Study Of Graphitic Carbon Nitrides And Its Nanocomposites On The Catalytic Thermal Decomposition Of Perchlorate Ammonium

Ammonium Perchlorate?AP?, as a kind of widely used oxidizer, its decomposition properties significantly affected the combustion performances of solid propellants. By studying the effect of catalysts on AP thermal decomposition, resulting that an evaluation system for combustibility of propellants was established according to the various catalysts. This thesis was focused on two aspects:?1? the preparation, characterization of the bulk graphitic carbon nitride?g-C₃N₄? as well as its catalytic applications for AP thermal decomposition;?2? the preparation of g-C₃N₄-based compounds as well as the catalytic applications for thermal decomposition of AP. The work as follows:g-C₃N₄, TeO₂ NPs/g-C₃N₄ hybrids and SnO₂ NPs/g-C₃N₄ hybrids were prepared via high-temperature calcination methods as well as applied to the catalysis thermal decomposition of AP. The morphology and size of as-prepared catalysts were carried out by Field emission scanning electron microscope?FESEM?, Transmission electron microscope?TEM? and Atom force microscope?AFM?; crystalline structure and chemical composition was recorded on X-ray diffraction?XRD? and X-ray photoelectron spectroscope?XPS?; bonding linking was investigated by Ultraviolet and visible spectrophotometer?UV-vis? and Fourier transform infrared spectroscopy?FTIR?; the thermal decomposition process of AP was study on Thermogravimetry-Thermogravimetry analysis?TG-TGA?, Differential thermal analysis?DTA?, Differential scanning calorimetry?DSC? and Thermogravimetry-Fourier transform infrared spectroscopy?TG-FTIR?. The results indicating that the as-prepared catalysts have the intrinsic catalytic effects to some extents. The temperature of second decomposition peak?HTD? was decreased by 70 °C under the catalysis of bulk g-C₃N₄, 100 °C for TeO₂ NPs/g-C₃N₄ and Sn O2 NPs/g-C₃N₄ hybrids. Moreover, by studying the effect of weight ratios and heating ratios of catalyst on the AP decomposition, the apparent decomposition heat of AP in the presence of 10 wt% g-C₃N₄ reaches up to 1362.6 J?g^-1, which is much higher than that of the pure AP(574.2 J?g^-1).The gas products during AP decomposition were determined by FTIR. All of the evolved products result from the two decomposition stages of HTD segment?350-400 °C?. The gas product at 408 °C were identified as H₂O, NH₃(3400-3650 and 1650-1620 cm^-1), HCl(1750-3000 cm^-1), N₂O, NO₂(2202-2238, 1380-1320 and 840-800 cm^-1) and ClO₃(1000-900 cm^-1). The peaks shifted to a higher temperature than that of the corresponding DTG curve because of the delay time between the gas generation and its detection by the FTIR instrument.Based on the analysis of the experimental data, a possible catalytic mechanism on the thermal decomposition of AP with g-C₃N₄ has been proposed. The unique surface structure of g-C₃N₄ consisting of triazine units connected by planar amino groups can be favorable for the adsorption and diffusion of perchloric acid via Lewis acid-base interactions, which has a low band gap?2.7 e V?. In addition, the conduction band electrons?ecb-? and valence band holes?h+? were generated on their surface under heat excitation, indicating that the oxidation of ammonium and reduction of perchlorate acid molecular. Finally, the production of small molecular promoted AP decomposition.