Synthesis And Catalytic Properties Of Nitrogen-rich Bimetallic Energetic Complexes

As the power source of various types of rockets and weapons,solid propellants have played a crucial role in their application and development.At present,ammonium perchlorate（AP）is often used as an oxidant in the solid propellant,but its decomposition is harmful to the environment.Therefore,it is imminent to find a green and pollution-free oxidant.5,5′-bistetrazole-1,1′-diolate（TKX-50）as a new high-energy and environmentally friendly ionic salt is expected to replace AP.High energy and adjustable burning rate have always been the unremitting goals of solid propellant technology research.Combustion catalysts are the most effective and significant method for improving the combustion characteristics of propellants.Nitrogen-rich energetic complexes have high performance,environmentally friendly,and excellent performance,which are in line with the development trend of green and environmentally friendly solid propellants,so they have great application prospects.Combining the two in propellants can show the effects that conventional catalysts cannot achieve.Therefore,in this study,the ligand H₂BTA·H₂O and 22 kinds of nitrogen-rich metal energetic complexes are synthesized by hydrothermal method,and are characterized by XRD,FTIR,Raman,XPS,EA,ICP,SEM,EDS,DSC and other means.The catalytic effect of nitrogen-rich metal energetic complexes on the thermal decomposition process of TKX-50 is further evaluated by TG-DSC.1.The calorific value of Nitrogen-rich bimetallic energetic complexes Li₃[Cu（BTA）₂（HBTA）]·2H₂O（8）,Na₃[Cu（BTA）₂（HBTA）]·2H₂O（13）and K₂[Cu（BTA）₂]·H₂O（18）are measured by Oxygen bomb calorimeter,The measured molar enthalpies of formation were 6525 J/g,6605 J/g,and 6804 J/g,respectively.The measured energy density of complex 18 is high,indicating its heat of explosion is high.The ligand H₂BTA·H₂O and 22 kinds of nitrogen-rich metal energetic complexes are tested by thermal analysis（DSC）using differential scanning calorimeter（DSC）.2.Differential scanning calorimetry（DSC）is used to study the effects of complexes 1-22on the thermal decomposition of TKX-50,and the complexes that had a significant promoting effect on the thermal decomposition of TKX-50 were selected.Then it is added into TKX-50according to different mass ratios,and the complexes with good catalytic performance are selected by comparing the influence on the thermal decomposition of TKX-50.It is found that the addition of Cu in the nitrogen-rich bimetallic energetic complexes makes the initial decomposition temperature shift to the lower temperature direction to the greatest extent;Li,Na,K,Co,Ni,and Mn-based single-metal complexes have similar catalytic activities;Cu-based bimetallic complex 8,complex 13 and complex 18 showed good catalytic activity.3.In order to further study the effects of Cu-based bimetallic energetic complexes 8,13and 18 on the thermal decomposition of TKX-50.Through TG-DSC test,it is found that when the addition amount is 10%and the heating rate is 20.0 K·min^-1,the addition of complex 8,complex 13 and complex 18 makes the initial decomposition temperature of TKX-50decreased by 20.5°C,21.3°C,29.8°C,respectively.By comparison,complex 18 can reduce the initial decomposition temperature of thermal decomposition of TKX-50 to a greater extent,and it is the most effective catalyst for thermal decomposition of TKX-50.The catalytic efficiency of the three nitrogen-rich bimetallic energetic complexes in the thermal decomposition process of TKX-50 is in the following order:complex 18>complex13>complex 8,which confirms that the nitrogen-rich Cu-based bimetallic energetic complexes have a positive effect on TKX-50 catalytic performance during thermal decomposition.Through further analysis of the TG curve,it is found that the analysis result of the TG curve is consistent with DSC.4.The apparent activation energies of nitrogen-rich bimetallic energetic complexes 8,13and 18 and TKX-50 composites are calculated by the method of Kissinger,Ozawa and Starink.when 10%of complex 8,complex 13 and complex 18 are added,the apparent activation energies of the composites decreased by 21.9 k J/mol,17.9 k J/mol and 13.7 k J/mol,respectively.The addition of nitrogen-rich energetic catalysts can reduce the activation energy of TKX-50,which further proves that nitrogen-rich energetic catalysts can effectively promote the thermal decomposition of TKX-50.Nitrogen-rich bimetallic energetic complex 8,complex 13 and complex 18 can significantly reduce the thermal decomposition peak temperature and activation energy of TKX-50,and promote the thermal decomposition of TKX-50.Among them,complex 18showed good catalytic activity for the thermal decomposition of TKX-50,and it can be used as a high-efficiency combustion catalyst containing TKX-50 solid propellant.