Tribofilm formation from TiC and nanocomposite TiAlC coatings,studied with focused ion beam and transmission electron microscopy

This work demonstrate how two different carbide coatings respond very differently to tribological stress and their very different ability to provide low friction tribofilms in dry sliding against steel. Both coatings, TiC and TiAlC, were deposited by DC-magnetron sputtering, but while the TiC is a thermodynamically stable coating, the TiAlC is made metastable with the addition of Al, and therefore releases carbon upon tribological testing. Thus, the TiAlC coating is shown to be self-lubricating on the atomic scale which makes very low friction achievable. The primary interest in this study is the differences in the tribofilms formed on the steel balls that have been sliding against the two coatings. Cross-section samples for transmission electron microscopy were extracted from the ball tribofilms using a focused ion beam instrument. X-ray photoelectron spectroscopy and Raman analysis were employed to provide information on the chemical and structural characteristics of the tribofilms. It was shown that tribofilms on steel balls largely inherit the structure and composition that evolve in the coating wear tracks, that the tribofilm microstructure greatly affects the friction level. It was also shown that tribofilm delamination, occurring with tribofilm growth, was initiated in weak ribbon like regions inside the tribofilm.     

Experimental investigation of surface crack initiation, propagation and tension stiffening in self-compacting steel–fibre-reinforced concrete

To investigate crack initiation and propagation in reinforced, self-compacting, steel?Cfibre-reinforced concrete (SCSFRC) members, tie elements were tested in tension. Strain and surface crack formation were monitored with an optical strain measurement system based on digital image correlation. In addition, to capture the softening behaviour (???Cw) of the material, uni-axial tension testing was performed on SCSFRC cylinders. The results show that, with the optical strain measurement system, it was possible to detect different cracking modes and to follow the crack growth. It was especially of interest to recognize that high fibre amounts tend to change a sudden opening of a crack (as in non-fibrous concrete) into a more stable procedure. It was found that, for a given crack width, the SCSFRC specimens exhibited a noticeably higher tension stiffening than the specimens without fibres. Moreover, at a given load, the crack widths decreased by as much as 65% for the SCSFRC specimens with a nominal fibre content of 1%. For the uni-axial tension tests the results showed that with higher fibre content, for this type of fibre and concrete, both the peak stress and the residual tensile stress were increased. Additionally, it was noted for both specimen types that the scatter in fibre distribution decreased with increasing fibre content.     

Long-term performance assessment of the Telegraph Road Bridge using a permanent wireless monitoring system and automated statistical process control analytics

The purpose of this study is to advance wireless sensing technology for permanent installation in operational highway bridges for long-term automated health assessment. The work advances the design of a solar-powered wireless sensor network architecture that can be permanently deployed in harsh winter climates where limited solar energy and cold temperatures are normal operational conditions. To demonstrate the performance of the solar-powered wireless sensor network, it is installed on the multi-steel girder bridge carrying northbound I-275 traffic over Telegraph Road (Monroe, Michigan) in 2011; a unique design feature of the bridge is the use of pin and hanger connections to support the bridge main span. A dense network of strain gauges, accelerometers and thermometers are installed to acquire bridge responses of interest to the bridge manager including responses that would be affected by long-term bridge deterioration. The wireless monitoring system collects sensor data on a daily schedule and communicates the data to the Internet where it is stored in a curated data repository. Bridge response data in the repository are autonomously processed to extract truck load events using machine learning, compensate for environmental variations using nonlinear regression and to quantitatively assess anomalous bridge performance using statistical process control.     

Beurteilung von Korrosionsschutzsystemen für Offshore‐Windenergietürme – Teil 1: Problemstellung und Versuchsdurchführung

Assessment of corrosion protection systems for offshore wind energy towers – part 1: Introduction and test scenario. Based on field and on laboratory tests, the corrosion protective performance of different corrosion protection systems for offshore wind energy towers was investigated. The systems under investigation included duplex systems with Zn/Al metallization, multi‐layered organic systems, a single‐layer thick organic system, Zn/Mg metallization and cathodic protection of uncoated sections. Special field specimens and laboratory specimens were utilized in order to investigate the systems. Laboratory tests included immersion tests, ageing tests, test on cathodic compatibility and electro‐chemical impedance spectroscopy. Part 1 of the paper covers the general experimental design and details of the experimental procedures, whereas Part 2 deals with the results of the test programme.     

Herd-level risk factors associated with cow mortality in Swedish dairy herds

An increase in on-farm mortality (euthanasia and death) in dairy herds has been reported in several countries in the last decade. This does not only imply possible problems with animal welfare, but it also causes economic losses to the farmer. The objective of this study was to evaluate time trends in on-farm dairy cow mortality in Sweden and identify potential herd-level risk factors. Data were retrieved on all Swedish dairy herds enrolled in the milk recording scheme between 2002 and 2010. Herds with a herd size of <20 cows or a mortality rate (MR) of >40 dead or euthanized cows per 100 cow-years were excluded. Two different models were used: 1 multiple-year analysis, which included 6,898 herds during the period 2002 to 2010 and 1 single-year analysis including 4,252 herds for the year 2010, where other variables that were not present during the entire multiple year study were analyzed. The outcome variable was the number of euthanized and dead cows per year and season. A negative binomial regression model, adjusted for clustering within herd, was applied to both models. Fixed effects in the multiple-year analysis were breed, calving interval, herd size, milk yield, region, season, pasture period, and year. The fixed effects in the single-year analysis were breed, calving interval, conventional versus organic farming, herd size, housing system, milk yield, region, and season. The results demonstrated that MR gradually increased from 5.1 to 6.6 events per 100 cow-years during the study period. Swedish MR are consequently on par with, or even greater than, MR among dairy herds in other comparable countries. Higher mortality was associated with larger herd size, longer calving intervals, and herds that had Swedish Holstein as the predominant breed. Lower mortality was observed in herds with a higher herd average milk yield, during the fall and winter, and in organically managed herds. There were regional differences in mortality. An interaction between herd size and season was found in both models. Also, an interaction between housing system and milk yield was found in the single-year analysis. This first assessment of on-farm mortality in Swedish dairy herds confirmed that the MR has increased over the last few years. The study also identified some herd-level risk factors.     

Arctic vegetation damage by winter-generated coal mining pollution released upon thawing

Acid mine drainage (known as AMD) is a well-known environmental problem resulting from the oxidation of sulfidic mine waste. In cold regions, AMD is often considered limited by low temperatures most of the year and observed environmental impact is related to pollution generated during the warm summer period. Here we show that heat generation within an oxidizing, sulfidic, coal-mining waste-rock pile in Svalbard (78 degrees N) is high enough to keep the pile warm (roughly 5 degrees C throughout the year) despite mean annual air temperatures below -5 degrees C. Consequently, weathering processes continue year-round within the waste-rock pile. During the winter, weathering products accumulate within the pile because of a frozen outer layer on the pile and are released as a flush within 2 weeks of soil thawing in the spring. Consequently, spring runoff water contains elevated concentrations of metals. Several of these metals are taken up and accumulated in plants where they reach phytotoxic levels, including aluminum and manganese. Laboratory experiments document that uptake of Al and Mn in native plant species is highly correlated with dissolved concentrations. Therefore, future remedial actions to control the adverse environmental impacts of cold region coal-mining need to pay more attention to winter processes including AMD generation and accumulation of weathering products.     

Structural,mechanical and electrical-contact properties of nanocrystalline-NbC/amorphous-C coatings deposited by magnetron sputtering

Niobium-carbide nanocomposite coatings with a carbon content varying from 43 to 64 at.% were deposited by dual DC magnetron sputtering. X-ray diffraction, x-ray photoelectron spectroscopy and electron microscopy showed that all coatings consisted of nanometer sized NbC grains embedded in a matrix of amorphous carbon. Mechanical properties and electrical resistivity showed a strong dependency on the amount of amorphous carbon (a-C) and NbC grain size in the coating. The highest hardness (23 GPa), elastic modulus (295 GPa) and the lowest resistivity (260 μΩ cm) were measured for the coating with about 15% of a-C phase. Contact resistance measurements using a crossed cylinder set-up showed lowest contact resistance for the coating containing 33% a-C (140 μΩ at a contact force of 100 N), which is comparable to a Ag reference (45 μΩ at a contact force of 100 N). Comparison with TiC-based nanocomposites studied under similar conditions showed that the NbC system has less tendency to form a-C and that lowest contact resistance is obtained at comparable amounts of a-C phase in both material systems (33% for NbC compared to 35% for TiC). With these good electrical contact properties, the NbC nanocomposites can be considered as a potential material for electrical contact applications.     

Modification of wool fibers by atmospheric pressure plasma treatment

Shrink‐proofing processing of wool fabrics by vacuum plasma treatment has been studied for many years. However, as a wool shrink‐proofing processing method, discharge treatment under atmospheric pressure, such as corona and low‐temperature electric plasma treatment, has been studied recently. In this study, an attempt was made to improve shrink‐proofing and other properties of a wool fabric by low‐temperature plasma treatment. The wool fabric was treated by pulsed atmospheric pressure plasma using a dielectric barrier discharge apparatus of the Institute of Textile Technology at Denkendorf by varying the power and flow rate of air. Shrink‐proofing, dyeing yield and water‐absorbing properties increased to a greater degree with the increase in the treatment time. However, the effect was saturated at 3 min. On the other hand, hysteresis of shearing property at large shear angle (2HG5), which is one of the mechanical parameters for measuring fabric hand by the Kawabata evaluation system (KES), becomes larger with the treatment time. It can be concluded that shear hysteresis value is related to the improvement in shrink‐proofing and other properties of the wool fabric.     

The influence of nitrate on the physiology of the yeast Dekkera bruxellensis grown under oxygen limitation

A previous study showed that the use of nitrate by Dekkera bruxellensis might be an advantageous trait when ammonium is limited in sugarcane substrate for ethanol fermentation. The aim of the present work was to evaluate the influence of nitrate on the yeast physiology during cell growth in different carbon sources under oxygen limitation. If nitrate was the sole source of nitrogen, D. bruxellensis cells presented slower growth, diminished sugar consumption and growth‐associated ethanol production, when compared to ammonium. These results were corroborated by the increased expression of genes involved in the pentose phosphate (PP) pathway, the tricarboxylic acid (TCA) cycle and ATP synthesis. The presence of ammonium in the mixed medium restored most parameters to the standard conditions. This work may open up a line of investigation to establish the connection between nitrate assimilation and energetic metabolism in D. bruxellensis and their influence on its fermentative capacity in oxygen‐limited or oxygen‐depleted conditions. Copyright © 2013 John Wiley & Sons, Ltd.     

Exhaust Gas Catalysts for Heavy-Duty Applications: Influence of the Pd Particle Size and Particle Size Distribution on the Combustion of Natural Gas and Biogas

In this study, an experimental investigation concerning exhaust gas catalysts for heavy-duty diesel engines fuelled by natural gas or biogas is presented. Miniature monoliths, 2.5 wt% Pd/Al₂O₃, have been prepared, characterised and tested. Various methods have been used in order to obtain different palladium particle sizes, including incipient wetness and microemulsion technique. Crystallite sizes between 2 and 40 nm were obtained. We observed that the metal particle size influences the activity for methane oxidation. Moreover, the homogeneity of the active material was found to affect the reaction rate.