Nanomaterial Deposits Formed by DC Plasma Spraying of Liquid Feedstocks

An experimental system consisting of an axial feed plasma gun, a variable-rate liquid delivery system, a liquid atomizer-feeder, and a substrate movement and control system was designed and assembled for preparing nanograined ceramic deposits. Sprayed deposits were produced with different spray and sol feed parameters and investigated in both the as-sprayed and heat-treated conditions. As-sprayed deposits were predominately hydroxide phases and were strongly adherent to the substrates. Postspray heat treatment at 873 K led to conversion of the alumina and zirconia deposits to γ-alumina and tetragonal zirconia phases, respectively. Subsequent heat treatment at 1273 K resulted in densification of the deposits and formation of high-temperature phases. A small increase in the grain size was observed with heat treatment, but the specimens still retained nanosized grains.     

Efficient Low-Temperature Data Retention Lifetime Prediction for Split-Gate Flash Memories Using a Voltage Acceleration Methodology

In developing a fast statistical testing methodology to predict the postcycling low-temperature data-retention lifetime of split-gate Flash memories, word-line stress is used to accelerate the charge-gain effect responsible for bit-cell-current reduction among the tail-bits. To find out the voltage dependence on data-retention lifetime, various word-line stress voltages are performed to enhance the charge-gain effect of the erase-state cells. At an accelerated state, word-line stress lifetime tests can be completed within a much shorter test period and still provide accurate lifetime prediction for embedded Flash-memory products     

Processing of lipoxygenase-free soybeans and evaluation in foods

Lipoxygenase-free soybeans were processed into flour, concentrate, and isolate and compared to normal soybeans in bread, meat patties, and a beverage, respectively. Bread made with 20% normal or lipoxygenase-free soy flour had greater (P< 0.05) beany flavor than control yeast bread. There were no differences in beany flavor scores between soy flour types, normal and lipoxygenase-free. Ground beef patties made with 5% acid-washed or ethanol-washed soy protein concentrate had greater (P<0.05) beany flavor than control ground beef patties. Ground beef patties made with ethanol-washed concentrate were scored lower in beany flavor than those made with acid-washed concentrate from normal soybeans. There were no differences in beany flavor between normal and lipoxygenase-free soy isolate in 2%-fat or no-fat beverages. Comminuted meat products made with lipoxygenase-free soy proteins, especially ethanol-washed concentrate, have potential for making soy foods with less beany flavor than foods made with normal soy.     

Sex Pheromone Components of the Apple Leafminer, Lyonetia prunifoliella

Three methylated hydrocarbons, 10,14-dimethyloctadec-1-ene (10Me14Me-1-ene-18Hy = 5Me9Me-17-ene-18Hy), 5,9-dimethyloctadecane (5Me9Me-18Hy), and 5,9-dimethylheptadecane (5Me9Me-17Hy), are synergistic sex pheromone components of the leafminer Lyonetia prunifoliella. Compounds extracted from female pheromone glands were identified by coupled gas chromatographic–electroantennographic detection (GC-EAD), and one compound, 10Me14Me-1-ene-18Hy, also by coupled GC–mass spectrometry. In field trapping experiments, 10Me14Me-1-ene-18Hy, 5Me9Me-18Hy, and 5Me9Me-17Hy singly were unattractive to males but in ternary combination attracted numerous male moths. Attractiveness of the three-component blend significantly exceeded that of two-component blends. No attraction of males to pheromone lures without 10Me14Me-1-ene-18Hy indicates that this compound is essential for pheromone communication of L. prunifoliella. Common C-5 and C-9 methyl branches in lyonetiid pheromone hydrocarbons suggest a common biosynthetic pathway; the presence of 5Me9Me-17Hy and 5Me9Me-18Hy in pheromone blends of L. prunifoliella and Leucoptera malifoliella provides evidence for phylogeny of lyonetiid chemical communication. Determination of the stereoisomeric composition is required to completely describe the pheromone blend of L. prunifoliella and to support the hypothesis of phylogenetically related sex pheromones.     

Characterization of the Solvent Properties of Glycerol Using Inverse Gas Chromatography and Solubility Parameters

The production of glycerol from the synthesis of biodiesel has led to a market surplus of this polyhydric alcohol and additional research to find new applications for this versatile chemical. This study involves the use of inverse gas chromatography (IGC) to characterize the solute–solvent interactions between glycerol and a homologous series of aliphatic alcohols, in which the latter components are at infinite dilution in the glycerol, which is the stationary phase contained in a packed GC column. The IGC experiments were conducted between 51.5 and 111 °C for the n-alcohols ranging from methanol to n-butanol. All of the n-alcohol homologs exhibited positive deviations from Raoult’s law as based on mole fraction activity coefficients values ranging from 1.86 to 14.4. The measured mole fraction activity coefficients of the alcoholic solutes in glycerol showed good agreement with literature values, and in some cases with those predicted using existing theoretical models. The mole fraction activity coefficients increased going from methanol to n-butanol, reflecting the change in the alcohol’s cohesive energy densities relative to that for glycerol. The total solubility parameter of glycerol calculated from IGC data was found to be 34.8 MPa^1/2 which is in good agreement with that obtained using Hansen solubility parameter approach (31.6 MPa^1/2). This data can be used to characterize the solvent properties of glycerol as well as to provide thermodynamic data for the removal of the alcoholic solutes from glycerol.     

Charge photogeneration in hybrid solar cells: a comparison between quantum dots and in situ grown CdS

We demonstrate that blend films containing poly(3-hexylthiophene-2,5-diyl) and in situ grown CdS display a greater yield of photogenerated charges than a blend containing an equivalent amount of pre-synthesised CdS quantum dots. Moreover, we show that the greater charge yield in the in situ grown films leads to an improvement in device efficiency. The present findings also appear to suggest that charge photogeneration at the CdS/polymer heterojunction is facilitated by the formation of nanoparticle networks as a result of CdS aggregation.     

Process modeling of the low‐temperature evolution and yield of polycarbosilanes for ceramic matrix composites

The volatilization of polycarbosilanes is important to the processing and performance of polymer infiltration and pyrolysis‐based ceramic matrix composites. Low molecular weight (MW) polycarbosilane is often present in preceramic polymers and enhances viscosity for the purpose of composite infiltration. Due to the volatility of low MW chains, a model was developed to semi‐empirically determine the MW distribution and then predict the mass yield and evolution of the MW distribution as a function of temperature and time for StarPCS^? SMP‐10. The enthalpy of vaporization, the temperature dependence of the enthalpy of vaporization, the temperature dependence of the normal boiling point and a representation of the molecular weight distribution were fit using a series of thermogravimetric measurements, involving isothermal holds on a particular batch of SMP‐10. Once calibrated for SMP‐10 in this fashion, the molecular weight distribution of different batches of SMP‐10 could be fit using a thermogravimetric measurement involving a reduced temperature‐time series. The model was then predictive of mass loss over time for temperatures below the onset of curing (>90°C). Understanding this volatilization enables improved SiC yield, reduced processing time and minimizing void/bubble formation.     

Low-level CO in hydrogen-rich gas supplied by a methanol processor for PEMFCs

The present study developed a low-CO methanol processor for the online supply of hydrogen to a proton exchange membrane fuel cell (PEMFC) composed of a steam reformer, a catalytic combustor and a reactor for the removal of CO. Commercial Cu/ZnO/Al₂O₃- and Pt/Al₂O₃-based catalysts were used in the methanol steam reforming and the preferential oxidation (PROX) reactor, respectively. The steam reformer was successfully heated with a catalytic combustor at room temperature without any additional electrical power supply. Hydrogen gas was obtained at a flow rate of 43.0 L h⁻¹ using a feed flow rate of 39.5 ml h⁻¹ (S/C=1.1) and an operation temperature of 250 °C, corresponding to a power output of 59 W_e. The CO concentration could be maintained at 4–5 ppm for stable operation.     

Solute distribution around a coherent precipitate in a multicomponent alloy

The open system elastic constants for a multicomponent alloy are derived and used to determine the equilibrium solute concentration profile surrounding an isolated coherent M₂C carbide precipitate with a transformation strain with three unequal eigenstrains in an elastically anisotropic AF1410 steel. The open system bulk modulus was found to vary with stress in this alloy, indicating that the chemical thermodynamics of AF1410 in an open system can result in the material becoming nonlinearly elastic. However, the open system shear moduli are identical to their usual constant composition values as a result of the cubic symmetry of the solute expansion tensor. We find that the nonuniform stress field surrounding the misfitting precipitate will induce significant nonuniformities in the concentration of the chemical components in this alloy. At certain positions in the matrix, the change in the concentration of Cr and Mo due to the elastic stresses, relative to their average concentrations in the alloy, can be as large as 100 to 250 pct. Although the solute redistribution reduces the matrix effective bulk modulus by 12 pct, the coherent carbide elastic self-energy is reduced by only 0.45 pct, reflecting a large contribution of shear distortions to the elastic self-energy, which are relatively unaffected by the dilating solutes.