Nano-rare Earth Oxide In Salt To Help Solution Combustion Preparation And Catalytic Performance

High surface area ceria-based nanopowders and well-dispersed perovskite and NdCoO₃ nanopowders were prepared by a novel salt-assisted solution combustion synthesis (SSCS) for the first time and the catalytic effects of the products on thermal decomposition of ammonium perchlorate (AP) have been investigated by differential scanning calorimetry and thermogravimetry (DSC-TG). It was found that fluorite ceria-based nanopowders with high surface area and well-dispersed perovskite LaMnO₃ nanopowders can be directly obtained via a solution combustion process using ethylene glycol as a fuel without a subsequent heat treatment and that the introduction of inert soluble salt into the redox mixture solution produces the well-dispersed spherical ceria particles with particle size in the range of 5nm～6nm, increases the specific surface area of the ceria from 14.1m²/g to 156.74m²/g and enhances the specific surface area of Ce_0.75Zr_0.25O₂ from 17.34m²/g to 208.17m²/g, leading to the formation of mesoporous structure due to the loose agglomeration of 5nm～6nm spherical nanoparticles. The results show that the highly-dispersed perovskite LaMnO₃ nanocubes with particle size in the range of 30nm～50nm can be obtained by a SSCS under the proper conditions and that the well-dispersed perovskite NdCoO₃ nanoparticles with about 10nm in particle size and 43.22m²/g in specific surface area can be produced after a salt-assisted solution combustion process followed by 3-hour heat treatment at 500℃. Also, the added salt was found to promote the formation of the perovskite phase and prevent particles from agglomerating and sintering during the salt-assisted combustion synthesis of NdCoO₃ using glycine as a fuel. Finally, a mechanism scheme was proposed to illustrate the possible formation processes of well-dispersed nanoparticles.The as-prepared nano-sized rare earths oxides showed remarkable catalytic effects on the thermal decomposition of AP. According to the temperature decrease of the higher AP decomposition peak, the catalytic performance of the as-prepared samples are summarized as follows: (1) The LaMnO₃ and NdCoO₃ nanopowders show better catalytic effects than ceria-based nanopowders; (2) The amorphous LaMnO₃ and NdCoO₃ are better than the perovskite products;(3) Ce_0.75Zr_0.25O₂ solid solutions with higher specific surface area have better catalytic effect than those with lower specific surface area; (4) The doped (ReO_1.5)_0.2(CeO₂)_1.8 is better than the pure CeO₂ in catalytic decomposition of AP; (5) Among the investigated samples, the well-dispersed amorphous NdCoO₃ shows the best catalytic performance, decreasing the temperature of the second...