CL-20-based Explosive Ink:design And Micro-pen Direct Ink Writing

DIW(Direct Ink Writing)has an incomparable advantage on the micro-nanometer scale compared with traditional processing methods.In the field of energetic materials,the high precision charging of MEMS fuse explosive train with the direct ink writing technology has the characteristics of precision control,low cost,high efficiency,and ease of use.In this work,sub-micro CL-20 is used as the main explosive and waterborne polyurethane(WPU)and ethyl cellulose(EC)are used as binders.The appropriate solvent is selected to form a two-component binder system,the explosive ink for DIW was prepared.At the same time,three-dimensional numerical simulation of ink micro-flow extrusion process was carried out to study the relationship between the ink extrusion speed and applied pressure,micro-pen diameter and ink viscosity.Finally,the basic properties and detonation performance of explosive ink samples prepared by DIW were tested and characterized.The details are as follows:First,the sub-micro CL-20 explosive was prepared by mechanical ball grinding method.Scanning electron microscopy(SEM),X-ray diffraction(XRD)and differential scanning calorimetry(DSC)were used to analyze microstructure,phase analysis and thermal decomposition properties of the refined CL-20 samples.Second,using waterborne polyurethane(WPU)and ethyl cellulose(EC)as binders,select the appropriate solvent to form a two-component binder system.The explosive ink formula was optimized by testing the rheological properties,writing performance of the explosive ink and the safety performance,charge density,and detonation characteristics of the explosive ink samples.Finally,it was determined that the main explosive CL-20 accounted for 90% of the solid content of the molded sample,the concentration of waterborne polyurethane was 10%,the concentration of EC ethanol solution was 8%,the ratio of polyurethane to ethyl cellulose was 3:2,and the water-based anti-settling agent(alkylaryl polyether 410)was selected to ensure the long-term stability of the ink system.Then,a three-dimensional numerical simulation of ink micro-flow extrusion process was carried out to study the relationship between the ink extrusion speed and applied pressure,micro-pen diameter and ink viscosity.A semi-empirical formula of the cross-sectional area of the ink line and the width of the ink line was obtained through experiments,and the ink line width was calculated by simulating the speed and flow rate of the ink extrusion.At the same time,the wettability of the ink and the substrate was analyzed by testing the surface free energy of different materials.Finally,explosive ink samples prepared by DIW were tested and characterized.The microstructure shows that the explosive particles and binder in the explosive ink are dispersed evenly,and presents a honeycomb morphology with high porosity.The porosity increases with increasing EC content.XRD analysis shows that the phase of CL-20 in the explosive ink composite is still ?-CL-20.DSC analysis shows that the peak of decomposition temperature of CL-20-based explosives is 12-15°C earlier than that of sub-micro CL-20,and the apparent activation energy increases from 176.06 kJ/mol to 228.5 kJ/mol,an increase of 29.8%,thermal stability has increased dramatically.The detonation tests show that the prepared explosive ink can reliably and steadily detonate in small-sized channels,has a very small critical thickness(100 ?m),and the detonation speed is about 7300 m/s,decreased with the decrease of charge density.