共查询到20条相似文献,搜索用时 15 毫秒
1.
Takehiko Yagi 《Journal of Physics and Chemistry of Solids》1978,39(5):563-571
Unit-cell volumes of four alkali halides, LiF, NaF, KF and CSCl, were measured to 90 kbar and 800°C using X-ray powder diffraction techniques. NaCl was used as an internal pressure standard. Experimental results were analyzed based on Decker's equation of state for NaCl and thermal expansívities of these four materials were determined as a function of pressure. Volume dependence of thermal expansivity is different for the NaCl and CsCl structures. Comparisons of the present results with theoretical calculations by Birch and Anderson are presented. 相似文献
2.
S.K. Srivastava 《Journal of Physics and Chemistry of Solids》2006,67(11):2275-2281
In the present communication, the thermoelastic constants of ionic solids NaCl and KCl and the minerals MgO, CaO and Mg2SiO4 are analyzed using the tabulated data compiled by Anderson and Isaak. It is found that there exists a precise linear relationship between the thermoelastic constant and the thermal pressure. The proposed empirical relationship provides a method to estimate the thermoelastic properties out side the experimental data range. 相似文献
3.
《Physics letters. A》2006,360(2):362-366
The thermal expansivity and bulk modulus of ZnO with NaCl-type cubic structure were estimated by using the constant temperature and pressure molecular dynamics technique with effective pair potentials which consist of the Coulomb, dispersion, and repulsion interaction at high pressures and temperatures. It is shown that the calculated thermodynamic parameters including linear thermal expansion coefficient, isothermal bulk modulus and its pressure derivative are in good agreement with the available experimental data and the latest theoretical results. At an extended pressure and temperature ranges, linear thermal expansion coefficient and isothermal bulk modus have also been predicted. The thermodynamic properties of ZnO with NaCl-type cubic structure are summarized in the pressure 0–150 GPa ranges and the temperature up to 3000 K. 相似文献
4.
In the present investigation we have explained the thermal and compression properties of HCP iron (Fe) at high pressure with
variable temperature (isobars) and at high temperature with variable pressure (isotherm). The usual Tait equation of state
is modified by incorporating the effect of thermal pressure. The calculated values of pressure for different isotherms and
isochors and thermal expansivity (α) as a function of both temperature and pressure have been compared with those values obtained by Isaak et al and Wasserman et al.
相似文献
5.
M. R. Hopkins 《Zeitschrift für Physik A Hadrons and Nuclei》1957,147(2):148-160
A method of investigating the electrical and thermal conductivities of metals at high temperatures is described. The theory of the method depends upon the application of ideas which are fundamental in the study of electrical contact phenomena. The ratio of the thermal to the electrical conductivity of platinum has been determined from 1200° C to the melting point (1773° C) and from the melting point to 2300° C by making simultaneous observations of electrical potential and maximum temperature in a short wire through which current is passed. The wire terminates in two blocks of the same metal, and the ends of the wire are not assumed to be plane isothermal (and equipotential) surfaces. The wire remains in place when partly molten so that observations are extended well into the molten range. The method is independent of the exact geometrical configuration of the conducting system. The details of the arrangement of the apparatus and of the method of temperature measurement are given. The results are discussed in relation to the properties of the molten metal bridges formed between the electrodes of electrical contacts and to the value of theLorenz factor in theWiedemann-Franz law. 相似文献
6.
A. V. Yeganyan A. S. Kuzanyan V. Stathopoulos 《Journal of Contemporary Physics (Armenian Academy of Sciences)》2014,49(4):176-179
A generalized expression for approximate estimation of lattice component of thermal conductivity coefficient for solid-state crystal dielectrics at temperatures higher than the Debye temperature, is obtained, which is convenient for preliminary estimation of thermal conductivity coefficient and enables one to conduct a goal-directed search for low-conductivity materials. On the example of rare-earth magnesium hexaaluminates, it is shown that estimations according to the obtained expression are in good compliance with experimental data. 相似文献
7.
The microdynamics of soliton waves and localized modes of nonlinear vibrations of the acoustic and optical types in uranium
nitride has been investigated. It has been shown that, with an increase in the excitation energy in the spectral gap between
the bands of optical and acoustic phonons, the energies of solitons increase, whereas the energies of local modes decrease.
The previously experimentally observed unidentified quasi-resonant features, which shift in the gap with variations in the
temperature, can represent the revealed soliton waves and local modes. The microdynamics of heat conduction of uranium nitride
has been studied for the stochastic generation of soliton waves and local modes in the case of spatially distant energy absorption.
The thermal conductivity coefficient determined from the temperature gradient and the absorbed energy flux insignificantly
exceeds the experimentally observed values, which are decreased because of the presence of structural defects of different
types in the material. 相似文献
8.
A. V. Yeganyan A. S. Kuzanyan V. N. Stathopoulos 《Journal of Contemporary Physics (Armenian Academy of Sciences)》2016,51(1):61-64
Expressions for estimation of the thermal linear expansion coefficients and of the thermal conductivities of amorphous dielectrics above the Debye temperature are obtained. It is shown that for the compounds of the chemical composition corresponding to the rare-earth magnesium hexaaluminates taken as an example these parameters for amorphous compounds are less than for polycrystalline. 相似文献
9.
In the present study, we propose a suitable model to compute volume dependence of thermal expansivity which is applicable up to infinite pressure or compression. The newly developed model satisfies the constraints of infinite pressure as suggested by high-pressure thermodynamics. The compression dependence of thermal expansivity for lower mantle of the Earth is evaluated with the help of the proposed model. A close agreement between theory and the results predicted with the seismic data is found, which in turn reveals the validity of the present work. 相似文献
10.
S. N. Emirov G. G. Gadzhiev E. N. Ramazanova Z. Z. Abdulagatova E. M. Magomedmirzoev 《Bulletin of the Russian Academy of Sciences: Physics》2007,71(2):282-284
We present the results of our experimental studies of the thermal conductivity for SiC and SiC + 1.2% BeO ceramic samples as a function of the hydrostatic pressure up to 400 MPa in the temperature range 273–523 K. We show that pressure leads to a nonlinear increase in thermal conductivity and to an additional phonon scattering by lattice defects. 相似文献
11.
An ensemble of trapped C60 + ions has been heated with a continuous CO2 laser to a stationary state where, in time average, the same energy is emitted as absorbed. With 10 W laser power, equilibria have been reached, which correspond to temperatures between 1800 and 2000 K. The ions are confined in a radio frequency quadrupole field created by a set of ring electrodes (split ring electrode trap). The number of stored ions can be determined in two ways, on one side by extracting and counting them with a Daly detector, on the other side via imaging their thermal emission onto an intensified CCD camera. Single photon sensitivity and a spatial resolution of a few μm provide precise information on the geometrical distribution and the total number of the trapped C60 + ions. The spectral distribution of the emitted photons or their total number provides information on the internal energy of the ions. Trapping times of many minutes make it possible to follow very slow thermal loss of C2 from hot C60 + resulting in fragmentation rates between 10?1 and 10?3 s?1. Correlating them to the internal temperature leads to a curved Arrhenius plot. The resulting parameters are smaller than the values derived from nonequilibrium ensembles. 相似文献
12.
K. M. Shvarev 《Russian Physics Journal》1978,21(11):1453-1455
The radiative diffusion method is used to obtain an equation to calculate the radiative thermal conductivity of a conducting medium from the values of its resistivity, temperature, and refractive index. It is shown that for semiconducting materials with high resistivity ( 10–3 ·m) the radiative heat transfer compared to the other heat-transfer mechanisms is significant even at room temperature.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 82–85, November, 1978. 相似文献
13.
14.
M. I. Guseva V. M. Gureev B. N. Kolbasov S. N. Korshunov Yu. V. Martynenko V. B. Petrov B. I. Khripunov 《JETP Letters》2003,77(7):362-365
The sputtering of tungsten from a target at a temperature of 1470 K during irradiation by 5-eV deuterium ions in a steady-state dense plasma is discovered. The literature values of the threshold for the sputtering of tungsten by deuterium ions are 160–200 eV. The tungsten sputtering coefficient measured by the loss of weight is found to be 1.5×10?4 atom/ion at a deuterium ion energy of 5 eV. Previously, such a sputtering coefficient was usually observed at energies of 250 eV. The sputtering is accompanied by a change in the target surface relief, i.e., by the etching of the grain boundaries and the formation of a wavy structure on the tungsten surface. The subthreshold sputtering at a high temperature is explained by the possible sputtering of adsorbed tungsten atoms that are released from the traps around the interstitial atoms and come to the target surface from the space between the grains. The wavy structure on the surface results from the merging of adsorbed atoms into ordered clusters. 相似文献
15.
Chang NP 《Physical review D: Particles and fields》1994,50(8):5403-5408
16.
Recent achievements in solving the problem of the microscopic nature of the ferromagnetic-to paramagnetic-phase transition of ferromagnetic metals by employing the method of spin- and angle-resolved photoemission spectroscopy with synchrotron radiation (from the storage ring BESSY in Berlin) are briefly summarized. Emphasize is also given to the theoretical interpretation of the data, from which a short-range order in Fe near the Curie pointT
c
of at least 4 Å has been derived. This excludes the validity of the disordered local moment picture for Fe at high temperatures. 相似文献
17.
van Wüllen L Schwering G Naumann E Jansen M 《Solid state nuclear magnetic resonance》2004,26(2):84-86
We report MAS-NMR experiments at temperatures of approx. 1200 K using a CO(2) laser as the heating device. An internal NMR thermometer based on the (7)Li T1 data of Li(0.24)La(0.54)TiO(3) is used for temperature calibration. Using this setup, temperatures as high as 1191 K could be reached under MAS conditions as confirmed by the melting of Li(2)B(4)O(7) at 1191 K which could be followed by (7)Li-MAS-NMR. 相似文献
18.
The high-pressure and high-temperature behaviors of LiF and NaF have been studied up to 37 GPa and 1000 K. No phase transformations have been observed for LiF up to the maximum pressure reached. The B1 to B2 transition of NaF at room temperature was observed at ~28 GPa, this transition pressure decreases with temperature. Unit-cell volumes of LiF and NaF B1 phase measured at various pressures and temperatures were fitted using a P–V–T Birch–Murnaghan equation of state. For LiF, the determined parameters are: α0 = 1.05 (3)×10?4 K?1, dK/dT = ?0.025 (2) GPa/K, V 0 = 65.7 (1) Å3, K 0 = 73 (2) GPa, and K′ = 3.9 (2). For NaF, α0 = 1.34 (4)×10?4 K?1, dK/dT = ?0.020 (1) GPa/K, V 0 = 100.2 (2) Å3, K 0 = 46 (1) GPa, and K′ = 4.5 (1). 相似文献
19.
The knowledge of elasticity of the minerals is useful for interpreting the structure and composition of the lower mantle and
also in seismic studies. The purpose of the present study is to discuss a simple and straightforward method for evaluating
thermoelastic properties of minerals at high temperatures. We have extended the Kumar’s formulation by taking into the account
the concept of anharmonicity in minerals above the Debye temperature (θ
D). In our present study, we have investigated the thermophysical properties of two minerals (pyrope-rich garnet and MgAl2O4) under high temperatures and calculated the second-order elastic constant (C
ij
) and bulk modulus (K
T) of the above minerals, in two cases first by taking Anderson–Gruneisen parameter (δ
T) as temperature-independent and then by treating δ
T as temperature-dependent parameter. The results obtained when δ
T is temperature-dependent are in close agreement with experimental data. 相似文献
20.
A. V. Yeganyan T. I. Butaeva E. P. Kokanyan 《Journal of Contemporary Physics (Armenian Academy of Sciences)》2017,52(4):387-391
At high temperatures, the simple expression for thermal conductivity of crystals with the garnet structure is obtained, which allows one to determine this quantity if the lattice constant or density of these crystals is known. The thermal conductivity coefficients for the garnet crystals of different compositions calculated from the obtained formula are in a good agreement with the experimentally measured values. 相似文献