Preparation And Characterization Of The α-Al₂O₃Microcrystalline Ceramic Particles With Different Microstructure

In this paper, α-Al2O3microcrystalline ceramic particles with high hardness and high toughness were synthesized through combining sol-gel and two step sintering processes at atmospheric pressure,using industrial grade y-AlOOH nanoparticles as the main raw material And the relationship between the structure and the properties was also studied.The effects of different preparation conditions on the structure, hardness and toughness of α-Al2O3microcrystalline ceramic particles were discussed and optimal preparation conditions were preferred. Additives which can form magnetoplumbite phase were introduced into boehmite sol.Alumina microcrystalline ceramic particleswith high hardness, high toughness and a unique microstructure of lamellae were prepared at relatively low temperature.1.Influence of preparation conditions on the γ-AlOOH sol and alumina ceramic particlesUsing industrial grade γ-AlOOH nanoparticles as the main raw material,sintered alumina precursors were prepared by sol-gel process and α-Al2O3microcrystalline ceramic particles were prepared through two step sintering processes.The effects of sanding process on the size of γ-AlOOH sol particles and the phase transition temperature were discussed. Moreover, the effect of pH on the size of y-AlOOH sol particles was also analysed. Many factors influncing onthe structure and the properties of α-Al2O3microcrystalline ceramic particles, such as sintering temperature, sintering loading capacity and spray drying, were studied respectively.The samples were characterized in detail by XRD, SEM, TEM, TG-DSC, FTIR, particle size distribution analysis and hardness testing methods.The experimental results show that:The γ-AlOOH sol particles can be significantly refined by sanding process, d(o.i)=1.225μm, d(0.5)=1.841μm, d<o.9)=2.698μm after sanding5times;Thus, the grain size of α-Al2O3microcrystalline ceramic particles produced was significantly smaller and more uniform, with the average hardness value of22GPa.The best preparation process conditions were calcined at1350℃for1h and the load capacity was300g, with an average hardness value of22.1GPa. Spherical particles of alumina ceramic which have a microstructure similar to the ceramic particles of alumina ceramics can be obtained by spray drying.2. Preparation and characterization of α-Al2O3microcrystalline ceramic particles containing magnetoplumbite phaseUsing industrial grade γ-AlOOH nanoparticles as the main raw material,α-Al2O3microcrystalline ceramic particles containing magnetoplumbite phase were prepared through sol-gel process.Additives which can form magnetoplumbite phase were introduced into boehmbite sol. The samples were characterized in detail by XRD, SEM, TG-DSC, FTIR and hardness testing methods. The experimental results show that:01-Al2O3microcrystalline ceramic particles with the best microstructure and the highest average hardness value of20.9GPa were prepared, after the introduction of3%magnetoplumbite phase in nitrate form. The best microstructure is that the microstructure is compact and basically non-existent pores, the surface has lamellaes which are distributed relatively uniform and the thickness of the lamellaes is from10nm to60nm, the length of the lamellaes is from300nm to800nm.