Interface effects

We are including the conversion from erg to joule. The energy needed to increase the water s area is 

This is an order of magnitude more energy than is given offby the razor blade dropping through the surface. This suggests that a razor blade will, indeed, float on the surface of water. 

In the previous section, we showed that the surface tension was related to some thermodynamic functions, namely work and the Gibbs energy. What other thermodynamic manifestations are there for liquid surfaces Several of these manifestations involve the interactions of two (or more) phases at their surfaces. 

One thermodynamic variable, pressure, shows some unusual effects due to the presence of a surface. Consider a liquid in contact with another phase, like another liquid or even a gas or vacuum. Let us define region 1 as the liquid, and region 11 as the other phase in contact with the liquid. Together, these two regions represent our system, to be considered thermodynamically. 

Because we are interested in region I (the liquid), we will substitute for dV, to eliminate it. Equation 22.10 becomes 

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Wu R and Freeman A J 1994 Magnetism at metal-ceramic interfaces effects of a Au overlayer on the magnetic properties of Fe/MgO(001) J. Magn. Magn. Mater. 137 127-33... 

If one is only interested in the properties of the interface on scales much larger than the width of the intrinsic profiles, the interface can be approximated by an infinitely thin sheet and the properties of the intrinsic profiles can be cast into a few effective parameters. Using only the local position of the interface, effective interface Hamiltonians describe the statistical mechanics of fluctuating interfaces and membranes. 

However, the effective internal electric field in the device deviates from the field calculated using Eq. (9.10) due to the internally built-in field (see above) because of defect charging in the active layer [55] and interface effects [57],... 

A semiconductor can be described as a material with a Fermi energy, which typically is located within the energy gap region at any temperature. If a semiconductor is brought into electrical contact with a metal, either an ohmic or a rectifying Schouky contact is formed at the interface. The nature of the contact is determined by the workfunction, (the energetic difference between the Fermi level and the vacuum level), of the semiconductor relative to the mclal (if interface effects are neglected - see below) 47J. 

Figure 5.29. Bode (a) and corresponding Nyquist plot (b) of the circuit shown in inset which is frequently used to model a metal/solid electrolyte interface. Effect (c) of capacitance C2 on the Nyquist plot at fixed R0, R( and R2.

H. Marschner and V. Romheld, In vivo measurement of root-induced pH changes at the. soil-root interface—effect of plant species and nitrogen. source, Zeitschrift fur Pfianzenphysiolgie 111 24 (1983). 

Finally, one should note that a significant difference in behavior could exist between a very thin ( < 1 nm) and a thick oxide layer because of possible interface effects on the bulk oxide in the former case such effects should be negligible in the latter case. 

For ultrathin films, it should also be mentioned that Tg is strongly subjected to interface effects, thus it may be higher or lower than in the bulk material [3], This finding can be attributed to the interplay between surface and geometric confinement effects. Due to attractive interactions at interfaces, the molecular dynamics may be slowed down, resulting in an increase of Tg, whereas the confinement to a small layer may lead to an increase in the free volume, resulting in a decrease of Tg [4],... 

Kelly A. (1970). Interface effects and the work of fracture of a fibrous composites. Proc. Roy. Soc. Land. A 319, 95-116. 

Zeltner,W.A. Anderson, M.A. (1988) Surface charge development at the goethite/aqueous solution interface. Effects of CO2 adsorption. Langmuir 4 469—474... 

Fig. 6. Debonding of interfaces, effect of adhesion on PP/CaC03 composites filler CaC03, (pf=0.2,r=L8 pm...

The relative influence of the surface (or interface) effects, of course, must decrease with increasing thickness t of the layer(s). Since the surface effects contribute per unit surface area , one defines, for the layer, effective parameters such that Beff, or heff, equals gbuik 2bsurt/t. Here, the factor 2 is put in, because a layer has two surfaces. In practice, this simple l/t dependence works satisfactorily. For nanocrystallites, both the volume fraction and the volume to surface ratio of the crystallites (i.e. their radius) must be taken into account (see also section 8). In connection to these effects, (non-linear) contributions to the magnetoelastic coefficients due to surface strains and surface roughness are expected to be considerable. 

In practice, one determines b (H) with the field directed along the film direction (jc axis), and b (H) with the applied field along the y-direction (still inside the film plane). At saturation, one has ai = 1 and 2 = 1. respectively. When applied to cases where surface (interface) effects are important, it turns out that, with these field orientations, only... 

Szymczak (1997, 1999) has stressed the possibility to distinguish between pure interface effects, i.e. surface magnetostriction, and the effects of an interface diffusion layer. Since magnetic anisotropy and magnetostriction have the same origin, the surface magnetostriction is expected to have an intrinsic character. In Szymczak s notation (Voigt... 

Vasudevan, D., and A. T. Stone, Adsorption of catechols, 2-aminophenols, and 1,2-phenylenediamines at the metal (hydr)oxide-water interface Effects of ring substituents on the adsorption onto Ti02 , Environ. Sci. Technol., 30, 1604-1613 (1996). 

Similar to the molecular photosensitizers described above, solid semiconductor materials can absorb photons and convert light into electrical energy capable of reducing C02. In solution, a semiconductor will absorb light, and the electric field created at the solid-liquid interface effects the separation of photo-excited electron-hole pairs. The electrons can then carry out an interfacial reduction reaction at one site, while the holes can perform an interfacial oxidation at a separate site. In the following sections, details will be provided of the reduction of C02 at both bulk semiconductor electrodes that resemble their metal electrode counterparts, and semiconductor powders and colloids that approach the molecular length scale. Further information on semiconductor systems for C02 reduction is available in several excellent reviews [8, 44, 104, 105],... 

Ofor, O. (1995) Oleate adsorption at a Nigerian hematite-water interface effect of concentration, temperature, and pH on adsorption density. Journal of Colloid and Interface Science, 174, 345-50. 

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