查看更多>>摘要：? 2022 Elsevier B.V.In this work, we demonstrate a giant elastocaloric effect in a Ni50Mn33In14Si1Cu2 alloy. Owing to the large transformation entropy change and low thermal hysteresis, giant adiabatic temperature change (ΔTad) of ? 18.2 K is obtained on unloading from a maximum compressive strain of 6 % with a low stress of 145 MPa. Moreover, large specific adiabatic temperature variation (ΔTad/σmax) up to 126 K/GPa has been achieved. This ΔTad/σmax value significantly exceeds those in the typical shape memory alloys. The present results demonstrate that the target alloy exhibits a distinct advantage in the strength of elastocaloric effect, being crucial for practical applications of solid-state refrigeration. In addition, it is found that the cyclic stability can be effectively enhanced by one-step overstress superelastic training for the first cycle.
查看更多>>摘要：? 2022 Elsevier B.V.Deformation-induced martensitic transformation in Fe-Co-Ni-Cr-Mn high entropy alloy (HEA) thin film with nanocolumnar growth feature are revealed to readily occur at intermediate deposition power rather than low and high deposition power ranges. The high probability of deformation-induced martensitic transformation from face-centered cubic (FCC) to hexagonal close-packed (HCP) phase in 150 W-film results in low nanoindentation hardness and compressive yield strength, in comparison with 60 W- and 210 W-films. Dependence of the martensitic transformation probability has been explained in terms of the competition between grain size effect and nanocolumn cohesion effect on the phase metastability. The increased grain size with deposition power favors the mechanical instability of FCC parent phase caused by the weakened slip obstruction, while the enhanced nanocolumn cohesion with deposition power hinders the formation of HCP martensite due to the increased activation energy for martensitic transformation. The grain size effect is dominated over the cohesion between nanocolumn at low deposition power range, while column cohesion effect is dominant at high deposition power range, which gives rise to the crossover of FCC-to-HCP with deposition power. This work might provide a deeper understanding in phase metastability of sputtered films, for instance, the effect of deposition power on deformation-induced martensitic transformation.
查看更多>>摘要：? 2022 Elsevier B.V.High entropy alloys (HEAs), a new type of functional material, are rarely applied to prepare core-shell structured nanocomposites. In this work, FeCoNiCuTi@C nanocapsules have been prepared by arc discharging HEAs ingot under the atmosphere of methane, displaying the sphere shape with the average diameter of 72.1 nm and ~ 3 nm onion-like carbon shell and the single FCC phase. The melting points, crystal structure and electronegativity play the important role on determining the element composition and atomic percentage. Carbon facilitates protecting magnetic elements, improving EM parameters and enhancing resonance frequency. Good impedance matching, strong electromagnetic loss ability and large attenuation constant ensure the microwave can enter the nanocapsules to the largest extent and could be consumed. These advantages provide the basis for the excellent microwave absorption performance ( effective bandwidth of 5.52 GHz at 1.9 mm, maximal reflection loss of ?37.78 dB and absorption efficiency of 52.41 dB·GHz/mm at 1.8 mm) of FeCoNiCuTi@C nanocapsules.
查看更多>>摘要：? 2022 Elsevier B.V.Heteroatom-doped carbon dots with promising luminescent properties are excellent candidates for sensing and imaging applications. Herein, we reported a facile one-step hydrothermal synthesis of highly-fluorescent red-emitting carbon dots (R-CDs) with quantum yield of 37.2 %. R-CDs exhibit a maximum emission band at 640 nm under the excitation wavelength of 500 nm. Furthermore, R-CDs show excitation-dependent and solvent-engineered fluorescent characteristics that the luminescent properties could be greatly affected by polarity. Due to the sensitivity to polarity, a quick and precise approach for wide-range water detection in organic solvents has been developed. Because of the low autofluorescence background, R-CDs were applied to the zebrafish larvae imaging. Polarity-selective bright red light from R-CDs is seen in the low-polarity organs like yolk sac and eyes, which contain abundant lipids and lipoprotein. Our results demonstrate that R-CDs could be used as bio-imaging agents and fluorescent sensors for quantitative and visual water detection in various organic solvents.
查看更多>>摘要：? 2022 Elsevier B.V.Recently, there has been a growing interest in synthesizing new materials with unique physical properties. PANI/Bi2Te3 composites have attracted considerable attention due to the distinctive characteristics of the conductive polymer and semiconductor material. PANI/Bi2Te3 composites were prepared and irradiated with 100 KGy electrons from the electron beam accelerator. After the exposure to the radiation and increasing Bi2Te3 concentration, XRD shows an increase in the unit cell volume and the inter-chain distances where the grains were decreased. Besides TEM, SEM provided the topographic images and the nano-crystal size on the surface and showed the accumulation of the particles of the obtained materials. TGA demonstrates the degradation behavior compositions throughout the heating of the samples. Unexpected ferromagnetic behavior was achieved for the highest ratio of (PANI)0.3(Bi2Te3)0.7, confirmed by VSM and ESR. The ferromagnetic behavior was achieved without introducing any magnetic dopants, making these materials applicable in the future in magnetism.
查看更多>>摘要：? 2022 Elsevier B.V.Gold nanorods (Au NRs)/Ti3C2Tx composites were prepared by self-assembly method as surface enhanced Raman scattering (SERS) substrates. Due to strong electrostatic interaction, Au NRs are evenly arranged on the surface of Ti3C2Tx nanosheets, forming rich SERS hotspots. Au NRs/Ti3C2Tx have high sensitivity and good reproducibility for the determination of organic dyes such as rhodamine 6G, crystal violet and malachite green. The detection limits were 1 × 10?13, 1 × 10?13 and 1 × 10?12 M, respectively. The relative standard deviations of samples in 40 areas were 4.57 %, 2.79 % and 3.47 %, respectively. The synthesized SERS substrate is sensitive to adenine. For adenine molecules in the range of 1 × 10?5–1 × 10?9 M, SERS results show that the peak intensity is linear with adenine molecular concentration, and the detection limit can be as low as 1 × 10?9 M. In addition, adenine in aqueous solution has good anti-interference ability to other nucleic acids with similar structure, such as guanine, cytosine and thymine. Therefore, Au NRs/Ti3C2Tx are expected to become a potential substrate for unmarked, rapid and sensitive SERS detection of adenine in the field of bioanalysis.
查看更多>>摘要：? 2022 Elsevier B.V.Exploring efficient photocatalysts for photocatalytic degradation is of considerable importance for the long-term mitigation of environmental stress. Although defect engineering is an effective strategy to alter the electronic transport properties and light absorption capacity of TiO2, the synthesis of TiO2 rich in oxygen vacancies (OVs) via a green process at room temperature and with low energy consumption remains a challenge. Herein, amorphous TiO2 nanosheets rich in OVs were prepared by H2O2-assisted room-temperature oxidation of Ti3C2Tx MXene via a bottom-up approach. Notably, small amounts of C and Ti3+ were introduced during the preparation of carbon-doped TiO2 (C-TiOx), which was shown to possess abundant surface functional groups (e.g., –OH, –O, and –F) and two intermediate levels in its bandgap. Comparative experiments demonstrated that OVs play a key role in suppressing the recombination of photogenerated carriers and expanding the light absorption range of the photocatalyst. The unique quasi-two-dimensional structure of C-TiOx features a large number of exposed active sites, which are beneficial for improving its catalytic performance. Tetracycline (TC) was removed from the aqueous solution by the prepared photocatalysts C-TiOx and annealed-TiO2, and the former adsorbed 41.1% of TC. The TC removal efficiency of C-TiOx was 76%, which was higher than that of annealed-TiO2. This approach embodies a new strategy for introducing defects and doping in TiO2. Moreover, it is also thought that C-TiOx possesses promising characteristics suitable for a wide range of potential future applications.
查看更多>>摘要：The production of effective photocatalyst to generate H_2 and eliminate pollutants is still a challenge. A simple solvothermal approach is demonstrated for synthesizing a coupled P-C_3N_4/MIL-88A(Fe) composite wherein two-dimensional phosphorus-doped g-C_3N_4 nanosheets are attached to three-dimensional MIL- 88A. The P-CN/MIL-88A composite shows superior photocatalytic ability with a high hydrogen generation rate of 34.53 mmol/(g·h) and an ofloxacin degradation rate of 95.6%. The H_2 evolution rate of the composite is approximately 38.3 times that of bulk g-C_3N_4 (B-CN). The enhancement mechanisms resulting in high efficiency and adaptability are attributed to the Z-scheme (2D/3D) P-CN/MIL-88A heterojunction, which has unique synergistic interface properties, good photoinduced electron mobility, and good electron-hole pair separation ability. This work provides insights into the design of 2D/3D heterostructure photocatalysts for highly efficient and simultaneous photocatalytic H_2 production and antibiotic degradation.
查看更多>>摘要：? 2022 Elsevier B.V.In this study, an Al–based composite reinforced with nanometric γ–Al2O3 and submicron AlB2 particles was fabricated via chemical reactions between Al and boron oxide, followed by hot extrusion. The volume fraction of in–situ formed γ–Al2O3 and AlB2 is 11.2 vol% and 6.3 vol%, respectively. The average size of γ–Al2O3 and AlB2 is around 50 nm and 500 nm, respectively, and the α–Al grain is 1.26 μm in the longitudinal section. The γ–Al2O3 particles either distribute inside of α–Al grains or exhibit particle chains or networks locating along grain boundaries, while AlB2 particles are uniformly distributed among the matrix grains. The Young's modulus is averaged at 91 GPa, and the ultimate tensile strength and elongation of the composite at room temperature are averaged to be 426 MPa and 8.1 %, respectively. The yield strength at 350 °C is as high as 217 MPa. It is regarded that the relatively fine α–Al grains along with the γ–Al2O3 particles inside of α–Al grains and AlB2 particles are mainly responsible for room temperature strengthening, while the γ–Al2O3 particle chains or networks along grain boundaries play the key role in grain boundary strengthening at 350 °C. This work may provide new insights for designing and fabricating Al–based composite for elevated–temperature application.
查看更多>>摘要：? 2022 Elsevier B.V.In the present work a 3D hierarchical NiCo2O4@NiCo-LDH core-shell structure has been fabricated on activated carbon cloth through a facile hydrothermal strategy and an electrodeposition step. The core of the NiCo2O4 nanowires forms the nanoarray backbone on carbon cloth while the shell of NiCo-LDH nanosheets extends the electrochemical active sites and generates mesoporous hierarchical channels to facilitate electron and ion transport. Therefore, with the optimized mass ratio of 1.9 between NiCo-LDH and NiCo2O4, such a core-shell structure enhanced the areal capacitance of the as-prepared NiCo2O4@NiCo-LDH electrode up to 6092 mF/cm2 (or areal capacity of 0.846 mAh/cm2 at 2 mA/cm2 for the battery type pseudocapacitor) and obtain high specific capacitance of 1882 F/g under 1 A/cm2. The capacity retention rate can maintain 83.9 % after 5000 cycles at 30 mA/cm2. Furthermore, an all-solid-state asymmetric supercapacitor (ASC) was assembled using NiCo2O4@NiCo-LDH//activated carbon. Such an ASC exhibits a very high energy density of 49 Wh/kg at the power density of 750 W/kg and retains 30 Wh/kg at 7500 W/kg. The ASC shows its excellent cycling stability by keeping 83.3 % of initial capacity retention rate after 2000 cycles under 5 A/g. The assembled flexible all-solid-state supercapacitor with NiCo2O4@NiCo-LDH//activated carbon exhibits good mechanical stability and high specific capacity of 157 F/g under 1 A/g. The significantly improved electrochemical properties demonstrates the practical applications of the core-shell structure of NiCo2O4@NiCo-LDH on carbon cloth for novel ASC configuration design and development of next energy storage devices.
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