Thermal Shock Behavior of Zircon Based Refractories

Abstract

In service refractory materials are submitted to local temperature gradients that originate thermal stresses causing a thermal shock (TS) damage to the material. Practical tests for evaluating the thermal shock resistance (TSR) determine the variation or change of some characteristic property of the test sample like E (elastic module) or the strength before and after quenching. In this work, the microstructure and thermal shock behavior of Zircon based refractories are analyzed. Several compositions (eight), from pure Zircon to 70 % of Zircon were studied. The main structural and mechanical properties of the refractories were characterized, as modulus of rupture, elastic modulus, porosity, and microstructure. The dynamic elastic modulus E of the refractories was measured by the excitation technique. The TS behavior was evaluated by measuring the decrease in E and the modulus of rupture, before and after a quenching test. The influence of the presence of other phases was also analyzed. Refractories showed Zircon as the main crystalline phase. In some materials, m-ZrO2 appears coming from Zircon dissociation. The thermal shock behavior of refractory of high Zircon content is typical of the brittle ceramic materials. Materials showed a relation between elastic module and strength. Dynamic elastic modulus measurements have shown to be suitable for evaluation the TSR for these materials.

Normalized evaluation of thermal shock resistance for ceramic materials

“…A number of previous works have confirmed that there is a correlation between the degree of thermal shock damage and the change in flexural strength before and after quenching [13,19,28]. It is somewhat surprising from the above experimental data that the change degree of each material in flexural strength before and after thermal shock test can reflect its ability in the resistance to thermal shock.…”

“…In the past several decades, many strides aiming at the development of theories and methods for evaluating thermal shock resistance of ceramics have been reported [15][16][17][18][19]. However, the approaches currently used in the evaluation of thermal shock resistance are largely based on the research results of  Kingery [15] and Hasselman [16].…”

“…Over the past several decades, various methods for the determination of thermal shock resistance have been proposed or employed by a great many researchers [19][20][21][22][23][24][25]. Almost all of these methods applied to measure the thermal shock resistance of ceramic materials are often seen to consist of three steps: first, the samples are plunged into a cooling medium such as water, oil or air from an elevated temperature; then, the changes of material properties with different temperature differences after thermal shock treatment, frequently just for a single cycle, such as the loss of weight [15] and the decrease in strength or elastic modulus [13,19], have been traditionally employed to assess the thermal shock resistance of materials; finally, based on the data obtained from above steps, a designed factor intending to reflect the thermal shock resistance of ceramics is attained. Among a number of evaluation methods, a general indicator used to evaluate thermal shock resistance is the critical temperature difference, ΔT, determined at which there is a sudden decrease in flexural strength or elastic modulus [22], or at which the large crack causing the failure of a material is produced with an indentation-quench method [23].…”

Evaluación De Mezclas De Arcillas Para La Fabricación De Ladrillos Refractarios Que Sirvan Para La Reconversión Tecnológica De Los Hornos Utilizados en Norte De Santander

“…La tabla 3 muestra las propiedades como, contracción lineal de secado (C.S) y contracción en cocción (C.C), densidad aparente (D.A), absorción de agua (A.A), Resistencia a la flexión (R.F), porosidad aparente (P.A) y cono pirométrico equivalente (PCE). Estas propiedades son muy utilizadas en la evaluación y comparación de la calidad del producto, como parte de los criterios de selección y usos de los productos refractarios en variedad de aplicaciones industriales (13,14,15). La menor contracción de secado la presentó el prototipo de la mezcla MA arrojando un valor de 0,1%, y la más alta fue presentada por la mezcla MB siendo 0,34% su valor.…”

Effects of Solvent on the Phase Composition and Microstructure of ZrSiO₄ Film

“…Zirconium silicate (ZrSiO 4 ) is an important antioxidant material of non-metallic minerals due to its low expansion coefficient, low oxygen diffusion coefficient and excellent thermal shock resistance. As one of refractory [1], high temperature structural ceramics [2] and anti-oxidation materials [3], it also has a broad application prospect in environmental barrier coating [4] (EBC). Over past few years, ZrSiO 4 films have been prepared by kinds of methods such as atomic layer deposition [5] (ALD) method, chemical vapor deposition [6] (CVD) method, metal organic chemical vapor deposition [7] (MOCVD) method, sputtering [8] method and hydrolytic sol-gel [9] (HSG) method, etc.…”