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81.
Changwei Dun Guoxi Xi Ye Zhang Tingting Zhao Yumin Liu Xiaoying Heng Lu Yao 《Ceramics International》2018,44(17):20984-20991
In this study, we investigated the effects of substituting Li+ for Co2+ at the B sites of the spinel lattice on the structural, magnetic and magnetostrictive properties of cobalt ferrites. The Li+ substituted cobalt ferrites, Co1-xLixFe2O4, with x varying from 0 to 0.7 in 0.1 increments, were synthesized with a sol-gel auto-combustion method using the cathode materials of spent Li-ion batteries. X-ray diffraction analysis revealed that all the Co1-xLixFe2O4 nanopowders had a single-phase spinel structure and the lattice parameters decreased with increasing Li+ content, which can be proved by slight shifts towards higher diffraction angle values of the (311) peak. Field emission scanning electron microscopy was used to observe the fractured inner surface of the sintered cylindrical rods and the increased porosity resulted in a decreased magnetostriction. The oxidation states of Co and Fe in the cobalt ferrite samples were examined by X-ray photoelectron spectroscopy. High resolution transmission electron microscopy micrographs showed that most particles were roughly spherical and with sizes of 25–35?nm. Li+ substitution had a strong effect on the saturation magnetization and coercivity, which were characterized with a vibrating sample magnetometer. The Curie temperature was reduced due to the decrease in magnetic cations and the weakening of the exchange interactions. The magnetostrictive properties were influenced by the incorporation of Li+ at the B sites of the spinel structure and correlated with the changes in porosity, magnetocrystalline anisotropy and the cation distribution. 相似文献
82.
Y.J. Han Y.Z. Wang C.H. Yang Q. Yao J. Chen S.F. Huang 《Ceramics International》2018,44(13):15153-15159
This work reports the characteristics of nonstoichiometric Na0.5+xBi0.5+yTi0.96W0.01Ni0.03O3 (x?=?0.0%, y?=?1.0%; x?=?0.5%, y?=?2.0%; x?=?1.0%, y?=?4.0%) ceramic films derived from chemical solution deposition and the role played by excess Na/Bi in modifying microstructure and electrical properties. Single perovskite phase structure can be maintained in all compositions. Decreased grain size can be obtained with the increasing compensation for volatile Na/Bi elements. Particularly, extra amounts of 0.5?mol% Na and 2.0?mol% Bi leads to reduced leakage and enhanced ferroelectric polarization. Meanwhile, due to the high breakdown electrical field strength and large difference between maximum and remanent polarization, an excellent energy storage performance can be achieved in Na0.505Bi0.52Ti0.96W0.01Ni0.03O3 sample, which is distinguished by a recoverable energy storage density of 40.5?J/cm3 and an energy storage efficiency of 43.6% at 2515?kV/cm as well as a good frequency stability. Hence, the regulation for the content of volatile elements is effective to modify the electrical response of Na0.5Bi0.5TiO3-based materials. 相似文献
83.
Pure Na0.5Bi0.5TiO3 (NBT), donor W6+ doped NBT (NBTW), acceptor Ni2+ doped NBT (NBTNi), as well as donor W6+ and acceptor Ni2+ codoped NBT (NBTWNi) polycrystalline films are fabricated on indium tin oxide (ITO)/glass substrates via a chemical solution deposition method. The roles of aliovalent-ion substitution on the crystallinity, ferroelectric and dielectric properties of NBT film are mainly investigated. With the introduction of aliovalent-ion, the surface of the doped film becomes more uniform and the leakage current is reduced. Well saturated polarization-electric field (P-E) loops can be observed in W6+ and Ni2+ codoped NBT film due to its lowest leakage currents compared to those of other films. Also, the effect of voltage and frequency on the capacitance-voltage (C-V) curve and the dielectric tunability for the NBTWNi film is discussed. The ferroelectric and dielectric properties are largely improved in NBTWNi film, which can be ascribed to the synergetic effect of high-valence W6+ and low-valence Ni2+ ions. The cooperation between the acceptor and donor cations can effectively eliminate the mobile oxygen vacancies in NBT films. 相似文献
84.
85.
Li Lei Limin Li Shasha Wang Gaoyang Zhao Yoshifumi Oshima Yang Ren Lei Zhao Lihua Jin Yao Wang Chengshan Li Pingxiang Zhang 《Journal of the European Ceramic Society》2018,38(14):4694-4700
Highly (100)-oriented Ce1-x(Y0.2Zr0.8)xOδ (CYZO) films were prepared on biaxially textured NiW substrates by a chemical solution deposition approach using metal inorganic salts as starting materials. It has been found that both the preferential orientation and surface roughness of CYZO films decrease gradually with increasing of the doping percentage of Y3+ and Zr4+ ions. The epitaxial growth relationship of (220)CYZO//(200)NiW and [00?l]CYZO//[001]NiW was demonstrated by XRD texture measurement as well as atomic resolution STEM observation. XRD, Raman and XPS spectra results indicate that Y3+ and Zr4+ ions were indeed introduced into CeO2 lattice to substitute Ce4+ ions and form cubic fluorite CYZO solid solution. Moreover, CeO2 buffer layer can be endowed a strong enough capability to prevent element diffusion through co-doping of yttrium and zirconium, provided that an optimal doping ratio of them is adopted. This will provide a new approach to fabricating strong-barrier single buffer layer for coated conductor. 相似文献
86.
Junjun Chen Jian Chen Xiumin Yao Zhongming Chen Xuejian Liu Zhengren Huang 《Journal of the European Ceramic Society》2018,38(9):3083-3088
SiC/20?wt% ZrB2 composite ceramics were fabricated via pressureless solid phase sintering in argon atmosphere at different temperature. The effect of sintering temperature on microstructure, electrical properties and mechanical properties of SiC/ZrB2 ceramics was investigated. Electrical resistivity exhibits twice significant decreases with increasing sintering temperature. The first decrease from 1900?°C to 2000?°C is attributed to the obvious decrease of continuous pore channels in as-sintered materials. The second decrease from 2100?°C to 2200?°C results from the improvement of carbon crystallization and the disappearance of amorphous layers enveloping ZrB2 grains. Additionally, the increase of sintered density with increasing temperature caused greatly advance of flexural strength, elastic modulus and Vickers hardness. But excessive temperature is detrimental to flexural strength because of SiC grain growth. 相似文献
87.
Fu Li Qiao Liang Zheng Jingwu Ying Yao Li Wangchang Che Shenglei Yu Jing 《Journal of the European Ceramic Society》2018,38(4):1170-1178
Aluminum nitride powders were synthesized by carbothermal reduction-nitridation method using Al(OH)3, carbon black and Y2O3 as raw materials. The change of phase, microstructure and densification during the AlN synthesis and sintering process were investigated and the effects of Y2O3 was discussed. The results showed that Y2O3 reacted with Al2O3 to form yttrium aluminates of YAlO3 (orthorhombic and hexagonal phases), Y4Al2O9 and Y3Al5O12 at the low temperature of 1350 °C. YAlO3 could firstly be transformed into Y2O3 and then completely into YN when the firing temperature and holding time increased. However, YN could be oxidized into Y2O3 again after the carbon removal at 700 °C in the air atmosphere. There were two ways generating AlN when adding Y2O3 and the possible mechanism was proposed. Y2O3 from YN oxidation favored the densification of AlN ceramics because the liquid had better flowability and distribution in the sintering process at 1800 °C. 相似文献
88.
Utilization of bionics to develop stimuli responsive polymers that can heal damage with excellent restorability is particularly attractive for a sustainable society. Herein, inspired by chameleons, a hierarchical structural design strategy is proposed and illustrated to fabricate a healable photochromic material based on a self‐healable polymeric matrix and a finely dispersed photochromic spirooxazine. The self‐healable polymeric matrix is fabricated via the integration of multiple hydrogen bonds (H bonds) and covalent cross‐links into a biomass‐derived elastomer. The dynamic nature and soft characteristics enable the as‐prepared elastomer superior extensibility as well as self‐healing ability, while the covalent cross‐links can assist the reassociation of ruptured H bonds. The representative elastomer exhibits an extensibility of 2600% and toughness of 42.76 MJ m?3. Furthermore, it shows good self‐healing ability with complete recovery of scratch as well as restoration against 1900% of elongation and 24.1 MJ m?3 of toughness after healing at 60 °C for 24 h. This combination of moderate toughness, good self‐healing ability, and smart photochromic property in biomass‐derived materials should largely improve their applicability, reliability, and sustainability in various materials and devices. 相似文献
89.
Corrosion of a salt-coated Ni-superalloy has been studied at 900°C under a wet air and sulfur vapor ambient. The corrosion thickness, after an incubation of ~60 hr, linearly increases with the corrosion time t and the onset of surface spallation occurred at t ≈ 60 hr. The corroded layer consists of a corrosion front dominated by Cr3S4 scales and linear precipitate structures, an inner corrosion layer dominated by Ni3S2 and NiO, and an outer corrosion layer dominated by Al2O3 networks surrounding the Ni3S2 and/or NiO scale structures. The corrosion mechanism is discussed based on the coexistence of H2O, sulfur, and oxygen. 相似文献
90.