查看更多>>摘要：We report the effect of A-site disorder σ~2 on the structural, dielectric, ferroelectric (FE) and electrocaloric (EC) properties of lead-free Ba_(1-x-y)Sr_xCa_yTiO_3 (0.025 ≤ x ≤ 0.3, 0.275 ≤ y ≤ 0.113) perovskites. We have synthesized a series of samples with the same A-site cationic mean radius but different A-site ionic radii variance (i.e., A-site disorder) σ~2. The tetragonal distortion and FE Curie temperature TC are found to decrease with decreasing A-site disorder σ~2. The temperature of the maximum EC effect decreases from ~120-27 °C with decreasing disorder σ~2. The highest adiabatic temperature change ΔT obtained using both the direct and indirect methods reaches ~0.8 K for the sample with optimized A-site disorder σ~2. Our results suggest that, in addition to the lattice distortion, the lattice disorder might be a new and effective parameter for promoting the EC effect.
查看更多>>摘要：This paper presents an experimental and theoretical study on the oxidation states and occupation sites of Fe and Cu ions in the Y_3Fe_(5-x)Cu_xO_(12), (0.00 ≤ x ≤ 0.05) compound synthesized via sol gel method. Transmission electron microscopy images showed agglomerated coral-shaped particles, while selected area electron diffraction analysis confrmed the formation of YIG cubic structure, since the bright points correspond to the (004), (123), (024), (224), (022), and (112) YIG family planes. Fourier transform infrared and Raman spectroscopies testifed the YIG crystal structure formation and suggest that the Fe by Cu replacement occurs in the octahedral sites. The cation distribution and reticular energy were estimated theoretically, revealing that the more probable valence state combination corresponds to Cu~+-Fe~(2+) doped YIG confg-uration. The experimental study by X-ray Photoelectron Spectroscopy certifed the elements valence states and confrmed that Y, Fe and Cu are mainly in the Y~(3+), Fe~(3+), Fe~(2+) and Cu~+ oxidation states. The oxygen vacancies formation was also identifed through the deconvolution of XPS spectra for the oxygen region. Finally, the dopant occupation probability per site as function of dopant concentration per unit formula was calculated using a phenomenological model and suggested that Cu+ and Fe~(2+) cations prefer to occupy the octahedral sites in the YIG crystal structure.
查看更多>>摘要：A cubic Mn_(0.6)Fe_(0.4)S solid solution material has been synthesized using a scalable in situ sulfuration treatment of Prussian-blue analogs (PBAs), and its phase formation process and Li-storage mechanism were investigated. Increased treatment temperature and time encourage a phase transformation from hexagonal Fe_7S_8 to cubic FeS_2 during the sulfuration process, which results in the formation of a solid solution between cubic FeS_2 and cubic MnS. The resulting Mn_(0.6)Fe_(0.4)S solid solution electrode exhibits high initial coulombic efciency, excellent rate performance, and superior cycling stability (520 mA h g~(-1) after 1000 cycles at 1.0 A g~(-1)). Ex-situ X-ray diffractometry and electro-kinetics tests show that the doping-induced structural phase transition in Mn_(0.6)Fe_(0.4)S solid solution creates a favorable electronic structure and ensures rapid charge transfer kinetics during the lithiation/delithiation process, simultaneously achieving high energy conversion efciency and a long lifespan.
查看更多>>摘要：This study proposes a novel photosensor that uses curcumin:reduced graphene oxide/silicon (CU:rGO)/n-Si heterojunction, prepared at different molar ratios of rGO with CU. The CU:rGO was deposited on an n-Si by electrochemically. The EDX, XRD, SEM and absorbance analyses of CU:rGO flm were investigated. From the I-V measurements, the all CU:rGO/n-Si devices showed excellent rectifcation characteristics both in the dark and under various illumination intensities. The device with higher rGO ratio (labelled D1) had better performance overall having the rectifcation ratio of 86094, the ideality factor of 2.15 and photosensitivity of 198 (at 150 mW/cm~2), which was attributed to the extraordinary electro-optical properties of rGO. Hence, the electrical and optical properties of D1 device were analyzed in detailed. The typical I-V measurements were conducted both in dark and under AM 1.5 G illumination of various light intensities. The intensity of the incident light varied from 10 to 150 mW/cm~2. The photocurrent exhibited a strong dependence on the light intensity. The I-V measurements of another device (labelled D4) prepared under the same conditions were achieved at 365 nm and 395 nm wavelengths and it showed good sensitivity to light even in the UV region. Furthermore, both D1 and D4 devices operated in self-powered mode in visible and UV light without the need for any external voltage. According to the experimental results, the produced CU:rGO/n-Si devices can be potential devices for photosensor applications in a wide spectral region.
查看更多>>摘要：In order to further improve the oxidation resistance of CoCrFeNiAlx (x = 0.1, 0.5, and 1) high entropy alloys (HEAs), the surface of CoCrFeNiAl(x )prepared by vacuum arc melting is controlled by laser surface remelting (LSM) and the high-temperature oxidation properties of CoCrFeNiAlx before and after LSM is systematically studied. The results revealed that, with the increase of Al content, the parabolic velocity constant k(p )value gradually decreased after LSM treatment. Moreover, CoCrFeNiAl0.1 formed a continuous Cr2O3 oxide layer, CoCrFeNiAl0.5 formed an outer layer of Cr2O3 oxide film and an inner layer of Al2O3 precipitation, and CoCrFeNiAl1 formed a uniform and dense Al2O3 oxide layer on the entire area. After 100 h of oxidation, the oxide film thickness of three alloys is around 5 mu m, 4 mu m, and 3 mu m, respectively. The improvement in oxidation resistance after LSM can be ascribed to the formation of a dense re-melted layer, uniform distribution of the elements, refinement of the re-melted layer.(c) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：Currently, conversion-type lithium-ion battery (LIB) anode materials suffer from low conductivity and poor Li+ storage stability. Hence, g-C3N4-derived CN coating wrapped concave hollow ZnO@C dodecahedrons (ZnO@C@CN) were synthesized in this study and was used to address these challenges. The high-content pyrrolic-N-doped ZnO@C@CN-4 was precisely regulated by the solid-phase method, which can furnish complementary appearing defects, vacancies, and lithium storage sites. In addition, the CN coating and concave hollow structure improved the cycle stability and lithium storage capacity of the device. As LIBs anodes, the initial discharge specific capacity of ZnO@C@CN-4 was 1769.4 mA h g(-1), and the reversible discharge capacity was 546.2 mA h g(-1) after 1000 cycles at 1.0 A g-1. The rate performance data demonstrated that a capacity of 326.5 mA h g(-1) capacity was achieved at a current density of 2.0 A g(-1), and a high capacity of 678.1 mA h g(-1) was still maintained after 100 cycles from high to low current. The design concept of this work can be extended to the other lithium storage materials and would also provide new insights into the regulation of nitrogen doping. (C) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：The application of transition metal dichalcogenides (TMDs) in many optical devices has been seriously limited by its narrow band-gap and high electron-hole recombination rate. Therefore, more studied are desired for exploring the novel TMDs/Ga2O3 heterostructures with excellent photoexcitation properties and interfacial dynamics. Herein, the WSe2/Ga2O3 and MoS2/Ga2O3 heterostructures were successfully prepared by a two-step radio frequency magnetron sputtering method. The growth mechanism and interfacial charge transfer of the wide and narrow TMDs/Ga2O3 heterostructures are considered. The X-ray diffraction results show that the (002) orientation of the WSe2 and MoS2 was suppressed, which can be attributed to interfacial interaction. Compared to pure TMDs, the A1 g was blue-shifted in the Raman spectrum for the proposed heterostructures, which is related to the decrease of the electron density. The photoluminescence emission of TMDs/Ga2O3 heterostructures was enhanced mainly due to the transition from trions recombination to exciton recombination. Meanwhile, the transmission properties of electrons under the builtin electric field are further confirmed by the transient absorption spectroscopy. Effective charge separation not only reduces radiation emission rate but also significantly enhances the nonlinear optical response of TMDs. An open-aperture Z-scan measurement was carried out to confirm that Ga2O3 is a promising candidate for enhancing the saturable absorption or reverse saturable absorption of TMDs.(c) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：The fabrication of AlCo0.2CrFeNi2.1 high entropy alloy via laser metal deposition (LMD) was motivated and implemented by the demand for overcoming the strength-ductility trade-off of the as-cast alloys due to the Co concentration. The microstructure features of AlCo0.2CrFeNi2.1 alloy were characterized by scanning electron microscopy, X-ray diffraction, transmission electron microscopy, and electron back-scattered diffraction. The mechanical properties were evaluated by a tensile test at room temperature. The synergy of reduced Co content and LMD process led to the formation of hierarchical eutectic microstructures consisting of columnar grains, eutectic colonies, alternately arranged fcc(L12)+B2 lamellae, and coherent Cr-rich nanoprecipitates in B2. The growth direction of those eutectic structures was found to be mainly parallel to the building direction (BD). The fcc(L12)/B2 eutectics agreed well with the Kurdjumov-Sachs orientation relationship of [110}B2//[111}L12, and < 111 > B2// < 110 > L12. The LMD fabricated AlCo0.2CrFeNi2.1 exhibited anisotropic mechanical properties when stretched in BD and transverse direction (TD). An excellent combination of the ultimate tensile strength (1246 MPa) and ductility (17.1%) was achieved in the BD, better than the as-cast counterpart. The elevated mechanical properties could be attributed to the high cooling rate solidification induced microstructural refinement. The same interlamellar spacing in BD and TD embraced a nearly equal ability to block dislocation movement and gave rise to the similar yield tensile strength. The differences in grain/colony size induced boundary strengthening in BD and TD were evaluated to account for the remarkable changes in ultimate tensile strength as well as ductility. (c) 2022 Elsevier B.V. All rights reserved.
Shaterian, MaryamYulchikhani, MassoudAghasadeghi, ZahraArdeshiri, Hadi Hassani...
8页
查看更多>>摘要：Hydrogen is considered as one of the most renewable and also efficient fuels. When hydrogen is burned, its only product is water. But the most important issue in the use of hydrogen is its storage. Hydrogen must be stored reversibly in a way that is completely safe and has high storage efficiency. Due to obtaining high-efficiency hydrogen storage, new nanostructures based on barium hexaferrite nanostructures (BaFe12O19) and functionalized multi-walled carbon nanotubes BaFe(12)O(19 )nanocomposite (BaFe12O19/MWCNTs) are synthesized via sol-gel combustion method. The nanocomposites are confirmed through Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), Brunauer-Emmett-Teller (BET), and vibrating sample magnetometer (VSM) techniques. Further, the hydrogen storage capacity of BaFe12O19/MWCNTs nanocomposite is assessed by chronopotentiometry analysis (CHP). The XRD studies demonstrates that the average crystallite sizes of the BaFe12O19 and nanocomposite are estimated to be about 16.3 and 7.6 nm, respectively. Also, the VSM measurement shows a saturation magnetization values (Ms) of 20.1 and 1.3 emu/g for BaFe12O19 and BaFe12O19/MWCNTs nanocomposite, respectively. The electrochemical consequences indicate that the BaFe12O19/MWCNTs nanocomposite has a high capacity for hydrogen storage and discharge rate. The maximum discharge capacity of BaFe12O19/ MWCNTs nanocomposite reaches about 360 mAh/g in the first cycle to approximately 3600 mAh/g after 20 cycles under an optimal current of 2 mA. As a result, the BaFe12O19/MWCNTs nanocomposite showed a good capacity as a promising active ingredient for hydrogen storage devices.(C) 2022 Published by Elsevier B.V.
查看更多>>摘要：Antimony doped tin(IV) oxide (ATO) based materials are promising alternatives used in electrochemistry for water purification. However, their practical application remains a major bottleneck due to the drawback of poor stability. Therefore, we design a simple and viable strategy for preparing a series of TiO2 @ATO@MOx (TAM, M = Mn, Fe, Co, Ni, Cu, and Zn) electrodes. The oxygen evolution potential, electrode stability, and electrochemical activity toward methylene blue (MB) were studied and compared. When evaluated as electrode material toward methylene blue (MB) oxidation, TiO2 @ATO@NiO (TANi) exerts an excellent degradation efficiency and service lifetime; these are the highest values among these TAM electrodes. Cyclic voltammetry (CV) measurements demonstrated that NiO can effectively enhance roughness factor and voltammetric charge, indicating a large electrochemically active surface area and abundant electroactive sites. The addition of NiO effectively lowers the charge transfer resistance and enhances the electrode stability. Moreover, theoretical calculations based on the first-principle density functional theory (DFT) indicate that the conductive property of TAM is manipulated by MOx adding and thus an excellent electrochemical activity is achieved. Based on the experimental data and computational simulations, our work brings new important insights that will contribute to the development of high-performance and stable ATO-based electrode materials. (C) 2022 Published by Elsevier B.V.
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