Sol-gel matrix modified microstructured optical fibre towards a fluoride sensitive optical probe

In this article, we report an optical fluoride probe based on microstructured polymer optical fibers (MPOFs) which is modified with morin-Al complex doped silica gel film. This probe is fabricated by sol-gel fluxion coating process. Sol solution doped with morin-Al is directly inhaled into array holes of MPOF and then forms morin-Al-gel matrix film in them. The sensing probe shows different fluorescence intensity to different fluoride ion concentrations in the aqueous solution. The range of response is 550 mmol/L, under the condition of pH 4.6. Crown Copyright (C) 2009 Published by Elsevier B.V. All rights reserved.

A four-phase confocal elliptical cylinder model for predicting the effective thermal conductivity of coated fibre composites

A four-phase confocal elliptical cylinder model is proposed from which a generalised self-consistent method is developed for predicting the thermal conductivity of coated fibre reinforced composites. The method can account for the influence of the fibre section shape ratio on conductivity, and the physical reasonableness of the model is demonstrated by using the fibre distribution function. An exact solution is obtained for thermal conductivity by applying conformal mapping and Laurent series expansion techniques of the analytic function. The solution to the three-phase confocal elliptical model, which simulates composites with idealised fibre-matrix interfaces, is arrived at as the degenerated case. A comparison with other available micromechanics methods, Hashin and Shtrikman's bounds and experimental data shows that the present method provides convergent and reasonable results for a full range of variations in fibre section shapes and for a complete spectrum of the fibre volume fraction. Numerical results show the dependence of the effective conductivities of composites on the aspect ratio of coated fibres and demonstrate that a coating is effective in enhancing the thermal transport property of a composite. The present solutions are helpful to analysis and design of composites.

Electrochemical behavior of redox species at carbon fibre microdisk array electrode modified with mixed-valent molybdenum(VI, V) oxide

In this study, electrode responses to a large number of electroactive species with different standard potentials at the molybdenum oxide-modified carbon fibre microdisk array (CFMA) electrode were investigated. The results demonstrated that the electrochemical behavior for those redox species with formal potentials more positive than similar to 0.0 V at the molybdenum oxide-modified CFMA electrode were affected by the range and direction of the potential scan, which were different from that at a bare CFMA electrode. If the lower limit of the potential scan was more positive than the reduction potential of the molybdenum oxide film, neither the oxidation nor the reduction peaks of the redox species tested could be observed. This indicates that electron transfer between the molybdenum oxide film on the electrode and the electroactive species in solution is blocked due to the existence of a high resistance between the film and electrolyte in these potential ranges. If the lower limit of the potential scan was more negative than the reduction potential of the molybdenum oxide film (similar to - 0.6 V), the oxidation peaks of these species occurred at the potentials near their formal potentials. In addition, the electrochemical behavior of these redox species at the molybdenum oxide-modified CFMA electrode showed a diffusionless electron transfer process. On the other hand, the redox species with formal potentials more negative than similar to - 0.2 V showed similar reversible voltammetric behaviors at both the molybdenum oxide-modified CFMA electrode and the bare electrode. This can be explained by the structure changes of the film before and after reduction of the film. In addition we also observed that the peak currents of some redox species at the modified electrode were much larger than those at a bare electrode under the same conditions, which has been explained by the interaction between these redox species and the reduction state of the molybdenum oxide film. (C) 2000 Elsevier Science Ltd. All rights reserved.