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Ultrathin Pd45Pt44Ni11 spiral nanosheets with abundant Pt/Ni-segregated edges exhibit excellent ORR and OER dual-electrocatalysis in alkaline, showcasing a workable air cathode electrocatalyst for high-efficiency and rechargeable Zn–air batteries.

Dual-active-sites atomically coupled on ultrafine 1D nanowires (NWs) can offer synergic atomic heterojunctions (AHJs) and high atomic-utilization toward multipurpose and superior catalysis. Here, ≈2-nm-thick PtIr/IrO

Water pollution is a worldwide problem that requires urgent attention and prevention and exceeding use of heavy-metal ions is one of the most harmful factors, which poses a serious threat to human health and the ecological environment. In this work, a magnetic oxidized micro/mesoporous carbon (MOMMC) was prepared for the easy separation of Cu(II) and Pb(II) from water. The dual-template method was used to prepare micro/mesoporous carbon using sucrose as the carbon source, silica nanoparticles formed by tetraethyl orthosilicate as the microporous templates, and triblock copolymer F127 as the mesoporous template. MOMMC was obtained by oxidation using potassium persulfate and then magnetized through in situ synthesis of Fe3O4 nanoparticles. FTIR, TG-DSC, XRD, TEM, SEM, nitrogen adsorption–desorption isotherms, zeta potential, and VSM were used to confirm the synthetic process, structure, and basic properties of MOMMC. The high-saturation magnetization (59.6 emu·g−1) of MOMMC indicated its easy and fast separation from water by an external magnetic field. Kinetics studies showed that the adsorption of Cu(II) and Pb(II) on MOMMC fit the pseudo-second-order model well. Isotherm studies showed that the adsorption behavior of Cu(II) was better described by the Langmuir model, and the adsorption behavior of Pb(II) was better described by both Langmuir and Redlich–Peterson models. MOMMC obtained efficient adsorption for Cu(II) and Pb(II) with the large adsorption capacity of 877.19 and 943.40 mg·g−1 according to the Langmuir adsorption isotherm equation, and a better selectivity for Pb(II) was observed in competitive adsorption. MOMMC still possessed a large adsorption capacity for Cu(II) and Pb(II) after three adsorption–desorption cycles. These findings show that MOMMC represents an excellent adsorption material for the efficient removal of heavy-metal ions.

The acoustic impedance of perforated plates is influenced by fluid flow through the orifice. The present study employs the three-dimensional (3-D) time-domain computational fluid dynamics (CFD) approach to determine the acoustic impedance of perforated plates with bias flow, and the extraction method of acoustic impedance of perforated plates is presented. The non-dimensional acoustic impedance of orifices is predicted, and the good agreement between the numerical predictions and the measurements in published literature validates the present CFD approach. The numerical evaluations are carried out for different bias flow Mach number Mo (0.05–0.20) through the orifice, distribution form of the orifices, the ratio t/dh (0.2–0.5) of orifice thickness to diameter, Reynolds number Re of flow through the orifice and porosity φ (4.51%–24.93%) of the perforated plates. The effects of related parameters on the non-dimensional acoustic impedance of orifices are analyzed in detail. The expressions of acoustic impedance are obtained by using nonlinear regression analysis of the various results of the parametric studies. As an application of engineering calculation, the transmission loss (TL) of cross-flow perforated tube mufflers with flow is predicted by using Jing and Sun model and the present model via finite element computations. The comparison between measured and predicted values showed the accuracy of the present model.

A series of tem-responsive and protein-resistance property silica-di-block polymers SiO2-g-PMMA-b-P(PEGMA) hybrids are synthesized with methyl methacrylate (MMA) and poly (ethylene glycol) methyl ether methacrylate (PEGMA) by the surface-initiated atom transfer radical polymerization (SI-ATRP). The morphology in tetrahydrofuran (THF) solution, lower critical solution temperature (LCST), surface morphology, bovine serum albumin (BSA)-resistance property, and thermal stability of nanoparticles were analyzed. The results of 1H-NMR, GPC, and TEM prove that the silica-di-block hybrids have been obtained. The silica-di-block hybrids shows the LCST (52&ndash, 64 &deg, C) in aqueous solution. The hybrid films casted by THF present distributed uniform granular bulges and the film surface is relatively smooth (Ra = 15.4 nm ~ 10.5 nm). The results of QCM-D showed that only a small amount of BSA protein(△f = 18.6 ~ 11.8 Hz) was adsorbed on the surface of the films. The result of XPS also demonstrated that only a small amount of BSA protein was absorbed onto the surface of the film (N% = 1.86). The TGA analyses indicate that the thermal decomposition temperature of hybrids is 288 &deg, C. Thus, it is suggested that the hybrids are served as a suitable coating with BSA resistance property and thermal stability.

Surface defects on electrocatalysts can effectively reduce reaction barriers and facilitate the kinetics of hydrogen evolution and oxidation reactions (HER/HOR). However, precisely engineering such surface structures remains a significant challenge. Herein, penta-twinned (PTw) Rh@Ptx core–shell nanobranches (NBs) with intense surface strains were facilely synthesized using PTw Rh NBs as the seeds for overgrowth of active Pt-shells. Through precisely regulating the supply of Pt precursor solution via a micro-syringe pump, the ultrathin Pt-shells conform to and replicate the twin defects of the PTw Rh seeds. Significantly, the shell thickness can be precisely controlled from 1.0, 2.0, and 3.8 to 5.0 atomic layers. Due to the integration of surface twinned defects, compressive strain and the core–shell ligand effect, these Rh@Ptx NBs exhibit superior hydrogen redox electrocatalytic performance compared to state-of-the-art Pt/C. Among the prepared materials, the Rh@Pt0.83 NBs with a 3.8 atomic layer Pt-shell showed the highest mass activity (2.36 A mgPt−1) and specific activity (6.55 mA cm−2) for HER at –0.07 V and presented the lowest overpotential (44 mV) at 10 mA cm−2, less than half the overpotential of the commercial Pt/C (98 mV). In terms of HOR, the Rh@Pt0.83 NBs showed a superior exchange current density (1.97 mA cm−2), approximately 7 times higher than that of Pt/C. Our work provides a facile method to synchronously engineer the Pt-shell thickness and surface defects of Rh@Pt core–shell nanocatalysts for the creation of robust and bifunctional hydrogen redox electrocatalysts.

The hydrothermal aging cycles experiment was carried out on synthetic Silica fluoropolymer coating (SiO2-FP). The hydrothermal aging mechanism, surface properties and protective efficacy on sandstones was studied. For comparison, the same study was conducted for commercial protective material acrylic resin Paraloid B72 (PB72). The hydrothermal aging mechanism was studied by Fourier infrared spectroscopy attenuated total reflection technique (ATR-FTIR) and x-ray photoelectron spectroscopy (XPS) technology. The surface properties were characterized by field emission scanning electron microscope (SEM), the CR-400 color difference meter, static contact angle and GMT6503 Electronic universal Tensile machine. The capillary water absorption, water absorption by complete immersion (CI) and water vapor permeability were measured to evaluate the protective efficacy on sandstones after treatment. The results of ATR-FTIR and XPS indicated that part of the ester groups in PB72 was hydrolysed and the chemical structure of SiO2-FP was not changed but only microphase separation occurred after 360 h of aging. After 360 h of aging, the PB72 film had obvious change and the SiO2-FP film only shown a minor change; the color change of PB72 film was very obvious and the color change of SiO2-FP film was within the acceptable range; the PB72 film changed from hydrophobic to hydrophilic and the SiO2-FP film still retained high hydrophobicity (119.3°); the SiO2-FP had a higher adhesive strength than PB72 at the end of aging. Compared with PB72, the SiO2-FP can obviously reduce the capillary water absorption and had a higher protective efficiency (97.25%), much lower soakage capacity (0.60%), higher water vapor permeability (267.0 ± 2) and less influence on the water vapor permeability. All the results demonstrated that the SiO2-FP has much better anti-aging ability and longer durability under hydrothermal condition. The SiO2-FP can provide adequate protection for sandstones. The SiO2-FP can be used as a suitable protective coating on sandstones.

The perforated components are widely used in the intake and exhaust mufflers. The coupling between instable shear layer and acoustic fluctuation has a significant influence on the acoustic impedance of perforated components. To obtain practical and precise acoustic impedance of perforated plates in the presence of grazing flow, the three-dimensional (3D) time-domain computational fluid dynamics (CFD) approach was employed in the present study, and the extraction method of acoustic impedance was presented. The predicted non-dimensional acoustic impedance of the rectangular slot is consistent with the previous published measurement, which validates the accuracy of the present approach. Characterization of the turbulent boundary layer of flat-plate flow was studied and the relation between the convection velocity of vorticity and mean grazing flow velocity was provided. Numerical evaluations were carried out for different mean grazing flow Mach number Mmean (0.05–0.20), thickness to diameter ratio of orifice t/dh (0.2–0.5), porosity ϕ (4.51%–24.93%), and Reynolds number Re resulted from the orifice diameter dh (2 mm–6 mm), and their effects on the non-dimensional acoustic impedance of circular orifice were investigated in detail. The acoustic impedance formulae are obtained using the piecewise numerical fitting method based on the parameter analyses. As an application of engineering computation, the transmission loss of straight-perforated tube mufflers was predicted by using the present acoustic impedance model and the empirical impedance model of Lee and Ih via finite element computations. Comparison of the predicted and measured transmission loss (TL) results demonstrates that the present model yields highly accurate prediction.

The frequency-domain linearized Navier–Stokes equations (LNSEs) are used to describe the sound field of Helmholtz resonators and concentric perforated tube resonators in the presence of low Mach number flow. The numerical procedure of LNSEs method is performed in three steps, computational fluid dynamics (CFD) calculation, data transfer and acoustics calculation. The transmission loss predictions of the resonators exhibit good agreement with measurements published in the literature. The results show that the low Mach number flow shifts the resonance frequencies of resonators and changes the acoustic attenuation behavior, which may be attributed to the change of acoustic impedance of the opening and orifices. In order to weaken the effect of flow on the resonance frequency, the modified configurations of resonators are proposed by using the conical tubes to reduce the flow velocity passing the opening and orifices. Numerical results demonstrated that the influence of flow velocity on the resonance frequency of the modified resonators is less sensitive than the original configurations.

The finite element method is employed to calculate the transmission loss of three-pass perforated reactive and hybrid mufflers. The effects of perforated tubes and bulkheads on the transmission loss of three-pass reactive mufflers are investigated numerically. Two types of hybrid mufflers are considered, and the effects of sound-absorbing material filling and packed outlet tube on the acoustic attenuation performance of mufflers are analyzed. The perforations of the tubes and bulkheads and sound-absorbing material filling are demonstrated to have significant influence on the acoustic attenuation behaviors of the mufflers. The perforation of the tubes and bulkheads may shift the resonance from the low- to middle-frequency range. The sound-absorbing material filling in the middle chamber improves the acoustic attenuation performance at middle to higher frequencies and provides a relatively flat and broadband acoustic attenuation. It is found that the solid inlet or outlet tube replacing the perforated tube and sound-absorbing material filling in the middle chamber increases the pressure drops, while the rest configurations change the pressure drops slightly.

A series of amphiphilic silica/fluoropolymer nanoparticles of SiO2-g-P(PEGMA)-b-P(12FMA) were prepared by silica surface-initiating atom transfer radical polymerization (SI-ATRP) of poly(ethylene glycol) methyl ether methacrylate (PEGMA) and poly dodecafluoroheptyl methacrylate (P12FMA). Their amphiphilic behavior, lower critical solution temperature (LCST), and surface properties as protein-resistance coatings were characterized. The introduction of hydrophobic P(12FMA) block leads SiO2-g-P(PEGMA)-b-P(12FMA) to form individual spherical nanoparticles (∼150 nm in water and ∼170 nm in THF solution) as P(PEGMA)-b-P(12FMA) shell grafted on SiO2 core (∼130 nm), to gain obvious lower LCST at 36–52 °C and higher thermostability at 290–320 °C than SiO2-g-P(PEGMA) (LCST = 78–90 °C, Td = 220 °C). The water-casted SiO2-g-P(PEGMA)-b-P(12FMA) films obtain much rougher surface (125.3–178.4 nm) than THF-casted films (11.5–16.9 nm) and all SiO2-g-P(PEGMA) films (26.8–31.3 nm). Therefore, the water-casted surfaces exhibit obvious higher water adsorption amount (Δf = −494 ∼ −426 Hz) and harder adsorbed layer (viscoelasticity of ΔD/Δf = −0.28 ∼ −0.36 × 10−6/Hz) than SiO2-g-P(PEGMA) films, but present loser adsorbed layer than THF-casted films (ΔD/Δf = −0.29 ∼ −0.63 × 10−6/Hz). While, the introduction of P(12FMA) segments does not show obviously reduce in the protein-repelling adsorption of SiO2-g-P(PEGMA)-b-P(12FMA) films (△f = −15.7 ∼ −22.3 Hz) compared with SiO2-g-P(PEGMA) films (△f = −8.3 ∼ −11.3 Hz) and no obvious influence on water adsorption of ancient stone. Therefore, SiO2-g-P(PEGMA)-b-P(12FMA) is suggested to be used as protein-resistance coatings. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015

Two copolymer/SiO 2 hybrids are prepared by growing SiO 2 on the template of well -structured diblock copolymer PMMA-b-PMPS using a “grafting-to” approach. PMMA-b-PMPS is obtained by atom transfer radical polymerization (ATRP) of methyl methacrylate (PMMA) and 3-(trimethoxysilyl)propyl methacrylate (PMPS) using a brominated initiator end group termed 1H,1H,2H,2H-heptadecafluoro (F–Br) and a conventional initiator of ethyl 2-bromoisobutyrate (EBiB), respectively. The “grafting-to” approach is controlled at HCl for 24 h by hydrolysis and condensation of Si(OCH 3 ) 3 groups in PMPS with tetraethyl orthosilicate (TEOS) to gain both hybrids of F-PMMA-b-PMPS/SiO 2 (by F–Br initiator) and E-PMMA-b-PMPS/SiO 2 (by EBIB initiator). Comparatively, a little amount of fluorine content provided by F–Br is able to tighten the size of self-assembled micelles, to improve wettability and the viscoelasticity of F-PMMA-b-PMPS film due to F–Br migrating onto the film surface. Therefore, the surface of F-PMMA-b-PMPS film is sufficiently hydrophobic (99° and Δ f = 2941 Hz) than E-PMMA-b-PMPS film (94°and Δ f = 4820 Hz), and the viscoelasticity of the adsorbed layer for F-PMMA-b-PMPS (Δ D /Δ f = −0.112) film is much harder than E-PMMA-b-PMPS/SiO 2 (Δ D /Δ f = −0.071). On the other hand, the cross-linked silica in PMMA-b-PMPS/SiO 2 could also increase water contact angels of films (100–107°) and decrease the water absorption (Δ f = 704–798 Hz). The influence on the viscoelasticity of the adsorbed layer by the fluorine group is much more obvious than the cross-linked silica, therefore F-PMMA-b-PMPS/SiO 2 (Δ D /Δ f = −0.347) and F-PMMA-b-PMPS (Δ D /Δ f = −0.112) films have harder adsorbed layer than E-PMMA-b-PMPS/SiO 2 (−0.071) and F-PMMA-b-PMPS films (−0.042). However, compared with a slightly improvement in thermo stability by F–Br, the cross-linked silica in PMMA-b-PMPS/SiO 2 performs significantly improving thermal decomposition temperature at 300 °C and 350 °C.

Binary micro-nano rough morphology or structure shows a significant influence on hydrophobicity and icing-resistivity of the surface of coating materials. The leading cause for the classic Cassie state superhydrophobicity is the high area fraction of micro/nano air mattresses being in direct contact with a measured droplet. In this work, the dependence of static hydrophobicity on weight content of commercial surface-hydrophobicity-modified nano-silica in fluoropolymer based composite coatings has been investigated in detail via detecting static water contact angle (CA). It was found that elevating the weight content of hydrophobic nano-silica could contribute to a higher surface roughness, a more compact binary micro-nano morphology and a larger area ratio of air mattresses due to a stronger hypothesized phase separation. As a result, the remarkably improved water CA of composite coatings far higher than the neat polymer coating was observed relying on coating composition. Fortunately, the maximum static water CA of 167° was obtained in composite coating loaded with 50 wt% of hydrophobic nano-silica. For gaining the desired high comprehensive performances, it was advised to introduce 30 wt% of nano-filler into polymer. This work might open a facile route to achieve the promising superhydrophobic and anti-icing materials.

A Coulomb force at an interface, namely induced polarization, has been found to have a significant effect on the permittivity of 0-3 type polymer-based composites with Si-based semiconductor fillers. These composites have the disadvantage of a higher dielectric loss and conductivity but the advantage of a larger permittivity when compared to composites filled with surface modified Si-based semiconductors. In the present work, the dielectric and conductive properties of 0-3 type varied polymer-based composite systems containing α-SiC and SiO2@SiC nanoparticles, respectively, were investigated in detail. It was found that use of a SiO2@SiC filler instead of neat SiC could effectively decrease the Coulomb force between the SiC and polymer, the overall induced dipole moment, the real permittivity of SiC and thus the measured permittivity of the composite. As a result, significantly decreased dielectric loss and conductivity as well as elevated breakdown strength were obtained thanks to the reduced Coulomb force at the interface. The lowest loss and conductivity achieved were 0.03 and 6.05 × 10−7 S cm−1, respectively, at 100 Hz for 20 vol% SiO2@SiC-filled polyvinyl chloride (PVC)-based composite. Moreover, the dependence of interface-induced polarization on polymer polarity in three SiO2@SiC-loaded polymer-based composite systems was investigated and the lower polarity of polymer could favor the decline of induced polarity in the SiC. This work might lead to an easy way to obtain promising composite dielectric materials by suppressing the interface Coulomb force.

Silica/diblock fluoropolymer hybrids SiO2-g-PMMA-b-P12FMA for coatings were synthesized by the silica surface-initiating atom transfer radical polymerization (SI-ATRP) of methylmethacrylate (MMA) and dodecafluoroheptyl methacrylate (12FMA). Silica surface initiator (SiO2-initiator) was obtained by 10–25 nm fumed silica particles grafted hydrosilylated undec-10-enyl, 2-bromo-2-methyl propionate with a density of 0.573 mmol g−1. The SI-ATRP approach in this paper displays the diagnostic criteria of controlled radical polymerization by the analysis of 1H NMR, 19F NMR and SEC-MALLS analysis, after comparing with the conventional initiator of ethyl 2-bromoisobutyrate (EBiB) for the E-PMMA-b-P12FMA diblock copolymer. Three mass ratios of SiO2-initiator/MMA/12FMA as 1/72.50/18.15, 1/72.50/45.38 and 1/181.26/18.15 were used to obtain the SiO2-g-PMMA-b-12FMA hybrids. The hybrids show 25–30 nm core–shell particles in CHCl3 solution composed of a P12FMA core and PMMA shell, but densely twined together as agglomerated particles. The PMMA-b-P12FMA shell grafted onto silica particles obviously increases the surface roughness of the film (50–500 nm), more than the E-PMMA-b-12FMA film (30 nm), and thereby contributes to the hydrophobic (112–118°) and oleophobic (45–78°) properties of the films. Increasing the P12FMA concentration (1/72.50/45.38) could result in stronger migration of the P12FMA segments onto the film surface, and therefore led to a lower surface free energy (10.97 mN m−1), increased advancing and receding for water contact angles (112° and 108°) and the highest cetane contact angles (74° and 70°), the lower water absorption and viscoelasticity, but a high thermostability at 420–450 °C.