Pressure‐enhanced densification of TaC ceramics during flash spark plasma sintering

Abstract

Flash spark plasma sintering (FSPS) offers extremely high heating rates to consolidate ceramics at a short time. However, significant grain growth sometimes occurs accompanied by rapid densification. In this work, a FSPS apparatus available for applying pressure was used to sinter TaC ceramics from powder compacts without preheating. It is found that the use of a higher pressure can efficiently promote densification and retard significant grain growth. Dense bulk TaC ceramics (95.18%) with average grain size of 4.09 μm were obtained in 90 seconds under 80 MPa. Such a process should facilitate the fast preparation of refractory ceramics with fine-grained microstructure. K E Y W O R D Sdensification, flash spark plasma sintering, grain growth, tantalum/ tantalum compounds

Pressure‐assisted flash sintering of ZnO ceramics

“…If a thicker alumina tube is used, higher pressure can be applied in flash sintering. However, 26 MPa used in this work is sufficient to take advantage of the pressure‐enhanced effect on densification and controlling microstructure 26,37 . Taking into account the small height of the green body (~1.59 mm, calculated via the relative density and initial powder weight), the green body is directly preheated by the induction heating electrode.…”

“…Moreover, it has a compact configuration and uses lower power for rapid preheating and densification, which may offer an opportunity to improve efficiency and reduce the cost of flash sintering experiments, and to screen new ceramics on a laboratory scale. Finally, what we are more concerned about is the densification behavior and microstructure evolution of the sample during the pressure‐assisted flash sintering process, which is less studied than other electric field‐assisted sintering methods like SPS 26,37–43 and will be discussed later.…”

“…However, the difference in densification behavior with pressure variation in the initial stage (in the first ~3 s) is noticeable. It indicates that the pressure can provide additional non‐thermal effects on densification in the first 3 s. The difference in densification behavior with pressure changes in the initial stage can be explained as being dominated by the mechanical action of the applied pressure, because the pressure directly affects the rearrangement of the particles, the destruction of the agglomerates, the viscous sliding of the particles, and even the plastic deformation, especially in the case of smaller particle size of the initial stage 37,39,40,66 . As the pores close and the grains grow (Figure 8), the movement of the grains in the intermediate (~3–10 s) and final stages (~10–30 s) is restricted 40 .…”

“…Studies on the effects of the external pressure in other electric field‐assisted sintering methods like SPS have been widely reported, but there are few reports in flash sintering 26,37–43 . In this work, in order to make better use of the potential of pressure‐assisted flash sintering and to study the densification behavior and microstructure evolution of the sample during this process, a new experimental configuration is designed to implement pressure‐assisted flash sintering.…”

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

“…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.…”