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Ferroic dislocations in paraelectric SrTiO3
No full textFerroic systems under considerable geometrical restrictions at nanoscale have successfully introduced novel phases such as multiferroic and topological phases. However, ferroic orders completely disappear below the critical size limit of several nanometers and the geometry cannot be relied upon to produce a variety of phases. Here, via first-principles calculations, we demonstrate that a rich variety of phases and their transitions can be realized by dislocations in paraelectric SrTiO3. We show that atomic-scale ferroelectricity and (anti)ferromagnetism are induced by the strain concentration and nonstoichiometry intrinsic to dislocations in SrTiO3, resulting in ferroelectric-(anti)ferromagnetic-multiferroic phase transitions depending on the core structure. Furthermore, we also show that electrical polarization configurations strongly depend on the strain distribution around a dislocation and topological phases can be realized without geometrical restrictions. The present result suggests that the utilization of defects in a material is a powerful strategy to design ferroic orders below the critical size, thereby expanding the application of ferroic nanostructures to the atomic scale
Toughening Polylactic Acid by a Biobased Poly(Butylene 2,5-Furandicarboxylate)-b-Poly(Ethylene Glycol) Copolymer: Balanced Mechanical Properties and Potential Biodegradability
No full textPolylactic acid (PLA) is a biodegradable thermoplastic polyester produced from natural resources. Because of its brittleness, many tougheners have been developed. However, traditional toughening methods cause either the loss of modulus and strength or the lack of degradability. In this work, we synthesized a biobased and potentially biodegradable poly(butylene 2,5-furandicarboxylate)-b-poly(ethylene glycol) (PBFEG50) copolymer to toughen PLA, with the purpose of both keeping mechanical strength and enhancing the toughness. The blend containing 5 wt % PBFEG50 exhibited about 28.5 times increase in elongation at break (5.5% vs 156.5%). At the same time, the tensile modulus even strikingly increased by 21.6% while the tensile strength was seldom deteriorated. Such a phenomenon could be explained by the stretch-induced crystallization of the BF segment and the interconnected morphology of PBFEG50 domains in PLAS. The Raman spectrum was used to identify the phase dispersion of PLA and PBFEG50 phases. As the PBFEG50 content increased, the interconnected PBFEGS0 domains start to separate, but their size increases. Interestingly, tensile-induced cavitation could be clearly identified in scanning electron microscopy images, which meant that the miscibility between PLA and PBFEG50 was limited. The crystallization of PLA/PBFEG50 blends was examined by differential scanning calorimetry, and the plasticizer effect of the EG segment on the PLA matrix could be confirmed. The rheological experiment revealed decreased viscosity of PLA/PBFEGS0 blends, implying the possible greener processing. Finally, potential biodegradability of these blends was proved
Effect of Interface Pretreatment of Al Alloy on Bonding Strength of the Laser Joined Al/CFRTP Butt Joint
No full textIn the present research, the carbon fiber reinforced thermoplastic (CFRTP) was laser joined with the Al alloy whose joining interface was pretreated by laser micro-texturing, anodizing, and hybrid of laser micro-texturing and anodizing. The surface morphology of the pretreated Al joining interface and bonding strength of the corresponding Al/CFRTP butt joint were investigated. The results show that the laser micro-texturing has fabricated the micro-pit or micro-furrow in the Al joining interface. With the increasing of laser scanning times, the size of the micro-pit or micro-furrow decreases, when the laser scanning distance is constant. The bonding strength of the Al/CFRTP butt joint with Al joining interface pretreated by micro-texturing fluctuates with the increasing of laser scanning distance and times, reaching the maximum value of 20 MPa at laser scanning distance of 0.1 mm and 1 time. The anodizing pretreatment has formed the Al2O3 oxide layer on the Al joining interface. The Al/CFRTP butt joint with Al joining interface pretreated by anodizing obtains the maximum bonding strength of 11 MPa at anodizing time of 10 min. The hybrid pretreatment of micro-texturing and subsequent anodizing fabricates the regular grid structure with smooth micro-furrow and micro-pit, while the hybrid pretreatment of anodizing and subsequent micro-texturing fabricates the Al joining interface with explosive micro-pit and micro-furrow. The bonding strength of the Al/CFRTP butt joint with hybrid-pretreated Al joining interface is relative better than that of the Al/CFRTP butt joint with anodizing-pretreated Al joining interface but almost lower than that of the Al/CFRTP butt joint with micro-texturing pretreated Al joining interface. Such results should be attributed to the surface morphology of the Al joining interface
Formation of Excellent Cathode/Electrolyte Interface with UV-Cured Polymer Electrolyte through In Situ Strategy
No full textUV-cured polymer electrolyte is synthesized via photo-polymerization of poly (ethylene glycol) methyl ether methacrylate and poly (ethylene glycol) diacrylate. The obtained polymer electrolyte exhibits a high ionic conductivity of 2.95 x 10(-5) S cm(-1) at 30 degrees C, a wide electrochemical stable window of up to 4.69 V (vs Li/Li+) and excellent compatibility against lithium metal electrode over 800 h. Besides, an integrated cathode/electrolyte interface is constructed through pouring the polymer electrolyte precursor onto the cathode layer. This kind of the integrated cell exhibits faster Li-ion diffusion in cathodic electrochemical reactions than conventional cells. Moreover, LiMn0.8Fe0.2PO4 divide divide Li cells with integrated cathode/electrolyte interface deliver a reversible capacity of 164.7 mAh g(-1) at 0.1C and retains a capacity of 134.4 mAh g(-1) after 240 cycles at 0.2C. Furthermore, the integrated cells show satisfactory performance under disastrous conditions, presenting their high safety. The UV cross-linked polymer electrolyte is a promising polymer electrolyte candidate for high energy density all-solid-state lithium metal batteries
Advances in sustainable thermosetting resins: From renewable feedstock to high performance and recyclability
No full textIn polymer science and industry, the important role of thermosetting resin is well-recognized. However, most thermosets suffer from the overdependence on petroleum resource and in addition are linked to environmental concerns. The development of sustainable thermosetting resins thus has become an objective of contemporary research. Addressing this need generally requires renewable feedstocks, satisfied comprehensive properties, and long service life or recyclability. Herein, a systematic overview regarding recent advances in sustainable thermosetting resins is provided. Firstly, the origins and access of bio-based platform compounds successfully applied in the bio-based thermosetting resins are being discussed. Subsequently, the synthesis, structure-property relationships, and methodologies for the functionalization of three typical bio-based thermosets, including benzoxazine, epoxy resin and unsaturated polyester, are being reviewed. Finally, strategies for the recycling of bio-based thermoset waste products are being presented. The objective of this work is not only to summarize the recent progress on sustainable thermosets, but also help us understand them more deeply and widely in a short time, so as to promote their faster development. (C) 2020 Elsevier B.V. All rights reserved
PSS-PANI/PVDF composite based flexible NH3 sensors with sub-ppm detection at room temperature
No full textImproved ammonia (NH3) sensor is proposed based on polyaniline (PANI) with poly(styrene sulfonic acid) (PSS) as an additive, which was produced by in-suit polymerization of aniline on flexible porous polyvinylidenefluoride (PVDF) membranes and then treated with PSS aqueous solution. The whole film sensor fabrication process was low-cost and convenient in operation, suitable for large-scale commercial production. The results demonstrated that the appropriate addition of PSS could significantly improve the sensor response to NH3. The PSS-PANI/PVDF film sensor response was improved to approximately 70%, which was 2.8 times higher than that of the pure PANI/PVDF film with 25% response towards 1 ppm NH3 at room temperature. Furthermore, it still showed an excellent response of 9.4% for 0.1 ppm NH3. The fabricated film sensor showed remarkable long-term stability with response decreases less than 5% after 30 days, and excellent flexibility under 10,000 repeated bending times with a response value degradation of only 15.1% towards 1 ppm NH3. The flexible PSS-PANI/PVDF film offers potential applications in smart wearable devices for detecting sub-ppm NH3 under ambient conditions
Cold Spray Construction of Nanostructured Titania Coatings for Photocatalytic Applications
No full textNano-titania (TiO2) has drawn considerable attention for decades for its excellent photocatalytic activity. The use of photocatalyst TiO2 in the form of surface coating is usually desired for long-term recyclable photocatalytic performances. Yet deposition of the coatings with appropriate nanostructures persists challenging. Thermal spray processing usually triggered loss of photocatalytic anatase in the coatings. To retain anatase structure from starting TiO2 powder, in this study, cold spray was employed to deposit TiO2 nanostructured coatings using TiO2 nanoparticles as the starting feedstock. The mechanically blended Al-7.5 wt.% TiO2 powder was used as the feedstock for the coating fabrication, and Al was used as the binder for the nano-TiO2 particles. The coatings containing anatase phase were successfully fabricated and showed good long-term recyclable performance and service life. After methylene blue degradation testing for three times, the photocatalytic efficiency of the coatings still remained over 90% of the initial photocatalytic efficiency. After high-pressure gas purge and flame sweep processing, the coatings retained the initial nanostructures at their surfaces. The cold spray technical route might open a new window for making the coatings of temperature-sensitive nanosized particles for functional applications
Mesoporous WO3 modified by Au nanoparticles for enhanced trimethylamine gas sensing properties
No full textIn this paper, KIT-6 is used as a template to prepare ordered mesoporous materials WO3 and Au-loaded WO3 (Au-WO3). The pristine WO3 sensor and the Au-WO3 sensor are fabricated for the detection of 19 important gases, such as trimethylamine, formaldehyde and CS2. The results show that the Au-WO3 sensor has better selectivity and higher response to TMA. At a working temperature of 268 degrees C, the response (R-a/R-g) of the Au-WO3 sensor to 100 ppm of TMA is 41.56 and the response time is 1 s. In addition, the sensor has excellent response/recovery capabilities and stability. These high sensing performances are mainly attributed to the electronic and chemical sensitization of the noble metal Au and the presence of a high specific surface area supported by the mesoporous structure. Therefore, Au-doped mesoporous WO3 should be a promising material for a high performance TMA gas sensor
Black titanium dioxide@manganese dioxide for glutathione-responsive MR imaging and enhanced photothermal therapy
No full textMultifunctional nanoprobes with tumor microenvironment response are playing important roles in highly efficient theranostics of cancers. Herein, a kind of theranostic nanoprobe was synthesized by coating manganese dioxide (MnO2) on the surface of black commercial P25 titanium dioxide (b-P25). The resultant nanoprobe (b-P25@MnO2) possessed glutathione (GSH)-responsive magnetic resonance (MR) imaging and enhanced photothermal therapy (PTT). In tumor microenvironments, the excessive GSH was consumed by reacting with MnO2 to generate Mn2+ for GSH-responsive MR imaging, in which the longitudinal relaxation rate of b-P25@MnO2 was up to 30.44 mM(-1) s(-1), showing excellent cellular and intratumoraI MR imaging. Moreover, the prepared b-P25@MnO2 exhibited stable and strong photothermal conversion capability with a high photothermal conversion efficiency of 30.67%, by which the 4T1 tumors disappeared completely, indicating safe and highly efficient PTT performance. The current work developed GSH-responsive b-P25@MnO2 nanoprobes, demonstrated for MR imaging and enhanced PTT in cancers
Efficient Raman red laser with second-order stokes effect of diamond crystal
No full textAn efficient generation of red emission at 620 nm from an artificial diamond crystal based on the second-order stokes design is demonstrated. According to the cascaded stokes theory, the second-order stokes laser is crucial for controlling the output of the multi-stokes laser. In this work, applying a microcavity with the integrated coating design, the Raman red laser can be achieved the highest average output power of 1.95 W, a slope efficiency of 22.8%, a threshold of 1.5 W, pumped by a solid-state pulsed green laser. The achieved results offer a potential route towards generating highly efficient Raman red laser, and enrich the output waveband of red laser