Foam Sprayed Porous Insulating Refractories
Federal University of São Carlos, Materials Engineering Department, 13565-905 São Carlos – SP/Brazil
Revision 19.04.2012, 16.07.2012
Volume 4, Issue 4, Pages 93 - 97
Abstract
Porous ceramics can be applied as filters for molten metals, gases or water filtration, orthopedic implants and insulating refractories. The production of these materials is mainly based on techniques involving the addition of gases, lightweight compounds and/or combustible pore forming additives to the ceramic suspensions. The present work evaluates insulating refractory compositions designed according to the Andreasen packing model and prepared by using a novel direct foaming procedure (applying compressed air in equipment specially developed for large-scale production of porous ceramics). Density, porosity and pore size distribution, splitting tensile strength and thermal conductivity of the foamed specimens were measured. According to the results, the prepared refractories presented a high porosity content (>69 %), low thermal conductivity (0,3–2,3 W/m·K in the range of 200 to 1200 ºC) and improved splitting tensile strength (1,8–15,2 MPa). The evaluated foaming method is a feasible alternative for producing homogeneous refractory porous ceramics for thermal insulating applications. Additionally, by adjusting the composition particle size distribution, ceramic suspensions with enhanced fluidity and, consequently, fired samples with higher mechanical strength can be attained.
Keywords
foamed ceramics, porous, ceramics, insulating refractory materials
References
[1] Scheffer, M.; Colombo, P.: Cellular ceramics: structure, manufacturing, properties and applications. Weinheim 2005, 35–56
[2] Studart, A.R.; et al.: Processing routes to macroporous ceramics: A review. J. Amer. Ceram. Soc. 89 (2006) [6] 1771–1789
[3] Sepulveda, P.; Binner, J.G.P.: Processing of cellular ceramics by foaming and in situ polymerization of organic monomers. J. Europ. Ceram. Soc. 19 (1999) 2059–2066
[4] Woyansky, J.S.; Scott, C.E.; Minnear, W.P.: Processing of porous ceramics. Am. Ceram. Soc. Bull. 71 (1992) [11] 1674–1682
[5] Martynenko, G.M.; Maltsev, S.M.; Zabolotnyil, S.A.: Ceramoconcrete refractory and heat-insulating components in ferrous and nonferrous metallurgy. Refractories and Industrial Ceramics 50 (2009) [3] 163–165
[6] Mitsuhashi, T.: Evaluations of thermal and metent no. 4.822.679, 1989 [7] Tang, F.; et al.: Preparation of porous materials with controlled pore size and porosity. J. Europ. Ceram. Soc. 24 (2004) [2] 341–344
[8] Deng, Z.Y.; et al.: Microstructure and mechanical properties of porous alumina ceramics fabricated by the decomposition of aluminum hydroxide. J. Amer. Ceram. Soc. 84 (2001) [11] 2638–2644
[9] Overhoff, A.; et al.: New microporous materials for use in modern firing plants. cfi/Ber. DKG 82 (2005) [8] E1–E5
[10] Cerdan-Diaz, J.M.; Sanders, M.J.; Wellar, M.E.; Spray-applied ceramic fiber insulation. US pa
[11] Salvini, V.R.; et al.: Porous ceramics with tailored properties. Amer. Ceram. Soc. Bull. 86 (2007) 9401–9405
[12] Sach, J.; Seifert, H.; Foamed concrete technology: Possibilities for thermal insulation at high temperature. cfi/Ber. DKG 76 (1999) [9] 23–30
[13] Primachenko, V.V.; et al.: Super low thermal conductivity heat insulating lightweight material on the basis of calcium hexaluminate. In: Proc. of UNITECR’01, Cancùn, Mexico (2001), 1188–1192
[14] Cruz, C.R.V.; Refractories for steelmaking equipments. São Paulo: Associação Brasileira de Metais (1982) 515 (in Portuguese) chanical properties of refractories – fundamentals and applications. J. Tech. Assoc. Refrac. Japan 25 (2005) [1] 50–58
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