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Cu-Be alloys exhibit excellent comprehensive performance in electrics, thermotics, and mechanics, and hence, they attract much attention. Among them, low-Be copper alloys are more environmentally friendly and promising. This study explores the effects of different Ni contents and heat treatment parameters on the properties, microstructures, and precipitates of Cu-0.2 wt% Be-x wt% Ni (0 < x < 2.0) alloys. The experimental results demonstrate that the fast cooling rate of cast alloys during solidification contributes to retention of the solute atoms in the copper matrix, which is beneficial for subsequent solid solution treatment. Furthermore, solid solution treatment slightly reduces the electrical conductivities, microhardness values, and compressive yield strengths of Cu-0.2 wt% Be-1.0/1.6 wt% Ni alloys. The optimal solution temperature and time are about 925 ℃ and 60 min, respectively. Aging treatment significantly increases the electrical conductivities, microhardness values, and compressive yield strengths of Cu-0.2 wt% Be-1.0/1.6 wt% Ni alloys. The best aging temperature is around 450 ℃. However, the properties of Cu-0.2 wt%Be-0.4 wt%Ni alloys remain unaffected by solution and aging treatments. Around x = 1.0, Cu-0.2 wt% Be-x wt% Ni alloys possess the best comprehensive properties, which are about 72%IACS of electrical conductivity, 241 HV of microhardness, and 281MPa of compressive yield strength, respectively. TEM and EDS analyses reveal that the precipitate evolution of Cu-0.2 wt% Be-1.0 wt% Ni alloys with aging time is GP zones → γ″ → γ′. Notably, a distinct double-peak age strengthening phenomenon emerges with Cu-0.2 wt% Be-1.0/1.6 wt% Ni alloys. The precipitation of plenty of GP zones at the early stage of aging should account for the first strengthening peak, and the strengthening mechanism transformation of the γ″ or γ′ phase from shear to Orowan should induce the second strengthening peak. This work may help to design new low-Be copper alloys and their preparation processes. [ABSTRACT FROM AUTHOR]

A novel Ti–2Al–1.3V (wt.%) alloy was prepared by thermomechanical consolidation of a composite powder produced by high-energy ball milling of a mixture of TiH2 granules with a low oxygen content (0.1wt.%) and Ti–6Al–4V machining chips with a high oxygen content (0.8wt.%) at a mass ratio of 2:1. The microstructures and mechanical properties of the alloy in as-extruded state and after different heat treatments were investigated. The as-extruded alloy exhibits a martensite microstructure consisting of ultrafine and nanometer sized α' laths and aciculae and domains of layered structure containing δ(TiH) layers. The alloy in this state is brittle and fractures prematurely before yielding due to the ultrafine martensitic microstructure and hydrogen embrittlement associated with the high hydrogen content of the alloy. After vacuum annealing at 700°C for 6 h followed by furnace cooling, the alloy is further dehydrogenated with the hydrogen content being reduced to 0.008wt.%, the microstructure of the alloy changes into a full α/β lamellar microstructure with the continuous and discontinuous β layers being only 80–90 nm thick and the lamellar colony sizes being 10–30μm. The fine structured alloy in this heat treatment condition shows an excellent combination of high tensile yield strength of 996 MPa and ductility of 13.9%. After a further heat treatment of 980°C for 1 h followed by air cooling, the microstructure of the alloy consists of equiaxed α grains and α/βt lamellar structured domains (βt = β transformed structure), and unfortunately, this microstructure leads to a significant decrease of both the tensile yield strength (to 876 MPa) and the tensile ductility (to 7.4%). The fracture behavior of the alloy in different states is also studied, and the correlation between the microstructure and mechanical properties is discussed. [ABSTRACT FROM AUTHOR]

In this paper, gallium was used as alloying element to improve hydrogen storage properties of magnesium. Therefore, Mg– x wt% Ga (x = 5, 10, 25, 50) binary alloys were prepared by induction melting method. The microstructure and phase composition of Mg–Ga alloy were analyzed using X-ray diffractometer and scanning electron microscope. The results show that Mg–Ga binary alloys consist of Mg and Mg 5 Ga 2 phases. The Mg and Mg 5 Ga 2 react with H 2 to form Mg 2 Ga and MgH 2 during hydrogenation process. The hydrogen storage kinetics and thermodynamic properties of the alloys were tested using a Sieverts-type apparatus. It is found that the dehydrogenation rates of the samples increase with increasing gallium content, and they are all better than pure magnesium. Thermal analysis results indicate that increasing gallium content decreases dehydrogenation temperature of Mg–Ga alloy. The beneficial effects of adding gallium in magnesium is that interfaces and secondary phase resulted from alloying can promote the hydrogen desorption process of the alloy. The Mg–50 wt% Ga alloy has the lowest dehydrogenation activation energy. However, increasing gallium content inevitably reduces the hydrogen storage capacity of the Mg–Ga alloys. Furthermore, alloying with gallium does not change the thermomechanical properties of magnesium. [Display omitted] • Hydrogenation leads to the formation of Mg 2 Ga and MgH 2 in Mg–Ga alloy ingot powder. • Alloying Mg and Ga significantly reduces the hydrogen desorption temperature of MgH 2. • The hydrogen release kinetics of MgH 2 is greatly improved by increasing Ga content. • The dehydrogenation activation energy of the alloy decreases by increasing Ga content. • The E a of Mg–50 wt% Ga alloy is 116 kJ mol−1, which is 47 kJ mol−1 lower than MgH 2. [ABSTRACT FROM AUTHOR]

The deformation process of titanium with an initial crack was simulated under uniaxial tension by the molecular dynamics method. The effect of [0001], [ 1 ¯ 2 1 ¯ 0 ] and [ 2 1 ¯ 1 ¯ 0 ] orientations on the microstructure deformation mechanisms at the crack tip was investigated using embedded atom method potentials. In the simulation, various deformation evidence were clearly observed, such as dislocation nucleation and movement, stacking faults formation, deformation twinning and phase transformation. The stress–strain curves showed that orientations had a greater influence on the plastic stage and less on the elastic stage. By applying uniaxial tension with a constant strain rate along different orientations, microstructure deformation at the crack tip was analysed. When loading along [0001] orientation, twinning was the main deformation mechanism and stacking fault occurred and expanded along { 0001 } < 2 1 ¯ 1 ¯ 0 > slip system with the increase in strain. Applying uniaxial tension along [ 1 ¯ 2 1 ¯ 0 ] orientation, an abnormal 'secondary increase' phenomenon was observed in the stress–strain curve. At the same time, dislocation loops appeared at the crack tip and they expanded, merged with the increase in strain. The massive phase transformation from HCP to BCC was observed in the model when loading along [ 2 1 ¯ 1 ¯ 0 ] orientation, which was caused by multiple Shockley incomplete dislocations under the size limitation. [ABSTRACT FROM AUTHOR]

Abstract Nine groups of wire arc additive manufacturing (WAAM) aluminum alloy walls with different layers were deposited by variable polarity cold metal transfer arc mode using ER 5183. Their microstructures were characterized by optical microscopy and electron back scattered diffraction. For the top layer, grain size increased from 37 μm to 65 μm, and then stabilized at around 41μm, in accordance with the decrease of microhardness from 98.7 HV to 76.4 HV. As the number of deposited layers increased, the anisotropy in the bottom layers was weaken, and small-angle grain boundary may cause an increment to 96.1HV in the microhardness before stabilized around 81HV due to the heat accumulation. [ABSTRACT FROM AUTHOR]

Powder metallurgy (PM) Ti–6Al–2Sn–4Zr–2Mo–0.1Si–(0, 2, 4)W (wt%) alloys were fabricated by thermomechanical consolidation of TiH 2 -based powder compacts and subsequent heat treatments. Samples of the as-fabricated alloys were also heated at 650 °C for 200 h. The addition of 2 or 4 wt%W to the base alloy changed its microstructure of parallel α/β lamellar colonies and grain boundary α (α GB) to an interwoven α/β t microstructure consisting of α GB and a network of interpenetrating α plates with β transformed structure (β t) domains comprising variants of fine α laths and β matrix. The partition of the β stabilizing W between β and α phases and the low diffusivity of W atoms limited the growth of α plates/laths, decreasing the thickness of α plates/laths and increasing the volume fraction of β. The increased hardening of the β phase and enhanced α/β interface strengthening associated with the 4 wt%W addition led to a significant increase in the tensile strength of the alloy from 1281 ± 10–1411 ± 12 MPa. However, the high flow stress and the very fine microstructure caused significant strain localization in the weak α GB , resulting in premature fracture of the α GB (intergranular fracture) and the low ductility (1.4%). Here, premature fracture meant the fracture occurred prior to the alloy reaching its ultimate tensile strength. The heating caused the β interlaths in the W-free alloy to partially dissolve and become β particles distributed along the original lines of β interlaths accompanied by the precipitation of α 2 -Ti 3 Al in the α plates. The addition of W inhibited the dissolution of β interlaths and caused the precipitation of a higher volume fraction of α 2 precipitates during heating. The microstructural changes caused by heating resulted in a slight decrease in strength and a significant decrease in ductility for the W-free alloy, but a significant increase of the yield strength of the 2 W and 4 W alloys with some sacrifice of the tensile ductility. The microstructural reasons for the effects on mechanical properties were analyzed with the assistance of detailed characterization of the dislocations in the deformed specimens. • Effects of W alloying on a PM Ti–6Al–2Sn–4Zr–2Mo–0.1Si alloy are investigated. • W refines α plates and enhances formation of β transformed structure domains. • W enhances hardening of the β phase and α/β interface strengthening. • W increases the microstructural stability and prevents the strength reduction from heating. • High W content promotes α 2 precipitation strengthening of the alloy after heating. [ABSTRACT FROM AUTHOR]

Powder metallurgy (PM) α + β Ti-4Al-4Mo-4Sn-0.5Si alloys were fabricated through thermomechanical powder consolidation of TiH 2 -based powder compacts with two different processing routes: one involving blending the elemental powders (BE route) and the other involving mechanical milling a blend of elemental powders (MM route). With the MM + annealing + solution and aging (STA) route, a hierarchical microstructure consisting of necklace-like micron-scaled grain boundary α (α GB) segments and isolated submicron-scaled primary α (α p) rods dispersed in a β transformed structure (β t) matrix containing a high number density of nano-scaled secondary α (α s) laths was produced in the alloy. The alloy with the hierarchical microstructure achieved an excellent combination of a very high yield strength of 1339 MPa，an ultimate tensile strength of 1467 MPa and an excellent ductility of 10.4%. The increased strength was mainly due to the high fraction of β t matrix in which the fine-dispersed α s precipitates with different orientations efficiently blocked the dislocation motion during deformation. The excellent ductility achieved despite of the high flow stress can be attributed to the elimination of strain concentration in the α GB segments which prevented their cracking prior to the material reaching the necking point during plastic deformation. This was in contrast with the typical α/β t lamellar microstructure of the same alloy composition obtained with the BE + same heat treatment route where strain concentration in the α GB plates occurred due to the direct slip transmission from α colonies to adjacent parent α GB grains during plastic deformation, thus resulting in intergranular premature cracking. TEM observation demonstrated that the strain gradient from the α/β t interfaces to the domain interiors of both α GB segments and α p rods activated a high density of geometrically necessary dislocations near the interfaces, and caused an obvious synergistic strengthening effect which also contributed to the slow drop of strain hardening rate and thus was beneficial to improving the ductility. [Display omitted] • An α + β Ti alloy with a hierarchical microstructure is fabricated by a novel powder metallurgy (PM) route. • It achieves a superior combination of tensile strength (∼1467 MPa) and ductility (10.4%). • The high strength is mainly attributed to the precipitation strengthening and HDI strengthening. • The excellent ductility results from the effective strain partition balanced by α GB , α p and α s. • This study provides a novel approach for fabrication of PM Ti alloys with superior mechanical properties. [ABSTRACT FROM AUTHOR]

Electromagnetic levitation (EML) can provide a containerless environment and, consequently, large undercooling solidification for various metals. In this study, the microstructures, precipitated phase characteristics, properties, and strengthening mechanisms of Cu–0.2Be–1.6Co–1.6Ni alloy with different undercooling conditions were investigated using the EML method. The achieved undercooling range was 76–315 K. The microstructure of the alloy was mainly composed of dendrites and slender-strip precipitates. Under EML, the length and width of the precipitates decreased by an order of magnitude with increasing undercooling. The precipitates transformed from a α(Co) phase with a face-centered cubic structure to a metastable γ′ phase with a body-centered tetragonal structure. The microhardness increased almost linearly from 120 to 154 HV with enhanced undercooling. The electrical conductivity was higher than that of the master alloy and increased slightly with enhanced undercooling. Quantitative analyses of the strengthening mechanisms revealed the vital roles of solution and precipitation strengthening in the mechanical properties of EML alloys, whereby the former was weakened and the latter was strengthened as undercooling progressed. The simultaneous enhancement of the mechanical and electrical properties of Cu–0.2Be–1.6Co–1.6Ni alloy can be attributed to the increased solute precipitation and refined precipitates due to deep undercooling. [ABSTRACT FROM AUTHOR]

(1 − x)CoWO-xCuO dielectric ceramics were synthesized by the mixed oxide reaction method. W-based microwave dielectric materials with excellent properties have been reported heavily. The high sintering temperature seriously limited their commercial application in low temperature co-fired ceramics (LTCC) devices. CuO with a low melting point had been widely used as a liquid phase sintering aid. The addition of CuO had great effects on the sintering temperature, microstructure and microwave dielectric properties. When a small amount of CuO was added, the optimal sintering temperature could be decreased from 1200 to 950 °C, with no severe deterioration on the dielectric properties. The X-ray diffraction patterns indicated all samples to exhibit wolframite-like monoclinic P2/c (13) structure and no impurity phase. X-ray powder diffraction and SEM analysis revealed the formation of solutions between CoWO and CuO. Meanwhile, excellent microwave dielectric properties were obtained (permittivity of ~10.69, quality factor Q × f of ~20,000 GHz ( f = 10 GHz) and temperature coefficient of frequency τ of ~−35 ppm/°C) for 0.97CoWO-0.03CuO sintered at 950 °C. These features make (1 − x)CoWO-xCuO ceramics a promising candidate for LTCC application. [ABSTRACT FROM AUTHOR]

A novel lead-free, high dielectric constant, ultra-wide temperature stable dielectric ceramic Ba 1−x Bi x Ti 1−x −y Zn 0.75x W 0.25x+y O 3+y (0.22≤x≤0.30, y=0.015) was synthesized by the traditional solid-state reaction method. The phase composition, electric and dielectric properties of the Ba 1−x Bi x Ti 1−x −y Zn 0.75x W 0.25x+y O 3 ceramics were investigated. The P-V-L dielectric theory was introduced. And, the chemical bond energy was calculated to track the changes in micro-structure. The relationships between chemical bond energy and the macroscopic dielectric properties(ε r , dielectric stability and dielectric loss ) in Ba 1−x Bi x Ti 1−x−y Zn 0.75x W 0.25x+y O 3+y ceramics were discussed systematically. Owing to the inhomogeneous micro-structure and the diffusion in phase transition, Ba 1−x Bi x Ti 1−x−y Zn 0.75x W 0.25x+y O 3+y ceramics showed a stable permittivity (~800±15%) over a ultra-wide temperature range (−30 to 375 °C). Moreover, dielectric loss was less than 0.02 and the insulation resistance was over 10 12 Ω cm. These features suggested that the Ba 1−x Bi x Ti 1−x−y Zn 0.75x W 0.25x+y O 3+y ceramic could be considered as a promising candidate material for energy storage applications in harsh environment. [ABSTRACT FROM AUTHOR]

Flower-like CuO/ZnO hierarchical structures were prepared via a flexible two-step synthesis method, in which nanorods-assembled flower-like ZnO microstructures with the diameter about 430–1680 nm and the length about 3.6–8.8 μm were prepared in advance through a chemical solution method, and then a frost-like layer of CuO nanoparticles (NPs) decorated on the surface of ZnO nanorods (NRs) via an ionic-layer adsorption and reaction method. Compared with pure ZnO NRs, the flower-like CuO-decorated ZnO NRs show an obvious improvement in gas sensing performance. The gas sensing mechanism of the CuO-decorated ZnO NRs was discussed in relation to the catalytic effect of CuO and the introduction of the p-n junction between CuO and ZnO. [ABSTRACT FROM AUTHOR]

Two samples of an α + β Ti-4Al-4Mo-4Sn-0.5Si (wt%) alloy, one with fine prior β grains and a heterogeneous microstructure and the other with coarse prior β grains and a homogeneous microstructure were prepared by extrusion of compacts of TiH 2 /Al/Mo/Sn/Si powder blend at 1200 and 1300 °C respectively. The heterogeneous microstructure is manifested by softer Mo-rich regions with a full α/β lamellar structure containing a high number density of parallel and nanometer sized FCC δ (TiH) needles in a harder matrix with a microstructure consisting of interweaved α plates and β transformed structure (β t) domains and grain boundary α (GB α) layers. The matrix also contains a small fraction of Sn-rich regions which have the same microstructure as the matrix. The Mo-rich and Sn-rich regions form due to the limited diffusion of Mo and Sn alloying elements. This heterogeneous microstructure sustains a high tensile yield strength of 1199 MPa, a high strain hardening rate, and an excellent tensile ductility of 12.0%. In contrast, the homogeneous microstructure comprising of interweaved α plates and β t domains together with GB α layers sustains a similar high strength, but a clearly lower strain hardening rate and a significantly lower tensile ductility of 3.5%. Non-homogeneous deformation capacity, the release of energy by forming numerous microcracks and the intermittent growth of microcracks of the heterogeneous microstructure suggest that this microstructure has a high plasticity and high resistance to the growth of microcracks. • The α + β titanium alloy fabricated has a heterogeneous microstructure and fine prior β grains. • The heterogeneous microstructure encompasses softer Mo-rich regions in a matrix of α/β t microstructure. • This alloy exhibits a superior combination of high strength (YS: 1199 MPa and excellent ductility (12.0%). • This is attributed to the compatible deformation and high microcrack growth resistance of the microstructure. [ABSTRACT FROM AUTHOR]

A new lead-free, high dielectric constant, wide temperature stable dielectric ceramics was prepared by traditional solid-state method. The phase contribution, electric and dielectric properties of the BaTiO 3 –Na 0.5 Bi 0.5 TiO 3 –Nb 2 O 5 ceramics were investigated. The bimodal model was proposed to explain the phenomenon of ultra-broad temperature stable. The doping of CoO played a decisive role in the realization of a wide temperature range of − 50–350 °C stability. In addition, a relative higher dielectric constant and lower dielectric loss (ε r = 1365 ± 15%, tanδ = 1.513%) were obtained. These features suggest that the ceramics system can be considered as a promising candidate material for the next generation of MLCC. [ABSTRACT FROM AUTHOR]

• With an addition of 0.2 wt%Si, the Si atoms are equally in α and β phases. • Si solute atoms retard the growth of α phase, causing refinement of the α/β t lamellar structure. • Si atoms enhance solid solution strengthening and Si atoms enhanced α/β t interface strengthening. • Increasing the Si content to 0.5 wt% cause a further increase of the yield strength by 50 MPa. • With a high strength, the tensile ductility deteriorates, due to the premature fracture of grain boundary α layers. Ti-4Al-4Mo-4Sn-xSi (wt%) (x = 0, 0.2, 0.5) alloys were fabricated by hot extrusion of compacts of blends of TiH 2 , AlMo60 master alloy and other required elemental powders followed by heat treatments involving vacuum annealing, solution treatment, air cooling and aging. The microstructure of the alloys consists of α plates, lamellae of α and transformed β structure (β t), β t blocks as well as grain boundary α layers. With the addition of 0.2 wt%Si, the Si atoms exist in equal concentration in both α and β t regions as solute atoms, and they retard the growth of α phase, causing a decrease of the average thickness of α plates and lamellae and slight increase of the volume fraction of β t lamellae and blocks. The solid solution strengthening and enhanced α/β interface hardening brought by the 0.2 wt%Si cause the yield strength of the Ti-4Al-4Mo-4Sn alloy to increase significantly from 1030 to 1130 MPa with a slight decrease of the tensile ductility (7.4% vs 6.8%) and without changing the fracture behavior. With the addition of 0.5 wt%Si, the extra Si causes nanometer sized silicide (Ti 5 Si 3) precipitates to form in both α and β t regions and further microstructural refinement. The additional α/β interface hardening and precipitation hardening cause the yield strength of the alloy to increase further to 1177 MPa, but the tensile ductility deteriorates clearly with the elongation to fracture decreasing to 4.9%. The main reason for this ductility decrease is the premature fracture of grain boundary α layers caused by the higher flow stress which can induce more strain localization at the grain boundary α layers. [ABSTRACT FROM AUTHOR]

A powder metallurgy (PM) near α Ti–6Al–2Sn–4Zr–2Mo−0.1Si (wt.%) alloy was fabricated by in-situ dehydrogenation and hot extrusion of a TiH 2 -based powder compact and heat treatments. Three types of microstructures were obtained in the as-consolidated state and after different heat treatments. They are a basketweave microstructure consisting of a network of inter-penetrating α plates filled with domains of ultrafine β transformed structure (β t) (Type I microstructure), an α/β lamellar microstructure with most β layers being thin and discontinuous plus α layers at prior β grain boundaries (Type II microstructure) and an α/β t lamellar microstructure (Type III microstructure). Although the three types of microstructures render the alloy with a similar yield strength (1085–1109 MPa) and ultimate tensile strength (1217–1239 MPa) due to the balanced effects of various strengthening mechanisms, the Type II microstructure exhibits a significantly lower tensile ductility than the other two types of microstructures (elongation to fracture: 5.5% vs. 13–14%). Examination of dislocations in the tensile deformed specimens reveals that dislocations cutting through the thin β layers in the Type II microstructure during deformation. Such interactions between moving dislocations and thin β layers in the Type II microstructure are expected to be the primary reason for the clearly lower strain hardening rate, premature fracture of grain boundary α layers and low tolerance to strain localization observed in the tensile tests, fracture surface examination and DIC analysis. This correlation between the microstructures and tensile deformation behavior strongly suggests that preventing moving dislocations cutting through thin β layers by turning them into thicker and ultrafine structure strengthened β t lamellae or blocks is critically important in ensuring high tensile ductility of high strength PM near α titanium alloys. • Three types of microstructures are obtained in a PM near α titanium alloy. • All three types of microstructures render the alloy with a similar high strength. • Type II microstructure gives a much lower tensile ductility than other two types of microstructures. • The lower ductility is attributed to dislocation cutting of thin β layers in Type II microstructure. • Preventing the dislocation cutting through is key for both high ductility and high strength. [ABSTRACT FROM AUTHOR]

The microstructure of printed Cu wirings fabricated from air‐stable Cu complex inks is greatly modified by low‐temperature curing followed by intense pulsed light densification enhancement treatment. The resulting almost full densification of printed Cu wirings enables them to possess a high electrical conductivity of 50% bulk Cu. The dense structure also largely prevents the permeation of oxygen and water into the inner side of the Cu wirings, thereby improving their oxidation resistance and maintaining a stable resistance (R/R0 < 1.5) even after 1000 h aging at 85 °C‐85% RH. In addition, the dense and robust structure can improve the resistance to crack generation and propagation in Cu wirings during the bending, so as to improve their flexibility. The relative resistance of Cu wirings can be kept below 1.2 after 1000 bending cycles. All the results indicate that these highly densified Cu wirings fabricated from air‐stable Cu complex inks can be used to replace the noble metallic Au and Ag wirings for practical application in flexible electronics. In order to address the oxidation problem of Cu inks and enhance the oxidation resistance of printed Cu wirings, air‐stable Cu complex ink is used, and almost full densification of printed Cu wirings is successfully achieved by a two‐step sintering process consisting of low‐temperature curing and intense pulsed light treatment. [ABSTRACT FROM AUTHOR]

Low-activation structural materials for fusion applications beyond 700 °C are desired. High-entropy alloys (HEAs) with excellent properties at elevated temperatures are suitable for use in nuclear reactors. A newly developed V 35 Ti 35 Fe 15 Cr 10 Zr 5 HEA was fabricated by vacuum arc melting and the microstructure of as-cast and annealed sample was found to be composed of BCC solid solution phases. It was interesting to find that the yield strength of as-cast V 35 Ti 35 Fe 15 Cr 10 Zr 5 HEA increased with increasing the temperature below 500 °C, and it was much higher than that of vanadium alloy or martensitic steel for fusion reactors in the temperature range of room temperature to 900 °C. At 700 °C, the yield strength of V 35 Ti 35 Fe 15 Cr 10 Zr 5 HEA was about 500 MPa higher than that of vanadium alloy or martensitic steel, showing promise for high temperature applications. V 35 Ti 35 Fe 15 Cr 10 Zr 5 alloy had a relative low ductility below 700 °C, while the alloy exhibited a good ductility above 700 °C. [ABSTRACT FROM AUTHOR]

Low-loss (Zn 1- x Ni x )ZrNbTaO 8 (0.02 ≤  x  ≤ 0.10) ceramics possessing single wolframite structure are initiatively synthesized by solid-state route. Based on the results of Rietveld refinement, complex chemical bond theory is used to establish the correlation between structural characteristics and microwave performance in this ceramic system. A small amount of Ni 2+ ( x  = 0.06) in A-site with the fixed substitution of Ta 5+ in B-site can effectually raise the Q  ×  f value of ZnZrNb 2 O 8 ceramic, embodying a dense microstructure and high lattice energy. The dielectric constant and τ f are mainly affected by bond ionicity and the average octahedral distortion. The (Zn 0.94 Ni 0.06 )ZrNbTaO 8 ceramic sample sintered at 1150 °C for 3 h exhibits an outstanding combination of microwave dielectric properties: ε r = 27.88, Q × f  = 128,951 GHz, τ f = –39.9 ppm/°C. Thus, it is considered to be a candidate material for the communication device applications at high frequency. [ABSTRACT FROM AUTHOR]

Ni matrix nanocomposite coatings with a microstructure tailored by Cr and graphene particles were assembled at various current densities by electroplating. The tailoring effect of particles on the surface morphology, composition, microstructure, and properties of the nanocomposite coating was comprehensively explored. The results revealed that the contents of Cr and graphene particles in the nanocomposite coating were elevated by decreasing the current density, resulting in an increased amount of small dendrite-like surface structures. The embedded particles blocked the formation of [200] fiber texture and concurrently brought about crystallite refinement of the Ni deposits. A COMSOL simulation and BSE images revealed that the embedded particles tailored the microstructure of Ni deposits by heterogeneous nucleation, rearrangement, and local current density concentration. The current density concentration on the particles contributed to the selective growth of Ni deposits on the particles. The synergistic effect of the tailored microstructure and embedded particles substantially enhanced the corrosion resistance of the Ni–Cr–graphene nanocomposite coating. In 3.5 wt% NaCl media, the I corr of the nanocomposite coating electroplated at 1 A/dm2 (0.1 μA/cm2) was an order of magnitude lower than that at 20 A/dm2 (2.63 μA/cm2) owing to the strengthened synergistic effect. [Display omitted] • Cr and graphene tailored Ni matrix nanocomposite coatings were electroplated. • COMSOL simulation reflected the electroplating condition distorted by particles. • Current density concentrated on particles led to the tailored Ni microstructures. • The selective growth of Ni on particles induced the formation of valleys and voids. • Tailored microstructure and particles together enhanced the corrosion resistance. [ABSTRACT FROM AUTHOR]