Hiroaki Katsuki

Porous hydroxyapatite monoliths from gypsum waste

Porous hydroxyapatite (HAp) monoliths were synthesized from gypsum mold waste with diammonium hydrogen phosphate solution by hydrothermal treatment at 50-190°C and their properties studied. Gypsum waste samples could be completely converted to HAp with 0.5 mol dm –3 (NH 4 ) 2 HPO 4 at 50°C in 15 days and 100°C in 2 days. This paper describes the effect of hydrothermal reaction conditions such as reaction temperature, time and concentration of (NH 4 ) 2 HPO 4 on the formation of new HAp monoliths and their porous properties.

Synthesis and characterization of PSU-1, a novel cage-like mesoporous silicaElectronic supplementary information (ESI) available: X-ray diffraction patterns for uncalcined (Fig. 1s), calcined (Fig. 2s) and hydrothermally treated (Fig. 3s) samples of PSU-1. See http://www.rsc.org/suppdata/jm/b3/b303406b/

The synthesis of an ordered mesoporous silica, PSU-1 (Pennsylvania State University-1), has been successfully accomplished by co-crystallizing the reactive gels of SBA-15 and MCM-41 under microwave–hydrothermal (M–H) conditions at 373 K. The crystallized framework was characterized by means of powder X-ray diffraction (XRD), thermogravimetric analysis (TGA), transmission electron microscopy (TEM), pore size entrance modification, and nitrogen adsorption. The material has a specific Brunauer–Emmett–Teller (BET) surface area of about 700 m2 g−1 and a pore volume of about 0.55 cm3 g−1. Characterization data have demonstrated the presence of a cage-like framework for PSU-1 similar to that observed in FDU-1 and SBA-16. The cavity size for the cage-like framework of PSU-1 was found to depend on the chain length of the cationic surfactant used for MCM-41 gel formation. The PSU-1 framework with uniform pore size distribution was not obtained under conventional hydrothermal conditions suggesting that its formation depends highly on the synthesis methodology. Interestingly, the cage-like framework was found to undergo recrystallization under hydrothermal conditions to a hexagonal phase similar to SBA-15. The interaction between the cationic and neutral surfactants and the resulting mixed micellar environment has been considered to explain the crystallization mechanism for the mixed gel system. Based on such an understanding and available characterization data, a hybrid crystallization mechanism of (SoH+X−)(S+X−I+) has been proposed for the formation of PSU-1.

Microwave-assisted polyol synthesis of Ag powders

Silver metal powders were prepared through reduction of AgNO 3 in ethylene glycol using microwave-polyol (M-P) and conventional-polyol (C-P) reactions at 100-200 °C. Powders of Ag were rapidly produced by microwave-assisted reaction at temperatures above 160 °C. The formation yield of Ag powders from AgNO 3 reached 97.8% after treatment for 135 min at 140 °C and 98.6% after treatment for 23 min at 160 °C. Compared to the formation of Ag powders using a C-P reaction, a M-P reaction led to increased rate of formation by 6.5 times at 160 °C, 5.2 times at 140 °C, and 3 times at 130 °C. Silver particles of 0.3-2 μm in diameter were produced using M-P and C-P reactions at 100-120 °C. The particle size of Ag powders increased with increasing reaction temperatures and times, and particles strongly aggregated at 160 °C using C-P and M-P reactions.

Preparation and some properties of porous alumina ceramics obtained by the gelatination of ammonium alginate

This study was carried out to develop a new preparation process of porous alumina ceramics and to examine their porous properties. The gelatination of ammonium alginate by hydrochloric acid was used for the formation of a gel-like precursor composed of alumina particles and alginic polymer. By this simple chemical shaping process of green bodies, porous alumina ceramics with a very sharp pore size distribution and a porosity of 40 to 55% could be obtained after firing at 1000 to 1600°C. The porosity showed an improvement of 15–20% compared with that of porous materials prepared from conventional procedures such as the pressing and slip-casting methods. The optimum concentrations of ammonium alginate and hydrochloric acid were 0.3–2.0 wt% and over 0.1 n, respectively, from the standpoint of the mixing treatment of raw materials and the gelatination.

Solvothermal/Hydrothermal Synthesis of Metal Oxides and Metal Powders with and without Microwaves

Anatase and Ca, Sr and Ca0.5Sr0.5 hydroxyapatites were synthesized by conventional-hydrothermal (C-H) as well asmicrowave-hydrothermal (M-H)methods.Microwave-assisted reactions led to accelerated syntheses of anatase but no such acceleration of reactions could be detected with the syntheses of hydroxyapatites because the crystallization of the latter materials occurred at very low temperature. Cu and Au metal powders were produced by using glucose, fructose or sucrose as reducing agents under C-H conditions at 160 ℃, where fructose and sucrose were found to be stronger reducing agents than glucose. The crystallinity of all the powders was characterized by powder X-ray diffraction, and morphology and particle sizes were determined by scanning or transmission electron microscopy Graphical Abstract Solvothermal/ Hydrothermal Synthesis of Metal Oxides and Metal Powders with and without Microwaves

Vapor phase growth of monoclinic ZrO2 whiskers

Growth of ZrO2 whiskers by the reaction of ZrCl4 and O2 or H2O was examined at 1100°-1300°C. Only powder products were obtained at temperatures below 1200°C in both reaction systems. At 1250°-1300°C, however, monoclinic whiskers or needle crystals were produced. In ZrCl4-O2 system, the whiskers were grown on a mullite substrate together with flaky materials, bricky crystals and powder. Optimum conditions for the whisker growth were ZrCl4 1-3%, O2 0.25-0.35%, and total flow rate of the reactant gas 40-60cm3/min. The size of the whiskers was 0.1-2μm in width and 10-100μm in length. The growth axis was the ‹010› direction or perpendicular to the (104) plane. In ZrCl4-H2O system, no whiskers were formed on the substrate, but needle crystals (whisker-like) and powder were obtained at the outlet of the reaction tube. The monoclinic needles were very minute, their dimension being 0.05-0.5μm in width and 0.5-3μm in length. The growth axis was the ‹010› direction or perpendicular to the (104), (113) or (211) plane. Optimum conditions were ZrCl4 2-5%, H2O 3-4%, and total flow rate of the reactant 30-60cm3/min. Electron microscopic observation revealed that the whiskers and the needles had no particles on the tops, suggesting that both of them grew by a VS mechanism.