Synchrotron X-ray reflectivity studies of nanoporous organosilicate thin films with low dielectric constants

Quantitative, non-destructive X-ray reflectivity analysis using synchrotron radiation sources was successfully performed on nanoporous dielectric thin films prepared by thermal processing of blend films of a thermally curable polymethylsilsesquioxane dielectric precursor and a thermally labile triethoxy-silyl-terminated six-arm poly(epsilon-caprolactone) porogen in various compositions. In addition, thermogravimetric analysis and transmission electron microscopy analysis were carried out. These measurements provided important structural information about the nanoporous films. The thermal process used in this study was found to cause the porogen molecules to undergo efficiently sacrificial thermal degradation, generating closed, spherical nanopores in the dielectric film. The resultant nanoporous films exhibited a homogeneous, well defined structure with a thin skin layer and low surface roughness. In particular, no skin layer was formed in the porous film imprinted using a porogen loading of 30 wt%. The film porosities ranged from 0 to 33.8% over the porogen loading range of 0-30 wt%open131

Synthesis of Polycrystalline Zeolite Films and Thermal Conductivity Measurements by a 3-Omega Method NANO2004-46092

ABSTRACT Zeolites (nanoporous crystalline aluminosilicates) have important applications in catalysis and separations In this study, polycrystalline zeolite thin films [6] are synthesized and used to measure the thermal conductivity of zeolites by a 3-omega method reported recently [7]. By using a zeolite film with intergrown crystals rather than a compacted powder sample, thermal conductivities close to that of a single crystal can be obtained. The nanoporous zeolite MFI with pore size of approximately 0.6 nm was grown hydrothermally into oriented films (ca. 25 microns thin) by the secondary (seeded) growth method. The secondary growth consists of two steps. Firstly, zeolite nanocrystals (~ 100 nm in size) are deposited onto a glass substrate by dip coating from a zeolite suspension, at the rate of 2 cm/hour in order to obtain a uniform seed layer. The coated substrate is air dried for approximately 24 hours, and then is placed on the bottom of a Teflon autoclave, leaning on the wall of the autoclave. The membrane growth solution containing silica and alumina suspension is mixed at room temperature and poured into the autoclave. The autoclave is sealed and heated at 453 K for 1-3 days. The membranes are rinsed with hot water and then dried. Some of the membranes Copyright © #### by ASME are calcined in order to remove the organic template. SEM images of calcined MFI membrane and the X-Ray diffraction show an oriented columnar structure, as shown in The thermal conductivities of these thin films have been measured as a function of temperature using a 3ω method [7]. A thin copper strip deposited on the zeolite membrane ( ACKNOWLEDGMENTS We acknowledge financial support from the Georgia Institute of Technology and the National Science Foundation

Electrostatic Interaction of Multi-walled Carbon Nanotubes Composites with CdTe and CdSe Nanoparticles

Composites were prepared by the electrostatic interaction between carboxylated multi-walled carbon nanotubes (c-MWNTs) and either cadmium telluride (CdTe) or cadmium selenide (CdSe) nanoparticles. Multi-walled carbon nanotubes (MWNTs) were oxidized by an aqueous acid mixture, and both the CdTe and CdSe nanoparticles were stabilized by 2-(dimethylamino) ethanethiol hydrochloride in water to develop negatively and positively charged outer surfaces, respectively. Optical properties were investigated by UV/Vis and photoluminescence (PL) analyses. CdX (X = Te, or Se) nanoparticles showed emissions at the same position regardless of the existence of c-MWNTs. This result suggests that the interaction between CdX and c-MWNTs does not affect the photoluminescence of CdX nanoparticles in their composites. The binding energies and redox potential positions of the CdX nanoparticles in their c-MWNT-CdX composites shifted from those of the pure nanoparticles. These changes indicate that the electron densities on the interfaces of CdX nanoparticles and c-MWNTs were redistributed after the formation of composites due to the strong electrostatic interaction between the components. © KIM and Springer.FALS

Electrochemical oxidation of some basic alcohols on multiwalled carbon nanotube-platinum composites

Some composites of multiwalled carbon nanotubes, which were chemically treated in acidic and/or hydrogen peroxide solution, and platinum nanoparticles were prepared by the simple reduction in glycerol solution. Carboxylated and/or hydroxyl MWNTs were structurally analysed using X-ray photoelectron spectroscopy. In addition, the MWNT-Pt composites were characterized by XRD and TEM in detail. The electrochemical oxidation of some basic alcohols, which was catalyzed by the MWNT-Pt composites, was analysed by cyclic voltammetry. Their catalytic activities were studied with cyclic voltammograms of alcohols. © Indian Academy of Sciences.