| Controlled synthesis of nanocrystals is extensively studied in recent years in materials science. The properties of materials not only lie on constitute but related to its microstructure. The combustion properties are the most important technology of powders and explosives. Using the catalyst is the most method to improve the combustion properties of powder and explosives, especially solid propellants. In this dissertation, a series of nanometer catalysts of different microstructure were prepared, and the catalysis of different microstructure of nanometer catalysts on powder and explosives was investigated. The principal results of the dissertation are discussed as follows:Firstly, the CuO, Cu2O and LaCoO3 were screened out by thermal analysis, which have more strongly catalytic activities on the thermal decomposition of NH4ClO4 (AP) than the others. Then, the different microstructure of CuO, Cu2O and LaCoO3 were prepared using different systems and methods.CuO nanocrystals of different microstructure were synthesized using the aqueous and monobasic alcohol systems. In aqueous system, CuO nanocrystals were prepared by the quick-precipitation and hydrolysis method respectively. Results indicated that well-dispersed spherical, spindle- and needle-shaped CuO nanocrystals can be obtained by changing the temperatures and manners of adding NaOH in precipitation method. Needle-shaped CuO nanocrystals could be prepared by the hydrolysis method, and the presence of small amounts of cetyltrimethylammonium bromide (CTAB) could make needle-shaped CuO well dispersed. The concentration of reactant has great influence on the size of products. Compared with hydrolysis method, the CuO samples prepared by quick-precipitation have high specific surface area with 113 m2 g-1, and have blue shift in its UV-vis absorption spectrum. In monobasic alcohol system, the CuO nanocrystals were prepared using Cu(0Ac)2 as the starting materials and different monobasic alcohols as the solvent. The influence of adding small quantity of water and reaction condition on the microstructure of CuO nanocrystals was investigated in isopropanol system. The results indicated that morphology of CuO products convert sphere into rod after adding water. The time and quantity of adding water, the addition of precipitator have great effect on the size and morphology of CuO products. The reaction mechanism was discussed on the basis of experiment results.The Cu2O nanocrystals of different microstructure were prepared using ethylene glycol(EG) and aqueous systems. In EG system, the influence of the addition of polyvinylpyrrolidone (PVP) and water on the microstructure of CuO products was investigated. Results showed that well dispersed needle-shaped Cu2O nanocrystals can be obtained in the presence of PVP, and the needle can be converted into rod when small quantity of water was added into solution. The kind, molecular weight and quantity of stabilizer, the quantity of adding water and concentration of reactant have great influence on microstructure of Cu2O products. In aqueous system, the different microstructure of Cu2O can be obtained when different copper materials were used. Needle-shaped and polygonal Cu2O nanocrystals can be prepared by controlling the additive volume of NaOH solution using Cu(OH)2 as the copper materials. The uniform cubic Cu2O can be obtained using CuO as the copper materials and hydrazine hydrate as the reducing agent. The morphology and size of products would be different when there are some other ions in solution.The LaCoO3 nanocrystals of different microstructure have been prepared by stearic acid method and co-precipitation method. The rod-like and quasi spherical LaCoO3 nanocrystals can be obtained by changing the reaction temperature. The rod-like LaCoO3 can be prepared when precipitator was added by drop wise, but quasi spherical LaCoO3 nanocrystals were obtained by adding precipitator quickly. The rod-like can be converted into spherical LaCoO3 nanocrystals in the presence of PVP. The products are quasi spherical LaCoO3 nanocrystals prepared by stearic acid method, and the morphology of products has not changed when some stabilizer was added. Doping some metal ions has no influence on the average size of products.The catalysis of CuO, Cu2O and LaCoO3 nanocrystals of different microctructure on AP thermal decomposition was investigated. Result indicated morphology, dispersibilty and surface structure of CuO nanocrystals have great influence on their catalysis. Adding 2wt% CuO prepared in ethanol mixing with water and isopropanol systems in AP decrease the high temperature of AP decomposition by 105℃ and 104℃ respectively, and increase the exothermic quantity of decomposition from 590 J g-1 to 1400 J g-1. The Cu2O nanocrystals of different morphologies and surface structure have different influence on the thermal decomposition of AP. The polygonal Cu2O nanocrystals prepared in aqueous system have strong catalytic activities; however the cubic Cu2O nanocrystals have strong catalytic activities on the low temperature of AP decomposition. The Cu2O samples prepared in EG system whether there is addition of water or not decrease the high temperature of AP decomposition by 104℃. The Cu2O samples prepared in the absence of...
|
PDF Full Text Request