Thermal Decomposition of Zircon Refractories

Abstract

Zircon can be used to make refractory brick for the glass industry. At elevated temperatures it is known to dissociate into silica and zirconia. This study was undertaken because one of the factors that can adversely affect the quality of the glass melted in zircon-lined tanks is the degree of dissociation. The thermal dissociation of purified and unpurified zircon refractory was studied by ambient-and high-temperature X-ray diffraction (HTXRD) to understand the hightemperature performance of brick made from this material. Most of the data were collected on powders at or below 1650°C; however, data were collected between 1400°and 2000°C. In addition, small pieces of the refractory were heated to 1650°C, cooled to room temperature, and then examined under ambient conditions. The degree of dissociation was shown to be dependent on purity, particle size, peak temperature, and time at temperature. The HTXRD dissociation was monitored using the intensity of the tetragonal zirconia peaks. The monoclinic polymorph was measured in the ambient runs. High-temperature mass spectrometry (HTMS) showed that the silica is vaporized at elevated temperatures.

Zircon formation from amorphous powder and melt in the silica-rich region of the alumina–silica–zirconia system

“…Zircon (ZrSiO 4 ) is an important ceramic material, known for its high chemical and phase stability as well as for its low thermal expansion coefficient and low thermal conductivity [2][3][4]. Sintered zircon bodies present high chemical stability, high resistance to melt corrosion, excellent thermal shock resistance and good high temperature mechanical properties, therefore is widely applied in high temperature fields where sudden temperature changes are encountered.…”

The Unidirectional Crystallization of Metals and Alloys (Turbine Blades)

“…Dissociation temperature is 1285-2550 C, depending on the degree of purity-the lower the content of impurities, the lower the dissociation temperature [33,34]. Zirconium silicate contains 67.2% ZrO 2 and 32.8% SiO 2 .…”

Preparation of Fused Zirconia/Mullite Aggregates from Sillimanite, Zircon, and Alumina Mixtures via Plasma

“…The decomposition temperature of sillimanite and zircon depends on the particle size and also the impurity level of the raw materials . There are a number of synthesis technique, like conventional heating technique, direct sintering, plasma sintering, microwave sintering, etc., for the synthesis of MUZ composites.…”

“…The decomposition rate accelerates significantly at or above temperature of 1676°C. 11,12 Hence, required amount of alumina and zircon mixture following the Eq. (1) forms the zirconia mullite composite at or above temperature of 1700°C.…”

“…The decomposition temperature of sillimanite and zircon depends on the particle size and also the impurity level of the raw materials. 3,12,13 There are a number of synthesis technique, like conventional heating technique, direct sintering, plasma sintering, microwave sintering, etc., for the synthesis of MUZ composites. Among them, direct sintering and conventional sintering technique using high-temperature furnace requires a long sintering schedule for the synthesis of MUZ compsites 2,6,8 and 100% conversion of zirconia mullite from the minerals, like zircon, is a questionable task.…”