We have investigated the formation of tungsten oxide nanowires under different chemical vapor deposition (CVD) conditions. We find that exposure of oxidized tungsten films to hydrogen and methane at 900 degrees C leads to the formation of a dense array of typically 10 nm diameter nanowires. Structural and chemical analysis shows that the wires are crystalline WO3. We propose a chemically driven whisker growth mechanism in which interfacial strain associated with the formation of tungsten carbide stimulates nanowire growth. This might be a general concept, applicable also to other nanowire systems. 相似文献
Linearized equations governing the thermo-mechanical behaviour of a binary mixture of inviscid fluids are derived. Restrictions which are sufficient for the equations to have a unique solution are imposed on some of the material constants. The propagation of plane harmonic waves of small amplitude in the mixture is examined and the inequalities are shown to ensure a physically reasonable response. As an application of the theory properties of acoustic waves in a binary mixture of ideal gases are evaluated numerically. 相似文献
Environmentally benign synthesis of novel pegylated polyphenolics, by combining the extraordinary selectivities of a lipase and an oxidase to develop polymeric electrolytes for applications in dye sensitised solar cells. 相似文献
Self‐doped sulfonated polyaniline (PSA) has been synthesized on the surface of micellar nanoparticles made from positively charged surfactants by biocatalysis. The conformation forced by the electrostatic charge interactions between the positively charged micelle and the negatively charged PSA increases the conductivity of the PSA by three orders of magnitude. The pure PSA recovered from ion exchange, however, shows quite similar electrical properties compared with sulfonated polyanilines reported earlier. The increased conductivity of PSA complexes is as a result of the increased charge carrier concentration caused by a certain conformational locking.
Cerebral autoregulation is the mechanism which controls blood flow to the brain despite variations in blood pressure. Although important this mechanism is currently not well understood, with autoregulatory failure difficult to diagnose. In this paper we develop a simple model based upon those measurements available in the clinical setting. The model can replicate previous results and is used to investigate a variety of hypothetical autoregulatory responses. Furthermore the model has been extended by including the autoregulatory vessels themselves to explain the observed influence of increased carbon dioxide levels in the blood. A focus on only those measurements which may be realistically obtained in human patients avoids the need for estimating many unknown parameters or the modelling of complex and poorly understood physiological process necessary in previous, more complicated, models. 相似文献
In situ topochemical polymerization of two diacetylene monomers within nanoporous TiO2 thin films was carried out under visible light irradiation. One of the monomers used contains a carboxylic acid group, which could help to link the monomer onto the TiO2 surface covalently. UV-Vis absorption and Raman studies showed that both monomers were successfully photopolymerized. These results suggest that the covalent linkage of the diacetylene to the nanoparticle through the carboxylic acid group is not needed. Since photopolymerization of diacetylene is typically induced by excitation of the monomer at λ< 300 nm, the observed red shift of the photopolymerization wavelength is attributed to the photosensitization effect of TiO2. The morphological study of the polydiacetylene/TiO2 nanocomposite revealed that the diacetylene monomers were polymerized in the vicinity of the TiO2 nanoparticles. This is attributed to the fact that the electron-transfer process occurs at the interface of nanocrystalline TiO2 (nc-TiO2) and the diacetylene monomer and the polymerization is expected to be initiated near the nc-TiO2 surface. Photopolymerization of the carboxylated diacetylene monomer with other oxides nanoparticles, such as ZnO and SiO2 was also investigated.相似文献
We have used the formation of surface relief gratings (SRG) on azobenzene polymers to manipulate TiO2 nanoparticles and to fabricate TiO2 nanoparticle gratings. Suspensions of an azobenzene polymer (PDO3) and TiO2 were used to spin coat thin films on glass slide substrates. By interfering coherent light from an Argon laser on the surface of the PDO3‐TiO2 composite films, SRGs were fabricated. Atomic force microscopic images of the SRGs show TiO2 nanoparticles dispersed throughout the sample, and in particular, at the peaks of the SRG after oxygen plasma treatment. The lateral forces acting on the azobenzene polymer during the SRG fabrication drag the TiO2 nanoparticles. These results indicated that it is feasible to create TiO2 nanoparticle gratings with the composites. 相似文献