查看更多>>摘要:? 2022 Elsevier B.V.Rare earth is widely used in the fields of advanced materials, however, intrinsic reasons why rare earth should be added have been scarcely explained. Influences of europium on the structure and luminescent properties of CaWO4 thin films have been investigated in detail. The problem whether sputtering yields are the same for compounds has also been studied in this paper. Results obtained from X-ray photoelectron spectra favor that Eu element embodies as Eu3+ and Eu2+ simultaneously. What is more, sputtering yields of Ca, W and Eu are 0.77, 0.77 and 0.80, respectively. Hence, it can be concluded that compositions of deposits agree well with those of targets. Studies on X-ray diffraction reveal that only when x chemical formula Ca1–1.5xEux(VCa)0.5xWO4 is larger than 0.05, lattice constants will increase noticeably. Furthermore, the factor indicating preferential growth along the (004) plane of CaWO4 crystals has increased from 0.3 to 47 when x has increased from 0.05 to 0.24. This phenomenon may be correlated with significant improvement made on crystal mismatch because of the substitution of Ca2+ with Eu2+. Photoluminescence examination clearly demonstrates that the optimal excitation corresponding to WO42- has shifted from 223 to 200 nm due to doping of Eu. The excitation from 230 to 240 nm is ascribed to the charge transfer transition of O2-→Eu3+. Moreover, additional excitation band situated at 260–270 nm, which has been observed for Ca0.64Eu0.24(VCa)0.12WO4 thin films, is regarded as the charge transfer transition of O2-→Eu2+. In addition, intense and sharp emission peaking at 615 nm has been observed for Ca0.64Eu0.24(VCa)0.12WO4 thin film under ultraviolet light (200 nm ≤ λ ≤ 270 nm).
查看更多>>摘要:? 2022 Elsevier B.V.NaZn13-type La(Fe,Si)13 alloys are one of the most promising magnetocaloric materials near room temperature. However, the impact of lanthanide doping on their magnetocaloric properties has not been thoroughly investigated. Here, a series of Gd-doped La1?xGdxFe11.5Si1.5 (x = 0, 0.05, 0.1, 0.15, 0.2, 0.25) alloys were designed and synthesized by arc melting and annealing. The microstructure of different phases and their influence on magnetic properties were investigated. The Gd doping at La sites was confirmed by the lattice contraction revealed by X-ray diffraction and elemental mapping analysis. After saturation at around x = 0.1, extra Gd leads to formation of Gd-rich Gd2Fe16Si phase. Moreover, doping of extra Gd inhibits the formation of La(Fe,Si)13 phase, resulting in significantly increased amount of the impurity phases (α-Fe and LaFeSi phase). The change of microstructure and composition causes the magnetic transition to shift from first order to second order. Because of Gd doping, the Curie temperature of La1?xGdxFe11.5Si1.5 increases, and the maximum entropy change decreases. Understanding the effect of Gd on the microstructure and magnetic properties can help us develop more rare-earth-doped La(Fe, Si)13 alloys.
查看更多>>摘要:? 2022 Elsevier B.V.In this work, a new type of Yb3+/Er3+ co-doped lead-free glass-ceramics (GCs) containing Ba2NaNb5O15 nanocrystals was synthesized via traditional melt-quenching and controlled crystallization. The research results illustrate that a transparency of GCs can reach 50% at wavelength of 600 nm and the up-conversion (UC) luminous performance of GCs has been improved obviously compared with precursor glass (PG). And the dual-mode temperature measurement was carried out by fluorescence intensity ratio technology. Using thermally/non-thermally coupled energy levels (TCELs/non-TCELs), the maximum absolute sensitivities of Sa-max (TCELs) and Sa-max (non-TCELs) are 0.65% K?1 and 0.68% K?1, and the maximal relative sensitivities of Sr-max (TCELs) and Sr-max (non-TCELs) are 1.19% K?1 and 0.90% K?1, respectively. Furthermore, the discharge energy density (Wd) of 1.53 J cm?3 and the instantaneous discharge power density of 370 MW cm?3 with ultra-fast discharge time of 7 ns are simultaneously achieved in the GCs. These findings reveal the potential applications of new lead-free transparent Yb3+/Er3+ co-doped Ba2NaNb5O15 GCs for optical temperature measurement and energy storage.
查看更多>>摘要:? 2022 Elsevier B.V.2D BiOCl nanoplates with exposed (001) crystal surface were synthesized via a simple solvothermal method and the photodegradation property can be improved via adjusting volume ratios of ethylene glycol (EG)/absolute ethyl alcohol (EA). The photocatalytic results suggest that the BiOCl prepared by using the ratios (1:2) of EG/EA (BOC-EG:2EA) with exposed (001) plane displays excellent photocatalytic performance and the removal efficiency of RhB reaches 99% for only 10 min under visible light. The enormous improvement of removal efficiency originates from existence of the oxygen vacancies, the narrow band gap, and limited recombination rate of photoexcited electron-hole pairs. Additionally, the superoxide radical anions (·O2-) and photogenerated holes (h+) are confirmed to be the primary active species to accelerate the photoactivity. This work provides a new perspective to fabricate high-efficient photocatalysts used in relative wastewater treatment system.
查看更多>>摘要:? 2022 Elsevier B.V.Magnetic carbon-based composites derived from metal-organic frameworks have been regarded as potential microwave absorption (MA) materials. Here, we successfully fabricate magnetic CoFe alloy@nitrogen-doped carbon shell (CoFe@NC) composites with strong absorption, thin thickness, and wide bandwidth through the thermal decomposition of CoFe Prussian blue analogues. Annealing temperature has a remarkable influence on dielectric and magnetic behavior of composites, thereby improving the impedance matching and MA ability. When the annealing temperature of CoFe@NC composites is 600 ℃, the CoFe@NC composites show the best MA performance with the reflection loss (RL) value of ? 50.77 dB and the maximum effective absorbing bandwidth (RL ≤ ?10 dB) of 7.2 GHz (2.1 mm). The CoFe@NC composites possess superior MA properties because of the high dielectric loss deriving from nitrogen-doped carbon as the shell, high magnetic loss originating from CoFe alloy as the core and conduction loss. The superior MA performance of CoFe alloy@NC composites make them ideal candidates for high-efficient MA applications.
查看更多>>摘要:? 2022The extensive application of the layered Li-rich Mn-based cathode material is limited due to the inferior cycling stability, rate capability and voltage decay. The electrochemical performance of Fe3+ doping Li1.2Mn0.54Ni0.13Co0.13O2 cathode material synthesized by sol-gel method was investigated in this paper. It is indicated that Fe3+ doping Li1.2Mn0.54Ni0.13Co0.13O2 cathode material shows excellent electrochemical performance at high current intensity rates, especially the cycling stability and capacity retention. The cathode Li1.2Mn0.54Ni0.13Co0.12Fe0.01O2 exhibits excellent initial discharge capacities of 193.5 mAh g?1 at 1 C, 179.8 mAh g?1 at 2 C and 119.6 mAh g?1 at 5 C, and expresses remarkable capacity retention of 87.1% at 1 C and 84.0% at 2 C after 100 charge/discharge cycles, respectively. It is attributed to the beneficial effects of the Fe3+ doping in the cathode material, which enlarges the lithium layer spacing, decreases charge-transfer resistance and accelerates the Li+ diffusion, significantly slows down the decomposition of Li2MnO3, and efficiently alleviates the irreversible loss of lattice oxygen and the Mn dissolution during cycling.
查看更多>>摘要:? 2022 Elsevier B.V.Generally, Mg-Gd alloys need to be firstly solution treated at relatively high temperatures and then artificially aged at low temperatures to achieve adequate strength, which costs dozens of hours. Herein a Mg-10Gd-0.2Zr (wt%) alloy was reported to achieve excellent strength-ductility synergy with the product of ultimate tensile strength and elongation of 2791.3 MPa × % just by laser powder bed fusion (LPBF). The excellent strength-ductility synergy is attributed to the novel multi-scale hierarchical microstructure containing heterogeneous grain structure, intragranular lamellae substructure and nano-sized precipitates. Abnormal precipitation of a large number of intragranular β1 phases with blocky shape is first found in the as-built Mg-10Gd-0.2Zr alloy. The findings demonstrate that the unique heat and strain history during LPBF can be exploited to deliberately regulate the type, area number density, morphology and distribution of precipitates, thus controlling mechanical properties.
查看更多>>摘要:? 2022 Elsevier B.V.Constructing heterojunction has been proved to be an efficient strategy for enhancing the photocatalytic performance of g-C3N4 by prohibiting charge recombination and providing surface active sites. Herein, a novel structure of ultra-thin carbon bridged MoC quantum dots/g-C3N4 nanosheets was constructed for the first time to facilitate carrier transfer and accelerate surface reactions. In our designed composites, a surface-to-surface contact has been formed between conductive carbon layer and g-C3N4 nanosheet via ultrasonic assembly process. Moreover, there exist strong interfaces between MoC QDs and carbon layer because of the in-situ conversion method. As to this unique structure, the ultra-thin carbon layer functions as charge separation and migration high ways while the MoC QDs perform as noble-metal-free co-catalysts consuming the surface electrons promptly. Significantly, an optimal 40 wt% MoC QDs-C/g-C3N4 photocatalyst (MCCN) is synthesized with a hydrogen evolution rate of 2989 μmol h?1 g?1, which is 69.6 and 1.7 times higher than that of pure g-C3N4 and Pt/g-C3N4, respectively. Our work provides new insights on designing highly efficient heterojunction photocatalysts for water splitting.
查看更多>>摘要:? 2022 Elsevier B.V.The present work takes the benefit of employing a composite approach by reinforcing the pure Mg with bioinert and bioactive ceramic powders for strengthening and reducing their degradation inside the human body to make it a suitable candidate for orthopaedic implants. Hydroxyapatite (HAp) was selected as the bioactive material (a major constituent of the human bone). HAp was synthesized using the precipitation reaction method with Ca(NO3)2·4H2O as calcium and H3PO4 as phosphorus sources. The alkaline pH was maintained with the addition of NH4OH dropwise to assist the hydrolysis. The as-received Al2O3 was coated with TiO2 via the sol-gel route and characterised via X-ray diffraction, scanning electron microscopy, and transmission electron microscopy with selected area diffraction analysis. The samples were cast in three compositions, pure Mg, Mg-HAp-Al2O3 and Mg-HAp-TiO2@Al2O3. The microstructure, phase composition, mechanical and degradation performance (immersion and electrochemical tests) were analysed. The chemical route of synthesising the HAp and TiO2@Al2O3 powders resulted in uniform particle size. The addition of reinforcement particles in Mg enhanced mechanical properties and reduced corrosion rate. The cell viability of fabricated composites was observed above 80% at 20%, and 10% of extract solution and a noticeable improvement was observed with the employment of TiO2@Al2O3.
查看更多>>摘要:? 2022 Elsevier B.V.High-entropy quasicrystals contain both multiple principal alloying elements and complex crystal structures, in contrast to usual high-entropy alloys that have simple crystal structures; however, microstructures of high-entropy quasicrystal-related phases have seldom been revealed. In this paper, we report complex domains of approximants of high-entropy decagonal quasicrystal (HE-DQC) in Al20Si20Mn20Fe20Ga20 alloy, investigated by spherical aberration-corrected scanning transmission electron microscopy at atomic-level resolution. Importantly, a phase transition from HE-DQC to a (1/0, 2/1)–type orthorhombic approximant, with a = 0.73 nm, b = 1.23 nm, c = 2.24 nm, was revealed. We found that multi-point nucleations and growth of the oriented hexagonal structural blocks and phason flips of the basic structural blocks lead to this phase transition. This study benefits understanding of the formation of periodic structures in HE-DQC.