Functionalization of ethylene-propylene-diene terpolymer via the alder ene reaction

An ethylene-propylene-diene rubber (EPDM), containing 5 wt% 5-ethylidene-2-norbornene, was functionalized with maleic anhydride through the Alder Ene reaction at temperatures above 200°C in a co-rotating twin screw extruder. Characterization of the maleated product included FT-IR, ¹H and ¹³C NMR, and GPC. The degree of functionalization was determined by infrared analysis and by the mechanical properties of an ionic network formed by neutralizing the maleated rubber with zinc oxide. Increased temperature and maleic anhydride reactant concentration were found to improve the extent of reaction. Several Lewis acid species (SnCl₂?2H₂O, RuCl_n?xH₂O and AlCl₃) were tested as catalysts, and they were found to have a small effect on the degree of functionalization. This effect improved with reduced acid concentration. Among the Lewis acids examined, AlCl₃ gave rise to the greatest improvement of succinyl anhydride incorporation into the rubber.     

Integrative and multi-disciplinary framework for the 3D rehabilitation of large mandibular defects

The International Journal of Advanced Manufacturing Technology - The restoration of mandibular defects, especially large deformities is regarded as the most challenging surgical procedure owing to...     

Anodic oxidation of Ta/Fe alloys

The behaviour of iron during anodizing of sputter-deposited Ta/Fe alloys in ammonium pentaborate electrolyte has been examined by transmission electron microscopy, Rutherford backscattering spectroscopy, glow discharge optical emission spectroscopy and X-ray photoelectron spectroscopy. Anodic films on Ta/1.5 at.% Fe, Ta/3 at.% Fe and Ta/7 at.% Fe alloys are amorphous and featureless and develop at high current efficiency with respective formation ratios of 1.67, 1.60 and 1.55 nm V⁻¹. Anodic oxidation of the alloys proceeds without significant enrichment of iron in the alloy in the vicinity of the alloy/film interface and without oxygen generation during film growth, unlike the behaviour of Al/Fe alloys containing similar concentrations of iron. The higher migration rate of iron species relative to that of tantalum ions leads to the formation of an outer iron-rich layer at the film surface.     

Initial stages of plasma electrolytic oxidation of titanium

The initial stages of oxide growth on titanium are examined in a recently developed commercial alkaline pyrophosphate/aluminate electrolyte of interest for plasma electrolytic oxidation of light metal alloys. Constant current anodizing was employed, with resultant films examined by scanning and transmission electron microscopies and Rutherford backscattering spectroscopy. The initial film is relatively uniform and composed of TiO₂, with low concentrations of aluminium and phosphorus species incorporated from the electrolyte. With increase in voltage the film breaks down locally, and regions of original and modified film develop simultaneously, with the latter occupying more of the surface as the voltage rises. Porous regions due to dielectric breakdown also become increasingly evident. At 240 V, sparking commences, and the surface reveals extensive, relatively uniform porosity, with the coating now containing much enhanced concentrations of aluminium and phosphorus species compared with the coating at lower voltages. The films develop at low efficiency due to generation of oxygen. The oxygen is produced within the original film material and at sites of dielectric breakdown. The former type of film develops a two-layered morphology, with an outer layer of amorphous TiO₂ and an inner layer with numerous fine and course cavities. The cavities are due to the generation of oxygen that may be associated with the formation of anatase in the inner layer.     

Influence of current density on transport numbers in anodic oxide films on an anodized Al–5.7at.%W alloy

The ionic transport numbers in barrier anodic films, formed on an Al–5.7at.%W alloy in 0.1 M sodium tungstate electrolyte at 293 K, have been measured for current densities from 0.1 to 1000 mA cm⁻². For this purpose, a xenon marker was ion implanted with a fluence of 1.5 × 10¹⁵ ions cm⁻² into a film formed to 10 V on the alloy, which was then further anodized to 150 V. The position of the marker layer in the final film was determined by transmission electron microscopy and Rutherford backscattering spectroscopy. The cation transport number was 0.38, with no dependence upon current density to an accuracy of 10%.     

Grain orientation effects on copper enrichment and oxygen generation during anodizing of an Al-1at.%Cu alloy

Anodizing of solid-solution Al-1at.%Cu alloy in ammonium pentaborate electrolyte is shown to develop two distinct types of amorphous film. On alloy grains of {1 0 0} orientation, the alumina film is of uniform thickness and relatively featureless. For other grains, the film is of non-uniform thickness and contains oxygen bubbles. In both cases, copper species are distributed throughout the film. Copper is enriched in the alloy to ∼5.8×10¹⁵ Cu atoms cm⁻² for bubble-free grains, with similar or slightly lower levels for other grains. Evidently, copper enrichment alone does not lead to generation of oxygen. Other factors suggested to be involved, each dependent upon grain orientation, are the structure of the enriched alloy layer, the cyclic nature of the oxidation of copper, and the generation of modulated film compositions.     

Improvement of dielectric,optical, and photocatalytic properties of rare earth (Y) substituted Co−Mg nanoferrites

Journal of Materials Science: Materials in Electronics - The dielectric, optical and photocatalytic properties of yttrium (Y) substituted cobalt?magnesium (Co0.7Mg0.3YxFe2-xO4) (labeled as...     

Why security testing is hard

Software testing fairly readily detects a program's failure to do what it is designed to do, but does not detect all of the other things that it may do in the process. Some of these may compromise security. The article discusses the development of methods and software tools to deal with these bugs.     

Design and Power Optimization of High-Speed Pipeline ADC for Wideband CDMA Applications

This paper presents a 7-bit 64 MS/s pipeline A/D convertersuitable for wideband CDMA applications. Targeting atachieving low power dissipation at high speed, techniques suchas digital correction and optimal scaling of capacitor valuehave been employed. Switched-Opamp technique is used tofurther reduce power consumption. This ADC is implemented in0.5 m standard CMOS process. It operates from a single 3 V supply, and dissipates only 31 mW at 64 MS/s.