查看更多>>摘要：Three dimensional (3D) hybrid nanoarchitecture of two-dimensional (2D) reduced graphene oxide/one dimensional (1D) multiwalled carbon nanotube and zero-dimensional (OD) zirconium oxide (ZrO_2) nano-particles (rGO/MWCNT/ZrO_2) was synthesised by a simple hydrolysis method for high performance supercapacitors. To unlock the properties of individual materials to the maximum, binaries of ZrO_2 with GO and MWCNT were also synthesised. The increased wettability, integrated structure, and the synergistic effect of rGO, MWCNT, and ZrO_2 in rGO/MWCNT/ZrO_2 (GMZ) offer a capacitance of 357 F g~(-1) at 1 A g~(-1) with excellent capacitance retention of 98% across 5000 cycles. 1D structure of MWCNT creates an exceptional conductive network with rGO due to the confinement of electrons and ions without disturbing its electronic structure. The intriguing supercapacitor performance of differently dimensioned framework with ZrO_2 emphasises the engineered orientation and tuning of a designed environment for its appropriateness, uniqueness, and sensitivity to push up enhanced performance.
查看更多>>摘要：Lithium ion batteries (LIBs) based on solid state electrolytes have attracted much attention for their high safety and energy density. Li_(29)Zr_9Nb_3O_(40) powders as Li-ionic conductors were prepared using a sol-gel method in this work, and the related ceramics were sintered in air or in an oxygen-deficient atmosphere in which sample was covered with corundum crucible. All the sintered ceramics are consisted of orthorhombic phase. Li_(29)Zr_9Nb_3O_(40) ceramic sintered in oxygen-deficient atmosphere has conductivity of 1.03 × 10~(-3) S cm~(-1) at room temperature and has ionic transference number of 0.9996, while the ceramic sintered in air has conductivity of 4.41 × 10~(-5) S cm~(-1). The influence of oxygen vacancy on the migration path of Li-ion was discussed. The migration paths of Li-ions between two kinds of Li_(29)Zr_9Nb_3O_(40) ceramics were simulated and visualized by method of bond valence site energy with VESTA software.
查看更多>>摘要：Solid electrolytes are critical in the development of solid-state batteries, which have advantages in terms of safety and stability. Lithium Lanthanum Titanate (Li_(3x)La_(2/3-x)TiO_3) is regarded as one of the most favored candidate solid electrolytes. However, the doping dependences of ionic conductivity and microstructure are still poorly understood. In this work, nominal Li_(0.5-x)La_(0.5)(Ti_(1-x)Nb_x)O_3 (LLTN, x = 0, 0.01, 0.03, 0.05 and 0.07, labelled as LLTNO, LLTN1, LLTN3, LLTN5, LLTN7, respectively) ceramics are synthesized to investigate the above doping effects. The bulk ionic conductivity of LLTN5 sample reaches as high as 0.71 × 10~(-3) S/cm, which is approximately two times higher than the bulk ionic conductivity of the undoped sample at room temperature. The XRD refinement and Raman results indicate that niobium doping increases the lattice cell along the c-axis and stretch the Ti-0 bond, which extends the tunnels for Li-ions diffusion. This work suggests that it is effective to enlarge the lattice cell for the improvement of the Li-ion conductivity in LLTO.
查看更多>>摘要：The aim of this work was to propose the experimental partial isothermal section of the Al-Pd-Co phase diagram at 1035 °C and to study the structure of quasicrystalline approximant ε_n. Scanning electron microscopy including energy dispersive X-ray spectroscopy, X-ray diffraction and scanning transmission electron microscopy were used in the investigation. Calculation of atomic structures was performed using Monte Carlo simulation minimising Empirical Oscillating Pair Potentials energy. Besides the proposed partial isothermal section at 1035 °C, homogeneity ranges of phases ε_n, U, F, V,δ, and W were schematically projected. Various modifications of ε_n were observed and/or identified in the investigated alloys. The structures of ε_(22) and ε_(34) were experimentally observed in the Al-Pd-Co system for the first time. Furthermore, their atomic structure models were created. Last but not least, it was experimentally documented that the regular arrangement of tiles in ε_n structures can be interrupted by structural defects. The obtained results form a comprehensive picture of the individual structural modifications of the ε_n phase.
查看更多>>摘要：La-doped CeO_2 nanoparticles of composition Ce_(1-x)La_xO_(2-δ) (0 ≤ x ≤ 0.1) have been studied here as prospective electrolytes for intermediate temperature solid oxide fuel cells (IT-SOFCs). They were synthesized by auto-combustion method and the powder samples were calcined at 700 °C to get ultrafine nanocrystalline particles. They were characterized by XRD, Raman, FTIR, XPS, DRS, FESEM/EDX, particle size analyzer and ac-impedance techniques. Ionic conductivity was measured from 350 - 750 °C. The Ce_(0.90)La_(0.10)O_(2-δ) (0.1 LDC) and Ce_(0.95)La_(0.05)O_(2-δ) (0.05 LDC) showed a maximum conductivity of 8.89 ×10~(-3) and 8.32 ×10~(-3) S cm~(-1) at 700 °C, respectively. The σt of 0.1 LDC = 1.01 ×10~(-2) S cm~(-1) at 750 °C. The activation energy of 0.1 LDC and 0.05 LDC was found to be 0.70 eV and 0.87 eV, respectively. These values are higher than those reported for La-doped CeO_2 in literature. The SOFC performance with 0.05 LDC as electrolyte showed open circuit voltage of 0.81 V and maximum power density of 41 mW cm~(-2) at 650 °C using hydrogen as fuel.
查看更多>>摘要：High entropy alloys (HEAs) have attracted considerable attention due to their excellent mechanical properties, which provides new insights for designing next generation structural materials. A series of Al_(0.2)Co_(1.5)CrFeNi_(1.5)Ti_(0.5)B_x (x = 0, 0.15, 0.3, 0.45, 0.6, 0.75 and 0.9, in molar ratio) HEAs was prepared by vacuum arc melting to investigate the effect of boron doping on the phase evolution, microstructure transformation and mechanical properties. The results indicated that the HEAs with trace boron doping (x = 0.15) maintained single FCC phase, while it evolved to FCC phase, in-situ borides (TiB_2 and Cr_2B) and Laves phase when the boron molar ratio higher than 0.3. With the boron molar content increased from 0 to 0.9, the microstructures of the HEAs transformed from complete dendrite to dendrites, irregularly shaped TiB_2, needle-shaped Cr_2B and lamellar eutectic structure which composed by alternate layers of FCC phase and Laves phase. B doping improved the strength and hardness of the HEAs. The enhanced mechanical properties of the boron doped HEAs was attributed to the synergistic strengthening effect among interstitial solid solution strengthening, second phase strengthening, dislocation strengthening, fine grain strengthening and heterostructure strengthening.
查看更多>>摘要：The effects of Y and LaCe substitution in Nd-Fe-B multi-main-phase (MMP) magnets were investigated by co-mixing with the binary or ternary components. The microstructure and magnetic properties showed some differences after Y and LaCe-substitution. The coercivity was increased for the LaCe-substituted MMP magnets with two-types shell structures due to the stronger magnetic isolation between adjacent grains. Y-substituted MMP magnets with one-type shell structure exhibited a relatively lower coercivity due to the deterioration of anisotropy owing to the La/Ce/Y enrichment in the core-shell structure. The La element preferred to migrate to the grain boundary regions in the LaCe-substituted MMP magnets, while it was trapped in the 2:14:1 shell by the inducement of Y in the Y-substituted MMP magnets. This work provides new insights into the fabrication of La/Ce/Y magnets with high performance.
查看更多>>摘要：In this study, a 2 at% erbium doped cerium trifluoride (Er:CeF_3) single crystal was grown using the Bridgman method. The consequent absorption, infrared transmittance, and fluorescence spectra were recorded. The spectroscopic properties of Er:CeF_3 crystals were intensively studied based on the Judd-Ofelt (J-O) theory. The Ω_2, Ω_4, and Ω_6 parameters were fitted to be 5.206 × 10~(-20), 1.805 × 10~(-20), and 3.06 × 10~(-20) cm~2, respectively. The emission cross-section centered at 1564.6 nm was calculated to be 1.053 × 10~(-20) cm~2, and the corresponding fluorescence lifetime was measured to be 1.675 ms. Additionally, the magneto-optical (MO) performance of the Er:CeF_3 crystal was investigated for the first time. The Verdet constants of Er:CeF_3 at 532, 632.8, 1064, and 1310 nm are 231.0,165.4, 43.4, and 24.4 rad-T~(-1)-m~(-1), respectively, which are significantly higher than those of pure CeF_3 and traditional Tb_3Ga_5O_(12). The results show that the Er:CeF_3 crystal can be applied both to solid-state lasers and Faraday devices.
查看更多>>摘要：In this study, hollow cubic Cu_2MoS_4 nanoparticles were synthesized via a facile hydrothermal method. Following that, Rh single atoms were loaded onto the surface of Cu_2MoS_4 nanoparticles to prevent electron/ hole recombination. The cubic morphology of Cu_2MoS_4 nanoparticles and the presence of Rh atoms were investigated by Transmitting Electron Microscope (TEM). The crystal structure of the synthesized Rh-loaded Cu_2MoS_4 was studied by X-ray diffraction (XRD). The shift in Rh X-ray Photoelectron Spectroscopy (XPS) peaks indicated the intimate interaction between Rh and Cu_2MoS_4, providing a pathway for the charge transfer. The photocatalytic efficiency of the synthesized photocatalysts was significantly enhanced by introducing Rh single atoms onto the Cu_2MoS_4 surface. Consecutive photocatalytic dye degradation experiments revealed that Rh-loaded Cu_2MoS_4 nanoparticles could be recycled and reused multiple times with no drop in the photocatalytic efficiency. The improved photocatalytic performance of Rh-loaded Cu_2MoS_4 was attributed to a lower charge transfer resistance, higher charge transfer rate, and longer charge carrier lifetime. The most crucial reactive radical was detected to be O_2~-~ while e~- and h~+ are also playing an essential role in the photocatalytic degradation of RhB on Rh-loaded Cu_2MoS_4. This study highlighted the importance of forming a Schottky junction between Rh and Cu_2MoS_4 to enhance charge carrier separation and improve photocatalytic efficiency.
查看更多>>摘要：Zn-0.2Mg-(0, 0.05, 0.2, 0.4 wt%)Fe alloy rods were produced by indirectly extruding the as-cast ingots at 200 °C. The addition of minor Fe significantly improved the ductility of as extruded Zn-0.2Mg alloy without scarifying the strength. As 0.05 wt% Fe was added, the yield strength, ultimate tensile strength and elongation were increased from 216 MPa, 228 MPa and 1.85% for Zn-0.2Mg alloy to 240 MPa, 258 MPa and 42% for Zn-0.2Mg-0.05Fe. Texture variation from basal texture to non-basal texture alongside the grain refinement contributed the great improvement of ductility and slight increase of strength, respectively. As Fe content increased from 0.05 wt% to 0.4 wt%, the volume fraction and size of the second phases changed, leading to the reduction in elongation by 50% yet maintaining the yield strength and ultimate tensile strength.
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Elsevier