Addition of New Functions to Ziroconia Ceramics by Nano-sized Metal Dispersion

在这个项目中，我一直致力于多功能氧化锆基纳米复合材料的开发。几十年来，我一直致力于陶瓷/金属纳米复合材料的设计和开发，在陶瓷/金属纳米复合材料中，纳米金属分散在Al_2O_3、MgO等材料中。基于这一概念，我将这一技术应用于氧化锆基纳米复合材料。氧化锆因其应力诱导相变增韧而表现出高强度和高韧性是众所周知的。为了扩大这种陶瓷的应用范围，增加新的功能或实现多功能是必要的。因此，为了达到上述目的，我研究了发展过渡金属分散的氧化锆纳米复合材料。在这里，我选择了镍作为分散的功能金属纳米颗粒。本文采用多种制备工艺，取得了以下研究成果：(1)采用还原…法制备了纳米氧化锆/镍复合材料不同种类的ZrO_2/NiO复合粉末的多离子和烧结方法。当少量的纳米镍粒子分散到氧化锆中时，氧化锆的断裂强度得到了较大的提高。纳米镍的铁磁性在纳米复合材料中也是相容的。随着Ni颗粒尺寸的减小，样品的磁矫顽力以增大为主。此外，纳米复合材料的磁化强度对外加应力非常敏感，这为纳米复合材料的变形/断裂无损遥测提供了可能。(2)在氧化锆中加入极少量的NiO掺杂后，得到了具有四方结构的DONS固溶体，提高了其韧性。这是由于少量的NiO掺杂控制了氧化锆晶相结构的稳定性。这一事实表明，相变行为是可控的。此外，通过对固溶体进行气氛控制热处理，还可以得到纳米氧化锌/镍纳米复合材料，纳米镍颗粒在原位相继析出。这种纳米复合材料表现出了高韧性和铁磁性，这表明了这种新开发的“内还原方法”在制备陶瓷/金属纳米复合材料方面的优势。(3)采用溶液化学法制备了氧化锆/镍纳米复合材料的粉末。明确了该化学过程的适宜控制因素。这种方法可以得到纳米尺寸的纳米氧化锌-镍纳米复合粉末，这对开发氧化钛/镍纳米复合材料及相关材料更有价值。综上所述，本研究项目成功地开展了新型多功能氧化锆/镍纳米复合材料的研究工作。该材料兼具优异的力学性能和磁功能。所有这些新的制备技术都被认为是适用于另一种陶瓷纳米复合体系。较少

In this project, I have focused on the development of multi-functional zirconia-based nanocomposite materials. For over the decades I have concentrated to design and to develop ceramic/metal nanocomposite, in which nanometer-sized metal dispersed within Al_2O_3, MgO and so on. Based on this concept I have applied this technique to zirconia-based nanocomposite. Zirconia is well known to show high-strength and toughness due to its stress-induced phase transformation toughening. To enlarge the application of this ceramic, addition of new functions or realizing multifunctionality may be necessary. Therefore, I have investigated to develop transition metal dispersed zirconia nanocomposite in order to achieve above-mentioned purposes. Here, I selected Ni as dispersed functional metal nanoparticles. Several kinds of fabrication processing have been applied.In this research, followed results have been obtained.(1) Proposed ZrO_2/Ni nanocomposites have been successively prepared by using reduct … More ion and sintering method for various ZrO_2/NiO composite powders. Large enhancement of fracture strength of zirconia was achieved when small amounts of Ni nanoparticles were dispersed into zirconia. Ferromagnetism of nanosized-Ni was also compatible in this nanocomposite. Magnetic coercivity was dominantly increased with decreasing particle size of Ni. In addition, magnetization was found to be sensitive to applied stress, showing the possibility of non-destructive remote sensing of deformation/fracture of nanocomposites.(2) When very small amount of NiO dopant was added into zirconia, dens solid solution with tetragonal structure was prepared, which had improved toughness. This is due to the control of stability of crystal structure of zirconia by small amount of NiO dopant. This fact indicates that phase transformation behavior can be controlled. In addition, zirconia/Ni nanocomposites could also be obtained by atmosphere-controlled heat-treatment of this solid solution ; Nanosized Ni particles were successively in-situ precipitated. This nanocomposite was found to show both high-toughness and ferromagnetism, implying the advantage of this newly developed "internal reduction method" for making ceramic/metal nanocomposites.(3) Powder preparation for zirconia/nickel nanocomposite was also investigated by using solution chemical route. Appropriate control factors for this chemical processing have been clarified. This method allowed us to obtain nanocomposite powder of ZiO_2-NiO with nanometer-size, which is more useful for developing ZiO_2/Ni nanocomposite and related materials.In conclusion this research project has successively conducted to develop novel multifunctional zirconia/nickel nanocomposites. This material exhibited both excellent mechanical properties and magnetic functionalities. All these new preparation techniques are considered to be applicable to another ceramic nanocomposite systems. Less