The shape memory heat treatment effects on the microstructures and the mechanical properties of TiNi shape memory alloys fabricated by powder metallurgy (PM) process were investigated in this study. Through the optimization of the shape memory heat treatment conditions, PM TiNi alloy showed a high plateau stress of 454 MPa and a good shape recovery of 96.4% in 8% strain applied via the heat treatment at 773 K for 10 min. A longtime heat treatment applied to PM TiNi alloys caused an increase of the amount of Ti3Ni4 precipitates in the TiNi matrix, and led to the relative decrease of Ni solid solution in the matrix which resulted in the decrease of the plateau stress.
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.
2018 JSPM Distnguished Paper Award
Translucent polycrystalline alumina (TL-PCA) was one of the earliest modern ceramic materials used for practical applications as the material of the thin-wall straight tube of high-pressure sodium (HPS) lamps. To improve the brightness and save energy, the optical mechanical and chemical properties of the tubes under mass production manufacturing conditions have been investigated focusing on the sintering behavior of TL-PCA. With the development of manufacturing technologies for cylindrical and bulgy tubes, TL-PCA has been applied to light bulbs for ceramic metal halide lamps. In particular, the new forming process of gel-casting enables the precise duplication of three-dimensional (3D) cavities using a metal mold. The dimensional accuracies attained by such net-shape forming processes are sufficient for emitting light tubes; however, for the substrates of electronic devices, subnanometer-precision planarization finishing technologies are required. In this paper, the net-shape technologies for light tubes and the surface-finishing technology for TL-PCA to use as the substrates of electronic devices developed by NGK Insulators are reported.
Here we show an electrophoretic deposition process for a uniform coating of glass substrate surface with fluorescent silicon nanocrystals (SiNCs). The NCs with ~35% of photoluminescence quantum yields (PLQYs) were synthesized by thermal disproportionation of hydrogen silsesquioxane, followed by hydrosilylation of 1-decence. Next, the hollow-silica particles that are crammed of the decane-terminated NCs were prepared by taking advantage of a vacuum impregnation process. The PL spectra were measured as a function of temperature for films of NCs before and after silica encapsulation. It was observed that a rapid decrease of PL intensity with elevated temperature for the hydrogen-terminated NCs whereas the silica capsule suppresses a thermal quenching to give PL stability at high temperature. The presence of a silica capsule also allows electrophoretic deposition of the NCs to the surface of an ITO glass substrate.
Crystalline oriented SLFC(Sr2.45La0.55FeCoO7-δ) ceramics were fabricated by slip casting in a 6 T magnetic field followed by sintering, and their anisotropic electric conductivity was examined. The SLFC powder was synthesized from reagent grade SrCO3, La(OH)3, Fe2O3, and Co3O4 chemicals by the solid state reaction method. The slurry of the SLFC was prepared with ethanol as a solvent and poly ethylene imine as a dispersant. The crystalline orientation of the bulk body sintered at 1300°C for 24 h in air was characterized by X-ray diffraction (XRD). The c-plane of the SLFC unit cell was faced in the perpendicular direction to the applied magnetic field. The electric conductivity of the specimens in the parallel and perpendicular directions to the applied magnetic field were measured by 4-probe d.c. method. It was revealed that the textured SLFC has higher electric conductivity along the direction perpendicular to the c-axis.
Lanthanum silicate oxyapatite (LSO) has superior features for application of solid electrolyte in solid oxide fuel cells. Because LSO has a higher oxygen-ion conductivity compared with yttria stabilized zirconia at temperatures below 600°C. Textured LSO bulk ceramics were fabricated by using a magnetic field-assisted colloidal processing technique. The c-axis of LSO was aligned parallel to the applied magnetic field. The anisotropic electric conductivity of the textured bulk ceramics was evaluated by the complex impedance method. It was demonstrated that the conductivity was very high along the c-axis. Battery performance was higher in the textured LSO compared with the random LSO.