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In this work, phosphor-converted white laser diodes (pc-WLDs) with high color quality were fabricated by combining blue lasers and bicolor phosphor-in-glass (PiG) converters. The bicolor PiGs were prepared by printing and sintering green/red phosphor glass films on sapphire substrates, and then applied in the transmission type of pc-WLDs. The PiG-based white laser diodes (WLDs) display broadband emission and their optical performances were adjusted by varying the PiG film thickness. When the film thickness increases from 80 to $160~\mu \text{m}$ , the luminous flux and correlated color temperature (CCT) of PiG-based WLDs are gradually decreased, and they still have high color rendering index (CRI). At the film thickness of $160~\mu \text{m}$ , the PiG-based WLD achieves high color quality with a CRI of ${R}_{a} = {88}$ , ${R}_{{9}} = {91}$ , and ${R}_{{13}} = {93}$ , a CCT of 4571 K, and a chromaticity coordinate of (0.3525, 0.3541) at a laser power of 2.4 W. Furthermore, the PiG-based WLD has stable color quality at high laser power and the luminous flux reaches to 553 lm at a laser power of 5 W. The results indicate that the bicolor PiG-based WLDs realize high-quality white light, which can promote the practical applications of laser lighting in high-quality fields.

By using the transient finite element method, a three-dimensional wheelset-track coupled rolling contact model for high-speed rail is established, and the rationality and effectiveness of the model are verified by field measurements. Next, the wheel-rail contact stress states and relative slip characteristics are calculated and analyzed to reveal the cause of inner rail corrugation. Then, the vertical vibration acceleration of the rail/wheel is taken as the output variable to study the dynamic responses of the wheelset-track system. Finally, the parameter sensitivity analysis is carried out. The results show that the maximum normal/tangential contact stress between the inner wheel and inner rail is greater than that between outer wheel and outer rail due to the unbalanced load of inner rail caused by the excess superelevation of track structure, which indicates that the unbalanced load of the inner rail may aggravate the development of rail wear, and the rationality of the model established in this paper is verified. The wheel-rail relative slip region on the inner rail side appears periodically, and the distance between the two adjacent slip regions is close to the characteristic wavelength of the measured inner rail corrugation, which illustrates that the periodic variation of slip regions on the inner rail surface plays an important role in the formation of rail corrugation, and the validity of the model is verified. The periodic distribution of wheel-rail relative slip regions on the outer rail surface is not obvious, demonstrating that the outer rail tends to form uniform wear, which is consistent with the fact that the outer rail corrugation is slight in the measured section. The wheelset-track system has been in the process of unstable continuous oscillation in the analysis interval, combined with the analysis results of the wheel-rail relative slip characteristics, it can be concluded that the unstable self-excited vibration of wheelset-track system under the condition of tangential contact force reaching saturation is the main cause of rail corrugation. The dominant characteristic frequencies of vertical vibration accelerations of rail and wheel are all 561 Hz, the corresponding characteristic wavelength (148 mm) is close to the distance (150 mm) between the calculated adjacent slip regions, and is also close to the characteristic wavelengths (125 mm and 160 mm) of inner rail corrugation, which shows that the resonance phenomenon occurs in the wheelset-track system at the above frequency, thus leading to the increase of dynamic responses of wheelset-track system. The fastener vertical stiffness and wheel-rail coefficient of friction have significant effect on the development of rail corrugation, and the running speed determines the occurrence probability of inner/outer rail corrugation by affecting the track superelevation state.

Based on the metro vehicle-track spatial coupled model, the wheel-rail dynamic responses of tangential track under different composite corrugation irregularities and the development characteristics of composite corrugation irregularities were studied by simplifying rail surface composite corrugation irregularities into superimposed harmonic corrugations. The time domain analysis results demonstrate that the short wavelength corrugation irregularity has obvious influence on wheel-rail dynamic characteristics. The frequency domain analysis results show that the existence of rail corrugation will also lead to wheel-rail dynamic responses at higher frequencies. The wear frequency spectrum curves contain characteristic frequencies corresponding to wavelengths of composite corrugation irregularities, and the peak values are high, showing that composite corrugation irregularities are in the process of continuous development, and the development speed of shorter wavelength corrugation is faster than that of longer wavelength corrugation. The peak values of wear frequency spectrum curves also appear at frequency multiple points of passing frequencies corresponding to wavelengths of composite corrugation irregularities, which illustrates that corresponding wavelength corrugations can be easily formed. Meantime, rail corrugation has the trend of developing into short-wavelength corrugation.

In order to study the waterproof performance of non-curable rubber modified asphalt material at deformation joints, the grouting situation of non-curable rubber modified asphalt material in the def...

Developing highly efficient and durable eco-friendly heterogeneous catalysts for the Friedel–Crafts acylation (FCA) reaction has been a long-term and significant target, yet remains a great challenge. Herein, a series of Fe–Ni alloy nanoparticles (NPs) encapsulated inside N-doped carbon spheres (FexNi1−x@NC) was rationally fabricated by pyrolyzing the Fe–Ni bimetallic metal–organic frameworks (BMOFs-FexNi1−x) to this end. Various characterization results demonstrated that FeNi alloy NPs (25 nm) covered by a thin carbon shell (5 nm) were uniformly distributed throughout the entire carbon-based composite. A number of oxidized metal species (Fe3+, Ni2+) are present on the surface of the inner bimetallic core, which should be the main source of catalytically active centers of the carbon-wrapped metal NP catalysts. The composition-optimized Fe0.8Ni0.2@NC with relatively higher positive surface charges exhibited the highest catalytic activity and excellent stability for the acylation of aromatic compounds with acyl chlorides. The density functional theory calculations revealed that the catalytic activity of the FexNi1−x@NC catalysts could arise from the electron transfer, i.e., from the outermost layer of the carbon shell to the inner positively charged Fe-based metal NPs, which can lead to a positive charge distribution (by acting as weak Lewis acid sites) on the external surface of the carbon-encapsulated metal NP catalysts. In this case, the external carbon shell can function as ‘chainmail’ to transfer the Lewis acidity (positive charge), and also to protect the inner metal core from the destructive reaction environment, thus resulting in the formation of highly efficient and durable FCA catalysts.

The typical passing frequencies of corrugation were obtained by analysing the measured corrugation data in small radius curve track with Cologne-egg fasteners. The three-dimensional solid element model of track structure was established with the software ABAQUS, and modal analysis was carried out to determine the relationship between natural frequencies of track structure and passing frequencies of corrugation. By using the material wear model based on friction work theory, the frequency characteristics of corrugation and the development law of wear under different speeds were studied, and the control measures of corrugation were analysed. The new point of this study is to implement the above dynamic analysis from the perspective of vehicle (with flexible wheelsets) track space coupling, which can consider the coupled relationship in three directions of space. The results show that the generation of corrugation is closely related to the mechanical characteristics of track structure. Passing frequencies do not change with speeds, reflecting the frequency-fixing characteristics of corrugation. The analysis of control measures of corrugation shows that the smaller the friction coefficient is, the less likely the rail is to produce corrugation. The existence of rail vibration absorber can eliminate the generation of some short wavelength corrugation and reduce the rail bending vibration, which has a significant effect on the control of corrugation.

To study the wheel–rail contact and creep characteristics and the evolution law of corrugation with different wavelengths, the wave-like wear is idealized as continuous harmonic excitations consisting of three wavelengths and wave depths, and the vehicle–track space coupled dynamic model is established for specific analysis. The results show that when the wavelength is fixed and the wave depth increases, the average values of rail/wheel vertical vibration acceleration and wheel–rail longitudinal creepage/creep force increase and the average value of transverse creepage/creep force decreases. But, when the wave depth is fixed and the wavelength increases, the average values of rail/wheel vertical vibration acceleration and longitudinal creepage/creep force decrease and the average value of transverse creepage/creep force increases. Both longitudinal and transverse creepages/creep forces contain the characteristic frequency consistent with the passing frequency of initial irregularity. The characteristic frequencies of longitudinal creepages/creep forces tend to develop in the high-frequency band with the increase of wave depth, whereas the characteristic frequencies of transverse creepages/creep forces concentrate in the low-frequency band and decrease with the increase of wave depth. Under the condition of the same wavelength, with the increase of operation times, the wear amount increases slightly in the low-frequency band but greatly in the middle- and high-frequency bands, which shows that rail corrugation will gradually develop toward short wavelength corrugation at the constant velocity. When rail corrugation is formed, its development speed will gradually slow down with the increase of vehicle running times, and the development speed of short wavelength corrugation is faster than that of long wavelength corrugation.

The fast Li-ion pathways in crystals contribute to superionic conductivity-extraordinarily high ionic conductivity-of the Li10GeP2S12 (LGPS) structure. Composition tuning is expected to improve the conductivity. The phase behavior, microstructure, and ion dynamics of a series of solid solutions of xLi4GeS4-yLi3PS4 (4/1 ≥ x/y ≥ 1/2) were studied by multiple 7Li and 31P solid-state NMR methods. Li10GeP2S12 (Ge/P = x/y = 1/2) is the smallest x/y of the disordered LGPS structure. When the Ge/P ratio increases, the room-temperature Li ionic conductivity first increases to a maximum around x/y = 1/1.2 and then decreases. Meanwhile, a disordered LGPS structure transforms into an ordered LGPS' structure synchronously with conductivity reduction. The Li4GeS4-Li3PS4 phase diagram with the order-disorder structure transition was reconstructed accordingly. Both ordered LGPS' and disordered LGPS exhibit similar two-dimensional (2D) and one-dimensional (1D) Li diffusion paths. But the disordered LGPS structure is conducive to fast ionic conductivity, rooted in its fast 2D Li+ diffusion in the ab-plane rather than 1D diffusion along the c-axis. Two high-temperature relaxation processes are observed in the LGPS' structure, suggesting heterogeneous 2D jumps of rapid and slow rates, whereas only a single homogeneous 2D jump process was found in the LGPS structure. Our findings provide insight into understanding the relationship between structure order (or disorder) and ionic conductivity of superionic materials, offering guidelines for optimizing ionic conductivity for extensive solid electrolyte materials rather than LGPS materials.

Field investigation shows that most corrugations occur on the inner rail surface of curved tracks with a radius of less than 700 m. In order to explore the formation mechanism of metro corrugation, the relationship between wheel–rail stick–slip characteristics and rail corrugation is studied by combining single wheelset curving and a rigid–flexible coupling model. The numerical results illustrate that the lateral torsional stick–slip vibration of inner rail–inner wheel of the guiding wheelset on the small radius curve eventually leads to the generation of inner rail corrugation, and the lateral torsional stick–slip vibration of outer rail–outer wheel of the driven wheelset may also occur, but the intensity is weak and the probability is low. The lateral torsional stick–slip vibration of inner rail–inner wheel of the guiding wheelset on the large radius curve is also easy to cause inner rail corrugation, but the degree of inner rail corrugation is lower than that on the small radius curve, the outer rail on the large radius curve is still not easy to produce corrugation. The formation mechanism of rail corrugation on the straight track is different from that on the curve track, which is mainly related to the wheel–rail longitudinal torsional stick–slip vibration.

The Mooney–Rivlin hyperelastic model and Prony series viscoelastic constitutive model are used to verify the selected calculation parameters by finite element analysis compared with stress relaxation test data. Then, the ANSYS-PDS (ANSYS-probabilistic design system) module is used to analyze the sensitivity values of all random parameters to surface contact stress and the influence of hyperelastic and viscoelastic parameters on the surface contact stress relaxation. The results show that parameter values are reasonable. Random parameters that have great influence on the surface contact stress are α2 and C10, followed by α1, τ1 and C01, and the influence of τ2 is negligible, which shows that for the second-order viscoelastic model, the change in clay pot coefficient η2 has little effect on the surface contact stress. Moreover, with the increase in C10, the surface contact stress increases significantly; with the increase in α2, the surface contact stress decreases significantly, and the surface contact stress varies uniformly with C01. Stress relaxation mainly occurred on the first day of loading and remained basically stable within 1 year. The greater the values of hyperelastic parameters are, the smaller the stress attenuation is, and the opposite of viscoelastic parameters.

Low-cost hierarchical porous carbon materials with a controllable structure and high specific surface area as well as large pore volume were synthesized by a one-step route involving SnO2@chitosan precursor carbonization and subsequent SnO2 template removal. We found that when HPC CISC-29 is applied as the electrode in the supercapacitor device, it exhibits both high specific capacity (260.4 F g−1) and excellent rate capacitance retention (81.9%) from 0.1 A g−1 to 10 A g−1. CISC-29 shows superiority compared to conventional activated carbons for which specific capacitance and capacitance retention are 100–200 F g−1 and 60–70%, respectively. Solid-state NMR and NLDFT porosity distribution results reveal that the high specific capacitance is most likely associated with the optimized hierarchical porous structure, e.g. rich small-size micropores and their good connection with large-size mesopores. Finally, CISC-29 was complexed with Se to construct a cathode for lithium selenium batteries. Se@CISC-29 shows excellent performance with a specific capacity of 1207.0 mA h g−1 at 0.1 A g−1.

Vanadium hexacyanoferrate (VHCF) with an open-framework crystal structure is a promising cathode material for rechargeable aqueous metal-ion batteries owing to its high electrochemical performance and easy synthesis. In this paper, vanadium hexacyanoferrate cathodes were first used for constructing rechargeable aqueous sodium-ion batteries (VHCF/WO3) and tested in the new-type electrolyte (NaP-4.6) consisting of a polyethylene glycol (PEG)/H2O/NaClO4 electrolyte with a low H+ concentration (molar ratio of [H2O]/[Na+] is 4.6), which has high stability at a high current density as high as 1000 mA g-1 with a capacity retention of 90.3% after 2000 cycles at high coulombic efficiency (above 97.8%). To understand their outstanding performance, the proton-assisted sodium-ion storage mechanism and interphase chemistry of VHCF are investigated by solid-state NMR (ssNMR) technology. It is suggested that the H+ storage reaction is accompanied by the redox of vanadium atoms and Na+ intercalation is accompanied by the redox of iron atoms. It is also observed that the complex of polyethylene glycol (PEG) with Na+ (PEG-Na+) exists on the VHCF surface, which facilitates the stability of VHCF and promotes the alkali-ion transfer at a high current density. The results of the ssNMR study offer new insights into the intercalation chemistry of Prussian blue analogues with open-framework-structured compounds, which can greatly broaden our horizons for battery research.

In order to study the waterproof performance of elastic rubber gasket in shield tunnel lining joints, an innovative sensitivity analysis method is proposed by combining the Monte Carlo method with the stochastic finite element method (FEM) in this paper. The sensitivity values of the waterproof performance respecting to elastic rubber gaskets are obtained via the ANSYS Probabilistic Design System (PDS) module, in which the parameters of material hardness, coordinates of the hole center, apertures are selected as random input variables. Meantime, the extent of the tolerance effect of the random parameters on the waterproof performance is explored.

Inorganic phosphor-in-glasses (PiGs) are promising color converters for white light-emitting diodes (LEDs) and laser diodes (LDs) because of excellent heat resistance, phosphor versatility, and tunable luminescence. However, the long sintering time and poor preparation efficiency of PiGs limit their applications. Herein, we proposed an induction heating to prepare PiGs for white LEDs/LDs. Due to its fast and non-contact properties, this method realizes the rapid sintering of PiGs. The PiGs sintered under various induction time were carried out and their luminescent properties were investigated. As the induction time increases from 15 to 35 s, the maximum sintering temperature of PiG increases from 580 °C to 795 °C, and the PiG has a high emission intensity at 30 s. The PiG enables the white LED with a LE of 75.3 lm/W and a correlated color temperature (CCT) of 5290 K and the white LD with a luminous flux of 1040 lm and a CCT of 5703 K. The PiG-based white LEDs/LDs achieve excellent color stability even at high input current.

To solve the high cost and high sintering temperature of Ag nanoparticle inks and the poor storage stability of Ag precursor inks, an inexpensive and self-reducing Ag2O ink was designed for fabricating highly flexible printed conductors at low sintering temperature. The printed Ag2O inks can be in-situ reduced to Ag particles and form the conductive network, and the electrical properties and flexibility of the sintered Ag tracks were systematically investigated. Consequently, the printed Ag tracks sintered at 160 °C exhibit the low electrical resistivity of 1.38 × 10−4 Ω cm, and the relative resistances (R/Ro) of Ag tracks are less than 1.3 and 1.7 after 1000 times of the bending and twisting tests, respectively. These results demonstrate that the inexpensive Ag2O ink provides an attractive prospect for low temperature fabricating high-quality flexible printed conductors.

RSC Advances 8(31), 17435-17442 (2018). doi:10.1039/C8RA02561D, Published by RSC Publishing, London

The textile sample is rubbed with a dry friction cloth and a wet friction cloth respectively to evaluate the staining degree of the friction cloth. The tester for color fastness to rubbing provides two sets of test conditions through two friction heads of optional sizes: one for pile fabrics; The other is used for monochrome fabrics or large-area printed fabrics. Through the analysis of the original test method, the existing problems and defects of the original test method are obtained. A substitute material is used on the tester platform for testing samples, and the fixation method of the tester’s samples is improved in a pawn type, so as to solve the problem of uneven staining of friction cloth caused by uneven surface of friction head or friction medium and unilateral wear during friction.

Comparative fatigue tests were conducted on as-welded, weld toe peened specimens before and after fatigue loading. Fracture surface, residual stress, microstructure and hardness were determined. The test results showed that as the pre-fatigue loading period extended, deeper cracks may have initiated and propagated and the fatigue life improvement decreased. The processes of ultrasonic peening on welded joints with existing cracks were modeled by finite element analysis. The numerical results indicated that the mechanism of UIT improving fatigue performance included two factors: compressive residual stress and the change of crack orientation. Both effects reduced as the crack became deeper.

Graphene/ZnO (G/ZnO) composites were synthesized for the first time by a wet chemical method. X-ray diffraction and transmission electron microscopy analyses demonstrated that ZnO nanoparticles with an average diameter of about 5 nm uniformly covered the graphene surfaces. G/ZnO composites were dispersed in methyl methacrylate (MMA), polymerized at 75 °C for 30–35 min, and finally, dried at 45 °C for 10 h, to afford G/ZnO/PMMA organic glasses. UV–visible spectra showed that the band gaps of the G/ZnO/PMMA organic glasses were about 3.54 eV, larger than that of bulk ZnO because of the small size effect of ZnO nanoparticles. The nonlinear optical (NLO) and optical limiting (OL) properties of the G/ZnO/PMMA organic glasses were investigated by a modified Z-scan technique. The total NLO coefficient α 2 of the G/ZnO/PMMA organic glass was as high as 1530 cm/GW, which was approximately 5.6 and 7.8 times larger than those of G/PMMA and ZnO/PMMA organic glasses. The enhanced NLO properties of the G/ZnO/PMMA organic glasses led to excellent OL performance, which was attributed to the positive synergistic effects between graphene and ZnO.

Graphene/MoS2 (G/MoS2) composites were synthesized for the first time by a hydrothermal method, and then were dispersed in methyl methacrylate (MMA) to fabricate organic glass by a casting method. Here, the poly(methylmethacrylate) (PMMA) host can be obtained by the polymerization of MMA. The nonlinear absorption (NLA) properties of the G/MoS2/PMMA organic glasses were investigated by using an open-aperture Z-scan technique. The experimental results showed that the G/MoS2/PMMA organic glasses (the NLA coefficient β, was up to 2110 cm/GW) exhibited enhanced reverse saturable absorption (RSA) properties compared to G/PMMA (β = 242 cm/GW) and MoS2/PMMA (β = 365 cm/GW) organic glasses. The enhanced mechanism of RSA was analyzed in terms of the energy-level diagram of graphene and MoS2. The G/MoS2/PMMA organic glasses have very promising applications in optical devices such as optical limiters and optical shutters.

Graphene (G)/Fe nanocomposites with ferromagnetic properties at room temperature were fabricated by a facile and green method. Transmission electron microscope (TEM) and atomic force microscopy (AFM) amylases reveal that the α-Fe nanoparticles with a diameter of only about 10 nm were uniformly dispersed over the surface of the graphene sheets. Compared with other magnetic materials and the graphene, the nanocomposites exhibited significantly enhanced electromagnetic absorption properties. The maximum reflection loss to electromagnetic wave was up to −31.5 dB at a frequency of 14.2 GHz for G/Fe nanocomposites with a thickness of 2.5 mm. Importantly, the addition of the nanocomposites is only about 20 wt.% in the matrix. The enhanced mechanism is discussed and it is related to high surface areas of G/Fe nanocomposites, interfacial polarizations between graphene and iron, synergetic effect and efficient dispersity of magnetic NPs.

The ZnO nanowire (NW) array/TiO2 nanoparticle (NP) composite photoelectrode with controllable NW aspect ratio has been grown from aqueous solutions for the fabrication of dye-sensitized solar cells (DSSCs), which combines the advantages of the rapid electron transport in ZnO NW array and the high surface area of TiO2 NPs. The results indicate that the composite photoelectrode achieves higher overall photoelectrical conversion efficiency (η) than the ZnO NW alone. As a result, DSSCs based on the ZnO NW array/TiO2 NP composite photoelectrodes get the enhanced photoelectrical conversion efficiency, and the highest η is also achieved by rational tuning the aspect ratio of ZnO NWs. With the proper aspect ratio (ca. 6) of ZnO NW, the ZnO NW array/TiO2 NP composite DSSC exhibits the highest conversion efficiency (5.5 %). It is elucidated by the dye adsorption amount and interfacial electron transport of DSSCs with the ZnO NW array/TiO2 NP composite photoelectrode, which is quantitatively characterized using the UV-Vis absorption spectra and electrochemical impedance spectra. It is evident that the DSSC with the proper aspect ratio of ZnO NW displays the high dye adsorption amount and fastest interfacial electron transfer.

G/Ag2S composites were synthesized for the first time by a hydrothermal method. X-ray diffraction, scanning electron microscopy, and transmission electron microscopy analysis demonstrated that Ag2S nanoparticles with a diameter of about 130 nm uniformly covered the graphene surfaces. G/Ag2S composites were dispersed in methyl methacrylate (MMA), polymerized at 75 °C for 30-35 min, and finally dried at 45 °C for 10 h, to afford G/Ag2S/PMMA organic glasses. The nonlinear absorption (NLA) properties of the G/Ag2S/PMMA organic glasses with different amounts of G/Ag2S were investigated by an open-aperture Z-scan technique. The experimental results showed that the G/Ag2S/PMMA organic glass with an appropriate amount of G/Ag2S exhibited enhanced reverse saturable absorption (RSA) properties compared to G/PMMA and Ag2S/PMMA organic glasses, which was attributed to the notable synergistic effects between graphene and Ag2S. Both one-photon absorption (OPA) in Ag2S and two-photon absorption (TPA) in graphene played important roles in RSA processes of the G/Ag2S/PMMA organic glasses. The effective NLA coefficient βeff of the G/Ag2S/PMMA organic glasses was in the order of 10(3) cm GW(-1). Thus this kind of organic glasses have great promise in optical limiter and optical shutter applications.

In this work, we developed an efficient and facile method to fabricate branched polyaniline (PANI)/α-MoO3 organic/inorganic heteronanostructures. Scanning electron and transmission electron microscope measurements showed that PANI nanorods with an average diameter and length of about 55 and 110 nm respectively were grown perpendicularly on the surfaces of α-MoO3 nanorods and the density of the PANI nanorods could be readily controlled by simply changing the addition amount of aniline in the reaction system. The minimal reflection loss for the electromagnetic wave absorbent material was up to −33.7 dB at 16.88 GHz for the branched heteronanostructures/paraffin composites with a thickness of 2.0 mm, and all of the minimal reflection losses were less than those of the pure PANI nanorods in the frequency range of 2–18 GHz. More importantly, the content of the branched nanostructures in the paraffin matrix was only 10 wt%. Thus, the method presented here is a very efficient strategy to fabricate lightweight materials for strong electromagnetic wave absorbents.