查看更多>>摘要：In this study, the recrystallization process in deformed high-purity aluminum was investigated by using the internal friction (IF) and hardness measurement. In the heating process, two IF peaks were detected when the heating rate is 2 °C/min: a sharp peak (P1 peak) at ~139 °C and a wide peak (P2 peak) at ~278 °C (0.5 Hz). In the subsequent cooling process, the P1 peak disappears while the P2 peak remains. The P2 peak shifted towards higher temperatures with increasing frequency and can be ascribed to grain boundary relaxation. For the P1 peak, however, its position did not change with increasing frequency but shifted towards higher temperatures with increasing heating rate in the range of 1–5 °C/min, and the corresponding modulus varied abnormally in the temperature range of 115–160 °C. These facts indicated that the P1 peak is a non-relaxational peak and can be ascribed to the recrystallization process. The recrystallization activation energy deduced via the shift of peak position with heating rate by using the Kissinger equation is 57± 3 kJ/mol, which is as same as that deduced from the classical isothermal recrystallization process as assessed by microhardness measurement. The classical isothermal recrystallization temperature can be deduced from the peak temperature of P1 peak by simply adjusting the heating rate. This provided a method to determine the recrystallization temperature via internal friction measurement in a continuously heating process, which needs only two or three samples.
查看更多>>摘要：All-inorganic CsPbI3 quantum dots perovskite solar cells (QDPSCs) have wide potential application due to their excellent photoelectric properties with high environmental stability. However, the poor interface contact between the light absorption layer and hole transport layer (HTL) results in the serious carrier recombination and the large open-circuit voltage (VOC) loss. Herein, we introduce the insulating PMMA (poly(methyl methacrylate)) buffer layer into CsPbI3 quantum dots (QDs)/Cu12Sb4S13 QDs HTL interface in all-inorganic QDPSCs with the structure of FTO/c-TiO2/m-TiO2/CsPbI3 QDs/Cu12Sb4S13 QDs/Au. The interface carrier recombination is obviously suppressed and the significant VOC improvement from 1.04 V to 1.14 V is obtained with the incorporated PMMA buffer layer. The devices with PMMA buffer layer show the enhanced power conversion efficiency (PCE) of 10.99%, and the improvement of 9.71% is achieved compared to that of the control devices (10.02%). The stability is significantly enhanced due to the intrinsic hydrophobic characteristic of PMMA, and the devices retain 62.69% of their initial PCE after stored in air condition for 15 days, which is greatly improved compared with the control device without PMMA.
查看更多>>摘要：It remains a significant challenge to obtain CdS photocatalysts with high stability on a large scale. In this work, CdS are prepared using a simple KSCN molten salt method (CdS-MS) and conventional hydrothermal method (CdS-HT), respectively. CdS-MS consists of novel hollow hexagonal prisms, which is not reported so far. Under visible light irradiation (λ > 400 nm), CdS-MS shows a higher photocatalytic activity for the degradation of phenol, norfloxacin and RhB, which are 2.27, 2.11 and 1.05 times higher than CdS-HT. The higher photocatalytic activity of CdS-MS is mainly attributed to the novel hollow hexagonal prism microstructure and more sulfur defects, leading to the greater oxidation potential and higher charge separation efficiency. Furthermore, CdS-MS shows outstanding cycle stability. After four cycles, 90.6% of the degradation efficiency is retained for CdS-MS, while only 68.3% of the degradation efficiency is retained for CdS-HT. The higher stability of CdS-MS is mainly attributed to its unique morphology and surface valence of sulfur, which make it more difficult to agglomerate and occur photocorrosion, respectively. The reported method is simple and high-yielding, which is easy to extend to mass production.
查看更多>>摘要：Bimetallic NixCo3?xS4 (x = 1 or 2) with synergistic effect is a promising candidate material for sodium-ion battery (SIB) anodes because of its higher electrical conductivity than monometallic sulfides owing to its lower bandgap. In this study, samples of bimetallic sulfide NixCo3?xS4 with tunable chemical Ni/Co components are successfully grown on graphene foam (GF), forming free-standing Chinese knot-like nanowires (NiCo2S4 NWs/GF) and Chinese lantern-like nanoarrays (CoNi2S4 NAs/GF). When evaluate as anodes for SIBs at 0.3–3.0 V in ether-based electrolytes, the NiCo2S4 NWs/GF electrodes offer superior rate performance and cycling stability than the CoNi2S4 NAs/GF electrodes. More specifically, the NiCo2S4 NWs/GF electrode has a high capacity of 650–556 mAh g?1 at 0.1–2.0 A g?1 and 457 mAh g?1 after 200 cycles at 0.5 A g?1 with a high initial coulombic efficiency (ICE) of 95.6%. And its rate performance outperforms most existing electrodes those contain NiSx, CoSx, or NiCo2S4. The excellent electrochemical performance of the NiCo2S4 NWs/GF electrode is attributed to its unique composition, smaller size, and porous nanowires that can reduce the diffusion length of e- and Na+, and enhance reaction kinetics.
查看更多>>摘要：In the present study, synthesis of Zn2+ doped SnS2 (Sn1?xZnxS2) nanoparticles has been carried out using a novel thermal decomposition method. The characterization of Zn2+ doped SnS2 nanoparticles was done using various analytical techniques. XRD results indicate the formation of single phase up to x ≤ 0.5 and phase separation occurs when x ≥ 0.60. The morphology of SnS2 changes from flakes to flowers upon incorporation of Zn2+ as observed using scanning electron microscopy and transmission electron microscopy studies. The optical properties of Zn2+ doped SnS2 nanoparticles were studied by diffuse reflectance spectroscopy and the band gap of Zn2+ doped SnS2 nanoparticles can be varied from 2.24 eV to 2.48 eV. The Zn2+ doped SnS2 nanoparticles were explored as adsorbent for the removal of rhodamine B (RhB) from aqueous solutions.
查看更多>>摘要：Ni-doped SnO2 (Sn1?xNixO, x = 0.03, 0.05, 0.10, 0.12, and 0.15) powder samples were synthesized in a chemical auto combustion method and followed by calcination at 850 oC for 5 h. Initially, their structural characteristics were investigated through X-ray diffraction (XRD) which reveals that the prepared samples are nanocrystalline rutile tetragonal structure similar to host SnO2. The surface morphological image analyses were done by scanning electron microscopy (SEM) which revealed the spherical nature of grains along with the presence of voids. From Raman spectroscopy study, the presence of fundamental vibration modes of SnO2 like A1g modes at 634 cm?1, B2g modes at 773 cm?1 and Eg modes at 473 cm?1 along with the formation of defects i.e. oxygen vacancies in the sample have been confirmed. Similarly, Fourier transforms infrared spectroscopy (FTIR) shows the prominent peaks of Sn-O and Sn-O-Sn vibrations around 560 cm?1and 615 cm?1 respectively, and confirms the incorporation of Ni ions into pure SnO2 lattice by the small shifting in the positions of the peaks. Furthermore, from UV–visible spectroscopy, the decrease of bandgap with increasing Ni concentration has been noticed. The existence of room temperature ferromagnetism in Ni-doped SnO2 nanoparticles has been confirmed from the hysteresis loop of the vibrating sample magnetometer measurement (VSM) measurement. From all the above characterizations, it has been confirmed that up to x = 0.12 of Ni has been incorporated into host material SnO2.
查看更多>>摘要：In-situ synthesized Al matrix composites (AMCs) have drawn lots of interest recently relying on the designability of reinforcement configurations and promising mechanical properties. In this work, a new generation of AMCs reinforced by in-situ MgAl2O4 particles was fabricated based on Al-Mg-ZnO system using shift-speed ball-milling (SSBM) combined with reactive sintering method. The detailed microstructural characterization and comprehensive thermodynamic analysis rationalized the in-situ reaction mechanism, in which the substituted MgO was involved in the formation of homogeneously dispersed MgAl2O4 that forms robust interfacial bonding with matrix. In addition, the coefficient of thermal expansion mismatch strengthening and grain refinement acted in concert to render the impressive mechanical properties, achieving the yield stress of 347 MPa and ultimate tensile stress of 505 MPa. This work can be informative for the fabrication of high-performance in-situ MgAl2O4 reinforced AMCs based on Al-Mg-oxides system.
查看更多>>摘要：Strain-induced precipitation was systematically investigated in austenitic Inconel 617B superalloy (IN617B) after deformation of 0.2 true strain in its service temperature range (700–850 °C). The precipitation-time-temperature (PTT) curves obtained by stress relaxation experiments showed a classic C-shape with the nose temperature of 800 °C, and a minimum incubation period of 30 s, and the main strain-induced precipitate was M23C6 carbide. After specimens deformed at 800 °C to a strain of 0.2 were held between 10 and 1000 s, they underwent a second-pass strain test, during which the M23C6 precipitates evolved and influenced the flow stress; this behavior was investigated. During the nucleation, growth, and coarsening of the strain-induced precipitates, the morphology of the M23C6 particles gradually changed from spherical to polygonal with increasing size, but the precipitates always maintained their cube-on-cube orientational relationship with the austenitic matrix. During the nucleation stage before 30 s, many pre-precipitation clusters and weak static recovery softening led to low second-deformation flow stress, which persisted at approximately 630 MPa. In the precipitation growth phase before 360 s, recovery softening balanced precipitation hardening. The strain-induced precipitates grew larger, and they were able to pin dislocations. In addition, some complex microstructures resulting from particle collisions were observed. This resulted in the maximum rate of increase of the second deformation flow stress, which quickly reached almost 700 MPa. When the holding time was extended to 1000 s, the recovery softening effect further increased, while the M23C6 particles gradually coarsened; this weakened the increasing trend of the second deformation flow stress, which increased to only 715 MPa at 1000 s
查看更多>>摘要：In several scientific and technical fields, contactless optical thermometry has been successfully used for precise local temperature sensing. One of the primary goals at the moment is to enhance sensitivity and resolution. In this work, we report the synthesis of crystalline Yb3+-Er3+ and Yb3+-Ho3+ co-doped Na3Gd(VO4)2 (NGVO) microparticles by a citrate-based sol-gel method. The phase purity, vibrational modes, morphology and luminescence characteristics were evaluated by X-ray diffraction (XRD), Field emission scanning electron microscopy (FE-SEM), and Photoluminescence (PL). Temperature sensing in the visible region is allowed by an effective upconverted emission from rare-earth ions (Yb3+, Er3+, Ho3+) codoped into matrix. The luminescence intensity ratio (FIR) technique is used to record temperature sensing behaviors based on UC luminescence in Yb3+/Ln3+-codoped NGVO phosphors and high sensitivities were obtained. The Sr value of the NGVO Er3+/Yb3+ as a function of temperature are calculated to be 0.83% K?1. For the NGVO: Yb3+/Ho3+ phosphors, the Sr values were determined for TCLs and non-TCLs and reaches 1.37% K?1, and 1.90% K?1, respectively. These particles have a sub-degree thermal resolution at 295 K, making them excellent materials for accurate temperature sensing. The temperature-induced multicolor emissions in the analyzed samples suggest that the Er3+, Ho3+/Yb3+ co-doped NGVO crystals could have promising applications as a safety sign in high-temperature environments.
查看更多>>摘要：In this study, p-type carbon nitride (CN75) nanoparticles were introduced to precursors of NH2-MIL-53(Fe). A CN75 and NH2-MIL-53(Fe) p-n heterojunction was formed by solvothermal reaction. It showed that tiny loading of CN75 onto NH2-MIL-53(Fe) would boost the separation, migration and transfer of photo-induced carriers effectively. Meanwhile, its spectral response was broadened, which draw in efficient photocatalytic performance together. As for photocatalytic reduction of Cr(VI), the rate constant on CN75/NH2-MIL-53(Fe) was ca 1.8 and 25.3 times that by NH2-MIL-53(Fe) and CN75 under visible light (λ ≥ 420 nm), respectively. Reduction rate of CN75/NH2-MIL-53(Fe) (0.1 g/L) reached about 100% within 15 min at pH 2. Good activity could also be observed even under red light (λ: 650–660 nm). Besides, CN75/NH2-MIL-53(Fe) exhibited high stability after 5 cyclic runs, and the leaching of Fe3+ can be greatly suppressed after loading CN75. Structural analysis proved that the MOFs framework was well maintained. Thus, this research paper would provide useful information about the construction and synthesis of efficient and steady Fe-MOFs based photocatalyst for environmental remediation.
NSTL
Elsevier