粉体酸洗对镁铝尖晶石透明陶瓷性能的影响

Effects of Powder Acid-washing on Performance of Magnesium Aluminate Spinel Transparent Ceramic

镁铝尖晶石透明陶瓷具有优异的光学性能和力学性能,是红外窗口的理想候选材料。以商业镁铝尖晶石粉体为原料,通过酸洗处理降低粉体中的杂质含量以促进致密化。利用ICP、XRF和SEM等表征手段分析酸洗工艺对粉体中杂质含量和微观形貌的影响,采用无压预烧和热等静压处理制备镁铝尖晶石透明陶瓷,系统研究了粉体纯化处理对透明陶瓷致密化过程和性能的影响规律。结果表明,硝酸酸洗能够有效去除K、Ca、Na三种金属杂质,在不影响粉体粒径、表面形貌和团聚程度的前提下,使杂质含量降至1ppm。此外,硝酸酸洗后的粉体烧结活性得到显著提升,在不采用任何烧结助剂的情况下可将预烧温度降低30℃,从而实现透明陶瓷的低温制备,在1100 nm处透过率达到87%,接近理论透过率,初步结果表明,粉体酸洗也对所制备透明陶瓷的力学性能有一定促进作用。

Magnesium aluminate spinel transparent ceramics have excellent optical and mechanical properties,making them an ideal candidate for infrared windows.Commercial magnesium aluminate spinel powder was used as raw material,which was washed with acid to reduce the content of impurities.ICP,XRF and SEM were employed to check the efficiency of the acid-washing process in reducing the content of impurity and improvement in microstructure of the powder.Magnesium aluminate spinel transparent ceramics were obtained through pressureless presintering,followed by hot isostatic pressing,without using any sintering aids.The effects of acid-washing on densification process and properties of the transparent magnesium aluminate spinel ceramics were systematically studied.HNO_(3)acid-washing is an effective way to purify the powder,reducing the content of K,Ca and Na to be less than 1 ppm,while the particle size and surface morphology were not affected and no agglomeration was brought out.Moreover,HNO_(3)acid-washing resulted in an increase in sintering activity of the spinel powder.Comparatively,pre-sintering temperature of the HNO_(3)acid-washed powder was reduced by 30℃,thus leading to relatively lower sintering temperature to fabricate the transparent ceramics.The sample derived from the HNO_(3)acid-washed powder exhibited transmittance of 87%at 1100 nm to be closer to the theoretical level and had stronger mechanical properties.