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.

Measurement of the Electronic Grüneisen Constant Using Femtosecond Electron Diffraction

Abstract: We report the first accurate measurement of the electronic Gruneisen constant gamma(e) using a novel method employing the new technique of femtosecond electron diffraction. The contributions of the conduction electrons and the lattice to thermal expansion are differentiated in the time domain through transiently heating the electronic temperature well above that of the lattice with femtosecond optical pulses. By directly probing the associated thermal expansion dynamics in real time using femtosecond electron diffraction, we are able to separate the contributions of hot electrons from that of lattice heating, and make an accurate measurement of gamma(e) of aluminum at room temperature. This new approach opens the possibility of distinguishing electronic from magnetic contributions to thermal expansion in magnetic materials at low temperature.

Viscosity and elastic constants of amorphous Si and Ge

Abstract: The biaxial modulus and coefficient of thermal expansion of ion‐beam‐sputtered amorphous Si and Ge thin films were determined from curvature changes induced by differential thermal expansion. Viscous flow was measured by stress relaxation and was found to be Newtonian. The viscosity increased linearly with time as a result of structural relaxation, and its isoconfigurational activation enthalpy was 1.8±0.3 and 2.6±1.3 eV for amorphous Si and Ge, respectively. An atomistic model, based on a chain reaction of broken bond rearrangements, is proposed to describe the observation.

The characterization of thermal and elastic constants for an epoxy photoresist SU8 coating

Abstract: All of the thermal and elastic constants of the high-aspect ratio, negative, UV resist, SU8 coating were carried out, and the compliance matrix of the coating was obtained DSC, TGA, TMA, and DMTA techniques were utilized to study the thermal properties of the material The in-plane thermal expansion coefficient (TEC) (α1) was determined by TMA, and the glass transition behavior was studied by DMTA The TGA study provided information about the thermal stability of the material, and DSC was applied to study the thermal calorimetric properties of the material The in-plane Young's modulus (E 1) was measured by tensile tests The residual stresses of a 1D stretched ribbon sample and a 2D stretched membrane sample were measured by vibrational holography tests, and the in-plane Poisson's ratio (ν1) was also determined by holography The out-of-plane Poisson's ratio (ν2) was obtained by high pressure gas dilatometry measurements The bulk compressibility (κ) and the volumetric TEC (α v ) of the material were measured by a pressure-volume-temperature (PVT) apparatus Finally, the out-of-plane properties, including the out-of-plane TEC (α2) and the out-of-plane Young's modulus (E 2), were calculated from the measured in-plane properties and the volumetric properties Therefore, the compliance matrix of the studied SU8 coating could be obtained

Controllable thermal expansion of large magnitude in chiral negative Poisson's ratio lattices

Abstract: Lattices of controlled thermal expansion are presented based on planar chiral lattice structure with Poisson’s ratio approaching -1. Thermal expansion values can be arbitrarily large positive or negative. A lattice was fabricated from bimetallic strips and the properties analyzed and studied experimentally. The eective thermal expansion coecient of the lattice is about = 3:5 10 4 K 1 . This is much larger in magnitude than that of constituent metals. Nodes were observed to rotate as temperature was changed corresponding to a Cosserat thermoelastic solid.