Papers by Keyword: Thermal Transformation

Abstract: The boehmite (AlOOH) sol derived from aluminium isopropoxide was synthesized by Yoldas method. The physicochemical process and phase transition of AlOOH were investigated by TG-DSC, N2 adsorption-desorption, XRD and TEM. The results showed that upon heating, AlOOH lost the physicsorbed water first, and then lost the chemisorbed water at 242 °C, and the dehydroxylation occurred at 361 °C. The BET surface area, total pore volume and pore diameter increased, since the waters were lost. The orthorhombic AlOOH transformed to the cubic γ-Al2O3 at 361 °C, the cubic η-Al₂O₃ appeared after 484 °C, the monoclinic θ-Al₂O₃ and rhombohedral α-Al2O3 appeared after 1026 °C, and it totally turned into α-Al₂O₃ at 1237 °C.

Abstract: The article is devoted to an estimation of phase transformations of silicates magnesium at heating in the temperatures range from 0°C to 1100°С. The object of study is a silicates of magnesium containing oxide nickel ore. Differentially-thermal (NETZSCH 449 C - Jupiter), weights – spectrometer (QMS 403 C Aёolos), high-temperature X-ray diffraction, electron-probe microanalysis (JSM - 5900 LV) and chemical analysis methods have been used in the study. The temperature ranges of existence Mg6[(OH)8Si4O10] and Mg2Si2O6 are obtained. Parameters of an elementary cell of the above minerals and their changes with temperature and features of nickel distribution in magnesium silicates with various ration MgO/SiO2 are defined in this work.

Abstract: Four samples of Ba-exchanged zeolite A, bearing 0.27, 0.43, 0.58 and 0.74 meq/g Na residual amounts, were thermally treated in the temperature range 200-1500 °C for times up to 28 hours. The same samples were pressed at 30 and 60 MPa to manufacture cylindrical pellets, which were thermally treated at 1300 °C for 5 hours. Thermally treated materials were characterized by room temperature XRD. The sequence of thermal transformations that Ba-exchanged zeolite A undergoes (zeolite ® amorphous phase ® hexacelsian ® monoclinic celsian) and the strong mineralizing action developed by Na are confirmed. Pressing the Ba-exchanged zeolite A powder-like samples to obtain cylindrical pellets is found to expedite the sluggish final phase transition hexacelsian ® monoclinic celsian. The optimum residual Na content of Ba-exchanged zeolite A to be transformed into monoclinic celsian is assessed to range between 0.27 and 0.43 meq/g.