SEARCH · Engineering Papers
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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A new software program, xINTERPDF , that analyzes the intermolecular correlations in organic compounds via measured X-ray total scattering data is described.
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Photobleaching rates are investigated for thin films of poly(3-hexylthiophene) (P3HT) blends employing either an indene-C60 bisadduct (ICBA) or [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) as the electron acceptor. Relative to the bisindene, PCBM significantly enhances resistance to photobleaching of the P3HT donor polymer. We tentatively attribute a decrease in the charge transfer rate asthe mechanism responsible for the more rapid photobleaching in the sample containing the bisindene adduct. In order to elucidate the influence of the photobleaching rate on the initial performance of unencapsulated devices, we also monitored the time-dependent behavior for P3HT:fullerene inverted devices. Under conditions of constant illumination, we observe essentially identical behavior indevice performance parameters regardless of the energy levels of the electron acceptor. We conclude that over the time frame measured for these devices, the primary degradation mechanism of the active layer is independent of the electron acceptor, despite the enhanced tolerance to photobleaching it may impart to the donor material.
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SO3 additions, up to 3.0 wt%, were systematically investigated for effects on the physical properties of sodium borosilicate glass melted in air, with a sulfur-free composition of 50SiO2-10Al2O3-12B2O3-21Na2O-7CaO (wt%). Solubility measurements, using electron microscopy chemical analysis, determined the maximum loading to be ~1.5 wt% SO3. It was found that sulfur (here as sulfate) in this glass increased the glass transition temperature, thermal diffusivity, heat capacity, and thermal conductivity, and decreased the mass density. Structural analysis, performed with Raman spectroscopy, indicated that the borosilicate network polymerized with sulfur additions, presumably due to Na2O being required to charge compensate the ionic SO42- additions, thus becoming unavailable to form non-bridging oxygen in the silicate network. It is postulated that this increased crosslinking of the borosilicate backbone lead to a structure with higher dimensionality and average bond energy. This increased the mean free paths and vibration frequency of the phonons, which resulted in the observed increase in thermal properties.
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