RESUMEN
In order to realize effective monitoring for the working performance of seismic isolation structures, a multi-walled carbon nanotube (MWCNT)/methyl vinyl silicone rubber (VMQ) composite was prepared via mechanical blending using dicumyl peroxide (DCP) and 2,5-dimethyl-2,5-di(tert-butyl peroxy)hexane (DBPMH) as vulcanizing agents. The effects of the different vulcanizing agents on the dispersion of the MWCNT, electrical conductivity, mechanical properties, and resistance-strain response of the composites were investigated. The experimental results showed that the percolation threshold of the composites prepared with the two vulcanizing agents was low, while the DCP-vulcanized composites showed high mechanical properties and a better resistance-strain response sensitivity and stability, especially after 15,000 loading cycles. According to the analysis using scanning electron microscopy and Fourier infrared spectroscopy, it was found that the DCP contributed higher vulcanization activity, a denser cross-linking network, better and uniform dispersion, and a more stable damage-reconstruction mechanism for the MWCNT network during the deformation load. Thus, the DCP-vulcanized composites showed better mechanical performance and electrical response abilities. When employing an analytical model based on the tunnel effect theory, the mechanism of the resistance-strain response was explained, and the potential of this composite for real-time strain monitoring for large deformation structures was confirmed.
RESUMEN
Three different blending procedures were used to create multiwalled carbon nanotube (MWCNT)-modified chloroprene rubber (CR)/natural rubber (NR) blended composites (MWCNT/CR-NR). The effects of the blending process on the morphology of the conductive network and interfacial contacts were researched, as well as the resistance-strain response behavior of the composites and the mechanism of composite sensitivity change under different processes. The results show that MWCNT/CR-NR composites have a wide strain range (ε = 300%) and high dynamic resistance-strain response repeatability. Different blending procedures have different effects on the morphology of the conductive network and the interfacial interactions of the composites. If the blending procedures have wider conductive phase spacing and stronger interfacial contacts, the change in the conductive path and tunneling distance occurs more rapidly, and the material has a higher resistance-strain response sensitivity.
RESUMEN
The dispersion, electrical conductivities, mechanical properties and resistance-strain response behaviors of multiwalled carbon nanotube (MWCNT)/natural rubber (NR) composites synthesized by the different processing conditions are systematically investigated at both macro- and micro-perspectives. Compared with the solution and flocculation methods, the two roll method produced the best MWCNTs distribution since the materials are mixed by strong shear stress between the two rolls. An excellent segregated conductive network is formed and that a low percolation threshold is obtained (~1 wt.%) by the two roll method. Different from the higher increases in conductivity for the composites obtained by the solution and flocculation methods when the MWCNT content is higher than 3 wt.%, the composite prepared by the two roll method displays obvious improvements in its mechanical properties. In addition, the two roll method promotes good stability, repeatability, and durability along with an ultrahigh sensitivity (GFmax = 974.2) and a large strain range (ε = 109%). The 'shoulder peak' phenomenon has not been observed in the composite prepared by the two roll method, confirming its potential for application as a large deformation monitoring sensor. Moreover, a mathematical model is proposed to explain the resistance-strain sensing mechanism.
RESUMEN
Kashgarian loach, Triplophysayarkandensis (Day, 1877), a native species in the Tarim River of Northwest China, has been dramatically declined in population size in recent years. In this article, the mitochondrial genome of Kashgarian loach was first determined. The whole mtDNA sequence was 16,574 bp in length, which is similar to other bony fishes in gene order, including 2rRNA genes, 22tRNA, 13 protein-coding and 1 putative control region.