查看更多>>摘要：Lithium metal has been considered as one of the most promising anodes for the endeavoring pursuit of advanced batteries due to its ultra-high capacity of-3860 mAh g~(-1). To solve the current problems of lithium metal anode (LMA), such as unreliable dendritic growth, dead Li accumulation, and the resulted pulverization, three-dimensional frameworks have been adopted to maintain the structural integrity of LMA, but the issues including interfacial stability and affinity, undesired Li-ion deletion at the electrolyte/electrode interface are still challenging. Herein, by adopting hierarchical porous graphitic carbon (HPGC) as LMA skeleton and the atomic-level MgO for interface modification, the ideally uniform interface with strong Li affinity can effectively regulate the nucleation and deposition behavior of Li metal; while with the large quantity of Li~+ storage in the micro-porous of HPGC, both the spatial confinement of Li~+ flux and the increase in Li~+ concentration at electrode/electrolyte interface can be achieved to facilitate the planer Li metal electrodeposition. Furthermore, the delithiation of HPGC with slightly higher potential can effectively reduce the formation of dead-Li via preventing the depletion of Li with inexhaustible Li~+ storage during stripping process. The superiority of MgO@HPGC hosted LMA can be demonstrated both as coating layer and interior skeleton for different kinds of LMA applications, with enhancement in both long term cycling stability (-650 h) and high coulombic efficiency (-97%) over 390 cycles.
查看更多>>摘要：To explore the influence of sintering temperature on mechanical properties of Al_2TiO_5 (AT) flexible ceramics, the XRD/Raman, SEM and acoustic emission (AE) technology were used to estimate the phase composition, microstructure evolution and damage behaviors of AT ceramics, respectively. Results show that the diffraction peaks of AT increase before rising sintering temperature from 1300 °C to 1500 °C and then start to decrease at 1600 °C due to the decomposition of AT grains. In specimens with sintering temperature of 1300 °C and 1400 °C, intergranular fractures are more likely to occur, which controls the origination of AE events in the whole stage. And the fracture of big bodies composed by large number of fine AT grains is the main source of AE events with high energy level at initial stage. In addition, Thanks to the more trans-granular fracture in specimens with sintering temperature of 1500 °C and 1600 °C, the number of AE events in these two specimens are more than that of specimens with sintering temperature of 1300 °C and 1400 °C.
查看更多>>摘要：Copper Zinc Tin Selenide Cu_2ZnSnSe_4 (CZTSe) and Copper Zinc Tin Sulfide Cu_2ZnSnS_4 (CZTS) thin films were deposited from a multicomponent single target with different RF sputter powers and a constant annealing temperature of 450°C. One step deposition with in-situ annealing was performed in order to avoid the individual metal losses during the process. Effects of various deposition parameters were investigated to finely control the elemental ratio of the quaternary target which in-turn helps to obtain the desired stoi-chiometry suitable for solar absorber materials as confirmed from EDS analysis. The phase purity of thin films was investigated and confirmed using XRD and Raman spectroscopy. A thin film solar cell device with n-CdS, ZnO, ZnO:Al layers and Al grids over the prepared kesterite CZTX (X = S, Se) films were deposited on Mo coated soda lime glass using complete vacuum deposition technique. Even though the optical, electrical and structural results are promising, the conversion efficiency for these single step processed CZTSe and CZTS solar cell devices were limited to 3.72% and 2.6% due to possible interface effect and smaller grain size of the deposited films. Considering the industrial fabrication of kesterite thin film solar cells, this processes assures an environmental friendly approach with inherent purity leading to one-step reduction in the mass production process.
查看更多>>摘要：The laser powder bed fusion (LPBF) was employed to process the ZK60 Mg alloy. The effect of heat treatment on the microstructure and hardness of LPBF ZK60 Mg alloy was investigated. The results showed that the grain boundary of LPBF ZK60 Mg alloy was composed of a network Mg_7Zn_3 phase. Three types of precipitated phases were distributed inside the grains: the type-I is Zn-rich precipitated phase with Zr-rich core, the type-II is Zn-rich precipitated phase without Zr, the type-Ill is Zr-rich particle. When the solution treatment was used, the Mg_7Zn_3 phase at the grain boundary melted and merged into the matrix. The precipitated phase in the grain mainly evolved into Zn-rich phase with Zn_2Zr core. Continue with the aging heat treatment, the rod-shaped pY-MgZn precipitated phase separated out from the a-Mg matrix. The length of the rod-shaped precipitated phase undergone double aging is longer and the quantity is more than that of the single aging. The rod-shaped β_1-MgZn precipitated phase significantly improved the mechanical properties of LPBF ZK60 Mg alloy. The average hardness increased from 0.88 ± 0.025 GPa to 1.01 ± 0.010 GPa and the ultimate tensile strength increased to 287 ± 4 MPa after the solution treatment plus double aging heat treatment.
查看更多>>摘要：The uncontrollable dendritic behavior and volume expansion in alkali metal anodes have led to short-circuit issues and low Coulombic efficiency which significantly hamper the commercialization of alkali metal anodes. To address these issues, we report the fabrication of a novel functional host in which the alkaliphilic Cu(OH)_2 nanowires were uniformly grown on Cu foam (denoted as Cu(OH)_2-NWs@CF) for Li/Na anodes. The 3D network structure of Cu(OH)_2-NWs@CF with high specific surface area can not only effectively reduce local current density to guide homogeneous deposition of Li~+, leading to more controllable nucleation sites and dendrite-free Li deposition, but also minimize the volumetric strain during repeated Li/Na stripping/ plating processes, mitigating the volume change of the batteries. Benefitting from these advantages, the as-prepared Li/Na@CF composite anodes exhibit outstanding long-term cycle stability and structure maintaining ability. In particular, the Li@CF-based symmetric cells deliver elevated cycling performance under a moderate polarization voltage for nearly 1200 h at a current density of 1 mA cm~(-2). Similarly, the Na@CF-based symmetric cells can also cycle stably for 800 h at a current density of 0.5 mA cm~(-2). Furthermore, the Li@CF||LFP full cells show significantly improved rate capability and high cycle stability (97% capacity retention after 100 cycles). Our work demonstrates the effectiveness of the 3D copper foam framework with improved alkaliphilic ability for the development of safe and commercially viable alkali metal anodes.
查看更多>>摘要：The photocatalytic application of CdTe quantum dots (QDs) is restricted by the charge carriers recombination and tendency to aggregate in suspended systems. Novel functionalized CdTe (F-CdTe) QDs and CoNiAl layered double hydroxide (LDH) nanocomposite have been prepared to utilize the unique advantages of CdTe QDs. The nanocomposite is prepared via in situ synthesis of LDH in the presence of as-prepared F-CdTe QDs where the QDs partially intercalated in the interlayer spaces of LDHs. As a result of the effective electronic coupling between F-CdTe QDs and CoNiAl LDH, the light-harvesting ability has been enhanced and the absorption edge expands toward the higher visible light wavelengths. Moreover, the charge carriers recombination in nanocomposite has been considerably suppressed compared to the pristine CoNiAl LDH and F-CdTe QDs. Also, the nanocomposite shows remarkable enhancing in photocatalytic degradation of Acid Red 14 (ARM) and Bisphenol A (BPA) as the sample pollutants. The photogenerated holes and hydroxyl radicals have a determining role in the degradation of ARM. The plausible mechanism is proposed based on the experimental results and theoretical calculations. The prepared nanocomposite represents superior photocatalytic activity after 5 consecutive runs. So, the CdTe QDs can be effectively utilized in photocatalytic applications through the proposed promising approach.
查看更多>>摘要：The Mg~(-1)2Gd-2Er-0.4Zr (GE122K) is fabricated by double extrusion, and the effects of grain refinement and precipitate evolution on the mechanical performance of the extruded alloys are deeply analyzed. Scanning electron microscope results spectacle that some bulky precipitates in the single extruded alloy are fragmented to fine precipitates during double extrusion and distribute linearly along the extrusion direction (ED). The fine precipitates exhibit the strongest dispersion strengthening effect, whereas the bulky precipitates act as crack resources and decrease the elongation. After double extrusion, a refined grain structure with an average grain size of 2.7 urn is achieved, which is attributed to dynamic recrystallization (DRX). Moreover, double extrusion boosts the content of rare-earth elements into the matrix by dissolving the fine precipitates. During aging, extensive p' precipitates form in the double extruded alloy than in the single extrude alloy. As a result, refined grains and strong precipitation strengthening make a significant contribution to a high yield strength (YS) of 422 ± 1.59 MPa with an elongation (EL) of 6.5 ± 0.89% in the double extruded+peak-aged alloy (ACX_2). The possible strengthening mechanisms are discussed, and it is found that grain refinement and precipitate strengthening are the main contributors to the high strength of the GE122K alloy.
查看更多>>摘要：White light-emitting diodes (LEDs) are great candidates for general lighting. Phosphors have commonly been used for the color conversion layers of white LEDs; however, they backscatter more than half of the down-converted light, which is lost within the device, thus degrading the overall performance. In this study, we propose and demonstrate white LEDs with improved efficiency enabled by the intimate integration of Ag@SiO_2-supported blue InGaN/GaN nanorod LEDs together with green- and red-emitting perovskite nanocrystal (PNC) films as color conversion layers. The photoluminescence (PL) intensity of the blue LEDs (BLEDs) was significantly enhanced owing to the localized surface plasmon (LSP) effect of Ag@SiO_2 nano-particles. In addition, the perovskite PL intensity was improved by the high-power BLED backlight. The resulting PL intensity of the Ag@SiO_2 nanoparticle-embedded nanorod white LED was 62% greater than that of a planar white LED.
查看更多>>摘要：Toxic organic pollutants have a severe impact on the environment as well as the living organisms around the world. Surface-enhanced Raman spectroscopy (SERS) is considered to be one of the advanced sensing methods for the ultrasensitive detection of organic pollutants. Herein, a novel octahedral Ag_2SO_3 micro-crystal was synthesized using the silver-ammonia complex precipitation method for the detection of herbicide (4-chlorophenol) and synthetic dyes (sunset yellow and methylene blue dye). Ag_2SO_3 microcrystal exhibits superior sensitivity with an enhancement factor (EF) in the order of ~10~8. The large surface area with a rough octahedral morphology of Ag_2SO_3 favors the formation of abundant hotspots. The as-prepared Ag_2SO_3 also possesses excellent recyclability property via light irradiation attributed to the chemical enhancement mechanism. The capability of Ag_2SO_3 for the detection of 4-CP against interference in river water and honey was also investigated. It is assumed from the results that Ag_2SO_3 microcrystal is a promising substrate for reusable SERS applications.
查看更多>>摘要：In this paper, we have studied the correlation between the Curie temperature and tolerance factor of the (1-x)BHT-xBCT system. In a perovskite system, the distortion between the lattice parameters, a and c, can be used to investigate the tolerance factor. By changing the (Ba,Ca)TiO_3 ratio in the (l-x)BHT-xBCT system, the distortion of the lattice parameter can be varied. The tolerance factor is also related to the distortion values of perovskite systems. Therefore, the Curie temperature of (l-x)BHT-xBCT ceramics can be controlled by the tolerance factor. To confirm this assumption, we fabricated and analyzed (1 -x)BHT-xBCT ceramics for x = 0.3, 0.4, 0.5, 0.6, and 0.7, sintered at the various temperature range from 1400° to 1600 °C. We confirmed that the highest piezoelectric property, d_(33) of 540 pC/N was observed in the polymorphic phase transition (PPT) region when x = 0.5, for all sintering temperature conditions.
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Elsevier