Alumina ceramics and cemented carbides are ground by diamond wheel in many cases. And a vertical spindle surface grinding machines with a rotary table are widely used for grinding of these materials. In these type of machine tools, a cup grinding wheels are usually used. Grinding fluid is supplied from the center of the main shaft and spread by a simple centrifugal force conventionally. However, a loading occurs easily in this method. Two supply methods of grinding fluid were developed in order to improve the conventional method. A plate part and a groove part were set separately in the straight cup wheel. As a result, the grinding fluid flowed strongly and the ground chips were removed out effectively. The ground surface roughness of alumina ceramics and cemented carbides in this developed methods were smaller than that of the conventional method. And the loadings were not occurred using developed method even in the case of large depth of cut.

In order to fabricate dense ZrO₂-Al₂O₃ ceramics by pressure-less sintering, three kinds of granules of calcined neutralization co-precipitated 75 mol% ZrO₂(2.0 mol%Y₂O₃)-25 mol%Al₂O₃ powders added with a small amount of cellulose nanofiber (CNF), i.e., (2, 2, 6, 6-tetramethylpiperidine 1-oxyl)-oxidized (TEMPO) CNF, non-oxidized CNF and polyvinyl alcohol (PVA) were prepared and compacted. Then, they were sintered at 1523 K for 8.64·10⁴ s in air. The granules prepared via the addition of 0.15 mass% TEMPO-CNF revealed a low relative density D_r for powder compacts (43.0%), however, they showed the highest D_r (99.8%) of sintered ceramics with the excellent mechanical properties, i.e., Vickers hardness H_v of 15.4 GPa, fracture toughness K_IC of 18.2 MPa·m^1/2 and bending strength σ_b of 882 MPa. These properties are almost the same as those fabricated by pulsed electric-current pressure sintering (PECPS). This might be explained in terms of i) the charged 1^st particles induced by TEMPO-oxidized CNF addition could form the nano meter-gap between the primary particles in the granules, and then ii) this nano meter-gap could suppress the particle-sintering at relatively low temperatures, and then much densification at high temperatures could be achieved.

In this study, we investigated sinterabilities and electrical conductivities at 550-900°C of (La_0.97M_0.03)PO₄ (M = Ca, Sr, and Pb) with a monazite structure. It was found that the Pb substitution could improve the sinterability of LaPO₄ even at low sintering temperature. Although the Pb-substituted sample exhibited hole conduction at the high-temperature range, protonic conduction became to be observed with decreasing temperature. Compared with the Sr-substituted sample, (La_0.97Pb_0.03)PO₄ showed lower proton conductivity. Taking these results into account, we performed a co-substitution of Sr and Pb for LaPO₄ to enhance both the protonic conduction and the sinterability. As a result, it was demonstrated that (La_0.94Sr_0.03Pb_0.03)PO₄ had a higher relative density than Sr-substituted ones, and the co-substitution could improve the protonic conduction. It can be considered that the co-substitution is a promising way to prepare dense LaPO₄-based protonic conductors.

The titanite-based ceramics with nominal composition CaTi_1−xNb_4x/5SiO₅ (0 ≦ x ≦ 0.2) in which part x of Ti sites are occupied with Nb, showed a remarkable jump of the complex relative permittivity at x = 0.025 compared with that at x = 0 at 110 GHz. Real part increased from 22.5 to 39, and the imaginary part from 4 to 14 (tangent delta from 0.18 to 0.36). Non-reflection condition is fulfilled in both cases when 0 < x < 0.0125, d/λ₀ = 0.05 and x = 0.2, d/λ₀ = 0.045, where d is thickness of the plate sample and λ₀ is the wavelength of incident electromagnetic wave. The dominant dielectric dispersion may occurr due to difference of ionic polarization between Ti⁴⁺ and Nb⁵⁺ ions relative to O²⁻ ions, which becomes inactive and saturates at x = 0.025. From the measurement of the lattice parameters, a, b, c, and the angle β, characterizing monoclinic crystal structure, this saturation may have close correlation with some structural rearrangement of constituting atoms, Ti and Nb in CaTi_1−xNb_4x/5SiO₅.