查看更多>>摘要：Refractory high entropy alloy TiZrHfNbTa matrix composites reinforced with in-situ nitrides were prepared by vacuum arc melting. The designed composites are composed of BCC matrix and FCC nitride phases, with a particular orientation relationship between them: [111](BCC)parallel to[011](MN),(10 (1) over bar)(BCC)parallel to(200)(MN),(1 (1) over bar0)(BCC)parallel to(1 (1) over bar1)(MN). The composites show enhanced strengths both at room temperature and high temperature compared with the matrix alloy and increase with the increment of N content. The ambient and elevated temperature (1000 degrees C) compressive yield strength is up to 2125 MPa and 350 MPa, respectively, and decent fracture strains (> 19.3%) at room temperature are maintained. The underlying strengthening mechanisms are discussed systematically, and the increase in strength is mainly attributed to the combination of dislocation strengthening, load-transfer effect and Orowan strengthening. (C) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：Sintered cold compacted hexaferrite magnets with appreciable magnetic properties and crystallite alignment were made from non-magnetic precursors without applying an external magnetic field. This work presents a novel approach employing non-ferromagnetic interacting precursors comprising of platelet shaped six-line ferrihydrite and needle shaped goethite nanoparticles. A hydrothermal synthesis route was employed to produce platelet shaped six-line ferrihydrite of ~5 nm thickness. Needle shaped goethite nanoparticles were likewise prepared by hydrothermal synthesis with apparent dimensions of ~10 x 27 x 10 nm3 extracted from X-ray powder diffraction data. The powder diffraction Rietveld modelling also revealed the presence of an amorphous phase in the six-line ferrihydrite and a SrCO3 impurity. The presence of needle shaped goethite nanoparticles improves the alignment of magnets, while retaining the coercivity (Hc), in contrast to hexaferrite magnets prepared from six-line ferrihydrite by spark plasma sintering (SPS). The non-ferromagnetically interacting precursors were directly converted to the SrFe12O19 magnets by pressing them with conventional compaction technique followed by subsequent sintering of the pellets. Decoupling the pressing and sintering step is interesting for industrial production of magnets. The hexaferrite magnets prepared displayed good combination of saturation magnetization Ms = 70 Am2/kg and coercivity Hc = 297 kA/m with some degree of alignment of the crystallites Mr/Ms = 0.71. This procedure exploits the anisotropic shape of the crystallites and compaction using uniaxial pressure followed by sintering into aligned bulk magnets. Two sets of hexaferrite bulk magnets were prepared by sintering at 900 degrees C and held for 2 h and 1050 degrees C with a holding time 0 min. The hexaferrite magnets sintered at 1050 degrees C were subjected to transmission pole figure analysis. The texture index for each pellet were extracted from the pole figure analysis. Employing needle shaped goethite nanoparticles actually enhanced the alignment of the hexaferrite magnets. The magnet obtained from only six-line ferrihydrite displayed only a slightly improved texture index when compared with mixture of six-line ferrihydrite and goethite nanoparticles. (c) 2022 The Author(s). Published by Elsevier B.V. CC_BY_4.0
查看更多>>摘要：In this work, the structural evolution and photoluminescence (PL) of 200 nm pseudomorphic Ge0.9338Sn0.06 62 on Ge (001) substrate grown by low-temperature molecular beam epitaxy (MBE) after rapid thermal annealing (RTA) is studied. Under RTA at 350 degrees C or lower, the GeSn film is coherently strained on Ge substrate. As RTA temperature further increases, gradual strain relaxation of GeSn is enabled by generation of misfit dislocations and threading dislocations. As RTA temperature reaches 550 degrees C or beyond, Sn segregation occurs along with strain relaxation. The PL intensity of annealed samples is enhanced compared to that of as-grown sample probably due to improved crystal quality and strain relaxation (for RTA at > 350 degrees C) of GeSn. The sample annealed at 500 degrees C exhibits highest PL intensity due to formation of a Sn-componentgraded (SCG) heterojunction with highest Sn content in surface region resulted from interdiffusion of Ge and Sn. The formation of SCG heterojunction renders spontaneous confinement of optically pumped carriers in the surface region and enlarges occupation probability of carriers in Gamma valley. Additionally, the carrier confinement in the surface region reduces self-absorption of GeSn and suppresses nonradiative recombination near the GeSn/Ge interface. The results manifest that RTA is an appropriate approach to improve the light emitting property of GeSn grown by low-temperature MBE. (c) 2022 Elsevier B.V.
查看更多>>摘要：Achieving the broad effective absorption bandwidth (EAB), strong absorption capacity and thin matching thickness are still a huge challenge for the dielectric loss-type microwave absorbers. Here, the honeycomblike SnS2/ graphene oxide (GO) composites are fabricated via a facile chemical bath deposition method to optimize the microwave absorption performances. The 2D SnS2 nanosheets are uniformly and vertically grown on the GO sheets, forming a highly open hierarchical network, which can be beneficial to enhance the multiple scatterings and reflections of incident electromagnetic wave. Meanwhile, the impedance matching (Z) and attenuation constant (alpha) of composites are well-tuned by changing the SnS2 content in the composites. When the GO sheets are just completely coated by SnS2 nanosheets, the SnS2/GO composite exhibits excellent microwave absorption ability with the minimum reflection loss (RLmin) of - 59.2 dB and EAB of 5.4 GHz (12.3-17.7 GHz) at the thickness of only 1.45 mm, which is mainly ascribed to the strong interfacial polarization and good impedance matching. This work provides a significant guidance to achieve excellent absorption performance with broad EAB and strong absorption for dielectric loss-type absorbers. (c) 2022 Published by Elsevier B.V.
查看更多>>摘要：Present proposed mechanisms for ageing-induced martensitic stabilization cannot explain why the amount of martensites losing reverse transformation ability (RTA) positively depended on Ms temperatures in directly-quenched CuZnAl alloys owing to dynamic ageing during the cooling process of quenching and subsequent slow heating. We proposed and confirmed that the number of vacancies at martensites boundaries (N-vmb) was the key factor controlling the occurrence of martensitic stabilization and its resulting RTA or loss in shape memory effect, not the number of vacancies inside the martensites and their long-range diffusion. All reported results can be rationalized by the positive dependence of original N-vmb on the Ms temperature. (C) 2022 Published by Elsevier B.V.
查看更多>>摘要：Hydrophobic AlCoCrFeNi high-entropy alloy (HEA) was prepared by electrochemical dealloying using 5% of weight percent H2SO4 aqueous solution at low temperature. The results of energy-dispersive spectrometer (EDS), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyses revealed that the element contents of Al and Ni were greatly reduced after dealloying treatment, leading to the increase of body centered cubic (BCC, Fe-Cr) phase and consequently, the achievement of the protective barrier of Cr- enriched oxide film on the substrate surface. The static water contact angle increased with the extension of dealloying period and reached a maximum value of 127 +/- 1 degrees, showing pronounced hydrophobic performance after dealloying treatment. Meanwhile, the AlCoCrFeNi HEA specimens showed excellent mechanical properties involved compressive strength and micro-hardness. Compared with the as-cast AlCoCrFeNi HEA, the HEA specimens after dealloying treatment exhibited superior corrosion resistance in an acidic aqueous solution of 3-nitro-1, 2, 4-triazole-5-one (NTO) aqueous solutions confirmed by potentiodynamic polarization tests and electrochemical impedance spectra (EIS) analyses, which was credited to the Cr- and Fe-enriched oxide and hydrophobic surface. Data Availability: The raw/processed data required to reproduce these findings cannot be shared at this time as the data also forms part of an ongoing study. (c) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：Additive manufacturing (AM) technology can fabricate functionally graded materials (FGMs) with a layered gradient change in chemical composition and microstructure by changing the composition ratio of different filler materials layer by layer, which indeed have uneven and uncontrolled composition gradients between layers. In the present work, FGMs of stainless steel 308 L and Inconel 625, with continuous change in composition, were fabricated by dual-wire arc additive manufacturing (D-WAAM) by changing the speeds of dual wires in each single layer. The chemical composition, microstructure, phases, and mechanical properties of the FGM were investigated. The results showed that the composition gradient was smoothly distributed along the torch-travelling direction in each single layer, and the composition at the same position along the building direction was stable. With the increase in the content of Inconel 625, the austenite dendrites, which was the main microstructure, became finer first and then coarser, but there was no apparent abrupt change in microstructure in the gradient zone, which made the mechanical properties also show a smooth change. The mechanical properties were weak when the content of Inconel 625 was within 10-50 wt% due to the secondary phases (MC, Laves) distributed at the grain boundary. The proposed fabrication approach of FGM also showed advantages and flexibility in the design of gradient path, or the design of structure size if there is a requirement on the size in the building direction.(c) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：Recently, it has been a hot topic to explore lightweight high entropy alloys (HEAs) for their future potential application as engineering materials. In this work, novel lightweight Ti22Sc22Zr22Nb17V17, Ti24Sc20Zr22Nb17V17, Ti24Sc22Zr20Nb17V17, and Ti26Sc20Zr20Nb17V17 HEAs were fabricated by rapid solidification. The phase constituents and microstructures of the HEAs in the cast and annealed states were characterized by X-ray diffraction spectrum (XRD), scanning electron microscopy (SEM), transmission electron microscope (TEM), and energy dispersive spectrum (EDS), while their mechanical properties were also investigated in detail. The microstructures of the cast samples consist of the coarse equiaxed BCC dendrites with extremely heterogeneous chemical distributions and the intergranular structures that are made up of BCC and HCP precipitates. Both precipitates inside the intergranular structures exhibit slightly large worm-shaped and fine lamellar morphology features. After annealing at temperatures below 1273 K, the desolvation reaction occurs due to the strong solute redistribution, leading to the disappearance of the lamellar structures, the coarsening of the large worm-shaped BCC particles, and the solid phase separation of the equiaxed BCC dendrites. At 1273 K, the combined interaction from the eutectoid transformation and phase separation leads to the formation of the TiNbV-rich BCC, ScZr-rich HCP, and transitional BCC+HCP structures. Compared with reported lightweight HEAs (density <= 6.5 g/cm(3)), the present HEAs in the cast and annealed states exhibit excellent comprehensive mechanical properties, which are attributed to the combined effect from the solid-solution strengthening, second phase strengthening, and fine-grained strengthening. The present studies provide potential candidates as lightweight high-temperature structural materials in the future. (C) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：CoP3 is a promising electrocatalyst for the hydrogen evolution reaction, however it is still challenging for CoP3-based catalyst to deliver excellent activities in a wide pH range. In this work, the self-standing Ni-doped CoP3 nanowire arrays (Ni-CoP3 NWs) on carbon fiber paper were synthesized by hydrothermal method followed with an in situ phosphating process. The results show that the Ni doping effectively boosts the electrocatalytic hydrogen evolution for CoP3 NWs over the wide pH range with good stability. The Ni doped CoP3 NWs sample with the Ni: Co mole ratio of 10% (Ni-CoP3-10%) shows a low overpotential of 66 mV to afford the current density of 10 mA cm(-2) in 0.5 M H2SO4, which is the optimal catalytic performance in this work. Furthermore, Ni-CoP3-10% sample also shows excellent electrocatalytic performance in alkaline and neutral conditions, which needs the overpotential of 114 and 131 mV to afford the current density of 10 mA cm(-2) in 1 M KOH and 1 M PBS, respectively. The enhanced electrocatalytic activity can be ascribed to that the Ni doping improves the electron transport, increases the electrochemical active surface area and optimizes the Gibbs free energy of hydrogen adsorption for the CoP3 NWs, which develops it as a promising electrochemical catalyst for hydrogen evolution. (C) 2022 Published by Elsevier B.V.
Kim, Hoe JoonRajaitha, P. MaryHajra, SugatoPadhan, Aneeta Manjari...
9页
查看更多>>摘要：The high dielectric constant and lower dielectric loss make NdFeO3 materials ideal for potential use in many several applications. Specifically, NdFeO3 is a promising candidate for electrochemical sensing applications owing to its high thermal stability, and non-toxicity. In this present study, multiferroic NdFeO3 particles are synthesized using a solid-state reaction at a higher temperature. Structural studies confirm that NdFeO3 crystallizes in an orthorhombic symmetry. Elemental color mapping of the NdFeO3 sample reveals there is no impurity, and that the sample comprises Nd, Fe, and O elements. In addition, the Nyquist plot suggests the contribution of grain and grain boundary effect towards the resistive and capacitive characteristics of NdFeO3. Magnetic measurements at room temperature indicated an antiferromagnetic nature of the sample with a weak ferromagnetic component arising due to the canted nature of Fe3+. The non-collinear magnetic structure of NdFeO3 promotes the ferroelectric loop. Single-phase room temperature NdFeO3 multiferroics were coated upon the glassy carbon electrode with the aim of sensing hydrogen peroxide (H2O2) using a three-electrode electrochemical setup. The cyclic voltammetry technique showed an increase in the peak current with an upsurge in the concentration of H2O2 between 1 mM and 10 mM. The limit of detection, the limit of quantification, and sensitivity was calculated to be 0.87 mu M, 2.92 mu M, and 52.6 mu A mM(-1) cm(-2) respectively. The correlation coefficient R-2 was found to be 0.9792. The value of linearity with regression coefficient was calculated to be R-2 = 0.9922 from the effect of scan rate. NdFeO3 showed an excellent selectivity towards H2O2 in the presence of H2SO4, KCl, HCl, and NaOH, and good sensitivity for monitoring H2O2 in a real milk sample. The sensitivity of modified Glassy carbon electrode (GCE) in milk was calculated to be 46.58 mu A mM(-1) cm(-2). (C) 2022 Elsevier B.V. All rights reserved.
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