Phase transformation and grain coarsening of zirconia/mullite composites

2019-10-10 10:05:58

ZrO2 electron gel mullite microscopy

责任者: Wei, W.-C.J.;Kao, H.C.;Lo, M.H. 单位: Inst. of Mater. Sci. & Eng., Nat. Taiwan Univ., Taipei, Taiwan 来源出处: Journal of the European Ceramic Society(J. Eur. Ceram. Soc. (UK)),1996//,16(2):239-47 摘要: ZrO2/mullite composites (ZMC) with homogeneously dispersed ZrO2 grains were prepared from colloidal or sol-gel processes of the precursors, which were a mixture of colloidal pseudo-boehmite (γ-AlOOH), zirconia and silicic acid gel, or prepared from dissociated zircon with alumina powder. After pressureless sintering of the ZMCs, their microstructure was examined by means of X-ray diffractometry, scanning electron microscopy and analytical transmission electron microscopy techniques. The microstructure of the ZMCs showed a difference in scale. ZrO2 and mullite grains grown in the gel matrix were formed at temperatures as low as 1100 and 1300°C, respectively. Experimental results indicated that heat treatment from 1300 to 1600°C influences the growth of mullite and fine ZrO2 grains in ZMCs, especially for the composite prepared from sol-gel methods in which the ZrO2 grew from tens of nanometres to micrometre size. The effects of the presence of ultra-fine ZrO2 on retarding the grain growth of mullite and the increase of metastable t-phase ZrO2 are also discussed. The growth of fine ZrO2 grains in a mullite matrix belongs to a mechanism of coalescence 关键词: alumina;ceramics;grain growth;heat treatment;martensitic transformations;powder technology;scanning electron microscopy;silicon compounds;sintering;sol-gel processing;transmission electron microscopy;X-ray diffraction;zirconium compounds;phase transformation;grain coarsening;zirconia/mullite composites;ZrO2/mullite composites;pressureless sintering;X-ray diffractometry;scanning electron microscopy;analytical transmission electron microscopy techniques;microstructure;sol-gel methods;metastable t-phase ZrO2;coalescence mechanism;1100 to 1600 C;ZrO2-Al2O3SiO2