Effect of the binding interfaces of composite polydimethylsiloxane (PDMS) membranes on their pervaporation performance was studied. The membranes were made up of PDMS as active skin layer and polysulfone (PSF) or polyamide (PA) as supporting layer. PDMS-PSF membrane was numbered 1, and PDMS-PA membrane numbered 2. The pervaporation experiments were carried out by using the composite membranes and dilute ethanol-water mixture. The experimental measurements for the permeation performance under various operating conditions (e.g., feed concentration and temperature) showed that the specific permeation rate of membrane 2 was over membrane 1 by seven times at least. A resistance-in-series model was applied to formularize the transport of the permeants. Influence of the binding interfaces between the active skin layer and support layers in these membranes on pervaporation performance was analyzed. The cross section morphology of the membranes and chemical element distribution along membrane thickness were examined by using SEM and EDS. It was found that, although the PDMS intrusion layer into PSF near the interface was only about 2 mm, it gave significant effect on the permeation performance. It implied that the resistance produced by the intrusion layer into PSF was apparently larger than that of PDMS intruding PA and over intrinsic PDMS resistance. These should be probably attributed to structures and formation of the binding interfaces.

Fumed-silica-filled polydimethylsiloxane (PDMS)-polyamide (PA) composite membranes were prepared by the introduction of hydrophobic fumed silica into a PDMS skin layer. The cross-sectional morphology of these filled composite membranes was observed with scanning electron microscopy. Their pervaporation performances were tested with aqueous ethanol solutions at 30, 35, and 408C. Increasing the amount of the fumed silica resulted in significantly enhanced ethanol permeability of the membranes. When the content of the fumed silica in the PDMS skin layer was 20 wt %, the ethanol permeability increased to nearly twice that of the unfilled PDMS-PA composite membrane.

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The development of semiconductor materials and devices will lead to a new industrial technology revolution, in which the Silicon Carbide (SiC) substrate material has very excellent performance and it is especially suitable for manufacturing wave length lasers, white light emitting tubes, high-frequency, high-temperature and high-power devices, etc. This paper focuses on solving the key problems for producing large size and low defects of SiC crystals by the PVT method, such as the preparation and purification of the high purity raw material, the simulation of the temperature field, the control of the crystal defects and the growth of the large size SiC crystals.It is critical for the development of SiC industry.