Spark Plasma Sintering Synthesis Research Articles

Spark plasma sintering synthesis of ReB2-type medium-entropy diboride (W1/3Re1/3Ru1/3)B2 with high hardness

A new medium-entropy diboride (MEDB) (W1/3Re1/3Ru1/3)B2 has been synthesized by spark plasma sintering of elemental powders at 1600 °C. Despite the dissimilar structures of WB2, ReB2 and RuB2, the sintered MEDB consists of a single hexagonal ReB2-type phase (space group P63/mmc) with a relative density of 94.2% and an average grain size of 6.8 ± 2.2 μm. Structural refinement and electron microscopy measurements show that the W, Re, and Ru atoms occupy the same crystallographic site and are distributed uniformly in the lattice. The (W1/3Re1/3Ru1/3)B2 MEDB has Vickers hardnesses of 30.7 GPa at a load of 0.49 N and 20.5 GPa at a load of 9.8 N, which are comparable or higher than those reported for individual binary counterparts.

Composition, structure and properties of hard alloy products from electroerosive powders obtained from T5K10 hard alloy waste in kerosene

The paper implements scientific and applied principles of coupling the technology of obtaining new powder materials from waste of hard alloys of the T5K10 brand by electroerosive dispersion and the technology of compacting them by SPS synthesis. The aim of the work was to study the composition, structure and properties of carbide products made from powders obtained by electrodispersing T5K10 alloy waste in kerosene. Electrodispersion of T5K10 alloy waste was carried out in lighting kerosene on a patented installation. The consolidation of the obtained powder was carried out by the spark plasma sintering (SPS) method using the spark plasma sintering system SPS 25-10. The choice of powders obtained by electroerosive dispersion of the T5K10 hard alloy waste was justified by its cost and properties. The resource of tungsten-titanium-cobalt hard alloys from T5K10 electroerosion powders is determined not only by the properties of the feedstock, but also by the technology of their production (SPS synthesis). Based on the conducted experimental studies, it can be concluded that the use of the spark plasma sintering method to produce products from powder obtained by electroerosive dispersion of the T5K10 alloy will ensure high performance of products (cutting tools) due to the uniformity of the surface, favorable structure and low porosity of the product. It is noted that hard alloys made of electroerosion dispersed T5K10 alloy particles obtained by spark plasma sintering under conditions of rapid heating and short working cycle duration have higher physico-mechanical properties compared to industrial alloys from which the initial powder particles were obtained by suppressing grain growth and obtaining an equilibrium state with submicron and nanoscale grain. This study was funded by the Russian Science Foundation, grant No. 22-29-00123, https://rscf.ru/project/22-29-00123/.

Multi-type dislocation substructure evolution in a high-strength and ductile duplex high-entropy nanocomposites

Developing energy-efficient and scalable microstructural solutions that enable both an intrinsically high strength and high ductility has always been a pursuit in materials science. We have used a spark plasma sintering synthesis strategy to efficiently fabricate a duplex high-entropy nanocomposite composed of the high-entropy nano-intermetallic precipitates and high-entropy nanoscale solid-solution domains. The high-entropy nanocomposite with spontaneous phase separation accompanied by the reorganization of high-entropy components achieves the minimal lattice misfit (∼0.07%) integration of the high-entropy nano-intermetallic precipitates with the high-entropy nanoscale solid-solution domains. The resulting high-entropy nanocomposite exhibited a high tensile strength (i.e., a fracture strength close to 1.7 GPa) and large plasticity (i.e., a uniform elongation close to 20%). The duplex nanostructure in our high-entropy nanocomposite described herein had multi-type dislocation substructure evolution during deformation, including dislocation planar slip, coplanar dislocation arrays, dislocation walls, microbands, and stacking faults in solid-solution domains. Because of the dominance of multiple hardening modes, our high-entropy nanocomposite could ensure that the plasticity was large enough to maintain a high strength. Our findings break through the challenge of the tradeoff between efficiency and superb performance in preparing nanostructured materials, thereby significantly facilitating the development of high-performance nanocomposites and advanced nanostructured materials.

Comparative study of WC-based hard alloys fabrication via spark plasma sintering using Co, Fe, Ni, Cr, and Ti binders

The paper presents a method of fabrication and a comparison of the characteristics of obtained cemented carbide samples based on tungsten carbide with 10% metal binder. They were synthesized by spark plasma sintering (SPS) at different sintering temperatures: Co (1200 °C), Fe and Ni (1150 °C), Cr (1500 °C), and Ti (1400 °C). During the SPS-consolidation process, investigations of the dilatometric characteristics of samples of starting powders of identical granulometric composition obtained by mixing/grinding resulting in the fractional composition in the particle size range up to 10 μm are presented. The mechanism of phase formation and microstructure of the obtained materials is investigated by XRD, SEM, and EDS. The possibility of synthesizing hard alloys WC – 10%Ti and WC – 10% Cr by the mechanism of reaction SPS synthesis with a reduction in the synthesis time in comparison with traditional sintering methods has been demonstrated. Analyses have shown that during sintering of alloys containing Ti and Cr the volume content of WC decreases to 47% because of dissolution and interaction, while in alloys containing Co, Ni, and Fe, the volume content of WC remains unchanged (85–86%). This led to a dramatic change in hardness, fracture toughness, and strength when replacing Co, Ni, or Fe with Ti or Cr.

Facile Synthesis of a Common Na‐Ion Battery Cathode Material Na3V2(PO4)2F3 by Spark Plasma Sintering

In the pursuit of facile, fast, and efficient methods for the synthesis of various compounds for a variety of applications, spark plasma sintering (SPS) technique is considered to be a powerful and simple tool. Using this technique, a popular cathode material for Na‐ion batteries—Na3V2(PO4)2F3—is synthesized and characterized with X‐ray diffraction and scanning electron microscopy (SEM), and is electrochemically tested in Swagelok‐type cells in a galvanostatic mode. The obtained material is compared with the conventionally synthesized (via a solid‐state route) sample. SEM analysis shows 2 times smaller particles in the case of SPS‐synthesized material compared with the solid‐state‐synthesized material which is to be expected from the fast (40 min in total) SPS synthesis that practically excludes grain/particle growth and promotes much faster diffusion, thereby drastically enhancing the reaction kinetics. Electrochemical performance of the SPS‐obtained material shows an improvement in decreasing the overpotential and reducing the capacity loss at high C‐rates (8C).

Spark plasma sintering (SPS) synthesis and tribological behaviour of MAX phase composite of the family Tin+1SiCn (n = 2)

In this work we report on the spark plasma sintering (SPS) synthesis of Maxthal 312 (nominally-Ti3SiC2 but containing ancillary TiCX) and Maxthal 312-TiC composite as well as their dry sliding room-temperature tribological behaviour. The sintering procedure was further investigated to elucidate the decomposition of Ti3SiC2 by replicating the carbon-rich SPS sintering environment using DSC-TG analysis on the Maxthal 312 powder carried out in a graphite crucible. In the SPSed bulk products, Ti3SiC2 and TiCX were the major phases in the sintered Maxthal 312 disc whilst Ti3SiC2 and (TiCX + TiC) were the major phases in the sintered Maxthal 312-TiC composite disc. In addition, some traces of the compulsory intermediate phase (TiSi2) that has not been fully consumed coexisted in relatively small amounts in both bulk samples. Reconciling the SPS synthesis and the DSC-TG analysis, it appears that the formation of TiCX is attributed mainly to the intrinsic decomposition occurring at temperature above 1350 °C or partly due to the graphite paper used to wrap the powder during the SPS synthesis. Rotary dry sliding tribological behaviour of the sintered discs was then subsequently investigated using Al2O3 as a counterface at room temperature. The incorporation of TiC into the Ti3SiC2 matrix as well as the in-situ TiCX formed in the matrix during synthesis appears to improve the tribological behaviour of Ti3SiC2 for the tested conditions.

Influence of sintering environment on the spark plasma sintering of Maxthal 312 (nominally-Ti3SiC2) and the role of powder particle size on densification

Herein, we report on the synthesis of Ti3SiC2 via the Maxthal 312 (nominally-Ti3SiC2) commercial powder route using spark plasma sintering (SPS). The SPSed bulk samples contained ancillary phases (TiCX and TiSi2) irrespective of the sintering environment as confirmed by XRD phase analysis. The optimum sintering temperature below which intrinsic decomposition starts appears to be ∼1350 °C in vacuum and ∼1450 °C in argon atmosphere, respectively. The role of powder particle size on densification during spark plasma sintering (SPS) was investigated. Analysis of the SPS processing parameters (piston movement and piston speed) indicated that the densification of Maxthal 312 powder (nominally-Ti3SiC2) can be improved by reduction in particle size, thus promoting the Joule effect, necking, mechanical movement of particles and plastic deformation. Further investigation on the role of graphite heating element as well as environment during the SPS synthesis showed that the graphite paper employed during SPS as well as possible silicon loss during vacuum sintering were responsible for the decomposition at temperature below the melting point of Si and/or shifting of the resultant bulk sample composition away from monolithic phase.

Pulse Cathodoluminescence of the Impurity Centers in Ceramics Based on the MgAl2O4 Spinel

The spectral and luminescence decay kinetics of magnesium aluminate spinel ceramics prepared by spark plasma sintering (SPS) and the starting nanopowders were studied. It was demonstrated that two types of luminescence in spinel ceramics can be observed after pulse e-beam excitation. The first type is due to intrinsic defects, and the second type due to Cr3+ and Mn2+ ions. It was shown that the luminescence decay kinetics for Cr3+ and Mn2+ impurity ions can be approximated by the sum of two exponents. The decay times for the Cr3+ ion are 35 and 409 ns, for the Mn2+ ion are 29 and 340 ns. High-temperature exposure during SPS synthesis does not lead to a change in the nearest surroundings of impurity ions. In the luminescence spectra of ceramic and powder samples the intensity ratio changes of intrinsic and impurity centers is associated with strong diffuse scattering of light for spinel nanopowders.

Tailoring band gap and thermal diffusivity of nanostructured phase-pure ZnAl2O4 by direct spark plasma sintering synthesis

A rapid, one-step synthesis of pristine ZnAl2O4 by spark plasma sintering has been developed in this work. Using inexpensive reagents (ZnO and Al2O3) and the direct synthesis approach, a total synthesis time of five minutes was achieved. Varying the sintering parameters allows for tailoring of the density, crystallite size, and band gap. An extensive parameter study was performed to understand the formation of impurities at different conditions, and also to investigate the effect of using either γ– or α-Al2O3 as the aluminum source. The experimental results reveal that a heating ramp of 200°C/min up to 1000°C, and immediate cooling thereafter, produces pristine ZnAl2O4. The thermal diffusivity and band gap were found to be dependent on the synthesis conditions employed. The synthesis approach in this work provides a protocol for controlled preparation of bulk ZnAl2O4 with tunable properties.

AlFe2-xCoxB2 (x = 0-0.30): TC Tuning through Co Substitution for a Promising Magnetocaloric Material Realized by Spark Plasma Sintering.

AlFe2B2 and AlFe2-xCoxB2 (x = 0-0.30) were synthesized from the elements in three different ways. The samples were characterized by powder X-ray diffraction, Rietveld refinements, energy-dispersive X-ray spectroscopy, and magnetic measurements. Using Al flux the formation of AlFe2B2 single crystals is preferred. Arc melting enables the substitution of ∼6% Co. This substitution of Fe by Co decreases the Curie temperature TC from 290 to 240 K. The highest Co substitution up to 15% is achieved by spark plasma sintering (SPS). TC is reduced to 205 K. In all cases an excess of Al is necessary to avoid the formation of ferromagnetic FeB. Al13Fe4-xCox is the common byproduct. TC and the cobalt content are linearly correlated. The transition paramagnetic-ferromagnetic remains sharp for all examples. The magnetic entropy change of the Co-containing samples is comparable to AlFe2B2. SPS synthesis yields, in short reaction times, a homogeneous and dense material with small amounts of paramagnetic Al13Fe4-xCox as an impurity, which can serve as sinter additive. These properties make AlFe2-xCoxB2 a promising magnetocaloric material for applications between room temperature and 200 K.

Rapid and low temperature spark plasma sintering synthesis of novel carbon nanotube reinforced titanium matrix composites

Multi–walled carbon nanotube (MWCNT) reinforced titanium matrix composites were synthesized using a spark plasma sintering method at a low sintering temperature of 550 °C. The effects of the weight fraction of MWCNTs on the microstructures and the mechanical and thermal properties of the composites were investigated. No reaction products were detected in the composites, indicating that the MWCNTs in the composites maintained their structural integrity after sintering, and thus, because of their advantageous properties, could reinforce the titanium matrix. As a result, the compressive strength of the composite containing 0.4 wt.% MWCNTs reached 1106 MPa, which was an increase of 61.5% compared to that of pure titanium under at the same conditions. In addition, the results revealed that compressive strength of the bulk compacts increased initially and then decreased with an increase in weight fraction of MWCNTs. However, compressive strain of the sintered composites continued to fall at a slow rate. The microhardness and thermal diffusivity of the composites rose steadily with an increasing content of MWCNTs. When the weight fraction of MWCNTs in the composites exceeded 0.8%, the compressive strength of the composites declined significantly due to the increasing aggregation of the MWCNTs.

Investigation of Mg2Si formation from Si and Mg by using spark plasma sintering synthesis

AbstractIn this study, we fabricated Mg2Si from metal Mg and Si with different particle sizes (425 - 300, 300 - 180, and 75 μm or less) using spark plasma sintering (SPS) equipment. Additionally, the Mg2Si formation was investigated. A sieved Si powder was mixed with metal Mg powder in an inert gas (Ar) atmosphere. The mixture was placed in a graphite die while still in an Ar atmosphere and subjected to SPS at 923 K and 1113 K. The obtained sintering bodies were Mg2Si particles with a size of about 5 μm. Then, the sintered bodies were evaluated by X-ray diffraction (XRD). As a result, it was confirmed that generation of Mg2Si increased with decreasing Si particle size.

Improved thermoelectric performance of n-type Ca and Ca-Ce filled skutterudites

Thermoelectric (TE) technology for use in automotive waste heat recovery is being advanced by General Motors with support from the US Department of Energy. Skutterudites are a very promising material for this application of TE technology due to their superior mechanical properties and good TE performance. Double-filled YbxBayCo4Sb12 with ZT values around 1.1 at 750 K are the best performing n-type skutterudites produced on a large scale using an economically viable approach of melt spinning (MS) in conjunction with spark plasma sintering (SPS). Another economical production method on the tons scale, the melt quench annealing (MQA) technique, has been recently claimed by Treibacher Industrie AG, further information is available [G. Rogl et al., Acta Mater. 76, 434–448 (2014)]. A possible hurdle to commercial implementation of these materials is the use of rare earths as the fillers to reduce thermal conductivity and improve the electrical transport properties. It will be shown herein that skutterudites double-filled with Ca and Ce, both of which are lower-cost fillers, display markedly different TE properties depending on whether they are produced by MQA or MS + SPS synthesis techniques. Ca and Ce double-filled skutterudites prepared by MS + SPS have TE properties that are superior to the same compositions prepared by MQA and that are comparable to the best performing Yb and Ba filled materials. Furthermore, the results of this study suggest that the unusually poor transport properties of MQA Ca-filled skutterudites can be ascribed to deleterious secondary phases, which is contrary to reports in the literature attempting to explain these irregularities via band structure features.

Experimental study on phase formation of SiC doped MgB2: processing of Mg–B–SiC powders by spark plasma sintering

In order to study the effect of spark plasma sintering (SPS) technique synthesis SiC–MgB2 on the phase formation, the MgB2 and SiC–MgB2 bulks were fabricated with mixed powders by various SPS synthesis routes. The phase formation processes were investigated with the aid of X-ray diffraction analysis, TEM investigations and sintering theories. The solid–solid reaction between Mg and B powders formed MgB2 at low temperature. As the sintering temperature increases, the reactions of molten Mg with B form MgB2, and simultaneously, the molten Mg promotes the decomposition of SiC and nuclei of Mg2Si may form on the surface of SiC grains; the nascent MgB2 incorporates the carbon into lattice, hereby enhancing the SiC decomposition. The experimental results are in good agreement with the assumed chemical reaction.

Spark plasma sintering synthesis of intermetallic T2 in the Mo–Si–B system

Mo5SiB2 (T2) was synthesized by sparking plasma sintering (SPS) under different heating rates and sintering temperatures. The powder mixture with a T2 composition (Mo–12.5Si–25B (at.%)) failed to produce the T2 single-phase alloy due to the volatilization of Si during SPS process. Extra 0.5at.% Si added to this mixture offset the volatilization loss. It has been found that heating of the mixture at low heating rates favored the formation of binary phases in the solid state at medium temperatures. In this work, the T2 alloy with a fine-grained microstructure was obtained via a liquid–solid reaction when the mixture was heated fleetly to the temperatures above the silicon melting point at the rapid heating rate of 200°C/min. The sintering temperature at 1500°C for T2 synthesis is beneficial to enhance further densification, as well as to avoid abnormal grain growth at higher temperatures.

SPS synthesis and consolidation of TiAl alloys from elemental powders: Microstructure evolution

Some works have studied the sintering of TiAl by means of Spark Plasma Sintering (SPS) and it is believed that it is possible to obtain very fine microstructures and very interesting mechanical properties. As raw materials, normally pre-alloyed powders have been used, obtained by atomization or mechanical alloying. However, few works have studied the consolidation of elemental powders. This work presents the synthesis and densification of TiAl-based alloys by means of Spark Plasma Sintering (SPS) using elemental powders as raw materials. The selected composition was Ti–48Al–2Cr–2Nb. The densification process, the evolution of the microstructure with the temperature and the diffusion of the elements (including heavy metals Cr and Nb) are presented. In addition, SPS products are compared with TiAl alloys from elemental powders obtained by conventional methods.

Spark plasma sintering synthesis and mechanical spectroscopy of the ω-Al0.7Cu0.2Fe0.1 phase

Starting from a mixture of Al–Cu–Fe quasicrystalline (QC) particles and Al powder, a fully dense and almost Al–Cu–Fe ω single-phase alloy was produced by spark plasma sintering. This technique allows synthesising large samples with sizes suitable for mechanical spectroscopy experiments. Mechanical spectroscopy was selected because it is a relevant tool for detecting the presence of structural defects at both nano and microscopic scales. Young’s moduli were measured in the 15 kHz range as a function of temperature by the resonant frequency method. Young’s moduli behave similarly for typical metals and exhibit values that are comparable to those of the Al–Cu–Fe QC phase. The damping coefficient Q−1 was determined at various temperatures between room temperature and 840 K over a large frequency range, i.e. between 10−3 and 10 Hz. The results suggest that solid friction effects do occur. In addition, a relaxation peak is observed in the intermediate temperature range.

Synthesis by Spark Plasma Sintering: A new way to obtain electrode materials for lithium ion batteries

In the search of high-performance materials for lithium ion batteries, Li 2CoPO 4F offers many advantages like high theoretical capacity and high operating potential. The synthesis of Li 2CoPO 4F has been reinvestigated considering a conventional solid state reaction and an unconventional way. Due to the long heat-treatments required by the conventional approach, a beginning of grains coalescence is observed. Limiting particles growth has been allowed by a shorter reaction done by SPS (Spark Plasma Sintering). By this method, the synthesis of Li 2CoPO 4F was greatly shortened (from 10 h to 9 min), which favours the getting of submicrometric particles. The comparison of the electrochemical properties of the Li 2CoPO 4F obtained by the different ways confirms the advantages of SPS synthesis in performance enhancement.

Effect of n-type Dopants on CoSb3 Skutterudite Thermoelectrics Sintered by Spark Plasma Sintering

<TEX>$CoSb_3$</TEX> Skutterudites materials have high potential for thermoelectric application at mid-temperature range because of their superior thermoelectric properties via control of charge carrier density and substitution of foreign atoms. Improvement of thermoelectric properties is expected for the ternary solid solution developed by substitution of foreign atoms having different valances into the <TEX>$CoSb_3$</TEX> matrix. In this study, ternary solid solutions with a stoichiometry of <TEX>$Co_{1-x}Ni_xSb_3$</TEX> x = 0.01, 0.05, 0.1, 0.2, <TEX>$CoSb_{3-y}Te_y$</TEX>, y = 0.1, 0.2, 0.3 were prepared by the Spark Plasma Sintering (SPS) system. Before the SPS synthesis, the ingots were synthesized by vacuum induction melting and followed by annealing. For phase analysis X-ray powder diffraction patterns were checked. All the samples were confirmed as single phase; however, with samples that were more doped than the solubility limit some secondary phases were detected. All the samples doped with Ni and Te atoms showed a negative Seebeck coefficient and their electrical conductivities increased with the doping amount up to the solubility limit. For the samples prepared by SPS the maximum value for dimensionless figure of merit reached 0.26, 0.42 for <TEX>$Co_{0.9}Ni_{0.1}Sb_3$</TEX>, <TEX>$CoSb_{2.8}Te_{0.2}$</TEX> at 690 K, respectively. These results show that the SPS method is effective in this system and Ni/Te dopants are also effective for increasing thermoelectric properties of this system.

Spark plasma sintering synthesis of porous nanocrystalline titanium alloys for biomedical applications

The reason for the extended use of titanium and its alloys as implant biomaterials stems from their lower elastic modulus, their superior biocompatibility and improved corrosion resistance compared to the more conventional stainless steel and cobalt-based alloys [Niinomi, M., Hattori, T., Niwa, S., 2004. Material characteristics and biocompatibility of low rigidity titanium alloys for biomedical applications. In: Jaszemski, M.J., Trantolo, D.J., Lewandrowski, K.U., Hasirci, V., Altobelli, D.E., Wise, D.L. (Eds.), Biomaterials in Orthopedics. Marcel Dekker Inc., New York, pp. 41–62]. Nanostructured titanium-based biomaterials with tailored porosity are important for cell-adhesion, viability, differentiation and growth. Newer technologies like foaming or low-density core processing were recently used for the surface modification of titanium alloy implant bodies to stimulate bone in-growth and improve osseointegration and cell-adhesion, which in turn play a key role in the acceptance of the implants. We here report preliminary results concerning the synthesis of mesoporous titanium alloy bodies by spark plasma sintering. Nanocrystalline cp Ti, Ti–6Al–4V, Ti–Al–V–Cr and Ti–Mn–V–Cr–Al alloy powders were prepared by high-energy wet-milling and sintered to either full-density (cp Ti, Ti–Al–V) or uniform porous (Ti–Al–V–Cr, Ti–Mn–V–Cr–Al) bulk specimens by field-assisted spark plasma sintering (FAST/SPS). Cellular interactions with the porous titanium alloy surfaces were tested with osteoblast-like human MG-63 cells. Cell morphology was investigated by scanning electron microscopy (SEM). The SEM analysis results were correlated with the alloy chemistry and the topographic features of the surface, namely porosity and roughness.