Search results for "High temperature"
showing 10 items of 36 documents
Study of a chromia-forming alloy behavior as interconnect material for High Temperature Vapor Electrolysis
2011
In High Temperature Vapor Electrolysis (HTVE) system, the materials chosen for the interconnectors should have a good corrosion behaviour in air and in H2-H2O mixtures at 800°C, and keep a high electronic conductivity over long durations as well. In this context, the first goal of this study was to evaluate a commercial ferritic alloy (the K41X alloy) as interconnect for HTVE application. Oxidation tests in furnace and in microbalance have therefore been carried out in order to determine oxidation kinetics. Meanwhile, the Area Specific Resistance (ASR) was evaluated by Contact Resistance measurements performed at 800°C. The second objective was to improve our comprehension of chromia-formin…
Additive manufacturing, new elaboration technique of metallic materials : impact of the microstructure on high temperature durability of AISI 316L st…
2021
Additive Manufacturing (AM) processes are able to elaborate, in a single step, metallic parts with very complex geometry, as close as possible to their final dimensions, based on 3D CAD model. Despite a very large number of studies on AM parameters, very few studies report on the high temperature behavior of the metallic materials produced by these processes. This thesis work evaluates the impact of the Selective Laser Melting (SLM) process on the high temperature durability of the austenitic stainless steel AISI 316L, commercial grade widely used in the industry. For this purpose, the reactivity of SLM samples was studied in different conditions (atmosphere, temperature, isothermal or cycl…
Effect of coatings on long term behaviour of a commercial stainless steel for solid oxide electrolyser cell interconnect application in H2 /H2O atmos…
2014
Abstract K41X (AISI 441) stainless steel evidenced a high electrical conductivity after 3000 h ageing in H 2 /H 2 O side when used as interconnect for solid oxide electrolyser cells (SOEC) working at 800 °C. Perovskite (La 1 − x Sr x MnO 3 − δ ) and spinel (Co 3 O 4 ) oxides coatings were applied on the surface of the ferritic steel for ageing at 800 °C for 3000 h. Both coatings improved the behaviour of the steel and give interesting opportunities to use the K41X steel as interconnect for hydrogen production via high temperature steam electrolysis. Co 3 O 4 reduced into Co leading to a very good Area Specific Resistance (ASR) parameter, 0.038 Ω cm 2 . Despite a good ASR (0.06 Ω cm 2 ), La …
Easy Method for the Transformation of Levulinic Acid into Gamma-Valerolactone Using a Nickel Catalyst Derived from Nanocasted Nickel Oxide
2019
Different nickel catalysts have been tested for the transformation of levulinic acid into &gamma
Structural and conductivity study of the proton conductor BaCe(0.9−x)ZrxY0.1O(3−ı) at intermediate temperatures.
2009
International audience; The perovskite BaCe(0.9−x)ZrxY0.1O(3−ı) is prepared by solid-state reaction at 1400 ◦C and sintering at 1700 ◦C. It is characterised using X-ray diffraction, Raman spectroscopy and electrical measurements. A distortion fromthe cubic structure at roomtemperature is noticeable in the Raman spectra for 0.2 < x < 0.8, but not in the X-ray diffraction patterns. This work points out the rhombohedral nature of this distortion. Phase transitions are studied up to 600 ◦C. The direct current conductivity is measured as a function of oxygen partial pressure, and at a water vapour partial pressure of 0.015 atm. The total conductivity is resolved into an ionic and a p-type compon…
Photoelectrochemical and XPS Characterization of Passive films Grown on 316L Stainless Steel in High Temperature Water
2015
One of the major materials challenge for continued safe, reliable and cost-effective utilization of watercooled nuclear reactors for electricity production is development of improved understanding of the synergistic fundamental mechanisms responsible for corrosion and stress corrosion cracking degradation of austenitic steels and nickel base alloys
Critical-state effects on microwave losses in type-II superconductors
2006
We discuss the microwave energy losses in superconductors in the critical state. The field-induced variations of the surface resistance are determined, in the framework of the Coffey and Clem model, by taking into account the distribution of the vortex magnetic field inside the sample. It is shown that the effects of the critical state cannot generally be disregarded to account for the experimental data. Results obtained in bulk niobium at low temperatures are quantitatively justified.
High-pressure/high-temperature phase diagram of zinc
2018
The phase diagram of zinc (Zn) has been explored up to 140 GPa and 6000K, by combining optical observations, x-ray diffraction, and ab initio calculations. In the pressure range covered by this study, Zn is found to retain a hexagonal close-packed (hcp) crystal symmetry up to the melting temperature. The known decrease of the axial ratio (c/a) of the hcp phase of Zn under compression is observed in x-ray diffraction experiments from 300K up to the melting temperature. The pressure at which c/a reaches root 3 (approximate to 10GPa) is slightly affected by temperature. When this axial ratio is reached, we observed that single crystals of Zn, formed at high temperature, break into multiple pol…
Study of the high temperature behaviour of titanium alloy Ti6242S under complex atmospheres : aeronautical applications
2018
The use of titanium alloys in many applications (transport, energy, chemistry,...) allows significant weight savings in relation to the good mechanical properties/density ratio of these materials. Since titanium alloys are employed at high temperatures (T>500°C), their behavior in such conditions has to be studied in severe conditions in order to understand degradation mechanisms. Moreover, some specific conditions can be met during application, like thermal cycling, water vapour or presence of salts. These parameters are known to influence oxidation behavior of titanium alloys.In this thesis work, oxidation behavior of an aeronautics titanium alloy (Ti6242S) has been studied in air and moi…
NaCl induced corrosion of Ti-6Al-4V alloy at high temperature
2016
International audience; This paper presents a study on the Ti-6Al-4V behaviour in presence of NaCl deposit under dry and moistair environments at 560◦C. The results evidence a detrimental effect of the NaCl deposit with a synergisticeffect in presence of moist air environment. Treatments under dry and moist air with NaCl deposit for600 h, lead respectively to weight gains per unit area 5 and 15 times higher than observed under classicoxidation in dry air. Enhancement of the corrosion phenomenon is attributed to the presence of gaseousmetal chlorides, leading to the establishment of an active corrosion process.