查看更多>>摘要：? 2022 Elsevier B.V.Manganese oxides attract considerable attention as redox catalysts for abatement of environmental pollutants due to their relatively high activity and low costs contrary to noble metal catalysts. The present work is focused on the effect of cryptomelane-type MnO2 catalyst modification with Fe3+, Ce3+/Ce4+, Sn4+ on their phase composition, structural peculiarities, and catalytic activity in CO oxidation. The samples are investigated by XRD, Raman spectroscopy, XPS, XRF, and comprehensive HRTEM, with their catalytic activity being studied under the model dry conditions and simulated real exhaust conditions comprising CO, O2, and water balanced by inert. The Mn4+ substitution in the cryptomelane structure by Men+ is revealed to result in its monoclinic distortion, with the Sn- and Fe-doped cryptomelane-type MnO2 formation being accompanied by the formation of SnO2 and Fe1?xMnxO3/Fe1+xMn2?xO4, respectively. For Ce-doped samples, the K+ presence in the cryptomelane tunnels is essential to stabilize the cryptomelane structure and nanorod morphology. The cryptomelane structure stabilized by only Cen+ cations is collapsed during the sample calcination to form Mn2?xCexO3 and Mn3?xCexO4, while high Ce content does not favor the formation of the cryptomelane-type MnO2. The composites based on the Me-doped cryptomelane-type α-MnO2, especially those doped with Ce, are shown to be promising candidates to develop effective oxide-based catalysts for CO oxidation.
查看更多>>摘要：? 2022 Elsevier B.V.Piezoelectric materials are undeniably one of the most critical advanced materials in the modern era that can be used as energy harvesters and sensors. In many of these applications, flexibility is a key factor in guaranteeing the proper performance and durability of the device. Polyvinylidene fluoride (PVDF) is a structure-dependent piezoelectric polymer that can provide the required flexibility and piezo-response in its electroactive β-phase structure. The present research aims to investigate the effect of SiC additive and process parameters on the β phase formation in electrospun PVDF fibers. For this purpose, PVDF/SiC nanocomposites were prepared by the electrospinning method, and the effects of PVDF solution concentration, SiC wt%, and electrospinning voltage on β-phase fraction were studied using response surface methodology (RSM) approach for experimental design. The uniform and bead-free morphology of the fibers was observed using scanning electron microscopy (SEM). The results showed that the highest β content could be obtained at low PVDF concentrations, high electrospinning voltage and high SiC wt%. The dominant crystalline phase was determined by XRD analysis, and the β-phase fraction in nanocomposites containing different SiC loadings was estimated using FTIR spectroscopy. The presence of SiC nanoparticles enhanced the piezoelectric behavior of PVDF/SiC nanocomposites due to the higher β-phase fraction and improved charge transfer in the vicinity of semiconductive SiC nanoparticles. The optimum sample containing 3.98 wt% SiC nanoparticles was composed of 95.9% β-phase and showed a normalized piezoelectric sensitivity of 0.4737 mV/N, which was improved by about 350% compared to pure PVDF fibers. The obtained results show that PVDF/SiC nanocomposite fibers can be a promising choice for nanoenergy harvesters or flexible sensors with high sensitivity to small external loads.
查看更多>>摘要：? 2022 Elsevier B.V.The Zn3In2S6/Bi2MoO6 S-scheme heterojunctions with excellent redox ability were prepared. The photocatalyst was synthesized by hydrothermal reaction. In photocatalytic materials with different mass ratios, the highest reaction constant (Zn3In2S6/Bi2MoO6-10%) is 0.0463 min?1, which is 2.17 times higher than that of single Zn3In2S6. The experiment also proved that the Zn3In2S6/Bi2MoO6 had high stability. At the same time, the preparation cost of Zn3In2S6/Bi2MoO6 is also lower than that of other high-efficiency photocatalysts. The degradation path of metronidazole was inferred from the results of LC-MS. This study can provide a strong basis for the degradation of pollutants by S-scheme heterojunctions.
查看更多>>摘要：? 2022 Elsevier B.V.Perovskite oxides with a low overpotential and fine stability for oxygen evolution reaction (OER) are critical for achieving efficient energy conversion and storage. Herein, we reported a simple one-step approach to synthesize SrCo0.5Fe0.3Mo0.2O3-δ/Co3O4 heterostructure catalyst by adjusting the stoichiometric ratio of Co in the perovskite of SrCoxFe0.3Mo0.2O3-δ. Multiple active sites, abundant oxygen vacancies and rapid charge transfer induced by dispersed and tight interfaces generate unique synergy. SrCo1.7Fe0.3Mo0.2O3-δ oxide with optimized composite structure only needs 277 mV to reach a current density of 10 mA cm?2 and shows a negligible overpotential rise after chronopotentiometry test in 1.0 M KOH. The cost-effective hybrid approach reported in this work could be extended to other hybrid systems, and this excellent electrocatalyst could also be a promising candidate for overall water splitting.
查看更多>>摘要：? 2022 Elsevier B.V.Heterostructures with wide and narrow band gap semiconductors may harvest short and long wavelength light for enhancing photoelectric response. Here we adopt narrower-band-gap KBiO3 to combine with wider-band-gap NaBiO3 for KBiO3/NaBiO3 heterostructures by adding KOH into NaBiO3. The band gaps of the heterostructures change with the ratios of KOH:NaBiO3 in raw materials and are abnormally narrower than that of KBiO3. The interfaces between KBiO3 and NaBiO3 change with their ratios and then their interactions vary. The width and intensity of surface photovoltage spectra of the heterostructures increase notably in the visible light region, which results from prolonged lifetime of photogenerated electrons transferring from KBiO3 to NaBiO3.
查看更多>>摘要：? 2022 Elsevier B.V.Metal-organic frameworks (MOFs) have been widely investigated as electrocatalysts for the oxygen evolution reaction (OER). However, their catalytic performance needs to be further improved. Herein, a multi-pronged approach combining multi-metallic MOFs, 2D ultrathin structures and MOF hybridization was attempted. Specifically, the nanocomposite of lamellar NiFe-BTC and nanowire-like cobalt carbonate hydroxide hydrate (CCHH) was prepared on nickel foam (NF) by a two-step method. The as-prepared NiFe-BTC/CCHH/NF nanocomposite displayed excellent OER performance with an overpotential of 270 mV at a current density of 50 mA cm?2 and good stability in 1.0 M KOH. To construct an overall water splitting electrolytic cell, the phosphorization product of CCHH/NF (P-CCHH/NF) with high catalytic activity for hydrogen evolution reaction (HER) was used as the cathode. The water splitting electrolytic cell with NiFe-BTC/CCHH/NF as anode and P-CCHH/NF as cathode was highly efficient and stable, which only needed a voltage of 1.55 V to reach a current density of 10 mA cm?2. This multi-pronged approach is expected to inspire other researchers to design high-performance OER catalysts.
查看更多>>摘要：? 2022 Elsevier B.V.It is shown that CuIn alloys can be effectively used as spacers in GMR multilayers. Attention is paid to the method of obtaining of the homogeneous CuIn alloys. Magnetron targets Cu1-xInx with an indium content х = 2–8.7 at% have been used for preparation of exchange-coupled multilayers of the composition glass/Ta(5)/Ni48Fe12Cr40(5)/[Co90Fe10(1.3)/Cu1-xInx(2–2.2 nm)]7/Ta(5). A decrease in GMR ratio was found with an increase in the content of indium in the alloy Cu1-xInx. For x < 4.7 at% a slight decrease in magnetoresistance is observed. The sharpest decrease in the GMR ratio from 23.3% to 3.2% is observed when the indium content changes in the range x = 4.7–8.7 at%. It is demonstrated that the coercivity of CoFe/Cu1-xInx multilayers decreases more than 5 times when the indium content increases in the range of х = 0–4.7 at. %. A correlation between the crystallite sizes in multilayers and the change of coercivity has been revealed. It is shown that the substitution in the multilayers studied of Co90Fe10 alloy by Co-rich ternary ferromagnetic alloys Co77Fe17Ni6 and Co70Fe20Ni10 made it possible to obtain CoFeNi/CuIn multilayers with GMR ratio of 25–29%, extremely low coercivity of several Oe, and high linearity of the field dependence of magnetoresistance. The combination of these characteristics is useful for practical applications.
查看更多>>摘要：? 2022 Elsevier B.V.Nano-TiC powders were doped to increase the corrosion resistance of hot-deformed NdFeB magnets. Effects of the dopant content on their electrochemical corrosion behavior in sulphuric acid solutions were studied by various measurement techniques including potentiodynamic polarization, electrochemical impedance spectroscopy, scanning electron microscopy and X-ray photoelectron spectrometer. Results showed that low additions of nano-TiC especially at the optimum content of 0.5 wt% can obviously increase the resistances and reduce the corrosion current density. It is ascribed to the dopant hindrance effects on the dissolution of Nd-rich phases and the coverage increase of intermediate products on NdFeB substrate induced by nano-TiC that acted as the favorable sites for adsorption reactions. Maximum increase in inductive resistance and the corresponding reduction in current density were found to be 60.6% and 36.1%, respectively. In addition, the effect mechanism of nano-TiC on corrosion behaviors was discussed based on experimental results.
查看更多>>摘要：? 2022 Elsevier B.V.Bulk BaTiO3-xCoFe2O4, x = 0.1 – 0.6 magnetoelectric composites were prepared using the phosphate bonded ceramics approach. XRD analysis proved the purity of both phases. The dielectric properties are governed by a series of composition-dependent Maxwell-Wagner relaxations and conductivity at lower frequencies and a phase transition-related anomaly at higher frequencies. A dielectric constant as high as 616 – 9387i is observed at 500 K for BaTiO3-0.6CoFe2O4. The magnetic hysteresis demonstrates a high Ms/Mr ratio of 0.46, which is related to the around 30 nm size of the CoFe2O4 particles. The measured direct magnetoelectric coupling coefficient of 1.1 mV Oe?1 cm?1 is higher than that of the conventionally sintered ceramics and compatible with that of core-shell structures.
查看更多>>摘要：? 2022 Elsevier B.V.Magnetocaloric (MC) cooling is a vast research field nowadays which needs continuing development of MC materials. Besides, technological approaches of the fabrication and design of MC materials to be applied as the heat exchangers require a reinforcement. Heusler-type metamagnetic shape memory alloys (MetaMSMAs) exhibiting a large MC effect near room temperature, owing to the magnetic field induced first-order transformation, have been shown to be promising candidates for magnetic refrigeration, and the possibility of their fabrication by 3D printing technologies was experimentally demonstrated in the literature. In the present work we have elaborated a route for the room-temperature fabrication of MC ink incorporating the polymer binder and Ni(Co)-Mn-Sn MetaMSMA powder obtained from the preliminary melt-spun ribbon with tuned MC properties. The ink is used to print 2D films which do not require a subsequent heat treatment. The field-induced adiabatic temperature measurements reveal that the screen-printed samples displayed the same inverse MC effect as the ribbon, evidencing that room-temperature ink printing technology of MC intermetallics, elaborated for the first time in the present work, is promising for 2D printing of cooling microdevices for MEMS, flexible electronics etc.
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