Prepartion Of Microscale Cobalt Oxide And Its Nano-Composites Used To Catalyze AP

Ammonium perchlorate（AP）is a common oxidant for solid rocket propellants,and its thermal decomposition behaviors have an important influence on the combustion and energy release of solid propellants.Therefore,most of the catalysts in the formulation mainly control the combustion efficiency of propellants by changing the thermal decomposition of AP.In this paper,the three-dimensional porous reduction graphene oxide with good thermal stability was introduced into the solid propellant formulation,and the micro-nano scale and shape-controlled particles of Co₃O₄ are designed to load on reduction graphene oxide,forming Co₃O₄/rGO composite.The prepared materials were used as catalysts applying in HTPB propellants and the catalytic mechanism of different catalysts on thermal decomposition of AP was explored from the perspective of reaction kinetics.The burning rate data of HTPB propellants with diffierernt catalysts were tested and compared.Obtaining the following conclusion:The ellipsoid-like nano Co₃O₄ with an average particle diameter of 40 nm and the specific surface area of 169 m².g^-1 was prepared by hydrothermal method.And the corresponding rules between size and morphology of nano Co₃O₄ particles with synthesis process conditions were obtained with the assistance of XRD,SEM,BET,XPS and so on.The flower-shaped micronized Co₃O₄,which has an average particle size of 2μm and a specific surface area of41 m².g^-1,was obtained by solvothermal method.At the same time,the generation rules and morphology control methods of that micron-scale particle were explored.The liquid phase synthesis mechanism of micro-scale cobalt oxide were elaborated by combination with chemical reaction route analysis.In order to solve the problem of nano-catalyst agglomeration,according to the design principles of HTPB propellants,the three-dimensional porous reduced graphene oxide was finally selected as the carrier after a series of comparisons and analysis.And the mineral-rich flake graphite was used as raw material to successfully prepare the rGO with high porosity(241 m².g^-1),by hydrothermal method.The data of rGO,tested by means of characterization technologies,confirmed that the target product was obtained.On this basis,one-step hydrothermal synthesis of ultrafine cobalt tetroxide loaded three-dimensional rGO network structure,both could solve the problem of agglomeration,but also improve the stability of the catalyst in the matrix material.And the characterization results confirmed ultrafine Co₃O₄/rGO composite was successfully synthesized,accompanied with Co₃O₄ particles with particle size less than 30 nm,on the surface of Graphene sheets,between Graphene sheets,or in the inner pores of rGO.The catalytic effects of micro-scale tricobalt tetroxide and composite catalysts on the thermal decomposition of AP were tested by synchronous thermal analysis technology.The results showed that the low temperature decomposition peak of AP disappeared after adding the catalyst,which meant that the original thermal decomposition process consists of high temperature and low temperature stages transformed into that only having a high temperature stage.What is more is that the initial decomposition temperature,the terminational decomposition temperature,high temperature decomposition peak temperature were significantly advanced,indicating that the catalysts synthesized in this paper have a good thermal decomposition catalytic effect on AP.Micron flower-like Co₃O₄,nano-Co₃O₄,and composite catalyst advanced the pyrolysis peak temperature of AP by 122℃,148.7℃and125.2℃respectively.Thermal decomposition kinetics results showed that:the high temperature thermal decomposition activation energy of AP is about 267.3 k J.mol^-1,3%nano-Co₃O₄made AP′s high temperature thermal decomposition reaction activation energy reducing to 125.2 k J.mol^-1,meanwhile 3%composite catalyst make AP′s high temperature thermal decomposition reaction activation energy reducing to 127.5 k J.mol^-1.The reduction of activation energy showing that the nanocomposite catalyst solved the problem of agglomeration of nano-Co₃O₄,while maintaining the reactive activity of nano-Co₃O₄.The burning rate of propellants with 1%catalysts was measured by the static burning test,to prove the practical effect of the ultrafine tricobalt tetroxide and nanocomposite′catalyst effects.The results showed that 1%Co₃O_4,1%Co₃O₄/rGO composite could increase the burning rate of the propellants by 57.5%and 50.5%respectively,and decrease the burning rate pressure exponent.The decrease degree of the burning rate pressure exponent of HTPB propellants with 1%Co₃O₄/rGO composite was the biggest,indicating that the compound can significantly improve the combustion stability of the propellant.