Equal channel angular pressing (ECAP) was performed on extruded pure Mg, which was clad with a drilled pure Fe coat through an ECAP die to produce a pure Mg sample without obvious cracks at room temperature. After one-pass ECAP, the grain size decreased because of basal slip activation during the dynamic plastic deformation but the microstructure became inhomogeneous. The deformed texture was less scattered and inclined by ~20° from the normal direction toward the extruded direction, and low angle boundaries increased continuously. The mechanical properties decreased slightly as a result of the combined effect from a more refined microstructure and a weaker texture.

•MnO2/C composite with 492 F/g capacity were prepared by a one-step redox method.•Different drying processes were employed to regulate particle agglomeration.•The effects of agglomeration on MnO2/C performances were addressed accordingly.•Agglomeration was found a core impart fact for cycling stability.Amorphous MnO2/C composite is prepared by a facile redox reaction between potassium permanganate (KMnO4) and commercial black pen ink. Afterwards, two different drying processes, air drying or freeze drying, are employed to adjust the agglomeration state of particles in samples and explore its influence on capacitive performance. Experimental results indicate that the air-dried sample demonstrates much better cycling stability than the freeze-dried one (capacity retention at 5000 cycles: 70.9 vs. 60.7%), probably because of the relatively strong agglomeration between particles in this sample. Nevertheless, strong agglomeration seems to deteriorate the specific capacitance (from 492 down to 440.5 F/g at 1 A/g) due to the decrease of porosity and specific surface area. This study suggests that agglomeration of primary particles plays an important role to balance the specific capacitance and cycling stability for electrode materials.Download high-res image (127KB)Download full-size image

•AZ31/UCF/AZ31 composite sheets was fabricated by vacuum hot pressing (VHP) method at different temperatures.•The wettability and bonding strength of UCFs/AZ91 interfaces increased as the VHP temperature increased, which had beneficial effect on the mechanical properties of the sheets.•The fracture mechanism at 500 °C was the pullout of UCFs and delamination. At 560 °C, partial debonding between UCFs and AZ91 was the dominant failure mechanism.AZ31 Mg alloy/unidirectional carbon fiber (UCF)/AZ31 composite sheets were fabricated with AZ91 Mg alloy powder as an adhesive using vacuum hot pressing (VHP) at various temperatures. Both the wettability and bonding strength of the UCF/AZ91 interfaces increased with increasing VHP temperature, resulting in an improvement of the mechanical properties of the composite sheets. The fracture mechanism of the composite sheets at low VHP temperature (500 °C) was the pullout of UCFs and delamination. In contrast, at 560 °C, partial debonding between the UCFs and AZ91 was the dominant failure mechanism, and an S-type fracture path surrounding the UCFs was observed. The bonding strength of the UCF/AZ91 interface was weaker than that of the AZ91/AZ31 interface for this composite. The sheet prepared at 585 °C exhibited the largest ultimate tensile strength of 252 MPa and an elongation of 13.2%. This behavior was attributed to the enhancement of the interfacial bonding strength due to the formation of Al4C3 and MgAl2C2 phases at the UCF/AZ91 interface. The hardness and modulus reached maximum values of 9.9 and 61 GPa, respectively, near the UCF/AZ91 interface.

This work focused on preparing the highly transparent TiO2 nanotube array(TNT) film and measuring its photoelectric performance. The highly transparent TNT film was successfully fabricated on FTO glass combining the magnetron sputtering and anodization method. By comparing the photoelectric performance of transparent TNT and non-transparent TNT films obtaining in the same method, it was observed an interesting phenomenon under visible light irradiation that the photocurrent response of transparent TNT film was higher than that of non-transparent TNT film, while the photocatalytic activity of transparent TNT film was lower than that of non-transparent TNT film.

•Mesoporous birnessite-type K2Mn4O9 was prepared by a facile redox reaction.•K2Mn4O9/CNTs nano-composite was manufactured on the basis of K2Mn4O9.•They show capacitances up to 754 and 1055 F g−1 at 1A g−1, respectively.•K2Mn4O9/CNTs//AC asymmetric supercapacitor achieves an energy density of 62 Wh kg−1.A facile, scalable and cost-efficient redox reaction is developed to prepare micro-powders of a quasi-crystallised, mesoporous birnessite-type manganese oxide, K2Mn4O9. In 1 M KOH electrolyte, the K2Mn4O9 powder shows a high specific capacitance of 754 F g−1 at 1 A g−1 (calculated with the net weight of K2Mn4O9 micro-powder only). Meanwhile, the electrode retains 91% of its initial capacitance after 5000 cycles at a high current density of 5 A g−1. By simply adding carbon nanotubes (CNTs) into the reaction system, the specific capacitances of as-prepared K2Mn4O9/CNTs composites are further increased to 929 and 1055 F g−1 at 1 A g−1 in 1 and 6 M KOH electrolyte (corresponding to 69 and 77% of the theoretical capacitance of MnO2), or 600 and 674 F g−1 at 5 A g−1, respectively. Significantly, a maximum energy density of 62 Wh kg−1 at a power density of 852 W kg−1 could be achieved based on a K2Mn4O9/CNTs//activated carbon asymmetric supercapacitor (ASC). At the same time, the ASC device exhibits a decent long cycle life with 85% specific capacitance retained after 1000 cycles, suggesting its wide application potential in low-cost high energy density storage systems.

•Hollow Si/C composites were obtained from expandable microspheres (EMs) and Si NPs.•EMs were employed as self-template carbon precursors.•This method is one-step, environment-friendly and scalable.•A capacity of 684.6 mAh g− 1 (80% retention) at 50 cycles, 300 mA g− 1 was achieved.Si/C composites of carbon hollow structures loaded with Si nanoparticles (NPs) (Si/C-HSs) were prepared by one-step pyrolysis of a mixture of Si NPs and expandable microspheres (EMs). For the Si/C-HSs, hollow carbon shells with rough surfaces were formed by directly carbonizing the polymer shells of EMs, and the Si NPs fell into the void space or were loaded on the rough surfaces of the carbon shells. The EM-based carbon shells accommodated the volume expansion of the Si NPs and improved the electrical conductivity of the composites. As a result, the Si/C-HSs exhibited a high capacity (initial reversible capacity: 854.4 mAh g− 1 at 300 mA g− 1), stable cycling performance (capacity retention: 80% after 50 cycles), and excellent rate capability.

A simple approach is presented to form Au@TiO2 nanotube arrays. This approach consists of the formation of pure TiO2 nanotube arrays by a two-step anodization process, the coating of a Au nanofilm on the top of the pure TiO2 nanotube arrays, and the heat treatment of the TiO2 nanotube arrays coated with the Au nanofilm. The heat treatment leads to the diffusion of Au atoms into the TiO2 nanotube arrays, resulting in the formation of Au nanocrystals on the outer surface of the TiO2 nanotubes. X-ray diffraction, field emission scanning electron microscopy, and transmission electron microscopy are used to characterize the microstructural evolution of the Au@TiO2 nanotube arrays, which reveals the phase change of TiO2 from amorphous phase to anatase phase. The kinetics of the migration of Au atoms into the TiO2 nanotube arrays is studied. The diffusivity for the diffusion of Au atoms on the outer surface of the TiO2 nanotubes is in the range of 4.14–19.4 × 10−18 m2 s−1 for temperature in the range of 400–500 °C. The activation energy for the migration/diffusion of Au on the outer surface of the TiO2 nanotubes in the temperature range of 400 to 500 °C is 67.2 kJ mol−1. The growth of Au nanocrystals on the surface of the TiO2 nanotubes can be described as a first order reaction.

Two types of three-layered Al/Mg/Al clad sheets were fabricated by hot rolling. The first (sheet A) underwent a single pass with a small rolling reduction of 33% and the second (sheet B) underwent four passes with a large rolling reduction of 71%, and both were subsequently annealed at 200 °C for 1 h. Microstructural examination and tensile tests on the fabricated sheets revealed that 17.8-μm-thick intermetallic compound layers (IMCLs) appeared at AZ31/5052 interfaces in sheet B while none were observed in sheet A. The AZ31 layers in sheets A and B exhibited basal textures with intensities of 15.1 and 9.8, respectively, and only sheet A exhibited tensile twins (TTs) in the AZ31 layer. Recrystallization resulting in grains was preferred near the AZ31/5052 interface and the intersections between TTs. Owing to its larger rolling reduction, more extensive recrystallization was observed in the sheet B component layers than in sheet A. Sheet B exhibited better mechanical properties with a much higher ultimate tensile strength (UTS) than sheet A (230 versus 102 MPa) and a slightly larger elongation (19 versus 17%).This indicates that texture intensities and the extent of recrystallization of component layers have a significant effect upon the mechanical properties of clad sheets.

To improve the homogeneity and rolling formability of as-cast AZ91 magnesium, the effects of pre-homogenizing treatment on microstructure evolution, deformation mechanism, mechanical properties and tensile fracture morphology of hot-rolled AZ91 magnesium alloy were studied. The results showed that the amount of coarse β-Mg17Al12 phase decreases dramatically, being distributed along the grain boundaries as small strips after homogenizing. Twining plays a dominant role in the deformation mechanism of AZ91 alloys in the experimental condition, while dynamic recrystallization (DRX) considerably occurred in homogenized-rolled alloys, contributed to microstructure uniformity and β-Mg17Al12 phase precipitated refinement. The tensile strength of homogenized-rolled AZ91 alloys increases dramatically with elongation declining slightly in contrast to homogenized alloys. The fracture surface of homogenized-rolled specimen exhibits more ductile fracture with the manifestation of a large amount of dimples distributing higher density in matrix, while the micro cracks are prone to initiate around the Mg/Mg17Al12 phase interface and grain boundaries owing to the fragile interface bonding of two phases.

Three-layered 5052Al/AZ31Mg/5052Al (5052/AZ31/5052) clad sheets were fabricated by four-pass rolling and annealed under different conditions. Under the optimal annealing condition, homogeneous and equiaxial grains with an average AZ31 grain size of 5.24 µm were obtained and the maximum values of ultimate tensile strength and elongation of the clad sheet reached 230 MPa and 18%, respectively. Electron backscatter diffraction analysis showed that the AZ31 layer had a typical rolling texture with its c-axis parallel to the normal direction. The fraction of low-angle grain boundaries in the 5052 layer was nearly four times more than that in the AZ31 layer because of different deformation extent and recrystallization driving forces. The textures of Al3Mg2 and Mg17Al12 were similar to that of 5052 because of the deformation coordination during the rolling and recrystallization process. The orientation relationship between Mg17Al12 and AZ31 seemed to be (110) Mg17Al12//(10−11) AZ31.

Using magnetron sputtering, pure TiO2 nanofilms and Ag/TiO2 bilayer nanofilms doped with nitrogen were deposited on glass substrates. Heat treatment of the Ag/N-TiO2 nanofilms at 400 °C led to the formation of Ag nanoparticles, which were dispersed inside the TiO2 films as well as on the free surface of the TiO2 films. The photocatalytic activity of the Ag/N-TiO2 nanofilms with dispersed Ag nanoparticles was examined by UV-vis diffuse reflectance spectroscopy. The rate constants for the photodegradation of methylene blue (MB) in aqueous solutions of MB by N-TiO2-based nanofilms are about one order larger than those for self-degradation or for pure TiO2 nanofilms. The rate constants for the photodegradation of aqueous solutions of MB by the Ag/N-TiO2 nanofilms are larger than those for the N-TiO2 nanofilms. The Ag nanoparticles improve the photocatalytic activity of TiO2 films, possibly through the surface plasmon absorption effect of Ag nanoparticles, which activates photo-generated charge carriers through the transfer of plasmonic energy.

The thickness of intermetallic compound (IMC) layers at interface would significantly influence the interfacial bond strength, and the interfacial bond strength would further affect the tensile behavior of 5052 Al/AZ31B Mg/5052 Al tri-laminate structural clad sheets fabricated by hot rolling. In this manuscript, the relations among the thickness of IMC layers produced by post-roll annealing, the interfacial bond strength and the tensile behavior of clad sheets were investigated. No reactive diffusion phases were observed in the as-rolled clad sheets and in the rolled clad sheets annealed at 473 K for 1 h. When annealing at a temperature of 573 K for 0.5 h, 1 h, 2 h, 4 h, 8 h, new reaction diffuse phase layers with various thickness are formed at interface. Two types of reaction layers, viz., Al3Mg2 and Al12Mg17, adjacent to the 5052 Al side and AZ31B Mg side, respectively, are identified by EDS analysis. The effects of thickness of IMC layers on the normal bond strength and the shear bond strength were investigated. Uniaxial tensile tests of the clad sheets with and without IMC layers were investigated to reveal the relationships between the tensile behavior and the bond strength. Meanwhile, the fractured process of IMC layers and the delaminated process of tri-laminate composite sheets were also discussed during the uniaxial tensile testing.

Four alloys of Mg–8Li, Mg–8Li–3Al, Mg–8Li–3(Al–Si) and Mg–8Li–6(Al–Si) were prepared, using the vacuum suction casting. The hot-rolling process was used to deform the prepared alloys. The effects of the addition of Al–Si eutectic alloy and the hot-rolling on the microstructures and mechanical behavior of the dual-phase Mg–8Li alloys were investigated. Adding Al and Al–Si eutectic alloy in the Mg–8Li alloy led to the refinement of the microstructures. The experimental results show that adding Al–Si eutectic alloy dramatically improved the tensile strength of the dual-phase Mg–8Li alloys with a slight decrease of elongation. The as-rolled Mg–8Li–6(Al–Si) alloy had a tensile strength of up to ∼390 MPa with relatively large elongation.

Copper oxide thin films were prepared by a direct-current magnetron sputtering method followed by a thermal annealing treatment at 100–500 °C. The obtained films were characterized by X-ray diffraction, UV-vis absorption spectroscopy, scanning electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy. With the increase of the annealing temperature, it was found that the films transformed sequentially from amorphous to single-phase Cu (100 °C), mixed-phase of Cu and Cu2O (150 °C), single-phase Cu2O (200 °C), then to mixed-phase of Cu2O and CuO (300 °C), and finally to single-phase CuO (400–500 °C). Further analyses indicated that the Cu/Cu2O thin films and the Cu2O thin films presented no further oxidation even on the surface in air atmosphere. Additionally, the visible-light photocatalytic behavior of the copper oxide thin films on the degradation of methylene blue (MB) was also investigated, indicating that the films with pure Cu2O phase or Cu/Cu2O mixed phases have excellent photocatalytic efficiencies.

Infiltrationbehaviour of Zn-Al semi-solid slurries into carbon fibre (Cf) sheet during hot pressing was investigated. A parameter, termed Solid Fraction Increasing Rate (SFIR) vs. temperature drop, is proposed to evaluate the infiltrability of semi-solid slurry during hot pressing. The infiltrability of the slurry during hot pressing varies inversely with the value of its SFIR. The stronger infiltrability of Zn-8%Al slurry during hot pressing at 385 °C is attributed to its lower SFIR.

•Co3O4 and Co3O4/CoO were prepared by solution combustion at 350 °C in air.•The fuel/oxidizer molar ratio influenced effectively performance of products.•A specific capacitance of 362.8 F·g−1 (0.2 A·g−1) was achieved after annealing in N2.Co3O4 and Co3O4/CoO nanoparticles have been synthesized by a one-step solution combustion process by adjusting the molar ratio of citric acid (fuel) and Co(NO3)2·6H2O (oxidizer). The effects of citric acid/Co(NO3)2·6H2O molar ratios on phase composition and morphology of products were investigated by XRD and SEM. With the increase of the fuel dosage, the products transformed from granular aggregates of cubic Co3O4 into a mixture of cubic Co3O4 and tetragonal CoO with fluffy sheet morphologies. Electrochemical measurements indicated that the products (Co3O4) showed a capacitance up to 179.7 F·g−1 (at 0.2 A·g−1) when the citric acid/Co(NO3)2·6H2O molar ratio was 7/27. Significantly, the capacitance could be further improved by 102% (362.8 F·g−1 at 0.2 A·g−1) after annealing at 350 °C for 3 h under nitrogen atmosphere. This annealed sample also demonstrated decent rate performance (285.7 F·g−1 at 4 A·g−1) and cycling stability (73.5% retention after 1000 cycles). The current study suggests that this process has promise in large-scale production of electrode materials for supercapacitors.

This article describes a facile solvothermal synthesis method to prepare Fe2O3/AC composites for electrochemical capacitors from Iron (III) chloride hexahydrate (FeCl3·6H2O), activated carbon (AC, from petroleum coke), and four different precipitants (i.e., NaOH, CH3COONa, HMT, CO(NH2)2). X-ray powder diffraction (XRD), Scanning electron microscopy (SEM), Energy dispersive spectroscopy (EDS) and Thermogravimetric (TG) analysis show that the products consisted of nanosized α-Fe2O3 (weight ratios: 48.1, 47.9, 44.2, 44.3%) loaded onto AC particles (∼ 20 μm). Significantly, both kind and dosage of precipitants exhibit effects on the specific capacitances of Fe2O3/AC composites. The highest specific capacitance reaches up to 240 F g−1 (at a current density of 1 A g−1 in 6 M KOH aqueous electrolyte) when the molar ratio of CH3COONa: FeCl3 is 9. On the other hand, the sample prepared with NaOH: FeCl3 molar ratio being 1.5 exhibits excellent rate capability with specific capacitance of 215 F g−1 at 1 A g−1, and 89.3, 82.3, 78.1, 72.6 and 65.1% capacity retention at 2, 5, 10, 20, and 40 A g−1, respectively. These electrochemical performances are superior to other materials consisted of Fe2O3/carbon nanotube (CNT), graphene oxide (GO) or reduced graphene oxide (rGO) composites, demonstrating the great potential of Fe2O3/AC composites in the development of high-performance electrode materials for electrochemical capacitors.

•A zinc–yttrium coating can be formed on the surface of AZ91D magnesium alloy.•The coating contains a large amount of intermetallic compound Mg5Al2Zn2.•The microhardness values of the coating are much higher than that of the substrate.•The coating can improve the corrosion resistance of the substrate effectively.A zinc–yttrium coating on AZ91D magnesium alloy was conducted by diffusion treatment in order to improve its corrosion resistance and wear resistance. The microstructures and phase constituents of the zinc–yttrium coating were investigated using optical microscope (OM), X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive spectrum (EDS). The results reveal that a zinc–yttrium coating has been formed on the surface of magnesium specimens by the solidification of the liquid layer formed between the AZ91D magnesium alloy and the Zn, Y mixed powders. The microstructure of the zinc–yttrium coating is typical eutectic structure, which contains a large amount of intermetallic compound, such as Mg5Al2Zn2. In addition, the microhardness values of the intermetallic compounds are much higher than those of the substrate and this would greatly contribute to the enhancement of wear resistance. The results of electrochemical corrosion tests in 3.5 wt.% NaCl solution show that the corrosion resistance of the coated specimens has been increased significantly.

Novel Cu2O/Pt/TiO2 three-layered nanocomposite films were prepared by deposition on glass substrates using the magnetron sputtering method. Their structure, surface morphology as well as optical and photocatalytic properties were examined by X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, UV–visible spectroscopy, and photoluminescence spectroscopy. As a comparison, Cu2O/TiO2 double-layer films were also investigated. The results show that Cu2O/TiO2 double-layer films have relatively smooth surfaces with agglomerated Cu2O particle, whereas the surface layer of the Cu2O/Pt/TiO2 three-layered nanocomposite films was composed of fine nano-sized columnar Cu2O and they had a rough surface morphology due to the insertion of the Pt layer. The photocatalytic activity of the three-layered films is significantly higher than that of the Cu2O/TiO2 double-layered composite films. Such enhancement is closely related to the presence of the Pt layer and the rough surface, which was composed of fine nano-sized Cu2O columns; this increases the utilization of visible light as well as promotes the transfer of interfacial charge and the separation of photogenerated electron–holes.

TiO2 nanotube (TNT) arrays were fabricated by anodic oxidation of titanium foil in a fluoridebased solution, on which Cu2O particles were loaded via galvanostatic pulse electrodeposition in cupric acetate solutions in the absence of any other additives. The structure and optical properties of Cu2O-loaded TiO2 nanotube arrays (Cu2O-TNTs) were analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD) and UV-Vis absorption, and the photoelectrochemical performance was measured using an electrochemical work station with a three-electrode configuration. The results show that the Cu2O particles distribute uniformly on the highly ordered anatase TiO2 nanotube arrays. The morphologies of Cu2O crystals change from branched, truncated octahedrons to dispersive single octahedrons with increasing deposition current densities. The Cu2OTNTs exhibited remarkable visible light responses with obvious visible light absorption and greatly enhanced visible light photoelectrochemical performance. The I–V characteristics under visible light irradiation show a distinct plateau in the region between approximately −0.3 and 0 V, resulting in higher open-circuit voltages and larger short-circuit currents with increased Cu2O deposition.

In the paper, Si element was added in Mg–15Al alloy and processed by the equal channel angular processing (ECAP) for 4 passes using route Bc at 300 °C. Microstructure characteristics of experimental alloys before and after ECAP were observed by OM, SEM, EDS and XRD. Tensile test (25, 150 and 200 °C) was carried out by a WDW-100KN tensile testing machine. The results show that the grain size of as-cast Mg–15Al alloy was decreased with addition of 1 wt% Si element, and new Mg2Si phase formed in the matrix. Meanwhile, network β-Mg17Al12 phases tend to form with the increasing amount of β. After processing by ECAP, the net structure of β-Mg17Al12 phases was disappeared and the morphology was modified. Moreover, the grain size of α-Mg matrix was decreased sharply, from 11.3 μm (in Mg–15Al) to 5.98 μm (in Mg–15Al–1Si), and Coarse Chinese script Mg2Si phase emerged in Mg–15Al–1Si alloy was broken into particle with dimension of ~3 μm by ECAP simultaneously. As a result, the mechanical properties of Mg–15Al–1Si and Mg–15Al alloy were improved by ECAP and the increased amount of Mg–15Al–1Si alloy was greater than that of Mg–15Al, about 51.6 MPa in room temperature tensile strength. The Mg2Si phases with high melting were fragmented by ECAP and distributed uniformly in matrix, thus, the mechanical properties of ECAPed Mg–15Al–1Si alloy were more excellent at high temperature, comparing with other experimental alloys.

•The interface structure in Al/Mg plates evolves significantly at high temperatures.•Intermetallic layers form at the bond interface when heating at high temperatures.•The growth of the intermetallics layer follows the parabolic law.•Subsequent hot rolling results in a composite bond interface.Using a two-pass hot rolling process, Al(5052)/Mg(AZ31)/Al(5052) alloy laminated composite plates were fabricated. The first pass was performed at relatively low temperatures, and the second pass was performed at higher temperatures. No new phases formed at the bond interface after the first hot rolling pass. High temperature annealing with the annealing temperature at or above 300 °C caused the formation of continuous layers of the intermetallics Mg17Al12 and Al3Mg2 at the bond interface of Al(5052)/Mg(AZ31). The growth rate of the intermetallic layers increased with increasing the annealing temperature, while the incubation time decreased with increasing the temperature. A kinetic equation was developed to describe the growth of the intermetallic compound layers. The second hot rolling pass caused the break of the continuous intermetallic layers into fragments, which were intermittently dispersed at the bond interface.

•CuN, Cu and N-doped anatase TiO2 are studied by using DFT.•The Cu interstitial and N substitutional co-doped TiO2 are most favorable structure.•The band gap is the smallest in V region after CuN co-doped TiO2.•The activity of CuN co-doped is highest than that of corresponding single atom doped.Cu, N and CuN-doped anatase TiO2 are studied using density functional theory (DFT). It is found the band gap decreases after CuN co-doped. The intensity of adsorption spectra increases in the following order: CuN codoped⪢Cu-doped⪢N-doped⪢pure anatase in visible region, indicating that the electrons on the valence band easily transit to the conduction band. In other words, theoretic calculation shows that the photocatalytic activity of CuN co-doped is higher than that of the corresponding single Cu or N-doped.

The transparent C-doped TiO2 nanostructure films were fabricated on the silicate glass substrates by sol-gel spin-coated method. The as-prepared films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-visible absorption spectra (UV-vis) and X-ray photoelectron spectroscopy (XPS). The photocatalytic activity was evaluated via the photo-catalytic oxidation of methylene blue in aqueous under daylight irradiation at room temperature. The results show that the daylight-induced photocatalytic activities of the as-prepared films are improved by the C-doping. The calcination temperatures significantly affect the morphology, microstructure and photocatalytic activity of the as-prepared samples. At 723 K, the C-doped TiO2 films exhibit the highest photocatalytic activity due to the synergetic effects of good crystallization, appropriate oxygen vacancies and strong absorption in the near UV and visible-light region.

An as-cast magnesium alloy with high Al content Mg15Al was subjected to equal-channel angular pressing (ECAP) through a die with an angle of ϕ=90° at 553 K following route Bc. It is found that the network β-Mg17Al12 phases in the as-cast Mg15Al alloy are broken into small blocks and dispersed uniformly with increasing numbers of pressing passes. Moreover, many nano-sized Mg17Al12 particles precipitate in the ultra-fine α-Mg matrix. The grains are obviously refined. However, the grain structure is inhomogeneous in different areas of the alloy. The average size of the primary phase α-Mg is reduced to about 1 μm while grains of around 0.1–0.2 μm are obtained in some two-phase areas. With additional ECAP passes (up to 8), coarsening of the grains occurs by dynamic recovery. Room temperature tensile tests show that the mechanical properties of Mg15Al alloys are markedly improved after 4 ECAP passes. The ultimate tensile strength and elongation to failure increase from 150 MPa to 269.3 MPa and from 0.05% to 7.4%, respectively. Compared with that after 4 passes, the elongation to failure of the alloy increases but the strength of the alloy slightly decreases after 8 ECAP passes. Fracture morphology of the ECAP-processed alloy exhibits dimple-like fracture characteristics while the as-cast alloy shows quasi-cleavage fractures.

Tensile stress occurs in the vicinity of upper surface of the specimen in the severe plastic deformation zone, which increases the cracking and fracture tendency of the specimen and impedes the further ECAP processing. In this paper, the conventional ECAP die (Ψ = 16° and Φ = 90°) was modified to eliminate the tensile stress and enhance the compressive stress in the severe plastic deformation zone, therefore reducing the cracking and fracture tendency of the specimen. Finite element analysis demonstrated that the stress state changes from tensile to strongly compressive when using the modified die. A modified die was made and employed to extrude the commercially pure aluminum to verify its effectiveness experimentally. The billet was successfully extruded for 20 passes without obvious surface defects with the modified die, compared to 13–14 passes at most for the conventional die. Consequently, much more fine and uniform microstructure was obtained with the average grain size of 200–300 nm, while the average grain size is ∼500 nm in the case of using the conventional die.

The first-principles density-functional calculation was conducted to investigate the electronic band structures of titanium dioxide with heavy nitrogen doping (TiO2−xNx). The calculation results indicate that when x ⩽ 0.25, isolated N 2p states appear above the valence-band maximum of TiO2 without a band-gap narrowing between O 2p and Ti 3d states. When x ⩾ 0.50, an obvious band gap narrowing between O 2p and Ti 3d states was observed along with the existence of isolated N 2p states above the valence-band of TiO2, indicating that the mechanism proposed by Asahi et al operates under heavy nitrogen doping condition.

TiAl-based specimens were siliconized with two different kinds of cementation respectively, one is 23 vol.% Si + 77 vol.% Al2O3, and the other is 23 vol.% Si + 77 vol.% ZrO2. SEM observation showed that a Ti5Si3-based layer, in which some Al2O3 particles dispersed, formed on the surface after siliconization. Further observation showed that an extra outer Al2O3 layer existed on the surface of specimens siliconized with 23 vol.% Si + 77 vol.% Al2O3, while no such Al2O3 layer was found in specimens siliconized with 23 vol.% Si + 77 vol.% ZrO2. The cyclic oxidation test performed at 900 °C shows that the oxidation resistance was significantly improved by siliconizing. By comparison, the specimens that siliconized with 23 vol.% Si + 77 vol.% Al2O3 exhibits a better oxidation resistance than that with 23 vol.% Si + 77 vol.% ZrO2. It was deduced that the extra outer Al2O3 layer is beneficial to the oxidation resistance of siliconized TiAl-based alloy.