| Dihydroxylammonium 5,5'-bistetrazole-1,1'-diolate(TKX-50)is a new energetic salt with high energy storage,high detonation speed,low sensitivity and low toxicity,which has an excellent application prospect in the fields of solid propellant,weapons,civil blasting and so on.In this paper,the Spray-Freezing into Liquid(SFL)method and the Freeze-Drying method(FD)method were used to process TKX-50,and the products were analyzed.The morphology was characterized by Scanning Electron Microscope(SEM),the crystal form and structure were analyzed by X-Ray Diffractometer(XRD),the thermal decomposition process was studied by Differential Scanning Calorimetry(DSC),and the thermokinetic analysis software AKTS(Advanced Kinetics and Technology Solutions)was used to calculate the activation energy,correlation coefficient and pre-exponential factor of the thermal decomposition process by Kissinger method,Ozawa method and Friedman method.The results are as follows:Firstly,the three-dimensional structures of TKX-50 were constructed by SFL method,and the effects of concentration,solvent kind,spraying pressure and nozzle aperture on the micro-nano TKX-50 with three dimensional network structures were explored.The main results are as follows:(1)All the samples prepared by SFL method at different concentrations had fluffy three-dimensional network structures.The concentration had no obvious effects on the structures of the prepared samples.When the concentrations were 0.1mg/ml,0.3mg/ml and 0.5mg/ml respectively,the temperatures of thermal decomposition peaks were 232.979?,232.034? and 228.907?,respectively,and the activation energy calculated by Kissinger method were 112.819kJ/mol,163.271kJ/mol and 123.068kJ/mol.With the increase of concentration,the temperatures of thermal decomposition peaks of the samples decreased,while the apparent activation energy increased at first and then decreased.(2)The crystallinity of the sample prepared with formic acid as solvent was better than that of the sample prepared with deionized water.The temperature of thermal decomposition peak of the sample prepared with formic acid as solvent was 204.358?,and the apparent activation energy calculated by Kissinger method was 129.153kJ/mol.Compared with the sample prepared with deionized water as solvent,the temperature of thermal decomposition peak and apparent activation energy decreased by 27.676? and 34.118kJ/mol respectively.(3)When the spraying pressures were 0.2MPa,0.4MPa and 0.6MPa,respectively,the samples prepared by SFL method had fluffy three-dimensional network structures,and there were no significant differences in crystal forms.The temperatures of thermal decomposition peaks were 230.634?,232.034? and 230.419?,respectively,and the activation energy calculated by Kissinger method were 153.487kJ/mol,163.271kJ/mol and 134.498kJ/mol.With the increase of spraying pressures,the temperatures of thermal decomposition peaks and apparent activation energy increased at first and then decreased.(4)When the nozzle apertures were 0.2mm,0.5mm,1.0mm and 1.8mm,respectively,the sample prepared by SFL method had a three-dimensional network structure,and there was no significant difference in crystal form.The temperatures of thermal decomposition peaks were 233.245?,232.034?,233.177? and 234.187?,respectively,and the activation energy calculated by Kissinger method were 125.406kJ/mol,163.271kJ/mol,149.839kJ/mol and 128.960kJ/mol.With the increase of nozzle apertures,the temperatures of thermal decomposition peaks decreased at first and then increased,and the apparent activation energy increased at first and then decreased.Secondly,the effects of concentration,solvent kind and cooling rate on the micro-nano TKX-50 prepared by FD method were studied.The main results are as follows:(1)There was no crystal transformation in the process of FD method.When the concentrations were 0.1mg/mL,0.3mg/mL and 0.5mg/mL,the temperatures of thermal decomposition peaks were 241.387?,238.645? and 235.373?,respectively,and the activation energy calculated by Kissinger method were 154.385kJ/mol,143.020kJ/mol and 142.800kJ/mol.As the increase of concentration,the temperatures of thermal decomposition peaks and the apparent activation energy calculated by Kissinger method decreased,while the apparent activation energy calculated by Friedman method decreased first and then increased.(2)The crystallinity of sample prepared with formic acid as solvent was worse than that of the sample prepared with deionized water.The temperature of thermal decomposition peak was 216.402?,and the apparent activation energy calculated by Kissinger method was 134.133kJ/mol.Compared with the sample prepared with deionized water as solvent,the temperature of thermal decomposition peak and apparent activation energy of the sample prepared with formic acid as solvent decreased 22.243? and 8.887kJ/mol respectively.(3)In the study related to the cooling rate and freezing method,the temperature of thermal decomposition peak of the sample frozen in a cold trap was 237.281?,which was 1.364? lower than that of the sample frozen in a freezer.The apparent activation energy of the sample frozen in a cold trap calculated by Kissinger method was 151.125kJ/mol,which was higher than that of the sample frozen in a freezer(143.020kJ/mol).The morphology of the samples prepared by SFL method is quite different from that of the samples prepared by FD method.The samples prepared by SFL method had three-dimensional network structures with small particle size and nano particles on the grid.As for the samples prepared by FD method,there was no unified form with larger particle size in sub-micron level. |
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