Experimental Study of Ferrous Calcium Silicate Slags: Phase Equilibria at {\text{P}}_{{{\text{O}}_{2} }} Between 10?5?atm and 10?7?atm

Ferrous calcium silicate slags, whose principal components are “FeO _x ”-CaO-SiO₂, are widely used in copper smelting and converting operations. In the current study, high-temperature equilibration and rapid quenching techniques were used to study the phase equilibria of the ferrous calcium silicate slags. The compositions of phases in the slags were measured accurately using electron probe X-ray microanalysis (EPMA). The phase equilibria of the system have been characterized at oxygen partial pressures between 10⁻⁵ atm and 10⁻⁷ atm at selected temperatures between 1473 K and 1623 K (1200 °C and 1350 °C). The effects of oxygen partial pressure and temperature on the compositions of phases in the slags are presented.     

Hyperbranched polymers containing oxazoline monomers and succinic anhydride: Applications in fast drying,low solvent coating formulations

Melt-polycondensation of succinic acid anhydride with oxazoline-based diol monomers gave hyperbranched polymers with carboxylicacids terminal groups. ¹H NMR and quantitative ¹³C NMR spectroscopy coupled with DEPT-135 ¹³C NMR experiment showed high degrees of branching (over 60%). Esterification of the acid end groups by addition of citronellol at 160 °C produced novel white spirit soluble resins which were characterized by Fourier transform-infrared (FTIR) spectroscopy, gel permeation chromatography (GPC), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Blends of the new hyperbranched materials with commercial alkyd resins resulted in a dramatic, concentration dependent drop in viscosity. Solvent-borne coatings were formulated containing the hyperbranched polymers. Dynamic mechanical analysis studies revealed that the air drying rates of the new coating systems were enhanced compared with identical formulations containing only commercial alkyd resins.     

Development and hot-melt impregnation of a model controlled flow prepreg system

A controlled-flow epoxy-based model prepreg resin system was developed. The formulation of the model controlled-flow resin was designed from performance information obtained from a commercially available controlled-flow resin, presently used in the aircraft industry. Thermoanalytical techniques including rheometry were used to provide the necessary information to develop the model system along with a formulation methodology developed by Seferis and co-workers. The model resin formulation, which was a combination of tetraglycidyl ether of methylenedianiline (TGMDA), diglycidyl ether of bisphenol-A (DGEBA), carboxyl-modified butadiene/acrylonitrile rubber (CMBN), carboxyl-terminated butadiene/acrylonitrile rubber (CTBN), bisphenol-A (BPA), diaminodiphenyl sulfone (DDS), and dicyandiamide (DICY), was hot-melt impregnated into unidirectional carbon fibers on a laboratory scale hot-melt prepreg machine. A two-parameter, three-level design of experiments was performed on the prepreg processing parameters in which impregnation temperature and pressure were varied. Thus, a total of nine different experimental prepregs were produced and characterized by resin content, extent of impregnation, and tack. The results from the characterization of the nine experimental prepregs are compared with the effects of the prepreg processing conditions. These results are also compared with the results generated for the commercial controlled-flow resin. Collectively, this work provides a fundamental basis by which the analysis and rational utilization of controlled-flow matrix prepregs can be effected.     

A thermodynamically consistent framework for non-isothermal modelling of local heat generation and electromotive force in SOFC single electrodes

Mathematical models for single electrode reversible heat and non-isothermal electromotive force (EMF) of a solid oxide fuel cell (SOFC) are developed. These models estimate the volumetric reversible heat generation and EMF of electrochemical reactions, within each electrode at local conditions of temperature and pressure, based on entropy change of half reactions. The resulting equations are thermodynamically consistent. They inherently obey the conservation of energy law as the electrochemical energy released added to the heat of reactions at each electrode equate the enthalpy change of the reacted species. The equations are implemented to model electrodes in a tubular micro- solid oxide fuel cell (TμSOFC). The thermodynamic consistency of the model is numerically confirmed as the enthalpy of the reactants equates the electric energy released by the cell plus the sum of electrode heats plus electrolyte Ohmic heat. The effect of thermal gradients on the cell's overall EMF is found to be negligible. The reversible and irreversible heat generation of each electrode are distinguished. Overall, the anode is found to be endothermic, and the cathode exothermic.     

Mechanisms and Kinetics of Reduction of Solid NiO in CO/CO2 and CO/Ar Gas Mixtures

Metallurgical and Materials Transactions B - Experimental studies have been carried out on the reduction of dense nickel oxide in CO/CO2 and CO/Ar gas mixtures at temperatures between...     

Controlled Solidification of Liquids Within the SFC Primary Phase Field of the “Fe2O3”-CaO-SiO2 System in Air

Metallurgical and Materials Transactions B - To provide fundamental information on the phases and microstructures formed during sintering, a liquid with a bulk composition within the silico ferrite...     

Effect of psychrotrophic bacteria and of an isolated protease from Pseudomonas fluorescens M3/6 on the plasmin system of fresh milk

In the present study, we investigated the effect of Pseudomonas spp. growth on the plasmin enzymatic system in casein and whey fractions of fresh milk. Two bacterial strains, Pseudomonas spp. SRM28A and Pseudomonas fluorescens M3/6, were inoculated at a level of approximately 10(3) cfu/ml into fresh milk and incubated at 7 degrees C for 3 d. Bacterial counts were approximately 10(8) cfu/ml by d 3. Samples collected every 24 h were treated to separate the casein from the whey fraction. Casein and whey fractions were subjected to electrophoresis to visualize protein breakdown and plasmin activity and to colorimetric assays to quantify plasmin-related activities. With psychrotrophic bacterial growth, plasmin levels in casein fractions decreased significantly and in whey fractions increased then decreased significantly. Fresh milk results were similar for the two strains and were similar to earlier results with reconstituted nonfat dry milk. A transmission electron microscopy study by immunocytochemistry showed the presence of plasmin in casein micelles and its disappearance upon microbial growth in the milk. We hypothesized that extracellular microbial proteases produced by psychrotrophic microorganisms are responsible for this effect. To confirm this, an extracellular bacterial protease was isolated from Pseudomonas fluorescens M3/6 by ammonium sulfate fractionation and ion-exchange chromatography and incubated with fresh milk. Milk samples analyzed during incubation with the protease had significantly increased plasmin and plasminogen activities in the whey fraction within 5 h of incubation, while differences in activities in the casein fraction occurred at time 7.5 h for plasmin activity and 10 h of incubation for plasminogen activity. These quantitative data were supported by plasmin activity as visualized by casein-SDS-PAGE. These results suggest that growth of the Pseudomonas strains in fresh milk, and particularly their production of extracellular proteases, may be a causative factor in the release of plasmin from the casein micelle. Such plasmin release could affect the quality of cheeses and other food products that utilize dairy ingredients.     

Origin of petroporphyrins. 2. Evidence from stable carbon isotopes

Compared with the carbon-13 isotopic composition of the ubiquitous C32DPEP (DPEP, deoxophylloerythroetioporphyrin) the heavy but equivalent carbon-13 isotopic composition for the porphyrin structures 15(2)-methyl-15,17-ethano-17-nor-H-C30DPEP and 15,17-butano-, 13,15-ethano-13(2),17-propano-, and 13(1)-methyl-13,15-ethano-13(2),17-propanoporphyrin suggests a common precursor, presumably chlorophyll c, for these petroporphyrins isolated from the marine Julia Creek oil shale and the lacustrine Condor oil shale. Similarly, the heavy but variable carbon-13 isotopic composition of 7-nor-H-C31DPEP compared with C32DPEP is consistent with an origin from both chlorophyll b and chlorophyll c3. The equivalent carbon-13 isotopic composition for 13(2)-methyl-C33DPEP compared with C32DPEP suggests a common origin resulting from a weighted average of chlorophyll inputs.