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The flexural performance of a spliced composite slim beam with a slotted web (SCSB-SW) was assessed and prediction formulae of flexural capacity and initial stiffness for the beam were deduced. Through a four-point bending test, the flexural performance of the SCSB-SW was preliminary studied. The experimental results indicated that the section of the SCSB-SW conformed to the plane section assumption in the elastic stage. The beam failed in a ductile failure mode while there was no obvious relative slip between the steel beam and concrete slab in the failure stage. Finite-element models were developed and validated using the test results. A parametric analysis revealed that even if the cross-sectional dimensions and the position of the neutral axis in the beam are changed, the results predicted by the formulae still matched the numerical results well. The material strength, the thickness of the bottom flange of the steel beam and the concrete slab dimensions were found to play key roles in the flexural capacity of the beam, whereas the compressive strength grade of the concrete, the depth of the steel beam web and the dimensions of the concrete flange have significant effects on the initial stiffness of the beam.

The loading strategy of cocatalysts affects its activity exerting and atom utilization. Here, a novel strategy for loading precious metal (Pt) cocatalysts by means of ultrathin N-doped carbon layer is reported. The strategy is based on a pyrolysis process of predesigned N-containing polymers and Pt complexes on hard-template surface, during which Pt can be reduced by carbon from pyrolysis at high temperatures. Finally, the hollow TiO2 composite with stable and dispersed Pt on its inner surface was prepared. It shows an ultrahigh photocatalytic H2 production activity as high as 25.7 mmol h−1 g−1 with methanol as sacrificial regent, and displays an apparent quantum yield as 13.2%. The improved photocatalytic activity and stability can be attributed to the highly dispersed and ultrafine Pt nanoparticles, enhanced interaction between Pt-species and carbon support, fast photo-excited electron transport from the high graphitization degree of NC layers, ample oxygen vacancies/defects, as well as the manipulated local charge distribution of Pt/NC-layer configuration. Additionally, the universality of the proposed strategy was demonstrated by replacing metal sources (such as, Ru and Pd). This work presented a promising strategy for the design and development of novel photocatalysts, which shows a broad application prospect.

Direct conversion of syngas to aromatics (STA) over oxide-zeolite composite catalysts is promising as an alternative method for aromatics production. However, the structural effect of the oxide component in composite catalysts is still ambiguous. Herein, we investigate the size effect by selecting ZnCr2O4 spinel, as a probe oxide, mixing with H-ZSM-5 zeolite as a composite catalyst for STA reaction. The CO conversion, aromatics selectivity and space-time yield (STY) of aromatics are all significantly improved with the crystal size of ZnCr2O4 oxide decreases, which can mainly attribute to the higher oxygen vacancy concentration and thus the rapid generation of more C1 oxygenated intermediate species. Based on the understanding of the size–performance relationship, ZnCr2O4-400 with a smaller size mixing with H-ZSM-5 can achieve 32.6% CO conversion with 76% aromatics selectivity. The STY of aromatics reaches as high as 4.79 mmol gcat−1 h−1, which outperforms the previously reported some typical catalysts. This study elucidates the importance of regulating the size of oxide to design more efficient oxide-zeolite composite catalysts for conversion of syngas to value-added chemicals.

Aluminum (Al) powder is widely used in solid propellants. In particular, nano-Al has attracted extensive scholarly attention in the field of energetic materials due to its higher reactivity than micro-Al. However, the existence of aluminum oxide film on its surface reduces the heat release performance of the aluminum powder, which greatly limits its application. Hence, this paper used iron, a component of solid propellant, to coat micron-Al and nano-Al to improve the heat release efficiency and reactivity of Al powder. SEM, TEM, EDS, XRD, XPS, and BET were used to investigate the morphological structure and properties of pure Al and Fe/Al composite fuels of different sizes. The results show that Fe was uniformly coated on the surface of Al powder. There was no reaction between Fe and Al, and Fe/Al composite fuels had a larger specific surface area than pure Al, which could better improve the reactivity of pure Al. Besides, the catalytic effects of pure Al and Fe/Al composite fuels of different sizes on ammonium perchlorate and ammonium nitrate were explored. The results show that the catalysis of pure Al powder could be greatly improved by coating Fe on the surface of Al powder. Especially, the micron-Fe/Al composite fuel had a higher catalytic effect than the pure nano-Al powder. Hence, Fe/Al composite fuels are expected to be widely used in solid propellants.

Mg alloys are considered the most promising engineering materials because of their unique properties. However, the uncontrolled corrosion rate of these alloys limits their applications. Therefore, in this study, a micro-arc oxidation layer was used as a transition layer to “directly” grow a zinc-based metal-organic framework (MOF) composite coating on the surface of a Mg alloy (AZ91D). Herein, the two zeolitic imidazolate framework (ZIF-8) coatings with different morphologies were separately prepared by homologous metal oxide induction and a one-step in-situ growth method. The superhydrophobic composite coating showed strong hydrophobicity and self-cleaning properties, which could prevent the penetration of water and corrosive ions (Cl−) into the surface of AZ91D. Electrochemical tests demonstrated that the super-hydrophobic composite coatings greatly enhanced the corrosion resistance of AZ91D, and the corrosion current density decreased from 10−5 to 10−9 A/cm2. These results indicate that the ZIF-8 coatings are beneficial for improving the hydrophobicity and enhancing the corrosion resistance of Mg alloys. Therefore, MOF composite coatings provide a new strategy that can be used to prepare multifunctional anticorrosion coatings on metal substrates.

Hydroxyl-terminated polybutadiene/toluene diisocyanate (HTPB/TDI) system is widely used in composite solid propellants. The migrations of plasticizers and water molecules from solid propellants and surrounding environment to the inhibitor have always been the important issues. This study focuses on the preparation, characterization and anti-migration behavior of graphene oxide (GO)/HTPB nanocomposite liner. The GO/HTPB (GH) composite liners affect the migration of small molecules through a tighter cross-linked structure and weakening function of small molecule adsorption. The anti-migration performance of the liner at different temperatures was analyzed, and the influence of the added amount of GO on the anti-migration performance and adhesion performance was also systematically studied. The overall performance of the liner is optimized when the amount of GO filler is 0.3 wt%. After adding 0.3 wt% GO, the concentration of dioctyl sebacate (DOS) migrated into the liner is decreased by 23.28%, and the concentration of water molecules is decreased by 51.89%, indicating that the introduction of GO can significantly improve the anti-migration performance of the liner. In addition, the bond strength is greatly increased from 0.25 MPa to 0.95 MPa, which meets the application requirements of the current propellant system. This research provides an important way for the preparation of structure-function synergistic anti-migration composite liners.

Prefabricated dowels do not always provide intraradicular sealing in the root canal dentin, and the lack of sealing predisposes the dowel to adhesive failure and debonding. It is unclear if fiber-reinforced composite resin dowels provide better sealing.The purpose of this in vitro study was to evaluate the intraradicular sealing and morphological fit of prefabricated dowels and fiber-reinforced composite resin dowels in root canal dentin. The thickness of the resin cement layer and push-out bond strength were determined to assess their effects on the sealing of the dowels.A total of 50 permanent maxillary central incisors were endodontically treated and divided into 2 subgroups (n=25). In one group, prefabricated dowels were cemented; in the second group, fiber-reinforced composite resin dowels were placed. The thickness of the resin cement layer was assessed in 3 different locations: coronal, middle, and apical of the root canal dentin with fluorescence confocal laser microscopy. The push-out bond strength was then determined, and intraradicular sealing observed by using scanning electron microscopy.Fiber-reinforced composite resin dowels showed a closer intraradicular fit and seal in the root canal dentin, and the morphology of the apical portion of the fiber-reinforced composite resin dowels showed a sealing area with the gutta percha in the apical portion. The mean thickness of the resin cement layer was significantly reduced for the fiber-reinforced composite resin dowels compared with the prefabricated dowels (P.05) in the cervical area (197.0 μm versus 311.0 μm) and in the apical portion of the root canal (57.3 μm versus 131.6 μm). The mean push-out strength was higher for the fiber-reinforced composite resin dowels (22.98 N/mmThe morphological fit of fiber-reinforced composite resin dowels provides better intraradicular sealing in the cervical and apical portions, reducing the resin cement thickness. The increased push-out strength can therefore be assumed to result from increased frictional retention compared with prefabricated dowels.

Statement of problem Various strategies have been proposed to reduce the cement space of foundation restorations for endodontically treated teeth. However, they may add more operative steps, or the dentist must keep different sizes of drills and posts in stock. A 2-piece universal adjustable post system has been developed to overcome this problem, but whether the system has acceptable fatigue survival performance is unclear. Purpose The purpose of this in vitro study was to evaluate the fatigue survival and stress distribution of endodontically treated teeth without a ferrule and restored with different glass fiber post strategies versus a recently introduced universal 2-piece fiber post system. Material and methods Bovine incisor roots were randomly assigned to 3 groups as per the post used (n=13): adapted glass fiber post with post space preparation of the same size, composite resin-custom glass fiber post (CTM), and universal 2-piece glass fiber-reinforced composite resin post (UNI). The posts were adhesively luted, the composite resin core was added, and a composite resin crown was produced with computer-aided design and computer-aided manufacturing (CAD-CAM), and then adhesively luted to each core. A fatigue test was performed with the stepwise stress method (10 000 cycles/step; 20 Hz; load=100 N to 750 N; step=50 N) until fracture, and the failure mode analyzed. The stress distribution was evaluated by finite element analysis with the maximum principal stress criteria by following the parameters of the in vitro test. The solids were considered homogeneous, linear, and isotropic, except for the glass fiber post (orthotropic), and a load of 450 N at 30 degrees was applied. The fatigue failure load and the number of cycles for failure were analyzed with Kaplan-Meier and Mantel-Cox (log rank test) (α=.05). The finite element analysis results were analyzed with colorimetric graphs. Results The highest fatigue failure load and the number of cycles for failure were found in the UNI system, whereas the lowest results were found in the CTM group. All groups exhibited repairable failures. The finite element analysis showed the lowest stress in root dentin in the UNI system. The CTM system had the largest stress regions at the dentin and dentin-core interface. Conclusions The use of a 2-piece universal glass fiber post system resulted in more fatigue behavior compared with composite resin-custom glass fiber posts.

Polymer bonded explosives (PBXs) have high energy density, excellent mechanical properties and better thermal stability. In this study, droplet microfluidic technology was used to successfully prepare HMX/TATB microspheres. The effects of different binder types and binder concentrations on the morphology of the microspheres were studied, and results proved that NC/GAP (1:4) provides particles a regular spherical morphology and good dispersion. Subsequently, the influence of the concentration of the dispersed phase and the flow rate of the continuous phase on the particle size distribution of the microspheres was fully studied. The microspheres had narrow particle size distribution and high spherical shape. Under optimized process conditions, HMX/TATB microspheres were prepared and compared with the physical mixtures. The X-ray diffraction, differential scanning calorimetry, flow properties, bulk density, and mechanical sensitivity of the samples were also studied. Results showed that the crystal form of the microspheres remains unchanged, and the binder maintains good compatibility with explosives. In addition, the fluidity, bulk density, real density and safety performance of the microspheres are remarkably better than the physical mixture. This study provides a new method for preparing PBX with narrow particle size distribution, high spherical shape, excellent dispersion and high bulk density.

Natural fish scales demonstrate outstanding mechanical efficiency owing to their elaborate architectures and thereby may serve as ideal prototypes for the architectural design of man-made materials. Here bioinspired magnesium composites with fish-scale-like orthogonal plywood and double-Bouligand architectures were developed by pressureless infiltration of a magnesium melt into the woven contextures of continuous titanium fibers. The composites exhibit enhanced strength and work-hardening ability compared to those estimated from a simple mixture of their constituents at ambient to elevated temperatures. In particular, the double-Bouligand architecture can effectively deflect cracking paths, alleviate strain localization, and adaptively reorient titanium fibers within the magnesium matrix during the deformation of the composite, representing a successful implementation of the property-optimizing mechanisms in fish scales. The strength of the composites, specifically the effect of their bioinspired architectures, was interpreted based on the adaptation of classical laminate theory. This study may offer a feasible approach for developing new bioinspired metal-matrix composites with improved performance and provide theoretical guidance for their architectural designs.

The restoration of contaminated sites is attracting increasing attention because of environmental considerations. Barrier walls using cement-based solidified soil are a popular and effective method for enclosing contaminated sites. However, the working environment of cement-based solidified soils is often complicated and results in concern about the durability of the walls. Hence, the deterioration behaviour of solidified soils under a working environment should be investigated. A type of marine soft clay deposited in the coastal Lianyungang region of east China was solidified by a cement–metakaolin composite; then, the specimens were cured under standard, saline solution and cycled freeze–thaw environments. When the specimens reached the designed curing periods, the unconfined compressive strength, mass loss, pH value and mesostructure were determined. The results show that (a) both saline soaking and cycled freeze–thaw environments unavoidably reduce the durability of cement-based solidified soils and (b) metakaolin incorporation can effectively resist the deterioration behaviour of solidified soils under such environments. In this case, the optimal incorporation ratio is approximately 3·0%, and (c) although strength enhancement by chloride (Cl−) ions was primarily inhibited by the water medium, metakaolin incorporation suppresses cracking on the surface and strengthens the integrity of the solidified soils.

In this study, using a solution casting process, thermoplastic polyurethane elastomer (TPU) composites containing different contents of lead zirconate titanate (PZT) ferroelectric particles were produced. The damping treatment of composites at high volume of fillers was investigated. SEM micrographs showed that PZT particles had a proper distribution in the PU matrix. Differential scanning calorimetry (DSC) thermograms indicates that melting enthalpy decreases by raising PZT filler content. The results of the dynamic mechanical thermal analysis (DMTA) proved that the magnitude of loss factor (tan δ) strongly depends on PZT content, and it decreased from 0.51 to 0.27 as PZT content increased. The value of E0 increases to 0.32 GPa in the composite reinforced with 50 v% of PZT. The role of PZT on the acoustic behavior of TPU was measured using the acoustic absorption coefficient (a). The results showed that as PZT content increased from 0 to 50%, the acoustic absorption coefficient reached 0.25 at 6000 Hz frequency. The composites of PZT/PU with 0–3 connectivity were poled, and the optimal poling conditions that could be applied without sample breakdown were studied. Moreover, we prepared composites containing 70 vol% PZT particles by modifying the particles. Modification of PZT particles caused a decrease in both d33 and g33 constants of the PZT/PU composites.

Molten salt has been widely used in latent heat thermal energy storage (LHTES) system, which can be incorporated into hybrid photovoltaic/thermal solar system to accommodate the built environment. Solar salt (60 wt.% NaNO3 and 40 wt.% KNO3) was employed as the phase change materials (PCMs) in this study, and both aluminum oxide (Al2O3) nanopowder and metal foam were used to improve the properties of pure solar salt. The synthesis of the salt/metal foam composites seeded with Al2O3 nanopowder were performed with the two-step and impregnation methods, and the composite PCMs were characterized morphologically and thermally. Then pure solar salt, the salt/2 wt.% Al2O3 nanopowder and salt/copper foam composite seeded with 2 wt.% Al2O3 nanopowder were encapsulated in a pilot test rig, respectively, where a heater of 380.0 W was located in the center of the LHTES unit. The charging and discharging processes of the LHTES unit were conducted extensively, whereas the heating temperatures were controlled at 240 °C, 260 °C and 280 °C respectively. Temperature evolutions at radial, angular and axial positions were recorded, and the time-durations and volumetric mean powers during the charging and discharging processes were obtained and calculated subsequently. The results show that physical bonding between Al2O3 nanopowder and nitrate molecule has been formed from the morphological pictures together with XRD and FTIR curves. Slight changes are found between the melting/freezing phase change temperatures of the salt/metal foam composites seeded with Al2O3 nanopowder and those of pure solar salt, and the specific heats of the salt/Al2O3 nanopowder composite slightly increase with the addition of Al2O3 nanopowder. The time-duration of the charging process for the salt/copper foam composite seeded with Al2O3 nanopowder at the heating temperature of 240 °C can be reduced by about 74.0%, compared to that of pure solar salt, indicating that the heat transfer characteristics of the LHTES unit encapsulated with the salt/copper foam composite seeded with Al2O3 nanopowder can be enhanced significantly. Consequently, the mean volumetric powers of the charging process were distinctly enhanced, e.g., the volumetric mean power of heat storage can reach 110.76 kW/m3, compared to 31.94 kW/m3 of pure solar salt. However, the additive has little effect on the volumetric mean power of heat retrieval because of the domination of natural air cooling.

Biodegradable magnesium (Mg) and its alloy show huge potential as temporary bone substitute due to the favorable biocompatibility and mechanical compatibility. However, one issue deserves attention is the too fast degradation. In this work, mesoporous bioglass (MBG) with high pore volume (0.59 cc/g) and huge specific surface area (110.78 m2/g) was synthesized using improved sol-gel method, and introduced into Mg-based composite via laser additive manufacturing. Immersion tests showed that the incorporated MBG served as powerful adsorption sites, which promoted the in-situ deposition of apatite by successively adsorbing Ca2+ and HPO42−. Such dense apatite film acted as an efficient protection layer and enhanced the corrosion resistance of Mg matrix, which was proved by the electrochemical impedance spectroscopy measurements. Thereby, Mg based composite showed a significantly decreased degradation rate of 0.31 mm/year. Furthermore, MBG also improved the mechanical properties as well as cell behavior. This work highlighted the advantages of MBG in the fabrication of Mg-based implant with enhanced overall performance for orthopedic application.

Current wood-plastic materials available for selective laser sintering (SLS) are limited and often suffer from low-quality and mechanical strength. In this study, a new composite of peanut husk pow...

A composite system consisting of aminosilicate (APS) functionalized-fullerene quantum dots (C60 QDs) and bismuth vanadate (BiVO4-APS-C60) has been developed via a facile one-step hydrothermal process. The structural analysis by XRD revealed that the integrated QDs have not affected the crystal structure of the host BiVO4, while the XPS studies showed that these QDs have been integrated via the Bi-V-O-Si-C network. The optical studies indicated that both the C60 and APS-C60 QDs have hardly influenced the optical absorption properties of the composite system. On the other hand, the dispersion of aminosilicate functionalized-QDs considerably reduced the aggregation in the layers and yielded a few nanometer thick BiVO4 layers due to their inter-layer occupancy as seen from their high-resolution TEM images. The photoluminescence, photocurrent and electrochemical impedance studies showed that the integration of APS-C60 QDs greatly improved the photoactive properties of the composite by effectively enhancing the charge recombination resistance, charge separation and transfer process between the integrated materials and surroundings. As a result, BiVO4-APS-C60 composites showed the enhanced photocatalytic efficiency towards degradation of ciprofloxacin (CIP) molecules under solar light irradiation as compared to that of bare-BiVO4 and BiVO4-C60.

The prosthetic socket base material must have exhibited good mechanical properties. An experimental investigation about the behavior of different fibers reinforced laminated composite materials were done. This work has been done on seven laminated composites which were prepared by the Vacuum bagging technique from Polyester resin as a bonding matrix and reinforced with (Jute, Glass, Carbon, Perlon) fibers. Laminated specimens were characterized by mechanical tensile tests such as (Tensile Strength, Young’s Modulus, Elongation Percentage) and physical test (density) to measure specific strength and specific modulus. SEM test also had been studied for different laminated composite. The results of experimental work showed that the mechanical properties were changed with the type and number of reinforcing layers. So, the results showed that the best laminated composite specimens have three layers of Jute with four layers of Carbon fiber. Where tensile strength and modulus of elasticity reach (162 MPa. and 3.60 GPa.) respectively. And specific strength and specific modulus reach to (134 MPa.cm3/gm–2.544 GPa.cm3/gm). The smoothness of the fractured surface will increase, indicating a brittle to semi-ductile transformation, according to SEM results.

The aim of this study is to provide a review on silanized composite performance when exposed in a complex wet aqueous environment and the role of titanium coupling agent as a more stable and reinforcement material in the construction of dental composites. Silanes are considered as the most dominant materials used for surface modification of the filler added to the polymer material in dental applications. Due to the presence of silica in the silane structure, so, the silane coupling agent were considered to be more effective in modifying materials which are consisting of silica because of the similarity in their ordered structure. Silanes are relatively characterized by dehydration inside the oral aqueous environment. On the other hand, titanate coupling agents are effective in serving at a wet environment, because its ability to react with the positive proton available on the surface of the filler (H+). TCAs are superior in performance in comparison to silane by creating a strong internal bonding between the filler and polymer matrix, and having a significant effect on the dispersion and resolving of particles agglomeration and good hydrolytic stability inside the mouth. This paper presents a comparative study between the effects of silane coupling agents against the TCAs performance in oral environment.

This review reports the outcome of an research experimental on flexural behaviour of partially strengthened reinforced concrete beams along with Engineered Cementitious Composite (ECC). 6 beams were moulded and examined in total. Three beams were tested to determine the influence of plastic hinge length, whereas two beams were examined to determine the effect of large layers of ECC in the tension zone. The remaining beam acted as control beam. Along with beam specimens, cylinders and cubes were tested to evaluate the mechanical characteristics of both ECC and concrete. All the beams are strengthened using ECC plastic hinges and layers. And they could withstand maximum load than the regulate beams. Load capacities of reinforced concrete (RC) beams strengthened with ECC plastic hinges were 2.85 – 6.34 times more than those of the corresponding control beams. Similarly, RC beams having load capacities 5.71–8.45 times with ECC layers were even better. In general, ECC application increased the ductility of Reinforced concrete beams.

Statement of problem In computer-aided design and computer-aided manufacturing (CAD-CAM) dentistry, the CAD of the prosthesis represents the clinical prerequisite design to restore the treated tooth. However, how closely the CAM prosthesis shape matches the CAD, particularly in relation to different materials, is unclear. Purpose The purpose of this in vitro study was to evaluate onlays designed and manufactured with the same CAD-CAM system but manufactured with different materials. Material and methods A single standard tessellation language (STL) model was used to produce 6 composite resin onlays, 6 leucite glass-ceramic onlays, and 6 lithium disilicate glass-ceramic onlays. The onlays were digitized by using an X-ray microtomographic protocol with a metrological calibration. The CAD model was then compared with the scans of the different onlays. An analysis by region of interest was then carried out to assess the accuracy and reliability of the dimensional accuracy. Results The composite resin and the lithium disilicate glass-ceramic had the best dimensional accuracy. The leucite glass-ceramic exhibited a lack of trueness linked to consistent overmilling. The composite resin had less peripheral chipping than the glass-ceramics. Conclusions The composite resin and the lithium disilicate glass-ceramic material exhibited satisfactory dimensional accuracy. Milling the glass-ceramic before crystallization considerably improved dimensional accuracy.

A non-solvent induced phase separation (NIPS) process was used to fabricate a series of sulfonated polyethersulfone (SPES) membranes blending with different concentrations of SBA-15-g-PSPA with the applications in the ultrafiltration (UF) process. SBA-15 was modified with 3-methacrylate-propyltrimethoxysilane (MPS) to form SBA-15-g-MPS. It was further modified with the charge tailorable polymer chains by reacting with 3-sulfopropyl methacrylate potassium salt. The nanoparticles were uniformly dispersed and finger-like channels were developed within the membrane. The adding of surface modified SBA-15-g-PSPA nanoparticles has significantly improved membrane water permeability, hydrophilicity, and antifouling properties. The pure water fluxes of the composite SPES membranes were significantly higher than the pristine SPES membrane. For the membrane containing 5% (mass) of SBA-15-g-PSPA (MSSPA5), the pure water flux was increased dramatically to 402.15 L∙m–2∙h–1, which is ∼ 1.5 times that of MSSPA0 (268.0 L∙m–2∙h–1). The high flux rate was achieved with 3% (mass) of SBA-15 nanoparticles with retained high rejection ratio 98% for natural organic matter. The results indicate that the fashioned composite membrane comprising SBA-15-g-PSPA nanoparticles have a promising future in ultrafiltration applications.

Ferric acetylacetonate/covalent organic framework (Fe(acac)3/COF) composite was synthesized by interfacial polymerization method at room temperature. The crystal structure, morphology and porosity property of the composite were characterized by X-ray diffraction, scanning electron microscope, transmission electron microscope and nitrogen adsorption. The interaction between Fe(acac)3 and COF was investigated by Fourier transform infrared spectra and X-ray photoelectron spectroscopy. The Fe(acac)3/COF composite was used as a photocatalyst for the oxidation of benzyl alcohol under mild conditions. It exhibits high activity and selectivity for the reaction, of which the mechanism was investigated by determining its photoelectric properties. The Fe(acac)3/COF catalyst developed in this work has application potential in other photocatalytic reactions.

This article focuses on the composite ${H}_{∞ }$ synchronization problem for jumping reaction-diffusion neural networks (NNs) with multiple kinds of disturbances. Due to the existence of disturbance effects, the performance of the aforementioned system would be degraded; therefore, improving the control performance of closed-loop NNs is the main goal of this article. Notably, for these disturbances, one of them can be described as a norm-bounded, and the other is generated by an exogenous model. In order to reject the above one kind of disturbance, a disturbance observer is developed. Furthermore, combining the disturbance observer approach and conventional state-feedback control scheme, a composite disturbance rejection controller is specifically designed to compensate for the influences of the disturbances. Then, some criteria are established based on the general Lyapunov stability theory, which can ensure that the synchronization error system is stochastically stable and satisfies a fixed $ {H}_{∞ } $ performance level. A simulation example is finally presented to verify the availability of our developed method.

Carbon materials have excellent catalytic effects on the hydrogen storage performance of MgH2. Here, carbon-supported Ni3S2 (denoted as Ni3S2@C) was synthesized by a facile chemical route using ion exchange resin and nickel acetate tetrahydrate as raw materials and then introduced to improve the hydrogen storage properties of MgH2. The results indicated the addition of 10 wt.% Ni3S2@C prepared by macroporous ion exchange resin can effectively improve the hydrogenation/dehydrogenation kinetic properties of MgH2. At 100 °C, the dehydrogenated MgH2 Ni3S2@C-4 composite could absorb 5.68 wt.% H2. Additionally, the rehydrogenated MgH2 Ni3S2@C-4 sample could release 6.35 wt.% H2 at 275 °C. The dehydrogenation/hydrogenation enthalpy changes of MgH2 Ni3S2@C-4 were calculated to be 78.5 kJ mol−1/−74.7 kJ mol−1, i.e., 11.0 kJ mol−1/7.3 kJ mol−1 lower than those of MgH2. The improvement in the kinetic properties of MgH2 was ascribed to the multi-phase catalytic action of C, Mg2Ni, and MgS, which were formed by the reaction between Ni3S2 contained in the Ni3S2@C catalyst and Mg during the first hydrogen absorption–desorption process.

With the shortage of global fossil energy and the increasing crisis of environmental deterioration, hydrogen energy has become an environmentally benign alternative as a clean energy source. In most studies on photocatalytic hydrogen production, novel photocatalytic material has played an important role to enhance the hydrogen production rate. In this study, the optimal conditions for the synthesis of MoS2 were established through series of characterizations with 190 °C calcination temperature and 1 wt% PEG surfactant addition. The best conditions for synthesizing MOF include copper nitrate as the copper precursor, 30% ultrasonic amplitude, and 240 °C calcination temperature. After adding 1 wt% MOF in MOS2, a flower-like structure with small particle size, uniform distribution, regularity, and large surface pores, has been formed, where its unit is modified with many rough, porous, and high specific surface area octahedral structures. In addition, 1MOF/MOS2 has the most negative conduction band edge (−0.135 V), the smallest charge transfer resistance (Rct = 1.78 Ω), the largest photo current (11.1 mA/cm2), the lowest PL spectral peak intensity, and excellent photocatalytic stability. The above morphological features and optical properties can significantly form more active sites, enhance the electron transfer rate, and inhibit the electron-hole recombination, thus making the MOF/MOS2 composite photocatalyst achieve the maximum hydrogen production capacity (626.3 μmol g−1 h−1).

The heterogeneous magnesium (Mg) matrix nanocomposite with dispersed soft phase exhibits high strength and toughness. Herein, the deformation behavior and failure process were investigated to reveal the unique mechanical behavior of the heterogeneous microstructure under compression. The extensive plastic deformation is accompanied by the flattening and tilting of the soft phase, inhibiting strain localization and leading to strain hardening. Moreover, a stable crack multiplication process is activated, which endows high damage tolerance to the heterogeneous Mg matrix nanocomposites. The final failure of the composite is caused by crack coalescence in the shear plane along a tortuous path. The presence of dispersed soft phases within the hard matrix induces a noticeable change in mechanical response. Especially, the malleability of the heterogeneous Mg matrix nanocomposite is two and ten times higher than that of pure Mg and the homogeneous Mg matrix nanocomposite, respectively. The current study provides a novel strategy to break the trade-off between strength and toughness in metal matrix nanocomposites.

Magnesium hydride (MgH2) is one of the most promising hydrogen storage materials for practical application due to its favorable reversibility, low cost and environmental benign; however, it suffers from high dehydrogenation temperature and slow sorption kinetics. Exploring proper catalysts with high and sustainable activity is extremely desired for substantially improving the hydrogen storage properties of MgH2. In this work, a composite catalyst with high-loading of ultrafine Ni nanoparticles (NPs) uniformly dispersed on porous hollow carbon nanospheres is developed, which shows superior catalytic activity towards the de-/hydrogenation of MgH2. With an addition of 5 wt% of the composite, which contains 90 wt% Ni NPs, the onset and peak dehydrogenation temperatures of MgH2 are lowered to 190 and 242 °C, respectively. 6.2 wt% H2 is rapidly released within 30 min at 250 °C. The amount of H2 that the dehydrogenation product can absorb at a low temperature of 150 °C in only 250 s is very close to the initial dehydrogenation value. A dehydrogenation capacity of 6.4 wt% remains after 50 cycles at a moderate cyclic regime, corresponding to a capacity retention of 94.1%. The Ni NPs are highly active, reacting with MgH2 and forming nanosized Mg2Ni/Mg2NiH4. They act as catalysts during hydrogen sorption cycling, and maintain a high dispersibility with the help of the dispersive role of the carbon substrate, leading to sustainably catalytic activity. The present work provides new insight into designing stable and highly active catalysts for promoting the (de)hydrogenation kinetics of MgH2.

Reliable column–column connection contributes to a reduction in waste materials and enables structures to be demountable after their service life. This paper demonstrates the feasibility of using a bolted-flange connection with concrete-filled steel tube (CFST) columns subjected to axial compression load. Compression capacity, ductility, axial stiffness and toughness, as well as failure modes are discussed. The specimens are grouped into two categories: group I—connection without stiffeners and group II—connections supported by stiffeners. Three thicknesses of 2, 4 and 6 mm were used to manufacture the bolted flanges and stiffeners. The results showed that the proposed connection was effective to avoid a reduction in compression capacity. The various thicknesses of bolted flanges in group I specimens had a slight influence on the axial stiffness value and that influence was doubled in group II specimens. The stiffeners played a significant role in the toughness value and this was reduced with a reduction in the thickness of the stiffeners. In addition, an improvement in ductility was noticeable in stiffened specimens. Consequently, it can be inferred that bolted-flange joints have the potential to produce reliable and economical designs for CFST columns.

A powder thixoforging route combined with slurry based mixing process was proposed to fabricate graphene nanoplatelets (GNPs) reinforced magnesium matrix composites (MgMCs). The originally spherical and ball-milled ZK60 powders were used as matrices, respectively. The mixing of 0.05 wt.% GNPs with the spherical powder led to GNPs clusters and degraded the mechanical properties of the composite. In contrast, with the addition of an optimal content (0.1 wt.%) of GNPs, the composite fabricated from ball-milled powder achieved a joint enhancement in tensile yield strength (52%) and fracture toughness (19%), demonstrating a pronounced strengthening efficiency of 650% and a good balance between strength and toughness. The ball-milled powder endowed the composite with a homogenous distribution of GNPs and a denser microstructure with reduced Mg-Zn eutectics, and the thixoforging process offered a well-bonded Mg/GNP interface, making full use of the strengthening and toughening potential of GNPs. Theoretical predication based on a modified shear-lag model suggested that load transfer dominated the strengthening mechanisms. In-situ tensile tests verified that crack deflection, secondary cracks and GNPs bridging mainly accounted for the toughening mechanisms. A numerical model with consideration of GNPs orientations was also established to understand the toughening effect from GNPs bridging.

Although the clinical use of self-adhesive flowable composite resins is convenient, the decision to use flowable or conventional composite resin remains controversial.The purpose of this systematic review and meta-analysis was to assess the in vitro bond strength of self-adhesive flowable composite resins to enamel or dentin compared with conventional composite resins using etch-and-rinse or self-etch adhesive systems.Two independent reviewers performed searches in the PubMed (MEDLINE), Cochrane Wiley, Web of Science, Scopus, and Google Scholar databases for studies reporting on the bond strength of self-adhesive flowable and conventional composite resins to enamel and dentin published from January 2010 up to September 2020. A meta-analysis software program was used for the meta-analysis. Comparisons were conducted using standardized mean differences considering the random-effects model (α=.05).Twenty-two studies were considered for the meta-analysis. Immediate and long-term bond strength to enamel was improved when a conventional composite resin was used in combination with an adhesive system (P.001). Bond strength to dentin was improved by using an adhesive system in combination with a conventional composite resin (P.001).The bond strength of self-adhesive flowable composite resins is lower than that of conventional composite resins, indicating limited ability to bond to enamel and dentin.

This study investigated dry sliding wear properties of AZ31 magnesium alloy and B4C-reinforced AZ31 composites containing 5, 10, and 20 wt.% B4C with bimodal sizes under different loadings (10–80 N) at various sliding speeds (0.1–1 m/s) via the pin-on-disc configuration. Microhardness evaluations showed that when the distribution of B4C particles was uniform the hardness of the composites increased by enhancing the reinforcement content. The unreinforced alloy and the composite samples were examined to determine the wear mechanism maps and identify the dominant wear mechanisms in each wear condition and reinforcement content. For this purpose, wear rates and friction coefficients were recorded during the wear tests and worn surfaces were characterized by scanning electron microscopy and energy dispersive X-ray spectrometry analyses. The determined wear mechanisms were abrasion, oxidation, delamination, adhesion, and plastic deformation as a result of thermal softening and melting. The wear evaluations revealed that the composites containing 5 and 10 wt.% B4C had a significantly higher wear resistance in all the conditions. However, 20 wt.% B4C/AZ31 composite had a lower resistance at high sliding speeds (0.5–1 m/s) and high loadings (40–80 N) in comparison with the unreinforced alloy. The highest wear resistance was obtained at high sliding speeds and low loadings with the domination of oxidative wear.

The design of astonishing combinations of benzoxazine resins with various fillers is nowadays of great interest for high quality products, especially in ballistic armors. The objective of this study is to investigate a new hybrid material prepared as multi-layered composite plate by hand lay-up technique. Different composites were manufactured from Kevlar fabrics reinforced polybenzoxazine, which was filled with silane treated microcrystalline cellulose (MCC Si) at various amounts in the interlayers. The developed materials were tested for their flexural, dynamic mechanical and ballistic performance. The aim was to highlight the effect of adding different amounts of MCC Si on the behavior of the different plates. Compared to the baseline, the dynamic mechanical and bending tests revealed an obvious decrease of the glass transition of 21 °C and a notable increase in storage modulus and flexural strength of about 180 %and17%, respectively, upon adding 1% MMC Si as filler. Similarly, the ballistic test exhibited an enhancement in kinetic energy absorption for which the composite supplemented with 1% MCC Si had the maximal energy absorption of 166.60 J. These results indicated that the developed panels, with interesting mechanical and ballistic features, are suitable to be employed as raw materials to produce body armor.

To improve the safety of HMX, HMX/NH2-GO composite was prepared with aqueous ammonia functionalized graphene oxide (NH2-GO). The composite was characterized by SEM, Zeta potential, XPS, Raman spectrum, XRD, HPLC, DSC and BAM sensitivity test. The results indicated that the functionalization with aqueous ammonia can enhance the interaction between GO and HMX, and more efficiently desensitize the explosive. The optimal impact sensitivity of the HMX/NH2-GO composite can be not less than 40 J, which is also the most insensitivity compared to the previous reports prepared by coating desensitization with non-energetic desensitized material. Moreover, the potential reason for the different impact and friction sensitivity was also discussed, which may bring a novel perspective to achieve the desensitization of energetic material.

Statement of problem Studies on the friction and wear behavior of recently introduced chairside computer-aided design and computer-aided manufacture (CAD-CAM) restorative materials are lacking. Purpose The purpose of this in vitro study was to evaluate the wear behavior of chairside CAD-CAM materials against different types of antagonists (human tooth enamel, composite resin, and feldspathic porcelain). Material and methods Specimens (14×14×2 mm) of different CAD-CAM materials (Brilliant Crios, Lava Ultimate, Vita Enamic, Vita Suprinity) were obtained by using a low-speed precision cutter (n=10). Wear tests were performed with a 20-N load, 2.5-mm/s sliding speed, 1-mm sliding distance, and 1500 cycles via a tribometer according to ASTM-G133. The coefficient of friction (CoF) of the material pairs was measured and recorded by using a special software program. Surface roughness (Ra), maximum wear depth, and mean maximum wear depth were measured with a profilometer, and values were analyzed by using 2-way ANOVA and the Bonferroni correction. Vickers hardness of CAD-CAM specimens was determined with a microhardness tester. Microhardness values were analyzed by using 1-way ANOVA and Tukey post hoc tests. Worn surfaces were observed by scanning electron microscopy and a 3D noncontact profilometer to determine the wear pattern and primary wear mechanisms. Results Significant differences were found in the interactions between CAD-CAM materials and different types of antagonists (P Conclusions Vita Suprinity exhibited superior wear resistance and Ra against all antagonists compared with other CAD-CAM materials. However, Vita Suprinity increased the destructive effects on antagonists. The safety of CAD-CAM materials is best determined when the wear behavior of materials and their effect on the antagonist are evaluated together.

We report a unique composite of La0.4Sr0.4Ti0.9Ni0.1O3-δ (LSTN) nanoparticles interlaced with two dimensional Ti3C2Tx (MXene) nanosheets, providing high conductivity. LSTN heterostructure synthesized by the sol-gel method produces a large oxygen vacancy and creates a variable valence state while, MXene synthesized from Hydrofluoric acid (HF) treatment resulted in a highly hydrophilic and conductive surface, thereby enhancing the charge transferability. For OER, the LSTN/MXene 66.67% electrode exhibits a benchmark of 10 mA cm−2 at a potential of 1.56 (V vs RHE) in 1 M KOH. It has exhibited the lowest Tafel slope of 44 mV dec−1 and highest mass activity (60 mA g−1 @ 1.59 V) due to quicker ions diffusion and increased available exposed area. Moreover, the efficient LSTN/MXene 66.67% electrode showed good long-term durability during a 24 h stability test at a current density of 100 mA cm−2. The strong interfacial interaction and high charge transfer among LSTN nanoparticles and 2D MXene nanosheets not only provide good structural strength to the composite but also improves the redox activity of LSTN/MXene 66.67% catalyst towards OER. This work provides improved conductive properties of perovskite by developing a composite of perovskite and MXene, that has significantly enhanced electrochemical properties of the catalyst by undergoing fast kinetics.

The paper presents the synthesis and characterization of Copper metal matrix composite reinforced with silica using powder metallurgy route. The 5%wt of silica is reinforced with copper metal as matrix material. 5% wt Magnesium was added as wetting agent as copper shows poor wettability towards silica. The reinforced silica was extracted from agro waste rice husk ash under controlled conditions of sintering temperature and duration of heating from rice husk ash using alkali extraction method. Reflux method was used to extract nanosilica from silica. Silica and the composite were characterized for microstructural studies, elemental composition and surface morphologies using X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray (EDX) and Transmission Electron Microscopy (TEM). The synthesized copper silica composite was studied for structural, compositional and mechanical properties. The results showed that the copper metal matrix composite reinforced with silica showed improved mechanical behavior and can be used in all such applications where light weight and better mechanical strength from copper metal are expected. As the filler material silica is extracted from green route which partially replaces the expensive metal, this work reports a non-toxic, cost effective, light weight and improved mechanical strength substitute for copper metal applications.

International audience; Rational design and synthesis of low-cost trifunctional electrocatalysts with improved stability and superior electrocatalytic activity for oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER) are highly desirable but remain as the bottlenecks at the current state of technology. In this paper, the cobalt-iron (Co–Fe) composite supported on nitrogen-doped carbon nanotubes (CoFe composite/NCNTs) is synthesized. The intrinsic OER and HER catalytic activities of this CoFe composite/NCNTs composite are significantly improved with palladium (Pd) nanocluster decoration [Pd-coated (CoFe composite/NCNTs)]. The as-prepared Pd-coated (CoFe composite/NCNTs) catalyst exhibits excellent trifunctional electrocatalytic activity and stability due to the interfacial coupling between Pd and (CoFe composite/NCNTs). This catalyst is successfully employed in the water electrolysis cell as both OER and HER electrode catalysts, flexible rechargeable Zn-air battery as the bifunctional ORR and OER electrode catalyst. The cell voltage of this catalyst-coated electrodes requires only 1.60 V to achieve 10 mA cm−2 current density for water electrolysis cell, which is comparable to and even better than that of Pt/C and Ir/C based cell. The primary Zn-air battery using this catalyst shows a constant high open-circuit voltage (OCV) of 1.47 V and a maximum power density of 261 mW cm−2 in the flooded mode configuration. Most importantly, a flexible Zn-air battery with this catalyst runs very smoothly without a change in voltage gap during flat, bending, and twisting positions.

Aluminium-wood particle composites were formed by casting method. Different weight fractions of wood particle as reinforcement to the Aluminium alloys were used to produce the composites. The physical and mechanical properties such as density, impact strength, tensile strength, hardness and microstructure were investigated. The results showed that the density decreases with the percentage increase in reinforcement. Also, a significant enhancement in the ultimate tensile strength (UTS) of the composite compared to that of pure aluminium was achieved. The maximum UTS of the Aluminium -wood composite is 97.69 MPa and occurred at 20%wt wood particulate addition reinforcement while that of the unreinforced Aluminium is 40.189 MPa. The impact energy varies from 47.00 J to 89.00 J with a maximum value at 10%wt wood particulate addition while the hardness varies from 52.33BHN to 62BHN with a maximum value at 10%wt. All the mechanical behaviours investigated in the study generally showed that the Aluminium -wood composite exhibited better mechanical properties than the pure Aluminium. The microstructure examination revealed that the wood particles were uniformly distributed in the metal matrix composite.

Ultrathin conversion coatings, made from aligned graphene derivatives and ammonium zirconium carbonate (AZC), were fabricated on stainless steel by electrodeposition. Sulfonated graphene oxide (SGO) provided electron pathways and physical barriers to corrosive molecules. Electrodeposition ensured the alignment of SGO and the facile fabrication of the coatings. AZC is an environmental-friendly crosslinking agent, water-repellent and corrosion inhibitor. Upon dehydration reactions, AZC improved the cohesion between SGO layers and anchored the conversion coatings on metal substrates. When the mass ratio of SGO to AZC was 2:1, the corrosion current density of the composite coatings reached 0.098 ​μA ​cm−2, while that of the bared stainless steel was 1.04 ​μA ​cm−2, given a coating thickness of only 500 ​nm. The electrical conductivity of SGO/AZC composite coatings can be tailored from 3.84 ​× ​10−5 to 2.28 ​× ​10−3 ​S‧cm−1 by heat treatment and HI reduction, which satisfied the electrical conductivity requirement of wide applications in electronic industry, office appliances and petroleum storage.

With the rapid development of the electronic industry, the requirements for packaging materials with high thermal conductivity (TC) are getting higher and higher. Epoxy is widely used as package material for electronic package applications. But it's intrinsic TC can't meets the increasing demands. Adding high TC graphene into epoxy matrix is a proper way to reinforce epoxy composites. This review focuses on the filler modification, preparation process and thermal properties of graphene-filled epoxy resin composites. Different ways of covalent and non-covalent modification methods are discussed. The various kinds of graphene coating layer are also summarized. Then we analysis the hybrid filler system in epoxy composite. We hope this review will provide guidance for the development and application of graphene-filled epoxy resin composites.