Viscous flow activation energy adaptation by isochronal spark plasma sintering

Paul, Tanaji; Harimkar, Sandip P.

doi:10.1016/j.scriptamat.2016.08.018

Cited by 41 publications

(16 citation statements)

References 22 publications

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“…In our previous work, growth of the grains of LiZnTi ferrite (i.e., Li 0.43 Zn 0.27 Ti 0.13 Fe 2.17 O 4 ) was difficult at 920°C. This indicates that the method using Bi 2 O 3 substitution in the pre‐sintering process can effectively reduce the activation energy and promote grain growth at relatively low temperature . In other words, for the LiZnTiBi ferrite ceramics, the critical temperature of grain growth decreased to 920°C.…”

Section: Resultsmentioning

confidence: 80%

“…This indicates that the method using Bi 2 O 3 substitution in the pre-sintering process can effectively reduce the activation energy and promote grain growth at relatively low temperature. 24,25 In other words, for the LiZnTiBi ferrite ceramics, the critical temperature of grain growth decreased to 920°C. However, as seen in Figure S2, there are some small grains (only 1-3 lm) and pores between large grains.…”

Section: Microstructure Analysis Of Ferrite Ceramicsmentioning

confidence: 99%

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Investigation of grain boundary diffusion and grain growth of lithium zinc ferrites with low activation energy

Zhang

Xie

et al. 2018

J Am Ceram Soc

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Activation energy and diffusion kinetics are important factors for grain growth and densification. Here, Bi2O3 was introduced into Li0.43Zn0.27Ti0.13Fe2.17O4 ferrite ceramics via a presintered process to lower the reaction activation energy and to achieve low temperature sintering. Interestingly, Bi3+ ions entered the lattice and substituted for Fe3+ in the B‐site (i.e., a pure LiZn spinel ferrite). Also, SEM image results show that Bi2O3‐substituted LiZn ferrite ceramics have low critical temperature for grain growth (920°C), which is very advantageous for LTCC technology. This indicates that Bi2O3 is an excellent dopant for ceramics. Furthermore, to promote normal grain growth of the ceramics at low temperatures, different volumes of V2O5 additive were added at the final sintering stage. Results indicate that an optimal volume of V2O5 additive promotes grain growth (with no abnormal grains) and enhances magnetic performances of the ceramics at low sintering temperature. Finally, adding the optimal volume of V2O5 additive resulted in a homogeneous and compact LiZnTiBi ferrite ceramic with larger grains (average size of ~8 μm), high 4πMs (~4100 gauss), and low ΔH (~190 Oe) obtained (at 900°C). Moreover, the doping method reported in this study also provides a reference for other low temperature sintered ceramics.

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Section: Resultsmentioning

confidence: 80%

Section: Microstructure Analysis Of Ferrite Ceramicsmentioning

confidence: 99%

Investigation of grain boundary diffusion and grain growth of lithium zinc ferrites with low activation energy

Zhang

Xie

et al. 2018

J Am Ceram Soc

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“…[12][13][14][15][16] The applied pressure has been observed to not only aid in the rearrangement of powder particles and fragmentation of agglomerates, but also enhance the kinetics of sintering. [19,[21][22][23][24] Near fully dense samples with hardness and fracture toughness of about 1 300 HV and 1.6 MPa m 1/2 , respectively, were obtained. [19,20] The SPS process is thus extremely beneficial for the preservation of amorphous structure in sintered Fe-based amorphous alloys.…”

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confidence: 95%

“…[10,11] These advantages stem primarily from the effects of uniaxial pressure and high heating rates resulting from internal Joule heating. [19,20] The SPS process is thus extremely beneficial for the preservation of amorphous structure in sintered Fe-based amorphous alloys. [17,18] High heating rates, on the other hand significantly reduce the activation energy of the dominant densification mechanism.…”

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confidence: 99%

Densification and Crystallization in Fe–Based Bulk Amorphous Alloy Spark Plasma Sintered in the Supercooled Liquid Region

2017

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Spark plasma sintering of Fe 48 Cr 15 Mo 14 Y 2 C 15 B 6 bulk amorphous alloy at a range of temperatures in the supercooled liquid region (SLR) and above yielded near fully dense compacts. Upon sintering in the temperature range of 570-630 C in SLR, large increments in density are observed due to enhanced sintering resulting from drastic reduction in the viscosity of the alloy. Above 630 C, the absence of sufficient driving force for sintering and stiffening of the amorphous matrix from partial crystallization leads to sluggish densification. Analysis of the temperature profile in the sample and the die reveals that the temperature at the center of the sample is higher than that at the inner wall of the die as recorded by the thermocouple and the difference between the two is estimated to be between 31 and 53 C.

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“…One of the promising methods is the application of powder consolidation techniques such as hot pressing 23 , warm extrusion 24 , hot isostatic pressing 25 and spark plasma sintering (SPS) 26 . SPS is particularly advantageous as it enables the sintering of dense compacts at lower temperatures and shorter cycles [27][28][29][30] primarily due to Joule heating resulting from the passage of current through the powder compact 31,32 . These advantages have led to the widespread applicability of SPS as means for prosessing difficult to sinter materials such as metallic glasses, ceramics and their composites 30 .…”

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confidence: 99%

Crystallization Mechanism in Spark Plasma Sintered Bulk Metallic Glass Analyzed using Small Angle Neutron Scattering

Paul

Singh

Littrell

et al. 2020

Sci Rep

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Understanding the thermal stability of metallic glasses is critical to determining their safe temperatures of service. In this paper, the crystallization mechanism in spark plasma sintered Fe 48 cr 15 Mo 14 Y 2 c 15 B 6 metallic glass is established by analyzing the crystal size distribution using x-ray diffraction, transmission electron microscopy and in-situ small angle neutron scattering. Isothermal annealing at 700 °C and 725 °C for 100 min resulted in the formation of (Fe,Cr) 23 c 6 crystals, measured from transmission electron micrographs, to be from 10 to 30 nm. The small angle neutron scattering intensity measured in-situ, over a Q-range of 0.02 to 0.3 Å −1 , during isothermal annealing of the sintered samples, confirmed the presence of (Fe,Cr) 23 c 6 crystals. The measured scattering intensity, fitted by the maximum entropy model, over the Q-range of 0.02 to 0.06 Å −1 , revealed that the crystals had radii ranging from 3 to 18 nm. The total volume fraction of crystals were estimated to be 0.13 and 0.22 upon isothermal annealing at 700 °C and 725 °C for 100 min respectively. The mechanism of crystallization in this spark plasma sintered iron based metallic glass was established to be from pre-existing nuclei as confirmed by Avrami exponents of 0.25 ± 0.01 and 0.39 ± 0.01 at the aforesaid temperatures.

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Viscous flow activation energy adaptation by isochronal spark plasma sintering

Cited by 41 publications

References 22 publications

Investigation of grain boundary diffusion and grain growth of lithium zinc ferrites with low activation energy

Investigation of grain boundary diffusion and grain growth of lithium zinc ferrites with low activation energy

Densification and Crystallization in Fe–Based Bulk Amorphous Alloy Spark Plasma Sintered in the Supercooled Liquid Region

Crystallization Mechanism in Spark Plasma Sintered Bulk Metallic Glass Analyzed using Small Angle Neutron Scattering

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