In this study, we prepare Al₂O₃–CNT (carbon nanotube) composites with different contents of CNT, 1–20 vol % into the Al₂O₃ ceramics, for the purpose of improving damage and wear resistance. Al₂O₃–CNT composites are obtained by spark plasma sintering in conditions of 1400–1600°C in vacuum and 30–80 MPa. Hardness evaluated by Vickers indentation shows that the hardness of Al₂O₃–CNT composites can be enhanced when the CNT addition is less than 5 vol %. Toughness evaluated by Vickers indentation indicates that the toughness of the composites is comparable with that of an Al₂O₃ monolith. Hertzian indentations using a spherical indenter indicate the hard and elastic behavior of the composites by the addition of CNT. The wear rate and friction coefficients of the composites evaluated by the ball-on-disk method show that the composites represent low friction and reduced wear loss under constant contact load. The results indicate that the damage and wear resistance of Al₂O₃ ceramics can be enhanced by the addition of carbon nanotubes in optimum conditions.

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Al₂O₃–SiC–C castables with different particle size distributions (PSD) corresponding to different Andreassen distribution modulus (q) values, were fabricated, and their apparent porosity, permeability, pore size distribution and mean pore size, examined, after heat-treatment at different temperatures. The apparent porosity of Al₂O₃–SiC–C castable samples dried at 110°C for 24 h or fired at 1450°C for 3 h, decreases with increasing the q value from 0.21 to 0.23, but starts to increase on further increasing the q value to >0.23, i.e., it reaches the minimal value when q = 0.23.The change of permeabiliy with q is similar, although it reaches the minimal value when q = 0.22. The mean pore sizes of Al₂O₃–SiC–C castable samples dried at 110°C for 24 h increase with increasing q from 0.21 to 0.25, whereas for samples fired at 1450°C for 3 h, they have no obvious regularity. Pore size distributions of Al₂O₃–SiC–C castable samples after treated at different temperatures, are evidently scattered when q = 0.21, 0.22 and 0.25, but tend to become continuous when q = 0.23 and 0.24, in particular when q = 0.23. The Al₂O₃–SiC–C castable with q = 0.23 shows the best slag resistance because of its relatively narrow pore size distribution. In addition, our results reveal that PSD has little, whereas temperature has more obvious, effect on apparent porosity, permeability, mean pores size and pore size distribution of Al₂O₃–SiC–C castables.

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BaTi₄O₉ and BaSm₂Ti₄O₁₂ possess large dielectric performances and low dielectric loss, but their temperature-dependent properties could not meet with the practical use. In this paper, a composite ceramic system BaTi₄O₉/BaSm₂Ti₄O₁₂ (BaTi₄O₉ + xSm₂O₃, x = 20, 40, 60, 80 mol %) was prepared and their dielectric properties was presented. The composite ceramic precursor were modeled by a cool iso-static press (CIP) and calcined at 1300°C for 6 h. The measured densities of ceramic samples increased, but the relative densities decreased with the increase of x. XRD patterns showed there existed two phases of BaTi₄O₉ and BaSm₂Ti₄O₁₂ in the composite. The dielectric constants increased from 39.7 to 60.0, while the quality factors decreased from 8300 to 1500. At x = 40%, a near-zero temperature coefficient of +2.2 ppm/°C was achieved. The presence of pores, Ti³⁺ and Ti²⁺ was proposed to be the cause of the deviation from calculated dielectric properties.

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To decrease the environmental load due to current Pt dissolution processes that use strong acids in combination with oxidizing agents, the synthesis and dissolution of alkali metal platinates in hydrochloric acid (HCl) were examined. The alkali metal platinates were prepared by calcinating mixtures of Pt black and the alkali metal carbonates (Li, Na, K) at 600–800°C in air. Li₂PtO₃ powder was obtained through the calcination of a Pt black and Li₂CO₃ mixture at 600°C. The formation of NaPt₃O₄ and Na₂PtO₃ was confirmed upon the calcination of Pt black and Na₂CO₃ at 600–800°C; however, unreacted Pt also remained in the calcined samples. The calcination of Pt black and K₂CO₃ did not yield any Pt-containing oxides, even at 800°C. These results indicated that Li₂CO₃ was the most active reagent among the examined alkali metal carbonates for the formation of alkali metal platinates. The dissolution of the resulting Li₂PtO₃ in conc. HCl was monitored by inductively coupled plasma–optical emission spectrometry. The results showed that Li ions leached into HCl prior to the Pt, and the solubilities of the metals increased with decreasing calcination temperature. The dissolution behavior of Li₂PtO₃ was discussed based on the crystallite size and anisotropy of the crystal. A Pt dissolution process by way of these platinates is expected to benefit the establishment of recovery processes for PGMs with low environmental loads.

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Ni and NiO catalytic nanoparticles were precipitated onto mesoporous silica and zeolite by rotary chemical vapor deposition (RCVD) using NiCp₂ as a precursor. The diameter of the nanoparticles precipitated onto zeolite increased from 5 to 50 nm when the oxygen flow rate (R_O2) increased from 0 to 0.33 × 10⁻⁶ m³ s⁻¹, whereas that of the nanoparticles precipitated onto mesoporous silica was 5 nm, independent of R_O2. The nanoparticles could be precipitated inside of the mesoporous silica pores but outside the zeolite pores. The highest H₂ production rate in the methanol–steam reforming reaction was 1150 × 10⁻³ mol kg⁻¹ s⁻¹ at 633 K, which was achieved with a Ni/NiO catalyst on mesoporous silica, and this H₂ production rate is almost six times greater than that of the best Ni catalysts reported in literature.

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Cement composite of calcium phosphate was developed as a novel bioceramic material having biocompatibility, macro-porous structure, resorbability in vivo. The purpose of this study was to prepare and characterize the polarized calcium phosphate-citric acid-chitosan composite and to evaluate the effects of electrical polarization on bioactivity in order to enhance their biocompatibility. The characterization of the cement composite revealed that the surface is consisted with mixed phases of hydroxyapatite and CaHPO₄·2H₂O, having porous microstructure. The thermal analysis indicated that the appropriate temperature for electrical poling is below 100°C to inhibit the degradation of each component. The electrical measurements revealed that the cement composite has poling ability at 100°C through the proton migration among the lattice sites of OH, HPO₄ and H₂O molecules. The bioactivity was assessed by immersing the cement composites with or without electrical poling in simulated body fluid and evaluating the deposit and growth of bone-like apatite crystals on each surface. The negatively charged surface was accelerated compared to positively charged and non-poling surfaces.

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The conditions for the formation of hydroxyapatite [Ca₁₀(PO₄)₆(OH)₂; HAp] layer on the graphite sheet were examined via the processes of (i) the acid treatment of conc. nitric and sulfuric acids at 50°C for 24 h for the formation of carboxyl group, and (ii) the external heating (90°C, 1 h) and/or microwave heating (100°C, 5 min) of the acid-treated graphite sheet in the “apatite-dissolved solution” prepared by bubbling CO₂ gas into the HAp-dispersed water. The combination of external and microwave heating was effective in the formation of large amount of calcium phosphates, because the seed crystals of apatite formed by the evaporation of solvent from the apatite-dissolved solution (i.e., external heating) contributed to enhancing the formation of calcium phosphate layer through the microwave heating. The calcium phosphate layer formed by stacking the plate-like particles possessed the typical thickness of 4.9 µm, and was identified as HAp with Ca/P ratio of 1.72 or carbonate-containing HAp. Based upon the graphite sheet with HAp layer implanted into femur and tibia of the Japanese white rabbit for 4 months, the formation of calcified bone at the interfaces was found to show the excellent biocompatibility.

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A facile method to synthesize WO₃·H₂O square nanoplates via a mild aging (50°C) of ion-exchanged precursor was developed. The ion-exchanged precursor was prepared by passing the sodium tungstate solution (Na₂WO₄) through a protonated cation-exchange resin, and used as impurity-free acidified solution (H₂WO₄) for synthesizing WO₃·H₂O nanoplates. No shape-directing additive was employed. It was observed that the yellow particles were precipitated under aging at 50°C. After aging for 8 h, the precipitated particles were characterized as the WO₃·H₂O nanoplates, and their morphological evolution to square platelet proceeded with an increase of aging time. After aging for 24 h, the WO₃·H₂O square nanoplates were predominantly synthesized. The square nanoplates consisted of a few or several stacked thin layers (thickness, ~10 nm/layer), and provided the well-defined {010} facet for two dominantly exposed surfaces and {101} side facets. Their lateral dimension reached several hundreds of nanometers. It is thus demonstrated that the mild aging (50°C) of the ion-exchanged precursor is a simple and impurity-free synthetic route for WO₃·H₂O square nanoplates. In addition, the monoclinic WO₃ nanoplates were successfully obtained by dehydration-induced topochemical transformation of the WO₃·H₂O nanoplates.

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We report a direct observation of the negative thermal expansion in an iron-based perovskite oxide SrCu₃Fe₄O₁₂ by using a thermomechanical analyzer and strain gauge. Reversibility and small thermal hysteresis in the negative thermal expansion temperature range demonstrate that the negative thermal expansion of this compound is attributed to second-order phase transition.

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Anodic aluminum oxide (AAO)-template method is a synthesis process that AAO film with uniform pores is used as a template for 1-D nanostructure. In this study, we have synthesized well-defined TiO₂ nanorods or nanowires using AAO-template method. As for the first method, AAO template was immersed for 1 min in the Ti precursor solution with slightly decompressed atmosphere (Immersion setting, IS). As for the second method, AAO template was put on the filtering flask as a cover plate. Precursor solution was dropped on the AAO template for 1 min with vacuuming from the bottom part of AAO template (Vacuum and drop setting, VDS). With the calcination and HCl treatment to remove AAO, polycrystalline TiO₂ anatase nanorods and nanowires were successfully fabricated, just by changing the sample setting, viz., IS and VDS, respectively.

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