X-Ray diffraction line-broadening study on two vibrating, dry-milling procedures in kaolinites

Abstract

Due to the great technological importance of the microstructure of kaolinite, characterizing its evolution during dry milling of kaolin and analyzing the microstructural information obtained from different methods were the main aims of this work. The microstructural alteration of kaolinite is evaluated by X-ray diffraction and electron microscopy methods, comparing the results obtained and analyzing the correlations between them. The Warren-Averbach and Voigt-function methods of X-ray diffraction microstructural analysis have been applied successfully to the study of the effects of two different, vibrating-cup dry-milling configurations in the microstructure of kaolinite from the reflections corresponding to (00l) diffracting planes. The crystallite-size estimates obtained from the two methods correlate well. Field emission scanning electron microscopy measurements of kaolinite particle thickness are in good agreement with the crystallite size estimated by the two methods. The Warren-Averbach method also provided estimates of the contribution to line broadening. Vibrating-cup milling has been proved to be a more efficient method of strain comminution of kaolinites than other milling techniques, reaching extensive microstructural degradation within seconds.

X-ray Diffraction Microstructural Analysis of Swelling by Ethylene Glycol in Two Reference Clay Minerals

“…A rough correspondence could be found between crystallite thicknesses measured from FESEM images and apparent crystallite sizes calculated from X-ray diffraction data. These results were similar to those reported of 62.5 nm for unmilled kaolinite KGa1 [3] and of 8.2 nm for Na-smectite [13].…”

“…Table I includes main XRD profile fitting parameters and crystallite sizes calculated for the fractions of samples K and EDS in the pure and ethylene-glycol-oriented aggregates. Crystallite size for kaolinite in K fractions was smaller than that previously found (79 nm) in the untreated sample of the same reference clay [3]. EDS samples presented smaller montmorillonite crystallite size values than K (kaolinite) samples.…”

“…Field emission scanning electron microscopy (FESEM) images were performed in a HITACHI S4800 microscope as in [3], using Image J software for image treatment and measurements (http://imagej.nih.gov/ij/docs/guide/user-guide.pdf).…”

“…The main aims of this work are (i) to use powder X-ray diffraction microstructure analysis to compare the microstructure of kaolinites and smectites in industrially relevant granulometrical fractions; (ii) to verify the results by direct crystallite thickness measurements by field emission scanning electron microscopy as done by Pardo et al [3], and (iii) to asses the effect of ethylene-glycol treatment in both minerals at crystallite size level. * corresponding author; e-mail: fer.garciatomas@gmail.com…”

Crystalline Microstructure of Corundum Fillers Determined from Powder X-Ray Diffraction Patterns

“…Densification and re-crystallisation can be achieved by overgrinding of nanocrystalline corundum [14] but usually the maximum of frequency of crystallite size distributions migrates to smaller crystallite sizes after milling (e.g. [15]). The method of microstructural analysis of powder XRD patterns applied in [16] has been used in the present work for microstructural evaluation of industrial alpha-alumina fillers.…”