Research On Preparation Of High-quality TKX-50 And Its Composite Particles By Recrystallization Method

1,1’-dihydroxy-5,5’-tetrazolium dihydroxyamine salt（TKX-50）is a novel high energy density compound and one of the most promising third generation energetic materials.Industrial grade TKX-50 has shortcomings such as irregular crystal morphology,small particle size,large aspect ratio,and low intramolecular oxygen content,which affects its application in mixed explosives and propellants.Recrystallization is a key process in the production of TKX-50,and is also a common method to improve crystallization quality and application performance.In this paper,the crystallization thermodynamics and crystallization process optimization of TKX-50 have been carried out.High quality,large particle spherical TKX-50crystals have been prepared by recrystallization method,and they have been prepared with ammonium perchlorate（AP）by solvent-nonsolvent method TKX-50@AP The microstructure,thermal performance,and safety performance of core shell composite particles were tested and analyzed.The specific content of this paper is as follows:（1）The temperature range is determined by dynamic laser method between 293.15K-333.15K,TKX-50 was used in the solubility of seven pure solvents such as ethanol,water,ethyl acetate,toluene,formic acid,N,N-dimethylformamide（DMF）and N-methylpyrrolidone（NMP）and six H₂O-DMSO binary mixed solvents with different volume ratios,and the solubility model was established using the Apelblat equation and van’t Hoff equation.The dissolved thermodynamic parameters of TKX-50 in the above solvent were calculated by van’t Hoff equation.The solid-liquid surface tension and crystal surface entropy factor of TKX-50 in the corresponding system were calculated by Mermann equation and Barata equation.The results showed that formic acid and DMSO were good solvents for TKX-50,ethyl acetate,ethanol and water were bad solvents,and the dissolution process of TKX-50 was endothermic and non-spontaneous.（2）Compare the crystal morphology of TKX-50 obtained by dissolution crystallization method and cooling crystallization method,and determine the research process of spherical crystallization by cooling crystallization method.The effects of crystallization solvent,cooling initiation temperature,cooling rate,stirring rate,additives,seed quality,seed morphology and seed aspect ratio on the crystal morphology of TKX-50 were studied,and the optimal crystallization process conditions were determined.The results showed that the optimal conditions were as follows:H₂O-DMSO binary mixed solvent with w _DMSO=0.35,the initial cooling temperature was 50°C,the stirring rate was 300 r/min,the cooling rate was 0.5°C/min,the additive wasβ-cyclodextrin,and the seed species with small aspect ratio and good crystal morphology were added.（3）TKX-50 was recrystallized under the best crystallization process conditions,with spherical TKX-50 as the main body and ammonium perchlorate（AP）as the guest,and TKX-50@AP core-shell composite particles were prepared by solvent-non-solvent method.TKX-50,AP and TKX-50@AP complexes were compared and characterized by scanning electron microscopy,powder X-ray diffraction,infrared spectroscopy,thermal performance analysis and mechanical sensitivity.The results showed that the composite effect of AP and TKX-50 was good,and a dense cladding layer was formed in TKX-50 crystals,the thermal decomposition temperature Tp0 and thermal explosion critical temperature Tb of composite particles increased by 5.02°C and 4.14°C,respectively,the explosion probability of friction sensitivity decreased from 100%to 76%,and the impact sensitivity characteristic drop height increased from 64.5cm to 42.2cm.