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

在这个项目中，我专注于开发多功能氧化锆基纳米复合材料。在过去的几十年里，我一直专注于设计和开发陶瓷/金属纳米复合材料，其中纳米尺寸的金属分散在Al_2O_3， MgO等。基于这个概念，我将这项技术应用于锆基纳米复合材料。氧化锆由于其应力诱导的相变增韧而具有较高的强度和韧性。为了扩大该陶瓷的应用范围，可能需要增加新的功能或实现多功能。因此，我研究开发过渡金属分散氧化锆纳米复合材料以达到上述目的。在这里，我选择Ni作为分散的功能金属纳米颗粒。目前已应用了几种制备工艺。在本研究中，获得了以下结果：(1)对各种ZrO_2/NiO复合粉体分别采用还原离子法和烧结法制备了ZrO_2/Ni纳米复合材料。在氧化锆中加入少量的Ni纳米颗粒，氧化锆的断裂强度得到了较大的提高。纳米级镍的铁磁性在该纳米复合材料中也具有相容性。磁性矫顽力随Ni粒径的减小而显著增大。此外，磁化强度对外加应力敏感，显示了纳米复合材料变形/断裂无损遥感的可能性。(2)在氧化锆中加入极少量的NiO掺杂剂，制备出具有四方结构的齿状固溶体，提高了其韧性。这是由于少量的NiO掺杂剂控制了氧化锆晶体结构的稳定性。这表明相变行为是可以控制的。此外，对该固溶体进行气控热处理也可获得氧化锆/镍纳米复合材料；原位析出纳米级Ni颗粒。该纳米复合材料显示出高韧性和铁磁性，这意味着这种新开发的“内部还原法”在制造陶瓷/金属纳米复合材料方面具有优势。(3)采用溶液化学法制备了氧化锆/镍纳米复合材料粉末。阐明了该化学处理的适当控制因素。该方法使我们获得了纳米尺寸的ZiO_2- nio纳米复合粉体，为ZiO_2/Ni纳米复合材料及相关材料的开发提供了更有利的条件。综上所述，本课题已陆续开展了新型多功能氧化锆/镍纳米复合材料的研究。该材料具有优异的机械性能和磁性。这些新的制备技术被认为可以应用于其他陶瓷纳米复合材料体系。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