Integrated Construction And Reactivity Regulation Of B/KNO₃ Energetic Composites

With the miniaturization,dexterity and intelligent development of weapon systems and energy devices,higher requirements are put forward for the integrated assembly and energy release regulation of energetic materials.From the perspective of chemical reaction scale,compared with intramolecular energetic materials,intermolecular energetic composites show advantages in energy density and freedom of energy release regulation.Among them,boron/potassium nitrate（B/KNO₃）composite has the characteristics of high calorific value,high stability and high safety,which is very suitable for micro-scale application scenarios with high energy loss and has attracted more attention.Affected by the miniaturization of the physical size of micro-energetic devices,the built-in energetic materials often produce non-ideal reactive behavior due to energy dissipation.How to effectively control the reaction kinetics and energy transfer of energetic materials in a limited space is the key to realize the application of B/KNO₃ in micro-energy devices.In this study,the controllable integration of B/KNO₃ powder was realized with the help of ink-based idea.On the one hand,the limitation of inert oxide layer was eliminated by chemical modification,and on the other hand,the pressure and heat were purposefully channeled through structural arrangement,so as to realize its reactivity enhancement and energy release behavior regulation.On this basis,the application effect of B/KNO₃ energetic ink on small-scale combustion/explosion energy conversion components was explored.The main research contents and results are as follows.（1）B/KNO₃ energetic sticks with different binder types,binder content and fuel/oxidant composition ratio were prepared.The rheological properties of energetic inks,the morphology of energetic sticks,the combustion characteristics,pressure release characteristics and thermal decomposition characteristics of energetic composites were studied.The results show that the forming effect of energetic stick is strongly dependent on the rheological properties of energetic ink.Too high or too low consistency coefficient will affect the forming effect.Using fluorine rubber as a binder can greatly reduce the initial reaction temperature of the energetic composites and significantly improve the reaction characteristics of the energetic sticks.PVDF as binder at7 wt%is the optimal ratio to balance the molding effect of the sticks and the reaction characteristics.The reactivity of the energetic sticks has a strong dependence on the fuel/oxidant ratio.When the B content is between 20-30 wt%,the reactivity of the composite system reaches the strongest.（2）Two kinds of active metals,Al and Zr,were introduced into the B/KNO₃ system.Different energetic sticks were prepared by DIW technology,and the forming effect and reaction characteristics of different energetic sticks were studied.The results show that the addition of active metals has a positive effect on reducing the initial reaction temperature,improving the reaction characteristics of energetic composites,and reducing the agglomeration of solid phase products.The addition of nano-Al powder promotes the first stage reaction of the composite,while the addition of micron-Al powder mainly promotes the second reaction stage of the reactant.The addition of 7.5 wt%micron Al powder and 5 wt%nano Al powder increased the linear burning rate of the energetic sticks by 27%and 20.4%,respectively.With the increase of Zr/KNO₃ content from 10 wt%to 80 wt%,the peak temperature of the condensed-phase reaction of the composites decreased from 479.93°C to 362.11°C,and the linear burning rate increased from 62.14 to 136.76 mm·s^-1,which was an enhancement of about 120%.（3）Carbon nanotubes（CNT）and graphene oxide（GO）were added to the B/KNO₃ system as additives,and the energetic sticks were prepared with the help of DIW technology,and the molding effect and reaction characteristics were investigated.The results showed that the increase of CNT and GO from 2 wt%to 8 wt%decreased the peak temperatures of the energetic composites by 35.25°C and 15.07°C,respectively.The three exothermic peaks of the B/KNO₃/PVDF composites were changed into two consecutive exothermic peaks or a single exothermic peak.The addition of 2 wt%CNT increased the linear burning rate of the energetic sticks from 60.97 mm·s^-1 to 68.21 mm·s^-1,and the burning rate decreased to 35.59 mm·s^-1 with the continued addition of CNT to a value of 8 wt%.The burning rate decreased from 60.97mm·s^-1 to 38.65 mm·s^-1 with the increase of GO content to 8 wt%.（4）Energetic sticks with different thicknesses,energetic architectures with different spacing arrangements and different corner arrangements were prepared by DIW technology,and their flame propagation process and energy release behavior were studied.The results show that the energetic sticks have obvious size effect,and the energetic sticks with different sizes usually shows a’platform phenomenon’on its burning rate curve.The B/KNO₃ energetic stick has a platform between the thickness of 750-1400μm,while the Zr/B/KNO₃（ZPN/BPN）energetic stick has three platforms in the thickness of 100-200μm,400-600μm,and 800-1400μm.The energy coupling effect is widely present in the energetic structure of the interaction in the energy interaction area,and is controlled by the distance or angle of the stick.The linear burning rate of B/KNO₃ energetic stick increased from 60 mm·s^-1 to 237.7 mm·s^-1.（5）The charge of B/KNO₃/PVDF igniter ink and HMX-based booster ink in small-sized combustion/explosion energy conversion components was completed by using double nozzle direct ink writing technology,The influence of DIW process on the forming effect of energetic stick was investigated,and the influence of different components and different charge structures on the combustion/explosion energy conversion characteristics was studied.The results show that the forming effect of energetic stick is controlled by inlet pressure,nozzle speed,nozzle height and substrate temperature.The deflagration-to-detonation capability of the combustion/detonation energy conversion component is closely related to the type of charge,the size of the charge,the charge rate and contact area of the two-component charge.When the charge size is 6 mm×6 mm×60 mm,the two-component ratio is 1:5,and the explosive charge is HMX and CL-20,the device can realize the initial transformation from combustion to explosion.