ACOUSTIC-EMISSION IN THE PROCESS OF DEHYDRATION AND THERMAL-DECOMPOSITION OF NACLO4.H2O

The dehydration and thermal decomposition of NaClO4.H2O was investigated using a home-made simultaneous AE-DTA apparatus. A sensor with a resonant frequency of 140 kHz, 500 kHz, 1 MHz or 1.5 MHz was used for detecting acoustic emission signals. A wide-band sensor was used for monitoring the power spectra of the signals. Irrespective of the type of reaction holder or the kind of sample, powdered NaClO4.H2O samples give low- and high-temperature AE peaks in the region of 80-310-degrees-C and 450-580-degrees-C, respectively. The high-temperature AE peak consists of six peaks, a-f. Four peaks, b-e, are associated with the decomposition of NaClO4, whereas peaks a and f are due to the melting of NaClO4, and the solidification of molten product NaCl, respectively. The influence of the sample mass and the resonant frequency of the sensor on the low- and high-temperature AE peaks is examined. The power spectra of the signals emitted in peaks a-f are shown to have their major frequency distribution in a range 80-400 kHz.