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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.

Nanoporous Cu/Cu2O (NP-Cu/Cu2O) composites with a three-dimensional bicontinuous heterostructure are prepared by anodic oxidation of nanoporous copper (NP-Cu). The effects of electrolyte (pH 7–13) and anodic oxidation potential (0.1–1.0 V vs. SCE) on the morphologies and electrocatalytic performances of NP-Cu/Cu2O composites are investigated. The Cu2O/Cu content ratio increases with the increase of anodic oxidation potential, but decreases with the increase of pH value. The pore/ligament width ratio of NP-Cu/Cu2O composites prepared in pH 9–13 electrolytes is in the range of 0.6–1.0. The onset potential of NP-Cu/Cu2O negatively shifts, and the oxidation peak current density of NP-Cu/Cu2O composites prepared in pH 7–11 electrolytes is higher than that of NP-Cu. NP-Cu/Cu2O composite prepared in pH 11 electrolyte at anodic oxidation potential of 0.7 V exhibits the best electrocatalytic performance towards methanol oxidation.

Improvement of high-temperature mechanical properties of W–Cu based composites is highly desirable but still a challenge. Here it is achieved by combined effects of solid solution, dispersed nano-precipitation and highly stabilized nanostructure in the W–Cu–Cr–ZrC composite, which takes advantage of the in-situ precipitated Zr–Cr–C nanoparticles and phase-separated Cr thin films. The grain size of W phase in the W–Cu–Cr–ZrC composite retained at the nanoscale up to 1000 °C (close to Cu melting point) for a long duration. The high thermal stability of the nanostructure endows the composite with a compressive strength of 1150 MPa at 900 °C, which is approximately four times as high as that of the binary coarse-grained W–Cu composite. The effects of microstructure evolution on the mechanical properties at high temperatures and its mechanisms were disclosed. The results indicated the crucial role of the microstructural stability of W phase skeleton in the overall strength of the W–Cu based composites.

Simultaneously integrating heterogeneous interface and element doping into BiOCl crystals is a promising strategy to promote the visible-light-driven photocatalytic activity. Here we demonstrated a facile solvothermal route for one-pot coupling Bi nanodots with Ta-doped BiOCl nanosheets (denoted as Ta-BiOCl/Bi). This Ta-BiOCl/Bi sample presented a remarkable catalytic performance toward the visible-light-driven degradation of Rhodamine B and tetracycline solution than those of the Ta-BiOCl, BiOCl/Bi and BiOCl photocatalysts. The enhanced photocatalytic mechanism can be proposed as follows. Both Ta dopant level in energy band structure of BiOCl and LSPR effect of Bi species were beneficial to increasing the visible light absorption, and the formation of heterogeneous interface between Ta-BiOCl and Bi was responsibility for accelerating the separation of charge carriers. This work might arouse in-depth investigations on the development of novel one-pot strategy for the synthesis of high-active BiOX (X = Cl, Br and I)-based photocatalysts.

Cu-Ti alloy ingots were firstly prepared by the induction melting furnace at an argon atmosphere, and CuTiW alloys were fabricated by Cu-Ti alloys infiltrating W skeletons. The effects of Ti contents on the microstructure and properties of CuW alloys were studied. The results show that Ti element can diffuse into W skeletons during infiltration, and the Cu/W interface achieves a good metallurgical bonding. The electric conductivity and hardness of CuTiW alloys is improved after the solution and aging treatment due to the Cu3Ti particles precipitated in Cu matrix. The resistance to arc erosion is improved by the addition of Ti, the arc erosion area is increased and the erosion craters are dispersed effectively, and the breakdown pits hardly appear at the Cu/W interface. Compared with CuW alloy, the Cu-1.5 wt%TiW alloy exhibits the excellent electrical breakdown properties, the breakdown strength is increased by 54%, the chopping current is decreased by 19.3%, and the arc life-span is increased by 46.2%, respectively.

By virtue of spherical initial powders, novel W–Cu composite alloys of W60Cu40 and W70Cu30 have been fabricated by successive processes of powder mixing, cold pressing, sintering and infiltration under hydrogen atmosphere in this work. The phase composition and distribution, hardness, electrical conductivity and tensile behavior of the resultant composite alloys were investigated. Results revealed that the resultant W–Cu composite alloys exhibited excellent hardness improved by 7.3% (4.6%) and remarkably improved electrical conductivity by 23.3% (23.8%), compared with present commercial alloys. Further tensile tests revealed the superior strength of 423 MPa (485 MPa) with reliable strain of 8.8% (7.6%), which can be ascribed to the homogenous structure with alternate soft/conductive Cu and hard W phases free from blind holes.

The Cu–Ni–Mn–Fe alloy is prepared to study its precipitation behavior and mechanical properties during aging under elevated compression stresses. Transmission electron microscopy (TEM), scanning electron microscopy (SEM), x-ray diffraction (XRD), hardness and tensile tests are used for this investigation. The results indicate that the stress-aging treatment leads to the formation of fine, equiaxed grains and twins within the matrix of Cu–Ni–Mn–Fe alloy. During the stress-aging, the density of θ-MnNi precipitates initially decreases and then increases. The stress is further increased from 220 to 385 MPa, the vacancy concentration and dislocation density increase rapidly owing to creep deformation, while the strain-induced effect accelerates the precipitation of θ-MnNi. The results show that the tensile strength and hardness of Cu–Ni–Mn–Fe alloy initially decrease and then increase, and the tensile strength and hardness of the Cu–Ni–Mn–Fe alloy are 890 MPa and 274 HB under the compressive stress of 385 MPa, and the elongation remains at 8.72%. It is mainly attributed to the application of compression stresses during aging, which can enhance both the strength and ductility of the alloy.

A temperature-time program, i.e., continuous cooling annealing (CCA), was studied for the crystallization of amorphous alloy. The CCA crystallization behavior of Cu33Zr67 amorphous alloy was investigated by differential scanning calorimetry. Kinetic analysis indicates that commonly used methods (e.g., the Kissinger plot) become invalid. The general kinetic theory was applied for describing the CCA crystallization kinetics, and two kinetic recipes were proposed for the determination of kinetic parameters. By applying them to the measured data, reasonable parameter values were obtained. Accordingly, the CCA crystallization mechanisms of Cu33Zr67 amorphous alloy were determined as approximately continuous nucleation and 3-dimentional interface-controlled growth.

In the present work, several W-25 wt% Cu alloys have been prepared through combined processes of high-energy ball-milling, liquid-phase sintering and infiltration, using the precursors of industrial copper powders with an average particle size of 50 μm and tungsten powders with alternative average particle size of 8 μm, 800 nm, 600 nm or 400 nm. Microstructure characteristics, relative density, hardness and electrical conductivity of the WCu alloys were investigated to elucidate the effect of initial particle size of tungsten powders. EBSD was further utilized to reveal the orientation and grain size distribution in the WCu alloys prepared by 8 μm and 400 nm-sized tungsten powders. The results showed that the WCu alloy made by 400 nm-sized tungsten powders exhibited excellent homogeneity for both sintered tungsten powders and grains, together with the highest relative density of 98.9%, the highest hardness of 230 HB, and good electrical conductivity of 48.7% IACS. Moreover, it also showed highly improved arc erosion and mechanical wear resistances.

W-(10 to 15) wt.% Ti alloys were sintered at 1400 or 1500 °C and cooled under different cooling conditions. The microstructures and properties of W-Ti alloys were affected by the cooling conditions. XRD, SEM, EBSD, and TEM were carried out to investigate the effects of cooling conditions and sintering temperature on the microstructures of W-Ti alloys. The nanohardness and elastic modulus of the alloys were also investigated. The results showed that when the temperature was 1500 °C, the content of Ti-rich phase in W-(10 to 15) wt.% Ti alloys decreased obviously with the increase of cooling rate (the average cooling rate of furnace cooling, air cooling and water cooling was 0.2, 10, and 280 °C/s, respectively). For the W-10 wt.% Ti alloy, the content decreased from 20.5 to 9.7%, and the grain size decreased from 2.33 to 0.67 μm. When the temperature decreased to 1400 °C, the grain size was also decreased sharply with the increase of cooling rate, but there was a little change in the microstructure. Meanwhile, the grain sizes were smaller than those of the alloys sintered at 1500 °C. The nanohardness and elastic modulus increased with the increase of cooling rate, and the alloys sintered at different temperatures had different nanohardness and elastic modulus which depended on the cooling conditions. Sintering at a proper temperature and then cooling at a certain cooling condition was a useful method to fabricate alloy with less Ti-rich phase and high properties.

The corrosion mechanism of Zn-Cu-Ti alloy added with La in 3% NaOH solution was investigated by electrochemical testing and SEM observation. Polarization curves manifested that the overall corrosion kinetics of alloys are under anodic control. The anodic passivation of the Zn-Cu-Ti alloy is remarkably improved by the addition of La. Because La can effectively improve the hydrogen evolution/oxygen reduction over-potential of alloy elements, and the rare earth oxide film plays an important role in insulation that can strengthen the dielectric properties of Zn-Cu-Ti alloy, the corrosion resistance of Zn-Cu-Ti alloy is made significantly better by adding a trace amount of La. The improvement of corrosion resistance is not positively correlated with the adding amount of La to alloy. The Zn-Cu-Ti-0.5La alloy displays the best corrosion resistance behavior. The corrosion form of the alloys mainly belongs to a selective corrosion and the main solid corrosion products are Zn(OH)2 and ZnO.

The type test of CuW/CuCrZr arc contact used for ultra-high voltage system capacitor bank switch was conducted. Through the comparative analysis of morphologies, compositions, properties and microstructures of the contact materials before and after failure, it can be found that the abnormal open of moving arc contact and the arc erosion and mechanical wear of static arc contact are the major reasons affecting the arc contact failure. The failure mechanism and main affecting factors were investigated in detail. The results showed that arc erosion and mechanical wear are the two main factors that affect the service lifetime of arc contacts used for ultra-high voltage transmission lines and cannot be ignored. Therefore, improving the arc erosion resistance and mechanical wear resistance simultaneously is the key to prepare the arc contact materials with longer lifetime.

Al2O3/Cu composites (1.0 vol%) reinforced with different size of α-Al2O3 particles were fabricated by a powder metallurgy method and electrical sliding wear tests were performed on a self-made pin-on-disk electrical wear tester. The effect of Al2O3 particle size on electrical wear performance of the Al2O3/Cu composite was studied, and the wear mechanism of the Al2O3/Cu composite was also discussed based on worn surface observations. The results show that the tribological properties of A12O3/Cu composite are closely related to the mechanical properties. With an increase in Al2O3 particle size, the wear rates of A12O3/Cu composites have a reverse variation with hardness of A12O3/Cu composites. In the range of 50–100 nm, Al2O3/Cu composites have the highest wear resistance and mechanical properties. Microstructural observation revealed that the wear mechanisms of Al2O3/Cu composites were mainly adhesive wear and plastic deformation accompanied by a small amount of arc damage. In addition, the plastic...

A thin layer of copper (40–70 μm) was deposited on the surface of a nanoporous copper (NPC) matrix via a chemical deposition method that utilized the catalytic activity of the NPC itself to fabricate a new sandwich-type NPC (ST NPC) composite material. The effects of NPC aperture, chemical deposition time, and heat treatment on the mechanical properties of the ST NPC were studied. The results showed that an NPC matrix aperture of 150–160 nm helps to improve the mechanical properties of the sandwich-type NPC. On changing the deposition time, although the deposition thickness increases with the increase of time, the mechanical parameters of ST NPC become unstable because the deposited layer peels off from the surface of substrate NPC. Heat treatment greatly improved the interfacial adhesion between the panel and the interior pores, thus greatly improving the mechanical properties of the ST NPC. Besides mechanical properties, the thermal stability and corrosion resistance of the ST NPC were superior to those of the NPC substrate. However, catalytic performance of ST NPC was reduced owing to the as-obtained deposition layer, which increased the pore wall and decreased the porosity.

In this work, we reported the fabrication and characterization of CaWO 4 @CaWO 4 :Dy 3+ core/shell microspheres via a facile hydrothermal method without organic surfactant. The samples were characterized by XRD, SEM, EDS and photoluminescence. These core/shell microspheres were constructed by nanoparticles through a self-assembly way without any organic surfactant or template. The solid and hollow microspheres prepared through positive and reverse precipitation respectively were used as the precursor. The reduction of the surface energy and high temperature in the hydrothermal process provided the kinetics and thermodynamics motion of the self-assembly course respectively. The direct doped CaWO 4 :Dy 3+ and CaWO 4 @CaWO 4 :Dy 3+ (core–shell) microspheres show characteristic emission of Dy 3+ . The luminescent intensity of the core/shell phosphor was enhanced with respect to the direct doped one of the same doping concentration. The possible mechanism was also proposed.

In this article, novel W–Cu composites reinforced with topologically-inserted tungsten fibers (Wf) have been fabricated by hot-press sintering and infiltration method. By pre-sputtering of ~ 100 nm thick chromium layer onto the surface of Wf, the contiguity or connectivity between Wf and neighboring tungsten particles (Wp) or Cu after sintering and infiltration was enhanced. Combined SEM, TEM and STEM techniques confirmed that the intact interfaces of Wf/Wp and Wf/Cu free from precipitates, impurities and porosities would provide desirable strength and ductility. Further mechanical tests also validated its superior compressive strength and plasticity at various temperatures, together with significantly improved tensile strength (by 23.6%) and hardness (by 9.3%) for the W–Cu composite after reinforcement with Cr-coated Wf, which promotes the engineering application of the composite greatly.

TiB2p(-TiBw)/Cu hybrid copper matrix composites were fabricated by in situ reaction of Cu–Ti and Cu–B double-beam melts in combination with rolling. La was added on both sides of the melts and the effect of La addition on the microstructure and properties of TiB2(-TiB)/Cu hybrid composites were investigated. The results show that both the hybrid reinforcements and copper matrix are refined, and the reinforcements are more evenly distributed in the matrix with the addition of La. Meanwhile, the addition of La has no effect on the type of reinforcements. Accordingly, a good comprehensive performance of TiB2(-TiB)/Cu composites was achieved with addition of La and post-rolling treatment. Besides, the refinement mechanisms of reinforcements and copper matrix are analyzed. The reasons for the improved performance are also discussed.

W–Cu composites that are strengthened with tungsten carbide ceramic particles have been proposed thanks to their high melting point, high hardness and excellent high-temperature mechanical properties. In this paper, tungsten carbide-reinforced W-25 wt% Cu composites were fabricated via an in situ synthesis technique that used mixed tungsten, copper and graphite powders. The impact of the graphite content on the microstructure and properties of the W–Cu composite was investigated. The results showed that tungsten carbide phases formed through the carbonization reaction of tungsten and graphite at high temperature. With the generation of tungsten carbide phases, the hardness, vacuum arc erosion resistance, high-temperature strength and wear resistance of the W–Cu composites were improved. The improvement was very significant for the W–Cu composites with an increase in the graphite content. However, the electrical conductivity was slightly sacrificed for the W–Cu composites. Moreover, the effects of the graphite on the comprehensive properties were evaluated and compared with those of reinforced with CNTs. Based on the laboratory properties and preparation cost of W–Cu composites, graphite can be used for the industrial fabrication of in situ self-generated tungsten carbide-reinforced W–Cu composites.

Series of WMo solid solution nanopowders with a wide composition range were successfully synthesized by the sol-gel method combined with the hydrogen reduction. The phase constitution, powder morphology and electronic transfer or interaction of the synthesized WMo solid solution alloys were characterized by SEM, XRD, TEM, EDS, XPS and first-principle CASTEP calculation. The experimental results confirmed that W and Mo were evenly distributed in the solid solution nanopowders. Also, with the increasing Mo content, both experimental and theoretical results verified that the formation of solid solution led to a decrease of lattice parameter and an electronic transfer from Mo to W.

In this work, several ultrafine-grained W–Cu composites were prepared by sintering at different temperatures of 1050 °C, 1150 °C, 1250 °C and 1350 °C of 2 h followed by traditional infiltration. The sintering kinetics of tungsten particles, as well as the resultant density, mechanical properties including hardness and compressive behavior, and electrical properties including electrical conductivity and arc erosion behavior of the infiltrated composites were investigated comparatively. Results revealed that the composite pre-sintered at 1250 °C with the highest tungsten particle contiguity of 0.45 exhibited the highest hardness of 272 HV and compressive strength of 894.0 MPa with a pronounced deformation plasticity; besides, the good sinterability of its microstructure contributed to a well dispersed arc spots over 50 times of electrical breakdown tests, resulting in a superior and reliable electrical breakdown strength of 5.66 × 107 V/m.

In this paper, TiB2 particle-reinforced Cu and Cu–Cr composites were prepared by the vacuum arc melting technique. The tensile strength, electrical conductivity and wear properties of the composites were tested. The microstructure and wear morphology of the composites were characterized by SEM. The results showed that microscale TiB2 particles were dispersed uniformly in copper matrix, and the interface between the TiB2 particles and matrix was clean and well bonded. Nanoscale Cr particles were dispersed in the copper matrix. The friction coefficient and wear rate of the composites increased with increasing current. The dual-scale TiB2/Cu–Cr composites with nanoscale Cr particles and microscale TiB2 particles possessed a high strength and hardness, that was conducive to improving the wear resistance. Compared with the wear rate for composites prepared with powder metallurgy, when the current was 50 A, the wear rate of TiB2 particle-reinforced Cu and Cu–Cr composites prepared by vacuum arc melting decreased by 9.3% and 55.3%, respectively. The Cr particles strengthened the copper matrix and the TiB2 particles supported the friction process. The synergistic effect improved electrical wear resistance of the TiB2/Cu–Cr composite. Microstructural observations revealed that the main wear mechanisms of the composites were adhesive wear, abrasive wear and arc erosion.

In the present work, a novel CuW/Al composite was fabricated using an infiltration method by designing a porous W structure on the CuW surface. The evolution and growth kinetics of interfacial intermetallics compounds (IMCs) were studied. The metallurgical reaction between the CuW alloy and Al lead to the formation of five transition zones, which were layer-like, hypereutectic, eutectic, hypoeutectic and needle-like zones from the CuW side to the Al side. Three kinds of IMCs formed at the CuW/Al interface, which were identified as AlCu, Al2Cu and Al4W based on SEM, EDS and TEM analysis. In addition, the effects of temperature (690–740 °C) and holding time (10–60 min) on interfacial microstructure were investigated. The thickness of interface increased with increasing temperature and holding time. The growth kinetics of interface obeyed linear behavior and could be expressed as: y = 3.27 × 108 exp (-163/RT)t. Ab-initio calculations showed that Al2Cu formed first because of the low formation enthalpy. The results provide a guide for controlling the interfacial microstructure and promote the engineering application of the novel composite.

In situ heterogeneous Cu/TiB2 composites with a harmonic structure, where the soft domains of pure Cu are completely surrounded by the hard TiB2 enrichment domains, were fabricated by hot pressing. By controlling the ratio of the Cu powders during ball milling and vibrational blending, composites with different degrees of heterogeneity were obtained. The results of tensile testing show that the composites with proper degrees of heterogeneity possess an excellent combination of strength and ductility. In light of the loading–unloading–reloading tensile test and microstructure analysis results, the strengthening and toughening mechanisms of the heterogeneous composites are discussed. The high strength is attributed to back-stress hardening resulting from plastic incompatibility. The back-stress hardening associated with the strain partitioning results in an enhanced ductility.

To achieve an enhancement of mechanical properties, the WCu composite reinforced with short tungsten fibers was advocated. Characteristics including phase constituents, microstructure and mechanical properties (tensile, compressive and frictional behaviors) of the Wf reinforced WCu composite have been systematically investigated. The magnetron sputtered Ti layer on the surface of Wf effectively improved the sinterability of the composite, leading to excellent electrical conductivity of 56.55% IACS and hardness of 182 HB. Cross sectional EBSD results clearly reveals the sharp fiber texture according to the {110} pole figure of the Wf part, indicating a reserved texture structure although after high-temperature sintering and infiltration, which ensures the fiber strengthening effect. Further tests confirmed the enhancement of mechanical properties including high tensile strength of 549.0 MPa and compressive strength of 1047.8 MPa with large plasticity, as well as low friction coefficient of 0.494. A three dimensional model via numerical simulation further revealed that the smaller the angle between the axial direction of the inserted fibers and the loading direction, the easier it was to bear a higher stress, and the middle part of the fiber was more vulnerable to the accumulated damage.

Considering the advantages and disadvantages of CuW alloys with different single particle size of tungsten powder, CuW alloys with three kinds of tungsten powders: ultramicron (50 μm), micron(6–8 μm), submicron(0.4 μm) were prepared by the infiltration method. Microstructure of the CuW alloy with different grading ration of tungsten powder were characterized via field-emission scanning electron microscope (SEM). The Vacuum electrical breakdown properties were studied by electrical breakdown test. The results shows that the grading tungsten powders can form a variety of W-W sintered necks, strengthen the tungsten skeleton. SEM results show that a suitable ratio of grading tungsten powders can make the infiltrated copper phase more dispersed and uniform. Compared with the tradition CuW alloy, the conductivity is greater than 53.5%IACS, with the lowest hardness of 203HB, the lowest CuW/CrCu bonding strength of 417 MPa and the highest of 495 MPa, the hardness and electrical conductivity increased by 20%–30%, the bonding strength of new CuW/CrCu monolithic materials increased by 20%, vacuum electrical breakdown properties performed good.

Phase separation at nanoscale and highly dispersive nanoparticles were exploited to fabricate a novel type of nanocrystalline W-Cu-Cr-ZrC composite with special hierarchical structure. The microstructures were characterized elaborately and the formation mechanisms of the hierarchical structure were disclosed. It was found that the supersaturated Cr separated from W during sintering and segregated at profuse interfaces. Moreover, Cr can also interact with ZrC nanoparticles dispersed in W matrix, leading to the formation of Zr-Cr-C phase which exerts significant effect on inhibiting coarsening of W grains. On the other side, the dissolution of Cr and W contributes to the formation of Cu nanocrystalline structure. As a result, the prepared W-Cu-Cr-ZrC composite exhibits an ultrahigh hardness of 943HV owing to the synergy of nanocrystalline structure and dispersion strengthening of nanoparticles. The hardness has achieved the highest value among the W-Cu-based composites with the same Cu content reported in literature. This study provided a new strategy for production of high-performance W-Cu-based composites through combination of microstructural design with addition of doping element and nanoparticles.

Constructing isotype heterostructure is an effective way to promote the separation of photogenerated charge carriers for graphitic carbon nitride (g-C3N4). However, the interface derived from different source precursors is not good enough for the charge separation of g-C3N4/g-C3N4 isotype heterojunctions, resulting in a limited improvement of photocatalytic performance. Here, we presented a rational design and synthesis of the g-C3N4(bulk)/g-C3N4(nanosheet) (denoted as BCN/CNNS) isotype heterojunctions with tight interfaces for enhanced photocatalytic hydrogen evolution. Using glucose-modified melamine as the single-source precursor for the first time, an isotype heterojunction was in situ formed at the interface between bulk g-C3N4 and g-C3N4 nanosheet. Due to the enhanced visible light absorption and promoted charge carrier separation, the in situ formed BCN/CNNS isotype heterojunctions exhibited highly improved photocatalytic hydrogen evolution activity under visible light irradiation, which was 16.4 and 11.5 times than those of the bare BCN and CNNS, respectively. Such an in situ formed isotype heterojunction with tight interfaces originated from the thermal polymerization of single-source glucose-modified melamine would present a new avenue for developing efficient g-C3N4-based isotype heterojunction photocatalysts.

Mesocrystals are a new class of superstructures that are generally made of crystallographically highly ordered nanoparticles and could function as intermediates in a non-classical particle-mediated aggregation process. In the past decades, extensive research interest has been focused on the structural and morphogenetic aspects, as well as the growth mechanisms, of mesocrystals. Unique physicochemical properties including high surface area and ordered porosity provide new opportunities for potential applications. In particular, the oriented interfaces in mesocrystals are considered to be beneficial for effective photogenerated charge transfer, which is a promising photocatalytic candidate for promoting charge carrier separation. Only recently, remarkable advances have been reported with a special focus on TiO2 mesocrystal photocatalysts. However, there is still no comprehensive overview on various mesocrystal photocatalysts and their functional modifications. In this review, different kinds of mesocrystal photocatalysts, such as TiO2 (anatase), TiO2 (rutile), ZnO, CuO, Ta2O5, BiVO4, BaZrO3, SrTiO3, NaTaO3, Nb3O7(OH), In2O3−x(OH)y, and AgIn(WO4)2, are highlighted based on the synthesis engineering, functional modifications (including hybridization and doping), and typical structure-related photocatalytic mechanisms. Several current challenges and crucial issues of mesocrystal-based photocatalysts that need to be addressed in future studies are also given.

The continuous network structure induced by carbon nanotubes (CNTs) was introduced to TiB2/Cu composites by electroless deposition, slurry dispersion and powder metallurgy to enhance arc erosion resistance. The arc erosion characteristics of the TiB2/Cu-CNT composites at a current ranging from 10 A to 20 A were investigated. The mechanisms of enhanced arc erosion resistance by the CNT network structure were elaborated based on microstructure and physical characteristics as well. The results show that with the introduction of continuous CNT network structure, arc energy was reduced by more than 83%, there were almost no fluctuation of arc energy and the welding force was relatively low at current above 15 A for TiB2/Cu-1.2 vol% CNT composite in comparison with the CNT unreinforced TiB2/Cu composite. The continuous network structure facilitated the cathode arc motion and dispersed the cathode arc, mitigating the concentrated deterioration of arc erosion. Simultaneously, CNTs could float much easily at the surface of molten pool to weaken the Cu splashing. The CNT network structure delayed the formation of the deeper crater on the cathode and the protrusion with a sharper tip on the anode. Furthermore, it could prevent the formation of cracks and fracture of anode protrusion. Keywords: TiB2/Cu-CNT electrical contact materials, Designing and tailoring microstructure, The CNT network structure, Arc erosion characteristics, Arc erosion mechanism

Using first-principles calculations, we present a potential new way to improve the photocatalytic efficiency of the g-C

The kinetical recrystallization behaviors over wide ranges of annealing temperature of 1100–1200 °C and annealing time range of 0.5–16 h of a second-generation single-crystal superalloy have been investigated by combined model simulation, TEM and EBSD techniques. The kinetics represented by Johnson–Mehl–Avrami and Arrhenius equations revealed its complicated diffusion-controlled mechanism. With increasing annealing temperature and time, the recrystallized grain size exhibited a steady increasing tendency, and gradually, the subgrain boundaries in the original matrix were consumed and replaced by high angle grain boundaries, leading to improved Schmid factor. The dominant fraction of twins in the resultant microstructure indicated its significant role in strain energy dissipation, facilitating the complete progress of recrystallization.

The isothermal relaxation kinetics equations of free volume was derived based on the defect relaxation kinetics expressions. The equations were used to fit the isothermal thermal analysis curves of Al 85 Ni 8 Y 5 Co 2 amorphous alloy at different temperature and giving out several crucial parameters associated with the structure relaxation kinetics and metastable structure for example the kinetic coefficient and the fragile strength coefficient. The fitted parameters indicate excellent consistence with the previously reported data, manifesting isothermal thermal analysis based on the kinetics equations presented in this paper is applicable to investigate the metastable structure and structure relaxation of amorphous alloys, providing a novel method more convenient than the traditional viscosity monitoring method.

Copper powders were thermally treated in the air at a wide temperature range of 200–700 °C. It was found that thin CuO nanowires were grown at 300 °C and thick CuO nanowires were grown at 500 °C. The diameters of the thin CuO nanowires were distributed in the range of 5–10 nm, and the growth directions along [111] and [110] were observed. In addition, the thermally treated copper powders with ultrathin CuO nanowires showed a broad violet emission band peaking at 402 nm.

The effect of oxygen doping on the electronic and geometric structures of monolayer graphitic carbon nitride was calculated by first principle. It reveals the favorable O doping configurations over all the Fermi levels utilizing the Ab initio thermodynamics approach. The valence charge density difference contour map presents a weaker covalent nature on O–C bonds for O N2 -doped structure and a complex ionic-covalent character associated with O–N2 bonds for O i -doped structure. Based on the analysis of the electronic structures of the doped and un-doped systems, it is found that O doping facilitates the visible-light absorption of monolayer g-C 3 N 4 . Especially, O i doping shows an intrinsic semiconductor behavior and the occupied doping band can be avoided to be the recombination center. In addition, O doping causes slightly stronger delocalization of the HOMO and LUMO which facilitates the enhancement of the carrier mobility. Moreover, O i doping can induce more activity sites, and, thus, is beneficial for the separation of photogenerated e − /h + pairs to some extent.

The Vogel–Fulcher–Tammann relationship is a generic equation for describing the transport properties of supercooled fragile liquids. Coupling this reasonable equation, a kinetic model is derived in the present work for describing the crystallization kinetics of metallic glass in supercooled liquid region. In the modeling, a constant value for apparent activation energy is substituted by a temperature-dependent one, so that a model is carried forward to describe more general solid-state phase transformation kinetics. Then, recipes of kinetic analysis are proposed, and information about liquid fragility is obtained. Applying the newly proposed model, the evolution of apparent activation energy during the crystallization of many amorphous alloys can be explained. Finally, the crystallization kinetics of Zr55Cu30Al10Ni5 bulk metallic glass, respectively measured by isothermal and non-isothermal differential scanning calorimetry, is studied and interpreted using the present model.

To obtain W–Ti alloy with less Ti-rich solid solution, W powders were modified by high-energy ball milling to increase their microdefects and accelerate diffusion of Ti in W. Bulk W–10 wt.% Ti alloy was also fabricated using milled/unmilled W powders and TiH2 powders by solid sintering. XRD, SEM and TEM were used to study the effect of ball milling of W powders on the formation of Ti-rich phase and properties of W–Ti alloy. The results showed that the defects of W powders were successfully induced by ball milling, the grain boundary increased due to the grain refinement and the dislocation density increased by 100 times comparing to the unmilled powders. The milling effect still retained at elevated temperature. On the basis of the above results, the diffusion of Ti into W was promoted and the generation probability of Ti-rich phase was inhibited with its phase content reducing from 16.7% to 12.7%, which can be interpreted in terms of the improvement in interdiffusion coefficient of W–Ti alloy by 40 times. The physical properties such as microhardness and electrical conductivity of W–Ti alloy were also improved evidently.

Single phase of green-emitting X 2 −(Y,Gd)SiO5:Tb 3+ phosphoqr was successfully prepared at 1250 °C by a co-precipitation process. The photoluminescence of as-prepared Y 1.9 SiO 5 :0.1Tb 3+ and Y 1.85 Gd 0.05 SiO 5 :0.1Tb 3+ were investigated in vacuum ultraviolet region. Under 147 nm excitation, the phosphors showed main emission peak at 543 nm attributed to the 5 D 4 → 7 F 5 transition of Tb 3+ . According to the relative emission intensity of samples with different composition, the optimal substitution proportions of Tb and Gd for Y were determined to be 10% and 5%, respectively. Besides, Y 1.85 Gd 0.05 SiO 5 :0.1Tb 3+ maintained the short decay time of Y 2 SiO 5 :Tb 3+ phosphor only 3.5 ms, which is much shorter than the commercial green-emitting phosphor Zn 2 SiO 4 :Mn 2+ . As showed in the excitation spectrum, the 141 and 175 nm excitation bands were assigned to the charge transfer bands of Y–O and Gd–O, respectively. Compared to Y 2 SiO 5 :Tb 3+ , Gd 3+ provided another energy transfer channel from matrix to the luminescence center Tb 3+ , thereby enhancing the photoluminescence efficiency. The projected density of states of Y 2 SiO 5 and Gd 2 SiO 5 were also discussed in this work trying to understand the charge transfer mechanics of this phosphor.

The deformation characteristics of WC, as a typical hard ceramic material, were studied on the nanoscale using atomistic simulations for both the single-crystal and polycrystalline forms under uniaxial compression. In particular, the effects of crystallographic orientation, grain boundary coordination and grain size on the origin of deformation were investigated. The deformation behavior of the single-crystal and polycrystalline WC both depend strongly on the orientation towards the loading direction. The grain boundaries play a significant role in the deformation coordination and the potential high fracture toughness of the nanocrystalline WC. In contrast to conventional knowledge of ceramics, maximum strength was obtained at a critical grain size corresponding to the turning point from a Hall-Petch to an inverse Hall-Petch relationship. For this the mechanism of the combined effect of dislocation motion within grains and the coordination of stress concentration at the grain boundaries were proposed. The present work has moved forward our understanding of plastic deformability and the possibility of achieving a high strength of nanocrystalline ceramic materials.

As a significant metal chalcogenide, copper sulfide (Cu

In the present study, a novel ardh gene encoding d-arabitol dehydrogenase (ArDH) was cloned and expressed in Escherichia coli from a new isolated strain of Gluconobacter sp. JX-05. Sequence analysis revealed that ArDH containing a NAD(P)-binding motif and a classical active site motif belongs to the short-chain dehydrogenase family. Subsequently, the optimal pH and temperature, specific activities and kinetic parameter of ArDH were determined. In the co-biotransformation by the whole cells of BL21-ardh and BL21-xdh, 26.1g/L xylitol was produced from 30g/L d-arabitol in 22h with a yield of 0.87g/g. The xylitol production was increased by more than two times as compared with that of Gluconobacter sp. alone, and was improved 10.1% than that of Gluconobacter sp. mixed with BL21-xdh.

To investigate the effect of TiB2 particle size on the arc erosion behaviors of Ag–4wt.% TiB2 contact materials, ultrafine TiB2 powders were prepared by reactive ball milling with the mixture of Mg, B2O3 and TiO2 powders followed by acid wash. The phase constituents, size and morphology of the powders prepared were characterized by X-ray diffractometer (XRD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Two kinds of Ag–4wt.% TiB2 contact materials were subsequently consolidated by powder metallurgy using ultrafine TiB2 powders and coarse TiB2 powders. The microstructure of Ag–4wt.% TiB2 contact materials was characterized, and the relative density, hardness and electrical conductivity of AgTiB2 contact materials were determined utilizing Archimedes method, a hardness analyzer and an eddy electrical conductivity gage, respectively. The arc erosion of Ag–4wt.% TiB2 contact materials was tested, the surface morphologies of Ag–4wt.% TiB2 contact materials after arc erosion were characterized by scanning electron microscopy, the spatial distribution of TiB2 particles in Ag matrix was evaluated, and the arc duration and mass loss before and after arc erosion were determined as well. The results show that the relative density, electrical conductivity and hardness of Ag–4wt.% TiB2 contact materials consolidated using ultrafine TiB2 powders are 85.45%, 55.17% International Annealed Copper Standard and 49.20 Brinell Hardness, respectively. Compared with the Ag–4wt.% TiB2 contact material consolidated using coarse TiB2 powders, the Ag–4wt.% TiB2 contact material prepared by ultrafine TiB2 powders presents shallower arc erosion pits, larger erosion area, more uniform dispersion and shorter arc duration.

Copper matrix composites reinforced with MgO, Al2O3, SiO2, and SiC nanoparticles were fabricated by powder metallurgy. The tribological properties of the composites were examined using a self-made pin-on-disk electrical wear tester. Thermal expansion properties of the prepared composites were evaluated by their coefficient of thermal expansion from 50 to 500°C. The effect of the thermal expansion characteristics of reinforcements on the electrical wear performance of the composites was also studied. The results showed that the wear rates of MgO/Cu and Al2O3/Cu composites were lower than those of SiC/Cu and SiO2/Cu composites, which were also consistent with the difference between the coefficient of thermal expansion of the copper matrix and reinforcements. The relationship was analyzed by calculation of the thermal stress at the copper matrix–reinforcement interface in the electrical sliding process. Microstructural observation revealed that the wear mechanisms of the copper matrix composites were mainly ...

The effects of microstructure and composites evolution of C/SiC composites after corrosion on the internal friction were investigated and the internal friction mechanisms at different corrosion stages were discussed. The studies presented that the internal friction of C/SiC composites with defects was sensitive to the low frequency and high amplitude. In the initial corrosion stage, there was little change in interface of C/SiC composites and the corrosion under high temperature released the thermal stress at the interface, which decreased the internal friction. As the interface eroded in samples, the weaken interface became the important source of internal friction and improved the internal friction of samples. With the further development of the corrosion, SiC matrix in C/SiC composites was oxidized. The glassy oxide filled the cracks and restrained the matrix deformation, resulting in the little decrease in the internal friction of samples with high content oxide.