查看更多>>摘要：? 2022 Elsevier B.V.Ternary Co3O4-Ni(OH)2-graphene hybrid nanocomposites (NCs) can be fabricated using a facile, room-temperature kinetic spray process in a single step. The fabricated heterostructure electrodes are optimized to enhance the oxygen evolution reaction (OER) in 1.0 M KOH. The deposited films exhibit a mixture of nanosheet and nanoflake morphologies. Raman spectra reveal improvements in various disorder-related modes in the hybrid NCs due to the nanometer scale and the transformation of graphite-stacked layers into thin graphene nanosheets. X-ray photoelectron spectra indicate that strong synergy improvements in the heterostructure NCs are associated with a downshift of the active state's binding energies. Optimal Co3O4-Ni(OH)2-graphene hybrid ternary NCs exhibit the smallest OER overpotential of 262 mV @ 10 mA·cm?2, the lowest Tafel slope of 32 mV·dec?1, and long-term stability of 25 h at a polarization current of 50 mA·cm?2.
查看更多>>摘要：? 2022 Elsevier B.V.Refractory complex concentrated alloys, RCCAs, show great potential for ultrahigh-temperature applications. High-temperature strength is one of the key requirements for RCCAs to qualify for that purpose. Some RCCAs already show superior high-temperature strength than that of commercial Ni-based superalloys, but many other RCCAs do not. It is thus important to identify the key factors that control the high-temperature strength of RCCAs. In this work, based on a statistic analysis of the yield strength at 1000 °C (σy1000) for 55 reported RCCAs, interestingly, it is revealed that Mo-containing RCCAs have in general a higher σy1000 than those RCCAs not containing Mo. The effect of Mo is attributed to its larger electronegativity and hence the larger electronegativity difference to other alloying elements, rather than to its higher melting point. The previously established proposal that a large electronegativity difference favoring the charge transfer and creating an atomic-level pressure that contributes to the strengthening of RCCAs at room temperature, seems effective even at a high temperature of 1000 °C. In addition, the large electronegativity difference also favors the room-temperature strength of single-bcc-phase RCCAs. The findings from this work, further verified experimentally in six new RCCAs, shed light on new research directions to develop RCCAs with decent strength at both high temperatures and room temperature, using a simple descriptor on the electronegativity difference.
查看更多>>摘要：? 2022 Elsevier B.V.Experimental studies of the temperature dependence of internal mechanical losses in terms of Q?1 in the range from 25 to 120 °C used gypsum stone specimens from the Novomoskovskoye deposit (Tula region, Russia). This investigation is important to determine optimal modes of heat treatment of gypsum stone to obtain construction gypsum. The specimens were cylinders 40 mm in diameter and 75 mm in length with piezoelectric transducers at the ends. They included three types of rocks: gypsum, flint, and thin coal interlayers. The groups included specimens consisting of gypsum without flint layers, two layers consisting of a gypsum layer at one end and a flint layer at the other, and three layers with a flint layer in the middle part of the specimen. Losses Q–1 were determined as f0/(fmax – fmin), where fmax and fmin were frequencies at the level of 1/√2 of the maximum amplitude of sample longitudinal oscillations at the resonance frequency f0. In the temperature range up to 80 °C, the loss Q–1 increased monotonically, while the resonance frequency f0 decreased. There were two maxima of Q–1 and f0 at 85 and 110 °C. The phase transitions of gypsum from dihydrate to hemihydrates (α- and β-hemihydrates) and then to the anhydrous state (dehydrate) caused these maxima.
查看更多>>摘要：? 2022 Elsevier B.V.The composites formed by the coupling of ferrite and Metal-Organic Framework derivatives have attracted wide attention based on the outstanding microwaves absorption properties. In this paper, MnFe2O4 @ZIF-8 was used as the precursor and was carbonized at 700 °C under Ar atmosphere to obtain MnFe2O4 @FeO/C double shell structure. The carbon-coated composite structure is beneficial to enhance the interfacial polarization on the surface of powder particles and enhance the absorbing properties of the material significantly. Among others, the carbon content is controlled by adjusting the content of coated ZIF-8. The double shell nanoparticle shows excellent reflection loss value of ? 53.75 dB at 11.6 GHz with a matching thickness of 1.8 mm, and the corresponding effective absorption bandwidth is 4.74 GHz from 10.27 to 13.90 GHz and 16.89–18.0 GHz.
查看更多>>摘要：? 2022 Elsevier B.V.Magnetic oxides, especially Zinc-Nickel (Zn-Ni) ferrites, are used in devices that transmit and receive electromagnetic signals. We present the synthesis of Zn-Ni ferrite, Nickel ferrite and Zinc ferrite by sonochemically assisted solvohydrothermal method. The elemental analysis revealed that the content of Zn ion in the Zn-Ni ferrite is more. The VSM results displayed superparamagnetic behaviour of Zn-Ni ferrite which could be attributed to smaller particle size. Electromagnetic interference (EMI) shielding materials which dominantly shield by absorption mechanism contain both electric and magnetic dipoles. This is an intrinsic feature of Zn-Ni ferrite materials as it has both high value of magnetic permeability and dielectric constant. The higher contribution of absorption makes it a useful material for various applications such as Radar Absorbing Materials (RAMs). Total shielding efficiency of 28.5 dB for Ni-Ferrite and 30.5 dB for Zn-Ni-Ferrite in X band were obtained, all of which was dominated by shielding efficiency due to absorption. This implies more than 99.99% incident microwaves were successfully attenuated by the materials.
Nagy S.Farajollahi R.Jamshidi Aval H.Jamaati R....
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查看更多>>摘要：? 2022 Elsevier B.V.In this research, the effect of pre-heat treatment of mechtrod and post-processing heat treatment of coating on the microstructure and corrosion behavior of the nickel-aluminide reinforced Al-Cu-Mg alloy coating has been studied. Results show that under a similar heat treatment condition of mechtrod, no significant difference is observed in the coating efficiency of the samples with and without nickel-aluminide reinforcement. The presence of nickel-aluminide intermetallic has acted as a barrier to grain growth, preventing it from occurring to a large extent. After aging heat treatment, the abnormal grain growth (AGG) on a large scale and the AGG and normal grain growth (NGG) in coatings without and with nickel-aluminide, respectively, are well confirmed by Humphreys' model. After artificial aging, the presence of nickel-aluminide reduces the formation of S-Al2CuMg precipitates. Using solid solutionized consumable rod, the corrosion resistance of artificially aged nickel-aluminide containing coating is 64% and 59% higher than Al-Cu-Mg alloy substrate and artificially aged nickel-aluminide free coating, respectively.
查看更多>>摘要：? 2022 Elsevier B.V.The ubiquitous and further deterioration of electromagnetic environment has put forward higher demand for microwave absorption materials with the rapid advancement of 5 G communication and artificial intelligence. Rational manipulation of materials with unique heterojunctions and adjustable electromagnetic properties as lightweight and high-efficiency microwave absorption is the focus and difficulty of research at home and abroad. Schottky junction is designed and fabricated via implanting Fe/MnO2 nanocrystal confined in carbon matrix, wherein core nanoclusters are tailored. Manganese oxide coupling magnetic metallic iron lamellar nanocrystal benefits the improvement of static magnetization and tuning graphitization degree. The fascinating heterojunction by modifying a Schottky junction can not only enable balance among loss capacity and impedance matching, but also can accelerate the carrier migration and promote abundant interfaces. The efficient microwave absorption is optimized yielding maximum reflection loss of ? 53.60 dB and broadening the effective bandwidth of 6.35 GHz. Furthermore, tailoring the morphology of implanted core nanoclusters successfully realizes selective-frequency of microwave absorption. The ternary Fe/MnO2@C composite formed by the self-assembly of Fe/MnO2 nanocrystal core and carbon shell show superior advantages compared to binary composite (e.g., Fe@C, Fe@MnO2, MnO2@C) in microwave absorption performance. Thus, the performances of appropriately tailored nanoclusters with unique architecture endow optimal synergistic effects between magnetic and dielectric loss.
查看更多>>摘要：? 2022Methods of storing hydrogen for energy applications have been widely discussed, both across time and by people from various organisations and backgrounds. Recently, interest in hydrogen storage has developed for space exploration, for both terrestrial and extra-terrestrial applications, and more recently by politicians and business leaders for displacing carbon-intensive fuels. Hydrogen storage options range from solid to gas phases, with several detailed reviews focussing on metal hydrides such as alkali-earth alloys, chemical hydrides such as ammonia, and liquid organic carriers available. An overlooked part of the literature has been hydrogen storage in slurries, where each method of storage has unique advantages, challenges, and stages of research and development. Here, we focus on reviewing the literature on slush hydrogen and slurries of metal and chemical hydrides.
查看更多>>摘要：? 2022 Elsevier B.V.Embedded nanoscale Al particles are promising for improving the toughness of large eutectic Si-phase particles in Al-Si-based alloys. However, the composition and fine structure of such Al particles in Al-Si alloys with Cu addition remain poorly known. Here, through advanced aberration-corrected transmission electron microscopy and electron tomography, we reveal that the void-free particles are composed of a pure Al phase (face-centered cubic structure) and an AlCu phase with three types of crystallographic orientation relationships. The AlCu phase, which possesses a lattice constant of a = 0.300 nm and the space group of Pm3?m, grows at the interface between Al and Si phases. Our study suggests that these Al(Cu) composite particles are directly solidified from the melt during solidification, rather than indirectly precipitated from a Si-Al-Cu solid solution. Heterogeneous nucleation of the AlCu phase on Si surface planes plays a critical role in forming these Al(Cu) particles embedded inside the large brittle Si particles.
查看更多>>摘要：? 2022 Elsevier B.V.In this work, the porous poly(butylene succinate co adipate) (PBSA) was used as the drug matrix for transdermal drug delivery system (TDDS). The porous PBSA matrices were fabricated via solvent casting and particulate leaching method using Tween20 as a pore generator, and the matrices were capable of absorbing the drug solution within 3 s prior to the release. The Fe3O4 magnetic nanoparticles were successfully synthesized via co-precipitation method and successfully coated with pectin through the electrostatic attraction. The 5-fluorouracil, the model drug, was successfully loaded onto the pectin coated Fe3O4 magnetic nanoparticles through the hydrogen bonding. Under magnetic fields, the drug diffusion coefficient increased by the factors of 2 and 5 by the 157 and 247 mT permanent magnets, respectively, whereas the drug release duration was reduced. This was due to the magnetic attraction between the magnetic particles and the magnets. Under the combined electric voltage of 3 V and the magnetic flux of 157 mT, the drug diffusion coefficient increased and the release duration was reduced further, due to the combined driving forces between the magnetic attraction, the electrostatic repulsion of the negative charged pectin layer, and the electro-osmosis. The present work demonstrates the potentials and benefits of the porous matrices along with the combined magnetic and electric fields in the transdermal drug delivery.
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