties of BaCeO3
NASA Astrophysics Data System (ADS)
Zhang, Qingping; Ding, Jinwen; He, Min
2017-09-01
BaCeO3 exhibits impressive application potentials on solid oxide fuel cell electrolyte, hydrogen separation membrane and photocatalyst, owing to its unique ionic and electronic properties. In this article, the electronic structures, phonon spectra and thermal properties of BaCeO3 in orthorhombic, rhombohedral and cubic phases are investigated based on density functional theory. Comparisons with reported experimental results are also presented. The calculation shows that orthorhombic structure is both energetically and dynamically stable under ground state, which is supported by the experiment. Moreover, charge transfer between cations and anions accompanied with phase transition is observed, which is responsible for the softened phonon modes in rhombohedral and cubic phases. Besides, thermal properties are discussed. Oxygen atoms contribute most to the specific heat. The calculated entropy and specific heat at constant pressure fit well with the experimental ones within the measured temperature range.
Consistent neutron-physical and thermal-physical calculations of fuel rods of VVER type reactors
NASA Astrophysics Data System (ADS)
Tikhomirov, Georgy; Saldikov, Ivan; Ternovykh, Mikhail; Gerasimov, Alexander
2017-09-01
For modeling the isotopic composition of fuel, and maximum temperatures at different moments of time, one can use different algorithms and codes. In connection with the development of new types of fuel assemblies and progress in computer technology, the task makes important to increase accuracy in modeling of the above characteristics of fuel assemblies during the operation. Calculations of neutronphysical characteristics of fuel rods are mainly based on models using averaged temperature, thermal conductivity factors, and heat power density. In this paper, complex approach is presented, based on modern algorithms, methods and codes to solve separate tasks of thermal conductivity, neutron transport, and nuclide transformation kinetics. It allows to perform neutron-physical and thermal-physical calculation of the reactor with detailed temperature distribution, with account of temperature-depending thermal conductivity and other characteristics. It was applied to studies of fuel cell of the VVER-1000 reactor. When developing new algorithms and programs, which should improve the accuracy of modeling the isotopic composition and maximum temperature in the fuel rod, it is necessary to have a set of test tasks for verification. The proposed approach can be used for development of such verification base for testing calculation of fuel rods of VVER type reactors
Thermal response properties of protective clothing fabrics
Baitinger, W.F.
1995-12-31
In the industrial workplace, it becomes increasingly incumbent upon employers to require employees to use suitable protective equipment and to wear protective apparel. When workers may be subjected to accidental radiant, flame, or electric arc heat sources, work clothing should be used that does not become involved in burning. It is axiomatic that work clothing should not become a primary fuel source, adding to the level of heat exposure, since clothing is usually in intimate contact with the skin. Further, clothing should provide sufficient insulation to protect the skin from severe burn injury. If the worker receives such protection from clothing, action then may be taken to escape the confronted thermal hazard. Published laboratory test methods are used to measure flame resistance and thermal responses of flame resistant fabrics in protective clothing. The purpose of this article is to review these test methods, to discuss certain limitations in application, and to suggest how flame resistant cotton fabrics may be used to enhance worker safety.
Thermal properties of alkali-activated aluminosilicates with CNT admixture
NASA Astrophysics Data System (ADS)
Zmeskal, Oldrich; Trhlikova, Lucie; Fiala, Lukas; Florian, Pavel; Cerny, Robert
2017-07-01
Material properties of electrically conductive cement-based materials with increased attention paid on electric and thermal properties were often studied in the last years. Both electric and thermal properties play an important role thanks to their possible utilization in various practical applications (e.g. snow-melting systems or building structures monitoring systems without the need of an external monitoring system). The DC/AC characteristics depend significantly on the electrical resistivity and the electrical capacity of bulk materials. With respect to the DC/AC characteristics of cement-based materials, such materials can be basically classified as electric insulators. In order to enhance them, various conductive admixtures such as those based on different forms of carbon, can be used. Typical representatives of carbon-based admixtures are carbon nanotubes (CNT), carbon fibers (CF), graphite powder (GP) and carbon black (CB). With an adequate amount of such admixtures, electric properties significantly change and new materials with higher added value can be prepared. However, other types of materials can be enhanced in the same way. Alkali-activated aluminosilicates (AAA) based on blast furnace slag are materials with high compressive strength comparable with cement-based materials. Moreover, the price of slag is lower than of Portland cement. Therefore, this paper deals with the study of thermal properties of this promising material with different concentrations of CNT. Within the paper a simple method of basic thermal parameters determination based on the thermal transient response to a heat power step is presented.
NASA Astrophysics Data System (ADS)
Kaplun, A. B.; Meshalkin, A. B.
2013-08-01
Using methods and approaches developed by the authors, a new low-parametric state equation for describing the thermal properties of normal substances is obtained that allows us to describe the thermal properties of gases, liquids, and fluids over a range of densities from the ideal gas state to the triple point, except for a critical region, with a high degree of accuracy close to that of an experiment. The caloric properties and speed of sound are calculated for argon, nitrogen, and carbon dioxide without using any caloric data except for the enthalpy of an ideal gas. It is established that the calculated values of enthalpy, heat capacity, the speed of speed of sound, etc., are in good agreement with the experimental (reliably tabulated) data.
NASA Technical Reports Server (NTRS)
Harloff, G. J.
1986-01-01
Real thermodynamic and transport properties of hydrogen, steam, the SSME mixture, and air are developed. The SSME mixture properties are needed for the analysis of the space shuttle main engine fuel turbine. The mixture conditions for the gases, except air, are presented graphically over a temperature range from 800 to 1200 K, and a pressure range from 1 to 500 atm. Air properties are given over a temperature range of 320 to 500 K, which are within the bounds of the thermodynamics programs used, in order to provide mixture data which is more easily checked (than H2/H2O). The real gas property variation of the SSME mixture is quantified. Polynomial expressions, needed for future computer analysis, for viscosity, Prandtl number, and thermal conductivity are given for the H2/H2O SSME fuel turbine mixture at a pressure of 305 atm over a range of temperatures from 950 to 1140 K. These conditions are representative of the SSME turbine operation. Performance calculations are presented for the space shuttle main engine (SSME) fuel turbine. The calculations use the air equivalent concept. Progress towards obtaining the capability to evaluate the performance of the SSME fuel turbine, with the H2/H2O mixture, is described.
Atomic, Crystal, Elastic, Thermal, Nuclear, and Other Properties of Beryllium
Goldberg, A
2006-02-01
This report is part of a series of documents that provide a background to those involved in the construction of beryllium components and their applications. This report is divided into five sub-sections: Atomic/Crystal Structure, Elastic Properties, Thermal Properties, Nuclear Properties, and Miscellaneous Properties. In searching through different sources for the various properties to be included in this report, inconsistencies were at times observed between these sources. In such cases, the values reported by the Handbook of Chemistry and Physics was usually used. In equations, except where indicated otherwise, temperature (T) is in degrees Kelvin.
Thermal calculation for a furnace with three-tiered near-wall burners
NASA Astrophysics Data System (ADS)
Vafin, D. B.; Sadykov, A. V.
2016-03-01
The paper considers using a differential method for thermal calculation of a furnace with finding the thermal and aerodynamic parameters within the radiation chamber of a tube furnace. The furnace is equipped with acoustictype burners allocated in three tiers on the lateral walls. The method implies joint numerical solution of 2D radiation transfer equations using the S 2-approximation of the discrete ordinate method, of energy equations, flow equations, k-ɛ turbulence model, and single-stage modeling of gas fuel combustion. Typical results of simulation are presented.
Brandenburg, Jan Gerit; Potticary, Jason; Sparkes, Hazel A; Price, Sarah L; Hall, Simon R
2017-09-07
We report systematic temperature-dependent X-ray measurements on the most stable carbamazepine polymorph. This active pharmaceutical ingredient is used to demonstrate how the thermal expansion can probe certain intermolecular interactions resulting in anisotropic expansion behavior. We show that most structural features can be captured by electronic structure calculations at the quasi-harmonic approximation (QHA) provided a dispersion-corrected density functional based method is employed. The impact of thermal expansion on the phonon modes and hence free energy contributions is large enough to impact the relative stability of different polymorphs.
High pressure elasticity and thermal properties of depleted uranium
Jacobsen, M. K. Velisavljevic, N.
2016-04-28
Studies of the phase diagram of uranium have revealed a wealth of high pressure and temperature phases. Under ambient conditions the crystal structure is well defined up to 100 gigapascals (GPa), but very little information on thermal conduction or elasticity is available over this same range. This work has applied ultrasonic interferometry to determine the elasticity, mechanical, and thermal properties of depleted uranium to 4.5 GPa. Results show general strengthening with applied load, including an overall increase in acoustic thermal conductivity. Further implications are discussed within. This work presents the first high pressure studies of the elasticity and thermal properties of depleted uranium metal and the first real-world application of a previously developed containment system for making such measurements.
High pressure elasticity and thermal properties of depleted uranium
NASA Astrophysics Data System (ADS)
Jacobsen, M. K.; Velisavljevic, N.
2016-04-01
Studies of the phase diagram of uranium have revealed a wealth of high pressure and temperature phases. Under ambient conditions the crystal structure is well defined up to 100 gigapascals (GPa), but very little information on thermal conduction or elasticity is available over this same range. This work has applied ultrasonic interferometry to determine the elasticity, mechanical, and thermal properties of depleted uranium to 4.5 GPa. Results show general strengthening with applied load, including an overall increase in acoustic thermal conductivity. Further implications are discussed within. This work presents the first high pressure studies of the elasticity and thermal properties of depleted uranium metal and the first real-world application of a previously developed containment system for making such measurements.
Thermal properties of dielectric solids below 4 K. I - Polycarbonate
NASA Technical Reports Server (NTRS)
Cieloszyk, G. S.; Cruz, M. T.; Salinger, G. L.
1973-01-01
Polymers and other dielectric materials are frequently used for many purposes in the construction of cryogenic apparatus. Yet very few values of the thermal properties of these materials below 4 K have been reported. It is, however, known that one can not use the Debye theory to extrapolate to lower temperatures the measurements of the specific heat capacity above 1 K. The thermal conductivity also follows no theoretically predictable temperature dependence. As a by-product of our studies of the thermal properties of amorphous and partly crystalline materials below 4 K, we wish to report values for the thermal conductivity, specific heat capacity, and velocity of sound below 4 K in materials useful for the construction of cryogenic apparatus. In this article we will describe our measurement techniques and report values for polycarbonate (Lexan). In subsequent notes we will give values for other materials of interest.
Negative thermal expansion properties in tetragonal NbPO5 from the first principles studies
NASA Astrophysics Data System (ADS)
Li, Tao; Fu, Xiaonan; Chang, Dahu; Sun, Qiang; Wang, Fei
2017-03-01
By using the first-principles calculations based on density functional theory combined with quasi-harmonic approximation, we have studied the geometric structural, thermal properties, and the negative thermal expansion (NTE) properties of tetrahedral NbPO5. The variations of cell parameter and cell volume of tetrahedral NbPO5 with temperature show that it displays NTE behavior in the range of 473-800 K along a-axis and the corresponding average coefficient of thermal expansion (CTE) is approximately -0.766 ×10-6 K-1, while the c cell parameter and the cell volume display positive thermal expansion behaviors. These results are in consistent well with the experiment observations. Further vibrational modes analysis, together with Grüneisen parameters calculations, revealed that the transverse vibration of O corner atoms accompanying the rocking motions of corner-shared NbO6 octahedron and PO4 tetrahedron dominate the negative thermal properties of tetrahedral NbPO5. Our findings will provide an understanding for the underlying mechanisms of the NTE in oxides materials.
NASA Astrophysics Data System (ADS)
Azam, Sikander; Khan, Saleem Ayaz; Goumri-Said, Souraya; Kanoun, Mohammed Benali
2017-01-01
We report a theoretical investigation of electronic structures, optical and thermoelectric properties of two ternary-layered chalcogenides, MnBi4S7 and FeBi4S7 , by combining the first principles density functional calculations and semi-local Boltzmann transport theory. The calculated electronic band structure have demonstrated that both compounds exhibit indirect band gaps. The optical transitions are explored via the dielectric function (real and imaginary parts) along with other related optical constants including refractive index, reflectivity, and energy loss spectrum. These chalcogenides have exhibited interesting thermoelectric properties such as Seebeck's coefficient, electrical and thermal conductivity, and power factor as function of temperatures.
Thermal properties of continuously spun carbon nanotube fibres
NASA Astrophysics Data System (ADS)
Koziol, Krzysztof K.; Janas, Dawid; Brown, Elisabetta; Hao, Ling
2017-04-01
As indicated by theory and experimental measurements individual carbon nanotubes (CNTs) have very high values of thermal conductivity. One of the challenges is to achieve high thermal conductivity in macroscopic assemblies of CNTs such as fibres, films and composites, paving the way to a wide range of applications. CNT fibres have tremendous potential in succeeding as the future materials for a variety of applications when properties at the nanoscale are translated to their macroscopic assemblies. In this paper we report the measurements of thermal conductivity of continuously spun CNT fibres and its dependence on temperature. Thermal conductivity measurements were performed using in-house built temperature sensing microscope probe. Specific thermal conductivity of CNT fibres showed an order of magnitude advantage over the traditional materials used for heat dissipation.
Thermal property of insulation material for HTS power cable
NASA Astrophysics Data System (ADS)
Choi, Yeon Suk; Kim, D. L.; Shin, D. W.; Hwang, S. D.
2012-06-01
The thermal property of insulation material is essential in developing a high temperature superconductor (HTS) power cable operating at around liquid nitrogen temperature. The accurate estimate of the heat flux is difficult in the nonmetallic materials because nonmetallic materials have a high thermal resistance and low temperature gradient along the specimen. The objective of the present work is to develop a precise instrument for measuring the thermal conductivity of insulating materials over a temperature range of 30 K to approximately the room temperature by using a cryocooler. The thermal conductivity of Teflon is measured and the accuracy confirmation is carried out by comparing published data. In addition, the experimental results of apparent thermal conductivity of polypropylene laminated paper (PPLP) are presented and the temperature dependency is also discussed
Temperature-dependent thermal properties of Ru/C multilayers.
Yan, Shuai; Jiang, Hui; Wang, Hua; He, Yan; Li, Aiguo; Zheng, Yi; Dong, Zhaohui; Tian, Naxi
2017-09-01
Multilayers made of Ru/C are the most promising candidates when working in the energy region 8-20 keV. The stability of its thermal properties, including thermal expansion and thermal conduction, needs to be considered for monochromator or focusing components. Ru/C multilayers with periodic thicknesses of 3, 4 and 5 nm were investigated in situ by grazing-incidence X-ray reflectometry and diffuse scattering in order to study their thermal expansion characteristics as a function of annealing temperature up to 400°C. The thermal conductivity of multilayers with the same structure was also measured by the transient hot-wire method and compared with bulk values.
Thermal properties of the martian surface inferred from OMEGA data
NASA Astrophysics Data System (ADS)
Audouard, J.; Poulet, F.; Vincendon, M.; Bibring, J.; Gondet, B.; Langevin, Y.
2011-12-01
Martian surface temperatures are the results of radiative exchanges between the air and the shallow subsurface. Thermal inertia (TI) and the albedo are key parameters for modulating diurnal temperature variation of surfaces. TI, which represents the resistance to change in temperature of the upper few centimeters of the subsurface throughout the day, is independent of local time, latitude, and season. Thermal infrared spectrometers TES and THEMIS that measured the surface temperature have been frequently used to derive the thermal properties of the martian surface (see e.g. Putzig et al. 2005; Fergason et al. 2006). Global TI derivation techniques usually assume that the thermophysical properties of the soil are vertically uniform (Putzig et al. 2005), while vertical heterogeneities are observed (Putzig and Mellon 2007; Bandfield and Feldman 2008). As the thermal wave penetration depth varies with season, various apparent thermal inertias are derived as a function of season for a given location (Putzig et al. 2005). Surface temperatures (larger than ~200 K) can be derived from the OMEGA/Mars Express hyperspectral observations (Jouglet et al. 2007). Of special interest is the elliptical MEX orbit that makes possible to observe a given surface element at various local time and solar longitude. This allow us to explore different parts of the thermal response of martian soils and can be used to better constrain the properties of the subsurface. We have developed an operational pixel-to-pixel climate modeling interface using the Martian Global Climate Model (Forget et al. 1999), in order to compare the surface temperature measured by OMEGA with the modeled temperature. A systematic comparison data/model covering 4 Martian years will be discussed. A few local scale thermal inertia retrievals will be then presented and compared to previous studies based on TES/MGS and THEMIS/Mars Odyssey data. We will also investigate the thermophysical properties of soils where anomalous
Anharmonic properties in M g2X (X =C ,Si ,Ge ,Sn ,Pb ) from first-principles calculations
NASA Astrophysics Data System (ADS)
Chernatynskiy, Aleksandr; Phillpot, Simon R.
2015-08-01
Thermal conductivity reduction is one of the potential routes to improve the performance of thermoelectric materials. However, detailed understanding of the thermal transport of many promising materials is still missing. In this paper, we employ electronic-structure calculations at the level of density functional theory to elucidate thermal transport properties of the M g2X (X =C , Si, Ge, Sn, and Pb) family of compounds, which includes M g2Si , a material already identified as a potential thermoelectric. All these materials crystallize into the same antifluorite structure. Systematic trends in the anharmonic properties of these materials are presented and examined. Our calculations indicate that the reduction in the group velocity is the main driver of the thermal conductivity trend in these materials, as the phonon lifetimes in these compounds are very similar. We also examine the limits of the applicability of perturbation theory to study the effect of point defects on thermal transport and find that it is in good agreement with experiment in a wide range of scattering parameter values. The thermal conductivity of the recently synthesized M g2C is computed and predicted to be 34 W/mK at 300 °C.
First-principles calculations of the thermal stability of Ti 3SiC 2(0001) surfaces
NASA Astrophysics Data System (ADS)
Orellana, Walter; Gutiérrez, Gonzalo
2011-12-01
The energetic, thermal stability and dynamical properties of the ternary layered ceramic Ti3SiC2(0001) surface are addressed by density-functional theory calculations and molecular dynamic (MD) simulations. The equilibrium surface energy at 0 K of all terminations is contrasted with thermal stability at high temperatures, which are investigated by ab initio MD simulations in the range of 800 to 1400 °C. We find that the toplayer (sublayer) surface configurations: Si(Ti2) and Ti2(Si) show the lowest surface energies with reconstruction features for Si(Ti2). However, at high temperatures they are unstable, forming disordered structures. On the contrary, Ti1(C) and Ti2(C) despite their higher surface energies, show a remarkable thermal stability at high temperatures preserving the crystalline structures up to 1400 °C. The less stable surfaces are those terminated in C atoms, C(Ti1) and C(Ti2), which at high temperatures show surface dissociation forming amorphous TiCx structures. Two possible atomic scale mechanisms involved in the thermal stability of Ti3SiC2(0001) are discussed.
Liu, Gang; Zhou, Jian; Wang, Hui
2017-06-14
Based on Grüneisen's theory, the elastic properties and thermal expansion of bulk SnSe with the Pnma phase are investigated by using first-principles calculations. Our numerical results indicate that the linear thermal expansion coefficient along the a direction is smaller than the one along the b direction, while the one along the c direction shows a significant negative value, even at high temperature. The numerical results are in good accordance with experimental results. In addition, generalized and macroscopic Grüneisen parameters are also presented. It is also found that SnSe possesses negative Possion's ratio. The contributions of different phonon modes to NTE along the c direction are investigated, and it is found that the two modes which make the most important contributions to NTE are transverse vibrations perpendicular to the c direction. Finally, we analyze the relation of elastic constants to negative thermal expansion, and demonstrate that negative thermal expansion can also occur even with all positive macroscopic Grüneisen parameters.
"TPSX: Thermal Protection System Expert and Material Property Database"
NASA Technical Reports Server (NTRS)
Squire, Thomas H.; Milos, Frank S.; Rasky, Daniel J. (Technical Monitor)
1997-01-01
The Thermal Protection Branch at NASA Ames Research Center has developed a computer program for storing, organizing, and accessing information about thermal protection materials. The program, called Thermal Protection Systems Expert and Material Property Database, or TPSX, is available for the Microsoft Windows operating system. An "on-line" version is also accessible on the World Wide Web. TPSX is designed to be a high-quality source for TPS material properties presented in a convenient, easily accessible form for use by engineers and researchers in the field of high-speed vehicle design. Data can be displayed and printed in several formats. An information window displays a brief description of the material with properties at standard pressure and temperature. A spread sheet window displays complete, detailed property information. Properties which are a function of temperature and/or pressure can be displayed as graphs. In any display the data can be converted from English to SI units with the click of a button. Two material databases included with TPSX are: 1) materials used and/or developed by the Thermal Protection Branch at NASA Ames Research Center, and 2) a database compiled by NASA Johnson Space Center 9JSC). The Ames database contains over 60 advanced TPS materials including flexible blankets, rigid ceramic tiles, and ultra-high temperature ceramics. The JSC database contains over 130 insulative and structural materials. The Ames database is periodically updated and expanded as required to include newly developed materials and material property refinements.
"TPSX: Thermal Protection System Expert and Material Property Database"
NASA Technical Reports Server (NTRS)
Squire, Thomas H.; Milos, Frank S.; Rasky, Daniel J. (Technical Monitor)
1997-01-01
The Thermal Protection Branch at NASA Ames Research Center has developed a computer program for storing, organizing, and accessing information about thermal protection materials. The program, called Thermal Protection Systems Expert and Material Property Database, or TPSX, is available for the Microsoft Windows operating system. An "on-line" version is also accessible on the World Wide Web. TPSX is designed to be a high-quality source for TPS material properties presented in a convenient, easily accessible form for use by engineers and researchers in the field of high-speed vehicle design. Data can be displayed and printed in several formats. An information window displays a brief description of the material with properties at standard pressure and temperature. A spread sheet window displays complete, detailed property information. Properties which are a function of temperature and/or pressure can be displayed as graphs. In any display the data can be converted from English to SI units with the click of a button. Two material databases included with TPSX are: 1) materials used and/or developed by the Thermal Protection Branch at NASA Ames Research Center, and 2) a database compiled by NASA Johnson Space Center 9JSC). The Ames database contains over 60 advanced TPS materials including flexible blankets, rigid ceramic tiles, and ultra-high temperature ceramics. The JSC database contains over 130 insulative and structural materials. The Ames database is periodically updated and expanded as required to include newly developed materials and material property refinements.
The anomalous thermal properties of glasses at low temperatures
NASA Technical Reports Server (NTRS)
Pohl, R. O.; Salinger, G. L.
1976-01-01
While experimentally there is great regularity below 1 deg K in the behavior of a particular thermal property for all amorphous dielectrics it is not understood why these properties should differ from those of crystalline dielectrics, since it would seem that at low temperatures long-wavelength elastic waves, similar in both cases, would determine the thermal properties. A model involving systems having very few levels is used in the present study, although the relation between the model's systems and the nature of the glassy state is not known. It is shown, among other effects, that: specific heat measurements above 0.1 K indicate a distribution of local modes independent of energy; ultrasonic velocity measurements give information about phonon-local mode coupling parameters; and thermal expansion and far infrared experiments indicate a phonon-assisted tunneling model.
Scattering, Thermal Emission and Extinction: Column Density and Dust Properties
NASA Astrophysics Data System (ADS)
Foster, Jonathan
2013-07-01
We compare three different ways to measure the column density of molecular clouds using (1) scat- tered light (cloudshine), (2) thermal emission in the sub-millimeter and (3) extinction of background stars. Our methods for estimating the column density from thermal emission and from extinction of background stars use hierarchical Bayesian models to coherently infer correlations in the dust properties and the column density estimates. In particular, we measure the slope of the extinction law (Rv) from extinction estimates and the deviation from blackbody emission (beta) from the thermal emission estimates. These dust properties are related to the size distribution and compo- sition of dust. The comparison among these three methods therefore tells us about which regimes particular methods work or fail and about the properties of the dust at different depths inside the cloud.
Thermal conductivity and combustion properties of wheat gluten foams.
Blomfeldt, Thomas O J; Nilsson, Fritjof; Holgate, Tim; Xu, Jianxiao; Johansson, Eva; Hedenqvist, Mikael S
2012-03-01
Freeze-dried wheat gluten foams were evaluated with respect to their thermal and fire-retardant properties, which are important for insulation applications. The thermal properties were assessed by differential scanning calorimetry, the laser flash method and a hot plate method. The unplasticised foam showed a similar specific heat capacity, a lower thermal diffusivity and a slightly higher thermal conductivity than conventional rigid polystyrene and polyurethane insulation foams. Interestingly, the thermal conductivity was similar to that of closed cell polyethylene and glass-wool insulation materials. Cone calorimetry showed that, compared to a polyurethane foam, both unplasticised and glycerol-plasticised foams had a significantly longer time to ignition, a lower effective heat of combustion and a higher char content. Overall, the unplasticised foam showed better fire-proof properties than the plasticized foam. The UL 94 test revealed that the unplasticised foam did not drip (form droplets of low viscous material) and, although the burning times varied, self-extinguished after flame removal. To conclude both the insulation and fire-retardant properties were very promising for the wheat gluten foam. © 2012 American Chemical Society
Atomistic calculation of the thermal conductance of large scale bulk-nanowire junctions
Duchemin, Ivan; Donadio, Davide
2011-09-15
We have developed a stable and efficient kernel method to compute thermal transport in open systems, based on the scattering-matrix approach. This method is applied to compute the thermal conductance of a junction between bulk silicon and silicon nanowires with diameter up to 10 nm. We have found that beyond a threshold diameter of 7 nm, transmission spectra and contact conductances scale with the cross section of the contact surface, whereas deviations from this general trend are observed in thinner wires. This result allows us to predict the thermal resistance of bulk-nanowire interfaces with larger cross sections than those tractable with atomistic simulations, and indicate the characteristic size beyond which atomistic systems can in principle be treated accurately by mean-field theories. Our calculations also elucidate how dimensionality reduction and shape affect interfacial heat transport.
NASA Astrophysics Data System (ADS)
Richards, Simon D.; Davies, Nigel; Armishaw, Malcolm J.; Dobson, Geoff P.; Wright, George A.
2014-06-01
Monte Carlo methods are increasingly being used for whole core reactor physics modelling. We describe a number of recent developments to the MONK nuclear criticality and reactor physics code to implement parallel processing, mesh-dependent burn-up and coupling to both thermal hydraulics and gamma transport codes. Results are presented which demonstrate the e_ects of gamma heating in a MONK calculation coupled to the MCBEND Monte Carlo shielding code. Experimental validation of the mesh-dependent tracking and gamma coupling methods is provided by comparison with the results of the NESSUS experiment. The gamma heating calculated by coupled MONK-MCBEND, and the neutron heating calculated by MONK, both compare well against measurement. Finally results are presented from a parallel MONK calculation of a highly detailed PWR benchmark model, which show encouraging speed-up factors on a small development cluster.
Tian, Xiaojuan; Itkis, Mikhail E.; Bekyarova, Elena B.; Haddon, Robert C.
2013-01-01
Thermal interface materials (TIMs) are crucial components of high density electronics and the high thermal conductivity of graphite makes this material an attractive candidate for such applications. We report an investigation of the in-plane and through-plane electrical and thermal conductivities of thin thermal interface layers of graphite nanoplatelet (GNP) based composites. The in-plane electrical conductivity exceeds its through-plane counterpart by three orders of magnitude, whereas the ratio of the thermal conductivities is about 5. Scanning electron microscopy reveals that the anisotropy in the transport properties is due to the in-plane alignment of the GNPs which occurs during the formation of the thermal interface layer. Because the alignment in the thermal interface layer suppresses the through-plane component of the thermal conductivity, the anisotropy strongly degrades the performance of GNP-based composites in the geometry required for typical thermal management applications and must be taken into account in the development of GNP-based TIMs.
Optothermal Raman Studies of Thermal Properties of Graphene Based Films
NASA Astrophysics Data System (ADS)
Malekpour, Hoda
Efficient thermal management is becoming a critical issue for development of the next generation of electronics. As the size of electronic devices shrinks, the dissipated power density increases, demanding a better heat removal. The discovery of graphene's unique electrical and thermal properties stimulated interest of electronic industry to development of graphene based technologies. In this dissertation, I report the results of my investigation of thermal properties of graphene derivatives and their applications in thermal management. The dissertation consists of three parts. In the first part, I investigated thermal conductivity of graphene laminate films deposited on thermally insulating polyethylene terephthalate substrates. Graphene laminate is made of chemically derived graphene and few layer graphene flakes packed in overlapping structure. Two types of graphene laminate were studied: as deposited and compressed. The thermal conductivity of the laminate was found to be in the range from 40 W/mK to 90 W/mK at room temperature. It was established that the average size and the alignment of graphene flakes are parameters dominating the heat conduction. In the second part of this dissertation, I investigated thermal conductivity of chemically reduced freestanding graphene oxide films. It was found that the in-plane thermal conductivity of graphene oxide can be increased significantly using chemical reduction and temperature treatment. Finally, I studied the effect of defects on thermal conductivity of suspended graphene. The knowledge of the thermal conductivity dependence on the concentration of defects can shed light on the strength of the phonon - point defect scattering in two-dimensional materials. The defects were introduced to graphene in a controllable way using the low-energy electron beam irradiation. It was determined that as the defect density increases the thermal conductivity decreases down to about 400 W/mK, and then reveal saturation type behavior
NASA Astrophysics Data System (ADS)
Diascorn, N.; Sallee, H.; Calas, S.; Rigacci, A.; Achard, P.
2015-07-01
Organic aerogels based on polyurethane were elaborated via sol-gel synthesis and dried with supercritical carbon dioxide (CO2). The influence of the catalyst concentration was investigated, first in order to decrease the reaction kinetics, then to study its impact on the obtained materials properties. It was shown that this parameter also influences the global shrinkage and the bulk density of the resulting materials. Its effect on the dry materials was studied in terms of morphological, textural and thermal properties in order to determine the main correlations thanks to scanning electron microscopy (SEM), nitrogen adsorption, non-intrusive mercury porosimetry and thermal conductivity measurements. Results allowed us to demonstrate a correlation between the bulk density, the texture and the thermal conductivity of this family of polyurethane aerogels and to determine an optimal density range for thermal performance associated with a fine internal mesoporous texture.
Antioxidant Properties of Kynurenines: Density Functional Theory Calculations
2016-01-01
Kynurenines, the main products of tryptophan catabolism, possess both prooxidant and anioxidant effects. Having multiple neuroactive properties, kynurenines are implicated in the development of neurological and cognitive disorders, such as Alzheimer's, Parkinson's, and Huntington's diseases. Autoxidation of 3-hydroxykynurenine (3HOK) and its derivatives, 3-hydroxyanthranilic acid (3HAA) and xanthommatin (XAN), leads to the hyperproduction of reactive oxygen species (ROS) which damage cell structures. At the same time, 3HOK and 3HAA have been shown to be powerful ROS scavengers. Their ability to quench free radicals is believed to result from the presence of the aromatic hydroxyl group which is able to easily abstract an electron and H-atom. In this study, the redox properties for kynurenines and several natural and synthetic antioxidants have been calculated at different levels of density functional theory in the gas phase and water solution. Hydroxyl bond dissociation enthalpy (BDE) and ionization potential (IP) for 3HOK and 3HAA appear to be lower than for xanthurenic acid (XAA), several phenolic antioxidants, and ascorbic acid. BDE and IP for the compounds with aromatic hydroxyl group are lower than for their precursors without hydroxyl group. The reaction rate for H donation to *O-atom of phenoxyl radical (Ph-O*) and methyl peroxy radical (Met-OO*) decreases in the following rankings: 3HOK ~ 3HAA > XAAOXO > XAAENOL. The enthalpy absolute value for Met-OO* addition to the aromatic ring of the antioxidant radical increases in the following rankings: 3HAA* < 3HOK* < XAAOXO* < XAAENOL*. Thus, the high free radical scavenging activity of 3HAA and 3HOK can be explained by the easiness of H-atom abstraction and transfer to O-atom of the free radical, rather than by Met-OO* addition to the kynurenine radical. PMID:27861556
Antioxidant Properties of Kynurenines: Density Functional Theory Calculations.
Zhuravlev, Aleksandr V; Zakharov, Gennady A; Shchegolev, Boris F; Savvateeva-Popova, Elena V
2016-11-01
Kynurenines, the main products of tryptophan catabolism, possess both prooxidant and anioxidant effects. Having multiple neuroactive properties, kynurenines are implicated in the development of neurological and cognitive disorders, such as Alzheimer's, Parkinson's, and Huntington's diseases. Autoxidation of 3-hydroxykynurenine (3HOK) and its derivatives, 3-hydroxyanthranilic acid (3HAA) and xanthommatin (XAN), leads to the hyperproduction of reactive oxygen species (ROS) which damage cell structures. At the same time, 3HOK and 3HAA have been shown to be powerful ROS scavengers. Their ability to quench free radicals is believed to result from the presence of the aromatic hydroxyl group which is able to easily abstract an electron and H-atom. In this study, the redox properties for kynurenines and several natural and synthetic antioxidants have been calculated at different levels of density functional theory in the gas phase and water solution. Hydroxyl bond dissociation enthalpy (BDE) and ionization potential (IP) for 3HOK and 3HAA appear to be lower than for xanthurenic acid (XAA), several phenolic antioxidants, and ascorbic acid. BDE and IP for the compounds with aromatic hydroxyl group are lower than for their precursors without hydroxyl group. The reaction rate for H donation to *O-atom of phenoxyl radical (Ph-O*) and methyl peroxy radical (Met-OO*) decreases in the following rankings: 3HOK ~ 3HAA > XAAOXO > XAAENOL. The enthalpy absolute value for Met-OO* addition to the aromatic ring of the antioxidant radical increases in the following rankings: 3HAA* < 3HOK* < XAAOXO* < XAAENOL*. Thus, the high free radical scavenging activity of 3HAA and 3HOK can be explained by the easiness of H-atom abstraction and transfer to O-atom of the free radical, rather than by Met-OO* addition to the kynurenine radical.
Phonon thermal properties of graphene from molecular dynamics using different potentials.
Zou, Ji-Hang; Ye, Zhen-Qiang; Cao, Bing-Yang
2016-10-07
Phonon thermal transport in graphene has attracted significant interest in recent years. Phonon thermal properties of graphene are investigated by molecular dynamics simulations using the Tersoff, Tersoff-2010, REBO, and AIREBO potentials. By calculating the phonon properties and thermal conductivity of graphene, the performance of the potentials is evaluated based on comparisons with experimental data. It shows that the Tersoff-2010 and REBO display better dispersion curves for graphene than the original Tersoff and AIREBO. The Tersoff-2010 correctly provides the Γ point phonon velocities of the LA and TA branches as well as the G peak frequency with a value of 46 THz. In addition, the acoustic phonon relaxation time derived from the Tersoff-2010 satisfies the ideal relation "τ(-1) ∝ ν(2)." It is also found that the Tersoff-2010 provides the highest graphene thermal conductivity among the used potentials, and estimates about 30.0% contribution for flexural phonons to the total thermal conductivity. By comparison, the Tersoff-2010 potential is demonstrated to be the most suitable one to describe the phonon thermal properties of graphene.
Phonon thermal properties of graphene from molecular dynamics using different potentials
NASA Astrophysics Data System (ADS)
Zou, Ji-Hang; Ye, Zhen-Qiang; Cao, Bing-Yang
2016-10-01
Phonon thermal transport in graphene has attracted significant interest in recent years. Phonon thermal properties of graphene are investigated by molecular dynamics simulations using the Tersoff, Tersoff-2010, REBO, and AIREBO potentials. By calculating the phonon properties and thermal conductivity of graphene, the performance of the potentials is evaluated based on comparisons with experimental data. It shows that the Tersoff-2010 and REBO display better dispersion curves for graphene than the original Tersoff and AIREBO. The Tersoff-2010 correctly provides the Γ point phonon velocities of the LA and TA branches as well as the G peak frequency with a value of 46 THz. In addition, the acoustic phonon relaxation time derived from the Tersoff-2010 satisfies the ideal relation "τ-1 ∝ ν2." It is also found that the Tersoff-2010 provides the highest graphene thermal conductivity among the used potentials, and estimates about 30.0% contribution for flexural phonons to the total thermal conductivity. By comparison, the Tersoff-2010 potential is demonstrated to be the most suitable one to describe the phonon thermal properties of graphene.
Calculation and observation of thermal electrostatic noise in solar wind plasma
NASA Technical Reports Server (NTRS)
Kellogg, P. J.
1981-01-01
Calculations, both approximate algebraic and numerical, have been carried out for the noise due to electrostatic waves incident on a dipole antenna. The noise is calculated both for a thermal equilibrium plasma, and one having several components at different temperatures. The results are compared with measurements from the IMP-6 satellite. In various frequency ranges, the noise power is dominated by Langmuir oscillations, by electron acoustic waves and by ion acoustic waves. The measurements are consistent with all of these, although the ion waves are not definitely observed, due to interference from shot noise.
Calculation of momentum distribution function of a non-thermal fermionic dark matter
NASA Astrophysics Data System (ADS)
Biswas, Anirban; Gupta, Aritra
2017-03-01
The most widely studied scenario in dark matter phenomenology is the thermal WIMP scenario. Inspite of numerous efforts to detect WIMP, till now we have no direct evidence for it. A possible explanation for this non-observation of dark matter could be because of its very feeble interaction strength and hence, failing to thermalise with the rest of the cosmic soup. In other words, the dark matter might be of non-thermal origin where the relic density is obtained by the so-called freeze-in mechanism. Furthermore, if this non-thermal dark matter is itself produced substantially from the decay of another non-thermal mother particle, then their distribution functions may differ in both size and shape from the usual equilibrium distribution function. In this work, we have studied such a non-thermal (fermionic) dark matter scenario in the light of a new type of U(1)B-L model. The U(1)B-L model is interesting, since, besides being anomaly free, it can give rise to neutrino mass by Type II see-saw mechanism. Moreover, as we will show, it can accommodate a non-thermal fermionic dark matter as well. Starting from the collision terms, we have calculated the momentum distribution function for the dark matter by solving a coupled system of Boltzmann equations. We then used it to calculate the final relic abundance, as well as other relevant physical quantities. We have also compared our result with that obtained from solving the usual Boltzmann (or rate) equations directly in terms of comoving number density, Y. Our findings suggest that the latter approximation is valid only in cases where the system under study is close to equilibrium, and hence should be used with caution.
Fatigue properties of shuttle thermal protection system
NASA Technical Reports Server (NTRS)
Sawyer, J. W.; Cooper, P. A.
1980-01-01
Static and cyclic load tests were conducted to determine the static and fatigue strength of the RIS tile/SIP thermal protection system used on the orbiter of the space shuttle. The material systems investigated include the densified and undensified LI-900 tile system on the .40 cm thick SIP and the densified and undensified LI-2200 tile system on the .23 cm (.090 inch) thick SIP. The tests were conducted at room temperature with a fully reversed uniform cyclic loading at 1 Hertz. Cyclic loading causes a relatively large reduction in the stress level that each of the SIP/tile systems can withstand for a small number of cycles. For example, the average static strength of the .40 cm thick SIP/LI-900 tile system is reduced from 86 kPa to 62 kPa for a thousand cycles. Although the .23 cm thick SIP/LI-2200 tile system has a higher static strength, similar reductions in the fatigue strength are noted. Densifying the faying surface of the RSI tile changes the failure mode from the SIP/tile interface to the parent RSI or the SIP and thus greatly increases the static strength of the system. Fatigue failure for the densified tile system, however, occurs due to complete separation or excessive elongation of the SIP and the fatigue strength is only slightly greater than that for the undensified tile system.
A thermodynamic model of thermal end elastic properties of curium
NASA Astrophysics Data System (ADS)
Povzner, A. A.; Filanovich, A. N.; Oskina, V. A.
2013-11-01
A self-consistent thermodynamic model of curium is developed. In the framework of this model the temperature dependencies of heat capacity, coefficient of thermal expansion, bulk modulus and Debye temperature of Cm are calculated. It is shown that the phonon anharmonicity of Cm is weaker than in the case of Np and δ-Pu, but stronger than in lanthanides.
Thermal property measurement of insulating material used in HTS power device
NASA Astrophysics Data System (ADS)
Choi, Yeon Suk; Kim, Dong Lak
2012-10-01
An experiment to measure the thermal property of insulating material at cryogenic temperature has been performed. The main objective of this study is to develop a precise instrument for measuring the thermal property of insulating materials over a temperature range of 30 K to approximately room temperature by utilizing a cryocooler. In a vacuum chamber, the cold head of the cryocooler is thermally anchored to the copper link and used to bring the apparatus to a desired temperature. An electric heater is placed in the middle of test sample for generating uniform heat flux. The entire apparatus is covered by thermal shields and wrapped in multi-layer insulation to minimize thermal radiation in a vacuum chamber. For a supplied heat flux the temperature distribution in test sample, polypropylene laminated paper (PPLP), is measured in steady state, from which the effective thermal conductivity is calculated and presented with respect to the mean temperature. The correlation near liquid nitrogen temperature is derived from measured data. Moreover, using the measured thermal conductivity, we obtain the specific heat of PPLP by solving one-dimensional heat diffusion equation.
Direct calculation of thermal emission for three-dimensionally periodic photonic crystal slabs.
Chan, David L C; Soljacić, Marin; Joannopoulos, J D
2006-09-01
We perform direct thermal emission calculations for three-dimensionally periodic photonic crystal slabs using stochastic electrodynamics following the Langevin approach, implemented via a finite-difference time-domain algorithm. We demonstrate that emissivity and absorptivity are equal, by showing that such photonic crystal systems emit as much radiation as they absorb, for every frequency, up to statistical fluctuations. We also study the effect of surface termination on absorption and emission spectra from these systems.
Direct calculation of thermal emission for three-dimensionally periodic photonic crystal slabs
NASA Astrophysics Data System (ADS)
Chan, David L. C.; Soljačić, Marin; Joannopoulos, J. D.
2006-09-01
We perform direct thermal emission calculations for three-dimensionally periodic photonic crystal slabs using stochastic electrodynamics following the Langevin approach, implemented via a finite-difference time-domain algorithm. We demonstrate that emissivity and absorptivity are equal, by showing that such photonic crystal systems emit as much radiation as they absorb, for every frequency, up to statistical fluctuations. We also study the effect of surface termination on absorption and emission spectra from these systems.
Accurate calculated optical properties of substituted quaterphenylene nanofibers.
Finnerty, Justin J; Koch, Rainer
2010-01-14
The accurate prediction of both excitation and emission energies of substituted p-quaterphenylenes using a variety of established and newly developed density functional methods is evaluated and compared against experimental data, both from single molecules and from nanofibers. For calculation of the UV-vis excitation the MPW1K functional is the best performing method (with the employed TZVP basis set). After a linear scaling factor is applied, mPW2-PLYP, CIS and the very fast INDO/S also reproduce the experimental data correctly. For the fluorescence relaxation energies MPW1K, mPW2-PLYP, and INDO/S give good results, even without scaling. However, mPW2-PLYP involves second-order perturbation to introduce nonlocal electron correlation and therefore requires significantly more resources, so the recommended level of theory for a single methodology to investigate the optical properties of substituted phenylenes and related systems is MPW1K/6-311+G(2d,p), followed by INDO/S as a low-cost alternative. As an extension of a previous work on predicting first hyperpolarisabilities, we can now demonstrate that the chosen approach (HF/6-31G(d)//B3LYP/6-31G(d)) produces data that correlate well with the susceptibilities derived from measurements on nanofibers.
Montan, D.N.; Patrick, W.C.
1981-09-30
The Spent Fuel Test-Climax (SFT-C) is a test of retrievable deep geologic storage of commercially generated spent nuclear reactor fuel in granitic rock. Eleven spent fuel assemblies, together with six electrical simulators and 20 guard heaters, are emplaced 420 m below the surface in the Climax granite at the US Department of Energy Nevada Test Site. On June 2, 1978 LLNL secured funding for the SFT-C, and completed spent fuel emplacement May 28, 1980. This report documents a series of thermal calculations that were performed in support of the SFT-C. Early calculations employed analytical solutions to address such design and construction issues as drift layout and emplacement hole spacings. Operational aspects of the test required more detailed numerical solutions dealing with ventilation and guard-heater power levels. The final set of calculations presented here provides temperature histories throughout the test facility for evaluation of the response of the SFT-C and for comparison of calculations with acquired data. This final set of calculations employs the as-built test geometry and best-available material properties.
Thermal properties of CaMo O4 : Lattice dynamics and synchrotron powder diffraction studies
NASA Astrophysics Data System (ADS)
Senyshyn, A.; Kraus, H.; Mikhailik, V. B.; Vasylechko, L.; Knapp, M.
2006-01-01
The structure of calcium molybdate was studied by means of synchrotron based high-resolution powder diffraction methods in the temperature range 12-300K . The scheelite structure type was confirmed for CaMoO4 in the temperature region investigated and no structural anomalies were observed. Thermal expansion coefficients extracted from the thermal dependencies of the cell sizes are found to be in good agreement with the predictions from our lattice dynamics calculations that form the background for microscopic interpretation of the experimental data. From the analyses of experimental results and the calculated thermal expansion coefficients, elastic constants, phonon density of states, heat capacities, entropy, and Grüneisen parameters it is concluded that a quasiharmonic lattice dynamics approach provides a good description of these properties for CaMoO4 at temperatures below 800K .
Review on thermal properties of nanofluids: Recent developments.
Angayarkanni, S A; Philip, John
2015-11-01
Nanofluids are dispersions of nanomaterials (e.g. nanoparticles, nanofibers, nanotubes, nanowires, nanorods, nanosheet, or droplets) in base fluids. Nanofluids have been a topic of great interest during the last one decade primarily due to the initial reports of anomalous thermal conductivity (k) enhancement in nanofluids with a small percentage of nanoparticles. This field has been quite controversial, with multiple reports of anomalous enhancement in thermal conductivity and many other reports of the thermal conductivity increase within the classical Maxwell mixing model. Several mechanisms have been proposed for explaining the observed enhancement in thermal conductivity. The role of Brownian motion, interfacial resistance, morphology of suspended nanoparticles and aggregating behavior is investigated both experimentally and theoretically. As the understanding of specific heat capacity of nanofluids is a prerequisite for their effective utilization in heat transfer applications, it is also investigated by many researchers. From the initial focus on thermophysical properties of nanofluids, the attention is now shifted to tailoring of novel nanofluids with large thermal conductivities. Further, to overcome the limitations of traditional heat transfer media, phase change materials (PCMs) and hybrid nanofluids are being developed as effective media for thermal energy storage. This review focuses the recent progress in nanofluids research from a heat transfer perspective. Emphasis is given for the latest work on thermal properties of nanofluids, phase change materials and hybrid nanofluids. The preparation of nanofluids by various techniques, methods of stabilization, stability measurement techniques, thermal conductivity and heat capacity studies, proposed mechanisms of heat transport, theoretical models on thermal conductivity, factors influencing k and the effect of nanoinclusions in PCM are discussed in this review. Sufficient background information is also
Thermal and structural properties of ionic fluids.
Bartsch, Hendrik; Dannenmann, Oliver; Bier, Markus
2015-04-01
The electrostatic interaction in ionic fluids is well known to give rise to a characteristic phase behavior and structure. Sometimes its long range is proposed to single out the electrostatic potential over other interactions with shorter ranges. Here the importance of the range for the phase behavior and the structure of ionic fluids is investigated by means of grandcanonical Monte Carlo simulations of the lattice restricted primitive model (LRPM). The long-ranged electrostatic interaction is compared to various types of short-ranged potentials obtained by sharp and/or smooth cutoff schemes. Sharply cutoff electrostatic potentials are found to lead to a strong dependence of the phase behavior and the structure on the cutoff radius. However, when combined with a suitable additional smooth cutoff, the short-ranged LRPM is found to exhibit quantitatively the same phase behavior and structure as the conventional long-ranged LRPM. Moreover, the Stillinger-Lovett perfect screening property, which is well known to be generated by the long-ranged electrostatic potential, is also fulfilled by short-ranged LRPMs with smooth cutoffs. By showing that the characteristic phase behavior and structure of ionic fluids can also be found in systems with short-ranged potentials, one can conclude that the decisive property of the electrostatic potential in ionic fluids is not the long range but rather the valency dependence.
An assessment of the CORCON-MOD3 code. Part 1: Thermal-hydraulic calculations
Strizhov, V.; Kanukova, V.; Vinogradova, T.; Askenov, E.; Nikulshin, V.
1996-09-01
This report deals with the subject of CORCON-Mod3 code validation (thermal-hydraulic modeling capability only) based on MCCI (molten core concrete interaction) experiments conducted under different programs in the past decade. Thermal-hydraulic calculations (i.e., concrete ablation, melt temperature, melt energy, concrete temperature, and condensible and non-condensible gas generation) were performed with the code, and compared with the data from 15 experiments, conducted at different scales using both simulant (metallic and oxidic) and prototypic melt materials, using different concrete types, and with and without an overlying water pool. Sensitivity studies were performed in a few cases involving, for example, heat transfer from melt to concrete, condensed phase chemistry, etc. Further, special analysis was performed using the ACE L8 experimental data to illustrate the differences between the experimental and the reactor conditions, and to demonstrate that with proper corrections made to the code, the calculated results were in better agreement with the experimental data. Generally, in the case of dry cavity and metallic melts, CORCON-Mod3 thermal-hydraulic calculations were in good agreement with the test data. For oxidic melts in a dry cavity, uncertainties in heat transfer models played an important role for two melt configurations--a stratified geometry with segregated metal and oxide layers, and a heterogeneous mixture. Some discrepancies in the gas release data were noted in a few cases.
Thermal Properties of Lunar Regolith Simulants
NASA Technical Reports Server (NTRS)
Street, Kenneth W., Jr.; Ray, Chandra; Rickman, Doug; Scheiman, Daniel A.
2010-01-01
Various high temperature chemical processes have been developed to extract oxygen and metals from lunar regolith. These processes are tested using terrestrial analogues of the regolith. But all practical terrestrial analogs contain H2O and/or OH-, the presence of which has substantial impact on important system behaviors. We have undertaken studies of lunar regolith simulants to determine the limits of the simulants to validate key components for human survivability during sustained presence on the Moon. Differential Thermal Analysis (DTA) yields information on phase transitions and melting temperatures. Thermo-Gravimetric Analysis (TGA) with Fourier Transform Infrared (FTIR) analysis provides information on evolved gas species and their evolution temperature profiles. The DTA and TGA studies included JSC-1A fine (Johnson Space Center Mare Type 1A simulant), NU-LHT-2M (National Aeronautics and Space Administration (NASA)-- United States Geological Survey (USGS)--Lunar Highlands Type 2M simulant) and its proposed feedstocks: anorthosite; dunite; high quality (HQ) glass and the norite from which HQ glass is produced. As an example, the DTA and TGA profiles for anorthosite follow. The DTA indicates exothermic transitions at 355 and 490 C and endothermic transitions at 970 and 1235 C. Below the 355 C transition, water is lost accounting for approximately 0.1 percent mass loss. Just above 490 C a second type of water is lost, presumably bound in lattices of secondary minerals along with other volatile oxides. Limited TGA-FTIR data is available at the time of this writing. For JSC-1A fine, the TGA-FTIR indicates at least two kinds of water are evolved in the 100 to 500 and the 700 to 900 C ranges. Evolution of carbon dioxide types occurs in the 250 to 545, 545 to 705, and 705 to 985 C ranges. Geologically, the results are consistent with the evolution of "water" in its several forms, CO2 from break down of secondary carbonates and magmatic, dissolved gas and glass
Thermal properties of soils: effect of biochar application
NASA Astrophysics Data System (ADS)
Usowicz, Boguslaw; Lukowski, Mateusz; Lipiec, Jerzy
2014-05-01
Thermal properties (thermal conductivity, heat capacity and thermal diffusivity) have a significant effect on the soil surface energy partitioning and resulting in the temperature distribution. Thermal properties of soil depend on water content, bulk density and organic matter content. An important source of organic matter is biochar. Biochar as a material is defined as: "charcoal for application as a soil conditioner". Biochar is generally associated with co-produced end products of pyrolysis. Many different materials are used as biomass feedstock for biochar, including wood, crop residues and manures. Additional predictions were done for terra preta soil (also known as "Amazonian dark earth"), high in charcoal content, due to adding a mixture of charcoal, bone, and manure for thousands of years i.e. approximately 10-1,000 times longer than residence times of most soil organic matter. The effect of biochar obtained from the wood biomass and other organic amendments (peat, compost) on soil thermal properties is presented in this paper. The results were compared with wetland soils of different organic matter content. The measurements of the thermal properties at various water contents were performed after incubation, under laboratory conditions using KD2Pro, Decagon Devices. The measured data were compared with predictions made using Usowicz statistical-physical model (Usowicz et al., 2006) for biochar, mineral soil and soil with addition of biochar at various water contents and bulk densities. The model operates statistically by probability of occurrence of contacts between particular fractional compounds. It combines physical properties, specific to particular compounds, into one apparent conductance specific to the mixture. The results revealed that addition of the biochar and other organic amendments into the soil caused considerable reduction of the thermal conductivity and diffusivity. The mineral soil showed the highest thermal conductivity and diffusivity
NASA Astrophysics Data System (ADS)
Guo, San-Dong; Wang, Yue-Hua
2017-01-01
Two-dimensional (2D) materials may have potential applications in thermoelectric devices. In this work, the thermoelectric properties of orthorhombic group IV-VI monolayers AB (A = Ge and Sn; B = S and Se) are systematically investigated by the first-principles calculations and semiclassical Boltzmann transport theory. The spin-orbit coupling (SOC) is considered for their electron part, which produces observable effects on the power factor, especially for n-type doping. According to the calculated ZT, the four monolayers exhibit diverse anisotropic thermoelectric properties although they have a similar hinge-like crystal structure. The GeS along zigzag and armchair directions shows the strongest anisotropy, while SnS and SnSe show mostly isotropic efficiency of thermoelectric conversion. This can be explained by the strength of anisotropy of their respective power factor and electronic and lattice thermal conductivities. The calculated results show that the ZT between n- and p-type doping has little difference for GeS, SnS, and SnSe. It is found that GeSe, SnS, and SnSe show better thermoelectric performance compared to GeS in n-type doping and that SnS and SnSe exhibit higher efficiency of thermoelectric conversion in p-type doping. Compared to other many 2D materials, orthorhombic group IV-VI monolayers AB (A = Ge and Sn; B = S and Se) may possess better thermoelectric performance due to lower lattice thermal conductivities. Our work would be beneficial to stimulate further theoretical and experimental works.
NASA Astrophysics Data System (ADS)
Machado, F. A. L.; Zanelato, E. B.; Guimarães, A. O.; da Silva, E. C.; Mansanares, A. M.
2012-11-01
The photopyroelectric technique (PPE) was used for thermal characterization of biodiesel and their corresponding precursor vegetable oils. Different configurations of PPE were applied in these studies. The standard and inverse configurations allowed the determination of the thermal diffusivity ( α) and thermal effusivity ( e), respectively. From these two parameters the thermal conductivity was calculated. Measurements were performed for reference samples (water and ethylene glycol), biodiesel, and some corresponding precursor vegetable oils. The experiments showed good reproducibility, with uncertainties around 1 % to 2 % for all the samples. Lower values for both α and e of the biodiesel when compared to their corresponding precursor vegetable oils were observed, indicating that these thermophysical properties were sensitive to structural changes during the transesterification process.
NASA Astrophysics Data System (ADS)
Yu, Xia; Xie, Zhong-Xiang; Liu, Jun-Hun; Chen, Qiao; Li, Ke-Min; Zhang, Yong
2016-04-01
In this paper, we study ballistic thermal transport properties at low temperatures in semiconductor nanowires-based heterojunctions under hard-wall boundary conditions (HWBCs) and stress-free boundary conditions (SFBCs). Here, the numerical calculations for the asymmetric heterojunction (ASHJ) and symmetric heterojunction (SHJ) are done. When SFBCs are employed, the transmission coefficient exhibits different behaviors between ASHJ and SHJ especially at low frequency, but when HWBCs are employed, the transmission coefficient displays similar smooth platforms in both heterojunctions. In low temperature limit, the quantized thermal conductance can be observed in SHJ under SFBCs regardless of the structural details. However, this quantization cannot be observed in ASHJ under SFBCs, and the thermal conductance is strongly sensitive to the transverse width ratio rather than the slant angle. With increasing the transverse width ratio, the thermal conductance in both heterojunctions gradually increases especially, and such the increasing degree is more evident at higher temperatures. A brief analysis of these results is given.
NASA Astrophysics Data System (ADS)
Schindler, Stefan; Mergheim, Julia; Zimmermann, Marco; Aurich, Jan C.; Steinmann, Paul
2017-01-01
A two-scale material modeling approach is adopted in order to determine macroscopic thermal and elastic constitutive laws and the respective parameters for metal matrix composite (MMC). Since the common homogenization framework violates the thermodynamical consistency for non-constant temperature fields, i.e., the dissipation is not conserved through the scale transition, the respective error is calculated numerically in order to prove the applicability of the homogenization method. The thermomechanical homogenization is applied to compute the macroscopic mass density, thermal expansion, elasticity, heat capacity and thermal conductivity for two specific MMCs, i.e., aluminum alloy Al2024 reinforced with 17 or 30 % silicon carbide particles. The temperature dependency of the material properties has been considered in the range from 0 to 500°C, the melting temperature of the alloy. The numerically determined material properties are validated with experimental data from the literature as far as possible.
A short history of nomograms and tables used for thermal radiation calculations
NASA Astrophysics Data System (ADS)
Stewart, Seán. M.; Johnson, R. Barry
2016-09-01
The theoretical concept of a perfect thermal radiator, the blackbody, was first introduced by the German physicist Gustav Robert Kirchhoff in 1860. By the latter half of the nineteenth century it had become the object of intense theoretical and experimental investigation. While an attempt at trying to theoretically understand the behavior of radiation emitted from a blackbody was undertaken by many eminent physicists of the day, its solution was not found until 1900 when Max Planck put forward his now famous law for thermal radiation. Today, of course, understanding blackbody behavior is vitally important to many fields including infrared systems, illumination, pyrometry, spectroscopy, astronomy, thermal engineering, cryogenics, and meteorology. Mathematically, the form Planck's law takes is rather cumbersome meaning calculations made with it before the advent of modern computers were rather tedious, dramatically slowing the process of computation. Fortunately, during those early days of the twentieth century researchers quickly realized Planck's equation, and the various functions closely related to it, readily lend themselves to being given a graphical, mechanical, or numerically tabulated form for their evaluation. The first of these computational aids to appear were tables. These arose shortly after Planck introduced his equation, were produced in the greatest number, and remained unsurpassed in their level of accuracy compared to all other aids made. It was also not long before nomograms designed to aid thermal radiation calculations appeared. Essentially a printed chart and requiring nothing more than a straightedge to use, nomograms were cheap and extremely easy to use. Facilitating instant answers to a range of quantities relating to thermal radiation, a number were produced and the inventiveness displayed in some was quite remarkable. In this paper we consider the historical development of many of the nomograms and tables developed and used by generations
Prediction of threshold pain skin temperature from thermal properties of materials in contact.
Stoll, A M; Chianta, M A; Piergallini, J R
1982-12-01
Aerospace design engineers have long sought concrete data with respect to the thermal safety of materials in contact with human skin. A series of studies on this subject has been completed and some of the results have been reported earlier. In these studies over 2,000 observations were made of pain threshold during contact with materials at elevated temperatures. Six materials were used representing the full range of thermal properties from good conductors to good insulators. Previous reports gave methods for determining the maximum permissible temperatures for any material in safe contact with bare skin for 1-5 s solely from a knowledge of its thermal properties. This report presents the comparison of the theoretical and experimental contact temperatures at pain threshold and provides a method for deriving the skin temperature productive of threshold pain from the thermal properties of any material within the range of those studies. Ratios reflecting the heat transfer coefficient associated with the materials in contact are related to their thermal properties so that the skin temperature at pain threshold may be determined from that calculated from heat transfer theory. Tabular and graphical representation of these data permits interpolation within the range of properties so that any material of known thermal conductivity, density and specific heat may be assessed with respect to its effect on the skin temperature during contact to the end point of pain. These data, in conjunction with those already reported, constitute a system for the complete assessment of the thermal aspects of practically any material suitable for construction and manufacturing applications with respect to safe contact with human skin.
Thermal and thermomechanical properties of poly(butylene succinate) nanocomposites.
Makhatha, Mamookho E; Ray, Suprakas Sinha; Hato, Joseph; Luyt, Adriaan S
2008-04-01
This article describes the thermal and thermomechanical properties of poly(butylene succinate) (PBS) and its nanocomposites. PBS nanocomposites with three different weight ratios of organically modified synthetic fluorine mica (OMSFM) have been prepared by melt-mixing in a batch mixer at 140 degrees C. The structure and morphology of the nanocomposites were characterized by X-ray diffraction (XRD) analyses and transmission electron microscopy (TEM) observations that reveal the homogeneous dispersion of the intercalated silicate layers into the PBS matrix. The thermal properties of pure PBS and the nanocomposite samples were studied by both conventional and temperature modulated differential scanning calorimetry (DSC) analyses, which show multiple melting behavior of the PBS matrix. The investigation of the thermomechanical properties was performed by dynamic mechanical analysis. Results reveal significant improvement in the storage modulus of neat PBS upon addition of OMSFM. The tensile modulus of neat PBS is also increased substantially with the addition of OMSFM, however, the strength at yield and elongation at break of neat PBS systematically decreases with the loading of OMSFM. The thermal stability of the nanocomposites compared to that of the pure polymer sample was examined under both pyrolytic and thermo-oxidative environments. It is shown that the thermal stability of PBS is increased moderately in the presence of 3 wt% of OMSFM, but there is no significant effect on further silicate loading in the oxidative environment. In the nitrogen environment, however, the thermal stability systematically decreases with increasing clay loading.
Temperature-dependent thermal properties of ex vivo liver undergoing thermal ablation.
Guntur, Sitaramanjaneya Reddy; Lee, Kang Il; Paeng, Dong-Guk; Coleman, Andrew John; Choi, Min Joo
2013-10-01
Thermotherapy uses a heat source that raises temperatures in the target tissue, and the temperature rise depends on the thermal properties of the tissue. Little is known about the temperature-dependent thermal properties of tissue, which prevents us from accurately predicting the temperature distribution of the target tissue undergoing thermotherapy. The present study reports the key thermal parameters (specific heat capacity, thermal conductivity and heat diffusivity) measured in ex vivo porcine liver while being heated from 20 ° C to 90 ° C and then naturally cooled down to 20 ° C. The study indicates that as the tissue was heated, all the thermal parameters resulted in plots with asymmetric quasi-parabolic curves with temperature, being convex downward with their minima at the turning temperature of 35-40 ° C. The largest change was observed for thermal conductivity, which decreased by 9.6% from its initial value (at 20 ° C) at the turning temperature (35 ° C) and rose by 45% at 90 ° C from its minimum (at 35 ° C). The minima were 3.567 mJ/(m(3) ∙ K) for specific heat capacity, 0.520 W/(m.K) for thermal conductivity and 0.141 mm(2)/s for thermal diffusivity. The minimum at the turning temperature was unique, and it is suggested that it be taken as a characteristic value of the thermal parameter of the tissue. On the other hand, the thermal parameters were insensitive to temperature and remained almost unchanged when the tissue cooled down, indicating that their variations with temperature were irreversible. The rate of the irreversible rise at 35 ° C was 18% in specific heat capacity, 40% in thermal conductivity and 38.3% in thermal diffusivity. The study indicates that the key thermal parameters of ex vivo porcine liver vary largely with temperature when heated, as described by asymmetric quasi-parabolic curves of the thermal parameters with temperature, and therefore, substantial influence on the temperature distribution of the tissue undergoing
Thermal Properties of Lunar Regolith Simulants
NASA Technical Reports Server (NTRS)
Street, Kenneth; Ray, Chandra; Rickman, Doug
2010-01-01
Various high temperature chemical processes have been developed to extract oxygen and metals from lunar regolith. These processes are tested using terrestrial analogues of the regolith. But all practical terrestrial analogs contain H2O and/or OH(-), the presence of which has substantial impact on important system behaviors. We have undertaken studies of lunar regolith simulants to determine the limits of the simulants to validate key components for human survivability during sustained presence on the moon. Differential Thermal Analysis (DTA) yields information on phase transitions and melting temperatures. Themo-Gravimetric Analysis (TGA) with mass spectrometric (MS) determination of evolved gas species yields chemical information on various oxygenated volatiles (water, carbon dioxide, sulfur oxides, nitrogen oxides and phosphorus oxides) and their evolution temperature profiles. The DTA and TGAMS studies included JSC-1A fine, NU-LHT-2M and its proposed feed stocks: anorthosite; dunite; HQ (high quality) glass and the norite from which HQ glass is produced. Fig 1 is a data profile for anorthosite. The DTA (Fig 1a) indicates exothermic transitions at 355 and 490 C and endothermic transitions at 970 and 1235 C. Below the 355 C transition, water (Molecular Weight, MW, 18 in Fig 1c) is lost accounting for approximately 0.1% mass loss due to water removal (Fig 1b). Just above 490 C a second type of water is lost, presumably bound in lattices of secondary minerals. Between 490 and the 970 transition other volatile oxides are lost including those of hydrogen (third water type), carbon (MW = 44), sulfur (MW = 64 and 80), nitrogen (MW 30 and 46) and possibly phosphorus (MW = 79, 95 or 142). Peaks at MW = 35 and 19 may be attributable to loss of chlorine and fluorine respectively. Negative peaks in the NO (MW = 30) and oxygen (MW = 32) MS profiles may indicate the production of NO2 (MW = 46). Because so many compounds are volatilized in this temperature range quantification
Thermal Properties of Lunar Regolith Simulants
NASA Technical Reports Server (NTRS)
Street, Kenneth; Ray, Chandra; Rickman, Doug
2010-01-01
Various high temperature chemical processes have been developed to extract oxygen and metals from lunar regolith. These processes are tested using terrestrial analogues of the regolith. But all practical terrestrial analogs contain H2O and/or OH-, the presence of which has substantial impact on important system behaviors. We have undertaken studies of lunar regolith simulants to determine the limits of the simulants to validate key components for human survivability during sustained presence on the moon. Differential Thermal Analysis (DTA) yields information on phase transitions and melting temperatures. Themo-Gravimetric Analysis (TGA) with mass spectrometric (MS) determination of evolved gas species yields chemical information on various oxygenated volatiles (water, carbon dioxide, sulfur oxides, nitrogen oxides and phosphorus oxides) and their evolution temperature profiles. The DTA and TGAMS studies included JSC-1A fine, NU-LHT-2M and its proposed feed stocks: anorthosite; dunite; HQ (high quality) glass and the norite from which HQ glass is produced. Fig 1 is a data profile for anorthosite. The DTA (Fig 1a) indicates exothermic transitions at 355 and 490 C and endothermic transitions at 970 and 1235 C. Below the 355 C transition, water (Molecular Weight, MW, 18 in Fig 1c) is lost accounting for approximately 0.1% mass loss due to water removal (Fig 1b). Just above 490 C a second type of water is lost, presumably bound in lattices of secondary minerals. Between 490 and the 970 transition other volatile oxides are lost including those of hydrogen (third water type), carbon (MW = 44), sulfur (MW = 64 and 80), nitrogen (MW 30 and 46) and possibly phosphorus (MW = 79, 95 or 142). Peaks at MW = 35 and 19 may be attributable to loss of chlorine and fluorine respectively. Negative peaks in the NO (MW = 30) and oxygen (MW = 32) MS profiles may indicate the production of NO2 (MW = 46). Because so many compounds are volatilized in this temperature range quantification of
Structural, electronic and thermal properties of Mo{sub 3}Ir superconductors
Subhashree, G. Sankar, S.; Krithiga, R.; Devi, L. Vimala
2015-06-24
Self consistent first principle calculations on superconducting material Mo{sub 3}Ir of A15 phase have been performed to understand their fundamental characteristics of the structural, electronic and thermal properties. The bulk modulus (B{sub 0}), Debye temperature (θ{sub D}), density of states (N (E{sub F})) and electronic specific heat coefficient (γ) have been computed in terms of the electronic structure results obtained by using the tight-binding linear muffin tin orbital (TB-LMTO) method based on the density functional theory (DFT) within the local density approximation (LDA). Structural, electronic and thermal properties calculated here are found to corroborate well with the experimental and theoretical results of literature.
Effect of Amorphisation on the Thermal Properties of Nanostructured Membranes
NASA Astrophysics Data System (ADS)
Termentzidis, Konstantinos; Verdier, Maxime; Lacroix, David
2017-02-01
The majority of the silicon devices contain amorphous phase and amorphous/crystalline interfaces which both considerably affect the transport of energy carriers as phonons and electrons. In this article, we investigate the impact of amorphous phases (both amorphous silicon and amorphous SiO2) of silicon nanoporous membranes on their thermal properties via molecular dynamics simulations. We show that a small fraction of amorphous phase reduces dramatically the thermal transport. One can even create nanostructured materials with subamorphous thermal conductivity, while keeping an important crystalline fraction. In general, the a-SiO2 shell around the pores reduces the thermal conductivity by a factor of five to ten compared to a-Si shell. The phonon density of states for several systems is also given to give the impact of the amorphisation on the phonon modes.
Investigation of thermal conductivity and tribological properties of nanofluids
NASA Astrophysics Data System (ADS)
Gara, Luan
Nanofluids are engineered by dispersing and stably suspending nanoparticles with typical length on the order of 1--50 nm in traditional fluids. In the past decade, scientists and engineers have made great progresses in finding that a very small amount (< 1 vol %) of dispersed nanoparticles can provide dramatic improvement in the thermal properties of the base fluids. Therefore, numerous mechanisms and models have been proposed to account for the thermal enhancement of nanofluids. The molecular dynamics (MD) simulation has become an important tool in the study of dynamic properties of liquids, molecular solutions, and macromolecules. Therefore, MD simulation is a very helpful tool to model the enhanced thermal conduction and predict thermal conductivities of nanofluids. In recent years, investigations on the tribological properties of nanofluids have also been carried out. Some papers have reported that nanofluids are effective in reducing wear and friction. The mechanisms of friction reduction and anti-wear of nanoparticles in lubricants have been reported as colloidal effect, rolling effect, protective film, and third body. The objective of this research is to study the thermal conductivity and tribological properties of nanofluids. The thermal conductivity of nanofluids was investigated theoretically through MD simulation. Nanodiamond was selected as the nanoparticle and octane as the base oil. The Large-scale Atomic-Molecular Massively Parallel Simulator (LAMMPS) was used. The effects of the particle size, shape and concentration on the thermal conductivity of nanofluids was investigated. The thermal conductivity of oil based nanofluids with nanodiamond particles was also measured experimentally using transient hot-wire method. The tribological properties of nanofluids were studied through experimental investigation using commercially available nanopowders and nanofluids. Both water based and oil based nanofluids were investigated. A Universal Micro
High pressure elasticity and thermal properties of depleted uranium
Jacobsen, M. K.; Velisavljevic, N.
2016-04-28
Studies of the phase diagram of uranium have revealed a wealth of high pressure and temperature phases. Under ambient conditions the crystal structure is well defined up to 100 gigapascals (GPa), but very little information on thermal conduction or elasticity is available over this same range. This work has applied ultrasonic interferometry to determine the elasticity, mechanical, and thermal properties of depleted uranium to 4.5 GPa. Results show general strengthening with applied load, including an overall increase in acoustic thermal conductivity. Further implications are discussed within. Lastly, this work presents the first high pressure studies of the elasticity and thermalmore » properties of depleted uranium metal and the first real-world application of a previously developed containment system for making such measurements.« less
Investigation of thermo-physical properties of thermal insulation coating
NASA Astrophysics Data System (ADS)
Kopčok, Michal; Lukovičová, Jozefa; Kačur, Jozef; Pavlendová, Gabriela
2017-07-01
This paper examines the thermal properties of thermal insulation coating applied to the building materials surfaces. The main objective is to determine the insulation coating impact on the heat flux transfer. The heat flux is modelled in terms of the heat transfer coefficient on the surface of a solid body. The thermal conductivity and heat transfer coefficient are obtained from the solution of the inverse heat conduction problem in 3D, based on the temperature measurements. The real temperature evolution is perturbed due to intrinsic properties of the measuring apparatus. We correct this situation via modelling a thermocouple function. Afterwards the determination procedure of the heat flux transfer parameters is a standard solution of the inverse problem based on the minimization of discrepancy between corrected measured data and computed temperature data.
Experimental determination of thermal properties of alluvial soil
NASA Astrophysics Data System (ADS)
Kulkarni, N. G.; Bhandarkar, U. V.; Puranik, B. P.; Rao, A. B.
2016-12-01
In the present work, thermal conductivity and specific heat of a particular type of alluvial soil used in brick making in a certain region of India (Karad, Maharashtra State) are experimentally determined for later use in the estimation of ground heat loss in clamp type kilns. These properties are determined simultaneously using the steady-state and the transient temperature data measured in the setup constructed for this purpose. Additionally, physical properties of the soil are experimentally determined for use with six models for the prediction of the thermal conductivity of soil. The predictions from the models are compared with the experimental data. A separate data fitting exercise revealed a small temperature dependence of the soil thermal conductivity on the soil mean temperature.
TOPAZ2D heat transfer code users manual and thermal property data base
Shapiro, A.B.; Edwards, A.L.
1990-05-01
TOPAZ2D is a two dimensional implicit finite element computer code for heat transfer analysis. This user's manual provides information on the structure of a TOPAZ2D input file. Also included is a material thermal property data base. This manual is supplemented with The TOPAZ2D Theoretical Manual and the TOPAZ2D Verification Manual. TOPAZ2D has been implemented on the CRAY, SUN, and VAX computers. TOPAZ2D can be used to solve for the steady state or transient temperature field on two dimensional planar or axisymmetric geometries. Material properties may be temperature dependent and either isotropic or orthotropic. A variety of time and temperature dependent boundary conditions can be specified including temperature, flux, convection, and radiation. Time or temperature dependent internal heat generation can be defined locally be element or globally by material. TOPAZ2D can solve problems of diffuse and specular band radiation in an enclosure coupled with conduction in material surrounding the enclosure. Additional features include thermally controlled reactive chemical mixtures, thermal contact resistance across an interface, bulk fluid flow, phase change, and energy balances. Thermal stresses can be calculated using the solid mechanics code NIKE2D which reads the temperature state data calculated by TOPAZ2D. A three dimensional version of the code, TOPAZ3D is available. The material thermal property data base, Chapter 4, included in this manual was originally published in 1969 by Art Edwards for use with his TRUMP finite difference heat transfer code. The format of the data has been altered to be compatible with TOPAZ2D. Bob Bailey is responsible for adding the high explosive thermal property data.
Thermal treatment and mechanical properties of aluminum-2021
NASA Technical Reports Server (NTRS)
Brennecke, M. W.
1970-01-01
Mechanical properties, after thermal treatments, are summarized for sheet and plate of copper-rich, high-strength, heat-treatable aluminum-2021. The alloy is quench sensitive, quench rate and variations in aging affect corrosion behavior. Aging effects on yield strength, tensile strength, and elongation of sheet and plate are compared.
Phase diagram and thermal properties of strong-interaction matter
Gao, Fei; Chen, Jing; Liu, Yu-Xin; Qin, Si-Xue; Roberts, Craig D.; Schmidt, Sebastian M.
2016-05-20
We introduce a novel method for computing the (μ, T)-dependent pressure in continuum QCD, from which we obtain a complex phase diagram and predictions for thermal properties of the dressed-quark component of the system, providing the in-medium behavior of the related trace anomaly, speed of sound, latent heat, and heat capacity.
Densification and Thermal Properties of Zirconium Diboride Based Ceramics
2012-01-01
density as a function of time of attrition milled ZrB2 during spark plasma sintering to a final temperature of 1900°C...as a function of temperature during hot pressing (A) and spark plasma sintering (B) of ZrB2...effects of densification method ( sintering , hot pressing, or spark plasma sintering ) on the microstructure, mechanical, and thermal properties were
Thermal and mechanical properties of whole and milled pulses
USDA-ARS?s Scientific Manuscript database
Pulses are protein- and fiber-rich crops, and are consumed as staples in many parts of the world. As the global food demand increases pulse milling and processing technologies evolve. Pulses are primarily consumed whole, however fundamental physical, thermal and mechanical properties of pulse flours...
Bark thermal properties of selected central hardwood species
Gretel E. Hengst; Jeffery O. Dawson
1993-01-01
Some physical, thermal, and chemical properties of bark of eleven tree species native to the central hardwood region were measured to determine their potential to protect the vascular cambium from damage by fire. The relationship between dbh and bark thickness for each of sixteen species was determined. For purposes of monitoring seasonal trends, two species (Quercus...
Mechanical, thermal, and electrical properties of selected polymers
NASA Astrophysics Data System (ADS)
Reed, R. P.; Schramm, R. E.; Clark, A. F.
An extensive compilation has been completed on the mechanical, thermal, and electrical properties of six commercially available polymers. These data are discussed and summarized here as a function of temperature, radiation, and frequency. A brief description and characterization of each polymer is included.
Phase diagram and thermal properties of strong-interaction matter
NASA Astrophysics Data System (ADS)
Gao, Fei; Chen, Jing; Liu, Yu-Xin; Qin, Si-Xue; Roberts, Craig D.; Schmidt, Sebastian M.
2016-05-01
We introduce a novel method for computing the (μ , T )-dependent pressure in continuum QCD, from which we obtain a complex phase diagram and predictions for thermal properties of the dressed-quark component of the system, providing the in-medium behavior of the related trace anomaly, speed of sound, latent heat, and heat capacity.
Oats Protein Isolate: Thermal, Rheological, Surface & Functional Properties
USDA-ARS?s Scientific Manuscript database
Oat protein isolate (OPI) was extracted in 0.015 N NaOH in a 10:1 ratio solvent:flour and was precipitated by adjusting the pH to 4.5 and freeze-dried. The thermal properties of OPI were determined using Differential Scanning Calorimetry (DSC). OPI with 6% moisture content exhibited a glass transi...
2D calculations of the thermal effects due to femtosecond laser-metal interaction
NASA Astrophysics Data System (ADS)
Valette, S.; Le Harzic, R.; Huot, N.; Audouard, E.; Fortunier, R.
2005-07-01
Experimental results previously published have shown that the radial heat affected zone (HAZ) for a 500 nm thick Al sample in the femtosecond case is less than 2 μm [Appl. Phys. Lett. 80 (2002) 3886]. The spread of radial thermal effects for femtosecond pulses is calculated, by developing a two-dimensional version of the two temperature model (TTM). The case of an axi-symmetrical geometry is simulated by a finite element technique. A physical metallurgy approach is used to define and to estimate the radial HAZ width from the calculations. The evolution of the temperature as a function of time is studied, leading to a radial HAZ width of 220 nm for 500 nm thick Al samples. Similar calculations in the nanosecond regime are also performed and compared to the femtosecond case.
Wang, Hsin; Sluder, Scott; Storey, John Morse
2009-01-01
Exhaust gas recirculation (EGR) cooler fouling has become a significant issue for compliance with NOX emissions standards. This paper reports results of a study of fundamental aspects of EGR cooler fouling. An apparatus and procedure were developed to allow surrogate EGR cooler tubes to be exposed to diesel engine exhaust under controlled conditions. The resulting fouled tubes were removed and analyzed. Volatile and non-volatile deposit mass was measured for each tube. Thermal diffusivity of the deposited soot cake was measured by milling a window into the tube and using the Xenon flash lamp method. The heat capacity of the deposit was measured at temperatures up to 430 C and was slightly higher than graphite, presumably due to the presence of hydrocarbons. These measurements were combined to allow calculation of the deposit thermal conductivity, which was determined to be 0.041 W/mK, only ~1.5 times that of air and much lower than the 304 stainless steel tube (14.7 W/mK). The main determinant of the deposit thermal conductivity is density, which was measured to be just 2% that of the density of the primary soot particles (or 98% porous). The deposit layer thermal resistance was calculated and compared with estimates of the thermal resistance calculated from gas temperature data during the experiment. The deposit properties were also used to further analyze the temperature data collected during the experiment.
Foldable dome climate measurements and thermal properties
NASA Astrophysics Data System (ADS)
Sliepen, Guus; Jägers, Aswin P. L.; Hammerschlag, Robert H.; Bettonvil, Felix C. M.
2010-07-01
As part of a larger project for measuring various aspects of foldable domes in the context of EST and with support of the Dutch Technology Foundation STW, we have collected over a year of continuous temperature and humidity measurements, both inside and outside the domes of the Dutch Open Telescope (DOT) on La Palma5 and the GREGOR telescope on Tenerife.6 In addition, we have measured the wind field around each dome. Although the structure of both domes is similar, the DOT dome has a single layer of cloth, and is situated on top of an open tower. In contrast, the GREGOR dome has a double layer of cloth, and is situated on top of a tower-shaped building. These differences result in large differences in temperature and humidity insulation when the dome is closed. We will present the changes in temperature and humidity one can expect for each dome within one day, and the statistics for the variations throughout a year. In addition, we will show that the main advantage of a foldable dome is the near instantaneous equilibration of the air inside the volume originally enclosed by the dome and that of the environment outside the dome. This property allows one to operate a telescope without needing expensive air conditioning and dome skin temperature control in order to limit dome and shell seeing effects. The measurements give also information about the weather fluctuations at the sites of the domes. It was observed that on small time scales the temperature fluctuations are significantly greater during the day than during the night.
Optical and thermal properties of nasal septal cartilage.
Youn, J I; Telenkov, S A; Kim, E; Bhavaraju, N C; Wong, B J; Valvano, J W; Milner, T E
2000-01-01
The aim of the study was to measure the spectral dependence of optical absorption and reduced scattering coefficients and thermal conductivity and diffusivity of porcine nasal septal cartilage. Values of optical and thermal properties determined in this study may aid in determining laser dosimetry and allow selection of an optical source wavelength for noninvasive diagnostics for laser-assisted reshaping of cartilage. The diffuse reflectance and transmittance of ex vivo porcine nasal septal cartilage were measured in the 400- to 1,400-nm spectral range by using a spectrophotometer. The reflectance and transmittance data were analyzed by using an inverse adding-doubling algorithm to obtain the absorption (mu(a)) and reduced scattering (mu(a)') coefficients. A multichannel thermal probe controller system and infrared imaging radiometer methods were applied to measure the thermal properties of cartilage. The multichannel thermal probe controller system was used as an invasive technique to measure thermal conductivity and diffusivity of cartilage at three temperatures (27, 37, 50 degrees C). An infrared imaging radiometer was used as a noninvasive method to measure the thermal diffusivity of cartilage by using a CO(2) laser source (lambda = 10.6 microm) and an infrared focal plane array (IR-FPA) camera. The optical absorption peaks at 980 nm and 1,180 nm in cartilage were observed and corresponded to known absorption bands of water. The determined reduced scattering coefficient gradually decreased at longer wavelengths. The thermal conductivity values of cartilage measured by using an invasive probe at 27, 37, and 50 degrees C were 4.78, 5.18, and 5.76 mW/cm degrees C, respectively. The corresponding thermal diffusivity values were 1.28, 1.31, and 1.40x 10(-3) cm(2)/sec. Because no statistically significant difference in thermal diffusivity values with increasing temperature is found, the average thermal diffusivity is 1.32 x 10(-3) cm(2)/sec. The numerical estimate
NASA Astrophysics Data System (ADS)
Holmes, Jesse Curtis
Nuclear data libraries provide fundamental reaction information required by nuclear system simulation codes. The inclusion of data covariances in these libraries allows the user to assess uncertainties in system response parameters as a function of uncertainties in the nuclear data. Formats and procedures are currently established for representing covariances for various types of reaction data in ENDF libraries. This covariance data is typically generated utilizing experimental measurements and empirical models, consistent with the method of parent data production. However, ENDF File 7 thermal neutron scattering library data is, by convention, produced theoretically through fundamental scattering physics model calculations. Currently, there is no published covariance data for ENDF File 7 thermal libraries. Furthermore, no accepted methodology exists for quantifying or representing uncertainty information associated with this thermal library data. The quality of thermal neutron inelastic scattering cross section data can be of high importance in reactor analysis and criticality safety applications. These cross sections depend on the material's structure and dynamics. The double-differential scattering law, S(alpha, beta), tabulated in ENDF File 7 libraries contains this information. For crystalline solids, S(alpha, beta) is primarily a function of the material's phonon density of states (DOS). Published ENDF File 7 libraries are commonly produced by calculation and processing codes, such as the LEAPR module of NJOY, which utilize the phonon DOS as the fundamental input for inelastic scattering calculations to directly output an S(alpha, beta) matrix. To determine covariances for the S(alpha, beta) data generated by this process, information about uncertainties in the DOS is required. The phonon DOS may be viewed as a probability density function of atomic vibrational energy states that exist in a material. Probable variation in the shape of this spectrum may be
Thermal transport in van der Waals solids from first-principles calculations
NASA Astrophysics Data System (ADS)
Lindroth, Daniel O.; Erhart, Paul
2016-09-01
The lattice thermal expansion and conductivity in bulk Mo and W-based transition metal dichalcogenides are investigated by means of density functional and Boltzmann transport theory calculations. To this end, a recent van der Waals density functional (vdW-DF-CX) is employed, which is shown to yield excellent agreement with reference data for the structural parameters. The calculated in-plane thermal conductivity compares well with experimental room-temperature values, when phonon-phonon and isotopic scattering are included. To explain the behavior over the entire available temperature range one must, however, include additional (temperature independent) scattering mechanisms that limit the mean free path. Generally, the primary heat carrying modes have mean free paths of 1 μ m or more, which makes these materials very susceptible to structural defects. The conductivity of Mo- and W-based transition metal dichalcogenides is primarily determined by the chalcogenide species and increases in the order Te-Se-S. While for the tellurides and selenides the transition metal element has a negligible effect, the conductivity of WS2 is notably higher than for MoS2, which may be traced to the much larger phonon band gap of the former. Overall, the present study provides a consistent set of thermal conductivities that reveal chemical trends and constitute the basis for future investigations of van der Waals solids.
Calculation of thermal inertia from day-night measurements separated by days or weeks
NASA Technical Reports Server (NTRS)
Kahle, A. B.; Alley, R. E.
1985-01-01
The calculation of the thermal inertia of an area from remotely sensed data involves the measurement of the surface albedo and the determination of the diurnal temperature range of the surface in image format. The temperature-range image is calculated from surface thermal radiance measured as near as possible to the time of maximum surface temperature and (predawn) surface minimum temperature. Ordinarily, both surface-temperature images are measured within the same 12-hour period. If this is impossible, then the measurement of the predawn surface radiance within a 36-hour period has been considered to be adequate, although less satisfactory. The problems arising in connection with the impossibility to conduct measurements within the same 12-hour period are studied, and suggestions are made for cases in which only relative thermal inertia across an area is required. In such cases investigators should consider using the best day-night temperature pairs available, even if not acquired within a 12 to 36 hour period.
Calculation of thermal inertia from day-night measurements separated by days or weeks
NASA Technical Reports Server (NTRS)
Kahle, A. B.; Alley, R. E.
1985-01-01
The calculation of the thermal inertia of an area from remotely sensed data involves the measurement of the surface albedo and the determination of the diurnal temperature range of the surface in image format. The temperature-range image is calculated from surface thermal radiance measured as near as possible to the time of maximum surface temperature and (predawn) surface minimum temperature. Ordinarily, both surface-temperature images are measured within the same 12-hour period. If this is impossible, then the measurement of the predawn surface radiance within a 36-hour period has been considered to be adequate, although less satisfactory. The problems arising in connection with the impossibility to conduct measurements within the same 12-hour period are studied, and suggestions are made for cases in which only relative thermal inertia across an area is required. In such cases investigators should consider using the best day-night temperature pairs available, even if not acquired within a 12 to 36 hour period.
Thermal Properties of Oxides With Magnetoplumbite Structure for Advanced Thermal Barrier Coatings
NASA Technical Reports Server (NTRS)
Bansal, Narottam P.; Zhu, Dongming; Eslamloo-Grami, Maryam
2007-01-01
Oxides having magnetoplumbite structure are promising candidate materials for applications as high temperature thermal barrier coatings because of their high thermal stability, high thermal expansion, and low thermal conductivity. In this study, powders of LaMgAl11O19, GdMgAl11O19, SmMgAl11O19, and Gd0.7Yb0.3MgAl11O19 magnetoplumbite oxides were synthesized by citric acid sol-gel method and hot pressed into disk specimens. The thermal expansion coefficients (CTE) of these oxide materials were measured from room temperature to 1500 C. The average CTE value was found to be approx.9.6x10(exp -6)/C. Thermal conductivity of these magnetoplumbite-based oxide materials was also evaluated using steady-state laser heat flux test method. The effects of doping on thermal properties were also examined. Thermal conductivity of the doped Gd0.7Yb0.3MgAl11O19 composition was found to be lower than that of the undoped GdMgAl11O19. In contrast, thermal expansion coefficient was found to be independent of the oxide composition and appears to be controlled by the magnetoplumbite crystal structure. Thermal conductivity testing of LaMgAl11O19 and LaMnAl11O19 magnetoplumbite oxide coatings plasma sprayed on NiCrAlY/Rene N5 superalloy substrates indicated resistance of these coatings to sintering even at temperatures as high as 1600 C.
Thermal properties measurement of dry bulk materials with a cylindrical three layers device
NASA Astrophysics Data System (ADS)
Jannot, Y.; Degiovanni, A.
2013-09-01
This paper presents a new method dedicated to thermal properties (conductivity and diffusivity) measurement of dry bulk materials including powders. The cylindrical three layers experimental device (brass/bulk material/stainless steel) and the principle of the measurement method based on a crenel thermal excitation are presented. The one-dimensional modeling of the system is used for a sensitivity analysis and to calculate the standard deviation of the estimation error. Experimental measurements are carried out on three bulk materials: glass beads, cork granules, and expanded polystyrene beads. The estimated thermal properties are compared with the values obtained by other measurement methods. Results are in good agreement with theoretical predictions: both thermal conductivity and diffusivity can be estimated with a good accuracy for low density material like cork granules or expanded polystyrene beads since only thermal diffusivity can be estimated for heavier materials like glass beads. It is finally shown that this method like all transient methods is not suited to the thermal characterization of wet bulk materials.
Designing energy dissipation properties via thermal spray coatings
Brake, Matthew R. W.; Hall, Aaron Christopher; Madison, Jonathan D.
2016-12-14
The coefficient of restitution is a measure of energy dissipation in a system across impact events. Often, the dissipative qualities of a pair of impacting components are neglected during the design phase. This research looks at the effect of applying a thin layer of metallic coating, using thermal spray technologies, to significantly alter the dissipative properties of a system. We studied the dissipative properties across multiple impacts in order to assess the effects of work hardening, the change in microstructure, and the change in surface topography. The results of the experiments indicate that any work hardening-like effects are likely attributable to the crushing of asperities, and the permanent changes in the dissipative properties of the system, as measured by the coefficient of restitution, are attributable to the microstructure formed by the thermal spray coating. Furthermore, the microstructure appears to be robust across impact events of moderate energy levels, exhibiting negligible changes across multiple impact events.
Thermal properties of carbon black aqueous nanofluids for solar absorption.
Han, Dongxiao; Meng, Zhaoguo; Wu, Daxiong; Zhang, Canying; Zhu, Haitao
2011-07-18
In this article, carbon black nanofluids were prepared by dispersing the pretreated carbon black powder into distilled water. The size and morphology of the nanoparticles were explored. The photothermal properties, optical properties, rheological behaviors, and thermal conductivities of the nanofluids were also investigated. The results showed that the nanofluids of high-volume fraction had better photothermal properties. Both carbon black powder and nanofluids had good absorption in the whole wavelength ranging from 200 to 2,500 nm. The nanofluids exhibited a shear thinning behavior. The shear viscosity increased with the increasing volume fraction and decreased with the increasing temperature at the same shear rate. The thermal conductivity of carbon black nanofluids increased with the increase of volume fraction and temperature. Carbon black nanofluids had good absorption ability of solar energy and can effectively enhance the solar absorption efficiency.
Thermal properties of carbon black aqueous nanofluids for solar absorption
2011-01-01
In this article, carbon black nanofluids were prepared by dispersing the pretreated carbon black powder into distilled water. The size and morphology of the nanoparticles were explored. The photothermal properties, optical properties, rheological behaviors, and thermal conductivities of the nanofluids were also investigated. The results showed that the nanofluids of high-volume fraction had better photothermal properties. Both carbon black powder and nanofluids had good absorption in the whole wavelength ranging from 200 to 2,500 nm. The nanofluids exhibited a shear thinning behavior. The shear viscosity increased with the increasing volume fraction and decreased with the increasing temperature at the same shear rate. The thermal conductivity of carbon black nanofluids increased with the increase of volume fraction and temperature. Carbon black nanofluids had good absorption ability of solar energy and can effectively enhance the solar absorption efficiency. PMID:21767359
Thermal properties of carbon black aqueous nanofluids for solar absorption
NASA Astrophysics Data System (ADS)
Han, Dongxiao; Meng, Zhaoguo; Wu, Daxiong; Zhang, Canying; Zhu, Haitao
2011-07-01
In this article, carbon black nanofluids were prepared by dispersing the pretreated carbon black powder into distilled water. The size and morphology of the nanoparticles were explored. The photothermal properties, optical properties, rheological behaviors, and thermal conductivities of the nanofluids were also investigated. The results showed that the nanofluids of high-volume fraction had better photothermal properties. Both carbon black powder and nanofluids had good absorption in the whole wavelength ranging from 200 to 2,500 nm. The nanofluids exhibited a shear thinning behavior. The shear viscosity increased with the increasing volume fraction and decreased with the increasing temperature at the same shear rate. The thermal conductivity of carbon black nanofluids increased with the increase of volume fraction and temperature. Carbon black nanofluids had good absorption ability of solar energy and can effectively enhance the solar absorption efficiency.
Electronic and Thermal Properties of Graphene and Carbon Structures
NASA Astrophysics Data System (ADS)
Anthony, Gilmore; Khatun, Mahfuza
2011-10-01
We will present the general properties of carbon structures. The research involves the study of carbon structures: Graphene, Graphene nanoribbons (GNRs), and Carbon Nanotubes (CNTs). A review of electrical and thermal conduction phenomena of the structures will be discussed. Particularly carbon nanoribbons and CNTs have many interesting physical properties, and have the potential for device applications. Our research interests include the study of electronic structures, electrical and thermal transport properties of the carbon structures. Results are produced analytically as well as by simulation. The numerical simulations are conducted using various tools such as Visual Molecular Dynamics (VMD), Large Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS), NanoHub at Purdue University and the Beowulf Cluster at Ball State University.
NASA Astrophysics Data System (ADS)
Bohac, Vlastimil; Gustavsson, Mattias K.; Kubicar, Ludovit; Gustafsson, Silas E.
2000-06-01
The objective of this work is to improve measurements of transport properties using the hot disk thermal constants analyzer. The principle of this method is based on the transient heating of a plane double spiral sandwiched between two pieces of the investigated material. From the temperature increase of the heat source, it is possible to derive both the thermal conductivity and the thermal diffusivity from one single transient recording, provided the total time of the measurement is chosen within a correct time window defined by the theory and the experimental situation. Based on a theory of sensitivity coefficients, it is demonstrated how the experimental time window should be selected under different experimental situations. In addition to the theoretical work, measurements on two different materials: poly(methylmethacrylate) and Stainless Steel A 310, with thermal conductivity of 0.2 and 14 W/mK, respectively, have been performed and analyzed based on the developed theory.
NASA Astrophysics Data System (ADS)
Huang, Feng; Jiang, Nan; Wang, Yuefeng; Dong, Wei; Niu, Yanxiong
2008-03-01
Laser diode (LD) pumped slab laser, as an important high average power solid-state laser, is a promising laser source in military and industrial fields. The different laser diode pumping structures lead to different thermal effect in the slab gain medium. The thermal and stress analysis of slab laser with different pumping structure are performed by finite element analysis (FEA) with the software program ANSYS. The calculation results show that the face pumped and cooled laser results in a near one-dimension temperature distribution and eliminates thermal stress induced depolarization. But the structure is low pump efficiency due to the small thickness of slabs and the requirement to cool and pump through the same faces. End-pumped slab laser is high pump efficiency and excellent mode match, but its pumping arrangement is fairly complicated. The edge-pumped face-cooling slab laser's pump efficiency is better than face-pumping, and its pumping structure is simpler than end-pumped laser, but the tensile stress on surfaces may initiate failure of the gain medium so it is important to design so that the stress is well below the stress fracture limit. The comparison of the thermal effects with different pumping structure shows that, the edge-pumped slab laser has engineering advantages in high power slab laser's application. Furthermore, the end-pumped slab laser tends to get the best beam quality, so it is fit for the application which has a special requirement on laser beam quality.
Thermophysical and Thermomechanical Properties of Thermal Barrier Coating Systems
NASA Technical Reports Server (NTRS)
Zhu, Dongming; Miller, Robert A.
2000-01-01
Thermal barrier coatings have been developed for advanced gas turbine and diesel engine applications to improve engine reliability and fuel efficiency. However, the issue of coating durability under high temperature cyclic conditions is still of major concern. The coating failure is closely related to thermal stresses and oxidation in the coating systems. Coating shrinkage cracking resulting from ceramic sintering and creep at high temperatures can further accelerate the coating failure process. The purpose of this paper is to address critical issues such as ceramic sintering and creep, thermal fatigue and their relevance to coating life prediction. Novel test approaches have been established to obtain critical thermophysical and thermomechanical properties of the coating systems under near-realistic temperature and stress gradients encountered in advanced engine systems. Emphasis is placed on the dynamic changes of the coating thermal conductivity and elastic modulus, fatigue and creep interactions, and resulting failure mechanisms during the simulated engine tests. Detailed experimental and modeling results describing processes occurring in the thermal barrier coating systems provide a framework for developing strategies to manage ceramic coating architecture, microstructure and properties.
Optical characterization of thermal properties of biological tissue
NASA Astrophysics Data System (ADS)
Gutierrez-Arroyo, A.; Sánchez Pérez, C.; Alemán-García, N.; Piña-Barba, C.
2013-11-01
In this work we utilize heat conduction measurements trough the photothermal beam deflection technique to characterize thermal properties of biological tissue. We design a heat flux sensor based on the phenomenon of photothermal laser beam deflection within a thermo-optic slab (acrylic), where the deflection is quantified by an optical fiber angle sensor. We analytically model the heat flux sensor response based on heat wave propagation theory that well agree with experimental data. We present heat conduction measurements on different tissues applying a heat pulse. Hence we obtain the thermal effusivity coefficient of bovine tendon and chicken liver and heart. It has been shown that thermal conduction depends on the tissués chemical composition as well on their structural arrangements, so any modification in tissue will affect on heat conduction rendering this method potentially useful as an auxiliary in biomedical studies. Nowadays there are several thermal effusivity and diffusivity measurement techniques with classic calorimetry (using thermistors) for research and industrial applications. However there are only few integrated optical devices already proposed, turning this optical technique in an innovative and alternative sensing system for thermal properties characterization.
Characterization of thermal properties of municipal solid waste landfills.
Faitli, József; Magyar, Tamás; Erdélyi, Attila; Murányi, Attila
2015-02-01
Municipal waste landfills represent not only a source of landfill gases, but a source of thermal energy as well. The heat in landfills is generated by physical, chemical and microbiological processes. The goal of our study was to characterize the thermal properties of municipal solid waste (MSW) samples of the given landfill. A new apparatus was designed and constructed to measure heat flow. A systematic test series of 17 discrete measurements was carried out with municipal waste samples of 1.0-1.7 m(3). The thermal conductivity, heat diffusivity and specific heat capacity of the samples were determined. Analysing the results of the sampling and our experiments it was realized that the theoretical fundaments should be clarified. Two theories were developed for the serial and for the parallel heat flow in three phase disperse systems. The serial and parallel models resulted in different theoretical estimations. The measured thermal conductivity and heat diffusivity were better characterized by the parallel heat flow estimations. The results show that heat can flow parallel in solid, liquid and gas phases. Characterization of thermal properties serves to establish the fundament of heat extraction from municipal waste landfills. Copyright © 2014 Elsevier Ltd. All rights reserved.
Dependence of Optical and Thermal Properties on Substrate of Solar Thermal Collectors
NASA Astrophysics Data System (ADS)
Kafle, Bhim; Lamichhane, Rishi; Basnet, Sandesh
2017-07-01
The optical and thermal properties of the black crome based Solar thermal collectors (STCs) deposited on three different substrates (aluminium, Al; galvanized iron, GI; and stainless steel, SS) were investigated. The devices were prepared by two different methods: electro-deposition and dip coating and were heat treated at 300 °C. Each STC’s performance was evaluated by measuring optical and thermal properties: Optical properties were measured with UV-Vis, Raman and IR Spectroscopy. For later measurements, all the STC samples were kept inside an air tight glass box and are exposed to the solar radiation over all the sunshine hours in summer (from 7:30 am - 5 pm, August). Then, the instantaneous temperature was recorded, simultaneously, of all samples with IR-temperature sensor. Among all the samples, the STC with black chrome coated on Al substrate showed the highest temperature, reaching the maximum value of ca. 95 °C at about 1 pm. Moreover, the STC samples fabricated by dip coating found to possess as equal optical and thermal properties as samples prepared by electro-deposition.
Ab initio calculation of the thermodynamic properties of InSb under intense laser irradiation
Feng, ShiQuan; Cheng, XinLu; Zhao, JianLing; Zhang, Hong
2013-07-28
In this paper, phonon spectra of InSb at different electronic temperatures are presented. Based on the phonon dispersion relationship, we further perform a theoretical investigation of the thermodynamic properties of InSb under intense laser irradiation. The phonon entropy, phonon heat capacity, and phonon contribution to Helmholtz free energy and internal energy of InSb are calculated as functions of temperature at different electronic temperatures. The abrupt change in the phonon entropy- temperature curve from T{sub e} = 0.75 to 1.0 eV provides an indication of InSb undergoing a phase transition from solid to liquid. It can be considered as a collateral evidence of non-thermal melting for InSb under intense electronic excitation effect.
Fabrication, characterization, and thermal property evaluation of silver nanofluids.
Noroozi, Monir; Radiman, Shahidan; Zakaria, Azmi; Soltaninejad, Sepideh
2014-01-01
Silver nanoparticles were successfully prepared in two different solvents using a microwave heating technique, with various irradiation times. The silver nanoparticles were dispersed in polar liquids (distilled water and ethylene glycol) without any other reducing agent, in the presence of the stabilizer polyvinylpyrrolidone (PVP). The optical properties, thermal properties, and morphology of the synthesized silver particles were characterized using ultraviolet-visible spectroscopy, photopyroelectric technique, and transmission electron microscopy. It was found that for the both solvents, the effect of microwave irradiation was mainly on the particles distribution, rather than the size, which enabled to make stable and homogeneous silver nanofluids. The individual spherical nanostructure of self-assembled nanoparticles has been formed during microwave irradiation. Ethylene glycol solution, due to its special properties, such as high dielectric loss, high molecular weight, and high boiling point, can serve as a good solvent for microwave heating and is found to be a more suitable medium than the distilled water. A photopyroelectric technique was carried out to measure thermal diffusivity of the samples. The precision and accuracy of this technique was established by comparing the measured thermal diffusivity of the distilled water and ethylene glycol with values reported in the literature. The thermal diffusivity ratio of the silver nanofluids increased up to 1.15 and 1.25 for distilled water and ethylene glycol, respectively.
Fabrication, characterization, and thermal property evaluation of silver nanofluids
2014-01-01
Silver nanoparticles were successfully prepared in two different solvents using a microwave heating technique, with various irradiation times. The silver nanoparticles were dispersed in polar liquids (distilled water and ethylene glycol) without any other reducing agent, in the presence of the stabilizer polyvinylpyrrolidone (PVP). The optical properties, thermal properties, and morphology of the synthesized silver particles were characterized using ultraviolet-visible spectroscopy, photopyroelectric technique, and transmission electron microscopy. It was found that for the both solvents, the effect of microwave irradiation was mainly on the particles distribution, rather than the size, which enabled to make stable and homogeneous silver nanofluids. The individual spherical nanostructure of self-assembled nanoparticles has been formed during microwave irradiation. Ethylene glycol solution, due to its special properties, such as high dielectric loss, high molecular weight, and high boiling point, can serve as a good solvent for microwave heating and is found to be a more suitable medium than the distilled water. A photopyroelectric technique was carried out to measure thermal diffusivity of the samples. The precision and accuracy of this technique was established by comparing the measured thermal diffusivity of the distilled water and ethylene glycol with values reported in the literature. The thermal diffusivity ratio of the silver nanofluids increased up to 1.15 and 1.25 for distilled water and ethylene glycol, respectively. PMID:25489293
Fabrication of a nanostructure thermal property measurement platform.
Harris, C T; Martinez, J A; Shaner, E A; Huang, J Y; Swartzentruber, B S; Sullivan, J P; Chen, G
2011-07-08
Measurements of the electrical and thermal transport properties of one-dimensional nanostructures (e.g. nanotubes and nanowires) are typically obtained without detailed knowledge of the specimen's atomic-scale structure or defects. To address this deficiency, we have developed a microfabricated, chip-based characterization platform that enables both transmission electron microscopy (TEM) of the atomic structure and defects as well as measurement of the thermal transport properties of individual nanostructures. The platform features a suspended heater line that physically contacts the center of a suspended nanostructure/nanowire that was placed using in situ scanning electron microscope nanomanipulators. Suspension of the nanostructure across a through-hole enables TEM characterization of the atomic and defect structure (dislocations, stacking faults, etc) of the test sample. This paper explains, in detail, the processing steps involved in creating this thermal property measurement platform. As a model study, we report the use of this platform to measure the thermal conductivity and defect structure of a GaN nanowire.
NASA Astrophysics Data System (ADS)
Cartoixà, Xavier; Dettori, Riccardo; Melis, Claudio; Colombo, Luciano; Rurali, Riccardo
2016-07-01
We study thermal transport in porous Si nanowires (SiNWs) by means of approach-to-equilibrium molecular dynamics simulations. We show that the presence of pores greatly reduces the thermal conductivity, κ, of the SiNWs as long mean free path phonons are suppressed. We address explicitly the dependence of κ on different features of the pore topology—such as the porosity and the pore diameter—and on the nanowire (NW) geometry—diameter and length. We use the results of the molecular dynamics calculations to tune an effective model, which is capable of capturing the dependence of κ on porosity and NW diameter. The model illustrates the failure of Matthiessen's rule to describe the coupling between boundary and pore scattering, which we account for by the inclusion of an additional empirical term.
Pyroelectric and Thermal Properties of PZT-PVA Nanocomposites
NASA Astrophysics Data System (ADS)
Uma, S.; Philip, J.
2011-07-01
PZT-PVA nanocomposites were prepared by encapsulating PZT nanoparticles in polyvinyl alcohol (PVA) hydrogel. The XRD patterns confirmed the presence of PZT in the composite matrix. The pyroelectric coefficients and thermal transport properties were determined following sample heating and photothermal techniques. The results reveal that the pyroelectric coefficient and thermal parameters of the nanocomposites can be tuned by varying the PZT loading in the polymer matrix. The work offers the possibility of developing pyroelectric materials with high pyroelectric figure of merit, retaining the flexibility of the polymer matrix.
Mechanisms of Laser-Tissue Interaction: II. Tissue Thermal Properties
Ansari, Mohammad Ali; Erfanzadeh, Mohsen; Mohajerani, Ezeddin
2013-01-01
Laser-tissue interaction is of great interest due to its significant application in biomedical optics in both diagnostic and treatment purposes. Major aspects of the laser-tissue interaction which has to be considered in biomedical studies are the thermal properties of the tissue and the thermal changes caused by the interaction of light and tissue. In this review paper the effects of light on the tissue at different temperatures are discussed. Then, due to the noticeable importance of studying the heat transfer quantitatively, the equations governing this phenomenon are presented. Finally a method of medical diagnosis called thermography and some of its applications are explained. PMID:25606316
Burkes, Douglas; Casella, Amanda J.; Gardner, Levi D.; Casella, Andrew M.; Huber, Tanja K.; Breitkreutz, Harald
2015-02-11
The Office of Material Management and Minimization Fuel Thermo-physical Characterization Project at Pacific Northwest National Laboratory (PNNL) is tasked with using PNNL facilities and processes to receive irradiated low enriched uranium-molybdenum fuel plate samples and perform analyses in support of the Office of Material Management and Minimization Reactor Conversion Program. This work is in support of the Fuel Development Pillar that is managed by Idaho National Laboratory. A key portion of the scope associated with this project was to measure the thermal properties of fuel segments harvested from plates that were irradiated in the Advanced Test Reactor. Thermal diffusivity of samples prepared from the fuel segments was measured using laser flash analysis. Two models, one developed by PNNL and the other developed by the Technische Universität München (TUM), were evaluated to extract the thermal diffusivity of the uranium-molybdenum alloy from measurements made on the irradiated, layered composites. The experimental data of the “TC” irradiated fuel segment was evaluated using both models considering a three-layer and five-layer system. Both models are in acceptable agreement with one another and indicate that the zirconium diffusion barrier has a minimal impact on the overall thermal diffusivity of the monolithic U-Mo fuel.
Calculation of Thermally-Induced Displacements in Spherically Domed Ion Engine Grids
NASA Technical Reports Server (NTRS)
Soulas, George C.
2006-01-01
An analytical method for predicting the thermally-induced normal and tangential displacements of spherically domed ion optics grids under an axisymmetric thermal loading is presented. A fixed edge support that could be thermally expanded is used for this analysis. Equations for the displacements both normal and tangential to the surface of the spherical shell are derived. A simplified equation for the displacement at the center of the spherical dome is also derived. The effects of plate perforation on displacements and stresses are determined by modeling the perforated plate as an equivalent solid plate with modified, or effective, material properties. Analytical model results are compared to the results from a finite element model. For the solid shell, comparisons showed that the analytical model produces results that closely match the finite element model results. The simplified equation for the normal displacement of the spherical dome center is also found to accurately predict this displacement. For the perforated shells, the analytical solution and simplified equation produce accurate results for materials with low thermal expansion coefficients.
Local thermal properties of the surface of Vesta
NASA Astrophysics Data System (ADS)
Capria, M. T.; Tosi, F.; Capaccioni, F.; De Sanctis, M. C.; Palomba, E.; Ammannito, E.; Carraro, F.; Fonte, S.; Titus, T. N.; Combe, J.-P.; Toplis, M.; Sunshine, J.; Fulchignoni, M.; Russel, C. T.; Raymond, C. A.
2012-04-01
Temperature information has been obtained from the Dawn/VIR (Visible InfraRed imaging spectrometer) spectra acquired during the Vesta campaign. When combined with a thermophysical model, these temperatures can be used to derive surface thermal properties. Thermal properties are sensitive to several physical characteristics of the surface that are not all spatially resolved. Thus, the derivation of surface temperatures and thermal inertia can lead to the characterization of surface and sub-surface properties of Vesta and the determination of regolith properties. The model we are using solves the heat conduction equation and provide the temperature as a function of thermal conductivity, albedo, emissivity, density and specific heat. The model is applied to the actual shape of Vesta: for any given location, characterized by a well-defined illumination condition and a given UTC time to compute the thermal inertia that results in model temperatures providing a best-fit to surface temperatures as retrieved by VIR. The model has been already applied to the first Vesta full-disk data to derive the global average thermal inertia of Vesta. The values obtained are typical of fine-grained, unconsolidated materials (i.e. dust) and suggest a surface in which a dust layer is wide-spread on coarser regolith. The model is now being applied on small regions of the surface of Vesta. Specific regions are selected because they are interesting for some reason or appear different from the surroundings, such as, for example, dark and bright spots and other peculiar features. Given a location, the thermophysical code is applied until the obtained temperatures are matching (best-fit techniques are used) the temperatures derived from the VIR spectra. The thermal inertia, thermal conductivity, albedo and roughness values are then assumed to be characterizing the location under analysis. The results of the model must be carefully checked and interpreted by taking into account the context (from
Influence of surface scattering on the thermal properties of spatially confined GaN nanofilm
NASA Astrophysics Data System (ADS)
Hou, Yang; Zhu, Lin-Li
2016-08-01
Gallium nitride (GaN), the notable representative of third generation semiconductors, has been widely applied to optoelectronic and microelectronic devices due to its excellent physical and chemical properties. In this paper, we investigate the surface scattering effect on the thermal properties of GaN nanofilms. The contribution of surface scattering to phonon transport is involved in solving a Boltzmann transport equation (BTE). The confined phonon properties of GaN nanofilms are calculated based on the elastic model. The theoretical results show that the surface scattering effect can modify the cross-plane phonon thermal conductivity of GaN nanostructures completely, resulting in the significant change of size effect on the conductivity in GaN nanofilm. Compared with the quantum confinement effect, the surface scattering leads to the order-of-magnitude reduction of the cross-plane thermal conductivity in GaN nanofilm. This work could be helpful for controlling the thermal properties of GaN nanostructures in nanoelectronic devices through surface engineering. Project supported by the National Natural Science Foundation of China (Grant Nos. 11302189 and 11321202) and the Doctoral Fund of Ministry of Education of China (Grant No. 20130101120175).
Thermal and Thermoelectric Properties of Nanostructured Materials and Interfaces
NASA Astrophysics Data System (ADS)
Liao, Hao-Hsiang
Many modern technologies are enabled by the use of thin films and/or nanostructured composite materials. For example, many thermoelectric devices, solar cells, power electronics, thermal barrier coatings, and hard disk drives contain nanostructured materials where the thermal conductivity of the material is a critical parameter for the device performance. At the nanoscale, the mean free path and wavelength of heat carriers may become comparable to or smaller than the size of a nanostructured material and/or device. For nanostructured materials made from semiconductors and insulators, the additional phonon scattering mechanisms associated with the high density of interfaces and boundaries introduces additional resistances that can significantly change the thermal conductivity of the material as compared to a macroscale counterpart. Thus, better understanding and control of nanoscale heat conduction in solids is important scientifically and for the engineering applications mentioned above. In this dissertation, I discuss my work in two areas dealing with nanoscale thermal transport: (1) I describe my development and advancement of important thermal characterization tools for measurements of thermal and thermoelectric properties of a variety of materials from thin films to nanostructured bulk systems, and (2) I discuss my measurements on several materials systems done with these characterization tools. First, I describe the development, assembly, and modification of a time-domain thermoreflectance (TDTR) system that we use to measure the thermal conductivity and the interface thermal conductance of a variety of samples including nanocrystalline alloys of Ni-Fe and Co-P, bulk metallic glasses, and other thin films. Next, a unique thermoelectric measurement system was designed and assembled for measurements of electrical resistivity and thermopower of thermoelectric materials in the temperature range of 20 to 350 °C. Finally, a commercial Anter Flashline 3000 thermal
Thermoelectric properties of AgSbTe₂ from first-principles calculations
Rezaei, Nafiseh; Akbarzadeh, Hadi; Hashemifar, S. Javad
2014-09-14
The structural, electronic, and transport properties of AgSbTe₂ are studied by using full-relativistic first-principles electronic structure calculation and semiclassical description of transport parameters. The results indicate that, within various exchange-correlation functionals, the cubic Fd3⁻m and trigonal R3⁻m structures of AgSbTe₂ are more stable than two other considered structures. The computed Seebeck coefficients at different values of the band gap and carrier concentration are accurately compared with the available experimental data to speculate a band gap of about 0.1–0.35 eV for AgSbTe₂ compound, in agreement with our calculated electronic structure within the hybrid HSE (Heyd-Scuseria-Ernzerhof) functional. By calculating the semiclassical Seebeck coefficient, electrical conductivity, and electronic part of thermal conductivity, we present the theoretical upper limit of the thermoelectric figure of merit of AgSbTe₂ as a function of temperature and carrier concentration.
Thermal properties of silicon nitride beams below 1 Kelvin.
Wang, G.; Yefremenko, V.; Novosad, V.; Datesman, A.; Pearson, J.; Shustakova, G.; Divan, R.; Chang, C.; McMahon, J.; Bleem, L.; Crites, A. T.; Downes, T.; Mehl, J.; Meyer, S. S.; Carlstrom, J. E.; Univ. of Chicago
2010-01-01
We have investigated the thermal transport of long, narrow beams of silicon nitride at cryogenic temperatures. Simultaneously employing a superconducting Transition Edge Sensor (TES) as both a heater and a sensor, we measured the thermal conductance of 1 {micro}m thick silicon nitride beams of different lateral dimensions. Based upon these measurements, we calculate the thermal parameters of the beams. We utilize a boundary limited phonon scattering model and assume the phonon mean free path to be temperature independent in the calculation. In the temperature range from 300 mK to 530 mK, the following results are obtained for 20 (30) {micro}m beams: the volume heat capacity is 0.083 T+0.509 T{sup 3} J/m{sup 3}-K, the width dependent phonon mean free path is 9.60 (11.05) {micro}m, and the width dependent thermal conductivity is 5.60 x 10{sup -3} T+3.41 x 10{sup -2} T{sup 3} (6.50 x 10{sup -3} T+3.93 x 10{sup -2} T{sup 3}) W/m-K.
WETAIR: A computer code for calculating thermodynamic and transport properties of air-water mixtures
NASA Technical Reports Server (NTRS)
Fessler, T. E.
1979-01-01
A computer program subroutine, WETAIR, was developed to calculate the thermodynamic and transport properties of air water mixtures. It determines the thermodynamic state from assigned values of temperature and density, pressure and density, temperature and pressure, pressure and entropy, or pressure and enthalpy. The WETAIR calculates the properties of dry air and water (steam) by interpolating to obtain values from property tables. Then it uses simple mixing laws to calculate the properties of air water mixtures. Properties of mixtures with water contents below 40 percent (by mass) can be calculated at temperatures from 273.2 to 1497 K and pressures to 450 MN/sq m. Dry air properties can be calculated at temperatures as low as 150 K. Water properties can be calculated at temperatures to 1747 K and pressures to 100 MN/sq m. The WETAIR is available in both SFTRAN and FORTRAN.
Direct calculation of modal contributions to thermal conductivity via Green-Kubo modal analysis
NASA Astrophysics Data System (ADS)
Lv, Wei; Henry, Asegun
2016-01-01
We derived a new method for direct calculation of the modal contributions to thermal conductivity, which is termed Green-Kubo modal analysis (GKMA). The GKMA method combines the lattice dynamics formalism with the Green-Kubo formula for thermal conductivity, such that the thermal conductivity becomes a direct summation of modal contributions, where one need not define the phonon velocity. As a result, the GKMA method can be applied to any material/group of atoms, where the atoms vibrate around stable equilibrium positions, which includes non-stoichiometric compounds, random alloys, amorphous materials and even rigid molecules. By using molecular dynamics simulations to obtain the time history of each mode’s contribution to the heat current, one naturally includes anharmonicity to full order and can obtain insight into the interactions between different modes through the cross-correlations. As an example, we applied the GMKA method to crystalline and amorphous silicon. The modal contributions at each frequency result from the analysis and thereby allow one to apply a quantum correction to the mode heat capacity to determine the temperature dependence of thermal conductivity. The predicted temperature dependent thermal conductivity for amorphous silicon shows the best agreement with experiments to date. The GKMA method provides new insight into the nature of phonon transport, as it casts the problem in terms of mode-mode correlation instead of scattering, and provides a general unified formalism that can be used to understand phonon-phonon interactions in essentially any class of materials or structures where the atoms vibrate around stable equilibrium sites.
Quasiclassical calculation of the quasiparticle thermal conductivity in a mixed state
NASA Astrophysics Data System (ADS)
Adachi, Hiroto; Miranovic, Predrag; Ichioka, Masanori; Machida, Kazushige
2007-03-01
We report the result of calculation of the quasiparticle thermal conductivity κxx(∇T⊥B) in the vortex state of a two-dimensional superconductor. We compute κxx for both s-wave and d-wave superconductors, taking account of the spatial dependence of normal Green's function g, which is neglected in the previous studies using the Brandt-Pesch-Tewordt (BPT) method. Our results indicate that κxx based on the BPT method is slightly underestimated due to its incoherent spatial averaging procedure.
A simple nonequilibrium molecular dynamics method for calculating the thermal conductivity
NASA Astrophysics Data System (ADS)
Müller-Plathe, Florian
1997-04-01
A nonequilibrium molecular dynamics method for calculating the thermal conductivity is presented. It reverses the usual cause and effect picture. The "effect," the heat flux, is imposed on the system and the "cause," the temperature gradient is obtained from the simulation. Besides being very simple to implement, the scheme offers several advantages such as compatibility with periodic boundary conditions, conservation of total energy and total linear momentum, and the sampling of a rapidly converging quantity (temperature gradient) rather than a slowly converging one (heat flux). The scheme is tested on the Lennard-Jones fluid.
Thermal properties of poly(3-hydroxybutyrate)/vegetable fiber composites
NASA Astrophysics Data System (ADS)
Vitorino, Maria B. C.; Reul, Lízzia T. A.; Carvalho, Laura H.; Canedo, Eduardo L.
2015-05-01
The present work studies the thermal properties of composites of poly(3-hydroxybutyrate) (PHB) - a fully biodegradable semi-crystalline thermo-plastic obtained from renewable resources through low-impact biotechno-logical process, biocompatible and non-toxic - and vegetable fiber from the fruit (coconut) of babassu palm tree. PHB is a highly crystalline resin and this characteristic leads to suboptimal properties in some cases. Consequently, thermal properties, in particular those associated with the crystallization of the matrix, are important to judge the suitability of the compounds for specific applications. PHB/babassu composites with 0-50% load were prepared in an internal mixer. Two different types of babassu fibers with two different particle size ranges were compounded with PHB and test specimens molded by compression. Melting and crystallization behavior were studied by differential scanning calorimetry (DSC) at heating/cooling rates between 2 and 30°C/min. Several parameters, including melting point, crystallization temperature, crystallinity, and rate of crystallization, were estimated as functions of load and heating/cooling rates. Results indicate that fibers do not affect the melting process, but facilitate crystallization from the melt. Crystallization temperatures are 30 to 40°C higher for the compounds compared with the neat resin. However, the amount of fiber added has little effect on crystallinity and the degree of crystallinity is hardly affected by the load. Fiber type and initial particle size do not have a significant effect on thermal properties.
A first principles study of the electronic structure, elastic and thermal properties of UB2
NASA Astrophysics Data System (ADS)
Jossou, Ericmoore; Malakkal, Linu; Szpunar, Barbara; Oladimeji, Dotun; Szpunar, Jerzy A.
2017-07-01
Uranium diboride (UB2) has been widely deployed for refractory use and is a proposed material for Accident Tolerant Fuel (ATF) due to its high thermal conductivity. However, the applicability of UB2 towards high temperature usage in a nuclear reactor requires the need to investigate the thermomechanical properties, and recent studies have failed in highlighting applicable properties. In this work, we present an in-depth theoretical outlook of the structural and thermophysical properties of UB2, including but not limited to elastic, electronic and thermal transport properties. These calculations were performed within the framework of Density Functional Theory (DFT) + U approach, using Quantum ESPRESSO (QE) code considering the addition of Coulomb correlations on the uranium atom. The phonon spectra and elastic constant analysis show the dynamic and mechanical stability of UB2 structure respectively. The electronic structure of UB2 was investigated using full potential linear augmented plane waves plus local orbitals method (FP-LAPW+lo) as implemented in WIEN2k code. The absence of a band gap in the total and partial density of states confirms the metallic nature while the valence electron density plot reveals the presence of covalent bond between adjacent B-B atoms. We predicted the lattice thermal conductivity (kL) by solving Boltzmann Transport Equation (BTE) using ShengBTE. The second order harmonic and third-order anharmonic interatomic force constants required as input to ShengBTE was calculated using the Density-functional perturbation theory (DFPT). However, we predicted the electronic thermal conductivity (kel) using Wiedemann-Franz law as implemented in Boltztrap code. We also show that the sound velocity along 'a' and 'c' axes exhibit high anisotropy, which accounts for the anisotropic thermal conductivity of UB2.
Strain-modulated electronic and thermal transport properties of two-dimensional O-silica
NASA Astrophysics Data System (ADS)
Han, Yang; Qin, Guangzhao; Jungemann, Christoph; Hu, Ming
2016-07-01
Silica is one of the most abundant materials in the Earth’s crust and is a remarkably versatile and important engineering material in various modern science and technology. Recently, freestanding and well-ordered two-dimensional (2D) silica monolayers with octahedral (O-silica) building blocks were found to be theoretically stable by (Wang G et al 2015 J. Phys. Chem. C 119 15654-60). In this paper, by performing first-principles calculations, we systematically investigated the electronic and thermal transport properties of 2D O-silica and also studied how these properties can be tuned by simple mechanical stretching. Unstrained 2D O-silica is an insulator with an indirect band gap of 6.536 eV. The band gap decreases considerably with bilateral strain up to 29%, at which point a semiconductor-metal transition occurs. More importantly, the in-plane thermal conductivity of freestanding 2D O-silica is found to be unusually high, which is around 40 to 50 times higher than that of bulk α-quartz and more than two orders of magnitude higher than that of amorphous silica. The thermal conductivity of O-silica decreases by almost two orders of magnitude when the bilateral stretching strain reaches 10%. By analyzing the mode-dependent phonon properties and phonon-scattering channel, the phonon lifetime is found to be the dominant factor that leads to the dramatic decrease of the lattice thermal conductivity under strain. The very sensitive response of both band gap and phonon transport properties to the external mechanical strain will enable 2D O-silica to easily adapt to the different environment of realistic applications. Our study is expected to stimulate experimental exploration of further physical and chemical properties of 2D silica systems, and offers perspectives on modulating the electronic and thermal properties of related low-dimensional structures for applications such as thermoelectric, photovoltaic, and optoelectronic devices.
Calculation of Divertor Thermal Response as a Function of Material Composition for NSTX
NASA Astrophysics Data System (ADS)
Chaffin, Michael; Maingi, Rajesh
2007-11-01
Present tokamak designs use a magnetic divertor to deposit heat from the edge plasma onto Plasma Facing Components (PFCs) designed to remove the heat. Studying how this heat is distributed under various discharge conditions gives insight into how heat deposition can be optimized, and how different materials respond to plasma heating. In the National Spherical Torus eXperiment (NSTX), infrared cameras are used to measure divertor surface temperature, from which heat flux is computed using a 1D semi-infinite slab model with constant thermal conductivity. Here, a 1D simulation of the PFCs incorporating temperature-dependent thermal properties is used to compute heat flux profiles resolved across time and tile thickness. The PFC response to a given heat flux is also computed, and comparisons of resulting temperature profiles are made for a variety of materials including ATJ graphite (presently in the NSTX divertor), pyrolytic graphite, molybdenum, and tungsten.
Electronic and thermal properties of TiFe{sub 2} compound: An ab initio study
Sathyakumari, V. S.; Sankar, S. Mahalakshmi, K.; Subashree, G.; Krithiga, R.
2015-06-24
A systematic study of electronic, and thermal properties such as the Density of states, Fermi energy, Debye temperature and specific heat coefficient, has been carried out using the results of electronic bandstructure and related characteristics of the Laves phase compound, TiFe{sub 2}. Computation of electronic bandstructure and associated properties has been carried out using the tight-binding-linear-muffin-tin-orbital (TB-LMTO) method within atomic sphere approximation (ASA). The calculated values are compared with the available results of literature.
Electronic and thermal properties of TiFe2 compound: An ab initio study
NASA Astrophysics Data System (ADS)
Sathyakumari, V. S.; Sankar, S.; Mahalakshmi, K.; Subashree, G.; Krithiga, R.
2015-06-01
A systematic study of electronic, and thermal properties such as the Density of states, Fermi energy, Debye temperature and specific heat coefficient, has been carried out using the results of electronic bandstructure and related characteristics of the Laves phase compound, TiFe2. Computation of electronic bandstructure and associated properties has been carried out using the tight-binding-linear-muffin-tin-orbital (TB-LMTO) method within atomic sphere approximation (ASA). The calculated values are compared with the available results of literature.
Thermal properties of operative endoscopes used in otorhinolaryngology.
MacKeith, S A C; Frampton, S; Pothier, D D
2008-07-01
To measure the thermal properties of operative endoscopes used in otorhinolaryngological practice. A series of endoscopes of varying diameters and angulations were attached to a light source and temperature measurements taken of their shaft and tip; a measurement was also taken 5 mm in front of the endoscope tip. Temperature changes took place rapidly. The amount of heat produced by the endoscopes was maximal at the tip, with larger diameter endoscopes attaining a higher temperature. Temperatures on the shaft and in front of the tip reached relatively constant temperatures independent of the type of endoscope. The maximum temperature achieved was 104.6 degrees C for the 4 mm, 0 degrees endoscope. Cooling occurred rapidly after the light source was switched off. The heat produced by some endoscopes is sufficiently great to cause thermal injury to tissues. Awareness of the temperatures produced by these endoscopes should prompt clinicians to actively cool their endoscopes during a procedure, before any thermal injury is caused.
NASA Technical Reports Server (NTRS)
Wallyn, P.; Mahoney, W. A.; Durouchoux, Ph.; Chapuis, C.
1996-01-01
We calculate the intensities of the positronium de-excitation lines for two processes: (1) the radiative combination of free thermal electrons and positrons for transitions with principal quantum number n less than 20, and (2) charge exchange between free positrons and hydrogen and helium atoms, restricting our evaluation to the Lyman-alpha line. We consider a low-density medium modeled by the case A assumption of Baker & Menzel and use the "nL method" of Pengelly to calculate the absolute intensities. We also evaluate the positronium fine and hyperfine intensities and show that these transitions are in all cases much weaker than positronium de-excitation lines in the same wavelength range. We also extrapolate our positronium de-excitation intensities to the submillimeter, millimeter, and centimeter wavelengths. Our results favor the search of infrared transitions of positronium lines for point sources when the visual extinction A, is greater than approx. 5.
NASA Astrophysics Data System (ADS)
Chemia, Zurab; Dolejš, David; Steinle-Neumann, Gerd
2015-10-01
We explore the effects of variable material properties, phase transformations, and metamorphic devolatilization reactions on the thermal structure of a subducting slab using thermodynamic phase equilibrium calculations combined with a thermal evolution model. The subducting slab is divided into three layers consisting of oceanic sediments, altered oceanic crust, and partially serpentinized or anhydrous harzburgite. Solid-fluid equilibria and material properties are computed for each layer individually to illustrate distinct thermal consequences when chemical and mechanical homogenization within the slab is limited. Two extreme scenarios are considered for a newly forming fluid phase: complete retention in the rock pore space or instantaneous fluid escape due to porosity collapse. Internal heat generation or consumption due to variable heat capacity, compressional work, and energetics of progressive metamorphic and devolatilization reactions contribute to the thermal evolution of the slab in addition to the dominating heat flux from the surrounding mantle. They can be considered as a perturbation on the temperature profile obtained in dynamic or kinematic subduction models. Our calculations indicate that subducting sediments and oceanic crust warm by 40 and 70°C, respectively, before the effect of wedge convection and heating is encountered at 1.7 GPa. Retention of fluid in the slab pore space plays a negligible role in oceanic crust and serpentinized peridotites. By contrast, the large volatile budget of oceanic sediments causes early fluid saturation and fluid-retaining sediments cool by up to 150°C compared to their fluid-free counterparts.
NASA Technical Reports Server (NTRS)
Zhu, Shen; Li, C.; Su, Ching-Hua; Lin, B.; Ben, H.; Scripa, R. N.; Lehoczky, S. L.; Curreri, Peter A. (Technical Monitor)
2002-01-01
Tellurium is an element for many II-VI and I-III-VI(sub 2) compounds that are useful materials for fabricating many devices. In the melt growth techniques, the thermal properties of the molten phase are important parameter for controlling growth process to improve semiconducting crystal quality. In this study, thermal diffusivity of molten tellurium has been measured by a laser flash method in the temperature range from 500 C to 900 C. A pulsed laser with 1064 nm wavelength is focused on one side of the measured sample. The thermal diffusivity can be estimated from the temperature transient at the other side of the sample. A numerical simulation based on the thermal transport process has been also performed. By numerically fitting the experimental results, both the thermal conductivity and heat capacity can be derived. A relaxation phenomenon, which shows a slow drift of the measured thermal conductivity toward the equilibrium value after cooling of the sample, was observed for the first time. The error analysis and the comparison of the results to published data measured by other techniques will be discussed.
NASA Technical Reports Server (NTRS)
Zhu, Shen; Su, Ching-Hua; Li, C.; Lin, B.; Ben, H.; Scripa, R. N.; Lehoczky, S. L.; Curreri, Peter A. (Technical Monitor)
2002-01-01
Tellurium is an element for many II-VI and I-III-VI(sub 2) compounds that are useful materials for fabricating many devises. In the melt growth techniques, the thermal properties of the molten phase are important parameter for controlling growth process to improve semiconducting crystal quality. In this study, thermal diffusivity of molten tellurium has been measured by a laser flash method in the temperature range from 500 C to 900 C. A pulsed laser with 1064 nm wavelength is focused on one side of the measured sample. The thermal diffusivity can be estimated from the temperature transient at the other side of the sample. A numerical simulation based on the thermal transport process has been also performed. By numerically fitting the experimental results, both the thermal conductivity and heat capacity can be derived. A relaxation phenomenon, which shows a slow drift of the measured thermal conductivity toward the equilibrium value after cooling of the sample, was observed for the first time. The error analysis and the comparison of the results to published data measured by other techniques will be discussed in the presentation.
Cheng, Yehong; Zhou, Shanbao; Hu, Ping; Zhao, Guangdong; Li, Yongxia; Zhang, Xinghong; Han, Wenbo
2017-05-03
Graphene aerogels with high surface areas, ultra-low densities and thermal conductivities have been prepared to exploit their wide applications from pollution adsorption to energy storage, supercapacitor, and thermal insulation. However, the low mechanical properties, poor thermal stability and electric conductivity restrict these aerogels' applications. In this paper, we prepared mechanically strong graphene aerogels with large BET surface areas, low thermal conductivities, high thermal stability and electric conductivities via hydrothermal reduction and supercritical ethanol drying. Annealing at 1500 °C resulted in slightly increased thermal conductivity and further improvement in mechanical properties, oxidation temperature and electric conductivity of the graphene aerogel. The large BET surface areas, together with strong mechanical properties, low thermal conductivities, high thermal stability and electrical conductivities made these graphene aerogels feasible candidates for use in a number of fields covering from batteries to sensors, electrodes, lightweight conductor and insulation materials.
Berna, G. A; Bohn, M. P.; Rausch, W. N.; Williford, R. E.; Lanning, D. D.
1981-01-01
FRAPCON-2 is a FORTRAN IV computer code that calculates the steady state response of light Mater reactor fuel rods during long-term burnup. The code calculates the temperature, pressure, deformation, and tai lure histories of a fuel rod as functions of time-dependent fuel rod power and coolant boundary conditions. The phenomena modeled by the code include (a) heat conduction through the fuel and cladding, (b) cladding elastic and plastic deformation, (c) fuel-cladding mechanical interaction, (d) fission gas release, (e} fuel rod internal gas pressure, (f) heat transfer between fuel and cladding, (g) cladding oxidation, and (h) heat transfer from cladding to coolant. The code contains necessary material properties, water properties, and heat transfer correlations. FRAPCON-2 is programmed for use on the CDC Cyber 175 and 176 computers. The FRAPCON-2 code Is designed to generate initial conditions for transient fuel rod analysis by either the FRAP-T6 computer code or the thermal-hydraulic code, RELAP4/MOD7 Version 2.
Acousto-mechanical and thermal properties of clotted blood.
Nahirnyak, Volodymyr M; Yoon, Suk Wang; Holland, Christy K
2006-06-01
The efficacy of ultrasound-assisted thrombolysis as an adjunct treatment of ischemic stroke is being widely investigated. To determine the role of ultrasound hyperthermia in the process of blood clot disruption, the acousto-mechanical and thermal properties of clotted blood were measured in vitro, namely, density, speed of sound, frequency-dependent attenuation, specific heat, and thermal conductivity. The amplitude coefficient of attenuation of the clots was determined for 120 kHz, 1.0 MHz, and 3.5 MHz ultrasound at room temperature (20 +/- 2 degrees C). The attenuation coefficient ranged from 0.10 to 0.30 Np/cm in porcine clots and from 0.09 to 0.23 Np/cm in human clots. The experimentally determined values of specific heat and thermal conductivity for porcine clotted blood are (3.2 +/- 0.5) x 10(3) J/kg x K and 0.55 +/- 0.13 W/m x K, respectively, and for human clotted blood are (3.5 +/- 0.8) x 10(3) J/kg x K and 0.59 +/- 0.11 W/m x K, respectively. Measurements of the acousto-mechanical and thermal properties of clotted blood can be helpful in theoretical modeling of ultrasound hyperthermia in ultrasound-assisted thrombolysis and other high-intensity focused ultrasound applications.
Effect of thermal modification on rheological properties of polyethylene blends
Siriprumpoonthum, Monchai; Nobukawa, Shogo; Yamaguchi, Masayuki; Satoh, Yasuo; Sasaki, Hiroko
2014-03-15
We examined the effects of thermal modification under flow field on the rheological properties of linear low-density polyethylene (LLDPE) with high molecular weight, low-density polyethylene (LDPE), and their blends, without thermal stabilizer. Although structural changes during processing are not detected by size extrusion chromatography or nuclear magnetic resonance spectroscopy, linear viscoelastic properties changed greatly, especially for the LLDPE. A cross-linking reaction took place, leading to, presumably, star-shaped long-chain branches. Consequently, the modified LLDPE, having high zero-shear viscosity, became a thermorheologically complex melt. Moreover, it should be noted that the drawdown force, defined as the uniaxial elongational force at a constant draw ratio, was significantly enhanced for the blends. Enhancement of elongational viscosity was also detected. The drawdown force and elongational viscosity are marked for the thermally modified blend as compared with those for the blend of thermally modified pure components. Intermolecular cross-linking reactions between LDPE and LLDPE, yielding polymers with more than two branch points per chain, result in marked strain-hardening in the elongational viscosity behavior even at small strain. The recovery curve of the oscillatory modulus after the shear modification is further evidence of a branched structure.
Functional Properties of Tooth Pulp Neurons Responding to Thermal Stimulation
Ahn, D.K.; Doutova, E.A.; McNaughton, K.; Light, A.R.; Närhi, M.; Maixner, W.
2012-01-01
The response properties of tooth pulp neurons that respond to noxious thermal stimulation of the dental pulp have been not well-studied. The present study was designed to characterize the response properties of tooth pulp neurons to noxious thermal stimulation of the dental pulp. Experiments were conducted on 25 male ferrets, and heat stimulation was applied by a computer-controlled thermode. Only 15% of tooth pulp neurons (n = 39) responded to noxious thermal stimulation of the teeth. Tooth pulp neurons were found in both the superficial and deep nuclear regions of the subnucleus caudalis (Vc) and in the interface between the nucleus caudalis and interpolaris (Vc/Vi). Thirty-seven neurons had cutaneous receptive fields and were classified as either NS (16) or WDR (21) neurons. Repeated heat stimulation of the dental pulp sensitized and increased the number of electrically evoked potentials of tooth pulp neurons. These results provide evidence that both the Vc and Vc/Vi regions contain neurons that respond to noxious thermal stimulation of the dental pulp, and that these cells may contribute to the sensitization process associated with symptomatic pulpitis. PMID:22257665
Determination of thermal physical properties of alkali fluoride/carbonate eutectic molten salt
NASA Astrophysics Data System (ADS)
An, Xue-Hui; Cheng, Jin-Hui; Su, Tao; Zhang, Peng
2017-06-01
Molten salts used in high temperatures are more and more interested in the CSP for higher energy conversion efficiency. Thermal physical properties are the basic engineering data of thermal hydraulic calculation and safety analysis. Therefore, the thermophysical performances involving density, specific heat capacity, viscosity and thermal conductivity of FLiNaK, (LiNaK)2CO3 and LiF(NaK)2CO3 molten salts are experimentally determined and through comparison the general rules can be summarized. Density measurement was performed on the basis of Archimedes theory; specific heat capacity was measured using the DSC technique; viscosity was tested based on the rotating method; and the thermal conductivity was gained by laser flash method with combination of the density, specific heat capacity and thermal diffusivity through a formula. Finally, the energy storage capacity and figures of merit are calculated to evaluate their feasibility as TES and HFT media. The results show that FLiNaK has the largest energy storage capacity and best heat transfer performance, LiF(NaK)2CO3 is secondary, and (LiNaK)2CO3 has the smallest.
Rheological and thermal properties of PP-based WPC
NASA Astrophysics Data System (ADS)
Mazzanti, V.; Mollica, F.; El Kissi, N.
2014-05-01
Wood Plastic Composite (WPC) has attracted great interest in outdoor building products for the reduced cost and the possibility of using recycled materials. Nevertheless the material shows two problems: the large viscosity due to the presence of high concentrations of filler and the degradation of cellulose during processing The aim of this work was to investigate the rheological and thermal properties of WPC. The material used for the experiments was a commercial PP-based WPC compound, with different concentrations of natural fibers (30, 50, 70% wt.). The thermal properties were studied to check for degradation of natural fibers during the subsequent rheological tests. Analyzing the storage and loss moduli and the complex viscosity curves obtained using a parallel plate rheometer it was possible to observe some features related to the viscoelastic nature of the composite.
Thermodynamic properties and transport coefficients of two-temperature helium thermal plasmas
NASA Astrophysics Data System (ADS)
Guo, Xiaoxue; Murphy, Anthony B.; Li, Xingwen
2017-03-01
Helium thermal plasmas are in widespread use in arc welding and many other industrial applications. Simulation of these processes relies on accurate plasma property data, such as plasma composition, thermodynamic properties and transport coefficients. Departures from LTE (local thermodynamic equilibrium) generally occur in some regions of helium plasmas. In this paper, properties are calculated allowing for different values of the electron temperature, T e, and heavy-species temperature, T h, at atmospheric pressure from 300 K to 30 000 K. The plasma composition is first calculated using the mass action law, and the two-temperature thermodynamic properties are then derived. The viscosity, diffusion coefficients, electrical conductivity and thermal conductivity of the two-temperature helium thermal plasma are obtained using a recently-developed method that retains coupling between electrons and heavy species by including the electron–heavy-species collision term in the heavy-species Boltzmann equation. It is shown that the viscosity and the diffusion coefficients strongly depend on non-equilibrium ratio θ (θ ={{T}\\text{e}}/{{T}\\text{h}} ), through the plasma composition and the collision integrals. The electrical conductivity, which depends on the electron number density and ordinary diffusion coefficients, and the thermal conductivity have similar dependencies. The choice of definition of the Debye length is shown to affect the electrical conductivity significantly for θ > 1. By comparing with literature data, it is shown that the coupling between electrons and heavy species has a significant influence on the electrical conductivity, but not on the viscosity. Plasma properties are tabulated in the supplementary data.
Study on the thermal storage properties of Al-Si-Cu-Mg alloy
NASA Astrophysics Data System (ADS)
XIE, Yi; WAN, Ke-yang; XIE, Guo-sheng; HU, Jia-rui; YIN, Fu-cheng; GONG, Jing
2017-04-01
Based on thermodynamic calculation technology, the thermodynamic data of six alloys (inc. Al-Si and Al-Si-Cu-Mg systems) was calculated. The microstructure, phase transformation temperature and latent heat of the Al-4%Cu-12%Mg-7%Si alloy and Al-13%Si alloy were also verified by X-ray diffraction(XRD), scanning electron microscopy/Energy-dispersive system (SEM/EDS) and Differential scanning calorimetry (DSC). The results show that The enthalpy change value of Al-Si-Cu-Mg alloy is larger than that of Al-Si alloy from 800 °C to 400 °C, while its phase transformation temperature is lower. In particular, the enthalpy value of Al-4%Cu-12%Mg-7%Si alloy is 85% higher than that of Al-13%Si near eutectic alloy, and its initial temperature of phase transformation is about 74 °C lower. The former has relatively low phase transformation temperature and over-dimensioned latent heat of phase transformation, displaying the excellent thermal storage property. Therefore, the alloy is a good potential solar energy thermal storage material. The results in the paper also indicated that thermodynamic calculation is of value in seeking new potential solar energy thermal storage materials for solar thermal power generation system.
NASA Astrophysics Data System (ADS)
Pavlík, Zbyšek; Fiala, Lukáš; Vejmelková, Eva; Černý, Robert
2013-05-01
The effective thermal conductivity and effective specific heat capacity of hollow brick blocks are investigated as a function of moisture content. While the effective specific heat capacity as a heat storage parameter is calculated using the linear theory of mixtures, the effective thermal conductivity as a heat transport parameter is analyzed using the effective media theory. At first, the effective thermal conductivity of the dry hollow brick block is calculated using a combination of properties of the brick body and air cavities, and verified using experimental data. Then, the effective thermal conductivity of the brick body is analyzed as a function of moisture content both theoretically and experimentally, and appropriate homogenization formulas are identified. Finally, the effective thermal conductivity of the whole hollow bricks is expressed as a function of moisture content from the dry state to water saturation.
NASA Astrophysics Data System (ADS)
Bandriyana, B.; Utaja
2010-06-01
Thermal stratification introduces thermal shock effect which results in local stress and fatique problems that must be considered in the design of nuclear power plant components. Local stress and fatique calculation were performed on the Pressurize Surge Line piping system of the Pressurize Water Reactor of the Nuclear Power Plant. Analysis was done on the operating temperature between 177 to 343° C and the operating pressure of 16 MPa (160 Bar). The stagnant and transient condition with two kinds of stratification model has been evaluated by the two dimensional finite elements method using the ANSYS program. Evaluation of fatigue resistance is developed based on the maximum local stress using the ASME standard Code formula. Maximum stress of 427 MPa occurred at the upper side of the top half of hot fluid pipe stratification model in the transient case condition. The evaluation of the fatigue resistance is performed on 500 operating cycles in the life time of 40 years and giving the usage value of 0,64 which met to the design requirement for class 1 of nuclear component. The out surge transient were the most significant case in the localized effects due to thermal stratification.
Thermal conductivity of the Lennard-Jones liquid by molecular dynamics calculations
NASA Astrophysics Data System (ADS)
Vogelsang, R.; Hoheisel, C.; Ciccotti, G.
1987-06-01
Precise results for the thermal conductivity of the Lennard-Jones liquid obtained by equilibrium molecular dynamics (MD) are presented. These are compared in detail with previous nonequilibrium MD results. Effects due to the truncation of the potential and the particle number dependence are considered. The contributions of the partial correlation functions to the total one were separately calculated. Main results are: (i) in contrast to the viscosity, the thermal conductivity is rather insensitive to the MD conditions, even for the state corresponding virtually to the triple point of argon. The reason for this originates from the simple short ranged time decay of the correlation function. (ii) For the states considered, the partial correlation function involving the ``potential-potential'' term governs the transport coefficient. (iii) Nonequilibrium MD and MD give consistent values, except for the nonequilibrium method devised by Heyes which generates data far off the range permitted by the error bars. (iv) The computed thermal conductivities fall well in line with experimental data for argon.
Bandriyana, B.; Utaja
2010-06-22
Thermal stratification introduces thermal shock effect which results in local stress and fatigue problems that must be considered in the design of nuclear power plant components. Local stress and fatigue calculation were performed on the Pressurize Surge Line piping system of the Pressurize Water Reactor of the Nuclear Power Plant. Analysis was done on the operating temperature between 177 to 343 deg. C and the operating pressure of 16 MPa (160 Bar). The stagnant and transient condition with two kinds of stratification model has been evaluated by the two dimensional finite elements method using the ANSYS program. Evaluation of fatigue resistance is developed based on the maximum local stress using the ASME standard Code formula. Maximum stress of 427 MPa occurred at the upper side of the top half of hot fluid pipe stratification model in the transient case condition. The evaluation of the fatigue resistance is performed on 500 operating cycles in the life time of 40 years and giving the usage value of 0,64 which met to the design requirement for class 1 of nuclear component. The out surge transient were the most significant case in the localized effects due to thermal stratification.
Thermal Model of Europa: Calculating the Effects of Surface Topography and Radiation from Jupiter
NASA Astrophysics Data System (ADS)
Bennett, Kristen; Paige, D.; Hayne, P.; Greenhagen, B.; Schenk, P.
2010-10-01
Europa's surface temperature distribution results from global effects such as insolation and heat flow, as well as local topography and possibly active tectonic processes. Accurate surface temperature models will greatly benefit future orbital investigations searching for global-scale variations in heat flow and local thermal anomalies resulting from frictional heating on faults or diapirs (Paige et al, this meeting). At the global scale, a major challenge for such models is the strong influence of Jupiter on the solar and infrared flux at Europa's surface. At the local scale, the thermal signature is dominated by complex topography. In order to address these two problems, we developed a model that modifies the Digital Moon program created by D. Paige and S. Meeker (2009) that uses a 3-dimensional geodesic gridding scheme to calculate the surface temperature of a body due to multiple scatterings of radiation and heat flow. We can account for Jupiter's influence on Europa by including data on Jupiter's solar and infrared radiation (which accounts for roughly 30% of the radiation at Europa), and on Europa's orbit (as Europa spends several minutes out of its 3.55 day orbital period in Jupiter's shadow). To address the issue of Europa's complicated terrain, we have simulated the effects of local heat flow as well as added topography and surface roughness to the thermal model by using digital elevation models produced by Schenk and Pappalardo (2004) that show altitude changes of several hundred meters and tectonic features that may produce regions of anomalously high heat flow.
Thermal properties of the Tin odd isotopes 117,119,121Sn
NASA Astrophysics Data System (ADS)
Kadi, H.; Benhamouda, N.
2016-07-01
We propose to study the thermal properties of the odd isotopes of Tin: 117,119,121Sn. To this end, one used two methods to evaluate the properties of these elements. The first theoretical consideration uses a simple prescription to perform the calculation of these properties based on those of even-even neighboring isotopes, assuming the quasi-particle entropy extensivity. The even-even elements are treated as part of the Modified Lipkin-Nogami (MLN) method that allows to take into account the quantal and statistical fluctuations. The second theoretical approach consists of the generalization of the MLN formalism in the case of odd systems, by using the blocking technique. Then, this approach is applied to evaluate the thermal properties of the considered elements. The obtained results by both theoretical approaches are compared to the experimental data. The latter are deduced from the experimental level density within the canonical ensemble. It appears that the assumption of quasi-particle entropy extensivity at low excitation energy allows a simple and an effective treatment of thermal properties of odd nuclei. Indeed, this approach allows to give a good reproduction of experimental data in the particular in the region where the pairing transition occurs.
Thermal properties of SFR-HPC exposed to high temperatures
NASA Astrophysics Data System (ADS)
Scheinherrová, Lenka; Pavlík, Zbyšek
2017-07-01
In this paper, a non-adiabatic method was used for the assessment of specific heat capacity of steel fibre reinforced high performance concrete in the temperature range 105-1000 °C. The tested SFR-HPC mix was produced from CEM II 42.5 R, ground granulated blast furnace slag, silica sand with maximum particle size of 2 mm, silica fume, brass-coated steel fibres, superplasticizer on polycarboxylate ether basis and batch water. For the studied material, properties after 2 hours thermal treatment at the temperatures of 105 °C, 200 °C, 400 °C, 600 °C, 800 °C, and 1000 °C respectively were tested. Among them, bulk density, matrix density, total open porosity and thermal parameters as thermal conductivity, thermal diffusivity and specific heat capacity were measured. The measured specific heat capacity exhibited high dependence on temperature and pointed to the structural changes that studied material underwent at high temperatures. Accordingly, the obtained residual parameters revealed the thermally induced damage of SFR-HPC and critical temperatures for its functionality.
Thermal properties of degraded lowland peat-moorsh soils
NASA Astrophysics Data System (ADS)
Gnatowski, Tomasz
2016-04-01
Soil thermal properties, i.e.: specific heat capacity (c), thermal conductivity (K), volumetric heat capacity (C) govern the thermal environment and heat transport through the soil. Hence the precise knowledge and accurate predictions of these properties for peaty soils with high amount of organic matter are especially important for the proper forecasting of soil temperature and thus it may lead to a better assessment of the greenhouse gas emissions created by microbiological activity of the peatlands. The objective of the study was to develop the predictive models of the selected thermal parameters of peat-moorsh soils in terms of their potential applicability for forecasting changes of soil temperature in degraded ecosystems of the Middle Biebrza River Valley area. Evaluation of the soil thermal properties was conducted for the parameters: specific heat capacity (c), volumetric heat capacities of the dry and saturated soil (Cdry, Csat) and thermal conductivities of the dry and saturated soil (Kdry, Ksat). The thermal parameters were measured using the dual-needle probe (KD2-Pro) on soil samples collected from seven peaty soils, representing total 24 horizons. The surface layers were characterized by different degrees of advancement of soil degradation dependent on intensiveness of the cultivation practises (peaty and humic moorsh). The underlying soil layers contain peat deposits of different botanical composition (peat-moss, sedge-reed, reed and alder) and varying degrees of decomposition of the organic matter, from H1 to H7 (von Post scale). Based on the research results it has been shown that the specific heat capacity of the soils differs depending on the type of soil (type of moorsh and type of peat). The range of changes varied from 1276 J.kg-1.K-1 in the humic moorsh soil to 1944 J.kg-1.K-1 in the low decomposed sedge-moss peat. It has also been stated that in degraded peat soils with the increasing of the ash content in the soil the value of specific heat
Fundamental Thermal and Mechanical Properties of Boride Ceramics
2014-02-28
approved for public release. 6 Figure 1. Neutron diffraction intensity as a function of temperature for representative Zr11B2 and SiC planes...of structure-property relationships began by measuring the magnitude of thermal residual stresses in ZrB2-SiC ceramics. Neutron diffraction and...the isotopes of boron, 10B, is a strong neutron absorber and its content was minimized in the ceramics for this study. Ceramics were prepared from
Detonation Properties and Thermal Behavior of FOX-7-Based Explosives
NASA Astrophysics Data System (ADS)
Trzciński, W. A.; Cudziło, S.; Chyłek, Z.; Szymańczyk, L.
2013-01-01
Phlegmatized FOX-7 (1,1-diamino-2,2-dinitroethylene, DADNE) and mixtures with cyclotetramethylene tetranitramine (HMX) were prepared and their detonation properties (the detonation velocity, detonation pressure, acceleration ability, and detonation energy) were investigated. The sensitivity of these compositions to mechanical stimuli (friction, impact, and shock wave) were determined, and the thermal stability and compatibility of the components were tested. This work furthers the investigation into new compositions for low vulnerability ammunition.
Characterization of mouthguard materials: thermal properties of commercialized products.
Gould, Trenton E; Piland, Scott G; Shin, Junghwan; McNair, Olivia; Hoyle, Charles E; Nazarenko, Sergei
2009-12-01
Several mechanisms have been purported to describe how mouthguards protect the orofacial complex against injury. As the properties needed for these mechanisms to be effective are temperature and frequency dependent, the specific aim of this study was to provide a comprehensive thermal characterization of commercial mouthguard materials. Five commercially representative thermoplastic mouthguard materials (Essix Resin, Erkoflex, Proform-regular, Proform-laminate, and Polyshok) were tested. Differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) techniques were implemented to measure thermal transitions and mechanical properties. Measurements were conducted three times per sample. One-way ANOVA and one-sample t-tests were used to test for differences between commercial products on selected mean thermal property values. The DSC measurements indicated no differences between commercial materials for mean glass transition (p=0.053), onset melt (p=0.973), or peak melt (p=0.436) temperatures. Likewise, DMA measurements revealed no differences between commercial materials for the mean glass transition (p=0.093), storage modulus (p=0.257), or loss modulus (p=0.172) properties, respectively. The one-sample t-tests revealed that glass transition temperatures were different from intra-oral temperature (p<0.005) for all materials. Commercialized mouthguard materials are sensitive to repetitive heating and cooling cycles, prolonged thermal treatment, and have glass transitions well below their end-use intra-oral temperature. As such, these materials are functioning as elastomers and not optimal mechanical damping materials. Dental clinicians, healthcare practitioners, or end-users should be aware that these materials are at best problematic with respect to this protective mechanism.
Thermal conductivity of silicene calculated using an optimized Stillinger-Weber potential
NASA Astrophysics Data System (ADS)
Zhang, Xiaoliang; Xie, Han; Hu, Ming; Bao, Hua; Yue, Shengying; Qin, Guangzhao; Su, Gang
2014-02-01
Silicene, the silicon-based counterpart of graphene with a two-dimensional honeycomb lattice, has attracted tremendous interest both theoretically and experimentally due to its significant potential industrial applications. From the aspect of theoretical study, the widely used classical molecular dynamics simulation is an appropriate way to investigate the transport phenomena and mechanisms in nanostructures such as silicene. Unfortunately, no available interatomic potential can precisely characterize the unique features of silicene. Here, we optimized the Stillinger-Weber potential parameters specifically for a single-layer Si sheet, which can accurately reproduce the low buckling structure of silicene and the full phonon dispersion curves obtained from ab initio calculations. By performing equilibrium and nonequilibrium molecular dynamics simulations and anharmonic lattice dynamics calculations with the new potential, we reveal that the three methods consistently yield an extremely low thermal conductivity of silicene and a short phonon mean-free path, suggesting silicene as a potential candidate for high-efficiency thermoelectric materials. Moreover, by qualifying the relative contributions of lattice vibrations in different directions, we found that the longitudinal phonon modes dominate the thermal transport in silicene, which is fundamentally different from graphene, despite the similarity of their two-dimensional honeycomb lattices.
This cost calculator is designed as a guide for municipal or local governments to assist in calculating their expected costs of implementing and conducting long-term stewardship of institutional controls and engineering controls at brownfield properties.
Ab Initio Study of the Structural, Electronic, and Thermal Properties of Alloy
NASA Astrophysics Data System (ADS)
Benkaddour, I.; Khachai, H.; Chiker, F.; Benosman, N.; Benkaddour, Y.; Murtaza, G.; Omran, S. Bin; Khenata, R.
2015-07-01
The results of a first-principle study of the structural, electronic, and thermal properties of a alloy, using the full-potential linear muffin-tin-orbital (FP-LMTO) method in the framework of density functional theory, within both the local density approximation and the generalized gradient approximation are presented. The composition effect on lattice constants, bulk moduli, band gaps, and effective masses is analyzed. The quasi-harmonic Debye model, using a set of total energy versus volume calculations obtained with the FP-LMTO method, is applied to study the thermal and vibrational effects. The temperature effect on the lattice parameters, thermal expansions, heat capacities, and Debye temperatures is determined from the non-equilibrium Gibbs functions. The microscopic origins of the bowing parameter were explained using the approach of Zunger and coworkers.
Optical properties of bismuth sulfide thin film prepared by thermal evaporation method
NASA Astrophysics Data System (ADS)
Kachari, T.; Rahman, A.
2015-04-01
Two types of thin films of Bi2S3 have been prepared on chemically cleaned glass substrate by thermal evaporation technique. Either by thermal evaporation of Bi2S3 powder or by thermal evaporation of bismuth and sulfur from two separate source. (Both annealed for 3 h in air inside an oven). Optical properties of these annealed films have been studied by measuring transmittance, absorbance and reflectance of the films. Optical constants such as absorption coefficient, extinction constants, refractive index, dielectric constants etc. of both types of Bi2S3 films have been calculated. Optical band gap of type (I) and (II) films have been found to be 1.647 and 1.668 eV respectively. The crystalline structure and purity of these Bi2S3 films have been studied by taking X-ray diffraction and X-ray fluorescence spectra. Surface morphology of the films has been studied by scanning electron microscopy.
Thermal transport properties of bulk and monolayer MoS2: an ab-initio approach
NASA Astrophysics Data System (ADS)
Bano, Amreen; Khare, Preeti; Gaur, N. K.
2017-05-01
The transport properties of semiconductors are key to the performance of many solid-state devices (transistors, data storage, thermoelectric cooling and power generation devices, etc). In recent years simulation tools based on first-principles calculations have been greatly improved, being able to obtain the fundamental ground-state properties of materials accurately. The quasi harmonic thermal properties of bulk and monolayer of MoS2 has been computed with ab initio periodic simulations based of density functional theory (DFT). The temperature dependence of bulk modulus, specific heat, thermal expansion and gruneisen parameter have been calculated in our work within the temperature range of 0K to 900K with projected augmented wave (PAW) method using generalized gradient approximation (GGA). Our results show that the optimized lattice parameters are in good agreement with the earlier reported works and also for thermoelastic parameter, i.e. isothermal bulk modulus (B) at 0K indicates that monolayer MoS2 (48.5 GPa)is more compressible than the bulk structure (159.23 GPa). The thermal expansion of monolayer structure is slightly less than the bulk. Similarly, other parameters like heat capacity and gruneisen parameter shows different nature which is due to the confinement of 3 dimensional structure to 2 dimension (2D) for improving its transport characteristics.
Ab initio study of structural, electronic, and thermal properties of Pt1-xPdx alloys
NASA Astrophysics Data System (ADS)
Ahmed, Shabbir; Zafar, Muhammad; Shakil, M.; Choudhary, M. A.; Hashmi, Muhammad Raza-Ur-Rehman
2017-01-01
We report a systematic theoretical study of Pt1-xPdx alloys using ab initio density functional theory (DFT) by pseudo potential method. We have used super cell approach to investigate structural, electronic and thermal properties of Platinum (Pt), Palladium (Pd) and their alloys Pt1-xPdx(x = 0.00, 0.25, 0.50, 0.75, 1.00). The calculated lattice constants and bulk moduli are in good agreement with available literature data. The results of electronic properties revealed that the alloys are metallic in nature. The thermal properties were investigated through density functional perturbation theory (DFPT) and quasi-harmonic approximation. The contribution to the free energy from the lattice vibration was calculated using the phonon densities of states (DOS) derived by means of the linear-response theory. The DFPT with quasi-harmonic approximation methods was applied to determine the phonon DOS and thermal quantities i.e., the Debye temperatures, vibration energy, entropy and constant-volume specific heat.
Lindsay, L.; Kuang, Y.
2017-03-13
Intrinsic thermal resistivity critically depends on features of phonon dispersions dictated by harmonic interatomic forces and masses. We present the effects of functional group mass variance on vibrational properties and thermal conductivity (κ ) of functionalized graphene from first principles calculations. We also use graphane, a buckled graphene backbone with covalently bonded Hydrogen atoms on both sides, as the base material and vary the mass of the Hydrogen atoms to simulate the effect of mass variance from other functional groups. We find non-monotonic behavior of κ with increasing mass of the functional group and an unusual cross-over from acoustic-dominated tomore » optic-dominated thermal transport behavior. We connect this cross-over to changes in the phonon dispersion with varying mass which suppress acoustic phonon velocities, but also give unusually high velocity optic modes. Further, we show that out-of-plane acoustic vibrations contribute significantly more to thermal transport than in-plane acoustic modes despite breaking of a reflection symmetry based scattering selection rule responsible for their large contributions in graphene. Our work demonstrates the potential for manipulation and engineering of thermal transport properties in two dimensional materials toward targeted applications.« less
NASA Astrophysics Data System (ADS)
Lindsay, L.; Kuang, Y.
2017-03-01
Intrinsic thermal resistivity critically depends on features of phonon dispersions dictated by harmonic interatomic forces and masses. Here we present the effects of functional group mass variance on vibrational properties and thermal conductivity (κ ) of functionalized graphene from first-principles calculations. We use graphane, a buckled graphene backbone with covalently bonded hydrogen atoms on both sides, as the base material and vary the mass of the hydrogen atoms to simulate the effect of mass variance from other functional groups. We find nonmonotonic behavior of κ with increasing mass of the functional group and an unusual crossover from acoustic-dominated to optic-dominated thermal transport behavior. We connect this crossover to changes in the phonon dispersion with varying mass which suppress acoustic phonon velocities, but also give unusually high velocity optic modes. Further, we show that out-of-plane acoustic vibrations contribute significantly more to thermal transport than in-plane acoustic modes despite breaking of a reflection-symmetry-based scattering selection rule responsible for their large contributions in graphene. This work demonstrates the potential for manipulation and engineering of thermal transport properties in two-dimensional materials toward targeted applications.
Low-rank coal thermal properties and diffusivity: Final report
Ramirez, W.F.
1987-06-01
This project developed techniques for measuring thermal properties and mass diffusivities of low-rank coals and coal powders. Using the concept of volume averaging, predictive models have been developed for these porous media properties. The Hot Wire Method was used for simultaneously measuring the thermal conductivity and thermal diffusivity of both consolidated and unconsolidated low-rank coals. A new computer-interfaced experiment is presented and sample container designs developed for both coal powders and consolidated coals. A new mathematical model, based upon volume averaging, is presented for the prediction of these porous media properties. Velocity and temperature effects on liquid-phase dispersion through unconsolidated coal were determined. Radioactive tracer data were used to determine mass diffusivities. A new predictive mathematical model is presented based upon volume averaging. Vapor-phase diffusivity measurements of organic solvents in consolidated lignite coal are reported. An unsteady-state pressure response experiment with microcomputed-based data acquisition was developed to estimate dispersion coefficients through consolidated lignite coals. The mathematical analysis of the pressure response data provides the dispersion coefficient and the adsorption coefficient. 48 refs., 59 figs., 17 tabs.
Mechanical and thermal properties of bulk ZrB2
NASA Astrophysics Data System (ADS)
Nakamori, Fumihiro; Ohishi, Yuji; Muta, Hiroaki; Kurosaki, Ken; Fukumoto, Ken-ichi; Yamanaka, Shinsuke
2015-12-01
ZrB2 appears to have formed in the fuel debris at the Fukushima Daiichi nuclear disaster site, through the reaction between Zircaloy cladding materials and the control rod material B4C. Since ZrB2 has a high melting point of 3518 K, the ceramic has been widely studied as a heat-resistant material. Although various studies on the thermochemical and thermophysical properties have been performed for ZrB2, significant differences exist in the data, possibly due to impurities or the porosity within the studied samples. In the present study, we have prepared a ZrB2 bulk sample with 93.1% theoretical density by sintering ZrB2 powder. On this sample, we have comprehensively examined the thermal and mechanical properties of ZrB2 by the measurement of specific heat, ultrasonic sound velocities, thermal diffusivity, and thermal expansion. Vickers hardness and fracture toughness were also measured and found to be 13-23 GPa and 1.8-2.8 MPa m0.5, respectively. The relationships between these properties were carefully examined in the present study.
Electrical and thermal properties of graphite/polyaniline composites
Bourdo, Shawn E.; Warford, Brock A.; Viswanathan, Tito
2012-12-15
A composite of a carbon allotrope (graphite) and an inherently conducting polymer, polyaniline (PANI), has been prepared that exhibits an electrical conductivity greater than either of the two components. An almost 2-fold increase in the bulk conductivity occurs when only a small mass fraction of polyaniline exists in the composite (91% graphite/ 9% polyaniline, by mass). This increase in dc electrical conductivity is curious since in most cases a composite material will exhibit a conductivity somewhere between the two individual components, unless a modification to the electronic nature of the material occurs. In order to elucidate the fundamental electrical properties of the composite we have performed variable temperature conductivity measurements to better understand the nature of conduction in these materials. The results from these studies suggest a change in the mechanism of conduction as the amount of polyaniline is increased in the composite. Along with superior electrical properties, the composites exhibit an increase in thermal stability as compared to the graphite. - Graphical abstract: (Left) Room temperature electrical conductivity of G-PANI composites at different mass ratios. (Right) Electrical conductivity of G-PANI composites at temperatures from 5 K to 300 K. Highlights: Black-Right-Pointing-Pointer Composites of graphite and polyaniline have been synthesized with unique electrical and thermal properties. Black-Right-Pointing-Pointer Certain G-PANI composites are more conductive and more thermally stable than graphite alone. Black-Right-Pointing-Pointer G-PANI composites exhibit a larger conductivity ratio with respect to temperature than graphite alone.
Thermal Properties of Moving UV Features in Prominences
NASA Technical Reports Server (NTRS)
Kucera, Therese A.
2003-01-01
Multi-thermal features with speeds of 5-70 kilometers per second perpendicular to the line of sight are common in the prominences which showed traceable motions. These speeds are noticeably higher than the typical speeds of 5-20 kilometers per second observed in H-alpha data from "quiet" prominences and are more typical of "activated" prominences in which H-alpha blob speeds of up to 40 kilometers per second have been reported. In order to make a more quantitative determination of the thermal properties of the moving features seen in the UV, we use the SOHO instruments SUMER and CDS to take a time series of exposures from a single pointing position, providing a measurement of spectral line properties as a function of time and position along the slit. The resulting observations in lines spectral lines in a range of "transition region" temperatures allow us to analyze the thermal properties of the moving prominence sources as a function of time.
Configuration space Faddeev calculations. I. Triton ground state properties
NASA Astrophysics Data System (ADS)
Payne, G. L.; Friar, J. L.; Gibson, B. F.; Afnan, I. R.
1980-08-01
The formulation of Faddeev-type equations in configuration space is discussed. Numerical solutions are obtained using splines and the method of orthogonal collocation. Triton observables and wave-function probabilities are calculated for s-wave NN interaction models of Malfliet and Tjon and the tensor force model of Reid. Comparison with previously published triton results is made; our full five-channel results for the Reid soft-core potential are in excellent agreement with those obtained by Afnan and Birrell using separable expansion methods. NUCLEAR STRUCTURE 3H, Faddeev calculations configuration space.
Oliveira, A Virgílio M; Gaspar, Adélio R; Quintela, Divo A
2008-11-01
The present work is dedicated to a comparative analysis of calculation methods about clothing insulation with a thermal manikin operating under the thermal comfort regulation mode. The serial, global, and parallel calculation methods are considered and the thermal insulation results for garments (30) and ensembles (9) are discussed. The serial and parallel methods presents the higher and lower values, respectively, and the differences were sometimes significant. Considering the results for the effective thermal insulation, the mean values of the relative differences between the serial and global methods were 25.7% for the daily wear garments, 45.2% for the cold protective garments and 38.5% for the ensembles. The corresponding mean values for the global and parallel methods were 8.7, 15.8, and 10.5%, respectively. Since any uneven clothing insulation is to be expected as a source of error, particular care must be required when the calculation methods deal with cold protective clothing.