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Simultaneously integrating mesocrystalline stacking superstructures, porous nanosheets and defective oxygen vacancies (OVs) into BiOCl crystals is an available strategy to enhance the visible-light-driven photocatalytic activity. Herein, we report a facile etching agent-assisted hydrothermal approach to achieve one-pot fabrication of mesocrystalline BiOCl porous nanosheet stacking superstructures with defective OVs, which show high catalytic activities towards to the visible-light-driven degradation of organic dyes. The formation of stacking superstructure in a mesocrystalline BiOCl is responsibility for increasing the transport of charge carriers. Experimental results and theoretical calculations suggest that the presence of OVs is beneficial to tuning the energy band structure for the improvement of visible light harvesting, prolonging the lifetime and enhancing the oxidation activity of photogenerated charge carriers. Additionally, the porous morphology and thin nanosheet building block could supply abundant active sites for photocatalysis. This research might arouse in-depth investigations on the development of novel precursor-modified strategy for the synthesis of high-active BiOX (X = Cl, Br and I)-based photocatalysts.

The Cu-Cr-Nb alloys were prepared by vacuum induction melting with different cooling methods. The effects of niobium contents and different cooling methods on the microstructures and properties of these alloys were investigated. The microstructures were characterized by optical microscope, scanning electron microscope and transmission electron microscope. The electrical conductivity, hardness and the tensile strength of Cu-Cr-Nb alloys were tested as well. The results showed that the as-cast microstructures of Cu-Cr-Nb alloys consist of primary α phase dendritic and eutectic phase. With the addition of element Nb, the microstructures were refined and the secondary dendritic arm spacing obviously decreased. Compared with the furnace cooling, the homogeneous and refined microstructures were obtained by the graphite mold, and the hardness of the alloys is enhanced greatly. After the heat treatment, two reinforcing phases of Cr and Cr2Nb are precipitated from the copper matrix. The comprehensive properties were obtained when the Nb content is 0.4%. The Cu-1.2Cr-0.4Nb alloy performed by direct aging treatment without solution treatment exhibits the higher performance, the hardness and electrical conductivity are 143HB and 84%IACS, respectively. In addition, the tensile strength and the elastic limit of the Cu-1.2Cr-0.4Nb alloy can reach up to 413.0 and 238 MPa.

Synergistic strengthening is increasingly explored for developing high-performance metal matrix composites. In the present work, copper matrix composites reinforced with carbon nanotubes (CNTs) and TiB2 microparticles were fabricated via electroless deposition, powder metallurgy, hot extrusion, and water quenching. The synergistic strengthening effect of the nano-and micro-reinforcements was elaborated and analyzed based on experimental investigation and theoretical calculation. (1CNT-4TiB2)/Cu composite exhibited a better combination of the tensile strength of 375 MPa with elongation of 32.4% than other composites, representing 86.3%, 71.5%, and 22.8% strength increment in comparison with pure Cu, 4TiB2/Cu composite, and 1CNT/Cu composite, respectively. The strengthening efficiency of CNTs in (1CNT-4TiB2)/Cu composite is markedly higher than that in 1CNT/Cu composite (126.7 and 82.3, respectively), confirming the synergistic strengthening effect in enhancing the mechanical properties. Quantitative analysis and experimental characterization indicated that the thermal mismatch and load transfer mechanism of CNTs were the main factors contributing to the tensile strength enhancement of the composite. The synergistic strengthening effect was attributed to that TiB2 microparticles improved the homogeneous dispersion of CNTs, promoting the proportion of thermal mismatch and load transfer mechanisms. The present work may provide a new sight into improving the synergistic strengthening effect in metal matrix composites.

In the present study, a TiB2 particle-reinforced Cu/Cu-0.5Cr composite was prepared by vacuum arc melting (VAM). The microstructure, mechanical properties and electrical conductivity of the composite after heat treatment were studied. The results show that the micro–nano dual-scale particle-reinforced TiB2/Cu-0.5Cr (VAM) composite possessed high strength, high hardness and high electrical conductivity. The nano-Cr particles were uniformly dispersed in the copper matrix, and the particle size was below 20 nm. The TiB2 particles were also uniformly dispersed and had good bonding with the copper matrix. After peak aging at 475 °C for 4 h, the comprehensive properties of the TiB2/Cu-0.5Cr (VAM) composite were improved. The hardness and electrical conductivity were 99.6 HBW and 82.3% IACS, respectively. The tensile test results show that the tensile strength of the TiB2/Cu-0.5Cr (VAM) composite was 401 MPa, which is higher than that of the TiB2/Cu (VAM) composite. The TiB2/Cu-0.5Cr (VAM) composite had high strength and hardness due to the strengthening of the micro–nano dual-scale particles and the good interface bonding. Based on the tensile fracture morphology of the composite, the failure mechanism of the composite was determined and is discussed.

Arc erosion behaviors of TiB2/Cu composites with single-scale and dual-scale TiB2 particles fabricated by powder metallurgy were studied. It was revealed that the dual-scale TiB2/Cu composites had fewer structure defects compared with the single-scale TiB2/Cu composites, and TiB2 particles with different size were uniformly distributed in the copper matrix. When the ratio of 2 μm over 50 μm TiB2 particles is 1:2, the density of TiB2/Cu composite is 98.5% and shows best mechanical and thermal properties. The arc duration and energy of TiB2/Cu composites increase with the increase of electric current in contact material testing. Compared with the single-scale TiB2/Cu composites, the arc erosion of dual-scale TiB2/Cu composite with 2 μm+50 μm (1:2) TiB2 was slighter. The anode bulge area and cathode erosion pit of dual-scale TiB2/Cu composite was smaller. The dual-scale TiB2 particles optimize the microstructure and thermal stability of the composite, which is conducive to alleviating arc erosion. The synergistic effect of different sized TiB2 particles in the matrix improved the arc erosion resistance of TiB2/Cu composite during arcing.

Copper matrix composites reinforced with 1, 3, 5, 7 vol.% Cu-coated SiC whiskers of consistent orientation (SiCw/Cu) were prepared by powder metallurgy and hot extrusion. The microstructure of composites was investigated by scanning electron microscopy. The SiC whiskers were arranged along the direction of hot extrusion and distributed uniformly. The composites were fabricated into specimens with different whisker orientations, and their electrical conductivity was tested. The effects of SiC whiskers orientation and content on the electrical conductivity of composites were investigated through experiment. Results show that the SiC whiskers content was the major factor affecting the electrical conductivity of the composites. With increasing SiC whisker orientations angel, the electrical conductivity of composites is improved. The electrical conductivity model has been established by taking into account the SiC whiskers content, whisker orientation and microstructure parameters, and the results were in good agreement with experimental data. Graphical abstract: Copper matrix composites reinforced with SiC whiskers of consistent orientation were prepared. The orientation of SiC whiskers changes from 0∘ to 90∘, resulting in electrical conductivity anisotropy of composites.

Heterojunction engineering is an effective strategy to enhance the photodegradation activity via improving the spatial charge separation. However, the poor interface interactions and stability limit the photocatalytic activity and stability of traditional heterojunctions. Herein, robust BiOCl/ZnO p–n heterojunctions with semi-coherent interfaces were prepared by a one-pot hydrothermal method to improve the activity and stability toward photocatalytic degradation than that of the counterpart, in which the semi-coherent interfaces exhibited lower phase boundary energy, resulting in highly-stable interfaces between BiOCl and ZnO as well as the formation of the built-in electric field in this robust p–n heterojunction for enhanced charge separation. The cycle test results verified that the BiOCl/ZnO heterojunctions with semi-coherent interfaces can maintain the photocatalytic degradation activity at the initial level even after 10 cycles, while deactivation of the sample without semi-coherent interfaces occurred after 3 cycles only. Optical and electrical properties revealed that BiOCl/ZnO heterojunctions with semi-coherent interfaces possessed the highest electron migration and charge separation efficiency, resulting in the highest photodegradation activity. Density functional theory (DFT) calculations and electron spin-resonance (ESR) results verified that the enhanced charge separation was assigned to the type-II photocatalytic mechanism, leading to the enhancement of ˙OH and ˙O2− reactive oxygen species. This work would provoke the development of one-step construction of new highly active BiOX (X = Cl, Br, and I)-based heterogeneous photocatalysts with stable semi-coherent interfaces.

High-strength and highly conductive copper matrix composites can not only maintain excellent electrical and thermal conductivity but also enhance the strength and hardness of materials, showing that composites have a bright future for development. Predictions of the effective electrical conductivity of copper matrix composites disagree with experimental data due to the dependence of the composites on several factors. Most prediction models simply consider the influence of the particle volume fraction on conductivity. In the present study, the influence of the volume fraction and the size of the TiB2 particle on the electrical conductivity of TiB2/Cu composites are investigated. The obtained electrical conductivity results correlate with the volume fraction, size, and distribution of particles in a pure copper matrix. A modified model for predicting the electrical conductivity is proposed where the particle spacing parameters are introduced into the existing Maxwell model. The particle spacing parameter, as a fitting parameter, fits the experimental data of the copper matrix composites excellently.

In this work, ultrafine-grained W-Cu composites without and with reinforcement of tungsten fibers (Wf) were prepared by successive processes of mechanical alloying, cold pressing, sintering and infiltration. For Wf reinforced W-Cu composite, the introduction of Wf coated with magnetron sputtered Cr, improved the sinterability and contiguity of Wf with the neighboring W powders, eliminating porosity between Wf and the matrix and improving the interfacial strength. Further compressive tests demonstrated that, compared with conventional commercial W-Cu composite made of micron-sized tungsten powders, for the ultrafine-grained W-Cu composite reinforced with Cr-coated Wf, the compressive strength increased dramatically by 122.9%, 43.6% and 91.3%, when deformed at room temperature, 300 °C and 500 °C, respectively. Besides, the electrical breakdown strength increased impressively by 118%, which can be ascribed to the arc dispersion from the increased fraction of grain boundaries in the ultrafine-grained structure free from blind holes.

To achieve a combined enhancement of mechanical properties with improved arc erosion resistance, a novel strategy of two-step ball-milling and hot-press sintering under hydrogen for fabricating hierarchical W-Nb-Cu composite reinforced with in-situ nanocrystalline fcc-Nb was advocated. Characteristics including phase constituents, microstructure, mechanical properties and arc erosion behavior of the W-3 wt.%Nb-30 wt.%Cu composite have been systematically investigated. The crystal structure, grain size and phase distributions, as well as the specified surface work function of the three components of W, Cu and Nb were identified by XRD, TEM, EBSD experiments and DFT calculation. The enhanced mechanical properties were considered to result from the grain refinement of W and Cu with gradient micron to ultrafine scale, and the interfacially precipitated nanocrystalline fcc-Nb, which also acted as the first breakdown phase for effective dissipation of arc energies.

The fabrication of carbon nanotubes (CNTs)-reinforced copper matrix composites with excellent performances is a challenging task because of the weak interfacial bonding between CNTs and copper matrices. In the present work, an alloying element—titanium—was intentionally added to the bonding interfaces of laminated CNTs/Cu composites via the flake powder metallurgy method. Due to the in situ formed intermediate layer of TiC and Cu3Ti particles, the interfacial bonding of the composites was significantly improved. In combination with the architecture design, the locally alloyed 0.2 wt% CNTs/Cu-0.5Ti composite exhibits both improved ultimate tensile strength (407 ± 22 MPa) and ductility (9.7%) compared with the unalloyed composite containing the same CNT concentration. Since titanium was locally added solely to the interface, the inclusion of titanium had a negligible effect on the lattice parameters of the copper matrix, and the electrical conductivities of the bulk composites were maintained at a relatively high level.

The internal friction of C/SiC composites was studied by forced vibration at the frequency and amplitude modes, and the effects of microstructural defects on the internal friction of C/SiC composites were investigated systematically and the internal friction mechanism was also discussed. Test results indicated that the microstructure defects in C/SiC samples improved the internal friction and had greater effects on the internal friction tested at low frequency and high amplitude. The slip friction of weak interphase was the main internal friction mechanism for C/SiC samples with interphase damage, and the internal friction increased slowly with the porosity. As the interphase was corroded completely, the pores in C/SiC composites became the main factor controlling the internal friction, and the internal friction increased rapidly with the porosity.

A novel Al4W/Al12W composite, which can be used as a structural material in the automotive and aerospace industries, was developed and successfully fabricated in-situ using an infiltration method in vacuum environment. The microstructure and phase analyses of the Al4W/Al12W composite were performed using a scanning electron microscope equipped with energy dispersive spectrum and X-ray diffractometer. To quantify the characteristics of the composite, electron backscattering diffraction analysis and first-principles calculations were then performed. The composite was obtained at 800 °C, and the Al4W phase was distributed homogeneously on the Al12W with holding time above 40 min at 800 °C. The grain size of Al4W increased, while its relative content decreased with longer holding time. The structural stability of Al4W was superior to that of Al12W. The microstructural evolution of Al4W/Al12W composite was also elucidated. The defined microstructure promised favorable engineering applications of the novel composite.

The application of templating and etching agents for the synthesis of mesoporous graphitic carbon nitride (mpg-C3N4) is not environmentally friendly, motivating attempts to develop a green and efficient strategy to construct mpg-C3N4 with improved photocatalytic performance. Herein, for the first time, we demonstrate a general carbonated beverage-assisted hydrothermally-reformed commercial melamine (MA) strategy for the synthesis of mpg-C3N4 nanosheets. Although the dosage of carbonated beverage (including Coca-Cola, Pepsi-Cola, Sprite and Fanta) is very small for the modification of MA precursors, the improvement in the photocatalytic activity of the mpg-C3N4 products is very remarkable. With the unique structural advantages for aligned energy bands and charge carrier migration, and numerous photocatalytic sites, the visible-light-driven photocatalytic hydrogen evolution rate (HER) of mpg-C3N4 nanosheets synthesized from a Coca-Cola-reformed MA precursor is 15.1 times higher than that of bulk g-C3N4, achieving an apparent quantum yield of 7.7% at 420 nm. Similarly, mpg-C3N4 nanosheets synthesized from Pepsi-Cola-, Sprite- and Fanta-reformed MA precursors also exhibit enhanced photocatalytic HERs.

Titanium dioxide (TiO2) nanostructures have been extensively investigated in the field of photocatalysis, and many previous review articles have summarized the progress made in the design and synthesis of crystalline TiO2 with tailored nanostructures. However, the physical and chemical properties of TiO2, including light absorption, surface adsorption, and charge carrier separation, are related to the disordered arrangement of intrinsic atoms. Therefore, amorphous TiO2 (am-TiO2) with long-range atomic disorder plays an important role in the photocatalytic performances. Unfortunately, at present we still know less about amorphous TiO2-based materials than crystalline ones from a scientific viewpoint, and a comprehensive review on am-TiO2 is lacking and highly desirable to further advance the development of novel function-oriented TiO2-based nanostructures. In this review, we comprehensively summarize the structural characteristics, optical properties, synthesis principles and current morphologies of am-TiO2 nanostructures. In particular, photocatalytic applications with regard to am-TiO2-based nanostructures are highlighted. Additionally, we briefly propose several perspectives on the challenges and new direction for future investigation. This review will act as a useful guideline for researchers who are currently concentrating on TiO2 materials to fabricate novel amorphous-based nanomaterials for photochemical applications.

In the present work, the ultrafine-grained W-25 wt.%Cu composites doped with multi-walled carbon nanotubes (CNTs) have been prepared through combined processes of high-energy ball-milling, liquid-phase sintering and infiltration. Furthermore, the microstructure, hardness and electrical conductivity of the ultrafine-grained W-Cu composites doped with different contents of CNTs were investigated. Meanwhile, the wear resistance, compressive performance at different temperatures and arc erosion resistance were evaluated in comparison with the W-Cu composite without CNTs. The results revealed that the hardness, wear resistance, compressive performance and arc erosion resistance of the W-Cu composites doped with CNTs were enhanced dramatically due to the introduction of tungsten carbide phases after sintering and infiltration. Keywords: W-Cu composite, CNTs, Tungsten carbide, Wear resistance, Compressive performance

Doping and exfoliation are effective strategies to improve the photocatalytic activity of bulk graphitic carbon nitride (g-C3N4). Therefore, it can be inferred that engineering element-doping and exfoliation into g-C3N4 would further enhance the photocatalytic performance. Herein, we demonstrated a KOH-assisted hydrothermal-reformed melamine strategy for achieving the simultaneous K-doping and exfoliation of g-C3N4. The as-synthesized K-doped g-C3N4 ultrathin nanosheets displayed much enhanced photocatalytic hydrogen evolution rate (HER) of about 13.1 times higher than that of the bulk g-C3N4 under visible-light irradiation, achieving an apparent quantum efficiency of 6.98% at 420 nm. The improved photocatalytic HER can be attributed to the high surface area offering numerous photocatalytic active sites, enlarged conductive band edge optimizing photoreduction potential, and K-doping promoting charge generation and separation as well as the long life-time of photogenerated carriers. This work would provide a promising way to integrate co-doping and exfoliation into new g C3N4 based materials.

Exposed high-index facets with a high density of low-coordinated atoms (including edges, steps and kinks) can provide more high-active sites for chemical reactions. Therefore, great progress has made in the facet-dependent application of various high-index faceted micro-/nanostructures in the past decades. Previous review papers have mainly highlighted the advances in high-index faceted noble metal nanocrystals. However, to date, there is no specialized review paper on high-index faceted metal oxides and their facet-dependent applications. Thus, in this review, the existing high-index faceted metal oxide micro-/nanostructures, including Cu2O, TiO2, Fe2O3, ZnO, SnO2 and BiVO4, are reviewed based on their characterization, synthesis engineering and facet-dependent applications in the fields of catalysis, sensors, lithium-ion batteries and carbon monoxide oxidation. Also, several challenges and perspectives are presented. Hopefully, this review article will be a useful guideline and resource for researchers currently concentrating on high-index faceted metal oxides to design and synthesize novel micro-/nanostructures for overcoming the practical environment-, biology- and energy-related problems.

Graphitic carbon nitride (g-C3N4) has been considered as a promising metal-free photocatalyst, but the bulk still suffers from a low specific surface area and poor quantum efficiency. Exfoliation of the bulk into porous heteroatom-doped nanosheets has been confirmed to be an effective strategy for improving the photocatalytic activity. However, purposefully designing targeted precursors towards the synthesis of porous heteroatom-doped g-C3N4 nanostructures for enhanced photocatalytic activity is still a challenge. Here, we intentionally design and construct a new hydroxylated and carbonylated melamine precursor for preparing targeted porous O-doped g-C3N4 nanosheets based on the thermal polymerization reaction pathway. The as-prepared porous O-doped g-C3N4 nanosheets possess a high specific surface area which provides more active sites, and exhibit enhanced transfer and separation of charge carriers, thus displaying an about 18-fold higher hydrogen production activity than the bulk counterpart. This work would stimulate widespread investigations into the development of a designated precursor-reforming strategy for synthesizing highly-active g-C3N4 photocatalysts.

Nanoporous tungsten was prepared by a strategy combining mechanical alloying and chemical dealloying at room temperature. The feature size of the nanoporous structure is adjustable by modifying dealloying medium and duration. The formation of nanoporous tungsten is dependent on the surface diffusion of W atoms and their diffusivity in the dealloying medium is in a magnitude order of 10−20 m2 s−1. The structure of nanoporous tungsten has a high activation energy for surface diffusion, which contributes to its extremely high thermal stability. The nanoporous tungsten may be promising for applications at high temperatures.

SiC coating was prepared on the graphite substrate and the effects of substrate morphology on the thermal radiation properties of SiC coating were investigated. As the surface roughness of the graphite substrate decreasing from 2.95 to 0.68 μm, the total emissivity of SiC coating increased 28.33% at 1000 °C and 36.21% at 1600 °C, respectively. At the same time, the spectral emissivity of SiC coating on the graphite substrate all presented the obvious characteristic thermal radiation of SiC. Those results meant that the thermal radiation properties of the coating were both dominated by the substrate and coating. A simple coating model had been established to explain the effect of the substrate morphology on the heat flow between the substrate and coating. The rough substrate morphology enhanced the energy dissipation at interface and weakened the thermal radiation properties of coating finally.

Nanoporous copper oxides were formed by thermal oxidation of nanoporous copper at 150°C–270°C. The oxidation process of nanoporous copper was investigated by using XRD, SEM, nitrogen adsorption, HRTEM and nanoindentation. The variation of microstructures and mechanical properties was analyzed. The results showed that the content of copper oxides increased, the ligament gradually coarsened, and the mechanical properties of nanoporous structure were improved with the increase of oxidation temperature. When the oxidation temperature was below 210°C, the ligament surface was oxidized to Cu2O, and the composite structure of Cu2O@Cu was formed. The formation of CuO occurred since 220°C, and the composite structure of CuO/ Cu2O@Cu was formed. CuO nanowires were grown on the ligament surface at 250°C; the specific surface area, elastic modulus and hardness of nanoporous structure are 1.37, 3.31 and 7.58 times that of the nanoporous copper, respectively.

Transient liquid phase bonding of aluminium and copper (without interlayer, Al-11Si-4Cu-2Mg and Al-4.5Si-2Cu-1Mg foil) were carried out in sandwich-like coupon assemblies under different temperature in vacuum environment. The interfacial structure and composition of the bonding interface were investigated. The bonding strength and resistivity were tested. Two layers of compounds were formed on the interface in all the bonding joints. The main difference in the joints using different interlayer was the microstructure of the Al2Cu and Al2Cu/Al interfacial structures. The interface of the joint without interlayer consisted mainly of Al–Cu eutectic (Al2Cu + Al) near Al side and the Al2Cu phase presented a continuous reticular structure. In the joints using interlayer, the formation of Al2Cu can be significantly inhibited. The shear strengths of the joints using Al-11Si-4Cu-2Mg foil at 575 °C reached to 77 MPa which was close to the shear strength of Al base metal. The resistivity of TLP joint was near the theoretical resistivity and then it has good conductivity.

Better understanding the crystal-facet engineering of a crystal with tailored architecture has demonstrated a significant implication for rational design and synthesis of promising micro-/nanostructure. In the past decades, extensive investigations have been devoted to the development of cuprous oxide (Cu2O) crystals with tailored architectures, which can provide a meritorious platform for not only revealing the structure-property-performance relationship and but also improving the performances in their practical applications. Several previous reviews have mainly reported the partial summaries of the advances in facet-dependent properties of Cu2O crystals. However, a comprehensive summary on Cu2O crystals is lacking and highly desirable to further promote the development of function-oriented Cu2O-based micro-/nanostructures. In this review, we will comprehensively highlight the important progresses in Cu2O crystals with tailored architectures, including the synthetic strategies and corresponding growth mechanisms, the fundamental properties of different crystallographic facets, the functional modifications (including doping and hybridization), and their potential applications. Several urgent issues and perspective are also discussed.

Porous/dense ZnO bilayer films were grown by thermal oxidation of ZnS films deposited with gallium in air. The microstructures and photoluminescent properties of the as-grown ZnO bilayer films were investigated by XRD, SEM, HRTEM, XPS and PL. It was found that Ga doping contributed to the growth of ZnO dense layer, which covers the ZnO porous layer formed due to the evaporation of sulfur oxides. The diffusion-limited Ga gradient distribution along the thickness of ZnO films was observed. The remained Ga on the surface region led to the formation of ZnGa2O4 layer covering the ZnO film. The growth mechanism and morphology of the ZnO film covered by ZnGa2O4 grown by physical vapor deposition of metal gallium are quite different from that of the ZnO film covering ZnGa2O4 grown by manual application of molten gallium. Meanwhile, the formation of ZnGa2O4 was prohibited by altering Ga deposition distance. Higher Ga doping decreased the concentration of oxygen vacancy, which reduced the visible emission from ZnO film in combination with existence of ZnGa2O4 layer.

In the present work, direct and detailed insights with respect to the statistical information on boundary type of discontinuous precipitates and their advancing reaction fronts in a Re-containing single crystal superalloy DD6 have been obtained by EBSD. With the annealing time prolonging, the reaction fronts proceeded into the original matrix for gradual release of grit-blast induced stress. The average recrystallized grain diameter and the average depth of recrystallization were respective 0.83 μm and 3.98 μm for the specimen annealed at 1050 °C for 10 min, which, after 16 h, had grown to the average values of 3.22 μm and 31.17 μm. The reaction fronts of discontinuous precipitation have been confirmed to be high-angle grain boundaries, but do not always correspond to CSL type. Besides the role of strain energy dissipation for recrystallization, the formation of twin structure has no direct relationship with the proceeding of reaction fronts. The information of boundary type of discontinuous precipitation and its advancing reaction fronts would provide new insight into the cellular recrystallization behavior.

The acceleration effect of cobalt on carburization of tungsten at low temperatures was studied by a series of experiments of W, C and Co reactions and theoretical evaluations. Due to Co addition, the formation temperature of WC was greatly reduced (e.g. a decrease from 1300 °C to 850 °C by addition of 1.0 wt% Co). Below the formation temperature of the ternary phase, the converted fraction of W carburization increases with increased Co. Modeling of reaction kinetics revealed that the process of W carburization is dominated by carbon diffusion, and the reaction rate constant is increased much with the increase of Co. The mechanism was proposed that Co acts as the medium for rapid diffusion of C atoms and promotes W carburization by accelerating reaction diffusion kinetics. The present findings will facilitate to develop methods for synthesis of WC-Co composite powders at low temperatures.

Doping protocols have been widely investigated due to their effectiveness in tuning the energy band gaps of photocatalysts for improved photocatalytic activity. Here, we demonstrated the efficient and facile hydrogen peroxide-assisted hydrothermal reforming of melamine to synthesize a new oxygen (O)-doped precursor that was then transferred to O-doped g-C3N4 nanosheets, with an increased conductive band edge compared to bulk g-C3N4, via direct thermal polymerization. Owing to synergistic interaction between the 2D ultrathin nanosheet structure with large surface area and the enhanced conductive band edge caused by appropriate oxygen doping, the as-synthesized O-doped g-C3N4 nanosheets showed highly enhanced photocatalytic hydrogen evolution activity, about 10.7 times higher than pristine C3N4 under visible light irradiation, achieving an apparent quantum yield of 13.04% at 420 nm. Significantly, this precursor pre-doping strategy might provide a promising pathway for preparing heteroatom-doped g-C3N4.

Ultrathin CuO nanorods have been readily synthesized by simply mixing Cu2+/OH−/ethanol with water at high temperature. Such CuO nanorods display high sensitivity, low detection limit, fast amperometric response and good selectivity, which might add greater value to non-enzymatic glucose detection.

Unusual designated-tailoring on the preferential growth of ZnO meso-/nanocrystals with different shapes and sizes was successfully achieved through a very facile precursor-hydrolysis process in a water/organic solvent system. The shape-evolution of ZnO from mesocrystal to nanocrystal was achieved by increasing the amount of water in the reaction system under otherwise the same conditions, which can be attributed to selective-capping and preferential growth mechanisms based on DFT calculations. Typically, nanoparticle-aggregated cone-like ZnO mesocrystals enclosed by curved (101) and flat (000) surfaces were prepared in a lower amount of water, while various ZnO crystals without curved (101) surfaces were synthesized in a higher amount of water. In particular, “surface heterojunctions” were constructed in cone-like ZnO mesocrystals with co-exposed curved (101) and flat (000) surfaces, and these displayed greater photocatalytic degradation of methyl orange dye compared to the ZnO nanocrystals. This investigation is of great significance to the synthesis of additive-free ZnO mesocrystals, and offers a good opportunity to understand the formation mechanism and fundamental significance of the preferential growth of ZnO mesocrystals. Importantly, it is believed that the water-induced synthetic strategy reported here could provide a promising way to design more and more metal oxide architectures with controllable morphologies.

In the present work, direct and detailed investigation was carried out with respect to the precipitation in the grit-blasted single-crystal superalloy of DD6 after thermal exposure at 1100°C for 8 h. The precipitation was confirmed to be an orthorhombic topologically close-packed phase of P. In the phase, abundant atomic stacking faults were clearly revealed by bright field transmission electron microscope imaging and high-resolution HAADF imaging. Furthermore, statistical analysis for the 42 P phase particles observed by electron backscattered diffraction revealed that they had a mean size of 0.21 µm and volume percentage of 0.172% in the recrystallised region. The orientation distribution was essentially random besides very weak textures of {511} and {921} .

Cu9Al4Fe/1Cr18Ni9Ti stainless steel bimetallic composite was prepared by the method of vacuum casting. The microstructure morphology, mechanism bonding and mechanical property of Cu9Al4Fe/1Cr18Ni9Ti bimetallic composite were observed by scanning electron microscope, energy disperse spectroscopy, X-ray diffraction, transmission electron microscope and nano-indentation analysis techniques respectively. The research results are as follows: The interface transition layer of Cu9Al4Fe/1Cr18Ni9Ti bimetallic composite maintains straight and a certain thickness and no obvious defects are observed. The phase on the transition zone is consisted of α-Fe based solid solution, γ-Fe based solid solution, NiAl phase and AlCr2 phase. The micro-hardness and elastic modulus of the interface transition layer are higher than the two matrix alloys. The fracture of Cu9Al4Fe/1Cr18Ni9Ti bimetallic composite prefers to occur between 1Cr18Ni9Ti and the interface transition layer, and the fracture mode is cleavage fracture.

In this work, a method of chemical co-precipitation combined with hydrogen reduction was used to prepare Mo-25Cu nanopowder. Phase distribution and thermodynamic analysis of the powder with calcination and reduction at different temperatures were analyzed, and the reaction mechanism was obtained. The prepared Mo-25Cu nanopowder sintered at high temperature to form the alloy block, and the microstructure, morphology and properties of the Mo-Cu composite were compared with those of the Mo-Cu alloy sintered directly with mixed powder in micron size. Mo-25Cu compacts prepared by sintering at 1200 °C in a hydrogen atmosphere with synthetic powder show good sinterability and excellent physical as well as mechanical properties with a relative density of 96.6%, electrical conductivity of 36.2%IACS and Vickers hardness of 2.68 GPa, respectively.

Doping modifications can endow BiOCl with dramatically improved photocatalytic performance via modifying the electronic structure. Here, the hierarchical Ni-doped BiOCl microflowers self-assembled by 2D nanosheets were synthesized through a one-step solvothermal method. Notably, the as-obtained Ni-doped BiOCl sample presented a remarkably enhanced photocatalytic degradation activity, totally decomposed Rhodamine B aqueous solution (15 mg/L) within 5 min under visible-light irradiation. Based on the experimental and calculated results, the introduction of Ni can narrow the band-gap and form defect energy levels simultaneously, resulted in a red shift in the absorption edge and much stronger absorption in the visible-light range. In addition, Ni-doped BiOCl exhibits an enhanced photocurrent density and a suppressed peak intensity of PL emission, indicating the efficient transportation and suppressed recombination of photoinduced charge carriers. This study sheds light on a possible application of Ni-doped BiOCl in photocatalytic degradation of organic pollutants under visible-light irradiation and provides a feasible strategy to synthesis of high active Ni-doped BiOX (X = Cl, Br and I) photocatalysts.

A copper alloy of Cu–1.9 wt-%Ti–0.7 wt-%B was fabricated by vacuum induction melting and casting followed by cold working and annealing. Four strengthening methods has been involved during the prep...

In this work, detailed experimental insights regarding the microstructural features on surface recrystallisation of a grit-blasted single crystal superalloy DD6 have been obtained by transmission electron microcopy (TEM), scanning transmission electron microcopy (STEM), scanning electron microscopy and electron backscattered diffraction (EBSD) techniques. The broadened diffraction ring arcs typical for micro-textures revealed the fragmented finer grains after surface grit-blasting. Energy dispersive spectroscopy analysis and STEM mapping confirmed the characteristic elements for differentiation of γ′ and γ phase, and the precipitated secondary or tertiary γ′ in the recrystallised region was characterised by dark field TEM. Moreover, the recrystallisation depth was feasibly revealed by ion-etching and further used for EBSD imaging without polishing. The resulted EBSD pole figures and misorientation profiles confirmed that the recrystallised region exhibited a rather random orientation, destroying t...

MgO/Cu composites containing a 1.0% volume fraction of MgO particles were prepared by internal oxidation and powder metallurgy, respectively. The interfacial bonding state between the MgO particles and Cu matrix was characterized by scanning electron microscopy and transmission electron microscopy. The effect of the MgOp/Cu interfacial bonding state on the arc erosion resistance of the MgO/Cu composites was investigated, and the arc erosion resistance was examined using a JF04C electrical composite testing system. The results indicate that the 1.0 vol% MgO/Cu composite with a semicoherent MgOp/Cu interface experiences a lower arc erosion rate and smaller fluctuations of arcing energy than those of the 1.0 vol% MgO/Cu composite with an incoherent MgOp/Cu interface. Erosion morphology observations further indicate that a solid to liquid phase transformation occurs under arcing and MgO particles dispersed in the molten copper both prevent the copper matrix from splashing and enhance the arc erosion resistance of the MgO/Cu composites. While the shallow electric erosion pits are distributed uniformly on the arc surface of the MgO/Cu composites with a semicoherent interface, the MgO/Cu composite with an incoherent interface has deep and uneven pits on its arc surface, characterized by large electric erosion molten droplets.

The present investigation aims to explore the evolution of microstructure and mechanical properties in Zn–Cu–Ti alloys during severe hot-rolling deformation. Twin deformation and dynamic recrystallisation are two important deformation modes of Zn–Cu–Ti alloys during hot rolling at 300 °C. Twin deformation and dynamic recrystallisation (DRX) appear one after the other. They not only consume the deformation stored energy but also inhibit initiation and growth of cracks. The elongation rate of Zn–Cu–Ti alloys has a rising trend with the increase in hot-rolling deformation. It is mainly due to grain refinement caused by increasing the ratio of DRX and twin deformation. The tensile strength of Zn–Cu–Ti alloys is found to decrease with the increase in hot-rolling deformation. This is because the solid-solution strengthening effect of copper is weakened by more deformation-induced precipitation of e phase (CuZn5). The solid-solution strengthening effect of copper plays an important role in the strengthening effect of Zn–Cu–Ti alloys.

Cu-W composites and CuCr alloy were bonded with mixed Cu-Fe powder interlayers using the liquid diffusion bonding technique at 1380 °C for 1 h. Microstructures of the CuW/CuCr joints with Cu-Fe powder interlayers were investigated and compared via field-emission scanning electron microscopy and energy-dispersive X-ray spectroscopy. Tensile tests were examined to evaluate the resulting joints. The results show that a diffusion solution layer about 2–3 μm width formed at the Cu/W interphase and the interfacial strength can reach up to 400 MPa when Cu-3wt%Fe interlayer is introduced into the interfacial region between Cu-W and CuCr alloy. Furthermore, the interfacial fracture morphology presents more transgranular cleavage fractures of W particles. However, when the content of Fe in the powder interlayers is above 3 wt%, the interfacial strength decreases gradually with the increasing of Fe content. After Cu-15 wt%Fe interlayer was applied, Fe 7 W 6 phase is found in W skeletons and micro-cracks appear at the CuW/CuCr interface. Therefore, the interfacial strength declines to 263 MPa. The fraction of cleavage fracture decreases and the cracks propagate cross different areas of the CuW/CuCr interface.

Lap joints of friction stir welding between aluminium and stainless steel sheets were conducted using a welding tool with a cutting pin. The atomic diffusion of Fe–Al system during the severe plastic deformation was investigated. The interfacial microstructure and metallurgical reaction was analysed. The metallurgical reaction layers were identified as a compounds containing a phase of Al3Fe, partial solid solution of Fe and Al, and amorphous with a thickness of 0.9–3.3 μm which depending on the process parameters. The interdiffusion coefficient between Al and Fe atoms is about 4 orders of magnitude compared with that under thermal equilibrium state. The nanocrystalline and partial amorphous were formed near the interface which may caused by the enhanced atomic diffusion.

Zinc stannate (ZnSnO3 and Zn2SnO4), which is generally called zinc tin oxide (ZTO), possesses unique physical and chemical properties that have received much attention in recent decades. Efforts have been devoted to exploration and investigation of morphological ZTO micro/nanostructures because of their high electron mobility, high electrical conductivity, attractive optical properties and good stability compared with their binary counterparts. Consequently, ZTO-based micro/nanostructures with well-tuned composite, crystalline phase and morphology have been rationally developed and used in the fields of solar cells, sensing, anode materials for lithium batteries, nanodevices and catalysts. However, a comprehensive review on morphological ZTO micro/nanostructure is lacking, and this is imperative to highlight progress in function-oriented ZTO micro/nanostructures. The present review highlights significant advancements in morphological ZTO micro/nanostructures, including synthetic strategies leading to growth of different ZTO micro/nanostructures, the fundamental properties, and their current applications. Several emerging issues and prospective research directions in this field are also discussed.

As a significant metal chalcogenide, copper sulfide (Cu2-xS, 0 < x < 1), with a unique semiconducting and nontoxic nature, has received significant attention over the past few decades. Extensive investigations have been employed to the various Cu2-xS micro-/nanostructures owing to their excellent optoelectronic behavior, potential thermoelectric properties, and promising biomedical applications. As a result, micro-/nanostructured Cu2-xS with well-controlled morphologies, sizes, crystalline phases, and compositions have been rationally synthesized and applied in the fields of photocatalysis, energy conversion, in vitro biosensing, and in vivo imaging and therapy. However, a comprehensive review on diversified Cu2-xS micro-/nanostructures is still lacking; therefore, there is an imperative need to thoroughly highlight the new advances made in function-directed Cu2-xS-based nanocomposites. In this review, we have summarized the important progress made in the diversified Cu2-xS micro-/nanostructures, including that in the synthetic strategies for the preparation of 0D, 1D, 2D, and 3D micro-/nanostructures (including polyhedral, hierarchical, hollow architectures, and superlattices) and in the development of modified Cu2-xS-based composites for enhanced performance, as well as their various applications. Furthermore, the present issues and promising research directions are briefly discussed.

Mesoporous micro-/nanostructures acting as supports for catalysts or used directly in catalysis reactions generally show fascinating performances that could lead to great potential for application. In the past few decades, extensive efforts have been devoted to the exploration and enrichment of graphitic carbon nitride (g-C3N4) based research. Especially, mesoporous g-C3N4 (mpg-C3N4) with controllable porosity and electronic/atomic structure can bring to bear unique physicochemical properties and has been widely applied in the fields of photocatalysis, adsorbents, sensors and chemical templates. However, a comprehensive summary on mpg-C3N4 micro/nanostructures is less reported and there is an urgent need to further promote the development of function-oriented mpg-C3N4-based materials. Herein, we will overview the significant advances in functional mpg-C3N4 polymers, including general synthesis strategies and growth mechanisms, modifications of electronic/atomic structures and interfacial properties (such as exfoliation, doping and hybridizing), as well as their current applications. Finally, several emerging issues and perspectives are also proposed.

Hollow micro/nanostructures possess fascinating physicochemical properties that would generate great application potential in the fields of catalysis, sensing and energy conversion. In the past decades, much more efforts have been employed in the exploration and enrichment of copper-based binary oxides, CuxO (x = 2, 1); thus a number of CuxO micro/nanostructures with well-controlled ingredients and morphologies have been rationally synthesized and applied. However, a thorough summary on hollow CuxO materials has been lacking so far and it is urgently necessary to further promote the progress in novel function-directed CuxO-based micro/nanostructures. In this review, we will comprehensively summarize the important advances in hollow CuxO micro/nanostructures with tailored morphologies, including the universal synthesis strategies and formation mechanisms, the interfacial Cu–O atomic structures as well as the intrinsic properties, and their potential applications. Remarks on emerging issues and promising research directions are also discussed.

In situ TiB whisker and TiB2 particle hybrid reinforced copper matrix composites were fabricated by vacuum induction melting. The phase constitution of the composites varies with their chemical composition. Thermodynamic and kinetic assessments were used to analyze the phase selection of titanium borides during solidification. The precipitations of TiB whisker and TiB2 particle from Cu–Ti–B liquids are both thermodynamically favored, and the phase selection is thus controlled by the competition of nucleation and growth kinetics between the two titanium borides. For the case of the three liquids studied in this work, the nucleation conditions are satisfied except for the formation of TiB in Cu–2at.%Ti–4at.%B liquid. With the change of chemical composition, the growth rate is altered rapidly for TiB, but remains nearly unchanged for TiB2.

The effects of Cr alloying interlayer on the microstructure and mechanical properties of the dissimilar CuW/CuCr joints prepared by sintering-infiltration method were studied. The hardness and electrical conductivity of the CuCr alloy side and the tensile strength of the CuW/CuCr integral materials were tested. The interfacial microstructure and fracture morphology of the CuW/CuCr joints were characterized by X-ray diffraction, optical microscopy, scanning electron microscope equipped with energy dispersive spectrometry. The results show that both the electrical conductivity and hardness of the CuCr alloy side of the aged CuW/CuCr joints are higher than those in the solid solution and infiltration condition. With increase of the Cr content, the regions of eutectic phase are expanded gradually on the CuCr alloy side, and the morphology of Cr particles changes from spot shape to rod-like shape. The highest interfacial bond strength can reach up to 446.66 MPa when Cu 15 wt%Cr alloy is introduced into the interfacial region between CuW and Cu Cr alloy. The interfacial fracture morphology presents more cleavage fractures of W particles, and the Cu/W interphase has a good metallurgical bond.

An improved hot-press method with the sintering temperature just beneath the melting point of copper was applied to prepare copper matrix composites. Cu-based hybrid composites reinforced with most TiB2 particles and a small amount of TiB whisker have been in-situ synthesized from the primary Cu, Ti (or TiH2) and B powder mixtures. The reinforcement in TiB2(-TiB)/Cu composites often appears as bubble-like cluster, which is believed to result from the local melting of Cu-Ti intermetallic compound forming in pre-sintering stage. Subsequently, the formation mechanism of the reinforcement was identified as the in-situ reaction occurring at the original site of Ti (or TiH2) by diffusing B from Cu matrix into Cu-Ti liquids. As compared with Cu-Ti-B system, the composites fabricated from Cu-TiH2-B powder mixture have more favorable microstructures and thus better overall performance.

Two-dimensional nano- or micro-scale fractal dendritic coppers (FDCs) were synthesized by electroless immersing of Cu-Al alloys in hydrochloric acid solution containing copper chloride without any assistance of template or surfactant. The FDC size increases with the increase of Al content in Cu-Al alloys immersed in CuCl2 + HCl solution. Compared to Cu40Al60 and Cu45Al55 alloys, the FDC shows hierarchical distribution and homogeneous structures using Cu17Al83 alloy as the starting alloy. The growth direction of the FDC is , and all angles between the trunks and branches are 60°. Nanoscale Cu2O was found at the edge of FDC. Interestingly, nanoporous copper (NPC) can also be obtained through Cu17Al83 alloy. Studies showed that the formation of FDC depended on two key factors: the potential difference between CuAl2 intermetallic and α-Al phase of dual-phase Cu-Al alloys; a replacement reaction that usually occurs in multiphase solution. The electrochemical experiment further proved that the multi-branch dendritic structure is very beneficial to the proton transfer in the process of catalyzing methanol.

Cu2 O/CuOx (x=0, 1) nanocomposites with well-defined morphologies have been widely applied in catalytic reactions. However, people still understand less about tuning interfacial Cu-O atomic structures for enhanced catalytic applications, and a special review on this topic has not been reported so far. Herein, we summarize our understanding on tuning interfacial Cu-O atomic structures based on the literature, including the formation as well as evolution mechanism of Cu-O interfaces in Cu2 O/CuO and Cu2 O/Cu systems, and the improved performances in the fields of CO oxidation, NOx oxidation, photoelectrocatalysis, water gas shift reaction, photodegradation of organic dyes, hydrogen evolution, and photoreduction of CO2 . Finally, we briefly propose several potential research directions.

An in-situ reaction strategy to synthesize W‒Cu based nanocomposite co-doped with Cr and WC was proposed, and the resultant multicomponent nanocrystalline bulk has a homogeneous distribution of various phases. As compared to the conventional coarse-grained W‒Cu composite, the prepared nanocrystalline W‒Cu based composite exhibits fourfold hardness and twofold wear resistance. The enhancement of the wear resistance is attributed to the restricted formation and delamination of the mechanically mixed layer and the increased strain gradient induced by the hard phases on the worn surface. The formation of the refined nanostructure with well-aligned crystallographic orientation relationship results in significant hardening of the worn surface. The present work opens up new opportunities to achieve superior hardness and wear resistance of metal matrix composites based on design and fabrication of multicomponent nanostructures.