Well-defined SiO₂-coated Fe nanoparticles with various SiO₂ thickness from 1.2 to 27.8 nm have been successfully prepared by controlling the amount of tetraethyl orthosilicate and by the subsequent reduction of SiO₂-coated Fe₃O₄ nanoparticles with CaH₂. The saturated magnetization of the SiO₂-coated Fe nanoparticles increased with decreasing SiO₂ thickness. The saturated magnetization of the SiO₂-coated Fe nanoparticles with SiO₂ thickness of 2.7 nm or more have slightly decreased by 192 hr and did not change above 192 hr throughout atmospheric exposure, whereas that with SiO₂ thickness of 1.2 nm steeply decreased in 24 hr and continued to decrease above 24 hr.

Molecular dynamics simulations were performed to study six grain boundaries of α-alumina (Al₂O₃) with a glassy phase of anorthite (CaAl₂Si₂O₈) composition. We calculated excess energy, diffusion constant and ratio of excess volume with different thickness of the glassy film. It was found that excess energy for some grain boundaries exhibited a minimum. When the thickness of the glassy film was thick adequately, excess energy corresponded to the energy of alumina-glass interface and they were different for each interface. Diffusion constants depended on the thickness of the glassy film. The diffusion constant of thin film was smaller than that of thick film. Excess volume was the maximum when the thickness of the glassy film was 0.2~0.3 nm. When the atomic arrangement of the crystals didn’t fit each either, the excess volume of the grain boundary with the glassy film was smaller than that of the pure grain boundary. When the glassy film width was nm order, the atomic arrangement of the glassy phase was regular and the atomic diffusion behavior was approached that of a solid (crystalline) phase. We need to consider not only solid-liquid interface but also solid-solid (crystalline) interface for the structure of ceramics made by liquid phase sintering.

Solid solution strengthening effect by oxygen (O) and nitrogen (N) atoms of α-titanium (Ti) materials was quantitatively evaluated using Labusch model by consideration of the experimental data. When using Labusch model to predict solid solution strengthening improvement, an application of the isotropic strains by solute elements is generally assumed to estimate Fm value, which is the maximum interaction force between the solute atoms and dislocations. It is, however, difficult to exactly calculate Fm value for α-Ti materials with O and N solute atoms because the anisotropic strains are induced in α-Ti crystal with hcp structure by these elements. In this study, Fm value was experimentally derived from the relationship between 0.2% yield stress and solute elements (O and N atoms) content of Ti sintered materials. As a result, the strengthening improvement was proportional to c^2/3/S_f (c: soluted atom content, S_f: Schmid factor), and its factor of proportionality of Ti-O and Ti-N materials was 4.17 × 10³ and 3.29 × 10³, respectively. According to this analysis, it was clarified that Fm value of Ti-O and Ti-N materials was 6.22 × 10⁻¹⁰ and 5.21 × 10⁻¹⁰, respectively, and then the estimated strengthening improvement by using these values was significantly agreed with the experimental results of Ti sintered materials with O and N solution atoms.

The influence of strain in the Nd-Fe-B was investigated by using the structural phase transition of BaTiO₃ in films consisting of a Mo top layer (10 nm), Nd-Fe-B (30 nm), and a Mo bottom layer (20 nm) deposited onto BaTiO₃ (001) substrates by sputtering. As a result, it was found that the magnetization along the easy axis jumps up in magnitude by 3% at around 280 K. This significant effect is certainly due to the lattice strain accompanying the structural phase transition of BaTiO₃ from orthorhombic to tetragonal. First-principles calculations were applied to simulate the relationship between magnetization, magnetocrystalline anisotropy and the strain in the Nd-Fe-B main phase. It was also found that the magnetization along the easy axis increases as the lattice constant of the a-axis expands, which shows mostly good agreement with the experimental results under some assumptions.

The WC-Co cemented carbides with the addition of Ti(C,N) base particles with different sizes were fabricated by liquid phase sintering and their microstructures were mainly investigated in detail comparing the microstructure of the alloys with VC and Cr₃C₂ addition. It was found that the WC grain growth was more strongly inhibited with increasing Ti(C,N) content and with decreasing Ti(C,N) particle size. The degree of inhibition by the addition of Ti(C,N) particle with about 0.1 μm size was lower than that of VC addition and was almost same as that of Cr₃C₂ addition. Considering the results about the relationship between WC grain size and Ti(C,N) particle size and the analysis of Co phase composition, it was seen that the mechanism of grain growth inhibition by the addition of Ti(C,N) particles was the pinning (Zener) effect by the second phase particle, which was different from the mechanism for the addition of VC and Cr₃C₂ reported previously. The case that one Ti(C,N) particle contacts plural WC grains was often observed, so that the pinning effect was considered to work by many Ti(C,N) particles neighboring one WC grain. The very important result that the pinning effect by Ti(C,N) addition enable to develop the new type of ultra-fine cemented carbide was obtained in this study.