Specific heat capacity
The specific heat or heat capacity Cp denotes the amount of energy needed to heat one kilogram of a material exactly one Kelvin.
There are substances that have a high heat capacity and thus require a lot of energy to heat up, such as water, but also those that are relatively easy to heat, such as iron or lead. The determination of Cp is particularly interesting when it comes to energy distribution during heating, use of waste heat, heat storage, insulation or thermal resistance.
For almost all components, the Cp value is known today and is determined by default. Of course, this already starts in the development of materials, of which mostly only small samples exist.
By means of DSC, the specific heat can be determined on the basis of only a very small amount of sample by performing a measurement against a sapphire disk over the desired temperature range.
Sapphire is a material whose specific heat is very linear with temperature and therefore well suited as a calibration standard. In a Cp measurement, the sample to be examined is heated at a defined heating rate and the heat absorption of the sample is determined by comparison with the environment.
In the normal case, if the sample does not undergo phase transformation or reaction, then the sample temperature is always slightly lower than the ambient temperature or in this case the temperature of the crucible in which the sample is located. From this difference can then be calculated on the basis of the sapphire calibration, the exact amount of energy that has flowed during heating in the sample.