Spark Plasma Sintering Technology Research Articles

Metal Carbide Additives in Graphite‐Silicon Composites for Lithium‐Ion Batteries

AbstractThe pathway for improving lithium‐ion batteries′ energy density strongly depends on finding materials with enhanced performance. Although great efforts have been done, on the anode‐side, graphite is still the best choice. In the last decade, silicon elements are attracting growing attention as anode since their use can theoretically increase specific capacity of the negative electrode side. However, as the electrochemical mechanism involves the alligation of a large amount of Li, the silicon electrode experiences huge volume changes (more than 300 % of its initial volume), leading to fractures and pulverizations of the electrode. Herein, we propose for the first time using Molybdenum and Chromium Carbides as additive to stabilize graphite/silicon composites. Spark plasma sintering technology is used to sinter the electrode powders. We demonstrated that the presence of molybdenum or chromium carbides promotes the performance of C/Si electrodes, improving the cycling stability compared to pristine graphite/silicon electrodes.

Microstructure and properties of porous Si3N4 ceramics fabricated by digital light processing combined with spark plasma sintering

Sintering process is an important factor affecting the properties of porous Si3N4 ceramics. However, there are few studies on the properties of porous Si3N4 ceramics fabricated by combining digital light processing (DLP) technology and spark plasma sintering (SPS) technology. In this study, a method to prepare porous Si3N4 ceramics by combining DLP with SPS technology was proposed, and ceramic samples were successfully prepared. The effect of sintering temperature and holding time of SPS technology on the microstructure and properties of porous Si3N4 ceramics prepared by DLP technology was discussed. With the increase of sintering temperature from 1600 °C to 1700 °C, the conversion content of α-Si3N4 phase to β-Si3N4 phase increased from 19.19% to 76.72%. The fracture mode of porous Si3N4 ceramics gradually transformed from intergranular to transgranular. The porosity of Si3N4 ceramics gradually decreased from 40.34 ± 4.9% to 30.54 ± 2.7% with opposite trend in bulk density. And the flexural strength increased from 109.1 ± 7.6 MPa to 249.5 ± 4.0 MPa. When the sintering temperature was 1700 °C, the content of β-Si3N4 increased first and then remained essentially constant with the increase of holding time from 5 min to 15 min. The porosity increased from 30.54 ± 2.7% to 35.15 ± 2.5%, while the variation in bulk density were opposite. And the flexural strength severely decreased from 249.5 ± 4.0 MPa to 126.1 ± 7.2 MPa. This research provides valuable insights into the DLP-forming ceramic materials sintered by SPS technology.

Effects of spark plasma sintering parameters on properties of Fe-based bulk amorphous alloys

Fe-based bulk amorphous alloys were prepared by spark plasma sintering (SPS) with different parameters. The thermal stability of Fe-based bulk amorphous alloys was characterized by differential scanning calorimetry (DSC) to determine the thermodynamic characteristic temperature, such as glass transition temperature (Tg) and crystallization temperature (Tx). X-ray diffraction (XRD), Archimedes drainage method, universal material testing machine, Electrochemical workstation and scanning electron microscope (SEM) were utilized to analyze the phase composition, relative density, compressive strength, corrosion performance, and fracture morphology and corrosion morphology of Fe based bulk amorphous alloys. This experiment show that Fe-based amorphous powder can be made into Fe-based bulk amorphous alloy with the size of φ12 × 9 mm by SPS technology. Meanwhile, the sample prepared with the parameters of sintering temperature of 560 ℃, sintering pressure of 550 MPa and the holding time of 1 min basically maintains the amorphous structure, and it has good compressive strength of 678 MPa, Microhardness of 1351.2 HV, density of 94.4 %, and perfect corrosion resistance.

Optimization of Spark Plasma Sintering Technology by Taguchi Method in the Production of a Wide Range of Materials: Review.

This paper reviews the production of sinters using the spark plasma sintering method. SPS (spark plasma sintering) technology has been used for several decades, mainly in laboratories, to consolidate a huge number of both new and traditional materials. However, it is now more often introduced into practical industrial use, with equipment as early as the fifth generation capable of producing larger-size components at competitive costs. Although the mechanism of sintering with the use of this method is not yet understood, the effectiveness of the SPS process for the rapid and efficient consolidation of a wide range of materials with novel micro-structures remains indisputable. With a relatively wide variation in chemical composition, the structure allows the selection of appropriate consolidation parameters for these materials. The influence on the values of apparent density and mechanical properties depends on the parameters of the spark plasma sintering process. In order to achieve a density close to the theoretical density of sinters, optimization of the sintering parameters, i.e., sintering temperature, heating rate, sintering time, pressing pressure and protective atmosphere, should be carried out. In this paper, the optimization of spark plasma sintering of Si3N4-Al2O3-ZrO2 composite was carried out using the Taguchi method. The effects of four sintering factors, namely heating rate, sintering time, sintering temperature and sintering pressure, on the final density were investigated. Optimal sintering conditions were proposed and a confirmation experiment was conducted. The optimal combination of sintering conditions for spark plasma sintering (SPS) of Si3N4-Al2O3-ZrO2 composite for high apparent density was determined as A3-B3-C3-D2. Based on ANOVA analysis, it was found that the apparent density of sintering was significantly influenced by sintering temperature, followed by pressing pressure, sintering time and heating rate. Validation of the developed mathematical model predicting the apparent density of sinters showed close agreement between the predicted response results and experimental results.

Sintering and characterization studies of aluminum-dinickel boride composites

The mechanical mixing of dinickel boride and aluminium powders was achieved with a Turbula mixer. The admixed powders were fabricated via the spark plasma sintering technology using an optimized sintering condition. The microstructures, phases, and hardness results of the consolidated compacts were examined. The results showed that the sintered composites had an average relative density of 99.6%. The hardness values of the composites were upgraded (34.3–37.4 HV1) with increasing Ni2B particles. An in-situ phase was revealed from the microstructures and diffractograms of the sintered composites because of the interface reaction between the ceramic particle and aluminium matrix.

Microstructure, mechanical property and cutting performance of (Ti,W)C/Mo/Co/Ni cermet tool material prepared by spark plasma sintering and high frequency induction heating

The (Ti,W)C/Mo/Co/Ni cermet tool material is produced using a combination of spark plasma sintering and high frequency induction heating (HFIH-SPS) mixed sintering technology. This study investigates the influence of various sintering parameters on the microstructure and mechanical properties of (Ti,W)C/Mo/Co/Ni cermet tool material. The findings indicate that the rapid sintering densification of (Ti,W)C/Mo/Co/Ni cermet tool material can be achieved by the mixed sintering technology at a lower sintering temperature. The rapid sintering process observed in this study can be mainly attributed to the plasma activation effect generated by pulse current and the Joule heat effect produced by the metal particles under high frequency induction. The optimized relative density of the (Ti,W)C/Mo/Co/Ni cermet tool material reaches 99.10%, with the hardness of 20.28 ± 0.58 GPa, the fracture toughness of 7.74 ± 0.14 MPa·m1/2 and the flexural strength of 796.12 ± 36.55 MPa. The indentation of (Ti,W)C cermet exhibits a regular cross shape, and the indentation edge is smooth, which indicates a good fracture toughness. The high mechanical properties of (Ti,W)C/Mo/Co/Ni cermet tool material are mainly attributed to the interaction between crystal grain boundary solute strengthening and dislocation movement. The tool has shown good cutting performance during the subsequent dry cutting of 40Cr steel, with the lowest surface roughness Ra value of 1.097 µm.

Effect of HA Content on Microstructure and Properties of Ti-27Nb-17Ta-8Zr/HA Composite.

In this paper, Ti-27Nb-17Ta-8Zr/HA series composite materials were prepared by spark plasma sintering (SPS) technology. The medical titanium alloy (Ti-27Nb-17Ta-8Zr) with good mechanical properties, wear resistance, and corrosion resistance was combined with the hydroxyapatite (HA) bioactive ceramic with high biological activity and bone-binding ability. Moreover, the density, microstructure evolution, metal/ceramic reaction, mechanical behavior, in vitro bioactivity, and influencing mechanisms of composite materials with different HA contents were studied. The research results indicate that all biological composite materials are composed of β-Ti solution, α-Ti, and ceramic phases (Ti2O, CaTiO3, CaO, TixPy). With the increase of HA content, the compressive strength and yield strength of the composite material show a trend of first increasing, then decreasing, and then slowly increasing. After soaking in SBF artificial simulated body fluid for 5 days, the deposition of elements such as Ca and P on the surface significantly increased, while elements such as Ti, Nb, Ta, and Zr were evenly distributed in the matrix, demonstrating good in vitro mineralization ability and facilitating the attachment and growth of osteoblasts.

WC-10 wt.%Co hard alloy fabrication via spark plasma sintering of mechanically activated powders

Subject of research: the paper presents a method of hard alloy fabrication via spark plasma sintering technology performed for mechanically activated powders of mixed WC compositions with 10 wt % Co.
 Methods and objects of research: mechanical activation of the powders was carried out in a ball planetary mill by wet milling/stirring in anhydrous isopropanol medium using a milling container and balls made of WC.
 Main results of research: the paper presents experimental data on the densification dynamics (kinetics and sintering stages) during spark plasma sintering at temperatures of 1000, 1100, 1150 and 1200 С. The results of studies of the phase composition, microstructural organization and physical and mechanical properties of WC-10wt.%Co hard alloy are given. Optimal sintering parameters (1200 C, 9 min) are determined. Hardness and mechanical strength of WC-10wt.%Co hard alloy samples increase as the sintering temperature increases with reaching the density of 99.6 % of the theoretical value. It is shown that with increasing temperature from 1000 to 1200 C the average WC grain size slightly increases from 3.3 m to 3.9 m with increasing contribution of the share of larger grains with size 4 m.

Transient liquid phase bonding assisted spark plasma sintering of La-Fe-Si magnetocaloric bulk materials

The poor mechanical properties of La-Fe-Si based alloys restrict the potential of these magnetocaloric materials. Hence, a novel transient liquid phase bonding (TLPB) processing technique was deployed during spark plasma sintering (SPS) of La-Fe-Si based bulk materials. A series of binder-free LaFe11.8Si1.2 bulk materials were prepared by SPS and hot-pressing sintering (HPS). Transient melting, which occurred during SPS, accelerated the decomposition of the 1:13 phase, resulting in low porosity and high strength. Compared to HPS samples, SPS samples have significantly larger maximum compressive strength (σbc)max of ∼637.9 MPa at a strain of 4.7%, good thermal conductivity of ∼7.6 W·m−1·K−1 at 300 K, and a large (−ΔSM)max value of ∼11.7 J·kg−1·K−1 at TC= 193 K under a magnetic field change of 0 − 5 T. Thus, binder-free La-Fe-Si based bulk magnetocaloric materials with an excellent property set have been successfully prepared by TLPB assisted SPS technology.

Microstructural Characterization and Prior Particle Boundary (PPB) of PM Nickel-Based Superalloys by Spark Plasma Sintering (SPS).

This research investigates the microstructure and defects of powder metallurgy (PM) nickel-based superalloys prepared by spark plasma sintering (SPS). The densification, microstructural evolution, and precipitate phase evolution processes of FGH96 superalloy after powder heat treatment (PHT) and sintering via SPS are specifically analyzed. Experimental results demonstrate that SPS technology, when applied to sinter at the sub-solidus temperature of the γ' phase, effectively mitigates the formation of a prior particle boundary (PPB). Based on experimental and computational findings, it has been determined that the presence of elemental segregation and Al2O3 oxides on the surface of pre-alloyed powders leads to the preferential precipitation of MC-type carbides and Al2O3 and ZrO2 oxides in the sintering necks during the hot consolidation process, resulting in the formation of PPB. This study contributes to the understanding of microstructural modifications achieved through SPS technology, providing crucial information for optimizing sintering conditions and reducing the widespread occurrence of PPB, ultimately enhancing the material performance of PM nickel-based superalloys.

SPS preparation of La10Si6O27 and the effect of sintering temperature on electrical conductivity

La10Si6O27 powder was synthesized by a high-energy ball milling method and its sintered body was prepared by spark plasma sintering (SPS) technology. Phase structure, microscopic morphology, density, porosity and oxide ion conductivity of La10Si6O27 were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), Archimedes method and alternating current (AC) impedance spectrum, respectively. XRD results showed the ball-milled powder could form apatite-type La10Si6O27 at 1400 ℃. The crystal structure of La10Si6O27 sintered body remained stable. SEM results showed that La10Si6O27 sintered body using SPS sintering method had better sintering between grains and a large reduction in open pores compared to conventional sintering. Grains of the sintered body were clearly visible and the grain size was uniform, about 1 µm. Archimedes method analysis showed relative density of La10Si6O27 sintered body is 100%, and open porosity is 0. Electrical conductivity of La10Si6O27 sintered body has an Arrhenius relationship with temperature.

Microstructure and mechanical properties of WC-TiC0.4 composites doped with ZrO2 or 3Y-ZrO2

The ZrO2 or 3Y-ZrO2 incorporated WC-TiC0.4 composites were consolidated employing spark plasma sintering (SPS) technology at different temperatures. The impacts of ZrO2 and 3Y-ZrO2 as toughening agents on the densification, phase composition, microstructure and mechanical properties of the WC-based composites were assessed. The results revealed that the WC-5 wt% TiC0.4–9 wt% ZrO2 (W5Ti9Zr) composite required a lower sintering temperature of 1700 °C for nearly full densification than WC-5 wt% TiC0.4–9 wt% 3Y-ZrO2 (W5Ti9Zr-3Y) composite. The diffraction peaks of monoclinic ZrO2 (m-ZrO2) existed only in the W5Ti9Zr composite. The evenly dispersed ZrO2 and 3Y-ZrO2 achieved the relatively homogeneous and fine microstructure in W5Ti9Zr and W5Ti9Zr-3Y composites. Moreover, the semi-coherent interfaces of (W1-x, Tix)Cn layer with WC, (W1-x, Tix)Cn layer with m-ZrO2, and (W1-x, Tix)Cn with m-ZrO2 brought about a rise in the fracture toughness of W5Ti9Zr composite. The W5Ti9Zr composite yielded the better comprehensive mechanical properties with a combination of hardness (20.8 GPa) and fracture toughness (9.9 MPa·m1/2) as compared to those of W5Ti9Zr-3Y composite. Furthermore, the main toughening mechanisms of W5Ti9Zr and W5Ti9Zr-3Y composites included grain refinement of WC matrix, a mixed transgranular and intergranular fracture, stress-induced transformation of t-ZrO2 to m-ZrO2, and crack deflection.

CaSiO3-HAp Metal-Reinforced Biocomposite Ceramics for Bone Tissue Engineering.

Reconstructive and regenerative bone surgery is based on the use of high-tech biocompatible implants needed to restore the functions of the musculoskeletal system of patients. Ti6Al4V is one of the most widely used titanium alloys for a variety of applications where low density and excellent corrosion resistance are required, including biomechanical applications (implants and prostheses). Calcium silicate or wollastonite (CaSiO3) and calcium hydroxyapatite (HAp) is a bioceramic material used in biomedicine due to its bioactive properties, which can potentially be used for bone repair. In this regard, the research investigates the possibility of using spark plasma sintering technology to obtain new CaSiO3-HAp biocomposite ceramics reinforced with a Ti6Al4V titanium alloy matrix obtained by additive manufacturing. The phase and elemental compositions, structure, and morphology of the initial CaSiO3-HAp powder and its ceramic metal biocomposite were studied by X-ray fluorescence, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and Brunauer-Emmett-Teller analysis methods. The spark plasma sintering technology was shown to be efficient for the consolidation of CaSiO3-HAp powder in volume with a Ti6Al4V reinforcing matrix to obtain a ceramic metal biocomposite of an integral form. Vickers microhardness values were determined for the alloy and bioceramics (~500 and 560 HV, respectively), as well as for their interface area (~640 HV). An assessment of the critical stress intensity factor KIc (crack resistance) was performed. The research result is new and represents a prospect for the creation of high-tech implant products for regenerative bone surgery.

Origin of improved average power factor and mechanical properties of SnTe with high-dose Bi2Te3 alloying

Chemical bond and defect engineering have profound impact on energy band and crystal structure of materials, which can adjust physicochemical and mechanical properties of materials. BiSn and VSn are simultaneously designed in SnTe material system via the (SnTe)x(Bi2Te3) alloying form, which was realized by vacuum melting and spark plasma sintering technology. Both point defects increase band gap and decrease ΔEL−Σ, which improves obviously Seebeck coefficient of SnTe. The high-efficiency improvement in the middle temperature zone makes average power factor of (SnTe)24(Bi2Te3) achieves 1656 μWm-1K−2(323K–773K). BiSn induces strong coupling hybridization between Te-5s and Te-5p, and forms the lower bonding state. The lower bonding state and the larger -IpCOHP increase bond strengthen, which result in the smaller thermal expansion coefficient and the higher hardness. Bonding evolution makes thermal expansion coefficient of SnTe reduce by 27%, and Vickers hardness increase by 44%. Higher average power factor, lower thermal expansion coefficient and higher hardness can improve output power density and service life, which provides strategies for exploiting high-power thermoelectric devices with suitable mechanical properties.

Microstructure evolution, property analysis, and interface study of 3%CF-3%SiC-10%SiC functional gradient aluminum matrix composites

To overcome the limitations of the low strength and plasticity in the application of aluminum (Al)-based composites, a functional gradient Al matrix composites of 3 vol% carbon fiber (CF)-3 vol% SiC-10 vol% SiC, with excellent comprehensive performance, was prepared by spark plasma sintering (SPS) technology. The microstructure of the layers and interlayer interfaces of the functional gradient composites (FGC) was analyzed in depth, and the mechanical properties and thermal conductivity were investigated. The results show that the differences in size and content between the CF and the SiC give different microstructural characteristics to the FGC's various layers. The 3% and 10% SiC layer have a faster dynamic recrystallization process for the same deformation. The FGC has excellent mechanical properties, with a yield strength 167.12% higher than that of the pure Al and plasticity close to that of the pure Al. Before and after the hot rolling, the yield strength of the FGC is 149.65% and 62.46% higher than that of the single CF reinforced Al matrix composites, respectively. The interlaminar stresses generated by the changes in grain size and grain orientation are responsible for the interface failure. The texture evolution reveals two different recrystallization mechanisms in the CF and SiC layers. The difference in morphology and size of recrystallization grains under the two mechanisms leads to different mechanical properties of each layer.

High-Efficiency Spark Plasma Sintered Ge0.3Si0.7:P Thermoelectric Energy Converters with Silicone Phosphide as a Source of Phosphorus Doping

ABSTRACT A spark plasma sintering technology has already become rather common for the fabrication of GexSi1-x nanostructured thermoelectric solid solutions. Such trend is related with a number of opportunities and technological tools that enable precise properties manipulation. The present paper is devoted to discussing the modulation of GexSi1-x spark plasma sintering technique that consists in the use of silicon phosphide as a source of n-type doping within the process of sintering. The composition of the sintered powder is investigated. The synthesis of a solid solution was carried out in the process of sintering. The SiP is a chemically stable non-toxic compound that can replace toxic phosphorus in thermoelectric technology thus reducing the safety requirements of the corresponding technology process. The paper investigates the effect of SiP concentration on thermoelectric characteristics. The impurity distribution is analyzed, and the association of phosphorus atoms into clusters at a very high doping level is shown. The distribution of impurity elements was controlled by EMF analysis in a scanning electron microscope. It was shown that sintering of Ge-Si-SiP powder mixture allowed obtaining the phosphorus doped GexSi1-x material with high electron concentration that demonstrate high level of thermoelectric properties. The obtained thermoelectric characteristics are compared with the world's best nanostructured materials

Studies of the microstructure of intermetallides based on Ti-Al-Nb, after spark plasma sintering

This article presents the results of an analytical review of domestic and foreign studies on the problem of obtaining intermetallic materials. Brief characteristics of powder mixtures of intermetallides of various types, general information about the structure and their physical and mechanical properties, methods for obtaining intermetallides are presented. There was also an extensive examination of the spark plasma sintering method, which has recently become widespread. The elemental and phase composition of materials obtained by spark-plasma sintering and their change in the obtained depths of dispersed precursors are investigated. The workpieces obtained by spark plasma welding and by self-propagating high-temperature synthesis are also considered. The diffusion pair method and the directed crystallization method were discussed. Particular attention was paid to the formation of the obtained intermetallites using spark plasma sintering technology, conclusions were drawn about the prospects of spark plasma treatment. The characteristics of the phase equilibrium of a triple system based on titanium, the phase composition of the corresponding alloys and their structures are considered.

Solidification of cesium containing magnetic zeolite sorbent by spark plasma sintering

The possibility of effective solidification of spent sorbents containing radioactive cesium by spark plasma sintering (SPS) technology for their safe and long-term disposal was studied. The kinetics of consolidation spent sorbent based on magnetic zeolite after adsorption saturation with cesium (∼23 wt %) under SPS conditions in the range of 700–950 °C was carried out. The structural, elemental and phase composition changes during high-rate (minutes) heating of zeolite powder saturated with Cs+ ions was studied by SEM, EDX and XRD methods. As a result, ceramic samples with mineral-like structure of Fe-substituted pollucite CsFeSi2O6 were successfully obtained. It was determined that the optimal temperature of SPS consolidation was 900 °C, at which the formation of CsFeSi2O6 ceramics with a relative density of 91.2%, compressive strength of 497.6 MPa, Vickers microhardness of 1019 HV, rate of cesium leaching of 2.33 × 10−8 g/cm2 × day was reached. It was found that the mechanism of cesium diffusion from the volume of ceramics corresponded to flushing from the available surface of the sample, the lowest diffusion coefficient was 2.71 × 10−16 cm2/s, as well as the lowest penetration depth of the solution into the volume of ceramics was 1.04 × 10−5 cm. The adsorbents prepared by SPS up to 900 °C retained the magnetization, and at higher temperature the magnetization decreased, which was caused by phase and structural changes of ceramics. The characteristics of ceramic obtained from spent adsorbent complied with the requirements of GOST R 50926–96 and ISO 6961:1982 for solidified Cs-containing radioactive waste.

Effect of Fractal Ceramic Structure on Mechanical Properties of Alumina Ceramic–Aluminum Composites

In conventional ceramic-metal matrix composites, with the addition of the ceramic phase, although it can significantly improve the performance of the material in one aspect, it tends to weaken some of the excellent properties of the metal matrix as well. In order to meet the high toughness and high strength requirements of composites for practical production applications, researchers have searched for possible reinforcing structures from nature. They found that fractal structures, which are widely found in nature, have the potential to improve the mechanical properties of materials. However, it is often not feasible to manufacture these geometric structures using conventional processes. In this study, alumina ceramic fractal structures were prepared by 3D printing technology, and aluminum composites containing fractal ceramic structures were fabricated by spark plasma sintering technology. We have studied the effect of the fractal structure of alumina ceramics on the mechanical properties of composites. The compression strength of samples was measured by a universal testing machine and the torsional properties of samples were measured by a torsional modulus meter. The results show that a fractal structure improves the compressive strength of aluminum/alumina ceramic composites by 10.97% and the torsional properties by 17.45%. The results of the study will provide a new method for improving the mechanical properties of materials.

Preparation and properties of Ti(C,N)-based cermets with graphene nanosheet addition by spark plasma sintering

The application of Ti(C,N)-based cermets remains limited due to their low toughness. The fracture toughness of cermets can be significantly improved by using advanced sintering methods and appropriate additives. Here, cermets were prepared by spark plasma sintering (SPS) technology with graphene nanosheets (GNSs) and nano-scale tungsten carbide (WC) as additives. The effects of GNSs and sintering conditions on the microstructure, mechanical properties, and magnetic properties of Ti(C,N)-based cermets were studied. The results show that the sample with 0.6 wt% GNSs fabricated at 1450 °C, 8 min, and 35 MPa has a denser microstructure and better mechanical properties. The cermet has a Vickers hardness of HV 2415.40 and fracture toughness of 10.6 MPa·m1/2. Compared with the specimen without GNSs, the hardness and fracture toughness are significantly improved by 44.58% and 92.73%, respectively. A certain amount of GNSs can increase the movement of hard phases in the liquid phase, inhibiting their solubility and grain growth, and greatly improving the fracture toughness of cermets. The addition of nano-WC is conducive to promoting the formation of a (Ti,W) (C,N) rim phase and improving properties of cermets. SPS can activate particle surfaces and promote the densification of cermets.