Densification as an exothermic process revealed by rapid high temperature consolidation of BaTiO₃ nanopowder

Abstract

Densification is an exothermic process according to the classical sintering theories; however, it has never been explored experimentally. In the present work, such heat release was successfully detected from nanosized BaTiO₃ nanopowder compact, which was rapidly consolidated by spark plasma sintering. A reduction of total power consumption was observed immediately when rapid densification occurred. The effects of the deviation of overall electric resistance on total power consumption were analysed. The temperature at which a falling inflection point of the power supply was observed can be used as an indicator of the minimum temperature required for densification. This would be of help for defining the ‘kinetic window’ for processing of nanoceramics in sintering practice.

Keywords:

• Spark plasma sintering
• Sintering
• Densification
• Nanocrystalline materials

Acknowledgements

This work was supported by European Commission through the Marie-Curie ITN project ‘FUnctional Nitrides for Energy Applications, FUNEA’ (FP7-PITN-GA-2010-264873) and Berzelii Center EXSELENT. The authors appreciate the fruitful discussions with Mats Nygren, Zhaohui Ren, Jing Zhao and Ji Zou.