Electrical, Microstructural and Physical Characteristics of Talc-based Cordierite Ceramics Ahmed Yahya, AbdelMonem Soltan, Ragab Mahani, Baher El-Kaliouby, Sayed Kenawy, et al. Silicon, 2023 The aim of this work is to study the effect of various talc rocks for the preparation of talc-based cordierite ceramics. Raw talc and sintered cordierite-based ceramic samples (1000-1375ºC for 2 h) were characterized using XRD, XRF, TGA-DTG, laser PSDs, Archimedes method, SEM-EDAX and dielectric relaxation spectrometer (DRS). Results show that impurity oxide contents, particle size and mineralogical changes of green batches influenced the microstructure densification and crystallization of orthorhombic and hexagonal cordierite. The complex electric modulus plot shows the existence of two relaxation processes associated with the capacitive contribution grain boundaries and grain at low and high frequencies, respectively. The dielectric loss reached much lower values (0.0004–0.0007) for the ceramics composed of higher cordierite phase composition (87.00 to 92.00wt.%) that sintered at 1350 and 1375ºC. Such ceramics could be promising in electronic applications like capacitors, microwave devices and wireless communication.
Cordierite ceramic through glass and ceramic routes from kaolin and talc Ahmed Yahya, Esmat Hamzawy, Baher El-Kalioby, Abdel Monem Soltan, Sayed Kanawy Ibrahim Egyptian Journal of Chemistry, 2021 Based on kaolin and talc, cordierite was prepared through melt quench and ceramic process of two compositions. The sintering process of ceramics between 1000 and 1300 °C shows mainly the manifestation of cordierite with little ratios of spinel, enstatite, mullite and cristobalite. However, the sintering of their corresponding glasses between 1100 and 1200 °C shows the crystallization of cordierite as the main phases with little cristobalite and spinel. In microstructure, the sintering of ceramic samples gave nano size rounded- or rod- crystals either free or in clusters in glassy matrix but sintering of the corresponding glasses show clear euhedral to subhedral tetragonal to hexagonal crystals in submicron scale that are spread in residual glassy matrix. The density of the sintered ceramic samples was between 1.96 and 2.43 g/cm3 which corresponding to their porosity are between 29.34 and 5.46 % respectively, whereas as density of the sintered glasses were between 1.90 and 2.35 gm/cm3 which corresponding to their porosity between 36.20 and 3,30 % respectively. The sintered glass samples gave low and negative coefficient of thermal expansion values between 6.38 and -9.56 X 10-7 °C-1 (in the range ~ 24 -500 and 700 °C). The microhardness values were between 468 and 577 Kg/mm2. This cordierite ceramic can be used as refractoriness in electric heater supports, such as electric stove or heater cooling plate and ceramic heater base.
