Amorphization grinding

X [Fe(C5H5)2]2 [Tc8(/i-Br)8Br4JBr2 Black fine needle-like crystals with metallic lustre. Insoluble in orgaic and inorganic solvents but does not decompose. Grinding yields amorphous black powder. 

US patent 6,696,458, Compositions and formulations of 9-nitrocamptothecin polymorphs and methods of use thereof [101]. Amorphous forms of 9-nitrocamptothecin are obtained by grinding or pulverizing different polymorphic forms of 9-nitrocamptothecin, and the polymorphic forms are characterized by having an X-ray powder diffraction pattern with discernable diffraction lines at different scattering angles for Cu Ka radiation. 

For example, amorphous clarithromycin was prepared by grind and spray-drying processes, and XRPD was used to follow changes in crystallinity upon exposure to elevated temperature and relative humidity [59]. Exposure of either substance to a 40°C/82% RH environment for seven days led to the formation of the crystalline form, but the spray-dried material yielded more crystalline product than did the ground material. This finding, when supported with thermal analysis studies, led to the conclusion that the amorphous substances produced by the different processing methods were not equivalent. 

Materials mined from the Earth s crust are usually highly heterogeneous mixtures of amorphous and crystalline solid phases. Crushing and grinding operations are employed to liberate individual pure grains in the 10-50 pm size range. One of the most widely used (10 tons per... 

Grinding or abrasion during sample preparation produces a disturbed, disordered or amorphous surface layer which is hydrous. Acid leaching removes this material. 

Voigt [1705] prepared transparent Ge02 glasses on hydrolysis of Ge(OEt)4 the temperature of glass formation is about l(XfC lower in comparison with that used in conventional methods. On crystallization of amorphous oxide prepared on hydrolysis of Ge(OPri)4, a mixture of two phases, crystoballite and a-quartz, is formed. On further thermal treatment, phase transition of crystoballite to a-quartz occurs, while grinding in air results in the transition to a rutile-type structure on treatment at temperatures higher than 1050°C all phases are tranferredto a-quartz [1766]. 

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