A Combined Electrochemical and Microstructural Analysis of Model AlMgSi(Cu) Alloys

Application prospects in automotive and aerospace industry have led to extensive studies on AA6xxx alloys in recent years because of their attractive combinations of properties. The benefits include formability, weldability, high strength to weight ratio and low cost. The main alloying elements in the commercial AA6xxx are Mg, Si, Fe and Cu. Mg and Si are usually used for strengthening purposes by precipitation hardening treatments at the expense of ductility. Cu is added to AlMgSi alloys to improve its ductility, for enhancement of the peak hardness and the precipitation hardening kinetics and furthermore it reduces the time to reach the peak hardness.Materials Science and EngineeringMechanical, Maritime and Materials Engineerin

Evacuation plan of the city of almere: Simulating the impact of driving behavior on evacuation clearance time

The evacuation clearance time is one of the key indicators in an evacuation plan and is determined by the expected behavior of the endangered residents and roadway network characteristics. The city of Almere has developed an evacuation plan in case of the emergency of a flooding, but assumes a normal driving behavior of the evacuees. In this paper a microscopic S-Paramics simulation framework in an evacuation condition is set up to assess the impact of variations in driving behavior on the evacuation clearance time. Different scenarios in terms of acceleration rate, maximum speed, mean headway and minimum gap distance have been developed. The results show that increases in acceleration rate and in maximum speed do not have a significant impact on the evacuation clearance time. It is also found that a reduction both in mean headway and in minimum gap significantly reduce the evacuation time. Therefore, it is very important to consider the driving behavior in an evacuation condition for an evacuation plan.Transport & PlanningCivil Engineering and Geoscience

Conventional and Pulse Cathodic Protection of Reinforced Concrete: Electrochemical Approach and Microstructural Investigations

Design and ConstructionCivil Engineering and Geoscience

Corrosion Performance of Carbon Steel in Simulated Pore Solution in the Presence of Micelles

This study presents the results on the investigation of the corrosion behavior of carbon steel in model alkaline medium in the presence of very low concentration of polymeric nanoaggregates [0.0024 wt % polyethylene oxide (PEO)113-b-PS70 micelles]. The steel electrodes were investigated in chloride free and chloride-containing cement extracts. The electrochemical measurements (electrochemical impedance spectroscopy and potentiodynamic polarization) indicate that the presence of micelles alters the composition of the surface layers (i.e., micelles were indeed absorbed to the steel surface) and influences the electrochemical behavior of the steel, i.e., the micelles lead to an initially increased corrosion resistance of the steel whereas no significant improvement was observed within longer immersion periods. Surface analysis, performed by environmental scanning electronic microscopy, energy-dispersive x-ray analysis, and x-ray photoelectron spectroscopy, supports and elucidates the corrosion performance. The product layers in the micelles-containing specimens are more homogenous and compact, presenting protective ?-Fe2O3 and/or Fe3O4, whereas the product layers in the micelles-free specimens exhibit mainly FeOOH, FeO, and FeCO3, which are prone to chloride attack. Therefore, the increased “barrier effects” along with the layers composition and altered surface morphology denote for the initially increased corrosion resistance of the steel in chloride-containing alkaline medium in the presence of micelles.Design and ConstructionCivil Engineering and Geoscience

Observations Of Suspended Particle Size Distribution On An Energetic Ebb-Tidal Delta

Sustainable management of barrier islands and tidal inlet systems requires a knowledge of sediment transport pathways throughout the system. This paper places in situ suspended sediment observations (obtained using a LISST) in context with seabed sediment samples and hydrodynamic measurements to identify such pathways. The results indicate two distinct populations of sediment in suspension on the ebb-tidal delta: locally resuspended fine sand and (largely flocculated) mud exported from the Wadden Sea on ebb tide. This reinforces the notion of the strong dependence of sediment pathways on particle size. Future work will combine additional lines of evidence to better distinguish suspended sand from sand-sized flocs and provide a more robust definition of these pathways.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Coastal EngineeringEnvironmental Fluid Mechanic

Electrochemical Measurements in Cement Extract Solutions on Reinforcing Steel, Previously Conditioned in Concrete

The corrosion behavior of reinforcing steel, previously embedded in concrete and maintained in conditions of corrosion and two regimes (conventional and pulse) of cathodic protection (CP), was characterized using electrochemical measurements in cement extract (CE) solutions of pH 12.6. The investigation aimed at determination of the properties of the product layers, previously formed on the steel surface. The study further allowed evaluation of the CP effectiveness in terms of steel surface oxidation/reduction behavior in the alkaline medium of CE. Based on the similar electrochemical behavior of protected specimens, it can be concluded that the pulse CP is as effective as the conventional CP regime. Moreover, the surface film, formed in pulse CP conditions appears to be more homogeneous and resistive, compared to the conventional CP regime.Delft University of Technolog

Drying Effects on Corrosion Properties of Cr(VI) and Cr(III) Treated Electrogalvanized Steel

Materials Science and EngineeringMechanical, Maritime and Materials Engineerin

Performance of the SRON Ti/Autransition edge sensor x-ray calorimeters

In the early 2030s, ESAs new X-ray observatory, Athena, is scheduled to be launched. It will carry two maininstruments, one of which is the X-ray Integral Field Unit (X-IFU), an X-ray imaging spectrometer, which will consist of an array of several thousand transition-edge sensors (TESs) with a proposed energy resolution of 2.5 eV for photon energies up to 7 keV. At SRON we develop the backup TES array based on Ti/Au bilayers with a transition temperature just below 100 mK. In this contribution we will give a broad overview of the properties and capabilities of these state-of-the-art detectors. Over the years we have fabricated and studied a large number of detectors with various geometries, providing us with a good understanding of how to precisely control the properties of our detectors. We are able to accurately vary the most important detector properties, such as the normal resistance, thermal conductance and critical temperature. This allows us to finely tune our detectors to meet the demands of various applications. The detectors have demonstrated excellent energy resolutions of below 1.8 eV for 5.9 keV X-rays. By tuning the properties of the devices, they can be optimally matched to various read-out schemes using both AC and DC biasing. The next step is to increase the size of our TES arrays from our current kilo-pixel arrays towards the full-sized array for X-IFU.Accepted Authors ManuscriptImPhys/Optic

Small Size Transition-Edge Sensors for Future X-Ray Applications

Large arrays of transition edge sensors (TESs) are the baseline for a number of future space observatories. For instance, the X-ray integral field unit (X-IFU) instrument on board the ATHENA space telescope will consist of ∼ 3000 TESs with high energy resolution (2eV at X-ray energies up to 7 keV). In this contribution we report on the development of an X-ray TES array as a backup detector technology for X-IFU. The baseline readout technology for this mission is time domain multiplexing where the detectors are DC biased. Specifically, we report on the characterization of four different Ti/Au TESs with the following dimensions (L × W): 30 × 15 , 30 × 30 , 50 × 25 and 50×50μm2, all of which are coupled to a 2.3μm thick Au absorber of area 240×240μm2. We have performed our characterization using our standard frequency domain multiplexing readout connecting only pixels at low frequencies, where nonlinear effects due to the AC biasing are negligible. Promising energy resolution has been obtained, for instance 1.78±0.10eV and 1.75±0.10eV at 5.9 keV for the 50 × 25 and 50×50μm2 detectors respectively. Uniformity over a kilo-pixel array (of detectors with the same geometry) has been also studied, confirming the high quality of our fabrication process.Funding Information: This work is funded by the European Space Agency (ESA) under ESA CTP Contract No. 4000130346/20/NL/BW/os. Publisher Copyright: © 2022, The Author(s).ImPhys/Optic

Impact of the Absorber-Coupling Design for Transition-Edge-Sensor X-Ray Calorimeters

Transition-edge sensors (TESs) are the selected technology for future spaceborne x-ray observatories, such as Athena, Lynx, and HUBS. These missions demand thousands of pixels to be operated simultaneously with high energy-resolving power. To reach these demanding requirements, every aspect of the TES design has to be optimized. Here we present the experimental results of tests on different devices where the coupling between the x-ray absorber and the TES is varied. In particular, we look at the effects of the diameter of the coupling stems and the distance between the stems and the TES bilayer. Based on measurements of the ac complex impedance and noise, we observe a reduction in the excess noise as the spacing between the absorber stem and the bilayer is decreased. We identify the origin of this excess noise to be internal thermal fluctuation noise between the absorber stem and the bilayer. In addition, we see an impact of the coupling on the superconducting transition in the appearance of kinks. Our observations show that these unwanted structures in the transition shape can be avoided with careful design of the coupling geometry. The stem diameter appears to have a significant effect on the smoothness of the TES transition. This observation is still poorly understood, but is of great importance for both ac and dc biased TESs.ImPhys/Optic