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  • Author or Editor: S. Hajimirsadeghi x
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Abstract  

Thermogravimetry (TG) and differential thermal analysis (DTA) in the non-isothermal mode have been used to examine the thermal behaviour of the micron sized aluminum (Al) powder/potassium chlorate pyrotechnic systems in air, in relation to the behaviour of the individual constituents. The effects of different parameters of Al powder, such as particle size and its content in the mixtures, on their thermal property were investigated. The results showed that, the reactivity of Al powder in air increases as the particle size decreases. Also, it was found that neat Al with 5 m particle sizes (Al5) has a fusion temperature of about 647C, that for 18 m powder (Al18) is 660C. Pure potassium chlorate has a fusion temperature around 356C and decomposes at 472C. DTA curves for Al5/KClO3 (30:70) mixture showed a maximum peak temperature for the ignition of mixture at 485C. Also, by increasing the particle size of Al powder, the ignition temperature of the mixture increased. On the other hand, the oxidation temperature increased by enhancing the Al content of the mixtures. In this particular study, we observed that the width of reaction peak for the mixtures corresponds to their Al contents of samples.

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Abstract  

Data on the thermal stability of organic materials such as diaminofurazan (DAF) and diaminoglyoxime (DAG) was required in order to obtain safety information for handling, storage and use. These compounds have been shown to be a useful intermediate for the preparation of energetic compounds. In the present study, the thermal stability of the DAF and DAG was determined by differential scanning calorimetery (DSC) and simultaneous thermogravimetery-differential thermal analysis (TG-DTA) techniques. The results of TG analysis revealed that the main thermal degradation for the DAF and DAG occurs in the temperature ranges of 230–275°C and 180–230°C, respectively. On the other hand, the TG-DTA analysis of compounds indicates that DAF melts (at about 182°C) before it decomposes. However, the thermal decomposition of the DAG started simultaneously with its melting. The influence of the heating rate (5, 10, 15 and 20°C min−1) on the DSC behaviour of the compounds was verified. The results showed that, as the heating rate was increased, decomposition temperatures of the compounds were increased. Also, the kinetic parameters such as activation energy and frequency factor for the compounds were obtained from the DSC data by non-isothermal methods proposed by ASTM E698 and Ozawa. Based on the values of activation energy obtained by ASTM and Ozawa methods, the following order in the thermal stability was noticed: DAF>DAG.

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Abstract  

In this paper, the thermal behaviours of N-{bis[benzyl(methyl) amino]phosphoryl}-2,2-dichloroacetamide (BMA) and N-{bis[dibenzylamino]phosphoryl}-2,2-dichloroacetamide (DBA) were studied by thermogravimetery (TG) and differential scanning calorimetery (DSC) techniques under the non-isothermal conditions. The results showed that BMA melts about 120 °C before it decomposes. BMA decomposition occurs in three continuous steps, in the 170–400 °C temperature range. Each thermal degradation stage for BMA results an exothermic peak in the DSC curve. On the other hand, applying TG-DSC techniques indicates that DBA melts about 175 °C before it decomposes. This compound decomposes in the temperature range of 200–600 °C in three steps. Activation energy and pre-exponential factor for each compound were found by means of Kissinger method and were verified by Ozawa–Flynn–Wall method. Activation energy obtained by Kissinger method for the first stage of BMA and DBA decompositions are 151.8 (±2.0) KJ mol−1 and 138.7 (±2.6) KJ mol−1, respectively. Finally, the thermodynamic parameters (ΔG #, ΔH # and ΔS #) for first step decomposition of DBA and BMA were determined.

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