Synthesis of Nd3+,Cr3+-codoped YAG Ceramics for High-Efficiency Solid-State Lasers

Nd,Cr-codoped transparent YAG (Y₃Al₅O₁₂) ceramics with excellent optical properties were fabricated by a solid-state reaction method using Al₂O₃, Y₂O₃, Nd₂O₃, and Cr₂O₃ powders of 99.99 wt% purity. The mixed powder compacts were sintered at 1750°C for 20 h under vacuum and annealed at 1400°C for 20 h in an oxygen atmosphere. The Nd,Crcodoped YAG ceramics consisted of grain sizes ranging from 5 to 35 μm and exhibited a pore-free structure. The optical transmittance of a 0.8 at.% Nd,0.4 at.% Cr: YAG ceramic at 1000 nm was nearly equivalent to that of a 0.8 at.% Nd: YAG single crystal. In addition, the fluorescence intensity of the 0.8 at.% Nd,0.4 at.% Cr: YAG ceramic excited by a xenon lamp was double that of the 0.8 at.% Nd:YAG single crystal.     

Effectiveness of both ZnCl2- and SnCl2-containing molten salt catalysts for hydrogenation of Big Ben coal in the absence of a solvent

Hydrogenation of Big Ben coal (Australian bituminous coal) with 9.8 MPa H₂ for 3h at 400 °C has been carried out using a batch autoclave system in the presence of a molten salt catalyst such as ZnCl₂, SnCl₂, ZnCl₂-KCl-NaCl (3:1:1 mol ratio) and SnCl₂-KCl (3:2). The hexane-soluble (HS) yield decreases in the order: SnCl₂-KCl, SnCl₂, ZnCl₂-KCl-NaCl, ZnCl₂. The use of SnCl₂-containing melt is characterized by higher yields of both HS and benzene-soluble (BS) fractions and the suppression of gas yield compared with the use of ZnCl₂. The average aromatic unit and the molecular weight of HS increase in the order: ZnCl₂, ZnCl₂-KCl-NaCl, SnCl₂, SnCl₂-KCl. Chromatographic separation of HS fractions indicates that the saturate content is lowest and polar-material content is highest with the SnCl₂-KCl melt: this fact coupled with the structural parameters suggests that HS material with SnCl₂-KCl melt has, on average, a reasonably-high-molecular-weight skeleton which has more alkyl chains and heteroatoms. Micrographs of resulting benzene-insoluble (Bl) materials clearly indicated that the Bl particles were larger when ZnCl₂ was used than when the other melts were used, the Bl particles in these cases being of similar size. Lewis acidity and the viscosity of the molten salt appear to be related, in part, to the size of the Bl particles.     

Stabilization of poly(vinyl chloride). VIII. Synergisms between epoxy compounds and metal soaps

Effects of bisphenol A type epoxy compounds involving various average molecular weights on the zinc stearate/calcium stearate and the cadmium stearate/barium stearate synergetic soaps induced thermal stabilization of poly(vinyl chloride) (PVC) were investigated by colorimetry. The remarkable stabilization effects of epoxides could not be observed on the PVC films without synergetic soaps, while the stabilization of PVC was markedly enhanced by combined use of epoxides and synergetic soaps. The appearance of excessive coloration of cool color producing metal chloride–polyene complexes which were an origin of abrupt discoloration of stabilized PVC was retarded by using epoxides together with synergetic soaps. Moreover, as for PVC with or without synergetic soaps, the epoxy compounds did not inhibit the formation of longer polyene chains which were a chromophore for yellow orange of aged PVC. Further colorimetries and IR or X-ray photoelectron spectroscopies on the various PVC containing epoxy compounds and zinc chloride indicated that the epoxy groups caught the zinc chloride. The synergetic effect between epoxy compounds and synergetic metal soaps is ascribed to the action that the epoxides serve as an acceptor for the excessive cool color producing metal chloride produced from zinc stearate and cadmium stearate to retard the abrupt discoloration of stabilized PVC.     

Lasioderma chemistry sex pheromone of cigarette beetle (Lasioderma serricorne F.)

A chemical study of the sex pheromone of the cigarette beetle was carried out. Seven components were isolated from active fractions of column chromatography of the female extract, and their structures were elucidated by spectroscopic evidence and confirmed by synthesis to be (4S,6S,7S)-4,6-di-methyl-7-hydroxynonan-3-one (serricornin) (I), 2,6-diethyl-3,5-dimethyl-3,4-dihydro-2H-pyran (anhydroserricornin) (II), 4,6-dimethylnonan-3,7-dione (III), 4,6-dimethylnonan-3,7-diol (IV), 4,6-dimethyl-7-hydroxy-4-nonen-3-one (V), (2S,3R)-2,3-dihydro-3,5-dimethyl-2-ethyl-6-(l-methyl-2-oxobutyl)-4H-pyran-4-one (serricorone) (VI) and (2S,3R)-2,3-dihydro-3,5-dimethyl-2-ethyl-6-(1-methyl-2-hydroxybutyl)-4H-pyran-4-one (serricorole) (VII).These structural features suggested that the occurrence of these components might be related to the polyketide biosynthesis. The behavioral bioassay and BAG experiments revealed the biological role of each component in the copulatory behavior of this insect.     

Influence of solvent on size of poly(p‐oxybenzoyl) whiskers prepared from p‐acetoxybenzoic acid

Poly(p‐oxybenzoyl) (POB) crystals are prepared by the polymerization of p‐acetoxybenzoic acid (p‐ABA) at 320°C in various solvents to clarify the influence of miscibility between oligomer and solvent on the morphology as well as the size of the crystal. Concerning the morphology, whiskers are formed in less miscible solvents such as liquid paraffin and Barrel process oil B27. On the other hand, bundle‐like aggregates of fibrillar crystals tend to be formed in the solvents having higher miscibility such as Therm S 900 and 800, which are aromatic heat exchange media. Further, the solvents having higher temperature at which p‐ABA is completely dissolved during polymerization (T_s) yield a larger number of the whiskers with smaller width. The higher supersaturation of oligomers in less miscible solvents causes the formation of a larger number of nuclei with smaller size. Bundle‐like aggregates are formed in the solvents whose T_s is lower than 140°C by the fibrillation of pillar‐like crystals during polymerization owing to the reorganization. This shows a clear relationship between the width and T_s, and between the number of the crystals and T_s. Hence, the size of the whisker such as the length and the width can be predicted by the calculation with T_s, which is very valuable for the preparation of POB whiskers for use as industrial materials. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1129–1136, 2003     

High-temperature 1H n.m.r. study of oxidized coal

Two coking coals, a caking and a non-caking coal are examined in a Bruker pulsed ¹H n.m.r. spectrometer in the temperature range 293–730 K. One coking and the caking coal are oxidized in air at 383 K for 13 days. Temperatures of signal appearance and loss are noted as well as the temperatures of minimum signal half-peak width ($\text{ΔH}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$). There occurs no change in the above three temperatures with oxidation of the coals. The variation of ($\text{ΔH}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$) with temperature of the coal is also measured. Changes in ($\text{ΔH}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$) are more pronounced for the caking coal. The softening and solidification temperatures are below and above, respectively, those reported using the Gieseler method. Values of ($\text{ΔH}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$) increase beyond the minimum value as the fluidity continues to increase. This may be caused by an increase in average molecular weight of constituent molecules and/or an increasing concentration of free radicals in the fluid phase. This experimental approach may afford a new method to characterize coals which are to be used in liquefaction processes.     

Microstructure and Oxidation-Resistant Property of Sol-Gel-Derived ZrO2-Y2O3 Films Prepared on Austenitic Stainless Steel Substrates

The effect of Y₂O₃ addition to the oxidation resistance of sol-gel-derived zirconia films coated on austenitic stainless steel substrates was examined. The oxidation weight gain measurement and XRD analyses of oxides showed that addition of Y₂O₃ reduces oxide formation. TEM observations revealed that the films are joined to the substrates via an amorphous layer with concentrated Si, and the layer grew thicker by adding Y₂O₃ or elevating the firing temperature. Lattice constants of the films were shown to be more expanded than the zirconia powders prepared from the coating liquids.     

Characterization of packing structure of tape cast with non-spherical natural graphite particles

A three-dimensional microstructure of green and pressed tapes cast with graphite particles of non-spherical shape were examined quantitatively on the basis of the distribution of void sizes among the packed particles. The distributions measured over the cross-sections of the tape in three directions were expressed by the theoretical ones deduced for non-spherical particles. Particle shape was characterized by shape indices defined by Fourier analysis of particle outlines measured over the corresponding cross-sections of the green tape. The relationships were totally established between the limiting packing density, characterizing the void size distribution at the same section voidage, and the shape index of particle over the section. As a result, the normalized median void diameter as well as the limiting packing density of the pressed tape was found to increase with the particle shape index, corresponding to wider void size distribution. Therefore, based on developed correlations, the optimization of packing microstructure of the cast tape can be expected to result in high performance battery by using shape-modified graphite particles.     

PERFORMANCE OF A PRESSURIZED TWO-STAGE FLUIDIZED GASIFICATION PROCESS FOR PRODUCTION OF LOW-BTU GAS FROM COAL CHAR

A two-stage pressurized fluidized-bed gasification process has been developed to produce low-heating value gases from coal char. The reactor was 0.075 m id. and 1.4 m long, and gasification experiments were conducted under pressures up to 790 kPa and at temperatures up to 1323 K. A partition disc was used to divide the fluidized bed into two stages, using the first stage as a partial combuster and gasifier and the second stage as a gasifier. The disc was designed to control compositions of coal char particles in both stages so that the heat required for the endothermic gasification reaction in the second stage can be provided by the heat of combustion in the first

For conditions examined here, the disc with an opening ratio of 40° was found to give optimum distribution of the char particles in both stages without ash agglomeration. It was also shown that all oxygen gas was completely consumed within the first stage

The heating value of the product gas increased with the char feed rale. However, there may be an oplimum Teed ratio of char and sand-particles since the higher char feed rate causes more frequent ash agglomeration as well as less carbon conversion     

Improved lipase-catalyzed incorporation of long-chain fatty acids into medium-chain triglycerides assisted by supercritical carbon dioxide extraction

Displacement of the equilibrium of the lipase-catalyzed interesterification between medium-chain triglyceride (MCT) and long-chain polyunsaturated fatty acid was accomplished by the removal of by-products with continuous supercritical carbon dioxide (SC−CO₂) extraction at 60°C and 100 kg/cm². The incorporation of eicosapentaenoic acid to MCT was appreciably improved by this method and was 1.3 times higher than that of the equilibrium state (47 wt%) that was obtained in a closed system. The immobilizedMucor miehei lipase was stable for more than 180 h in SC−CO₂ at 60°C and 100 kg/cm². Presented at ISF-JOCS World Congress, Tokyo, Japan, September 26–30, 1988.