The effect of TiB₂ and TiN contents on the phase formations and their mechanical properties in the binary systems of Ti–TiB₂ and Ti–TiN, and in the ternary system of Ti–TiB₂–TiN was investigated. In the binary systems, TiB₂ and TiN addition improved the hardness of Ti but reduced its bending strength. In the ternary system of Ti–TiB₂–TiN, the addition of TiB₂–TiN mixture to Ti further improved the hardness to around Hv = 10.0 GPa compared to 7.0 GPa in the binary systems, but it did not improve the bending strength. The increase of hardness in the binary system of Ti–TiB₂ was mainly attributed to the formation of TiB (or non-stoichiometric solid solution of TiB_1−x) and to remaining TiB₂ in samples with high TiB₂ contents. The reduction of bending strength, however, was attributed to the disappearance of metallic Ti, to the formation of TiB_1−x, and to porous structure in samples with high TiB₂ contents. The increase of hardness in the binary system of Ti–TiN was attributed mainly to the formation of non-stoichiometric solid solution of TiN_1−x. The reduction of bending strength was attributed to the large crystal growth of flake like structure of TiN_1−x. The further improvement of hardness in the ternary system of 80Ti–20(TiB₂–TiN) was attributed to the formation of fine crystals of TiB (or TiB_1−x) within the flake like structure of N-diffused α(Ti) crystal phase. The reduction of bending strength is mainly attributed to the large growth of flake like structure of N-diffused α(Ti) crystal phase.

Various kinds of conducting ion species in solids have been discovered by selecting the NASICON-type three-dimensional network structure. By introducing high-valence Nb⁵⁺ into NASICON-type solids, both the thermal stability and crystallinity of NASICON-type trivalent cation conductors were simultaneously improved, leading to 13 kinds of trivalent cations that were newly reported to migrate in solids. In addition, highly selective low-temperature operative gas sensors were successfully fabricated using the (Al_0.2Zr_0.8)_20/19Nb(PO₄)₃ solid, which possesses a high trivalent cation conductivity of over 10⁻⁴ S·cm⁻¹ at 600 °C, as well as high thermal and chemical stabilities.

High-intensity laser irradiation promotes a chemical reaction between the vapor phase and the film surface in the chemical vapor deposition (CVD) process, resulting in a high-speed deposition and a significant oriented growth of various kinds of oxides, nitrides, carbides, and their compounds and composites. TEM observation revealed unique microstructures, such as columnar, feather-like, and single-crystalline growth, in the produced CVD coatings. This CVD process enables the combination of high-speed epitaxial growth and excellent properties for structural and functional ceramic coatings. Traditional ceramics, such as Al₂O₃, TiO₂, Al₂TiO₅, BaAl₁₂O₁₉, BaTiO₃, YBa₂Cu₃O_7−δ, and CeO₂, can be still highly valued as practical materials by functionalization of ceramic coatings with the control of orientation and nanostructure.

Dense silicon carbide (SiC) ceramics were fabricated through hot-pressing with a novel combination of rare earth oxides and fluorides (CeO₂–CeF₃, Nd₂O₃–NdF₃, Gd₂O₃–GdF₃ and Y₂O₃–YF₃) as additive. Effects of these additive combinations on microstructure, phase composition, flexural strength and thermal conductivity of SiC ceramics were evaluated. The samples with 1 wt %Nd₂O₃–2 wt %NdF₃ (1Nd2Nd sample) and 1 wt %Gd₂O₃–2 wt %GdF₃ (1Gd2Gd sample) additive exhibited the highest thermal conductivity of 187.8 W/m·K and highest flexural strength of 607.6 MPa respectively. Impedance spectroscopy analysis was employed to further investigate the variations of defects and impurities in SiC ceramics. 1Nd2Nd sample exhibited a higher fitting grain and grain boundary resistance that suggested a lower concentration of V''''_Si vacancies than other samples, which resulted in a higher thermal conductivity. On the other hand, the highest flexural strength of 1Gd2Gd sample was attributed to a combined effect of its small grain size, contiguous microstructure and low content of grain boundary phases. All in all, Re₂O₃–ReF₃ additive combinations are suitable for tailoring and improving the thermal conductivity and flexural strength of SiC ceramics.

Liquid phase bonded (LPB) porous SiC with neck bonding phases consisting of yttrium aluminate (Y₄Al₂O₉, Y₃Al₅O₁₂), yttrium silicate (Y₂Si₂O₇), and Al₂O₃ were fabricated using varying amounts of an Al₂O₃–Y₂O₃–SiO₂ bonding additive in Ar at 1500 °C for 1 h. LPB porous SiC ceramics exhibited unimodal pore-size distributions, porosities of 36.6–44.8 %, and pore sizes of 7.7–8.5 µm. The particle-size distribution of SiC powders was an important factor in determining the pore characteristics, including pore-size distribution, pore shape, porosity, and pore size, and the flexural strength as well as the gas permeability of LPB porous SiC ceramics. The porosity and pore size increased, and the pore-size distribution narrowed by using SiC powders with a narrow size distribution. The flexural strength of porous SiC varied in the range of 39.7–66.7 MPa and was mainly dependent on the porosity, pore shape, pore size, and solid boning area varied by the SiC particle-size distribution. A relatively high permeability (1.28–1.84 × 10⁻¹² m²) of LPB porous SiC was attained mainly due to the unimodal pore size distribution of pores with sizes of 7.7–8.5 µm.

Drying process is necessary in the preparation and application of refractory castables. In this work, the effects of conventional drying, microwave drying and freeze drying on the composition and properties of cured calcium aluminate cement (CAC) pastes were comparatively investigated. The differences in the microstructures evolution process under various drying mechanisms were discussed. The results show that metastable CAH₁₀ and C₂AH₈ are completely transformed into stable phases in the conventional dried pastes, while a small amount of flaky C₂AH₈ remained in pastes dried via microwave. Nevertheless, the major hydrates in the freeze-dried pastes are CAH₁₀ and C₂AH₈. In addition, the pores in pastes dried by microwave are mainly distributed in the range of 20–2000 nm, while the freeze-dried pastes contain more gel pores and show higher elastic modulus. A new approach to effectively regulate the pore structure of CAC bonded materials via non-conventional drying methods is proposed in the present work.

Fundamental gas-sensing properties of porous (pr-)In₂O₃ powders loaded with and without 0.5 mass % noble metal (pr-0.5N/In₂O₃ and pr-In₂O₃, respectively, N: noble metal (Au or Pd)) to NO₂, H₂, and ethanol balanced with dry air were investigated at 30 °C under UV-light irradiation (main wavelength: 365 nm). The spherical pr-0.5N/In₂O₃ and pr-In₂O₃ powders were prepared by ultrasonic-spray pyrolysis employing polymethylmethacrylate microspheres with a diameter of ca. 70 nm, which were synthesized by ultrasonic-assisted emulsion polymerization. The Au loading largely improved the NO₂ response of the pr-In₂O₃ sensor, a ratio of the resistance in NO₂ to that in air, especially under weak UV-light irradiation, because of the relatively large resistance in air. On the other hand, the Pd loading efficiently increased the difference in the conductance of the pr-In₂O₃ sensor between in NO₂ and in air under the whole UV-light irradiation range. The UV-light irradiation is effective in improving the NO₂-sensing properties of these sensors at room temperature, but the sensing performance was a little inferior to that operated at elevated temperatures under no UV-light irradiation. These sensors also responded to reducing gases, H₂ and ethanol, under UV-light irradiation, and the responses to ethanol were much larger than those to H₂. However, the responses to both the gases were much smaller than that to NO₂.

Strontium titanate (SrTiO₃) particles are expected to be applied to various catalysts, and many kinds of synthesis procedures of SrTiO₃ particles with a high specific surface area have been proposed. This study investigates a synthesis procedure of preparing SrTiO₃ particles with a high specific surface area by minimizing the crystallization temperature to the least possible value. The SrTiO₃ particles are prepared by maintaining spherical hydrous titania particles with smooth or porous surfaces in highly concentrated strontium hydroxide solutions at ≤120 °C. When porous hydrous titania particles are used as the raw material and the Sr/Ti ratio in the reaction solution is set at 10, spherical protrusions of SrTiO₃ develop on the surface of the original hydrous titania, even at a low temperature (25 °C). Single-phase SrTiO₃ particles with spherical protrusions composed of very fine crystallites are obtained by treatment at 40 °C for 24 h. These particles have a high BET specific surface area of 237 m² g⁻¹. The process developed herein is eco-friendly and effective for fabricating various perovskite-type compounds with a high specific surface area.

To create a highly photocatalytic performance in addressing the global environmental issues, we develop a highly efficient photocatalyst engineered by a combination of control of exposed facet in TiO₂ and composite with the non-noble metal nanoparticle. The formation of a fluorinated surface during crystal growth assists the morphology control of TiO₂ with coexposed {001}/{101} facets. In addition, the deposition of nano-sized Sn particles (>10 nm) is achieved via photochemical reduction on the faceted TiO₂ from anhydrous chelated tin(II) complexes by amino acid. Here, the bidentate ligands (i.e., carboxyl and amino group) in proline molecular play a vital role in associating the strong interaction between TiO₂ surface and chelated Sn complexes. The optimal balance in the ratio of exposed {001}/{101} facets and loading amount of Sn nanoparticles are essential factors for an enhancement of photocatalytic activity for efficiently consume photo-exited electrons in the degradation of azo-dye water pollutants.