Phase formation processes

Froment M, Lincot D (1995) Phase formation processes in solution at the atomic level Metal chalcogenide semiconductors. Electrochim Acta 40 1293-1303... 

It is clear that surface reconstruction phenomena play an important role in electrochemical 2D and 3D phase formation processes. lindsay [2.11] has shown that in the underpotential range (cf. Chapter 3) 2D Pb monolayer domains are formed preferentially along the stripes of reconstructed Au(lll) surfaces. 

First theoretical interpretations of Me UPD by Rogers [3.7, 3.12], Nicholson [3.209, 3.210], and Schmidt [3.45] were based on an idealized adsorption model already developed by Herzfeld [3.211]. Later, Schmidt [3.54] used Guggenheim s interphase concept" [3.212, 3.213] to describe the thermodynamics of Me UPD processes. Schmidt, Lorenz, Staikov et al. [3.48, 3.57, 3.89-3.94, 3.100, 3.214, 3.215] and Schultze et al. [3.116-3.120, 3.216] used classical concepts to explain the kinetics of Me UPD and UPD-OPD transition processes including charge transfer, Meloiy bulk diffusion, and nucleation and growth phenomena. First and higher order phase transitions, which can participate in 2D Meads phase formation processes, were discussed controversially by various authors [3.36, 3.83, 3.84, 3.92-3.94, 3.98, 3.101, 3.110-3.114, 3.117-3.120, 3.217-3.225]. 

Bewick and Thomas [3.110-3.114, 3.270] measured electrochemically and by optical means different Me UPD systems Ag(A 0/Pb, H, ClOd", acetate and citrate, CnQikt)/ h H C104, acetate, and AgQikt)m SOd with Qikt) = (111), (100), and (110). Potentiostatic pulse measurements showed non-monotonous current transients for Ag(lll) substrates which are attributed to a first order phase transition. As an example, a current transient in the system Pig hkt)/Vf, H, SOd is shown in Fig. 3.46. In the case of Ag(lOO) and Ag(llO) substrates, higher order phase transitions were supposed. Clear evidence of a participation of 2D nucleation and growth steps in the 2D Meads phase formation process was found in the system Cu(lll)/Pb H", ClOd", acetate [3.270]. Non-monotonous current transients and a discontinuity in the q(lsE,fi) isotherm were observed (Fig. 3.13). 

Experimental results recently obtained in the systems Au(/zifeO/X and Ag(hkl)/X with X" = Cr, Br, J as well as in the system AuQikl)/uraci e did not give clear evidence of phase transitions of higher order in 2D phase formation processes. Isotherms, transients, and X-ray scattering data were found not to be self-consistent. Furthermore, the interpretation of the data is not in full agreement with modern phase transition theories. 

The results obtained in the system k x hkl)/Cv , where 2D Me UPD phenomena occur followed by a Stranski-Krastanov growth mechanism in the OPD range, show that electrochemical 3D Me phase formation processes can be used for structuring and modification of metal single crystal surfaces in the nanometer range. Local electrochemical processes are initiated by in situ local probe methods using appropriate polarization routines. 

Growth Modes of2D and 3D Metal-Phase Formation Processes 17... 

A fiorther advantage of electrochemical in-situ SPM studies of two- and three-dimensional phase formation processes is the possibility of controlling accurately the supersaturation or undersaturation, Ap, which can be correlated, in the absence of other kinetic hindrances with overpotential and underpotential, respectively [11] ... 

This interphase exchange current modeling of the solid phase formation process serves to emphasize the varied perspectives from which useful information can be drawn to aid in describing and understanding corrosion processes in varied systems. Rarely are the real systems simple and many pieces of data are examined before the models do incorporate the full ranges of... 

Two-dimensional (2D) phase transitions on surfaces or in adlayers have received increased attention in recent years [1-4] as they are related to important aspects in surface, interfadal and materials science, and nanotechnology, such as ordered adsorption, island nucleation and growth [2, 5-7], surface reconstruction [8], and molecular electronics [9], Kinetic phenomena such as catalytic activity and chirality of surfaces [10-12], selective recognition of molecular functions [13], or oscillating chemical reactions [14] are directly related to phase-formation processes at interfaces. 

Time-resolved in situ STM experiments [360] performed in the so-called x-t mode (one scanline is recorded as a function of time) revealed first structural details of these phase formation processes. Figure 18 indicates that... 

The thermodynamic and statistical mechanical analysis of first-order and/or continuous phase transitions demonstrated clearly that models based on the MEA are often inadequate. Lattice gas models (LGM), and approximations based on the quasiseries expansion techniques (e.g. the low-temperature series expansion (SE)) are more appropriate. MG simulations have also been developed as a powerful approach to unravel the role of lateral interactions in various phase formation processes. 

Phase-Formation Processes of Titanium Nitrides During Combustion of Ferrotitanium in Nitrogen... 

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