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Journal of Alloys and Compounds
Elsevier Science S.A.
Journal of Alloys and Compounds

Elsevier Science S.A.

0925-8388

Journal of Alloys and Compounds/Journal Journal of Alloys and CompoundsSCIISTPEI
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    N/O/P co-doped hierarchical porous graphitic carbon materials for high-rate supercapacitors

    Li Y.Wang H.Zhou Y.Wu S....
    9页
    查看更多>>摘要:Heteroatoms-doped hierarchical porous carbons have attracted considerable interest owing to their efficient utility in supercapacitors. However, the increase of defects tends to sacrifice the electrical conductivity of carbon materials. Therefore, it is of great significance to build a good conductive network by increasing the graphitization degree of porous carbons. Here, this study reports the use of serine phosphate protic salt ([Seri][H2PO4]), Pluronic F127 and cobalt nitrate to engineer the N/O/P co-doped hierarchical porous graphitic carbon materials. The Co2+ catalyzes the graphitization of porous carbons under high temperature. A large number of mesopores, highly doped heteroatoms (O: 4.2 wt%, N: 4.07 wt%, P: 0.81 wt%) and conductive carbon skeleton boost the ultrafast transport of electrons and ions, resulting in high specific capacitance, wide operating voltage and outstanding rate performance. The symmetric supercapacitor assembled in KOH electrolyte shows good frequency response with the scan rate up to 1.5 V s?1 on the working voltage of 0–1.3 V. At the same time, when the power density reaches up to 21.3 kW kg?1, its energy density remains 8.74 W h kg?1. Furthermore, the symmetric supercapacitor delivers a high energy density of 81.42 W h kg?1 at the power density of 875 W kg?1 with an ultrahigh working voltage of 3.5 V in 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIMBF4) electrolyte. More promisingly, all-solid device based on the optimized sample exhibits outstanding flexibility, which greatly broadens its practicability. This work marks the importance of the balance between porous structure, heteroatom doping and high conductivity for advanced supercapacitors.

    Effect of melt superheating treatment on corrosion resistance of Al2CoCrCuFeNi high entropy alloy in 0.5 M HNO3 solution

    Guo J.Xing X.Zhang X.Xu L....
    7页
    查看更多>>摘要:Al2CoCrCuFeNi high-entropy alloy (HEA) was heated by vacuum arc furnace at different powers (5.26kW, 6.15 kW, 7.28 kW, 8.26 kW) to different temperatures above the liquidus point (labeled as T1, T2, T3 and T4). The structure and corrosion resistance were investigated by means of X-ray diffraction, scanning electron microscopy with spectroscopy (SEM/EDS), transmission electron microscopy (TEM), and electrochemical workstation. It was found that the HEAs with different superheating temperatures were all simple face-centered cubic (FCC) and body-centered cubic (BCC) solid solutions without complex phases. As the superheating temperature increased, the structure of HEAs became dense, the segregation decreased, and some fine-scale precipitations were formed at T4. When the heating temperature reached T3 or higher, the corrosion current density of the alloy decreased by more than 1/2, and the range of the passivation zone also became wider, indicating that the corrosion resistance was significantly improved. It was found that the pitting potential Eb ranked: T1<T2<T4<T3, indicating that the alloys labeled as T3 and T4 had better pitting resistance than those labeled as T1 and T2. The potential range of the stable passivation region △E ranked: T1<T2<T3<T4, which proved that the passivation film on the surface of HEA became more and more stable as the superheating temperature increased.

    Waste biomass-assisted synthesis of TiO2 and N/O-contained graphene-like biochar composites for enhanced adsorptive and photocatalytic performances

    Zhong M.Su B.Lei Z.Han Y....
    9页
    查看更多>>摘要:Titanium dioxide (TiO2) is a promising semiconductor photocatalyst for degradation of organic pollutants but is hampered by bandwidth prohibition and high probability of photo-generated electron-hole recombination. Searching for effective modification strategies to alleviate these issues is thus particularly significant. Herein, two series of composites of TiO2 and graphene-like biochar (PC) were prepared via a simple biomass-assisted pyrolysis coupled with activation strategy and characterized by various techniques. The methylene blue (MB)-simulated waste water was used to evaluate their adsorptive and photocatalytic performances. The results showed that the optimal TiO2-PC composite delivered an excellent photocatalytic performance, nearly 4 times as TiO2. The enhanced performance was probably caused by the synergistic effect among the graphene-like PC, the self-introduced N/O heteroatom, and the interaction between TiO2 and PC. Furthermore, the possible photocatalytic process was also proposed. This work may provide a guidance on preparing high-performance composites through a simple, cheap, and environmental biomass-assisted strategy for highly-efficient photocatalysis application.

    Mechanosynthesis of multiferroic hybrid organic-inorganic [NH4][M(HCOO)3] M = Co2+,Mn2+,Zn2+,Ni2+, Cu2+ formate-based frameworks

    Vit V.Righi L.Orlandi F.Griesi A....
    6页
    查看更多>>摘要:The family of compounds with formula [NH4][M(HCOO)3], with M a divalent D-metal, is characterized by porous frameworks hosting NH4+ cations exhibiting at low temperature a spontaneous ferroelectric polarization. The presence of magnetically active divalent metal determines the occurrence of antiferromagnetic ordering below 30 K opening the avenue for a rational formulation of a new class of multiferroic materials. We demonstrate that this intriguing class of compounds can be synthetized with a mechanochemical approach. This novel route of synthesis was applied to the series [NH4][M(HCOO)3] with M= Cu2+, Co2+, Mn2+, Zn2+ and Ni2+ using as reactants ammonium formate and the corresponding di-hydrated metal formates. The milling duration of the process correlates with the thermal stability of the di-hydrated metal formates indicating that the first step of the mechanosynthesis process is represented by the removal of water molecules. The characterizations of the final products indicate the presence of single phase [NH4][M(HCOO)3] compounds with an excellent degree of crystallinity.

    High temperature 0.63BiFeO3-0.37BaTiO3 based ceramics with large electromechanical properties by simple A-site K+ doping

    Kang F.Zhang L.Wang Z.Sun Q....
    9页
    查看更多>>摘要:Designing high temperature piezoelectric ceramics with large electromechanical properties is key to the actuators application in harsh environment. BiFeO3-BaTiO3 based piezoelectric ceramics are the promising candidates due to their high electromechanical properties and high Curie temperature. Here, the simple A-site single K+ doped 0.63Bi1?xKxFeO3-0.37BaTiO3 (abbreviated as 0.63B1?xKxF-0.37BT) ceramics with positive temperature dependent electromechanical properties were fabricated via conventional solid phase method. The electromechanical properties in the 0.63B1?xKxF-0.37BT ceramics are closely related to the content of K+ doping. The excellent electromechanical properties of S= 0.26% and d33*=861 pm/V under low electric field of 30 kV/cm at 105 ℃ are achieved in the 0.63B0.9975K0.0025F-0.37BT ceramic, which is conducive to their application at high temperature. Combined with the microstructure and PFM, the optimized electromechanical properties in 0.63B0.9975K0.0025F-0.37BT ceramic are mainly due to more nanodomains switching facilitated by the large grain size and local structural heterogeneity. The site engineering of A-site single ion doping is an efficient and simple strategy for BF-BT based piezoelectric ceramics to achieving excellent electromechanical properties under low electric field at high temperature.

    The roles of Sn4+ in affecting performance of Potassium Sodium Niobate ceramics

    Xie L.Chen H.Chen Q.Xing J....
    7页
    查看更多>>摘要:In the KNN ceramics system, the contradictory relationship between piezoelectricity and phase transition temperature has received extensive attention from researchers. Herein, by studying the doping mechanism of Sn4+ in 0.957(K0.48Na0.52)NbO3-0.003BiCoO3-0.04(Bi0.5K0.5)Zr1-xSnxO3 (KNN-BC-BKZ1-xSx), the coexistent of excellent piezoelectricity and ideal Curie temperature is realized in KNN ceramics. The addition of Sn4+ keeps R-O-T coexistence system in KNN-BC-BKZ1-xSx ceramics, thereby maintaining the low energy barrier of domain rotation. Further investigation has shown that the substitution of Sn4+ can promote grain growth and increase the density of ceramics. In addition, the optimal comprehensive properties (d33 = 391 pC/N, kp = 0.518, TC = 332 °C, d33* = 512 pm/V) are simultaneously obtained at x = 0.15. Particularly, due to growth of grain size, excellent temperature stability is obtained within a broad temperature range. The discovery of Sn4+ doping is useful to the development of KNN-based materials with both piezoelectric electrical properties and Curie temperature as it provides a new idea for enhancing performances of ceramics.

    Mixed oxides of the Pr1?xSrxMnO3(0.1≤x≤0.5) system synthesized by a chemical route: Structural, electric and magnetic characterization

    Aguilar C.J.Diosa J.E.Mosquera E.Alcazar G.A.P....
    17页
    查看更多>>摘要:In this work, ceramic powders of thePr1?xSrxMnO3 (PSMO) system, praseodymium manganites doped with strontium in concentrations 0.1≤x≤0.5, were synthesized using the polymeric precursor method (Pechini). The powders obtained were characterized using X-ray diffraction (XRD) and Raman, UV-Vis diffuse reflectance and photoluminescence spectroscopies. Bearing in mind the potential uses of the synthesized PSMO systems, their magnetic and electrical characteristics were determined. Samples heat treated at 900 °C were found to have a single crystalline phase with an orthorhombic perovskite type structure Pnma, a primary particle size of ~32nm and a crystallite size of< 40 nm, a result that would indicate that the primary particles are in fact monocrystals. The Raman spectroscopy results revealed the characteristic vibrations of the synthesized Pr1?xSrxMnO3 mixed oxides and reinforced the fact that for concentrations between 0.1 and 0.5 of strontium, the oxides corresponded to the Pnma space group. Furthermore, the energy gap value varied between 1.61 and 1.51eV and the Urbach energy between 990 and 640meV by increasing the Sr concentration in the manganite. The magnetic characterization meanwhile showed that (Tc) - the ferromagnetic to paramagnetic semiconductor transition temperature - increased as the Sr doping increased, being very close to room temperature, Tc=295K, for a Sr content of x=0.4. The electrical resistivity measurements moreover showed a metal-semiconductor transition, at temperatureTMI?sc, which also gave the highest value for this sample, and which increased when the applied magnetic field increased (TMI?sc = 283 K at 2T). The TC values showed a linear correspondence with temperature TMI?sc, indicating a strong correlation between the magnetic and electrical properties of the Pr1?xSrxMnO3 system samples.

    Optimization of photogenerated charge transport using type-II heterojunction structure of CoP/BiVO4:WO3 for high efficient solar-driver water splitting

    Quang N.D.Van P.C.Majumder S.Jeong J.-R....
    11页
    查看更多>>摘要:Bismuth vanadate oxide (BiVO4) is one of the most efficient light-absorber metal oxides for the photoelectrochemical (PEC) water splitting; however, the fast charge recombination and poor kinetics for water oxidation have hindered full utilization of their theoretical performance. The optimization of the band alignment to facilitate charge transport and injection is of paramount importance to achieve the ideal water splitting performance of the photoelectrode. In this study, a type-II heterojunction CoP/BiVO4:WO3 structure has been fabricated for highly efficient PEC water splitting. The WO3 layer in the junction readily collects the photoelectrons harvested from the BiVO4 layer owing to its highly conducting nature, enabling efficient bulk charge transport from the BiVO4:WO3 junction to the fluorine-doped tin oxide (FTO) substrate. In addition, the cobalt phosphide (CoP) nanoparticles (NPs) play the role of the hole conducting layer from the light-absorber layer to the water as well as a catalyst to enhance surface charge injection efficiency at the photoelectrode surface. As a result, the CoP/BiVO4:WO3 photoanode reveals a remarkable photocurrent density of 2.81 mA cm?2 at 1.23 V (vs. RHE) with a negative shift of the onset potential (610 mV) compare to that of bare BiVO4. Moreover, the CoP/BiVO4:WO3 electrode shows a highly stable photocurrent density for at least 5 h.

    Porous engineering enables one-dimensional CoxOy/C composite to enhance lithium storage

    Tong R.Yan Y.Lu X.Li Y....
    9页
    查看更多>>摘要:Herein, in order to improve performance of cobalt oxides for lithium-ion battery anodes, a one-dimensional porous CoxOy composed of CoO and Co3O4 has been fabricated and further coated by a characteristically porous layer of carbon through a facile integrated porous engineering. The as-prepared CoxOy@porous carbon (CoxOy@PC) composite therefore integrates the advantages of the one-dimensional and porous structures. Thus architecture successfully boosts the structural stability and efficiently enhances the electrochemical kinetics of the CoxOy@PC anode. The results reveal that the CoxOy@PC anode shows significantly improved performance with 964.7 and 908.6 mA h g?1 at 200 and 1000 mA g?1 after 200 and 100 cycles, respectively. It demonstrates that the porous engineering plays an important role in improving performance of CoxOy@PC anode, which is conducive to mitigation of volume change, permeation of electrolyte, and ion diffusion and mass transport. This CoxOy@PC therefore shows great promise in application of high-performance anode for lithium-ion batteries. Moreover, this study gives an efficient strategy to concern the intrinsic drawbacks of the cobalt oxide anodes, which could be extended to other high capacity of metallic oxide-based anodes toward high energy-density batteries.

    Resistive switching characteristics of sol-gel derived La2Zr2O7 thin film for RRAM applications

    Tseng H.-T.Hsu T.-H.Tsai M.-H.Huang C.-L....
    10页
    查看更多>>摘要:Amorphous La2Zr2O7 thin films were fabricated using the sol-gel method and the bipolar resistive switching behavior of the metal(Al or Ti)/LZO/ITO devices were systematically investigated. The effect of film thickness, top electrodes, and post-annealing treatment conditions on the RS characteristics of the La2Zr2O7 thin films were also discussed. The film thickness increases significantly as the number of spin-coating layers increases, leading to a higher operation voltage and fewer switching cycle times. In addition, the RS properties of the devices are affected by the work function difference between the top and the bottom electrodes. All devices exhibited similar conduction mechanisms, which are described by the ohmic conduction in the low resistance state and space-charge limited current in the high resistance state. Moreover, the RS performance can be profoundly improved by the post-annealing treatment because of the formation of a thicker AlOx interface layer between the Al and LZO thin films, which was revealed via TEM images. The optimized RRAM performances are 1971 cycle times and high stable retention time for over 105 with a Ron/Roff ratio of around 101 at a post-annealing temperature of 300°C. The multilevel RS performances are also observed. Besides, this device maintained a large enough memory window in the retention test at 85°C thermal stress. The longer life is to be expected.