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Dry Grinding (dry + grinding)
Selected AbstractsEffects of Dry Grinding on the Structural Changes of Kaolinite PowdersJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 7 2000Pedro J. Sánchez-Soto The present study examined the effects of dry grinding, using ball-milling, on the structure of reference well-crystallized (KGa-1) and poorly crystallized (KGa-2) kaolinite powders from Georgia. Grinding produced a strong structural alteration, mainly along the c axis, resulting in disorder and total degradation of the crystal structure of the kaolinite and the formation of an amorphous product. The surface area increased with grinding time, mainly in KGa-2 (maximum value 50.27 m2/g), a result associated with particle-size reduction. These particles became more agglomerated with grinding, and the surface area decreased after 30 min, as confirmed by scanning electron microscopy and particle-size-distribution analysis. There was a limit to particle-size reduction with grinding time. When grinding time was increased, the original endothermic differential thermal analysis (DTA) effects of dehydroxylation in both samples shifted to lower temperatures, decreased in intensity, then disappeared completely after 120 min of grinding. The temperature of the characteristic first exothermic effect shifted slightly to lower temperatures with grinding, although the DTA effects did not increase with grinding time in either kaolinite sample, at least up to 325 min. The amorphous, mechanically activated kaolinite converted into low-crystalline mullite nuclei at a lower temperature than did the unground samples, as deduced by thermal and X-ray observations. This effect was especially important for the KGa-2 sample. Grinding did not seem to influence the formation of silicon-aluminum spinel from kaolinite. The present results may explain why ground kaolinite samples prepared via different routes,e.g., with differences in grinding,behave differently during high-temperature transformations, as reported in the related literature. [source] Dry Grinding of Mefenamic Acid Particles for Enhancement of its Water Dissolution RatePARTICLE & PARTICLE SYSTEMS CHARACTERIZATION, Issue 3 2007Tomohiro Iwasaki Abstract This paper details an investigation into the enhancement of the water dissolution rate of mefenamic acid (MA) by means of a dry grinding treatment. The physico-chemical properties of the ground MA particles were analyzed by measurements of specific surface area, powder X-ray diffraction patterns, differential scanning calorimetry thermograms and infrared spectra, and the effects of the change in the physico-chemical properties (especially, crystalline structure) on the dissolution rate were studied. The polymorphic transition from Form I (original) to II and the change of the molecular structure of MA did not occur in the grinding treatments. However, the specific surface area of the MA particles increased, and the crystallinity decreased (i.e., the amorphization level increased) as the grinding progressed. Hydrogen bonds formed between the carboxyl groups of the opposed asymmetric MA molecules were broken gradually after the grinding limit was attained in the grinding system, resulting in an effective improvement of the initial dissolution rate. [source] Supramolecular Catalysis in the Organic Solid State through Dry Grinding,ANGEWANDTE CHEMIE, Issue 25 2010Anatoliy Chemische Mechanik: Eine H-Brücken-vermittelte Selbstorganisation und mechanochemische Effekte wurden genutzt, um eine supramolekulare Katalyse im Festkörper zu bewirken. Das Zermörsern eines physikalischen Gemenges eines Olefins mit katalytischen Mengen eines ditopen Templats erwies sich als effiziente Methode für eine Cokristall-Bildung als Startpunkt des Katalysekreislaufs (siehe Schema). [source] Effects of Dry Grinding on the Structural Changes of Kaolinite PowdersJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 7 2000Pedro J. Sánchez-Soto The present study examined the effects of dry grinding, using ball-milling, on the structure of reference well-crystallized (KGa-1) and poorly crystallized (KGa-2) kaolinite powders from Georgia. Grinding produced a strong structural alteration, mainly along the c axis, resulting in disorder and total degradation of the crystal structure of the kaolinite and the formation of an amorphous product. The surface area increased with grinding time, mainly in KGa-2 (maximum value 50.27 m2/g), a result associated with particle-size reduction. These particles became more agglomerated with grinding, and the surface area decreased after 30 min, as confirmed by scanning electron microscopy and particle-size-distribution analysis. There was a limit to particle-size reduction with grinding time. When grinding time was increased, the original endothermic differential thermal analysis (DTA) effects of dehydroxylation in both samples shifted to lower temperatures, decreased in intensity, then disappeared completely after 120 min of grinding. The temperature of the characteristic first exothermic effect shifted slightly to lower temperatures with grinding, although the DTA effects did not increase with grinding time in either kaolinite sample, at least up to 325 min. The amorphous, mechanically activated kaolinite converted into low-crystalline mullite nuclei at a lower temperature than did the unground samples, as deduced by thermal and X-ray observations. This effect was especially important for the KGa-2 sample. Grinding did not seem to influence the formation of silicon-aluminum spinel from kaolinite. The present results may explain why ground kaolinite samples prepared via different routes,e.g., with differences in grinding,behave differently during high-temperature transformations, as reported in the related literature. [source] | ||||||||||