| With the development of modern weapon system,the high energy insensitive explosive has become a hot topic in the field of explosive research and development.Crystal morphology and temperature are important factors to the sensitivity of explosives,and it is possible to control the crystal morphology,reduce the crystal defects and sensitivity of explosives through changing crystallization solvent and temperature.The screening process of crystallization solvents can be reduced by predicting the crystal morphology in different solvents theoretically.Adding high polymer binders to the single-compound explosives can also reduce the explosive sensitivity,and improve the mechanical properties.The whole research work mainly consists of the two parts:In the first part,1,3,3-trinitroazetidine(TNAZ),2,6-diamino-3,5-dinitropyridine-1-oxide(ANPyO)and trans-1,4,5,8-tetranitro-1,4,5,8-tetraazadacalin(TNAD)were studied.The attachment energy(AE)model was employed to predict the growth morphologies and the main crystal faces in vacuum.The molecular dynamics(MD)method was performed to calculate the interactions of crystal faces and different solvents,whilst the growth habits in solvents were predicted using the modified AE model.The results indicate that the morphology of TNAZ crystal in vacuum is dominated by the six faces of(002),(111),(02 0),(1 02),(02 1)and(1 1 2),and the crystal shape is similar to polyhedron.The morphology of ANPyO crystal in vacuum is dominated by the four faces of(1 1 0),(1 0 0),(10-1)and(11-2),and the crystal shape is similar to ellipsoid.The morphology of TNAD crystal in vacuum is dominated by the four faces of(1 1 0),(0 1 0),(100)and(001),and the crystal shape is similar to octahedron.In ethanol solvent,the crystal morphology of TNAZ becomes more regular and(1 1 1)and(020)faces disappear.In N,N-dimethyl-formamide(DMF)and trifluoroacetic acid(CF3COOH)solvents,the crystal morphology of ANPyO becomes very close to a flake,according well with the experiment results.In dimethyl sulfoxide(DMSO)solvent,the growth rate of TNAD(00 1)face is the slowingest and the crystal morphology becomes similar to the cuboid.The second part concentrates on the structures and properties of TNAZ,ANPyO,TNAD super cells and their polymer bonded explosives(PBXs).The relationships of sensitivity with some parameters,such as bond length,the interaction energy of trigger bond and the cohesive energy density,were investigated.The stability,compatibility of PBXs systems and the influence of polymer binders on mechanical properties of explosives were studied.The results indicate that the lattice parameters(a,b and c)and volume increase with the increasing temperature,while the crystal density decreases gradually;and the calculated results accord well with the experimental results.The thermal expansion property of TNAZ is anisotropic,the volume and linear expansion coefficients decrease as the temperature increases.The maximum bond length,the interaction energy of the trigger bond(N-NO2)of TNAZ and TNAD,C-NO2 of ANPyO,and the cohesive energy density can be used as parameters to evaluate the sensitivity of the three single-compound explosives.However,these parameters are inapplicable to the sensitivity of PBXs.The binding energies of the unit quality binder with TNAZ(002),ANPyO(110)and TNAD(001)faces are in the order of PEG>PGN>F2311>F2603,PEG>PGN>F2603>F2311,and PEG>PGN>F2603>F2311,respectively,which indicates that the PBXs composed of PEG and faces are the most stable,and the compatibility are the best.The analysis of radial distribution function indicates that the interactions of PEG,PGN with TNAZ(002),ANPyO(110)and TNAD(001)faces include electrostatic force,van der Waals force and hydrogen bond.The hydrogen bond also exists between F2603 and TNAD(001)face,however,the hydrogen bond strength in F2603 PBX is weaker than that in PGN and PEG PBXs.The rigidity of the PBXs can be reduced,while the flexibility,toughness and mechanical properties can be improved by adding small amounts of PE,PGN,F2311 and F2603. |
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