Spark Plasma Sintering Technology Research Articles

Ce3+ doped Lu3Al5O12 ceramics prepared by spark plasma sintering technology using micrometre powders: Microstructure, luminescence, and scintillation properties

Ce3+ doped Lu3Al5O12 (Ce:LuAG) ceramics were fabricated by the solid-state reaction method through spark plasma sintering (SPS) from 1350 °C to 1700 °C for 5 min at a pressure of 50 MPa using micro powders. The average grain size of the SPSed ceramics gradually grew from 0.42 µm (1400 °C) to 1.55 µm (1700 °C), which is nearly one order of magnitude lower than that of vacuum sintered (VSed) Ce:LuAG ceramics (~24.6 µm). Characteristic Ce3+ emission peaking at around 510 nm appeared and 92% photoluminescence intensity of room temperature can be reserved at 200 °C revealing excellent thermal stability. The maximum radioluminescence intensity reached around 3 times of VSed Ce:LuAG ceramics and 7.8 times of BGO crystals. The maximum scintillation light yield under γ-ray (137Cs) excitation reached 9634 pho/MeV @ 2 μs. It is concluded that SPS technology is a feasible way to develop Ce:LuAG ceramics and further optical enhancement can be expected.

Densification and strengthening mechanism in spark plasma sintering of B4C–VB2 ceramics via carbide boronizing

To reduce the negative effects of the long-time and B2O3 phase on the traditional sintering process for B4C-based composite ceramics, nearly fully dense B4C–VB2 composite ceramics were prepared by reactive spark plasma sintering (SPS) technology at 2000 °C with B and V8C7 powders as raw materials in this paper. The effects of the degassing time during SPS on the microstructure and the mechanical properties of the final products were investigated in detail. The results revealed that the proper degassing time was beneficial for the vent of B2O3 during the sintering process, which refined the grain size, promoted densification and improved the mechanical properties of the composite ceramic. However, the redundant degassing time increased the holding time at high temperature, resulting in abnormal grain growth and mechanical performance deterioration. In the present work, the optimal degassing time was 6 min, and the final product prepared under the above conditions exhibited excellent comprehensive performance with a relative density of 99.2%, Vickers hardness of 31.2 GPa, bending strength of 654 MPa and fracture toughness of 5.7 MPa m1/2. In addition, the strengthening and toughening mechanisms of the products were mainly attributed to the residual thermal stresses and bridging structure caused by the fine B4C and VB2 grains distributed uniformly.

Mechanical and tribological characterisation of AlCoCuFeNi HEA reinforced magnesium composites prepared via spark plasma sintering

In this paper, high-entropy alloy (HEA) particle-reinforced magnesium matrix composites were successfully prepared by the spark plasma sintering (SPS) technology. The effect of the addition of HEA particles on the microstructural evolution, compressive properties and wear properties was investigated. Given its weak binding with other HEA elements, Cu was the element that separated in the initial HEA-reinforced material and combined with Mg to produce CuMg2 dispersed in the matrix. The microhardness of the SPSed composite was 45.9% higher than that of the magnesium matrix. The SPSed composite with HEA particle content of 15 vol.% had the best compressive strength, and the ultimate compressive strength reached 269 MPa. With increased AlCoCuFeNi particles, the matrix could avoid fatigue wear, and the abrasive wear mechanism dominated.

Fabrication of nano-ZrO2 strengthened WMoNbTaV refractory high-entropy alloy by spark plasma sintering

WMoNbTaV refractory high-entropy alloy (RHEA) is facing the contradiction between strength and plasticity at room temperature, which greatly restricts its processing, forming and subsequent engineering applications. In the present work, WMoNbTaV and WMoNbTaV with 1 mass% additions of m-ZrO2 (WMoNbTaV-1ZrO2) RHEAs were successfully prepared by ball milling and spark plasma sintering technologies. The grain refinement of the one phase body-centered cubic alloy by presence of m-ZrO2 is determined by microstructural analyses to be 31.5%. The yield strength, ultimate strength and fracture strain of WMoNbTaV-1ZrO2 are 2171.1 MPa, 2461.4 MPa and 12.7% respectively, which are surprisingly increased by 69.0%, 62.5% and 32.3%, in comparison with that of WMoNbTaV without m-ZrO2, respectively. More importantly, they are remarkably superior to the same alloy prepared by the vacuum arc-melting method. A model is presented to study the strengthening mechanism of WMoNbTaV-1ZrO2, and the theoretical calculation shows that the extraordinary high strength is mainly due to the inherent strength in the multi-principal element WMoNbTaV alloy and grain boundary strengthening caused by the addition of m-ZrO2 particles.

Remanufacturing of the waste refractory Mo–10Nb sputtering target by spark plasma sintering technology

Mo–10Nb refractory sputtering targets used in the flat panel display industry have attracted extensive attention, whereas the shortcoming of low target utilization is now urgently needed to be solved. This work is to repair the waste Mo–10Nb target by spark plasma sintering (SPS) at 1550 °C and 10 min, and the feasibility is demonstrated. It is shown that the repaired target retains identical phases and high purity. Clean and strong bonds are found at the repair interface. Regardless of the position, the repaired target exhibits finer grains as well as higher density, microhardness, and thermal conductivity compared with the original target. The two targets are then sputtered to obtain relevant films. Both films consist of the same phases and show columnar appearances. Mo, Nb, O, and C are present in both films, where Mo and Nb exist in the form of pure Mo, MoO2, MoO3, pure Nb, and Nb2O5. A higher sputtering rate, smaller film thickness deviation, grain size and surface roughness, less oxidation, and larger elastic modulus and nano-hardness are obtained from the film prepared by the repaired target. SPS is proven to be a well-suited method for producing the regenerated target.

Evaluation of Mechanical and Electrical Performance of Aging Resistance ZTA Composites Reinforced with Graphene Oxide Consolidated by SPS.

This paper presents a study of Al2O3–ZrO2 (ZTA) nanocomposites with different contents of reduced graphene oxide (rGO). The influence of the rGO content on the physico-mechanical properties of the oxide composite was revealed. Graphene oxide was obtained using a modified Hummers method. Well-dispersed ZTA-GO nanopowders were produced using the colloidal processing method. Using spark plasma sintering technology (SPS), theoretically dense composites were obtained, which also reduced GO during SPS. The microstructure, phase composition, and physico-mechanical properties of the sintered composites were studied. The sintered ZTA composite with an in situ reduced graphene content of 0.28 wt.% after the characterization showed improved mechanical properties: bending strength was 876 ± 43 MPa, fracture toughness—6.8 ± 0.3 MPa·m1/2 and hardness—17.6 ± 0.3 GPa. Microstructure studies showed a uniform zirconia distribution in the ZTA ceramics. The study of the electrical conductivity of reduced graphene oxide-containing composites showed electrical conductivity above the percolation threshold with a small content of graphene oxide (0.28 wt.%). This electrical conductivity makes it possible to produce sintered ceramics by electrical discharge machining (EDM), which significantly reduces the cost of manufacturing complex-shaped products. Besides improved mechanical properties and EDM machinability, 0.28 wt.% rGO composites demonstrated high resistance to hydrothermal degradation.

Synthesis and characterization of extremely hard and strong (W,Ti,Ta)C cermet by spark plasma sintering

In this study, spark plasma sintering (SPS) technology was used to prepare (W,Ti,Ta)C cermet. The mechanical properties and microstructure of the (W,Ti,Ta)C cermet under different sintering temperatures, holding times, and sintering pressures were studied by orthogonal experiments, and optimal sintering parameters were obtained. The results show that under a sintering temperature of 1400 °C, holding time of 10 min, and sintering pressure of 30 MPa, the grain size of the cermet was uniform, the relative density was higher, and the mechanical properties were optimal. The Vickers hardness and flexural strength of the cermet were 20.39 ± 0.3 GPa and 1389 ± 35 MPa, respectively. Solid solution strengthening at the grain boundary was shown to improve the interfacial bonding force of the cermet, which is the main reason for the improved flexural strength and fracture toughness of the (W,Ti,Ta)C cermet.

Dependence of composition of SiC–Al2O3 composite absorbers on microwave heating characteristics

Spark plasma sintering technology was used to prepare SiC–Al2O3 composite absorbers with a range of compositions. Scanning electron microscopy showed that of the components was uniform in all compositions. The influences of composition, heating time, and microwave power of the composite absorbers on their heating characteristics were analyzed. As the microwave power was increased from 500 W to 1000 W, the temperature achieved by the absorber increased. After being heated for 24 min at a microwave power of 1000 W, all samples maintained a constant temperature. The absorber with 40mass% Al2O3 content reached the highest temperature (952 °C); the absorber with 95 mass%Al2O3 content achieved the lowest temperature (313 °C). These findings have importance as a reference for precise temperature control in microwave heating of composite absorber.

Microstructure and properties of WC-CoCuFeNi composites fabricated by spark plasma sintering

In this work, a novel low-cost WC-CoCuFeNi cemented carbide has been produced by spark plasma sintering technology. The CoCuFeNi medium-entropy alloy binder has a face center cubic structure with more slip systems and shows good bonding behavior with WC. The newly-developed cemented carbides exhibit a good combination of hardness and fracture toughness. The hardness and fracture toughness of WC-20 wt% CoCuFeNi are up to 1506.7 HV30 and 10.33 MPa·m1/2, respectively. These results show the WC-CoCuFeNi cemented carbides could be a promising substitute for WC-Co.

Large electrocaloric effect in two-step-SPS processed Pb(Sc0.25In0.25Nb0.25Ta0.25)O3 medium-entropy ceramics

Ferroelectric ceramic with a large electrocaloric (EC) effect at a very low electric field is very attractive in the next solid state refrigeration technology. In this work, two Pb(Sc0.25In0.25Nb0.25Ta0.25)O3 (PSINT) medium-entropy ceramics were successfully synthesized by a spark plasma sintering (SPS) technology, including one-step-SPS processed and two-step-SPS processed samples. A large EC effect (△T ∼ 0.85 K) with a high EC strength (△T/△E ∼ 0.021 K cm/kV) around room temperature are obtained at a very low electric field (∼40 kV/cm) in the two-step-SPS processed sample. Moreover, the working temperature range is very broad (∼120 K), which can be responsible for the high relaxation degree of the dielectric peak. It can be believed that the PSINT medium-entropy ceramics can be promising candidates for application in the next-generation EC cooling devices.

Synthesis of amorphous KAlSi3O8 for cesium radionuclide immobilization into solid matrices using spark plasma sintering technique

An effective sorption material for cesium radionuclides immobilization in highly safe and reliable solid-state matrices was proposed. Prepared aluminosilicate (КAlSi3O8) adsorbent had amorphous mesoporous structure and Cs+ ions sorption capacity of ∼3.7 mmol/g. The physical-chemical characteristics of (Cs, К)AlSi3O8 sample saturated with Cs + ions were studied using XRD, FT-IR, SEM-EDX, and DTA-TG methods. Firstly, solid-state aluminosilicate matrices were obtained using spark plasma sintering (SPS) technology with high values of relative density (up to 99.9%), compressive strength (31.3–79.2 MPa), and Vickers microhardness (0.9–5.3 GPa). The sample obtained at 1000 °C had a low value of Cs+ leaching from matrices (RCs within the range of 10-7 g cm-2·day-1) and cesium diffusion coefficient (De 9.07 × 10-14 cm2/s). It was shown that prepared aluminosilicate cesium matrices comply with regulatory requirements of GOST R 50926-96 and ANSI/ANS 16.1.

Experimental research on moulding of graphene/PEKK composite powder by spark plasma sintering technology

Experimental research on moulding of graphene/PEKK composite powder by spark plasma sintering technology

Preparation of infrared axial gradient refractive index lens based on powder stacking and the sintering thermal diffusion method

The gradient refractive index (GRIN) lens is widely used in the visible band, but it is still elusive in the infrared band. In this paper, we propose a new method of fabricating chalcogenide GRIN by spark plasma sintering (SPS) technology based on powder stacking and sintering thermal diffusion. We replaced Se in Ge11.5As24Se64.5 glass with S and prepared several Ge11.5As24Se(64.5-x)Sx glasses as infrared transmission GRIN materials. The maximum refractive index difference (Δn) of the matrix glass is 0.18. The effects of heat treatment temperature and time on diffusion depth and concentration-dependent thermal diffusion coefficient were investigated. The diffusion depth of 100 µm was demonstrated under the condition of 400 °C-48 h by this method. The thickness of the glass layer can be well controlled by powder stacking. The obtained GRIN glass is highly transparent in the near- and mid-infrared wavelength region.

Cytotoxicity and Ion Release of Functionally Graded Al<sub>2</sub>O<sub>3</sub>- Ti Orthopedic Biomaterial

The aim of this study was to evaluate the biocompatibility of Al2O3-Ti functionally graded material (FGM) successfully fabricated by Spark Plasma Sintering (SPS) technology, and to compare with pure Ti and alumina. Pre-osteoblast MC3T3-E1 cells were used to examine cell viability, proliferation and differentiation using lactate dehydrogenase (LDH) cytotoxicity detection kit, MTT assay and Alkaline Phosphatase (ALP) colorimetric test at different time points. Furthermore, ion release from the materials into the culture medium was assessed. The results showed cell viability over 80% for FGM and alumina which dismissed any cytotoxicity risk due to materials or manufacturing. The results of MTT tests identified superiority of FGM than Ti and alumina, particularly in late proliferation. Nevertheless, in cell differentiation, all materials performed similarly with no statistical differences. Furthermore, it was indicated that Ti had no ion release, while alumina had small amount of Al ion dissolution. FGM, however, had more ions detachment, particularly Al ions.

THE PROPERTIES OF THE SECONDARY COPPER ALLOY

The use of scrap metal and waste solves the problems of preservation of natural resources, reduces energy and economic costs. In mechanical engineering, aluminum bronzes are one of the most popular, they are used in products where such indicators as high strength and ductility, wear resistance and corrosion resistance are needed. (Research purpose) The research purpose is to make a surfacing electrode from scrap copper alloys, to investigate the properties and the coating processes when applying this material. (Materials and methods) The article presents the microstructure and microhardness of the secondary bronze coating and the material for surfacing by the method of electroerosive dispersion of bronze scrap. A compact semi-finished product was created from the resulting powder using spark plasma sintering technology, which was applied to steel samples by electric spark treatment. (Results and discussion) The study of the microhardness of the coatings showed that the coatings made of bronze BrAZh9-4 have a microhardness approximately 1.7-2 times greater than sintered bronze, while the characteristics of the thermal influence zone and its presence directly depend on the substrate material and the electrode material. When getting materials by this method, the elemental composition can be adjusted depending on the required tasks. (Conclusions) The studied material after spark plasma sintering consists of finely dispersed spherical grains, which affects the application parameters and coating characteristics. When applying a coating with the same electrode to different grades of steel, the coating changes with the same parameters of the material application.

High-temperature mechanical properties of ZrB2/SiC/Si3N4 ceramic tool materials with dual composite architectures

ZrB 2 /SiC ceramic granules with uniform a size and spherical shape were prepared by spray drying technology. ZrB 2 /SiC ceramic granules were added into ceramic matrix, and ZrB 2 /SiC/Si 3 N 4 ceramic tool materials with double composite architectures were prepared by spark plasma sintering technology. The mechanical properties from room temperature to 1100°C were measured. The hardness, flexural strength and fracture toughness at room temperature are 18.0 GPa, 589.0 MPa and 5.93 MPa m 1/2 , respectively. While the fracture toughness at 1100°C reach 6.1 MPa m 1/2 increase by 74.3% compared with the ceramic tool material without double composite architectures. At high temperature, the improvement of fracture toughness is due to the addition of ZrB 2 /SiC ceramic granules that deflect the cracks and propagates along the boundary between the granules and the matrix, which greatly increase the path during the crack propagation process, thereby improving the fracture toughness of the ceramic tool material.

Effect of Ti content on preparation and properties of TiB<sub>2</sub>-SiC-Ti materials

Since the 21st century, low atomic number material coating has been considered as one of methods for treating the first wall of controllable thermonuclear fusion device . The TiB<sub>2</sub> material with high melting point, high hardness, low coefficient of thermal expansion, excellent wear resistance and low atomic number has entered into people’s field of vision. Single TiB<sub>2</sub> is difficult to sinter and process into other products. Therefore, adding ceramic and metal additives to TiB<sub>2</sub> matrix material to effectively improve the mechanical properties and processability of the material has become a research hotspot. On the basis of the existing researches of TiB<sub>2</sub>-SiC, in the present work the metal Ti powder is added as the second additive to improve the properties of TiB<sub>2</sub> composite. The TiB<sub>2</sub> and SiC are mixed at a mass ratio of 2 to 3, then two kinds of TiB<sub>2</sub>-SiC-Ti materials with different amounts of Ti content are prepared by spark plasma sintering (SPS) technology. The materials are irradiated by a He<sup>+</sup> beam with energy of 60 keV and ion fluence of 2 × 10<sup>17</sup> ions/cm<sup>2</sup> at room temperature. The material is heat-treated at 1500 ℃ before and also after irradiation. The performances of prepared samples, the effect of irradiation on materials and the results of high temperature heat treatment are characterized by energy dispersive spectroscopy, Raman spectrum, grazing angle x-ray diffraction spectrum, Vickers hardness, wear resistance test, and scanning electron microscope. The results show that the surface morphology and toughness of TiB<sub>2</sub>-SiC-Ti material with 3% Ti mass fraction are poor as shown in SEM images. The wear resistance test indicates that the material surface is seriously worn and the wear resistance is poor. The X-ray diffraction spectrum and Raman spectra show that the material is oxidized seriously at 1500 ℃, which is likely to be the cause of the poor compactness of materials. Raman spectra, Grazing angle X-ray diffraction spectrum and some Vickers hardness data before and after irradiation indicate that the material with low Ti content possess better crystal structure and weaker irradiation hardening. In conclusion, the TiB<sub>2</sub>-SiC-Ti material with 3% Ti mass fraction exhibits lower density, poorer wear resistance and lower hardness, while the material with lower Ti mass fraction is more resistant to irradiation than the material with 6% Ti mass fraction at room temperature.

Изготовление керамических композитов на основе порошка нитрида кремния с осажденной спекающей добавкой

The process of spray drying synthesis of the charge compositions based on silicon nitride α-Si3N4 with organic compounds of aluminum and yttrium in the molar ratio of 3:5 (stoichiometry of yttrium-aluminum garnet) as the sintering additive is considered. The sintered compositions 91.5 % wt. Si3N4 + 8.5 % wt. additive (in terms of garnet) were investigated by X-ray diffraction analysis and scanning electron microscopy as well as by the methods of thermal analysis. The charge compositions were annealed in four stages up to a temperature of 1000℃ in order to decompose organics and form the oxide phase of the sintering additive. High-speed (100 °C/min) spark plasma sintering (SPS) technology was used to produce 10 mm ceramic samples in vacuum, under uniaxial pressure of 70 MPa. The microstructure, mechanical properties and phase composition of ceramics were investigated. Influence of preliminary annealing of charge compositions on structure, phase composition and physical-mechanical properties of ceramics were studied. It is established that preliminary multistage annealing of charge compositions influences the SPS kinetics as well as the density and phase composition of the ceramic. It has been established that the kinetics of SPS of the pre-annealed powders has two-stage character of the shrinkage. In this case denser ceramic microstructure is formed than in the case of reaction synthesis of sintering additive (for charge composition without pre annealing) during the SPS, but pre annealing slows down the growth of elongated β-Si3N4 grains and the volume of sintering additive phase increases. It is shown that in the case of sintering ceramics from unannealed charge compositions the material has lower density but higher hardness. Based on the Yang-Kutler model, the activation energy of the SPS process is determined and it is shown that the compaction kinetics of Si3N4 with sintering additive powders is determined by the intensity of viscous flow of the oxide phase on the grain boundaries of ceramics.

Structure and properties of sintered corrosion-resistant steel manufactured from electroerosive powders

This work solves the problem of saving expensive chrome. This problem is proposed to be solved by grinding their waste of corrosion-resistant steels and reusing them. One of the most promising and industrially non-applicable methods for grinding any electrically conductive material is the electroerosion method. Comprehensive theoretical and experimental research is required to develop technologies for the reuse of electroerosive powders and evaluate the effectiveness of their use. The purpose of this work was to study the structure and properties of sintered samples from electroerosive corrosionresistant powders obtained in butyl alcohol. To perform the planned studies, Kh13 steel waste was selected as the dispersible material. Waste steel Kh13 was processed at a voltage on the electrodes of 100–110 V; the capacity of the discharge capacitors is 45 UF and the pulse repetition rate is 65–75 Hz. Butyl alcohol was used as the working fluid. The resulting powder was consolidated by spark plasma sintering (SPS) using the SPS 25-10 spark plasma sintering system. Based on the conducted experimental studies aimed at studying the structure and properties of sintered samples from electroerosive corrosion-resistant powders obtained in butyl alcohol, the high efficiency of the spark plasma sintering technology is shown, which provides a uniform heat distribution over the sample, controlled porosity and high physical and mechanical properties with a short working cycle time and grain growth suppression. The work was supported by a scholarship of the President of the Russian Federation for young scientists and graduate students (SP-945.2019.1).

Effects of theTiB2-SiC Volume Ratio and Spark Plasma Sintering Temperature on the Properties and Microstructure of TiB2-BN-SiC Composite Ceramics

TiB2-BN composite ceramics combine excellent electrical conductivity, thermal shock resistance, high-temperature resistance, corrosion resistance, and easy processing of TiB2 and BN. However, in practical applications, their high-temperature oxidation resistance is poor and the resistivity distribution is uneven and changes substantially with temperature. A TiB2-BN-SiC composite ceramic with stable and controllable resistivity was prepared by introducing SiC into the TiB2-BN composite ceramics. In this work, spark plasma sintering (SPS) technology was used to prepare TiB2-BN-SiC composite ceramics with various TiB2-SiC ratios and sintering temperatures. The samples were tested by XRD, SEM, and thermal and mechanical analysis. The results show that as the volume ratio of TiB2-SiC was increased from 3:1 to 12:1, the resistivity of the sample decreased from 8053.3 to 4923.3 μΩ·cm, the thermal conductivity increased from 24.89 to 34.15 W/(m k), and the thermal expansion rate increased from 7.49 (10−6/K) to 10.81 (10−6/K). As the sintering temperature was increased from 1650 to 1950 °C, the density of the sample increased, the mechanical properties were slightly improved, and the resistivity, thermal expansion rate, and thermal conductivity changed substantially. The volume ratio and sintering temperature are the key factors that control the resistivity and thermal characteristics of TiB2-SiC-BN composite ceramics, and the in situ from liquid phases of FeB and FeO also promotes the sintering of the TiB2-BN-SiC ceramics.