Preparation of Ti3SiC2–TiC composite from TiC, SiC, and Ti was performed using Spark Plasma Sintering (SPS). Initial powders were mixed using a planetary ball mill for 2 h with 90 RPM. The number of ...milling media was varied to obtain the best homogeneity of the samples between 70 and 250. SPS was performed at 1450, 1550, and 1600 °C in Ar and vacuum. By decreasing the amount of TiC in the initial mixture unreacted Ti5Si3 appeared in the final composition. Samples were subjected to 10 h oxidation tests at 900, 1000, and 1100 °C using thermogravimetry. The ideal sintering regime (highest oxidation resistance) was found to be 1550 °C with 10 min dwell time in Ar atmosphere. Oxidation kinetics of the prepared compacts was found to be following the parabolic law. The lowest overall oxidation rate was observed for the samples with the highest (above 87 wt%) Ti3SiC2 content. On the other hand, sample with Al addition was the most prone to oxidation. The phase composition of the samples played a higher role in their oxidation behaviour than their porosities.
Spark plasma sintering (SPS), also known as pulsed electric current sintering (PECS) or field-assisted sintering technique (FAST), belongs to a class of powder metallurgy techniques. In SPS, the ...sample is simultaneously subjected to a uniaxial pressure and electrical current in a vacuum or protective atmosphere. Although the fundamental principles of this procedure were first proposed over 50 years ago, SPS acquired major importance only within the last 20 years. Scholars come to realize that SPS technique enables control of the powder surface condition, atomic diffusion behavior, and phase stability and crystal growth behavior, as well as accelerating densification of hard-to-sinter materials. This review summarizes the latest research findings with respect to experimental procedures, densification behaviors, microstructural characteristics, and mechanical properties of various traditional and novel materials synthesized using SPS, mainly highlighting the heating mechanisms in SPS and the effects induced by multi-physical fields on materials. In addition, influences of operating parameters containing current, voltage, and uniaxial pressure on product characteristics are reviewed for a wide range of materialsincluding hard-to-sinter materials, carbon-containing materials, nanocrystalline materials, non-equilibrium materials, gradient materials, interconnect materials, complex shape materials, and advanced functional materials.
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•Effects of current, electric fields and pressure on SPS processing and micro-mechanisms in materials are investigated.•The state-of-the-art concepts of SPS devices for R&D and industrial application are presented.•The common technological superiority and optimization mechanisms of applying SPS in every material system are illustrated.•Overview on the design, experiment and simulation of both structural and functional materials developed by SPS technique.
•SPS-densified Cr-doped U3Si2 pellets display uniform microstructure and homogeneous distributions of additives•SPS-densified Cr-doped U3Si2 pellets are mechanically strong and tough, and display ...greatly improved oxidation resistance•The onset temperature for oxidation of the Cr-doped U3Si2 pellets is over 550 oC in air and 520 oC in steam•The 10 wt% Cr-doped U3Si2 pellet can maintain its integrity without pulverization under steam oxidation at 360 oC for 24 hours
Dense Cr-doped U3Si2 composite fuels were manufactured by spark plasma sintering, and the effects of Cr addition on mechanical properties and oxidation resistance were investigated. Dynamic oxidation testing by thermogravimetric analysis revealed significantly improved oxidation resistance of U3Si2 with minimal doping of 3 wt% Cr. The onset oxidation temperature increased to above 550 °C in air and ∼520 °C in steam conditions for the 5 wt% and 10 wt% Cr-doped composites. Steam corrosion testing under 360 °C for 24 hours indicated well-maintained pellet integrity without pulverization for the 10 wt% Cr-doped U3Si2 pellet which only showed minor surface oxidation. The first promising results open up the possibility of designing and manufacturing metal additive-doped U3Si2 composite fuels with significantly-improved corrosion resistance as a potential candidate for accident tolerant fuels.
Mechanically alloyed (MA) NbMoTaWVCr refractory high-entropy alloy (HEA) powders were sintered by spark plasma sintering (SPS) at temperatures of 1400–1700 °C. The microstructural evolution and ...mechanical properties of sintered HEAs were subsequently investigated. During the MA process, only a supersaturated body-centered cubic (BCC) structured solid solution was formed. However, C15 Laves phase (Cr,V)2(Ta,Nb) and Ta2VO6 particles were precipitated from the disordered BCC phase during the sintering process at temperatures ≤1500 °C. When the sintering temperature increased to 1600 °C, the Laves phase was transferred to C14 structure and its volume fraction was dramatically reduced. The plasticity of the refractory HEA was strongly affected by the fraction, size and distribution of Laves phase and oxide particles. The NbMoTaWVCr alloy sintered at 1500 °C obtained an excellent combination of yield strength (3416 MPa) and failure plasticity (5.3%) at room temperature. The extraordinary high strength of this HEA could be dominantly attributed to the grain boundary strengthening from the micron-sized BCC phase (1.24 μm), interstitial solid solution strengthening from O in the matrix and the inherent solid solution strengthening in the multi-principal element NbMoTaWVCr alloy.
•A fine-grained refractory NbMoTaWVCr HEA was successfully synthesized by MA-SPS.•Laves and oxide phases were precipitated from the BCC solid solution during SPS.•The fraction of Laves phase was reduced with the increase of sintering temperature.•The HEA showed strength higher than those of most other HEAs in the literature.•Ultra-high strength of the HEA was controlled by various strengthening mechanisms.
In this work a novel process methodology to concurrently improve the compressive strength (2078 MPa at a strain rate of 5 × 10−4 s−1) and strain-to-failure (over 40%) of bulk tungsten materials has ...been described. The process involves the in situ formation of intragranular tungsten oxide nanoparticles, facilitated by the application of a pressure of 1 GPa at a low sintering temperature of 1200 °C during spark plasma sintering (SPS). The results show that the application of a high pressure of 1 GPa during SPS significantly accelerates the densification process. Concurrently, the second phase oxide nanoparticles with an average grain size of 108 nm, which are distributed within the interiors of the W grains, simultaneously provide strengthening and plasticity by inhibiting grain growth, and generating, blocking, and storing dislocations.
In this work a novel process methodology to concurrently improve the compressive strength (2078 MPa at a strain rate of 5 × 10−4 s−1) and strain-to-failure (over 40%) of bulk W materials has been described. The process involves the in situ formation of intragranular tungsten oxide nanoparticles, facilitated by the application of a pressure of 1 GPa at a low sintering temperature of 1200 °C during spark plasma sintering (SPS). Display omitted
Pixelated sintering of α-Al2O3 Cornu, Iñaki; Cheype, Maxime; Baudier-Pons, Marion ...
Journal of the European Ceramic Society,
10/2022, Letnik:
42, Številka:
13
Journal Article
Recenzirano
Odprti dostop
The sintering of α-alumina by a brand new and innovative technique, called pixelated sintering (PS), is here studied. Densification and grain growth by PS of perfectly controlled granular compacts ...are analysed and compared to results obtained using Spark Plasma Sintering (SPS) and Pressure-Less SPS (PL-SPS). Materials are exposed to the same temperature profiles whatever the sintering technique used in order to assess the potential of PS in terms of microstructure control. It is shown that PS can be used as an alternative technique to SPS for fast sintering with the advantages of a much simpler and cost-effective set-up, as well as a better control of the localised heat input. PS also appears to be a very modular technology in the way it controls the temperature gradients allowing its implementation for multi-step sintering approaches, as well as for the fabrication of large and complex parts.
The development of a novel ZrB2–VB2–ZrC composite using ZrB2, vanadium and graphite nano-flake powders via reactive spark plasma sintering was studied. The in-situ formation of VB2 and ZrC enhance ...the densification, sinterability and mechanical properties. A relative density of 99.17% was achieved for ZrB2–20 vol% VB2–20 vol% ZrC composite after RSPS at 1900 °C for 7 min under 40 MPa. The hardness and fracture toughness of the novel composite are improved by 50% and 40%, respectively, in comparison with a monolithic ZrB2 ceramic. Thermodynamic calculations and microstructural analyzes revealed that the in-situ formed VB2 and ZrC phases derived from the reaction between a transient VC phase with ZrB2 matrix. These phases were also found to be strong inhibitors of grain growth, and consequently result in improved sinterability and mechanical properties. Due discussions about the formation mechanism, characteristics and influences of such refractory reinforcement phases were investigated and schematically illustrated.
This study aims to understand the effect of the electrical field on microstructure evolution during field‐assisted sintering or spark plasma sintering (FAST/SPS) of 10 mol% gadolinium‐doped ceria ...(GDC) with experimental and numerical methods. The novelty of this study has been the observation of enhanced grain growth in the region closer to the anode, even under FAST/SPS conditions with electrical fields less than 5 V/cm. The grain growth kinetics, including determination of activation energy and grain‐boundary mobility, were analyzed along the cross section of the samples for different temperatures and dwell periods. With an increase in distance from the anode, reduction in the activation energy for grain growth and grain‐boundary mobility was observed. These observations attributed to the attraction of oxygen ions to the anode region under an electrical field with an increase in defects along the grain boundaries. Thereby an increase in the grain‐boundary mobility and larger grains in that region were observed. A homogenous microstructure was observed in a case where the current did not flow through the sample. Furthermore, a numerical strategy has also been developed to simulate this behavior in addition to heat generation, heat transfer, and densification using Finite Element Methods (FEM) simulations. The simulation results provided an insight into the presence of a potential difference across the cross section of the samples. The simulation results were also in good agreement with the experimental observations.
Enhanced grain growth in the anode region during FAST/SPS of gadolinium‐doped ceria. Grain size as a function of dwell time obtained for sintering temperatures between (A) 1100 – 1300 °C and (B) 1400 °C
The phase transition of fullerene C60 under high pressure and high temperature has been widely studied, but the research on the spark‐plasma sintering of C60 is limited, and the mechanical properties ...of synthesized materials are still unknown. In this study, a series of amorphous carbon materials were synthesized by spark‐plasma sintering fullerene C60 at different temperatures. The structural characterizations showed that they were composed of multi‐graphene fragments with different sizes, curvatures, and ordering degrees. The densities of the synthesized amorphous carbons were 1.3‐1.4 g/cm3, which were lower than the values for graphite, but the mechanical properties were excellent. The highest compressive strength, indentation hardness, and elastic recovery of the amorphous carbons synthesized at different temperatures could reach up to ~1.25 GPa, ~3.8 GPa, and ~85.5%, respectively, which are far better than the values for commercial isotropic graphite materials.
TiB2-Ti3AlC2 composite ceramics were fabricated by spark plasma sintering (SPS) technique. The effects of Ti3AlC2 additive on the densification, mechanical properties and resistance to ...high-temperature aluminum liquid erosion of composite ceramics were investigated, and the mechanisms of densification and erosion resistance were highlighted, respectively. At sintering temperature of 1800 °C, pressure of 40 MPa, and holding time of 10 min, TiB2 composite ceramic with 40 wt% Ti3AlC2 acquired 98.9 % densification, 98.2 % thermal shock resistance, and 13.71 MPa∙m1/2 fracture toughness. The in-situ decomposition of Ti3AlC2 was clearly observed during the sintering process, and the generated liquid Al induced the liquid phase sintering mechanism, promoting the densification of composite ceramics. Besides, the simultaneous in-situ generation of TiC phase strengthened the TiB2 matrix and induced a mixed toughening mechanism of transgranular fracture and intergranular fracture, resulting in superior mechanical properties and better resistance to high-temperature erosion of TiB2-Ti3AlC2 composite ceramics.
•High-performance TiB2-40 wt% Ti3AlC2 composite ceramics were successfully fabricated using SPS technique.•Ti3AlC2 decomposed at about 1340 °C to in-situ generate liquid Al and TiC.•Liquid Al would induce liquid-phase sintering mechanism.•The TiC phase strengthened the TiB2 matrix and induced the mixed toughening mechanism.•Three stages of erosion: friction of aluminum liquids, intergranular corrosion and intergranular diffusion.
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