[en] Highlights: • Anisotropic indexes, 3D graphs and projections of β-M₄AlN₃ are discussed. • Elastic anisotropy of β-M₄AlN₃ is in a sequence of β-Ta₄AlN₃ > β-Nb₄AlN₃ > β-V₄AlN₃. • The order of minimum thermal conductivity is β-V₄AlN₃ > β-Nb₄AlN₃ > β-Ta₄AlN₃. In this study, the first-principles calculations were employed to investigate the elastic, thermal properties, and the anisotropies in elastic modulus, Debye temperature and thermal conductivity of the ternary nitrides β-M₄AlN₃ (M = V, Nb, Ta). The results showed that they are brittle and not potentially superhard materials. The anisotropy indexes, 3D surface constructions and 2D planar projections were employed to characterize the anisotropies in elastic modulus and thermal conductivity. The sequences of anisotropies in both elastic modulus and thermal conductivity are β-V₄AlN₃ > β-Nb₄AlN₃ > β-Ta₄AlN₃. Besides, the sound velocities, Debye temperatures, and anisotropies were also discussed.

[en] Unique architecture of reinforcement is explored for developing advanced metal matrix composites (MMCs). In the present study, Cu matrix composites reinforced by carbon nanofillers with reticulate structure were prepared by powder metallurgy. It was found that the high-efficiency strengthening effect was achieved by employing the hybrids of carbon nanotubes (CNTs) and reduced graphene oxide (RGO) as reinforcements in the Cu matrix. The tensile test results showed that the ultimate tensile strength of ~ 409 MPa was achieved in Cu matrix composite with 1.5 vol% of CNT-RGO hybrids, which is significantly higher than that reinforced with individual CNTs or RGO (~ 226 and ~ 259 MPa, respectively). Strengthening mechanisms including grain refinement, generation of dislocations by thermal mismatch, load transfer and Orowan looping system were discussed to understand the strengthening behaviors of CNT-RGO hybrids in MMCs. This work underscores the importance of interconnected architecture of reinforcements for improving mechanical properties of the composites and provides an insight to understand the strengthening behaviors of reticulate reinforcements in the composites.

[en] Highlights: • Cu/buckypaper composites were prepared by Cu sulfate electrodeposition process. • Oxygen-containing functional groups were introduced by acidification and oxidation. • Functional groups contributed to good interface bonding and thicker transition layers. • Small deposition current density helped to obtain high electrical conductivity. • High ampacity obtained due to the reticulate structure formed in the transition layer. Cu/buckypaper composites were prepared through electrodeposition of Cu onto buckypaper from a Cu sulfate electrolyte. The oxygen-containing functional groups were introduced to the surface of carbon nanotubes (CNTs) through acidification and oxidation. Incorporation of functional groups was shown to facilitate the spontaneous reduction of Cu ions on the surface of CNTs during immersion treatment. Under small deposition current density of 1 mA cm⁻², Cu ions could penetrate into the reticulate structure of buckypaper and nucleate homogeneously on the CNTs, which led to the formation of a thicker transition layer. Functionalization also increased the nucleation rate of Cu on the CNTs. When the current density was 1 mA cm⁻², the electrical conductivity of Cu/oxidized buckypaper composite reached the maximum value of 4.09 × 10⁵ S cm⁻¹ which was 76% of pure Cu. The ampacities of all the composites were obviously improved compared with electrodeposited pure Cu. The Cu/oxidized buckypaper composite had the maximum ampacity of 15437 A cm⁻², which was 65% and 14% higher than that of pure Cu and Cu/original buckypaper composite, respectively. Good interface bonding and reticulate structure of CNTs formed in the transition layers are responsible for the relatively high electrical conductivities and high ampacities of Cu/buckypaper composites.

[en] Microlaminated carbon nanotubes (CNTs) reinforced Cu matrix composites were prepared by combination of composite electrodeposition and spark plasma sintering (SPS). Interdiffusion transition regions formed between CNTs and Cu matrix under high sintering temperature, which were responsible for the balanced strength and ductility of the composites.

[en] Highlights: • Effect of anions on the structure of copper vanadate during ion-exchange is presented in detail. • Due to the dissolution effect of acetate on sodium vanadate nanowire array, copper vanadate spheres composed of nanosheets are formed. • The copper vanadate nanowire arrays exhibit a remarkably high storage capacity of up to 997.76 mAh g⁻¹ in 3–0.01 V versus Li/Li⁺. -- Abstract: Copper vanadate materials have a higher gravimetric capacity and energy density than those of the traditional vanadium oxide or vanadate electrodes because of the multistep oxidation-reduction reactions. This work presents the synthesis of nano-structured copper vanadates using ion-exchange reaction of sodium vanadate nanowire arrays in an aqueous solution, containing copper acetate or copper nitrate. The morphology, crystal structure, composition and lithium-storage performance of the materials are measured and characterized thoroughly. Due to the dissolution effect of the acetate anion on the sodium vanadate nanowire arrays, copper vanadate spheres composed of nanosheets are produced. By contrast, after the ion-exchange reaction in the copper nitrate solution, the sample maintains its original nanowire arrays structure. The copper vanadate nanowire arrays synthesized in copper nitrate solution for 48 h followed with calcination at 300 °C for 2 h exhibit a remarkably high storage capacity of up to 997.76 mAh g⁻¹ in 3–0.01 V versus Li/Li⁺, thus showing a great potential for application in lithium-ion batteries.

[en] A novel carbonized polymer dots (CPD)/copper (Cu) composite was successfully synthesized via molecular level mixing (MLM) and spark plasma sintering (SPS) process. Microstructure analysis shows that the CPD clusters are well dispersed at the Cu grain interfaces by forming an amorphous carbon (AC) network with a large number of inserted graphene carbon dots (some of them show the typical graphene microstructure). Mechanical properties of the CPD/Cu composite are remarkably higher than that of pure Cu sample, which increases initially with CPD wt.% and then decreases. 0.4 wt% CPD/Cu composite obtains ~47% higher strength than that of pure Cu matrix. Meanwhile, the thermal conductivity is improved from 305 W/m·K to 360 W/m·K without any adverse impact on the mechanical properties. This study provides new insights into the preparation of the advanced Cu composite with enhanced comprehensive performance.

[en] Highlights: • Surface and intratube decoration of CNTs is carried out in CNTs/Cu composite. • Uniform distribution and strong interface bonding obtained due to CuO on CNT surface. • Increased interfacial shear stress obtained due to pressure from Cu inside CNTs. • Decreased intra-tube resistivity obtained due to Cu inside CNTs. • Strength, ductility and conductivity increase simultaneously in CNT/Cu composite. Strength and ductility are often a paradox in carbon nanotubes (CNTs) reinforced Cu matrix composite, as well as strength and electrical conductivity. Interface and characteristics of CNTs are critical factors in determining the mechanical properties and conductivity of Cu matrix composites. In the present study, a novel tactic by surface and intratube decoration of CNTs is adopted to break the above mentioned dilemmas. By decorating the surface of CNTs with CuO nanoparticles and taking advantage of the good wettability between CuO and Cu matrix, uniform dispersion of CNTs is realized through ball milling. In the final composite, CuO nanoparticles on the surface of CNTs are reduced to Cu. High density interfacial dislocations and interfacial disordered areas are formed between Cu matrix and CNTs, thus forming a strong interfacial bonding. By decorating the inner walls of CNTs with Cu nanoparticles, the interfacial shear stress between Cu matrix and CNTs is improved due to the extrusion effect of Cu nanoparticles on the inner walls. Moreover, the Cu filled inside the tubes can also reduce the intra-tube resistivity of CNTs by increasing their conducting cross-section. Consequently, the Cu matrix composite with simultaneous improvement of strength (272 MPa), ductility (14.3%) and conductivity (93.6% IACS) is achieved in our present study. This tactic provides a new idea to deal with the strength-ductility and strength-conductivity dilemmas in CNTs reinforced metal matrix composites.