Preparation,Characterization And Performance Of Cobalt-Based Metal Oxides And Their Corresponding Thermites

Energetic materials?EMs?raise more and more research interests due to their wide application in propellants,explosives,pyrotechnics and other fields.Improving the thermal decomposition property of energetic components is the main challenge we face,and the addition of combustion catalysts can improve this problem.In this paper,cobalt-based metal oxide including Co₃O₄nanowires,Mg Co₂O₄nanowires,and honeycomb Zn Co₂O₄which can be used as combustion catalysts were successfully prepared.The effects of these three metal oxides as combustion catalysts on the thermal decomposition behavior of ammonium perchlorate?AP?,2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzi-tane?CL-20?,cyclotrimethylenetrinitramine?RDX?and 1,3,5,7-tetranitro-1,3,5,7-tetrazocane?HMX?were investigated by differential scanning calorimetry?DSC?,thermogravimetry-differential thermogravimetry?TG-DTG?and thermal analysis kinetics.In addition,Al/Co₃O₄,Al/Mg Co₂O₄and Al/Zn Co₂O₄were prepared and the thermite reaction of them was discussed.The following is the main content of this work:?1?Co₃O₄,Mg Co₂O₄and Zn Co₂O₄were successfully prepared using nickel foam?NF?as a template.After that,three kinds of thermites,Al/Co₃O₄,Al/Mg Co₂O₄and Al/Zn Co₂O₄,were prepared by physical mixing.?2?The phase composition and morphology of the as–prepared NWs were analyzed by a series techniques including X-ray powder diffraction?XRD?,X-ray photoelectron spectroscopy?XPS?,Fourier infrared spectrometer?FT-IR?,scanning electron microscopy?SEM?,transmission electron microscope?TEM?,and the N₂adsorption-desorption test.It was proved that Co₃O₄,Mg Co₂O₄,Zn Co₂O₄and thermites all have higher purity.The metal oxides grown on the NF had uniform morphology and high surface area.?3?The effects of Co₃O₄,Mg Co₂O₄,Zn Co₂O₄as combustion catalysts on the thermal decomposition behavior of AP,CL-20,RDX and HMX were studied by DSC,TG-DTG test and thermal analysis kinetics.Compared with pure AP,the exothermic decomposition peak temperatures of Co₃O₄/AP,Mg Co₂O₄/AP and Zn Co₂O₄/AP composites decreased by122.96,126.38 and 101.87°C,respectively,and their apparent activation energies were reduced by 7.25,15.44 and 17.88 k J·mol^–1.Compared with pure CL-20,the exothermic decomposition peak temperatures of Co₃O₄/CL-20,Mg Co₂O₄/CL-20 and Zn Co₂O₄/CL-20composites were lowered by 4.46,6.60 and 7.87°C,and their apparent activation energies were reduced by 5.00,10.65 and 7.87 k J·mol^–1.The exothermic decomposition peak temperatures of Co₃O₄/RDX,Mg Co₂O₄/RDX and Zn Co₂O₄/RDX decreased by 2.45,7.17,and 4.39°C earlier than RDX,the apparent activation energy was reduced by 67.36,86.96,and 51.57 k J·mol^–1,respectively.Co₃O₄/HMX,Mg Co₂O₄/HMX and Zn Co₂O₄/HMX had exothermic decomposition peak temperatures which were 0.80,1.40,and 1.32°C lower than HMX,respectively,and their apparent activation energies had decreased by 24.19,86.22 and 81.45 k J·mol^–1.DSC test and the study of the thermal decomposition kinetics showed that the addition of a small amount of catalyst reduced the thermal decomposition peak temperature of AP,CL-20,RDX and HMX,and the apparent activation energy.The decrease of thermal decomposition peak temperature and the activation energy indicated that Co₃O₄,Mg Co₂O₄and Zn Co₂O₄had good catalytic activities for AP,CL-20,RDX and HMX.This can be attributed to the fact that the samples grown on the NF have porous structures and large specific surface areas,and they can provide rich active sites for the thermal decomposition reaction.?4?Based on the consistent morphology and size of Co₃O₄and Mg Co₂O₄,the catalytic performance of single metal Co₃O₄and bimetal Mg Co₂O₄was also compared.DSC tests showed that when catalyzing AP,CL-20,RDX and HMX,the effect of Mg Co₂O₄was better than Co₃O₄.?5?The thermite behavior of Al/Co₃O₄,Al/Mg Co₂O₄and Al/Zn Co₂O₄was analyzed by DSC data.The peak temperatures of the thermite reaction were 598.94,611.58,and612.24°C,and the heat release determined by DSC was 3149,4181 and 4479 J·g^-1,respectively.For Al/Co₃O₄and Al/Mg Co₂O₄,the exothermic heat of thermite reaction of Mg Co₂O₄with aluminum powder was higher than that of Co₃O₄.