![]() These discontinuities allow detection of the glass transition temperature where a supercooled liquid transforms to a glass. ![]() At the glass transition temperature, rearrangements that occur in an amorphous material lead to characteristic discontinuities of coefficient of thermal expansion and specific heat. The thermal expansion of glasses is slightly higher compared to that of crystals. In general, liquids expand slightly more than solids. Thermal expansion generally decreases with increasing bond energy, which also has an effect on the melting point of solids, so high melting point materials are more likely to have lower thermal expansion. Unlike gases or liquids, solid materials tend to keep their shape when undergoing thermal expansion. ALLVAR Alloy 30, a titanium alloy, exhibits anisotropic negative thermal expansion across a wide range of temperatures. Fairly pure silicon has a negative coefficient of thermal expansion for temperatures between about 18 and 120 kelvin. Other materials are also known to exhibit negative thermal expansion. For example, the coefficient of thermal expansion of water drops to zero as it is cooled to 3.983 ☌ and then becomes negative below this temperature this means that water has a maximum density at this temperature, and this leads to bodies of water maintaining this temperature at their lower depths during extended periods of sub-zero weather. If an equation of state is available, it can be used to predict the values of the thermal expansion at all the required temperatures and pressures, along with many other state functions.Ĭontraction effects (negative thermal expansion) Ī number of materials contract on heating within certain temperature ranges this is usually called negative thermal expansion, rather than "thermal contraction".
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