Etching rates of borosilicate, borophosphosilicate, phosphosilicate, and arsenosilicate glass films in various buffered hydrogen fluoride solution (BHF) have been studied. Etching rates were found to depend on the glass composition and dopant concentration as well as the concentration of ammonium fluoride in the BHF. This phenomenon is clearly different from the etching rate of thermal SiO2 oxide which is hardly affected by the concentration of ammonium fluoride in excess of equimolar to the HF concentration. The etching rates of the doped films may sometimes be higher than that of a nondoped SiO2 film but the rate is reduced when certain other dopants are present. This phenomenon is attributable to valence differences between silicon and the dopant elements. If the doped film is electrophilic compared to silicon, the etching rate is higher; if it is nucleophilic, the etching rate is lower. By controlling the type and concentration of the dopant and the concentration of NI-I~ in BHF, it is possible to etch the doped film and thermal oxide at either the same rate or selectivity with respect to one another.

In situ observations of crack growth and damage progression were conducted under creep conditions for P92 and titanium aluminides inter-metallic compound. A proposed analysis of stress induced particle diffusion was applied to stress induced vacancy diffusion. Results obtained from this analysis were successfully correlated with the experimental behaviour of macroscopic damage progression and a theoretical characteristic of creep deformation was derived. It was found to be in good agreement with experimental characteristics of creep deformation. Furthermore, the experimental characteristics of creep damage progression which concern voids and micro crack formations at grain boundary were found to be well correlated with those of deformation. From these results, correlation between vacancy diffusion in nano-scale, creep damage in mezzo-scale and creep deformation in macro-scale were successfully realized.

The vapor-liquid equilibrium of the binary system HF-H20 was determined, especially in the range of low water concentrations. The purity of anhydrous hydrogen fluoride used in this work was 9N (99.9999999%) with a conductivity of 0.7 • 10 -6 Scm-' (water concentration of 0.033 ppm). We elucidated that the vapor-liquid equilibrium of the binary system HF-H20 obeyed Raoult's law below 1 x 10 3 tool dm -3 (18 ppm) water concentration. We determined the activity coefficients of HF and H20 at the boiling point of the binary system HF-H20. Munter et al.(1, 2) reported the vapor-liquid equilibrium

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