Evaporation of Submicron Platinum Particles in a Shock Tube

A series of shock‐tube experiments was carried out to determine the evaporation rate of submicron platinum particles suspended in xenon‐argon and pure xenon carrier gases. The particle suspensions were produced by electrically exploding platinum wire in the carrier gases in a chamber attached to the end of the shock tube. Visible radiation from the shock‐heated aerosols was recorded by a drum camera viewing a strip along the centerline of the shock tube and by a photomultiplier viewing a point near the shock‐tube end wall. The duration of the short pulse, ∼100 $\mu$ sec, of intense continuum radiation behind the reflected shock was used to determine approximately the evaporation time of the particles and, more precisely, the temperature dependence of the particle‐evaporation time. The experimental results confirmed an analytical prediction that the platinum particles could be vaporized readily in the short high‐temperature residence time available in a shock tube. Furthermore, since the experimental temperature dependence of the evaporation time agreed with theory and since this agreement is sensitive to the saturation vapor pressure assumed for platinum, the results appear to confirm the accuracy of the tabulated (by Hultgren et al.) vapor pressure of platinum at high temperatures ( ≈ 3700°K). The technique described provides a useful method for introducing metallic test samples into shock tubes, and it further suggests an experimental approach to the determination of metallic vapor pressures at high temperatures.