Decomposition Of Ammonium Dinitramide Research Articles

On the mechanism of thermal decomposition of ammonium dinitramide (review)

Despite significant progress in studying thermal decomposition of ammonium dinitramide (ADN), the kinetics of the process at the level of elementary stages has not been adequately understood. The aim of this review is to summarize various published data, which are of interest for studying and simulating the processes of thermal decomposition and combustion of ADN. Considerable attention is paid to physical and chemical properties of ADN, dinitramide and its anion N(NO2) 2 - , which play a key role in ADN decomposition. Various paths of decomposition of ADN, dinitramide, and N(NO2) 2 - are discussed. Results illustrating alternative points of view on the decomposition process are presented.

Kinetics analysis of thermal decomposition of ammonium dinitramide (ADN)

Kinetics analyses were performed on the thermal decomposition of ammonium dinitramide (ADN) using thermogravimetry-differential thermal analysis–mass spectrometry–infrared spectroscopy (TG-DTA–MS–IR). The main evolved gases were determined to be NH3, H2O, N2, NO, N2O, and NO2. The apparent activation energies of the exothermic, mass-change and gas-evolving reactions were analyzed on the basis of Friedman methods. The apparent activation energy of evolving N2 has the same value as that of evolving H2O since they occur by the same mechanism. A Friedman plot obtained from the DTA data has a curve similar to those obtained from N2 and H2O. The reaction that generated N2 and H2O plays an important role in the exothermic reaction in the decomposition of ADN. The activation energy for the N2O evolution reaction has a range of approximately 120–152 kJ mol−1 with reaction progress values between 0.1 and 0.9. Quantum chemistry calculations revealed that the total energy barrier of dinitramic acid unimolecular decomposition and ammonium-dinitramic ions collision-induced decomposition is 149.9–156.0 and 160.6 kJ mol−1, respectively. These values are reasonable compared with the experimental value of 152 kJ mol−1.

Thermal decomposition characteristics of mixtures of ammonium dinitramide and copper(II) oxide

Ammonium dinitramide (ADN) is one of the most promising new solid oxidizers for rocket propellants, since its oxygen balance and energy content are relatively high, and it does not contain halogens. To gain a better understanding of the thermal decomposition mechanism of ADN, the thermal decomposition of ADN and copper(II) oxide (CuO) mixtures was investigated. The thermal behavior and activation energy associated with the decomposition of ADN/CuO mixtures were analyzed using sealed cell differential scanning calorimetry (SC-DSC). SC-DSC results showed that CuO affects the thermal characteristics of ADN and promotes its decomposition. Thermogravimetry–differential thermal analysis–evolved gas analysis was also performed, and in addition, the decomposition behavior was observed using hot stage microscopy. From the results, a thermal decomposition mechanism was proposed for ADN/CuO. In this mechanism, copper dinitramide Cu[N(NO2)2]2 is generated at the surface of the CuO almost simultaneously with the melting of the ADN. Next, a significant exothermic reaction occurs, associated with the decomposition of Cu[N(NO2)2]2, followed by decomposition of CuO via [Cu(NH3)2](NO3)2 and Cu(NO3)2.

Condensed Phase Behavior in the Combustion of Ammonium Dinitramide

AbstractThis paper reports on the thermal and combustion behaviors of ammonium dinitramide (ADN). The thermal behavior is measured by a pressure thermogravimetric analysis (TGA) at pressures below 8 MPa. The burning rates of pure ADN and ADN/ammonium nitrate (AN) mixtures are measured in the range 0.2–12 MPa, and the burning temperature profiles are obtained using thermocouples with diameters of 5 and 25 μm. This report mainly focuses on the condensed‐phase behavior in the vicinity of a burning surface. The temperature profiles are complicated because the ADN decomposition and AN dissociation compete during the condensed phase, and the bubbles of the decomposition gas and gas‐phase flame also affect the surface temperature. AN addition helps to understand the effects of AN during the condensed phase, and it was shown that the burning temperature rises to the critical temperature of AN. Based on these experimental results, the pressure dependency of the burning rates is also discussed.

Role of Additives in the Combustion of Ammonium Dinitramide

AbstractThe thermal decomposition behavior and combustion characteristics of mixtures of ammonium dinitramide (ADN) with additives were studied. Micrometer‐sized particles of Al, Fe2O3, TiO2, NiO, Cu(OH)NO3, copper, CuO, and nanometer‐sized particles of aluminum (Alex) and CuO (nano‐CuO) were employed. The thermal decomposition was measured by TG‐DTA and DSC. The copper compounds and NiO lowered the onset temperature of ADN decomposition. The heat value of ADN with Alex was larger than that of pure ADN in closed conditions. The burning rates and temperature of the pure ADN and ADN/additives mixtures were measured. CuO and NiO enhance the burning rate, particularly at pressures lower than 1 MPa, because of the catalyzed decomposition in the condensed phase; the other additives lower the burning rate. This negative effect on the burning rate is explained based on the surface temperature measurements by a physicochemical mechanism, which involves a chemical reaction, a phase change of the ammonium nitrate, and the blown‐off droplets of the condensed phase.

Thermal decomposition of the high-performance oxidizer ammonium dinitramide under pressure

Ammonium dinitramide (ADN) is a promising new oxidizer for solid propellants because it possesses both high oxygen balance and high energy content, and does not contain halogen atoms. A necessary characteristic of solid propellants is chemical stability under various conditions. This study focused on the thermal decomposition mechanism of ADN under pressurized conditions. The pressure was adjusted from 0.1 to 6 MPa, while ADN was heated at a constant rate. The exothermal behavior and the decomposition products in the condensed phase during heating were measured simultaneously using pressure differential scanning calorimetry (PDSC) and Raman spectrometry. PDSC analyses showed the multiple stages of exotherms after melting. The exothermal behavior at low temperatures varied with pressure. Analysis of the decomposition products indicated that ammonium nitrate (AN) was generated during decomposition of ADN at all pressures. At normal pressure, AN was produced at the same time as start of exotherm. However, the temperature at which the ratio of ADN in chemical species in the condensed phase began to decrease under high pressure was higher than that at atmospheric pressure despite the existence of significant exotherm. At initial stage, thermal decomposition of ADN that does not generate AN was thought to be promoted by increased pressure.

Ionization of ammonium dinitramide: decomposition pathways and ionization products

The decomposition pathways of ionized ammonium dinitramide (ADN) have been analyzed using the B3LYP and the M06-2X density functional theory methods, coupled cluster theory and the composite CBS-QB3 method. Ionization and subsequent decomposition of the major decomposition products have also been studied. The ADN+ ion dissociates into the stable DN radical and NH4 + with a dissociation enthalpy of 50 kJ/mol. The subsequently formed DN+ ion has an activation enthalpy of 102 kJ/mol for decomposition into N2O, O2 and NO+. A competing pathway for ionization and decomposition of ADN involves the HDN+ ion, which dissociates into \({\text{NO}}_{ 2}^{ + }\) and HNNO2 with a barrier of only 17 kJ/mol. The ionization product \({\text{HNNO}}_{ 2}^{ + }\) is stable toward further decomposition, and the barrier for isomerization to HONNO+ is 167 kJ/mol. The computed adibatic ionization potentials of ADN, HDN, DN and HNNO2 are 9.4, 11.5, 10.2 and 10.9 eV, respectively. The results of the study have implications for the future use of ADN in propellants for electromagnetic space propulsion.

Influences of aging on thermal decomposition mechanism of high performance oxidizer ammonium dinitramide

Ammonium dinitramide (ADN) is one of the several promising new solid propellant oxidizers. ADN is of interest because its oxygen balance and energy content are high, and it also halogen-free. One of the most important characteristics of a propellant oxidizer, however, is stability and ADN is known to degrade to ammonium nitrate (AN) during storage, which will affect its performance. This study focused on the effects of aging on the thermal decomposition mechanism of ADN. The thermal behaviors of ADN and ADN/AN mixtures were studied, as were the gases evolved during their decomposition, using differential scanning calorimetry (DSC), thermogravimetry–differential thermal analysis-infrared spectrometry (TG–DTA-IR), and thermogravimetry–differential thermal analysis-mass spectrometry (TG–DTA-MS). The results of these analyses demonstrated that the decomposition of ADN occurs via a series of distinct stages in the condensed phase. The gases evolved from ADN decomposition were N2O, NO2, N2, and H2O. In contrast, ADN mixed with AN (to simulate aging) did not exhibit the same initial reaction. We conclude that aging inhibits early stage, low temperature decomposition reactions of ADN. Two possible reasons were proposed, these being either a decrease in the acidity of the material due to the presence of AN, or inhibition of the acidic dissociation of dinitramic acid by NO 3 − .

Thermal behavior of new oxidizer ammonium dinitramide

Ammonium dinitramide (ADN) is a promising new oxidizer for solid propellants because of its high oxygen balance and high energy content, and halogen-free combustion products. One of the characteristics needed for solid propellants is stability. Heat, light, and moisture are factors affecting stability during storage, manufacture, and use. For practical use of ADN as a solid propellant, clarification of the mechanism of decomposition by these factors is needed to be able to predict lifetime. This study focused on thermal decomposition of ADN. Exothermal behavior of ADN decomposition was measured by isothermal tests using high-sensitive calorimetry (TAM) and non-isothermal tests using differential scanning calorimetry (DSC). Based on these results, analysis of the decomposition kinetics was conducted. The activation energy determined by TAM tests was lower than that from DSC tests. Thus, the decomposition path in TAM tests was different from that in DSC tests. The amount of ADN decomposition predicted from TAM tests was closer to that found under real storage conditions than the amount of decomposition predicted from DSC tests. Non-isothermal tests may not be able to precisely predict the lifetime of materials with a decomposition mechanism that changes with temperature, such as ADN. The lifetime predicted from DSC results was much longer than that from TAM tests especially at low temperature. It is necessary to use isothermal tests to predict the long-term stability at low temperature.

Combustion and thermal decomposition of ammonium dinitramide catalyzed by carbon nanotubes

The catalysis of carbon nanotubes(CNTs),carbon nanotubes supporting ferric oxide(Fe2O3/CNT) and carbon nanotubes supporting iron and copper(Fe·Cu/CNT) on the combustion and thermal decomposition of ammonium dinitramide(ADN) were investigated through burning rate measurements and TG analysis.Results show that all three catalysts increase the burning rate of ADN.The burning rates are related to combustion pressure by a power function and the pressure exponents decrease with the amount of catalyst for all of the three catalysts.When 3mass% of catalyst is used the burning rate of ADN at 4MPa increases from 30.49 to 50.59,39.72 and 38.79mm·s-1 and the pressure exponents decrease from 0.81 to 0.36,0.67 and 0.75 for the CNTs,Fe2O3/CNTs and Fe·Cu/CNTs respectively,TG tests show that all three catalysts decrease the thermal decomposition temperature of ADN.The primary thermal decomposition temperatures of ADN decrease to 18.3℃,12.1℃,and 11.6℃ for the CNTs,Fe2O3/CNTs and Fe·Cu/CNTs respectively when 1mass% catalyst was added to ADN.

The anomalous solid state decomposition of ammonium dinitramide: a matter of surface polarization

Polarized dinitramide anions on the surface of solid ammonium dinitramide (ADN) have a decomposition barrier that is reduced by 16 kcal mol(-1) and explain the anomalous solid state decomposition of ADN.

Thermal decomposition kinetics of ammonium dinitramide–guanylurea dinitramide mixture analyzed by isoconversional methods

The thermal decomposition kinetics of a mixture of high-energy oxidizers ammonium dinitramide (ADN) and guanylurea dinitramide (GUDN) have been studied by nonisothermal differential scanning calorimetry (DSC). Friedman's and Vyazovkin's advanced isoconversional (AIC-V) methods were used to investigate the dependence of activation energy ( E a) on conversion ( α). A strong dependence of E a on α was observed, indicating a complex decomposition process. E a is ∼165–175 kJ mol −1 at the start of the reaction, then reaches a maximum of ∼196–199 kJ mol −1 at α = ∼0.4, followed by a strong decrease to ∼135 kJ mol −1 near the end. E a has also been determined for the mixture and the individual components using Kissinger's method. Our results suggest that the decomposition of ADN greatly influences the observed E a dependence on α. This is further supported by Fourier transform infrared (FTIR) results and the enthalpy values of exothermic decomposition.

PHYSICAL AND CHEMICAL PROCESSES GOVERNING THE COMBUSTION OF BINARY COMPOSITIONS OF AMMONIUM DINITRAMIDE WITH GLYCIDYLAZIDEPOLYMER

The paper presents a study of the burning behavior and flame structure of compositions consisting of ammonium dinitramide (ADN) and glycidylazidepolymer (GAP). Unlike neat ADN and GAP, the ADN/GAP binary mixtures appeared to burn steadily within the whole pressure interval, showing no breaks on the burning rate vs. pressure dependences. In the lowpressure area, the mixtures burn with rates less than those of pure ADN and exceed it as pressure grows above 10 MPa. In the whole pressure interval, the mixtures burn with the rates higher than those of pure GAP. It was determined on the basis of flame structure investigation that the surface temperature of ADN/GAP mixtures is controlled by the dissociation reaction of ammonium nitrate (AN) formed in the condensed phase during ADN decomposition. Physical and chemical processes responsible for the observed combustion behavior of the mixtures are discussed.

Combustion of Ammonium Dinitramide, Part 2: Combustion Mechanism

Temperature profiles in the ammonium dinitramide (ADN) combustion wave were measured in the 0.04-10 MPa pressure interval using thin tungsten-rhenium thermocouples. The data obtained suggest that the ADN decomposition reaction in the condensed zone plays a dominant role in burning at low pressures. The heat feedback from the gas to the surface appeared to be negligibly small. It has been concluded that the reaction of AN dissociation to form NH 3 and HNO 3 controls the ADN burning surface temperature. The three-zone flame structure of the ADN combustion wave has been found, and the main chemical reactions occurring in the zones have been proposed. At low pressures (below 1 MPa), the burning of ADN can be satisfactorily described by a condensed-phase combustion model with the rate-controlling reaction being the ADN decomposition in the melt. A gas-phase model with the rate-controlling reaction being HNO 3 decomposition in the first flame can be used at high pressures (above 10 MPa). In the middle pressure interval, ADN shows combustion instability caused by deficiency of heat produced in the condensed material. In this area the fast but energy-limited heat-release process in the condensed phase has to adapt itself to the slow but energy-rich heat-release process in the gas phase.

Thermal Decomposition of Ammonium Dinitramide Vapor in a Two-Temperature Flow Reactor

The thermal decomposition of ammonium dinitramide (ADN) was studied using a two-temperature flow reactor. The vapor pressure at temperatures of 80-140°C and the heat of vaporization of ADN were determined. From the results obtained a mechanism for the thermal decomposition of ADN was proposed that includes the ADN vaporization stage, i.e., the transition from the condensed to the gaseous state in the form of the molecular complex NH$3·HN(NO2)2 (ADN vapor) followed by dissociation into NH3 and HN(NO2)2. The composition of the products from the thermal decomposition of ADN vapor at temperatures of 160–900°C was determined by mass spectrometry. The effective rate constant was determined for the dissociation of ADN vapor at temperatures of 160–320°C. The thermal decomposition of ADN vapor in a flow reactor was modeled using the proposed mechanism and the reaction rate constant for ADN vapor dissociation. Key words: ammonium dinitramide, dinitramide, molecular beam mass spectrometry, thermal decomposition, two-temperature flow reactor.

Flame structure of ADN/HTPB composite propellants

Visual flame characteristics, burning rates, and final flame temperatures for propellants based on ammonium dinitramide (ADN) and hydroxyl-terminated polybutadiene (HTPB) at different HTPB concentrations (3–20%) have been studied at pressures of 0.05 to 0.6 MPa. The flame structure was studied by probing molecular-beam mass-spectrometry, thin thermocouples, and video recording. The burning-zone width at 0.1 MPa was ∼1.5 mm. Thermocouples revealed temperature fluctuations of about ±400 K at 0.1 MPa in the flame zone within 1.5 to 4 mm from the burning surface. Along with temperature fluctuations, fluctuations also occurred in the intensities of the mass peaks of mass spectra of samples withdrawn from the flame. These are a consequence of the nonhomogeneous and nonstationary combustion of the propellant. Video recordings revealed the existence of several brightly luminous flame jets (torches) of about 1 mm in diameter at the burning surface, disappearing from one site and re-appearing at another. Combustion products were found remote from the burning surface and in its immediate vicinity by using molecular-beam mass spectrometry. The reactions in the condensed phase (mainly the ADN decomposition reaction) control ADN/HTPB propellant combustion. The oxidation of HTPB decomposition products in the gas phase increases the heat release there and accelerates reactions in the first and second zones of the ADN flame.

Thermal analysis of ammonium dinitramide (ADN)

Kinetic constants of decomposition were determined for ADN and prilled ADN by DSC and TG. Pressure DSC at 550 psi air or helium had similar kinetic constants for prilled ADN, namely 29 kcal/mol activation energy and a log frequency factor of ∼14.0 min −1. These values were similar to those found in sealed sample pans in which the decomposition gases were confined. DSC and TG runs in open sample pans in nitrogen or helium had higher activation energies and frequency factors, namely 40–43 kcal/mol and 18–20 min −1, respectively. Thus, it appears that confinement of the ADN decomposition gases either under pressurization or a sealed environment accelerates the decomposition of prilled ADN. Kinetics of decomposition of unprilled ADN at atmospheric pressure in nitrogen or helium by DSC and TG were E a=37 kcal/mol and log A=17 min −1. Unprilled ADN had lower activation energies and frequency factor for decomposition than prilled ADN which contained stabilizers. The effect of sample containment (i.e. aluminum, coated aluminum, gold, and glass ampoules) on the shape of the DSC curve of ADN was investigated. Isothermal TG in vacuum of ADN in the 45–75°C region and the DSC analysis of the TG residues showed unusual results in the 60°C region. The rate and enthalpy of decomposition of four dinitramide salts and their dielectric relaxation were related to the basicity of the cation.

Molecular-Beam Mass-Spectrometry to Ammonium Dinitramide Combustion Chemistry Studies

The methods for the study of flame structure and kinetics of the thermal decomposition of solid propellant by probing mass spectrometry are described. The developed methods were applied to the study of ammonium dinitramide (ADN) combustion chemistry. The study has shown that along with ADN decomposition, sublimation takes place to give gaseous ADN followed by dissociation to yielding ammonia and dinitraminic acid (HD). Gaseous ADN has been observed in ADN decomposition products. The structure of ADN combustion zones at 1-6 atm was studied using a molecular-beam mass-spectrometry as well as a microthermocouple technique. Three combustion zones have been observed. Gaseous ADN has been discovered in the first cool flame zone at 3 atm. Gaseous ADN dissociation on NH3 and HD followed by HD decomposition in the near-surface zone are key reactions resulting in a temperature rise of about 150 K. The second high-temperature zone is found within 6-8 mm from the ADN burning surface at 6 atm. The main reaction in this zone is ammonia oxidation by nitric acid and the combustion temperature is 1400 K. The third zone was observed at 40 atm, the measured final temperature was —2000 K. The obtained data form the basis for the development of a chemical mechanism of reactions in both the ADN flame and combustion model.

The new energetic material ammonium dinitramide and its thermal decomposition

The new energetic material ammonium dinitramide (ADN), NH 4N(NO 2) 2, has been investigated with regard to its thermal properties and decomposition behaviour. Thermal decomposition of ADN is observed after complete melting at 91.5 °C. The main decomposition pathway is based on the formation of NH 4NO 3 and N 2O followed by the thermal decomposition of NH 4NO 3 to N 2O and H 2O at higher temperatures. Side reactions forming NO 2, NO, NH 3, N 2 and O 2 are described and a mechanism for the acid-catalyzed decomposition of hydrogen dinitramide, dissociation product of ADN, is proposed.

Thermal Decomposition Studies on Ammonium Dinitramide (ADN) and 15N and 2H Isotopomers

The thermal decomposition of ammonium dinitramide (ADN) and potassium dinitramide (KDN) were examined neat and in solution. Isothermal kinetics were measured (160−220 °C) by monitoring dinitramidate loss and were found to be first-order. Ammonium ion loss and gas formation were not good measurements of ADN decomposition since they reflect the fate of the ADN decomposition product ammonium nitrate. Kinetics of decomposition were nearly identical for ADN neat (proteo- and deutero-), ADN in water (1 or 20 wt %), ADN in various pH aqueous buffers, and for aqueous KDN (1 wt % in water or deuterium oxide). The activation energy, calculated for ADN, was about 40 kcal/mol (167 kJ/mol) for neat ADN and 37 kcal/mol (155 kJ/mol) for aqueous solutions of ADN. Decomposition of ADN in aqueous buffers suggested that under the conditions of these studies decomposition of dinitramidate or its parent acid proceeds at about the same rate at pH 3, pH 5, and unbuffered but decreased by about 40% at pH 9. Neat KDN was unique i...