Synthesis of glass ceramics from kaolin and dolomite mixture |
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| Authors: | Mohamed Reda Boudchicha Fausto Rubio Slimane Achour |
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| Affiliation: | 1.Engineering Mechanics and Materials Laboratory, Mechanical Engineering Department, Faculty of Technology,Université 20 Ao?t 1955 de Skikda,Skikda,Algeria;2.Ceramics and Glass Institute,Consejo Superior de Investigaciones Cientificas,Madrid,Spain;3.National Polytechnic School,Constantine,Algeria |
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| Abstract: | Cordierite- and anorthite-based binary glass ceramics of the CaO–MgO–Al2O3–SiO2 (CMAS) system were synthesized by mixing local and abundant raw minerals (kaolin and doloma by mass ratio of 82/18). A kinetics study reveals that the activation energy of crystallization (E a) calculated by the methods of Kissinger and Marotta are 438 kJ·mol?1 and 459 kJ·mol?1, respectively. The Avrami parameter (n) is estimated to be approximately equal to 1, corresponding to the surface crystallization mechanism. X-ray diffraction (XRD) analysis shows that the anorthite and cordierite crystals are precipitated from the parent glass as major phases. Anorthite crystals first form at 850°C, whereas the μ-cordierite phase appears after heat treatment at 950°C. Thereafter, the cordierite allotropically transforms to α-cordierite at 1000°C. Complete densification is achieved at 950°C; however, the density slightly decreases at higher temperatures, reaching a stable value of 2.63 kg·m?3 between 1000°C and 1100°C. The highest Vickers hardness of 6 GPa is also obtained at 950°C. However, a substantial decrease in hardness is recorded at 1000°C; at higher sintering temperatures, it slightly increases with increasing temperature as the α-cordierite crystallizes. |
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