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The preparation of CdS/CdTe structures as well as its preliminary use for the fabrication of solar cells is reported. CdS films were prepared using the chemical bath technique while CdTe films by isothermal close space sublimation with alternated exposure to Cd and Te sources in isothermal conditions. Annealings in CdCl2 were also performed in isothermal conditions by exposing the sample to CdCl2 vapors. Preliminary results of solar cells fabricated with these novel procedures are reported. [ABSTRACT FROM AUTHOR]

The main features of atomic layer epitaxy regime are outlined. In this growth regime the reactants should be supplied periodically under growth conditions that assist the occurrence of a terminated-reaction between each reactant and the growing surface. In each independent reaction or exposure of a reactant the amount of material incorporated on the surface depends on the atomic reconstructions characteristic on the temperature range. So, in this way the layer thickness is determined by the amount of reaction cycles and it is not necessary a good control of the reactant fluxes and exposure times. This makes this technique particularly interesting in nanotechnology where the control of the amount of deposited material and dimensions are crucial. Moreover, in this paper a variant of the atomic layer controlled growth originally designed in the laboratories of the Physics Faculty and the Institute of Science and Technology of Materials of the University of Havana is presented. This technique has been designated as isothermal closed space sublimation. Some characteristics and applications are shown and discussed. [ABSTRACT FROM AUTHOR]

The aim of this work was to develop a model that relates freezing kinetics of coffee brews to their sublimation kinetics. This has been achieved by assuming that the mean size of the ice crystal formed during freezing is equal to the mean pore size left by the subliming ice. The sublimation kinetics and the heat and mass transport properties of the coffee brews were determined by carrying out experiments using brews with three different solids content (0.1, 0.2 y 0.4 kg solids/kg solution) and three different freezing temperatures (- 18, -30 and -70 °C). The sublimation model developed in this work is based on the well known uniformly-retreating-ice front (URIF) model and includes transient variations in physical properties and permeability. For the latter, a semi-theoretical equation has been developed in this work, which also includes the mean pore size. It is concluded that the mean hydraulic radius of ice crystals formed during freezing can be used to link freezing kinetics with sublimation kinetics and temperature patterns within the drying material, which can give considerable insight into the quality changes occurring in the process. [ABSTRACT FROM AUTHOR]

In this work, the results on the self regulated growth of II-VI semiconductors using the Closed Space Sublimation technique are reported. The main features of the method are: i) the sublimation occurs by exposing the substrate to elemental sources alternately; ii) the whole system is at the same temperature. This last condition warrants the self regulation mechanism. In fact, in isothermal conditions, the driving force for the growth can only be due to the difference in composition between the source and the growth surface. Once that difference is eliminated, the growth stops. With this method, films of ZnTe, CdTe compounds and ZnxCd1-xTe alloys have been obtained. The influence of different parameters in the regulation mechanism is discussed, as well as the use of different transport gases. Epitaxial films were obtained as can be concluded from x-Rays and electron diffraction patterns as well as from high resolution electron microscopy images. The growth rate in terms of monolayers per cycle varies depending of the exposure times and other growth parameters. This dependence is discussed in this work. [ABSTRACT FROM AUTHOR]

At present the sugar industry is doing great efforts in order to increase its energetical efficiency through the elevation of the vapour pressure generated, and consequently, of its temperature, what really permits its use of a more efficient way in the generation of electrical energy. The vapours obtained from these equipment and from others that use direct vapour have a temperature higher than the normally required for the technological necessities of the sugar production process, and although in some ocassions it isn't taken into consideration, it's a factor that must be considered on account of the losses of sacarose and decomposition by heating. In this work a review of the impact over sugar decomposition by the use of vapour with high temperature in the process permits us to show a methodology with the purpose of designing an equipment that permits to introduce a water flow in the vapour flow with the finality of obtaining a temperature that doesn't affect the sugar in the evaporation process. [ABSTRACT FROM AUTHOR]

In this paper it is made a study about polarity, acentric, compressibility and polarity parameter factors, and its relation with vapor pressure in P.V.T. state equations and the thermodynamic properties determination in polar and non polar pure substances. A computation program was implemented in order to calculate the previously mentioned parameters . It was confirmed that the obtained results are in good agreement with important data sources. [ABSTRACT FROM AUTHOR]