Narrow Results

TiC/TiN-reinforced composite coatings were fabricated on the substrate of Ti–6Al–4V alloy using laser remelting. X-ray diffraction (XRD) was used to identify the phases in the laser-clad composite coating; the interface characterization of the dilution zone-clad zone (IDC) and the dilution zone-heat-affected zone (IDH) was observed with a scanning electron microscope (SEM). The results show that the microstructure of a cross-section has stratification characterization, and consists of the clad zone (CZ), the dilution zone (DZ), the diffusion layer (DL) and the heat-affected zone (HAZ). The layer-by-layer microstructure results from the boundary layer phenomenon of viscous melt-fluid and diffusion. The kind of reinforced particle has an effect on the interface morphology, microstructure and flow characterization of the melt-fluid. The phase constitution in the clad zone consists of (Cr–Ni–Fe), TiC, Ni₄B₃, Ti₂Ni, Cr₂B and M₂₃C₆ for TiC+NiCrBSi coating, and (Cr–Ni–Fe), TiN, NiB, Cr₂Ti and Ti₂Ni for TiN+NiCrBSi coating. The interfaces of the IDC in the NiCrBSi-clad layer is clear and clean; those of TiC+NiCrBSi and TiN+NiCrBSi are illegible. Ti–Ni phases with acicular microstructure link dilution zone and clad zone, and two kinds of phase with acicular microstructure, are similar in composition and shape.

Porous titania coatings with Ca and P elements were synthesized by plasma electrolytic oxidation (PEO). The treatment was carried out in an electrolyte containing calcium acetate monohydrate and disodium phosphate dodecahydrate (Ca/P = 5), and 4–20 μm micropores were prepared on the coatings by applied pulse frequencies of 200–1000 Hz. The surface structure, chemical composition of the TiO₂ coatings, and time-dependent variation of electric currents were studied. The result revealed that the coating micropores, which could be controlled in size, increased with higher frequency, and the coatings mainly consisted of anatase and rutile phases with varying fractions. Based on our experiment, the formation mechanism of micropores and phases of the PEO coatings was further discussed in details.

Micro-arc oxidation coatings were fabricated on 7E04 aluminum alloy substrates by micro-arc oxidation (MAO) in the electrolytes with the graphite addition varying from 0 to 8g/L (0, 2, 4, 6, 8g/L). The effect of graphite concentration on the surface morphologies, micro-hardness, thickness, phase composition and corrosion resistance of coatings was investigated. With the graphite powder concentration increasing, the oxidation voltage decreased gradually and the thickness of coatings firstly dropped down and then went up. It is found that the size of micro-pores and sintered discs declined with increase of graphite concentration. The XRD results indicated that MAO coatings mainly consisted of $\gamma$-Al₂O₃, $\theta$-Al₂O₃, SiO₂ and a little $\alpha$-Al₂O₃. The corrosion resistance of coatings was improved with the addition of graphite powder. The study reveals that the appropriate graphite powder in the electrolytes is essential to promote the performance of the coatings.

This paper has summarized five surface strengthening methods, and these methods could to improve the surface properties of materials. The selection of mechanical parts materials has determined according to their working conditions. The work-piece in using cannot avoid defects in the material. This paper has introduced surface deformation enhancement, surface phase transformation enhancement, ion implantation technology, surface diffusion and infiltration technology, chemical transformation technology and surface coating technology. And has also included the principle of every surface technology, various technologies, parameters, strengthening characteristics, as well as strengthening effect and matters needing attention. The hardness, residual stress and corrosion resistance off mechanical parts could be improved through these surface strengthening methods. It is convenient to find the strengthening method and parameters in this paper when strengthening mechanical parts.

Structural transformations during the synthesis of mayenite (Ca₁₂Al₁₄O₃₃) were investigated. The samples were prepared by a solid–state reaction and the transformations were researched by means of XRD, Rietveld analysis, SEM, and Raman spectroscopy. The three key phases (CaAl₂O₄, Ca₃Al₂O₆, Ca₅Al₆O₁₄) were identified and their role in the mayenite formation was assigned. The optimal low temperature pathway of the mayenite synthesis involving Ca₅Al₆O₁₄ intermediate was proposed.

Unsaturated hyperbranched polyester resin (UHPR) prepared by ourselves shows best comprehensive performance in linear unsaturated polyester resin (UP-191) curing system and is considered as a kind of toughness and reinforcement additive. The effect of molecular weight and content of the UHPR on the performance of the UHPR/UP-191 hybrid materials are discussed in detail, and their performance has maximum with the increase of content and molecular weight of UHPR. The impact strength of the hybrid materials containing 10–15 wt% UHPR-2 is 1.86 kJ/m², and which almost is 1.69 times of UP-191 performance, furthermore, the tensile and flexural strength can also be enhanced about 45.71% and 23.66%, respectively. The fracture surface micrograph of hybrid materials show non micro-phase separation of the UHPR/UP-191 blends which facilitates an enhanced interaction to achieve excellent toughness and strength of the cured systems by SEM and the results also are explained by a novel situ reinforcing and toughening mechanism.

Highly proton-conducting hybrid materials (P₂W₁₇V/PEG and P₂W₁₇V/PEG/SiO₂) were prepared by heptadecatungstovanadodiphosphoric heteropoly acid with Dawson structure (P₂W₁₇V, 90 wt.%), polyethylene glycol (PEG, 10 wt.% and 5 wt.%) and silica gel (SiO₂, 0 wt.% and 5 wt.%). The products were characterized by the infrared (IR) spectrum, X-ray powder diffraction (XRD) analysis and electrochemical impedance spectrum (EIS). The result reveals that their conductivity values are 1.02 × 10^-2 and 2.58 × 10^-2S ⋅ cm^-1 at room temperature (26°C) and 75% relative humidity (RH), respectively. Their conductivities increase with higher temperature and these activation energies of proton conduction are 9.51 and 14.95 kJ⋅mol^-1, which are lower than that of pure heteropoly acid (32.23 kJ⋅mol^-1). These mechanisms of proton conduction for these two materials are Grotthuss mechanism.

This study aimed to develop an effective, environmentally benign composite catalyst composed of carbon materials and titanium dioxide (TiO₂). Carbon-doped titanium dioxide (C–TiO₂) was prepared by coating TiO₂ onto macro-mesoporous carbon (MMC). The structure, morphology and surface chemistry states of the C–TiO₂ were characterized by XRD, TEM, XPS, UV-vis and FTIR. The photocatalytic activity of C–TiO₂ was evaluated based on the decomposition of an aqueous methyl orange solution in visible light. C–TiO₂ significantly improved photocatalytic activity. A possible mechanism for the improvement of the photocatalytic activity of C–TiO₂ in visible light was proposed. The results of the analysis suggested that MMC played key roles as the support, absorbent, location of photo-generated electron transfer, and carbon-doping source during methyl orange photodegradation.

A ternary heteropoly acid (HPA) H₆SiW${}_{10}$V₂O${}_{40}\cdot$14H₂O was prepared and investigated in this paper. The structure feature and hydration of this HPA was characterized by IR, XRD, UV, and TG-DTA. This HPA exhibits a high proton conductivity, which is $7.4\times 10^{-3}$S$\cdot$cm${}^{-1}$ at 25${}^{\circ }$C and 70% relative humidity. It is a novel high proton conductor. The conductivity increases with higher temperature, and it exhibits Arrhenius behavior, with the activation energy value of 21.02kJ$\cdot$ mol${}^{-1}$ for proton conduction, indicating the proton conduction mechanism is dominated by vehicle mechanism.

Fe₃O₄ hollow microspheres with good dispersibility and high saturation magnetization were synthesized through a facile one-step solvothermal method. The formation mechanism of the hollow structure was studied by taking time-dependent experiments. Porous $\alpha$-FeOOH and $\alpha$-Fe₂O₃ nanosheets were firstly fabricated. Fe₃O₄ solid spheres aggregated by small particles were obtained from the transition of $\alpha$-FeOOH and $\alpha$-Fe₂O₃. Finally, the solid sphere is transferred to hollow sphere through Ostwald ripening. The maximum saturation magnetization of the hollow spheres is $115.4\pm 0.1$emu/g, which is higher than some results reported in references. The Fe₃O₄ hollow spheres show potential applications in microwave absorption and photocatalysis.

ZnO/Bi₄V₂O${}_{11}$ nanocomposites were prepared via a facile hydrothermal method by loading different amounts of ZnO onto the surface of Bi₄V₂O${}_{11}$. The resulting ZnO/Bi₄V₂O${}_{11}$ composites showed excellent photocatalytic activity than that of pure ZnO under visible light irradiation. When the ratio of ZnO to Bi₄V₂O${}_{11}$ was 1:1 (ZB2), the photocatalytic activity was best, which could degrade RhB almost completely within 30min. The enhanced photocatalytic activity of ZnO/Bi₄V₂O${}_{11}$ composites could be mainly ascribed to the efficient charge separation and the increased specific surface area. Based on the experimental and bandgap calculations, a possible photocatalytic mechanism was proposed.

Fenton process has been widely applied for environmental restoration. However, acidic and neutral solutions are always needed in order to obtain an excellent catalytic activity. Flower-like MoS₂ was firstly used as a Fenton catalyst with higher activity in alkaline solution than that in acidic and neutral ones. The catalytic mechanism indicated that $•\mathrm{\text{OH}}$ and $•{\mathrm{\text{O}}}_2^{-}$ radicals formation induced the excellent catalytic activity in alkaline solution. Effects of pH, catalyst dosage, H₂O₂ and RhB concentrations on catalytic activity were studied, and the quantitative relations were established. The experimental result demonstrated that the catalyst was stable in alkaline solution. The leaching Mo was smaller than 2mg/L.

Designing highly efficient catalysts for PMS activation is of great significance for the degradation of organic pollutants. Here, a Cu decorated MnO catalyst (Cu-MnO) has been synthesized for forceful PMS activation to drive antibiotic degradation. As expected, the Cu-MnO particles exhibit superior catalytic activity for tetracycline (TC) degradation with the high degradation rate of 91% after 60 min due to the synergetic redox coupling of Mn and Cu species. In addition, the experimental parameters (catalyst concentration, PMS dosage, initial pH value, initial TC concentration, and reaction temperature) were also explored to optimize the reaction conditions and improve the efficiency of TC degradation. At the same time, the most likely reaction path of TC degradation was speculated based on quenching experiment. This work provides a new idea for efficient activation of PMS.