Ikuo Yanase

Thermal Property and Phase Transition of the Synthesized New Cubic Leucite-type Compounds

New cubic leucite-type compounds, CsMSi2O6 (M=B0.2Al0.8,Al0.2Fe0.8), Cs2MSi5O12 (M=Cd, Mg, Ni, Zn) have been synthesized by the two-stage heat treatment of the solid-state reaction. The thermal expansion properties of the synthesized leucite-type compounds have been studied with HTXRD and LTXRD in the temperature range of 123 to 1273 K. The thermal expansion rate of CsB0.2Al0.8Si2O6 was found to be considerably smaller than that of CsAlSi2O6, while the thermal expansion property of Cs2MSi5O12 (M=Mg, Zn, Cd) was found to have a linear relationship in the temperature range of 298 to 1273 K. By using Rietveld analysis it was found that the thermal expansion rate decreased with increasing the Si—O—M(Si) angle for cubic leucite-type compounds at 298 K, and that the phase transitions of CsAlSi2O6 and Cs0.9Al0.9Si2.1O6 were due to the relationship between the bond angle of Si—O—M(Si) of the three-dimensional framework structure and the space ratio in the unit cell at 298 K.

Effect of Molecular Structure of Polyols with Different Molecular Characteristics on Synthesis of Boron Carbide Powder

Crystalline boron carbide (B4C) powder was synthesized by the carbothermal reduction of condensed products formed from boric acid (H3BO3) and polyols with different molecular characteristics, i.e., glycerin, mannitol, and poly (vinyl alcohol) (PVA). The effect of the molecular structure of the polyol on the thermal decomposition conditions and the obtained morphology of the B4C powder was discussed in this study. The thermal decomposition in air of each condensed product was performed before the carbothermal reduction in order to eliminate the excess carbon, where the decomposition conditions varied with the type of polyol. Crystalline B4C powder with less residual free carbon was synthesized from the thermally decomposed products by heating at 1250 °C for 5 h in an Ar flow. The thermal decomposition conditions and the particle size of the obtained B4C powder reflected the molecular characteristics of the polyols.

Fabrication of Zr2WP2O12/ZrV0.6P1.4O7 composite with a nearly zero-thermal-expansion property.

Graphical abstract

Preparation of Crystalline Turbostratic Boron Nitride Nanoparticles by Combination of Precursor Compound Formation and Impurity Segregation from Boric Acid and Urea

Crystalline turbostratic boron nitride (t-BN) was prepared by a combination of precursor compound formation and impurity segregation from boric acid (H3BO3) and urea. A mixed material was prepared by separately dissolving H3BO3 and urea in distilled water then blended them, which was followed by drying. A precursor compound including oxygen was formed from the mixed material upon low-temperature heat treatment at 250 °C. The oxygen-containing impurity was segregated as a boron oxide component by the hydrolysis of the precursor compound during the grinding process in air, leading to the effective layered structure formation and layer stacking of t-BN. Crystalline t-BN nanoparticles with well-stacked layered structures were prepared by leaching the segregated impurity in a hot aqueous solution of the product formed by heat treatment at 1300 °C in an Ar flow.