Controlling current flow in sintering: A facile method coupling flash with spark plasma sintering

Gorynski, Claudia; Tamburini, Umberto Anselmi; Winterer, Markus

doi:10.1063/1.5119059

Cited by 14 publications

(4 citation statements)

References 40 publications

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“…To ensure that, a SPS experiment has been conducted with BN-spacers in between the graphite punch and the Mn-Al-C powder. As BN is an electrical insulator, this configuration ensures that the electric current does not flow through the powder but only through the graphite die and pistons [25]. Similar annealing conditions (i.e.…”

Section: Resultsmentioning

confidence: 99%

“…Additionally, to investigate the effect of electric current during the SPS process, boron nitride (BN) spacers were used between the powder and the graphite punches, while the other parameters (pressure, time and temperature) were kept fixed. By employing this methodology, it is ensured that the electric current flows solely through the graphite tools and not through the sample [25]. For the SPS process, the ribbons are crushed into powder and since the temperature is not high enough to promote sintering, only porous cylindrical samples (around 70% relative density) were obtained.…”

Section: Methodsmentioning

confidence: 99%

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Formation of pure $$\tau$$-phase in Mn–Al–C by fast annealing using spark plasma sintering

et al. 2022

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Mn–Al–C is intended to be one of the “gap magnets” with magnetic performance in-between ferrites and Nd-Fe-B. These magnets are based on the metastable ferromagnetic $$\tau$$ τ -phase with L1$$_0$$ 0 structure, which requires well controlled synthesis to prevent the formation of secondary phases, detrimental for magnetic properties. Here, we investigate the formation of $$\tau$$ τ -phase in Mn–Al–C using Spark Plasma Sintering (SPS) and compare with conventional annealing. The effect of SPS parameters (pressure and electric current) on the phase formation is also studied. Single $$\tau$$ τ -phase is obtained for annealing 5 min at $$500~^\circ \hbox {C}$$ 500 ∘ C with SPS. In addition, we show that the initial grain size of the $$\epsilon$$ ϵ -phase is influencing the $$\tau$$ τ -phase transformation and fraction at a given annealing condition, independently of the annealing method used. A faster transformation was observed for smaller initial $$\epsilon$$ ϵ -grains. The samples obtained by SPS showed comparable magnetic properties with the conventional annealed ones, reaching coercivity of 0.18 T and saturation magnetization of 114 Am$$^2$$ 2 /kg in the optimized samples. The similarity in coercivity is related to the microstructure, as we reveal the presence of structure defects like twin boundaries and dislocations in both materials. Graphical abstract

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Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Formation of pure $$\tau$$-phase in Mn–Al–C by fast annealing using spark plasma sintering

et al. 2022

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“…The pre‐compacted short cylindrical green sample (e.g., 0.1 g ZrN powder, 3.1 mm diameter, and ∼2.5 mm thickness from dry pressing) was enclosed within insulating h‐BN tubes and contacted by the top and bottom graphite electrodes. The sample assembly force electrical current to only go through the sample, distinguishing it from typical spark plasma sintering (SPS), 39 where the exact current pathway is determined by the electrical resistance of both the tool (i.e., graphite die set) and the sample. (If the powder compact in SPS exhibits high resistance, current will travel almost exclusively through the graphite die body.…”

Section: Methodsmentioning

confidence: 99%

Effects of processing conditions on flash sintering of commercial ZrN

Eskandariyun,

Das,

Dubois

et al. 2024

J Am Ceram Soc.

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Flash sintering (FS) is a potentially rapid and low‐cost manufacturing technique for advanced ceramics. There are still many unknowns about ceramic FS, especially for highly conductive high‐temperature ceramics (HTC), which often display decreased bulk conductivity with increasing temperature. This study qualitatively characterizes the flash behavior of highly conductive HTC materials using zirconium nitride (ZrN) as an example. The effects of processing parameters (e.g., DC voltage/electrical field strength, voltage ramp rate, post‐flash holding time, mechanical pressure, sample milling, and choice of electrode materials) on ZrN flash behavior are also qualitatively studied and linked to samples microstructure and hardness. It is observed that best densification was achieved using 5 min Spex‐milled ZrN powder under 25 MPa of applied pressure and constant 8 V DC. The potential mechanism for ZrN FS and the similarity and difference from FS of conventional oxides like YSZ have been proposed based on experimental observations, and the directions for future research are also pointed out.

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“…Recent investigations in FSPS 4‐8 use mostly a modification of the classical SPS to achieve FS conditions. This is usually done through the insertion of a nonconductive sleeve (eg, BN 9 ) between the powder (or pre‐compacted/partially pre‐sintered pellet) and the graphite die, or alternatively in a die‐free configuration. Commercial instruments enabling FSPS processing with higher voltage characteristics (>10 V), using independent external heating of the die or precise time application of the electric field, are under development or in early application stage.…”

Section: Introductionmentioning

confidence: 99%

Power‐controlled flash spark plasma sintering of gadolinia‐doped ceria

et al. 2020

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Flash spark plasma sintering (FSPS) is a newly developed technique for consolidation of powder materials into dense compacts. This method belongs to the group of electrical field-assisted sintering (FAST) techniques. It combines the voltage/current characteristics of flash sintering (FS), 1,2 usually performed in pressure-less dog-bone configuration, with the sintering cell design typical of spark plasma sintering (SPS). 3 Recent investigations in FSPS 4-8 use mostly a modification of the classical SPS to achieve FS conditions. This is usually done through the insertion of a nonconductive sleeve (eg, BN 9) between the powder (or pre-compacted/partially pre-sintered pellet) and the graphite die, or alternatively in a die-free configuration. Commercial instruments enabling FSPS processing with higher voltage characteristics (>10 V), using independent external heating of the die or precise time application of the electric field, are under development or in early application stage. In the presented paper, we describe the pressure-assisted FS compaction of powder in an SPS configuration using such a newly developed instrument. We have chosen ceria as a sintering probe not only for its

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Controlling current flow in sintering: A facile method coupling flash with spark plasma sintering

Cited by 14 publications

References 40 publications

Formation of pure $$\tau$$-phase in Mn–Al–C by fast annealing using spark plasma sintering

Formation of pure $$\tau$$-phase in Mn–Al–C by fast annealing using spark plasma sintering

Effects of processing conditions on flash sintering of commercial ZrN

Power‐controlled flash spark plasma sintering of gadolinia‐doped ceria

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