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We studied the fracture strain of polycrystal ɑ-iron at three different hydrogen concentrations and for three crystal sizes with molecular dynamics simulations (MDs). As the hydrogen concentration increases, a fine crystal model's fracture resistance is prone to below a comparatively coarse grain model. This finding elucidates that the most vulnerable area can alter from coarse grain zone to fine-grain zone in the welding heat-affected zone (HAZ) with the effect of hydrogen. A simplified model is thus built to predict the strain energy increment in different crystal size systems caused by the introduction of hydrogen atoms. This strain energy increment is not equal to the fracture energy reduction induced by the same amount of hydrogen insertion, demonstrating that elastic volume expansion of grain boundary (GB) caused by hydrogen is not the determining mechanism of intergranular failure. The density of triple or multi-junctions of GBs, which is typically dependent on the volume fraction of GBs, is the crucial factor for intergranular failure caused by hydrogen embrittlement.

Crystallization of a CaO–Al2O3–MgO–SiO2 (CAMS)–based glass–ceramic with different additives, Fe2O3 and CeO2, was investigated. The compositions of crystals formed in the glass–ceramic were related to the coordination polyhedron of Fe–O and Ce–O in the glass matrix. Fe existed in the glass network in a form of [Fe3+O4–SiO4] (variant of Q2), which facilitated the formation of diopside. CeO2 addition led to the formations of [CeO4] and [CeO6]. [CeO4] was assembled in the diopside crystal, forming a Ce-containing diopside solid-solution. As a glass modifier, [CeO6] consumed Na ions, achieving electric neutrality and increasing the fraction of Q4 (SiO2 O2/2)2−. This enables the precipitation of albite and anorthite. EBSD observation of CaCe4(SiO4)6O crystal

For high-temperature, sand-bearing, and high-pressure water injection pipelines, failure of commonly used organic epoxy coatings occurs frequently, which needs to be solved urgently. Ceramic coating is excellent alternative to solve this problem, attributed to its high hardness, high temperature resistance, and corrosion resistance. However, ceramic coatings prepared till date suffer from some problems, such as high porosity, and poor toughness. To improve overall performance of composite ceramic coating, herein, ceramic-lined composite steel pipes were synthesized by centrifugal self-propagating high-temperature synthesis (centrifugal-SHS), via doping different concentrations of SiO2 in the Al/Fe2O3 reaction system. The microstructure and phase of composite ceramic coatings after addition of SiO2 were analyzed by optical microscopy with super depth of focus, scanning electron microscopy, energy dispersive spectroscopy, and X-ray diffraction. Effects of SiO2 on the density and porosity, microhardness and fracture toughness, compression-shear strength and crushing strength of composite ceramic coatings were investigated by Archimedes method, Vickers indentation microfracture method, shearing test, and squeezing test, respectively. Results showed that the introduction of appropriate amount of SiO2 reduced cooling rate of reaction system, thus improving the densification level and strength of coatings. Furthermore, in reaction system, FeAl2O4 phase disappeared, owing to excessive Al, which could improve corrosion resistance of composite ceramic coatings. The optimum doping concentration of SiO2 was found to be 4 wt%, in which composite ceramic coating showed excellent properties.

Carbon capture and storage (CCS) technology is considered to be one of the key technologies to reduce CO2 emissions. This paper reviews the industry corrosion accidents of CCS transportation system, in which the pipeline corrosion risk is analyzed, and the pipeline corrosion theory is summarized. Also, the effect of impurities on gas phase properties is discussed. We analyze the corrosion mechanism of multicomponent impurities on metals in a supercritical CO2 environment from the aspects of corrosion rate and corrosion products. We also describe the mechanism of pitting and stress corrosion of metals in a supercritical CO2 environment. Besides, the formation mechanism of FeCO3 protective layer and the research status of corrosion resistant alloys in supercritical CO2 are reviewed and analyzed. Finally, a series of shortcomings and prospects of the current research are put forward.

The simulation, fabrication and measurement of the high-voltage H-bridge SiC diode module is reported. The SiC module is consisted with 8 self-designed 3.3 kV30 A SiC Schottky diodes (SBDs), in which each bridge arm is connected by double SBD chips to achieve 60A current. Q3D is used to establish simulation model and make network division of the module. Two parasitic parameters, parasitic inductor and circuit resistance, are extracted from the circuits, which are about 37.5 nH and 1.9 mΩ, respectively. By establishing the geometric model and finite element model, finite element analysis software ANSYS is used to calculate steady-state thermal conduction, and the temperature gradient distribution of the formed chips. The results show that the maximum junction temperature of the chip is about 100°C, and the distribution of the temperature field is reasonable. As the lateral conduction of heat increases the effective heat dissipation area, there is no obvious concentration of heat. Under the condition of the test at room temperature and static, the module voltage drop is about 2.1 V, the leakage current is less than 5 uA, and the breakdown voltage is more than 3700 V, respectively. The fabricated 3300 V devices exhibit large safety margin. The insulation voltage exceeds 7000V, thus ensure the safety of the system. The thermal resistance of the chip is about 0.21 K/W, which is basically consistent with the simulation results.

To investigate the effect of hydrogen atoms on the size of the plastic deformation zone, molecular dynamics (MD) simulations were performed on a single crack model. The model uses pre-charged hydrogen to quantify the compression effect of hydrogen atoms on the plastic zone during cyclic loading. The results show that stress release at the crack tip occurs mainly in the form of plastic deformation, and the degree of compression in the plastic zone increases with increasing hydrogen concentration. A compression factor, which considers hydrogen concentration, is found with the help of the simulation results. A modified fatigue crack growth rate (FCGR) model, combined with the compression factor, was then used to predict the hydrogen-assisted fatigue crack growth rate. The proposed model shows excellent agreement with the experimental data for X100 steel, and it provides a new framework to describe hydrogen-assisted cracking.

Modification of glass network and crystallization process of a CaO–AlO–MgO–SiO (CAMS) based glass ceramic to form diopside through addition of iron oxide were investigated using differential thermal analysis (DTA), Raman spectrum, X-ray diffraction, SEM and EBSD techniques. The experimental results showed that addition of FeO led to remarkable reductions in both the glass transition temperature (Tg) and crystallization temperature (Tp) of the CAMS glass ceramic. At addition level below 5 wt%, the Tg and Tp temperatures were 651°C and 903°C, respectively, and the crystallization only occurred on the surface of the glass ceramic samples. Increasing the addition level to 10 wt% and 15 wt%, not only led to reduction in the Tg and Tp temperatures to 643-641°C and 892-876°C, respectively, but also promoted the formation of crystalline diopside throughout the CAMS samples. Based on the results of Raman spectrums, it was confirmed that FeO addition reduced the strength of glass connection as a result of chemical reactions between the isolated Si–O tetrahedron and Fe ion, forming FeO–SiO, which can be regarded as Q unit. And this is the first experimental evidence that proving the approach of Fe mending glass network. Microstructural examination also identified the formation of large numbers of spherical Fe-enriched regions within the CAMS glass matrix as a result of the amorphous phase separation due to the FeO addition. The interfaces between the Fe-enriched regions and the glass matrix acted as preferred nucleation sites for the diopside, facilitating the crystallization. Crystallographic analysis using EBSD technique determined the as the most favorite growth direction for the diopside crystals in the CAMS based glass ceramic.

Purpose The purpose of this paper is to quantify the influence of alternating current (AC) interference on hydrogen evolution reaction of X80 steel. Design/methodology/approach The hydrogen evolution potential was obtained by cathodic potentiodynamic polarization curve. The instantaneous potential under AC interference was obtained by high-frequency acquisition with three-electrode system. Electrochemical impedance spectroscopy and Tafel polarization curves were used to study the influence mechanism of AC interference on instantaneous potential. Findings It was concluded that the hydrogen evolution reaction could occur on X80 steel under AC interference. There were critical AC current densities of about 100 to 200 A/m2, beyond which the cathode reaction of X80 steel changed from oxygen absorption to hydrogen evolution. Besides the pH value, the initial polarization potential EZ and impedance module of the steel/electrolyte interface under AC interference were also the factors that affected the critical AC densities in different solutions. Originality/value This research quantified the hydrogen evolution capacity of X80 steel under AC interference, which could be applied to clear the effect of AC interference on hydrogen evolution reaction.

Colloidal perovskite quantum dots are candidate materials for solution-processable lasers, although stimulated emission in a semiconductor usually occurs in the multiexciton regime. Due to the quantum-confinement effect of semiconductor quantum dots, the non-radiative recombination transition dominates the relaxation of multiexcitons. Hence, the implementation of low-threshold stimulated emission of perovskite quantum dots in the single-exciton regime is meaningful. Herein, we show that this problem can be partially solved by employing a locally enhanced electric field. By applying the metal surface plasmon resonance energy-transfer effect, we demonstrate a considerable reduction of the optical gain threshold due to the newly generated coupling level induced by the local surface plasmon, and obtain optical gain in the single-exciton regime at room temperature in colloidal perovskite quantum dots. At the same time, we achieve a more than fourfold reduction in the amplified spontaneous emission threshold. This may provide a new concept for the further design of low-threshold stimulated emission colloidal nanocrystal lasers and even for improving their energy conversion efficiency.

Efficient interfacial light-electric interconversion in van der Waals heterostructures is critical for their optoelectronic applications. Using time-resolved terahertz spectroscopy and transient absorption spectroscopy, the charge transfer and the dynamical interlayer excitons were investigated in the heterostructures comprising monolayer WSe2 and monolayer graphene with varying stacking order on a sapphire substrate. Herein, a more comprehensive understanding of ultrafast charge transfer and exciton dynamics in two-dimensional heterostructures is shown. Owing to the effective electric field induced by the sapphire substrate, the WSe2/graphene heterostructure exhibits positive terahertz photoconductivity after photoexcitation, while negative terahertz photoconductivity is observed in the graphene/WSe2 heterostructure. The transient absorption spectra indicate that the exciton lifetimes also exhibit a considerable difference, where WSe2/graphene exhibits the longest exciton lifetime, followed by monolayer WSe2, while graphene/WSe2 exhibits the shortest lifetime. These observations provide a new idea for using van der Waals heterostructures in electronic and photonic devices.

We have investigated the magnetic properties and the magnetocaloric effect of GdScO 3 single crystal. A paramagnetic-antiferromagnetic magnetic phase transition has been observed in GdScO 3 single crystal at low temperature, with Gd 3+ sublattice in [001] direction ( T N = 2.6 K) and [010] direction ( T N = 2.8 K). This compound shows noticeable giant magnetocaloric effect with the maximum value of magnetic entropy change that come up to 47.3 J/kg K in [001] direction and 52.5 J/kg K in [010] direction for a field change of 70 kOe around its Neel temperature. The large magnetocaloric effect is due to the localized 4 f moment of Gd 3+ ( J = S = 7/2) ions. Taking the interactions of the system into consideration, the magnetization and magnetic entropy change can both be well fitted by the molecular field theory based on mean field approximation. The giant magnetocaloric effect suggest that GdScO 3 could be a potential material for magnetic refrigeration in low-temperature region.

We reported a superhydrophobic silica-coated surface with a water contact angle of 160° with a 4 μL water droplet, and transparency of 70-86% in the wavelength range of 380-800 nm. The silica film was synthesized at room temperature (22 °C) using sol-gel process by a simple, cost-effective and uniform spin-coating by mixing silicon dioxide sol-gel with γ-(2, 3-epoxypropyloxy) propyltrimethoxysilane (KH-560). The durability of the coating could be effectively enhanced by controlling the ratio of KH-560 and modified silicon dioxide sol-gel. It was believed that this process that we used can hold a great potential in super-hydrophobic surface fabrication.

Hydrogen embrittlement has been extensively studied for decades; however, the atomistic origins of hydrogen embrittlement remain debated. Here, we studied the role of body-centered cubic (bcc) to face-centered cubic (fcc) phase transition at the crack tip on hydrogen embrittlement in alpha iron at room temperature. Molecular dynamics simulations were performed to examine the propagation of [10 1 ¯ ](101) crack. The results indicate that in the absence of hydrogen atoms, the phase transition could release the strain energy and postpone the crack propagation. Hydrogen atoms would form a nanosize hydrogen-rich region ahead of the crack tip and inhibit phase transition, thus enhancing brittle crack growth. A general expression is provided to predict the hydrogen concentration beyond which the phase transition does not occur. In addition, a simplified crack growth model is proposed to predict the risk level during the operation.

Organic electrode materials have high capacity, and environmentally friendly advantages for the next generation lithium-ion batteries (LIBs). However, organic electrode materials face many challenges, such as low reduction potential as cathode materials or high reduction potential as anode materials. Here, the influence of chemical functionalities that are capable of either electron donating or electron withdrawing groups on the reduction potential and charge-discharge performance of anthraquinone (AQ) based system is studied. The cyclic voltammetry results show that the introduction of two —OH groups, two —NO2 groups and one—CH3 group on anthraquinone structure has a little impact on the reduction potential, which is found to be 2.1 V. But when three or four—OH groups are introduced on AQ structure, the reduction potential is increased to about 3.1 V. The charge-discharge tests show that these materials exhibit moderate cycling stability.

In this paper, a low loss jammed-array wideband sawtooth (JAWS) filter is built based on a finite reflection virtually imaged array (FRVIA) which has a lower reflectivity of the exit surface compared to a virtually imaged phased array (VIPA). This filter can be used as an edge filter to interrogate the fiber Bragg grating (FBG) sensors. A fast FBG sensing system is set up to detect the strain wave of iron pipe to demonstrate the use of this interrogator. The result shows that the JAWS based interrogation system has advantages of high speed, low loss and high sensitivity.

Developing and establishing an efficient pre-treatment approach for the precise extraction of nitrated-polycyclic aromatic hydrocarbons (N-PAHs) from real-life samples is critical for ensuring their safety. In this study, a novel crystalline magnetic covalent organic framework with a grapevine structure not a single core–shell, Fe3O4@TAPT-DMTA-COF, was fabricated via chemical bonding. Unchanging the reticulated structure and high crystallinity of TAPT-DMTA-COF, the combination made this material possess not only simple operation via magnetic decantation but also remarkable chemical stability. Fe3O4@TAPT-DMTA-COF had a large surface area (1578.45 m2/g), and rich electronegative triazine-groups, which makes it become a superior magnetic enrichment material for trace N-PAHs. For N-PAHs analysis, low limits of detection (LODs) (1.43–17.24 ng/L), excellent relative standard deviations (RSDs ≤ 11.52%), and wide linearity (10–5000 ng/L) were obtained. Real-life applications based on this composite have been successfully explored by capturing the N-PAHs emitted from food and environmental samples.

In the current study, the effect of hydrogen atoms on the intergranular failure of &alpha, iron is examined by a molecular dynamics (MD) simulation. The effect of hydrogen embrittlement on the grain boundary (GB) is investigated by diffusing hydrogen atoms into the grain boundaries using a bicrystal body-centered cubic (BCC) model and then deforming the model with a uniaxial tension. The Debye Waller factors are applied to illustrate the volume change of GBs, and the simulation results suggest that the trapped hydrogen atoms in GBs can therefore increase the excess volume of GBs, thus enhancing intergranular failure. When a constant displacement loading is applied to the bicrystal model, the increased strain energy can barely be released via dislocation emission when H is present. The hydrogen pinning effect occurs in the current dislocation slip system, &lt, 111&gt, {112}. The hydrogen atoms facilitate cracking via a decrease of the free surface energy and enhance the phase transition via an increase in the local pressure. Hence, the failure mechanism is prone to intergranular failure so as to release excessive pressure and energy near GBs. This study provides a mechanistic framework of intergranular failure, and a theoretical model is then developed to predict the intergranular cracking rate.

Inoculation of single cells into separate culture chambers is one of the key requirements in single-cell analysis. This paper reports an innovative microfluidic chip integrating two pneumatic microvalves to screen and print single cells onto a well plate. The upper and lower size limits of cells can be dynamically controlled by regulating the deformation of two adjacent microvalves. Numerical simulations were employed to systematically study the influence of membrane dimensions and pressure on the deflection of a valve. A mathematical model was then modified to predict the size of cells captured by a microvalve at various pressures. The membrane deflection was further studied using confocal imaging. The critical pressure trapping beads of various sizes was experimentally determined. These experiments validated the accuracy of both numerical simulations and the mathematical model. Furthermore, single beads and endothelial cells with the desired size range were screened using dual valves and printed onto well plates with 100% efficiency. Viability studies suggested that the screening process had no significant impact on cells. This device enables dynamic regulation of both the lower and the upper size limits of cells for printing. It has significant application potential in inoculating cells with desired sizes for various fields such as clonal expansion, monoclonality development and single-cell genomic studies.

The ultrafast charge transfer and dynamical interlayer excitons were investigated in the heterostructures comprising WSe2/WS2 and WSe2/graphene bilayer. The results reveal the stacking order affect the charge transfer and therefore the formation of exciton in the heterostructure significantly.

The preparation of phase change fibers with controllable morphology, structure and enhanced thermal conductive property is of particular importance to many applications and still remains a challenge. In this study, core–sheath composite phase change microfibers with enhanced thermal conductive property are successfully prepared by microfluidic strategy, which consist of Rubitherm®27 (RT27) core and poly(vinyl butyral) (PVB) sheath blended with aluminum oxide nanoparticles (Al2O3 NPs). The effects of Al2O3 NPs on the morphologies, mechanical properties, phase change properties and thermal conductive properties of the produced composite microfibers are systematically investigated. The morphologies of the composite microfibers are continuous cylindrical shape with core–sheath structure. The modified Al2O3 NPs are uniformly dispersed in PVB matrix, and the thermal conductive property of the composite microfibers has improved significantly. The surface temperature of the Al2O3-incorporated composite microfibers changes faster than that of microfibers without Al2O3. The melting and crystallization times of the composite microfibers with 12% Al2O3 are decreased by 47.1 and 39.5%, respectively. It is expected that the results can provide a valuable guidance for fabrication of phase change microfibers with satisfactory heat conductive properties as well as fast thermal regulation properties.

BiOCl nanosheets with oxygen vacancies on the exposed {010} facets were assistant-synthesized by triethanolamine(TEOA) via hydrothermal method. We explored the surface properties, crystal structure, morphology and optical absorption ability of the prepared samples via various characterization technologies. The results indicate that the morphologies and microstructures of the obtained samples depend on the amount of TEOA in the synthesis. The addition of TEOA induces the production of oxygen vacancy on the surface of the samples. Therefore, the synthesized samples with TEOA-assistance hold higher photoactivity for the degradation of colorless antibiotic agent Ciprofloxacin(CIP) under visible light(λ⩾420 nm). The obtained sample upon the addition of 20 mL of TEOA exhibits the highest photocatalytic performance, which is nearly 14 times as high as that of the sample prepared without TEOA and twice as high as that of the prepared samples with NaOH or NH3·H2O. The possible degradation mechanism was discussed on the basis of the experiment results.

Tubular material parameters play a major role in part manufactory process planning and reliable finite element simulations. The hydraulic bulging test is one of the most credible ways to determinate tubular material properties, especially flow stress. In this paper, an on-line measurement method based on three-dimensional (3D) digital image correlation method (DIC) is applied to determinate material parameters of tube using Swift law. Both a practical bulging machine and a self-developed measurement system are introduced. The free-bulging test is performed for AlMg2.5 aluminum alloy tube. The axial curvature radius is calculated by extracting the bulging profile based on the cosine model and the axial strain is computed accurately by tracking a series of points around the pole dome. Finite element simulations on tube are conducted to validate the method. The results indicate that the material parameters obtained from the present method are reliable to define the flow stress in the tube hydroforming process.

Object Electroencephalogram (EEG) electrodes play an important role in the applications of wearable brain-computer interfaces (BCI). Although traditional wet gel-based electrodes can obtain low contact impedance and high signal-to-noise ratio (SNR), cumbersome procedures including skin preparation, gelling, and hair cleaning make them inconvenient to use. Dry electrodes can avoid these shortcomings; however, they can hardly achieve impedance and SNR as good as wet electrodes. This study aims to develop a novel micro-seepage electrode, which possesses both high convenience of dry electrode and low contact impedance of wet electrode, and assess contact impedance, comfort level, and EEG signal quality of the proposed electrode. Method The proposed micro-seepage electrode can continuously provide a small amount of electrolyte from flexible brush-pen like tips to scalp, which keeps the scalp-electrode interface moist like that of wet electrodes. The electrode can be put on and taken off easily like dry electrode, and there is also no need to wash hair after use. This study investigated the contact impedance of the electrode with regard to electrolyte type, recording duration, and contact pressure on the occipital area. In addition, this study compared SNR and classification accuracy of steady-state visual evoked potentials (SSVEPs) between the proposed electrode and the wet electrode. Result The proposed electrode can be set up very quickly. The flexible and elastic tips make it comfortable to wear. Using the contact lens cleaning solution as electrolyte, the average impedance of the electrode was 12.1 kΩ@10 Hz. The impedance kept below 20 kΩ for more than 8 h on volunteers’ scalp. The SNR and classification accuracy of SSVEPs obtained by the proposed electrodes were comparable to those of wet electrodes. Significance The proposed micro-seepage electrode can provide a comfortable and convenient solution for high-quality EEG acquisition.

We propose a flexible, dry, and antibacterial electrode with a low and stable skin electrode contact impedance for bio-potential signal monitoring. We fabricated a bacterial cellulose/polyaniline/AgNO3 nanocomposite membrane (BC/PANI/AgNO3) and used it for bio-potential signal monitoring. The bacterial cellulose (BC) provides a 3-D nanoporous network structure, and it was used as a substrate material in the BC/PANI/AgNO3 nanocomposite membrane. Polyaniline (PANI) and AgNO3, acting as conductive and antibacterial components, respectively, were polymerized and deposited on the surfaces of BC nanofibers to produce uniform thin film membrane with flexible, antibacterial, and conductive properties. Various measurements were conducted, in terms of antibacterial activity, skin electrode contact impedance, and qualitative analysis of ECG signal recordings. The BC/PANI/AgNO3 membrane revealed 100% antibacterial activities against both the Staphylococcus aureus and Escherichia coli bacteria. The skin electrode contact impedance of the proposed BC/PANI/AgNO3 electrode is lower than that of the Ag/AgCl gel electrode, with the same active area. In addition, the electrocardiogram (ECG) signals acquired with the proposed electrodes have stable characteristic waveforms, and they are not contaminated by noise. The waveform fidelity of the BC/PANI/AgNO3 membrane electrodes over 800 ECG cardiac cycles is 99.49%, and after the electrodes were worn for 24 hours, a fidelity of 98.40% was recorded over the same number of cardiac cycles. With the low and stable skin electrode contact impedance, the proposed dry BC/PANI/AgNO3 membrane electrode provided high fidelity for ECG signal recordings, thus offering a potential approach for bio-potential signal monitoring. With the above benefits, the novel flexible and dry BC/PANI/AgNO3 electrode has a significant antibacterial. Most of all, it is the first research to develop antibacterial in the electrode design., This paper presents the development and validation of a flexible, dry and antibacterial electrode with low and stable skin electrode contact impedance for bio-potential signal monitoring.

In this study, a convenient and sensitive method for the detection of resveratrol was established based on phosphorescence quenching of resveratrol for MPA-capped Mn:ZnS QDs. The quenching intensity was in proportion to the concentration of resveratrol within a certain range. Under optimal conditions, the present assay was valid for detecting resveratrol in the range from 0.03 μM to 14 μM with a detection limit of 0.01 μM. The mechanism of action was also explored, and its application in actual samples was also demonstrated with satisfactory results. This study aims to provide a convenient method for the detection of resveratrol.

The influence of Fe2O3 addition to the nucleation process of Cr2O3-containing CaO-MgO-Al2O3-SiO2 (CAMS) based glass ceramic was investigated by Raman spectroscopy, differential scanning calorimetry (DSC), X-Ray diffraction (XRD), electron back-scattered diffraction (SEM-EBSD) and transmission electron microscope (TEM). The experimental data illustrated that the single Cr2O3-doped specimens were insufficient in achieving the desired nucleation rate for high degree of polymerization. However, with the introduction of Fe2O3 to the Cr2O3-containing samples, the newly generated [FeO4] mended the glass network by inserting [Fe3+O4-SiO4] unit into the original Si-O network, which was helpful for the migration of the coordination polyhedron in the glass matrix. Additionally, [FeO4] unit and [MgO4] are equivalent when generating spinel crystal. Hence, the generated [FeO4] benefited the formation of spinel and diopside phases. This resulted in massive fine spinel crystal distribution in the glass matrix, which promoted the precipitation of diopside. Crystallographic examination confirmed the formation of partial diopsides on the spinel {111} lattice plane with epitaxial growth. The orientation relationships were 〈 112 〉 spinel / / 〈 001 〉 diopside and ( 111 ) spinel / / ( 002 ) diopside . However, when higher Fe2O3 (that is, 2 wt% Cr2O3+15 wt% Fe2O3) was added to the glass system, abnormal grain growth of spinel occurred, which resultantly reduced the nucleation rate.

All-inorganic perovskite has attracted significant attention due to its excellent nonlinear optical characteristics. Stable and low-toxic perovskite materials have great application prospects in optoelectronic devices. Here, we study the nonlinear optical properties of CsPbCl x Br 3 − x ( x = 1 , 1.5, 2) nanocrystals (NCs) glass by open-aperture Z-scan. It is found that the two- (2PA) and three-photon absorption (3PA) intensity can be adjusted by the treatment temperature and the ratio of halide anions. The perovskite NCs glass treated at a high temperature has better crystallinity, resulting in stronger nonlinear absorption performance. In addition, the value of the 2PA parameter of CsPbCl 1.5 Br 1.5 NCs glasses decreases when the incident pump intensity increases, which is ascribed to the saturation of 2PA and population inversion. Finally, the research results show that the 2PA coefficient ( 0.127 cm GW − 1 ) and 3PA coefficient ( 1.21 × 10 − 5 cm 3 GW − 2 ) of CsPbCl 1 Br 2 NCs glass with high Br anion content are larger than those of CsPbCl 2 Br 1 and CsPbCl 1.5 Br 1.5 NCs glasses. This is mainly due to the greater influence of Br anions on the symmetry of the perovskite structure, which leads to the redistribution of delocalized electrons. The revealed adjustable nonlinear optical properties of perovskite NCs glass are essential for developing stable and high-performance nonlinear optical devices.

The exciton effect in two-dimensional (2D) transition metal dichalcogenides (TMDs) plays a dominating role in describing the optical and optoelectronic properties. However, the interplay between the excitons and free carriers has not yet been understood upon photoexcitation in 2D TMDs. Here, we first present a study of the dynamical interplay of excitons and unbound electron–hole pairs using time-resolved terahertz (THz) spectroscopy (TRTS) in a few-layer WS2 laminate. Our experimental results demonstrate that the Auger recombination is observed in the relaxation process of the mobile charge carriers rather than that of excitons upon photoexcitation. The transient complex THz photoconductivity spectroscopy of WS2 is well described by the Drude–Lorentz model of free carriers modulated by the exciton polarization field. Our results provide a comprehensive understanding of nonequilibrium carrier kinetics (both excitons and free carriers) in WS2 laminate, and should be applicable to other 2D systems.

Parylene-C (PC) is one of the most frequently used materials for flexible implantable electrode. Its interface with metal or other PC layer is critical in PC–metal-PC “sandwich” implantable neural electrodes in relation to their long-term reliability. In this study, we aim to develop a method to improve metal-PC and PC–PC adhesion in PC-based neural electrodes. “Nano-forest” structure, composed of nanopillar array is fabricated on the surface of bottom PC by oxygen reactive ion etching (RIE). The contribution of this layer of nano-structure to mechanical adhesion and sealing property are evaluated respectively. The results verify that for PC based “sandwich” electrode, not only the mechanical adhesion among three layers, but also the sealing ability between PC layers are significantly improved.

Hot-electron bolometers (HEBs) made with MgB 2 have proven to have a large intermediate frequency and have shown potential for a low noise into the terahertz range. Although practical results from these mixers have been achieved fairly quickly, effort is still needed to realize an MgB 2 HEB with improved sensitivity to compete with state-of-the-art mixers. Here, we present the results of our mixer work to achieve MgB 2 HEBs based on hybrid physical chemical vapor deposition grown films, with improved sensitivity and higher temperature operation. A new fabrication process is developed which utilizes even thinner films (

This paper aims to develop a flexible and cost-effective dry electrode with low and stable contact impedance. With these benefits, the electrode can be practically used in ubiquitous bio-potential monitoring with similar signal-to-noise ratio as commercial wet electrode. A self-wetting electrode is developed by the aid of moisture naturally created by skin under the electrode. It consists of a layer of ethylcellulose fiber paper coated with PEDOT/PSS (PCwPEDOT) and a thin layer of parylene. PCwPEOT, which has a large contact area composed of micro-scale fibers, is a 30- $\mu \text{m}$ flexible membrane that acts as the electrode material. A 3- $\mu \text{m}$ parylene bonding at the backside of PCwPEOT, as a high-performance vacuum membrane, can collect moisture or sweat naturally evaporating from the skin and store it in the PCwPEDOT layer. This design increases the humidity of skin, especially the water content in the corneum, acting as electrolyte containing ions, increases effective contact area between electrode and skin, and decreases the impedance of the electrode. With an environmentally friendly and cost-effective fabrication process, the 33- $\mu \text{m}$ thickness of electrode is light and flexible. It can be tailored to proper size according to the application. It achieves lower contact impedance compared with dry electrodes with a similar structure. Its recording performance is comparable to commercial patch electrode. The proposed electrode provides high-quality signals, and comfortable user experience in bio-potential recording. It is feasible for developing a long-term wearable system for bio-potential monitoring.

In this paper, waterborne ultraviolet (UV)-curing wood coatings were modified by nano MgCO3 puree, and prepared by optimizing the process parameters. The mechanical properties (hardness, adhesion and resistance impact strength) and gloss of waterborne UV-curing wood coatings modified by nano MgCO3 puree were tested. It was found that the mechanical properties of coatings increased when nano MgCO3 content increased from 0 to 3.0%. Waterborne UV-curing wood coatings had good hardness, adhesion and impact strength when the nano MgCO3 content was 3%-4%. The hardness was 3H, the adhesion was grade 1, and impact strength was 40 kg∙cm. However, when nano MgCO3 content was higher than 4%, the mechanical properties of coatings decreased. As the nano MgCO3 content gradually increasing, the gloss of waterborne UV-curing wood coatings modified by nano MgCO3 puree decreased. When the nano MgCO3 content was 4.0%, the gloss of coating was 33%. When the nano MgCO3 content exceeded 4.0%, the gloss of waterborne UV-curing wood coatings displayed matte.

Previous atomistic simulations of hydrogen embrittlement in bcc iron have provided atomistic mechanisms for crack propagation and been used to develop predictive models. In order to bridge the nano-scale simulations to realistic field operations, in current study molecular dynamics (MD) simulations were first used to predict a hydrogen concentration that corresponds to ductile to brittle transition (DTB). The estimated hydrogen concentration was then used to assess the critical hydrogen concentration that induces DTB transition in experimental specimens. Apparently, the calculated critical hydrogen concentration is much larger than the actual concentration found in pipeline steel under routine operations. Recent experiments found that while the presence of minor cycles (i.e., R = Kmin/Kmax > 0.9) in underload spectra would only make small contribution to crack propagation in air, they could enhance crack growth significantly in the presence of hydrogen atoms. Therefore, it is reasonable to expect that minor cycles have a significant effect on accumulating hydrogen atoms in the plastic zone and inducing a DTB transition in the aqueous environment where diffusible hydrogen atoms can be generated. Based on this hypothesis, the theoretical critical hydrogen value obtained from atomistic simulation was then used to calculate the number of hydrogen atoms required to saturate the plastic zone. Furthermore, the number of minor cycles required to accumulate hydrogen atoms to cause a DTB transition could be assessed. The prediction based on this model and experimental results are in good agreement. The atomistic mechanism for DTB due to the accumulation of hydrogen during cyclic loading validated in current study implies the importance of the loading spectrum in hydrogen-assisted cracking.

Hydrogen embrittlement (HE) is a serious industrial problem that can reduce the ductility, cause catastrophic brittle failures of susceptible materials. Although previous atomistic HE study is able to quantify hydrogen delivery to the crack tip with the stress intensity distribution, no mathematical model has been proposed to quantify the hydrogen effects in the complex loading spectra. In current study, we first employ molecular dynamics (MD) simulation to study propagation behavior of a single crack with pre-charged hydrogen under cyclic loading. The MD simulation demonstrates that hydrogen atoms will diffuse to the crack tip during loading and unloading and form hydrogen rich region. Once hydrogen-rich region forms, cracks can propagate during unloading because of the brittle nature due to hydrogen accumulation. After the crack tip passes through hydrogen-rich region, it becomes blunted, and re-starts to accumulate hydrogen atoms. In a separate simulation, we closely monitor the hydrogen accumulation during ten cyclic loads and found that hydrogen atoms accumulate linearly in a nano-size region ahead of crack tip. Based upon the MD simulation results, we proposed a new model that could be used to quantify hydrogen accumulation effects in cyclic loading, especially minor cycles. Furthermore, the proposed model was used to predict the acceleration factor for crack growth in the presence of hydrogen and it shows excellent agreement with experimental results.

Graphene oxide (GO) is an attractive option for large scale production of graphene. On the other hand, the graphene obtained by the reduction of GO has inevitable structural defects, and the vacant lattice sites will significantly restrict its conductivity. It has been demonstrated that thermal annealing in hydrogen is an efficient method to reduce defects and heal the lattice in GO samples. However, it is still not clear how the defects and/or disordering influence the photoelectric conversion efficiency and the carrier relaxation pathway in GO. Herein, time-domain terahertz (THz) spectroscopy is employed to characterize the properties of the multilayer GO films which were annealed in hydrogen at various temperatures. Upon photoexcitation, a transient increase of the conductivity was observed for the reduced graphene oxide (RGO) samples. The ultrafast carrier relaxation process can be well assigned to the carrier–carrier scattering and carrier–phonon coupling. Our results demonstrated that the RGO films ...

The morphologies, sizes, compositions and volume fractions of dendritic phases in in situ Ti-based metallic glass matrix composites (MGMCs) containing beryllium (Be) with the nominal composition of Ti47Zr19Cu5V12Be17 (mole fraction, %) were investigated using XRD, SEM, EBSD, TEM, EDS and three-dimensional reconstruction method. Moreover, visualized at the nanoscale, Be distribution is confirmed to be only present in the matrix using scanning transmission electron microscopy–electron energy loss spectroscopy (STEM–EELS). Based on these findings, it has been obtained that the accurate chemical compositions are Ti28.3Zr19.7Cu8V6.4Be37.6 (mole fraction, %) for glass matrix and Ti62.4Zr18.4Cu2.6V16.6 (mole fraction, %) for the dendritic phases, and the volume fractions are 38.5% and 61.5%, respectively. It is believed that the results are of particular importance for the designing of Be-containing MGMCs.

The effects of temperature on bulk hydrogen concentration and diffusion have been tested with the Devanathan&ndash, Stachurski method. Thus, a model based on hydrogen potential, diffusivity, loading frequency, and hydrostatic stress distribution around crack tips was applied in order to quantify the temperature&rsquo, s effect. The theoretical model was verified experimentally and confirmed a temperature threshold of 320 K to maximize the crack growth. The model suggests a nanoscale embrittlement mechanism, which is generated by hydrogen atom delivery to the crack tip under fatigue loading, and rationalized the &Delta, K dependence of traditional models. Hence, this work could be applied to optimize operations that will prolong the life of the pipeline.

Compared with the common self-healing coating, the self-healing polymer/graphene composite coating has better self-repairing ability and anti-corrosion performance. This is attributed to the superior physical and chemical properties of graphene, which can be used as the energy conversion center, energy transfer medium or corrosion medium shield in coatings. And according to different healing mechanisms, graphene can play different roles. In this paper, the function of graphene in self-healing coating and the application status of self-healing polymer/graphene composite coating are discussed in detail. First, the function of graphene is introduced from the intrinsic and extrinsic self-healing mechanisms. Second, the optimization measures of graphene properties and self-healing polymer/graphene composite coatings are summarized. And for graphene, the effects of its structure, size, electrical conductivity and dispersion on the self-healing properties are analyzed in detail. Finally, the current application problems of self-healing polymer/graphene composite coatings are analyzed, and the future development direction of self-healing polymer/graphene composite coatings is discussed.

Methane hydrate has the potential to become a high quality medium for gas storage and a special fuel because of its high efficiency for gas storage and its combustibility. It is important to study the factors that affect the combustion characteristics of methane hydrate. In this paper, the effects of gas content and ambient temperature on the combustion of methane hydrate spheres are investigated experimentally. The combustion flame of methane hydrate spheres with high gas content is bright yellow, whereas the combustion flame of methane hydrate spheres with low gas content is dim blue. With an increase in gas content, the methane hydrate sphere is easier to ignite and the combustion rate, residual gas content, flame height, flame oscillation frequency, and flame brightness all increase. However, the flame temperature at a height of 3 cm from the center of the sphere decreases. This is mainly because of the combustion of hydrate spheres with high gas content in a severe fuel excess state. The combustion characteristics of methane hydrate spheres in the ambient temperature range of 293 K–303 K are very similar. Also, the flame is bright yellow with insufficient combustion. With an increase in the ambient temperature, there are no differences in the residual gas content of methane hydrate spheres; the combustion rate, flame height, flame oscillation frequency, and flame brightness decrease slightly, and this is related to the self-preservation process. However, the flame temperature at a height of 6 cm from the center of the sphere increases. The increase in ambient temperature may have a similar effect with a decrease in gas content, and the root cause of this is that the slower release of methane is beneficial for mixing with the air in a better proportion. In addition, the combustion is more sufficient. The slower emission of combustion products also reduces the flow velocity, weakens the oscillation of the flame, and improves the stability of the flame.

In the current research, the dependence of hydrogen embrittlement (HE) on the temperature in X90 steel is studied through experimental tests and molecular dynamics simulations. Slow strain rate tests (SSRT) were applied to X90 specimens in the air and the simulated groundwater solution (called NS4), respectively. The fracture morphologies of the specimens were observed by scanning electron microscope (SEM). The results indicate that the temperature threshold of hydrogen embrittlement (HE) in X90 steel is 313 K, beyond which the HE would be weakened with the rise of temperature, and below which the HE would be enhanced with the rise of temperature. To illustrate the underlying mechanism of this phenomenon, molecular dynamics simulations were applied to quantify the correlation of temperature with hydrogen diffusivity, and the results of Devanathan-Stachurski tests were used to quantify the bulk hydrogen concentration at different temperatures. A theoretical model was thus developed based on hydrogen potential thermodynamics to predict the threshold temperature. The predictive model matches well with experimental results, revealing the promoting effect of hydrogen diffusion and accumulation on the crack growth, which is fundamental for understanding hydrogen-induced damage in structural materials.

Electro-deposition, electrical activation, thermal oxidation, and reactive ion sputtering are the four primary methods to fabricate iridium oxide film. Among these methods, reactive ion sputtering is a commonly used method in standard micro-fabrication processes. In different sputtering conditions, the component, texture, and electrochemistry character of iridium oxide varies considerably. To fabricate the iridium oxide film compatible with the wafer-level processing of neural electrodes, the quality of iridium oxide film must be able to withstand the mechanical and chemical impact of post-processing, and simultaneously achieve good performance as a neural electrode. In this study, parameters of sputtering were researched and developed to achieve a balance between mechanical stability and good electrochemical characteristics of iridium oxide film on electrode. Iridium oxide fabricating process combined with fabrication flow of silicon electrodes, at wafer-level, is introduced to produce silicon based planar iridium oxide neural electrodes. Compared with bare gold electrodes, iridium oxide electrodes fabricated with this method exhibit particularly good electrochemical stability, low impedance of 386 kΩ at 1 kHz, high safe charge storage capacity of 3.2 mC/cm2, and good impedance consistency of less than 25% fluctuation.

The aesthetic defects of polymeric polarizers have a serious impact on the quality of thin film transistor liquid crystal display (TFT-LCD) panels. However, some of these slight and transparent defects can barely be imaged and characterized using conventional illumination. To inspect these special defects, a new and automated inspection method is proposed that employs structured-light illumination. A machine vision system that uses a LCD monitor to produce a binary stripe pattern was designed to enhance the imaging defects. Thus, subsequent image processing is straightforward and simple because of this enhancement. One hundred and fifty defect samples were successfully imaged and then processed and characterized by the Robust Principal Component Analysis (RPCA) algorithm. The total inspection accuracy was up to 99%. The experiments demonstrate that the width of the luminous stripe should be optimized at 2 to 3 times the size of the defect. The mechanism of the imaging enhancement is preliminarily discussed.

The phoxonic crystal sensor is theoretically investigated in this paper. Based on the phoxonic crystal with dual surface mode bandgaps, both optical and acoustic waves can be confined near the surface. Thus dual cavities, one optical cavity and one acoustic cavity, are designed and integrated in the same phoxonic device. The sensor aims at determining the refractive index and sound velocity of different liquids by utilizing surface optical and acoustic waves. The sensitivities can be estimated by the variations of the cavity resonant frequencies in the response spectra. The relation between the frequency and the measuring physical parameters, i.e., the refractive index or the sound velocity, can be approximated by a linear function. By optimizing each cavity the photonic and phononic sensitivities can reach 199 nm/RIU and 2.79 MHz/ms −1 , respectively. This work can serve as a reference for the design of novel phoxonic sensors.

A novel type of composite hollow microfiber with K+-responsive controlled-release characteristics based on a host–guest system is prepared by embedding K+-responsive poly(N-isopropylacrylamide-co-acryloylamidobenzo-15-crown-5) (P(NIPAM-co-AAB15C5)) microspheres in the wall of poly(lactic-co-glycolic acid) (PLGA) microfibers as “micro-valves” using a controllable microfluidic approach. By adjusting the volume change of microspheres in response to the environmental K+ concentration, the release rate of the encapsulated drug molecules from the composite hollow microfibers can be flexibly regulated owing to the change in the interspace size between the microfiber wall and microspheres. When the environmental K+ concentration is increased, due to the formation of stable 2 : 1 “sandwich-type” host–guest complexes of 15-crown-5 units and K+ ions, P(NIPAM-co-AAB15C5) microspheres change from a swollen state to a shrunken state. Thus, the interspace size becomes larger, resulting in a rapid increase in the release rate of encapsulated drugs. When the ambient K+ concentration is decreased, the interspace size becomes smaller due to isothermal swelling of microspheres caused by the decreased amount of host–guest complexes, resulting in a decrease in the release rate. The K+-responsive drug release behaviors are reversible. This kind of K+-responsive hollow microfiber with K+-concentration-dependent controlled-release properties provides a new mode in the design of more rational drug delivery systems, which are highly attractive for biomedical applications.

In recent years, superhydrophobic materials have shown tremendous industrial application value in many fields. Especially in the field of anti-corrosion, the superhydrophobic coating can capture the air to form many "air bags" on the surface of the substrate, so it has a strong water-repellent ability, thus isolating the corrosion media and achieving remarkable anti-corrosion performance. Various preparation technologies of superhydrophobic coatings have been proposed, but each has its own defects. As a relatively mature industrial processing method, electrodeposition shows unique advantages. However, there are few reviews on the preparation of anticorrosive superhydrophobic coatings by electrodeposition till now. In this paper, the general theory of superhydrophobic surface, including factors affecting wettability and theoretical wetting models, is firstly reviewed. Secondly, the mechanism, application status and anti-corrosion performance of superhydrophobic coatings prepared by metal electrodeposition, non-metallic electrodeposition, and composite electrodeposition are summarized in detail, respectively. The internal mechanism of process conditions, especially crystal modifiers, to regulate the coating morphology is described. Moreover, new developments over the years in electrodeposition such as pulse electrodeposition, magnetic field-induced electrodeposition, ultrasonic-assisted electrodeposition for the fabrication of superhydrophobic coatings are also presented. Finally, the deficiency of this technology is pointed out, and the future research directions of improving the durability of superhydrophobic coatings are proposed.

Natural gas (methane) hydrates have great potential as fuels. It is necessary to study the flame characteristics to evaluate its energy efficiency when directly burned as a fuel and the risk of storing and transporting natural gas as the form of hydrate. Here, the flame characteristics in the combustion of methane hydrate spheres under natural convective flow conditions were investigated. Physical parameters related to the flame, such as height, brightness, oscillation frequency, and temperature were used to characterize the combustion process. The results showed that the combustion process was divided into four stages according to the changes in flame characteristics. The flame height was mainly affected by the mass change rate and the diameter of methane hydrate sphere. Further, the combustion of methane hydrate spheres was unstable, as reflected in the oscillation of the flame height with a period of ~0.1 s. A ‘dark region’ was found near the methane hydrate sphere surface, characterized by a dark flame and low temperatures. Increasing the initial center temperature had little effect on the flame characteristics, causing only a slight increase in flame height. The diameter of the hydrate spheres, on the other hand, had a significant effect on the combustion behavior. As the sphere diameter increased, the flame height increased dramatically, the oscillation frequency decreased, and the maximum flame temperature remained unchanged.

Smart anticorrosive coatings have better anticorrosion ability than traditional anticorrosive coatings. This is attributed to the development of active protection performance in the smart anticorrosive coating based on the passive barrier of the traditional coating. Smart anticorrosive coating can effectively respond to environmental changes, heal coating defects, and prevent further corrosion. In this study, the application prospects of smart anticorrosive coatings for protection of metal corrosion are reviewed from two aspects of extrinsic and intrinsic self-healing. First, the related concepts of healing due to coating are introduced. Second, the development of nano-container, anticorrosion performance, existing problems, and optimization measures of the extrinsic healing smart anticorrosive coating are introduced. Third, the mechanism, anti-corrosion performance, existing problems, and optimization measures of intrinsic healing smart anticorrosive coating are summarized. Finally, the development direction of smart anticorrosive coating is put forward, and the possible application prospects of these smart coatings to attain a long-term effect in the future are discussed.