查看更多>>摘要：? 2022 Elsevier B.V.As a new kind of high-magnetostriction alloy, MnCoSi shows large magnetostriction during a metamagnetic transition. However, this alloy suffers from low strength, which is caused by the cracks generated from a martensitic transformation during cooling. In this paper, we will report that curing the mixture of MnCoSi-based powders and epoxy under a magnetic field is a promising method to enhance the strength and, meanwhile, maintain good magnetostrictive property. The MnCoSi-based powders used here have a low content of Ni, which can sharply reduce the critical field needed to drive the metamagnetic transition and tune the metamagnetic transition to be second-order. Profited from this improvement, [001]-textured Mn1-xNixCoSi/epoxy composites with enhanced strength and reversible magnetostriction are produced under a magnetic field of 1 T. The obtained magnetostriction is comparable to that of famous Terfenol-D and Fe-Ga alloys. Besides, the factors that can influence the texture and magnetostriction are discussed here.
查看更多>>摘要：? 2022 Elsevier B.V.Diluted magnetic semiconductor materials have attracted extensive attention as candidate materials for a new generation of multifunctional spintronic devices. At present, doping is an effective method to adjust the physical properties of semiconductor materials. Here, the Gd doped AlN (AlN:Gd) hierarchical microstructures were synthesized from mixtures of Al and Gd2O3 powder and N2 working medium by improved arc discharge method. The samples were analyzed by X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, energy dispersive X-ray spectroscopy, scanning electron microscopy, photoluminescence (PL) spectroscopy and vibrating sample magnetometer. The analysis results show that Gd ions are successfully doped into AlN hierarchical microstructures. The PL spectrum excited by 200 nm exhibits a sharp emission line at 318 nm corresponding to 6P7/2-8S7/2 transitions of the Gd3+ ion, and a broad emission band round at 395 nm, which is related to with Al vacancy and O impurity defects. The magnetization curves suggest AlN:Gd hierarchical microstructures process room-temperature ferromagnetic behavior. The latter first-principle calculations indicate that the main origin of the magnetism in AlN:Gd arise from Al vacancies rather than magnetic Gd dopants. Our results suggest that the AlN:Gd hierarchical microstructures are promising materials for spintronic applications.
查看更多>>摘要：? 2022 Elsevier B.V.NaGd(MoO4)2: Er3+/Yb3+ up-conversion fluorescence materials was prepared by a sol-gel method. And the effects of activator ion doping concentration, sensitizer ion doping concentration and calcination temperature on the temperature sensitivity of NaGd(MoO4)2: Er3+/Yb3+ materials were studied. The samples were characterized by XRD, SEM and fluorescence spectra. The temperature sensitivity of different powder was calculated by using the temperature measurement formula of fluorescence intensity ratio. At this time, the results show that the temperature sensitivity is the highest when the concentration of Er3+ is 0.5% in the range of 0.3–2.0% and when the concentration of Yb3+ is 28% in the range of 16–32%. Under the condition of 0.5% Er3+/ 28% Yb3+, a higher value of 0.0268 K?1 can be obtained. Then, the change of temperature sensitivity with doping concentration was analyzed based on the theory of energy transition and the analysis of fluorescence lifetime. In addition, with the calcination temperature increasing from 700 ℃ to 1100 ℃, it is found that the fluorescence intensity and temperature sensitivity of the calcination temperature at 800 ℃ are both great. At the same time, the influence of doping concentration of Er3+， doping concentration of Yb3+ and calcination temperature on the sensitivity was compared. It was found that the influence of Er3+ ion doping concentration was more significant. These results indicate that Er3+ and Yb3+ co-doped NaGd(MoO4)2 powder has a great application prospect in temperature sensing.
查看更多>>摘要：? 2022 Elsevier B.V.In this study, the polymorphism of Ta2Ni3Se8, a three-component one-dimensional chalcogenide material, was discovered. It was confirmed through X-ray diffraction and transmission electron microscopy analyses that the newly identified tetragonal phase of the compound (T-Ta2Ni3Se8) had a different crystal structure from the previously reported orthorhombic phase (O-Ta2Ni3Se8). Conventional O-Ta2Ni3Se8 is a semiconductor material with ambipolar characteristics, whereas T-Ta2Ni3Se8 showed a metallic characteristic in which the electrical resistance slightly increased as the temperature increased. The change in electrical properties due to the variation in lattice isotropy according to the transformation of the crystal system (orthorhombic to tetragonal) is expected to be an important starting point for polymorphism studies of multi-component low-dimensional materials in the future.
查看更多>>摘要：? 2022 Elsevier B.V.In this paper, a new high-performance tunable band-selective (UV-Visible) photodetector (PD) based on RF sputtered a-SiC active layer is demonstrated. SiC thin-films were deposited on glass substrate by RF magnetron sputtering method at different sputter power values ranging from 60 W to 120 W. The samples morphological, structural, optical and photodetection properties were investigated by carrying out XRD, SEM, EDS, UV-Vis spectroscopy and photoresponse measurements. It was revealed that the sputtering power could modulate the optical behavior of a-SiC alloy, tuning favorable visible absorbance at high sputter power. This phenomenon is correlated with the influence of the RF power on the SiC film structural properties and compositions. Interestingly, measurements showed that a-SiC PD elaborated at 60 W of RF power can detect UV radiation with a high responsivity of 138 mA/W, low noise effects, superior detectivity of 7.8 × 1012 Jones, while maintaining the visible blindness property. On the other hand, the prepared device at high sputtering power exhibits extended photoresponse characteristics, yielding 426 mA/W and 77 mA/W of responsivity values over UV and visible ranges, respectively. Therefore, the present investigation can provide a new strategy for the design and fabrication of photodetector devices based on SiC platform with broadband and solar-blind adjustable sensing purposes according to the desired application.
查看更多>>摘要：? 2022 Elsevier B.V.The α-FAPbI3 perovskite nanocrystals exhibit interesting optical properties, which make them attractive for versatile optoelectronic applications; however, the spontaneous phase transformation to the non-perovskite phase (δ-FAPbI3) in humid conditions requires a new strategy to improve the phase stability of the material. We employed 3-Aminopropyl triethoxysilane (APTES)-assisted reprecipitation and sol-gel methods at ambient temperature to prepare stable α-FAPbI3 nanocrystals embedded in a silica matrix. Transmission electron microscopy (TEM) and X-ray diffraction analysis determined that ultrafine perovskite nanocrystals (11.5 ± 3 nm) were uniformly distributed in a silica matrix. Investigations of the optical properties of the synthesized materials revealed that about 94% of the photoluminescence (PL) emission of silica-encapsulated FAPbI3 nanocrystals was preserved under humid conditions (60%) after at least a month, while the PL emission of untreated FAPbI3 was significantly decayed after few days. The thermal analysis also determined that the thermal stability of FAPbI3 nanocrystals was improved by silica encapsulation. The red-emitting silica-encapsulated FAPbI3 nanocrystals with a wavelength of 720 nm were used to fabricate white light-emitting diodes (LEDs) in a vertical structure consisting of a blue-chip, PMMA/CsPbBr3 QDs, and PMMA/FAPbI3-SiO2 QDs. Stable perovskite-based white LEDs with a color gamut of 144% NTSC were fabricated, which was better than many phosphor-based and perovskite-based LEDs. The synthesized composite perovskite nanocrystals could be used for next-generation optoelectronic devices.
查看更多>>摘要：? 2022 Elsevier B.V.This work reports the synthesis and electrochemical properties of activated carbon nanofibers (ACNF) composited with Li2FeSiO4 for supercapacitors. The prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Brunauer-Emmett-Teller analyzer (BET), transmission electron microscopy (TEM), and thermal gravimetric analyzer (TGA). The electrochemical properties were tested using a variety of techniques, such as cyclic voltammetry (CV), galvanostatic charge-discharge (GDC), and electrochemical impedance spectroscopy (EIS). The structural transformation during charging and discharging processes was studied by in-situ time resolved X-ray absorption spectroscopy (in-situ TRXAS). The ACNF/Li2FeSiO4 presented monoclinic structure with space group of P21/n, although there was a small impurity of FeO. The structural transformations of iron upon cycling in the + 2 to + 3 state were responsible for high capacity of ACNF/Li2FeSiO4 materials. The maximum specific capacitance of 158 Fg?1 at 2 mVs?1 and 201 Fg?1 at 0.25 Ag?1 with the corresponding specific energy of 17.8 Whkg?1 and specific power of 99.7 Wkg?1 were observed. Moreover, this composite material exhibited an excellent cycle performance through maintaining over 85% of its initial capacitance after 1000 cycles. The interesting electrochemical properties of ACNF/Li2FeSiO4 composite nanostructure make it a potential candidate for supercapacitors.
查看更多>>摘要：? 2022 Elsevier B.V.Lightweight, high-strength –electromagnetic(EM) absorption materials are in pressing requirement in both military and civilian fields. Porous silicon carbide (SiC) has attracted increasing attention as an EM absorption material. However, it's absorption performance is still limited. In this work, the SiC foam/FeSiCr composites were prepared by a simple sacrificial template method coupled with an immersion process. FeSiCr particles were anchored on the three-dimensional porous SiC skeletons with polyurethane resin serving as a binder. Benefiting from the multiscale synergistic effect and coating strengthening efficacy, the obtained SiC foam/FeSiCr hybrids exhibited excellent EM absorption properties and high mechanical strength. Especially, the SiC foam/FeSiCr-40 sample possessed the best EM absorption ability with a minimum reflection loss (RLmin) value of ?31.2 dB at 4.3 GHz at a thickness of 5 mm. Meanwhile, it also had a relatively high compressive strength of 5.62 MPa which was superior to that of the pure SiC foam (3.25 MPa). Moreover, the SiC foam/FeSiCr composites exhibited preferable salt spray corrosion resistance properties due to the chemical inertness of SiC and FeSiCr particles. Due to their excellent overall performance, SiC foam/FeSiCr composites have a great potential for application as structural absorption materials in ocean environments with high salt fog atmosphere. In addition, this work also provides guidance regarding the design and preparation of other structural absorption materials.
查看更多>>摘要：? 2022 Elsevier B.V.The low electronic conductivity and severe volume change hinder the commercialization of Sb2S3 anode, despite many efforts have been made to improve its electrochemical properties in the past decades. Many of these methods are complicated and different kinds of chemicals are required. Herein, a facile high-temperature melting method was employed to prepare high-performance Sb2S3 anode with nanosizing bulk natural stibnite and wrapping activated carbon. The activated carbon can provide nano-pores that absorb the molten Sb2S3. This structure can not only promote electronic conductivity but also provide accommodation for the volume change of Sb2S3 nanoparticles. More importantly, compared to other methods such as the hydrothermal method, the advantage of this method is that natural stibnite (95 wt% Sb2S3) was directly used as the Sb2S3 source without other synthetic or purification processes. Benefiting from these merits, the Sb2S3 composite anode exhibits good cyclic stability and excellent rate property, which delivers a high capacity of over 450 mAh g?1 even at a current density of 5 A g?1, proving that the Sb2S3 composite can serve as a promising anode for advanced lithium-ion batteries.
查看更多>>摘要：? 2022 Elsevier B.V.In this work, we have successfully synthesized pristine MoS2 (P-MoS2) and Sn-doped MoS2 (D-MoS2) by hydrothermal method for photocatalytic degradation of dye. To enhance the catalytic activities, the samples are dried by the lyophilization process. The structural and morphological analysis were done by XRD, FE-SEM, HR-TEM, UV-Vis and XPS techniques. Dye degradation experiments were conducted for Rhodamine B (RhB) using the synthesized samples under visible light irradiation to compute their photocatalytic activity. We observed that the Lyophilized Sn-doped MoS2 (DL-MoS2) showed enhanced photocatalytic activity than the other synthesized samples. In particular, DL-MoS2 showed a quick and overall degradation ability for RhB in just 20 min with good reusability behaviour and photostability. The excellent photocatalytic activity of DL-MoS2 may be due to accelerated electron transfer upon Sn doping and fast generated electron-hole pair because of a higher surface area of 127 m2/g. Our study revealed that the DL-MoS2 is a good photocatalyst for the complete degradation of RhB dye.
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