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.

Structure and thermodynamic properties of nanocrystalline metals.

Abstract: Nanocrystalline (nc) metals show significant differences in their thermodynamic properties, such as specific heat at constant pressure and thermal expansion, in comparison to polycrystalline metals These properties are explained in terms of a macroscopic analysis Based on a quasiharmonic approximation, the thermodynamic quantities are calculated as functions of the excess volume of the grain-boundary component in nc metals The enhancements of the specific heat and the thermal expansion coefficient are accompanied by a reduction of the Debye temperature The results show good agreement with experimental data

Tuning the thermal expansion properties of optical reference cavities with fused silica mirrors

Abstract: We investigate the thermal expansion of low thermal noise Fabry–Perot cavities made of low thermal expansion (LTE) glass spacers and fused silica (FS) mirrors. The different thermal expansion of mirror and spacer deforms the mirror. This deformation strongly contributes to the cavity’s effective coefficient of thermal expansion (CTE), decreasing the zero crossing temperature by about 20 K compared to an all-LTE glass cavity. Finite element simulations and CTE measurements show that LTE rings optically contacted to the back surface of the FS mirrors allow to tune the zero crossing temperature over a range of 30 K.

Viscosity and Glass Transition in Amorphous Oxides

Abstract: An overview is given of amorphous oxide materials viscosity and glass-liquid transition phenomena. The viscosity is a continuous function of temperature, whereas the glass-liquid transition is accompanied by explicit discontinuities in the derivative parameters such as the specific heat or thermal expansion coefficient. A compendium of viscosity models is given including recent data on viscous flow model based on network defects in which thermodynamic parameters of configurons—elementary excitations resulting from broken bonds—are found from viscosity-temperature relationships. Glass-liquid transition phenomena are described including the configuron model of glass transition which shows a reduction of Hausdorff dimension of bonds at glass-liquid transition.

Free volume theory and nonlinear thermoviscoelasticity

Abstract: The rheological behavior of polymers in the neighborhood of the glass transition is investigated in the framework of the free volume theory of nonlinear viscoelastic behavior. Free volume theory as normally applied above the glass transition is modified to account for the effect of the residual volume of vacancies below the glass transition; this modification is accomplished by modeling the changes in the state of the polymer as the sum of viscoelastic changes and a random disturbance deriving from the thermal collisions between molecule segments. The changes in mechanical properties in passing across the glass transition follow from the freezing-in of relaxation mechanisms and of free volume; the model, which also incorporates a time-dependent coefficient of thermal expansion under isobaric conditions, does not require additional parameters other than those characterizing the rubbery state. The pressure dependence of the glass transition is found to be in qualitiative agreement with measurements on PVAc, while the ratio of the glassy and rubbery heat capacities is found to coincide with the ratio of the equilibrium bulk compliances in the glassy and rubbery domains.