Study On Molecular Design,synthesis And Application Of Furazan Compounds

To enhance energy is the driving force of the solid propellants development. In fact, increase of propellant energy is depended on the research and application of high-energy materials. Furazans, one kind of high-nitrogen compounds, have many advantages, such as, high and positive standard enthalpy of formation, high crystal density, acceptable thermal stability and sensitivity. Moreover, they can be synthesized simply from the cheap raw materials and have high productivity,. Addition of furazans into the compsite solid propellants may inccrease the energy of propellants obviously.However, the research on the synthesis and application furazans in our country is just starting now. The main problems are the shortage of methods to predict the theoretical properties of the compounds, and the absence of the knowledge about the structure-activity relationship between the molecular characteristics of furazan and the performance of propellants with them. Hence, the works, such as, the synthesis methods and molecular characteristics of furazans, the influence of the compounds on the performance and the primary combustion properties of the propellants, should be investigated systematically. These results can give the theoretical guidance to the molecular design, synthesis and application of the high-energy density compound(HEDC).The objective of this dissertation is to improve the performance and the primary combustion properties of the fuel-rich propellants by addition of furazans. The structure-activity relationship between the molecular characteristics of high-nitrogen HEDC and the propellants performance was the main task of the author. The molecular characteristics, such as, the molecular configurations, electronic distributions and thermodynamic properties of furazans were studied by means of the computational chemistry. The coding method to describe the molecular characteristics of HEDCs has been established. The method of the artificial neural network was used to calculate and predict the standard enthalpies of formation of HEDC crystals. Six of furazans were synthesized. The influence of the molecular charcteristics of furazans on its sensitivity was investigated. With the suppositional uniform design and stepwise linear regression analysis methods, the quantitative structure-activity relationship between the molecular properties of furazans and the propellants performance has been established. The actions of furazans on the performance and primary combustion properties of the fuel-rich propellants were investigated.The results from the quantum chemistry calculations showed that furazan ring is approximately a flat conjugated ring, but the conjugation is weak. Furzan ring is an electron-deficient group, so the electron-rich group in fuzan will be attacked by oxidizing group instead of the furazan ring when furzan derivatives are oxidized. The N-O bond is the weakest bond in the furazan ring because of the least population of N-O bond in furazan ring, so it will be broken firstly when furazan is stimulated.The calculated results indicated that, the thermodynamic properties of furazans are increased linearly with the temperature below 300 K. The changing rate of the standard molar enthalpy of furazans increases with the enhancement of temperature, while the changing rates of standard molar entropy and standard molar thermal capacity at constant pressure of furazans decrease.The coding method has been established to describe molecular configurations of HEDCs. With the molecular codes and the artificial neural network method, a software which calculate the standard formation enthalpy of HEDC crystals was developed. The average relative error of the calculated enthalpies of the 70 high-nitrogen compounds is only 0.36%.Six of furazans were synthesized from 3,4-diamino-furazan(DAF). One of the fused-ring furazan, DNMz F, is never reported before.The sensitivities of the furazans, the furazan/AP mixtures and the propellant slurry contained furazan were characterized. The experimental results showed that the sensitivities of the furazan are in according with analysis results of its electron structure. The furazan/AP mixtures are more sensitive than furazan. The sensitivities of furazan/AP mixtures are affected by the oxygen balance of the mixture. The propellant slurry contained furazan are less insensitive than the furazan/AP mixtures.Quantitative structure-activity relationship(QSAR) between the properties of high-nitrogen compounds, shuch as, the atom numbers, content, oxygen banlance and standard enthalpy of formation, and the theoretical specific impulse of propellants was obtaintd by means of the suppositional uniform design experiments and stepwise regression analysis. The average relative errors of two QSARs in the fuel-rich propellant and solid rocket propellant were-1.92% and-2.79% respectively. The performance of the propellants with high-nitrogen compounds could be estimated by the QSARs fast and accurately. On the basis of the QSARs, the effects of high-nitrogen compounds on the specific impulses of the fuel-rich and solid rocket propellants were studied.When AP are partly substituted by the energetic additives, the specific impulse of the fuel-rich propellants increased, the flame temperature and average molecular weight of the gas products in the propellant-air system also increased. The order of the specific impulse of the fuel-rich propellants with the same content of energetic additives is: Mz F > DAF > DAAz F > RDX > DNAF. With the higher content of energetic additives, the flame temperature of the propellant-air system and the specific impulse of the propellants will rise. The numbers of C atoms and O atoms in the energetic additives are the most significant factors on the specific impulse of the fuel-rich propellants.When the Al-Mg alloy are substituted by the energetic additives, the specific impulse of the fuel-rich propellants and the flame temperature of the propellant-air system reduced, but the average molecular weight of the gas products in the system increased. With the content increase of energetic additives, the specific impulse of the propellants and the flame temperature of the propellant-air system reduced, the average molecular weight of the gas products in this system increased. The order of the specific impulse of the fuel-rich propellants with the same content of energetic additives is: Mz F > DAF > DAAz F > RDX > DNAF.The primary burning rate and pressure exponent of the fuel-rich propellant can be increased by partial substitution of AP with DNAF or RDX. When the content of DAF, Mz F and DAAz F is high, the primary burning rate of the fuel-rich propellant reduced. The primary burning rate of the fuel-rich propellant with furazan will be imcreased along with the rise of oxygen balance and combustion temperature.