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Microstructure and corrosion behavior of AlCrTiV-X (X = Cu, Mo, CuMo) high-entropy alloy films in 3.5 wt.% NaCl solution
No full textIn this work, the microstructure and corrosion behavior in 3.5 wt.% NaCl solution, of AlCrTiV-based high-entropy alloy (HEA) films with Cu, Mo, and Cu/Mo, prepared by DC magnetron sputtering, are investigated. The results indicate that all these HEA films are composed of a single BCC phase, but with different lattice constant and different surface topographies. The AlCrTiV, AlCrTiVCu, and AlCrTiVMo HEA films display the surface with tetrahedral nanoparticles, but the AlCrTiVCuMo HEA film shows the surface with near-spherical nanoparticles. Among these HEA films, the AlCrTiVCu HEA film shows the best corrosion-resistance, owing to the dense surface morphology and relatively small surface feature size, but the AlCrTiVCuMo HEA film with the minimum surface feature size has the worst corrosion-resistance, which is due to the obvious holes on its surface and the relatively low content of Al and Cr elements. However, these four HEA films all show a better corrosion-resistance than 304SS, explained by the formation of stable oxides comprising of Al2O3, Cr2O3, etc
Ultrastable porous organic/inorganic polymers based on polyhedral oligomeric silsesquioxane (POSS) hybrids exhibiting high performance for thermal property and energy storage
No full textIn our work, we have been synthesized two-hybrid porous organic-inorganic microporous polymers (POIPs) through a simple and friendly Heck coupling reaction at a moderate temperature of cubic octavinylsilsesquioxane (OVS) with brominated fluorene (F-Br-2) and anthraquinone (A-Br-2); respectively, to afford POSS-F-POIP and POSS-A-POIP. FTIR, solid-state C-13, and Si-29 NMR spectroscopy analyses were carried out to confirm the chemical structures of these POIP materials and the presence of POSS units within their framework. TGA measurements revealed that POSS-A-POIP possesses high thermal stability (T-d10: 600 degrees C, and char yield: 83 wt%) due to the presence of rigid anthraquinone and POSS units. Furthermore, POSS-A-POIP features pseudocapacitor with high symmetry and high specific capacitance of 152.5 F g(-1) at 0.5 A g(-1) when compared with the POSS-F-POIP (36.2 F g(-1) at 0.5 A g(-)1()). The excellent energy storage performance of POSS-A-POIP could be attributed to the Faradaic reaction of anthraquinone and the pi-conjugated system
Structure and tribocorrosion behavior of TiAlCN coatings with different Al contents in artificial seawater by multi-arc ion plating
No full textIn this work, titanium aluminum carbonitride (TiAlCN) coatings with different aluminum (Al) contents were prepared on Ti-6Al-4V alloys using reactive co-sputtering in multi-arc ion plating system. The role of Al content (14.4 at.%-21.5 at.%) on the structure, mechanical properties and tribocorrosion behavior of TiAlCN coatings were studied. According to the x-ray diffraction (XRD) and High-resolution transition electron microscope (HRTEM) results, the TiAlCN coatings possess a nanocomposite structure composed of nanocrystalline TiN/TiC/AlN embedded in an amorphous carbon matrix. When the Al content is low (14.4 at.%), the coatings exhibits ultra-high hardness (42.6 GPa). Further increase of the Al content, the hardness of the coating reduced, as the formation of amorphous carbon increased in the coating (16.8 and 21.5 at.%). In addition, the coating with 14.4 at.% Al content also reveal better tribocorrosion performance in artificial seawater than other high Al content coatings as well as the substrate. This is owing to the denser structure can prevent the penetration of the corrosive media thus limits the material loss. Moreover, the material loss in tribocorrosion experiment is not only caused by the summation of pure corrosion and pure wear loss, but also the synergism between corrosion and wear takes a large proportion of the total volume loss
Supramolecular Hydrogel with Orthogonally Responsive R/G/B Fluorophores Enables Multi-Color Switchable Biomimetic Soft Skins
No full textMany living creatures have evolved to show diverse appearance color changes in response to multiple environmental stimuli for attraction, warning, or disguise in their environments. However, it is challenging to construct artificial soft polymer hydrogels with similar multi-responsive multicolor tunable behaviors, but such materials can serve as soft biomimetic skins to dramatically enhance the function of certain machines. Herein, a specially designed material structure to present an innovative class of supramolecular fluorescent polymeric hydrogels with the integrated properties of wide multi-color tunability, multi-responsiveness, self-healing, and remolding capacities is proposed. A key feature of this rational hydrogel design is that multiple fluorophores (blue (B) aggregation-induced emissive and red/green (R/G) lanthanide coordinated ones) are organized separately into different polymer chains of one single supramolecular polymer network. Consequently, the B and R/G fluorophores are engineered to be orthogonally responsive, and the fluorescence intensity of each fluorophore can be controlled independently by different external stimuli, which contribute to multi-responsive multicolor fluorescence response. Besides, the hydrogels also have satisfying self-healing and remolding capacities. All of these promising advantages together further enabled the construction of soft biomimetic color-changing skins that can help the existing robots achieve the desirable camouflaging function
Electrostatic enhanced surface segregation approach to self-cleaning and antifouling membranes for efficient molecular separation
No full textMembranes with excellent antifouling properties and persistent high permeance are eternal pursuits in membrane technology. Herein, we proposed an electrostatic enhanced surface segregation approach toward the antifouling and self-cleaning membranes for molecular separation. A copolymer containing quaternary ammonium (QA) segments was designed as the surface segregation agent in the casting solution, while polysulphonic acid (PSA) was designed as the crosslinking agent in the coagulation bath. Driven by the electrostatic interactions between the positively charged QA and negatively charged sulphonic groups, the copolymer and PSA were in-situ assembled during the non-solvent induced phase separation (NIPS) processes, generating a selective separation layer on the polymeric matrix. The segregation of copolymer was enhanced, leading to a high surface coverage of ionic QA and sulphonic groups and a significantly improved surface hydrophilicity. Accordingly, the membrane exhibited a high water permeance up to 124 Lm(-2) h(-1) bar(-1) with dye rejection over 95%. Moreover, the membrane exhibited excellent antifouling performance with the ultralow total permeance decline of 1.2% and the ultrahigh permeance recovery ratio of 99.8% against emulsified oil, as well as the self-cleaning property against crude oil. Hopefully, this study can afford a novel and generic approach to antifouling and self-cleaning membranes for diverse separations
Expand band gap and suppress bipolar excitation to optimize thermoelectric performance of Bi0.35Sb1.65Te3 sintered materials
No full textBismuth-telluride-based alloys have been the state-of-art thermoelectric candidates near room temperature. However, sintered samples with higher ZT values in a wide temperature range are still urgently needed for further applications. Especially owing to the small band gap, the minority carriers are boosted at higher temperature and the thermoelectric properties are severely deteriorated. Here, we prepared p-type Bi0.35Sb1.65Te3-Se-x(x) samples by hot pressing to enlarge the band gap and suppress the bipolar excitation. Although the carrier concentrations are slightly increased by the tiny Se alloying, the Seebeck coefficients above 400 K are significantly improved, and the bipolar and lattice contributions to thermal transport are obviously reduced. The x = 0.04 sample thus achieves an average value of 1.1 between 300 and 500 K, and the constructed thermoelectric device produces an output power density of 0.36W cm(-2) and conversion efficiency of 5.24% at a temperature difference of 200 K. These results suggest that Se-doped Bi0.35Sb1.65Te3 is a robust candidate for low-grade heat harvest near room temperature. (C) 2021 Elsevier Ltd. All rights reserved