Rapid Densification and Deformation of Li‐Doped Sialon Ceramics

Abstract

Two lithium‐doped sialon ceramics were densified and superplastically deformed by spark plasma sintering (SPS). Rapid densification with linear shrinkage rates of approximately 5 × 10−3 s−1 were observed for samples heated at a rate of 100°C/min up to ∼1400°C under a uniaxial pressure of 40 MPa. Isothermal deformation by SPS‐preprepared, fully densified ceramics performed at T≥ 1450°C yielded strain rates in the order of 10−2 s−2. It is suggested that a high heating rate promotes material transport via formation of a nonequilibrated oxygen‐rich liquid of low viscosity. This finding most likely holds true for other liquid‐phase sintered ceramics as well and has implications for cost‐effective manufacturing of ceramic components.

Hydrodynamics of slot‐rectangular spouted beds: Effect of slot configuration on the local flow structure

“…The increase in the shrinkage rate with increasing heating rate is even more pronounced in the case of liquid phase sintering. We ascribed the enhanced densification kinetics to the formation of an excess of a non‐equilibrium liquid phase that accelerates the particle sliding via grain boundaries 16. Due to the high heating rate applied, a concentration gradient is built up in the liquid, so that the liquid formed close to the Si 3 N 4 particles is rich in nitrogen, whereas the nitrogen content decreases further away from the Si 3 N 4 particles, as illustrated in Figure 3.…”

Oxidation of β-SiAlONs prepared by a combination of combustion synthesis and spark plasma sintering

“…In our previous papers [5][6][7], β-SiAlON powders were successfully synthesized under only 1 MPa of nitrogen pressure assisted with mechanical activation. Sintering methods such as pressureless sintering [8], hot isostatic pressing [2], and spark plasma sintering (SPS) [9] have been previously used to produce dense β-SiAlONs. Among these aforementioned methods, SPS technique is similar to conventional hot press (HP), but it allows a pulsed direct current instead of external heating source to heat the sample through the die, so the die also acts as a heating source.…”

Ultralow-Temperature Superplasticity in Nanoceramic Composites

“…The observed enhanced ductility is thought to be associated with the enhanced grain sliding at the boundary of the glassy/liquid phase resulting from the electric-fieldinduced motion of charged species. [20][21] In the present study, the combination of sinter-forging strategies and noVel spark-plasma-sintering effects was utilized for the first time to lower deformation temperatures and enhance the deformation rates in ceramic nanocomposites. Here we started with a porous preform instead of fully dense blanks and simultaneously consolidated and superplastically formed the specimens in the SPS equipment.…”

“…SPS has been demonstrated to be not only an effective sintering process for fabricating fully dense nanocrystalline ceramics and composites − but also a new forming method for enhancing ceramic ductility. − The first attempt to apply the SPS approach to speed up superplastic forming was by Shen et al, who started with fully dense ceramics that sinter via either transient or permanent liquid-phase modes. The observed enhanced ductility is thought to be associated with the enhanced grain sliding at the boundary of the glassy/liquid phase resulting from the electric-field-induced motion of charged species. − …”