Porosity in composite zirfon® membranes

The composite Zirfon® membranes are made of a polysulfone network and zirconium oxide as an inorganic filler. These composite membranes are actually being used for a variety of ultrafiltration purposes and as separator material in different types of electrochemical cells.The main techniques which have been used for the characterization of the porous structure of these membranes are mercury intrusion porosimetry, scanning electron microscopy (SEM) and gas adsorption.As a major result it has been observed that the amount of ZrO₂ which is present in the membrane plays a dominant role: the structure of a composite Zirfon© membrane is completely different from the structure of a pure polysulfone membrane. The membrane becomes denser with increasing amounts of ZrO₂. There is also a strong indication that ink-bottle shaped pores are present and that their volume reduces with increasing amounts of ZrO₂.     

Applications of antioxidants in physiologically functional foods: Safety aspects

Intense public and scientific debate exists over whether the intake of some nutrients above the recommended dietary allowances may provide benefits beyond their traditional functions. However, excessive intakes of nutrients are well documented to cause adverse effects. This review focuses on methods that may be useful for identifying chronic intakes that result in adverse effects and for identifying intakes that provide a reasonable margin of safety from these effects. Groups responsible for nutrition and health policy must establish effective criteria for establishing safety limits, for validating end points, and determination of data acceptability. These criteria are needed to minimize toxicity while maximizing potential health benefits of exaggerated nutrient intake.     

Producing thin strips by twin-roll casting—part II: Process modeling and development

Extensive modeling work has appeared over the last decade and has contributed significantly to the fundamental understanding of the physical phenomena involved in twin-roll casting, such as fluid flow, heat transfer, and thermomechanical processing. The commitment of metals producers to the technology is strong, which is evidenced by numerous pilot-scale casters that have been constructed worldwide. Together with the process models, these casters have been instrumental in developing new process designs and in improving and optimizing the performance of existing twin-roll casters. Current R&D efforts are intensive in both the aluminum and the steel industries, with the former aiming to gain a higher productivity and the latter striving to scale up from pilot plants to commercial production.     

Enhancing the mechanical properties of titanium alloys with rapid heat treatment

This article shows that a significant improvement in the mechanical properties of high-strength titanium alloys can be reached by using a special heat treatment based on rapid heating into the β-field. Such a treatment allows the production of a high-temperature β-phase with a fine-grained microstructure and optimal chemical inhomogeneity, which strongly determines the mechanism and kinetics of phase transformations on cooling and further annealing or aging. A wide range of final microstructures with an enhanced combination of mechanical properties can be obtained.     

An optical roughness sensor for real-time quality measurement

As part of the intelligent processing efforts of the Spray Forming Technology Group at the David Taylor Research Center, a laser stripe sensor has been implemented to monitor preform characteristics. The preform surface roughness is measured in real time and the correlation to preform quality in terms of porosity levels is assessed. The laser stripe method is not a direct indicator of quality, but it can be used with other sensors and advanced control techniques for control of the spray-forming process.     

Ion mobility in Nafion-117 membranes

Transport phenomena in Nafion-117 perfluorosulphonic membranes have been studied by different techniques. Membrane electric conductivity has been measured under alternative current as a function of the equilibrating concentrations of MCI (M = Li, Na, K) and HCl solutions. Conductivities were found to increase for lithium and sodium membrane forms and decrease for the potassium form with an electrolyte concentration increase. The obtained data were compared with the results of diffusion permeability, ion-exchange kinetics, ⁷Li and ³⁵Cl NMR measurements. In all cases permeability increased with electrolyte concentration growth. Diffusion coefficients and transport numbers for different counter- and co-ions were determined. The obtained data are discussed with the use of the two-phase membrane structure model. The selectivity of membrane sorption was found to increase with growth of cation radius.     

Laser remelting of cast iron: a Mössbauer study

The Mössbauer spectroscopy in backscattering technique (CXMS) was used to analyse cw-CO₂ laser-treated samples of cast iron. The depth profile as revealed by Mössbauer phase analysis is discussed in connection with the initial microstructure.