Homogeneous physical mixture

At about the same time, Koblitz and co-workers (14) observed the formation of a homogeneous physical mixture of PVdF and a solid PMMA resin, although they placed primary emphasis upon minor amounts of PMMA as a processing aid for PVdF. Our work, which is described below, was chiefly concerned with PMMA-rich systems, in... 

Stabilization of Ru based oxides by valve metal oxides has not been studied in such detail using photoelectron spectroscopy. The most common compositions, however, with relatively high valve metal content, are not in favor of formation of a solid solution. Studies of the phase formation in Ru/Ti mixed oxides has shown [49] that homogeneous solutions are formed for compositions with Ru < 2% or Ru > 98% (see Section 3.1.1). Therefore electrodes with other compositions are better described as physical mixtures and the electrochemical behaviour is most likely that of a linear superposition of the single components. It has to be considered, however, that the investigations performed by Triggs [49] concern thermodynamic equilibrium conditions. If, by means of the preparation procedure, thermodynamic equilibrium is... 

Figure 13.28. Vapor-liquid equilibria of some azeotropic and partially miscible liquids, (a) Effect of pressure on vapor-liquid equilibria of a typical homogeneous azeotropic mixture, acetone and water, (b) Uncommon behavior of the partially miscible system of methylethylketone and water whose two-phase boundary does not extend byond the y = x line, (c) x-y diagram of a partially miscible system represented by the Margules equation with the given parameters and vapor pressures Pj = 3, = 1 atm the broken line is not physically significant but is...

From the different characterization techniques, it follows that catalysts have been prepared that display a homogeneous distribution of the supported phase on the support pellets, with an increased interaction as compared with a physical mixture of iron oxide and titania. Tn the case of a pure anatase support, the interaction leads to the formation of a mixed oxide of iron and titanium. 

Conductometry — is a nonselective analytic method based on monitoring conductivity of a physical mixture, a solution or a homogeneous solid material. This... 

Eutectic Mixture A general example for a eutectic mixture system is shown in Figure 5b, where curves PQ and RQ represent the temperatures at which homogeneous liquid-solutions begin to crystallize. Above the curves P-Q-R, the two components are liquid. Line TQU represents the temperature at which solid mixtures of A-molecule and B-molecule begin to melt, and the two components are completely solid below the line T-Q-U. The small and large areas of PQT and RQU represent mixtures of A-molecule crystals in liquid A/B-molecule and solid B-molecule crystals in liquid A/B-molecule, respectively. It is important to note that the eutectic is a physical mixture, not a molecular compound. Below the eutectic temperature, all mixtures are solid. 

These are very intimate mixtures composed of two or more sohd phases that differ in composition and each with particle sizes of 10 to 20 mn. Solid phases of these dimensions produce sols when dispersed in a liquid. Two or more sols of different composition can be uniformly mixed and gelled to obtain compositionally different nanocomposites. Figure 13.1a shows the transmission electron microscopy (TEM) picture of a sol-gel nanocomposite of mulhte composition consisting of spherical sihca particles (20 nm) and rod-like alumina (boehmite) particles (approximately 7 nm). Such a uniform physical mixture can be distinguished from a homogeneous sol-gel material which does not show any nonuniformity because it is mixed on an atomic scale (Figure 13.1b). The compositionally... 

The major assumption made in the present quantitative impurity analysis is the model of instantaneous nucleation, which is characterized by extremely rapid onset and is consistent with a relatively small n value ( 2 for SX) (52). The homogeneous and heterogeneous nucleation processes can proceed simultaneously. However, the former can occur only in the bulk material of molten SX, whereas the latter is initiated by contact with the surface of the form II seeds present. The number of nuclei formed by heterogeneous nucleation is proportional to the surface area of the metastable phase, and will be proportional to x, the weight fraction of SX-II, if the same specific surface area is assumed for both preexisting nuclei and SX-II particles added (as in physical mixtures). Therefore Ax, the total number of nuclei formed at x c 1 can be expressed by... 

So far, we have considered the motion of fluids of homogeneous physical and chemical composition. In practice, one often meets more complicated situations in which the fluid contains dissolved substances (contaminants or reactants) and is a solution or a mixture. 

As Table 4.1 shows, several bimetalhc DENs have been employed as homogeneous catalysts, predominately for hydrogenations. The most detailed studies have been with aUyl alcohol hydrogenation and the partial hydrogenation of 1,3-cyclooctadiene (1,3-COD) test reactions. In these studies, turnover frequencies (TOEs), which can be normalized per mole of nanoparticles, can be compared as a function of the metaUic atomic ratio in the DENs. Comparison with physical mixtures of monometalhc DENs with the same net atomic ratio allows investigators to directly compare both the magnitude and direction of changes to rationally prepared control materials. 

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