The driving force in sintering is decreasing surface energy; as the sintering proceeds, adjacent particles partially coalesce owing to viscous flow (as in glass) or to diffusion processes (as in crystalline materials), and consequently the total surface area decreases.
The thermal transformation started with neck formation between adjacent particles (Fig. 1, center).
It is notable that particles seems to merge together and became embedded with the adjacent particles.
Self-assembly of nanocrystals can be observed, showing uniform gaps between the adjacent particles (Figure 3b).
g i : The best position which has been found by the adjacent particles.
Following melting, the forces of surface tension drive two adjacent particles to fuse.
Typically, the particles were arranged in chain-like structures, i.e. most particles had two adjacent particles on roughly opposite sides.
The distances between the centers of two adjacent particles and the particle diameter are important parameters affecting SERS activity.
Most of conventional MREs models are based on magnetic dipole interactions between two adjacent particles of the chain.
Besides, the minimum gap between adjacent particles can be flexibly controlled by changing the thickness of the shell elements.
The models are found to adequately predict the observed trends, but do not capture the interaction of adjacent particles.
