The Vaporization and Physical Properties Of Certain Refractories, Part I. Techniques And Preliminary Studies

Abstract:
Simple effusion studies of the vaporization of rhodium, iridium, and osmium have been taken by the Knudsen effusion technique. The rate of effusion was determined by condensing the molecular beam on a target. Rhodium was studied from 2051 to 2205°K. In this temperature range, its heat of vaporization was found to be 129 Kcal/mole. Iridium was studied from 2100 to 2600° K. In this range, its tentative heat of vaporization is 155 ± 5 Kcal/mole. It was noted that some interaction between the iridium, the thoria liner, and the tungsten outer liner of the effusion cell may have occurred. No data were obtained for the vaporization os osmium because of extensive interaction between the thoria liner and the tungsten outer liner of the effusion cell.

Mass spectrometric studies have been made of the vaporization of thoria from tungsten effusion cells. Interactions between thoria and tungsten at elevated temperatures were noted. Tentative data on the vaporization of thoria to ThO an ThO₂ were obtained and are presented.

Mass spectrometric studies of the vaporization of Al₂O₃ in contact with tungsten have been made in conjunction with compatibility studies of tungsten and Al₂O₃. Data are given for the vaporization of Al₂O₃ in tungsten to yield Al, AlO, Al₂, and WO₂.  More information will be needed before thermodynamic calculations can be made for this system.

The continuously monitored effusion apparatus, the null-point effusion apparatus, the oscillating cup viscometer, and the sessile drop equipment have been constructed and calibrated.

The viscosity of fused silica has been determined at temperature up to 2560°C where η = 10^4.44 poises. The viscosity of alumina has been measured using an iridium crucible up to 2200°C and determined to be approximately 13 poises.