The Relation of Viscosity, Nuclei Formation, and Crystal Growth in Titania‐Opacified Enamel

Abstract

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.

The influence of particle size distribution on the surface appearance of glazed tiles

“…Beginning at 35 min milling time (D 50 w 3 mm) the fired samples had presented an increase in the contact angle between the glaze and the tile surface, probably due to a greater interaction of the melted glaze with air during heat treatment [3,6,[15][16][17]25]. This is the reason why the contact angle increased with longer milling times (Fig.…”

“…During firing if the surface tension between the glaze and the tile surface increases (due to the extreme particle size reduction and glaze composition) a strong interaction between the glaze and air occurs, resulting in air encapsulation by the glaze [3,6,[15][16][17]25]. The glaze coat is filled with air bubbles.…”

“…Viscosity is very sensitive to minor differences in composition, allowing for theoretical studies in glass structure or the evaluation of important glass properties, such as bubble retention, flow over ceramic bodies, quality control, glaze preparation and manufacturing [5,6]. Viscosity controls several processes at different temperatures in tile manufacturing.…”

“…Viscosity controls several processes at different temperatures in tile manufacturing. Its magnitude during firing determines the glaze flow over the ceramic body, forming a uniform layer without draining off the surfaces [6]. Viscosity also determines the facility of gas bubble elimination during glaze formation.…”

Development of TiO2 white glazes for ceramic tiles☆

“…present in the raw materials produced nonwhite coats until more pure forms of TiO 2 became available [2]. Some studies reported the relationship between TiO 2 crystallite size and shape and the resulting reflectance and color, identifying rutile and anatase phases, with the acicular rutile particles occurring at higher temperatures or longer firing times and the rounded anatase particles forming earlier in the firing process [3]. Blue color was associated with the smaller rounded anatase particles and yellow color, formed at the later stages of firing, was associated with the dissolution of the anatase particles at the expense of the larger rutile particles.…”