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NASICON (Na Super Ionic CONductor) type materials are an important class of solid-state electrolytes due to their high ionic conductivity along with decent chemical and electrochemical stability. In this study, a medium-entropy Li 1.5 Zr 1.0 Sn 0.5 Al 0.5 (PO 4) 3 (LZSAP) ceramic electrolyte was prepared via a solid-state synthesis method. Rietveld refinement confirmed the rhombohedral structure of the conventionally sintered sample (LZSAP-CS) at 1000 °C. The spark plasma sintering (SPS) technique was used for the densification of the pellet and resulted in ∼2.64 times higher room temperature conductivity (∼4.42 × 10−5 S cm−1) than that of the LZSAP-CS. The activation energy, calculated in the 30–100 °C range, decreased from 0.37 ± 0.01 eV for LZSAP-CS to 0.31 ± 0.01 eV for spark plasma sintered LZSAP pellet. The transference number of Li+ was ∼0.98, indicating that Li+ is the predominant charge carrier in this electrolyte. Further investigation of the lithium metal-electrolyte interface was conducted using a symmetric Li|LZSAP-SPS|Li cell configuration, demonstrating stability for over 500 h at 5 μA cm−2. LZSAP extends the list of suitable solid-state electrolytes for all-solid-state lithium batteries. [Display omitted] [ABSTRACT FROM AUTHOR]

This paper studied the densification, phase composition, microstructure and properties of polycrystalline La 0.6 Ce 0.3 Pr 0.1 B 6 bulks prepared by SPS. The dense specimen (98.9 % in relative density) with the average grain size of 15.46 μm has been determined to be a CsCl-type single-phase substitutional solid solution without any impurities or other secondary phases. The homogenous elemental distributions of La, Ce and Pr have been confirmed by both microscale and nanoscale. The room temperature (RT) Vickers hardness (H v), indentation fracture toughness (K IC) and flexure strength of the dense specimen have been measured to be 23.0 GPa, 2.04 MPa m1/2 and 305.1 MPa, respectively. The Berkovich hardness (H B) and elastic modulus (E) of the dense specimen have been measured to be 30.0 GPa and 376.0 GPa, respectively, by nanoindentation tests at a maximum load of 40 mN. In comparison with the polycrystalline LaB 6 bulk, the lower work function Φ of 2.64 eV evaluated by UPS and the larger thermionic emission current densities measured at the same operating condition suggest that the polycrystalline La 0.6 Ce 0.3 Pr 0.1 B 6 bulk is a superior-performance thermionic cathode material. [ABSTRACT FROM AUTHOR]

Transparent Er-doped Y 2 O 3 ceramics were fabricated using the spark plasma sintering (SPS) technique without any sintering additives to achieve fine-grained mid-infrared laser ceramics. The average grain size of ceramics was typically 300 nm and their in-line optical transmittance in the 2.7 μm mid-infrared range reached approximately 99 % of the theoretical value. The fluorescence spectra and lifetimes confirmed that the ceramics fabricated using SPS exhibited emission characteristics nearly identical to those fabricated using other sintering techniques. Despite the numerous pores in the ceramics and considerably reduced transmittance at an excitation wavelength of 976 nm (approximately 90 % of the theoretical value), a successful laser oscillation at 2.7 μm in the mid-infrared region was achieved. To the best of our knowledge, this is the first report on mid-infrared laser operation for fine-grained ceramics having grain sizes below 500 nm. We believe that this study will contribute to further improvements in the optical properties and development of fine-grained transparent ceramics as new laser materials, particularly non-cubic materials. [ABSTRACT FROM AUTHOR]

In this paper, the influence of antimony concentration and different sintering techniques on the structural, microstructural, and electrical properties of antimony-doped barium stannate, BaSn 1- x Sb x O 3 (BSSO, x = 0.00, 0.04, 0.06, 0.08 and 0.10) was investigated. BSSO-based ceramic samples were obtained by conventional and spark plasma sintering. The XRD analysis confirmed the single-phase, cubic BaSnO 3 lattice system in all conventionally sintered samples. Apart from the dominant cubic phase, the spark plasma sintering conditions led to the formation of a secondary phase, Ba 2 SnO 4 , in all samples. FESEM analysis revealed the presence of low angle grain boundaries (LAGBs) in BSSO samples with high antimony concentration (x = 0.08), independently of the sintering technique. However, the fraction of LAGBs is significantly higher in the BaSn 0.92 Sb 0.08 O 3 - SPS sample due to the simultaneous exposure of the conductive sample to the effects of high temperature and pressure during sintering process. These boundaries have low activation energy and allow free charge carrier transport through the grain boundary region. The high dopant concentration and the presence of large fraction of LAGBs in BaSn 0.92 Sb 0.08 O 3 - SPS sample reflected on its electrical properties through low and almost temperature-independent electrical resistivity in the temperature range of 25–150 °C. [ABSTRACT FROM AUTHOR]

In this study, x ZrB 2 -AlCoCrFeNi (x = 0,5,10,15) (wt%) based high entropy alloy (HEA) composites were prepared by Spark Plasma Sintering (SPS). The influence of ceramic particle ZrB 2 content on the densification behavior, microstructural evolution, and mechanical properties of the composites was investigated through scanning electron microscopy, X-ray diffraction, and mechanical performance testing. The results indicate that the HEA composites undergo a phase transformation, from (FCC + BCC + B2) structure to (FCC + BCC + B2+Laves) structure with the addition of ZrB 2. The incorporation of ZrB 2 facilitates the emergence of the Cr precipitate phase, and the grain size of this phase enlarges as the ZrB 2 content rises. Additionally, when the ZrB 2 content is 10 %, the maximum compressive strength reached 2071 MPa. Furthermore, at the ZrB 2 content of 15 %, the composite material achieves a maximum densification of 99.13 % and a maximum hardness of 1222.2 HV. [ABSTRACT FROM AUTHOR]

In this work, SiC–AlN–TiB 2 –VC multiphase ceramics with high bending strength were prepared via spark plasma sintering (SPS) at 1900 °C-2100 °C. The effects of interface reactions and solid solution reactions on microstructure and mechanical properties of these multiphase ceramics were investigated. Results show that the densification of multiphase ceramics is promoted effectively by the addition of Y 2 O 3. Yttrium aluminum oxide with low melting point is formed due to the reaction between Al 2 O 3 (on the surface of AlN) and Y 2 O 3 , which promotes the densification of SiC multiphase ceramics. Solid-solution reaction and interface reaction occur between matrix (SiC) and reinforcing phases (AlN, TiB 2 , and VC). Furthermore, solid-solution reactions occur between SiC and AlN, between AlN and TiB 2 , and between TiB 2 and VC. Al 5 C 3 N phase is generated by interfacial reaction between SiC and AlN. Layered, rod-like BN(C) phase is formed at grain boundaries due to the reaction between AlN and B 2 O 3 on the surface of TiB 2 particles. Mechanical strength of multiphase ceramics is improved by the formation of solid solutions and the occurrence of these interfacial reactions. When sintered at 2000 °C, SiC multiphase ceramics with added Y 2 O 3 exhibit excellent properties, including relative density of 99.8 %, Vickers hardness of 27.1 GPa, and bending strength of 666 MPa. [ABSTRACT FROM AUTHOR]

To enhance the density of SiC and improve the purity of the SiC, carbon is frequently used as a sintering additive. SiC ceramics were prepared in this study by using various carbon sources (graphitic carbon microsphere, carbon black, and flake graphite) combined with B 4 C through spark plasma sintering (SPS) at temperatures ranging from 1800 °C to 1900 °C. Among the above carbon sources, the graphitic carbon microspheres were created by hydrothermal carbonization combined with catalytic graphitization. The influence of the carbon sources on the phase compositions, microstructure, physical properties, and oxidation resistance of the SiC specimens was investigated. The findings revealed that the SiC specimens prepared with graphitic carbon microsphere had a smaller crystallite size than those prepared with other kinds of carbon. The SiC specimens prepared with graphitic carbon microsphere displayed high relative density, hardness, fracture toughness, and remarkable oxidation resistance. This was attributed to the lower oxygen content, better dispersion, and higher chemical reactivity of graphitic carbon spheres. In terms of the oxidation resistance of SiC specimens, factors such as purity (residual carbon) and porosity were found to have a more significant impact than grain size. In general, the use of carbon sources with high reactivity and good dispersion is an effective method in preparing SiC ceramics. [ABSTRACT FROM AUTHOR]

Highly robust ceramics materials are promising materials for applications in the automobile, aerospace, and ceramic cutting tool industries. However, conventional ceramics are typically brittle, which limits their suitability for advanced applications. In this study, with zeolite imidazolium salt skeleton-8 (ZIF-8) as a carbon source, discharge plasma sintering is used to create carbon nanonetworks derived from metal-organic frameworks (MOFs) in situ on the grain boundaries of zirconia-toughened alumina (ZTA) ceramic. ZTA exhibits maximum bending strength (719 ± 20.5 MPa) and fracture toughness (7.91 ± 0.7 MPa m1/2) at MOF concentrations of 1.0 wt% and 2.0 wt%, respectively, which are 1.37 and 1.88 times higher than that of the unmodified sample. This demonstrates that the MOF-derived carbon nanonetworks significantly improve the mechanical properties of the ceramic. The finite element analysis results indicate that the carbon nanonetworks can effectively disperse the stress inside the material and transfer the concentrated stress from the internal defects to the two-phase grain boundary on the surface of the sample, thereby contributing to strengthening and toughening. Overall, this work validates that the in situ production of carbon nanonetworks from MOFs is an effective strategy to enhance the mechanical properties of ZTA ceramics. Moreover, it offers new approaches for reinforcing and toughening other ceramic materials. [ABSTRACT FROM AUTHOR]

Dysprosium (Dy)‐doped (Y1−xDyx)3Si2C2 (x = 0, 0.1, 0.3, 0.5) solid solution ceramics were successfully fabricated using an in situ reaction spark plasma sintering technology, for the first time. The effect of various Dy doping contents (x) on the microstructure, mechanical, and thermal properties of (Y1−xDyx)3Si2C2 ceramics was investigated. The (0 2 0) crystal plane spacing of (Y0.5Dy0.5)3Si2C2 was 7.813 Å, which was smaller than that of Y3Si2C2, due to the fact that the atomic radius of Dy is smaller than that of Y. The Dy doping facilitated the consolidation of (Y1−xDyx)3Si2C2, thus a highly dense (Y0.5Dy0.5)3Si2C2 ceramic material with a low open porosity of 0.14% was successfully obtained at a relatively low temperature of 1 200°C. As the content of Dy doping (x) increased from 0 to 0.5, the purity of (Y1−xDyx)3Si2C2 ceramics increased from 88.3 to 90.7 wt.%, while the grain size of (Y1−xDyx)3Si2C2 ceramics decreased from 0.59 to 0.46 µm. As a result, the Vickers hardness and thermal conductivity of the (Y0.5Dy0.5)3Si2C2 material was 7.1 GPa and 9.8 W·m−1·K−1, respectively. [ABSTRACT FROM AUTHOR]

Recently multielements solid solution has shown significant improvement to the mechanical properties of parent MAX phases. Therefore, in this work, five elements with different radii were incorporated to check the effect on properties of MAX phases. (Nb0.8Ti0.05Zr0.05Mo0.05Hf0.05)4AlC3 (MAXHf) and (Nb0.8Ti0.05Zr0.05Mo0.05Ta0.05)4AlC3 (MAXTa) ceramics were successfully synthesized using the spark plasma sintering technique. The microstructure and elemental map analysis results further confirmed that the five transition metals were successfully solid soluted at the M‐sites of the hexagonal M4AlC3 unit cell. The mean elemental compositions for M‐site elements were achieved as Nb0.85Ti0.052Zr0.035Mo0.027Hf0.036 and Nb0.847Ti0.051Zr0.043Mo0.025Ta0.033 for MAXHf and MAXTa ceramics, respectively. The electrical and thermal conductivities of multielement solid solution MAX phases were decreased compared to pure Nb4AlC3. However, Mechanical properties were significantly increased with the solid solution of five transition metals. The fracture toughness, flexural strength, compressive strength and Vickers hardness (10 N) of MAXHf and MAXTa ceramics were achieved as 8.87 MPa m1/2, 448 MPa, 867 MPa, 6.5 GPa and 10.36 MPa m1/2, 557 MPa, 1039 MPa, 8.2 GPa, respectively. The enhanced mechanical properties suggest the effectiveness of the solid solution strengthening effect and provide new opportunities to further tailor the mechanical properties of the MAX phase ceramics. [ABSTRACT FROM AUTHOR]

In this study, TiB 2 –TiC, TiB 2 –TiC-GNP, and TiB 2 -TiC-BN composites were produced via spark plasma sintering (SPS). The densification and sintering behavior, phase and Raman spectroscopy analyses, microstructural properties, Vickers microhardness, and wear behavior of the binary and ternary composites were investigated. The addition of various amounts of TiC to TiB 2 resulted in nearly complete densification. The TiB 2 –TiC-GNP specimens exhibited a relative density of more than 99 %; in contrast, the addition of BN did not contribute to the densification. The Vickers hardness of the GNP-added composites was ∼25 GPa, whereas hBN addition to the matrix decreased the hardness to ∼22 GPa (∼9 % decrease). According to the wear test, the addition of GNPs did not result in a significant change in the TiB 2 –TiC matrix; however, the addition of hBN increased the specific wear rate of the matrix by ∼100 %. The GNPs did not have a negative effect on the densification, microstructural, or mechanical properties, such as the Vickers hardness and wear resistance. Hence, they were determined to be a more suitable sintering aid for matrix composition than hBN. [ABSTRACT FROM AUTHOR]

Two advanced manufacturing processes, spark plasma sintering (SPS) and selective laser sintering (SLS), have been developed for synthesis of (Zr,Nb,Ta,Ti,W)C compositionally complex carbide (CCC) via reactive sintering of a powder mixture of constitute monocarbides. X‐ray diffraction analysis confirmed that the single‐phase CCC can be formed by both SPS and SLS. While a homogenous microstructure with uniform metal element distributions was developed during SPS, three‐layer microstructures with a thin TiC‐rich layer and two TaC‐rich layers along with a TiO2‐rich surface layer containing W nanoparticles were formed during SLS. In addition, cellular structures with W, Zr, and Ti element segregation and dislocations on cell boundaries were observed in the SLS‐CCC sample, indicating the effect of nonequilibrium conditions on microstructure formation during laser melting followed by rapid cooling and solidification process. Compared to the SPS‐CCC sample, the SLS‐CCC showed enhanced hardness and reduced thermal conductivity, which may be related to their unique cellular structures. [ABSTRACT FROM AUTHOR]

High‐performance piezoelectric ceramic materials are required for piezoelectric sensors under harsh conditions in nuclear power plants, aeronautics, and aerospace. In this work, a lead‐free high‐Curie‐temperature (TC ∼792°C) Aurivillius‐type sodium bismuth niobate, Na0.5Bi2.5Nb2O9 (NBN), was fabricated through spark plasma sintering (SPS). The textured NBN ceramics with a high orientation factor of 83% exhibit significantly enhanced piezoelectric performance with a piezoelectric constant d33 of 31.2 pC/N, three times higher than that of nontextured NBN (d33 ∼ 11.6 pC/N). More importantly, the textured NBN ceramics maintain excellent electrical properties at high temperature, with a high in situ d33 of 35.9 pC/N, very low dielectric loss tanδ = 2.5% (@ 100 kHz) and high dc electrical resistivity ρ of 7.5 MΩ cm at 500°C. These results suggest that the textured NBN ceramics are good high‐temperature piezoelectric ceramic materials, and have promising applications in the field of high‐temperature piezoelectric sensors. [ABSTRACT FROM AUTHOR]

Plasma etching is a crucial step in semiconductor manufacturing. High cleanliness and wafer‐to‐wafer reproducibility in the etching chamber are essential in order to successfully achieve nanometer‐sized integrated functions on the wafer. The trend toward the application of more aggressive plasma compositions leads to higher demands on the plasma resistance of the materials used in the etching chamber. Due to its excellent etch resistance, yttrium aluminum garnet Y3Al5O12 (YAG) is starting to replace established materials like SiO2 or Al2O3 in this kind of application. In this study, reactive spark plasma sintering (SPS) was used to manufacture highly dense YAG ceramics from the respective oxides. In addition, yttrium was replaced with heavier lanthanoids (Er, Lu), intending to investigate the role of the A‐site cation in the garnet type structure on the plasma erosion behavior. The produced materials were exposed to fluorine‐based etching plasmas mimicking the conditions in the semiconductor manufacturing apparatus and the erosion behavior was characterized by atomic force microscopy (AFM), secondary ion mass spectrometry (SIMS), transmission electron microscopy (TEM), and profilometry. The induced chemical gradient in the samples is limited to a few nanometers below the surface, which makes its characterization challenging. For advanced analysis, we developed a correlative characterization method combining SIMS and scanning TEM (STEM)–energy‐dispersive spectroscopy (EDS) enabling us to examine the structural and chemical changes in the reaction layer locally resolved. In the case of lanthanoid aluminates, an altered reaction layer and reduced fluorine penetration compared to YAG were found. However, a correlation between the characteristics of the induced chemical gradient and the determined physical erosion rates was not evident. [ABSTRACT FROM AUTHOR]

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Al 2 O 3 -based ceramic tool materials synergistically reinforced by SiC whiskers (SiC w) and SiC particles (SiC p) were prepared via spark plasma sintering (SPS) technique. The densification behavior, sintering kinetics and optimal ratios of SiC w and SiC p on Al 2 O 3 -based ceramic tool materials were investigated. Results indicated that densification mainly occurred from 1200 to 1450 °C. Grain boundary sliding or grain boundary diffusion was the primary cause of densification at 1200–1350 °C. Whereas, dislocation climbing was the main densification mechanism at 1400–1450 °C. W25P5 sintered at 1450 °C had a large relative density, small grain size and the best mechanical properties with the fracture toughness of 7.35 ± 0.19 MPa m1/2, Vickers hardness of 21.79 ± 0.21 GPa, and relative density of 98.86 ± 0.15 %. The synergistic toughening mechanisms included crack deflection, whisker bridging and whisker pull-out. [ABSTRACT FROM AUTHOR]

Misfit‐layered calcium cobaltite [Ca2CoO3‐δ]0.62[CoO2] is an outstanding p‐type semiconducting thermoelectric with strong anisotropic properties. Texture engineering is crucial for enhancing its thermoelectric performance in polycrystalline ceramics. The in‐plane orientation of the grains improves the Seebeck coefficient and electrical conductivity, while the multi‐scale parallel interfaces scatter phonons and reduce thermal conductivity. Here, a tandem process of spark plasma sintering and edge‐free spark plasma texturing is used to produce dense and highly textured calcium cobaltite ceramics. The resulting ceramic shows a high degree of texturization, secondary phases, and enhanced electrical conductivity of 246 S cm−1 together with a strongly improved Seebeck coefficient of 224 µV K−1 at 1073 K. High grain ordering leads to carrier mobility of 0.49 cm2 V−1 s−1, which has a positive effect on both parameters. With a power factor of 12.4 µW cm−1 K−2 at 1073 K in air, previous thermoelectric performances of calcium cobaltite are surpassed, regardless of its form: pristine, doped, or composite. By combining the high power factor with a relatively low thermal conductivity, a remarkable figure‐of‐merit of 0.49 at 1073 K in air is obtained for the textured polycrystalline ceramic, which reaches 60 % of the figure‐of‐merit of a calcium cobaltite single crystal. [ABSTRACT FROM AUTHOR]

The main objective of this investigation is the consolidation and flexural strength of alpha silicon carbide ceramics produced without additives by spark plasma sintering. Using the design of the experiment method, we optimized temperature and dwell to achieve fully dense silicon carbide bulks. The consolidation process of silicon carbide was analyzed similarly to the creep of bulk ceramics, and it was determined that the activation energy for the densification process was 596 ± 39 kJ/mol, while the stress exponent n was below 2. Bulk additive‐free silicon carbide ceramics gradually increased flexural strength as the temperature rose to 2000°C. The flexural strength at 2000°C was influenced by the loading rate, and under 2.5 mm/min, it reached a maximum of 2.08 GPa. To explain this phenomenon, a deformation mechanisms map was created, indicating that diffusion creep is the most probable mechanism for the strain sensitivity of SiC at 2000°C. Transmission electron microscopy indicated a substantial rise in twin density within the α‐SiC grains at 2000°C, indicating the activation of a previously unreported self‐reinforcing mechanism. [ABSTRACT FROM AUTHOR]

Spark plasma sintering (SPS) is one of the most promising technologies for producing polycrystalline transparent ceramics. However, it has limitations regarding the complexity of the geometries that can be produced. This study addresses these limitations by combining additive manufacturing techniques with spark plasma sintering. Additionally, a Multiphysics sintering model based on the continuum theory of sintering is employed to predict the outcomes of the SPS process, particularly the microstructure of the densified parts. As a result, the geometrically complex Al 2 O 3 transparent parts manufactured in this study exhibit a uniform microstructure, high density (∼99 %), and a linear transmittance of 16 % at 490 μm. [ABSTRACT FROM AUTHOR]

Tungsten carbide (WC), renowned for its exceptional hardness and wear resistance, plays an essential role in various industrial applications (cutting tools, abrasives, and wear-resistant components). While traditional methods involve hot pressing, Spark Plasma Sintering (SPS) combined with Additive Manufacturing (AM) offers a cutting-edge approach, utilizing high-voltage electric current and mechanical pressure for rapid densification, particularly advantageous for fabrication of complex shape components made from challenging materials like nanosized binderless tungsten carbide. The study encompasses the entire spectrum of the powder's characterization, extending to the development of an intricate finite element simulation tailored for SPS sintering. Sintering cycles underscore the exceptional quality of the powder, demonstrating full density microstructures even under low-temperature (1550 °C) and low-pressure (50 MPa) conditions. The nanosized powder exhibits minimal microstructural coarsening, reflecting the high quality of the initial pure tungsten carbide nano powder. The core of this study revolves around the methodology employed for deriving constitutive parameters, following the Skorohod-Olevsky theory of continuum sintering. The derivation methods include variations in temperature, heating regimes, and stepwise pressure application during SPS. Additionally, a grain growth model is formulated based on microstructural analysis. Critical parameters, including the apparent sintering activation energy (800 kJ/mol) and the creep law stress exponent (n = 4.0), are discussed. The article concludes with the integration of the mechanical sintering model into finite element method (FEM) software, considering thermal and electrical aspects for a comprehensive SPS-AM modeling approach and its application to complex shape production. The research aims to enhance the understanding of SPS for tungsten carbide, providing insights for its application in manufacturing cutting-edge components in challenging environments. [ABSTRACT FROM AUTHOR]

A dual phase high‐entropy (Hf,Nb,Ta,Ti,Zr)C–(Hf,Nb,Ta,Ti,Zr)B2 ultra‐high temperature ceramic was synthesized using a single step boro‐carbothermal reduction route. The synthesized powder was densified by spark plasma sintering at 2000°C, resulting in complete solid solution formation and a relative density of ≈99%. The dual phase ceramic was 43 vol% high‐entropy carbide and 57 vol% high‐entropy boride. The grain sizes were 0.85 ± 0.34 µm for the carbide and 0.87 ± 0.33 µm for the boride with minimal residual oxide (0.2 vol%) detected in the microstructure. The resulting composition had a higher microhardness than the individual boride and carbide ceramics across the range of testing loads with maximum hardness of 47.5 ± 4 GPa at a load of 0.49N. The high hardness is attributed to the minimum residual oxide, submicron grains, favorable carbide‐to‐boride ratio, homogeneous metal distribution within the phases, uniform microstructure, and synergistic dual phase hardening. [ABSTRACT FROM AUTHOR]

Aiming at the issues of small critical size and low glass forming ability of Fe-based amorphous alloys, this work focuses on solving the problem of preparing both large size and excellent properties. The highly dense FeCrMoBC bulk metallic glasses with diameter of 20 mm were prepared by spark plasma sintering, and the key role of heat treatment on the microstructure and properties of Fe-based bulk metallic glasses was investigated. The microstructure of Fe-based bulk metallic glasses was adjusted by annealing treatment, and the effects of annealing on the hardness and wear resistance of Fe-based bulk metallic glasses were studied. The results show that annealing induces partial crystallization of the alloy to construct in-situ amorphous nanocrystalline composites. After annealing at 650 °C for 1 h, Fe-based bulk metallic glasses precipitated Cr23C6 and B6Fe23 hard nanocrystalline phases. The highest Vickers hardness, highest fracture toughness, lowest friction coefficient, wear volume and wear rate were obtained, with values of 1514.68Hv, 2.81 MPa·m1/2,0.59, 4.72 × 10− 3mm3 and 2.62 × 10− 6mm3·N− 1·m− 1, respectively. Abrasive wear is the main form of wear, and the wear resistance is superior to that of GCr15. FeCrMoBC bulk metallic glasses exhibit outstanding hardness and wear resistance, providing new material options for the manufacture of high-performance advanced equipment. [ABSTRACT FROM AUTHOR]

A study was carried out to prepare a magnet with a c-axis alignment present in the melt-spun ribbons to be used as a precursor magnet for the hot deformation process. Melt-spun ribbons prepared at a wheel speed of 23 m/s resulted in nanograins with columnar grains having the <001> texture on the exposed side and very fine equiaxed nanograins on the wheel side of the ribbon. The ribbons were stacked and consolidated using the SPS technique with the variation of temperature (temperature series) and pressure (pressure series), which resulted in Nd2Fe14B grains in two-grain zones, namely (i) fine grain and (ii) coarse grain zones. The fine grains grow with temperature and dominate the coercivity mechanism in the temperature series, and the grains do not grow in the pressure series; hence, the coercivity is not affected by pressure. The calculation of the intensity ratio of I(006)/I(105) in SPS compacted samples in both temperature and pressure series showed evidence of texture retention; however, the texture was not strong enough to influence the magnetic properties. The best magnetic properties of Hc of 12.2 kOe and (BH)max of 11.6 MGOe were obtained in the temperature series sample prepared at temperature of 600 °C, pressure of 150 MPa, and dwell time of 2 min. [ABSTRACT FROM AUTHOR]

The aim of this work is to obtain Cu-13.5Al-4Ni alloy for use as shape memory alloy by Spark Plasma Sintering (SPS) of mechanically alloyed powder. The study investigates the structural and microstructural changes in terms of crystal parameters, crystallite sizes, and phases evolution during mechanical alloying and spark plasma sintering of Cu-13.5Al-4Ni powders. We obtained alloyed powders with a structure composed of α(Cu), AlNi intermetallic compound and small amounts of elemental Al through the mechanical alloying technique. After spark plasma sintering at 900 °C, the microstructure consists of an AlNi compound distributed at the edge of α(Cu) grains. The crystallite sizes of both, α(Cu) and AlNi are in nanoscale order after 16 h of milling (9 and 6.5 nm respectively). After sintering at 900 °C (in Ar atmosphere, without holding time), the crystallite sizes increase to 46 nm for α(Cu) and to 40 nm for AlNi compound. Also, the Cu-13.5Al-4Ni compacts achieve a final density after sintering at 900 °C of around 80% from the theoretical density. [ABSTRACT FROM AUTHOR]

High-conductivity tellurium-based glasses were anticipated to be the attractive candidates in chalcogenide glass systems on account of their distinctive characteristics and extensive application prospects. In this paper, the high-density (>96%) Sn8[(Ga2Te3)34(SnTe)66]92 bulk glass with the density of 5.5917 g/cm3 was successfully prepared by spark plasma sintering (SPS) technology at 460 K, using a 5 min dwell time and 450 MPa pressure. The room-temperature thermal conductivity of Sn8 bulk materials significantly decreased from 1.476 W m−1∙K−1 in the crystalline sample to 0.179 W m−1∙K−1 in the glass, and the Seebeck coefficient obviously increased from 35 μV∙K−1 in to 286 μV∙K−1, indicating that the glass transition of tellurium-based semiconductors could optimize the thermal conductivity and Seebeck coefficient of the materials. Compared to the conventional tellurium-based glassy systems, the fabricated Sn8 bulk glass presented a high room-temperature conductivity (σ = 6.2 S∙m−1) and a large glass transition temperature (Tg = 488 K), which was expected to be a promising thermoelectric material. [ABSTRACT FROM AUTHOR]

In the present study, CoCrFeNi HEAs were prepared in nanocrystalline structure and consolidated via conventional sintering and spark plasma sintering. Investigation of microstructures were implemented by using x-ray diffraction (XRD), focused ion beam microscopy (FIB), and transmission electron microscopy (TEM) with respect to sintering type and temperature. The findings have showed that the as-milled single-phase face centered cubic (fcc) crystal structure was retained after conventional sintering at 1000 and 1100°C, whereas spark plasma sintering yielded additional phase (Cr7C3) at the same temperatures. The as-milled grain size was increased from 10 nm to 450 nm and 1.5 µm after conventional sintering at 1000 and 1100°C, respectively, revealing that the nano-structured CoCrFeNi alloy does not remain thermally stable after long exposures at elevated temperatures. On the other hand, the grain size was retained around 353 nm after spark plasma sintering at 1100°C, which is dramatically smaller than that of conventional sintering. Accordingly, the hardness of mechanically alloyed CoCrFeNi HEA reduced from 4.6 GPa to 2.1 GPa after conventional sintering at 1100°C due to the significant grain growth, whereas the enhanced hardness of 3.6 GPa was maintained after consolidation at the same temperature with spark plasma sintering. [ABSTRACT FROM AUTHOR]

This paper describes the principles of obtaining wear-resistant coatings based on titanium diboride that are deposited on the cutting tool for use in the machining of chromium–nickel alloys. The spark plasma sintering of samples from the TiB2/Ti powder composition was studied, and the influence of sintering modes on the characteristics of the ceramic targets was analyzed. The regularities of the magnetron sputtering of sintered targets were revealed. The dependences of the physical and mechanical properties of coatings formed on hard alloy substrates on deposition conditions were established. The wear resistance of carbide samples with TiB2-based coatings under friction-sliding conditions and coated carbide ball-end mills in milling Inconel 718 chromium–nickel alloy that is widely used in the industry was assessed. [ABSTRACT FROM AUTHOR]

The microstructure and thermoelectric properties of materials based on p-type Bi0.5Sb1.5Te3 and n-type Bi2Te2.4Se0.6 solid solutions doped with graphene are studied. The samples are obtained by spark plasma sintering of powders prepared by melt spinning and crushed in a ball mill together with graphene plates, which are introduced in an amount of 0.05, 0.1, and 0.15 wt %. Scanning electron microscopy is used to study the composition and microstructure. The samples with p-type conductivity have a fine-grained (on the order of hundreds of nanometers) structure with microsized tellurium-based eutectic inclusions. The samples with n-type conductivity contain grains with melted edges. The thermoelectric parameters are measured: Seebeck coefficient, electrical conductivity, thermal conductivity at room temperature and in the temperature range from 100 to 700 K; and the thermoelectric figure of merit is calculated. When adding 0.15 wt % of graphene plates to a p-type solid solution, the maximum thermoelectric figure of merit (ZT)max of the material increases by 13% and is equal to 1.3 at 420 K. For a sample with n-type conductivity doped with graphene, the highest value of (ZT)max = 0.83 at 470 K is obtained by adding 0.1 wt % of graphene plates. [ABSTRACT FROM AUTHOR]

Micrometer-sized diamonds were incorporated into silicon nitride (Si3N4) matrix to manufacture high-performance Si3N4-based composites using spark plasma sintering at 1 500 °C under 50 MPa. The effects of the diamond content on the phase composition, microstructure, mechanical properties and thermal conductivity of the composites were investigated. The results showed that the addition of diamond could effectively improve the hardness of the material. The thermal conductivity of Si3N4 increased to 52.97 W/m·k at the maximum with the addition of 15 wt% diamond, which was 27.5% higher than that of the monolithic Si3N4. At this point, the fracture toughness was 7.54 MPa·m1/2. Due to the addition of diamond, the composite material generated a new substance, MgSiN2, which effectively combined Si3N4 with diamond. MgSiN2 might improve the hardness and thermal conductivity of the materials. [ABSTRACT FROM AUTHOR]

n‐type Dy‐doped Ca2MnO4 powders with the Ruddlesden–Popper structure were synthesized by the combustion method and sintered by conventional sintering and spark plasma sintering (SPS). Conventional sintering fails to densify Ca2MnO4, but the addition of Li2O proves to be a highly effective sintering additive, albeit with a detrimental impact on electrical conductivity. In contrast, SPS at 850°C for 1 min yields nanostructured, nearly fully dense samples, demonstrating superior outcomes. The dimensionless figure of merit ZT reaches 0.02 at 750°C. Additionally, the best sample exhibits a remarkable hardness value of 10.7 GPa, underlining the excellent mechanical properties achieved through this innovative approach. [ABSTRACT FROM AUTHOR]

A novel high-entropy M 4 AlC 3 phase ceramic (M=Ti, V, Mo, Nb, Ta) was synthesized by three-step solid phase sintering, and the textured high-entropy M 4 AlC 3 composites were prepared for the first time by SPS uniaxial pressing of nano flakes generated via reactive ball milling. The microstructure were characterized in detail and Maud software was used for Rietveld refinement analysis of phase composition content. The results showed that Ti, V, Mo, Nb, Ta were successfully dissolved in M 4 AlC 3. On this basis, the density, hardness and mechanical properties before and after texture were tested. The results showed that the textured composite achieved 12.1 GPa Vickers hardness (//C-axis), 2.2 GPa compressive strength (//C-axis), 8.8 fracture toughness of MPa m1/2 (//C-axis) and 726 MPa bending strength (//C-axis). Dispersively distributed nano-Al 2 O 3 and texturization played a key role in strengthening and toughening. This work can provide an important reference for the subsequent preparation and texturing of high-entropy MAX ceramics. [ABSTRACT FROM AUTHOR]

Alumina-yttrium aluminum garnet (YAG)-zirconia composites are often produced by the melt solidification method. In the present study, we investigated the fabrication of α-Al 2 O 3 /Y 3 Al 5 O 12 (YAG)/ZrO 2 composite by Spark Plasma Sintering (SPS) of powders synthesized by Pechini's sol-gel method. The ternary composites with homogenous microstructure and high density were produced by SPS at 1300 °C for 15 min. The addition of ZrO 2 promoted the sintering of composites, resulting in a higher density and, in turn, higher hardness. A change in the indentation fracture behavior as the result of ZrO 2 addition was observed. [ABSTRACT FROM AUTHOR]

Research laboratories worldwide use the spark plasma sintering (SPS) technique for sintering metallic and ceramic matrix composites. Typically, the SPS sintered parts are low circular cylinders (discs). The upscaling and industrialization of SPS technology face two challenges: the limitation of shaping non-cylindrical parts and the inhomogeneous sintering of large-sized products. This paper addresses these challenges in sintering axisymmetric shells within an SPS setup with improved thermal insulation. The paper considers the sintering of a 75 mm shell as a case study. The shell material is a zirconia-carbon nanotube composite. Finite element analysis revealed that homogeneous sintering of such a shell requires careful thermal insulation of the entire setup. Investigation of phases, microstructure, density, microhardness, and fracture toughness in the sintered shell showed a homogeneous structure and uniform properties. [ABSTRACT FROM AUTHOR]

TiB 2 -reinforced TiCN-based cermets were successfully fabricated by spark plasma sintering (SPS) from a TiCN-Ti-B 4 C-Co system. The effects of Ti/B 4 C composite powders (TBCs) addition on the sintering behavior, microstructure, mechanical properties, and wear resistance were investigated. The results indicated that all the cermets with different TBCs contents were composed of TiCN, TiB 2 , and Co without other impurities. Moderate addition of TBCs could effectively promote densification and refine TiCN grain. The Vickers hardness and fracture toughness simultaneously increased with TBCs addition. The cermet with 30 wt% TBCs addition possessed excellent mechanical properties (Vickers hardness of 1725 HV and fracture toughness of 7.1 MPa m1/2). The strengthening and toughening mechanisms were investigated in detail. The wear resistance property was significantly enhanced by the in-situ incorporation of TiB 2 owing to the improved hardness and grain refinement. [ABSTRACT FROM AUTHOR]

The development of a high-power and long-life thermionic ceramic cathode poses significant challenges, namely the need for high electron emission capacity at low temperature and excellent machinability. In this paper, the first-principles method was used to obtain the (La 0.5 Ba 0.5)B 6 with the lowest work function, and (La 0.5 Ba 0.5)B 6 –ZrB 2 composite with high relative density of 98.08 % was prepared by spark plasma sintering (SPS) at T = 1800 °C, under which the densification mechanism transformed from the particle rearrangement into the grain boundary diffusion, and the corresponding apparent activation energies were 282.75 kJ/mol and 466.54 kJ/mol, respectively. The maximum current density of 12.93 A/cm2 at T = 1500 °C of the composite was higher than that of 11.71A/cm2 at T = 1600 °C of LaB 6 , which can be attributed to the high Fermi level and weak electronic constraints of (La 0.5 Ba 0.5)B 6. The practical work function distribution (PWFD) of 0.36 eV indicated the composite had excellent emission uniformity. [ABSTRACT FROM AUTHOR]

Silica-based glass ceramics have been extensively used in biomedical applications due to their superior biocompatibility and controllable properties. However, their low mechanical strength limits their application. This could be addressed by optimizing the crystalline phase which determines their final properties. Silicon nitride has attracted attention due to its combination of good mechanical and biological properties. Therefore, to combine the advantage of silica-based glass and silicon nitride ceramic, this study developed a silicon nitride-silicon dioxide (Si 3 N 4 –SiO 2) glass ceramics. The effects of spark plasma sintering parameters on the structural and mechanical properties of Si 3 N 4 –SiO 2 glass ceramics were investigated. Full densification was reached at a sintering temperature of 1300 °C, a holding time of 10 min and an applied pressure of 80 MPa (relative density = 99.19 %). No silicon oxynitride (Si 2 N 2 O) crystalline phase was formed in the sintered glass ceramics, as confirmed by XRD. The interface between the β-Si 3 N 4 crystalline and amorphous SiO 2 was investigated by HRTEM, and the results indicated that an amorphous interfacial oxide was formed at the interface. The mechanical properties increased with increasing sintering temperature, as a result of the increased density. The Si 3 N 4 –SiO 2 glass ceramics sintered at 1500 °C exhibited the highest value of toughness and flexural strength, at 4.6 ± 0.28 MPa m1/2 and 360 ± 27 MPa. The indentation cracks observed by SEM showed that the large β-Si 3 N 4 grains promoted crack deflection, while the equiaxed Si 3 N 4 grains with a lower aspect ratio led to transgranular fracture. The mechanical properties of these Si 3 N 4 –SiO 2 glass ceramics are comparable to commercial glass ceramics, indicating their promising aspects in biomedical applications. [ABSTRACT FROM AUTHOR]

The results of structural studies and assessment of the bending strength of a VKNA-4U alloy based on nickel aluminide are presented. It is for the first time that this alloy was produced by spark plasma sintering of mechanically activated powders of the starting components. The mechanical activation of the powders lasted for 1.5, 3.5, and 5 min. X‑ray diffraction analysis was performed to determine the optimal duration (3 min 30 sec) of mechanical activation for this alloy. To obtain a dense low-defect workpiece, the VKNA-4U alloy was sintered at a heating temperature of 1100 °C, a pressure of 40 MPa, and a holding time of 5 min. This material has higher ultimate bending strength at room temperature (σbend = 1215 ± 65 MPa) than the strength of Ni3Al intermetallic compound produced in similar conditions and microhardness 690 ± 25 HV. [ABSTRACT FROM AUTHOR]

The paper deals with transparent MgAl2O4 ceramics reinforced with 0.1 vol.% Al2O3 nanofibers and manufactured by spark plasma sintering at 1400°C and 100 MPa. The microstructure of MgAl2O4 ceramic samples is studied by the X-ray phase analysis and scanning electron microscopy. The optical properties are investigated in 190 to 8000 nm wavelength range. The influence of Al2O3 nanofibers on optical and mechanical properties of ceramics is discussed herein. [ABSTRACT FROM AUTHOR]

Sc2O3–CeO2–Y2O3– stabilized zirconia (ScCeYSZ) nanoparticles with different percentages of stabilizer agents [sample1: 1.8 wt.% (Sc2O3) 8.3 wt.% (CeO2) 1.9 wt.% (Y2O3), sample 2: 1.1 wt.% (Sc2O3) 9.0 wt.% (CeO2) 1.9 wt.% (Y2O3), sample 3:.5 wt.% (Sc2O3) 9.6 wt.% (CeO2) 1.9 wt.% (Y2O3) stabilized zirconia] were synthesized with Pechini method and consolidated by spark plasma sintered method. The results showed that despite the [(sample)1: 1.8 wt.% (Sc2O3) 8.3 wt.% (CeO2) 1.9 wt.% (Y2O3)] had lower density and higher porosity percentage compared to other samples, it had better calcium–magnesium–alumina–silicate (CMAS) corrosion resistance compared to other samples and the yttria‐stabilized zirconia nanopowders (nano‐YSZ) sample. It was due to the higher acidic nature and tetragonality of the (sample)1 sintered body compared to other samples and YSZ ceramic in the CMAS corrosive medium. Moreover, the results of phase and microstructural analysis following CMAS corrosion revealed the formation of the monoclinic phase and rod‐shaped CaAl2Si2O8 particles on the surface of the sampled sintered sample. However, the nano‐YSZ sample corroded homogenously and delamination occurred after the CMAS corrosion test. [ABSTRACT FROM AUTHOR]

AlCoCrFeNi2.1 eutectic high‐entropy alloy was introduced to join Cf/SiC composite by spark plasma sintering technique. The influence of holding times on microstructure, shear strength and fracture behavior of the joints was studied. When held for 7 min, the typical microstructure of the Cf/SiC‐AlCoCrFeNi2.1‐Cf/SiC joint was Cf/SiC composite → CrSi2 + FCC + Al8Cr5 + graphite → CrSi2 + FCC + Al8Cr5 → CrSi2 + FCC + Al8Cr5 + graphite → Cf/SiC composite. As the holding time extended, the Ni–Si and Fe–Si brittle phases in the joint gradually reduced, and the diffusion transition layer continued to thicken. The maximum joint strength was 23.9 MPa, which was obtained at 1450°C for 7 min. Analyzed by scanning electron microscopy and energy dispersive spectroscopy, the fracture modes of the joints joined at different holding times were all brittle fracture. [ABSTRACT FROM AUTHOR]

Cobalt-based ternary superalloys were prepared from the consolidation of high purity cobalt, tungsten and tantalum elemental powder using spark plasma sintering technique. The composition of the alloys was fixed, so also were the sintering pressure (50 MPa) and heating rate (150 °C/min). However, the samples sintering temperatures were varied from 800 to 1400 °C, with holding time of 10 and 15 min. The microstructure, phase and crystallographic characterizations were done using scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDS), optical microscopy and X-ray diffraction spectroscopy. Mechanical properties of the Co-alloys were evaluated using Vickers microhardness analytical data. Sintering data analysis indicates a two-step major and minor densification modes in the samples, and morphological images show evolution in the microstructure based on varied sintering parameters. Phase partitioning due to spinodal decomposition was observed in the alloys (1000 to 1400 °C). Crystallographic peak intensities were observed to increase with sintering temperature up to 1200 °C, whereas structural amorphization occur at 1400 °C. The microhardness improved from 358.74 to 594.64 HV for sintered alloy at 1200 °C. Alloy samples sintered at 1200 °C and of 10 min dwelling time have optimum mechanical property. [ABSTRACT FROM AUTHOR]

The Al 2 W 3 O 12 ceramic with near-zero thermal expansion is a promising candidate for thermal shock resistance applications. However, the often-reported microcracks in the microstructure hinder the practical use of Al 2 W 3 O 12. This work focuses on optimising the material processing—powder synthesis, calcination, milling, and sintering—to prepare dense polycrystalline Al 2 W 3 O 12 with fine microcrack-free microstructure. The amorphous powder produced by the co-precipitation method had the highest specific surface area reported for this material, resulting in improved sinterability. Two rapid sintering methods were employed—Rapid Pressure-less Sintering and Spark Plasma Sintering. Both methods led to shorter processing times and lower sintering temperatures. However, Al 2 W 3 O 12 samples produced by Spark Plasma Sintering were nearly fully dense with a density of ∼98% of theoretical density, the best value reported to date for this phase. The obtained fine crack-free microstructure of the samples led to a superior mechanical response compared to that achieved by Rapid Pressure-less Sintering. [ABSTRACT FROM AUTHOR]

Dense silicon carbide (SiC) composites with 0–30 vol% (ZrN-TiB 2) were fabricated by using liquid phase spark plasma sintering at a relatively lower sintering temperature (1800 °C) and shorter holding time (5 min). The effects of co-addition of ZrN and TiB 2 on densification, mechanical properties, and electrical conductivity of SiC ceramics were investigated. The reinforcement significantly enhanced density of sintered composites, while the phase analysis and microstructure confirm the suppression of β→α phase transformation in the SiC matrix. The fracture toughness ranged from 4.1 to 4.6 MPa·m0.5, hardness from 19.5 to 20.3 GPa, and electrical conductivity from 4.85 ×101 to 1.25 ×103 (Ω·cm)−1. Incorporating conductive reinforcements and nitrogen additives enhanced electrical conductivity. Successful wire-EDM cutting of SiC-ZrN-TiB 2 composites demonstrate the feasible alternative to conventional machining of non-oxide ceramics with a maximum material removal rate of 8.54 mm2/min. [Display omitted] [ABSTRACT FROM AUTHOR]

In this study, binderless TiC 70 N 30 ceramic composites with varying graphite (TiC 70 N 30 –Gr) reinforcements were fabricated via spark plasma sintering and their effect on densification was assessed. Subsequently, the electrochemical behaviour of TiC 70 N 30 –Gr composites was evaluated in 0.5 mol/L hydrochloric acid (HCl), 0.5 mol/L sulphuric acid (H 2 SO 4) and 0.5 mol/L nitric acid (HNO 3) solutions using open circuit potential, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) methods. The corrosion behaviour of TiC 70 N 30 -based ceramic composites with and without graphite reinforcement exhibited high corrosion resistance in the acidic electrolytes. Composites with 0.5 and 1.0 wt% graphite content showed lower Icorr values of 0.452 µA and 0.081 µA in 0.5 mol/L HCL and 0.5 mol/L HNO 3 , respectively, while specimen without graphite addition showed better corrosion resistance in 0.5 mol/L H 2 SO 4 (0.041 µA). Based on the corrosion results, the corrosion properties of TiC 70 N 30 ceramic composites in HCl and HNO 3 solutions were significantly enhanced upon the incorporation of graphite reinforcements. However, the corrosion test results conducted in H 2 SO 4 solution showed that the addition of graphite had a negligible influence on the corrosion resistance of the titanium carbonitride (TiCN) composites. [ABSTRACT FROM AUTHOR]

The silicides (MeSi 2 , Me = Ta, Zr, W, Mo) with strong Si supply capability are promising for improving the loose and porous HfO 2 skeletons from ablation resistant coatings for carbon-based materials. Herein, MeSi 2 modified HfB 2 -SiC coatings prepared by spark plasma sintering were evaluated under oxyacetylene ablation condition (2.4 MW/m2) to analyze the protection mechanism. Experimental and theoretical analyses show that, MoSi 2 can be considered as the optimal Si additive and HfB 2 -SiC-MoSi 2 coating exhibits the lowest linear variation rate of −0.19 μm/s. The by-product retention of WO x and ZrO 2 derived from WSi 2 and ZrSi 2 will cause rapid thickening of Hf-Si-O layer, while the by-product (Hf 6 Ta 2 O 17) from TaSi 2 leads to severe consumption of HfO 2 skeleton (0.29 μm/s). The disparate mechanisms of MeSi 2 addition are jointly decided by the fluctuation of Hf-O bond length (0.219–0.229 nm) in Me modified HfO 2 solid solutions, as well as the differently dynamic consumption of MeO x by-products. [ABSTRACT FROM AUTHOR]

Aluminum nitride (AlN), prized for its high thermal conductivity and electronic insulating properties, finds widespread use in electronic applications, particularly as a substrate material. However, its relatively low fracture toughness limits its application. In this study, to enhance both the thermal and mechanical properties of AlN ceramics, we thoroughly investigate the microstructure, thermal, and mechanical properties of self-reinforced AlN ceramics fabricated by spark plasma sintering, with self-reinforcement achieved through the integration of AlN whiskers within the AlN matrix. Unlike previous studies utilizing conventional pressureless sintering with limited sintering conditions, this work employs spark plasma sintering with a wide range of temperatures (1600–1900 °C) and holding times (10–30 min), providing a comprehensive understanding of the sintering behavior. Microstructural features, observed through optical and scanning electron microscopy, reveal distinct toughening mechanisms via crack deflection and branching, with a maximum 20% enhancement. The self-reinforced AlN ceramics exhibit remarkable improvements in thermal conductivity, reaching up to 150 W m−1 K−1, surpassing reported values for spark plasma-sintered AlN ceramics. Adding AlN whiskers enhances the thermal and mechanical properties of AlN simultaneously, particularly at 1800 °C for 10 min with controlled grain size and nicely integrated AlN whiskers. This work not only contributes valuable insights into the complex relationship between processing parameters, microstructure, and resulting thermal and mechanical properties but also highlights the enhanced thermal and mechanical properties of self-reinforced AlN ceramics. [ABSTRACT FROM AUTHOR]

YFeO 3 (YFO) ceramics were synthesized by reverse co-precipitation at different pH values followed by microwave sintering (MS) and spark plasma sintering (SPS) techniques. Also, the effect of the grain size on the magnetic and dielectric properties of the sintered ceramics was examined using various characterization methods. Moreover, FESEM micrographs showed that the particle size of the calcined samples has declined by increasing the pH value. Furthermore, the magnetization curves exhibited weak ferromagnetic behavior in the pre-sintered powder samples. Besides, the M s value was enhanced from 1.26emu/g to 2.3emu/g by an increase in pH from 8.5 to 10.5 owing to reducing the particle size and subsequently raising the amount of uncompensated surface spins. Furthermore, the powder samples showed an increase in the H c and M r values from 15Oe to 28Oe and 0.127emu/g to 0.296emu/g, respectively, with a reduction in particle size from 0.632 μm to 0.272 μm. Additionally, the specimens processed through the sintering techniques demonstrated a remarkable reduction in magnetic characteristics. Therefore, a decrease in magnetic saturation values from 2.3emu/g to 0.43emu/g for the MS sample and to 0.17emu/g for the SPS specimen was attributed to a marked reduction in the amount of free surfaces and subsequently uncompensated surface spins. At last, the observed dielectric characteristics of all the sintered pellets had a common dielectric behavior. This signifies that by increasing the frequency the ε ′ and tanδ decline at lower frequencies and become frequency-independent at higher frequencies based upon the Maxwell-Wagner polarization theory. On the other hand, the ε ′ value for the SPS sample produced at pH = 10.5 underwent a decline of 2.5 times at the low frequency of 200 Hz compared to the MS one due to the significant decrement of the grain boundaries on account of the coarsening of grains. • The reverse co-precipitation method has been chosen to synthesize the YFeO 3 powders. • Through the particle size reduction, the higher pH levels resulted in the increased magnetization. • The spark plasma sintering method resulted in a higher grain growth compared to the microwave route. • The microwave sintering outperformed the spark plasma sintering in magnetic and electrical properties. [ABSTRACT FROM AUTHOR]

Ternary half-Heusler (HH) alloys are under intense investigations recently towards achieving high thermoelectric (TE) figure-of-merit (ZT). Of particular interest is the ZrNiPb-based HH alloy, where an optimal value of ZT ~ 0.7 at 773 K has been achieved by co-doping Sn and Bi at Pb site. In this work, we identify an excellent ZT of 1.3 in ZrNi1+xPb0.38Sn0.6Bi0.02 (x = 0.03, at 773 K) composite alloy. This is achieved by synergistic modulation of electronic as well as thermal properties via introduction of minor phase of full-Heusler (FH) in the HH matrix through compositional tuning approach. These Ni-rich ZrNi1+xPb0.38Sn0.6Bi0.02 (0 ≤ x ≤ 0.07) alloys were synthesized via energy efficient and time-curbed techniques that involved Arc melting followed by consolidation via spark plasma sintering. These alloys were characterized by XRD and SEM, which show formation of nanocomposites comprising of HH matrix phase and FH secondary minor phases. Enhancement in ZT is mainly attributed to a synchronized increase in power factor (~42%) and ~25% decrease in its thermal conductivity. Here, TE compatibility factor (S) was also calculated for all samples. The value of |S| ~ 2.7 V−1 (at 773 K) is observed for x = 0.03, which is ~17% higher than bare HH composition (x = 0.0). The theoretically calculated TE device efficiency of best-performing sample ZrNi1.03Pb0.38Sn0.6Bi0.02 is estimated to be η ~ 13.6%. Our results imply that deliberately controlled fine tuning in compositions of HH compounds through compositional tuning approach would lead to novel off-stoichiometric HH phases with enhanced ZT value for efficient TE device fabrication. [ABSTRACT FROM AUTHOR]

Copper-based composites with different quality scores for NbC particle reinforcement were prepared by spark plasma sintering. The microstructure of the copper-based composites with different NbC contents was studied, and the influence of NbC content on the density, electrical conductivity and hardness of the copper-based composites was investigated. The results showed that the electrical conductivity of the Cu-4 wt% NbC composite material after spark plasma sintering was 70.4% IACS (IACS is the percentage of the ratio of the conductivity of the sample to a certain standard value. The annealed copper wire with a density of 8.89 g cm−3, a length of 1 m, a weight of 1 g and a resistance of 0.15328 Ohm is used as this certain standard value), and the hardness was 63.4 HV. The strengthening mechanisms of NbC in copper-based composites were dispersion strengthening and fine crystal strengthening. During the spark plasma sintering process, the Zener pinning of NbC particles slowed grain boundary migration, which effectively prevented the pure copper grains from growing and thus enhanced the pure copper. The proportion of NbC in the raw powder was changed to adjust the proportion of fine crystals, and then the mechanical properties of the material were adjusted. Additionally, NbC caused a preferred orientation of pure copper and reduced some of the stress in the material. [ABSTRACT FROM AUTHOR]

The authors study compacted materials obtained using different periods of the mechanical activation of mixtures whose compositions correspond to alloys of grades VKNA-1V and VKNA-4U, with subsequent electric spark sintering. The maximum strengths of the compacted materials are reached after 3.5 min of mechanical activation: 1200 MPa for VKNA-1V and 1100 MPa for VKNA-4U. [ABSTRACT FROM AUTHOR]