0000000000266520
AUTHOR
Adel Megriche
Natural fluorapatite as a raw material for Portland clinker
Abstract The present work focuses on the mineralogy and the reactivity of clinkers made from the integration of natural fluorapatite in the raw meals with percentages ranging from 0 up to15%. The samples were characterized by infrared spectrometry, X-ray diffraction and microscopy techniques. The distribution of phosphorous and fluorine into clinkers minerals was determined by MEB/EDS mapping. The mineralogical composition was determined by XRD/Rietveld and the samples reactivity followed by isothermal microcalorimetry. It has been found that fluorine stabilizes C3S and β-C2S which still are found with high levels of P2O5. Cements obtained from up to 8% natural fluorapatite incorporation st…
Dielectric relaxation phenomenon and conductivity in lead-free ceramics
Abstract Relaxation phenomena and electric conductivity of (1-x) KNbO3-xK0.5Bi0.5TiO3 system where x = 0, 0.025, 0.05, 0.075, 0.1, 0.2, 0.3 have been studied at high temperature. A relaxation behavior was observed in temperature range 400 K ≤ T ≤ 550 K for orthorhombic solid solutions at room temperature. The activation energy (Ea) of this phenomenon was range from 0.68 eV for x = 0–0.489 eV for x = 0.075 with τ0 = 10−13 s. The relaxation was attributed to hopping of oxygen vacancies for solid solutions x ≤ 0.075. Substitution by K0.5Bi0.5TiO3 does not affect the electrical conductivity of KNbO3 too much, while the mobility of species such as oxygen vacancies and oxygen ions allow the incre…
Does phosphorus affect the industrial Portland cement reactivity?
Abstract The effect of phosphorous on the mineralogy and reactivity of Portland cement has been investigated through an industrial clinkers series. The samples were collected from the same Tunisian cement plant and classified according to the content of P2O5 from 0.5% to 1.1%. All samples were manufactured at the same thermal and cooling conditions as well as possible. The specimens were characterized by X-ray fluorescence spectrometry and optical microscopy techniques and their mineralogy was determined by X-ray powder diffraction coupled to the Rietveld analysis. The cements reactivity prepared from the clinkers was followed by means of isothermalcalorimetry. The compressive strength of t…
Effect of mechanical stirring and temperature on dynamic hydrothermal synthesis of titanate nanotubes
Abstract In the late century, it has been clearly demonstrated that titanate nanotubes (TNTs) are attractive nanomaterials with various potential applications due to their interesting properties. In this work, an essential reaction parameter, rarely considered in the literature, has been studied: stirring during hydrothermal synthesis. For this purpose, an intermittent mechanical stirring, ranging from 0 to 20 min/h, has been applied during the TNTs synthesis using a new dynamic hydrothermal reactor. It was proved that a long stirring cycle (more than 10 min/h) at 150 °C and an overall reaction time of 16 h promotes nanoribbons synthesis instead of nanotubes. In this context, a detailed mor…