Thermal expansion and cold contraction refers to the characteristics that an object will expand when heated and contract when cold. Because the motion of particles (atoms) in the object will change with the temperature, when the temperature rises, the vibration amplitude of particles increases and the object expands; However, when the temperature drops, the vibration amplitude of particles will decrease, causing the object to contract.
Most general objects are applicable to the natural law of thermal expansion and cold contraction. However, the ceramic fiber module will not expand after heating, but also have a shrinkage rate of less than 3%. The reason stems from the structural characteristics of ceramic fiber itself.


The microstructure of ceramic fiber is a mixed structure composed of solid fiber and air. Its microstructure is characterized by the existence of solid phase and gas phase in the form of continuous phase. In this structure, the solid material exists in the form of fiber with a diameter of 2 ~ 5um and a length of 30 ~ 250mm, and forms a continuous solid skeleton, while the gas phase continuously exists in the skeleton gap of the fiber material, and the porosity is greater than 90%. Therefore, the expansion of ceramic fiber after heating will be converted by its own pores, which will not be obvious. This is the reason why the ceramic fiber module does not expand after heating.
During the application of ceramic fiber module in high-temperature furnace, due to the long-term high-temperature environment, the fiber filaments constituting the solid skeleton collapse due to self weight or brittle fracture, resulting in the collapse of the skeleton, the aggregation of fiber filaments and the reduction of void space. Therefore, the ceramic fiber products will shrink to a certain extent from the appearance, and the shrinkage rate is generally less than 3%.
Therefore, in the application of ceramic fiber module, we should follow the principle of high refractory temperature rather than low, select materials reasonably, and reduce the linear shrinkage of ceramic fiber as much as possible; Secondly, the ceramic fiber module + blanket structure shall be compacted as much as possible during construction to prevent cracks in the furnace lining caused by high temperature shrinkage and damage to the furnace body; At the same time, it is suggested that when selecting ceramic fiber module furnace lining, the surplus of ceramic fiber cotton blanket should be prepared for filling the gap in the later stage.

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