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How nanoparticles will try to reduce their overall surface energy? (Single…
How nanoparticles will try to reduce their overall surface energy?
Single Nanoparticle
Surface adsorption
Chemical or physical adsorption of terminal chemical species onto the surface by forming chemical bonds or weak attraction forces such as electrostatic or van der Waals forces
Surface atoms or ions shift inwardly
The lattice parameter, a become smaller
surface restructuring
Combining surface dangling bonds into strained new chemical bonds
composition segregation or impurity enrichment
On surface through solid-state diffusion and pushing all impurities outwards
Overall System
(A group of nanoparticles)
Combining individual nanostructures together to form large structures as to reduce the overall surface area
Agglomeration of individual nanostructures through chemical bonds and physical attraction forces at interfaces without altering the individual nanostructures
The smaller the particles, the greater the bonding forces
Specific mechanisms of combining individual nanostructures into large structures
Sintering
, in which individual structures merge together
Replace solid-vapor interface by solid-solid interface and becomes polycrystalline
Ostwald ripening
, in which relatively large structures grow at the expense of smaller ones
the smaller ones disappear completely and become a single crystal and occurs at relatively low temperature.
Pee Kai Xuan 138724 EBB 339 Task 1