应用正电子湮没谱学研究CaO添加对Al_(2)O_(3)纳米陶瓷烧结过程的影响  

Application of positron annihilation to study the effect of calcium oxide addition on the sintering process of alumina nanoceramics

作　　者：杨炫烨 赵文增 张思敏 文海懿 吴奕初[1] YANG Xuanye;ZHAO Wenzheng;ZHANG Simin;WEN Haiyi;WU Yichu(School of Physics and Technology,Hubei Key Laboratory of Nuclear Solid State Physics,Wuhan University,Wuhan 430072,China)

机构地区：[1]武汉大学物理科学与技术学院、湖北省核固体物理重点实验室,武汉430072

出　　处：《核技术》2025年第2期34-43,共10页Nuclear Techniques

基　　金：国家重点基础研究发展计划(No.2019YFA0210003);国家自然科学基金(No.12275200)资助。

摘　　要：利用对原子尺度缺陷特别灵敏的正电子湮没谱学技术,并结合X射线衍射(X-ray Diffraction,XRD)、扫描电子显微镜(Scanning Electron Microscopy,SEM)等表征手段,研究了少量氧化钙添加量对氧化铝纳米陶瓷烧结过程中的微观缺陷、物相和显微形貌的影响。XRD及SEM实验结果表明,CaO/Al_(2)O_(3)纳米陶瓷的烧结过程可以分为两个阶段:室温至900℃未发生相变,而900~1100℃发生明显相变。少量Ca O的添加(如1%质量分数)起初均匀地分布在Al_(2)O_(3)中,随着烧结温度升高将与Al_(2)O_(3)反应形成第二相并在高温下转变为液相,传质机理由固相扩散变成液相流动,可以降低烧结温度,延缓γ-Al_(2)O_(3)纳米陶瓷转变为α-Al_(2)O_(3)过程,在1100℃烧结后出现不同网状结构的板片状结构。正电子湮没寿命谱分析表明,相变前后Ca O/Al_(2)O_(3)纳米陶瓷中的空位团和微孔洞的大小及数量随烧结温度的变化规律与Al_(2)O_(3)纳米陶瓷不同,由于第二相的形成并在高温下转变为液相,导致CaO/Al_(2)O_(3)纳米陶瓷中更容易产生空位团及微孔洞,并且一部分微孔洞相变前会逐渐合并形成宏观孔洞,而Al_(2)O_(3)纳米陶瓷内的微孔洞则会随着相转变及晶粒生长而消失,仅在样品表面还存留微量的微孔洞。[Background]The preparation of alumina ceramics is usually sintered under atmospheric pressure,and the sintering temperature is usually above 1800℃to achieve densification of alumina.High temperature and long-term heat preservation often make the grains of alumina ceramics overgrow,and it is impossible to predict what defects and porosity that occur inside the crystal,resulting in the decline of the comprehensive properties of alumina ceramics.Previous work predominantly focuses on studying the stable nanoα-phase alumina(α-Al_(2)O_(3))sintering process,microstructure,and abnormal grain growth,but few studies on the variations in microstructure and defects during the sintering process of metastableγ-phase alumina(γ-Al_(2)O_(3)),let alone use CaO as an additive in nanoceramic alumina.[Purpose]This study aims to apply positron annihilation lifetime spectroscopy combined with X-ray diffraction(XRD)to investigating the impact of calcium oxide(CaO)addition on the sintering process of Al_(2)O_(3)nanoceramics.[Methods]Firstly,γ-phase nanoscale alumina powder with an average grain size of 20 nm,99.99%pure and nano-calcium oxide powder with an average grain size of 160 nm,98%pure was used as raw ceramic materials.Tablet samples of Al_(2)O_(3)nanoceramics and Al_(2)O_(3)nanoceramics doped with CaO(with a mass fraction of 1%CaO)were pressured under consistent experimental conditions.Then,the samples were sintered from 500℃to 1100℃for 2 h,and cooling to room temperature.XRD was used to characterize the phases and compounds of the sample,and field emission scanning electron microscope(SEM)was employed to observe the microscopic morphology of the sample cross-section,accompanied by an EDS spectrometer for elemental composition analysis.Finally,a radioactive isotope 22Na with intensity of about 0.5×10^(6)Bq was used as positron source and fast-fast coincidence positron lifetime spectroscopy was applied to characterizing the sample defects.The total count of each lifetime spectrum was over 106,and all samples were mea

关 键 词：正电子湮没 氧化铝/氧化钙 相变 缺陷 

分 类 号：TB332[一般工业技术—材料科学与工程]