Interstitial solutes

Fig. 7.7. Solid-solution structures. In interstitial solutions small atoms fit into the spaces between large atoms. In substitutional solutions similarly sized atoms replace one another. If A-A, A-B and B-B bonds hove the some strength then this replacement is random. But unequal bond strengths con give clustering or ordering.

Hydrogen has a very low solubility in the iron lattice, which makes direct observation of the location of the hydrogen atom in the lattice very difficult. The hydrogen definitely occupies an interstitial site in the bcc iron lattice. Two such sites are normally associated with interstitial solutes in bcc structures, the tetrahedral and the octahedral sites (see Fig. 8.39). Indirect evidence suggests that hydrogen occupies the tetrahedral site. 

Complete and Incomplete Ionic Dissociation. Brownian Motion in Liquids. The Mechanism of Electrical Conduction. Electrolytic Conduction. The Structure of Ice and Water. The Mutual Potential Energy of Dipoles. Substitutional and Interstitial Solutions. Diffusion in Liquids. 

Ideal and Nonrideal Solutions. Treatment of Solutions by Statistical Mechanics. A Solution Containing Diatomic Solute Particles. A Solution Containing Polyatomic Solute Particles. An Interstitial Solution. Review of Solutions in General. Quantities De-pendent on, and Quantities Independent of, the Composition of the Solution. Unitary Quantities and Cratic Quantities. Molality and Activities on the Molality Scale. 

Derive equation (51) from (SO) and in the case of an interstitial solution derive (56) from the appropriate expression for W. ... 

While the osmotic concentration of renal cortical tissue is isotonic, interstitial solute concentration begins to rise at the border between renal cortex and renal medulla to... 

A second way for a solid to accommodate a solute is interstitially, with solute atoms fitting in between solute atoms in the crystal stmcture. An important alloy of this type is carbon steel, a solid solution of carbon in iron, also shown in Figure 12-4. Steels actually are both substitutional and interstitial alloys. Iron is the solvent and carbon is present as an interstitial solute, but varying amounts of manganese, chromium, and nickel are also present and can be in substitutional positions. 

Fig. 2.10. Relationship between Na/Li and temperature (Fouillac and Michard, 1981). KCS Kettelman interstitial solutions concentrated samples. KDS Kettelman interstitial solutions, diluted samples. CB Cesano Brine. ETB El Tatio Brine. WBIS Basalt in interaction resulting solution. H Hveragerdi and G Geysir.

First, lithium introduced into NiO (61, 62) acts as an acceptor (forms a substitutional solution), and, as shown by Schwab and Block, it may also function as a donor (form an interstitial solution). Indeed, as shown by Bielanski and Deren (64), with increasing concentration of lithium added the manner of its inclusion is changed (the substitutional solution at low concentrations is changed at high concentrations to the interstitial solution). ... 

Equation (S.21) is normally used in metallic systems for substitutional phases such as liquid, b.c.c., f.c.c., etc. It can also be used to a limited extent for ceramic systems and useful predictions can be found in the case of quasi-binary and quasi-temary oxide systems (Kaufman and Nesor 1978). However, for phases such as interstitial solutions, ordered intermetallics, ceramic compounds, slags, ionic liquids and aqueous solutions, simple substitutional models are generally not adequate and more appropriate models will be discussed in Sections 5.4 and 5.5. 

Metal/hydrogen systems have been treated successfully by the assumption that, at low hydrogen concentrations, deviations from Sieverts Law result from an elastic interaction energy among the absorbed hydrogen atoms. The interaction is attractive in nature since including a hydrogen atom into an interstitial site results in a local expansion of the metal lattice. It is well known that lattice dilation exerts an attractive interaction with interstitial solute atoms. Under this... 

This type of constraint will be absent in amorphous materials because any of the Nc components can be added (or removed) anywhere in the material without exchanging with any other components. The dNi will also be independent for interstitial solutes in crystalline materials that lie in the interstices between larger substitutional atoms, as, for example, carbon atoms in body-centered cubic (b.c.c.) Fe, as illustrated in Fig. 8.8. In such a system, carbon atoms can be added or removed independently in a dilute solution. 

Another system obeying Fick s law is one involving the diffusion of small interstitial solute atoms (component 1) among the interstices of a host crystal in the presence of an interstitial-atom concentration gradient. The large solvent atoms (component 2) essentially remain in their substitutional sites and diffuse much more slowly than do the highly mobile solute atoms, which diffuse by the interstitial diffusion mechanism (described in Section 8.1.4). The solvent atoms may therefore be considered to be immobile. The system is isothermal, the diffusion is not network constrained, and a local C-frame coordinate system can be employed as in Section 3.1.3. Equation 2.21 then reduces to... 

Following Shewmon, consider the metallic couple specimen consisting of two different metals, A and B, shown in Fig. 3.12 [18]. The bonded end is at temperature T and the open end is at T2. A mobile interstitial solute is present at the same concentration in both metals for which Qt1rans = -84 kJ/mol in one leg and Q jrans = 0 in the other. Assuming that the interstitial concentration remains the same at the bonded interface at T, derive the equation for the steady-state interstitial concentration difference between the two metal legs at T2. Assume that Tj > T2. 

Consider the diffusional flux in the vicinity of an edge dislocation after it is suddenly inserted into a material that has an initially uniform concentration of interstitial solute atoms. 

SYNERESIS. The contraction of a gel with accompanying pressing out of the interstitial solution or serum. Observed in the clotting of blood, with silicic arid gels. etc. See also Colloid Systems. 

Reactions 5 and 6 explain certain processes observed in pelagic sediments. For example, according to Lynn and Bonatti (32) manganese-containing carbonates form from interstitial solutions. Further, mobilization of silica and manganese that has been assumed to be caused by processes in the interstitial solutions in sediments, has been observed by Arrhenius (4). 

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