High performance thermal insulator ceramic foams with tailored microstructure

Reference Presenter Authors
14-024 Pedro Ivo Batistel Galiote Brossi Pelissari Pelissari, P.B.(Universidade Federal de São Carlos); Angélico, R.A.(Universidade de São Paulo); Salvini, V.R.(Universidade Federal de São Carlos); Pandolfelli, V.C.(Universidade Federal de São Carlos); Ceramic foams are promising material to be applied for thermal insulation at high and ultra-high temperature. Their microstructure can be tailored to maximize the thermal radiation scattering which is the key feature to reduce the effective thermal conductivity at high temperatures. Recent research by the present authors highlighted the existence of an optimum pore size range for the effective thermal conductivity minimization at temperature from 1000 to 1500 °C. Nevertheless, the limitations of the methodology to calculate the radiation share of thermal conductivity do not unravel the influence of others microstructure parameters. Based on that, the present work applies computational methods to efficiently estimate the dependency of the effective thermal conductivity on the microstructure parameters of the ceramic foams, with focus on the pair correlation function of the pores position. The optical features of a representative elementary volume (REV), generate via YADE – DEM software, were obtained by two different approaches, the Mie-Lorentz T – Matrix method and the discrete dipole approximation (DDA). The results obtained matched for spherical pores when considering thermal radiation emitted by blackbodies from 1000 to 1800 °C. The pores pair correlation function has a great impact on the optimum pore size range that minimize the thermal conductivity for porosity lower than 70 %. For highly porous ceramic foams (90 % of porosity), the pore size distributions parameters have a significant effect on the effective thermal conductivity and showed distinct optimum pore size range for the different distributions (normal and log-normal). Additionally, it has been seen that the pore connections decrease the thermal radiation scattering and increase the effective thermal conductivity. These new findings provide guide lines for ceramic foams microstructure design resulting in a high performance thermal insulator for high temperature applications.
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