The Effects of Single-Wall Carbon Nanotubes on the Shear Piezoelectricity of Biopolymers

Shear piezoelectricity was investigated in a series of composites consisting of increased loadings of single-wall carbon nanotubes (SWCNTs) in poly (gamma-benzyl-L-glutamate), or PBLG. The effects of the SWCNTs on this material property in PBLG will be discussed. Their influence on the morphology of the polymer (degree of orientation and crystallinity), and electrical and dielectric properties of the composite will be reporte

Laser ablation of energetic polymer solutions: Effect of viscosity and fluence on the splashing behavior

ISSN:0947-8396ISSN:1432-0630ISSN:0340-379

Laser-Induced Surface Modification at Anatase TiO₂ Nanotube Array Photoanodes for Photoelectrochemical Water Oxidation

Nanostructured titanium dioxide (TiO₂) presents considerable potential as a photoanode in low cost, sustainable photoelectrochemical systems for solar water splitting. The wide band gap combined with the presence of trap states and reduced water oxidation kinetics limit, however, the photocurrent performance to only ∼1 mA cm^–2. Increasing the disorder of the crystal structure at the surface, on the other hand, has been proven to increase light absorption via band gap narrowing, and conversion efficiency. In this work, anodized TiO₂ nanotubes have been irradiated with a pulsed UV laser in deionized water environment to introduce lattice disorder. As a result, the photocurrent improved by 1.6-fold under simulated sunlight compared with pristine TiO₂ nanotube arrays at 1.23 V_RHE. For all samples the water oxidation reaction kinetics is determined to be the limiting step for the solar-to-current conversion at low bias (0.5–0.7 V_RHE), while modified nanotube arrays display a 78% water oxidation selectivity at 1.23 V_RHE, compared to 65% for the pristine TiO₂ nanotubes. The electronic density of states of the modified nanotubes is evaluated using electrochemical impedance spectroscopy, revealing that selective laser irradiation improved the number density of shallow donors while reducing the density of deep trap states

Planar defects as Ar traps in trioctahedral micas: A mechanism for increased Ar retentivity in phlogopite

The effects of planar defects and composition on Ar mobility in trioctahedral micas have been investigated in samples from a small marble outcrop (~500m 2) in the Frontenac Terrane, Grenville Province, Ontario. These micas crystallized during amphibolite-facies metamorphism at ~1170Ma and experienced a thermal pulse ~100Ma later at shallow crustal levels associated with the emplacement of plutons. 87Rb/ 86Sr ages of the phlogopites range from ~950 to ~1050Ma, consistent with resetting during the later thermal event. The same phlogopites however, give 40Ar/ 39Ar ages between ~950 and 1160Ma, spanning the age range of the two thermal events. This result is intriguing because these micas have undergone the same thermal history and were not deformed after peak metamorphic conditions. In order to understand this phenomenon, the chemical, crystallographical, and microstructural nature of four mica samples has been characterized in detail using a wide range of analytical techniques. The scanning electron microscope (SEM), electron microprobe (EMP), and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) data show that the micas are chemically homogeneous (with the exception of Ba) and similar in composition. The Fourier transform infrared spectroscopy and Mossbauer results show that the M sites for three of the micas are dominated by divalent cations and the Fe 3+/(Fe 2++Fe 3+) ratio for all four phlogopites ranges from 0.10 to 0.25. The stable-isotopic data for calcite indicate that this outcrop was not affected by hydrothermal fluids after peak metamorphism. No correlation between chemical composition and 87Rb/ 86Sr and 40Ar/ 39Ar age or between crystal size and 40Ar/ 39Ar age is observed. The only major difference among all of the micas was revealed through transmitted electron microscope (TEM), which shows that the older 1M micas contain significantly more layer stacking defects, associated with crystallization, than the younger micas. We propose that these defect structures, which are enclosed entirely within the mineral grain may serve as Ar traps and effectively increase the Ar retentivity of the mineral. As this phenomenon has not been previously documented in micas, this may have significant implications for the interpretation of 40Ar/ 39Ar ages of minerals which have similar defect structures