Measurements of the surface tension of the Iron-Silicon system using electromagnetic levitation
2000 Volume 40 Issue Suppl Pages S157-S159
Details
2000 Volume 40 Issue Suppl Pages S157-S159
Surface tension measurements have been carried out on binary alloys of iron and silicon, and on pure iron using the levitated drop technique. The alloy compositions (atomic percent) chosen were Fe+25% Si, Fe+37.5% Si, Fe+50% Si, Fe+62.5% Si, Fe+75% Si. Attempts were also made to measure the surface tension of pure silicon by this method, which unfortunately resulted in only one successful measurement. Surface tension is derived from measurements of the oscillation frequencies of a liquid droplet levitated in the magnetic field of a radio frequency coil, which also inductively heats the sample. It is therefore necessary for the material under study to be electrically conducting, and whilst the alloy samples levitated readily, it was necessary to pre-heat the silicon to about 800°C before it would levitate. The difficulties the electrical conduction of silicon imposes on the measurement are discussed. In order to produce high purity samples, with low oxygen contents, samples were prepared in a cold crucible levitator under an argon +10% hydrogen atmosphere.
The surface tension values obtained in this study were:
Fe 1.89-0.44×10-3 (T-1537 [°C]) Nm O content <5 ppmFe+25% Si 1.69-0.19×10-3 (T-1263 [°C]) Nm O content 10 ppmFe+37.5% Si 1.51-0.24×10-3 (T-1247 [°C]) Nm O content 5 ppmFe+50% Si 1.17+0.19×10-3 (T-1407 [°C]) Nm O content <5 ppmFe+62.5% Si 1.02-0.14×10-3 (T-1298 [°C]) Nm O content 10 ppmFe+75% Si 0.87+0.24×10-3 (T-1242 [°C]) Nm O content 31 ppm
A single value for the surface tension of silicon of 0.78 Nm at 1900°C was obtained.
