Al_2O_3-氮化硼纳米晶包覆的3%氧化钇稳定的四方氧化锆多晶复合陶瓷粉体的制备

Preparation processes of 3% yttria-stabilized tetragonal zirconia polycrystalline ceramic composite powders coated with nano-sized Al_2O_3-boron nitride

目的研究非均相沉淀法制备3%氧化钇稳定的四方氧化锆多晶陶瓷(3Y-TZP)/3%Al_2O_3复合粉的最佳pH值;3Y-TZP/3%Al2O3/10%BN双相包覆中,合成Al_2O_3及非晶氮化硼(BN)的最佳热处理温度。方法不同pH值(6.5、7.5、8.5、9.5)下,通过非均相沉淀法合成Al_2O_3前驱体包覆3Y-TZP粉,通过透射电镜(TEM)选出包覆形貌较均匀的一组。将此pH下制备的复合粉经不同的温度(800、1 000、1 200、1 400 ℃)处理后,硼酸尿素反应烧结法(N_2保护下,850 ℃煅烧5 h,850 ℃煅烧3 h及800 ℃煅烧5 h,800 ℃煅烧3 h)合成10%BN包覆3Y-TZP/3%Al_2O_3粉,通过TEM、能谱分析及X射线衍射(XRD)选出形貌及相组成最佳的一组。结果当pH值为8.5时,3%Al2O3前驱体均匀地包覆在3Y-TZP颗粒周围;3%Al_2O_3前驱体经1 200 ℃煅烧,再包覆10%BN,在N_2保护下800 ℃煅烧5 h,此时可见3Y-TZP颗粒周围包覆Al2O3及非晶BN,3Y-TZP/3%Al_2O_3/10%BN复合粉中Al-B-O化合物较少,且t-ZrO_2所占的比例最多。结论合成Al_2O_3前驱体包覆3Y-TZP的最佳p H值为8.5;双相包覆中,Al_2O_3前驱体的最佳处理温度为1 200 ℃,合成非晶BN的适宜条件为N_2保护下800 ℃煅烧5 h。

Objective In this work, we aim to determine the optimum pH value for the preparation of 3% yttria-stabilized tetragonal zirconia polycrystalline （3Y-TZP）/3%Al2O3 and optimum calcination temperature of Al2O3 precursor and amorphous boron nitride （BN） for Al2O3-BN coating 3Y-TZP powders. Methods The 3Y-TZP/3%Al2O3 composite powders were prepared through the heterogeneous precipitation method under different pH values （6.5, 7.5, 8.5, and 9.5） and analyzed through trans-mission electron microscopy （TEM） to determine the optimum coating morphology. Al2O3 precursor, which was prepared under the optimum pH value, was calcined at different temperatures （800, 1 000, 1 200, and 1 400 ℃）. The amorphous BN coating 3Y-TZP/3%Al2O3 powder was prepared via in situ reaction with boric acid and urea （calcined with N2 at 850 ℃ for 5 and 3 h and 800 ℃ for 5 and 3 h）. TEM, energy dispersive spectrometry （EDS）, and X-ray diffraction （XRD） were performed to characterize the results. Results The optimum coating morphology was obtained at 8.5 pH. When the Al2O3 precur-sor was calcined at 1 200 ℃ and coated with BN （calcined with N2 at 800 ℃ for 5 h）, the Al-B-O compound was less, and t-ZrO2 was more represented. Conclusion The optimum pH value for 3Y-TZP/3%Al2O3 composite preparation is 8.5. For the preparation of Al2O3-BN coating 3Y-TZP powders, the optimum calcination temperature of the Al2O3 precursor and amorphous BN are 1 200 and 800 ℃, respectively.