Thermal Shock Resistance Measurements

There are many methods to measure thermal shock resistance. The most cmivenient are quenching heated material - water and heated material — air. In order to simulate the specific service conditions of refractories, several other methods of thermal shock testing have been investigated. 

Initially, the thermal shock resistance according to ASTM 38-89 [112] was measured by quenching the bricks in water, while the appearance of the cracks and the cracking of the material were fixed. The technique of quenching in water is described in DIN 51068-1 [113]. Quenching in air (compressed air) is described in standard DIN 993-11 [114]. 

A new standard ASTM C-1171-05 [115] estimates the appearance of cracks in refractory material on thermal cycling by the decrease in strength and change in the sound velocity in the samples. 

Usually, the strength is measured after one thermal shock, though it is possible to make several cycles and measure the strength degradation after each cycle. Rectangular bars or rods are tested for bending strength. 

According to ASTM C-1171-05 [115], the recommended furnace temperature is 1,200 °C (for specific material and service conditions, it may be changed), the time in the furnace is 10-30 min, and the cooling regime may vary - from quenching in the water to quenching in the air on fireclay or on a metallic surface. The values of 

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One way of measuring thermal shoek resistanee is to drop a piece of the ceramic, heated to progressively higher temperatures, into cold water. The maximum temperature drop AT (in K) which it can survive is a measure of its thermal shock resistance. If its coefficient of expansion is a then the quenched surface layer suffers a shrinkage strain of a AT. But it is part of a much larger body which is still hot, and this constrains it to its original dimensions it then carries an elastic tensile stress EaAT. If this tensile stress exceeds that for tensile fracture, <7js, the surface of the component will crack and ultimately spall off. So the maximum temperature drop AT is given by... 

Some kind of thermal shock loading is inevitable during service of FMs. In addition, most FMs have anisotropic thermal-expansion coefficients due to their unique architectures. In 2004, Koh and co-workers investigated the thermal shock resistance of Si3N4/BN FMs [29], They observed their excellent thermal shock resistance by measuring the retention of the flexural strength after thermal shock test, as shown in Fig. 1.17. The monolithic Si3N4 exhibited... 

The thermal shock resistance is a measure of the temperature range through which glass vessels, of normal waU-thickness, may be suddenly cooled without breakage. 

In this study, we discussed the graded and miscible blend of polyvinyl chloride(PVC)/ polymethacrylate(polymethyl methacrylate(PMMA) or polyhexyl methacrylate(PHMA)) by a dissolution-diffusion method, and characterized graded structures of the blends by measuring FTIR spectra and Raman microscopic spectra, and thermal behaviors around the glass transition temperature(Tg) by DSC method, or by SEM-EDX observation. Finally, we measured several types of mechanical properties and thermal shock resistance of the graded polymer blends. 

Because the alumina composites show (ATc)exp/ (A< 1, which indicates that the thermal shock resistance is overestimated by equation 1, the fracture behavior of alumina-filled composites is examined in further detail. As shown in Figure 7, debonding of the interface is observed in the thermal-shock test specimen but not in the fracture-toughness test specimen Therefore, for the evaluation of thermal shock resistance by equation 1 without overestimation, KIc should be measured under the condition in which the same fracture pattern as that seen in the thermal shock test is obtained. 

Experimental Details Measuring Thermal Shock Resistance... 

Properties of deposits that are important to boiler behavior and management include emittance and absorbance, thermal conductivity, strength, tenacity and thermal shock resistance, viscosity, and porosity. Methods for measurement of each of these properties are available, while techniques for prediction or correlation of these properties are in various states of development. Figure 10 illustrates the... 

The thermal shock resistance ofunidirectionally reinforced SiC/RBSN composites was evaluated using the water quench method. Both room temperature flexural (Fig. 8) and tensile properties (Fig. 9) of 1-D SiC/RBSN composites were measured before and after quenching and compared with the flexural properties of quenched unreinforced RBSN under similar conditions. 

The present study aims at investigating the Reaction Bonded Silicon Carbide (RBSC) process to produce porous mullite-bonded SiC ceramics. Wu and Claussen (1991) reported a technique to produce mullite ceramics starting from Al, SiC and AI2O3 powder mixtures. However for the purpose of this study it was decided to use only SiC and Al 03 as the precursor powders with SiC as the major component so that after completion of the reaction the microstructure would be SiC bonded with mullite phase, with no residual alumina. This material was then tested for its mechanical properties like Young s modulus. Modulus of Rupture. Properties of Silicate-based SiC refractories have been reported to a certain extent by Reddy and others. Its potential use as a refractory material has been evaluated by measuring its thermal shock resistance. A sample refractory that has been designed in the... 

Sensors for measurements of oxygen in molten steel are the most important application in liquid metal sensing. As an electrolyte MgO partially stabilized, zirconia is used because of its high thermal shock resistance due to phase transformations. 

The selection of the thermal management materials for electronic packaging purposes demands close examination of thermophysical characteristics, such as thermal conductivity and diffusivity, specific heat capacity, coefficient of thermal expansion, and thermal shock resistance. A variety of measurement techniques have been developed to evaluate these properties, but this chapter focuses on thermal conductivity and diffusivity evaluation methods. Each of them is suitable for a limited range of materials, depending on the thermal properties and the medium temperature. The precise determination of the thermal properties of bulk composite materials is challenging. For instance, loss terms for the heat input intended to flow through the sample usually exist and can be difficult to quantify. 

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