Study On The Preparation And Properties Of Metal/Al Nanocomposites With Core-shell Structure

In order to improve the combustion performance of composite solid propellant, this dissertation is intended to discuss the modification of micrometer Al powder in the conventional AP/HTPB/Al propellant formula with core-shell nanocomposites. The influence on the oxidation performance of Al powder, thermal decomposition of AP and AP/HTPB propellant, and catalytic performance in combustion of AP/HTPB propellant, were explored. Detailed experimental data and powerful theoretical evidence were obtained for the enhancement of combustibility and energy features for AP/HTPB propellant. The details are described as below:Firstly, the core-shell Ni-B/Al, Cu/Al, Ni/Al and Co/Al nanocomposites were prepared respectively by means of electroless plating and in-situ displacement, and an overall characterization was given for different nanocomposites. The results showed Ni-B, Cu, Ni, Co nanoparticles could be applied to the surface of Al particle in continuous and uniform manner, wherein, the Co particle presented in both spherical and sheet profiles in the Co/Al nanocomposites. Compared with the electroless plating, the displacement has the merits of simple process, fast reaction and quantified coverage, which can be introduced as a practicable and preferred method for modified Al powder coated with metallic nanoparticle.Secondly, the influence on the oxidation performance of Al powder in the core-shell nanocomposites has been investigated and the results show that: (1) the oxidation performance of core-shell nanocomposites has been improved relatively compared with the raw Al powder; (2) As the mass fraction of nanometer metal layer increases, the oxidation performance increases correspondingly;(3) The size and profile of metallic nanoparticles being coated on the surface of Al powder also have an influence on the oxidation performance of composite powder. For instance, the coating of micro-sized Cu particles failed to improve the oxidation performance of Al powder in an obvious manner, spherical Co coating is better than that of sheet Co nanoparticle; (4) For the simple mixture of nano-sized metallic particles with the Al powder, no apparent improvement of oxidation performance can be obtained. Based on the testing results, the oxidation mechanism was put forward for Al powder and the core-shell nanocomposites.Thirdly, a contrastive analysis has been conducted between the core-shell nanocomposites and single metallic nanoparticle in respect of catalytic performance for thermal decomposition of ammonium perchlorate (AP) and AP/HTPB propellant. The results showed the core-shell nanocomposites had a better catalytic effect compared with single metallic nanoparticle, while the sheet-profiled Co/Al nanocomposite was the best choice, which decreased the high temperature decomposition peak of AP and AP/HTPB propellants by 179.9℃and 60.5℃respectively.Finally, a contrastive study was carried out for the effect between the core-shell nanocomposites and single metallic nanoparticle on combustion performance of AP/HTPB propellant. The burning rate was measured with target line method and the pressure index was calculated. The catalytic effect of different catalysts for propellant on combustion performance were explored. The results showed that the core-shell nanocomposites had a better performance than single metallic nanoparticle in respect of the burning rate and pressure index. Cu/Al nanocomposites increased the burning rate by 40.34 % and 30.06 % for AP/HTPB propellant under the pressure of 5 MPa and 10 MPa respectively, and decreased the pressure index by 37.23 % under the pressure of 5-11 MPa.