Prepared By Its Catalytic Properties Of Ultrafine And Nano-rare Earth Oxide In Mechanical And Chemical Research

In this paper, preparation of ultrafine yttria and nano-sized perovskite NdCoO₃, LaCoO₃ and LaMnO₃ via a mechanochemical process was investigated and their catalytic effects on thermal decomposition of ammonium perchlorate(AP) were investigated by DTA.Utrafine yttia powder with particle size D50 below 0.5 μm was prepared by a wet-solid-phase mechanochemical process using industrially available hydrate yttrium oxalate and ammonia as raw materials. The influencing factors on the particle size of yttria such as sort of additive, milling rate, milling mode, milling time, calcining manner and calcining temperature were studied. The preparation processes were investigated by XRD, FT-IR and SEM et c, and the possible mechanism of the reaction was discussed. DTA results indicated that the addition of the 2% obtained yttria into AP incorporated two small exothermic peaks of AP into a strong exothermic peak of AP, decreased the temperature of AP exothermic peak from 452 ℃ to 341℃ and increased the apparent decomposition heat from 515 J·g(-1) to over 1246 J·g^-1, showing stronger catalytic property for AP thermal decomposition than micron-sized yttria。The nano-sized perovskite NdCoO₃, LaCoO₃ and LaMnO₃ were synthesized by two mechanochemical route using different starting materials. In the first route, NdCoO₃, LaCoO₃ and LaMnO₃ with average particle size in 20 nm, 15nm and 100nm, respectively, were prepared via a mechanochemical reaction between hydrate chloride and sodium hydroxide and subsequent calcination. The proper addition of NaCl into the milling mixture followed by calcination led to the formation of well-dispersed nanocubes of NdCoO₃ and LaCoO₃ with the specific surface areas in 15.115 m²·g^-1 and 17.969 m²·g^-1, respectively. The addition of the 2% as-synthesized NdCoO₃, LaCoO₃ and LaMnO₃ into AP decreased the temperature of the AP decomposition peak to 308℃, 333℃ and 331℃, respectively. In the other route, the perovskite NdCoO₃ and LaCoO₃ were obtained via milling the mixture of Re₂O₃ and CO₃O₄ using a planetary ball mill and subsequent calcination. In the synthesis process, the introduction of ZnO acting as a mill-assisting reagent and an inorganic template increased the specific surface areas of NdCoO₃ and LaCoO₃ to 51.956 m²·g^-1 and 34.213 m²·g^-1, respectively, which is rare for the perovskite oxides. DTA showed that the so-obtained NdCoO₃ and LaCoO₃ respectively decreased the temperatures of the AP decomposition peak to 322℃ and 334℃.The mechanochemical process of superfine and nano-sized rare earths oxide described...