Development of Ceramic/Metal Mutual Nanocomposites with Superior Strength and Toughness

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Nanocomposites technology is well known to improve 2 to 4 times the fracture strength of ceramic materials even at high temperatures. The high-temperature creep rate is also improved 3 to 4 orders by this technology. The purpose of this project are to clarify the mechanisms of mechanical property improvements and to develop various kinds of multi-functional ceramic materials (Intermaterials) by applying this nanocomposite technology. The final target of this project is to propose the nano/cluster composite concept with better mechanical properties, based on the nanocomposite technology.The main results obtained from this project is as follows : 1) In the ceramic/eramic and ceramic/metal nanocomposites, new processing to homogeneously disperse the nano-sized second phases were developed, and the mechanisms of mechanical property improvements by the nano-sized second phase dispersions were clarified. 2) Based on the above-mentioned informations, new ceramic materials, in which the fracture strength and toughness were simultaneously improved, were developed by the micro/nano hybrid concept in the ceramic/ceramic composite systems, and by the mutual nanocomposite concept in the ceramic/metal composite systems especially Zirconia/Mo nanocomposite system. 3) Furthermore, new material design to improve the mechanical properties of ceramic materials by the soft and week second phase dispersions was proposed. By applying this concept, significantly improved strength, toughness, thermal shock fracture resistance and chemical inertness were harmonized with the machinability like metals in the Si3N4/BN nanocomposite. In the BaTi03/Ni nanocomposite system, the high strength with the improved ferroelectricity was obtained. For example, the fracture strength was improved 2 to 3 times by dispersing the nano-sized Ni particulates, and the same level improvement was also observed for the dielectric constant.