Microstructural Characterization of Cofired Tungsten-Metallized High-Alumina Electronic Substrates

Microstructural characterization of a high-Al₂O₃ substrate containing cofired thick-film tungsten metallization, with particular emphasis on the metal/ceramic interface, was conducted. The substrate contained tabular Al₂O₃ grains surrounded by a continuous calcium magnesium aluminum silicate glass containing particles of monoclinic ZrO₂ and reduced rutile (TiO_{2- x} ). The metal/ceramic adhesion was caused by mechanical interlocking between the W and Al₂O₃ grains by the glass phase which penetrated the porous W layers during sintering; there was no interfacial reaction or diffusion zone. The mechanical properties of the W metallization did not limit interfacial strength. Heat treatments of the substrate at 1400 K in air and under vacuum resulted in the devitrification of the intergranular glass. The most abundant devitrification product was anorthite (CaAl₂Si₂O₈), accompanied by magnesium aluminate titanate, magnesium aluminate spinel, α-cristobalite (SiO₂), and α-cordierite (Mg₂Al₄Si₅O₁₈). In addition, small rutile particles precipitated within the Al₂O₃ grains.     

Wood‐Plastic‐Composites: Rheologische Charakterisierung und Füllverhalten im Spritzgießprozess

Wood‐plastic composites (WPC) show a complex and completely different material and flow behavior in comparison to pure polymers. Especially the flow behavior is very important for the processing of these composites. In the following article results of rheological characterization and investigations of the filling behavior during the injection molding process are presented. Furthermore, appearing challenges and possible methods of resolution are discussed.     

Regularity of nanopores in anodic alumina formed on orientated aluminium single-crystals

On aluminium single crystals with (1 1 1), (1 1 0) and (1 0 0) orientation, nanoporous alumina layers were formed in a two-step anodization process within sulphuric acid. The pore ordering within the hexagonal arrangement of the nanopores was documented by scanning electron microscopy (SEM), described on the basis of defect thermology and analyzed quantitatively by image evaluation. The best ordering was obtained in nanoporous alumina on (1 0 0) aluminium. We supposed that this is caused by the interface energy term within the driving force for the formation of the nanoporous alumina, since – in contrast to (1 1 1) and (1 1 0) aluminium as substrate – in the case of (1 0 0) aluminium the interface energy is minimised in the waved interface between aluminium and hexagonally arranged nanoporous alumina.     

Water quality and taste sensitivity for basic tastes and metallic sensation

The aim of the study was to investigate the influence of water quality on taste sensitivity for basic tastes and metallic sensation. To familiarize subjects with sensory analysis, they were asked to recognize tastes, distinguish between different concentrations of basic tastes, and realize their own taste sensitivity. The International Standard ISO 3972 describes a set of tests to measure taste sensitivity. A “neutral, tasteless, still and odourless water, preferably of known hardness” is recommended for preparing the dilutions and for rinsing the mouth. The standard also recommends a series of dilutions for acid (citric acid), bitter (caffeine), salty (sodium chloride), sweet (sucrose), umami (monosodium glutamate) and metallic (iron(II)sulfate). The question arises if water quality affects taste sensitivity.MethodsTwenty-three female subjects (mean age: 22), who were recruited at the University of Applied Sciences Hamburg, Faculty of Life Sciences, were tested. Deionized water, spring water and tap water were used for taste dilutions. In each experiment, subjects were initially familiarized with the basic tastes.ResultsIn comparison to taste thresholds in spring water, the recognition thresholds are higher using tap water, and lower using deionized water. When using deionized water, sour was detected by all subjects at the lowest concentrations. Iron(II)sulfate could best be matched to metallic sensation in deionized water. Results indicate that taste sensitivity is influenced by water quality.     

Thermally Activated Martensitic Transformations in Mg-PSZ

The thermally activated, stress-assisted martensitic tetragonal → monoclinic ( t → m ) and tetragonal → orthorhombic ( t → o ) transformations in a high-toughness Mg-PSZ were investigated by monitoring the phase assemblage with Raman spectroscopy after a variety of heat treatments and loading conditions. After a short anneal at 1000°C, which transforms m - and o -ZrO₂ to the t polymorph, isothermal t → m and t → o transformations occur at room temperature during the months following the anneal. The transformation rates in the annealed samples are greatly enhanced under external stress. Alternatively, samples containing regions of significant residual stress, introduced by indentation for example, and then annealed at relatively low temperatures, underwent additional thermally activated transformation in the stressed regions. The thermodynamics and kinetics of this complex transformation "plasticity," and its effect on mechanical properties, are discussed.     

Aging of anhydride‐hardened epoxies in lubricants at elevated temperatures

In automotive under‐the‐hood applications, electronics respectively their packaging materials come in contact with automotive fluids. The effect of automatic transmission fluid (ATF) on an anhydride‐cured epoxy was investigated at temperatures up to 180 °C for up to 1000 h. This study has shown that ATF retards the oxidative aging of the epoxy, presumably due to oxygen consumption. Whereas in air the material underwent a thermo‐oxidative aging with a mass loss of up to 4% and a strong broadening of T_g to higher temperatures, in ATF a temperature dependent distinctive drop of T_g from 142 to 126 °C after 1000 h aging at 180 °C, and a mass loss of maximum 1% was observed which might be a thermal decomposition of the epoxy material. A slight broadening of the damping factors might indicate an intrusion of ATF components. A color change of the samples could be observed after aging in air and ATF, with the discoloration in air being more intense. An explanation for the color change might be either a minor amount of oxygen causing an oxidative discoloration reaction or the intrusion of colored ATF degradation products. While the oxidation‐kinetics in air exhibited Arrhenius temperature‐dependence the mechanism in ATF changed above 165 °C. An acceleration of aging tests at temperatures beyond 150 °C is, therefore, not possible. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44877.     

Burn Rate Models for Gun Propellants

In the past, Vieille's law and minor modifications of it described sufficiently the linear burning rate of gun propellants which governs the design of charges by interior ballistic simulations. Recent developments to increase the performance led to new gun concepts and innovative propellants. These are the electrothermal‐chemical gun, porous and foamed charges as well as formulations exhibiting a temperature independent burning. Vieille's law cannot fully meet experimental results in these cases. Approaches based on the heat flow equation in the solid energetic material give simplified formulas to extend the validity. These burning rate models have the ability to describe the experimentally determined burning behavior at least in a simplified or qualitative way. More sophisticated methods consider complex geometrical structures in the solid or take into account the actual progress in phase behavior and reaction kinetics of heterogeneous combustion. The dependence of the burning rate on initial temperature, on phase transitions, porous structure and gaseous reactions can be described.     

Distribution of atmospheric SF6 near a large urban area as recorded in the vadose zone

Local emissions of SF6 are of interest for studying their impact on the use of SF6 as a groundwater-dating tool near source regions as well as for investigating the spatial distributions of (inert) gaseous compounds spreading from urban or industrial centers. A precondition for the use of SF6 in such studies is the capability to document the temporal and spatial evolution of SF6 in and around source regions with sufficient resolution. Here we present a time series of SF6 measurements in soil air at a site (Sparkill, NY) about 25 km north of New York City carried out between May 2000 and January 2002. The data show that, below about 2 m depth, the vadose zone integrates atmospheric SF6 mixing ratios over time scales greater than 1 month. SF6 mixing ratios in soil air at these depths match averaged high-resolution atmospheric measurements performed at Lamont-Doherty Earth Observatory in Palisades, NY, located about 3 km south of Sparkill. To a first-order approximation, a simple one-dimensional diffusion model reproduces the measured SF6 profiles in the vadose zone, suggesting that the soil indeed acts as a low-pass filter for inert atmospheric gases. These findings indicate that measurements of soil air can be used to determine the spatial pattern of SF6 excess relative to the remote atmosphere for a given region. A transect of soil profiles from Manhattan to the tip of Long Island indicates that emissions from sites close to New York City lead to significant SF6 excesses (ca. 25% or more) above the clean air mixing ratios over distances of the order of 80 km.     

Die faktische Kraft des Normativen

Ohne Zusammenfassung     

Residual analysis for ARCH(p)-time series

In this paper we provide consistency and distributional convergence results for functions of residuals from an ARCH(p)-time series. An application to a goodness-of-fit problem is also discussed.