Preparation Of FOX-7 Nanosheets And Their Performances

Due to the high specific surface area,layered energetic materials have the advantages of high energy release rate and high combustion efficiency.Moreover,they can produce increased surface combustion and reduce the sensitivity through interlayer slip,which has outstanding application prospects.As a simple explosive with excellent comprehensive properties,1,1-diamino-2,2-dinitroethylene(FOX-7)can be prepared into layered explosives with excellent properties due to its special symmetrical molecular structure and layered crystal structure with waveform?stacking.Therefore,in this paper,FOX-7 is selected as the research goal.FOX-7 nanosheets are prepared by solvent-non-solvent method under different conditions.The effects of the type and amount of crystal form control agents on the crystalline morphology and properties of FOX-7 are studied,and its application is explored.The main contents in the paper are as follows:(1)Using nitrobacterial cellulose(NBC)as crystallization inducer,the self-assembled FOX-7 nanosheets were successfully prepared by solvent-non-solvent method.The average grain size of prepared FOX-7 nanosheets are less than 40 nm.When the addition amount of NBC is 5 wt%,the prepared FOX-7 nanosheets have the thinnest thickness of 50-100 nm.Compared with raw FOX-7,the prepared FOX-7 nanosheets have higher apparent thermal decomposition enthalpy,which increases with the increase of the NBC content.In the crystallization process of FOX-7,the layered structure NBC's inducing and restricting effects on the growth of the FOX-7 crystal eventually led to the formation of self-assembled FOX-7 nanosheets.Meanwhile,NBC participates in the formation of FOX-7 nanosheets.When the content of NBC was 5 wt%,the prepared FOX-7 nanosheets showed the lowest impact sensitivity.(2)Using N,N-dimethylformamide(DMF)as solvent,FOX-7 nanosheets were prepared with different types of surfactants as crystal control-additives.When the crystal control-additives are Tween-20 and PVP,the prepared FOX-7 nanosheets have smooth surface,which is nanosheets self-assembly stacking structure.Moreover,the crystal planes acted by the two surfactants are different,which are(0 2 1)and(1 0 1)crystal plans respectively.FOX-7 nanosheets prepared with PVP surfactant has more concentrated heat release and high energy release efficiency.In addition,the apparent activation energy of the prepared FOX-7 nanosheets decreases with the increase of PVP concentration,the apparent activation energy of the sample prepared at n_pvp:n _FOX-7=1:10 is 33.24%lower than that of the raw FOX-7.In the crystallization process of FOX-7,PVP induced the formation of nanosheets of FOX-7,and then stacked along the(0.21)crystal plane.(3)FOX-7/CL-20 composites were prepared by mechanical mixing and solvent ultrasonic compounding of FOX-7 nanosheets and CL-20.The samples prepared by solvent ultrasonic mixing were more evenly dispersed,and CL-20 is dispersed on the surface or between layers of FOX-7 nanosheets.The FOX-7/CL-20 composite has higher thermal stability and energy release efficiency than the raw CL-20.When FOX-7 nanosheets prepared by adding 5 wt%NBC is mixed with CL-20,the impact sensitivity of the composite system is reduced most obviously,and its characteristic drop height increased by 15 cm.