A bentonite sample taken from Reşadiye (Tokat/Turkey) deposit was mixed with distilled water. The formed permanent aqueous suspension was separated by decantation from the flocculated solid fraction. The deflocculated mass percent of the bentonite was evaluated almost 60% by weighing. The bentonite and its permanently suspended solid fraction are examined by using X-ray diffraction, chemical, thermal, cation exchange, and particle size analyses. Mineralogy and chemical composition of the samples were discussed with respect to the experimental results. A sodium-rich aluminum, iron, and magnesium smectite was determined as the major clay mineral in the bentonite and also illite as minor one. Clinoptilolite, plagioclase, quartz, opal-CT, calcite, magnesite, and dolomite are the nonclay minerals found in the bentonite as impurities. The suspension contains large amount sodium-rich smectite and plagioclase whereas lesser opal-CT. Particle size of the bentonite and deflocculated fraction was found to be lesser than 11 µm and 2 µm, respectively.
The kinetic parameters of the thermal degradation of sepiolite were evaluated with a new method based on thermal analysis data. Thermogravimetric/differential thermal analysis curves were recorded for the natural and preheated sepiolite samples in the temperature range 25–800°C for 4 h. The temperature-dependent height of the exothermic heat flow peak for the thermal decomposition of sepiolite located at ~850°C on the differential thermal analysis curve was taken as a kinetic variable for the thermal degradation. A thermal change coefficient was defined depending on this variable because this coefficient fit to the Arrhenius equation was assumed as a rate constant for the thermal degradation. The Arrhenius plot showed that the degradation occurs in three steps. Two of these are due to stepwise dehydration and the third originated from dehydroxylation of sepiolite. Three activation energies were obtained that increase with the increasing temperature interval of the steps.
Methacrylamide (MAA) including halloysite (H) with different contents was polymerized in aqueous medium with the in situ technique by using benzoyl peroxide as a radical initiator. Halloysite, polymethacrylamide (PMAA), and prepared composites were examined with X‐ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA) and differential thermal analysis (DTA), and nitrogen adsorption/desorption (N2‐AD) techniques. The XRD results showed that the crystal structure of halloysite unchanged by the formation of the composites, but completely transformed to the metahalloysite. The SEM images exhibited that the composites have a spongy and porous‐shaped morphology. The TEM view revealed that the halloysite particles distributed in the PMAA of both fiber bundle and exfoliated forms. Thermal analysis demonstrated the improved thermal stability of composites relative to the pure PMAA due to the incorporated halloysite. Furthermore, surface area, micro‐ and mesopore volume, and moisture retentions of the composites decreased with increasing PMAA content.
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