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Super-Small TiO2 Nanoparticles Homogeneously Embedded in Mesoporous Carbon Matrix Based on Dental Methacrylates and KOH Activation
No full textMesoporous TiO2/C nanohybrids with large specific surface area and well-defined pore size distribution are prepared by KOH activation treatment using dental resin monomers as solvent and carbon source. Super-small sized TiO2 nanoparticles are uniformly distributed in porous carbon to realize a significant improvement of the electrochemical properties. The morphology, BET specific surface area and pore size distribution are characterized by SEM, TEM and N-2 adsorption/desorption isotherm, respectively. The prepared mesoporous TiO2/C delivers a reversible capacity as high as 387 mAh/g after 100 discharge/charge cycles at 0.2 C current density (1 C=335 mA/g) in conjunction with a good rate capability (184, 70, and 92 mAh/g at 1, 2, and 5 C current densities, respectively)
Effect of pre-existing nuclei on microstructure and magnetic properties of high B-s FINEMET-like nanocrystalline alloys
No full textThe effect of conventional annealing and rapid annealing on the magnetic properties and microstructure of Fe78+2xSi7.2-xB13-xCu0.8Nb1 (x = 0, 1, 2) alloys is discussed systematically. The study was found that the existence of a large number of pre-existing nuclei in the amorphous phase of Fe82Si5.2B11Cu0.8Nb1 alloy can produce tiny nanocrystals and thus result in excellent soft magnetic properties. When the average nanocrystal size is 16 nm using rapid annealing, the best soft magnetic performance can be obtained, in which B-s reaches 1.80 T, H-c is 5 A/m, and mu is 20,000 at 1 kHz. The crystallization kinetics shows that as the Fe content increases, the incubation time of nucleation of the alloys decreases, and the nucleation is faster and easier. In addition, a large number of pre-existing crystal nuclei not only greatly reduces the nucleation activation energy of the alloy but also achieves grain refinement and excellent magnetic properties through grain competition growth
Fabrication of environmentally friendly Losartan potassium film for corrosion inhibition of mild steel in HCl medium
No full textThe present study aimed to find a suitable alternative for traditional and hazardous corrosion inhibitors. A green antihypertensive drug-Losartan potassium (LP) with superior corrosion protection ability was developed for the first time. Gravimetric method, potentiodynamic polarization, AC impedance, and scanning vibrating electrode technique (SVET) were combined to evaluate the corresponding inhibition performance towards Q235 steel in HCl medium. The results indicated that LP exhibited superior mixed-type corrosion protection to steel at different temperatures owing to the formation of compact and ordered LP-adsorption film on steel surface. Specifically, the inhibition performance values increased to 88.9%, 91.8%, and 92.0% for 5 mM LP at 298, 308, and 318 K, respectively. Meanwhile, N-Fe bond from X-ray photoelectronic spectroscopy (XPS) implied multiple anchoring interaction between steel and LP with nitrogen atoms as active sites. Based on DFT calculation and molecular dynamics (MD) simulation, the obtained low energy gap (AE) and high Ebinding, values as well as radial distribution function (RDF) analysis represented strong chemisorption of LP on Fe substrate, which theoretically explained the favorable inhibition effectiveness of LP compound at molecular or atomic level
All-Optically Reconfigurable Plasmonic Metagrating for Ultrafast Diffraction Management
No full textHot-electron dynamics taking place in nanostructured materials upon irradiation with Is-laser pulses has been the subject of intensive research, leading to the emerging field of ultrafast nanophotonics. However, the most common description of nonlinear interaction with ultrashort laser pulses assumes a homogeneous spatial distribution for the photogenerated carriers. Here we theoretically show that the inhomogeneous evolution of the hot carriers at the nanoscale can disclose unprecedented opportunities for ultrafast diffraction management. In particular, we design a highly symmetric plasmonic metagrating capable of a transient symmetry breaking driven by hot electrons. The subsequent power imbalance between symmetrical diffraction orders is calculated to exceed 20% under moderate (similar to 2 mJ/cm(2)) laser fluence. Our theoretical investigation also indicates that the recovery time of the symmetric configuration can be controlled by tuning the geometry of the metaatom, and can be as fast as 2 ps for electrically connected configurations
Y Designed a novel EP plus GO/ZRC plus GO coating with bilayered structure for enhancing corrosion resistance of steel substrate
No full textThe study aimed to provide an effective way to combine the advantages of both the zinc-rich epoxy coating and the graphene-based coating. Herein, we introduce ZRC + GO/EP + GO and EP + GO/ZRC + GO coatings with bilayered structure. In addition, the bilayered ZRC, ZRC + GO and EP + GO coatings were also fabricated to comparatively investigate the anticorrosion mechanisms of the coatings. In order to obtain better dispersion of GO in waterborne coatings, ionic liquid (1-aminoethyl-3-methylimidazolium bromide) was successively grafted on GO, which was confirmed by XPS, Raman and FT-IR results. The results obtained from electrochemical impedance spectroscopy (EIS) and salt spray test proved that the as-prepared EP + GO/ZRC + GO coating presented superior corrosion protection which was derived from the synergistic effect of barrier property and cathodic protection endowed by the special bilayered structure of the coating. Besides, SEM, EDS and XRD results of the coating-exfoliated steel substrates also revealed the steel substrate coated by EP + GO/ZRC + GO was not obviously corroded at the end of the immersion
Contribution of Different Pretreatments to the Thermal Stability and UV Resistance Performance of Cellulose Nanofiber Films
No full textHot water (HW), green liquor (GL), and sodium chlorite (SC) pretreatments were used to pretreat sugarcane bagasse (SCB) and spruce (SP) and then to prepare cellulose nanofibers (CNFs) through high-pressure homogenization to explore the effect of physicochemical properties on the thermal stability and ultraviolet (UV) resistance performance of CNF films. The results indicated that the lignin content of HW-pretreated CNFs was higher than that of GL- and SC-pretreated CNFs, and the hemicellulose content of HW-pretreated CNFs was lower than that of GL- and SC-pretreated CNFs. The synergy of lignin and hemicellulose impacted the thermal stability of CNF films. The thermal stability of all the SP CNF films was higher than that of all the SCB CNF films. Hot water pretreatment improved the thermal stability of CNF films, and green liquor and sodium chlorite pretreatment decreased the thermal stability of CNF films. The highest thermal stability of SP-HW CNF films reached 392 degrees C, which was 5.4% higher than that of SP-SC CNF films. Furthermore, the ultraviolet resistance properties of different CNF films were as follows: SCB-HW > SCB-GL > SCB-SC and SP-HW > SP-GL > SP-SC. Green liquor pretreatment is an effective method to prepare CNFs. Conclusively, this research provides a basic theory for the preparation of CNFs and allows the improvement of CNF films in the application of thermal stability management and UV resistance fields
Microstructural Charactistics of Plasma Sprayed NiCrBSi Coatings and Their Wear and Corrosion Behaviors
No full textNickel-based alloys are commonly used as protective coating materials for surface protection applications owing to their superior resistance to corrosion, wear and high-temperature oxidation. It is urgent to study the fundamental mechanism between the structure and corrosion properties of the Nickel-base composite coatings. This paper, therefore, focuses on clarifying the mechanisms of the microstructure influencing the acid corrosion and mechanical characteristics of the as-sprayed NiCrBSi coating and post-heat-treated coating. The formation mechanisms of the amorphous phase of flat particles during the plasma spray process were studied by using X-ray diffraction analysis, Raman spectroscopy and confocal laser scanning microscope at first. Then the evolutionary process of the corrosion structure and phase of the coating in the accelerated corrosion experiment is directly visualized by using scanning electron microscopy and energy spectrum analysis. The mechanical properties of the amorphous NiCrBSi coatings are lastly measured by microhardness and friction wear tests. The critical phenomena and results help to elucidate the relative influence of the surface features of atmospheric plasma sprayed coatings on acid corrosion responses and wear resistance, aiming at contributing to the development of a protective technique for electrical engineering
Effect of polyaniline-based plate on the anticorrosion performance of epoxy coating
No full textHerein, the effects of the addition of polyaniline-based plate (PANP) on the anticorrosive properties of epoxy coatings on Q235 mild steel were investigated. PANP was synthesized by a chemical oxidation method, and the barrier effect of the epoxy coatings containing PANPs were characterized by water absorption and oxygen permeability tests. Electrochemical impedance spectroscopy and scanning vibrating electrode technique were utilized for studying the anticorrosion performance and self-healing ability of different coatings. The corrosion product beneath the coatings was characterize by scanning electron microscopy and X-ray powder diffraction. Thanks to the strong barrier effect caused by the well-dispersed PANPs and self-healing behavior derived from the electroactivity of PANPs. The epoxy coating containing 1.0 wt% PANPs has improved corrosion protective performances such as water absorption (2.23 % after 40-day immersion), and O-2 shielding effect (7.92 x 10(-15) cm(3) cm cm(-2) s(-1) Pa-1). Also, the impedance modulus of this coating still reached 1.94 x 10(9) Omega cm(2) after 40 days of immersion in a 3.5 wt% NaCl solution
High temperature indentation creep mechanisms of metal-ceramic nanolaminates
No full textCreep, as one of the mechanical properties for evaluating the resistance of deformation under a persistent stress, is extremely important in the application of metal/ceramic nanolaminates. In this work, the creep behaviors of Al/SiC nanolaminates with layer thickness of 10 nm and 100 nm were studied by means of nanoindentation in the temperature range from 25 degrees C to 150 degrees C. It was found that the stress exponent of nanolaminates for layer thickness of 100 nm increased with an increase in temperature. The stress exponent of Al was obtained by inverse methodology based on the finite element simulations, indicating that the creep mechanism changed from dislocation-grain boundary interaction to Coble creep. In the contrary, nanolaminates with layer thickness of 10 nm exhibited temperature-independent creep behaviors. This was rationalized by the co-deformation of Al and SiC layers beneath the indenter, which was dominated in the whole temperature range. In addition, all of these conclusions were further confirmed by the detailed transmission electron microscopic observation, the activation energy and the activation volume analysis
Electron Irradiation Induced Phase-separation Behavior in AlF3 Doped Alumina Ceramic with Superior Sensitivity
No full textAn electron irradiation induced fast phase-separation behavior was observed under convention Transmission electron microscopy (TEM) observation of spark plasma sintered AlF3 doped alumina ceramic. Spherical nanocrystalline Al precipitates separated out from original alumina grain surface within several seconds under transmission electron microscopy electron irradiation. By high resolution TEM observation combined with diffraction patterns analysis, it was found that the original alumina grain surface was in highly defected state. After electron irradiation under TEM, the defects on original alumina surface vanished accompanied by the precipitation of nanocrystalline Al particles. By thoroughly analysis of the defect reaction during doping process and the feature of cation sub-lattice of alumina, a defect assisted interstitial atom segregation mechanism was proposed to explain this behavior. According to this mechanism, doped F ions first occupied oxygen vacancy sites with corresponding Al ions at intrinsic interstitial sites. After oxygen vacancies being fully occupied, both F and Al ions tended to settle down at intrinsic octahedron interstitial sites, which resulted in a metastable doping state. Under the act of 1/3 [1 (1) over bar 00] partial dislocation of alumina matrix, distorted cation sub-lattice generated double aggregated vacant octahedron sites. When these doublets vacant octahedron sites were occupied by foreign Al ions, stacking faults composed of about three sequences were generated as that observed in high resolution TEM. Meanwhile, the segregated doping Al ions at double aggregated octahedron sites along the stacking faults worked as early stage precipitations. Under electron irradiation, with the ablation of F ions, the unstable segregated Al ions separated out as nano precipitation with the reconstruction of alumina lattice