Search results for "passivity"
showing 10 items of 34 documents
Electrochemical behaviour of copper-nickel alloys as immobilisation matrices for the storage of fission products in CO2-enriched synthetic groundwater
2013
International audience; The surface properties of nickel and copper alloys exposed to simulated French Callovo-Oxfordien ground-water (aerated and CO2-saturated solutions) have been evaluated from electrochemical impedance spectroscopy in conjunction with X-ray photoelectron spectroscopy. The kinetic reactions and physical properties of the layers grown on the alloy's surfaces, change versus the Ni content in the alloys and the presence of CO2 in the solution. Nickel alloys retain favourable passive properties in such environments, whereas oxide products on copper alloys are insufficiently protective when formed in the absence of dissolved oxygen in the electrolyte. A maximum addition of 30…
Investigation on passivity of titanium under steady-state conditions in acidic solutions
2011
Abstract The passivity of titanium was studied using potentiostatic polarization combined with Mott–Schottky analysis in acidic solutions. The oxide layer was characterized as an n-type semiconducting, oxygen deficient oxide (TiO1.993–1.996) with a donor density in the range of 1019–1020 cm−3 depending on electrode potential and electrolyte pH. The calculated thickness for the inner oxide layer was in the range of 1–4 nm, increasing linearly with applied potential and exponentially with electrolyte pH. The potential- and pH-dependence of the inner oxide thickness was interpreted by a modified point defect model for the migration-controlled oxide growth, in which the rate-determining step in…
Passive Behavior and Passivity Breakdown of AISI 304 in LiBr Solutions through Scanning Electrochemical Microscopy
2014
The passive behavior and passivity breakdown of AISI 304 stainless steel in LiBr solutions has been investigated by means of scanning electrochemical microscopy (SECM). The sample generation - tip collection (SG-TC) mode was used to operate the SECM and the tip potential was biased to detect the electroactive species. The evolution of the current at the ultramicroelectrode tip with the applied potential within the passive range was followed at different LiBr concentrations. Results show that the absolute value of the current at the tip increases with the applied potential. Additionally, SECM was also used to detect stable pits formed on the stainless steel surface in a 0.2 M LiBr solution. …
Effect of silicon on corrosion resistance of Ti–Si alloys
2011
Abstract The corrosion resistance of Ti–Si alloys has been studied in acid solutions and the alloys exhibit a high resistance to corrosion. SEM examinations combined with EDAX allowed to conclude that the passive films on Ti–Si alloys are mainly composed of TiO 2 /SiO 2 oxides. XPS analysis indicated the formation of Si–O and Si–O–Ti bonds in the passive film, respectively corresponding to SiO 2 and Si-doping TiO 2 . The effect of silicon on the corrosion was correlated to the formation of a stable SiO 2 film, Si-doping on TiO 2 and the extended lattice imperfections formed along TiO 2 /SiO 2 grain boundaries and phase-boundaries. The calculated donor densities based on the point defect mod…
Passivity Breakdown: Development and Application of Local Chemical and Electrochemical Probe Methods
2018
Abstract The most identified classes of phenomena at the origin of the passivity breakdown and the electrochemical and chemical factors controlling the induced localized corrosion are summarized before introducing the scientific concepts at the origin of the design of the local probe techniques used in recent advances in understanding localized corrosion processes. Examples concerning the surface reactivity of aluminium alloys are presented to support a final discussion on the needs for experimental developments with capabilities to support modelling.
Passivity-based output feedback control of Markovian jump systems with discrete and distributed time-varying delays
2013
In this article, we present a new method in designing mode-dependent passivity-based output feedback controllers for Markovian jump systems with time-varying delays. Both discrete and distributed delays are considered in the model. A Lyapunov–Krasovskii function is constructed to establish new required sufficient conditions for ensuring exponentially mean-square stability and the passivity criteria, simultaneously. The method produces linear matrix inequality formulation that allows obtaining controller gains based on a convex optimisation method. Finally, a numerical example is given to illustrate the effectiveness of our approach.
A passivity approach to control of Markovian jump systems with mixed time-varying delays
2013
This paper investigated the problem of control design for a class of stochastic systems with Markovian jump parameters and time-varying delays. For the model under consideration, a passivity-based approach is introduced for designing mode-dependent output feedback controllers with mixed discrete and distributed delays. A Lypunov-Krasovskii function (LKF) is defined to establish new required sufficient conditions for ensuring exponentially mean-square stability and the passivity criteria, simultaneously. Moreover, controller gains are calculated based on a convex optimization method by solving a Linear Matrix Inequality (LMI). Finally, simulation results are provided to illustrate the effect…
Semiconductor electrochemistry approach to passivity and passivity breakdown of metals and metallic alloys
2004
AbstractA critical appraisal of the use of the theory of semiconductors in characterising passive films on metals and alloys is provided, with special emphasis on the use of Mott-Schottky theory for the location of characteristic energy levels of the passive film-electrolyte junction. Some inconsistencies between theory and experimental results in the case of thin passive films are discussed together with possible alternative ways for overcoming such problems. The role of semiconducting properties in determining the pitting behaviour of passive films on W in solutions containing halide is presented and discussed. The validity of a recently proposed correlation between the solid state proper…
El rol cambiante de los recursos personales en la empleabilidad percibida de los jóvenes en diferentes condiciones del mercado de trabajo
2020
Personal resources and labor market are factors that contribute to perceived employability. However, how changing labor market conditions affect the relationship between personal resources like career enhancing strategies, personal initiative, and career passivity with self-perceived employability remains unclear. Recent events in Spain give an opportunity to examine if personal resources predict perceived employability differently during normal and harsh labor conditions. Two representative samples of young people were surveyed during a normal labor condition (in 2008, before the big recession, n = 1,992) and a harsh condition (in 2011, with 46% young unemployment rate, n = 1,208). …
Dynamic Output Feedback Passive Control of Uncertain Switched Stochastic Systems with Time-Varying Delay
2013
Published version of an article in the journal: Mathematical Problems in Engineering. Also available from Hindawi: http://dx.doi.org/10.1155/2013/281747 Open Access This paper is concerned with the issues of passivity analysis and dynamic output feedback (DOF) passive control for uncertain switched stochastic systems with time-varying delay via multiple storage functions (MSFs) method. Firstly, based on the MSFs method, a sufficient condition for the existence of the passivity of the underlying system is established in terms of linear matrix inequalities (LMIs). Furthermore, the problem of dynamic output feedback passive control is investigated. Based on the obtained passivity condition, a …