查看更多>>摘要：? 2022 Elsevier B.V.An Al-Mn-Mg-Sc-Zr alloy was additively manufactured and subsequently deformed to investigate the effect of high defect densities on the precipitation behavior, work hardening capability and ductility. For this, the LPBF-fabricated alloy was deformed by rotary swaging up to a true strain of 2.5 following a laser powder bed fusion (LPBF) process. Compared to the LPBF condition, swaging results in a refinement of the microstructure by one order of magnitude and an increased hardness and ultimate tensile strength (UTS) which is mainly attributed to the finer microstructure of the swaged alloy. By annealing, a higher peak-aging hardness of (209 ± 2) HV0.1 and UTS of (717 ± 2) MPa of the swaged alloy at a lower peak-aging temperature of 300 °C (1 h) was obtained. Significant improvement of uniform elongation by enhanced work hardening capability of the swaged and annealed alloy is obtained for annealing temperatures above 300 °C while strength is only moderately affected. The significant improvement of aging kinetics is discussed alongside a profound microstructural characterization of the heterogeneous grain structure and precipitate distribution.
查看更多>>摘要：? 2022 Elsevier B.V.In this study, biomass carbon supported with iron and cobalt bimetal (FeCo/BC) was synthesized by a one-pot calcination method to activate peroxymonosulfate (PMS) and peroxydisulfate (PDS) for bisphenol A (BPA) degradation. Characterization with X-ray diffraction, X-ray photoelectron spectroscopy and high resolution transmission electron microscopy showed that Fe0, Fe3O4, Co0 and CoO nanocrystals were included in FeCo/BC materials. The degradation results showed Fe0.6Co0.4/BC had excellent catalytic activation performance for PMS or PDS. The Fe0.6Co0.4/BC (0.0050 g) combined with 0.25 g·L?1 of PMS could completely degrade 20 mg·L?1 BPA within 8 min, and the same amount of BPA could be removed with 0.020 g Fe0.6Co0.4/BC in the presence of 0.25 g·L?1 PDS within 20 min. The corresponding total organic carbon removal rates reached 83.49% and 77.5% respectively after 2 h. The Fe0.6Co0.4/BC also had good adaptability to solution pH and practical water body. After five cycles, the degradation rates of BPA in the two systems were all over 90%, and excellent magnetism was beneficial to the reuse of catalysts. Electron paramagnetic resonance and free radical quenching tests indicated that SO4?-, ?OH, and 1O2 were the main active species involved in the BPA degradation. This work not only provided a promising catalyst for the degradation of organic pollutants, but also elucidated the synergistic effect between Fe-Co bimetal alloys during PMS and PDS activation, which would facilitate the design, synthesis, and application of catalytic materials with high efficiency.
查看更多>>摘要：? 2022 Elsevier B.V.The Co-Ti-Sn family of alloys from their half- to full-Heusler compositions are synthesized. Co1.5TiSn, a compound predicted by our theoretical calculations, is successfully synthesized in the L21 structure with cobalt vacancies in the tetrahedral sites. The saturated magnetic moment at 5 K is measured to be ~ 0.6 μB∕formula unit, consistent with density functional theory (DFT) predictions of half-metallicity in the compound. A cluster expansion-based analysis of the alloy system indicates the Co1.5TiSn compound to be nearly on the convex hull, within DFT accuracy. Our experimental realization of the Co1.5TiSn compound suggests that it is either kinetically or entropically stabilized.
查看更多>>摘要：? 2022 Elsevier B.V.In situ fabrication of TiB whiskers (TiBw) reinforced Ti-matrix composites (TMCs) was carried out with the addition of TiB2 particles in Ti6Al7Nb matrix using low energy ball milling and subsequent consolidation via Spark Plasma Sintering (SPS). The ball mixing of 0.5 %, 1.5 %, and 3 % TiB2 resulted in its distribution ratio (RD) of 1.05, 3.2, and 6.5, respectively. The in situ TiBw formations as a reaction between the Ti6Al7Nb matrix and TiB2 particles resulted during sintering. This TiBw inclusion in different regions caused the retardation of grains from growing and resulted in grain refinement. The presence of a stiff TiBw phase in combination with grain refinement was ascribed to the increased hardness and higher strength in the fabricated composites. Maximum hardness (~ 496 Hv) and strength (~ 2233 MPa) was achieved in the 3 % TiB2 containing composites among all. The biological response showed better cell adhesion and proliferation without any toxic effect on all fabricated samples when compared to the wrought Ti6Al7Nb. The enhanced cell proliferation on the TiBw composites than the pure alloy demonstrates them as promising materials for biomedical applications.
查看更多>>摘要：? 2022 Elsevier B.V.AlSi9Mg aluminum alloy flywheel housing components were formed via squeeze casting and T6 heat treatment was applied to the formed components. The influence of solid solution temperature, solid solution time, aging temperature and aging time on the microstructure and mechanical properties of AlSi9Mg aluminum alloy components formed by squeeze casting were investigated. The results showed that T6 heat treatment changed the morphology of the eutectic silicon in the microstructure from long fibrous to short rods and round spheres. The spheroidization of eutectic Si phase was more obvious with an increase of solution temperature, and the eutectic Si phase not dissolved in the matrix became coarse and grew with an extension of solution time. In terms of mechanical properties, the tensile strength and elongation of AlSi9Mg specimens after heat treatment showed an increasing trend with a rise of solution temperature, but the yield strength decreased, while the three mechanical properties of specimens all improved first and then decreased with an increase of solution time, aging temperature and aging time. Comprehensive consideration of three mechanical properties showed that the optimal heat treatment process parameters in this experiment were solution temperature of 540 ℃, solution time of 180 min, aging temperature of 175 ℃ and aging time of 300 min. In addition, β''?Mg2Si strengthening phases and disc-shaped strengthening phases were precipitated during T6 heat treatment, which were also one of the reasons for the improvement of the casting properties.
查看更多>>摘要：? 2022 Elsevier B.V.One of the key challenges in the development of eco-friendly piezoceramics is to simultaneously get large piezoelectric charge coefficient d33 and high depolarization temperature Td in a facile and effective manner. In this study, we demonstrated that built-in field Eb caused by simple quenching in 0.93Bi0.5Na0.5TiO3-0.07BaTiO3 piezoceramic, which promoted the Td from 140 ℃ to 184 ℃ and accompanied by the superior thermal stability of real-time d33 (~140 ± 2.5pC/N) in a wide working temperature range of 25–170 ℃. Structural analyses illustrated that quenching induced spontaneous phase transition from tetragonal P4bm to rhombohedral R3c, which facilitated not only the development of Eb but also the increase of field-induced R3c phase ratio, thereby strengthening the stability of field-induced ferroelectric state. Thus, our work validated a simple and effective method for designing high-performance piezoelectric materials with increasing Td and temperature stability without sacrificing the large piezoelectric response.
查看更多>>摘要：? 2022 Elsevier B.V.The perovskite structure materials used as an oxygen ion conductor in solid oxide fuel cells have been widely studied. Here, we report novel property of NaNbO3-based ceramics about oxygen ion conduction. The grain size is significantly increased as well as the structural symmetry is enhanced with bismuth doping. Based on the analysis of AC impedance in serial pO2, nearly pure oxide ions conduction characteristic was realized in Na0.4Bi0.2NbO3 composition. Remarkably, electrical conductivity of Na0.4Bi0.2NbO3 sharply increased 3 orders of magnitude to 0.01 S/cm at 700 °C compared to that of NaNbO3 oxides. This study not only discovered the novel ionic conductor properties of Na0.4Bi0.2NbO3, but also provided a new candidate for the solid electrolyte of medium-temperature solid oxide fuel cells (IT-SOFCs).
查看更多>>摘要：? 2022 Elsevier B.V.In this work, the nitrogen vacancy (NV) luminescence properties and their phonon sidebands in both high and low nitrogen diamonds after electron irradiation and subsequent annealing were thoroughly investigated. From the extracted results, it was demonstrated that the phonon sidebands were caused by the phonon emission behavior of the electrons located in the NV center during the induced transition process from the laser excitation. On top of that, the phonon energies of the NV0 (neutral) and NV— (negatively charged) centers were estimated at about 45 meV and 63 meV, respectively. As the measurement temperature increased, the excited electrons were more likely to return to the ground state by employing non-radiative transitions without generating phonon sidebands. As a result, the synchronous quenching of the NV luminescence and their phonon sidebands effect takes place. The complex lattice environment of the NV centers in the high nitrogen diamond leads also to a smaller thermal quenching activation energy, while the phonon process at a relatively high measurement temperature results in the manifestation of more obvious phonon sidebands of the NV centers.
查看更多>>摘要：? 2022 Elsevier B.V.The core-shell quantum dots (CSQDs) are three-dimensional (3D) confined semiconductor nanoparticles that are widely researched to accommodate the needs of modern-day applications. In addition to chemical stability, the shape, size, and surface modification of CSQDs play a vital role in the carrier confinement resulting in a wide range of optoelectronic applications such as solar cells, light-emitting diodes (LEDs), luminescent solar concentrators (LSCs), etc. The current review highlights the classifications and applications of CSQD systems based on semiconductor materials. The aspects related to the characterization, properties, and theoretical modeling of colloidal semiconductor CSQDs focusing on the role of the shell have been presented. Also, the altering of bandstructure from the viewpoint of lattice-mismatched strain, carrier dynamics, and its application in optoelectronic devices has been highlighted. Further, the article emphasized the different techniques used for theoretical modeling of the different shaped CSQD systems. To conclude, the article discussed in detail the recent progress in the theoretical modeling of quantum dot solar cells (QDSCs) using the detailed balance model and its limitations based on modification in the recombination current density.
查看更多>>摘要：? 2022For the absorption of plants, it is important to synthesize phosphors with emission bands in the red region. Herein, a series of new red phosphors Sr1-xLa2+xAl2-xO7: xMn4+ (SLA: xMn4+) were synthesized by the high temperature solid-state reaction. The inconsistent charge number of Mn4+ dopant and substituted Al3+ ion can be compensated by manual adjusting of the proportion of Sr2+ and La3+ in the same crystallography site. The phosphor shows emission band at around 713 nm, which fits well with the absorption of Pfr (far-red light-absorbing phytochrome), meaning that the SLA: 0.006Mn4+ can promote plant growth. Furthermore, co-doped phosphor SLA: 0.006Mn4+, 0.006Dy3+ was prepared with interesting temperature-dependent luminescence. With temperature increasing, the emitting intensity of Mn4+ has a more pronounced decline in comparison with Dy3+. Due to this feature, SLA: 0.006Mn4+, 0.006Dy3+ can be used as a non-contact optical thermometer with Sa of 0.018 K?1 at 450 K and Sr of 1.458% K?1 at 425 K.
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