Matrix Effects On The Melting Of Bismuth And Indium Nanoparticles

The melting point depression occurs when the particle size is of the order of nanometers.The size effect of melting point depression with a decreasing particle size have been proved.With the size evolution from micrometer scale to nanoscale and large scale integrated circuits of the microelectronic and optoelectronic devices,the diameter of metal wires have reduced a new nanometer regime.There is significant influence of the melting point change of metallic nanomaterials on the stability and lifecycle of devices.Thus,it is important for material selection and process design to accurately predict the melting point of metallic nanomaterials and its size dependence.However,on the one hand,understandings to melting of metallic nanoparticles and its size dependence remain quite controversial and,on the other hand,an indefinite conclusion to matrix effects on the melting of metallic nanoparticles.Further,there still lacks systematic data,mainly due to the difficult requirements to look for matrix materials.These requirements for studying the melting of metallic nanoparticles are that small metallic particles are dispersedly embedded in a matrix which should be chemically inert with metallic nanoparticles.In order to expand the above slim range of materials,the melting behavior of Bi and In nanoparticles embedded in different matrix materials prepared by using high-energy ball milling are studied.The materials analysis and testing technology are used to show the relation between the melting point and the particle sizes of metallic nanoparticles by means of characterization of melting temperature and particle sizes.Matrix effects on the melting of metallic nanoparticles are explored according to the experimental data.Furthermore,preliminary efforts are carried out to look for a matrix where Pb,Sb,Al nanoparticles embedded in the matrix.The main results are as follows:(?)Results from X-ray diffraction analyses showed that oxidation rate of metallic nanoparticles prepared by direct milling will be slow by increasing the volume ratio of metal powders.Compared with the direct mechanical milling method,the thermal stability of sample prepared by mechanochemical synthesis is much more stable.(?)Results from TEM analyses showed that high-energy ball milling preparation of Bi and In nanoparticles embedded in different matrix materials were investigated,the metallic nanoparticles were dispersedly embedded in matrix materials.Compared with employing mechanically milled Bi-Li F and In-Li F systems,these results showed that under the Al-Li F system,the better the crystal lattice of Al and Li F is matched,the more significant the melting point depression will be.(?)We analyzed the relation between the melting point and the particle sizes of Bi and In nanoparticles embedded in different matrix materials obtained by the measured data,in accordance with our research group recent theoretical calculations.On the basis,we compared the data about the size dependence in the melting of Bi and In nanoparticles embedded in different matrix materials with those from reported results and found insignificant influence of the matrix on the melting of metallic nanoparticles.