Cordierite, Mg2 Al4 Si5 O18, is a ternary compound within the MgO-Al2 O3 -SiO2 system. It is a widespread commercial material due for its unusually low coefficient of thermal expansion, low thermal mass, low dielectric loss factor, low density, volume resistivity and high resistance to thermal shock. These physical-mechanical properties give this mineral phase a high industrial value. Particularly high grade cordierite is widely used in various industrial fields such as automotive, catalysis, electrical devices, etc.. Cordierite can be synthesized from natural raw materials (e.g. talc, stony kaolinite, andalusite) or synthetic powders, which have high purity and are readily available (Gonzalez-Velasco et al., 1999; Khabas et al., 2003; Cao et al., 2016). In this study, to synthesize cordierite, natural raw materials quarried in Sardinia and available at low commercial cost were used in the following first series of 15 syntheses: 1) talc + low iron bauxite + opal at 1250°C and 1300°C; 2) talc + low iron bauxite + quartz at 1250°C and 1300°C; 3) talc + low iron bauxite + opal + quartz at 1250°C and 1300°C; 4) talc + low iron bauxite + kaolin 1 at 1250°C and 1300°C; 5) talc + low iron bauxite + kaolin 1 + opal at 1250°C and 1300°C; 6) talc + low iron bauxite + kaolin 1 + quartz at 1250°C and 1300°C; 7) talc + kaolin 1 at 1300°C; 8) talc + low iron bauxite + kaolin 2 + opal at 1300°C; 9) talc + low iron bauxite + kaolin 2 at 1300°C. The raw materials were milled to powder, placed into a closed crucible and sintered in an oxidizing furnace for 2h at designed temperatures (Succi, 2007). To maximize the cordierite content in the synthesis product, both mineralogical and chemical analyses of the starting phases were carried out in order to precisely balance the chemical composition of the starting mixture for the synthesis. The XRD patterns of the synthetized material specimens were analyzed by Rietveld method which allowed us to highlight the most reactive phases and the optimal mixtures, among the tested ones. Cordierite content exceeding 75% was obtained in the most promising synthesis.
First insights on the synthesis of cordierite from Sardinian raw materials
Martucci A.;Alberti A.;Mancinelli M.;
2024
Abstract
Cordierite, Mg2 Al4 Si5 O18, is a ternary compound within the MgO-Al2 O3 -SiO2 system. It is a widespread commercial material due for its unusually low coefficient of thermal expansion, low thermal mass, low dielectric loss factor, low density, volume resistivity and high resistance to thermal shock. These physical-mechanical properties give this mineral phase a high industrial value. Particularly high grade cordierite is widely used in various industrial fields such as automotive, catalysis, electrical devices, etc.. Cordierite can be synthesized from natural raw materials (e.g. talc, stony kaolinite, andalusite) or synthetic powders, which have high purity and are readily available (Gonzalez-Velasco et al., 1999; Khabas et al., 2003; Cao et al., 2016). In this study, to synthesize cordierite, natural raw materials quarried in Sardinia and available at low commercial cost were used in the following first series of 15 syntheses: 1) talc + low iron bauxite + opal at 1250°C and 1300°C; 2) talc + low iron bauxite + quartz at 1250°C and 1300°C; 3) talc + low iron bauxite + opal + quartz at 1250°C and 1300°C; 4) talc + low iron bauxite + kaolin 1 at 1250°C and 1300°C; 5) talc + low iron bauxite + kaolin 1 + opal at 1250°C and 1300°C; 6) talc + low iron bauxite + kaolin 1 + quartz at 1250°C and 1300°C; 7) talc + kaolin 1 at 1300°C; 8) talc + low iron bauxite + kaolin 2 + opal at 1300°C; 9) talc + low iron bauxite + kaolin 2 at 1300°C. The raw materials were milled to powder, placed into a closed crucible and sintered in an oxidizing furnace for 2h at designed temperatures (Succi, 2007). To maximize the cordierite content in the synthesis product, both mineralogical and chemical analyses of the starting phases were carried out in order to precisely balance the chemical composition of the starting mixture for the synthesis. The XRD patterns of the synthetized material specimens were analyzed by Rietveld method which allowed us to highlight the most reactive phases and the optimal mixtures, among the tested ones. Cordierite content exceeding 75% was obtained in the most promising synthesis.I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
