A review on surface coating strategies for anti-hygroscopic of high energy oxidizer ammonium dinitramide

Ammonium dinitramide(ADN),which has the advantages of high energy density,no halogen and low characteristic signal,is not only considered as a new high-energy oxidizer that is expected to replace the traditional oxidizer ammonium perchlorate(AP)in solid propellants,but also a good performance explosive in itself.However,due to the strong hygroscopicity of ADN,its application in solid propellants and explosives is greatly limited.Solving the hygroscopicity of ADN is the key to realize the wide application of ADN.In this paper,we systematically review the research progress of anti-hygroscopic strategies of ADN coating.The surface coating methods are focusing on solvent volatilization,solvent-non-solvent,melt crystallization and atomic layer deposition technology.The characteristics of the different methods are compared and analyzed,and the basis for the classification and selection of the coating materials are introduced in detail.In addition,the feasibility of material for surface coating of ADN is evaluated by several compatibility analysis methods.It is highly expected that the liquid phase method(solvent volatilization method,solvent-non-solvent method)would be the promising method for future ADN coating because of its effective,safety and facile operation.Furthermore,polymer materials,are the preferred coating materials due to their high viscosity,easy adhesion,good anti-hygroscopic effect,and heat resistance,which make ADN weak hygroscopicity,less sensitive,easier to preserve and good compatibility.

A review on the high energy oxidizer ammonium dinitramide:Its synthesis,thermal decomposition,hygroscopicity,and application in energetic materials

Ammonium dinitramide(ADN)is considered as a potential substitute for ammonium perchlorate in energetic materials due to its high density,positive oxygen balance,and halogen-free characteristics.However,its application has been severely limited because of its strong hygroscopicity,difficult storage,and incompatibility with isocyanate curing agents.In order to better bloom the advantages of the highly energetic and environment-friendly ADN in the fields of energetic materials,an in-depth analysis of the current situation and discussion of key research points are particularly important.In this paper,a detailed overview on the synthesis,thermal decomposition,hygroscopic mechanism,and antihygroscopicity of ADN has been discussed,its application in powdes and explosives are also presented,and its future research directions are proposed.

Studies on ammonium dinitramide and 3,4-diaminofurazan cocrystal for tuning the hygroscopicity

Ammonium dinitramide(ADN)is a promising oxidizer with high energy characteristic,which is a relatively new environmentally friendly oxidizer without halogens and carbon elements.However,ADN has high hygroscopicity when exposed to high humidity air,restricting its applications on the solid propellants.In this paper,a novel energetic cocrystal composed of ammonium dinitramide and 3,4-diaminofurazan(DAF)was proposed and successfully synthesized by antisolvent crystallization method,and the properties of the cocrystal were systematically investigated by analytical characterization and theoretical simulation calculations.The formation of the cocrystal was confirmed by powder X-ray diffraction,differential scanning calorimetry,scanning electron microscopy,infrared spectroscopy and Raman spectroscopy,indicating that the synthesized product was a cocrystal.Through theoretical studies,the ADN/DAF cocrystal structure was predicted,and the powder X-ray diffraction,morphology,water sorption capacity of ADN/DAF cocrystal were calculated,which was consistent with experimental phenomena.The results showed that newly prepared cocrystal of ADN/DAF had lower hygroscopicity compared to pure ADN,and the water sorption capacity was reduced from 15.35%to 7.90%.This may be due to the formation of N-H…O medium-strength hydrogen bonds between the ammonium ion of ADN and the O atom of DAF in the cocrystal,which prevents the binding of water molecules in the air and ammonium ions and reduces the probability of ADN binding to water molecules,leading to the reduction of cocrystal hygroscopicity.The newly prepared energetic cocrystal can provide theoretical and technical guidance for the study of the anti-hygroscopicity of ADN and advance the practical application of ADN.

Fabrication of alginate-based microspheres with cellular structure for tuning ammonium dinitramide performance

Recently,an emerging category green of energetic material ammonium dinitramide(ADN)has exhibited promising application in propellants due to its outstanding merits in energy release and environmental friendliness.It can be considered to substitute traditional oxidizer of ammonium perchlorate(AP)in military systems and aerospace.In this paper,a novel spherical energetic composite ADN/copper alginate(CA)with a microporous structure was designed and prepared by the W/O gel emulsion method,and a desirable porous microsphere structure was obtained.Multiple characterization techniques were used to investigate the structure and properties of ADN/CA composites.The results showed that ADN crystals were homogeneously encapsulated in an alginate-gel matrix.Thermal decomposition temperature was reduced to 151.7℃compared to ADN,while the activation energy of them was reduced from 129.73 k J/mol(ADN)to 107.50 k J/mol(ADN/CA-4).In addition,as-prepared samples had lower impact and frictional sensitivity than ADN.The mechanism of sensitivity reduction and decomposition are also discussed.Constant-volume combustion tests show that peak pressure of the ADN/CA-4 achieves 253.4 k Pa and pressurization rate of 2750.4 k Pa/s.Hence,this has a promising application in improving the combustion performance and safety performance of solid propellants.

Energetic Abilities of Solid Composite Propellants Based on 3,4,5-Trinitropyrazole and Ammonium Dinitramide

The investigation aims at the expansion of the basis of formulations of solid composite propellants by introducing new compositions with lower sensitivity to mechanic impact and improved thermal stability.The formulations based on trinitropyrazole(TNP)contains a binder(a hydrocarbon or active one),aluminum and inorganic oxidizer ADN.The results show that a binary formulation TNP+active binder(18%-19%)(volume fraction)with no metal is well designed which would achieve high specific impulse(at Pc∶Pa=40∶1)of 248s,high density of 1.80g/cm3 and combustion temperature Tcabout 3 450K.In terms of energy,metal-free compositions with TNP lose a bit to those with HMX,only if HMX fraction in formulation is higher than 45%-50%.

Thermochemical Properties and Non-isothermal Decomposi-tion Reaction Kinetics of N-Guanylurea Dinitramide (GUDN)

The constant-volume combustion energy, cUD(GUDN, s, 298.15 K), enthalpy of solution in acetic ether, solmHQD and kinetic behavior of the exothermic decomposition reaction of the title compound (GUDN) are deter-mined by a precise rotating bomb calorimeter, a Calvet microcalorimeter and DSC, respectively. Its standard en-thalpy of combustion, cmHQD (GUDN, s, 298.15 K), standard enthalpy of formation, fHQDm (GUDN, s, 298.15 K) and kinetic parameters of the exothermic main decomposition reaction in a temperature-programmed mode [the apparent activation energy (aE) and pre-exponential factor (A)] are calculated. The values of cUD (GUDN, s, 298.15 K), cmHQD (GUDN, s, 298.15 K), fmHQD(GUDN, s, 298.15 K) and solmHQD of GUDN are (-7068.64±2.37) J·g-1, (-1467.66±0.50) kJ·mol-1, (-319.76±0.58) kJ·mol-1 and (165.737±0.013) kJ·mol-1, respectively. The kinetic model function in integral form and the value of aEand A of the exothermic main decomposition reaction of GUDN are 220.20 kJ·mol-1 and 1021.18 s-1, respectively. The critical temperature of thermal explosion of GUDN is 217.6 ℃

Analysis of Porosity and Preheating Temperature on the Decomposition and Combustion Characteristics within 5 N Ammonium Dinitramide(ADN)-based Monopropellant Thruster

In this study,the effects of porosity of the fore-catalytic bed and after-catalytic bed and preheat temperature on the decomposition and combustion characteristics of a 5N ammonium dinitramide(ADN)-based thruster were numerically investigated in terms of the distribution of components,temperature,and pressure.The results indicated that the porosity of the fore-catalytic bed and preheating temperature significantly affected the decomposition and combustion characteristics.The porosity of the fore-catalytic bed was optimized,and the thrust performance was demonstrated to improve with increasing of porosity of the after-catalytic bed and pre-heating temperature.The results were favorable for the investigation of decomposition and combustion characteristics and could also be beneficial to the design and manufacture of different types of ADN-based thrusters.

Advances in phase stabilization techniques of AN using KDN and other chemical compounds for preparing green oxidizers

Research and development of green oxidizers and green fuels as a possible replacement for ammonium perchlorate(NH4ClO4,AP) and hydrazine(N2H4) respectively has been increased considerably in the recent years.AP and hydrazine are the oxidizer and fuel entities,and used in solid and liquid rocket motors respectively.AP is highly toxic and led to adverse health effects,while hydrazine is carcinogenic in nature.AP is in use from the last several decades for rocket and space shuttle propulsion,while hydrazine is used in upper stage liquid propelled rocket motors.It’s a tough task to replace AP with the currently available green oxidizers;since their ballistic properties are weaker when compared to AP and also they can’t be successfully deployed in a solid rocket motor at present Some important available solid green oxidizers are ammonium nitrate(AN),ammonium dinitramide(ADN),hydroxyl ammonium nitrate(HAN),and hydrazinium nitroformate(HNF).However,AN is one of the cheap and readily available oxidizer,and has great potential to use in solid/liquid rocket motors.Tremendous progress has been envisaged till now,and more progress will be there in the coming future over the development of AN based green energetic materials(GEM’s).A concise overview has been presented over the development of phase stabilized ammonium nitrate(PSAN) and AN/KDN based green oxidizers in the present review paper.

Thermal Behavior, Specific Heat Capacity and Adiabatic Time-to-explosion of GDN

A new compound, [（NH2）2C=NH2]＋N（NO2）2-（GDN）, was prepared by mixing ammonium dinitramide （ADN） and guanidine hydrochloride in water. The thermal behavior of GDN was studied under the non-isothermal conditions with DSC and TG/DTG methods. The apparent activation energy（E） and pre-exponential constant（A） of the exothermic decomposition stage of GDN were 118.75 kJ/mol and 10^10.86 s^-1, respectively. The critical temperature of the thermal explosion（Tb） of GDN was 164.09 ℃. The specific heat capacity of GDN was determined with the Micro-DSC method and the theoretical calculation method, and the standard molar specific heat capacity was 234.76 J·mol^-1·K^-1 at 298.15 K. The adiabatic time-to-explosion of GDN was also calculated to be a certain value between 404.80 and 454.95 s.