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.     

Miscibility and adhesive properties of EVA‐based hot‐melt adhesives. II. Peel strength

A series of ethylene vinyl acetate copolymers (EVA) were blended with some tackifier resins that were made from wood extracts, and possible relations between their miscibility and properties as hot‐melt adhesives (HMA) were investigated. From our previous report on miscibility of various EVA‐based HMAs, we chose some blends that represent some of the typical miscibility types and investigated their peel strengths. When the blends were miscible at testing temperatures, the temperature at which the maximum value of peel strength was recorded tended to move toward higher temperature as tackifier content of blends increased. This result corresponds to the storage modulus of the blends whose curves tended to move toward higher temperature as tackifier content of blends increased when blend components were miscible as well as their maximum values of tan δ, or glass transition temperatures. It was characteristic for peel strength that there existed second peaks on peel strengths curves at ～ 100°C, which adhesive tensile strengths for the blends did not have. In terms of relationship between miscibility and HMA performances, we suggest that there are several factors other than miscibility that affect absolute values of peel strength more directly than miscibility; this idea has to be investigated further in the a future study. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 726–735, 2002     

Thermal Expansions and Chemical Durabilities of Yttria–Aluminosilicate Glasses Containing Na2O and ZrO2

Properties of glasses in the system Y₂O₃–Al₂O₃–SiO₂ containing Na₂O and ZrO₂ were investigated. The difference between the thermal expansion coefficients (Δα) at temperatures above T _g and those below T _g, microhardness, density, and chemical durability were measured in relation to the Al₂O₃/Y₂O₃ molar ratio. These glasses were found to have a smaller value of Δα than that of a commercial coating glass.     

Purification of steryl esters from soybean oil deodorizer distillate

Soybean oil deodorizer distillate (SODD) contains steryl esters in addition to tocopherols and sterols. Tocopherols and sterols have been industrially purified from SODD but no purification process for steryl esters has been developed. SODD was efficiently separated to low b.p. substances (including tocopherols and sterols) and high b.p. substances (including 11.2 wt% DAG, 32.1 wt% TAG, and 45.4 wt% steryl esters) by molecular distillation. The high b.p. fraction is referred to as soybean oil deodorizer distillate steryl ester concentrate (SODDSEC). We attempted to purify steryl esters after a lipase-catalyzed hydrolysis of acylglycerols in SODDSEC. Screening of industrially available lipases indicated that Candida rugosa lipase was most effective. Based on the study of several factors affecting hydrolysis, the reaction conditions were determined as follows: ratio of SODDSEC/water, 1∶1 (w/w); lipase amount, 15 U/g reaction mixture; temperature, 30°C. When SODDSEC was agitated for 24 h under these conditions, acylglycerols were almost completely hydrolyzed and the content of steryl esters did not change. However, study with a mixture of steryl oleate/trilinolein (1∶1, w/w) indicated that about 20% of constituent FA in steryl esters were exchanged with constituent FA in acylglycerols. Steryl esters in the oil layer obtained by the SODDSEC treatment with lipase were successfully purified by molecular distillation (purity, 97.3%; recovery, 87.7%).     

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.     

Dynamic Mechanical Properties and Adhesive Joint Strengths of Emulsion Polymers Produced by Power Feed Technique. II. Chemical Structure of Grafted Power Feed Polymer

Power feed copolymers were synthesized using styrene and n-butyl acrylate through a non-uniform feeding emulsion polymerization. Poly(vinyl alcohol) (PVA) was used as a protective colloid, onto which vinyl monomers were grafted. With the increase of PVA, grafting was also increased. Feeding method did not affect grafting nor grafting efficiency to a great extent. However, the amount of initiator had a negative correlation against grafting or grafting efficiency. From NMR spectroscopy, it was known that n-butyl acrylate monomer grafted onto PVA rather than copolymerized with styrene monomer. In order to increase the cohesive strengths of each phase, grafting was introduced to the power feed polymerization. In these cases, the chemical structure of grafted power feed polymer was investigated.     

Formation of 2,4-dinitrophenylhydrazones and regeneration of carbonyl groups in polyethylene film irradiated with ultraviolet light

2,4-Dinitrophenylhydrazine was reacted on polyethylene films irradiated in air with ultraviolet light. The changes in amount of carbonyl groups and 2,4-dinitrophenyl-hydrazones formed in the films were inferred by comparing their absorptions in the infrared and ultraviolet spectra, respectively. The amount of hydrazones formed increased with increase in the reaction time, and rates of the increase gradually decreased with increase in the reaction time. A comparison of the change in amount of hydrazones formed in the irradiated films with the change in amount of carbonyl groups formed in the irradiated films and the change in wettability with H-bonding liquids of the irradiated films showed that the amount of hydrazones formed seemed to be affected by amount of carbonyl groups in the surface zone of the film. The carbonyl groups were regenerated from the hydrazones with increase in the regeneration times, and rates of the regenerations gradually decreased with increase in the regeneration times. The regeneration was facilitated by raising the temperature in the levulinic acid solution, by adding dilute hydrochloric acid to the levulinic acid, or by raising the temperature in the levulinic acid solution containing hydrochloric acid.     

Production of structured lipids containing essential fatty acids by immobilizedRhizopus delemar lipase

An attempt was made to produce structured lipids containing essential fatty acid by acidolysis with 1,3-positional specificRhizopus delemar lipase. The lipase was immobilized on a ceramic carrier by coprecipitation with acetone and then was activated by shaking for 2 d at 30°C in a mixture of 5 g safflower or linseed oil, 10 g caprylic acid, 0.3 g water and 0.6 g of the immobilized enzyme. The activated enzyme was transferred into the same amount of oil/caprylic acid mixture without water, and the mixture was shaken under the same conditions as for the activation. By this reaction, 45–50 mol% of the fatty acids in oils were exchanged for caprylic acid, and the immobilized enzyme could be reused 45 and 55 times for safflower and linseed oils, respectively, without any significant loss of activity. The triglycerides were extracted withn-hexane after the acidolysis and then were allowed to react again with caprylic acid under the same conditions as mentioned above. When acidolysis was repeated three times with safflower oil as a starting material, the only products obtained were 1,3-capryloyl-2-linoleoylglycerol and 1,3-capryloyl-2-oleoyl-glycerol, with a ratio of 86∶14 (w/w). Equally, the products from linseed oil were 1,3-capryloyl-2-α-linolenoyl-glycerol, 1,3-caprylol-2-linoleoyl-glycerol, and 1,3-capryloyl-2-oleoly-glycerol (60∶22∶18, w/w/w). All fatty acids at the 1,3-positions in the original oils were exchanged for caprylic acid by the repeated acidolyses, and the positional specificity ofRhizopus lipase was also confirmed to be strict.     

Hydrothermal Synthesis of Cerium(IV) Oxide

CeO₂ powders have been prepared from cerium(III) nitrate, cerium(IV) sulfate, and cerium(IV) ammonium sulfate under hydrothermal conditions at 120° to 200°C for 5 to 40 h. The effects of the starting cerium compounds, hydrothermal treatment temperature, and the concentration of the solutions on the crystal growth of CeO₂ were investigated. CeO₂ powders hydrothermally synthesized at 180°C for 5 h from cerium(IV) salts had very fine particle sizes (30 Å); on the other hand, the powder from the cerium(III) salt had a relatively coarse particle size (160 Å). Although the crystallite size of the powder synthesized from the cerium(IV) compounds depended on the treatment temperature, that from the cerium(III) compound was insensitive to the treatment temperature. The mechanisms for the growth of CeO₂ particles under hydrothermal conditions are discussed.