Measuring the Coefficient of Thermal Expansion

Switching to a polycrystalline mullite fiber furnace body has significantly improved our thermal expansion measurement workflow. Because the furnace body itself neither absorbs nor conducts heat, the chamber now reaches 1600 °C in about 40 minutes rather than requiring several hours, delivering both energy savings and shorter test cycles. Temperature is controlled by a programmable controller, allowing adjustable heating rates, and the temperature sensor achieves a control accuracy of approximately 1 °C. For displacement measurement, we use sensors with sub-micrometer resolution, which greatly enhances the accuracy of the calculated thermal expansion coefficient. Imported sensors can offer even better performance, but high-quality domestic sensors are also suitable for most applications. The entire test process can be automated by computer to minimize operator intervention and improve measurement reliability. If budget constraints preclude a computer-controlled setup, displacement can be measured with a micrometer. In that case, micrometer-level precision is still achievable, but data processing must be done manually and overall accuracy may be somewhat affected. Nevertheless, this approach is sufficient for general measurements. A basic thermal dilatometer configuration includes: a heating furnace, a thermocouple for temperature measurement, a temperature controller, a displacement sensor, a push rod, a small carriage, a computer, and test software. The coefficient of thermal expansion is a key indicator of a material’s physical properties and is increasingly important in research and production. Continued development of diverse dilatometer models supports evolving scientific and industrial needs and helps advance materials research.

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