Chapter 3 Thermal/electrochemical/magnetic properties

Coefficient of thermal expansion

Change in length per unit of the original length of a material when its temperature is raised by 1 K (1 °C).

Thermal conductivity

Property that describes the thermal energy transport in watts per second through a specimen 1 cm thick with a cross-sectional area of 1 cm2 when the temperature differential between the surfaces of the specimen perpendicular to the heat flow is 1 K (1 °C).

Thermal diffusivity

Measure of the speed with which a temperature change will proceed through an object when one surface is heated.

Concentration cell

Electrochemical corrosion cell in which the potential difference is associated with the difference in concentration of a dissolved species, such as oxygen, in solution along different areas of a metal surface; Pitting corrosion and crevice corrosion are types of this corrosion.

Crevice corrosion

Accelerated corrosion in narrow spaces caused by localized electrochemical processes and chemistry changes, such as acidification and depletion in oxygen content; Crevice corrosion commonly occurs when microleakage takes place between a restoration and the tooth.

Corrosion

Chemical or electrochemical process in which a solid, usually a metal, is attacked by an environmental agent, resulting in partial or complete dissolution.

Electromotive series

Arrangement of metals by their equilibrium values of electrode oxidation potential; Used to judge the tendency of metals and alloys to undergo electrochemical (galvanic) corrosion.

Galvanic corrosion

Accelerated attack occurring on a less noble metal when electrochemically dissimilar metals are in electrical contact within a liquid corrosive environment.

Galvanic shock

Pain sensation caused by the electrical current generated when two dissimilar metals are brought into contact in the oral environment.

Pitting corrosion

Highly localized corrosion occurring at metal surface defects such as pits, scratches, and cracks in which the region at the bottom is oxygen-deprived and becomes the anode while the surface around it becomes the cathode; Thus metal at the base preferentially ionizes and goes into solution, causing the defects to enlarge.

Stress corrosion

Degradation caused by the combined effects of mechanical stress and a corrosive environment, usually exhibited as cracking.

Tarnish

Process by which a metal surface is dulled or discolored when a reaction with a sulfide, oxide, chloride, or other chemical causes surface discoloration through formation of a thin oxidized film.

Magnet

Metallic material in which the component atoms are so ordered that it can attract iron-containing objects or align itself in an external magnetic field.

Tesla

Unit of flux density (T) of the magnetic field produced by a magnet.