Segregation phenomena

Similar segregation phenomena may also occur by adsorption or absorption of hydrogen. However, the enthalpies of hydride formations are much smaller when compared to those of oxide formation. The results on hydrogen-induced surface segregation are rather controversial. The exclusion of oxygen traces in the bulk and surface of the alloys is crucial for proper studies of surface segregation induced by hydrogen. 

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Ullrich M. Segregation phenomena in a bulk of balls (in German). Chem Ing Tech 1969 41 903-907. 

Small particles of binary alloys have been investigated in detail in static EXAFS experiments, but if information about the dynamic behavior of the alloy composition and the segregation phenomena is desired, time-resolved combined EXAFS/XRD studies are necessary. Figure 18 shows the atomic structure of a small binary particle of a Ni-Au alloy as predicted from Monte Carlo simulations (60). Ni and Au do not form a miscible alloy in the bulk but can form a stable alloy at the surface. The structural and chemical changes that occur when such particles are exposed to different... 

Two of this year s articles discuss the fluid-mechanical aspects of systems where material transfer may occur, accompanied by chemical reaction or heat transfer. Fulford analyzes thin-film flow in terms of the flow regimes and of surface disturbances, and relates recent experimental findings to the theoretical framework. Rietema discusses segregation phenomena in heterogeneous reactions, in relation to conditions of flow and of mass transfer. 

Surface segregation phenomena and the surface composition of bimetallic catalysts are controlled by the surface free energies of the constituents of the bimetallic particles. The deposition of metal on metal in relation to bimetallic catalysts has been discussed by Dodson [63]. 

Fredriksson H., Segregation phenomena in iron-base aiioys. Scand. J. Metallurgy, 5 (1976), 27-32... 

Flow properties of powders are important parameters in mixing and segregation phenomena, essentially during storage. 

In case < 0, bonding of like atoms is energetically preferred, leading in principle to separation of the alloy into a mixture of A and B rich solid-solution phases, each with nearly homoatomic SRO clusters, compared to short range A-B mixed or heteroatomic clusters in the former case of V >0. In other words, the tendency to order (or phase-separate) is manifested to some, local degree also in most solid solutions, where the distribution of atoms in the crystal is not entirely random, and should be incorporated too in any theoretical quantitative evaluation of surface segregation phenomena. Moreover, many alloys of... 

This approach can be applied to segregation phenomena in other two-phase alloys, such as reported recently for polycrystalline Fe99Pdi with a small fraction of ordered FePd nuclei [86]. Positive entropy and enthalpy characterize the observed increase in segregation level with temperature. 

S.M. Foiles, Calculation of the surface segregation of alloys using the embedded atom method in P. A. Dowden and A. Miller Eds. Surface segregation phenomena, CRC, Boston, 1990. 

P.A. Dowben, A. Miller (eds.), Surface Segregation Phenomena, CRC Press, Boca Raton, 1990. 

In Sect. 2 the coexistence conditions of high polymer mixtures are described. Here we focus on the internal interface between two coexisting phases with a bilayer morphology. The properties of this interface determine phase coexistence characteristics necessary to describe segregation phenomena discussed in Sects. 3 and 4. 

So far we have described separately the segregation phenomena occurring at both surfaces of thin films composed of binary polymer mixtures. Now we dis-... 

The 77 values of (3-lg/PGA films (0.1 wt% PGA in the bulk phase) showed an antagonic behavior when compared to the tto( single (3-lg and PGA films, which should be attributed to their high degree of esterification (higher hydrophobicity) that allows them to rapidly adsorb at the interface. However, in the presence of KO at 0.5% (Figure 25.1a), the system showed a more cooperative adsorption. Similarly, KLVF at 0.5% increased tt of the mixed system. The increased cooperativity as PGA increased from 0.1 to 0.5% may be ascribed to an increase of segregation phenomena in the bulk solution. 

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