A short overview is given on the rationalization of preparative processes of complex oxide nanoparticles. After a brief introduction associated with mechanochemical effects as a background, merits of combining mechanical activation and subsequent chemical treatments for the synthesis of complex oxide nanoparticles are emphasized. Mechanical stressing on the stoichiometric mixture of all the ingredients at an appropriate stage significantly reduces the subsequent calcination temperature. It is necessary for attaining high crystallinity and phase purity, while suppressing grain growth. A precursor with preformed embryos or nuclei is appropriate for subsequent low temperature solid-state synthesis. This is realized by careful choice of the starting ingredients and sparing mechanical stressing, usually exerted by a grinding mill. The procedure leads to complex oxide materials with high crystallinity and small particle size, simultaneously. A case study is given on the preparation of garnet type cubic Li₇La₃Zr₂O₁₂ (c-LLZO), A possibility of application to all solid Li ion battery is also refeered.

One of the representative high-strength titanium (Ti) alloys used as biomaterials is a commercial Ti-6Al-4V (Ti-64). It has, however, serious problems because Ti-64 contains vanadium, one of highly toxic elements, as the necessary additive to improve the mechanical strength. In this study, in order to develop a high-strength and biocompatible Ti alloy for application to biomaterials, powder metallurgy (PM) α-Ti material with zirconium (Zr) and oxygen (O) solid solution (Ti(Zr,O) alloy) was fabricated from the elemental mixture of CP Ti and ZrO₂ powders. During solid-state sintering process, the additive ZrO₂ particles were decomposed by reaction with CP Ti powder, and then Zr and O atoms were dissolved in the α-Ti crystals as substitutional and interstitial elements, respectively. These solution elements caused a remarkable increment of the lattice constant of α-Ti (hcp) crystal, and resulted in the significant improvement of tensile strength of Ti alloys. For example, Ti(Zr,O) alloy showed 0.2% yield stress of 1153 MPa when using CP Ti powder mixed with 3 wt.% ZrO₂ particles, which was greatly high compared to PM CP Ti material with 0.2% YS of 463 MPa. In addition, the solid solution strengthening mechanism of this alloy was investigated in detail.

In this work, we focused on Pr_1+xSr_1−xGa₃O_7+x/2 with oxide-ion conduction, and investigated crystal and electronic structures of the materials by using neutron and synchrotron X-ray sources. In addition, we discussed oxide-ion conduction paths in the crystal on the basis of the results of the structural analyses. It was found by the Rietveld refinement that excess oxide ions were introduced into interstitial positions of the crystal and the interstitial oxide ions were located at a center of the Ga-O pentagonal ring in average. From nuclear density distribution obtained by the maximum entropy method, it was suggested that oxide ions diffused from O1 site to O3 site and/or from O3 site to another O3 site via the ring center and slightly off-centered positions. Such conduction paths of Pr_1+xSr_1−xGa₃O_7+x/2 are similar to that of La_1+xSr_1−xGa₃O_7+x/2, indicating an insignificant effect of the rare earths on the oxide-ion conduction property.

Titanium and its alloy have passive state film, which were formed on the surface by action of moisture and oxygen in the air. Titanium shows superior corrosion resistance due to the protection of passive state film. Recently, Fe solid-solution strengthened sintered titanium alloys made by powder metallurgy process is developed to achieve high strength, high ductility and low cost. However, evaluation of corrosion resistant property has not been carried out. For the purpose of evaluating the corrosion resistance of the material quantitatively, we employed electrochemical methods. Seven kinds of iron solid-solution strengthened sintered titanium with different Fe contents (0, 0.2, 0.6, 1, 2, 3, and 4 weight%) and three kinds of melted titanium alloys with different Fe contents (0, 0.2, and1 weight%) were prepared.

Potentio-dynamic polarization curve measurement was carried out for these materials. According to the results of polarization curve, corrosion rate of iron solid-solution strengthened sintered titanium increased with iron level. However, it shows approximately equivalent corrosion resistant to melted titanium alloys.