Spark Plasma Sintering Method Research Articles

Optically stimulated luminescence properties of In-doped CsBr transparent ceramics

0.01, 0.1, 0.5, and 1% In-doped CsBr transparent ceramics were synthesized by the spark plasma sintering method. Their photoluminescence and optically stimulated luminescence (OSL) properties were evaluated. All the samples showed transparency with transmittances of 40–60%. Luminescence due to 3P1–1S0 transitions of In + appeared at 500 nm. OSL emission peaks were confirmed at 500 nm upon constant stimulation light at 630 nm. A 0.1% In-doped sample showed the highest OSL intensities in prepared samples and the dose-response relationship was linear from 0.01 to 1000 mGy. The spatial resolution of X-ray images was confirmed from 5.00 LP/mm by using OSL of a 0.1% In-doped sample.

Transport properties of mechanochemically synthesized copper (I) selenide for potential applications in energy conversion and storage

This work studied the thermal stability, electrical, and thermoelectrical properties of copper(I) selenide, Cu2Se synthesized by high-energy milling in a planetary ball mill. The phase composition was investigated by X-ray powder diffraction analysis and scanning electron microscopy. The conversion of the precursors during mechanochemical synthesis and the stability of the product was monitored by thermal analysis. The dependence of electrical properties on the product porosity was observed. For the densification of Cu2Se, the method of spark plasma sintering was applied to prepare suitable samples for thermoelectric characterization. High-temperature thermoelectric properties of synthetic Cu2Se were compared to its natural analogue-mineral berzelianite in terms of its potential application in energy conversion. Based on the results a relatively high figure-of-merit, ZT parameter (~ 1.15, T = 770 K) was obtained for undoped Cu2Se, prepared by rapid mechanochemical reaction (5 min). Cyclic voltammetry measurements of Na/NaClO4/Cu2Se cell implied that mechanochemically synthesized Cu2Se could be used as a promising intercalation electrode for sodium-ion batteries.

Optical, scintillation, and TSL properties of Ce-doped LiMgAlF6

Ce differently (0, 0.01, 0.1, 1, 2 and 5% with respect to Mg) doped LiMgAlF6 ceramics were synthesized by the spark plasma sintering (SPS) method. In photoluminescence (PL), emission bands appeared at 300 nm with 30 ns day time, and these emission properties were almost the same in scintillation under X-ray irradiation. Further, thermally stimulated luminescence (TSL) was observed after X-ray irradiation, and the primary glow peak temperature was 160 °C with a lower detection limit of ∼10 mGy.

Sr-substitution effects on crystal structure and thermoelectric properties of misfit layered cobaltate, [Ca2CoO3]pCoO2

Misfit-layered cobaltate [Ca2CoO3]pCoO2 is a promising thermoelectric (TE) material that can operate at high temperature in air. Partial substitution of Ca with Sr has been suggested to enhance TE properties. To comprehend the unresolved effects of Sr-substitution on the TE properties, we have prepared single-phase polycrystalline samples of Sr-substituted [Ca2CoO3]pCoO2, i.e., [(Ca1-xSrx)2CoO3]pCoO2, using a spark plasma sintering (SPS) method followed by O2 annealing. We analyzed the crystal structure by powder X-ray diffraction, evaluated the average valence state of Co ions by X-ray photoelectron spectroscopy, and measured temperature-dependent TE properties. Upon Sr-substitution, the average valence state of Co ions slightly increased. The electrical resistivity perpendicular to the SPS pressing direction increased, while that along the SPS pressing direction was almost unchanged. The Seebeck coefficient and the thermal conductivity were less affected by the Sr-substitution. The figure-of-merit zT perpendicular to the SPS pressing direction tended to decrease with Sr-substitution, reflecting the increase in electrical resistivity.

Effect of Nitrogen Atmosphere Annealing of Alloyed Powders on the Microstructure and Properties of ODS Ferritic Steels.

Oxide Dispersion Strengthened (ODS) ferritic steels are promising materials for the nuclear power sector. This paper presents the results of a study on the sintering process using the Spark Plasma Sintering (SPS) technique, focusing on ODS ferritic steel powders with different contents (0.3 and 0.6 vol.%) of Y2O3. The novelty lies in the analysis of the effect of pre-annealing treatment on powders previously prepared by mechanical alloying on the microstructure, mechanical, and thermal properties of the sinters. Using the SPS method, it was possible to obtain well-densified sinters with a relative density above 98%. Pre-annealing the powders resulted in an increase in the relative density of the sinters and a slight increase in their thermal conductivity. The use of low electron energies during SEM analysis allowed for a fairly good visualization of the reinforcing oxides uniformly dispersed in the matrix. Analysis of the Mössbauer spectroscopy results revealed that pre-annealing induces local atomic rearrangements within the solid solution. In addition, there was an additional spectral component, indicating the formation of a Cr-based paramagnetic phase. The ODS material with a higher Y2O3 content showed increased Vickers hardness values, as well as increased Young's modulus and nanohardness, as determined by nanoindentation tests.

Effect of Al content in CoCrFeNiAlx HEA on mechanical properties and high temperature oxidation resistance of WC-10%CoCrFeNiAlx hard alloy

The CoCrFeNiAl high-entropy alloy, with varying Al compositions, was utilized as the bonding phase in this study to fabricate WC-10%CoCrFeNiAlx (where x represents the mole ratio of Al element, ranging from 0 to 1) hard alloys using the Spark Plasma Sintering method. The investigation focused on elucidating the influence mechanism of microstructure and properties of CoCrFeNiAlx high-entropy alloys on the mechanical properties of WC-10%CoCrFeNiAlx hard alloys. Isothermal oxidation testing was subsequently conducted to examine the impact of Al content on the high-temperature oxidation resistance of WC-10%CoCrFeNiAlx hard alloys. Finally, a comparison was made between the mechanical properties and high temperature oxidation resistance of WC-10%CoCrFeNiAlx hard alloys and conventional WC-6Co cemented carbide. The findings suggest that as the Al content increases, the CoCrFeNiAlx high-entropy alloy undergoes a transition from a single Face-Centered Cubic (FCC) phase to a combination of FCC and Body Centered Cubic (BCC) phases, ultimately transforming into a BCC phase. This evolution results in a gradual enhancement in hardness. The mechanical properties of WC-10CoCrFeNi hard alloy exhibit exceptional characteristics when the Al content is eliminated, with hardness, fracture toughness, and bending strength reaching 1702 MPa, 13.0 MPa·m1/2, and 1378 MPa respectively. As the Al content increases in WC-10%CoCrFeNiAlx hard alloys, there is a corresponding increase in hardness while fracture toughness and bending strength gradually decrease. Furthermore, an enhancement in high temperature oxidation resistance is observed. Finally, in comparison to the conventional WC-6Co hard alloy, the mechanical properties of WC-10CoCrFeNiAlx hard alloys exhibit similarity while demonstrating a significant enhancement in oxidation resistance.

Integrated preparation of B4C–TiB2 multilayer graded ceramics with high hardness and high toughness

AbstractThe enhancement in the comprehensive performance of hardness, toughness, and strength is significant for ceramic materials. In this study, the B4C–TiB2 multilayer graded ceramics were designed and integrally manufactured by spark plasma sintering method using B4C and TiB2 as raw materials. The B4C–TiB2 multilayer graded ceramics feature a transition from the top layer with high hardness to the bottom layer with high toughness, passing through an intermediate layer. The gradient change of this material is observed in both the hardness and fracture toughness, reaching values of 36.2–28.4 GPa and 2.2–6.2 MPa m.5. The compressive strength reaches up to 2960 MPa, whereas the bending strength gets to 677 MPa in the appropriate loading direction. The structure forms a gradient pattern with high hardness on the front side, high toughness on the back side, and overall low density and high strength. This study may facilitate the development of impact‐resistant performance of lightweight materials.

Electrothermal Simulation of the Production of Alumina by Spark Plasma Sintering

Although the spark plasma sintering (SPS) method is a very advantageous technque in many aspects, the inability to clearly read the temperature formed on the material during sintering and heterogeneous temperature distributions are the biggest problems of this process. Therefore, it is a common situation that samples taken from different regions of the produced material have different densities and mechanical properties. In this study, the temperature distributions, current density and joule heating effect of the entire setup consisting of the alumina (Al2O3) sample to be sintered, inconel electrodes, graphite dies, punches and spacers, as well as the critical regions in this setup, are modeled by using finite element software. According to the results, the temperature is maximum at the centre of the Al2O3 sample and the temperature gradient along its radius is 22.4°C. The temperature difference between the inner wall of the hole which is opened in the graphite mold to measure the sintering temperature and the centre of the Al2O3 sample is around 40°C. In addition, during the SPS process, Al2O3 is not heated directly by the joule effect and the temperature gradient in the sample occurs due to mold surface radiation.

Production of Sm2Fe17N3 Bulk Magnets

Sm2Fe17N3 powder exhibits excellent magnetic properties but is unstable and decomposes into α-Fe and SmN phases at high temperatures. Therefore, the key to producing Sm2Fe17N3 bulk magnets is to reduce the deterioration of Sm2Fe17N3 powder during sintering. Herein, Sm2Fe17N3 bulk magnets were made using the spark plasma sintering (SPS) method with the addition of zinc stearate powder and zinc powder. Adding small amounts of zinc stearate powder and zinc powder improved the magnetic anisotropy and the coercivity of the magnets, respectively. The magnets produced by the SPS method using zinc stearate powder and zinc powder exhibited enhanced magnetic properties almost comparable to those of Sm2Fe17N3 powder.

Enhanced treatment of p-nitrophenol and coking wastewater through electrochemical and electrochemical-ozonation coupling process utilizing a novel Ti4O7 reactive electrochemical membrane anode

Organic pollutants in water could be removed by electrochemical treatment using a reactive electrochemical membrane (REM) with Magnéli phase Ti4O7, yet it is challenging to design suitable porosity to realize effective mass transfer and enhance the reactivity. Here, a novel Ti4O7 REM was prepared by a spark plasma sintering (SPS) method, which showed excellent electrochemical reactivity and mass transfer rate for organic pollutants in water. Compared to other Ti4O7 REMs, the novel Ti4O7 REM achieved a 140–9000-fold decrease in charge transfer resistance and a 5–110-fold increase in mass transfer rate. The p-nitrophenol in water can be completely removed in the REM system, with a maximum total organic carbon (TOC) removal rate of 85%. Then the REM system obtained an amazing removal rate of TOC (50.1%) and UV254 (89.6%) in the electrochemical treatment of real coking wastewater. In addition, to further enhance the removal efficiency, a coupled oxidation process with the novel Ti4O7 REM and O3 aeration was investigated. The TOC removal rate and energy consumption were 57.1% and 165.2 kWh (kg TOC)−1 at the optimal conditions within a short treating time. Our findings highlighted an innovative REM for a broad range of potential environmental applications.

Mechanical properties and high-pressure behavior of high entropy carbide (Mo, Nb, Ta, V, W)C

High-entropy carbides (HECs) often exhibit superior mechanical properties compared to single-component carbides. In this work, the (Mo0.2Nb0.2Ta0.2V0.2W0.2)C0.9 (named as Mo-HEC) was synthesized using the spark plasma sintering (SPS) method. The mechanical properties of Mo-HEC were evaluated using Vickers hardness and nanoindentation tests. The results indicate that Mo-HEC exhibits relatively high toughness, with hardness value surpassing the average hardness of constituent monocarbides. Nanoindentation tests on grains with different orientations revealed an isotropic mechanical behavior of Mo-HEC. Furthermore, the structural stability of Mo-HEC under extreme compression was explored by in situ high-pressure X-ray diffraction. Its cubic structure can be retained up to 58 GPa, and a bulk modulus of 334 GPa was obtained, which is among the highest reported values for HECs. The favorable mechanical properties, structural stability, and high bulk modulus suggest the significant potential of Mo-HEC for applications under extreme conditions.

Tunable yellow and orange emission of Ce, Eu doped multilayered YSZ/YAG ceramics

Eu3+ and Ce3+ doped YSZ/YAG multilayered luminescent ceramics were consolidated by the Spark Plasma Sintering (SPS) method. The optimal modes were explored during the SPS process for functionally graded ceramics (FGCs) structure fabrication. The introduction of rare-earth (RE) oxides into FGCs with different concentration leads to a shift in the temperature range of intense shrinkage to lower temperatures from 1280 °C to 1100–1190 °C and a decrease in the relative shrinkage during the SPS process by 3–6%. Morphological, optical and luminescent properties have been investigated in detail for fabricated YSZ/YAG ceramics with different arrangement of the layers. The nature of luminescent centers in FGCs was studied using time-resolved cathodoluminescent and steady-state photoluminescent (PL) spectroscopy. The PL efficiency of YSZ/YAG ceramics were analyzed and optimal compositions of the FGCs layers were determined. The YSZ/YAG novel functional multilayered ceramics could be promising candidate for light-emitting devices application.

High mechanical strength Si anode synthesis with interlayer bonded expanded graphite structure for lithium-ion batteries

Despite advancements in silicon-based anodes for high-capacity lithium-ion batteries, their widespread commercial adoption is still hindered by significant volume expansion during cycling, especially at high active mass loadings crucial for practical use. The root of these challenges lies in the mechanical instability of the material, which subsequently leads to the structural failure of the electrode. Here, we present a novel synthesis of a composite combining expanded graphite and silicon nanoparticles. This composite features a unique interlayer-bonded graphite structure, achieved through the application of a modified spark plasma sintering method. Notably, this innovative structure not only facilitates efficient ion and electron transport but also provides exceptional mechanical strength (Vickers hardness: up to 658 MPa, Young’s modulus: 11.6 GPa). This strength effectively accommodates silicon expansion, resulting in an impressive areal capacity of 2.9 mA h cm−2 (736 mA h g−1) and a steady cycle life (93% after 100 cycles). Such outstanding performance is paired with features appropriate for large-scale industrial production of silicon batteries, such as active mass loading of at least 3.9 mg cm−2, a high-tap density electrode material of 1.68 g cm−3 (secondary clusters: 1.12 g cm−3), and a production yield of up to 1 kg per day.

Thermoelectric properties of sintered Ba2AgSi3 crystals and search for impurities to control conductivity type by first-principles calculation

In this study, the basic properties of Ba2AgSi3 were investigated in detail from both experimental and computational viewpoints. Polycrystalline Ba2AgSi3 formed by an arc-melting apparatus under an argon atmosphere was ground into powders, and then powder samples were sintered using the spark plasma sintering method. Both n-type and p-type samples were obtained. This may be due to a slight deviation from the stoichiometric composition. The energy bandgap of Ba2AgSi3 was measured to be around 0.17 eV from the temperature dependence of electrical conductivity and was in agreement with that by first-principles calculations. Sintered samples exhibited a high Seebeck coefficient of −273 μV K−1 and a high power factor of 0.38 mW m−1 K−2 at 307 K for n-type samples. They were 217 μV K−1 and 0.23 mW m−1 K−2, respectively, at 320 K for p-type samples. The electronic structures of impurity-doped Ba2AgSi3 were also discussed using first-principles calculations to investigate the insertion site of impurity atoms. The calculations suggest that the substitution of B (P) at any Si site shifts the Fermi level and transforms it into p-type (n-type) semiconductors. On the other hand, substitution of Ba or Ag sites with B or P is unlikely to occur in terms of formation energy.

Microstructure and mechanical properties of SiCp/CF/Al hybrid composites with heterostructure constructed by macroscopic “core-shell” structure

Designing heterostructure is an effective way to comprehensively improve the strength-ductility of composites. However, the current methods of heterostructure integration consumes a large amount of energy. In this study, a macroscopic “core-shell” structure is designed with low cost and low energy consumption. The SiC particles (SiCp) and carbon fiber (CF) reinforced aluminum-based hybrid composite (SiCp/CF/Al) with heterostructure was fabricated utilizing the spark plasma sintering (SPS) method. The microstructure, interfacial structure, and mechanical properties of the SiCp/CF/Al before and after hot rolling were comprehensively investigated. The results revealed that the Vickers hardness values of the rich particle zone with high SiCp content were 54.32% and 48.10% higher than those of the poor particle zone before and after hot rolling, respectively. The synergistic strengthening effect of SiCp and CF significantly enhanced the yield strength and plasticity of the SiCp/CF/Al. Before and after hot rolling, the yield strength of SiCp/CF/Al was 242.68% and 173.16% of single CF-reinforced Al matrix composites, respectively. The extrinsic toughening was achieved through crack passivation and deflection at the interface of the rich particle zone and poor particle zone. Furthermore, the hindering and storing effects of the SiCp and CF on dislocations represented the primary intrinsic toughening mechanisms.

Production of Mn-Ga Magnets.

Mn-based magnets are known to be a candidate for use as rare-earth-free magnets. In this study, Mn-Ga bulk magnets were successfully produced by hot pressing using the spark plasma sintering method on Mn-Ga powder prepared from rapidly solidified Mn-Ga melt-spun ribbons. When consolidated at 773 K and 873 K, the Mn-Ga bulk magnets had fine grains and exhibited high coercivity values. The origin of the high coercivity of the Mn-Ga bulk magnets was the existence of the D022 phase. The Mn-Ga bulk magnet consolidated at 873 K exhibited the highest coercivity of 6.40 kOe.

High-Entropy Diborides-Silicon Carbide Composites by Reactive and Non-Reactive Spark Plasma Sintering: A Comparative Study.

The reactive spark plasma sintering (R-SPS) method was compared in this work with the two-step SHS-SPS route, based on the combination of the self-propagating high-temperature synthesis (SHS) with the SPS process, for the fabrication of dense (Hf0.2Mo0.2Ti0.2Ta0.2Nb0.2)B2-SiC and (Hf0.2Mo0.2Ti0.2Ta0.2Zr0.2)B2-SiC ceramics. A multiphase and inhomogeneous product, containing various borides, was obtained at 2000 °C/20 min by R-SPS from transition metals, B4C, and Si. In contrast, if the same precursors were first reacted by SHS and then processed by SPS under the optimized condition of 1800 °C/20 min, the desired ceramics were successfully attained. The resulting sintered samples possessed relative densities above 97% and displayed uniform microstructures with residual oxide content <2.4 wt.%. The presence of SiC made the sintering temperature milder, i.e., 150 °C below that needed by the corresponding additive-free system. The fracture toughness was also markedly improved, particularly when considering the Nb-containing system processed at 1800 °C/20 min, whereas the fracture toughness progressively decreased (from 7.35 to 5.36 MPa m1/2) as the SPS conditions became more severe. SiC addition was found to inhibit the volatilization of metal oxides like MoO3 formed during oxidation experiments, thus avoiding mass loss in the ceramics. The benefits above also likely took advantage of the fact that the two composite constituents were synthesized in parallel, according to the SHS-SPS approach, rather than being produced separately and combined subsequently, so that strong interfaces between them were formed.

Effects of Magnetic Fe Doping on the Thermoelectric Properties of TiNiSn Nanomaterials prepared via melt spinning method

As a kind of high temperature thermoelectric material, TiNiSn compound has the characteristics of high power factor and high thermal conductivity. Its thermoelectric performance is largely limited by the high thermal conductivity. In this paper, TiNiFexSn(x=0-0.05) samples are prepared by melt spinning combined with spark plasma sintering method. The results show that there are nanocrystals existed in the samples with a size of around 200nm. The grain size of the samples is refined through the melt-spinning process, and the lattice thermal conductivity is lower compared with the arc-melted samples. With the increase of Fe content, the lattice thermal conductivity of TiNiFexSn samples decreases, reaching a minimum value of 3.31W/mK when x=0.02, which is 44% lower than that of TiNiSn matrix. The carrier concentration of TiNiFexSn samples increases due to the doping of Fe, resulting in an increase of electrical conductivity and decrease of Seebeck coefficient and finally improvement of the power factor. The maximum zT value of TiNiFe0.03Sn sample is 0.54 at 900K, which is 35% higher than that of TiNiSn samples. This work shows that the melt spinning and magnetic Fe doping can effectively improve the thermoelectric properties of TiNiSn.

Enhanced energy storage performance with improved phase transition field in PBLZST AFE ceramics by the SPS method

PLZST-based antiferroelectric dielectric capacitors are the most advantageous materials in pulse power devices. However, the PbO volatilization, low recoverable energy density and efficiency (Wrec and η) hinder the large-scale development and application. An effective strategy was proposed by modifying the antiferroelectric with a linear dielectric material Ca(Zr,Ti)O3 via spark-plasma-sintering (SPS). This research achieved a remarkable Wrec of 5.54 J/cm3, exceptionally high recoverable energy storage intensity (ρ) of 20.52 × 10−3 J/kV∙cm−2 and η of 83%. The enhancement in Wrec and ρ resulted from the enhanced phase-transition-field by the decreased tolerance factor and increased electronegativity difference, the grains refinement and stoichiometric ratio accuracy by SPS. The increase of η was due to the non-ferroelectrically Ca2+ on the A-site and the improved insulation by SPS. Moreover, the rapid and low temperature sintering helped inhibit lead volatilization and increased mechanical hardness (HV > 7 GPa). Our work demonstrates that PBLZST-based ceramics prepared by SPS can be exploited for enhanced energy-storage performance under a low voltage in an environmentally-friendly way.

Atomic‐resolution Interfacial Microstructure and Thermo‐electro‐magnetic Energy Conversion Performance of Gd/Bi0.5Sb1.5Te3 Composites

Thermo‐electro‐magnetic materials with simultaneously large magnetocaloric (MC) and thermoelectric (TE) effects are the core part for designing TE/MC all‐solid‐state cooling devices. Compositing MC phase with TE material is an effective approach. However, the elemental diffusion and chemical reaction occurring at the two‐phase interfaces could significantly impair the cooling performance. Herein, Gd/Bi0.5Sb1.5Te3 (Gd/BST) composites were prepared by a low‐temperature high‐pressure spark plasma sintering method with an aim to control the extent of interfacial reaction. The reaction of Gd with the diffusive Te and the formation of GdTe nanocrystals were identified at the Gd/BST interfaces by the atomic‐resolution microscope. The formed antisite defects and enhanced {000 l} preferential orientation in BST are responsible for the increased carrier concentration and mobility, which leads to optimized electrical properties. The heterogeneous interface phases, along with antisite defects, favor the phonon scattering enhancement and lattice thermal conductivity suppression. The optimized composite sintered at 693 K exhibited a maximum ZT of 1.27 at 300 K. Furthermore, the well‐controlled interfacial reaction has a slight impact on the magnetic properties of Gd and a high magnetic entropy change is retained in the composites. This work provides a universal approach to fabricating thermo‐electro‐magnetic materials with excellent MC and TE properties.