Oxidation, atomistics kinetics

One of the greatest advances that theory has made over the past decade has been its ability to examine the sensitivity of the state of the working surface to changes in reaction conditions and surface structure. This has required the ability to integrate ab initio-derived thermodynamic and kinetic results into phase equilibrium as well as atomistic kinetic simulations. The oxide and sulfide surfaces are sufficiently stable that useful studies can be carried out. CO oxidation catalyzed by Ru02 demonstrated that the maximum turnover rate occurs under conditions where the surface is in a disordered state at the boundaries of two phases, one of which is completely covered with oxygen adatoms and a second which is partially covered with CO. 

Experiments have shown that Aoxide spinel formation is on the order of 10 4cm at ca. 1000°C [C.A. Duckwitz, H. Schmalzried (1971)]. Using Eqns. (10.45) and (10.46) with the accepted cation diffusivities (on the order of 10 10 cm2/s), one can estimate from j% that each A particle crosses the boundary about ten times per second each way. In other words, quenching cannot preserve the atomistic structure of a moving interface which developed during the motion by kinetic processes. This also means that heat conduction is slower than a structural change on the atomic scale, unless one quenches extremely small systems. 

Keywords solid oxide fuel cell modeling kinetic Monte Carlo frequency response atomistic density functional theory electrochemistry... 

NO form a number of higher oxides, such as N02 and N03 that compete with adsorbed NO and atomic oxygen for platinum surface sites. Several atomistically detailed models of the NO oxidation reaction based on DFT-derived parameters for the reaction kinetics have been reported [58,59]. These models are successful in describing the sensitivity of the reaction kinetics to surface coverage. They are somewhat limited in terms of the surface species and the reaction steps considered. 

There are many intriguing issues concerning whisker growth such as, why do Sn films grow whiskers spontaneously at room temperature, whereas Au films do not There are also the issues of driving force, kinetics, and specific atomistic mechanism/s associated with whisker growth. The cracked oxide theory (COT), as initially proposed by K.N. Tu [54], addresses these necessary conditions somewhat differently than the above described recrystallization concept. 

By ignoring the specifics of the atomistic mechanism (dislocation, recrystallization, cracked oxide, etc.), Choi et al. constructed a generalized mathematical model that related the dynamics of whisker growth to a stress factor (the driving force) and diffusion constants that are determining factors in the kinetics of whisker growth. 

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