【作者】 刘伟；

【导师】 谢志鹏；

【作者基本信息】 清华大学 ， 材料科学与工程， 2013， 博士

【摘要】 透明氧化铝陶瓷材料是第一个实现透明的陶瓷材料。它具有耐高温、耐腐蚀、高强度、高硬度、化学稳定性和生物相容性等结构陶瓷所固有的属性，同时具备透光这一功能属性，已在能源、机械、军工、电子、半导体、医学等高技术领域得到愈来愈多的应用。本文从助烧剂的引入方式、注射成型粉体表面改性、颗粒优化堆垛、烧结动力学四个角度对透明氧化铝陶瓷成型与烧结工艺的基础问题展开了研究。本论文首先采用化学沉淀方法以硝酸盐的形式引入助烧剂离子（Mg2+和Y3+）制备透明氧化铝陶瓷，实现了助烧剂离子在氧化铝粉体表面的包覆，阐述了助烧剂离子的化学沉淀机理，对烧结体中助烧剂在基体中的微观结构及分布状态进行了表征。结果表明，相比传统的湿法球磨该法可实现助烧剂离子以较精细的尺寸更加均匀地分布在氧化铝基体中，化学沉淀法制备的透明氧化铝陶瓷在紫外-可见光区域直线透过率最高可达21.3%。采用高温气氛烧结在生产成本及透光率之间寻求了较好的平衡。采用硬脂酸球磨预改性方法注射成型制备透明氧化铝陶瓷，与传统工作中在混料的过程中引入硬脂酸不同，本研究在混料之前通过球磨的方式引入硬脂酸，可将极限固含量由58vol%提升到64vol%。硬脂酸在粉体表面形成了稳定的包覆层，论证了硬脂酸改性机理系酯化反应，修正了前人关于硬脂酸改性路易斯酸碱反应机理的解释。通过坯体气孔结构分析证明了62vol%为最优固含量，在该固含量下制备的透明氧化铝陶瓷在紫外-可见光区域的透光率最高达到15.3%。该技术已经应用到生物陶瓷和陶瓷工艺品的制备中，在一定程度上解决透光率低下与鼓泡开裂等缺陷问题。采用喷雾冷冻造粒制备了结构均匀，无团聚，无粘结剂偏析的造粒颗粒，该法能够促使陶瓷颗粒获得非常均匀的堆垛状态。建立了高纯超细氧化铝粉体常压烧结和放电等离子烧结的动力学窗口。通过对比两种烧结方式的动力学窗口，提出了粉体处理过程中的颗粒堆垛优化及烧结过程中的颗粒重排过程是制备透明氧化铝陶瓷的关键因素这一理念。采用放电等离子烧结制备了透明氧化铝陶瓷，在紫外-可见光区域直线透光率最高达到20.3%。更多还原

【Abstract】 Transparent alumina is the first transparent ceramic. It posses the inherentattributes of structural ceramics such as high temperature resistance, corrosion resitance,resistance to corrosion, high strength, high hardness, chemical stability andbiocompatibility, along with the functional attribute of translucency. There is anincreasing trend for transparent alumina in the application of energy, machinery,military, electronics, semiconductor, medical, and other high-tech areas. BasicResearches are conducted concerning the forming and sintering technologies oftransparent alumina in this thesis from three aspects: the introduction of sintering aids,injection molding of surface modified powders, and the sintering kinetics.A novel approach was adopted to fabricate transparent alumina ceramics inducedby doping additives via chemical precipitation. It realized the coating of sintering aidsions onto the surface of the alumina powder. The mechanism of chemical precipitationof the sintering aid ions was explained. The microstructure and the distribution state ofsintering aids in the sintered body were characterized. It is found that the dopants aresmaller and more homogeneously dispersed via chemical precipitation in the transparentalumina sample as compared with conventional wet ball milling. The real in-linetransmission in the UV-VIS region of the sample prepared by chemical precipitationtransmittance is up to21.3%. Furthermore, it is believed that the approach of chemicalprecipitation followed by H2sintering at high temperature within short sintering timecould make a good balance between the real in-line transmission and the cost.A strategy to greatly improve solid loading for ceramic injection molding by aprior ball milling treatment of ceramic powders with SA was adopted to fabricatetransparent alumina. Different from the traditional work in which SA has beenintroduced just in the powder blending process, we have successfully prepared thefeedstock with a much higher solid loading up to64vol%by a prior ball millingtreatment of ceramic powders with a small amount of SA before the traditional blendingprocess. It can be attributed to that SA can be coated homogeneously around the powdersurfaces by an esterification reaction induced by ball milling treatment. The Lewis acid-base reaction mechanism raised by previous literatures is corrected.62vol%isproved to be the optimal solid loading through the analysis of pore structure of thecompacts. The real in-line transmission in the UV-VIS region at such solid loadingreaches15.3%. The technology has been applied to bio-ceramics and light sourcematerial (metal halide lamp). It solves the problems of low transparency and defectssuch as bubbling and cracking to some extent.Spray freeze granulation was adopted to prepare granules with uniform structure,without agglomeration and without binder segregation. The kinetics windows were builton both pressureless sintering and spark plasma sintering of high-purified and ultrafinealumina. The idea that particle packing in the powder treatment and particlerearrangement in sintering is key factors to obtain complete densification were raised.Transparent alumina was prepared via spark plasma sintering and the real in-linetransmission is no less than20.3%in the UV-VIS region.更多还原