Spark Plasma Sintering Research Articles

Selective laser sintering and spark plasma sintering of (Zr,Nb,Ta,Ti,W)C compositionally complex carbide ceramics

AbstractTwo 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.

The effect of particle size on densification and mechanical properties of Fe-based bulk metallic glasses by spark plasma sintering

The effect of particle size on densification and mechanical properties of Fe-based bulk metallic glasses by spark plasma sintering

Solid‐State Bonding of Iron or Steel with Stainless Steels by Spark Plasma Sintering Bonding

In this study, pure iron, S45C carbon steel (Fe–0.45mass%C), carburized iron, and nitrided iron are bonded with two types of stainless steels, i.e., SUS304 austenitic stainless steel (Fe–18mass%Cr–8mass%Ni) with face center cubic structure or SUS430 ferritic stainless steel (Fe–18mass%Cr) with body center cubic structure by a spark plasma sintering (SPS) machine. Bonding experiments are carried out by SPS bonding. It is found that the bonding temperature of the S45C/SUS samples is lower than that of Fe/SUS samples, and carbon atoms in the S45C play important role on the bonding performance. The bonding temperature for SUS304/SUS430 sample is more than 30 °C higher than those for the Fe/SUS and S45C/SUS samples. The presence of thin chromium oxides on both stainless steels reduces the bonding performance of SUS304/SUS430 sample. Better bonding performance is found for the carburized and nitrided iron for bonding with stainless steels. However, continuous single‐phase layer on the surface leads to reduce the bonding performance. It is concluded that not only the concentration of carbon and nitrogen but also the phase configuration in the iron at interface strongly influences the bonding performance between iron alloys and stainless steels by SPS bonding.

W–CeO2 Core–Shell Powders and Macroscopic Migration of the Shell via Viscous Flow during the Initial Sintering Stage

To retard the mutual contact of W grains to inhibit their growth, in this study, CeO2·2H2O was first coated on the surface of pure W (undoped) particles by a weight percentage of 4% using a wet chemical method to prepare CeO2·2H2O-doped W-based (doped) powders, with W particles as the core and CeO2·2H2O as the shell (W–CeO2·2H2O core–shell structure), without hydrogen reduction treatment. The undoped and doped powders were subsequently sintered using a spark plasma sintering (SPS) apparatus to fabricate bulk materials. The macroscopic migration of the CeO2 shell in the core–shell W–CeO2 system via viscous flow during the initial sintering stage was studied through simulations and experiments. The results showed that a core–shell structure with W particles as the core and CeO2·2H2O as the shell was successfully prepared. The doped powder contained approximately 3.97% CeO2, consistent with the designed content of 4%. The shell materials migrated among the selected four sintered powders, filling the pores and contributing to the improvement in the relative density of the sintered bulk.

Investigation of Microstructure, Mechanical, and Tribological Behavior of Nano‐Y2O3, TiO2, ZrO2‐Dispersed W–Ni–Nb–Mo–Zr Alloys Fabricated by Spark Plasma Sintering

W–Ni–Nb–Mo–Zr alloys with 1.0 weight% (wt%) Y2O3 (alloy A), TiO2 (alloy B), ZrO2 (alloy C) dispersion synthesized by mechanical alloying for 20 h have been subjected to spark plasma sintering at 1150 °C with 65 MPa pressure and 5 min holding time. X‐ray diffraction analysis reveals the occurrence of intermetallics (W2Zr, NiNb, Ni10Zr7, MoNi), which improves the strength of the alloys. Field‐emission scanning electron microscopy analysis shows that the grain size of alloy A is less compared to alloy B and C. Energy‐dispersive spectroscopy reveals the presence of oxides at the matrix interface. Maximum % relative sintered density, ultrahigh hardness, excellent compressive strength, % compressive strain at the maximum compressive load of 99.5%, 20.42 GPa of 2.55 GPa, 9.7%, respectively, have been recorded for alloy A. Maximum texture intensity of 1.5 is recorded for alloy A which supports the superior mechanical properties. The specific wear rate of alloy A is around 2.78 times less compared to alloy C. The crystal structure transformation of ZrO2 from monoclinic to tetragonal after sintering deteriorates the mechanical properties and wear resistance in alloy C. The article also reports the operative wear mechanism in the studied oxide dispersion‐strengthened alloy.

Radio frequency‐assisted zirconium carbide matrix deposition for continuous fiber‐reinforced ultra high temperature ceramic matrix composites

AbstractZirconium carbide (ZrC) is considered to be a potential candidate for ultra high temperature applications due to its high melting point, good chemical inertness, and ablation resistance, but the monolithic form suffers from low fracture toughness and hence poor thermal shock resistance. Reinforcing it using continuous carbon fibers (Cf) to create an ultra high temperature ceramic matrix composite is an obvious solution, however densifying ZrC requires the use of very high temperatures combined with significant pressure, such as obtained by using hot pressing or spark plasma sintering, which risks damaging fibers. In the present work, radio frequency‐assisted chemical vapor infiltration (RF‐CVI) has been investigated with a view to forming Cf/ZrC composites. These initial experiments revealed the ability to deposit pure, nano‐grained, and near stoichiometric ZrC with deposition occurring preferentially from the center of the sample due to the nature of the inverse temperature profile developed. The deposited ZrC grains were in the range of 4–9 nm in size and had a lattice parameter of 0.4750 nm. The work also showed that the use of RF‐CVI enabled the minimization of early pore sealing, a common problem for conventional CVI.

Spark plasma sintering of Co-W-Ta ternary superalloys: densification mechanism, phase, microstructural and mechanical properties

Spark plasma sintering of Co-W-Ta ternary superalloys: densification mechanism, phase, microstructural and mechanical properties

Effects of Zr, Al, and Al+Zr Addition on Phase Evolution Characteristics and Strengthening Mechanisms of Fe‐42Ni‐2Y2O3 Oxide Dispersion Strengthening Steels Developed by Mechanical Alloying and Spark Plasma Sintering

In the present study, Fe‐42 wt% Ni‐2 wt% Y2O3 super‐invar‐based steels have been explored to study the effects of Zr, Al, and Zr+Al addition on phase evolution, strengthening mechanisms, and mechanical behavior. Three different compositions, such as Fe‐42Ni‐2Y2O3‐2Zr (2YZr), Fe‐42Ni‐2Y2O3‐2Al (2YAl), and Fe‐42Ni‐2Y2O3‐2Zr‐2Al (2YAlZr), are developed by mechanical alloying (MA) followed by spark plasma sintering (SPS) at 1100 °C with an applied pressure of 60 MPa. The 2YZr alloy after SPS shows the evolution of a uniform grain size of ≈1.7 μm, whereas 2YAl reveals the formation of bimodal grain structure sintered under the same condition. Conversely, the combined effect of Al and Zr addition results in the evolution of ultrafine grained structure (≈380 nm) after SPS at the same condition (i.e., at 1100 °C). The superior mechanical strength of the 2YAlZr alloy (5.3 GPa/1415 MPa) is attributed to the evolution of uniformly dispersed extremely fine (60 nm) high‐density Al‐ and Zr‐rich oxide complexes in the ultrafine grained matrix. The analysis of strengthening contributions to the yield strength is found to be correlated well with the experimental results and attributed to the morphology of microstructural constituents, their stability, and volume fraction of dispersoids in the matrix.

Pressed Solid Target Production of 89Zr and its Application for Antibody Labelling.

Zirconium-89 ( 89Zr, t1/2=3.27d) is an important + emitting radionuclide used in Positron Emission Tomography (PET) immuno studies due to its unique characteristics and increased demand due to simple and cost-effective production capacity. Production of 89Zr is achieved primarily through solid natural yttrium targets via different target preparation methodologies, such as electrodeposition, pressed foils, and spark plasma sintering. In this study, we have investigated the pressed solid target methodology. The Yttrium Oxide (Y2O3) powder was pressed to pellet form and stacked over a different back support plate, such as platinum (Pt), niobium (Nb), and tantalum (Ta). The target was irradiated with approximately 12 MeV proton beam for 10-60 minutes at 20µA current. The irradiated target was purified through a solid phase extraction method via hydroxamate-based resin by manual or automatic approach. The purified 89Zr was analyzed using gamma scintigraphy, and specific activity was calculated through Deferoxamine (DFO) chelation. 89Zr radionuclide via pressed target was effectively produced with a production yield of 20-30 MBq/µA.h, and the purification was achieved in 35 minutes with (87.46)% average recovery and >98% purity while using automated purification, but manual purification took 2 hours with (91 ± 2)% recovery and >98% purity. The production yield was comparable to the reported pressed target approach. Deferoxamine (DFO) chelation with 89Zr-oxalate was performed with purity >98% and specific activity of 25-30 µCi/mmol. In this study, we explored the production of 89Zr by pressed targets and purification via manual or automated methods with good radionuclide purity. The chelation with DFO or its analog was performed with good labeling efficiency and stability</p>.

Synthesis and reaction mechanism of high injected electron concentration and low work function [Ca24Al28O64]4+:(4e-) by Sol-gel method combined with spark plasma sintering

The high injected electron concentration and low work function C12A7:e- was successfully prepared by the sol-gel method combined with spark plasma sintering(SPS) using calcium nitrate, aluminum nitrate, citric acid, and ethylene glycol as raw materials. By analyzing the morphology of carbon and its role in the reactive synthesis, we reveal the reaction synthesis mechanism of C12A7:e- under the SPS. The analysis shows that C12A7:e- started to be generated at 800 °C. During the SPS reaction sintering process, carbon atoms from citric acid and ethylene glycol were excited by a pulsed current at high temperature, forming the carbon ions C22- and C (gas). Both act as reducing agents and react with the free oxygen ions O2- in the C12A7 cage cavity to form gaseous CO or CO2, enabling electrons to be injected into the cage cavity, thus generating C12A7:e-. Meanwhile, the graphene oxide (GO) formed on the surface of C12A7:e- grain is produced by the precursor of sol-gel synthesis in the high temperature oxidation environment, which will be conducive to improving the stability of C12A7: e- in air and high temperature oxidation resistance.

Bulk graphene-based composites with artificial nacre-like laminated structure: Microstructure and mechanical properties

In this study, the bulk Cu/reduced graphene oxide (Cu/rGO) composites featuring an artificial nacre-like laminated structure were successfully fabricated using spark plasma sintering (SPS), and the microstructure and mechanical properties of the resulting composites were investigated. The Cu/rGO composites demonstrated a distinct laminated structure, and their relative densities increase with Cu addition. Moreover, the presence of trace amounts of in-situ interfacial reaction products (CuO and CuO2,) were observed to enhance the adhesive strength at the Cu-rGO interface. Mechanical testing of the composites showed notable improvements in both compressive strength and ductility compared to a bulk monolithic rGO sample. Specifically, the bulk rGO composites with a 35.05 wt% addition of Cu displayed an enhancement of ∼67 % in compressive strength and ∼19 % in ductility relative to the pure rGO sample. These improvements are attributed to synergetic strengthening and toughening mechanisms within the rGO composites. The enhanced strength and ductility of the Cu/rGO composites significantly boost their wear resistance. This research not only demonstrates the effectiveness of incorporating Cu into rGO matrices but also suggests a promising avenue for the development of novel bulk rGO composites with engineered laminated structures.

Calibration of a constitutive model for polycrystalline diamond sintering process

Polycrystalline diamond is mostly pressed at high temperature in actual production. Thus, circumferential strain data of powder moulding are difficult to collect at high temperatures. As a result, the parameters of DPC constitutive model cannot be obtained using conventional testing methods. Moreover, the use of conventional equipment to test the mechanical properties becomes challenging because of the extremely high hardness and compressive strength of polycrystalline diamond. Sintering tests of polycrystalline diamond were carried out at 1360 °C and 223 Mpa using the spark plasma sintering (SPS) method, and displacement–load data were obtained. The spark plasma sintering experiment of polycrystalline diamond under high temperature and pressure was carried out using the Drucker Prager/Cap (DPC) model with relative density to obtain accurate displacement and load numbers. Combined with USDFLD subroutine, the experiment of polycrystalline diamond sintering was simulated on ABAQUS. Based on the complex method, ABAQUS-MATLAB platform is used for the reverse identification of constitutive parameters. The constitutive model parameters of polycrystalline diamond sintering process are obtained. This approach can describe the mechanical behaviour of polycrystalline diamond powder in the sintering process. In addition, the inverse identification method of the constitutive model in the sintering process of polycrystalline diamond based on ABAQUS and MATLAB solves the problem on the difficulty to observe the sintering of polycrystalline diamond under high temperature and high-pressure environment. Moreover, the constitutive model parameters of the sintering process are obtained, thereby reducing the cost and condition constraints in the actual experiment. A novel technique involves obtaining powder constitutive parameters at high temperature from the sintering point of view. This approach is important to simulate sintering of polycrystalline diamond and its composite products. Foundation itemNational Natural Science Foundation of China (Grant No. 52075438), the Key Research and Development Program of Shanxi Province of China (Grant No. 2020GY-106), the Open Project of State Key Laboratory for Manufacturing Systems Engineering (Grant No. sklms2020010), and the Open Research Fund of Key Laboratory of Oil & Gas Equipment of Ministry of Education (Grant No. OGE201702-110).

Effects of sintering method and Al2O3 content on microstructure and mechanical properties of WC-10Co cemented carbide

Ultra-high toughness and ultra-high hardness WC-10Co-xAl2O3 cemented carbides were successfully prepared by vacuum liquid phase sintering (VS) and spark plasma sintering (SPS) using ultrafine WC and commercial Co powders as raw materials, respectively. The effects of nano-Al2O3 content and sintering process on the relative density, average grain size, microstructure and mechanical properties of WC-10Co alloys were investigated. The results showed that the densification degree of the samples decreased with the increase of Al2O3 content. In addition, the relative densities of the samples prepared by SPS were lower than those of the samples prepared by VS. For the samples prepared by VS, the average grain size increased first and then decreased as the Al2O3 content increased from 3 wt% to 9 wt%, and the percentage of coarse grain showed the same trend. When the addition of Al2O3 was 6 wt%, the average grain size reached the maximum value of 1.39 ± 1.03 μm. Meanwhile, the sample with 6 wt% Al2O3 had a typical inhomogeneous dual-grain structure, and the percentages of fine grain (< 1 μm) and coarse grain (> 1 μm) were about 50%, which displayed the highest fracture toughness of 18.59 MPa·m1/2. The dual-grain structure not only improved the toughness, but also compensated the loss of hardness. However, for the samples prepared by SPS, with the increase of Al2O3 content, the average grain size of WC decreased, while both hardness and toughness were continuously improved. When the Al2O3 content increased to 9 wt%, the grain size reached the minimum value of 0.25 ± 0.08 μm, and meanwhile, the hardness and toughness reached the maximum value of 19.69 GPa and 12.29 MPa·m1/2, respectively. Moreover, as the Al2O3 content increased, the transverse rupture strength (TRS) of the samples prepared by VS increased first and then decreased, and the TRS of sample with 3 wt% Al2O3 reached the maximum value of 1410 MPa. However, the TRS of the sample prepared by SPS showed a decreasing trend.

Enhanced physical and mechanical properties of Cu-based nanocomposites with bundled multi-layered carbon nanotubes incorporation: fabrication and comparative analysis via conventional sintering and SPS techniques

The current investigation delves into the influence of incorporating bundled multi-layered graphene sheets, specifically multiwalled carbon nanotubes (MWCNTs), on the microstructure, as well as the physical and mechanical attributes of Cu-based nanocomposites. Various weight percentages (1%, 2%, 3%, and 5%) of MWCNTs were infused into the Cu matrix, and the fabrication of these nanocomposites was conducted through the powder technology route. The fabrication process occurred under an argon atmosphere utilizing both conventional sintering and spark plasma sintering (SPS) techniques. The conventionally sintered Cu-based nanocomposite reinforced with 1% MWCNT exhibited the highest relative density (~86%), hardness (~551.12 MPa), compressive strength (~459 MPa), and outstanding resistance to wear. Conversely, the SPS-fabricated nanocomposite reinforced with the same MWCNT concentration demonstrated the highest relative density (approximately 94.25%) and compressive strength (~688 MPa), while the nanocomposite reinforced with 2% MWCNT displayed the highest hardness (~1178 MPa) and resistance to wear. Notably, a higher concentration of MWCNTs was observed to adversely affect the physical, mechanical, and wear properties of the Cu-MWCNT nanocomposites, irrespective of the chosen sintering technique for their production.

Investigation of Cenosphere-Based Lightweight Ceramic Matrixless Syntactic Foam Through Spark Plasma Sintering

Investigation of Cenosphere-Based Lightweight Ceramic Matrixless Syntactic Foam Through Spark Plasma Sintering

Synthesis of B-site high-entropy BaTi0.2Hf0.2Zr0.2Y0.2Nb0.2O3 with water sensing properties

A barium-based perovskite structured ceramic with five different B-site cations was prepared by a solid-state synthesis method. The phase and chemical homogeneity of the synthesised material was verified using x-ray diffraction and energy dispersive x-ray spectroscopy, showing the successful synthesis of a single-phase perovskite structure with Ba A-site and Ti, Hf, Zr, Y, Nb, B-site cations. Ultra-high vacuum x-ray photoelectron spectroscopy was used to reveal the valence states of the constituent elements. Conventional, two-step and spark plasma sintering were used to form dense pellets with limited grain growth. The room temperature electrical characteristics of the sintered pellets were investigated by electrochemical impedance spectroscopy where a conductivity increase of two orders of magnitude was observed in a water-bearing atmosphere. Synchrotron-based ambient-pressure x-ray photoelectron spectroscopy performed under water-bearing and dry conditions suggest that the conductivity increase is related to the incorporation of hydroxyl groups into the perovskite structure.

Low-cost Ti-6Al-4V containing low content nano-carbon solid solution for achieving high strength and good ductility

With the rapid advancement of the aerospace industry, in addition to higher requirements for material properties, the cost-effective of its production have also attracted more attention. In this work, titanium matrix composite with high performance and low cost was designed using ball milling, spark plasma sintering and hot rolling process, i.e. hydrogenated dehydrogenated Ti and AlV powders as the precursor of Ti-6Al-4 V matrix, and a low content (0.15 wt%) reduced graphene oxide (rGO) with high-activity was selected to reinforce the matrix alloy. The as-rolled composite shows obvious texture orientation along the rolling direction without pores and microcracks. The incorporation of rGO led to the activation of the as-rolled composites along the {0001}[112¯0] type base slip. The as-rolled composite containing only 0.15 wt% rGO exhibits superior yield strength (1308.1 MPa) and ultimate tensile strength (1444.3 MPa), which are 11% and 9.3% higher than those of the matrix alloy, respectively, and the elongation remains at ∼5.6%. The strengthening mechanisms are mainly attributed to the solid solution strengthening effect of interstitial carbon in the matrix after the incorporation of rGO. This work highlights the development potential of low-cost and high-strength titanium matrix composites

Thermal Conductivity of AlSi12/Al2O3-Graded Composites Consolidated by Hot Pressing and Spark Plasma Sintering: Experimental Evaluation and Numerical Modeling

Functionally graded metal matrix composites have attracted the attention of various industries as materials with tailorable properties due to spatially varying composition of constituents. This research work was inspired by an application, such as automotive brake disks, which requires advanced materials with improved wear resistance on the outer surface as combined with effective heat flux dissipation of the graded system. To this end, graded AlSi12/Al2O3 composites (FGMs) with a stepwise gradient in the volume fraction of alumina reinforcement were produced by hot pressing and spark plasma sintering techniques. The thermal conductivities of the individual composite layers and the FGMs were evaluated experimentally and simulated numerically using 3D finite element (FE) models based on micro-computed X-ray tomography (micro-XCT) images of actual AlSi12/Al2O3 microstructures. The numerical models incorporated the effects of porosity of the fabricated AlSi12/Al2O3 composites, thermal resistance, and imperfect interfaces between the AlSi12 matrix and the alumina particles. The obtained experimental data and the results of the numerical models are in good agreement, the relative error being in the range of 4 to 6 pct for different compositions and FGM structure. The predictive capability of the proposed micro-XCT-based FE model suggests that this model can be applied to similar types of composites and different composition gradients.

Influence of CePO4 on high temperature anti-friction and anti-wear behaviors of nickel-based h-BN composite coatings

Solid lubricating coatings which offer and maintain anti-friction and anti-wear are urging to develop in the advanced technology applications over a wide range of temperatures. The h-BN composite coatings on the Inconel X750 superalloy is prepared by spark plasma sintering (SPS) technology to obtain low friction and wear over a broad temperature ranging from room temperature (RT) to 800 °C using a high temperature rotary tribometer. The influence of the contents of h-BN and CePO4 powders of the tribological properties of the composite coatings was studied systemically under different temperatures. The experimental results show that the composite coatings with 20 wt% h-BN show excellent high temperature anti-friction behaviors. Coefficient of friction (CoF) of the composite coatings with 20 wt% h-BN with CePO4 powder is lowest about 0.12 among the composite coatings at 800 °C. The CePO4 powders are helpful to improve the sintering behaviors and reduce the wear rate of the composite coatings at elevated temperature. The synergistic lubrication mechanism of h-BN and CePO4 of the composite coatings are investigated systematically. The high temperature anti-friction and anti-wear mechanism of the composite coatings is due to the formation of a layered gradient lubrication film on the worn surface.

Microstructure and Mechanical Properties of Multi-interface Tungsten Fibre/Aluminium Alloy Composites Prepared by Spark Plasma Sintering

Microstructure and Mechanical Properties of Multi-interface Tungsten Fibre/Aluminium Alloy Composites Prepared by Spark Plasma Sintering