Vapour-solid

Vacuum evaporation Evaporation at reduced pressure in accordance with the Clausius equation, followed by condensation on a cold surface 1 solid 1 vapour solid on 2 M, Al M2 Fe... 

Cantor (1895) has indicated that the deiv-point, or temperature at which vapour condenses on a solid surface, must be different from the saturation temperature for the vapour over the surface of its own liquid, because of the different surface tensions between (vapour)/(solid) and (vapour)/(liquid). 

It should be noted that the curves of humidity plotted against either temperature or enthalpy have a discontinuity at the point corresponding to the freezing point of the humidifying material. Above the temperature 90 the lines are determined by the vapour liquid equilibrium and below it by the vapour-solid equilibrium. 

Vapour-solids equilibrium 753 Variable area flowmeters 257... 

Up to now we have considered the relationship between the concentration of active particles in systems like gas (vapour) - solid body (semiconductor) and variation of conductivity of a semiconductor. In connection to these systems we mentioned numerous relationships which may be used for quantitative assessment of the content of gaseous media on the basis of data provided by semiconductor sensors when analyzing various active components. 

The term sublimation strictly refers to the phase change solid -> vapour, with no intervention of a liquid phase. In industrial applications, however, the term usually includes the reverse process of condensation or desublimation solid -> vapour -> solid. In practice, it is sometimes desirable to vaporise a substance from the liquid state and hence the... 

Fig. 2.2 5D values versus time for two beakers that have equal surface areas and equal volumes undergoing isotopic exchange in sealed systems. In both experiments at 21 and 52° C isotope ratios progress toward an average value of —56%o via exchange with ambient vapour. Solid curves are calculated, points are experimental data (after Criss, 1999)... 

There is a distinct region of small aggregates or clusters which falls between the atomic (or molecular) domain and that of condensed matter. These small particles and clusters possess unique properties and have several technological applications. The formation of these particles involves a vapour-solid, a liquid-solid, a solid-solid or a vapour-liquid-solid type of phase change governed by nucleation and it is important that the size of the growing nucleus is controlled (Multani, 1981 Hadjipanyas Siegel, 1994). 

The process is characterised by the electrofluorination of volatile organic substrates within the matrix of pores of a carbon anode immersed in molten KF 2HF as electrolyte (as in a mid-temperature fluorine generator cell), and depends on the phenomenon that the anodically charged porous carbon is not wetted by the electrolyte. The fluorination probably takes place at the three phase interface of organic vapour, solid carbon, and liquid electrolyte in close proximity to, or at the sites where fluorine is being evolved. 

The prediction of the thermal conductivity is not as simple for the composite reinforced with SiC whiskers. In fact, as mentioned earlier, the thermal conductivity of the reinforcement phase plays an important role. However, for SiC whiskers, their chemical composition can vary drastically depending on the manufacturing process, which is not the case for Si3N4 whiskers. In fact, the influence of the manufacturing process is drastic the thermal conductivity of SiC(w) produced by the vapour-solid process is around 20 W/m K as opposed to 100-250 W/m K for whiskers produced by the vapour-liquid-solid process. Using a Si3N4 matrix with a nominal thermal conductivity of... 

Vapour + vapour —> solid Chemical vapour deposition, radio frequency-induced plasma, ... 

Desublimation Vapour Solid ESA Recovery of phthalic anhydride from non-condensible gas... 

Metal nanowires are obtained in good yields by the nebulized spray pyrolysis of a methanolic solution of metal acetates.165 This method has been employed for the synthesis of single-crystalline nanowires of zinc, cadmium and lead (see Fig. IS). The nanowires seem to grow by the vapour-solid mechanism. ZnO nanotubes... 

Smoke is a cloud of very small solid or liquid particles floating in the air they are produced by various substances in a vaporized state. The smoke is obtained from vapour. Solid or liquid materials are difficult to make into smoke even when they are divided into tremendously small particles. The mechanism of generating smoke is quite different from that of sparks which are produced from a solid or liquid substance directly at a burning surface. 

When the vapour pressure is raised by an amount A p above the vapour-solid equilibrium vapour pressure, the layer grows with a speed proportional ioAp until the surface is covered. But to start a new layer a two-dimensional nucleus must be formed (F ig. 115) for which the rate of nucleation has been found to be proportional to A being a constant. 

If we remove the liquid phase we have the sub-system vapour + solid 1 + solid 2 which now has only three components, and in which only the second of the reactions can occur. The projection of the mono variant line of this sub-system on the T, p) plane is coincident with the projection of the mono variant line of the parent system. ... 

In addition, the vapour-solid (VS) mechanism was proposed to explain whisker growth for some materials. It should be pointed out that the morphology of the crystal growth has a very complex relationship with the catalyst and the processing conditions. 

A whisker is fabricated according to the vapour-solid or vapour-liquid-solid mechanisms with the aid of certain special catalysts [17], It involves nucleation at preferred locations such as the terrace, ledge and kink on a substrate surface, and defects in crystal structures developed along a special direction of impingement of nuclei. Two-dimensional and three-dimensional microstructures have also been... 

CaO, C02 CuS04, H 0 FeClj, H20 Na2S04, HsO. Fe, C Solids (CaCOj, CaO)—gas (C02) Solids C11SO4 sH20, CuSO HjO, CuS04, ice— liquid solutions—water-vapour Solids FeCl3 anhydrous and several hydrates, ice —liquid solutions—water-vapour Solids anhydrous salt, hepta and deka hydrate, ice—liquid solutions—water vapour Solids alloys (steels)—liquid—vapour... 

Cantor12 pointed out that the dew-point, or temperature of condensation of a vapour on a solid surface, must differ from the saturation temperature for vapour over its own liquid, on account of the different surface tensions at the vapour/solid and vapour /liquid interfaces. 

Bivariant Systems.—If we examine Figs. 3 and 4, we see that the curves OA, OB, OC, which represent diagrammatically the conditions under which the systems, solid and vapour, liquid and vapour, solid and liquid, are in equilibrium, form the boundaries of three fields or areas. These areas give the conditions of temperature and pressure under which the single phases, solid, liquid and vapour, are capable of stable existence. These different areas are the regions of stability of the phase common to the two curves by which the area is enclosed. Thus, the phase common to the two systems represented by OA (solid and vapour) and OB (liquid and vapour) is the vapour phase and the area enclosed by the curves AO and OB is therefore the area of the vapour phase. Similarly, the area AOC is the area of the solid phase, and BOC the area of the liquid phase. 

First-order phase transitions can be of several types, e.g. vapour liquid, vapour solid, liquid solid, solid -> solid. In practice, they are brought about by changes in pressure and/or temperature. Figure 9... 

Hiza, Herring, and co-workers have discussed several single-pass and recirculation methods for studying vapour-liquid and vapour-solid equilibrium... 

Howe, J. M., Interfaces in Materials Atomic Structure, Thermodynamics and Kinetics of Solid-Vapour, Solid-Liquid and Solid-Solid Interfaces, John Wiley Sons, New York, 75-86, 1997. 

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