A novel investigation of the thermal decomposition mechanism of (MTNI) and (KNO2) using time resolved pulsed photoacoustic technique

We report a novel approach based on time resolved pulsed photoacoustic (PA) technique to study the thermal decomposition mechanism of 1-methyl-2,4,5-trinitroimidazole (MTNI) and potassium nitrite (KNO2). The technique is based on the detection of free –NO2 molecules which is released due to thermal decomposition from these samples. The second harmonic i.e. λ = 532 nm pulses of 7 ns width at repetition rate 10 Hz obtained from Q-switched Nd:YAG laser is employed to record the PA spectrum. The recorded PA spectrums show the presence of first five even longitudinal acoustic modes i.e. 2nd, 4th, 6th, 8th and 10th with different intensities and frequency shift. In addition, the thermal decomposition mechanism of MTNI and KNO2 is crossed examined by TG-DTA technique which provides direct information of weight loss and heat flow thermal zones. The PA based temperature study is carried out for MNTI and KNO2 separately. We have obtained several highly resolved thermal zones which clearly demonstrate the process of thermal decomposition. Finally, the effect of pressure and input laser energy on PA signal has also been studied.