SIMULTANEOUS MEASUREMENTS OF ACOUSTIC-EMISSION AND DIFFERENTIAL THERMAL-ANALYSIS FOR DIFFERENT KCLO4 SAMPLES

Simultaneous measurements of acoustic emission (AE) and differential thermal analysis (DTA) were made for three types of KClO4 samples (powders, dendrite crystals and one single crystal) using a home-made AE-DTA apparatus. Sensors of resonated frequency 140 KHz, 500 KHz, 1 MHz and 1.5 MHz were used. Irrespective of the type of sample, KClO4 gives low and high temperature AE peaks at temperatures of 180-330-degrees-C and 560-640-degrees-C respectively. Scanning electron micrograph observation showed that the low temperature AE peak results from the break-up of large particles (crystals) and/or liquid release from their surfaces. The AE signals due to the transition of KClO4 from orthorhombic to cubic form overlap with the low temperature peak and become more appreciable with increasing resonance frequency of the sensor. The high temperature AE peak consists of three peaks, a, b and c. The lower temperature part (560-590-degrees-C) of peak a is attributed to a precursory event of the melting. Peaks a and b, which suggest a two-step decomposition, exhibit different frequency dependencies. Peak c, due to the solidification of molten KCl product, does not vary with the type of sample. In the case of a single crystal, an independent intense peak appears as the precursory event of the melting at 550-590-degrees-C.