查看更多>>摘要：? 2022 Elsevier B.V.V impurities were intentionally introduced into β-Ga2O3 crystals as n-type dopants to improve the n-type conductivity of single-crystal substrates. A high-quality 0.20 mol% V-doped β-Ga2O3 single crystal was fabricated, and the effects of air annealing on the structure and the electrical and optical performances of V-doped β-Ga2O3 single crystals were systematically studied. The V-doped β-Ga2O3 crystal exhibited a high crystal quality, smooth surface, and high carrier concentration. In comparison, the crystalline quality of β-Ga2O3 was improved, and it showed a flat surface after the annealing treatment. Compared with that before annealing, the carrier concentration decreased from 5.90 × 1018 to 9.51 × 1017 cm?3, the optical transmittance increased in the near-infrared region, and the peak intensity of the Ag(3), mid-frequency Ag(8),Ag(9), and Ag(10) phonons were changed, which were attributed to the electron traps of the gallium vacancy (VGa) and the two cation vacancies paired with one cation interstitial atom (2VGa1-Gai) complex. After annealing, the oxygen vacancy (VO) was compensated, and the Ga3+ content decreased, which were related to the decrease in the free electron concentration. The variations in the VO and VGa concentrations resulted in a decrease in the blue luminescence peak area ratio and the formation of a green luminescence peak, respectively. These results can facilitate a better comprehension of the structural and property changes in V-doped β-Ga2O3 crystals owing to air annealing.
查看更多>>摘要：? 2022 Elsevier B.V.Ultrasonic vibration-assisted (UVA) forming is expected to be an effective way to improve the forming ability of Ni-based superalloy thin-walled sheet. However, the deformation characteristics and mechanism of this material under ultrasonic field keep unclear. To this end, experiments of UVA tension followed by quasi-in-situ EBSD were conducted. The tensile mechanical properties under different amplitudes were investigated, and the quasi-in-situ microstructure evolutions of the feature areas on non-UVA/UVA tensile specimens were compared. Experimental results show that ultrasonic vibration reduces the stress response, but the fracture may occur in advance under excessive ultrasonic amplitude. During the UVA deformation, the easy-to-deform grains with initial orientation close to<101>along the tensile direction rotate to<111>and<001>orientations, which then have a tendency to rotate back to<101>orientation in subsequent deformation. In addition, low-angle grain boundaries and dislocation density are also promoted. Based on the experimental results, a new perspective of the acoustic softening mechanism considering grain rotation and dislocation slip was proposed. The ultrasonic vibration facilitates grain rotation to coordinate plastic deformation. Meanwhile, the superposition of the ultrasonic field intensifies the atomic inherent vibration. The lattice resistance required for dislocation slip decreases accordingly.
查看更多>>摘要：? 2022 Elsevier B.V.The large-scale commercialization of Ni-rich LiNi1?x-yCoxMnyO2 is hindered by the rapid capacity decay, which is caused by structural instability, interface side reaction, and surface phase transition. In this study, the Ni-rich cathode is modified with Ti and La through a one-step sintering method. Ti and part La diffuse into the cathode particles, and the rest of La is coated on the surface of the particles in the form of La4NiLiO8. The La and Ti modified cathodes show excellent cycling performance even at a high cut-off voltage of 4.5 V. The modified cathode has an initial capacity of 195.5 mAh g?1 and capacity retention of 87% after 200 cycles. The rate performance is also improved, and the capacity at 5 C reaches 178.3 mAh g?1. The improved cycling performance is attributed to the modification of La and Ti, which avoids structural degradation and maintains the mechanical integrity of the cathode particles during cycling. The improvement in rate performance is attributed to the fact that the Li+ diffusion coefficient is increased due to the modification.
查看更多>>摘要：? 2022 Elsevier B.V.Transition metal doping is an effective strategy to improve the properties of phase-change random access memory (PCRAM), while the underlying mechanism remains to be sufficiently investigated. Herein, a Cr-doped Sb2Te film is fabricated by co-sputtering and the enhancement mechanism of Cr-doping is deeply investigated by experiments and first-principles calculations. The CrxSb2Te film exhibits excellent performances involving high crystallization temperature (238.9 °C) and good data retention (10 years @161.7 °C) for Cr0.56Sb2Te, low density change rate (3.8%) and high reversible switching speed (5 ns) for Cr0.29Sb2Te, providing a variety of options for different applications. The calculated results show that Cr atoms preferentially substitute the Sb1 site and the Cr–Te bonds display a stronger ionic bond character in contrast to the covalent bonded Sb–Te, thus improving the crystalline phase stability and crystallization temperature. Moreover, ab initio molecular dynamics simulations demonstrate that in the amorphous phase Cr atoms locate in defective octahedral coordination. Meanwhile, the homopolar Sb–Sb wrong bond increased with Cr doping and the Cr atoms tend to form tight cluster in the amorphous phase which could benefit for the fast phase-change speed. Our present findings of Cr0.29Sb2Te PCRAM device clearly reveal the enhancement mechanism by Cr doping which provides guidance for developing high-performance PCRAM devices.
查看更多>>摘要：? 2022 Elsevier B.V.Two-dimensional perovskite Sr2Nb3O10 (SNO) nanosheets were synthesized using a typical calcination-exfoliation method. SNO nanosheets were then directly coated on the CuZnS film to construct a p-n heterojunction responsive in ultraviolet region. The as-integrated CuZnS/SNO device achieves a maximum responsivity of 14.8 mA/W and detectivity of 1.87 × 1011 Jones at 3 V and 300 nm, greatly exceeding pure SNO. In particular, the hybrid photodetector can steadily operate at zero bias with high on/off ratio (>3000) and fast response speed (1.1/7.9 ms), which is primarily ascribed to the efficient separation of photoinduced electron-hole pairs driven by the built-in electric field at the p-n junction interface. Moreover, the device exhibits decent responsivity (0.28 mA/W), good detectivity (4.61 × 1010 Jones), high spectral selectivity (R300/R400 = 2500), and wide linear dynamic range (59 dB) at 0 V, showcasing excellent self-powered features at 300 nm. This work strongly provides a promising avenue for developing high-performance self-powered ultraviolet photodetectors for practical applications.
查看更多>>摘要：? 2022 Elsevier B.V.Constructing efficient and inexpensive bifunctional catalysts with oxygen reduction reaction (ORR) and oxygen evolution reactions (OER) is urgently requisite for advanced Zn-air batteries. Herein, a composite material consisting of cobalt-cobalt phosphide nanoparticles in situ coupled with N-doped carbon (Co-Co2P @ NC) is conveniently engineered via a facile all-in-one carbonization/phosphorization process. Specifically, Co-Co2P @ NC implements unprecedented bifunctional catalytic activities with a positive ORR half-wave potential of 0.858 V and a low OER potential of 1.598 V at 10 mA cm?2, outperforming the benchmark catalysts and is on a par with recently reported non-precious metal-based catalysts. These impressive electrocatalytic performances are attributable to the synergistic coupling effects between metallic Co, Co2P and NC, extraordinary specific surface area, rich active species and conductive carbon frameworks. Prominently, a rechargeable aqueous ZAB with Co-Co2P @ NC as an air cathode catalyst delivers an ultra-long term cycling stability of more than 2000 h (over continuous 6000 cycles) with a small change of charge-discharge voltage gap from 0.841 V to 0.890 V at 2 mA cm?2. Beyond that, both button-like and foldable quasi-solid-state ZABs also exhibit admirable performance even under the limited electrolyte condition, evidently indicating the wide adaptability and feasibility in practical energy conversion and storage.
查看更多>>摘要：? 2022 Elsevier B.V.Herein, the 3D flower-like V2Al1-xCTz with an estimated petaloid nanosheet thickness of 10–20 nm were firstly obtained by etching the submicro-sized V2AlC precursors, which were synthesized at 1000 °C holding for 5 h in (Na,K)Cl melt by a facile molten salt method, in 40 wt% HF at room temperature. The synthesis mechanism of V2AlC is possibly related to the disproportionation reaction of V-ions on carbon surface in molten salts to form V2C, followed by the intercalation of Al into V2C. Subsequently, the 3D flower-like V2Al1-xCTz was applied as an anode in lithium-ion batteries, releasing ~215.2 mA h g?1 in the continuous 500 cycles at 0.5 A g?1, which exhibits the superiority in the reversible capacity in contrast with some reported micro-sized layered V2CTz MXenes. Such excellent electrochemical characteristics of V2Al1-xCTz could be mainly ascribed to its unique submicro-sized flower-like morphology with high specific surface areas and abundant electrochemical sites for accommodating the reversible insertion/extraction of Li-ions.
查看更多>>摘要：? 2022 Elsevier B.V.As an all-inorganic solid state lighting material, phosphor-in-glass (PiG) receives much attention in high-power white lighting. However, poor heat-dissipation performance and low color rendering index (Ra) caused by low doping concentration of phosphor limit its application in white laser diodes (wLDs). Herein, phosphor-in-glass films on sapphire (PiFS) with heat-conducting properties and high Ra were newly synthesized via screen printing technology, which is highly desired for high-power wLEDs/wLDs. The interfacial corrosion product of CaWO4 between nitride phosphor (CaAlSiN3:Eu2+) and borosilicate glass (BS-glass) was found and investigated in detail firstly to determine the sintering temperature. Laminated structure of PiFS with red layer inside and green layer outside was intentionally designed to effectively avoid “reabsorption” effect between the red and green emitting phosphors. Compared with the opposite laminated structure, the PiFS exhibited the higher luminance efficiency (LE) and better optical properties (Ra = 85, CCT = 5362, CIE = (0.3348, 0.3156)) in wLDs. Notably, the adjustable optical characteristics can be achieved by changing the concentration of phosphor, the number of printing layers and the driving current for the application of PiFS in wLED and wLDs. High quality white light in wLED with CIE coordinates (0.3679, 0.3648) was also acquired and showed the excellent color rendering property (Ra = 90.8) and low color correlated temperature (CCT = 4280 K). Further, the working temperature of PiFS stabilized at 47 °C when applied in wLDs (1 W), which greatly prevented the phenomenon of “thermal quenching” for the phosphors caused by high temperature under high power LDs. Thus, high Ra PiFS prepared by this strategy has better heat dissipation and optical properties than PiG, indicating a prospective application in high-power white LEDs/LDs.
查看更多>>摘要：? 2022 Elsevier B.V.A facile and scalable method is reported for MgV2O5 (MVO) interconnected with a porous nitrogen-doped carbon (NC) sphere network using a hydrothermal technique. The synthesized MgV2O5-N-doped Carbon (MVO-NC) nanocomposite has an orthorhombic crystal plane and a sheet-like MVO with a porous NC network based on structural and morphological analyses. In an aqueous electrolyte, the hydrothermally produced MVO-NC electrode demonstrates good charge–discharge performance, with an exceptional cycling retention of 97.05% over 5000 cycles. At 2 A g?1, the MVO-NC has a higher specific capacitance of 358 F g?1 than other MVO electrode compositions (272 F g?1) and V2O5 (146 F g?1). Owing to the highly redox-active MVO-NC composite and exceptionally porous activated carbon components, the hybrid supercapacitors achieve a maximum energy density of 38 W h kg?1 and maximum power density of 8000 W kg?1. The two-dimensional porous network structure of the MVO, along with the porous NC, creates sufficient interstitial space for electrolyte accommodation, thereby allowing a rapid and reversible electrochemical process.
查看更多>>摘要：? 2022 Elsevier B.V.Herein, sulfur-doped graphene modified Li4Ti5O12@C nanocomposite (SG-T@C) has been firstly fabricated via a sol-gel method assisted with solid-state route. In this composite, the Li4Ti5O12@C nanocrystals (T@C) are homogeneously dispersed into the two-dimensional sulfur-doped graphene. The introduced sulfur-doped graphene acted as conductive bridge within the resulted nanocomposite, thereby enhancing the electrical conductivity of T@C nanoparticles. The as-fabricated SG-T@C displays superior high-rate performance for lithium-ion batteries. It can deliver the capacities of 171.9 and 145.2 mAh/g at 0.1 and 10 C respectively. Besides, SG-T@C exhibits 96.2% capacity retention at 20 C over 800 cycles, demonstrating an excellent cycling stability. Therefore, the designed SG-T@C can be used as an advanced electrode for lithium-ion batteries.
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