Inverse correlation between cohesive energy and thermal expansion coefficient in liquid transition metal alloys

The volume expansion coefficients (α) of twenty-five glass-forming transition metal alloy liquids, measured using the electrostatic levitation technique, are reported. An inverse correlation between α and the cohesive energy is found. The predicted values of α from this relationship agree reasonably well with the published data for thirty other transition metal and alloy liquids; some disagreement was found for a few alloys containing significant amounts of group III and IV elements. A theoretical argument for this empirical relationship is presented.     

Relation between a linear thermal expansion coefficient and residual stresses

A method of determining the residual stresses in metallic sheets is proposed. It consists in finding the strain field induced by central point heating and calculating the field of residual stresses using a functional relation between a linear thermal expansion coefficient and residual stresses.     

Heat capacity, root-mean-square displacements of atoms and thermal expansion coefficient of europium hexaboride

The temperature dependences of the specific heat capacity c _p(T), thermal expansion coefficient α(T) of europium hexaboride, and root-mean-square displacements of Eu and B atoms are determined in the temperature range from helium to room temperature (5–300 K).     

用光学干涉法测量材料的高温线膨胀系数

采用石英传递杆将高温区材料的线膨胀量传递到室温区,并利用标准件进行标定的方法消除由传递带来的附加线膨胀量的影响,利用迈克耳孙干涉仪测量微小位移的原理,测量材料的线膨胀系数;测量相对误差仅为1.0％,而且测量过程非常直观简单.     

Negative thermal expansion coefficient in the Kondo lattice

The thermal expansion coefficient is calculated for a two bands Fermi liquid : it is shown that the interband electronic transfer can give a large contribution. The calculation is applied to the Kondo lattice: the thermal expansion coefficient α can be negative for a certain range of values of the Kondo temperature, and a pseudo-gap is necessary. The experimental results about CeAl₃ are correctly interpreted by our model.     

Investigation of the thermal expansion and heat capacity of the CaCu3Ti4O12 ceramics

The thermal expansion of the CaCu₃Ti₄O₁₂ ceramics has been measured over a wide temperature range 120?C1200 K. The high quality of the samples under study has been confirmed by good agreement of the results of measurements of the heat capacity in the range 2?C300 K and in the vicinity of the phase transition of magnetic nature at 25 K with the data for the single crystal. No anomalies in the thermal expansion that can be associated with the phase transition at 726?C732 K assumed by other investigators have been found. The influence exerted on the thermal expansion by the heat treatment of the sample in a helium atmosphere and in air has been investigated.     

Isotope effect for the thermal expansion coefficient of germanium

The first experimental and theoretical investigation of the difference in the temperature behavior of the linear expansion coefficients of single crystals grown from isotopically highly enriched and natural germanium is reported. A comparison of the data for ⁷⁰Ge and ^natGe crystals reveals the significant influence of isotopic composition over a wide range of temperatures 30–230 K. Zh. éksp. Teor. Fiz. 115, 243–248 (January 1999)     

Bond theory model to study cohesive energy,thermal expansion coefficient and specific heat of nanosolids

The fraction of surface atoms and the dangling bonds on the surface affect the thermodynamical properties of the nanostructured solids. A bond theory model is extended to study the size dependent thermodynamical properties at nanoscale. The theory is applied to analysis the size and shape dependence of cohesive energy, thermal expansion coefficient and specific heat of Ag, Au, Cu and Se nanosolids. The relaxation factor is incorporated at low dimension of nanosolids, which is expressed as the ratio of dangling bonds and the total bonds of atoms. It is predicted that the cohesive energy decreases with decrease in particle size. On the same ground, the model is proposed to analyze the thermal expansion coefficient and specific heat of the nanomaterials. It is reported that the thermal expansion coefficient and specific heat increase as particle size decreases. The predictions agree well with available experimental or simulation results.     

Studies of the heat capacity and thermal expansion of the Na0.95K0.05NbO3 solid solution

The heat capacity and thermal expansion of ceramic samples of the Na_0.95K_0.05NbO₃ solid solution have been investigated over a wide temperature range of 100–750 K. The observed anomalies in the heat capacity and thermal expansion at T ₄ = 297 K, T ₃ = 535 K, T ₂ = 665 K, and T ₁ ≈ 710 K correspond to the sequences of phase transitions N → Q → G → S → T1. It has been shown that, as a result of the phase transitions, the unit cell volume at T ₄ and T ₂ decreases, and at T ₃ and T ₁, increases with increasing temperature. The directions of the shift of the phase transition temperatures induced by hydrostatic pressure have been determined. It has been established that all structural transformations are accompanied by relatively small variations in the entropy. Different mechanisms of the structural distortions have been discussed.     

Modulus of elasticity and thermal expansion coefficient of glassy solids

A linear correlation between the modulus of elasticity and the inverse square of the thermal expansion coefficient for inorganic glasses has been found. The nature of interrelation between linear and nonlinear properties of solids has been discussed.     

Measurement of thermal expansion coefficient of nonuniform temperature specimen

A new technique is developed to measure the longitudinal thermal expansion coefficient of C/C composite material at high temperature. The measuring principle and components of the apparatus are described in detail. The calculation method is derived from the temperature dependence of the thermal expansion coefficient. The apparatus mainly consists of a high temperature environmental chamber, a power circuit of heating, two high-speed pyrometers, and a laser scanning system. A long solid specimen is resistively heated to a steady high-temperature state by a steady electrical current. The temperature profile of the specimen surface is not uniform because of the thermal conduction and radiation. The temperature profile and the total expansion are measured with a high-speed scanning pyrometer and a laser slit scanning measuring system, respectively. The thermal expansion coefficient in a wide temperature range (1000 - 3800 K) of the specimen can therefore be obtained. The perfect consistency between the present and previous results justifies the validity of this technique.     

Relationship between the thermal expansion coefficient, plasmon energy, and bond length of ternary chalcopyrite semiconductors

A simple relation between the average bond length and plasmon energy, that is, d=15.30(?ω_p)^−2/3, has been proposed for A^IIB^IVC^V₂ and A^IB^IIIC^VI₂ chalcopyrite semiconductors. The average linear thermal expansion coefficient (α_L) of these semiconductors has been calculated using plasmon energy data. The linear expansion coefficients (α_a) and (α_c) of the lattice parameters a and c, respectively, have also been calculated. The calculated values of d, α_L, α_a and α_c have been compared with the experimental values and the values reported by different workers. A fairly good agreement has been obtained between them.     

On the thermal expansion of nanoparticles

Magnetite nanoparticles with an average particle size of 7.5 nm were studied by Mössbauer spectroscopy in the 100–300 K temperature range. Using experimental data on the temperature variation of isomer shifts in the partial spectra of ⁵⁷Fe nuclei in the A and B crystal sublattices, the linear thermal expansion coefficient of the ultradisperse magnetite particles in the temperature range studied was estimated within the framework of the molecular orbital formalism: α=(1.2±0.2)×10^?4K^?1.     

On the empirical correlation between the superconducting Tc and the Hall coefficient

It is shown that the occurence of superconductivity and the sign of the Hall coefficient are correlated in transition and non-transition elements and alloys.     

Thermodynamic properties of clathrates: I. The heat capacity and entropy of argon in the argon quinol clathrates

Measurements have been made of the heat capacity C_p from ～ 13°k to ～ 273°k of five clathrates of argon and β-quinol. The argon content ranged from ～ 20 per cent to ～ 80 per cent of the maximum possible amount. Over much of the temperature range studied, C_p proved to be a linear function of the argon content, but from 13°k to 20°k, and from 50°k to 100°k the relation between C_p and argon content is obscure, and may, in fact, be non-linear. Estimates have been made of the contribution to C_p made by a mole of argon in the temperature region where C_p is a linear function of composition, and these experimental values have been compared with those calculated according to the theory of J. H. van der Waals, which is based on the cell model of Lennard-Jones and Devonshire. The agreement between theory and experiment is satisfactory.     

动态双光栅测量金属热膨胀系数

在双光栅测量音叉微小振幅的理论基础上,利用静光栅纵向位移对金属热膨胀系数进行测量.本文给出了动态双光栅测量金属热膨胀系数的理论拓展与实验结果.     

Temperature dependence of thermal expansion coefficient of crystals with cubic syngony

A simple analytic temperature relationship for the thermal expansion coefficient of crystals with cubic syngony was obtained, and the thermal expansion coefficients of some crystals of this class were determined experimentally; the results agreed satisfactorily with the curve obtained from formulas (5) and (6). The temperature range from liquid nitrogen up to temperatures around 1000 ° K was investigated, and the results were compared with data given by other authors.