RESUMEN
Monodispersed LiFePO4 nanocrystals with diverse morphologies were successfully synthesized via a mild and controllable solvothermal approach with a mixture of ethylene glycol and oleic acid as the solvent. Morphology evolution of LiFePO4 nanoparticles from nanoplates to nanorods can be simply realized by varying the volume ratio of oleic acid to ethylene glycol. Moreover, the mechanism of competitive adsorption between ethylene glycol and oleic acid was proposed for the formation of different morphologies. Electrochemical measurements show that the LiFePO4/C nanorods have an initial discharge capacity of 155 mA h g(-1) at 0.5 C with a capacity retention of 80% at a high rate of 5 C, which confirms that LiFePO4/C nanorods exhibit excellent rate capability and cycling stability.
RESUMEN
(1) Background: It is simpler and more environmentally friendly to use supercritical CO2 fluid technology to process skincare viscose fabrics. Therefore, it is significant to study the release properties of drug-loaded viscose fabrics to choose suitable skincare drugs. In this work, the release kinetics model fittings were investigated in order to clarify the release mechanism and provide a theoretical basis for processing skincare viscose fabrics with supercritical CO2 fluid. (2) Methods: Nine kinds of drugs with different substituent groups, different molecular weights, and different substitution positions were loaded onto viscose fabrics using supercritical CO2 fluid. Then, the drug-loaded viscose fabrics were placed in an ethanol medium, and the release curves were drawn. Finally, the release kinetics were fitted using zero-order release kinetics, the first-order kinetics model, the Higuchi model, and the Korsmeyer-Peppas model. (3) Results: The Korsmeyer-Peppas model was the best-fitting model for all the drugs. Drugs with different substituent groups were released via a non-Fickian diffusion mechanism. On the contrary, other drugs were released via a Fickian diffusion mechanism. (4) Conclusions: In view of the release kinetics, it was found that the viscose fabric can swell when a drug with a higher solubility parameter is loaded onto it using supercritical CO2 fluid, and the release rate is also slower.
RESUMEN
Millions of tons of feather are produced worldwide each year and considered as a solid waste owing to technical or cost constraints to provide valuable functional characteristics. In this study, a novel and ecofriendly method to recycle waste feather and obtain a type of explosion down via flash explosion with a supercritical fluid of carbon dioxide (SCF-CO2) was developed for the first time. The effects of flash explosion parameters on the structures and properties of feather were explored by orthogonal experiments. A mechanism involving two-step procedures for the developed SCF-CO2 flash explosion is proposed. The obtained results indicate that reinforcements of flash explosion conditions, particularly the system pressure, were readily conducive to transfer the original feather to a soft down with an improved separation ratio, as well as easily weaken or break hydrogen and disulfide bonds associated in feather macromolecules. Moreover, efficient modifications of the physical characteristics, structures and surface morphologies of the waste feather were obtained by the SCF flash explosion to produce a uniform, slender and fibrous explosion down, as demonstrated by scanning electron microscopy, Fourier-transform infrared spectroscopy, and X-ray diffraction analysis. Further tests on the SCF explosion down treated at 70.0 °C at 15.0 MPa for 30.0 min and at 90.0 °C at 20.0 MPa for 20.0 min showed remarkable enhancements in warmth retention along with comparable thermal degradation nature, as well as enhanced softness, down-proof, and other service properties in comparison to the original feather. The SCF-CO2 flash explosion is a promising approach with environment-friendly characteristics to obtain high efficiency and quality of the explosion down by recycling of waste feather.
RESUMEN
(1) Background: Supercritical CO2 fluid (SCF-CO2)-assisted impregnation presents advantages on loading active drugs to polymer substrates, since it enables the realization of a drug-loaded polymer without any solvent residue. Besides, CO2 gas and drugs can be recycled and utilized again. Resveratrol-loaded diacetate fiber by SCF-CO2-assisted impregnation was done to give diacetate fiber biological activity function for enhancing its added value. (2) Methods: The effect of SCF-CO2 temperature, pressure and treatment time on loading ability (LA) of resveratrol onto diacetate fiber was explored by ultraviolet visible spectrophotometer. The variation of structure and property of diacetate fiber was analyzed by characterization instruments. (3) Results: LA had been increasing with SCF-CO2 treatment time, temperature and pressure when SCF-CO2 was above 70 °C, 12 MPa. The inhibiting rate of resveratrol to free radicals was affected positively by SCF-CO2. After resveratrol was impregnated by SCF-CO2 it appeared some small white granular substances on the surface of diacetate fiber. It had a good interaction between resveratrol and molecular chain of diacetate fiber. (4) Conclusions: Resveratrol was well-loaded onto the diacetate fiber by SCF-CO2 assisted impregnation.
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Superior flame retardant textiles are urgently needed to address high fire and heat risks. This study provides a simple and effective strategy to improve the flame retardancy of textiles through a synergistic effect between the blended fibers, and a system with synergistic in flame retardant vinylon (FRV)/poly(m-phenylene isophthalamide) (PMIA) blended fibers is discovered. The FRV/PMIA 50/50 exhibits a much higher time to ignition and a lower peak heat release rate than those of the neat components, indicating a synergistic flame retardancy between constituents. The corresponding mechanism is explored. The residual char layer formed by blended fibers connects together and keeps the original fiber shape, which acts as a barrier slowing heat transmission and gas diffusion. Concurrently, thermal degradation analysis of blended fibers implies that both components mutually interact with each other, resulting in a higher experimental amount of incombustible gases at an early degradation stage and lower experimental amount of combustible gases at a later degradation stage as compared to the theoretical one. Therefore, the synergistic flame retardancy in FRV/PMIA blended fibers is attributed to the actions in the condensed and gas phases during pyrolysis. This work provides an effective strategy to design fireproof textiles.
RESUMEN
With the increasing city size, high-power electromagnetic radiation devices such as high-power medium-wave (MW) and short-wave (SW) antennas have been inevitably getting closer and closer to buildings, which resulted in the pollution of indoor electromagnetic radiation becoming worsened. To avoid such radiation exceeding the exposure limits by national standards, it is necessary to predict and survey the electromagnetic radiation by MW and SW antennas before constructing the buildings. In this paper, a modified prediction method for the far-field electromagnetic radiation is proposed and successfully applied to predict the electromagnetic environment of an area close to a group of typical high-power MW and SW wave antennas. Different from currently used simplified prediction method defined in the Radiation Protection Management Guidelines (H J/T 10. 3-1996), the new method in this article makes use of more information such as antennas' patterns to predict the electromagnetic environment. Therefore, it improves the prediction accuracy significantly by the new feature of resolution at different directions. At the end of this article, a comparison between the prediction data and the measured results is given to demonstrate the effectiveness of the proposed new method.