Assessing structure of refractory parts

Strelov, K. K.

doi:10.1007/bf01301491

Cited by 4 publications

(11 citation statements)

References 4 publications

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“…The specific surface area S was measured by the BETabsorption method. 33 For monofractional periclase beds of mean grain sizes 2-5 mm this parameter ranged between 0.4 and 0.5 m 2 /g. Specific area in polyfractional packed beds was significantly larger, i.e., S ‫ס‬ 2.0 m 2 /g.…”

Section: Preparation and Characterization Of Samplesmentioning

confidence: 94%

“…The smoothing of the surface may be attributed to migration of melted silicate. 33 A few ''craters'' appeared on the polished surface of the plate, which mark locations where particles were detached from the surface. When high-temperature heating was repeated two or more times, the number of smoothed particles lying on the plate increased.…”

Section: Preparation and Characterization Of Samplesmentioning

confidence: 99%

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Thermal Conductivity of Packed Beds of Refractory Particles: Experimental Results

Fedina

Litovsky

Shapiro

et al. 1997

Journal of the American Ceramic Society

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Experimental data on thermal conductivity of packed beds composed from various refractory particles (corundum, silica, magnesia, baddeleyite, yttrium oxide, spinel) obtained in the temperature range 400-2000 K in various gases are presented. It is found that thermal conductivity of a bed composed from crushed refractory particles may change after the first and subsequent heatings. This occurs as a result of smoothing of particle surfaces and decreasing of contact heat barrier resistances between the granules. The influence of smoothing is most significant for beds composed from particles with sizes below 2 mm. In polydisperse beds, containing micrometer-size particles, sintering processes were found to occur at temperatures above 1600 K. This led to a sharp increase of the bed thermal conductivity. In regimes where sintering did not take place, decreasing of particle size resulted in a decrease of the effective thermal conductivity. This is attributed to the increased number of contacts between the particles and the scattering of thermal radiation.

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Section: Preparation and Characterization Of Samplesmentioning

confidence: 94%

Section: Preparation and Characterization Of Samplesmentioning

confidence: 99%

Thermal Conductivity of Packed Beds of Refractory Particles: Experimental Results

Fedina

Litovsky

Shapiro

et al. 1997

Journal of the American Ceramic Society

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“…Thus, the formation of a heterogeneous structure by combining components with rather different coefficients of thermal expansion makes it possible to obtain a system of microstructurally small cracks that reduce the modulus of elasticity and effectively inhibit the propagation of larger cracks [ 5 , 9 ]. It has been noted that thermal shock resistance of a material can be improved by creating a fragmentary structure [ 10 ] and by reinforcing it with fibers of different nature: metallic, ceramic, and carbon [ 11 , 12 ]. A structure of controlled fragmentation is more mobile and the grains and crystals in such a structure can expand freely without causing additional stresses.…”

Section: Introductionmentioning

confidence: 99%

Effect of Hollow Corundum Microspheres Additive on Physical and Mechanical Properties and Thermal Shock Resistance Behavior of Bauxite Based Refractory Castable

et al. 2021

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This paper analyses the effect of hollow corundum microspheres (HCM) on both physical-mechanical properties (density, ultrasonic pulse velocity, modulus of elasticity, and compressive strength) and thermal shock resistance behavior of refractory medium cement castable with bauxite aggregate. Moreover, the scanning electron microscopy (SEM) results of HCM and refractory castable samples are presented in the paper. It was found that the replacement of bauxite of 0–0.1 mm fraction by HCM (2.5%, 5%, and 10% by weight of dry mix) had no significant effect on the density and compressive strength of castable, while the modulus of elasticity decreased by 15%. Ultrasonic pulse velocity (Vup) values and the visual analysis of the samples after thermal cycling showed that a small amount of HCM in composition of refractory castable could reduce the formation and propagation of cracks and thus increase its thermal shock resistance.

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confidence: 99%

“…Transformation is accompanied by a change in volume by 4.9% and frequent thermal cycling in this temperature range may leads to a reduction in object strength. A highly porous and microcracked structure of diatomite lightweight objects is compensated by weakening of internal stresses and thereby an increase in object thermal shock resistance since this is realized in the technology of periclase-chromite thermal shock resistant objects [2,8].It is possible to compensate the negative effect of cristobalite and readily-melting liquid phase during heating of diatomite and thereby increase the operating temperature of an object with introduction of additions of high-temperature oxides and regulation of the material structure. One of the cheapest and most accessible oxides in the binary oxide -SiO 2 system in question is CaO, with whose reaction, considering the highly active and amorphous structure of diatomite, proceeds at quite a low temperature.…”

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Diatomic heat insulation materials with increased application temperature

Kashcheev¹,

Sychev²,

Zemlyanoi³

et al. 2009

Refract Ind Ceram

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Results are provided for a study of an increase in application temperature for diatomite objects. Different molding methods and sample mix compositions are described for preparing objects based on diatomite with an application temperature up to 1150°C.The problem of effective use and saving of energy resources includes a list of critical technologies, and energy saving technology, i.e. in priority areas of the development of science and technology and engineering. As is well known [1], there is dissipation into the environment through protective structures of up to 40% of heat with a temperatures of gases discharged from 300 to 160°C, and therefore a reduction in this heat loss is an effective way of reducing the energy expended for manufacturing a production unit, and consequently increasing its competitiveness in domestic and world markets.Heat insulating materials in a refractory lining of a heating unit fulfil an important task, i.e. they retain heat and maintain the temperature at the required production level [2]. For the practical long-term use of any materials as a heat insulator two main characteristics are important [3]. The temperature of the long-term application and the accumulation capacity. The temperature of long-term application depends on the form of the lightweight material and its production technology. The most widespread aluminosilicate lightweight objects and unmolded mixes at the working temperature and with prolonged operation, gradually sinter and there is shrinkage. Here joints of the lining open, there is formation of shrinkage cracks and other defects; the process is accompanied by an additional increase in the thermal conductivity of the lining and heat loss. Silica lightweight heat insulation materials, in contrast to aluminosilicate materials, during prolonged operation and at operating temperatures do not sinter, and in some cases there is a small growth of them (0.1 -0.2%), providing lining tightness. The thermal conductivity of the material is practically unchanged and it remains constant over the whole operating period.Silica raw material is encountered in natural and technical materials in amorphous and crystalline states: in quartzites, quartz sands, tripolite, diatomite, opoka, and marshallite [4]. Of the amorphous materials for producing lightweight objects for industrial purposes there is extensive use of Inzensk deposit (Ul'yanov region) diatomite, as the purest with respect to impurity content. The main technological positions for production and the properties of foam-diatomite objects are given in publications [2,3]. Diatomites of the Inzensk deposit contain 74.80 -88.15% SiO 2 , 3.34 -9.75% (Al 2 O 3 + TiO 2 ), 2.37 -5.26% (Fe 2 O 3 + FeO), 0.47 -0.85% CaO, 0.61 -1.71% MgO, 0.96% K 2 O, 0.74% Na 2 O; Dm cal 2.73 -5.88%. Diatomite is a light porous self-cementing sedimentary rock, forming from residues of microscopic algae and radiolarian skeletons. The amorphous nature of the silica distinguishes it from normal silica. The greatest size of individual skeletons (up to 1...

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Assessing structure of refractory parts

Cited by 4 publications

References 4 publications

Thermal Conductivity of Packed Beds of Refractory Particles: Experimental Results

Thermal Conductivity of Packed Beds of Refractory Particles: Experimental Results

Effect of Hollow Corundum Microspheres Additive on Physical and Mechanical Properties and Thermal Shock Resistance Behavior of Bauxite Based Refractory Castable

Diatomic heat insulation materials with increased application temperature

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