The Debye theory of solid-state heat capacities

“The Debye theory of solid-state heat capacities” gives a careful account of the Debye cut-off. We start by looking at a monatomic linear chain, leading to degrees of freedom and the equipartition of energy at the high-temperature (classical) limit. Reasonable approximations lead more naturally to the Born–von Karman model than to Debye, but Debye follows via a further reasonable step.

TEMPERATURE DEPENDENCE OF HEAT CAPACITY OF ALUMINIUM, COPPER, SILICON, MAGNESIUM AND ZINC AND COMPARISON WITH DEBYE THEORY

The results of comparison of heat capacity of aluminum, copper, silicon, magnesium and zinc with Debye's theory depending on temperature are given in the paper. It was revealed that the main components of the heat capacity of metals are the lattice component; is a component due to thermal expansion and is an electronic contribution. It is proposed that when creating the theory of heat capacity, it is necessary to take into account the anharmonicity of the oscillations of atoms in the nodes of the crystal lattice and the change in Debye temperature.

Gravitational and Coulomb Potentials Interference in Heliosphere

Interference of gravitational and Coulomb potentials in the entire heliosphere is considered, it is being manifested in generation of two opposite flows of charged particles: 1) that are neutral or with a small charge to the Sun, and 2) in the form of a solar wind from the Sun. According to the Einstein --- Smoluchowski relation Te(R) = eDe / µe ~ (E/N)0.75 based on the N experimental values (heavy particles number density --- the ne electron concentration), the Te electron temperature in the entire heliosphere was for the first time analytically calculated depending on the charge of the Sun and distance to it R. Calculated values of the registered ion parameters in the solar wind were compared with experimental observations. Reasons for generating the ring current in inhomogeneous heliosphere and inapplicability of the Debye theory in describing processes in the solar wind (plasma with current) are considered

Calorimetric Research into the Heat Capacity of Novel Nano-Sized Cobalt(Nickelite)-Cuprate-Manganites of LaBaMeIICuMnO6 (MeII = Co, Ni) and their Thermodynamic Properties

The isobaric heat capacities of novel nano-sized cobalt-cuprate-manganite of lanthanum and barium LaBaCoCuMnO6 and nickel-cuprate-manganite of lanthanum and barium LaBaNiCuMnO6 were investigated by dynamic calorimetry over the temperature range of 298.15‒673 K. It is found that a λ-shaped effect is observed on the curve of the heat capacity dependence on temperature of LaBaCoCuMnO6 at 523 K, while LaBaNiCuMnO6 also has a similar effect at 473 K. Equations for the temperature dependence of the heat capacity of cobalt(nickelite)-cuprate-manganite of lanthanum and barium are derived with allowance for the temperatures of phase transitions. Based on the experimental data, the fundamental constants ‒ the standard heat capacities of the compounds under study were found. Irrespective of the experimental data, we also calculated the standard heat capacities of the mentioned compounds using the Debye theory using the characteristic temperatures of the elements, their melting points, the Koref and Nernst-Lindemann equations. The obtained calculated data on C0p (298.15) of the compounds were in satisfactory agreement with the experimental data on the standard heat capacity. The standard entropies of LaBaCoCuMnO6 and LaBaNiCuMnO6 were calculated by the ion increment method. We calculated the temperature dependences of the enthalpy Ho(T)- Ho(298.15), entropy ΔSo(T), and the reduced thermodynamic potential ΔФ**(Т).

Shear Viscosity of Aqueous Electrolyte Solutions

The kinematic shear viscosity of aqueous electrolyte solutions has been studied. The temperature dependence of this parameter is shown to be described by an exponential formula at T < Td and a formula of the argon-like type at T > Td, where Td is the temperature of the dipole ordering, in the whole considered concentration interval. Main attention is focused on the peculiarities in the temperature and concentration dependences of the shear viscosity in the argon-like interval. It is shown that the root-like concentration dependence can appear, only if the Debye theory of dilute electrolyte solutions is applicable. Beyond its validity domain, the series expansion of the kinematic shear viscosity in the concentration parameter should have an analytical character. The latter behavior is inherent in the concentration dependence of the shear viscosity in the majority of experiments. The error of reproducing the experimental data did not exceed the experimental one, i.e. it was smaller than 4–5%.

Effects of Grain Sizes and Impurities on Thermal Conductivity in Aluminum Nitride

The effects of grain sizes and oxygen impurities on thermal conductivity in aluminum nitride (AlN) ceramics has been calculated by density functional perturbation theory (DFPT) and quasi-harmonic approximation (QHA) combined with Debye theory in the paper. From 300K up to 1000K, the predicted thermal properties are compared with experimental data. The agreements with experiment suggest that the theoretical method used in the paper is an effective approach. From our theoretical study, the reduction of thermal conductivity is greater between grain sizes of 1μm and 5μm, while it’s smaller between 8μm and 10μm. Oxygen defects bring about greater influence on thermal conductivity at low temperature than at high temperature. The influence of the oxygen defect is not as significant as the grain sizes when the oxygen concentrations are less than 0.70 at. %, so it’s more important to increase the grain sizes than reduce the oxygen contents in the preparation process to achieve high thermal conductivity AlN ceramics.

Thermal Stress of Building Materials Containing Plasticizer Characterised by Alternating Electric Field

Paper deals with the applicability of impedance spectroscopy method to testing of cement-based composites prepared from a mix of type CEM I cement and siliceous sand, as well as by substituting 25 % of sand with shredded automobile tires and by adding acrylic polymer binder (10 % w/w of the polymer mass to cement mass). The monitoring of structural changes in the thermal stress is very important, for example for determining the reliability of the whole structure. Samples were intentionally degraded by high-temperature (in a temperature range from 25 °C to 400 °C). The primary monitored magnitudes were electrical capacitance C, the relative permittivity εr and components of electric impedance |Z|. Based on the Debye theory of dielectric the models were created, their applications and received parameters measured dielectric material is characterized and discussed the uniqueness of determining the values of model parameters. Development of electrical parameters and permittivity at each temperature areas reliably show thus structural changes and thus the structural reliability.

Non-Destructive Tracking of Structural Changes of Concrete Mixtures during Thermal Stress

This paper deals with the application of the method of impedance spectroscopy to testing of cement-based composites prepared from a mix of cement mortar and quartz sand, which were intentionally degraded by high-temperature treatment (in the temperatures range from 25 °C to 400 °C). The monitoring of structural changes in the thermal stress is very important, for example for determining the reliability of the whole structure. Based on the Debye theory of dielectric the models were created, their applications and received parameters measured dielectric material is characterized and discussed the uniqueness of determining the values of model parameters. Development of electrical parameters and permittivity at each temperature areas reliably show these structural changes and thus the structural reliability.