Better Designing and Evaluation of Insulating Foamed Ceramics
Federal University of Sao Carlos, (GEMM), (FIRE Associate Laboratory), Sao Carlos, SP, 13565-905/Brazil
Revision 05.02.2015, 12.02.2015
Volume 7, Issue 2, Pages 90 - 94
Given the importance of energy costs and environmental concerns, insulating foamed ceramics have received much attention in recent years. This group of porous materials presents key properties such as low density and thermal conductivity, controlled permeability and high surface area allowing their use in many industrial processes aiming to reduce heat losses and energy consumption. However, they are subjected to stresses when used in use. Therefore, the understanding of the thermomechanical behaviour of these materials is a key issue for selection and design for structural applications. This paper is organized into two parts. The first one shows the effect of direct-foaming processing on the physical and morphological properties of macro-porous ceramics. The second part discusses the values of mechanical properties such as the compressive and flexural strengths, and the elastic modulus. In addition, a data compilation highlighting the relationship between porosity (P) and mechanical properties of foamed ceramics is shown. Finally, the results for the fracture toughness and the fracture energy of foamed ceramics are discussed. The paper also highlights that the understanding of the processing techniques and evaluation methods of porous ceramics are the correct path to generate suitable materials for a more sustainable environment where saving energy is a key aspect.
foamed ceramics, environmental friendly processing, thermal insulating ceramics, mechanical properties
 Ohji, T.; Fukushima, M.: Macro-porous ceramics: Processing and properties. Int. Mater. Rev. 57 (2012) 115–131  Salvini, V.R.; et al.: Green and reliable macroporous ceramic processing. Accepted paper for publication in The Amer. Ceram. Soc. Ceramic Transactions from the MS&T13 meeting.  Ashby, M.F.: The mechanical properties of cellular solids. Metall. Trans. A. 14 (1983) 1755–1769  Gibson, L.J.; Ashby, M.F.: Cellular solids, structure and properties. 2nd Ed. Cambridge 1999  Colombo, P.; Hellmann, J.R.; Shelleman, D.L.: Mechanical properties of silicon oxycarbide ceramic foams. J. Amer. Ceram. Soc. 84 (2001) 2245–2251  Rice, R.W.: Relation of tensile strength-porosity effects in ceramics to porosity dependence of Young’s modulus and fracture energy, porosity character and grain size. Mater. Sci. and Engin. A112 (1989) 215–224  Zheng, M.; Zheng, X.; Luo, Z.J.: Fracture strength of brittle porous materials. Int. J. of Fracture 58 (1992) R51–R55  Sakai, M.; Ichikawa, H.: Work-of-fracture of brittle materials with microcracking and crack bridging. Int. J. of Fracture 55 (1989) 65–79  Salvini, V.R.; Pandolfelli, V.C.; Bradt, R.C.: Extension of Hasselman’s thermal shock theory for crack/microstructure interactions in refractories. Ceramics Int. 38 (2012) 5369–5375  Pickett, G.: Equations for computing elastic constants from flexural and torsional resonant frequencies of vibration of prisms and cylinders. Proc. Amer. Soc. Testing Mater. 45 (1945), 846–865  Kingery, W.D.; Bowen, H.K.; Uhlmann, D.R.: Introduction to ceramics. 2nd Ed. New York 1976, 787–790  Magrabi, S.A.; Dlugogorski, B.Z.; Jameson, G.J.: Bubble size distribution and coarsening of aqueous foams. Chem. Engin. Sci. 54 (1999) 4007–4022  Doerre, E.; Huebner, H.: Alumina: Processing, properties, and applications. Berlin 1984, 81– 95
Göller Verlag GmbH