查看更多>>摘要：The configurations of nitrogen species have a crucial influence on the transition metal-nitrogen-doped carbon catalysts (M-N-C). Whereas, how to build more sp2 hybrid N (including pyridinic and graphitic N) to enhance the catalytic activity and charge transfer rate of the carbon-based ORR catalysts remains a challenge. Herein, Co-embedded nitrogen-enriching platanus bark-derived porous carbon (PBPC) material (Co-N-C) was developed from the pyrolytic platanus bark, assisted by impregnating cobalt salt and ethylene-diamine nitriding strategy. The synthesized catalyst exhibits a high nitrogen content of 5.02%, of which over 2/3 are high conductivity sp2 hybrid N (consist of pyridinic and graphite-N), suggesting the unity of high activity and conductivity. Thus, it delivers a competitive half wave potential and a lower Tafel slope (69.55 mV dec~(-1)) than Pt-C-20% catalyst. The ZAB with Co-N-C-900 catalyst exhibits a higher open-circuit potential and a peak power density up to 3.5 times (186.17 mW cm~(-2)) higher than that of the Pt-C-20%. During the durability test for 100 cycles (16.7 h), the voltage gap only increased by 4.2%, nevertheless, the Pt-C-20%-based ZAB encountered a catastrophic polarization surge in less than 16 h. When assembling a flexible ZAB, it performs excellent flexibility in bending tests, and the voltage gap merely increased by 1.7% after 100 cycles (16.7 h).
查看更多>>摘要：The paper presents a review of the authors' studies of advanced functional composites of graphene based materials with metals, alloys, intermetallic compounds and their hydrides, and on the creation on their basis of hydrogen-storage materials for a compact and safe hydrogen storage, electrode materials for nickel-metal hydride batteries, highly efficient catalysts for the hydrogenation of metals and organic compounds as well as their integration into the hydrogen energy systems for the backup electric power and for the H-based energy storage.
查看更多>>摘要：Application of the super-wettability material is one of the most ideal approaches to achieve oil/water separation. The construction of the super-wettability material surface is the key to significantly boost the separation efficiency. In this work, the ZnO@Cu_2O honeycomb-likes hierarchical micro/nano-structure copper mesh (ZnO@Cu_2O/CM) is facilely fabricated through the combination of oxidation and hydrothermal deposition. Accordingly, superhydrophilicity/underwater superoleophobicity can be achieved, which endows over 99% separation efficiency as well as considerable permeation flux (>38120 L-m~(-2)-h~(-1)) for ZnO@Cu_2O/CM toward various oil/water mixtures. Besides, the combination of ZnO and Cu_2O produces a p-n heterostructure to further reduce the recombination rate of electron and hole, resulting in the improved the photocatalytic activity. The removal efficiency for methylene blue (MB) of ZnO@Cu_2O/CM could be improved to 98.1%, nearly 1.6 times than that of Cu_2O/CM. Various stability tests demonstrate that the material exhibits good mechanical stability, anti-corrosive property and thermal durability under harsh environments. Furthermore, cyclic experiments reveal that ZnO@Cu_2O/CM exhibits fascinating reusability. In conclusion, the as-synthesized dual-functional mesh performs favorable photocatalytic activity and super-wettability, which can realize wastewater remediation at low cost and energy consumption.
查看更多>>摘要：In this study, the electrocaloric (EC) effect was enhanced at room temperature for (Ba_(0.904)Ca_(0.096)) (Zr_(0.136)Ti_(0.864)-xFe_x)O_3 (BZT-0.32BCT-xFe 0 ≤ x ≤ 0.015) thin films prepared on Pt/Ti/SiO_2/(100)Si substrates. The existence of an orthorhombic phase in the Fe-doped thin films at room temperature was confirmed by X-ray diffraction and Raman spectra. Tetragonal, orthorhombic, and rhombohedral phases coexist in all the investigated Fe-doped thin films. The relative content of the orthorhombic phase is most prominent at x = 0.0075. The BZT-0.32BCT-xFe thin film exhibits excellent properties with a giant EC effect (ΔT = 22.99 K, E = 1050 kV/cm, and T = 307 K) at x = 0.0075 compared to the undoped thin film, stemming from multiphase coexistence and a larger orthorhombic phase. The results of this study are useful for developing lead-free electrocaloric materials with superior properties.
查看更多>>摘要：Effect of Mn content on the microstructure and corrosion resistance of Al-Cu-Mg-Mn alloys was examined by optical microscope (OM), scanning electron microscope (SEM), tensile tests, pitting corrosion and electrochemical tests. It is shown that increase of Mn content can accelerate the aging process of the Al-Cu-Mg-Mn alloys, which is beneficial to shorten heat treatment time. Polarization curves indicate that the corrosion current density and corrosion rate of Al-4Cu-2Mg-1.2Mn alloy are the lowest compared with Al-4Cu-2Mg-0.6Mn and Al-4Cu-2Mg-0.9Mn alloys for both the as-cast and heat-treated conditions. Electrochemical impedance spectroscopy (EIS) tests also demonstrate that Al-4Cu-2Mg-1.2Mn alloy displays the highest resistance. The maximum pitting corrosion depth of the as-aged Al-4Cu-2Mg-1.2Mn and Al-4Cu-2Mg-0.6Mn alloys is about 65 um and 110 um, respectively. Therefore, Mn addition can improve the mechanical properties and corrosion resistance of the Al-Cu-Mg alloys.
查看更多>>摘要：The CrCoNiSi_xAl_x(x = 0.1, 0.2) medium entropy alloys (MEAs) were designed to achieve significant improvement in strength and strain hardening via the minor addition of Si and Al elements to the CrCoNi MEA. The B2 + σ precipitation structure was formed on the CrCoNiSi_(0.2)Al_(0.2) MEA. Compared to CrCoNi MEA, the yield and ultimate tensile strengths of the CrCoNiSi_(0.2)Al_(0.2) MEA enhanced from 380 MPa to 850 MPa and 790-1287 MPa, respectively, while the uniform elongation was 23±5% that outperformed various advanced steels and Al-added MEAs/HEAs. The Orowan+shearing precipitation hardening mechanisms together with the deformation twins in a face-centered cubic (FCC) matrix were identified to improve the strength and strain hardening capacity. These findings provide guidance for the development of precipitation-hardened MEAs/HEAs with strength-ductility synergy.
查看更多>>摘要：The effect of Cu addition on the microstructural evolution and mechanical properties of hypoeutectic Al-10Mg_2Si alloys was investigated. It was found that Cu addition could effectively refine the primary a-Al grain. Simultaneously, the coarse eutectic Mg_2Si was also modified to be fine coral-like. The constitutional supercooling and the multiple nanosized precipitating layers at the edge of the eutectic Mg_2Si cause the branching and refining of the eutectic Mg_2Si through effectively restricting the growth of eutectic Mg_2Si, while the Cu-rich clusters and nanosized precipitates on the surface of the end of the eutectic Mg_2Si prevent the diffusion of the solute atoms such as Al, Mg and Si, and the growth of eutectic Mg_2Si grains is physically limited, resulting in the decrease of the length of eutectic Mg_2Si. The strength and ductility of the Cu-added Al-10Mg_2Si alloys were simultaneously improved, and the fracture failure mode transforms from brittle failure to ductile failure. The mechanism of mechanical properties enhanced by Cu addition was discussed.
查看更多>>摘要：Because of their multiple chemical valence states, multi-element transition metal oxides can undergo reversible redox reactions between the different valence states during charging and discharging. However, the low electrical conductivity of transition metal oxides limits the rate of electron transfer. The combination of transition metal oxides with three-dimensional carbon substrate is a promising but extremely challenging strategy to prepare high specific capacitance, stable and environmentally friendly supercapacitor electrode materials. Here we report a facile one-step vapor deposition synthesis of network-like FeNb_2O_6 nanostructures directly growing on flexible carbon cloth (CC). The as-prepared FeNb_2O_6/CC composite has good electrical conductivity, and the network-like structure also makes it have large specific surface area. Resultantly, the composite exhibits an high specific capacity of 365.9 mAh g~(-1) at a current density of 2.5 A g~(-1). And at the current density of 25 A g~(-1) a specific capacity of 75.9 mAh g~(-1) can still be maintained.
查看更多>>摘要：Na_(0.44)MnO_2 microrods with high crystallinity have been prepared by a simple solid-phase method and then coated with ln_2O_3 by precipitation method. 1 wt% ln_2O_3 coating could improve the sodium-storage capability of Na_(0.44)MnO_2 microrods significantly. The original Na_(0.44)MnO_2 microrods could provide the maximum discharge capacity of 100.3 mAh g~(-1) under a wide voltage of 2.0-4.5 V at 1 C, but the discharge capacity rapidly decreases to 70.4 mAh g~(-1) after 400 cycles, which was only 70.3% of the maximum capacity. However, the Na_(0.44)MnO_2 coated with 1 wt% In_2O_3 exhibited a high discharge capacity of 90.9 mAh g~(-1) after 400 cycles, with high-capacity retention of 86.7% in the same case. Moreover, compared with Na_(0.44)MnO_2, 1 wt% In_2O_3 coated Na_(0.44)MnO_2 shows better rate capability. Even at a high current density of 10 C, the discharge capacity is 63.6 mAh g~(-1), much larger than the 32.9 mAh g~(-1) of the pristine Na_(0.44)MnO_2. The mechanism of In_2O_3 coating improving the electrochemical performance of Na_(0.44)MnO_2 microrods was studied in detail.
查看更多>>摘要：In this paper, the mechanism on the nucleation of orientation-preferred Cu_6Sn_5 at different temperatures and solder compositions was investigated. Results suggest that affected by temperature and solder composition, the distribution of clusters in solder plays an important role in the formation of preferred orientation. Higher temperature, Ag element and an appropriate amount of Cu element are favorable for the nucleation of orientation-preferred Cu_6Sn_5. However, the increase of Cu-Sn clusters size with the increase of Cu addition will lead to the nucleation of Cu_6Sn_5 in liquid solder, which does not need to follow the rule of the minimal lattice mismatch between Cu_6Sn_5 and Cu substrate. Meanwhile, the addition of Cu and Ag is conducive to the increase of grain size. Besides, the difference in solder volume between the central and edge region results in the difference in grain orientation. Furthermore, a model is established to illustrate that how the reflow temperature, Cu and Ag content affect the nucleation of orientation-preferred Cu_6Sn_5 through affecting the cluster evolution. The results have significant meaning in understanding and controlling the formation of Cu_6Sn_5 preferred orientation and improving the reliability of solder joints.
NSTL
Elsevier