Nanoparticle surface premelting-induced low-temperature sintering and large shrinkage of particle beds in additive manufacturing

Abstract

Understanding the thermophysical properties (e.g., thermal shrinkage and thermal conductivity) of the ceramic nanoparticle packed beds in additive manufacturing are crucial for improving the manufacturing accuracy. In this work, we firstly modeled the surface premelting process of nanoparticles, which is likely responsible for low-temperature sintering, and subsequently established thermal shrinkage model of nanoparticle packed beds. The model captures the experimental results well. The results show that with the increase of the sintering temperature, the changing tendencies of both the volume shrinkage (related with accuracy) and the thermal conductivity (related with heat diffusion) of nanoparticle beds all depend on the melting degree of nanoparticles, thus has a same trend. The smaller the nanoparticles, the lower their premelting temperature, thus the lower the sintering temperature of the nanoparticle beds and the greater shrinkage the nanoparticle beds in the additive manufacturing. The porosity of nanoparticle beds which is usually less than 85 % has a neglectable effect on the shrinkage. This work provides methods to predict both sintering temperature in thermal processing and also shrinkage of nanoparticle beds in additive manufacturing.