【作者】 赵志江；

【导师】 孙旭东； 李晓东；

【作者基本信息】 东北大学 ， 材料学， 2010， 博士

【摘要】 氧化铝陶瓷具有强度高、耐高温、耐腐蚀、耐磨损及良好的介电性能等特性,在电子、冶金、机械、交通、能源、航空航天和生物领域得到广泛的应用。如何改进Al2O3粉体及其复合陶瓷的制备工艺,以改善材料的微观结构,提高其性能和可靠性,成为目前陶瓷研究领域的重点。离心成型作为胶态成型的一种,具有坯体密度高,均匀性好,成型缺陷少的优点,因而是制备高性能陶瓷及其复合材料的先进方法之一。本文系统研究了采用离心成型法制备Al2O3陶瓷、Al2O3-ZrO2陶瓷基复合材料、以及Al2O3/Ni梯度材料的工艺过程以及这些材料的微观组织和力学性能。采用硫酸铝铵热分解法制备了颗粒尺寸为60～100nm的高纯α-Al2O3纳米粉体,并用离心成型方法制备了高性能Al2O3陶瓷材料。研究表明,分散剂添加量、pH值、固相含量对浆料性能有显著的影响；采用流动性好、固相含量高、稳定性好的浆料以及合适的离心成型工艺,制备出密度高,均匀性好的陶瓷坯体,并通过后续的真空烧结获得了显微组织均匀细小,力学性能优异的Al2O3陶瓷材料。实验结果表明：当分散剂聚羧酸胺的添加量为1wt%,浆料pH为11,固相含量为38vol%时浆料具有良好的流动性和稳定性,获得的坯体相对密度达到52.36%；试样在空气中1200℃温度下经120min预烧,然后在1550℃经150min真空烧结后,得到呈半透明状的氧化铝陶瓷,其烧结密度、强度、硬度、断裂韧性分别为3.98g/cm、712 MPa、19.4GPa、3.92MPa·m1/2。1500℃和1550℃下真空烧结的样品平均晶粒尺寸均小于5μm。采用离心成型方法制备了Al2O3-5vol%ZrO2复合材料,并对其坯体密度、Al2O3和ZrO2分布、烧结密度,以及显微组织和力学性能进行了系统的实验研究。实验结果表明,通过采用合适的分散剂含量和固相含量,可以获得流动性和稳定性良好的浆料,避免离心成型过程中发生Al2O3和ZrO2因比重不同产生的相分离。压坯密度随固相含量的增加而有所增大,并且不同固相含量试样的底部区域压坯密度稍高于其它部位；除固相含量30%试样底部区域外,所有试样的烧结密度沿坯体高度无明显变化,氧化铝、氧化锆分布沿高度方向几乎不发生变化；经1450℃烧结得到了显微组织细小均匀、Al2O3晶粒小于2μm、性能优良的Al2O3/5vol%ZrO2复合材料,其抗弯强度为710 MPa,显著高于干式成型法制备的复合材料的强度(620 MPa).Al2O3-5vol%ZrO2(?)内离心成型和干压成型试样性能对比发现,压坏密度提高了5%,烧结温度降了50℃,抗弯强度得到显著提高。采用离心成型方法制备了组分呈连续梯度分布的Al2O3/Ni功能梯度材料。通过调制复合粉末浆料的特性,可调控离心成型过程中Al2O3和Ni因比重和颗粒尺寸不同产生的相分离程度,从而获得所需的Al2O3和Ni的梯度分布。在实验的基础上优化了浆料中粘结剂和固相的含量以及浆料的球磨时间。对梯度复合材料试样的气孔率,三点抗折强度、硬度等性能及其影响因素进行了研究。实验结果表明：粘结剂(聚乙二醇)含量为2wt%、固相含量为63vol%、球磨时间为36小时的条件下制备的浆料,适合用于离心成型方法制备Al2O3/Ni梯度材料。采用离心成型制备出气孔率为0.4%,显微组织和硬度均呈连续梯度分布、力学性能优良的Al2O3/Ni梯度材料。通过调整固相含量和粘结剂含量,可调控Al2O3/Ni梯度材料的成分梯度,对组织结构进行设计和控制。采用改进Stober法制备出符合胶晶模板要求的单分散SiO2微球,并发现在反应过程中始终保持高氨水浓度更有利于单分散SiO2微球的生成。当浓度高于0.5 vol%时,SiO2微球悬浮液可在玻璃基板上形成有序度较高的二维胶晶模板。离心沉降法可快速制备出大尺寸蛋白结构SiO2光子晶体。SiO2光子晶体为面心立方结构,结构内的主要缺陷为溶剂挥发所形成的裂纹以及堆垛层错。向三维有序SiO2胶晶模板的孔隙内填充Sb2S3,而后通过HF溶液腐蚀掉SiO2胶晶模板,进而制备出反蛋白结构Sb2S3光子晶体。更多还原

【Abstract】 Alumina ceramics possess the attractive properties of high strength and excellent heat resistance, corrosion resistance, abrasion resistance and dielectric properties. They are used widely in the industrial areas of electronics, metallurgy, machinery, transportation, energy, aerospace and biotechnology. Attentions of researchers have been specially paid to the improvement of Al2O3 powders and fabrication technologies of alumina based composites, aiming at refining microstructure and improving properties and reliabilities of alumina ceramics. Centrifugal slip casting, as a colloidal compaction method of ceramics, has the advantages of high green density, good green homogeneity, and low compaction defects. It is thus one of the advanced processing methods of high performance ceramics and composites. In the present work, the centrifugal slip casting fabrication of Al2O3 ceramics, Al2O3-ZrO2 ceramic matrix composites, and Al2O3/Ni functionally gradient materials (FGM) have been systematically investigated.High purityα-Al2O3 nanopowders with particle sizes ranging from 60～100nm were prepared from the high temperature decomposition of aluminum ammonium sulfate. Centrifugal compaction of theα-Al2O3 nanopowders was investigated to fabricate high performance alumina ceramics. It was found that the amount of dispersant, pH value, and solid content have a remarkable effect on the properties of alumina ceramic slurry. Using a slurry of good fluidity, comparatively high solid content and good stability, alumina greenbodies of high density and good homogeneity has been produced. Alumina ceramics of fine microstructure and good mechanical properties has been obtained from the greenbodies using vacuum sintering. The alumina slurry made with a polycarboxylic dispersant addition of lwt%, a pH value adjusted to 11, and a solid content of 38 vol% has good fluidity and stability, and the density of the greenbody obtained by centrifugal slip casting is 52.36%. Translucent alumina ceramics were fabricated by a pre-heat-treatment at 1200℃for 120 min, flowed by vacuum sintering at 1550℃for 150 min, with a average grain size less than 5μm. The density, three point bending strength, hardness and fracture toughness of the alumina ceramic are 3.98g/cm3,712MPa,19.4GPa and 3.92MPa·m1/2, respectively.The Al2O3-5vol%ZrO2 ceramic matrix composites were fabricated by the centrifugal slip casting method, and the compact density, distribution of Al2O3 and ZrO2, relative density of the sintered composites, microstructure and mechanical properties of the composites were studies in detail. The results show that slurry with good fluidity and stability can be obtained by using suitable amount of dispersant and adopting optimum solid content, which can avoid the phase separation due to the density difference between Al2O3 and ZrO2 during the centrifugal compaction process. For the sintered samples made with 40 vol% and 45 vol% solid content slurries, the microstructure is homogenous through out the sample, and there is nearly no obvious difference in Al2O3 and ZrO2 distribution and sample density along the centrifugal direction. After sintering at 1450℃, the composite sample is homogenous in both microstructure and density, with a mean particle size less than 2μm. For the Al2O3-5vol%ZrO2 composites, compared with the conventional dry compaction method, the centrifugal slip casting process is advantageous in 5% higher green density,50℃lower in sintering temperature, and remarkable higher bending strength (710 MPa compared to 620 MPa).The Al2O3/Ni functionally gradient composites with continuous gradient distribution of phases were fabricated by the centrifugal slip casting method. Though adjusting the characteristic of the slurry, it is possible to control the degree of phase separation due to the density difference between Al2O3 and Ni during the centrifugal slip casting profess, so that the required gradient distribution of Al2O3 and Ni in the functionally gradient composites can be achieved. On the basis of experiment, the amount of binder and solid content in the slurry and ball milling time were optimized. The influencing factors on porosity, three point bending strength and hardness were investigated. It is show that the slurry made with 2 wt% PEG binder,63 vol% solid contents, and a milling period of 36 hours is suitable for the fabrication of the Al2O3/Ni functionally gradient composites by centrifugal slip casting. An Al2O3/Ni functionally gradient composite with excellent mechanical properties, low porosy (0.4%), and a continuous gradient distribution of microstructure and hardness was produced. The composition gradient of the Al2O3/Ni FGM can be tailored by adjusting the solid content and amount of dispersant, and thus its microstructure can be designed and controlled.Monodispersed SiO2 microspheres were prepared by a modified Stober method. Retaining high concentration of ammonium hydroxide was beneficial to the preparation of monodispersed SiO2 microspheres. Highly ordered two dimensional colloidal crystal can be readily obtained by dropping single droplet of SiO2 microsphere suspension with concentration higher than 0.5 vol%. Large size highly ordering three dimensional SiO2 photonic crystal can be easily prepared by centrifugal settling method. The 3D SiO2 photonic crystal had FCC structure, and the main defects were stacking faults and cracks induced by solvent evaporation. Filling the pore of SiO2 photonic crystal with Sb2S3 and then removing SiO2 by hydrogen fluoride etching, the inverse opal structure Sb2S3 photonic crystal was obtained.更多还原