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Impact of Thermal Diffusion on Densification During SPS
Author(s) -
Olevsky Eugene A.,
Froyen Ludo
Publication year - 2009
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1551-2916.2008.02705.x
Subject(s) - materials science , consolidation (business) , spark plasma sintering , sintering , creep , grain boundary diffusion coefficient , thermal diffusivity , ceramic , diffusion creep , grain boundary , surface tension , thermal , composite material , forensic engineering , thermodynamics , microstructure , physics , accounting , engineering , business
Spark‐plasma sintering (SPS) has the potential for rapid (with heating rates reaching several hundred K/min) and efficient consolidation of a broad spectrum of powder materials. Possible mechanisms of the enhancement of consolidation in SPS versus conventional techniques of powder processing are categorized with respect to their thermal and athermal nature. This paper analyzes the influence of thermal diffusion, which is an SPS consolidation enhancement factor of a thermal nature. The Ludwig–Soret effect of thermal diffusion causes concentration gradients in two‐component systems subjected to a temperature gradient. The thermal diffusion‐based constitutive mechanism of sintering results from the additional driving force instigated by spatial temperature gradients, which cause vacancy diffusion. This mechanism is a commonly omitted addition to the free‐surface curvature‐driven diffusion considered in conventional sintering theories. The interplay of three mechanisms of material transport during SPS is considered: surface tension‐ and external stress‐driven grain‐boundary diffusion, surface tension‐ and external stress‐driven power‐law creep, and temperature gradient‐driven thermal diffusion. It is shown that the effect of thermal diffusion can be significant for ceramic powder systems. Besides SPS, the results obtained are applicable to the ample range of powder consolidation techniques, which involve high local temperature gradients.The case study conducted on the alumina powder SPS demonstrates the correlation between the modeling and experimental data. It is noted that this study considers only one of many possible mechanisms of the consolidation enhancement during SPS. Further efforts on the modeling of field‐assisted powder processing are necessary.