Unraveling the Role of Grain Boundary Anisotropy in Sintering: Implications for Nanoscale Manufacturing

Sintering is a thermal processing technique used to consolidate particle compacts into structures broadly used in optical, catalytic, electronic, and structural applications. Of particular interest is the sintering of nanocrystalline particles, as it leads to reduced sintering temperatures and faster processing times and it enables the fabrication of bulk nanostructured or nanoporous materials. However, the lack of knowledge of the role of grain boundary (GB) geometry in sintering rates limits our ability to manipulate densification and coarsening processes. Herein, we leverage atomistic simulations to investigate the sintering behavior of a series of [001] tilt GBs in Ni over 200 ns using the two-particle geometry. The energy and self-diffusion for these GBs are calculated, and several geometric features describing the morphological evolution are tracked over time. Particle rotation, resulting in the temporal evolution of GB misorientation, is observed in several systems. Our results show large variations in particle neck growth and shrinkage rates as a function of GB type and suggest faster sintering rates with increased GB misorientation angle. Further, it is found that nanoparticles sinter at a much slower rate than predicted from GB-based sintering models, suggesting that the process is not dominated by a single mechanism. As a measure of sintering stress, we track the temporal evolution of particle neck curvatures, which are shown to decrease over time at a rate dependent on GB geometry. In broad terms, our simulation results provide future avenues to employ particle orientations and resultant GB types as a strategy to fabricate sintered materials with controlled nanostructured features.