Thermal Properties and Diffusion

In course

Description

This lecture covers the fundamental concepts of thermal properties and diffusion in materials, discussing topics such as thermal expansion coefficient, thermal stress, atomic diffusion, ductility, toughness, endurance limit, linear thermal expansion, specific heat capacity, thermal diffusion, and temperature dependence of material properties. The instructor explains how temperature affects the dimensions and mechanical properties of materials, emphasizing the importance of understanding these phenomena to prevent serious problems and accidents.

Official source

https://mediaspace.epfl.ch/media/0_v3tetj1e

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Related lectures (35)

Related concepts (34)

Heat capacity

Heat capacity or thermal capacity is a physical property of matter, defined as the amount of heat to be supplied to an object to produce a unit change in its temperature. The SI unit of heat capacity is joule per kelvin (J/K). Heat capacity is an extensive property. The corresponding intensive property is the specific heat capacity, found by dividing the heat capacity of an object by its mass. Dividing the heat capacity by the amount of substance in moles yields its molar heat capacity.

Heat capacity ratio

In thermal physics and thermodynamics, the heat capacity ratio, also known as the adiabatic index, the ratio of specific heats, or Laplace's coefficient, is the ratio of the heat capacity at constant pressure (CP) to heat capacity at constant volume (CV). It is sometimes also known as the isentropic expansion factor and is denoted by γ (gamma) for an ideal gas or κ (kappa), the isentropic exponent for a real gas. The symbol γ is used by aerospace and chemical engineers.

Molar heat capacity

The molar heat capacity of a chemical substance is the amount of energy that must be added, in the form of heat, to one mole of the substance in order to cause an increase of one unit in its temperature. Alternatively, it is the heat capacity of a sample of the substance divided by the amount of substance of the sample; or also the specific heat capacity of the substance times its molar mass. The SI unit of molar heat capacity is joule per kelvin per mole, J⋅K−1⋅mol−1.

Thermal insulation

Thermal insulation is the reduction of heat transfer (i.e., the transfer of thermal energy between objects of differing temperature) between objects in thermal contact or in range of radiative influence. Thermal insulation can be achieved with specially engineered methods or processes, as well as with suitable object shapes and materials. Heat flow is an inevitable consequence of contact between objects of different temperature.

Relations between heat capacities

In thermodynamics, the heat capacity at constant volume, , and the heat capacity at constant pressure, , are extensive properties that have the magnitude of energy divided by temperature. The laws of thermodynamics imply the following relations between these two heat capacities (Gaskell 2003:23): Here is the thermal expansion coefficient: is the isothermal compressibility (the inverse of the bulk modulus): and is the isentropic compressibility: A corresponding expression for the difference in specific heat capacities (intensive properties) at constant volume and constant pressure is: where ρ is the density of the substance under the applicable conditions.