Dynamics of mechanical,acoustical, and electrical properties of epoxy‐amine compositions during cure

Dynamics of mechanical, acoustical, and electric properties is studied in the cure of three samples of polymeric compositions produced on the basis of epoxy oligomer with different content of the curing agent. The measurements were made in a parallel mode with an automated measuring complex. Variations in elastic modules, sound speed, attenuation coefficient, relaxation of the shear stress, electric resistance of the samples during the complete cure in the transition from a liquid into a glass state are considered. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Numerical modeling and experimental study of thermally induced residual stress in the direct diode laser heat treatment of dual-phase 980 steel

The direct diode laser application has been found useful in the localized heat treatment of metal parts because of its wider beam and more uniform energy distribution with respect to other lasers with Gaussian-like energy distribution. In this study, an uncoupled thermomechanical finite element model is developed to study the temperature field and thermally induced stress evolution in high-strength dual phase (DP) 980 steel during its direct diode laser heat treatment. Thermal analysis results are experimentally validated through thermocouples and then input into a mechanical model as transient temperature loading in order to acquire the thermally induced stresses and strains. The effect of martensite phase transformation on residual stress distribution in heat-treated DP980 steel is considered. An X-ray diffraction technique is used to measure the residual stress distribution at the top surface of the heat-treated coupons of DP980 steel. The numerical results show that compressive stresses are located at the laser–material interaction zone. After heat treatment, tensile stresses are retained at the heat-treated DP980 steel coupons. There is qualitative agreement between the numerically predicted and experimentally measured residual stresses. The effect of the overlapping ratio on the residual stress and hardness of the heat-treated DP980 steel is also experimentally and numerically investigated.     

From coffee industry waste materials to skin‐friendly products with improved skin fat levels

Spent coffee grounds (SCG), which are the residue obtained from the treatment of coffee with hot water or steam, can be used for industrial applications, due to the high content in lipids. The cosmetic products might be a suitable application for these types of residues because the barrier properties of the stratum corneum (SC) are largely dependent on the intactness of the lipid lamellae that surrounds the corneocytes. The purpose of this work was to assess the feasibility of using the lipid fraction of SCG extracted with supercritical carbon dioxide in the development of new cosmetic formulations with improved skin lipids (sebum) and hydration. The use of spent coffee lipid extract in cosmetic industry seems to be a suitable approach to recycle the wastes from coffee industry. Emulsion containing 10% of the lipid fraction of SCG (SpentCofOil cream) presented promising characteristics in the improvement of sebum skin levels with a good acceptance by consumers when compared to an emulsion containing 10% w/w of green coffee oil (GreenCofOil cream) and a placebo without coffee oil (NoCofOil cream). Practical applications: In this work, the authors develop and characterize a cream containing 10% of the lipid fraction of SCG extracted with supercritical carbon dioxide with improved skin lipids (sebum) and hydration.     

Electrolytic Corrosion of Titanium Carbonitride Composites

The corrosion properties of TiCN, TiCN – AlN, and (TiCN – AlN) – (Fe – Cr) ceramics as well as those of the individual components TiN and TiC in a 3% NaCl solution have been investigated. The kinetics and the mechanism of anode dissolution of metals and oxidation of specimens have been studied by using polarization curves, chemical and x-ray phase analyses, Auger electron spectroscopy, and scanning electron microscopy (SEM). TiCN and TiCN – AlN composites have been found to be the most corrosion-resistant. The presence of a metallic binder in the titanium carbon nitride somewhat decreases the corrosion resistance of the ceramics. On the whole, however, the ceramics developed boast a significantly higher corrosion resistance than that of structural steel.     

BINARY EXTRACTION OF PLATINUM METALS

ABSTRACT

The equations describing the regularities of interphase distribution of platinum metals as their chloro complex acids in systems containing binary extractants have been derived. The dependencies of distribution coefficients of platinum metals on the composition of both phases, and their aqueous acidity have been determined when both binary extraction and a combination of anion-exchange and binary extraction occurred. The interrelation of the binary extraction constant of chloro complex acids of platinum metals with the extraction constant of hydrochloric acid and the anion-exchange constant is described. We studied platinum metal extraction by salts of organic acids and organic bases and showed that in the systems involving binary extractants, such as salts of quaternary ammonium bases, the distribution of platinum metals proceeds via either anion-exchange or binary mechanisms depending on the composition of the system. With increasing pH, the distribution coefficients of platinum metals decrease according to the regularities of binary extraction due to forming thermodynamicaHy stable binary extractants, R4NA

When the anion-exchange extraction occurs, the distribution of complex acids of platinum metals in the systems containing binary extractants is affected by interactions of the extractants and the extracted compounds with the organic acids. Interactions between extractants in the chloride form and the molecules of organic acids have been shown to be largely responsible for the extraction characteristics. The binary extractant systems are preferred in the development of solvent extraction processes for the recovery and the stripping of platinum metals.     

SOLVENT EXTRACTION OF PALLADIUM FROM CHLORIDE SOLUTIONS BY ALKYLAMMONIUM DI(2-ETHYLHEXYL)DITHIOPHOSPHATES

ABSTRACT

The extraction of palladium (II) from chloride solutions (over a wide region of aqueous acidity) by di(2-ethylhexyl)dithiophosphates of tetraoctylammonium, tri-n-octylammonium and di-n-octylammonium in toluene at the constant chloride concentration has been studied. A synergistic effect was shown to be observed in these systems and it is explained by the formation of unusual complexes with mixed ligands. It has been established the palladium complexes, such as (R₃NH)[PdCl₂A], (R₃NH)[PdCl₂A] and (R₂NH₂)[PdCl₂A], involving both alkylammonium cation and dialkyldithiophosphate anion are extracted under conditions of the loaded organic phase using distribution methods depending on a composition of aqueous and organic phase. At the excess of R₃NHA or R₂NH·HA, PdA₂ is extracted into the organic phase. Table 8 reports the results obtained and indicates the domains of existence of the various species of palladium (II) extracted into the organic phase in the binary ex-tractant systems in comparison with the initial systems     

Preparation and characterization of ethylene‐vinyl acetate nanocomposites: enhanced flame retardant

Ethylene‐vinyl acetate (EVA) nanocomposites with enhanced flame retardance were prepared by the sol–gel process in the melt. Two EVAs with different vinyl acetate (VA) contents and aluminium isopropoxide were used as organic and inorganic phases. The nanocomposites were prepared in a batch mixer under constant processing conditions and were analysed by several characterization techniques. Aluminium isopropoxide presented low activation energy, which allows the synthesis of the nanoparticles without a post step treatment. The reaction mechanism is proposed. Nanocomposites with smaller and well dispersed metal nanoparticles were produced with an EVA with higher VA content. EVA nanocomposites achieve the requirements for 94 V‐0 classification. © 2013 Society of Chemical Industry     

Measurement and correlation of the individual ionic activity coefficients of aqueous electrolyte solutions of KF,NaF and KBr

Ion selective electrodes were used to measure the activity coefficients of individual ions at 298.2 K in aqueous solutions of KF, KBr and NaF up to 3, 2 and 1 molal, respectively. The mean ionic activity coefficients of the electrolytes obtained from the values of individual ions show good agreement with values reported in the literature. The experimental results confirm that the activity coefficients are different for the anion and the cation in an aqueous solution of a single electrolyte. It is also confirmed that the deviation from ideality for each ion depends on its counterion. The Khoshkbarchi—Vera equation was used to correlate the experimental data.