Simple physical mixture

There are thus multiple effects by which the properties of the nanocarbon-semiconductor hybrid material can be different from the simple physical mixture of the two components [1] The nanocarbon offers an effective way for an efficient dispersion of the semiconductor, thus preventing agglomeration, but also providing a hierarchical structure [15] for efficient light harvesting and eventually easy access from gas/liquid phase components (in photocatalytic reactions) or electrolyte (in DSSC). 

The examples are shown in Figure 9.1.10, which gives x-ray diffractograms of three types of physical mixtures of PVP-stabilized Pd, Pt, and Au monometallic nanoparticles, and the corresponding PVP-stabilized bimetallic nanoparticles (53). The diffraction patterns of the physical mixtures are consistent with the sum of two individual patterns, and are clearly different from those of the bimetallic nanoparticles, which have two broader peaks, indicating that several interatomic lengths exist in a single particle. By XRD one can easily understand if the obtained multi-metallic nanoparticles have an alloy structure or are simple physical mixtures of monometallic particles. 

As part of a more extensive study of cocrystals formed by isonicotinamide with carboxylic acids, 1 1 products containing the dicarboxylic fumaric or succinic acids [59]. In the structures of these particular cocrystals, the typical discrete dimeric synthon was not observed, but instead effectively infinite assemblies of one-dimensional chains were found instead. In a subsequent work, cocrystals of isonicotinamide containing mixed fumaric/succinic acids were prepared using both solid-state grinding and solution crystallization [60]. A full physical characterization of the products demonstrated that the products consisted of a single cocrystal phase, and were not simple physical mixtures of two cocrystal components. Such solid solutions were proposed as yet another method whereby one might obtain even finer control over the physical properties of cocrystal systems proposed as drug substances. 

This amorphous solid did yield a crystalline structure after 5 months of storage, but the crystals were those of urea only. This is in contrast to simple physical mixtures of the two solids that clearly showed crystalline mixtures of both tolbutamide and urea. In contrast to the tolbutamide-urea system, the tolbutamide-PEG system showed similar degrees of crystallinity for both the rapid-cooled and slow-cooled systems. Dissolution profiles for this system were compared for the rapid-cooled, slow-cooled, and physical mixture samples. The profiles for all three samples were very similar however, the extent of release from the rapid-cooled sample was approximately 10% higher than that of the other two samples at any given time during the dissolution process. 

Thus although ruthenium and copper are immiscible in the bulk, ruthenium-copper aggregates can be prepared that have surface properties very different from those of pure ruthenium. The ruthenium-copper aggregates exhibit chemisorption and catalytic properties which would not be expected for simple physical mixtures of ruthenium and copper granules. The presence of the copper clearly has a marked effect on surface processes occurring on ruthenium. On the basis of the chemisorption and catalytic results, we conclude that the copper tends to cover the ruthenium surface. We thus adopt the view that copper is chemisorbed on the ruthenium. 

To produce simple physical mixtures, such as that oi miscible fluids, two or more uniformly divided solids, or, phases where no reaction or changes of particle size take pla... 

Various fatty acids are used in the production of structured lipids these may include both n-3 and n-6 fatty acids. Structured lipids containing MCFA and LCFA may modify the absorption rates because MCFA are rapidly oxidized for energy, whereas LCFA are oxidized very slowly. These specialty lipids are strucmrally and metabolically different from simple physical mixtures of medium-chain and long-chain triacylglycerols. 

A note on partial molar properties In case you are beginning to wonder why there are so many questions and problems about concentrations I will answer by telling you that you need concentrations in about four out of every five problems in physical chemistry. The matter of fact is that a lot of chemistry and all of biochemistry takes place in solutions. Then there are problems inherent to solutions. Solutions are considered simple physical mixtures of two or more different kinds of molecules, with no chemical bonds made or broken. For a really well-behaved solution physical chemists have a name, by analogy with the gas laws an ideal solution. Yet solutions are actually complicated systems whose molecular nature we are only now beginning to understand [1, 2, 3, 4]. Two solvents, when mixed, often release heat (or absorb heat) and undergo change in volume. Think of a water sulfuric acid (caution]) mixture or a water DMSO (dimethyl sulfoxide) mixture. After the solvent mixture equilibrates you will find that its volume is not equal to the sum of the volumes of the pure solvents (it is usually smaller). In physical chemistry we treat these problems by using the concept of molar volume, V. Molar volumes are empirical numbers - they are determined by experimental measurements for different solvent compositions. Read the next problem. 

The purpose of the present paper is to clarify the role of structure of the interface between Au and Ti02 for the genesis of high catalytic activity. To do this, we have investigated the effect of preparation conditions for deposition-precipitation on the size of gold particles. A simple physical mixture of Au colloid and Ti02 powder was also prepared for comparison. 

Plasticizers are bulky organic molecules, generally 300-600 g/mole in molecular weight, and also somewhat polar so as to be compatible with the PVC matrix. Good plasticization involves interspersing plasticizer molecules between PVC chains, breaking the small amount of native PVC crystallinity, and internally lubricating the polymer blend. While there is no formal chemical bond between plasticizer and polymer, the polar attraction between them makes plasticized PVC more than a simple physical mixture. The two are not readily separable in normal use. 

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