Lithium silicate (Li₄SiO₄) is one of the most promising carbon dioxide (CO₂) capture materials at high temperatures. In this study, Li₄SiO₄ on silica (SiO₂) porous structure was tried to fabricate in solid state reaction for CO₂ capture materials. Li₂CO₃ reacted with amorphous SiO₂ on the surface of silica porous structure made by template method, resulting in the formation of Li₄SiO₄ porous structure on silica support at 800 °C. The obtained Li₄SiO₄ porous structure can capture CO₂ at 600 °C and release it at 700 °C, and could be used stably and repeatedly. This Li₄SiO₄ porous structure is expected to be useful as a CO₂ capture material at high temperature.

Calciprotein particles (CPP), found in the blood, are composite nanoparticles consisting of the protein fetuin-A and solid-phase calcium phosphate. Among these, amorphous CPP (a-CPP), composed of fetuin-A/amorphous calcium phosphate nanoparticles, are non-pathogenic. In contrast, crystalline CPP (c-CPP), which contain calcium phosphate crystals and result from the agglomeration of a-CPP, are known to cause inflammation and vascular calcification. We have developed an in vitro synthesis method for CPP and studied the phase transition process from a-CPP to c-CPP. This study evaluates the influence of atmospheric carbon dioxide on this transition by examining microscopic structures using field emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction analysis, and infrared spectroscopy. We found that the transition from a-CPP to c-CPP was significantly accelerated by atmospheric carbon dioxide. This phenomenon can be attributed to the formation of carbonate-containing hydroxyapatite, which is expected to have a highly symmetric hexagonal structure conducive to crystal growth.

The functions of ceramics depend on their composition, atomic structures, and meso/macroscopic structure, and controlling all these factors can lead to desired performances. However, achieving simultaneous control has been challenging, necessitating the development of advanced ceramic synthesis methods. This review focuses on our precise syntheses of ceramics using multi-step processes that incorporate liquid phase reactions. Through this approach, we successfully synthesized microporous silicates, oxynitride nanoparticles, oxyfluorides with controlled morphology, and nitrides with well-dispersed dopants. These results demonstrate the broad applicability of this concept to various types of ceramics, regardless of their composition.

All-solid-state batteries have shown promise as possible energy-storage devices of the future, with the potential to overcome the limitations of present-day conventional batteries. The curvature of ionic conduction pathways occurs inside solid electrolytes, and investigations into the magnitude of this curvature, i.e., “tortuosity,” enable us to analyze their ionic conduction performance. This study investigated the correlation between the filling ratio and ionic conductivity to evaluate tortuosity using the Bruggeman equation. Our block model theory suggests that the ionic conductivity for a uniform block-shaped void distribution is proportional to the square of the filling ratio. When this relationship is applied to the Bruggeman equation, the Bruggeman exponent, which is an indicator of tortuosity for a solid electrolyte, is determined to be α = 2. This theoretical value of the Bruggeman exponent was different from that of the spherical void model (α = 1.5) proposed previously. Impedance measurements revealed that the Bruggeman exponent of an Li₃PS₄ glass electrolyte is approximately 1.8, which is similar to but slightly lower than that determined by the block model. Cross-sectional scanning electron microscopy images revealed that the electrolyte has a uniform block void distribution, as in the block model. Monte Carlo simulations suggest that the actual, slightly lower Bruggeman exponent (α = 1.8) stems from the electric field. Tortuosity analyses using the block model and impedance measurements enable us to evaluate the macroscopic ionic conduction performance of solid electrolytes.

BaCO₃, Y₂O₃ and SiO₂ powders weighed at Ba:Y:Si molar ratios of x:26:16 with x = 9.0–14.0 were mixed in a planetary ball mill, compacted, and calcined at 1300 °C for 12 h. The calcined compacts were reground in a planetary ball mill and recompacted to form disk-shaped powder compacts that were then heated at 1600 °C for 2 h. X-ray diffraction measurements revealed that the ceramic disks were mainly composed of the tetragonal oxide, Ba_xY₂₆Si₁₆O_71+x (x ≈ 10.2), with some secondary phases. A ceramic disk with the highest relative density of 96 % respect to the theoretical density of the tetragonal oxide was obtained at x = 10.8. The granular and elongated grains of the tetragonal oxide were contained in a matrix of fine oxide grains. The relative dielectric constant (ε_r) and dielectric loss (tan δ) measured for the ceramic disk at frequencies of 10 Hz and 1 MHz were 5410 and 0.07, and 380 and 0.44 at 25 °C, and 7000 and 0.08 and 3830 and 0.334 at 325 °C, respectively.

In this study, improvement of material properties such as compressive strength of chelate-setting cements, which is determined by chelate-bonding between inositol phosphate (IP6) and hydroxyapatite (HAp), and cytotoxicity of cements fabricated using the osteoblastic cell line MC3T3-E1, was investigated. The use of HAp powder with a high specific surface area (HApHS), synthesized by a wet process under ultrasonic irradiation, instead of the commercially available HAp powder improved the material properties of the cement. The compressive strength of the cement specimens fabricated from IP6-surface-modified HAp and HApHS powders was higher than that of cement specimens without IP6 surface modification. Moreover, the compressive strength of the HApHS-based cement specimens increased with increasing IP6 concentration. Cytotoxicity tests using Transwell^®-permeable support revealed that the cement specimens had no cytotoxicity. The fabricated non-cytotoxic HApHS powders could be useful as a new raw material for preparing chelate-setting cements with improved materials properties.