Hi, does anybody know why the melting points of materials drop down when its size gets smaller down to nano-scale? For a nano particle set in another high-melting-point material, how does its Tm go?
Roughly speaking, the surface to volume ratio being high for a cluster makes it melt at a lower temperature. This is true of most metals and non-metallic isolated clusters that have been studied, except for tin and gallium, which exhibit the reverse behavior. There is as yet (I'm not up to date on this, but as of a couple yrs ago) no theoretical basis for this anomaly in Sn and Ga..wangasu said:Hi, does anybody know why the melting points of materials drop down when its size gets smaller down to nano-scale?
Most measurements are done on surface deposited nanoparticles (since these are easier to study) but even in bulk embedded clusters the depression of melting point, T(bulk) - Tm , is inversely proportional to the cluster radius. The reason for the lowering of Tm in bulk embedded clusters is simply that large mismatch at the interface leads to poor bonding between the cluster and the matrix, thereby making the interface susceptible to melting just like a surface is.For a nano particle set in another high-melting-point material, how does its Tm go?
This is actually well understood and is, in fact not exactly as you (or I, previously) have stated it.wangasu said:it might be more interesting to continue to ask why the increasing effect of free surface or mismatched interface leads to the lowing of Tm? do you have any idea about it?