Construction Of Cu₂O Nano Hollow Structure And Its Catalytic Study On Thermal Decomposition Of Ammonium Perchlorate

Ammonium perchlorate(AP)is an important oxidant of composite solid propellant,and its decomposition behavior directly affects the performance of propellant.At present,it is urgent to to improve the decomposition efficiency of AP at lower combustion temperatures to meet the demand for high energy production.Previous studies have demonstrated that the proton transfer mechanism of AP thermal decomposition is converted to electron transfer mechanism after introducing catalysts,which is an effective method to reduce the decomposition temperature of AP.Nanomaterials are often used as catalysts due to their unique structure,among which transition metal oxides have excellent catalytic activity in the thermal decomposition of AP.Cu₂O is considered to be one of the most promising thermal combustion catalysts based on the variable valence state of its cuprous ions,as it tends to capture or release surface lattice oxygen in redox reactions,which can accelerate the decomposition rate of AP at both low and high temperature stages.Current studies have shown that the catalytic activity of Cu₂O is closely related to its surface structure,and hollow structure has more active sites.Therefore,on account of the above research background and the previous work of our team,by selecting appropriate additives and reducing agents,combined with the control of reaction concentration,temperature,time and other experimental parameters,the effect on the growth behavior of Cu₂O crystals was realized,and the construction of hollow structure about Cu₂O was finally achieved.The main work is as follows:(1)Under the action of sodium dodecyl sulfate(SDS)and using NH₂OH·HCl as the reducing agent and acid etchant,Cu₂O tetradecahedral nanocages with a particle size of about 300 nm were successfully synthesized by wet chemical method.The formation of nanocages can be attributed to the directional adhesion mechanism and acid etching mechanism.Among them,the existence of SDS,on the one hand,makes the Cu₂O particles have a clear facet,on the other hand as a capping agent to protect the active sites.Low temperature decomposition(LTD)and high temperature decomposition(HTD)reduced by 27.1 ^oC and 107 ^oC in adding Cu₂O nanocages,respectively,and the heat release increased by more than twice in comparison with pure AP.The nanocages effectively expose more active edges and corners,so that they have higher free energy and easier to react with the reactant,exhibiting excellent catalytic performance in the reaction.(2)Using NH₄⁺as structure-directing agent,Cu₂O hollow spheres with large specific surface area(30.9 m²·g^-1)were synthesized by chemical reduction method.This is caused by the self-transformation process of metastable aggregated particles and local Ostwald ripening.In the thermal decomposition experiment of catalytic AP,it was found that Cu₂O hollow spheres can reduce the temperatures of low temperature decomposition and high temperature decomposition by 31.6 ^oC and 125 ^oC,respectively.Compared with pure AP,the heat release increased by 1.5 times,and the activation energy decreased by 56.0%.This is because the Cu₂O hollow spheres have large surface area,and the adsorption capacity is improved due to the loose structure.The catalytic area and active sites of the continuous reaction are increased,thereby exhibiting more excellent catalytic performance.There are 31 figures,10 tables and 130 references in this paper.