Optical dilatometry for the control of microstructure development during sintering

An optical method for the in situ measurement of sintering shrinkage has been developed. It relies on a simple and robust CCD camera technique and is applicable up to high temperatures (2000 degreesC) and heating rates (10 K/min) in industrial furnace atmospheres. A resolution of less than 1 mum for a sample diameter of 10 mm has been achieved using a special geometrical arrangement and a smart image analysis algorithm. Systematic errors are small (<0.1%) and can be corrected by an additional measurement. A high reproducibility of shrinkage measurement has been observed in various sintering experiments. The optical dilatometer is very flexible: it has been used also for an accurate temperature calibration and for wetting experiments and it can be adjusted to different furnace types.