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This study focuses on the microstructures and soft-magnetic properties of the Al1.5Fe3Co3Cr1 multi-principal-element alloy (MPEA) in different states. The MPEA was prepared using arc melting and suction-casting, followed by various heat treatments. The crystal structures were analyzed using X-ray diffraction (XRD), while the microstructures were characterized by means of transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The results reveal that the MPEA consists mainly of coherent body-centered cubic (BCC) and B2 phases, with a moderate lattice misfit (ε = 0.14~0.21%) between them. The homogenized alloy shows the presence of coarse equiaxed grains and micro-scale cells, and it has good soft-magnetic properties with MS = 127 emu/g and HC = 143.3 A/m (1.8 Oe). The thermal stability of the alloy is found to be optimal after aging at 873 K, as there are no significant changes in microstructures and soft-magnetic properties. However, when the aging temperature increases to 973 K, the BCC nanoprecipitates are coarsened, leading to a decrease in the soft-magnetic properties. [ABSTRACT FROM AUTHOR]

WC-Si 3 N 4 composite structural material with excellent mechanical properties is essential for achieving high-strength connections between WC and Si 3 N 4. Proper powder mixing process can significantly improve the mechanical properties of sintered samples. This study investigates the effects of two different ball milling methods: (1) mixing WC powder, Si 3 N 4 powder, and sintering aid powders and then ball milling for 24 h (BM24); and (2) ball milling WC powder, Si 3 N 4 powder, and sintering aid powders separately for 12 h and then ball milling in same jar for 12 h (BM12 + 12), as well as WC content on sintering shrinkage behavior of mixed powders. Furthermore, the bonding between the layers of one-time sintered sample of the WC-Si 3 N 4 composite structure was investigated. The results showed that the microstrains of powders prepared by BM24 mixing process were greater than those of the powders prepared by BM12 + 12 mixing process. Shrinkage displacements and shrinkage rates during sintering of BM12 + 12 powders were greater than those of BM24 powders to varying degrees. Moreover, sintering temperature at which shrinkage rate of composite powders reaches its maximum value gradually increases as WC content decreases, while maximum value of shrinkage rate gradually decreases. Additionally, mechanical properties of all BM12 + 12 samples were better than those of BM24 samples. WC-Si 3 N 4 composite structure sample sintered with BM12 + 12 powders had a smooth transition between the layers without any defects. [ABSTRACT FROM AUTHOR]

Heavy rare-earth (HRE) elements are important for the preparation of high-coercivity permanent magnets. A further understanding of the thermodynamic properties of HRE phases, and the magnetization reversal mechanism of magnets are still critical issues to obtain magnets that can achieve better performance. In this work, the Nd–Dy–Fe–B multicomponent system is investigated via the calculation of the phase diagram (CALPHAD) method and micromagnetic simulation. The phase composition of magnets with various ratios of Nd and Dy is assessed using critically optimized thermodynamic data. γ-Fe and Nd2Fe17 phases are suppressed when partial Nd is substituted with Dy (<9.3%), which, in turn, renders the formation of Nd2Fe14B phase favorable. The influence of the magnetic properties of grain boundaries (GBs) on magnetization reversal is detected by the micromagnetic simulations with the 3D polyhedral grains model. Coercivity was enhanced with both 3 nm nonmagnetic and the hard-magnetic GBs for the pinning effect besides the GBs. Moreover, the nucleation and propagation of reversed domains in core-shell grains are investigated, which suggests that the magnetic structure of grains can also influence the magnetization reversal of magnets. This study provides a theoretical route for a high-efficiency application of the Dy element, realizing a deterministic enhancement of the coercivity in Nd–Fe–B-based magnets. [ABSTRACT FROM AUTHOR]

In this study, WC‐8Co cemented carbides were prepared by spark plasma sintering. When the samples sintered at 1300℃ were cooled to room temperature, the samples were sintered multiple times at 1250℃. The changes in microstructure and mechanical properties of WC‐8Co cemented carbides prepared by multiple spark plasma sintering were studied. The hardness of cemented carbides increased in the first two sintering, reaching 16.5 GPa. However, the hardness decreased seriously in the last two sintering. The attenuation rates of hardness were 6.2% and 2.5% due to the abnormal coarse grains. Furthermore, the crack path along the grain boundary was almost straight, causing a decrease in the indentation fracture toughness of cemented carbides. Additionally, the grains of cemented carbides were abnormally coarsened, and the morphologies of grains became unstable due to multiple sintering. [ABSTRACT FROM AUTHOR]

In order to develop a new high‐performance binder phase, four different alloys Co‐Ni‐Fe, Co‐Ni‐Cr, Co‐Ni‐Nb, and AlCoCrNiNb0.5 were used as a binder in cemented carbides. The room‐temperature mechanical properties and high‐temperature flexural strength of cemented carbides were studied. The results show that the optimal mechanical properties for the WC‐8(Co‐Ni‐Fe, Co‐Ni‐Cr, Co‐Ni‐Nb, and AlCoCrNiNb0.5) can be obtained at the sintering temperatures of 1200°C, 1350°C, 1350°C, and 1300°C, respectively. Compared with cemented carbides with Co as binder phase, the hardness of the four kinds of alloys is increased, the WC grain size becomes finer, but the fracture toughness is slightly decreased. When the temperature is under 600°C, there is no visible oxidation of the four kinds of cemented carbides, and their bending strengths are basically not reduced. When the temperature increased from 600°C to 900°C, the WC‐8(Co‐Ni‐Nb) and WC‐8(Co‐Ni‐Fe) samples present the better high‐temperature bending resistance compared with the WC‐8(Co‐Ni‐Cr) and WC‐8AlCoCrNiNb0.5 samples, with respective decrease in bending strength of 11.7% and 7.3%. [ABSTRACT FROM AUTHOR]

Si 3 N 4 /Ti(C, N) ceramic tool materials were investigated in this work. The effects of Ti(C, N) addition and sintering temperatures on the mechanical properties, phase transformation, and microstructures of Si 3 N 4 /Ti(C, N) ceramic tool materials were considered. Ti(C, N) addition promoted the densification and phase transformation, especially at low sintering temperatures. The optimum mechanical properties could be obtained by addition of 10 wt% Ti(C, N) at 1650 °C. Its relative density, Vickers hardness, and fracture toughness were found to be 99.76 ± 0.07 %, 17.11 ± 0.38 GPa and 7.35 ± 0.64 MPa m1/2, respectively. The microstructure of Si 3 N 4 /Ti(C, N) was uniform and no abnormal grain growth could be observed. The increase in fracture toughness was attributed to the combination of pulling-out of β-Si 3 N 4 , crack-bridging, and crack-deflection. [ABSTRACT FROM AUTHOR]

WC-Co cemented carbide tools offer better cutting performance when cutting difficult-to-machine materials, such as high-temperature alloys, titanium alloys, and high-strength steels. In this paper, high performance WC-8 wt.% Co cemented carbide materials with cBN and VC were prepared by spark plasma sintering. The effects of cBN and VC content on mechanical properties and microstructure of WC-8 wt.% Co-VC-cBN cemented carbide materials were studied. The results show that the relative density, Vickers hardness, and fracture toughness of WC-based cemented carbide materials decreased significantly as the content of cBN and VC increased. WC-8 wt.% Co-0.2 wt%VC-1 wt.% cBN (named as YG8V2B10) cemented carbide material had the optimal properties when sintered at 1250 °C. Its Vickers hardness, fracture toughness, and flexural strength are 20.81 GPa, 13.01 MPa m1/2, and 1630 MPa, respectively. High-temperature flexural strength of YG8V2B10 was also investigated. The flexural strength of YG8V2B10 cemented carbide materials decreased as the temperature increased. When the temperature of YG8V2B10 cemented carbide material exceeded 400 °C in air, matrix at the surface of YG8V2B10 was oxidized, which leads to a significant decrease in the flexural strength. [ABSTRACT FROM AUTHOR]

In this study, ultrafine tool materials were produced by spark plasma sintering using three sets of WC-8Co nanopowders mixed by different methods. Effects of powder preparation method and sintering temperature on the consolidation of WC-8Co cemented carbides were investigated. At sintering temperature of 1250 °C, cemented carbide sintered from the powder mixed by ultrasonic vibration method exhibited homogeneous microstructure, high relative density (99.1%), small average grain size (280 nm), and excellent mechanical properties (H V : 18.8 GPa, K IC : 11.4 MPa⋅m1/2). However, cemented carbide sintered from heavily ball-milled powder (ball milling for 24 h) showed increased grain coalescence and microdefects as well as lower relative density of 94.6%. Moreover, its hardness decreased to 17.7 GPa due to the decrease in relative density. Furthermore, straight cracks along grain boundary became dominant, causing fracture toughness to decrease to 10.5 MPa⋅m1/2. Additionally, high sintering temperature caused grain coarsening, which was detrimental to mechanical properties of cemented carbides. [ABSTRACT FROM AUTHOR]

• A small section of Σ1 boundary can disrupt the HAGB network efficiently. • A small grain size was maintained. • Formation mechanisms were proposed for Σ1 boundaries. • Σ1 boundaries have significant application potential in GBE. Σ3 boundaries improve the intergranular corrosion resistance of high nitrogen austenitic stainless steels. However, the regeneration of these boundaries is, unfortunately, accompanied by significant grain coarsening. 18Mn18Cr0.5N and 18Mn18Cr0.6N steels were thermo-mechanically processed and the corresponding microstructures were evaluated. Formation mechanisms were proposed for Σ1 boundaries in different R-Σ3-Σ1-type junctions. These boundaries formed during grain growth accompanying Σ3 formation and reaction. After 30% cold tension and cyclic heating between 500 °C and 1100 °C, numerous Σ1 boundaries were formed and disrupted the high angle grain boundary network efficiently. Moreover, a small grain size was maintained. Σ1 boundaries have significant application potential in grain boundary engineering. [ABSTRACT FROM AUTHOR]

Ba0.7Sr0.3TiO3 ceramics has been synthesized by solid state reaction method. The effects of sintering time on microstructure and electric properties of Ba0.7Sr0.3TiO3 ceramics have been investigated. XRD patterns show that all ceramic samples are single tetragonal phase. The grain size increases with sintering time. Ba0.7Sr0.3TiO3 ceramics show obvious relaxor behavior because of its broadening dielectric peaks and frequency dispersion phenomenon. As sintering time increases, the Curie temperature does not change significantly and the diffuseness of the phase transition of Ba0.7Sr0.3TiO3 ceramics slightly enhances. Moreover, the remnant polarization and coercive field have no obvious changes with the increasing of sintering time. [ABSTRACT FROM AUTHOR]

WC-Co cemented carbides, with low binder content (Co content <4 wt.%), have become prospects as ultra-precision cutting tool materials as a result of their high hardness, which can be ground to a sharp cutting edge when machining tools. In this paper, three cemented carbides, with Co content of 1 wt.%, 2 wt.% and 3 wt.%, were systematically investigated. The mode of preparation, properties, microstructure and ultra-precision turning of these cemented carbides were studied. It has been researched that 0.1 wt.% VC could effectively refine the WC grains to exhibit excellent properties. The optimum sintering temperatures for WC-1Co-VC, WC-2Co-VC and WC-3Co-VC were 1350, 1300 and 1300 °C, respectively. The resultant cemented carbides displayed extremely high hardness (2450, 2377 and 2325 kg/mm2), high relative density (>99%), specific fracture toughness (8.89, 9.01 and 10.17 MPa·m1/2) and transverse rupture strength (1274, 1387 and 1474 MPa). During oxidation, from room temperature to 400 °C, there was a slight reduction in the strength of the cemented carbides with no oxide formed. From 400 to 600 °C, their strength decreased significantly with apparent oxides formed on the surface. At 800 °C, all the cemented carbides experienced a severe drop in strength and massive oxidation on the surface and fracture surface. The cemented carbides were used to make cutting tools used for ultra-precision turning of brass. The surface roughness after machining with the three modified cemented carbide tools, with increasing Co content, were 22, 14 and 17 nm, respectively. [Display omitted] • Low binder WC-Co cemented carbide tool materials were prepared based on spark plasma sintering. • WC-1Co-VC, WC-2Co-VC, and WC-3Co-VC exhibited high hardness of 2450, 2377, and 2325 kg/mm2. • The transverse rupture strength and oxidation of three prepared cemented carbides were studied at high temperatures. • Ultra-precise turning of brass with prepared tools resulted in flat surfaces with surface roughness down to 14 nm. [ABSTRACT FROM AUTHOR]

Magnetoelectric composite ceramics Fe3O4/PbZr0.52Ti0.48O3 with different molar ratios (Fe3O4/PbZr0.52Ti0.48O3 = 1:1, 1:2 and 1:8) were prepared by combining hydrothermal method and sol–gel method, effects of molar ratio on the structure, dielectric and multiferroic properties were investigated. The results indicate that the synthesized composites show bi-phase structure, ruling out the presence of any obvious impurity phases. The grains can be divided into two types, the larger grain is attributed to PbZr0.52Ti0.48O3 while the smaller one can be considered to be Fe3O4. With the molar ratio increasing, the grain shape of PbZr0.52Ti0.48O3 changes from stripe to bulk-like while the shape and size of Fe3O4 is near the same. Both the dielectric constant and loss decrease with frequency, the specimen with the molar ratio of 1:8 shows the largest dielectric constant, while the sample has the lowest dielectric loss when the molar ratio is 1:2. With the increase of molar ratio, the height of the relaxation peak decreases and the peak position shifts to higher temperature. When the molar ratio is 1:8, the relaxation peak disappears due to less interface polarization. The remnant polarization increases with increasing the molar ratio, the maximum value is 1.12 μC/cm2, obtained at 1 kHz when the molar ratio is 1:8. Anomalous magnetic properties are observed, in which the magnetization increases first and then decreases with molar ratio, the largest saturation magnetization is ~ 30 emu/g when the ratio is 1:2 due to the strong interface interaction. The sample with the ratio of 1:1 shows the largest magnetic loss because of the highest content of magnetic phase. The magnetization shows a monotonic variation behavior with the molar ratio, indicating the strong interface interaction between the two phases. The maximal ME coupling coefficient is about 5.12 mV/(cm.Oe) for the sample 1:2 due to the stronger magnetic and ferroelectric properties. [ABSTRACT FROM AUTHOR]

(Ba0.85Ca0.15)(Zr0.1−xHfxTi0.9)O3 (BCZHT) ceramics were fabricated by a conventional solid-state reaction method. The effects of Hf4+ on microstructure and electric properties of BCZHT ceramics have been systematically investigated. The x-ray diffraction (XRD) results indicate that the introduction of Hf4+ in BCZHT ceramics induces phase transition from an orthorhombic phase to the coexistence of tetragonal and orthorhombic phases, and the lattice constant decreases with the increasing of Hf4+ content caused by substitution of Hf4+ for Zr4+ at B sites. As Hf4+ content increases, the densification of BCZHT ceramics is enhanced and the grain size increases. The introduction of Hf4+ at B sites results in the fall of the Curie temperature and the increase of dielectric constant in BCZHT ceramics. The temperature dependences of dielectric properties of BCZHT (x = 0, 0.05 and 0.1) ceramics show obvious diffuse phase transition characteristics, and the diffuseness of phase transition is enhanced with increasing of Hf4+ content. But there is no frequency dispersion phenomenon in BCZHT (x = 0, 0.05 and 0.1) ceramics. The substitution of Hf4+ for Zr4+ at B sites of BCZHT ceramics makes its remnant polarization increase, which results from the interaction of increased grain size and tolerance factor. When temperature is above its Curie temperature, the polarization–electric field curves of BCZHT (x = 0, 0.05 and 0.1) ceramics still show nonlinear characteristics, which further proves that there is diffuse phase transition and relaxor-like behavior. Moreover, the piezoelectric coefficient of BCZHT ceramics increases as Hf4+ content increases. [ABSTRACT FROM AUTHOR]

Organic–inorganic hybrid perovskites with 3D perovskite structure have gained much attention as light harvesting materials in thin-film photovoltaics. This is because of their outstanding light-absorption characteristics, charge-transport dynamics and their simple processability using lab-scale solution and vapor phase deposition techniques. However, the inherent instability and lead toxicity of lead-based PSCs are the major problems at present. Recent studies have shown that the (CH3NH 3 ) 3 Bi2I9 (MBI) 0D bismuth-based compound can be used as an optical absorption layer in solar cells. In this paper, the (CH3NH 3 ) 3 Bi2I9 was doped with Cl− and a series of (CH3NH 3 ) 3 Bi2I 9 − x Clx films were prepared. The effects of different doping amounts on the microstructure, photovoltaic properties and ferroelectric properties were systematically investigated. Scanning electron microscope (SEM) and Atomic force microscope (AFM) analysis showed that with the increase of doping content, the density of the films increased and the roughness decreased. The photoelectric conversion efficiency of (CH3NH 3 ) 3 Bi2I 9 − x Clx raises with the increase of doping content. For example, the photoelectric conversion efficiency of (CH3NH 3 ) 3 Bi2I3Cl6 is 0.473%. We find that the leakage current descends into the increase in doping content, which may be due to the increase in the film density and the decrease of porosity. These research results have a positive effect on the development of Bi-based lead-free perovskite. [ABSTRACT FROM AUTHOR]

(Ca1−xSrx)3(Ti1−yMny)2O7 (CSTMO) ceramics with hybrid improper ferroelectricity were prepared by conventional solid-state reaction method. Effect of Sr2+ and Mn4+ contents on microstructure, dielectric and ferroelectric properties have been systematically investigated. The XRD results show that CSTMO ceramics is single phase with orthorhombic structure. The lattice constants and average grain size increase with the increasing of Sr2+ content and decrease with the increasing of Mn4+ content. The introduction of Mn4+ deteriorates the densification of CSTMO ceramics to some extent, and the substitution of Sr2+ with higher content can improve the densification by promoting a rapid interdiffusion movement via grain-boundary. (Ca0.8Sr0.2)3(Ti0.9Mn0.1)2O7 ceramics present the highest dielectric constant and dielectric loss, while the dielectric loss of (Ca0.8Sr0.2)3(Ti0.95Mn0.05)2O7 ceramics has a significant reduction. The leakage current of CSTMO ceramics decreases with the increasing of Sr2+ and Mn4+ content. The leakage behavior suggests that the Ohmic conduction and Schottky emission dominate the leakage current of CSTMO ceramics. Moreover, the remnant polarization decreases with the increasing of Sr2+ because of its suppression for the rotating and tilting angle (a−a−c+) of oxygen octahedron. And the electrical polarization decreases with the increasing of Mn4+ content due to the instability of MnO6 rotation. [ABSTRACT FROM AUTHOR]

Magnetoelectric multiferroic materials have attracted great attention due to their intriguing properties and potential applications. In this paper, (1 − x) Co0.8Cu0.2Fe2O4-xBa0.6Sr0.4TiO3 (x = 0, 0.4, 0.45, 0.475, 0.5, 0.525, 0.55, 1) composites were prepared by the conventional solid-state method combining with a sol-gel process. The effect of x on the microstructure, dielectric and multiferroic properties has been systematically investigated and discussed. The results confirm pure bi-phase Co0.8Cu0.2Fe2O4 and Ba0.6Sr0.4TiO3 composites except for slight impurity phases, which are indexed as BaCuO2/BaFe12O19. All the samples show uniform and relatively smooth surfaces with the mean grain size of ∼ 1.5 μm which decreases slightly with the increase of x, demonstrating the moderating effect of the ferroelectric phase on the grain size. The dielectric constant shows intense dependence on the components and the highest value is obtained when x = 0.525. The ferroelectric loops demonstrate that the coercive field and remnant polarization of the sample x = 0.525 are higher than other samples except for the pure Ba0.6Sr0.4TiO3 specimen at room temperature. The Co0.8Cu0.2Fe2O4 shows better magnetic properties and the performance of magnetization decreases with the decrease of Ba0.6Sr0.4TiO3; meanwhile, the impurity phase and inhomogeneous structure have certain influences on the magnetic properties. [ABSTRACT FROM AUTHOR]

In the present work, Ni0.5Zn0.5Fe2O4/Pb0.8Zr0.2TiO3 nanocomposite with different molar ratio (1: 2, 1: 3, 1: 5, 1: 7) was prepared by hydrothermal method and sol-gel method, and the effect of molar ratio on the microstructure, dielectric and multiferroic properties was systematically investigated. X-ray diffraction and transmission electron microscopy analysis reveal inhomogeneous structures with isolated ferrite embedded into the ferroelectric (FE) matrix. Both the dielectric constant and the loss decrease firstly, and then increase with the increase of molar ratio, which is caused by the different microstructures and the formation of impurity phase. The dielectric resonance peak decreases firstly and then increases with increasing molar ratio, which is based on FE phase transition of Pb0.8Zr0.2TiO3 tuned by the magnetic phase. Among them, the nanocomposite with the molar ratio of 1:5 shows better FE properties and the lowest leakage current density, the saturation polarization, remnant polarization and coercive field are 3.74, 1.51 µC/cm2 and 7.93 kV/cm, respectively, at the measure frequency of 2 kHz. Unexpectedly, the magnetization first decreases and then increase with the increase of molar ratio, this abnormal behavior may be the result of the interface coupling effect between magnetic and FE phases. Also, this high sensitivity of multiferroic properties towards the molar ratio between magnetic and FE phases can be applied to the application in magnetoelectric devices. [ABSTRACT FROM AUTHOR]

In order to prepare high-performance and stable performance silicon nitride-based ceramic cutting tools, orthogonal experiment was carried out firstly to study the influence of sintering temperature and sintering aids (MgSiN 2 , Y 2 O 3 and CeO 2 ) on the densification and mechanical properties of the Si 3 N 4 materials by spark plasma sintering. The results showed that Si 3 N 4 ceramics with 5 wt%MgSiN 2 , 3 wt%Y 2 O 3 and 1 wt%CeO 2 sintering aids had the best relative density and mechanical properties at 1650 ℃. Secondly, the effects of sintering temperature on the densification, microstructure and mechanical properties of Si 3 N 4 ceramics with 5 wt%MgSiN 2 , 3 wt%Y 2 O 3 and 1 wt%CeO 2 sintering aids were studied in detail. The results showed that the relative density of Si 3 N 4 ceramics reached the maximum of 99.40 ± 0.14% at 1650 ℃, the Vickers hardness and fracture toughness were 16.53 ± 0.12 GPa and 6.89 ± 0.20 MPa m 1/2 , respectively. The grain shapes were composed of equiaxed α-Si 3 N 4 and long columnar β-Si 3 N 4 , and the transformation rate of α-Si 3 N 4 to β-Si 3 N 4 was 42.5%. Finally, the statistical distribution of the relative density, phase transformation rate and mechanical properties of Si 3 N 4 ceramics with 5 wt%MgSiN 2 , 3 wt%Y 2 O 3 and 1 wt%CeO 2 sintering aids at 1650 ℃ was investigated. It was found that the mechanical properties of silicon nitride ceramics sintered by spark plasma sintering were less dispersive, and the hardness and fracture toughness obeyed the two parameters Weibull distribution well. [ABSTRACT FROM AUTHOR]

In recent years, superheavy forgings that are manufactured from 600 t grade ingots have been applied in the latest generation of nuclear power plants to provide good safety. However, component production is pushing the limits of the current free-forging industry. Large initial grain sizes and a low strain rate are the main factors that contribute to the deformation of superheavy forgings during forging. In this study, 18Mn18Cr0.6N steel with a coarse grain structure was selected as a model material. Hot compression and hot tension tests were conducted at a strain rate of 10−4·s−1. The essential nucleation mechanism of the dynamic recrystallization involved low-angle grain boundary formation and subgrain rotation, which was independent of the original high-angle grain boundary bulging and the presence of twins. Twins were formed during the growth of dynamic recrystallization grains. The grain refinement was not obvious at 1150°C. A lowering of the deformation temperature to 1050°C resulted in a fine grain structure; however, the stress increased significantly. Crack-propagation paths included high-angle grain boundaries, twin boundaries, and the insides of grains, in that order. For superheavy forging, the ingot should have a larger height and a smaller diameter. [ABSTRACT FROM AUTHOR]

The present work developed a novel high-strength and energetic Al 2 Ti 6 Zr 2 Nb 3 Ta 3 high entropy alloy (HEA) containing a BCC/B2 coherent microstructure. The microstructural evolution of BCC/B2 with both the aging temperature (873 ∼ 1073 K) and aging time (up to 200 h) was investigated, from which it was found that the cuboidal BCC nanoparticles are coherently-precipitated into the B2 matrix in 873 K-aged state due to a moderate lattice misfit (ε ∼ - 0.76%). The increase of aging temperature could destroy the BCC/B2 coherency and accelerate the formation of brittle Zr 5 Al 3 phase. Especially, the BCC/B2 microstructure exhibits an excellent thermal stability, as evidenced by the fact that these cuboidal BCC nanoprecipitates were not coarsened obviously at 873 K with the particle size from r ∼ 10 nm in 24 h-aged state to r ∼ 20 nm in 200 h-aged state. This alloy possesses prominent mechanical properties with high yield strength at both room temperature (σ YS = 1193 MPa) and elevated temperatures (1060 MPa at 873 K and 106 MPa at 1273 K), where the high strength was discussed in light of the precipitation strengthening mechanism. Importantly, the current alloy has an ultrahigh combustion calorific capacity with a value of 10240 J·g−1, showing a great potential to be used as novel high-performance energetic structural materials. [Display omitted] • A high-strength and energetic HEA was developed with the cluster formula approach. • High-strength of alloy was realized by forming a BCC/B2 coherent microstructure. • The BCC/B2 coherent microstructure exhibits a higher thermal stability at 873 K. • The alloy has an ultrahigh combustion calorific value of 10240 J·g−1. [ABSTRACT FROM AUTHOR]

Both regular and defective onion-like carbon (OLC) nanoparticles were prepared by the arc-discharge process using hexane (C 6 H 14 ) and ethanol (C 2 H 5 OH) as carbon sources. The formation of defective sites in OLC nanoparticles is ascribed to the introduction of oxygen of ethanol. It is shown that high vacuum or using raw materials without oxygen is favorable to form regular onion-like microstructure. For defective OLC/paraffin composites, the valuable microwave-absorption areas (<−10 dB) increase with the weight fraction increasing from 20% to 50%. The further increasing of concentration (60%) will decrease greatly the microwave absorption due to the strong reflection of incident microwave induced by the high conductivity of system. The reflection loss (RL) exceeding −10 dB can be obtained for 50% defective OLC/paraffin composites in the thickness range of 1.4–3.4 mm. The large amounts of defective sites are responsible for the excellent microwave-absorption performances of defective OLC/paraffin composites. [ABSTRACT FROM AUTHOR]

The hot ductility of an 8 pct Cr roller steel was determined between 1173 K and 1473 K (900 °C and 1200 °C) at strain rates of 0.01 to 10 s through tensile testing. The fracture morphology was observed using scanning electron microscopy, and the microstructure was examined through optical microscopy and transmission electron microscopy. The dependence of the hot ductility behavior on the deformation conditions, grain size, and precipitation was analyzed. The relationship between the reduction in area and the natural logarithm of the Zener-Hollomon parameter (ln Z) was found to be a second-order polynomial. When ln Z was greater than 40 s, the hot ductility was poor and fracture was mainly caused by incompatible deformation between the grains. When ln Z was between 32 and 40 s, the hot ductility was excellent and the main fracture mechanism was void linking. When ln Z was below 32 s, the hot ductility was poor and fracture was mainly caused by grain boundary sliding. A fine grain structure is beneficial for homogenous deformation and dynamic recrystallization, which induces better hot ductility. The effect of MC carbide particles dispersed in the matrix on the hot ductility was small. The grain growth kinetics in the 8 pct Cr steel were obtained between 1373 K and 1473 K (1100 °C and 1200 °C). Finally, optimized preheating and forging procedures for 8 pct Cr steel rollers are provided. [ABSTRACT FROM AUTHOR]

TiAl alloys are ideal high-temperature structural materials for aerospace applications. However, their ductility, bending strength and machinability are poor at room temperature, thus severely limiting their practical application. In this study, carbon nanotubes (CNTs) were used as additives, and Ti–48Al–2Cr–8Nb was used as the original powder to prepare CNTs/TiAl alloys by employing spark plasma sintering. The effects of different CNT contents on the microstructure, hardness and bending strength of CNTs/TiAl alloys were investigated. The results indicated that CNTs reacted with the matrix to generate granular TiC and Ti 2 AlC reinforced phases stacked into bands at the grain boundaries, limiting grain growth. The Ti 2 AlC phase content increased with increasing CNT content. When the contents of the TiC and Ti 2 AlC phases were high, agglomeration occurred, leading to defects such as pits and cracks on the surface, which explains the weakened mechanical properties of the CNTs/TiAl alloys at room temperature. When the CNT content was 0.4 wt%, the average grain size was approximately 32 μm under the effects of fine grain strengthening and second phase strengthening. Moreover, the mechanical properties of the composite were the best at room temperature. The Vickers hardness and bending strength at room temperature were 377 HV and 879 MPa, respectively, and the compressive strength and strain were 2554 MPa and 31.86%, respectively. The fracture mode was mainly transgranular. [ABSTRACT FROM AUTHOR]

Abstract: A Sr2Fe1.5Mo0.5O6–Sm0.2Ce0.8O1.9 (SFMO–SDC) nanocomposite material has been prepared by the self-combustion method. The phase structure and morphology of the material have been characterized by means of X-ray powder diffraction (XRD) and scanning electron microscopy (SEM). These results show the coexistence of perovskite and fluorite structures within the porous microstructure which are uniformly distributed throughout the prepared samples. The electrochemical performance of the material has been investigated by electrochemical impedance spectroscopy (EIS) measurements. Using an SDC interlayer SFMO–SDC composite cathode is prepared and applied onto a standard YSZ (8% Y2O3-stabilized ZrO2) electrolyte. A low polarization resistance of the prepared sample is obtained and remarkable performance of the SFMO–SDC based IT-SOFCs is achieved. It is demonstrated that the SFMO–SDC/SDC/YSZ/NiO–YSZ fuel cell reached power densities of 2.21, 1.66, 1.16 and 0.71 W cm−2 at 800, 750, 700 and 650 °C, respectively, in humidified H2 (3 vol% H2O). [Copyright &y& Elsevier]

Abstract: Polysulfonamide fibers were treated with sulfuric acid and sodium hydroxide solution with different concentration respectively. The strength retention rate of the fibers was examined after the treatment. The morphologies of the fiber surface were characterized using scanning electron microscope and the degradation has been evaluated by FTIR. Based on the experimental results, possible corrosion mechanisms are addressed. [Copyright &y& Elsevier]

Abstract: The hot deformation behavior of a 12%Cr ultra-super-critical rotor steel was investigated in the temperature range of 900–1200°C and strain rate range of 0.01–10s−1. The processing maps of the material were derived by using dynamic materials model and Prasad instability criterion. The deformation mechanisms of different regions in the processing maps and corresponding microstructures were discussed in combination of the change in Zener–Hollomon parameter. The results showed that for 12%Cr ultra-super-critical rotor steel, the flow stress, microstructural evolution and efficiency of power dissipation are closely related to the Zener–Hollomon parameter. The lower the Zener–Hollomon parameter is, the larger the extent of flow softening becomes, the more easily the dynamic recrystallization may occur, and the bigger the dynamic recrystallization grain size is. Moreover, the higher the Zener–Hollomon parameter, the lower the power dissipation rate. Flow instability occurring under high Zener–Hollomon parameter is manifested as flow localization. During the hot tension at 1s−1, the thermoplasticity of 12%Cr ultra-super-critical rotor steel is the worst at 950°C. [Copyright &y& Elsevier]

Abstract: Hot-compression and hot-tension experiments were conducted on a Gleeble3500 thermal–mechanical simulator, and the microstructure diagram of Super304H austenitic heat-resistant stainless steel as well as its thermoplastic diagram under different deformation conditions was obtained. Based on the dynamic material model theories and Prasad instability criterion, its hot processing maps were developed. The deformation mechanisms of different regions in the maps were analyzed, and corresponding microstructures were investigated. The results show that for Super304H steel, the critical Z value, below which the complete dynamic recrystallization may occur, is about 4.23×1020. During the hot tension at 0.1 and 1s−1, the total elongation and reduction in area increased with the increase of deformation temperature ranging from 800 to 1100°C. As for the hot working of Super304H austenitic heat-resistant stainless steel, large-strain deformation can be carried out at 1100°C and at the strain rate above 0.5s−1. [Copyright &y& Elsevier]

Abstract: Continuously graded anode functional layers (CG-AFLs) were fabricated on the Ni–YSZ anode substrates by electrophoretic co-deposition (EPD) technique. The microstructure and composition of the CG-AFLs were investigated. The result showed that uniform and graded structure in AFL was obtained. The single cells were constructed on the basis of CG-AFLs, with a maximum output power density greater than 1.10Wcm−2 obtained at 800°C for the cell with 9.8μm-thick CG-AFL. Electrochemical impedance spectroscopy (EIS) indicated that the excellent cell performance was contributed to the enlargement of triple phase boundary (TPB) by adding the CG-AFL. [Copyright &y& Elsevier]

In this work, the microstructural evolution and mechanical properties of new body-centered cubic (BCC)-based Al-Ti-Zr-Nb-Ta-Mo-V refractory high-entropy alloys (RHEAs) with coherent B2 precipitation are investigated. These designed alloy ingots were solid-solutionized at 1573 K for 2 h and then aged at 873 K for 24 h, in which each treatment was followed by water quenching. It was found that there exists phase separation of BCC matrix, Ti/Zr-rich BCC1 and Nb/Ta-rich BCC2 in these alloys. Moreover, ultra-fine spherical B2 nanoparticles with a size of 3~5 nm were dispersed in BCC2 matrix. These B2 nanoparticles could be coarsened up to 25~50 nm after aging and the particle morphology also changes to a cuboidal shape due to a moderate lattice misfit (ε = 0.7~2.0%). Also, Zr5Al3 phase could coexist with the B2 phase, where the difference between them is that the Ti element is enriched in B2 phase, rather than in Zr5Al3. Among them, the solutionized Al2Ti5Zr4Nb2.5Ta2.5 RHEAs exhibit good compressive mechanical property with a high yield strength of 1240 MPa and a large plasticity, which is mainly attributed to the coherent precipitation in the BCC matrix. [ABSTRACT FROM AUTHOR]

The WC-Co/(Ti, W)C graded cemented carbide was prepared by spark plasma sintering. The substrate is WC-8Co, and the hard layer is (Ti, W)C solid-solution. The effects of sintering temperature and holding time on the microstructure and properties of graded cemented carbide were analyzed. The hard layer is mainly formed by dissolving WC in the Co-phase and then by solid-solution reaction with TiC. As the sintering temperature increases, the migration rate of WC increases. When the holding time is 5 min, the thickness and the W content of the (Ti, W)C solid-solution hard layer increases with the increasing of sintering temperature. The thickness of the (Ti, W)C solid-solution can reach 51 ± 2 μm at the sintering temperature of 1700 °C for the holding time of 5 min. The hardness of hard layer surface increases first and then decreases with the increasing of sintering temperature. The Vickers hardness is the highest at 1600 °C, which can reach HV 0.2 21.53GPa. As the holding time increases, the thickness of the solid-solution hard layer increases, but the rate of growth decreases. As the thickness increases, the difference in the W element concentration between the solid-solutions of the same pitch decreases along the layer depth direction, and W element concentration in the entire hard layer increases. The oxidation behavior of graded cemented carbide at 400 °C and 600 °C was investigated. The (Ti, W)C hard layer has superior oxidation resistance relative to the WC-Co substrate. • A new method for fabricating WC-based graded cemented carbide. The hard layer on the surface is (Ti, W)C solid-solution. • At the sintering temperature of 1500 °C, Co-phase can migrate away from the WC-Co system to (Ti, W)C hard layer. • (Ti, W)C hard layer have excellent hardness and oxidation resistance compared to WC-Co substrate. • The thickness and grain size of (Ti, W)C hard layer can controlled by sintering temperature and holding time. [ABSTRACT FROM AUTHOR]

The n-SiC (nanometer SiC) is added to be the additive in order to improve the mechanical performance of Si3N4 ceramics. A microwave sintered the ceramics at different temperature and holding times. The results shows that the Si3N4/n-SiC ceramics (85 wt% Si3N4 + 5 wt% n-SiC + 5 wt% Al2O3 + 5 wt% Y2O3) have the best mechanical properties at 1600 °C, which is beneficial to the densification and β-Si3N4 phase formation for 10 min: the density, hardness, and fracture toughness were 97.1%, 14.44 GPa, and 7.77 MPa·m1/2, which increased by 2.8%, 7.0%, and 13.1%, respectively, when compared with the ceramics (90 wt% Si3N4 + 5 wt% Al2O3 + 5 wt% Y2O3). [ABSTRACT FROM AUTHOR]

In this work, Ti‐48Al‐2Cr‐8Nb alloy is sintered via spark plasma sintering with pre‐alloyed powders prepared by the atomized method. The densification mechanism and microstructure evolution of the spark plasma sintered Ti‐48Al‐2Cr‐8Nb alloy are analyzed. The sintering process is divided into two stages of densification and microstructure transformation. First, the densification mechanism of the powder materials at different sintering temperatures is investigated. At the beginning of the sintering process, the powder particles are closely rearranged under pressure. In the middle of the sintering process, the plastic deformation of the powder particles and the material migration between the adjacent particles promote the densification into the high‐speed stage. In the late stages of sintering, the unique equilibrium phase transition of the TiAl alloy allows the densification to be completed quickly. Additionally, the formation process and phase transition mechanism of the near gamma structure, the duplex structure, the full‐lamellar structure, and spherical structure in Ti‐48Al‐2Cr‐8Nb alloy are systematically studied. [ABSTRACT FROM AUTHOR]

Silicon nitride (Si3N4) based ceramic tools exhibit good machinability in cutting materials such as gray cast iron, ductile iron, malleable cast iron, and superalloys due to excellent high-temperature mechanical properties. In this paper, high-performance Si3N4-based ceramic tools containing tungsten carbide (WC) and cobalt (Co) were studied. Effects of the WC content and Co content on mechanical properties and a microstructure of Si3N4-based ceramic materials were analyzed. Results showed that Si3N4-based ceramic material containing 10 wt % WC and 1 wt % Co had the best comprehensive mechanical properties at a sintering temperature of 1650 °C and holding time of 6 min, achieving Vickers hardness, fracture toughness, and room temperature bending strength of 16.96 GPa, 7.26 MPa·m1/2, and 1132 MPa, respectively. The microstructure of Si3N4-based ceramic tool material is uniform without obvious abnormal growth. The Si3N4-based ceramic tool was mainly composed of α-Si3N4, β-Si3N4, and WC phases. [ABSTRACT FROM AUTHOR]

(1 − x)BaTiO3–xBiAlO3 relaxor ferroelectric ceramics were prepared by the conventional sintering (CS) and the microwave sintering (MWS) methods, respectively. The microstructure, the dielectric properties, the relaxation characteristic, the ferroelectric and the energy storage properties were investigated in detail. The results show that a single perovskite phase exists in ceramic samples sintered by CS and MWS. The addition of BiAlO3 into BaTiO3 and the MWS method result in the reduction of the grain size and the porosity of BaTiO3 ceramic. This leads to the enhanced diffuse transition and frequency dispersion. The dielectric constant and loss decrease with increasing the BiAlO3 content, and the temperature and the frequency stabilities are enhanced by introducing BiAlO3 into BaTiO3. The remnant polarization (Pr) increases initially and then decreases with the increase of BiAlO3 content, the maximum values of Pr (9.5 μC/cm2 for CS and 7.27 μC/cm2 for MWS) are obtained at x = 0.02. The addition of BiAlO3 can elevate the variation of polarization ΔP (Pmax − Pr), its maximum values (12.56 μC/cm2 for CS ceramic and 12.2 μC/cm2 for MWS ceramic) are acquired at x = 0.04, 0.08, respectively. The energy storage properties indicate that the energy storage density (Wrec) increases, while the energy storage efficiency (η) firstly decreases and then increases with the increase of x. [ABSTRACT FROM AUTHOR]

Superheavy forgings are increasingly used in the nuclear industry. The strain rate is extremely low during hot forging due to the huge size of the superheavy forging; in fact, the surface temperature of the forging decreases obviously during each deformation step. Hot-deformation behavior differs from that of isothermal deformation. In this study, 18Mn18Cr0.6N steel was selected as a model material. Hot-compression tests were conducted using a Gleeble 3800 simulator at a strain rate of 10−4 s−1 and continuous cooling rates of 0.0125 Ks−1 and 0.025 Ks−1. The microstructure was observed using electron backscatter diffraction analysis and transmission electron microscopy. The flow stress increased with increasing strain: the higher the cooling rate, the higher was the hardening rate. Continuous cooling inhibited dynamic recrystallization by delaying its nucleation. The subgrain/cell size increased linearly with increasing final temperature of deformation in the temperature range 1273 to 1448 K. An intense <001> texture formed in 0.8-strained specimens and the matrix exhibited a low Taylor factor orientation. Most dislocations were separately distributed in subgrains and did not entangle with each other or with the subgrain boundary. Dislocation arrays transferred easily through boundaries and dislocation accumulation at boundaries was weak. This study contributes to understanding the hot-forging process of superheavy forgings. [ABSTRACT FROM AUTHOR]

3D printing of metallic microstructures is highly desirable for many practical applications such as microelectronics, terahertz photonics, microelectromechanical systems, and electrochemisty. Unfortunately, high resolution microprinting of 3D metal structures with widely tunable feature sizes, high conductivities, high melting points, and highly smooth surfaces remains challenging for current microfabrication technologies. Herein, 3D printing of metallic microstructures of feature sizes ranging from ≈10 to ≈200 μm by combining femtosecond laser micromachining of 3D glass microchannels and microfluidic electroless plating is demonstrated. The proposed technique allows for producing 3D metallic structures of almost arbitrary geometries embedded in glass since the continuous flow of the plating solution enables controllable deposition of metal films inside the through microchannels. Moreover, freestanding metallic 3D microstructures are fabricated by removing the glass matrix with a wet chemical etching. As a nonthermal processing, the surface roughness of the fabricated metallic structures is as low as ≈20 nm. The 3D microstructures can be made of either silver or copper covered with a thin layer of silver, which are shown to have a high conductivity. As a proof‐of‐concept demonstration, a 3D metal scaffold structure with a size of ≈5 × 5 × 2 mm3 is printed. Glass‐channel molding assisted 3D printing of free‐standing metal microstructures is demonstrated using femtosecond laser internal processing and microfluidic electroless plating. Using this approach, 3D metal microstructures with widely tunable feature sizes (10–200 µm), flexible configurations, high conductivity, and high surface smoothness can be printed. [ABSTRACT FROM AUTHOR]

Zn-Ni-Al2O3 composite coatings with different Ni contents were fabricated by low-pressure cold spray (LPCS) technology. The effects of the Ni content on the microstructural and mechanical properties of the coatings were investigated. According to X-ray diffraction patterns, the composite coatings were primarily composed of metallic-phase Zn and Ni and ceramic-phase Al2O3. The energy-dispersive spectroscopy results show that the Al2O3 content of the composite coatings gradually decreased with increasing of Ni content. The cross-sectional morphology revealed thick, dense coatings with a wave-like stacking structure. The process of depositing Zn and Ni particles and Al2O3 particles by the LPCS method was examined, and the deposition mechanism was demonstrated to be mechanical interlocking. The bond strength, micro hardness and friction coefficient of the coatings did not obviously change when the Ni content varied. The presence of Al2O3 and Ni increased the wear resistance of the composite coatings, which was higher than that of pure Zn coatings, and the wear mechanism was abrasive and adhesive wear. [ABSTRACT FROM AUTHOR]

The advantages of stainless steel/carbon steel clad plates include corrosion resistance, low cost, good ductility, etc., which are usually used as chief load-bearing components. But the low bonding strength and bearing capacity of clad plates severely limit their wide application. 316 L/Q235B/ 316 L clad plates are prepared by the longitudinal corrugated rolling (LCR) method. The deformation characteristic, mechanical property and microstructure evolution of the LCR plates are investigated by combining finite element method (FEM) and experiments. The effects of LCR and traditional flat rolling (FR) processes on the performance of clad plates are compared and analyzed. The results show that the LCR plates' shear strength is increased up to 14%, 16% and 19% at the peak, waist and trough, and the tensile and bending strengths of LCR plates are increased by 7.1% and 16.2% compared with FR plates, respectively. The grains are equiaxed at the peak and lamellar at the trough in the 316 L layer in the LCR process. The grains are equiaxed at the peak and trough of LCR plates in the Q235B layer in the LCR process. The deformation mechanisms of the LCR and FR processes are illustrated according to FEM results. The grain state and metal flow of LCR plates can be changed by the fluctuant effective strain and temperature distributions caused by the special roll shape. In the LCR process, the opposite shear stresses in the rolling direction (RD) and the transverse direction (TD) can form cross shear zones, which improves the clad plates' bonding strength. [ABSTRACT FROM AUTHOR]

[Display omitted] • The prominent soft magnetic properties are ascribed to their special coherent microstructure. • A short-time ball-milling does not change the coherent BCC/ L2 1 structure of MEA powders. • The prominent soft magnetic and high resistivity, which contributes to the excellent electromagnetic wave-absorbing properties. • Al 1.5 Co 3.5 Fe 3.5 flake powders possess the maximum effective bandwidth of 7.01 GHz with a sample thickness of 1.7 mm. Magnetic alloy powders show a great superiority in the balance of permittivity and permeability for electromagnetic (EM) wave-absorption. However, it is necessary to enhance their effective absorption bandwidth (Δf) and impedance matching due to their insufficient soft-magnetic properties and low resistivity, which would be solved by high/medium-entropy alloys (HEAs/MEAs). In this report, we designed Al 1.5 Co 3.5 Fe 3.5 and Al 1.5 Co 3 Fe 3 Cr MEAs with prominent soft-magnetic property and high resistivity. It is contributed to the special coherent microstructure with ultrafine magnetic body-centered-cubic nanoprecipitates uniformly-distributed into the L2 1 matrix, which could not be changed by ball-milling. Thus, alloy powders possess excellent EM properties, as evidenced by the minimum reflection loss of −42.2 dB at 14.52 GHz and the largest Δf = 7.01 GHz in 5 h-milled Al 1.5 Co 3.5 Fe 3.5 , better than existing alloy powders. The wave-absorbing behavior of MEA powders was discussed from both permittivity and permeability. The current findings offer a useful design strategy for developing high-performance absorbers. [ABSTRACT FROM AUTHOR]

One kind of Al 2 O 3 /Ti(C,N) micro-nano-composite ceramic tool material with acceptable properties was prepared by microwave sintering. Effects of sintering temperature and holding time on densification, mechanical properties and microstructure were studied. The optimal relative density, fracture toughness and Vickers hardness were 98.4±0.30, 6.72±0.28 MPa m 1/2 and 18.42±0.59 GPa, respectively, which were obtained at 1550 °C for 10 min. Compared to the conventional sintering, the sintering temperature and holding time of microwave sintering were reduced by 14% and 89%, respectively. The microwave sintering made the sizes of some particles keep in nano-scale, which leaded to the formation of intragranular structures. The residual stress in the intragranular structures increased the ratio of grain boundary toughness to grain toughness of matrix ( K cb / K cg ), and thus the micro-Al 2 O 3 grains were more inclined to transgranular fracture. [ABSTRACT FROM AUTHOR]

The present work developed a novel low-density (7.71 g/cm3) and high-strength Fe-Ni-base high-entropy superalloy with a composition of Fe-33.2Ni-13.4Co-13.8Cr -3.1Al-2.2Ti-1.1Nb-1.7Mo-0.03C-0.015B-0.03Zr (wt. %), which contains spherical γ' nanoparticles coherently-precipitated into FCC-γ matrix. These γ' nanoprecipitates were coarsened slowly at 1023 K with the particle size being ∼40 nm after 1000 h-aging, showing a great microstructural stability due to lower lattice misfit between γ/γ'. Thus, this superalloy exhibits excellent mechanical properties at room and high temperatures, as evidenced by the yield strength being 743 MPa at 1023 K. The involved strengthening mechanisms were further discussed. Moreover, it has a superior creep-resistant property with the rupture lifetime of 61.5 h under 450 MPa/973 K. Also, it possesses a prominent strain-hardening capacity due to the presence of abundant stacking faults in γ' nanoprecipitates. The current work opens a new way to design low-density superalloys with stable coherent microstructure at high temperatures. [Display omitted] [ABSTRACT FROM AUTHOR]

Rice bran as a by-product of rice processing can be used to produce oil. Aqueous enzymatic extraction (AEE) of rice bran oil (RBO) was performed in this study. The physicochemical properties, fatty acid compositions, bioactive compounds, antioxidant activity and thermal behavior of AEE-extracted oil (AEEO) were evaluated and compared with those of Soxhlet-extracted oil (SEO). It was found that iodine value and saponification value in the AEEO were higher than the SEO. AEEO with lower acid value and peroxide value was considered to be a high quality. The contents of wax and phospholipid in AEEO were lower, which could simplify the refining steps. Additionally, AEEO exhibited a higher content of unsaturated fatty acids (76.31%), sum of tocopherols and tocotrienols (1004 mg/kg), sterols (7749 mg/100 g), squalene (2962 mg/kg), oryzanol (2.43 g/100 g). The antioxidant activity of AEEO (EC50 = 5.52 mg/mL) was better than that of SEO (EC50 = 8.66 mg/mL). Moreover, AEEO was found to have lower crystallization and melting points. Scanning electron microscope (SEM) results showed the destruction of cell walls and the decrease of substances in the cell by AEE. Overall, the present results showed the improvement in the quality of the AEEO for green extraction of RBO. • AEE was a promising approach for green extraction of RBO. • AEEO showed higher contents of bioactive compounds. • AEEO presented no phospholipids and lower content of wax. • The antioxidant activity of AEEO was better than that of SEO. • AEEO exhibited lower crystallization and melting points. [ABSTRACT FROM AUTHOR]

Mn 0.5 Mg 0.5 Fe 2 O 4 /Ba 0.8 Sr 0.2 Ti 0.9 Zr 0.1 O 3 composite ceramics were prepared by sol-gel method and the effects of molar ratio (3:1, 2:1, 1:1, 1:2, 1:3) between the magnetic and ferroelectric phases on the microstructure, dielectric, ferroelectric and magnetic properties have been comparatively investigated. The results indicate that the obtained composite ceramics show bi-phase structure, without other apparent impurities. The surface is relatively uniform except for some pores, and the grain size of all the samples is near 1 μm. The dielectric constant shows decreasing trend with the molar ratio while the loss presents the opposite behavior. Only one relaxation peak can be observed when the molar ratio is less than 1:1, but two peaks are found when the molar ratio exceeds 1:1. The height of the peak decreases with the frequency and molar ratio while the position shifts to higher temperature range with the molar ratio. The dielectric loss increases sharply with the temperature and it is amounts to several thousand when the temperature is lager than 300 °C in the lower molar ratios. Both the resident polarization and coercive electric field increase with the measured voltage while they decrease with the frequency. The leakage current decreases with the molar ratio due to the lower conductivity of Mn 0.5 Mg 0.5 Fe 2 O 4. The magnetization shows a monotonic variation behavior with the molar ratio, indicating the strong interface interaction between the two phases. The maximal ME coupling coefficient is about 800 mV/(cm.Oe) for the sample 3:1 due to the stronger magnetic properties. • Mn 0.5 Mg 0.5 Fe 2 O 4 /Ba 0.8 Sr 0.2 Ti 0.9 Zr 0.1 O 3 composites were prepared by sol-gel method. • The obtained composite ceramics show bi-phase structure, with the grain size of all the samples is near 1 mm. • Relaxation peaks can be observed in the temperature dependence of dielectric constant. • The magnetization shows abnormal behavior due to the strong interface interaction between the two phases. [ABSTRACT FROM AUTHOR]

Abstract Si 3 N 4 -based composite ceramic tool materials were fabricated by microwave sintering. The effects of Ni and Co on the mechanical properties, phase transformation and microstructure of the Si 3 N 4 -based composites were studied, and the toughening mechanism was analyzed. The optimum comprehensive mechanical properties with the relative density of 97.15 ± 0.2%, Vickers hardness of 17.28 ± 0.17 GPa and fracture toughness of 6.59 ± 0.12 MPa m1/2 were obtained at 1650 ℃ when the content of Ni was 2 wt%. Ni can promote the formation of grains with high aspect ratio more effectively than Co, but the hardening effect of Co was higher than Ni. Both of two metals would restrain the phase transformation of Si 3 N 4 from α phase to β phase. The main toughening mechanism was the combined action of pulling-out of β-Si 3 N 4 columnar crystals, crack bridging by columnar crystals and crack deflection. [ABSTRACT FROM AUTHOR]

Si 3 N 4 -based composite ceramic tool materials with (W,Ti)C as particle reinforced phase were fabricated by microwave sintering. The effects of the fraction of (W,Ti)C and sintering temperature on the mechanical properties, phase transformation and microstructure of Si 3 N 4 -based ceramics were investigated. The frictional characteristics of the microwave sintered Si 3 N 4 -based ceramics were also studied. The results showed that the (W,Ti)C would hinder the densification and phase transformation of Si 3 N 4 ceramics, while it enhanced the aspect-ratio of β-Si 3 N 4 which promoted the mechanical properties. The Si 3 N 4 -based composite ceramics reinforced by 15 wt% (W,Ti)C sintered at 1600 °C for 10 min by microwave sintering exhibited the optimum mechanical properties. Its relative density, Vickers hardness and fracture toughness were 95.73 ± 0.21%, 15.92 ± 0.09 GPa and 7.01 ± 0.14 MPa m 1/2 , respectively. Compared to the monolithic Si 3 N 4 ceramics by microwave sintering, the sintering temperature decreased 100 °C，the Vickers hardness and fracture toughness were enhanced by 6.7% and 8.9%, respectively. The friction coefficient and wear rate of the Si 3 N 4 /(W,Ti)C sliding against the bearing steel increased initially and then decreased with the increase of the mass fraction of (W,Ti)C., and the friction coefficient and wear rate reached the minimum value while the fraction of (W,Ti)C was 15 wt%. [ABSTRACT FROM AUTHOR]