Tungsten trioxide (WO₃) nanorods are synthesized on the surface of graphene (GR) sheets by using a one-step in-situ hydrothermal method employing sodium tungstate (Na₂WO₄·2H₂O) and graphene oxide ...(GO) as precursors. The resulting WO₃/GR nanocomposites are characterized by X-ray diffraction, Raman spectroscopy, transmission electron microscopy, scanning electron microscopy and X-ray photoelectron spectroscopy. The results confirm that the interface between WO₃ nanorod and graphene contains chemical bonds. The enhanced optical absorption properties are measured by UV-vis diffuse reflectance spectra. The photocatalytic activity of the WO₃/GR nanocomposites under visible light is evaluated by the photodegradation of methylene blue, where the degradation rate of WO₃/GR nanocomposites is shown to be double that of pure WO₃. This is attributed to the synergistic effect of graphene and the WO₃ nanorod, which greatly enhances the photocatalytic performance of the prepared sample, reduces the recombination of the photogenerated electron-hole pairs and increases the visible light absorption efficiency. Finally, the photocatalytic mechanism of the WO₃/GR nanocomposites is presented. The synthesis of the prepared sample is convenient, direct and environmentally friendly. The study reports a highly efficient composite photocatalyst for the degradation of contaminants that can be applied to cleaning up the environment.
We report experimental results on the mechanical response of dissimilar tailor-welded blanks (TWB) from an advanced- and an ultra-high-strength steel for automotive applications. These are the ...dual-phase steels DP 780 and DP 1180, respectively. First, we present the tensile and anisotropic properties of the two base-materials. During testing, the full-fields of strain and temperature are acquired, using the Digital Image Correlation (DIC) and Infrared Thermography (IR) techniques. The latter is critical, since both materials are prone to deformation-induced heating, which establishes a temperature gradient along the test-section, and which in turn limits the ductility observed. We then describe the laser-welding apparatus, and microstructural observations and measurements around the weld-seam. Subsequently, we test tensile coupons from the TWBs, with the weld-seam oriented transversely, 45° and parallel to the longitudinal direction of the loading. We detail the failure modes and the macroscopic load–displacement responses. Furthermore, with the aid of the DIC and IR images, we probe the local strain and temperature fields and their evolution, and correlate these to the overall response and failure of the TWB tensile coupons.
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•Tension of DP780 and DP1180 Tailor Welded Blanks is examined with Digital Image Correlation and Infrared Thermometry.•The presence of the laser weld-seam affects the mechanical response.•The deformation-induced heating limits the ductility observed.•In every case, the TWB specimens failed earlier than base-material ones.
In this study, hydrothermal carbon doped with phosphorus using phytic acid (PA) and Sodium tripolyphosphate as functional monomers was successfully synthesized by the hydrothermal route combined with ...microwave-assisted hydrothermal carbon as matrix material. The uranium(VI) adsorption capacity by phytic acid functionalized microwave-assisted hydrothermal carbon (MHC-PA) was up to 382.2 mg/g at pH of 6.0 and the temperature of 298.15 K. The adsorption mechanism of uranium(VI) onto the MHC-PA was mainly the chelation of P=O, P–OH functional group and uranium(VI), which improves the selective adsorption performance of MHC-PA for uranium(VI).
The stamping forming quality of high strength steel is poor at ambient temperature, which easily causes defects such as wrinkle, crack and springback. This article aimed at the defects in automotive ...rocker arm parts and proposed a multi-objective optimization scheme. The parameters of the drawing process are optimized by finite element simulation of parts. The variable blank holder force model was introduced, and the response surface multi-objective optimization functions between process parameters with maximum springback displacement and maximum thinning ratio were constructed by B-Benhnken test. The objective functions were solved by a non-dominated sorting genetic algorithm with elite hierarchy (NSGA-II), and the Pareto optimal solution set of optimization problem was obtained. The optimal solution results were numerically simulated, and qualified parts with good formation were obtained in trial production, which verified the feasibility of the multi-objective optimization scheme.
Pectin degradation in the cell walls and middle lamella greatly affects the texture and the quality of the fruit including the taste and storage time. This directly affects its acceptability, supply ...to the consumer market, and economic benefits. It is therefore essential to establish the relationship between the chemical changes of pectin and the texture of the fruit to improve its preservation. This study was designed to evaluate the degradation of pectin in the peels of Tarocco blood orange and the textural changes during postharvest storage and further investigate their relationship over the study period. The texture of the fruit was characterized using the texture profile analyzer and the degradation of pectin was investigated by testing the content of the pectin, degree of esterification, and galacturonic acid content. The physicochemical properties, such as weight loss, moisture content, and anthocyanin content were also measured. Furthermore, the structural changes of the pectin were analyzed by molecular weight determination and FTIR test. The results showed that the M
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of pectin decreased from 568.05 kDa to 362.55 kDa, with a 42.1% decline in pectin content for storing for 63 d. The gradual solubilization, depolymerization, and de-esterification of the pectin consequently led to the decline in the textual properties of the fruit during postharvest storage. This can be applied and lead to improvements in quality control and process design in the food industry and the marketplace for the fruit during storage and preservation.
Premna microphylla turcz leaves (PMTL) is a resource-rich, biodegradable, renewable biomass. Here, a microsphere adsorbent was prepared from PMTL by a self-crosslinking method without any addition of ...chemical cross-linking agent, and characterized by SEM, FTIR, and XPS. The influence of preparation methods and conditions on the properties of the microspheres was studied and the self-crosslinking mechanism was analyzed. The effects of temperature, pH, contact time, uranium concentration, and adsorbent dosage on its adsorption performance toward to uranium were systematically explored. The results showed that PMTL endogenous pectin binding with endogenous Ca2+, Mg2+ and other metal ions to form an ‘egg box’ structure might be the mechanism of its self-crosslinking to form microspheres. The adsorption isotherms fitted well by the Freundlich model and the experimental maximum adsorption capacity of microspheres was 346.65 mg·g−1 at pH of 5, and kinetics data correlated well with the pseudo-second order model. The adsorption mechanism might be the coordination bonding between the uranium and oxygen-containing groups (hydroxyl and carboxyl groups), and the ion exchange between the uranium and metal ions (mainly Ca2+ and Mg2+). The PMTL microspheres are promising in treating uranium-containing wastewater in a more cost-effective and environmentally friendly manner.
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•The combination of natural biomass with unique advantages and non-traditional emulsion suspension method.•The self-crosslinking of endogenous pectin and endogenous metal ions without the addition of any exogenous substance.•Due to the coordination and ion exchange, the adsorption capacity of PMTL microspheres for uranium reaches 346.65 mg·g−1.
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•Cr3C2-VC/Co-based cladding layers was fabricated by laser cladding.•Plastic deformation and carbides/cobalt interfaces were characterized and evaluated by HAADF-EDS, EBSD and ...HRTEM.•The agglomeration of a substructure of nanostructured powders was found to influence the carbide growth strongly.
Cladding layers were prepared on carbon steel using nanostructured carbide-strengthened cobalt (Co)-based alloy (using nanostructured tungsten carbide as hard phases) as a deposited material by multi-track laser cladding. In addition to Co-based alloy, the deposited materials contained nanostructured chromium carbide (Cr3C2), vanadium carbide (VC), or Cr3C2 and VC. Compared with the substrate, all cladding layers had an improved oxidation resistance with an increased time (0–50 h) at 800 °C. Cr2C3 had a higher oxidation-resistance performance than VC and the mutual reaction of Cr2C3 and VC. The constitution and phases of the cladding layers indicated hexagonal-close-packed-α and body-centered-cubic-β cobalt and hard carbides, such as CoCx, V8C7, and Cr3C2, and some decarburization as Co3W3C and WC1-x. Elemental inter-diffusion occurred between the different phases as indicated by transmission electron microscopy and electron backscattered diffraction. Mixed carbide has a larger misorientation than the cobalt matrix, and electron backscattered diffraction has considerable potential to evaluate plastic deformation. The average grain size of the hard carbides was much larger than that of the original deposited material. The carbides grew rapidly through interfacial diffusion, boundary migration, and coalescence, which followed the Kirkendall effect and Ostwald-coarsening mechanism. This research helps to understanding the microstructure, oxidation resistance, grain growth, and interfacial behavior in multi-track laser-cladding layers.
Micro- and nano-structured WC reinforced Co-based cladding layers on Ti6Al4V substrates were synthesized by laser cladding. The structure, phase composition, and wear behavior were investigated by ...scanning electron microscopy (SEM), X-ray diffraction (XRD), and friction-wear tests. High-angle annular dark field-energy dispersive spectroscopy (HAADF-EDS), transmission electron microscopy (TEM) and lattice images confirmed the XRD and SEM results. The interfaces exhibited good metallurgical bonding between the cladding layer and substrate owing to their high chemical affinity for each other. The cladding layer was composed of α(α′)-titanium, eutectics of CoTi2, β-titanium, TiC, eutectics of TiCTiB2, VC (Cr3C2), (Ti, W)C1−x, W, TiB2, and Co3W3C phases formed by the dissolution of WC. VC inhibited grain growth more effectively than Cr3C2 or the combined effects of VC and Cr3C2. The wear resistance of the micro-/nano-WC cladding layers was markedly improved compared with those of Ti6Al4V. Nano-WC tended to convert into tungsten, however, the cladding layers easily became hard and brittle owing to aggregates of carbides or oxides. This effect resulted from interfacial boundaries formed by major differences at the α-Ti/α-Ti (Cr3C2, TiB2) interfaces in terms of the chemical and structural contributions to the surface energy.
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•Micro-/nano-structured WC reinforced Co-based cladding synthesized on Ti6Al4V.•α-Ti/α-Ti (Cr3C2, TiB2) interface was characterized by HAADF-EDS and HR-TEM.•Influence of powder deposited on cladding layers, WC dissolution, and η-carbide formation discussed.
Increasing the thickness of the Invar (Ni42Fe50.9C0.6Mn3.5Nb3) interlayer from 1 to 1.5 mm resulted in a continuous metallurgical bonding, free of voids and oxide films. Invar as a pre-placed buffer ...also led to higher bending strength because of the stress relaxation. When the thickness was increased to 2 mm, the porosity in the fusion zone increased and cracks developed near the fusion boundary on the WC-Co side, lowering the strength. The fusion boundary, heat affected zone and the fusion zone on the WC-Co side were susceptible to cracking. Transmission electron microscopy revealed high densities of dislocations. Energy dispersive spectroscopy suggested that long-range solute diffusion occurred inside the WC grains and at the WC/Fe (Ni)/WC interfaces.
•The aluminum alloy 6082 in this study is an extruded material after aging.•Compare the traditional constitutive equation of the material and the strain-compensated Arrhenius model with the newly ...established PSO-BP network model.•Use statistical analysis methods for data analysis.
It is important to model the flow behavior of an aged aluminum alloy AA6082 as an extrusion material before design and optimize of the forming process. In this study, the isothermal compression tests were carried out on Gleeble-3800 thermal simulator in the temperature range of 423−773 K and the deformation condition of 0.01–1.0 s−1 to study the cold temperature and hot deformation behavior of aluminum alloy AA6082. Considering the experimental error, the discussion based on friction and temperature correction is carried out. According to the modified data, based on the traditional Arrhenius constitutive model, a method combining the strain compensation Arrhenius model and PSO-BP neural network was proposed to describe the flow behavior of aluminum alloy AA6082. The prediction ability and stability of the model are evaluated by using the linear correlation coefficient(r), the average relative errors (AARE), the Root mean square errors(RMSE) and the relative errors (RE) in statistical analysis. The results show that the 3-10-8-1 double hidden layer neural network model based on PSO-BP has higher effect in predicting the flow characteristics of aging aluminum alloy AA6082 than that of Arrhenius model based on strain compensation. The linear correlation coefficient, mean relative error and root mean square error are 0.9996 %, 2.001 % and 1.665 MPa respectively.
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