The Chemical Durability of B_2O_3-V_2O_5-CaO System Glasses

The chemical durability of B_2O_3-V_2O_5-CaO system glasses was studied in this paper. The reason of choosing this system is that the glasses containing plenty of B_2O_3 and V_2O_5 have high electric conductivity, viz. O (10^6) ohms (nearly 200℃). The twenty kinds of the glasses in this system were fused in the electric furnace. The fused glasses were powdered into the particles of 35-60 meshes (Tyler), and 2g of them were immersed in 50ml water of 30,50 and 70℃, while being stirred during 10,20,40 and 80 minutes respectively. Then the amounts of vanadium dissolved into the water were measured by chelatometric titration. The results were as follows. 1) The experimental data were tested by analysis of variance and it was found that log of dissolved amounts was linear function of log of dissolving time, and was linear function of reciprocal of absolute temperature of the water. 2) Generally, in the domain of glasses containing more than CaO 35mol, the dissolving phenomena were simple. That is, there was one minimum value of dissolved amounts at about VO_<2.5>/B_2O_3=0.7-1.0,but in the domain containing less than CaO 35mol, the phenomena were very complex. Especially in CaO 20mol, there were two maximum and one minimum value at the certain value of VO_<2.5>/B_2O_3. 3) The glass of 40 B_2O_3-20VO_<2.5>-40CaO (mol%) was the most durable one, and 20 B_2O_3-40VO_<2.5>-40CaO was weakest in this system, and roughly, the composition of good resistant glasses was in the center of this system.