Yoh Sasaki

Hot corrosion behavior of boiler tube materials in refuse incineration environment

Abstract Thermal spraying has emerged as an important tool of increasingly sophisticated surface engineering technology. The different functions of the coating, such as wear and corrosion resistance, thermal or electrical of insulation can be achieved using different coating techniques and coating materials. The purpose of a hot corrosion resistant coating is to serve as a effective solid-state diffusion barrier between oxygen (or other gaseous) and the base metal. The 50%Ni–50%Cr alloy coating produced by the detonation spray method exhibited the most corrosion resistance in a laboratory test. This paper presents the hot corrosion test results of the 50%Ni–50%Cr alloy spray coated boiler tubes at the actual refuse incineration plant. This plant had operated for about 7 years without any problems and the coated tubes are expected to have longer life.

Keggin-type polyacid clusters on apatite: characteristic catalytic activities in solvent-free oxidation

We found that Keggin-type phosphometalates are effective catalysts for solvent-free oxidation with urea–H2O2 by dispersing on fluorapatite solid phase. In the solid phase system the phosphomolybdate (NH4)3PMo12O40 was more effective than the phosphotungstate (NH4)3PW12O40, whereas the latter was much superior to the former in the liquid-phase reaction with aqueous H2O2. In situ formation of novel peroxo-type species from (NH4)3PMo12O40/FAp and urea–H2O2, which may lead to the high catalytic activity in the solid phase system, was observed by 31P solid-state NMR.

Conformational and color polymorphism of achiral 2-methyl-3-(2-naphthalenylthio)-1,4-naphthalenedione

An achiral compound, 2-methyl-3-(2-naphthalenylthio)-1,4-naphthalenedione, shows conformational and color polymorphism, and each polymorph shows different optical properties and can be controlled by changing crystallization conditions.

Cetylpyridinium dodecatungstate on fluorapatite: efficient and reusable solid catalyst for solvent-free epoxidation

We have developed a new catalytic solid phase system for epoxidations using urea–hydrogen peroxide complex (urea–H2O2) and cetylpyridinium dodecatungstate ((CetylPy)10 [H2W12O42]) catalyst on fluorapatite. In the solid phase system epoxidations of cyclic alkenes and allylic alcohols proceeded without solvent at room temperature to afford the corresponding epoxides in good yields. The recovered solid catalyst phase was reusable for the reaction.

The Tandem Beckmann and Huisgen-White Rearrangement as an Alternative to the Baeyer-Villiger Oxidation of the 9-Azabicyclo[3.3.1]nonan-3-one System: A Facile Route to (±)-Dihydropalustramic Acid

The transformation of the «fork head ketone» (1) into the corresponding bicyclic lactone (4) via the Beckmann followed by the Huisgen-White Rearrangement is described. An α-ethyl-substituted bicyclic ketone (5) was converted efficiently to dihydropalustramic acid (6), a degradation product from the alkaloid palustrine

Thermoluminescence of Calcium-Deficient Fluoridated Hydroxyapatite

We recently found that β-tricalcium bis(orthophosphate) (β-TCP) as well as α-TCP was readily hydrolyzed to calcium-deficient fluoridated hydroxyapatite (de-FHAp) [Ca10-z(HPO4)z(PO4)6-z(F·OH)2-z·mH2O] in the presence of NH4F. We examined the thermoluminescence (TL) characteristics of de-FHAp with various fluoride contents prepared from α-TCP and β-TCP. The de-FHAp was compressed and heated at 700◦C and 900◦C for the TL measurement. The de-FHAp treated at 700◦C showed the TL glow peaks at 90◦C and 190◦C. The former peak was higher than the latter. On the other hand, TL glow peaks for the sample of 900◦C appeared at 50◦C, 130◦C, and 165◦C. The difference of these TL glow curves may be due to the structural change of de-FHAp to a mixture of FHAp and β-TCP when the sample was heated at 900◦C. The TL glow peak intensity increased with the fluoride contents in FHAp. The TL intensity of FHAp from α-TCP was higher than that from β-TCP. The intensity of TL glow peak for 90◦C and 190◦C increased linearly with the flux of X-ray irradiation up to about 1.8 C/kg.

Syntheses and Mechanical Properties of Calcium Phosphate--Methacrylate Phosphate Composites

There has been considerable interest in the bioactive bone cements based on calcium phosphates. We report herein the syntheses of surfacemodified composites and their compressive strength. The surface modification of calcium phosphate were achieved by the treatment of calcium phosphate with methacylate ethyl-2-phosphate (MEP) in acetone. Successively, the modified calcium phosphate was mixed with MEP, which were polymerized by heating in the presence of benzoyl peroxide. The compressive strength of the surface-modified composites are as follows; α-TCP∗-MEP composite/21 MPa, β-TCP∗-MEP composite/ 53 MPa, Hap∗-MEP composite/22 MPa. The compressive strength of the corresponding non-modified composites are as follows; α-TCPMEP composite/4 MPa, β-TCP-MEP composite/49 MPa, HAp-MEP composite/11 MPa. By the surface modification of calcium phosphate the compressive strength was substantially improved.

The Catalytic Activities of Poly Acid/Apatites in the Epoxidation Using Urea-Hydrogen Peroxide

For comparing the utility of the solid phase, silica gel, calcium fluoride, tricalcium phosphate (α-TCP) and apatites (HAp, FAp) were used in the epoxidation reaction of cyclooctene with H2WO4 catalyst and urea-H2O2. The order of catalytic activities of H2WO4/solid was FAp∼HAp> CaF2 ∼ silica gel> α-TCP. Under solvent-free conditions, in general, the surface area of solid phase is the most important factor for accelerating the reaction. However, the activities order was inconsistent with the order of the solid surface area, silica gelÀ HAp ∼ FAp ∼ CaF2 > α-TCP. Apatite having low surface area was the most effective as the solid disperse phase. Because of cation and anion-exchange ability and affinity for organic compound, apatite may moderately interact with both the inorganic catalyst and alkenes to assist the tungstic acidcatalyzed epoxidation reactions.