| This thesis used "the preparation of powders-reaction mechanism research-powders characterization-sintering ceramics-characterization of ZTA" as the research process systematically studied the zirconia toughened alumina (ZTA) nanocomposites. We first investigated the influence of process conditions on preparation of Al2O3-ZrO2 nano composites powders in conventional reactor and RPB. The morphology of nanopowders, particle size, particle size distribution, degree of agglomeration, uniformity of element distribution were investigated systematically by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray energy dispersive analysis (EDS), X-ray diffraction (XRD) and Zetasizer Nano. Then, Homemade Al2O3-ZrO2 nanopowders were used as raw materials to prepare ZTA nano composite ceramics and we used the available condition explored the optimum conditions of molding and sintering. Scanning electron microscopy (SEM) was used to test the morphology of ceramics. The density and opening porosity of the ZTA ceramics were calculated by Archimedes’principle.Based on the various tests of Al2O3-ZrO2 nanopowders and ZTA ceramics, finally results were obtained as follows:(1) In conventional reactor, Al2O3-ZrO2 nanopowders were prepared by reverse coprecipitation method. ZrOCl2, Y(NO3)3, and AlNH4(SO)2 were taken as reactant, used NH4HCO3 as precipitant and used PEG 2000 as dispersing agent (amount of precipitant 2 wt%). In the process of the reaction, reaction temperature and stirring ration were set to 45 ℃ and 700 r·mn-1, the titration speed of reactant was 2 mL·min-1. Only under this condition, could we prepared the tetragonal phase ZrO2, spherical nanoparticles (about 50 ran), particles with narrow particle size distribution (30-70 nm). The Al element and Zr element of the nanopowders were uniformed distribution without obvious enrichment phenomenon.(2) The introduction of RPB reactor solved the uneven distribution and agglomeration of components. It could prepare uniformity nanopowders, shorten the preparation time, simplify the process, make aluminum ions and zirconium ions completely precipitated at the same time and increase the feed rate greatly. This thesis we explored the influence of three variables (feed rate, rotational speed and the times of cycles) on the properties of Al2O3-ZrO2 nanopowders. And the results showed that Al2O3-ZrO2 nanopowders would have the most outstanding properties if the feed rate 1000 mL·min-1 the speed rate of RPB was 1400 r·min-1 and the times of cycles were 0. Compared to the results of conventional reactor, it can be found that Al2O3-ZrO2 nanopowders obtained by RPB reactor have more outstanding properties. For example, the the shape of the particle is closer to spherical, the particle size is smaller (40 nm), the particle size distribution is narrower (30～50 nm) and the distribution of Al element and Zr element are more homogeneous. In addition, RPB has the faster feed rate (500 times), shorter reaction time (1/500) and lower energy cost (1/70) in preparation of Al2O3-ZrO2 nanopowders. Therefore, we can safely confirm that the introduction of RPB has the great significance in large-scale preparation of Al2O3-ZrO2 nanopowders.(3) We successfully explored the effect of forming pressure, binder, sintering temperature and drying methods, various reactors on the properties of ZTA ceramics. And eventually draw the optimal conditions were that the forming pressure was 200MPa, the concentration of the binder was 1.5 wt%, and the sintered temperature was 1550 ℃. Moreover, we also proved that the excellent properties of Al2O3-ZrO2 nanopowders could obtain the excellent properties of ZTA ceramics. Especially, ZTA ceramics prepared by RPB could achieve high density and low porosity at 1500 ℃. |
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