Effects of Current Confinement on the Spark Plasma Sintering of Silicon Carbide Ceramics

Abstract

Despite numerous works have recently reported the densification of silicon carbide (SiC) ceramics using the Spark Plasma Sintering (SPS) technique, the effect of the localized electric current flow near the specimen over the liquid phase sintering process of SiC ceramics and on their microstructural features has not been completely addressed. In the present work, two different SPS setups affecting current flow are selected, one based on the ordinary die/punch setup configuration, and the other employing a BN electrically insulating coating on the inner wall of the die to force the electric current to locally flow through the inner graphite foil in contact with the ceramic compact. The effective electrical resistance and the energy consumed during the SPS runs for both setups, as well as the sintering behavior, microstructure, and mechanical properties of the SPSed materials are analyzed. The BN die coating considerably increases the effective resistance of the system, decreases the power consumption, and accelerates the SiC densification. Besides, ceramic specimens experience significantly higher real temperatures than the set values and, accordingly, coarser microstructures and tougher materials than those for the ordinary setting are produced. The thermoelectrical properties of SiC materials are proposed as fundamental in their SPS process, especially when electrical current is forced through the inner part of the SPS setting around the specimen.

Highly-porous hierarchical SiC structures obtained by filament printing and partial sintering

“…The average mesopore size for the N0-1500 struts is about 1/3 the original size of the SiC powders, being therefore coincident with the rule that pore size is within a half and a fifth of the powders size [4]. These materials present slight differences regarding the phase analysis, All the structures consist of a mixture of the cubic phase, -SiC (3C), and two hexagonal polytypes, α-SiC, while both N7 structures show, in addition, the presence of yttrium aluminum monoclinic, YAM, (Al2Y4O9), in agreement with the occurrence of liquid phase sintering process that predicts the precipitation of different Y-aluminate phases depending on the SPS sintering conditions [24].…”

Prominent local transport in silicon carbide composites containing in-situ synthesized three-dimensional graphene networks

“…Despite there is not a significant increase in the mean grain size (i.e. d50 = 0.54 μm vs. 0.50 μm for the starting powder), there is a 25% increase in the number of grains above 1 µm in this G/β-SiC composite [45]. Fig.…”

All-Materials-Inclusive Flash Spark Plasma Sintering

“… 56 for ceramic powders (ZrB 2 , MoSi 2 , Al 2 O 3 ) in flash conditions and by Román-Manso et al . 57 for the densification of SiC. However, in contrast with the above-mentioned techniques, the different current patterns employed in this paper demonstrate that an unordinary thermal runaway can be instigated by the electric current assistance for all kinds of the tested materials.…”