By bidirectionally freeze-casting silver nanowire (AgNW) suspension, we synthesized hierarchical AgNW aerogel (AgNWA). The AgNWA shows two hierarchical levels: (1) AgNW fabric-like ribbons of interlacing AgNWs and (2) axially and radially aligned assembly of AgNW ribbons. The AgNW ribbons are also connected by AgNW bridges. The AgNWAs have ultrahigh porosity (∼99.7%) and anisotropic electrical and thermal properties. Furthermore, AgNWA is used to enhance phase change materials (PCMs) for high-efficiency thermal energy storage. AgNWA-paraffin PCM nanocomposite was synthesized by infiltrating the AgNWA with paraffin. The PCM composite shows anisotropic electrical conductivity, ∼ 130% thermalefficiency enhancement, and strong reliability against thermal cycling. Moreover, the effective PCM composite's thermal capacity (latent heat) is also significantly enhanced, implying a strong AgNW-paraffin interfacial bonding. Thus, a hierarchical and anisotropic AgNWA is fabricated via a bidirectional freezecasting technique, and it can largely enhance the performance and reliability of PCMs. This provides important insights into the design of oriented three-dimensional network of nanomaterials and also thermal energy storage composites with high performance and reliability.
Organic phase change materials (PCMs) show much potential for thermal energy storage, but the liquid leakage tendency limits their practicality. This can be mitigated by encapsulation using a polymer shell. Fatty acids are promising for encapsulation due to the potentially strong bonding with the polymer shell materials to potentially enhance the overall thermal efficiency. Previous studies on encapsulating fatty acids are on the micro-or mesoscales, but in this study, the focus is on nanoscale encapsulation, which has the advantage of enhanced thermal conductivity. A nanoencapsulated poly(methyl methacrylate)shelled lauric acid core system is created. The system has strong performance characteristics: high latent heat (up to 130 J/g) and particularly excellent thermal reliability (over 2000 cycles). Moreover, by changing the surfactants, the PCM capsule size can be tuned between 400 and 1000 nm with a shell thickness range of 20−100 nm. Controlling of molecular diffusion and flow is potentially the dominant mechanism for greatly enhancing the reliability of nanoencapsulated energy storage materials. Furthermore, infrared spectroscopy (IR) is proved to be a fast search tool to test the PCM encapsulation conditions. Conventionally, differential scanning calorimetry (DSC) is used to evaluate the PCM encapsulation. Compared to DSC, the IR-based technique is much faster (<1.0 min), requiring a minimal sample amount (<0.1 mg), and is consumable-free. Thus, the IR-based technique could help greatly speed up the finding of optimal conditions for fabricating highperformance encapsulated PCMs.
This paper studied the configuration of spinning technology of PTT (polytrimethylene terephthalate)/PET (polyethylene terephthalate) bicomponent fiber via measurements obtained from the elasticity testing of fabrics made of them. The effects of four main spinning parameters on the elasticity of two series, named Z and Q, of interwoven fabrics were explained, including different ways of binding, intrinsic viscosity differences, and the percentage contents of PTT and the temperature of the hot plate. The experimental results indicated that the elongation ratios of the fabrics, which were made of PTT/PET bicomponent filaments spun by the parallel bound method, with larger differences in the intrinsic viscosity of the two ingredients and a higher temperature of the hot plate, were much larger than that of its corresponding counterparts. The elastic modulus ratio (m) and the PTT contents exhibited a cross-impact on crimp curves of PTT/PET bicomponent filament fabrics. The elongation ratios of fabrics made of PTT/PET bicomponent filaments would augment effectively as the hot plate temperature increased within a temperature range under the same posttreatment.
The models of polyethylene terephthalate (PET) non-circular cross-section (NCCS) fibers were established, and the characteristic parameters of non-circular cross-section fiber used in this numerical simulation were extracted. Furthermore, the differences of refracted light intensity ratio Irz and the direction of refracted light βt among circular, trilobal and quadri-lobal cross-section fibers were analyzed theoretically. The results show that the refracted light intensity ratios Irz of these fibers were in the range of 0.94~0.95. Both the trilobal and quadri-lobal cross-section fibers' βt, which was the angle of refracted light to Y-axis, changed non-monotonically and much more intricately than that of circular cross-section ones. Moreover, according to the theory of geometrical optics, the effects of trilobal and quadri-lobal cross-section shapes on the changes of internal refracted light and transmitted light in fibers were also conducted. The results suggested that the refracted and transmitted light were changed more effectively in the quadri-lobal cross-section fiber. The results of the experiment show that the shielding properties of quadri-lobal cross-section filament fabrics were better than that of the counterparts with circular fibers, but the difference was limited or insignificant.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.