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The (AlCoCrFeNi)1-X (WC-10Co)X composite coatings were fabricated on 06Cr13Ni5Mo steel by high-velocity oxygen-fuel (HVOF) spraying. The coatings' microstructure, mechanical properties, and corrosion performance were characterized, and the cavitation erosion resistance of the coatings was tested in 3.5 wt% NaCl medium. The influence of the microstructure, mechanical properties, and corrosion resistance on cavitation erosion resistance were discussed. The microhardness and local plastic deformation resistance of the coatings were increased by WC-10Co, while the corrosion resistance of the composite coatings was decreased by severe galvanic corrosion. The cavitation erosion mechanism of the coatings was lamellar spalling. In NaCl medium, the (AlCoCrFeNi)75(WC–10Co)25 (HEA75/WC25) coating showed lower cavitation erosion resistance than the AlCoCrFeNi (HEA) coating, which was caused by the galvanic corrosion, uncoordinated deformation and the low bonding strength of the HEA/WC-10Co interface. For the HEA75/WC25 coating and (AlCoCrFeNi)50(WC–10Co)50 (HEA50/WC50) coating, the cavitation erosion damage of the HEA75/WC25 coating was higher than that of the HEA50/WC50 coating. When the microstructure and corrosion resistance of the coatings were similar, the cavitation erosion resistance was mainly affected by the mechanical property.

The (AlCoCrFeNi)1-X(WC-10Co)X composite coatings were fabricated by HVOF spraying and their microstructures, mechanical properties and cavitation erosion behaviors were tested. The effects of WC-10Co on the cavitation erosion mechanisms were discussed by compared the differences of volume losses and eroded surface morphologies between the coatings. The cavitation erosion resistance of the coatings was about 3 times as that of the 06Cr13Ni5Mo steel. With the addition of WC-10Co, the cavitation erosion resistance of the coating was slightly increased. In the initial stage of cavitation erosion test, the cavitation erosion damage was concentrated on the interface, which was caused by the uncoordinated deformation and poor mechanical properties of the interface between HEA and WC-10Co. When the WC-10Co distributed below the HEA region, the WC-10Co played a strong supporting role and improved the impact resistance of the HEA region. The cavitation erosion mechanism of the HEA1 coating was lamellar spalling. The cavitation erosion mechanisms of the HEA2 and HEA3 coatings were particles spalling and lamellar spalling.

A computational fluid dynamics (CFD) compatible and fully local transition closure model is proposed for three-dimensional hypersonic boundary layers considering crossflow effects. The transition m...

In this study, we developed ashless cellulose filter papers as calibration standards in laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) to rapidly determine multi-element concentrations in airborne fine particulate matter (PM2.5). To achieve this, the papers were treated by immersion in standard solutions, followed by evaporation of the solutions. The homogeneity of the paper standards was studied, and the results demonstrated that the elements were homogeneously distributed at the paper centers with slight fluctuations (i.e., relative standard derivation ≦ 8%). The instrument signal drift and instability were compensated using a pseudo internal standard (197Au). The limits of detection established for LA-ICP-MS were obtained by the ablation of 11 lines on the procedural blank filter paper containing 0.5% HNO3, with values ranging from 0.01 (Sr) to 0.49 μg g−1 (Fe). The accuracy of the LA-ICP-MS determinations was validated using certified reference materials (CRMs) and analyzed using six line scans. The results showed acceptable analytical errors (

In this study, three kinds of WC-based cermet coatings including WC–CoCr coating, WC–Ni coating and WC–Cr3C2–Ni coating were prepared by the high-velocity oxygen-fuel (HVOF) spraying process. Scanning electron microscopy (SEM), energy disperse spectroscopy (EDS) and Vickers hardness tester were used to analyze the microstructure and mechanical properties of these coatings. The WC–CoCr coating presented the highest average microhardness of 1205 HV0.3, and then followed by the WC–Cr3C2–Ni coating (1188 HV0.3) and the WC–Ni coating (1105 HV0.3). The abrasive wear behavior of the WC-based coatings under the conditions of different applied loads and sediment concentrations were studied by a wet sand-rubber wheel tester. The results indicated that the abrasive wear loss rates of all the coatings increased with the increment of applied load or sediment concentration. In addition, the coatings with higher microhardness appeared to have higher abrasive wear resistance. The abrasive wear resistance of the WC-based coatings was 4–90 times higher than that of AISI 304 stainless steel under the same testing condition. The abrasive wear mechanism of the WC-based coatings was deduced to be the extrusion and removal of binder phases, as well as the fragmentation and peel-off of hard phases.

The first Zintl cluster containing a distorted Bi6 triangular prism, [Bi6Mo3(CO)9]4-, has been synthesized and structurally characterized. Quantum chemical calculations indicated that the distorted cage cluster features multiple local σ-aromaticity.

Co–Al porous intermetallics were fabricated by an efficient and energy-saving method of thermal explosion (TE) reactions. The effects of Co/Al molar ratios on the temperature profiles, phase compositions, expansion behaviors, density, pore characteristics, and oxidation resistance were investigated. When the target furnace temperature was set at 700°C, there was an obvious exothermic peak in the temperature profiles. The ignition temperatures were in the range of 600–645°C, and the combustion temperatures were in the range of 984–1,421°C. Co–Al porous intermetallics had the open porosity of 27–43%, and the pores were from nonfully dense green compacts and explosion behaviors of TE. The specimen with Co:Al = 2:9 possessed a higher open porosity of 42.8%, the lowest density of 1.86 g cm−3, and the largest volume expansion of 76.7%. The porous specimens with Co:Al = 1:1 possessed the highest open porosity of 43.2%, the lowest volume expansion of 12.3%, and the highest density of 3.42 g cm−3. All Co–Al porous intermetallics showed excellent oxidation resistance at 650°C in air, especially the specimen with Co:Al = 1:1 had the highest oxidation resistance.

Sandwich-type clusters with the planar fragment containing a heterometallic sheet have remained elusive. In this work, we introduce the [K(2,2,2-crypt)]4{(Ge9)2[η6-Ge(PdPPh3)3]} complex that contains a heterometallic sandwich fragment. The title compound is structurally characterized by means of single-crystal X-ray diffraction, which reveals the presence of an unusual heteroatomic metal planar fragment Ge@Pd3. The planar fragment contains a rare formal zerovalent germanium core and a peculiar bonding mode of sp2-Ge@(PdPPh3)3 trigonal planar structure, whereas the nonagermanide fragments act as capping ligands. The chemical bonding pattern of the planar fragment consists of three 2c-2e Pd-Ge σ-bonds attaching Pd atoms to the core Ge atom, while the binding between the planar fragment and the aromatic Ge9 ligands is provided by six 2c-2e Pd-Ge σ-bonds and two delocalized 4c-2e σ-bonds. The synthesized cluster represents a rare example of a sandwich compound with the heteroatomic metal planar fragment and inorganic aromatic capping ligands.

Heterometallic clusters have attracted broad interests in the synthetic chemistry due to their various coordination modes and potential applications in heterogeneous catalysis. Here we report the synthesis, experimental, and theoretical characterizations of four ternary clusters ([M2(CO)6Sn2Sb5]3− (M = Cr, Mo), and [(MSn2Sb5)2]4−, (M = Cu, Ag)) in the process of capturing the hypho- [Sn2Sb5]3− in ethylenediamine (en) solution. We show that the coordination of the binary anion to transition-metal ions or fragments provides additional stabilization due to the formation of locally σ-aromatic units, producing a spherical aromatic shielding region in the cages. While in the case of [Mo2(CO)6Sn2Sb5]3− stabilization arises from locally σ-aromatic three-centre and five-centre two-electron bonds, aromatic islands in [(AgSn2Sb5)2]4− and [(CuSn2Sb5)2]4− render them globally antiaromatic. This work describes the coordination chemistry of the versatile building block [Sn2Sb5]3−, thus providing conceptual advances in the field of metal-metal bonding in clusters.

We investigated the coexistence of superconductivity and antiferromagnetic order in the compound Er$_{2}$O$_{2}$Bi with anti-ThCr$_{2}$Si$_{2}$-type structure through resistivity, magnetization, specific heat measurements and first-principle calculations. The superconducting transition temperature $T_{\rm c}$ of 1.23 K and antiferromagnetic transition temperature $T_{\rm N}$ of 3 K are observed in the sample with the best nominal composition. The superconducting upper critical field $H_{\rm c2}$(0) and electron-phonon coupling constant $\lambda$$_{e-ph}$ in Er$_{2}$O$_{2}$Bi are similar to those in the previously reported non-magnetic superconductor Y$_{2}$O$_{2}$Bi with the same structure, indicating that the superconductivity in Er$_{2}$O$_{2}$Bi may have the same origin as in Y$_{2}$O$_{2}$Bi. The first-principle calculations of Er$_{2}$O$_{2}$Bi show that the Fermi surface is mainly composed of the Bi 6$p$ orbitals both in the paramagnetic and antiferromagnetic state, implying minor effect of the 4$f$ electrons on the Fermi surface. Besides, upon increasing the oxygen incorporation in Er$_{2}$O$_{x}$Bi, $T_{\rm c}$ increases from 1 to 1.23 K and $T_{\rm N}$ decreases slightly from 3 to 2.96 K, revealing that superconductivity and antiferromagnetic order may compete with each other. The Hall effect measurements indicate that hole-type carrier density indeed increases with increasing oxygen content, which may account for the variations of $T_{\rm c}$ and $T_{\rm N}$ with different oxygen content.

Free-standing rotary triboelectric nanogenerators (rTENG) can accomplish special tasks which require both high voltage and high frequency. However, the reported high performance rTENG all have complex structures for output enhancement. In this work, an ultra-simple strategy to build high performance rTENG is developed. With only one small paper strip added to the conventional structure, the output of the TENG is promoted hugely. The voltage is triplicated to 2.3 kV, and the current and charge are quintupled to 133 µA and 197 nC, respectively. The small paper strip, with the merits of ultra-simplicity, wide availability, easy accessibility and low cost, functions as a super-effective charge supplement. This simple and delicate structure enables ultra-high durability with the 2.3 kV voltage output 100% maintained after 1 000 000 cycles. This charge supplementary strategy is universally effective for many other materials, and decouples the output enhancement from any friction or contact on the metal electrodes, emphasizing a critical working principle for the rTENG. Atmospheric cold plasma is generated using the paper strip rTENG (ps-rTENG), which demonstrates strong ability to do bacteria sterilization. This simple and persistent charge supplementary strategy can be easily adopted by other designs to promote the output even further.

High-temperature corrosion affects many components used in coal-fired power plants. A possible solution is the use of protective coatings. In this study, Ni-Cr alloy coatings with different Cr contents (30 at.%, 45 at.%, and 50 at.%) and Ni-Cr-Ti coatings were deposited on 20G boiler steels by high-velocity arc spraying. The hot corrosion behavior of the coatings was characterized in the aggressive environment of Na2SO4 + 30% K2SO4 molten salt under cyclic conditions at 750°C. x-Ray diffraction analysis, optical microscopy, and scanning electron microscopy were used to analyze the phase composition, microstructure, and corrosion products of the coatings. The corrosion kinetic curves of the coatings, established by thermogravimetry, conformed to the classic parabolic law, revealing that the Ni-Cr-Ti coatings exhibited better hot corrosion resistance than the Ni-45Cr or Ni-30Cr coatings. However, among the four tested coatings, the Ni-50Cr coating was found to offer the best protection with the lowest values of mass gain per area (2.9 mg/cm2) and parabolic rate constant (kp, 0.215 × 10−11 g2 cm−4 s−1). This can be explained by the formation of Cr2O3 and NiCr2O4. Therefore, such high-velocity arc-sprayed Ni-50Cr coatings could be used as protective layers for hot components in boiler tubes.

In this paper, the high-velocity oxygen-fuel (HVOF) spraying technology was used to prepare the iron-based amorphous coatings onto the substrate of 45 steel. Three parameters of spray distance, oxygen flow and kerosene flow were optimized by the Taguchi method, with the porosity of the coatings as object. The statistical tools including orthogonal experimental design, signal-to-noise ratio and analysis of variance were used to optimize the spray parameters. The results indicated that the kerosene flow showed the highest effect on the porosity of the coatings, while the oxygen flow exhibited the least influence. It was found that the coating with lowest porosity was deposited under the spray distance of 380 mm, the oxygen flow of 1840 scfh, and the kerosene flow of 6.8 gph. The potentiodynamic polarization and electrochemical impendence spectroscopy (EIS) results manifested that the iron-based amorphous coating prepared with proper spray parameters exhibited superior corrosion resistance to the hard chromium coating. Besides, the coating with lower porosity exhibited better corrosion resistance than the coating with higher porosity.

The microcapsules of multilayered shells structure loaded with dicyclopentadiene (DCPD) were prepared via one-part strategy in Pickering emulsions stabilized by hydrolyzed poly(glycidyl methacrylate) (PGMA) nanoparticle. The target microcapsules had polyurethane (PU) inner shell layer, phenol-formaldehyde (PF) outer shell layer, and PGMA outermost layer. Meanwhile, in order to compare with the target microcapsules, the microcapsules of double layered shells (Sample 1) were both acquired. Size distribution, morphology, chemical structure and reaction heat of the capsules were studied by particle size analysis, scanning electron microscopy (SEM), fourier transform infrared spectra (FTIR), nuclear magnetic resonance (NMR), and differential scanning calorimetry (DSC). It was found that the ingredients of PF, PU and PGMA were contained in the target microcapsules of multilayered shells, and the encapsulated core materials still kept high chemical reactivity. The resistant properties against thermal and solvent were evaluated by thermogravimetric analysis (TGA) and the solvent immersion test. When the IPDI content was suitable, the multilayered shells microcapsules (Sample 2, 3) possessed excellent thermal and solvent resistances comparing with Sample 1. In addition, the coatings embedded Sample 3 have displayed good self-healing performance by SEM, electrochemical impedance spectroscopy (EIS), salt immersion test and the tensile analysis of tapered double cantilever beam (TDCB) fracture specimens.

A Fe-based amorphous/nanocrystalline coating was prepared on the AISI 321 steel by the high-velocity oxygen-fuel (HVOF) thermal spraying technology in this paper. Cavitation erosion behavior and mechanism of the coating was studied through the analysis of curves for cavitation erosion resistance versus time and the observation of eroded particles, with the AISI 321 steel as a reference. It was found that the Fe-based coating had better cavitation erosion resistance than the AISI 321 steel, and exhibited obvious periodic failure behavior in the cavitation erosion process. Besides, the crystallization of the amorphous phase under the effect of shock wave was observed. The cavitation erosion mathematic model of the coating was also established. The model indicated that the cavitation erosion resistance of the coating was related to the grain size and the fracture energy per unit area of the coating. Small grain size and high fracture energy per unit area were benefit to improve the cavitation erosion resistance of the Fe-based coating.

Quantitative determination of the concentrations of elements and systematical characterization of their distribution in foraminifer is of vital significance. Quantitative elemental imaging by LA-ICP-MS is a useful alternative method; however, a methodology for high spatial resolution elemental imaging of foraminifer has not been obtained. In this work, a laser ablation spot size of 16 μm and a line scan speed of 8 μm s−1 were selected for elemental imaging after optimization; then, a two-point calibration strategy (TPCS) was established by combining NIST SRM 610 and NIST SRM 612 glasses with MACS-3 as external standards. The concentrations of Mg and Sr in four carbonate reference materials obtained by TPCS were close to the reference values with relative errors less than 10%. TPCS can avoid incorrect calibration caused by inhomogeneously distributed internal standards (e.g., 43Ca) between foraminifer shells and holes. A methodology for quantitative LA-ICP-MS elemental imaging of foraminifer was then developed, and high spatial resolution elemental images of Mg, Sr, and Ba were obtained. The spatial resolution of these images was calculated to be 16 × 0.40 μm per pixel. Elemental imaging of the Mg/Ca, Sr/Ca, and Ba/Ca ratios of a second foraminifer further confirmed the reproducibility of the elemental imaging methodology. The Mg/Ca ratio and the calcification temperature were found to gradually increase from the inner chambers (f-0) to the final chamber (f-1), while Sr was distributed more homogeneously and Ba showed little uptake in foraminifer shells. All these results demonstrate that this elemental imaging methodology is applicable to providing visual evidence to distinguish the elemental distributional differences in foraminifer.

To improve photoelectrochemical properties of Si nanowires (SiNWs), MoS2/SiNWs is prepared via two-step method. SiNWs is synthesized by metal−catalyzed electroless etching (MCEE) method and MoS2 is subsequently deposited onto SiNWs through the direct thermal decomposition method. MoS2 is introduced as both light absorber and catalyst for hydrogen evolution reaction (HER). Moreover, it forms a heterojunction with SiNWs that contribute to the charge separation. Herein, MoS2/SiNWs attains excellent hydrogen evolution reaction (HER) catalysis with onset potential of 55 mV. A photocurrent density of 25 mA cm− 2 at −1.0 VRHE were achieved under simulated solar illumination, which is about 6 times higher than that of SiNWs, and the carrier concentration is increased by 100−fold. The enhanced photocatalytic activity of MoS2/SiNWs toward HER is attributed to the Schottky junction at the interface, which enhances the photo−generation of electron−hole pairs and suppresses the charge recombination, making them promising earth−abundant alternatives to noble metal−based photocathode for HER.

Suitable semiconductor and its efficient coupling with catalysts is vital to hydrogen evolution reaction (HER). Herein, Ternary heterostructured MoS2/Ag/p-type silicon nanowires (SiNWs) array photocathode are constructed by a simple two-step method, where Ag is self-reduced on SiNWs via Galvanic Displacement method and MoS2 is subsequently loaded by direct thermal decomposition. Ag interfacial layer is introduced between Si and MoS2 to facilitate the charge transfer and suppress the recombination of photo-generated electron-hole pairs. MoS2/Ag/SiNWs exhibits an onset potential of 62 mV and photocurrent density of 50 mA cm−2 at −1.0 VRHE, as well as good stability. Besides, MoS2/Ag/SiNWs is capable of generating 325.9 μL hydrogen per minute. The superior HER catalytic activity of MoS2/Ag/SiNWs is contributed to the improved charge transport at the solid–solid interfaces by virtue of Ag layer, allowing more electrons flow from SiNWs to MoS2 and thus effectively separating the photoelectrons and holes. This work demonstrates the potential of novel heterostructure for robust and efficient photoelectrochemical HER.

In this study, the high-temperature oxidation behaviour of arc-sprayed Ni–Cr coatings with high Cr contents of 30, 45 and 50 at.% was investigated in comparison with reference AISI 1020 steel. X-ra...

During the process of aerodynamic shape design of supersonic and hypersonic space planes, laminar flow design and boundary layer transition prediction play important roles in aero-thermal numerical simulations and aero-thermal protection design. Therefore, in this study, a computational fluid dynamics compatible transition closure model for high speed laminar-to-turbulent transitional flows is formulated with consideration of the analysis results from stability theory. The proposed model contains two transport equations to describe the transition mechanism using local variables. Specifically, the eddy viscosity of laminar fluctuations and intermittency factor are chosen to be the characteristic parameters and modeled by transport equations. Accounting for the dominant instability modes at supersonic/hypersonic conditions, the first- and second- modes are modeled using local variables through the analysis of laminar self-similar boundary layers. Then, the present transition model is applied with compressibility corrected k $k$ - ω $\omega$ shear stress transport turbulence model. Thus, as the main significance of the current work, the present model is enabled to capture the overshoot phenomena as well as predict the transition onset position. Finally, comparisons between the predictions using the present model and the wind tunnel experimental results of several well-documented flow cases are provided to validate the proposed transition turbulence model.

The present study was designed to investigate the mechanical performance of ultra high molecular weight polyethylene (UHMWPE) reinforced by silver nanoparticles. The Ag/UHMWPE nanocomposites were prepared by a plate vulcanizing machine and tested with a contact angle micrometer, UMT friction tester, electronic universal testing machine and MicroXAM three-dimensional profilometer to characterise the wettability, ball indentation hardness, creep resistance, compression properties, and friction and wear performance. A scanning electron microscope (SEM) was employed to describe the morphology of the Ag/UHMWPE nanocomposites surfaces following the friction and wear tests. These results demonstrate that the compressive yield strength, ball indentation hardness and creep resistance increased with an increase in the content of silver nanoparticles. The contact angle of the Ag/UHMWPE nanocomposites with bovine calf serum decreases with an increase in the content of silver nanoparticles and this change increases the wettability of the Ag/UHMWPE nanocomposites. Therefore, the friction coefficient decreases, but the wear mechanism changes from scratch and furrow to fatigue flakes when the mass fraction of silver nanoparticles exceeds 0.3%. The composite with a silver nanoparticles mass fraction of 0.3% exhibits a low friction coefficient and good wear resistance.

Phenol–formaldehyde microcapsules containing solvent and epoxy resin are successfully prepared via in situ polymerization. Resin–solvent capsules are produced in high yield (up to 82.33%) and high core content (up to 86.3%), of which the diameter distribution ranges between 51 and 323 μm depending on the agitation rate varying from 400 to 1200 rpm. Chemical structure of the capsules is studied by FTIR, and surface morphology is further characterized by optical and electron microscopes. It is found that the capsules possess a rough and compact shell. Meanwhile, encapsulated core materials still keep sufficiently high chemical reactivity, and healing efficiencies effectively exceed 100% with the addition of 20 wt% microcapsules in the host polymer matrix.

Electron cyclotron resonance is induced to enhance the discharging performance of a cusped field thruster, by feeding microwave into the channel. Due to a critical combination of ECR discharge and DC discharge, propellant utilization is significantly improved, with varying degrees of impact on other parameters. The DC mode, the ECR mode and the combined mode are achieved and analyzed respectively. A Faraday probe and a retarding potential analyzer are employed to diagnose the plume plasma, and approximate calculated thrust is given. In addition, high frequency electric field simulation is carried out to indicate the microwave feeding process in different mass flow rate conditions, making use of a Particle-In-Cell simulation result. The result shows that the ECR enhancement is particularly effective in low mass flow conditions, and the special plasma distribution in the cusped magnetic field leads to the propellant utilization trend in the combined mode.

As the application requirements of semiconductor lasers continue to increase, severe challenges are brought to the reliability of semiconductor lasers. In order to promote the study of laser failure, this paper proposes an effective failure analysis method for packaged semiconductor lasers with a simple sample preparation and home-made photon emission microscopy (PEM) system. The new simple sample preparation process for failure analysis is presented and the necessary polishing fixture is designed so that sample can be obtained without expensive and complex micro-/nano-processing. Two types of home-made PEM experimental systems were established for observing the failure from the front facet and active region of semiconductor lasers. Experimental results showed that, with the proposed sample preparation flow, the home-made PEM experimental system effectively observed the leakage defects from the front facet and dark spot defects (DSDs) in the active region of semiconductor lasers. The method can help researchers and laser manufactures to perform effective failure analysis of packaged semiconductor lasers.

A Fe-based amorphous/nanocrystalline coating was prepared by the high-velocity oxygen fuel (HVOF) spraying process. The coating was characterized by x-ray diffraction, scanning electron microscopy and transmission electron microscopy. The corrosion resistances of the Fe-based coating and a reference electroplated hard chromium (EHC) coating were evaluated in a 3.5% NaCl solution, a 1 mol/L HCl solution and a 1 mol/L NaOH solution using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). All of the results indicated that the corrosion resistance of the Fe-based coating was superior to the resistance of the EHC coating in both the 3.5% NaCl solution and the 1 mol/L HCl solution due to the dense structure and fewer defects of the Fe-based coating. However, the corrosion resistance of the Fe-based coating was inferior to corrosion resistance of the EHC coating in the 1 mol/L NaOH solution. This could be ascribed to the drastic passivation of the EHC coating in an alkaline environment.

A novel method was developed to encapsulate 1-benzyl-2-methylimidazole (1B2MZ) to produce microcapsule-type latent curing agent using thiol-click reaction in an oil/water emulsion. The fabrication process was significantly simplified and required reaction time was greatly shortened due to the efficiency of click chemistry. In the oil phase, 1B2MZ was mixed with reactive monomers, 1,3,5-tri-2-propenyl-1,3,5-triazine-2,4,6 (1H, 3H, 5H)-trione (TTT) and tris[2-(3-mercaptopropionyloxy)ethyl] isocyanurate (TEMPIC) which would polymerize to result in polythioether shell of microcapsules by following a photoinitiated thiol-ene mechanism. Polyvinyl alcohol (PVA) aqueous solution acted as water phase. The whole reaction process lasted for 20 min, which was enough for almost full conversions of monomers. The generated latent curing agent had good spherical shapes with smooth outer surfaces and the mean diameter distributed in the range of 105.7 to 18.17 μm by adjusting PVA concentration or viscosity of oil phase. The curing behavior, kinetics and releasing mechanism of latent curing agent were studied by differential scanning calorimetry (DSC) and scanning electron microscope (SEM). This microcapsule-type latent curing agent had a long storage life for 30 days when mixed with epoxy resin at 20 °C, and the mixture could be cured at 100 °C within 1 h.

The sliding wear properties of high-velocity oxygen-fuel (HVOF) sprayed nanostructured WC-CoCr cermet coatings against Al 2 O 3 under dry friction at different temperatures were investigated using a pin-on-disk high-temperature tribometer. The microhardness data of the coatings were also statistically analyzed by using the Weibull distribution. The results showed that nanostructured coatings exhibited a mono-modal distribution under indentation load of 100 g, and a bimodal distribution under indentation load of 300 g. With increasing test temperature, the coatings showed an increase in wear rate. The evolution of the sliding wear mechanism of the coatings with the increase of the temperature was extrusion deformation at room temperature, carbide particle pull-out, oxidation wear and adhesive wear at 200 °C, and a combination of binder extrusion and fatigue delamination coupled with oxidation wear at 500 °C.

Single crystals of CeSbTe with a ZrSiS-type structure were synthesized using vapor transport method. The stoichiometry is deviated from the nominal composition, which may cause some disorder in this compound. The physical properties were characterized by measuring the magnetic susceptibility, electrical resistivity, Hall resistivity and specific heat. One antiferromagnetic (AFM) transition related to Ce3+ ions was found at [Formula: see text] K, and a field-induced metamagnetic transition was observed below [Formula: see text]. The moderately enhanced Sommerfeld coefficient [Formula: see text] mJ mol-1 · K-2 and the estimated Kondo temperature [Formula: see text] K, indicate that CeSbTe is a moderately correlated AFM Kondo lattice compound with crystalline electric field effect. The carrier concentration of CeSbTe derived from the Hall coefficient is in the order of 1021 cm-3, lower than most Kondo metals, which indicates that CeSbTe is a low-carrier-density Kondo semimetal.

In this study, an AlCoCrFeNi high-entropy alloy (HEA) coating was fabricated by HVOF spraying process. The HEA coating was consisted of the BCC phase (Al-rich phase) and FCC phase (Al-poor phase). The BCC phase was main phase. The mechanical performances and corrosion resistances of the coating and 06Cr13Ni5Mo martensitic stainless steel were analyzed in detail. The cavitation erosion behaviors and mechanisms of the HEA coating and 06Cr13Ni5Mo steel were investigated in distilled water and 3.5 wt% NaCl solution. The effects of microstructures, mechanical properties and corrosion properties on cavitation erosion mechanisms were discussed through the observation of eroded surface morphologies. The results showed that the cavitation erosion resistance of the AlCoCrFeNi coating was about 3.5 times that of the 06Cr13Ni5Mo steel in both solutions. In the 3.5 wt% NaCl solution, corrosion damage aggravated cavitation erosion damage, although the enhancement effect of corrosion on cavitation was limited. The corrosion environment did not change the cavitation erosion mechanisms of the two materials. The cavitation erosion mechanism of the HEA coating was lamellar spalling caused by the extension of the interlaminar cracks. Due to the lower plastic deformation resistance, the cavitation erosion mechanism of the 06Cr13Ni5Mo steel was material spalling caused by plastic deformation and fatigue fracture.

The use of polytetrafluoroethylene (PTFE) filter paper immersed in reference solutions is proposed as a novel external calibration strategy for the quantification of trace elements in fine particulate matter (PM2.5) by direct solid sampling–electrothermal vaporization–inductively coupled plasma-mass spectrometry (DSS-ETV-ICP-MS). This technique facilitated the simultaneous quantification of Mg, Mn, Cu, Zn, As, Sr, Cd, and Pb concentrations in PM2.5 samples collected on the PTFE filter paper. The feasibility of using this calibration method for DSS-ETV-ICP-MS was evaluated by studying physical samples collected in Hangzhou, China, and an NIST standard reference material (SRM) 1648a. The obtained results were in agreement with effective elemental concentrations (Dr 0.997) under the limits of detection (LODs) at the µg L−1 level were achieved using elemental platinum as an internal standard. Therefore, this study suggests that using filter paper as the support in immersion standard solutions is a reliable method for calibration and PM2.5 trace elements quantification by DSS-ETV-ICP-MS.

We propose a nonlocal continuum model to describe the size-dependent superelastic responses observed in recent experiments of shape memory alloys. The modeling approach extends a superelasticity formulation based on the martensitic volume fraction, and combines it with gradient plasticity theories. Size effects are incorporated through two internal length scales, an energetic length scale and a dissipative length scale, which correspond to the gradient terms in the free energy and the dissipation, respectively. We also propose a computational framework based on a variational formulation to solve the coupled governing equations resulting from the nonlocal superelastic model. Within this framework, a robust and scalable algorithm is implemented for large scale three-dimensional problems. A numerical study of the grain boundary constraint effect shows that the model is able to capture the size-dependent stress hysteresis and strain hardening during the loading and unloading cycles in polycrystalline SMAs.

We report an efficient and novel method for encapsulation of isophorone diisocyanate (IPDI) in polythioether microcapsules via thiol-ene click reaction based on Pickering emulsion, which has significantly improved and simplified the preparation process. The resultant microcapsules have spherical shapes with a layer of poly(glycidyl methacrylate) (PGMA) particles covering outside. The diameter ranges from 82.1 to 160.8 μm, which is controlled by the concentration of PGMA particles, and the typical shell thickness is about 9 μm. Moreover, the core content is up to 71% by adjusting the adding ratio of core/shell monomers. Remarkably, the microcapsules have excellently environmental stability that only 18% of the core content drops (from 63.2% to 51.8%) after immersion in water for seven days. These microcapsules could keep their integrity and uniformly disperse in acrylate coatings. In addition, they are proved to be a good self-healing candidate for coatings applied in wet environment.

The transport, magnetic and thermodynamic properties of the cerium oxide bismuth compound Ce2O2Bi are systematically investigated in a wide temperature regime. The compound crystallizes in the anti-ThCr2Si2-type structure consisting of a separated Bi2− square net layer between the CeO layers. In the high temperature regime 200–300 K, the compound shows the conventional metallic behavior and localized 4 f electrons of Ce3+ ions. In the low temperature regime 15–30 K, the resistivity increases with a logarithmic temperature dependence, accompanied with the negative magnetoresistance and a low carrier density. Further decreasing temperature, the resistivity drops rapidly below 6.2 K, signaling an antiferromagnetic ordering transition within the Kondo phase. Both susceptibility and specific heat display a similar transition around the same temperature, accompanied with a reduced magnetic entropy. A large Sommerfeld coefficient ∼ 336 mJ/mol K2 is obtained by fitting the specific heat data and no superconductivity is observed down to 0.3 K. All these observations suggest that Ce2O2Bi is a rare low carrier density Kondo lattice compound whose interlayer hybridization between 4 f electrons of Ce3+ ions and conduction 6 p electrons of Bi2− ions plays a crucial role.

Hot corrosion has been considered as a serious problem in boiler tubes because of poor quality fuels which result in the presence of salt contaminants such as Na2SO4, K2SO4 and NaCl. To solve this problem, FeCrNiAlMnB/Cr3C2 coating was fabricated on AISI 1020 steel substrate by high velocity arc spray technique, and the hot corrosion behavior of the coating was investigated in the presence of Na2SO4 + 25 wt% K2SO4 and Na2SO4 + 25 wt% NaCl at 650 °C and 750 °C. Phase composition, microstructure and corrosion products of the coating were characterized by XRD and SEM/EDS techniques. The results showed that the coating exhibited much less mass gain and superior hot corrosion resistance as compared with bare AISI 1020 steel, and kinetics studies indicated parabolic characteristic for the coating under different corrosion conditions. Different morphologies attributed to corrosion products which consisted of (Fe, Cr)2O3, FeCr2O4 (Na2SO4 + 25 wt% K2SO4) and (Fe, Cr)2O3, FeO, Na2CrO4, NaFeO2 (Na2SO4 + 25 wt% NaCl) were observed after exposition to above two molten salts. The destructive effect of Na2SO4 + 25 wt% NaCl on the coating was much greater than that of Na2SO4 + 25 wt% K2SO4 due to the reaction between NaCl and protective oxide layer, which formed Cl2 and further destroyed the uncorroded coating as well as led to the formation of cracks in the protective oxide layer.

The high efficiency multi-staged plasma (HEMP) thruster, also known as the cusped field thruster, becomes a candidate microthruster of new generation space observation missions for its low complexity and potential long life over a wide range of thrust. Since there is a lack of relevant research of the wall material effects on the HEMP thruster, a low-power HEMP thruster with three different dielectric wall materials is tested to discover the effects on performance and discharge characteristics. A Faraday probe, a retarding potential analyzer, and a Langmuir probe are employed to diagnose the plume, and the plasma behavior differences in ionization and acceleration processes are indicated. The result shows that the secondary electron emission coefficient of the wall material has definite effects under a low mass flow rate, which is similar to the effects on the Hall thrusters, but no distinct difference is found in high flow rate conditions.

Tuning bandgap and phases in the ternary 2D transition metal dichalcogenides (TMDs) alloys has opened up unexpected opportunities to engineer optoelectronic properties and explore potential applications. In this work, a salt-assisted chemical deposition vapor (CVD) growth strategy is reported for the creation of high-quality monolayer W1- x Rex S2 alloys to fulfill a readily phase control from 1H to DT by changing the ratio of Re and W precursors. The structures and chemical compositions of doping alloys are confirmed by combining atomic resolution scanning transmission electron microscopy-annular dark field imaging with energy dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy, matching well with the calculated results. The field-effect transistors (FETs) devices fabricated based on 1H-W0.9 Re0.1 S2 monolayer exhibit a n-type semiconducting behavior with the mobility of 0.4 cm2 V-1 s-1 . More importantly, the FETs show high-performance responsivity with a value of 17 µA W-1 in air, which is superior to that of monolayer CVD-grown WS2 . This work paves the way toward synthesizing monolayer ternary alloys with controlled phases for potential optoelectronic applications.

We systematically investigated the modulation effects of substrates on the ferromagnetism properties of Fe3GeTe2 experimentally and theoretically. The polar refractive magnetic circular dichroism results demonstrate that the ferromagnetism could be modulated significantly by selecting different substrates. We explain this phenomenon using the first-principles calculation, revealing that it was induced by the lattice distortion and charge redistribution between the interfaces. Our work is useful to understand the fundamental mechanism of tunable ferromagnetism and paves the way for exploring interface physics and practical spintronic applications of two-dimensional ferromagnetic van der Waals crystals.

Under extreme thermal environment, ablation process of thermal protection system is a key issue in atmospheric re-entry and hypersonic flight vehicles; it displays a strong coupling between ablation mass, velocity and heat transfer. This article presents a method for combining the ablating and melting process, building a right triangle carbon-carbon model for ablation mixed with octadecane phase change material to absorb the heat of combustion delaying the movement of burning interface. For the moving of boundary, it is treated by the modified Stefan model coupled with chemical reaction and thermal radiation at the front leading boundary. The governing equation of heat transfer considering the melting process of phase change material is given by referring the enthalpy method. The effect of volume ratio and aerodynamic heating on the ablation interface and net heat flux on the interface are investigated. Result shows that high volume ratio of the phase change material delays the movement of the interface, and decreases the net heat flux of the interface; on the other hand, high aerodynamic heat accelerates the movement of the interface and increases the interface net heat flux at a given time point. This study can give a rule on how the volume ratio of phase change material influence the ablative process quantitatively.

We report the discovery of superconductivity with T c of about 5.3 K in a new misfit layered compound (SnSe)1.16(NbSe2)2. High resolution transmission electron microscopy and selected area electron diffraction of the single-crystalline samples clearly reveal the misfit layered structure. Based on the McMillan equation, the electron-phonon coupling constant λ e – ph is estimated to be about 0.96, which is close to strong coupling range. The estimated out-of-plane and in-plane upper critical magnetic fields are 8.9 T and 15.5 T respectively. H c 2 ab (0) is 1.74 times the value of Pauli paramagnetic limit. Moreover, there is a positive curvature in the H c 2 ( T ) curves near T c , indicating a feature of multi-band superconductivity. The temperature dependence of specific-heat in superconducting state can be fit by a two-band BCS model, which confirms further the multi-band superconductivity. The reduced charge transfer between the two subsystems may account for the enhanced T c comparing with (SnSe)1.16(NbSe2).

The self-healing of passive film on Ti after being damaged in Hank's physiological solution greatly fluctuates with time and its mechanism has been investigated by in-situ X-ray absorption fine structure spectroscopy (XAFS) and surface enhanced Raman spectroscopy (SERS) in a novel electrochemical repassivation set-up. The self-healing response is instant and the current density decays within 50 s due to the increase of the ratio of O and Ti atoms. The increase of the coordination number of Ti O contributes to the decrease of current density until 6000 s. Moreover, the in-situ structure evolution is vastly different from that of ex-situ. Two time-dependent adsorbed intermediates exist during self-healing, the adsorption layers of Ti OHads and Ti OH, and finally the interface forms a stable passive film of O Ti OH after 1000 s with good corrosion resistance. Besides, in-situ XAFS and SERS exhibit a high disorder and amorphous nature of passive film on Ti, and the crystallinity increases from 300 s to 6000 s. Additionally, the time-dependent structure evolution and mechanism of self-healing of titanium passive film in local atomic scale will help to understand the corrosion science and protection in healthcare.

With a limited number of built-in power monitors to detect the optimum operating points of all switch units, we demonstrated a 32 × 32 MZI-based silicon electro-optical switch operating with nanosecond speeds.

To construct large-scale silicon electro-optical switches for optical interconnections, we developed a method using a limited number of power monitors inserted at certain positions to detect and determine the optimum operating points of all switch units to eliminate non-uniform effects arising from fabrication errors. We also introduced an optical phase bias to one phase-shifter arm of a Mach–Zehnder interferometer (MZI)-type switch unit to balance the two operation statuses of a silicon electro-optical switch during push–pull operation. With these methods, a 32 × 32 MZI-based silicon electro-optical switch was successfully fabricated with 180-nm complementary metal–oxide–semiconductor (CMOS) process technology, which is the largest scale silicon electro-optical switch to the best of our knowledge. At a wavelength of 1520 nm, the on-chip insertion losses were 12.9 to 16.5 dB, and the crosstalk ranged from −17.9 to −24.8 dB when all units were set to the ‘Cross’ status. The losses were 14.4 to 18.5 dB, and the crosstalk ranged from −15.1 to −19.0 dB when all units were in the ‘Bar’ status. The total power consumptions of the 32 × 32 switch were 247.4 and 542.3 mW when all units were set to the ‘Cross’ and ‘Bar’ statuses, respectively.

Fe-based amorphous/nanocrystalline coatings were prepared on the AISI 321 steel substrate by the high-velocity oxygen-fuel (HVOF) thermal spraying technology. The effect of selected parameters (oxygen flow, kerosene flow and spray distance) on the cavitation erosion resistance (denoted as Rc) of the coating were investigated by using the Taguchi method. Statistical tools such as design of experiments (DOE), signal-to-noise (S/N) ratio and analysis of variance (ANOVA) were used to meet the expected objective. It was concluded that the kerosene flow had greater influence on the Rc of the coating and followed by the spray distance and the oxygen flow, respectively. The optimum spray parameters (OSP) were 963 L/min for the oxygen flow, 28 L/h for the kerosene flow, and 330 mm for the spray distance. The Rc of the coating increased with the increase of hardness or the decrease of porosity, and the hardness had a greater influence on Rc than the porosity. The Fe-based coating deposited under the OSP exhibited the best cavitation erosion resistance in distilled water. The cracks initiated at the edge of the pores and the interfaces between the un-melted or half-melted particles, and finally leaded to the delamination of the coating.

Electromigration (EM), creep, and thermal fatigue (TF) are the most important aspects of the reliability of electronic solder joints, the failure mechanisms of which used to be investigated separately. However, current, mechanical loading, and temperature fluctuation usually co-exist under real service conditions, especially as the magnitude of current density is increasing with joint miniaturization. The importance of EM can no longer be simply ignored when analyzing the creep and TF behavior of a solder joint. The published literature reports that current density substantially changes creep rate, but the intrinsic mechanism is still unclear. Hence, the purpose of this study was to investigate the effects of EM on the creep and TF behavior of Sn58Bi solder joints by analyzing the evolution of electrical resistance and microstructure. The results indicated that EM shortens the lifetime of creep or TF of Sn58Bi solder joints. During creep, EM delays or suppresses the cracking and deforming process, so fracture occurs at the cathode interface. During TF, EM suppresses the cracking process and changes the interfacial structure.