The Future Circular Collider FCC-ee is a study toward a high luminosity electron-positron collider with a centre-of-mass energy from 91 GeV to 365 GeV. Due to the beam parameters and pipe dimensions, collective effects and electron cloud can be very critical aspects for the machine and can represent the main limitations to its performance. An estimation of the electron cloud build up in the main machine components and an impedance model are required to analyze the induced instabilities and to find solutions for their mitigation. Special attention has been given to the resistive wall impedance associated with a layer of nonevaporable getter (NEG) coating on the vacuum chamber required for electron cloud mitigation. The studies presented in this paper will show that minimizing the thickness of this coating layer is mandatory to increase the single bunch instability thresholds in the proposed lepton collider at 45.6 GeV. For this reason, NEG thin films with thicknesses below 250 nm have been investigated by means of numerical simulations to minimize the resistive wall impedance. In parallel, an extensive measurement campaign was performed at CERN to characterize these thin films, with the purpose of finding the minimum effective thickness satisfying vacuum and electron cloud requirements.
Vanadium oxide microcrystallites are electrodeposited at room temperature. The effect of the deposition current density on the structural, morphological and electrochemical properties of the coatings is studied. The electrochemical activity of the material is found to improve with the deposition current density utilized during electrodeposition. At the highest deposition current values, marked amounts of lithium charge are observed to interchange with the material owing to the increased coverage of its structure. The highest specific capacitance of 145 F g −1 measured in 1 M LiClO 4 is comparable to previously reported values using different electrolytes such as NaCl, LiCl and KCl.
The turn to language in social psychology is closely related to the study of prejudice as racist discourse has been the subject matter of some of the ground‐breaking discourse analytic work. A widely accepted argument was that there seems to be a norm against prejudice informing Western societies: people commonly engage in denials of prejudice when they make negative comments about minorities. Recent work has argued that, due to ideological shifts in the wider societal context or because denying prejudice may not be people's only rhetorical concern, it is possible to find people admitting prejudice. We examine how people in Greece, Greek majority and immigrants, formulate admissions of racism in interviews on migration and citizenship in Greece. Drawing on Ideological Dilemmas and Critical Discursive Social Psychology, we argue that these admissions ironically operate within the norm against prejudice and discuss our findings in relation to the wider socio‐political Greek context.
Amorphous vanadium pentoxide coatings were electrodeposited at room temperature on ITO glass substrates using a solution of vanadyl (IV) acetylacetonate in methanol. The electrochemical performance of the coatings as a function of deposition current density was studied using a classical three-electrode potentiostatic cell system and a solution of 1 M LiClO 4 in polypropylene carbonate as an electrolyte. The sample grown using deposition current density of 1 mA cm −2 was found to exhibit the best electrochemical activity in terms of the fastest bleaching kinetics and the highest charge storage due to the increased roughness of the structure.Vanadium pentoxide has attracted a considerable interest for its potential application in lithium-ion batteries and electrochromics. 1-3 In both applications, lithium ion insertion into vanadium oxide follows the reactionHowever, the charge capacity and charging-discharging response are limited by the low diffusion coefficient of Li ions in the V 2 O 5 matrix. 4,5 Improvements have been demonstrated by porous materials because they provide high surface area resulting in a higher charge capacity and a very short diffusion path for lithium ions allowing rapid charging-discharging response. 6,7 Physical and chemical methods have been used for the fabrication of vanadium oxides including sputtering, 8,9 pulsed laser deposition, 10,11 chemical vapor deposition, 12-14 sol-gel, 15 hydrothermal growth 16 and electrodeposition. 17 Among these, electrodeposition has many advantages over the other methods in terms of economical and environmental benefits since low temperatures are employed and no toxic chemicals are required. In addition, the morphological and structural characteristics of the final products can be simply controlled by varying the deposition current density, deposition voltage, electrolyte's properties and deposition time. 18 In this work, electrodeposition was used to fabricate vanadium oxide coatings at room temperature. The effect of deposition current density on the morphological and electrochemical performance of the oxides was investigated. ExperimentalA three-electrode electrochemical cell was utilized for the deposition of vanadium oxide coatings. Platinum, Ag/AgCl and ITO glass substrates were used as the counter, reference and working electrodes respectively. The electrolyte was a 0.04 M green solution of vanadyl acetylacetonate (VO(acac) 2 ) in methanol (CH 3 OH). Prior to electrodeposition, indium tin oxide (ITO) glass substrates were ultrasonically cleaned with 2-propanol, acetone, MilliQ H 2 O and dried with N 2 . The deposition of the oxides was carried out using deposition current densities of 0.5, 0.7 and 1 mA cm −2 for constant deposition time of 120 min. Finally, each freshly deposited sample was dried in air at room temperature. z E-mail: dimitra@iesl.forth.gr X-ray diffraction (XRD) measurements were performed using a Siemens D5000 Diffractometer for 2θ = 10.0-60.0 degs. Raman measurements were performed in a Nicolet Almega XR micro-Raman system using...
Lithium-ion batteries have numerous advantages, including excellent energy density with high stability. One of the limitations regards the preparation of anode materials at low cost and high safety with good performance. Over the past decade, research has been focused on their improvement as composites, taking advantage of the synergistic effects between the materials. The object of this mini review is to summarize the synthetic strategies of composite electrodes based on graphene that are utilized for lithium-ion chemistries. Emphasis will be given on chemical vapor deposition and how this route can overcome the electrode issues for large-scale deployment.
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