查看更多>>摘要：? 2022 Elsevier B.V.In this paper, CuO/MnO2 composites with different morphology were successfully fabricated by simple and economical electrodeposition and successive ionic layer adsorption and reaction (SILAR) method as electrode materials for supercapacitors (SCs). The spherical and wheat-shaped CuO/MnO2 composites were obtained by changing the deposition voltage. The wheat-shaped CuO/MnO2 composite electrodes exhibited better electrochemical performance than the spherical. Its areal capacitance is up to 261.4 mF/cm2 at a current density of 1 mA/cm2 in 1 M Na2SO4 electrolyte and the capacitance retention reaches 90% after 1000 charge-discharge cycles. The symmetric aqueous SCs was then assembled with wheat-shaped CuO/MnO2 as positive and negative electrode materials respectively. The SCs exhibited not only outstanding specific capacitance of 152.7 mF/cm2 at 1 mA/cm2, but also good cycling stability of 74.2% after 500 charge-discharge cycles. Furthermore, its operating voltage window reaches 1.6 V, which results in an outstanding energy density of 54.3 μWh/cm2 and a power density of 5040 μW/cm2. This strategy of changing the morphology of materials by changing the deposition voltage provides an ideal scheme for improving the properties.
查看更多>>摘要：? 2022 Elsevier B.V.Zero dimensional perovskite CsPbX3 and Cs4PbX6 (X[dbnd]I, Br and Cl) quantum dots are becoming a potential object for optoelectronic device applications. However, the instability of perovskite CsPbX3 and Cs4PbX6 quantum dots in air hinders their wide practical application. The perovskite quantum dots embedded in glass matrix can improve their stability, and the perovskite CsPbX3 quantum dots embedded in the glass were extensively reported. In this work, a novel borophosphate glass containing Cs4PbBr6 quantum dots was prepared. The morphological characteristics of Cs4PbBr6 quantum dots in the glass were analyzed by transmission electron microscopy. The luminescence characteristics of Cs4PbBr6 quantum dots are exhibiting the green luminescence. The luminescence intensity of Cs4PbBr6 quantum dots embedded in glass can still maintain about 94% after immersion in water for 240 h, which overcome the instability of perovskite Cs4PbBr6 quantum dots affected easily by environment. The results demonstrated that the boron phosphorus fluorine antimony glass containing Cs4PbBr6 quantum dots may have a potential application prospect in solid-state lighting and display area.
查看更多>>摘要：? 2022 Elsevier B.V.Sintering of ferrite materials requires sensitive control of homogeneity that affects electromagnetic properties. The paper proposes a method for analysis of chemical homogeneity of ferrite ceramics based on mathematical analysis of differential temperature dependences of the initial permeability near the Curie point. The method was tested on model samples of LiTiZn ferrite ceramics doped with Al2O3 or ZrO2 of 0.10, 0.25, 0.5 0.75, and 1 wt%. It was found the effect of doping agents on the ferrite lattice parameter is insignificant, and they are not indicated on the diffraction patterns as separate peaks. SEM data show a weak effect of Al2O3 doping agent on the average grain size of ferrite ceramics. At the same time, the effect is more pronounced for ZrO2 due to secondary recrystallization. In this case, the coercive force shows a particular increase as compared with undoped samples: by 23% and 60% for Al2O3 and ZrO2 respectively of doping agents’ concentration increased to 1 wt%. The paramagnetic-to-ferrimagnetic transition of ferrites near the Curie point is highly sensitive to chemical homogeneity of the material. It was shown that the width of the differential temperature dependence peak of the initial permeability can be used to assess chemical homogeneity of ferrimagnetic ceramics. The peak width was found to increase by 75%. Therefore, the proposed method revealed a higher sensitivity compared to XRD and hysteresis loops.
查看更多>>摘要：? 2022 Elsevier B.V.Reduced graphene oxide (rGO)-Mn(NO3)2·4H2O pastes were screen-printed on a carbon cloth substrate and then calcined using a nitrogen atmospheric-pressure-plasma-jet (APPJ) and/or tube furnace to convert it into rGO-MnOx. The rGO-MnOx electrodes were then used in a PVA/H2SO4 gel-electrolyte supercapacitor (SC). The SCs were characterized by cycle voltammetry (CV) and galvanostatic charging/discharging (GCD). The results reveal better performance of the APPJ-processed SCs in comparison with furnace-processed ones under the same processing temperature, possibly owing to the synergetic effect of heat and reactive nitrogen plasma species. The rGO-MnOx SC is also superior to the rGO-SnOx SC reported in our previous study processed under similar APPJ processing. The rGO-MnOx SC processed by APPJ at 620 °C for 8 min exhibits the best areal capacitance of 57.01 mF/cm2 as evaluated by GCD with a capacitance retention rate of 84.41% after a 10,000-cycle CV test.
查看更多>>摘要：? 2022 Elsevier B.V.In this study, a new perovskite compound Ba(Y0.25Zr0.5Nb0.25)O3 with three B-site elements is reported. This was successfully synthesized by solid-state reaction method at 1300 °C for 6 h using BaCO3, Y2O3, Nb2O5 and ZrO2 as raw materials. The structural properties of Ba(Y0.25Zr0.5Nb0.25)O3 were studied by X-ray diffraction (XRD) technique and further refined by Rietveld method as well as the transmission electron microscopy (TEM). The result shows that the space group of Ba(Y0.25Zr0.5Nb0.25)O3 is Pm-3 m with lattice constant a= 4.2081 ?. By using the empirical formula with the ionic radius and tolerance factor, the calculated lattice constant (a=4.2079 ?) is similar to the measured value, which also proved that the lattice constant prediction model of ideal perovskites is still applicable to multi-B sites perovskites. Compared with BaZrO3, the partly substitution of Zr atoms by Y and Nb atoms has an improvement on increasement of the lattice constant. This study provides insights into the process of designing new perovskites as buffer materials to solve the lattice mismatch problem for large lattice constant perovskites thin film.
查看更多>>摘要：? 2022 Elsevier B.V.In this study, SrGd2O4: xSm3+ (x = 0%, 0.5%, 1%, 2%, 3%, 4%, and 5%) phosphors were synthesized using solid state reaction method. X-ray diffraction (XRD) measurements confirmed a orthorhombic structure (space group Pnam (62)) of synthesized compounds. Following irradiation with 10 Gy beta dose, the sample doped with 0.5% Sm exhibited the highest integrated thermoluminescence (TL) intensity with the IRSL-TL wideband blue filter. In order to evaluate dose-response, samples were irradiated with beta radiation for 0.1–10 Gy. The Hoogenstraaten's method, the initial rise method, combined with the TM-Tstop experiment, and glow curve fitting package were employed to determine the number of peaks, the trap structure, and the kinetic parameters of the thermoluminescence glow curve of Sm doped SrGd2O4. Based on the glow curve deconvolution obtained using software package, the component TL glow peaks present in the complex glow curve are composed of well-isolated five overlapping glow peaks.
查看更多>>摘要：? 2022 Elsevier B.V.The corrosion resistance of 7075 aluminum (Al) alloy treated by ultrasonic surface rolling process (USRP) in a chloride environment was studied in this work. The effects of different USRP passes on the surface state (surface roughness and residual stress), surface microstructure, and corrosion resistance of this alloy were investigated through microstructural characterization, stress relaxation, immersion testing and electrochemical measurement. The results revealed that all USRP-treated samples demonstrated significantly improved corrosion resistance. However, the main factors that led to this performance enhancement were not the same. After 3 USRP treatment passes, the reduction in surface roughness and the increase in surface compressive residual stress improved the corrosion resistance of the 7075 Al alloy. After 7 USRP passes, the larger number of grain boundaries caused by surface grain nanocrystallization led to the rapid enrichment of passive elements, which formed a dense passive film on the alloy surface. At the same time, the dissolution of precipitates and the disappearance of precipitation-free zones (PFZ) reduced the corrosion caused by anodic dissolution. Meanwhile, the primary mechanism that controlled the corrosion rate was transformed from the surface state to the surface microstructure, which further improved the corrosion resistance of the 7075 Al alloy.
查看更多>>摘要：? 2022 Elsevier B.V.Secondary aluminum dross is a solid waste discharged during aluminum processing and melting. Calcium aluminate glass-ceramics was manufactured from secondary aluminum dross without adding nucleating agent. Phase transition of glass-ceramics was studied. Nucleation temperature was set at 846 ℃ according to differential scanning calorimetry and X-ray diffraction results. Field-emission transmission electron microscopy was applied to observe microstructure of the thermally treated parent glass. During nucleation process, omphacite grew from glass network. Omphacite growth consisted of two steps: migration of silicon group and cation; growth of omphacite. After parent glass was thermally treated at 846 ℃ for 3 h, silicon group and cation migrated and formed silicon enrichment field. A little of omphacite crystal formed in silicon enrichment field. When thermal treatment time was increased to 12 h, more independent omphacite crystals grew in silicon enrichment field. The independent omphacite crystals grew larger and contacted with each other to form a large omphacite crystal. The large omphacite crystal became nucleus of glass-ceramics. Omphacite nucleation had two effects on crystallization of glass-ceramics. First, omphacite crystal became nucleus, which provided surface for growing crystals. Second, omphacite growth consumed silicon group in glass network, which decreased polymerization degree of glass network and promoted crystallization. In calcium aluminate glass-ceramics with silicon, omphacite crystal could act as the nucleus without additional nucleation agents.
查看更多>>摘要：? 2022 Elsevier B.V.The NiCr/Al nanomultilayered films with different Al thicknesses (tAl) were prepared by magnetron sputtering. The structural evolution of the Al nanolayer with the increase in tAl was investigated. When the Al layer thickness changed from 1.2 nm to 2.4 nm, the Al layer could keep the co-epitaxial growth with the adjacent NiCr layer. Accordingly, the crystallization degree improved. When the Al layer thickness changed from 2.4 nm to 3.0 nm, the transformation from the coherent to incoherent interfaces took place between the NiCr and Al layers. Meanwhile, the co-epitaxial growth with the adjacent NiCr nanocrystallites was destroyed, the crystallinity and the grain size decreased, leading to the increase of the resistivity under the combined effects of the grain boundary scattering and interface scattering. The interfacial evolution of NiCr/Al nanomultilayered films was closely related to the changes of electrical properties. When the Al layer thickness changed from 3.0 nm to 3.6 nm, the surface quality of the film was improved, which effectively reduced the scattering of defects and vacancies during the electron transport, resulting in the decrease of the resistivity of the NiCr/Al nanomultilayered film.
查看更多>>摘要：? 2022 Elsevier B.V.Luminescence thermometry based on the variation of the fluorescence intensity ratio (FIR) of rare-earth materials has become fascinating owing to their applicability in chemically and electromagnetically harsh environments. Relevant to their practical applicability, a wide temperature sensing range is urgently required for luminescent thermometric materials besides possessing a high relative sensitivity. Herein, we have demonstrated that pyrochlore La2Zr2O7:Pr3+ (LZOP) nanoparticles (NPs) can serve as a promising optical temperature sensing material over a wide temperature range of 620 K. Specifically, we have taken advantage of the intervalence charge transfer state (IVCT) of Pr3+ doping ion for luminescence temperature sensing and confirmed excellent optical thermometric performance from the LZOP NPs in a temperature sensing range of 85–705 K. The thermal sensing here could be measured by exploiting one thermometric parameter, i.e. the FIR between 1D2→ 3H4 and 3P0 → 3H4 transitions of Pr3+, and thus we only need to use one calibration formula for the whole temperature range. A maximum relative sensitivity of> 0.4%·K?1 from 165 to 205 K and a low temperature uncertainty of 1.21 K at 185 K is obtained. Based on the proposed configurational coordinate diagrams, A high-lying IVCT state was demonstrated to be the cause for slow thermal quenching at high temperatures, which broadened the working range of our thermometric sensing materials. This work provides a useful inspiration for exploring appropriate host materials with slow thermal-quenching channels to develop optical thermometric materials over a wide temperature sensing range.
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