Melting Temperature and Coefficient of Thermal Expansion

The melting temperature has naturally the physical dimension of a temperature. To find a relation wifh ofher quantities in a dimensionless form, we go through tables and discover that the coefficient of thermal expansion has the dimension of a reciprocal temperature. Now there could be some natural relation between these two quantities. We can fix a zero temperature as reference state or infinite temperature as reference state. It is more reasonable to fix zero temperature as reference state. Therefore, coming from low temperature, it is more likely to choose the coefficients of thermal expansion in the solid state than the coefficients of thermal expansion in the liquid state. 

In Fig. 11.3, the coefficients of thermal expansion at room temperature, as far as available, are plotted against the melting temperatures of the elements. It looks like there is indeed a relation between the coefficients of thermal expansion and the melting temperatures. Elements with a big coefficient of thermal expansion will 

Question 11.1. Metals with a low melting point are ductile, whereas metals with a high melting point are brittle. Think about ductile and brittle. Are these contradictory concepts Choose a physical quantity to characterize this property, e.g., various methods for measuring hardness. Make a plot of melting point against hardness. 

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Thermal ejfects, such as extreme heat or cold, or rapid changes in temperature, can cause temporary or permanent changes in the physical characteristics of optical materials. The critical material characteristics are melting temperature and coefficient of thermal expansion. For example, thermal expansion of a material can be particularly important in applications in which the optical component is subjected to localized heating, caused by high laser light power. As a result, non-uniform material density introduces distortion of the beam paths (e.g. thermal leasing). 

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