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.

Measurements of stress during vapor deposition of copper and silver thin films and multilayers

Abstract: Copper and silver single layer and multilayered thin films were thermal vapor deposited onto cantilevered substrates [Si(100) with native oxide] near room temperature in ultrahigh vacuum. The total force per unit width (F/w) in the film during and after deposition was determined from the change in substrate curvature measured in situ by a laser scanning technique. The intrinsic component of F/w was obtained by subtraction of the thermal component, which was obtained by measuring the product of the biaxial modulus of the film (Yf) and the difference in coefficients of thermal expansion of the substrate and the film (Δαs−f) while each sample was still in the ultra‐high vacuum deposition chamber. For all samples, the measured value of YfΔαs−f was substantially lower than the calculated value based on the {111} biaxial modulus and the coefficients of thermal expansion of the bulk materials, even though x‐ray diffraction indicated strong {111} film texture. During deposition, a general trend in F/w was found r...

Crystal structure, thermal expansion and electrical conductivity of perovskite oxides BaxSr1-xCo0.8Fe0.2O3-δ (0.3 ≤ x ≤ 0.7)

Abstract: BaxSr1-xCo0.8Fe0.2O3-delta (0.3 0.5 compositions. Furthermore, conductivity relaxation behaviors were also investigated at temperature 400-550 degrees C. Generally, Ba0.4Sr0.6Co0.8Fe0.2O3-delta and Ba0.5Sr0.5Co0.8Fe0.2O3-delta are potential cathode materials. (c) 2005 Elsevier Ltd. All rights reserved.

Anisotropic thermal expansion in wurtzite-type crystals

Abstract: The temperature dependence of the lattice parameters of six wurtzite-type crystals, BeO, AlN, GaN, ZnO, CdSe, and CdS, has been measured by X-ray powder diffractometry. The thermal expansion changes nonlinearly with temperature and is anisotropic; the expansion along the a-axis is larger than that along the c-axis (more than 50% larger in ZnO, CdS and CdSe), resulting in a decrease of the c/a ratio with increasing temperature. The calculated Gruneisen parameters range between 0.27 and 1.45 and have a positive correlation with the bulk moduli. The anisotropic thermal expansion is associated with the anisotropies of both elasticity and anharmonicity.

Resistivity of a composite conducting polymer as a function of temperature, pressure, and environment: Applications as a pressure and gas concentration transducer

Abstract: The resistivity of a commercial carbon‐filled composite conducting polymer (ET‐Semicon■) has been measured as a function of temperature between 80 and 400 K and under pressure up to 1.5 GPa (15 kbar). Large changes in resistivity were observed. The resistivity was also very sensitive to the presence of certain solvents and hydrocarbons. The results are explained as percolation effects caused by changes in volume due to pressure, thermal expansion, or dissolved solvents. The material studied is found to have a wide range of potential applications for pressure measurements and as a transducer for gas or liquid concentration.

Thermal stresses and thermal expansion in a uniformly heated functionally graded cylinder

Abstract: The exact solution is derived for the problem of uniformly heating a cylinder whose elastic moduli and thermal expansion coefficient vary linearly with radius. The solution shows that the radial and tangential stresses are largest in magnitude at the center of the cylinder whereas the deviatoric stress is largest in magnitude at the outer edge of the cylinder. The effective thermal expansion coefficient is found to be essentially given by the volumetric average of the local thermal expansion coefficient, with the variation in moduli having only a small effect. In the case of a material with uniform moduli but a spatially variable thermal expansion coefficient, the effective thermal expansion coeffi cient is exactly equal to the volumetric average; this result is an extension of those derived by Levin and Schapery for n-component materials.