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Nouari Saheb - One of the best experts on this subject based on the ideXlab platform.
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Effect of temperature and magnesia on phase transformation kinetics in stoichiometric and non-stoichiometric Cordierite ceramics prepared from kaolinite precursors
Journal of Thermal Analysis and Calorimetry, 2019Co-Authors: Smail Lamara, Djaida Redaoui, Foudil Sahnoune, Nouari SahebAbstract:The influence of temperature and magnesia content on the formation of phases and their transformation kinetics in stoichiometric and non-stoichiometric Cordierite ceramics prepared from Algerian kaolinite precursors was investigated. High-temperature X-ray diffraction was used to study the formation of phases and their transformations. Non-isothermal differential thermal analysis was used to determine kinetic parameters for the formation of μ and α Cordierite. Activation energies were calculated by Kissinger, Boswell, and Ozawa equations. The Augis–Bennett and Matusita equations were used to calculate the mode of crystallization ( n ) and dimension of growth ( m ) parameters, respectively. The synthesized materials showed similar phase transformations, which finally led to the formation of Cordierite in stoichiometric kaolinite–magnesia mixture, and Cordierite along with other phases in kaolinite–magnesia mixture containing excess magnesia. The activation energy for the formation of α Cordierite was higher than that of μ Cordierite. Energies of formation of μ and α Cordierite phases in the non-stoichiometric samples were higher than those in the stoichiometric sample. The activation energy was less sensitive to the calculation method; however, it changed significantly with MgO content. Activation energies between 573 and 964 kJ mol^−1 were obtained. Magnesia changed the crystallization mode and crystal growth dimension. The kinetic parameters n and m , for the formation of μ or α Cordierite, had values between 2 and 3.
Shiangpo Hwang - One of the best experts on this subject based on the ideXlab platform.
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effects of b2o3 p2o5 additives on microstructural development and phase transformation kinetics of stoichiometric Cordierite glasses
Journal of the American Ceramic Society, 2004Co-Authors: Shiangpo HwangAbstract:The microstructural development and phase-transformation kinetics of stoichiometric Cordierite glasses containing B2O3 and/or P2O5 additives were highly affected by the microstructural characteristics of the μ-Cordierite and the type of additives. The addition of B2O3 tended to cause the formation of μ-spherulitic dendrites with thin dendritic arms, which promoted the formation of α-Cordierite, either from crystallization of the residual glass or from transformation of μ-Cordierite. P2O5 had the opposite effect: Increasing the temperature increased the growth rate of α-Cordierite more than that of μ-Cordierite.
Lj. Kostic-gvozdenovic - One of the best experts on this subject based on the ideXlab platform.
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Phase-transformation kinetics in triphasic Cordierite gel
Journal of Materials Research, 2001Co-Authors: Rada Petrović, Dj. Janaćković, Slavica Zec, Saša Ž. Drmanić, Lj. Kostic-gvozdenovicAbstract:A triphasic Cordierite-type gel was prepared from silica sol, boehmite sol, and an aqueous solution of Mg(NO3)2 · 6H2O. The silica sol was obtained from water glass by the ion exchange method, while boehmite sol was obtained by peptization of freshly prepared Al(OH)3. Phase transformations occurring in the gel were studied by differential scanning calorimetry, x-ray diffractometry, and Fourier transform infrared spectrometry. Spinel was observed to crystallize from the gel prior to cristobalite; their reaction subsequently yielded α-Cordierite. At higher temperatures, α-Cordierite transformed into modulated β-Cordierite. Kinetic parameters of α-Cordierite formation and α-Cordierite to modulated β-Cordierite transformation were determined by differential scanning calorimetry under nonisothermal conditions. Formation of a-Cordierite was found to be a diffusion-controlled process, with an overall activation energy of Ea = 1242 ± 66 kJ/mol. During the α → β-Cordierite transformation, a modulated phase was formed by surface transformation of α-Cordierite. The overall activation energy for the formation of the modulated structure is Ea = 583±77 kJ/mol.
Smail Lamara - One of the best experts on this subject based on the ideXlab platform.
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Effect of temperature and magnesia on phase transformation kinetics in stoichiometric and non-stoichiometric Cordierite ceramics prepared from kaolinite precursors
Journal of Thermal Analysis and Calorimetry, 2019Co-Authors: Smail Lamara, Djaida Redaoui, Foudil Sahnoune, Nouari SahebAbstract:The influence of temperature and magnesia content on the formation of phases and their transformation kinetics in stoichiometric and non-stoichiometric Cordierite ceramics prepared from Algerian kaolinite precursors was investigated. High-temperature X-ray diffraction was used to study the formation of phases and their transformations. Non-isothermal differential thermal analysis was used to determine kinetic parameters for the formation of μ and α Cordierite. Activation energies were calculated by Kissinger, Boswell, and Ozawa equations. The Augis–Bennett and Matusita equations were used to calculate the mode of crystallization ( n ) and dimension of growth ( m ) parameters, respectively. The synthesized materials showed similar phase transformations, which finally led to the formation of Cordierite in stoichiometric kaolinite–magnesia mixture, and Cordierite along with other phases in kaolinite–magnesia mixture containing excess magnesia. The activation energy for the formation of α Cordierite was higher than that of μ Cordierite. Energies of formation of μ and α Cordierite phases in the non-stoichiometric samples were higher than those in the stoichiometric sample. The activation energy was less sensitive to the calculation method; however, it changed significantly with MgO content. Activation energies between 573 and 964 kJ mol^−1 were obtained. Magnesia changed the crystallization mode and crystal growth dimension. The kinetic parameters n and m , for the formation of μ or α Cordierite, had values between 2 and 3.
Thomas Ludwig - One of the best experts on this subject based on the ideXlab platform.
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contact metamorphism in pelitic rocks on the island of kos greece eastern aegean sea a test for the na in Cordierite thermometer
Journal of Petrology, 1998Co-Authors: Angelika Kalt, Rainer Altherr, Thomas LudwigAbstract:into Cordierite by a coupled substitution involving tetrahedral and Most of the applicable thermometers involving Cordierite require octahedral sites, whereas Na may not be charge-balanced by additional Fe–Mg phases and knowledge of pressure and fluid phase lattice oxygen. The results obtained suggest that the experimentally composition. These conditions are not necessarily met with natural established relationship between Na contents of Cordierite and Cordierite-bearing metamorphic rocks. A potential pressure-intemperature is a useful thermometer for Cordieriteand plagioclasedependent geothermometer for Cordieriteand plagioclase-bearing bearing metapelitic rocks. The nature of Na incorporation in Cordierite rocks is the experimentally determined inverse linear relationship and its relation to fluid composition, however, must be constrained between temperature and Na contents of Mg-Cordierite coexisting by further experiments. with NaOH or albite and NaOH. In this paper, the Na-inCordierite thermometer is empirically tested on Cordierite-bearing metapelites from the island of Kos, contact metamorphosed by a quartz monzonite intrusion. The variety of phase assemblages in the metapelites allows for tight constraints to be placed on temperatures