Hydrogen titanate nanotubes (H-TTNT) were synthesized by the alkali hydrothermal method followed by proton exchange and then submitted either to thermal treatment or to acid hydrothermal reaction to generate TiO2-anatase nanocrystals of different morphologies. The samples were characterized by XRPD, TGA, sulfur analysis, N2 physisorption, UV-Vis spectroscopy and TEM. Their photocatalytic activities were determined by measuring the NO conversion in inert gas stream passed through the powder catalyst bed under UV radiation. Incomplete transformation into anatase resulted in nanomaterials with low activity due to coexistence with H-TTNT or TiO2-B precursors. Anatase specimens derived from H-TTNT aged in strong sulfuric acid media contained equidimensional nanoparticles, but retention of sulfate negatively affected their photocatalytic activity. Combining milder acidic pH with higher aging temperature, allowed synthesis of a sulfate free anatase with the same optical properties and specific surface area as the counterpart produced by calcination of H-TTNT at 550°C; however, the former exhibited truncated bi-pyramid nanocrystals and the other adopted the form of nanorods. This latter showed the highest photocatalytic activity for NO abatement, outperforming the benchmark photocatatyst TiO2-P25; this improved activity was tentatively ascribed to the maximization of high energy {001} facets in anatase nanorods formed during calcination of H-TTNT.
We study an extension of the classical Paley–Wiener space structure, which is based on bilinear expansions of integral kernels into biorthogonal sequences of functions. The structure includes both sampling expansions and Fourier–Neumann type series as special cases, and it also provides a bilinear expansion for the Dunkl kernel (in the rank 1 case) which is a Dunkl analogue of Gegenbauer’s expansion of the plane wave and the corresponding sampling expansions. In fact, we show how to derive sampling and Fourier–Neumann type expansions from the results related to the bilinear expansion for the Dunkl kernel. 相似文献
This report presents an assessment on colloidal stability of functionalized multiwalled carbon nanotubes based nanofluids. To this end, an innovative technique that allows for measurement of settling velocity during centrifugation is applied. This method also enables measurements without dilution, inferring further accuracy to the experimental study. The results suggest that functionalization techniques enable the production of highly stable nanofluids. It is also found, that the colloidal stabilities of these nanofluids are characterized by hindered settling. The settling velocity decreases when the nanoparticles volume fraction rises from 0.25% to 1.50% due to the increase of interparticle interaction. Furthermore, a high aspect ratio of nanoparticles directly contributed to an increase in colloidal stability. It is expected that these results may significantly contribute to proper tailor of nanofluids engineering, ensuring a long term stable dispersion enhancing industrial application suitability. 相似文献
Common thermoplastic films used in the packaging industry have a thickness lower than 100 μm, and present low absorption to CO2 laser radiation. This characteristic renders the use of cutting parameters, predicted by models developed for thicker thermoplastics inappropriate. In addition, the usual procedures involve the use of an assisting gas, responsible for removing the melted material, which, when processing thin films, induces changes in position in the material. A new theoretical model describing the temperature distribution on thin thermoplastic material during laser cutting was later developed. The heat conduction was solved analytically by the Green function method and heating and cooling thermal stress evolution was taken into consideration. The laser beam diameter over the samples provides the possibility of obtaining two cut operations: a simple cut, on beam focus, and a cut with welding, defocusing the beam. Engineering parameters predicted by the model were applied to cutting superposed high- and low-density polyethylene and polypropylene samples, transparent and white, with thicknesses between 10 and 100 μm, and experimentally validated.Proper modeling and the introduction of a reflective substrate under the samples allowed the improvement of process efficiency and the achievement of cutting operations up to 20 m s−1, and cut with welding up to 14 m s−1; an order of magnitude of improvement on industrial speeds previously attained for this operation. 相似文献
We consider the problem of identifying boundary values of holomorphic functions on bounded domains in ℂ2. We use the quaternionic analysis techniques to extending the CR structure to a pure function theoretical nature. The advantage of our procedure lies in the fact that it also runs for domains
with fractal boundary. 相似文献
Journal of Solid State Electrochemistry - Thymol, a potent agent for microbial, fungal, and bacterial disease, has low aqueous solubility and it is genotoxic, i.e., is capable of damaging... 相似文献