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91.
High resolution XPS analysis of chemical functionalised multi-wall carbon nanotubes (MWCNTs) and single wall carbon nanotubes (SWCNT) was done with ESCA300 (overall instrument resolution of 0.35 eV). Information to the degree of functionalisation was ascertained by argon ion bombardment of the samples followed by XPS analysis to detect the functional groups, the percentage atomic concentration of various elements present and whether or not the detected functional groups imposed a chemical shift on the CNT atoms. The results show that true chemical functionalisation was achieved and by argon ion bombardment these functional groups can be altered relative to the C 1s carbon atoms of the CNT. The choice of chemicals used for functionalisation, the techniques employed and the types of nanotubes treated are important factors in chemical characterisation. The carbon atom on the nanotube ring to which the functional group (atom) is bonded, the chirality of the CNT, the electronegativity of the functional group, the bond type and whether the CNT is single-wall or multi-wall, or cut (short) could play a role in determining the chemical shift on the CNTs atoms. These investigations are relevant to chemical functionalisation of carbon nanotubes for various applications for example DNA sensors and other biomedical sensors. 相似文献
92.
A comprehensive experimental investigation was performed to understand the pullout behavior of polypropylene fibers from a cementitious matrix. The effect of embedded length on the pullout characteristics, the development of the interfacial bond with age of curing of matrix and the effect of exposure to degrading environments, like seawater and salt water, on the interfacial bond between the fibers and cementitious matrix were studied. The aim of these experiments was to understand the properties of fiber/matrix interface, which are of primary significance in predicting the overall behavior of fiber-reinforced cement-based composites. Polypropylene fibers have a weak bond with cementitious matrix because of smooth surface of fibers, which does not allow for sufficient friction to develop between the two. In this study a new method to improve the frictional bond by means of mechanical indentations of fibers was also proposed. The bonding performance was characterized by means of pullout tests of the plain and modified fibers from a cementitious matrix. An optimum level of fiber modification for maximization of bond efficiency was determined experimentally. 相似文献
93.
Measurements of relaxation times, T1 and T2, and self-diffusion coefficients, D, for small molecules, viz., H2O, dioxane and t-butanol, in the gel system cellulose/H2O are reported and compared with those for H2O in a polyacrylamide gel of the same polymer content. The temperature dependence of T1 and D can for all the penetrants be represented by Arrhenius type relations which merely are parallel shifts by the same amount, towards smaller values, of those obtained without polymer. The T2 values for H2O in both gels pass through a shallow minimum over the considered temperature interval (14°?44°C). Furthermore, relaxation times T1 of D2O in the gel system cellulose/D2O are reported; in a plot of ln T1 vs. 1/T, a plateau region is observed at higher temperatures. 相似文献
94.
Using a novel sorption technique, the diffusion of some series of solutes in polyacrylamide gels has been investigated with regard to: (a) molecular size of solute; (b) concentration of solute and gel polymer; and (c) temperature. The approach used also yields the partition coefficient pertaining to sorption equilibrium. The ratio, , where Do refers to diffusion in the pure solvent, is found to reflect in part the characteristic interactions between solute and gel polymer. The temperature results indicate that the apparent activation energy for solute diffusion is approximately independent of the polymeric component for dilute gels. 相似文献
95.
T.I.T. Okpalugo P. Papakonstantinou H. Murphy J. Mclaughlin N.M.D Brown 《Carbon》2005,43(14):2951-2959
The surface compositional and any structural changes that occur on carbon nanotubes using air-atmospheric pressure dielectric barrier discharge (APDBD) for functionalization are investigated employing Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), thermal gravimetric analysis (TGA), X-ray diffraction (XRD), and neutron diffraction techniques. Atmospheric pressure plasmas (APP) are suggested to be particularly suitable for functionalization of aligned nanotubes, where wet chemical manipulation could damage or even destroy the highly desirable vertical alignment. In this work a detailed experimental study elucidating the effects of APDBD plasma treatment parameters (e.g. power density, discharge composition, inter-electrode gap and treatment time) on the electronic structure, physical, and chemical behaviour of carbon nanotubes has been conducted. In an atmospheric air we find an optimal oxidative functionalization of CNTs in our DBD system within few seconds (<5 s) at a discharge power of ∼0.5 kW. This investigation may find useful application as functionalization technique for CNT engineered devices and sensors. 相似文献
96.
Electrochemical pre-treatment of industrial wastewater to remove refractory and/or toxic organic components, making them more
amenable to biological treatment, is likely to be more cost-effective than using a physical or chemical process for complete
organic removal. This paper demonstrates the use of a carbon-based adsorbent material that preferentially removes chlorinated
organic compounds. Electrochemical regeneration of the adsorbent is shown to be a quick, easy and cheap process, because the
adsorbent is both highly electrically conducting and non-porous. High regeneration rates over a number of cycles were obtained
by passing a charge of 25 C g−1 through a bed of adsorbent particles, at a current density of 20 mA cm−2 for 10 min. The energy required to remove a kg of COD from an industrial wastewater was calculated to be 27 kWh. 相似文献
97.
Various metal halides have been dispersed in high and low molecular weight, amorphous poly(propylene oxide), by solution blending techniques, to give single phase polymeric complexes which remained thermoplastic even at very high salt loadings. These complexes were amorphous and showed a single well-defined glass transition temperature (Tg) by differential thermal analysis with the Tg of the complex up to 140°C greater than the Tg of the parent polymer. The Tg elevation depended upon both the amount and the type of salt added and for a given salt the elevation followed a sigmoidal curve which levelled out at high salt concentrations. The Tg data have been interpreted in terms of a chelate ring model involving the co-ordination of two adjacent ether oxygen atoms in the polymer backbone to the salt. Using this model it was possible to consider the complex as a random copolymer consisting of complexed and uncomplexed monomer units. The contribution of crosslinking by metal salts to the elevation of Tg was assessed by studying poly(tetramethylene glycol)-zinc chloride complexes in which chelate formation is entropically unfavourable. Mechanical data are reported for ZnCl2 complexes with high molecular weight poly(propylene oxide). The results indicate that ZnCl2 increased the rubbery modulus and this has been interpreted in terms of ZnCl2 forming a few, weak intermolecular crosslinks. 相似文献
98.
T. Venkatesan W. L. Brown C. A. Murray K. J. Marcantonio B. J. Wilkens 《Polymer Engineering and Science》1983,23(17):931-934
Thin polymer films were irradiated in a high vacuum environment with energetic (~2 MeV) ions. The emitted molecular species were studied with a quadrupole mass spectrometer during bombardment. The emitted species are predominantly small molecules. The efficiency of emission depends strongly upon the electronic energy loss of the incident ions in the film and, hence, upon the velocity and atomic number of the incident ion. The emission efficiency of all species decreases with increasing damage in the film. By pulsing the ion beam, the time dependence of irradiation induced emission of molecular species from the films has been studied. Emission delays of hundreds of milliseconds are observed in some cases. These delays are found to depend upon the emitted species as well as the host film and seem to be associated with diffusion of the species in the films. 相似文献
99.
C. J. Brown D. Pletcher F. C. Walsh J. K. Hammond D. Robinson 《Journal of Applied Electrochemistry》1993,23(1):38-43
Measurements of the mass transport limited current for the reduction of ferricyanide in 1M m potassium hydroxide and of copper(II) in 1.5 m sulphuric acid as a function of electrolyte flow rate are used to characterize the space-averaged mass transport properties of the FM01 laboratory electrolyser, with and without six types of polymer mesh turbulence promoters. In the absence of a promoter, the results followed the equation
For the cell with the preferred turbulence promoter, the corresponding equation is
Pressure drop data are also reported and it is confirmed that the presence of a turbulence promoter need not lead to a significant increase in the pressure drop over the reactor. 相似文献
100.
A new type of ion implantation technique is used to create a non-equilibrium Pt-Sn(IMP) near-surface alloy with ca. 8.6 at%
Sn. The surface composition was determined by low-energy ion-scattering (LEIS). The kinetics of the electrooxidation of CO
and 2% CO/H2 mixtures on Pt-Sn(IMP) is essentially identical to that of Pt3Sn(110). The fact that any non-equilibrium composition can be easily prepared by this implantation method opens an interesting
practical opportunity to create a new Pt-Sn alloy fuel cell catalyst having an otherwise unobtainable surface composition
of Sn. This method also appears to have general utility in alloy catalysis as a means of exploring compositions in thermodynamically
unfavorable regions of the bulk phase diagram.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献