Effect of prior mechanical and thermal treatment on the thermal decomposition of orthorhombic ammonium perchlorate (original) (raw)
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Journal of Physics and Chemistry of Solids, 1976
The thermal decomposition of ammonium perchlorate (AP) in its cubic modification has been studied in the temperature range MO-390°C. Two distinct regions of temperature dependence are observed for the rate constants of the decomposition. The activation energies in the two regions are found to he 20 + 2 kcalslmole and 60 f 2 kcalslmole. Prior mechanical and thermal treatment of the materials is seen to result in a marked increase in the thermal reactivity of AP in the range 300-370°C. Differential thermal analysis of pre-compressed AP shows pronounced changes in the exothermic characteristics of the material. Prior compression of AP in addition enhances the sublimation of the material. The activation energies are not altered by the pretreatment. The results are explained in terms of crystal imperfections and the role of dislocations in the thermal decomposition of AP.
Effect of prior mechanical treatment on the thermal decomposition of alkali metal perchlorates
Journal of Physics and Chemistry of Solids, 1976
The kinetics of the thermal decomposition of sodium, potassium, rubidium and caesium perchlorates show a pronounced dependence on the past mechanical history of the materials. The variation in the decomposition rate with strain energy and lattice distortion shows that crystal defects are important factors in the thermal reactivity of alkali metal perchlorates.
Kinetics of Thermal Decomposition of Cubic Ammonium Perchlorate
Chemistry of Materials, 1999
The methods of thermogravimetric analysis (TGA) and differential scanning calorimettry (DSC) have been used to study the thermal decomposition of ammonium perchlorate (AP). TGA curves obtained under both isothermal and nonisothermal conditions show a characteristic slowdown at the extents of conversion, R ) 0.30-0.35. DSC demonstrates that in this region the process changes from an exothermic to an endothermic regime. The latter is ascribed to dissociative sublimation of AP. A new computational technique (advanced isoconversional method) has been used to determine the dependence of the effective activation energy (E R ) on R for isothermal and nonisothermal TGA data. At R > 0.1, the E R dependencies obtained from isothermal and nonisothermal data are similar. By the completion of decomposition (R f 1) the activation energy for the isothermal and nonisothermal decomposition respectively rises to ∼110 and ∼130 kJ mol -1 , which are assigned to the activation energy of sublimation. The initial decomposition (R f 0) shows the activation energy of 90 kJ mol -1 for the isothermal decomposition and 130 kJ mol -1 for the nonisothermal decomposition. The difference is explained by different rate-limiting steps, which are nucleation and nuclei growth for isothermal and nonisothermal decompositions, respectively.
Low-temperature thermal decomposition of large single crystals of ammonium perchlorate
Chemical Physics Letters, 2008
Similarities and differences in the thermal behaviour of deuterated and nondeuterated ammonium perchlorate provide insights into the mechanism of its thermal decomposition. Thermal decomposition of NH 4 ClO 4 and ND 4 ClO 4 always begins in the bulk of the crystals. In both cases decomposition stops when the degree of conversion is about 30%, giving porous products which undergo the same phase transition as the parent single crystals. Thermal decomposition of the deuterated sample is slower, the volume fraction of pores appears to be lower and the sample has a small quantity of 'snow' on the surface. These effects are best rationalized as caused by proton transfer at the intersections of dislocations in the bulk of the crystals.
Effect of pressure and sample type on decomposition of ammonium perchlorate
Combustion and Flame, 2006
Differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and high pressure DSC (HP-DSC) have been used to study the thermal decomposition of ammonium perchlorate samples in the form of 2-mm monocrystals, 265-and 3-µm powders, and pellets pressed at 4 and 7 tons. HP-DSC runs have been performed to determine the effect of pressure on decomposition. TGA and DSC techniques have been employed to examine the effect of sample type on the kinetics of the process. The effects have been evaluated as changes in the temperature, reaction heat, and rate of decomposition. Isoconversional kinetic analysis has been carried out to detect changes in the effective activation energy of the process. These measurements and calculations show sublimation and decomposition for ammonium perchlorate to be highly dependent on sample preparation and applied pressure. This calculation finds that the activation energy for the early stages of sublimation/decomposition for all samples starts at ∼120 kJ mol −1 , which is followed by a dramatic drop to ∼60 kJ mol −1 at 20% mass loss. The activation energy for the later stages of sublimation/decomposition varies with sample type ranging from ∼95 to 145 kJ mol −1 .
Study of Thermal Decomposition Kinetics of Low
2000
The kinetics of the thermal decomposition of ammonium perchlorate at temperatures between 215 and 260°C is studied, in this work, by measuring the sample mass loss as a function of time applying the isothermal thermogravimetric method. From the maximum decomposition rate-temperature dependence two different decomposition stages, corresponding to two different structural phases of ammonium perchlorate, are identified. For the first region (215-235°C), corresponding to the orthorhombic phase, the mean value of the activation energy of 146.3 kJ mol-1 , and the pre-exponential factor of 3.43•10 14 min-1 are obtained, whereas for the second region (240-260°C), corresponding to the cubic phase, the mean value of the activation energy of 153.3 kJ mol-1 , and the pre-exponential factor of 4.11•10 14 min-1 are obtained.
2020
Ammonium perchlorate (AP) is the universal oxidiser in use for all the solid rocket propellant motors used for space exploration due to its high available oxygen content and thermal decomposition without any solid residue. The inclusion of reactive species in AP directly affect the viscoelastic and ballistic properties of the propellant. Variations in lattice configuration of AP change its physical and thermal characteristics dramatically. In the present work AP was doped with Copper perchlorate and Iron perchlorate through co crystallisation. The impact of inclusion of these ionic species in the lattice on the thermal decomposition characteristics of AP was examined. The incorporation affected the physical as well as the ballistic characteristics of the resultant AP. The incorporation of foreign ions into AP crystals significantly changed the crystal morphology. The decomposition temperature decreased visa -vis with normal AP. The activation energy remarkably decreased for the doped AP crystals.
Study of the thermal decompositions of some transition metal perchlorates
Journal of Thermal Analysis, 1977
The thermal decompositions of nickel(II), copper(II), cobalt(II) and manganese(II) perchlorates were studied by thermal analysis and kinetic measurements. Anhydrous perchlorates could not be prepared by heating and outgassing the samples in vacuum; oxides were obtained as the main solid decomposition products. In the case of cobalt and manganese perchlorates, oxidation of the metal ions was observed during the decomposition. In most cases the decompositions of the perchlorates followed the Avrami-Erofeyev kinetics. A correlation was found between the stabilities of the perchlorates and the effective field strengths of the cations.