Multiphase characterization

M. Melncci, G. BarbareUa, M. Gazzano, M. Cavallini, F. Biscarini, A. Bongini, F. Piccinelh, M. Monaii, M. Bandini, A. Umani-Ronchi and P. Biscarini, Synthesis, multiphase characterization and helicity control in chiral DACH-linked oligothiophenes, Chem. Eur. J., 12, 7304-7312 (2006). 

Other excellent methods of phase identification include TEM and electron diffraction. These may be more useful for low-Z materials, ultrathin films, and for characterizing small areas, including individual grains. For multiphase films with incomplete texture, these methods and XRD are complementary, since in commonly used geometries, they probe atomic planes perpendicular and parallel to the thin film surface, respectively. 

The fact that crystalline polymers are multiphase materials has prompted a new approach in characterizing their internal structure (lamellar thickness, perfection, etc.) and relating it to the hardness concept (volume of material locally deformed under a point indenter). In lamellar PE microhardness is grossly a given increasing function of lamellar thickness. In using the composite concept care must be exercised to emphasize and properly account for the non-crystalline phase and its various... 

Amine-terminated siloxane oligomers have also been utilized in the synthesis of various siloxane-amide and siloxane-imide copolymers, High molecular weight siloxane-amide copolymers have been synthesized by the solution or interfacial co-polymerization of siloxane oligomers with sebacoyl chloride or terephthaloyl chloride respectively 1S5,165). In some reactions diamine chain extenders have also been utilized. Thermal and dynamic mechanical characterization of these copolymers have shown the formation of multiphase systems160). Compression molded films displayed very good elastomeric properties. 

Synthesis of hydrolytically stable siloxane-urethanes by the melt reaction of organo-hydroxy terminated siloxane oligomers with various diisocyanates have been reported i97,i98) -yhg polymers obtained by this route are reported to be soluble in cresol and displayed rubber-like properties. However the molecular weights obtained were not very high. A later report56) described the use of hydroxybutyl terminated disiloxanes in the synthesis of poly(urethane-siloxanes). No data on the characterization of the copolymers have been given. However, from our independent kinetic and synthetic studies on the same system 199), unfortunately, it is clear that these types of materials do not result in well defined multiphase copolymers. The use of low molecular weight hydroxypropyl-terminated siloxanes in the synthesis of siloxane-urethane type structures has also been reported 198). 

ReveUin R, Dupont V, Ursenbacher T, Thome JR, Zun I (2006) Characterization of diabatic two-phase flows in microchannels flow parameter results for R-134a in a 0.5 mm channel. Int J Multiphase Flow 32 755-774... 

The multiphase fluid systems of interest are often opaque, and thus noninvasive techniques based on optical methods or using laser beams are not effective. Various experimental techniques are available and continue to be developed to characterize opaque multiphase flows. 

Losey, M. W, Schmidt, M. A., Jensen, K. F., Microfabricated multiphase packed-bed reactors characterization of mass transfer and reactions, Ind. Chem. Res. 

The importance of temperature-controlled scanning calorimetry for measurements of heat capacity and of scanning transitiometry for simultaneous caloric and pVT analysis has been demonstrated for polymorphic systems [9]. This approach was used to study an enantiotropic system characterized by multiphase (and hindered) transitions, the role of heat capacity as a means to understand homogeneous nucleation, and the creation of (p, T) phase diagrams. The methodology was shown to possess distinct advantages over the more commonly used combination of characterization techniques. 

A semibatch reactor is a variation of a batch reactor in which one reactant may be added intermittently or continuously to another contained as a batch in a vessel, or a product may be removed intermittently or continuously from the vessel as reaction proceeds. The reaction may be single-phase or multiphase. As in a batch reactor, the operation is inherently unsteady-state and usually characterized by a cycle of operation, although in a more complex manner. 

This system is more accurately defined as a multiphase (Cu-Cu20-CuO) system. Consequently, it has proven to be very difficult to characterize. The catalyst undergoes changes in its bulk chemical composition, activity, and selectivity during the oxidation of propylene. The final stationary-state composition is a function of the reaction mixture, the temperature, and the duration of the experiment. 

Let us concentrate a little longer on ceramics. Here micro-analysis only slowly won ground and the application of solid state physics lagged behind. Very slowly the relationship between the properties of a material and its microstructure was being discovered. Metallurgy had already been characterized by a theoretical approach for some time and consequently metals were about 15 times as important as ceramic materials in 1960 (see Ashby s graph). This was of course influenced by the fact that metals have relatively simple structures which, in their turn, simplify theoretical comtemplations. Ceramic structures are very often complex and are characterized by multiphase systems. However, at present ceramic materials are approached much differently than for instance in 1900. 

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