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Chromium nitride (CrN) ceramics were sintered at various temperatures by plasma activated sintering, and their thermoelectric properties were explored. The formation of Cr 2 N phase can be suppressed by venting N 2 gas into the chamber before sintering and increasing the sintering temperature to accelerate the densification process. Sintering temperature significantly impacted the thermoelectric properties. Higher sintering temperature led to an increase in the N content, reducing the electrical and thermal conductivity, and increasing the Seebeck coefficient. The single-phased CrN ceramic sintered at 1573 K exhibited excellent thermoelectric performance with a maximum power factor of 1002 μW·m−1·K−2, a thermal conductivity of 4.78 W·m−1·K−1, and a zT value of 0.20 at 973 K. Furthermore, this CrN ceramic also exhibited a high relative density of 97 % and a hardness of ∼11.9 GPa. Enhanced high-temperature thermoelectric properties and excellent mechanical properties make CrN ceramics suitable for thermoelectric applications in extreme environments. [ABSTRACT FROM AUTHOR]

Chromium nitride (CrN) is a promising structural and protective material with excellent mechanical properties and good wear and corrosion resistance. However, CrN tends to decompose into Cr 2 N at high temperatures, which makes the fabrication of single-phase and dense bulk CrN ceramics extremely challenging. In this work, a novel routine, ammonolysis followed by plasma activated sintering (PAS), has been proposed to fabricate single-phase and dense CrN ceramics. Single-phase CrN ceramics with a relative density of 98.2 %, higher than those in previous work, were successfully fabricated at the sintering temperature of 1200 °C. Its hardness and fracture toughness reach 11.9 GPa and 3.98 MPa m1/2, respectively, better than other CrN ceramics in literature. It exhibits friction coefficients of 0.75 to 0.45 and wear rates of 2.31 × 10−6 to 3.06 × 10−5 mm3 N−1 m−1 at the friction loads of 5–20 N. The successful fabrication of single-phase CrN ceramics can be attributed to the combined effect of the sintering atmosphere of extra N 2 and rapid densification. During densification, N 2 injected into the furnace will be encapsulated rapidly, creating a localized high nitrogen pressure that suppresses CrN decomposition and ultimately results in single-phase and dense CrN ceramic bulk. [ABSTRACT FROM AUTHOR]

AlN ceramics were prepared by plasma activation sintering (PAS) with compound additives yttrium acetylacetonate (Y(acac)3) and melamine (C3H6N6). The effects of compound additives on the microstructure, density, and thermal properties of AlN ceramic were studied. Y(acac)3 and C3H6N6 can form Y2O3, residual organic carbon and reducing gas during the heating process, which improves the AlN sintering performance at a temperature of 1 700 °C and the bulk thermal conductivity. When the content of Y(acac)3 is 10 wt% and C3H6N6 is 3 wt%, the thermal conductivity of AlN ceramics is 105.6 W/(m·K), which is much higher than that of AlN ceramics with Y2O3 under the same sintering conditions. This work provides theoretical reference for the preparation of high-performance AlN ceramic. [ABSTRACT FROM AUTHOR]

AgSTe based materials have recently been identified as promising thermoelectric materials that have favorable properties at room temperature. They are usually obtained by conventional processes involving melting, annealing, and sintering, which incur significant energy and time expenditures. The present investigation involved the synthesis of Ag 20 S 7 Te 3 compounds by a fast non-equilibrium methodology, i.e., plasma activated sintering from raw elemental powders. The monoclinic Ag 20 S 7 Te 3 phase crystal was successfully formed at a temperature of 673 K, accompanied by the presence of a secondary monoclinic phase, Ag 2 S. The Ag 20 S 7 Te 3 phase predominated in the monoclinic form, constituting a significant percentage at temperature of 873 K. Furthermore, the thermoelectric figure of merit (zT) of the AgSTe phase at 873 K was determined to be 0.42. The rapid sample synthesis described herein has the potential to significantly reduce the duration required for material synthesis, hence presenting a conspicuous advantage in the context of manufacturing on a wide scale. [Display omitted] • The work employed plasma-activated sintering, to synthesise Ag 20 S 7 Te 3 compounds using raw elemental powders. • The synthesis successfully produced the monoclinic Ag 20 S 7 Te 3 phase at a temperature of 873 K, combined with a secondary monoclinic phase, Ag 2 S. • The innovative approach of rapid high-temperature sintering successfully produced dense pellets, within a few minutes. • The figure of merit (zT) for the Ag 20 S 7 Te 3 at 873 K was determined to be 0.42, providing a quantitative value of the material's thermoelectric efficiency. [ABSTRACT FROM AUTHOR]

Fe doped La 2 CoMnO 6 perovskite La 2 Co (1-x) Fe x MnO 6 (abbreviated as LCF x MO, x = 0.1˜0.4) ceramics exhibiting P2 1 /n phase and dense structure with micron grains resulted from the lower sintering temperature of 930 °C were fabricated by plasma activated sintering. The Co2+/Mn4+ concentration in LCF x MO ceramics gradually increased with the increase of Fe doping, then decreased due to excessive doping, reflecting the change of order degree of B-site cations. The Co2+/Mn4+ concentration reached the highest value in LCF 0.2 MO, which proved the ascendant B-site cations ordering degree of LCF 0.2 MO. Moreover, the smaller grains resulted from rapid sintering period was also one of another cause of high order degree. It was found that the saturation magnetization was greatly enhanced by a small amount of Fe doping. Comparing to other Fe doped content of LCF x MO ceramics, the LCF 0.2 MO ceramic also had the largest saturation magnetization (57.05 emu/g). [ABSTRACT FROM AUTHOR]

Highly dense AlN–SiC composites with various SiC additions (0–50 wt-%) were fabricated at 1800°C by plasma activated sintering. The effect of SiC addition on structural, thermal and dielectric properties as well as microwave absorbing performance of the composites was investigated. The thermal conductivity decreases with increasing SiC addition, from 68.7 W (m K)−1 for 0 wt-% SiC to 19.38 W (m K)−1 for 50 wt-% SiC. On the contrary, the permittivity and dielectric loss increase gradually, from 7.6–8.5 to 22–26.7 and from 0.02–0.1 to 0.2–0.53, respectively. AlN–SiC composite with better thermal and dielectric properties in 30 wt-% SiC, whose thermal conductivity and dielectric loss are found to be 24.88 W (m K)−1 and 0.15–0.74, respectively. Furthermore, the composite exhibits microwave absorbing performance with the minimum reflection loss (RL) of −16.5 dB at 15.5 GHz and the frequency range of 2.6 GHz for RL below −10 dB (90% absorption). [ABSTRACT FROM AUTHOR]

Abstract In this work, a series of Cu x Bi 2 S 3 polycrystalline samples were successfully fabricated by vacuum melting combined with plasma activated sintering (PAS), and the effects of Cu doping on the composition, microstructure and thermoelectric properties were investigated. Cu dopant acts as donors to cause the improvement of electron concentration to increase the electrical conductivity over the whole temperature range significantly. The resulting power factor is high in spite of the decreased Seebeck coefficient, reaching 4.1–4.4 μWcm−1K−2 above 523 K, and the average power factor achieves 3.8 μWcm−1K−2. The lattice thermal conductivity is depressed because Cu doping and S vacancies contribute to the strong impedance for phonon propagation. As a consequence, a maximum ZT value of 0.62 at 723 K is obtained in the Cu 0.01 Bi 2 S 3 sample. Highlights • Cu doping makes the Bi 2 S 3 highly n-type and causes an upward movement of the Fermi level to the CBM. • Large quantity of S vacancies tends to create abundant dark nanodots. • The enhancement in power factor of Cu x Bi 2 S 3 samples is achieved. • An enhanced ZT value of 0.62 at 723 K is obtained in Cu 0.01 Bi 2 S 3 sample. [ABSTRACT FROM AUTHOR]

In this work, W/HfC composite materials were synthesized using plasma activated sintering. The influence of the sintering temperature and HfC weight fraction on the relative density, microstructure and compression strength were investigated. The results demonstrated that the sintering temperature and the HfC content significantly affected the microstructure of W/HfC composites. Moreover, the grain size of the W/HC composites decreased and the mechanical properties were improved remarkably due to the addition of HfC. The majority of HfC particles reacted with oxygen impurities to generate HfO2, which purified the grain boundaries and refined the grain size of the W matrix. The optimum content of HfC is 2 wt%, at which a high compressive strength of 1.98 GPa and a high strain of 34.7% were obtained. [ABSTRACT FROM AUTHOR]

Abstract Diamond/copper composite is considered to be one of the most promising electronic packaging materials, however, the inherently poor interfacial bonding between Cu and diamond make it difficult to obtain high thermal conductivity. In this paper diamond powder with an average particle size of 10 μm was modified with molybdenum carbide nano-coatings by magnetron sputtering and annealing process. Plasma Activated Sintering was then used to fabricate copper/diamond composites with different thickness of Mo 2 C interlayer. Field-emission scanning electron microscopy, transmission electron microscopy and X-ray diffraction were used to characterize the interlayer microstructure and phase composition of the diamond/copper composites. Differential thermal analysis, laser flash method and thermal-mechanical analysis were used to clarify the thermal properties of composites. The results indicated that diamond particles were distributed homogenously, discretely and randomly in the Cu matrix with improved interface wettability between diamond and copper by adding of Mo 2 C nano-coatings. The relative density and thermal conductivity increased with the thickening of Mo 2 C coatings, while the coefficient of thermal expansion decreased with the thickening of Mo 2 C coatings. The relative density, thermal conductivity, and coefficient of thermal expansion were 99.1%, 351 W·m−1·K−1, 9.27 × 10−6 K−1 with the Mo 2 C content of ~3.25 wt%. Highlights • Mo element has been loaded successfully on diamond powders by magnetron sputtering. • Cu-Mo 2 C dual coated diamond powders were successfully obtained. • High-density composites were obtained by low-temperature sintering. • The influence of Mo 2 C content on properties of the composites was discussed. [ABSTRACT FROM AUTHOR]

Abstract We reported an investigation of the influence of length scale on stabilization of boron carbide (B 4 C) during plasma activated sintering. In the current work, AA7075/B 4 C powders containing two types of B 4 C particles (Micro-B 4 C and Nano-B 4 C) were cryomilled for 8 h in liquid nitrogen, respectively. The characterization of as-cryomilled powders indicated that both Micro-B 4 C particles and Nano-B 4 C particles could distribute homogeneously in the matrix. AA7075/Nano-B 4 C powder have a finer particle size and grain size relative to that of the AA7075/Micro-B 4 C powder. The influence of length scale on stabilization of B 4 C particles during plasma activated sintering was investigated in details. The statistical grain diameter analysis from transmission electron microscopy observation revealed that the grain size of AA7075/Nano-B 4 C bulk (~77.4 nm) is finer relative to those of the AA7075 bulk (~193.5 nm) and AA7075/Micro-B 4 C bulk (~184.7 nm). The coupling effect of ex-situ Nano-B 4 C particles and in-situ dispersion particles contribute to the enhancement of the stabilization of the AA7075/Nano-B 4 C bulk. Graphical abstract Unlabelled Image Highlights • The grain refinement of the AA7075/B 4 C powders was conducted via cryomilling • Length scale on stabilization of B 4 C particles was investigated • The enhanced stabilization of AA7075/Nano-B 4 C was obtained [ABSTRACT FROM AUTHOR]

Oxygen content in n-type Bi 2 Te 3 -based alloys plays a crucial role in determining the thermoelectric properties. We aimed to control the residual oxygen that originated from the ball milling process; for this, sintering processes such as spark plasma sintering (SPS) and plasma activated sintering (PAS) were utilized. The reduction of oxygen content was successfully achieved with PAS, leading to improved electrical properties. With the removal of residual oxygen, the carrier concentration increased, resulting in reduced electrical resistivity. The phonon thermal conductivity was reduced due to the grain size of this sample, which was smaller than that of the hot-pressed (HP) samples. An enhanced value of the dimensionless figure of merit (ZT) of 0.83 at 473 K, an increase of 25.2% compared with that of the HP samples, was achieved. The selection of the appropriate sintering process should be considered to remove oxygen content, as well as to minimize grain growth. [ABSTRACT FROM AUTHOR]

Abstract In this paper, dual-scale Ti-6Al-4V titanium alloys were prepared by cryomilling and plasma activated sintering. The microstructure and mechanical properties of the samples with different structural organizations were investigated. The relative densities were evaluated by the drainage method. The microstructure and mechanical properties were characterized by OM, SEM, XRD, EBSD, TEM, universal testing machine and Vickers hardness test methods. The results show that the dual-scale Ti-6Al-4V titanium alloy with high strength can be prepared in a relatively short time by cryomilling and plasma activated sintering. The scale structure of the alloy is controlled by a relative amount of ball-milled powders. With the ball-milled powder content increases, the fraction of the β phase and the axial fine crystalline region is increasing. The dual-scale structure renders and the mechanical properties of the samples are more superior to the coarse crystal samples. In addition, the plastic deformation capability of the dual-scale structure is better than that of fine crystal samples. A relative density of 98.54%, the enhanced mechanical properties, including offset yield strength of 1544.19 MPa and a Vickers hardness of 427 HV were achieved, which is attributed to the different dual-scale structures. [ABSTRACT FROM AUTHOR]

Multiferroic laminated composites, (1-x)BCZT-xLCMO, consisting of Ba 0.85 Ca 0.15 Zr 0.10 Ti 0.90 O 3 (BCZT) layer and La 0.67 Ca 0.33 MnO 3 (LCMO) layer with different thickness ratios were prepared by Plasma Activated Sintering, and the effect of thickness ratio on their multiferroic properties was investigated. The SEM and TEM analyses demonstrated the high-quality interfacial bonding of BCZT layer to LCMO layer with a compact interface and semi-coherent boundary structure. The ferroelectric and ferromagnetic features confirmed that the (1-x)BCZT-xLCMO laminated composites were multiferroic in nature. Our results further indicated that the thickness ratio had a great influence on the multiferroic properties of the laminated composites, not only electrical and ferromagnetic properties but also magnetoelectric coupling effect. The (1-x)BCZT-xLCMO laminated composites exhibited the largest values of dielectric constant ε m  = 25097, remnant polarization P r  = 10.3 μC/cm 2 and piezoelectric coefficient d 33  = 355 pC/N. The high magnetoelectric coefficient with the maximum value of α E31  = 6.57 mV/cm·Oe was also obtained. [ABSTRACT FROM AUTHOR]

We report on an investigation of the influence of sintering temperature on microstructure and mechanical behaviors of the Al matrix composites. In this paper, the ultrafine grained AA7075/B 4 C composites was synthesized via cryomilling and one-step consolidation. X-ray diffraction (XRD) and transmission electron microscopy (TEM) were utilized for characterization of the grain size of the AA7075/B 4 C composites consolidated at various sintering temperatures. Our results indicated that the grain size increased gradually from ∼73.1 nm to ∼184.7 nm with the sintering temperature increasing from 350 °C to 450 °C. The formation of abnormal grain growth was observed in the AA7075/B 4 C composite consolidated at 500 °C B 4 C particles distributed homogenously, discretely and randomly in the Al matrix based on the observation in Field-emission scanning electron microscopy (FESEM). The porosities were found to decrease in the AA7075/B 4 C composites with the rising of sintering temperature. The Vickers hardness, compressive yield strength and fracture strength of the AA7075/B 4 C consolidated at 450 °C were 233 HV, 724.9 MPa and 834.5 MPa, respectively. The analysis of strengthening mechanisms revealed that increasing of sintering temperature resulted in the sacrifice of grain-boundary strengthening and dislocation strengthening. [ABSTRACT FROM AUTHOR]

Solid-state batteries with non-flammable inorganic solid electrolytes are one candidate to replace the currently-used liquid electrolyte. The inorganic ceramic solid electrolyte with garnet structure Li7La3Zr2O12, known as LLZO, has been developed, which has several superior advantages, such as high ionic conductivity (10-4~10-3S cm-1) at room temperature, wide electrochemical window (~6V), good chemical stability against Li metal anode. However, the total resistance of thick LLZO solid electrolyte is still too large to be applied in the industry. In order to reduce the resistance and improve the power density of LLZO solid electrolyte, ceramic membranes with micron thickness should be prepared. The sol-gel method was adopted to synthesize LLZO ultrafine precursor powders and tape-casting method is proposed to prepare LLZO green film with excellent machinability. DTA-TG was used to test thermal properties. The crystal structure, microstructure and electrochemical property of LLZO membrane electrolyte were investigated by XRD, SEM and EIS. The use of Plasma activated sintering (PAS) technology allows rapid densification of the ceramic membranes. The thickness of the ceramic membrane is about 130μm and its conductivity is 3.38×10-5 S/cm at room temperature. [ABSTRACT FROM AUTHOR]

In this paper, plasma activated sintering was used to prepare powder metallurgy TC4 titanium alloys, and the effects of the sintering process on the densification, microstructure, phase transition and mechanical properties were investigated. The densities were evaluated by a drainage method. The microstructures and mechanical properties were characterized by OM, SEM, XRD, EBSD, and TEM methods, a universal testing machine and a Vickers hardness tester. The results showed that the PAS method could significantly shorten the sintering time and reduce the sintering temperature. With an increase in the sintering temperature, the sample changed from an equiaxed microstructure with short plate-like mixed-shaped grains to a double lamellar transitional structure. This structural change led to a decrease in the plastic deformation ability and an increase in the microhardness and compression strength of the sample. A coherent relation among the secondary α grains was observed, which had both a beneficial and detrimental effect on the material properties. A relative density of 98.11% and enhanced mechanical properties including an offset yield strength of 1034.09 MPa, a tensile strength of 1028.14 MPa, a Vickers hardness of 389.7 HV, and a sectional shrinkage of 28.4% were achieved and attributed to different microstructures controlled by the PAS sintering system. [ABSTRACT FROM AUTHOR]

(Ba 0.85 Ca 0.15 )(Zr 0.10 Ti 0.90 )O 3 (BCZT) ceramics were prepared by Plasma Activated Sintering (PAS) followed by annealing, and the effect of annealing temperature on structural and electrical properties was investigated. XRD patterns and Raman spectra indicated that all the BCZT ceramics annealed at different temperatures exhibited MPB structure consisting of rhombohedral and tetragonal phases. A strong dependence of piezoelectric, dielectric and ferroelectric properties on annealing temperature was observed in the annealed BCZT ceramics. With increasing annealing temperature, the Curie temperature shifted toward lower temperature, while the activation energy of both grains and grain boundaries decreased gradually. BCZT ceramics annealed at the optimum temperature of 1400 °C exhibited the best properties of d 33 = 501 pC/N, ε m = 14000 and P r = 18.1 μC/cm 2 . [ABSTRACT FROM AUTHOR]

Highly dense La 0.67 Ca 0.33 MnO 3 (LCMO) ceramics were prepared by plasma activated sintering (PAS) and hot-pressing (HP). The comparison of structural, magnetic, and electrical transport properties of the LCMO ceramics after PAS and HP were investigated. XRD and SEM analyses confirmed that both samples exhibited orthorhombic phase with highly dense microstructure. The differences of magnetic and electrical transport properties in PAS and HP LCMO ceramics could be attributed to the different grain sizes, which have an effect on grain boundaries, domain states, Mn–O–Mn bond angles and Mn–O bond lengths. On analyzing the fitting data with several empirical equations, the conduction mechanism of the samples was found to be electron-magnon scattering in the ferromagnetic low-temperature region and variable range hopping (VRH) in the paramagnetic high-temperature region. [ABSTRACT FROM AUTHOR]

93W and Mo1 were bonded with and without Cu interlayer by plasma activated sintering. The bonding temperature was decreased greatly with Cu interlayer. Shear strength of 93W/Cu foil/Mo1 and 93W/Cu film/Mo1 were 148.4 MPa and 193.3 MPa, respectively. Elements were fully diffused at 93W/Cu and Cu/Mo1 interfaces. Fe-Ni binder in 93W alloy has a sound diffusion with Cu interlayer, and Ni enriched in diffusion interface and formed Cu-Ni alloy at the interface of the 93W/Cu film/Mo1 joint, which led to the increasing in bonding strength of joints greatly. [ABSTRACT FROM AUTHOR]

Zirconium carbide (ZrC 0.84 O 0.13 ) nanopowders were consolidated using plasma activated sintering with 0–8 wt% ZrH 2 as the sintering additive to improve the sinterability. Compared with pure ZrC sintering, ZrH 2 additive led to the higher sintering kinetics and lower sintering temperature. This improvement was attributed to the increased carbon-vacancy concentration in the non-stoichiometric ZrC in the presence of ZrH 2 additive during the sintering process. Fully dense and fine-grained ZrC ceramics (1.3 ± 0.2 μm) were achieved at 1650 °C with 6 wt.% ZrH 2 . The final product exhibited the Vicker’s hardness of 21.2 ± 1.0 GPa and fracture toughness of 2.2 ± 0.3 MPa m 1/2 . [ABSTRACT FROM AUTHOR]

Textured multiferroic Bi 5 Ti 3 FeO 15 -CoFe 2 O 4 (BTFO-CFO) ceramics were prepared via microwave hydrothermal synthesis followed by plasma activated sintering. BTFO-CFO ceramics with CFO nanoparticles distributed between the BTFO layers exhibit a high degree of texture ( f =0.8) along the c-axis crystallographic orientation, which was confirmed by a combination of XRD, SEM and TEM. BTFO-CFO composite ceramics exhibit desirable magnetic and ferroelectric properties due to the ferromagnetic phase (CFO) and textured ferroelectric phase (BTFO). The current work provides a feasible method to fabricate textured multiferroic composite ceramics. [ABSTRACT FROM AUTHOR]

Lead-free [Ba(Zr 0.2 Ti 0.8 )O 3 -x(Ba 0.7 Ca 0.3 )TiO 3 , BZT-xBCT] ceramics were prepared by Plasma Activated Sintering (PAS). The effect of composition fluctuation on structural and electrical properties of BZT-xBCT ceramics was investigated. It was found PAS can obtain compact BZT-xBCT ceramics and BZT-0.50BCT ceramic possessed a MPB structure consisting of rhombohedral and tetragonal phases. Impedance spectroscopy confirmed two contributions from grains and grain boundaries, and the ceramics showed typical characteristic of diffuse phase transition. As compared with the BZT-xBCT ceramics with the pseudo-cubic phase, PAS-ed BZT-0.50BCT ceramic exhibited better properties of d 33 = 127 pC/N, k p = 25.1%, ε r = 2614, ε m = 6655, and 2P r = 25.2 μC/cm 2 due to the existence of the MPB structure. [ABSTRACT FROM AUTHOR]

In the present study a novel bilayer composite consisting of a tough layer (AA7075) and hard layer (AA7075/B 4 C composite), was successfully synthesized using plasma activated sintering. No obvious defects such as porosity, cracks, or delamination were observed in the as-processed bilayer composite. Transmission electron microscopy results suggest that dislocation density in the vicinity of B 4 C particles is higher relative to that of the unreinforced layer, as imaged with the [011] zone axis. The precipitation behavior is significantly different in the two layers, despite identical process conditions. Moreover, no obvious precipitates free zones were observed in the interfacial region between the two layers. To provide insight into the mechanical behavior of the bilayer composites, we measured the bending strength on two different load-bearing surfaces. Our results indicate that when the AA7075/B 4 C layer was loaded under tensile conditions, the AA7075/B 4 C composite was prone to crack formation and catastrophic failure. In contrast, when the AA7075 layer was loaded in tensile, the bilayer composite achieved a notable bending strength value of 1234 ± 72 MPa, which is higher relative to that of aforementioned case (938 ± 85 MPa). Interestingly, no interfacial cracks or delamination were observed under these testing conditions. In addition, the fracture mechanisms that are active in the bilayer composites for the load bearing conditions studied were discussed in detail. [ABSTRACT FROM AUTHOR]

We reported an investigation of the influence of B 4 C contents on microstructure and mechanical behavior of AA2024/B 4 C composites. In our work, nearly full-dense AA2024/B 4 C composites with various B 4 C contents were fabricated by plasma activated sintering. Our results indicated that the B 4 C particles exhibit a network distribution in the composites with 7.5 wt % and 17.5 wt % B 4 C particles, adjacent particles of monolithic alloy are continuous or interpenetrated among the B 4 C particles in the powder boundary region. However, for the composite with 27.5 wt % B 4 C particles, the adjacent particles of monolithic alloy are interdicted due to the formation of severe aggregations. Improving the content of B 4 C particles will increase the hardness and compressive yield strength of the composites. However, the yield strength of the composite failed to be further improved when adding too much B 4 C because of the agglomeration of the reinforcements. With the content of 17.5 wt % B 4 C, the Vickers hardness and compressive yield strength of the consolidated composites were 203.2 HV and 564 MPa, respectively. In addition, quantitative analysis of the strengthening mechanisms revealed that increasing the weight fraction of the B 4 C particles results in larger augment in dislocation strengthening and load-bearing strengthening. [ABSTRACT FROM AUTHOR]

Al/SiC composites are excellent candidates to be applied in many area, however, the generation of Al 4 C 3 in Al/SiC composites result in their mechanical properties below expectation. In present work, Al matrix reinforced by SiC composites fabricated by plasma activated sintering (PAS) are investigated. Al/SiC composites synthesized in such a way can be well consolidated under 530 °C with a relative density higher than 99%. The interfacial microstructures of Al/SiC composites prepared under different temperatures are observed to analyze the sintering mechanisms. The results indicate that the oxide impurity on Al and SiC surface is firstly removed by the plasma activation. Due to the interfacial current effect and Peltier effect, local hotspots on the interface of SiC and Al cause the reaction of Al and SiC to form an Al–Si diffusion layer and Si 1-x C. Finally, the Al elements react with Si 1-x C to form Al 4 C 3. In addition, owing to PAS rapid sintering effect, high tensile strength 256 MPa is reached by different strengthening mechanisms. • Al matrix reinforced by SiC composites fabricated by plasma activated sintering (PAS) are firstly investigated. • Al/SiC composites s can be well consolidated under 530 °C with relative density higher than 99% by PAS. • The reaction of Al and SiC to form an Al–Si diffusion layer and Si 1-x C was explained based on the interfacial current effect and Peltier effect. • High tensile strength 256 MPa of Al/SiC composites prepared by PAS is reached by different strengthening mechanism. [ABSTRACT FROM AUTHOR]

Lead-free Ba 0.85 Ca 0.15 Zr 0.10 Ti 0.90 O 3 (BCZT) ceramics were prepared by Plasma Activated Sintering (PAS). The influence of PAS sintering temperature on the crystalline phase, microstructure, and, dielectric and ferroelectric properties of BCZT ceramics were studied. The phase structure of BCZT ceramics first changed from rhombohedral phase to the coexistence of rhombohedral and tetragonal phases and then to tetragonal phase as the sintering temperature increased. Microstructural characterization of BCZT ceramics indicated that PAS can obtain a compact microstructure at lower temperatures of 1150–1300 °C compared with that from common pressureless sintering. The BCZT ceramics showed different degrees of diffuseness with increased temperature, and the diffuseness exponents C are all approximately on the order of 10 5 °C. The dielectric and ferroelectric properties of BCZT ceramics were enhanced with increased sintering temperature. BCZT ceramics sintered at 1250 °C exhibited optimum properties of room-temperature ε r =2863, ε m =6650, and 2P r =25.24 μC/cm 2 , resulting from the relatively higher tetragonal phase content of the MPB between tetragonal and rhombohedral phases together with a compact microstructure. [ABSTRACT FROM AUTHOR]

WC-Co cemented carbides were rapidly diffusion bonded to 40Cr steels with pure Ni as interlayers by utilizing plasma activated sintering (PAS). The bonding was carried out at 750 °C for 13 min under a pressure of 40 MPa. It was found that the roughness of the initial surfaces still plays an important effect on the microstructure and mechanical behavior of the joints diffusion bonded by PAS irrespective of the electric current applied during bonding. The adoption of smoother original surfaces was significantly favorable to eliminate the interfacial interstices and microvoids. Correspondingly, the shear strength of the diffusion bonded joints increased with decreasing surface roughness. Additionally, the effect of interlayer thickness on the shear strength of the joints was also evaluated, and the results showed that the strength decreased sharply when thicker interlayer was employed. A maximum value of shear strength, 293.07 MPa, was obtained when the original surfaces was ground with P1200 grit SiC paper and at the same time 50 µm thick interlayer was used. In this case, the fracture initiated and run predominantly along the bonding interfaces instead of in the WC-Co substrate. [ABSTRACT FROM AUTHOR]

Ultra-fine hafnium carbide (HfC) powders were synthesized using a novel method combining liquid precursor conversion and plasma activated sintering (PAS). Solution-based processing was used to achieve a fine-scale mixing of the reactants, and further treatment by PAS allowed fast formation of HfC. We investigated the effect of the type of acid used during the liquid precursor conversion on the synthesized powders, where mixtures were prepared using salicylic acid, citric acid, or a combination of these. The results show that pure HfC powders (with an average particle sizes of 350 nm) were obtained at a relatively low temperature (1550 °C) using a HfOCl 2 ·8H 2 O precursor with the mixed acids. The oxygen content of the synthesized powders was only 0.97 wt%. The type of acid had a significant effect on the synthesis product. When using only citric acid, the temperature required to produce pure hafnium carbide increased to 1700 °C. In the case of a salicylic acid precursor, pure HfC was not obtained, even at a synthesis temperature of 1700 °C. [ABSTRACT FROM AUTHOR]

A novel chemical technique combined with unique plasma activated sintering (PAS) was utilized to prepare consolidated copper matrix composites (CMCs) by adding Cu-SnO-rGO layered micro powders as reinforced fillers into Cu matrix. The repeating Cu-SnO-rGO structure was composed of inner dispersed reduced graphene oxide (rGO), SnO as intermedia and outer Cu coating. SnO was introduced to the surface of rGO sheets in order to prevent the graphene aggregation with SnO serving as spacer and to provide enough active sites for subsequent Cu deposition. This process can guarantee rGO sheets to sufficiently disperse and Cu nanoparticles to tightly and uniformly anchor on each layer of rGO by means of the SnO active sites as well as strictly control the reduction speed of Cu. The complete cover of Cu nanoparticles on rGO sheets thoroughly avoids direct contact among rGO layers. Hence, the repeating structure can simultaneously solve the wettability problem between rGO and Cu matrix as well as improve the bonding strength between rGO and Cu matrix at the well-bonded Cu-SnO-rGO interface. The isolated rGO can effectively hinder the glide of dislocation at Cu-rGO interface and support the applied loads. Finally, the compressive strength of CMCs was enhanced when the strengthening efficiency reached up to 41. [ABSTRACT FROM AUTHOR]

We report on a study on the influence of Plasma activated sintering (PAS) parameters on the microstructure and mechanical properties of aluminum matrix composites (AMCs). In this paper a commercial Al alloy (7075) reinforced with 7.5 wt.% B 4 C were synthesized using PAS. Specifically, we studied the influence of temperature, in the range of 450 °C to 540 °C, and holding time on the densification behavior of Al-7075/B 4 C composites. Moreover, the influence of residual porosity on mechanical properties of Al-7075/B 4 C composites was established via measurements of Vickers hardness, bending and compressive strength. High mechanical properties including Vickers hardness 181.6 HV, bending strength 1100.3 MPa, high compression yield strength 878.0 MPa and fracture strength 469.3 MPa of the consolidated Al-7075/B 4 C composite sintered at 530 °C for 3 min were achieved and attributed to a fully dense microstructure and a strong interface between matrix and reinforcement. [ABSTRACT FROM AUTHOR]

High-performance thermoelectric BiCuSeO ceramics have been prepared by solid state reaction combined with plasma activated sintering (PAS). Phase compositional and microstructural studies indicate composites having refined grain sizes (600-700 nm) with nanostructured ZnSe secondary phase. Our results reveal that Zn doping can lead to a large change in the carrier concentration (from 0.036 × 1020 cm−3 to 1.50 × 1020 cm−3), thus resulting in an increased electrical conductivity of three orders of magnitude at room temperature. The highest power factor of 4.21 µWcm−1K−2 at 873 K has been achieved by 10% Zn doping. On the other hand, the lattice thermal conductivity has been suppressed significantly due to refined grains, point defects and the nano-inclusions of ZnSe phase. The dimensionless figure of merit ( ZT) could reach up to 0.90 at 873 K in the BiCuSeO oxyselenides by the 10% Zn doping, which makes Zn-doped BiCuSeO to be a promising candidate for thermoelectric applications. [ABSTRACT FROM AUTHOR]

Highlights: [•] Al-7075/B4C composites were fabricated by plasma activated sintering. [•] The high mechanical properties of Al-7075/B4C composites were measured. [•] A strong interfacial bonding of Al-7075/B4C composites was investigated. [ABSTRACT FROM AUTHOR]

Abstract: Fully dense bulk tantalum compacts of two different nitrogen contents with gradient structure within an individual particle were successfully synthesized by means of plasma activated sintering (PAS). Annealing of the compacts induces disappearing of the gradient structure due to the promoted diffusion of nitrogen in Ta matrix accompanied by enhancement of the strength. For the compact with low nitrogen content of 0.09wt.%, a drop in ductility was observed. While for the compact with nitrogen content of 0.215wt.%, improved strength was obtained without sacrificing its ductility. [Copyright &y& Elsevier]

Abstract: Rutile-phase TiO2 ceramic was rapidly fabricated by plasma activated sintering (PAS) at 650–850°C for 3min under 30MPa. The temperature and frequency dependences of the dielectric properties (dielectric constant and dielectric loss) for the dense TiO2 ceramic were investigated, and the dielectric behavior was briefly discussed. It was demonstrated that extraordinarily high dielectric constant (2–5×104) was observed in the whole experimental ranges of −160 to 200°C and 1kHz–1MHz. Moreover, the dielectric loss kept a relatively normal level, however, its temperature and frequency dependences were markedly different with those of the rutile-phase TiO2 preforms. The unusual dielectric behavior was related with the particular dielectric polarizations of the TiO2 ceramic and its dominant form of loss under different conditions. [Copyright &y& Elsevier]

Abstract: Eu2+-doped AlN phosphors were prepared by plasma activated sintering at 1600–1850°C for 5min and using AlN, SiC, and Eu2O3 as starting materials. The effect of Si concentration on the phase purity and photoluminescence (PL) properties of the prepared phosphors was investigated. The doping of Si from SiC favored the formation of pure wurtzite-type AlN phase and doping of Eu2+ into the AlN lattice. The prepared AlN:Eu2+ phosphors exhibited a strong blue emission at 465nm under the excitation at 330nm when Si was doped. The highest PL intensity was achieved when the phosphors were sintered at 1800°C. [Copyright &y& Elsevier]

Abstract: Starting from elemental powder mixtures of AgSn18SbTe20 and Sn50Te50, P-type AgSn18SbTe20 and Sn50Te50 bulk thermoelectric materials were fabricated by a combined process of mechanical alloying (MA) and plasma activated sintering (PAS). It was found that SnTe compound could be easily synthesized after milling only for 1h. Prolonging the milling time, Ag and Sb atoms diffused into the lattice of the primary SnTe compound gradually and SnTe-based solid solution was formed. The electrical resistivity and Seebeck coefficient of the as-PASed samples were measured from 323K to 723K. The maximum power factor of 1.98×10−3 Wm−1 K−2 was obtained at 673K for AgSn18SbTe20 and it was higher than that of the material with similar composition from previous published literature. [Copyright &y& Elsevier]

Abstract: Disordered Fe(Al) solid solution powders with nano-grain size were fabricated by mechanical alloying, and subsequently the milled powders were consolidated by plasma activated sintering (PAS) and hot pressing (HP), respectively. The effect of the two fabrication methods on microstructure and mechanical properties of Fe3Al was investigated. Disordered Fe3Al with submicron-grain size was obtained by PAS, while ordered Fe3Al with micron-grain size was obtained by HP. Compared with ordered Fe3Al with micron-grain size by HP, disordered Fe3Al with submicron-grain size by PAS had higher hardness and toughness. Fe3AlC0.5 was precipitated in all specimens with methanol addition during mechanic alloying. The precipitation of Fe3AlC0.5 improved the hardness of Fe3Al, but was harmful to the toughness of Fe3Al. [Copyright &y& Elsevier]

Abstract: In the present work, p-type (Bi,Sb)2Te3 alloys with excess Te addition were prepared by mechanical alloying and plasma activated sintering. A preferentially orientated microstructure with the basal planes (00 l) perpendicular to the pressing direction was formed, and the orientation factors of the (00 l) planes of the Bi0.5Sb1.5Te3 and Bi0.4Sb1.6Te3 alloys were 0.12 and 0.11, respectively. Effect of excess Te content on the thermoelectric properties of the (Bi,Sb)2Te3 alloys was investigated and the figure of merit of the Bi0.4Sb1.6Te3 alloys decreased from 5.26×10−3 to 4.44×10−3 K−1 with increasing the amount of excess Te to 8wt.%, this should be ascribed to the fact that the chemical composition of the δ matrix phase displayed indifference with varying excess Te content and the presence of free Te second phase. [Copyright &y& Elsevier]

Abstract: Starting from elemental bismuth, tellurium and selenium powders, n-type Bi2Te2.85Se0.15 solid solution with fine microstructure was prepared by mechanical alloying (MA) and plasma activated sintering (PAS) in the present work. The effect of PAS process on microstructure and thermoelectric properties of the sintered samples was investigated. The sintering temperature of PAS process (683K) was 80–100K lower than that of conventional hot pressing and the whole PAS process was also greatly shortened to about 30min. A preferentially orientated microstructure with the basal planes (00 l) perpendicular to pressing direction was formed in the PASed sample and the maximum figure of merit (Z) at room temperature was 1.80×10−3 K−1. [Copyright &y& Elsevier]

Abstract: Reactant material powders of pure WO3, Al and graphite have been milled at room temperature using a high-energy ball mill. After a few kiloseconds of milling (11ks), numerous fresh surfaces of the reactant materials are created as a result of the repeated impact and shear forces which are generated by the balls. After 43ks of milling, a mechanical solid state reduction is successfully achieved between the fresh Al and WO3 particles to form a product of nanocrystalline mixture of Al2O3 and W powders. A typical mechanical solid state reaction takes place between the W particles and graphite powders to obtain fine grains of nanocrystalline WC. Towards the end-stage of ball milling (360ks), the nanocrystalline WC grains (5nm) are embedded into the fine matrix of Al2O3 to form fine nanocomposite powders (less than 1μm in diameter) of WC–32 at.% Al2O3 material with spherical-like morphology. This composite powder was then consolidated under vacuum at 1963K, with a pressure ranging from 19.6 to 38.2MPa for 0.3ks, using a plasma activated sintering method. The consolidation step does not lead to a dramatic grain growth and the compacted samples that are fully dense still maintain their unique nanocrystalline characteristics. The elastic properties and the hardness of both the consolidated samples have been investigated. A model for fabrication of new refractory nanocomposite WC/Al2O3 materials at room temperature is proposed. [Copyright &y& Elsevier]

In this study, nanocrystalline NiAl intermetallic compound was obtained by mechanical alloying and PAS (plasma activated sintering method). Nanocrystalline NiAl powder was fabricated after 30 hr of milling with 2 wt.% stearic acid added as a PCA (process control agent) to the Ni-50at%Al composition. The grain size of the nanocrystalline NiAl powder was about 10 nm. Nanocrystalline NiAl powder was consolidated at 1000°C, 1100°C, 1200°C and 1300°C for 2 min with 30 MPa compressive force. The surface morphology of the NiAl consolidated at 1300°C was very regular and dense, above 96% of theoretical density (5.9 g/cm3). Al4C3 was observed in the NiAl consolidated at 1300°C by TEM analysis. It is thought that the carbons came from the stearic acid during the MA process and the graphite mold during the PAS process. The grain size of the NiAl consolidated at 1300°C did not increase but the grain shape became flat due to compressive force. [ABSTRACT FROM AUTHOR]