Thermal expansion

About: Thermal expansion is a research topic. Over the lifetime, 21040 publications have been published within this topic receiving 349407 citations. The topic is also known as: heat expansion.

Density and Thermal Expansion of Molten Manganese, Iron, Nickel, Copper, Aluminum and Tin by Means of the Gamma-Ray Attenuation Technique

Abstract: New experimental data for the density and the coefficient of thermal expansion of pure liquid Mn, Fe, Ni, Cu, Al and Sn at temperatures between melting and 1973K using the γ-ray attenuation technique are reported. An extensive study of sources of random and systematic errors has shown a maximum error of 0.75% in absolute density measurements. In the temperature range studied, the density behaves linearly with temperature. The density at the melting point and the coefficient of thermal expansion are in accordance with those of other studies. Comparison of the specific heat ratios γ calculated with the results of this study with those obtained using structural data from diffraction experiments shows large and even non-physical discrepancies, e.g., in the case of Mn. Solid-like viscoelastic behavior in the low-Q region is suggested as a possible cause of such anomaly while shear components would contribute noticeably to reduce the liquid compressibility. It is shown that expansivities of the present...

Structural anomalies associated with the electronic and spin transitions in LnCoO3

Abstract: A powder X-ray diffraction study, combined with the magnetic susceptibility and electric transport measurements, was performed on a series of LnCoO3 perovskites (Ln = Y, Dy, Gd, Sm, Nd, Pr and La) over a temperature range 100 - 1000 K. A non-standard temperature dependence of the observed thermal expansion was modelled as a sum of three contributions: (1) Weighted sum of lattice expansions of the cobaltite in the diamagnetic low spin state and in the intermediate (IS) or high (HS) spin state. (2) An anomalous expansion due to the increasing population of excited (IS or HS) states of Co3+ ions at the course of the diamagnetic-paramagnetic transition. (3) An anomalous expansion due to excitations of Co3+ ions to another paramagnetic state accompanied by an insulator-metal transition. The anomalous expansion is governed by parameters that are found to vary linearly with the Ln ionic radius. In the case of the first magnetic transition it is the energy splitting E between the ground low spin state and the excited state, presumably the intermediate spin state. The energy splitting E, determined by a fit of magnetic susceptibility, decreases with temperature. The values of E determined for LaCoO3 and YCoO3 at T = 0 K as 164 K and 2875 K, respectively, fall to zero at T = 230 K for LaCoO3 and 860 K for YCoO3. The second anomalous expansion connected with a simultaneous magnetic and insulator-metal transition is characterized by its center at T = 535 K for LaCoO3 and 800 K for YCoO3. The change of the unit cell volume during each transition is independent on the Ln cation and is about 1% in both cases.

High-Temperature Elasticity and Expansivity of Forsterite and Steatite

Abstract: The elastic constants and coefficients of thermal expansion of polycrystalline forsterite (Mg2SiO4) and steatite (MgSiO3) were determined from room temperature to 1000°K. Two elastic moduli, the adiabatic bulk modulus, Bs, and the shear modulus, G, decrease linearly with temperature above 500°K. The Gruneisen constant γ and a parameter δ, defined as — (dBs/dT)/αBs, calculated from the present data were virtually independent of temperature at the high-temperature range. Poisson's ratio, δ, rises linearly with temperature over the range of measurement; the slope is highest for materials with the lowest room-temperature value of σ.