Optimization of Extrusion Parameters for Preparing PCL‐Layered Silicate Nanocomposites Supported by Modeling of Twin‐Screw Extrusion

PCL‐based nanoclay (layered silicate) nanocomposites are prepared using a small scale intermeshing co‐rotating twin‐screw extruder. Improving the level of nanoclay dispersion in PCL nanocomposites is obtained by changing the extrusion parameters. Increasing the screw speed and decreasing the throughput leads to an improved dispersion quality, as observed from the improved mechanical properties of the nanocomposites as well as from their clearly affected rheological and crystallization behavior. Furthermore, a commercially available software that simulates the twin‐screw extrusion process (LUDOVIC) is used to asses the processing parameters applied for making the nanocomposites.

     

Long-term Hot Corrosion Behavior of Boiler Tube Alloys in Waste-to-Energy Plants

Accelerated corrosion of candidate alloys was induced by metal chlorides/sulfates at 500 °C. Results suggest that the corrosivity of the studied metal chlorides increases in the order CaCl₂ < NaCl < KCl < ZnCl₂ < PbCl₂ < FeCl₂. Mechanisms to explain the different impacts of chlorides were proposed. It is believed that materials exposed to chloride salts corrode through vicious cycles, in which a shorter path of the cycle leads to a higher corrosion rate. Experimental results confirmed that FeCl₂ with the shortest path of the corresponding vicious cycle has the highest corrosion rate. It is also confirmed that the sulfates of Zn and Pb are less corrosive than their chlorides for the alloys tested. A kinetic study on the hot corrosion of T22, Esshete 1250 and Sanicro 28 was carried out under simulated waste-to-energy (WTE) ashes at 500 °C for 1000 h. Results from the kinetic study show that T22, Esshete 1250, and Sanicro 28 exhibited comparable performance for short-term exposure; however, the degradation thickness presented a clear trend after the 1000-h exposures in terms of decreasing resistance to corrosion: T22 > Esshete 1250 > Sanicro 28. EDX maps confirmed the role of Ni/Cr for slowing the corrosion kinetics of these three alloys.     

Chip Formation in Micro-cutting

The miniaturisation context leads to the rise of micro-machining processes. Micro-milling is one of the most flexible and fast of them. Although it is based on the same principles as macro-cutting, it is not a simple scaling-down of it. This down-sizing involves new phenomena in the chip formation, such as the minimum chip thickness below which no chip is formed. This paper presents a review of the current state of the art in this field from an experimental and a numerical point of view. A 2D finite element model is then developed to study the influence of the depth of cut on the chip formation. After the model validation in macro-cutting, it highlights the phenomena reported in literature and allows to perform a minimum chip thickness estimation.     

Technical and business considerations of cobalt hydrometallurgy

Approximately 55,000 tonnes of cobalt are produced annually worldwide, which represents an estimated $1–3 billion in annual sales depending on cobalt price changes. Cobalt is a common impurity in both non-ferrous mineral sulfide and oxide processing. In this paper some business and technical considerations are presented to facilitate the decision-making process required to produce either an intermediate or a finished cobalt product via a hydrometallurgical route. Methods currently available and practiced for the recovery of cobalt are considered, and process requirements up- and down-stream associated with each chosen method are discussed. In particular, some environmental, energy, or other sustainable development implications of each process are mentioned. An outlook on the future of the cobalt industry and anticipated future trends is included.     

Segmentation of rodent whole-body dynamic PET images: an unsupervised method based on voxel dynamics

Positron emission tomography (PET) is a useful tool for pharmacokinetics studies in rodents during the preclinical phase of drug and tracer development. However, rodent organs are small as compared to the scanner's intrinsic resolution and are affected by physiological movements. We present a new method for the segmentation of rodent whole-body PET images that takes these two difficulties into account by estimating the pharmacokinetics far from organ borders. The segmentation method proved efficient on whole-body numerical rat phantom simulations, including 3-14 organs, together with physiological movements (heart beating, breathing, and bladder filling). The method was resistant to spillover and physiological movements, while other methods failed to obtain a correct segmentation. The radioactivity concentrations calculated with this method also showed an excellent correlation with the manual delineation of organs in a large set of preclinical images. In addition, it was faster, detected more organs, and extracted organs' mean time activity curves with a better confidence on the measure than manual delineation.     

Catalytic combustion of methane on aluminate-supported copper oxide

Copper oxide has been deposited onto high surface area magnesium aluminate spinel prepared from alumina and magnesium nitrate. The catalytic properties of such a solid have been investigated in methane combustion. At the laboratory scale a very good activity is observed (light-off of 530°C) and no CO is detected. Aging at 1000°C under water vapour has no influence on activity. The previous catalyst has been washcoated on monolith and tested on a rig either with methane or synthetic natural gas at very high GHSV under conditions close to those of a gas turbine. In that case also, a good activity was observed.     

In-depth study of the Ruddlesden-Popper LaxSr2−xMnO4±δ family as possible electrode materials for symmetrical SOFC

The Ruddlesden Popper (RP) manganites La_xSr_2?xMnO_4±δ with compositions 0.25 ≤ x ≤ 0.6 have been successfully synthesized as single phases by solid-state reaction in air. All those materials are not only stable in reducing atmosphere but they also maintain the K₂NiF₄-type structure with I4/mmm symmetry under redox cycling conditions with limited volume changes. The x = 0.5 phase was analyzed by in situ high temperature neutron powder diffraction (HTNPD), under flowing hydrogen, showing the formation of oxide-ion vacancies on the equatorial sites of the perovskite planes, during reduction process. The total electrical conductivity was optimized and found maximum for x = 0.5 with values of 35.6 S cm^?1 and 1.9 S cm^?1 at 800 °C in air and 3% H₂/Ar, respectively, what is judged to be sufficient for an active layer of symmetrical SOFC electrode. First Electrochemical Impedance Spectroscopy (EIS) measurements in both oxidizing and reducing conditions, using an YSZ electrolyte and a GDC buffer layer, are presented giving rise to promising values.     

Steady state analysis of free or forced oscillators by harmonic balance and stability investigation of periodic and quasi-periodic regimes

This article presents a practical and effective method to analyze the steady state regimes, periodic or quasi-periodic, and the stability of free and forced oscillators, based on the use of voltage and current probes. The efficiency of this method comes from the fact that it converts the analysis of an autonomous circuit into the analysis of a series of closely related nonautonomous circuits, which in turn relies on the power of the harmonic balance equation for these kinds of systems. The effectiveness of the method is shown by full analysis of a practical example.