Ammonium nitrate: a promising rocket propellant oxidizer

In this review data from the literature on thermal decomposition of ammonium nitrate (AN) and the effect of additives to their thermal decomposition are summarized. The effect of additives like oxides, cations, inorganic acids, organic compounds, phase-stablized CuO, etc., is discussed. The effect of an additive mainly occurs at the exothermic peak of pure AN in a temperature range of 200°C to 140°C.

Review on Thermal Decomposition of Ammonium Nitrate

Solid ammonium nitrate (NH 4 NO 3 ) exists in five stable polymorphic forms (designated as phases I, II, III, IV, and V) below its melting point at around 170°C. Phase IV is stable in a temperature range of −17°C ∼ 32°C and is the only phase that has been considered by the atmospheric research community until recently. In this study, we examine the IV ↔ III phase transition of NH 4 NO 3 and how relative humidity (RH) affects the transition path and the transition temperatures using in-situ microscopic Fourier Transform InfraRed spectroscopy. Two kinds of NH 4 NO 3 samples, powder produced from grinding commercially produced chemicals and single particles obtained by efflorescence of droplets on PTFE filters, were studied. The powder samples exhibit the IV↔III phase transition and the transition temperature depends on the RH while the single particle samples exhibit only the IV↔II transition at about 52°C (forward) and 48°C (reverse), bypassing phase III, with transition temperatures independent of the RH....

https://www.tandfonline.com/doi/pdf/10.1080/02786820701272038

FTIR Characterization of Polymorphic Transformation of Ammonium Nitrate

Studies on energetic compounds. Part 8 : Thermolysis of salts of HNO3 and HClO4

Ammonium nitrate (AN) has received attraction globally not only as a nitrogenous fertilizer but also as an oxidizer in gas generators and propellants. Nowadays, great attention is being focused on the development of composite solid propellants with green oxidizers in realizing eco–friendly combustion products. The ammonium perchlorate (AP), which is the work horse oxidizer in composite propellant, needs replacement due to its environmental and human health issues. In this context, AN is regarded as an alternative to AP because of its easy availability and environmentally friendly chlorine free combustion products. However, AN has its own inherent drawbacks such as hygroscopicity, room temperature phase transition, and low burning rate. Recently, several studies have been focused on its phase stabilization and burning rate modification so as to develop solid propellants with improved properties. The knowledge of thermal characteristics of AN is a crucial factor for its applications in propellants a...

Ammonium Nitrate as an Eco-Friendly Oxidizer for Composite Solid Propellants: Promises and Challenges

Modification of the room temperature phase (IV-III) of ammonium nitrate (AN) has been attempted using a variety of potassium salts namely, KF, KCl, KI, KNO3, K2CO3, K2SO4, KSCN and K2Cr2O7. No phase transition was observed when AN containing 1-2% by mass of these potassium salts is heated from room temperature (25 degrees C) onwards in DTA and DSC scans, but the linear expansion due to phase transition was still observable in TMA measurements. Complete arrest of the linear expansion occurs only when a higher concentration of the additive is used. Similarly, in thermal cycling experiments, complete phase modification in the temperature range -80 to 100 degrees C occurs only with a higher percentage of the potassium salt. The extent of modification, however, is found to be dependent both on the concentration, and the type of the anion. Potassium dichromate when used as an additive modifies the phase as well as the decomposition pattern of AN.

Phase Modification of Ammonium Nitrate by Potassium Salts

The thermal ignition behaviour of various mixtures of organic fuels, magnesium and ammonium nitrate (AN) has been examined by differential thermal analysis technique. It has been observed that the thermal decomposition/ignition of organic fuel-AN mixtures is modified significantly in the presence of magnesium metal. The decomposition characteristics of the binary mixtures of AN with various metals indicate the specific action of magnesium and zinc in lowering the decomposition temperature. A possible explanation for the low temperature decomposition is given in terms of the solid state reaction causing the fusion of AN which further reacts with the metal resulting in a highly exothermic reaction.

Thermal ignition studies on metallized fuel-oxidizer systems

The thermal ignition behaviour of ammonium perchlorate has been investigated in the presence of fuel-rich compounds such as tetramethylammonium perchlorate, trimethylammonium nitrate, carbon and cellulose. The ignition characteristics, as studied by differential thermal analysis, have been found to be strongly influenced by self-decomposition and other physicochemical properties of the additives. For a simple system, an analytical model proposed on the basis of the coupling of two exothermic decomposition reaction kinetics and a heat-balance equation, appears to explain to some extent the observed trend in peak ignition temperature when the composition is varied. The salient features of the analysis, as regards its application to fuel-oxidizer interactions in general, have been pointed out.

Thermal ignition behaviour of ammonium perchlorate in presence of fuel-rich compounds

The thermal decomposition of hydrazinium monoperchlorate (HP-1) in the molten state has been investigated using differential thermal analysis, thermogravimetric analysis, a constant volume manometric technique and mass-spectrometry. The stoichiometry of the reaction can be represented by the equation: 20 N2H5C1O4 → 13 NH4C1O4 + 3.5 Cl2 + 2 O2 + 13 N2 + 0.5 N2O + 0.5 H2 + + 23.5 H2O The data seem to indicate that the mechanism, which involves an associated complex, remains unchanged from 140 to 190°. Consequently, impurities capable of forming associated complexes with the hydrazinium or the perchlorate ion desensitize the thermal decomposition of HP-1, the extent of desensitization being determined by the size, the charge and the concentration of the impurity.

Thermal decomposition of hydrazinium monoperchlorate in the molten state

A thin-film thermometric device was used to record the temperature profiles of the exothermic reactions occurring between various substituted benzenes and anhydrous nitric acid. A comparison of the profiles indicated that the extent of exothermicity and the rate of heat evolution depend on the substituent/s on the benzene ring. The initial reaction was identified as nitration, which is accompanied by other exothermic reactions, especially in systems leading to ignition. The profiles of the self-igniting systems, amine-HNO3 and amine-N2O4, suggest that, apart from their individual exothermicities, the specific nature of the fuel-oxidizer reaction also plays an important role in the onset of ignition.

S. R. Jain

Papers

Phase Modification of Ammonium Nitrate by Potassium Salts

Thermal ignition studies on metallized fuel-oxidizer systems

Thermal ignition behaviour of ammonium perchlorate in presence of fuel-rich compounds

Thermal decomposition of hydrazinium monoperchlorate in the molten state

Temperature profiles of reactive biliquid systems prior to ignition