查看更多>>摘要：A Li_(0.27)K_(0.72)Ni_(0.6)Co_(0.2)Mn_(0.2)O_2 (LKNCM) cathode for potassium-ion batteries (PIBs) was obtained from LiNi_(0.6)Co_(0.2)Mn_(0.2)O_2 (NCM622) via ion exchange. In-situ X-ray diffraction and high-resolution transmission electron microscopy analyses showed the morphological and structural changes that occur during K~+-ion insertion. Particularly, the primary particles became porous, and the (003) interlayer distance expanded from 4.76 to 6.50 A, providing a potassiation/depotassiation framework. Inductively coupled plasma-optical emission spectroscopy revealed that 0.72 mol of K~+ ions were inserted into the Li-extracted NCM622 cathode per formula unit, indicating that the amounts of extracted Li~+ and inserted K~+ were similar. The developed LKNCM cathode exhibited a theoretical capacity of 160.79 mAh g~(-1) and an initial discharge capacity of 106.95 mAh g~(-1) with an average potential of 3.1 V vs. K/K~+. These results demonstrate that ion exchange enables layered NCM cathodes for lithium-ion batteries to be applied as cathodes for PIBs.
查看更多>>摘要：In this study, the nickel oxide (NiO_x) thin films were reactively sputtered at different working pressures in the oxide mode zone for application in flexible all-thin-film electrochromic devices (ATF-ECDs). The working pressure plays an important role on the various properties of the reactively sputtered NiO_x thin film including the deposition rate, grain structure (microstructure), morphology, chemical composition, optical properties and electrochemical properties. The flexible ATF-ECDs with ≥2 Pa NiO_x thin films perform high optical modulation and relatively fast response time during the electrochromic processes. The detailed electrochromic mechanism is discussed.
查看更多>>摘要：In this paper, polarization electric field (PEF) induced in GaN/In_xGa_(1-x)N superlattice (SL) was studied and found it can be treated as a reductant of thermal conductivity (k). Elastic properties and phonon group velocity are modified by the impact of interfacial PEF as by inverse piezoelectric effect. It improves scattering and thermal resistance at the boundaries because of dissimilarity in specific heat and group velocity, that decreases transmission coefficient of phonon and more acoustic mismatches resulting in reduction of in-plane (k_(ip)) as well as cross-plane (k_(cp)) thermal conductivities. k_(ip) of In_xGa_(1-x)N (5 nm)/ GaN (10 nm) SL with (without) interfacial PEF field are 7.807 (8.921), 7.350 (8.355) and 7.018 (8.090) Wm(-1)K~(-1) respectively, for x = 0.1,0.3 and 0.5; whereas k_(cp) for the similar compositions are respectively, 4.652 (5.710), 4.282 (5.221) and 4.081(5.185) Wm~(-1)K~(-1) at 300 K demonstrating the reduction exceeds 20%. It shows that the optimal k can be accomplished with the adaptation of nitride SL's electric field for thermoelectric improvements.
查看更多>>摘要：The magnetic anisotropy of SmCo-based permanent magnetic thin films are generally controlled by introducing buffer layer or heating substrate. However, the design for the multi-layer thin film system is complicated and the thickness of SmCo is limited due to a short range of interfacial stress/strain between the buffer layer and SmCo layer. In this work, the effects of temperature gradients, generated by RTP (rapid thermal process), on the magnetic anisotropy of the SmCo-based films were systematically investigated. The results show that the as-deposited films exhibit amorphous state. The out-of-plane coercivity of RTP-treated films is strongly correlated with the heating rate, and its optimum value (2810 Oe) is larger than that of the CTA (conventional thermal annealing) treated films (1670 Oe). For the RTP-treated films, the intensity of characteristic diffraction peaks for in-plane oriented SmCo_5 (200) and Sm_2Co_(17) (300) decreases, together with reducing the roughness. Besides, the grain size is finer and the contrast of magnetic domains becomes stronger for the RTP-treated films due to that the easy axis of SmCo_5/Sm_2Co_(17)phase gradually changes from in-plane to out-of-plane direction. It is suggested that the RTP treatment with a shorter annealing time has beneficial effects on obtaining finer microstructure and improving the out-of-plane magnetic anisotropy of the SmCo-based films. This work provides a novel way to control the magnetic anisotropy via annealing temperature gradients for permanent magnetic thin films, compared with conventional methods, to induce the magnetic anisotropy.
查看更多>>摘要：In this paper, we investigate the effects of a SiO_x interfacial layer on ON/OFF current ratios, endurance characteristics and read-disturb immunities of Ag/Cu_xO/SiO_x/n~+-Si write-once-read-many-times (WORM) memories. The Cu_xO active layers were prepared using a sol-gel process. After coating Cu_xO films on n~+-Si substrates, the Cu_xO/n~+-Si samples were annealed in air at 400 °C and 600 °C, respectively, to obtain a SiO_x interfacial layer at the Cu_xO/n + -Si interfaces. The 400 °C-annealed Cu_xO device shows an ON/OFF current ratio of 104. However, degradation of OFF state current (IOFF) with increasing read-pulse cycles and stress time is observed. For the 600 °C-annealed Cu_xO device, stable ON and OFF state currents can be observed both in an endurance test for over 1.2 × 104 read cycles and in a read-disturb test for 2 × 104 s. Moreover, a higher ON/OFF current ratio of 107 is obtained. A rigorous retention test executed at an elevated temperature of 85 °C indicates that the data retention time is expected to last for 10 years. The performance improvement of the 600 °C-annealed Cu_xO device is due to an increase in the thickness of the SiO_x interfacial oxide layer. The mechanism for the influence of the interfacial layer on memory performance is investigated and illustrated. The OFF state current of the memory is limited by hopping and trap-assisted tunneling transport in the SiO_x interfacial layer. In the ON state, conductive paths in the device cause that the carriers can easily migrate by Ohmic and space charge limited conduction.
查看更多>>摘要：The strengthening effect of composites is rather limited in comparison with the excellent properties of graphene due to difficulty in acquiring strong interfacial bonding. To enhance the interfacial bonding and reduce the interface mismatch between the matrix and reduced graphene oxide (rGO), a novel strategy in this study is proposed through generating hybrid layered double oxides (LDO) nanoparticles on rGO (LDO@ rGO). The 2024A1 composites with heterogeneous structure were constructed by ball milling and spark plasma sintering (SPS), which was reinforced by flake-like LDO@rGO-rich zones contained LDO@rGO in the Al matrix with fine grain size of ~1 um. The yield strength, elongation and fracture energy of 1 vol% LDO@ rGO/Al composite with heterogeneous microstructure were 69.6%, 63.9% and 140.5% higher than those of the composite reinforced by uniformly distributed 0.67 vol% graphene oxide (GO), respectively, achieving an improvement in the strength-ductility synergy of the fabricated LDO@rGO/Al composite. The rationally spatial arrays of LDO@rGO-rich and LDO@rGO-free zones are beneficial for promoting the synergistic strengthening of Orowan, solid solution, thermal mismatch and load transfer and simultaneously toughening the composite through enhanced crack deflection and bridging effects. The proposed method offers a promising route for fabricating composite with optimized and improved material properties by coupling interface and heterogeneous structure.
查看更多>>摘要：Mn_3O_4 is viewed as an attractive candidate for rechargeable aqueous zinc-ion battery cathode materials due to the advantages of low cost, eco-friendly nature as well as high capacity. However, it faces inherently poor electronic conductivity and poor cyclability during battery cycling. To improve the electrochemical performance, Mn_3O_4 nanoparticles anchored on carbon nanotubes (CNTs@Mn_3O_4) were fabricated by a facile one-step solution process at low temperature. Benefiting from the synergistic effect of nanoscale Mn_3O_4 and 1D CNTs, the conductivity and electrochemical performance of Mn_3O_4 are significantly improved. The prepared CNTs@Mn_3O_4 nanocomposites deliver a discharge capacity of 310 mAh g~(-1) at 100 mA g~(-1) and maintain 123 mAh g~(-1) at 1000 mA g~(-1) after 500 cycles, demonstrating good rate capability and cycling performance as a promising cathode material for low-cost neutral zinc-ion battery.
查看更多>>摘要：In recent years, molybdenum disulfide (MoS_2) with sandwich structure has been widely studied as cathode material of aqueous rechargeable zinc-ion batteries (ARZIBs), but inherent low capacity and short cycle life limit its further development. Here, we synthesized a novel hydrophilic spherical 1T-MoS_2 through hexadecyl trimethyl ammonium bromide (CTAB) template-assisted hydrothermal reaction as cathode materials for ARZIBs and systematically study its mechanism of electrochemical enhancement. The results suggest that stable spherical MoS_2 was prepared by in-situ reduction of molybdate ion under the electrostatic absorption of CTAB template and 0 element introduced by ethylene glycol (oil-phase solvent) not only increases the hydrophilicity of the material and facilitates the intercalation of ammonium ions and water molecules, but also promotes the formation of the 1 T phase by changing the electronic structure. Consequently, this modified electrode exhibits a reversible capacity of 110 mAh g~(-1) at the current density of 1.0 A g~(-1), and the capacity retention rate is up to 90% after 500 cycles, showing excellent cycling stability and rate performance.
查看更多>>摘要：The present work focuses on developing a low-cost medium entropy alloy (MEA) with desirable mechanical properties according to the benchmark CoCrFeMnNi high entropy alloy (MEA). By adjusting the ratio of each component and adding silicon to the system, the Fe_(50)Mn_(17.5)Cr_(12.5)Co_(10)Ni_5Si_5 MEA with a single face-centered cubic (FCC) phase was developed. After homogenization, hot rolling, cold rolling, and annealing, fully re-crystallized MEA specimens with grain sizes ranging from 10 pm to 149 pm were used for tensile tests. The microstructure of the elongated MEAs showed a ε-martensite transformation from the FCC phase to the hexagonal close-packed (HCP) phase, indicating the stacking fault energy (SFE) of the MEA was significantly reduced. The room-temperature deformed MEA showed improved mechanical properties in yield strength and tensile strength than the CoCrFeMnNi MEA. Meanwhile, the volume fraction of the HCP phase in cryogenic-deformed MEA is much larger than that in room-temperature deformed MEA; its yield strength was increased by two times, while the tensile strength exceeded the level of 1 GPa.
查看更多>>摘要：Broad emission bands in semiconducting oxides due to native defects could readily be an efficient source of white light if they are adjusted properly. In this work, Zn_2GeO_4 nanoparticles of 10 and 16 nm sizes, obtained by a precipitation method, are presented as potential white light emitter. Temperature dependence measurements have been performed to discuss the Zn_2GeO_4 luminescence, which consist of emission bands in the ultraviolet, blue and green regions. The analysis of these results provided some clues about the interplay between defect-related centres and the surface states in nanocrystalline Zn_2GeO_4. Finally, a highly efficient cold-white emission at room temperature has been achieved from this nanomaterial.
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Elsevier