New Sol–Gel Route for the Preparation of Pure α-Alumina at 950°C

An anhydrous alumina (Al₂O₃) sol was prepared from aluminum isopropoxide and an organic solvent, using an acetic acid stabilizer. The complete conversion of the dried sol to α-Al₂O₃ was accomplished at a temperature of 950°C by a single transition via γ-Al₂O₃. Al₂O₃ that was deposited via dip coating resulted in amorphous films, even after annealing at 1100°C, because of the silicon diffusion from the substrate. This phenomenon was avoided using a rapid thermal treatment in a flame after dip coating, which resulted in uniform thin films that are converted to α-Al₂O₃ via heat treatment.     

Enzyme-Assisted Synthesis of Titania under Ambient Conditions

A low-temperature procedure for the synthesis of TiO₂ was developed using a water-soluble titanium complex and enzymes. Titanium–lactate and titanium–glycolate complexes were used as precursors of TiO₂. Digestive enzymes were chosen as biocatalysts for the synthesis of TiO₂ in aqueous solutions. TiO₂ powders were deposited from reaction solutions having optimal pH values for the enzymes to exhibit their catalytic activities for their original substrates. TiO₂ has been synthesized by an enzymatic reaction in an aqueous solution under ambient conditions. The XRD measurements indicated that TiO₂ powders thus obtained usually have an amorphous phase. However, after calcination at 550°C, the anatase phase was confirmed. Interestingly, the minor phase of TiO₂, brookite, was found in the sample obtained from the titanium–glycolate complex catalyzed by lipase at pH 10 after calcination at 550°C.     

Genetic Basis to Divergence of Sex Pheromones in Two Closely Related Moths, <Emphasis Type="Italic">Ostrinia scapulalis</Emphasis> and <Emphasis Type="Italic">O. zealis</Emphasis>

Crossing experiments between two closely related moths, Ostrinia scapulalis and O. zealis, were conducted to gain insight into the genetic basis of the divergence of female sex pheromones. The sex pheromone of O. scapulalis comprises (E)-11- and (Z)-11-tetradecenyl acetates (E11 and Z11), and distinct genetic variation is found in the blend of components. This variation is largely controlled by a single autosomal locus with two alleles, A^E(sca) and A^Z(sca). E-type (A^E(sca)A^E(sca)) females produce a pheromone with amean E11:Z11 ratio of 99:1, whereas Z-type (A^Z(sca)A^Z(sca)) and I-type (A^E(sca)A^Z(sca)) females produce a pheromone with a mean of 3:97 and 64:36, respectively. O. zealis is distinctive in that it has a third pheromone component, (Z)-9-tetradecenyl acetate (Z9), in addition to E11 and Z11, and the typical blend ratio is 60:35:5 (Z9:E11:Z11). Our study revealed that Z9 production in O. zealis is mainly regulated by an autosomal recessive gene phr^(zea), which is suggested to be involved in the chain-shortening of a pheromone precursor fatty acid, and linked to A^E(zea), a gene corresponding to A^E(sca) in O. scapulalis. A few mutations in a gene involved in pheromone production could explain the dramatic shift between a two-component pheromone communication system in O. scapulalis and a three-component system in O. zealis.     

Oxidative coupling polymerization of racemic 3,3’-dihydroxy-2,2’-dimethoxy-1,1’-binaphthalene with copper(II)-(-)-sparteine complex

Summary The oxidative coupling polymerization of racemic 3,3’-dihydroxy-2,2’-dimethoxy-1,1’-binaphthalene with copper(II) chloride-(-)-sparteine [(-)Sp] in methanol at room temperature was carried out and the enantiomer-selectivity during the polymerization was examined. The (R)-monomer preferentially reacted, and the purity of the unreacted monomer reached 80%ee (S) after 15 h, while that of the polymerized monomer gradually decreased from 26%ee (R) as a function of the polymerization. The ratio of the rate constants of both enantiomers, s=k_R/k_S, was determined to be 2.3. The model coupling reaction of the mono-benzylated (R)-monomer with CuCl₂-(-)Sp showed that the R-configuration with respect to the carbon-carbon bonds between the monomer units was selectively constructed during the polymerization.     

Grafting polymer from poly(ethylene terephthalate) films by surface‐initiated ATRP

Surface‐initiated atom transfer radical polymerization (ATRP) from poly(ethylene terephthalate) (PET) film was studied. Poly(methyl methacrylate) (PMMA), poly (acrylamide) (PAAM), and their diblock copolymer (PMMA/PAAM) on the surface of PET film were successfully prepared by surface‐initiated ATRP. The structures and properties of the modified PET film were characterized by FT‐IR/ATR, X‐ray photoelectron spectroscopy (XPS), measurements of contact angles, and scanning electronic microscopy (SEM). The results indicate that the surface properties of PET film were greatly improved by grafted polymer. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

High-Temperature Multilayer Composites with Superplastic Interlayers

A high-temperature multilayer composite (MLC) with hot hard layers and superplastic layers was proposed in this communication. The hard layer can provide the MLC high-temperature strength; the superplastic layer can deform plastically at high temperatures, disperse the applied stress, and stop the crack from advancing. Such an MLC was prepared via tape casting in the Al₂O₃/MoSi₂+Mo₂B₅ system in the present work; in this system, Al₂O₃ was the hard layer and MoSi₂+Mo₂B₅ was the superplastic layer. The microstructures and the stress-displacement behaviors of the MLCs were investigated. Finally, the design rules for the high-temperature MLCs were discussed briefly.     

Controlled Oxygen Partial Pressure Sintering of (Pb,La)(Zr,Ti)O3 Ceramics

Transparent PLZT(7/60/40) ceramics with large piezoelectric coefficients were obtained using a two-step sintering process with controlled oxygen partial pressure. Specifically, low-oxygen-pressure and low-temperature sintering were used in the first step, followed by a high-oxygen-pressure, high-temperature sintering cycle. High-density ceramics with small grain sizes of about 3 µm were prepared. As a result, k _p= 0.71, k ₃₃= 0.78, d ₃₃= 850 × 10^-12 C/N, and a transparency of 15% (λ= 610 nm, thickness of 1 mm) have been achieved; 20% improvement of d ₃₃ was gained compared to conventional processed PLZT ceramics ( d ₃₃= 710 × 10^-12 C/N).     

Measurement of self-diffusion coefficients in Li ionic conductors by using the short-lived radiotracer of 8Li

For the effective use of short-lived radioactive beams, soon to be available at the Tokai Radioactive Ion Accelerator Complex, the authors have developed a radiotracer method for diffusion studies in solids. The experimental test was performed by the measurement of the diffusion coefficients of Li in a sample of the compound βLiAl using an α-emitting radiotracer of ⁸Li (T_1/2=0.84 s). It was found that the time-dependent yields of the α particles from the diffusing ⁸Li that was initially implanted in the sample could be used as a measure of the diffusivity of the tracer in a nondestructive way. The method was applied to measure the self-diffusion coefficients of Li in βLiGa, and for investigating how the Li diffusion in the Li ionic conductors is affected by the concentration of atomic defects (i.e., the existence of the atomic vacancies of Li and the defects in Ga sites that are replaced by Li).     

Anodic dissolution of gold in alkaline solutions containing thiourea, thiosulfate and sulfite ions

Gld dissolves electrochemically in alkaline solutions containing ligands to form complex ions with gold ion.Therefore,selective leaching of noble metals is expected without dissolution of base metals such as steels,aluminum alloys in scrap treatment.Gold electrodes were investigated using linear sweep voltammetry,EQCM method and potentiostatic eclectrolysis in alkaline solutions containing thiourea,Na2SO3 and Na2S2O3.The solution composition,electrode potential affect gold dissolution rate and current efficiency.The gold dissolved from anode electrode forms complex ions,suspension particles as compound precipitates and deposits on cathode electrode as a metal.Anodic efficiency for gold dissolution is between 10% and 22%.This is caused by the oxidation decomposition of sulfite ions and thiourea.The statbility of the alkaline solution containing these elements was also estimated by capillary electrophoresis technique.     

Low temperature superplasticity of a fine-grained ZK60 magnesium alloy processed by equal-channel-angular extrusion

Fine-grained ZK60 magnesium alloy with the grain size of 1.4 μm was processed by equal-channel-angular extrusion. The material exhibited low temperature superplasticity. The normalized plot suggested that the present material had equilibrium grain boundaries at the superplastic temperature in contrast to typical materials processed by severe plastic deformation.