Synthsis Of Nanocrystalline SnO₂,TiO₂,BaTiO₃ And Grain Growth Kinetics Of Nanocrystalline Materials

Since 80th of last century, Nanocrystalline materials had became thehot-spot of material science research because of the great capability fromthe particularity of micro-structure compared to the coarse crystallinematerials or amorphous materials. Analyses the grain growth behavior ofthe nanocrystallines materials has great significance to comprehend themechanism of the grain size control and micro-structure stability.For conventional polycrystalline or coarse meaterials, the drivingforce for grain growth results from the decrease of the system energy bydecreasing the total grain boundary energy, the rate of grain growth isproportional to the radius of curvature of the grain. But actually, theprocess of grain growth is affected not only diffusion but also reactivity,is the addition of many courses. In this text, we proposed a newisothermal model of grain growth for nanocrystallines by considering twoparts. And the proposed model was applied to some literature to get thefiner pertinence to the conventional model; this result indicated that theproposed model was applicable to the process of nanocrystalline graingrowth.In this paper, nanocrystalline SnO₂,TiO₂,BaTiO₃ were synthsizedvia diffirent liquid reaction method as the investigation object by the wideuse of these materials, to discuss the adaptability of the proposed modelapplicatied to the calcined process.As an n-type semiconductive material with a wide band gap,crystalline tin dioxide (SnO₂) has received a considerable amount ofattention over recent years because of many applications in various fields.In this paper, the nanocrystalline SnO₂ synthesized via chemicalprecipitation method with SnCl₄·5H₂O as raw material and NH₃·H₂O asprecipitator, obtained the grain size rang of 8～35nm.As the importantphotocatalysis materials and oxygen sensitive materials, nanocrystallines TiO₂ was comprehensive used in sewage disposal, combustion processesin automobile engines and air purge. The nanocrystalline TiO₂ wassysthesized through hydro-thermal method with Ti(SO₄)₂ and CO(NH₂)₂as raw materials with the grain size rang of 10～80nm. As the abroadapplied electronic ceramics materials, the homogeneous and stabilizationmicro-structure will advantage to the capability of the nanocrystallineBaTiO₃. Grained well decentralization and symmetrical dimensionnanocrystalline BaTiO₃ was employed sol-gel method with Ba(Ac)₂ andTiC(C₄H₉O)₄ as raw materials, glacial acetic acid and absolute ethylalcohol as solvent, and the grain size rang of 20～55nm.In this paper, the micro-structure of these nanocrystalline materialswas characterized by DSC/TG, XRD and TEM. And multiple scanningrates method was adoped to analyse the thermal analysis kinetic. Then theimpact of calcinations temperature and time over the grain growth,crystallographic and distortion of lattice was discussed by the result ofXRD. Study the grain growth kinetics of the three nanocrystallinematerials by compare with the conventional model and the proposedmodel. The analysis indicated that the new isothermal model can trulyreflect the grain growth behavior and more press close to the experimentreality than the conventional model.