Thermal Shock Resistance of a Kyanite-Based (Aluminosilicate) Ceramic

Abstract

This paper presents the results of a combined experimental and theoretical study of microstructure and thermal shock resistance of an aluminosilicate ceramic. Shock-induced crack growth is studied in sintered structures produced from powders with different particle size ranges. The underlying crack/microstructure interactions and toughening mechanisms are elucidated via scanning electron microscopy (SEM). The resulting crack-tip shielding levels (due to viscoelastic crack bridging) are estimated using fracture mechanics concepts. The implications of the work are discussed for the design of high refractory ceramics against thermal shock.

The Effects of Compressive Residual Stress on Properties of Kyanite-Coated Zirconia Toughened Alumina Ceramics

“…This can be attributed to the decomposition of the kyanite into mullite phase and SiO 2 at 1500 • C. The synthesis of mullite occurred through the reaction between SiO 2 and alumina in the coating slurry, as described by Equations ( 5) and (6). The results of XRD indicate that after pressureless sintering at 1600 • C for 2 h, the kyanite phase in the coating was almost completely transformed into the mullite phase, which agrees with the results from other researchers [12,13].…”

“…However, it is observed that the residual flexural strength of ZTA at 300 • C and kyanite-coated ZTA at 400 • C shows a steep fall. The critical temperature, at which the strength sharply drops off after quenching, is widely recognized as a crucial indicator for evaluating thermal shock resistance [13], but at the same quenching temperature, the strength of kyanite-coated ZTA is consistently greater than that of ZTA. Combined with Figure 6, it shows that after quenching, the surface of the ZTA produces a large number of small irregular cracks, and even some of the cracks have been extended; however, on the surface of the kyanite-coated ZTA, small cracks formed after quenching, and did not expand or connect with each other.…”

Thermal expansion behavior, phase transitions and some physico-mechanical characteristics of fired doped rice husk silica refractory

“…The early crystallization of the refractory at the temperature range between 850 ℃ and 1050 ℃ is as a result of the dopant (mineralizer)-slaked lime and the OH -group in opal, the presence of which lowers the inversion temperature of silica polymorphs [6][7][8][9]13,14]. In fact, Nayak and Bera [6] have reported that complete crystallization of RHS with 99.87% purity only takes place at about 1300 ℃.…”

“…For instance, anorthite was detected in the sintered refractory. One of the positive effects of these visco-elastic phases is that they are capable of forming shields around crack-tips, thus leading to better thermal shock resistance [8].…”

“…The second effect that the mineralizer has is the formation of alkali silicates, which are known to present dimensional stability to the refractory during use. Liquid phase sintered at lower temperature is thought to result from the formation of some visco-elastic phases, which inhibit crack propagation through the refractory body when in service [8]. Thus, it is necessary to study the expansion behavior of a formulated refractory in order to predict its behavior during service.…”