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 transmission 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 precursor 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.
Conclusions: 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.
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%Al₂O₃复合粉的最佳pH值；3Y-TZP/3%Al₂O₃/10%BN双相包覆中，合成Al₂O₃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Al₂O₃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（N₂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%Al₂O₃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%Al₂O₃前驱体经1 200 ℃煅烧，再包覆10%BN，在N₂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%Al₂O₃/10%BN复合粉中Al-B-O化合物较少，且t-ZrO₂所占的比例最多。结论 合成Al₂O₃前驱体包覆3Y-TZP的最佳pH值为8.5；双相包覆中，Al₂O₃前驱体的最佳处理温度为1 200 ℃，合成非晶BN的适宜条件为N₂保护下800 ℃煅烧5 h。.
Keywords: Al₂O₃-boron nitride coating; calcination temperature; composite ceramic; pH; zirconia.