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51.
Dealloyed nanoporous gold (np-Au) has applications as oxygen reduction catalysis in Li-air batteries and fuel cells, or as actuators to convert electricity into mechanical energy. However, it faces the challenges of coarsening-induced structure instability, mechanical weakness due to low relative densities, and slow dealloying rates. Here, monolithic np-Au is dealloyed from a single-phase Au25Ni75 solid-solution at a one-order faster dealloying rate, ultra-low residual Ni content, and importantly, one-third more relative density than np-Au dealloyed from conventional Au25Ag75. The small atomic radius and low dealloying potential of the sacrificing element Ni are intrinsically beneficial to fast produce high relative density np-Au, as predicted by a general model for dealloying of binary alloys and validated by experiments. Stable, durable, and reversible actuation of np-Au takes place under cyclic potential triggering in alkaline and acidic electrolytes with negligible coarsening-induced strain-shift. The thermal and mechanical robustness of bulk np-Au is confirmed by two-order slower ligament coarsening rates during annealing at 300 °C and 45 MPa macroscopic yielding strength distinctive from the typical early onset of plastic yielding. This article opens a rich direction to achieve high relative density np-Au which is essential for porous network connectivity, mechanical strength, and nanostructure robustness for electrochemical functionality. 相似文献
52.
Norman Kauss Andreas Heyn Oliver Michael Michael Schymura Paul Rosemann 《工业材料与腐蚀》2021,72(10):1656-1667
Nickel-free high-nitrogen-alloyed stainless steels like the P2000 (X13CrMnMoN18-14-3) were developed to enhance the strength and corrosion resistance of austenitic stainless steels like 304 and 316 while keeping the typical high ductility. The mechanical and corrosive properties of P2000 were investigated and compared with 304 and 316 to highlight the application opportunities of this new alloy. The microstructure of the solution-annealed condition was characterised by electron backscatter diffraction and the mechanical properties were studied by uniaxial tensile tests, Charpy impact tests and hardness measurements. The passivation behaviour was analysed using the electrochemical potentiodynamic reactivation, whereas the pitting corrosion resistance was compared by pitting potentials and pitting temperatures. However, secondary thermal influences or suboptimal heat treatment can impair the corrosion resistance due to the precipitation of secondary phases and the resulting sensitisation. Thermodynamic calculations and artificial ageing treatment in the range of 500–900°C for up to 100 h were used to determine critical time–temperature parameters for sensitisation. The microstructure of the various aged states was evaluated by scanning electron microscopy and compared with the degrading corrosion resistance characterised by the KorroPad method. 相似文献
53.
Ekaterina Koroleva Ilya Reshetov Ekaterina Babich Sergey Vakhrushev Dmitry Tagantsev Andrey Lipovskii 《Journal of the American Ceramic Society》2022,105(5):3418-3427
Broadband dielectric spectroscopy (BDS) was applied to study polarization phenomena in alkaline silicate glasses, in particular, properties and structure of subsurface (anodic) polarized layers forming in poling with deposited film electrodes of different structures. A model of poled glasses which does not contradict experimental data is proposed. In accordance with the model, a poled glass is presented as two resistor-capacitor circuits in a series connection, one of which is the polarized layer and another is the rest of the sample. It is found that the electric properties of the layers essentially depend on the structure of the anodic electrode used in glass poling. It is also shown that the dielectric response of poled glass samples is mainly determined by the electric properties of the submicron polarized layers and this gives an opportunity to reveal specific properties of the layers rather than ones of the glass sample bulk. Revealed temperature dependence of DC conductivity of the polarized layers obeys Arrhenius's law, and determining activation energy does not depend on the electrode. Finally, it is noted that today above-mentioned information about polarized layers can be obtained only by BDS. 相似文献
54.
Kowsik Ghosh M. Mangir Murshed Michael Fischer Thorsten M. Gesing 《Journal of the American Ceramic Society》2022,105(1):728-741
Mullite-type RMn2O5 (R = Y, rare-earth element) ceramics are of ongoing research attentions because of their interesting crystal-chemical, physical, and thermal properties. We report a detailed structural, spectroscopic and thermal analysis of the series of mullite-type RAlGeO5 (R = Y, Sm-Lu) phases. Polycrystalline samples are prepared by solid-state synthesis methods. Each sample is characterized by X-ray powder diffraction followed by Rietveld refinements, showing that they are isotypic and crystallize in the space group Pbam. The change of the metric parameters is explained in term of the lanthanide contraction effect. A rare inversion of Al/Ge between octahedral and pyramidal sites have been observed for these mullite-type so called O10 compounds, and the inversion parameter found to be between 0.22(1) and 0.30(1) for different R-cations. The <Al/Ge–O> bond distances and their bond valence sums (BVSs) support the respective inversions. Density functional theory (DFT) calculated phonon density of states (PDOS) and electronic band structures are compared for the vibrational and electronic band gap features respectively. Analysis of UV/Vis absorption spectra using both derivation of absorption spectra fitting (DASF) and Tauc's methods demonstrates that each of the RAlGeO5 O10 compounds is high bandgap semiconductor, possessing direct transition between 4.1(1) and 5.4(1) eV. Both Raman and Fourier transform infrared spectra show clear red shift (quasi-harmonic) of the vibrational wavenumbers with respect to the ionic radii of the R-cations. Selective Raman bands at higher wavenumber region further complement the inversion of Al/Ge between two coordination sites. The higher decomposition temperature of the RAlGeO5 compounds, compared to those of RMn2O5 phases, is explained in terms of higher bond strength of Al/Ge-O than those of Mn-O. Irrespective to the inversion between Al- and Ge-sites, the decomposition temperature also depends on the type of R-cation in RAlGeO5. 相似文献
55.
Tae-min Yeo Jung-Wook Cho Ivan Hung Zhehong Gan Sabyasachi Sen 《Journal of the American Ceramic Society》2022,105(10):6140-6148
The structure of mold flux glasses in the system CaO-(Na,Li)2O-SiO2-CaF2 with unusually high modifier contents, stabilized by the addition of ∼4 mol% B2O3, is studied using 7Li, 23Na, 19F, 11B, and 29Si magic-angle-spinning (MAS), and 7Li{19F} and 23Na{19F} rotational echo double-resonance (REDOR) nuclear magnetic resonance (NMR) spectroscopy. When taken together, the spectroscopic results indicate that the structure of these glasses consists primarily of dimeric [Si2O7]−6 units that are linked to the (Ca,Na,Li)-O coordination polyhedra, and are interspersed with chains of corner-shared BO3 units. The F atoms in the structure are exclusively bonded to Ca atoms, forming Ca(O,F)n coordination polyhedra. This structural scenario is shown to be consistent with the crystallization of cuspidine (3CaO·2SiO2·CaF2) from the parent melts on slow supercooling. The progressive addition of Li to a Na-containing base composition results in a corresponding increase in the undercooling required for the nucleation of cuspidine in the melt, which is attributed to the frustrated local structure caused by the mixing of alkali ions. 相似文献
56.
《Ceramics International》2022,48(15):21856-21867
In this work, ZnO nanowires with high aspect ratio were obtained by fast and simple electrochemical anodization. Morphological, structural and photoelectrochemical characteristics of the synthesized ZnO nanowires were evaluated by using different techniques: field emission scanning electron microscopy, atomic force microscopy, high resolution transmission electron microscopy, Raman spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, UV–VIS spectroscopy, Mott-Schottky analysis and photoelectrochemical impedance spectroscopy. The synthesized ZnO nanowires presented high roughness and high crystallinity. Besides, surface defects were identified in the sample. The value of the donor density (ND) was in the order of 1019 cm?3 in the dark and 1020 cm?3 under illumination. In addition, the ZnO nanowires presented good photosensibility, with a photocurrent density response 85 times higher than a ZnO compact layer, and lower resistance to charge transfer. The charge transfer processes taking place at the ZnO/electrolyte interface were studied, since these processes strongly influence the photoelectrocatalytic efficiency of the material. According to the results, the charge transfer of holes in the synthesized ZnO nanowires occurs indirectly via surface states. In this regard, surface states may be an important feature for photoelectrocatalytic applications since they could provide lower onset voltages and higher anodic current densities. 相似文献
57.
S.N. Shkerin A.V. Rudakova K.M. Bulanin A. Sh Khaliullina A.N. Meshcherskikh E.G. Vovkotrub L.A. Dunyushkina 《International Journal of Hydrogen Energy》2021,46(32):17007-17018
The present research describes the results of Raman spectroscopic study of undoped and Y-doped SrZrO3 having a great potential for application in proton-conducting fuel cells. Effects of yttrium doping and strontium nonstoichiometry on the local environment of cations and vibrational properties of strontium zirconate were investigated. Ceramic samples SryZr1-xYxO3-δ (x = 0, 0.02, 0.05; y = 0.94, 0.98, 1.00) were synthesized via a chemical solution method and sintered at 1650 °C. Microstructure, phase and chemical composition of the samples were characterized by Scanning Electron Microscopy (SEM), X-ray diffraction (XRD) and Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES). Analysis of Raman spectra peculiarities upon changes in Sr- and Y- concentrations has shown that yttrium ions can be partitioned over both A- and B-sites in the strontium-deficient zirconates with the dopant concentrations more than 2 at%. 相似文献
58.
为研究加工方式对玉筋鱼干风味的影响,实验按加工方式分为加盐煮制冷风干燥(boiling in salt solution followed by cold air drying,SCC)组和冷风干燥(cold air drying,CD)组。采用电子鼻技术、气相离子迁移谱(gas chromatography-ion mobility spectroscopy,GC-IMS)技术、氨基酸自动分析技术、高效液相色谱技术测定玉筋鱼干中的风味成分。结果表明,不同加工方式制作的玉筋鱼干在气味、滋味方面存在显著差异。电子鼻、GC-IMS技术均能区分不同工艺制作的玉筋鱼干气味,采用GC-IMS技术共分析出68 种挥发性成分,庚醛、戊醛、3-甲基丁醛对玉筋鱼干独特风味的形成有重要影响,其中3-甲基丁醛源自CD工艺,其区别于SCC工艺气味的关键物质。玉筋鱼干中的主要鲜味氨基酸是Glu,主要呈味核苷酸是肌苷酸;CD组玉筋鱼干中的鲜味氨基酸和甜味氨基酸含量占总游离氨基酸的比重高于SCC组,同时CD组滋味活性值、味精当量值均高于SCC组,所以仅采用CD工艺制作的玉筋鱼干滋味优于加盐煮制后CD工艺制作的玉筋鱼干。 相似文献
59.
Mehrzad Soleimany M.H. Paydar Shaorong Wang 《International Journal of Hydrogen Energy》2021,46(19):11115-11126
In the present work, effects of nickel oxide doping on flash-sinterability of BaZr0.1Ce0.7Y0.2O3-δ compound were investigated. A single-phase BZCY7 powder was synthesized by the solid-state reaction route. The effects of using 0.5, 1, 1.5, and 2 wt% of NiO additive on flash sintering of BZCY7 samples were examined. It was revealed that using 0.5 wt% of NiO additive can reduce the onset temperature of flash sintering in all the applied electric fields in the range of 100–500 V/cm and significantly enhances the sinterability of the BZCY7 compound. Microstructural investigations, using field emission scanning electron microscopy and energy-dispersive X-ray mapping, showed that NiO doping can lead to larger grain sizes, while no detectable segregation or second phase was observed. Utilizing electrochemical impedance spectroscopy, the total conductivity of samples at 600 and 700 °C was measured as 4.4 × 10?3 and 7.0 × 10?3 S/cm for the undoped BZCY7, and 8.6 × 10?3 and 1.4 × 10?2 S/cm for the 0.5 wt% NiO doped BZCY7 sample, respectively. The activation energies of conduction were determined as 0.37 and 0.41 eV for the doped and undoped samples, which represent the presence of predominant and facile protonic conduction. 相似文献
60.
Dispersion of nanocrystalline (94–350 nm) Ce0.9Gd0.1O2-δ in superfine (260–312 nm) Sm1.5Sr0.5NiO4+δ using modified precipitation technique is established using X-ray powder diffraction, scanning electron microscopy and transmission electron microscopy. Presence of Ce0.9Gd0.1O2-δ grains inhibits grain growth of Sm1.5Sr0.5NiO4+δ, which provides morphological stability (up to 1100 °C). Ce0.9Gd0.1O2-δ concentration dependent behaviours of ionic conductivity, surface exchange rate and electrode polarization resistance (Rp) of composites (determined using electrochemical impedance spectroscopy) are comprehended using percolation model. Three oxygen reduction reaction mechanisms are considered to understand electrochemical performance. Minimum Rp (0.81 Ω cm2 at 700 °C) for 70Sm1.5Sr0.5NiO4+δ:30Ce0.9Gd0.1O2-δ is correlated to percolation threshold (optimum (i) electrochemically active sites (ii) oxygen reduction reaction kinetics, (iii) O2- conductivity and (iv) charge transfer rate). Nano crystallite size of Ce0.9Gd0.1O2-δ is crucial for enhancement in electrochemical performance. Oxygen partial pressure dependent electrochemical impedance spectroscopy studies reveal dominance of coexisting non-charge transfer oxygen adsorption/desorption and bulk O2- diffusion. 相似文献