Preparation Process Of PbO/CNTs Composite Burning Rate Catalyst

Solid propellant is power sources of solid engines.Using a burning rate catalysts(BRCs)as an additive is an effective method to increase the burning rate of the propellant,reduce the pressure index and improve the combustion performance of the propellant.Nanometer lead oxide is one of the key metal oxides that regulate the ballistic performance of a solid propellant.But the nanometer lead oxide has the problems of easy agglomeration and difficulty in preparation.In order to solve this problem,a lots of researchers has studied the loading of nanometer lead oxides on the surface of carbon nanotubes(CNTs)to improve homogeneity of the nanometers.Additionally,carbon nanotubes themselves have the catalytic effect on the propellants.Therefore,PbO/CNTs has a double catalytic effect during combustion process of the propellants and is better than the catalytic effect of pure PbO or pure CNTs.In this thesis,highly dispersed PbO/CNTs complex BRCs were prepared using functionalized carbon nanotubes as carrier,lead acetate as catalyst precursor.The carbon nanotubes was firstly modified with concentrated nitric acid/sulfuric acid or concentrated nitrate acid and determined semi-quantitatively by FT-IR technique.The results showed that the optimized parameters for 2 g CNTs are:oxidation time 1 h,100 ml mixed acids(v:v=1:1),reaction temperature 125℃.With concentrated nitric acid as oxidation medium,the optimum time is 24 h at room temperature.Secondly,concentrated ammonia was employed to precipitate Pb(OH)2 on the CNTs,followed by calcinations,and prepared the PbO/CNTs composite BRCs.The catalyst was characterized by XRD and the results showed that the active species of the catalysts are nanometer lead oxide and lead.SEM and TEM were used to observe the microsurface morphology and particle size of the acidified carbon nanotubes and PbO/CNTs composite BRCs.It can be seen that the length of the CNTs is broken after the acid treatment.There are a lot of black amorphous particles appearing on the carbon nanotubes after the loading of the nanometer lead oxides,and the black amorphous particles are characterized further by Mapping technique and it was found that it was nano-lead oxides,indicating that nano-lead oxides have been successfully loaded on the carbon nanotubes.And the surface area of a PbO/CNTs sample was analyzed by physical adsorption and found that the specific surface area of the CNTs decreased from 64 m2.g-1 to 38 m2.g-1 after loading nano-PbO.The Pb weight percentagein the PbO/CNTs were determined by titration and the results showed that the maximum is 64%.The optimum preparation conditions of PbO/CNTs composite BCRst were determined by orthogonal experiment,which was determined that O-CNTs:Pb(OAc)2·3H2O(w/w)= 1:2,pH= 9,Tcalcin= 450℃ and t= 2 h.The effect of the PbO/CNTs composite BRCs on the thermal decomposition of AP,RDX and HMX was evaluated by DSC and the results indicated that the effect is great for AP and RDX,but inferior for HMX.Finally,The preparation of 20 g-scale PbO/CNTs complex BRCs was performed and the Pb content of each sample was round 60%.