查看更多>>摘要：? 2022 Elsevier B.V.(Ni0.2Cu0.2Zn0.6O)1.02(Fe2O3)0.98 based ferrites with combined B2O3-WO3-Co2O3 dopings were synthesized through solid state reaction. Subsequently, high-performance NiCuZn green tapes and multilayer chip inductors were fabricated via non-aquous tape casting. The results showed that an appropriate Co2O3 doping in the B2O3-WO3 contained NiCuZn ferrites could refine the crystalline grains, and reduce the permeability, and increase the Q factor of the ferrites. NiCuZn ferrite with 0.03 wt% B2O3, 0.7 wt% WO3, and 0.60 wt% Co2O3 sintered at 900 °C showed excellent electromagnetic properties: μi = 424.0 at 0.1 MHz, Q factor = 127.0, Bs = 283.5, Br = 79.5, Hc = 52.3, and a good co-firing compatibility with Ag electrodes. The resulting NiCuZn multilayer chip inductor (6 ×6 ×2 mm in dimention) exhibited an inductance of 26.0 μH (0.1 MHz, 0.25 V), and a Q factor of 8.5, and a DC superposition current of about 984 mA, thus guaranteeing this NiCuZn material a promising candidate for the LTCF applications.
查看更多>>摘要：? 2022 Elsevier B.V.In the current study, the high temperature oxidation behavior of AlCoCrFeNi high entropy alloy (HEA) following severe shear deformation was investigated. X-ray diffraction and transmission electron microscopy analysis confirmed spinodal distribution of B2 and BCC phase in the as cast specimen. In contrast, the processed specimen showed a dual phase microstructure (B2/BCC+FCC) after shear deformation. Electron backscattered diffraction analysis revealed significant grain refinement from 90 μm for the as-cast HEA to nearly 2 μm for the processed specimen. The processed specimen showed up to 66% reduction in the oxidation kinetics compared to the as cast alloy. The remarkable improvement in the high-temperature oxidation performance following processing is attributed to complete microstructure refinement. The current study provides a sustainable solution and a new pathway for addressing the looming problem of material deterioration at high temperatures.
查看更多>>摘要：? 2022 Elsevier B.V.This paper proposes a new way to detect recrystallization in beta-metastable alloys Ti5553 and Ti4733. Samples of these alloys were cold rolled and thermally treated. Internal friction was measured during heat cycles using a torsion pendulum. A correlation between recrystallization and sharp peak in internal friction specra was shown. The mechanism of dissolution of alpha phase triggering the recrystallization is proposed. In subsequent temperature cycles, the internal friction high temperature background decreases and stabilizes after three cycles. This is attributed with secondary recrystallization leading to grain growth. The size of the grains for different recrystallization time and temperature was measured and is coherent with the mechanical spectroscopy results. This result tends to prove that internal friction measurement can be used to optimize recrystallization treatment in beta metastable titanium alloys.
查看更多>>摘要：? 2022In this article, an ultrahigh sensitive and selective carbon monoxide (CO) gas sensor was developed and studied at room temperature utilizing the PPy/TiO2 nanocomposite. The gas sensors were fabricated through drop-casting the PPy/TiO2 nanocomposites on the surface of interdigitated electrodes. All the nanocomposites have been synthesized via a chemical oxidation method. Contrary to the pure PPy sensor, PPy/TiO2 sensor exhibited 4-fold enhanced sensitivity. Our sensor showed a superior response of order 93 at 270 ppm of carbon monoxide with high selectivity over the other interference gases. Additionally, our sensor exhibited a quick response time and a short recovery time of 36 s and 38 s, long-term stability, excellent repeatability, and satisfactory reproducibility. Accordingly, experimental findings proved that incorporating TiO2 into the PPy plays an influential role in enhancing the gas sensor performance. In this work, based on the outstanding CO sensing performance, the PPy/TiO2-based sensor might be considered a promising candidate for real-time gas sensor applications.
查看更多>>摘要：? 2022 Elsevier B.V.AlCoxCrFeNi (x = 2.2, 2.8) high entropy alloys (HEAs) were successfully prepared by multi-layer and multi-channel laser melting deposition (LMD). The tensile properties of the LMD-fabricated AlCoxCrFeNi HEAs were investigated. The phase evolution of these alloys was examined by X-ray diffraction and compared with existing models. The microstructure of the alloys was characterized using scanning electron microscopy and electron backscatter diffraction. It is found that Co element can promote the phase transformation from BCC phase to FCC phase in the as-deposited AlCoxCrFeNi HEAs, and the volume fraction of FCC phase increases from 51.4% to 74.6% as the Co content increases from 36.2 at% to 40.8 at%. With the increase of Co content, the grain size of BCC phase in the alloys decreases and a larger amount of fine needle-like BCC phase appears in the FCC matrix. Tensile testing shows that higher Co content in the deposited AlCoxCrFeNi alloy can enhance its plasticity without significantly compromising its ultimate strength. As the Co content increases, the fracture strain increases from 5.9% to 15.4%, while the yield strength reduces from 450 MPa to 360 MPa and the ultimate tensile strength increases from 734 MPa to 739 MPa. The variations in tensile properties of the AlCoxCrFeNi alloy result from phase structure changes and microstructure evolution. Through this research, it is demonstrated that enhancement of the tensile properties of the LMD-fabricated AlCoCrFeNi HEAs can be realized by increasing the content of Co element.
查看更多>>摘要：? 2022 Elsevier B.V.A new family of two-dimensional (2D) transition metal carbides, carbonitrides, and nitrides that were discovered and developed at Drexel University in 2011, which is called MXene and is applicable for several critical applications. These so-called MXene structures possess excellent properties e.g., rich surface chemistry, electronic structures, high electrical conductivity, hydrophilicity, thermal and mechanical stability, and large specific surface area, which have attracted tremendous attention. This review article will focus on some most recent progress and review comprehensively their fabrication methods and compositing with polymers and metals. A major part has been associated with the electrochemical applications, medical, flame retardance effect in a polymer matrix, and electromagnetic shielding properties. In addition, briefly, we will delve into a brief discussion on the current limitations, and future research needs, along with the various corresponding challenges in order to provide a better understanding of these new 2D materials.
查看更多>>摘要：? 2022 Elsevier B.V.In this work, the trace Ce atoms have been added into the low-alloyed Mg-Al-Ca matrix, and the microstructure and mechanical properties have been investigated. For the Mg-Al-Ca ternary alloy, the tensile yield strength (TYS) would be decreased from ~ 321 MPa at 260 °C (extrusion temperature) to ~ 294 MPa at 290 °C. In contrast, the Mg-Al-Ca-Ce alloy can still exhibit the high YS of ~ 350 MPa and elongation of ~ 12.1% at higher extrusion temperature of 290 °C. Microstructure characterization shows that the Ce addition can effectively induce the solute segregations along both dislocations and grain boundaries in Mg-Al-Ca-Ce alloy, which thus leads to the finer grain size of 0.7 ~ 0.8 μm at a wide range of extrusion temperature. Formation of subgrain with strong texture, residual dislocations due to segregation and profuse nano-precipitations can together contribute to the high yield strength of Mg-Al-Ca-Ce alloy. More importantly, the trace Ce atoms can promote the activation of non-basal dislocations in Mg matrix and also the weakened texture in DRXed grains. As a result, the ductility is also simultaneously improved by the trace addition of Ce atom into Mg-Al-Ca based alloy. The relevant results can shed light on designing the new high strength and low-alloyed Mg alloys.
查看更多>>摘要：? 2022 Elsevier B.V.Recently, BiI3 was discovered as a promising 2D semiconductor materials for photovoltaic and photodetector device, due to its suitable bandgap, high optical absorption coefficient, excellent electron mobility, and low carrier concentration. However, as so far, only the CVD/PVD grown BiI3 nanoflakes/films have been reported. Here, we firstly synthesized the O-doped BiI3 (OBI) bulk crystals via chemical vapor transport (CVT) method, and then systematically studied the electrical and optoelectronic properties of exfoliated multi-layer OBI nanoflakes. Back-gated field-effect transistor fabricated on the multi-layer OBI nanoflakes with van der Waals (vdW) bottom electrode contact exhibited n-type semiconducting characteristics. In addition, exfoliated multi-layer OBI based photodetector demonstrates an excellent photoresponse with good reproducibility at room-temperature for visible wavelengths, including a high photo-to-dark current ratio (2.16 ×104), a remarkable photoresponsivity (850 mA W?1), a fast response speed (rise/decay time of 3.2/2.9 ms), and a high specific detectivity (9.85 ×1012 Jones), which is favored by the ultralow dark current (～30 fA). These results indicated that the OBI crystals have great potential for future applications in highly sensitive and ultrafast visible-light photodetector.
查看更多>>摘要：? 2022 Elsevier B.V.The effect of ageing time and temperature on the deformation mechanism and corresponding tensile properties are investigated in a γ/γ′ Ni-based superalloy, HAYNES 282. Through a systematic variation in duration (24 h and 216 h) and temperature of ageing (650 °C and 760 °C), a significant variation in strengthening microstructural features was achieved in the resulting microstructures. While in one case (650 °C, 24 h ageing condition), a microstructure with no γ′ was observed, for the rest of the cases, γ′ precipitates of varied sizes were observed. In one specific case (760 °C, 216 h ageing condition), very fine (4–6 nm) MC carbides were observed along with γ′ precipitates; in which these tiny MC carbides became the deciding factor for strength over γ′ precipitates. While common knowledge of smaller γ′ precipitates giving higher strength could explain the higher strength at 760 °C, 24 h ageing condition as compared to 650 °C, 216 h ageing condition, the further increase in strength in case of 760 °C, 216 h ageing condition, even with much larger γ′ precipitates was something quite interesting and counterintuitive. This paper elucidates this puzzling observation. The variation of tensile properties of these wide varieties of microstructures will be described in this paper in light of the underlying deformation mechanisms. A change in deformation mechanism from planar slip (microstructure with no γ′) to twinning (microstructure with γ′) and Orowan-looping (microstructure with γ′ along with fine nano carbides) as a function of microstructure explains the difference in strength, ductility, and strain hardening phenomena among the varied ageing conditions.
查看更多>>摘要：? 2022 Elsevier B.V.In this work, we synthesized the Sr2InSbO6 (SISO) phosphors with good temperature sensing performances for luminescent thermometry. Both X-ray diffraction and Rietveld refinement results verified that SISO: Sm3+ phosphors have a monoclinic structure with the P21/n space group. Under the charge transfer band excitation, three dominating emission peaks which are attributed to the f-f transition of Sm3+ ions from the 4G5/2 excited level to the 6H5/2, 6H7/2, and 6H9/2 levels, respectively were observed. As the main concentration quenching mechanism was controlled by dipole-dipole (d-d) interaction, the optimum doping concentration in SISO:Sm3+ phosphors was found to be 3%. With the aid of the temperature-dependent fluorescence intensity and lifetime, the maximum relative temperature sensitivities, SR1 and SR2, of SISO:0.03Sm3+ phosphor were 10.9% K?1 and 2.15% K?1 at 523 K, respectively. On the account of these results, single-phase Sr2InSbO6:Sm3+ phosphors with remarkable temperature sensing performances can be applied in dual-mode optical thermometers.
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