Why don’t ceramic fiber modules expand and contract with heat?

Thermal expansion and contraction refer to the property that an object expands when heated and shrinks when cold. Since the movement of particles (atoms) in an object changes with temperature, when the temperature rises, the vibration amplitude of the particles increases, causing the object to expand; but when the temperature drops, the vibration amplitude of the particles decreases, causing the object to shrink.

The natural law of thermal expansion and contraction is generally applicable to general objects. However, the ceramic fiber module will not expand after being heated, but will also have a shrinkage rate of less than 3%. The reason lies in the structural characteristics of the ceramic fiber itself.

The structure of ceramic fiber is a mixed structure composed of solid fiber and air, and its microstructure is characterized in that both solid and gas phases exist as continuous phases. In this structure, the solid matter exists in the form of fibers with a diameter of 2 to 5 Um and a length of 30 to 250 mm, and constitutes a continuous solid phase 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 folded away by its own pores, and it will not be too obvious. This is the reason why the ceramic fiber module does not expand after being heated.

During the application of ceramic fiber modules in the high temperature furnace, due to the long-term high temperature environment, the fiber filaments that make up the solid-phase framework will collapse due to their own weight or brittle fracture, resulting in the collapse of the framework, the aggregation of fiber filaments, and the reduction of void space. Therefore, the ceramic fiber products will have For certain shrinkage, the shrinkage rate is generally less than 3%.

Therefore, when the ceramic fiber module is applied, it is necessary to follow the principle of high refractory temperature and reasonable selection of materials to minimize the linear shrinkage of the ceramic fiber; secondly, the ceramic fiber module + blanket structure should be compressed and compacted as much as possible during the construction process to prevent high temperature shrinkage This leads to gaps in the furnace lining and damage to the furnace body; at the same time, it is recommended that when ceramic fiber module lining is selected, there should be a margin of ceramic fiber cotton blanket for filling the gap in the later stage.

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