Dispersoid phase

Table 1 lists the liquid precursors employed for the synthesis of the dispersoid phase particles. The rationale behind the selection of the dispersoids (Si02, and AI2O3,) and their influence on the properties is as follows. 

It follows that if we adopt the one-phase concept the number of independent variables is the same as usual pressure, temperature, and relative concentrations. It would seem at first sight, therefore, that the two-phase concept would reduce the number of degrees of freedom by one. However, if we treat the solution as a two-phase system, we shall have to take into account that the thermodynamic properties of the solution depend on the concentration of the dispersoid phase. In fact, the osmotic pressure, vapour pressure, etc. of a colic id solution arc dependent on the number of particles in unit volume, i.e. the concehtration of the dispersoid phase. Consequently, from a thcrinodynamic point of view it is entirely irrelevant whether we adopt the point of view of the one-phase or the two-phase system As soon as we accept two phases, we must also accept one more independent variable, and the number of degrees of freedom is not altered. How we shall regard a particular colloid depends on the kind of equilibrium studied and is purely a matter of suitability. 

The concentration Cd of the dispersoid phase which will be introduced below, is a negligible variable in this case. 

Ternary Alloys. Almost ah commercial ahoys are of ternary or higher complexity. Ahoy type is defined by the nature of the principal ahoying additions, and phase reactions in several classes of ahoys can be described by reference to ternary phase diagrams. Minor ahoying additions may have a powerflil influence on properties of the product because of the influence on the morphology and distribution of constituents, dispersoids, and precipitates. Phase diagrams, which represent equhibrium, may not be indicative of these effects. 

The effect of dispersoids on the mechanical properties of metals has already been described in Section 5.1.2.2. In effect, these materials are composites, since the dispersoids are a second phase relative to the primary, metallic matrix. There are, however, many other types of composite materials, as outlined in Section 1.4, including laminates, random-fiber composites, and oriented fiber composites. Since the chemical nature of the matrix and reinforcement phases, as well as the way in which the two are brought together (e.g., random versus oriented), vary tremendously, we shall deal with specific types of composites separately. We will not attempt to deal with all possible matrix-reinforcement combinations, but rather focus on the most common and industrially important composites from a mechanical design point of view. 

The typical features of the phase diagram of Al-rare earth alloys are high liquid solubility, low solid solubility of rare earths and relatively low liquidus temperatures. The low diffusivity of rare earths in these alloys is an attractive feature from the point of view of the thermal stability of the dispersoids. 

A mode of mechanical alloying is reaction milling, developed for dispersion strengthened aluminum production [1], To produce aluminum dispersoid the aluminum powder is intensively dry milled with carbon powder. The transformed dispersed phase A14C3 is than produced by a chemical reaction, which starts during milling, and it is completed at the next heat treatment process. The resulting powder mixture is then pressed,... 

As an instance, the partial Ti-Si-B phase diagram is presented in Fig. 1. Silicon is not practically dissolved in TiB, and is fully concentrated in the metal matrix and in a ternary boro-silicide when it forms. This ternary boro-silicide phase of unknown structure (designated here as the T-phase) was found to be present as a very fine dispersoid around 200 nm in diameter in the three-phase eutectic (Ti) + T + TiB (Fig. 2). The ternary eutectic alloy hardness vv temperature plot shows a great potential for strengthening up to 600°C in comparison with the binary (Ti) + TiB (Fig. 3). 

Al—Zr. This system (Fig. 19) has a peritectic reaction at 660.8 0 at which solubiHty is 0.28% zirconium [7440-67-7], Zr, soHd and 0.11% Zr Hquid. The equiHbrium phase on the aluminum-rich end of the phase diagram is tetragonal Al Zr [12004-83-0], p. Coarse primary particles of p-phase have a tendency to form during soHdification when the zirconium content is much above 0.12%. A metastable form of Al Zr having a cubic LI2 structure, p, is formed when supersaturated zirconium precipitates as a dispersoid Although this phase is nonequiHbrium, it is extremely resistant to transformation to the equiHbrium P-phase. 

The structure and physical properties of the thermoplastic vulcanizates (TPE-V) produced in the process of the reactive processing of pol5rpropyl-ene (PP) and ethylene-octene elastomer (EOE) in the form of alloy, using the cross-linking system was analyzed. With the DMTA, SEM and DSC it has been demonstrated that the d5mamically produced vulcanizates constitute a typical dispersoid, where semicrystal PP produces a continuous phase, and the dispersed phase consists of molecules of the cross-linked ethylene-octene elastomer, which play a role of a modifier of the properties and a stabilizer of the two-phase structure. It has been found that the mechanical as well as the thermal properties depend on the content of the elastomer in the blends, exposed to mechanical strain and temperature. The best results have been achieved for grafted/cross-linked blends with the contents of iPP/EOE-55/45%. 

It seems likely that, amorphous phase formation by mechanical alloying of the mixture of elemental metal powders occurs in four stages (i) formation of very fine composite powder whereby particles my be understood as diffusion couples (ii) formation of solid solution (ii) collapse of supersaturated solution to the amorphous phase and (iv) gradual dissolution of residual crystallites (dispersoids) into the amorphous matrix. 

Photoreactive nanomatrix structures are novel functional nano-phase separated structures obtained by graft copolymerization, which consist of a dis-persoid of major elastomer and a matrix of minor functional polymer having carbon-carbon double bonds as a photoreactive site. The photoreaction of the polymer in the nanomatrix may cement the nanomatrix structure with not only crosslinking junctions of the elastomer in the dispersoid and chemical linkages... 

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