"Thermal expansion and contraction" is a common physical property of most substances: an object expands when heated and contracts when cooled. This is because as the temperature rises, the thermal vibrations of particles within the object intensify, causing the object's volume to increase; whereas, as the temperature drops, the particle vibrations weaken, causing the volume to decrease.
01 Why Ceramic Fibers Don't Expand When Heated
While most natural materials follow the principle of thermal expansion and contraction, ceramic fibers are an exception-they barely expand when heated, and instead exhibit slight contraction (linear shrinkage is typically less than 0.03). This unique property stems from their unique microstructure.
Ceramic fiber materials are composed of a large number of solid fibers and air. Their microstructure exhibits a mixed system of "continuous solid phase + continuous gas phase":
The solid phase consists of fiber filaments approximately 25μm in diameter and 30-250mm in length, forming a supporting skeleton.
The gas phase is distributed in the pores between the fibers, resulting in an overall porosity of over 90%. During heating, the thermal expansion of the fiber is "absorbed" or "buffered" by the high proportion of pores, resulting in virtually no volume expansion in the overall structure.
02 Why Shrinkage Occurs at High Temperatures
When ceramic fiber products are used in high-temperature furnaces for long periods of time, the fiber skeleton is subjected to continuous high temperatures, causing the fibers to break or collapse due to their own weight or embrittlement. This reduces internal voids and tightens the structure, resulting in slight volume shrinkage. This shrinkage often manifests as thinning of the module or surface concavity, with a linear shrinkage ratio typically not exceeding 0.03.
Application Recommendations
To minimize the risk of shrinkage during use, consider the following:
Material Selection Principles: Ceramic fiber materials with a refractory temperature higher than the actual furnace temperature should be preferred to minimize linear shrinkage at high temperatures.
Construction Density: The fiber modules should be fully compacted during construction to prevent cracks in the furnace lining caused by high-temperature shrinkage, which could affect service life.
Reserved Filling Material: When installing the ceramic fiber module lining, it is recommended to prepare a sufficient amount of ceramic fiber blanket for later caulking, repairing, and reinforcing edges and corners to ensure a tight and seamless overall structure.
SUNTHERM offers high-performance ceramic fiber materials with stable dimensional control and excellent shrinkage resistance, suitable for a wide range of industrial kiln systems.
