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In this study, the bonding of a CuW/Al composite with a Ni interlayer was designed and established by vacuum hot-pressing diffusion bonding. The interfacial microstructure was systematically discussed based on experimental characterization and first-principles calculations. The result indicated that the interface consisted of intermetallic compounds (IMCs) of Al3Ni2 and a few of Al3Ni. The interfacial microstructure significantly differed from the interface without the Ni interlayer. The growth kinetics of the Al3Ni2 layer followed a parabolic behavior, which was mainly affected by the volume diffusion mechanism. The interfacial thickness decreased significantly, and the average thickness was ~35 μm. The microstructural evolution revealed that Al3Ni2 was the phase that was formed first. By introducing a Ni interlayer, the interfacial strength was significantly enhanced due to the IMCs that were changed from Al–Cu and Al–W IMCs to Al–Ni IMCs. The maximum shear strength reached 90.9 MPa, which was increased by 76% compared to that of the sample without the Ni interlayer. An analysis of the fracture morphology analysis showed that the crack was prone to exist at the Al3Ni2/Ni interface and presented a cleavage fracture characteristic.

Diffusion bonding was successfully applied to join 304 stainless steel (SS) and tungsten (W) using interlayers of Cu and Ni, and the effect of bonding temperature on microstructure and strength of 304SS/Cu/W and 304SS/Ni/W joints is investigated. The present study shows that a sound 304SS/Cu/W joint with sufficient mutual diffusion across 304SS/Cu and Cu/W interfaces is obtained at a bonding temperature of 1000 ℃, in which solid solutions occur at Cu/W interface. The 304SS/Cu/W joint bonded at 1000 ℃ shows the highest shear strength of 277.2 MPa and good ductility. The occurrence of cracks at 304SS/Cu interface with the increasing of bonding temperature results in the decrease in shear strength of 304SS/Cu/W joints under brittle fracture. The 304SS/Ni/W joints are free of crack in the bonding temperatures of 850 ℃–1000 ℃, which shows the highest shear strength of 237 MPa bonded at 950 ℃ due to occurrence of intermetallic compound Ni4W in the diffusion layer close to Ni/W interface. No obvious diffusion layer at 304SS/Ni/W is observed following bonding at 850 ℃ and 900 ℃. The micro-voids in the diffusion layer bonded at 1000 ℃ are responsible for the lower shear strength of joint than that of 950 ℃.

2wt% TiB2/Cu composite powders were fabricated in situ by reactive gas atomization. The fabricated composite powder exhibits high sphericity, and the powder sizes range from 5 µm to 150 µm. The morphology of the Cu matrix and the distribution of the TiB2 particles in the composite powders vary with the powder size. The critical transitions of interface morphologies from dendritic-to-cellular and cellular-to-planar interfaces occurs when the composite powder sizes decrease to 34 µm and 14 µm, respectively. Compared with pure Cu droplets, the composite droplets undergo critical transition of the interface morphologies at a smaller droplet size corresponding to a higher cooling rate because the existence of TiB2 particles can cause instability in the advancing solidification front and heterogeneous nucleation. With decreasing powder size, the extent of the TiB2 particle interdendritic segregation decreases as the result of enhanced engulfment of TiB2 particles by the advancing solidification front.

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.

Surface heterojunction engineering has been demonstrated to be an efficient strategy for the spatial charge separation of photocatalysts. As a consequence, the improved photocatalytic activity is highly determined by the atom arrangement and coordination state of a crystallographic plane. A high-index facet exposed with a high density of low-coordination atoms generally displays better catalytic performance than the low-index one because of its high surface energy. Inspired by the above viewpoints, it is proposed that the construction of a surface heterojunction enclosed by different high-index facets or a mixed form of high-index and low-index facets is a promising avenue to further promote the photocatalytic activity. However, the synthesis of high-index facet based photocatalysts is highly challenging for surface heterojunctions. Herein, we prepare a polyhedral 30-faceted Cu2O microcrystal type-II surface heterojunction co-exposed with 24 high-index {332} facets and 6 low-index {001} facets using a capping agent-assisted liquid-phase reduction method. Compared to the common truncated octahedral (14-facet) Cu2O microcrystal co-exposed with 8 {111} and 6 {001} facets, the 30-faceted Cu2O possesses a highly improved photodegradation activity in the case of normalized specific surface area. Density functional theory (DFT) calculations and in situ photodeposition of metal and metal oxide nanoparticle results indicate that the 30-faceted Cu2O microcrystal is a well-matched {332}–{001} type-II surface heterojunction, which presents a beneficial pathway for efficient charge separation and more high-activity sites for photo-redox reaction than the truncated octahedral surface heterojunction. This work confirms the spatial charge separation and high-index facet dependence in polyhedral Cu2O surface heterojunctions, which provides theoretical guidance for surface heterojunction engineering to enhance photocatalytic activity.

Mesocrystals with highly ordered subunits can provide good charge transfer tunnels and more active sites for catalytic reactions. So far, single-component mesocrystals have been well-developed in metals or metal oxides in the past decades, but the construction of mesocrystals in nanocomposites has been a great challenge. Herein we demonstrated a simple, one-pot wet chemical strategy for the preparation of plate-like Ag–Cu2O composited mesocrystals (CMCs) without any organic capping agent, which broke through the traditional dependence on organic capping agents for the synthesis of mesocrystals. As expected, these unprecedented Ag–Cu2O CMCs displayed superior visible-light-driven photodegradation performance toward tetracycline solution compared to the core–shell Ag@Cu2O and pure Cu2O photocatalysts. The improved photocatalytic activity of Ag–Cu2O CMCs could be ascribed to the synergistic effect of an ordered crystallographic orientation, the Schottky barrier and localized surface plasmon resonance (LSPR) for simultaneously enhancing charge separation and transfer as well as visible light harvesting. This research might stimulate in-depth investigations on the exploration of new synthetic methods for the design and construction of novel composited mesocrystals.

In this study, the W (10–20%)–Cu composites were simultaneously fabricated using commercial, graded commercial, and graded jet-milled W powder. The results show that the W–Cu composites prepared with the graded jet-milled W powders have the highest density and best comprehensive performance due to the combined effect of the particle gradation and jet-milling treatment. Particle gradation is employed to increase the packing density of powders, thereby increasing the relative density of the compressed W skeleton, and the rounded powder with narrow particle size distribution after jet-milling treatment is used to reduce the enclosed pores formed during the process of compacting and infiltration. W–Cu composites with a high density of 16.25 g/cm3 can be directly obtained by conventional compacting at a low pressure of 300 MPa and following infiltration.

Cathode plate affects the quality and cost of gold refining. Ag-Ti bimetal cathode materials were fabricated by vacuum hot-press diffusion bonding in this paper. Microstructure morphology and an analysis of the bimetal show that metallurgical interface has been successfully constructed between the Ag and Ti. The interfacial layer consisted of the intermetallic compound AgTi and the solid solution α-Ti. The hardness at the interface reaches a maximum of 467 HV at a bonding temperature of 890 °C. The bath voltage of the Ag-Ti cathode plate is only 2/3 of that of the Ti cathode plate when the thickness ratio of Ag and Ti is 8:1. The gold yield is increased by 10 %, approaching 80 %.

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.

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.

Twin crystals with highly ordered atomic arrangement can not only promote the transport of free charge carriers (electrons and holes) inside a single crystalline photocatalyst, but also limit the recombination of photoexcited charge carriers owing to their self-building electrostatic field. Hence, the investigations on twin-dependent photocatalytic performances of crystalline micro-/nanostructures have received much attention in recent years. However, there is still no specialized review article on twin engineering of photocatalysts so far. Herein, the existing twinned micro-/nanostructures, mainly including metal sulfides and metal oxides, are overviewed on the basis of the synthesis engineering, transmission electron microscopy (TEM) characterization and twin-dependent photocatalytic mechanism. Some challenging issues and future directions are also discussed. Expectantly, this minireview would serve as a theoretical guidance for people who are now focusing on twin crystals to design and synthesize novel photocatalysts.

Influenza A virus (IAV) is a major human pathogen associated with significant morbidity and mortality worldwide. Through serial passage in mice, we generated a recombinant pdmH1N1 2009 IAV, A/Guangdong/GLW/2018 (GLW/18-MA), which encodes an mCherry gene fused to the C-terminal of a polymerase acidic (PA) segment and demonstrated comparable growth kinetics to the wild-type. Nine mutations were identified in the GLW/18-MA genome: PA (I61M, E351G, and G631S), NP (E292G), HA1 (T164I), HA2 (N117S and P160S), NA (W61R), and NEP (K44R). The recombinant IAV reporter expresses mCherry, a red fluorescent protein, at a high level and maintains its genetic integrity after five generations of serial passages in Madin-Darby Canine Kidney cells (MDCK) cells. Moreover, the imaging is noninvasive and permits the monitoring of infection in living mice. Treatment with oseltamivir or baicalin followed by infection with the reporter IAV led to a decrease in fluorescent protein signal in living mice. This result demonstrates that the IAV reporter virus is a powerful tool to study viral pathogenicity and transmission and to develop and evaluate novel anti-viral drugs, inhibitors, and vaccines in the future.

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.

Mesocrystals with highly ordered subunits can provide good charge transfer tunnels and more active sites for catalytic reactions. So far, single-component mesocrystals have been well-developed in metals or metal oxides in the past decades, but the construction of mesocrystals in nanocomposites has been a great challenge. Herein we demonstrated a simple, one-pot wet chemical strategy for the preparation of plate-like Ag-Cu2O composited mesocrystals (CMCs) without any organic capping agent, which broke through the traditional dependence on organic capping agents for the synthesis of mesocrystals. As expected, these unprecedented Ag-Cu2O CMCs displayed superior visible-light-driven photodegradation performance toward tetracycline solution compared to the core-shell Ag@Cu2O and pure Cu2O photocatalysts. The improved photocatalytic activity of Ag-Cu2O CMCs could be ascribed to the synergistic effect of an ordered crystallographic orientation, the Schottky barrier and localized surface plasmon resonance (LSPR) for simultaneously enhancing charge separation and transfer as well as visible light harvesting. This research might stimulate in-depth investigations on the exploration of new synthetic methods for the design and construction of novel composited mesocrystals.

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.

The effects of pore in C/SiC composites on thermal diffusivity and thermal radiation properties were investigated systematically. Pores were introduced into C/SiC by oxidizing carbon phase at 700 °C and damaged the thermal properties of C/SiC composites. Because of little changes in the pore shape and the pore orientation in C/SiC, thermal diffusivity of samples increased linearly with porosity. The pores within C/SiC absorbed and reflected the radiated heat, decreasing spectral emissivity. However, the temperature dependence of spectral emissivity didn’t change by the pore. With measurement temperature increasing, the pores weakened the thermal radiation property of samples gradually. A linear relation was suggested to quantify the negative effect of pores on the total emissivity.

Hybrid copper matrix composites reinforced by TiB whiskers and TiB2 particles were fabricated by in situ mixing casting in combination with rolling and annealing. During turbulent mixing and copper mold casting processes, the in situ reactions carried out completely, and the macrosegregation of reinforcements in the composites was overcome efficiently. By controlling the rolling and annealing parameters, unfavorable casting defects, including “chain-type” reinforcement clusters and shrinkage porosities that formed during the end stage of solidification, were eliminated. Accordingly, the uniform distribution of hybrid reinforcements in the as-annealed composites provided good comprehensive performance. Compared to the 2.6 wt%TiB2p/Cu composite, the (1.0 wt%TiB2p-0.9 wt%TiBw)/Cu hybrid composite exhibited both higher strength (492 MPa) and higher electrical conductivity (85.5% International Annealed Copper Standard). Therefore, the hybrid effect in the copper matrix composites can be explained by the fact that a better strengthening effect was achieved by adding less hybrid reinforcement, which helped maintain the electrical conductivity at a relatively high level.