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The influence of α s precipitates on electrochemical behavior and mechanical degradation of Ti-1300 alloy in artificial seawater have been studied. The results show that corrosion resistance and mechanical degradation have been significantly affected by the formation of acicular α s precipitates. The precipitated α s phase with an acicular shape around 40–60 nm in width are uniformly distributed inside β grain. Many α s precipitates are intersected each other and keep a well-defined Burgers orientation relationship with β matrix, which restricts the growth of other α s phases due to pinning effect. Within the electrolyte, the α s phases can form "microgalvanic cells" with their adjacent intergranular β phases, which dramatically deteriorate its corrosion resistance. The mechanical properties of the alloy are also degraded with the increase of immersion time due to the pitting reaction. The precipitated microstructure exhibits an inferior mechanical degradation behavior, and this is mainly because a lot of corrosion cavities are nucleate d and propagated at the interface between α s precipitates and prior β grains. Image 1 • Nano-scale acicular α s phases intersect each other in precipitated microstructure. • An inferior corrosion resistance and passive behavior are due to microgalvanic cells. • α s precipitates and α+β interphase are the preferential dissolution locations. • Corrosion pits lead to the mechanical degradation. [ABSTRACT FROM AUTHOR]

Due to their outstanding electrochemical properties, transition metal sulfides and hydroxides are often used as high-performance electrode materials for supercapacitors. The Mn-doped Co(OH) 2 /Ni 3 S 4 electrode material in this study, due to the synergistic reaction mechanism among Co(OH) 2 and Ni 3 S 4 and the increased active sites by the addition of Mn, the Mn-Co(OH) 2 /Ni 3 S 4 exhibits excellent electrochemical property. The electrochemical performance of the Mn-Co(OH) 2 /Ni 3 S 4 hybrid electrode was measured in an electrode cell made of 2 M KOH solution, showing a superior specific capacitance of 1107.0 C g−1 at 0.5 A g−1, in addition to the excellent capacity retention rate at 10 A g−1 is 72.7 % of that at 1 A g−1. The performance of the hybrid supercapacitor (HSC) assembled with Mn-Co(OH) 2 /Ni 3 S 4 compound and activated carbon (AC) was measured under the same electrolyte conditions, anwell-specificific capacity (157.2 F g−1 at 0.5 A g−1) was achieved, along with superior long-term stable charge/discharge capability (88.9 % of the original specific capacity after 35,000 cycles at 8 A g−1). Meanwhile, the most practical application is when the power density of 410.4 W kg−1, the assembled HSC device has an energy storage capacity of 58.8 W h kg−1, revealing that the developed Mn-Co(OH) 2 /Ni 3 S 4 has great application potential for supercapacitors in the future. [Display omitted] • Mn-Co(OH) 2 /Ni 3 S 4 was synthesized via co-precipitation, and hydrothermal processes. • Mn-Co(OH) 2 /Ni 3 S 4 electrode achieves a large specific capacity of 1107 C g−1 at 0.5 A g−1. • The specific capacity maintains 72.7 % when the current density is changed from 1 A g−1 to 10 A g−1. • Mn-Co(OH) 2 /Ni 3 S 4 //AC HSC obtains an energy density of 58.8 Wh kg−1 at a power density of 410.4 W kg−1. • The capacitance of the Mn-Co(OH) 2 /Ni 3 S 4 //AC maintains ∼89.0 % after 35,000 cycles. [ABSTRACT FROM AUTHOR]

Titanium matrix composites synthesized using powder metallurgy methods have attracted significant attention due to their extraordinary mechanical properties. In this study, cost-effective and high-performance TiC/Ti-6Al-4 V matrix composites were synthesized and characterized using a combined elemental powder mixing and spark plasma sintering method. Studies on the effect of graphene nanoplate (GNP) content on microstructures of Ti-6Al-4 V matrix composites showed typical Widmanstatten structures without apparent pores and microcracks. The grain size of composites was decreased significantly with the increase of GNP content, mainly due to the pinning effect of in-situ generated TiC particles at grain boundaries, which limited the rapid grain growth of the matrix. Mechanical test results showed that their yield strength and ultimate tensile strength were 889.0 MPa and 988.3 MPa, respectively, and their total fracture elongation was maintained at ∼14.2 %. GNPs/Ti-6Al-4 V exhibited superior strength (e.g., yield and ultimate tensile strength of 1028.4 and 1121.6 MPa, which are 14.4 % and 13.5 % higher than those of the matrix) and maintained a good ductility of ∼ 9.8 % with only 0.1 wt% GNP addition. Carbon nanomaterial (such as graphene nanoplates) induced the precipitation of needle-like nano-secondary phases in trigeminal grain boundary β phases, which strengthened the β-Ti soft phase. The reinforced strength of the composite is mainly attributed to the grain refinement, secondary α phases precipitation strength and dislocations strengthening. This work provides a new methodology for fabrication of high-performance titanium matrix composites (TMCs) combination blended elemental powder metallurgy (BEPM) and sintering technology. • BEPM and SPS were used to in-situ synthesize TiC/Ti-6Al-4 V composites. • GNPs induce precipitation α" in trigeminal grain boundary β, reinforcing β-Ti phase. • YS of composites are 1028.4 MPa, increased by 15.7 % compared to Ti-6Al-4 V alloy. • Strengthen mechanisms are grain refinement, α" precipitation and dislocations strengthening. [ABSTRACT FROM AUTHOR]

W70Cu30(W-30 wt.% Cu) alloys were fabricated using cold pressing and infiltration sintering methods from two types of powders, i.e., mixed copper-tungsten (M-Cu-W) powders and our newly developed copper-coated tungsten composite (Cu@W) powders. Microstructure, mechanical and arc-ablation properties of the W70Cu30 alloys were investigated, and the mechanism of enhanced physical/mechanical properties and arc-erosion resistance of the W70Cu30 alloys was discussed. For the W70Cu30 alloys prepared using the Cu@W powders, their physical properties, including hardness, electrical conductivity and relative density were much better than those prepared from the M-Cu-W powders. The W70Cu30 alloys fabricated from the Cu@W powders were free of cracks, and showed homogenous distributions of W and Cu network structures. Whereas for the alloys prepared from the M-Cu-W powders, segregation of Cu was observed and the segregation size was about 40–100 μm. Characterization of arc-erosion morphologies of the W70Cu30 alloys prepared with the Cu@W powders revealed the occurrence of evaporation of Cu phase; whereas that of W70Cu30 alloys prepared with the M-Cu-W powders revealed the occurrence of the sputtering of Cu. After arc breakdown for 200 times, mass loss of alloys made using the mixed powders was twice as much as those made using the coated composite powders. Based on the experimental results and theoretical analysis, an arc breakdown mechanism of the WCu-C alloys using the composite powders was proposed which is attributed to the formation of a homogeneous Cu-Cu network structure to uniformly disperse arc energy and dissipate the generated heat, thus prolonging the service life of the WCu alloy contacts. [ABSTRACT FROM AUTHOR]

Zirconium pentatelluride (ZrTe 5) single crystal has recently received significant attention because of its quantum electronic transport properties and is regarded as a promising candidate for low-temperature thermoelectric cooling and spintronic applications. However, single crystal of ZrTe 5 has generally small sizes and can only be produced in small quantities using a complicated process, whereas ZrTe 5 polycrystals are easily produced and their properties are easily adjusted. In this study, we focus on the magneto-transport properties at low temperatures of nanocomposites of ZrTe 5 produced using both hand-milling and ball-milling processes to investigate the impact of the microstructure. The ball-milled sample shows a low thermal conductivity of 1 W m−1 K−1, which is almost a constant below 300 K. However, due to its small grain sizes, the electron mobility is significantly decreased, thus their thermoelectric performances are not as good as that of the hand-milled sample. Also, below 25 K, the resistivity and the Seebeck coefficient of the ball-milled sample are decreased, which is associated with the energy barrier at their grain boundaries. Due to the larger grain sizes and fewer defects in the hand-milled sample, the external magnetic field shows a significant influence on its thermoelectric properties at low temperatures. These results indicate that polycrystalline ZrTe 5 with large grain sizes may exhibit similar quantum properties as those of single crystals. Image 1 • ZrTe 5 nanocomposites were synthesized by hand-milling and ball-milling. • Relation between the microstructure and thermoelectric properties is established. • Ball-milled sample has a very low thermal conductivity of 1 W m−1 K−1. • Magnetoresistance ratio is larger when grain size is bigger. [ABSTRACT FROM AUTHOR]

Cu–Cr–Zr alloys are often subjected to premature failures due to arc erosion at moment of their breakdown. In this paper, a series of simulated high-voltage arc ablation experiments were conducted to systematically investigate arc ablation characteristics of Cu–Cr–Zr alloys, their microstructure evolutions and anti-ablation properties after plastic deformation and microalloying. Results showed that during their arc ablation processes, a halo pattern was firstly formed on the surface under the action of high-temperature arc. This is followed by partial melting and splashing of Cu, forming of uneven and rough surfaces, and finally significant burning of the alloy. The degree of ablation of alloy is aggravated with the increased breakdown voltage. Due to a combined effect of solid solution strengthening, fine grain strengthening and deformation strengthening, the ablation resistance of the micro-alloyed and plastically deformed alloy has been significantly improved. The breakdown field strengths of commercial Cu–Cr–Zr alloy, heat-treated and deformed one, micro-alloyed and heat-treated one are 1.46 × 106 V/m, 1.67 × 106 V/m and 1.90 × 106 V/m, respectively. However, the breakdown strength of alloys after microalloying is unstable. Results show that there are no preferred phases for the first breakdown of arc ablation of Cu–Cr–Zr alloys. The second-phase particles with high-hardness and high-melting temperature hinder the splashing and flow of the molten copper, and inhibit the movement of the cathode spots during the ablation process. • Study the anti-arc ablation properties of plastic deformed and alloyed Cu–Cr–Zr. • The first breakdown of Cu–Cr–Zr is non-selective and forms halo in the surface. • The cathode spots expand to the surrounding area by the form of jumping. • The alloys after heat treated and deformed have excellent arc erosion resistance. [ABSTRACT FROM AUTHOR]