高氯酸铵热分解机理研究进展

综述了自20世纪30年代以来高氯酸铵(AP热分解机理研究的进展,指出AP的分解分为低温分解和高温分解阶段,而低温下的离解机理是整个热分解过程的研究热点,主要有电子转移机理和质子转移机理2种观点。AP热分解过程有大量中间反应,中间产物也参与中间反应,该特点决定了其分解过程的复杂性,因此需要深入探讨其热分解机理,以便为研究复合固体推进剂燃烧过程奠定理论基础。     

二氧化锰的制备及其对高氯酸铵和黑索金的催化性能

以KMn O4为锰源、CO(NH2)2为还原剂,在90℃水热条件下通过氧化还原反应制备Mn O2。采用X-射线衍射、扫描电镜和红外光谱等技术对所得产物进行表征。利用差示扫描量热技术研究了Mn O2对高氯酸铵(AP)和黑索金(RDX)热分解行为的影响,进行了热分解动力学分析,并探讨了二元体系的相容性。结果表明,Mn O2的添加使AP的分解过程提前,但对RDX的分解峰温影响很小。     

Specific features of thermal decomposition of ammonium perchlorate subjected to γ radiation

Results of studying thermal decomposition of ammonium perchlorate (AP) samples in the original form and after irradiation by γ-quanta of ⁶⁰Co by methods of differential scanning calorimetry and dynamic thermogravimetry with heating rates b = 0.1–0.3 K/sec are described. Irradiation is performed in air at a temperature of 298 ± 2 K and a dose rate of ≈0.2 Gy/sec in the range of absorbed doses D = 0–150 kGy. Preliminary irradiation is demonstrated to lead to substantial transformations of the pattern of thermal decomposition of ammonium perchlorate in the dynamic regime of heating: the single-stage process of decomposition of non-irradiated samples proceeding at b = 0.107 K/sec in the temperature range of 625 to 743 K is replaced by a multistage process. At D = 150 kGy, exothermal transformations accompanied by noticeable losses of sample mass are observed starting from 473 K. Within experimental errors, the total thermal effect of AP decomposition is found to be independent of the absorbed dose and amounts to −1150 kJ/kg on the average. __________ Translated from Fizika Goreniya i Vzryva, Vol. 43, No. 6, pp. 69–74, November–December, 2007.     

Effect of ammonia on the thermal decomposition of ammonium nitrate

The effect of the partial pressure of gaseous ammonia on differential thermal analysis and thermogravimetric curves of ammonium nitrate has been determined. Observed variations of the thermal effect and decomposition rate constitute a basis for considering the factors which determine the decomposition and equilibrium of exo- and endothermic processes.     

The anodic characteristics of manganese dioxide electrodes prepared by thermal decomposition of manganese nitrate

Manganese dioxide electrodes were prepared by a thermal decomposition of manganese nitrate solution on a titanium or a platinum substrate, and their anodic characteristics were investigated mainly in 1N H₂SO₄ and 1N KOH. The platinum-supported manganese dioxide electrode shows the good anodic characteristics with a relatively low overvoltage for oxygen evolution while the use of the titanium-supported one as an anode needs further modification to reduce its high resistivity resulting from the thick film of titanium dioxide in spite of good adhesion of the oxide film with the titanium substrate.The primary water or hydroxide ion discharge step is rate-controlling in the anodic evolution of oxygen on the platinum-supported manganese dioxide electrode in both acidic and alkaline solutions. The oxygen overvoltage is raised and the mechanical strength of the catalytic oxide on the platinum substrate is weakened by the anodic polarization in acidic solution. These phenomena are explicable on the basis of an increase in the oxygen content in the oxide. In conclusion, the presented results suggest that the manganese dioxide film is a practical usable material for the anodic evolution of oxygen as well as chlorine, especially in alkaline solutions.     

The effect of nitric oxide and nitrogen dioxide on the thermal decomposition of ammonium nitrate

The effect of the partial pressures of nitric oxide and nitrogen dioxide in the gaseous phase (0–0.1 MPa) on the profile of differential thermal analysis and thermogravimetric curves for ammonium nitrate, on its rate of decomposition (from 388 to 548 K), and on nitric acid concentration in the condensed phase have been investigated. Both compounds were found to increase the isothermal decomposition rate and also to lower the temperature of initiation. The results of these studies have led to the conclusion that as the factors causing an increase in the concentration of both compounds in ammonium nitrate increase, the possibility of ignition or explosion also increases.     

The catalytic effect of nanosized MgO on the decomposition of ammonium perchlorate

MgO nanoparticles with an average size of 30 nm were prepared by a traditional sol-gel method using magnesium chloride and NaOH aqueous solution as the raw materials. X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used to characterize the products. The catalytic effect of the MgO prepared on the decomposition of ammonium perchlorate (AP) was investigated by differential thermal analysis (DTA). The results indicate that MgO nanoparticles have a good dispersibility and a uniform crystallite size, also have an intense catalytic effect on the decomposition of AP comparing with commercial product.     

Effect of pretreatment on the sublimation of ammonium perchlorate

The effects of pretreatments on the sublimation of pure ammonium perchlorate (AP) were studied by differential thermal analysis. The addition of inorganic salts (doping), or preheating, lead to desensitisation of the sublimation process, whereas it was sensitised by precompression. Sublimation increased with decrease in the particle size of the AP from 500 to 200 microns, but decreased with a further decrease in size from 200 to 100 microns. The results are interpreted in terms of gross imperfections and strain in the AP crystals.