No abstract

ABSTRACT

A furnace for use in conjunction with the X‐ray spectrometer was developed which was capable of heating small powdered specimens in air to temperatures as high as 1850°C. This furnace was also used for the heating and quenching of specimens in air from temperatures as high as 1850°C. An area of two liquids coexisting between 20 and 93 weight % TiO2 above 1765°± 10°C. was found to exist in the system TiO2–SiO2, which is in substantial agreement with the previous work of other investigators. The area of immiscibility in the system TiO2–SiO2 was found to extend well into the system TiO2–ZrO2–SiO2. The two liquids were found to coexist over a major portion of the TiO2 (rutile) primary‐phase area with TiO2 (rutile) being the primary crystal beneath both liquids. The temperature of two‐liquid formation in the ternary was found to fall about 80°C. with the first additions of ZrO2 up to 3%. With larger amounts of ZrO2 the change in the temperature of the boundary of the two‐liquid area was so slight as to be within the limits of error of the temperature measurement. Primary‐phase fields for TiO2 (rutile), tetragonal ZrO2, and ZrTiO4 were found to exist in the system TiO2–ZrO2–SiO2. SiO2 as high cristobalite is known to exist in the system TiO2–ZrO2–SiO2.

This investigation shows that there is a relationship between viscosity, number of nuclei, and crystal growth during the firing of titania‐opacified enamels. This agrees with a similar relationship which Tammann found in his experiments with organic glasses. The history of the development of the size, shape, and relative number of particles per unit area of titanium dioxide crystals was traced from 650° to 1300°C. As the temperature increased from 700° to 1100°C., the color of the specimens viewed under reflected light changed from light blue to white and then to cream‐white. The methods used in this investigation were the measurement of viscosity, X‐ray analysis, differential thermal analysis, and the study by light microscopy and electron microscopy of very thin heat‐treated films which had been produced by blowing bubbles from high‐temperature melts.