Thermal Stability
Thermal stability of materials is a measure of the material’s tolerance to harsh environmental conditions caused by high temperatures. Generally speaking, any noticeable effect on the integrity of the material due to a high temperature exposure is an indication of its thermal instability. Materials with low thermal stability will generally begin to degrade as the material is exposed to increased temperatures. Degradation of the material can take many forms ranging from physical changes such as melting and cracking to chemical changes such as oxidation and chemical decomposition.
The study of a material’s thermal stability requires careful consideration of the materials thermal expansion, heat capacity, coefficient of thermal expansion, and thermal conductivity. These properties all influence the rate at which heat is transferred throughout the material and how it is dispersed. Thermal expansion is the rate at which a material changes in volume with a change in temperature. Heat capacity is the amount of energy required to increase the temperature of a given material. Lastly, thermal conductivity is the measure of the material’s ability to conduct heat energy.
A material’s thermal stability is further affected by its microstructure. In crystalline materials, the presence of defects such as dislocations can reduce the stability of the material due to increased thermal expansion near the defect. Dense materials composed of tiny particles generally have higher thermal stability than their more porous counterparts as the particles are able to hold onto their thermal energy for longer periods of time.
The thermal stability of a material can be improved through the use of protective coatings. Common coatings used to increase thermal stability include those made from metals, ceramics, and composites. These coatings act as a barrier, preventing the material from degrading while exposed to high temperatures. In certain cases, the coatings can even improve the thermal conductivity of the material, enhancing its ability to dissipate heat energy.
Understanding the thermal stability of a material is essential for designing materials that can withstand harsh environmental conditions such as high-temperature applications. Materials with greater thermal stability can be formed into components with higher temperatures and be designed to last longer. This makes the study of thermal stability a vital part of the discipline of materials science.
