Measurement of Fundamental Illite Particle Thicknesses by X-Ray Diffraction Using PVP-10 Intercalation

Abstract

Abstract~The thicknesses of fundamental illite particles that compose mixed-layer illite-smectite (I-S) crystals can be measured by X-ray diffraction (XRD) peak broadening techniques (Bertaut-WarrenAverbach [BWA] method and integral peak-width method) if the effects of swelling and XRD background noise are eliminated from XRD patterns of the clays. Swelling is eliminated by intercalating Na-saturated I-S with polyvinylpyrrolidone having a molecular weight of 10,000 (PVP-10). Background is minimized by using polished metallic silicon wafers cut perpendicular to (100) as a substrate for XRD specimens, and by using a single-crystal monochromator. XRD measurements of PVP-intercalated diagenetic, hydrothermal and low-grade metamorphic I-S indicate that there are at least 2 types of crystallite thickness distribution shapes for illite fundamental particles, lognormal and asymptotic; that measurements of mean fundamental illite particle thicknesses made by various techniques (Bertant-Warren-Averbach, integral peak width, fixed cation content, and transmission electron microscopy [TEM]) give comparable results: and that strain (small differences in layer thicknesses) generally has a Gaussian distribution in the lognormal-type illites, but is often absent in the asymptotic-type illites.

Illite “Crystallinity” Revisited

“…Accurate results may be obtained by removing the effect of swelling interlayers either by large scale expansion (Eberl et al, 1998a) or by heating (Drits et al, 1998). The KI properties for anchizone values (Table 2) may explain the good results of the Bertaut-Warren-Averbach method without using special treatment.…”

“…The Bertaut-Warren-Averbach method is not relevant for interstratified clay minerals without special treatment (Warren and Averbach, 1950;Drits et al, 1998;Eberl et al, 1998a), as shown by Lanson and Kiabler (1994). Accurate results may be obtained by removing the effect of swelling interlayers either by large scale expansion (Eberl et al, 1998a) or by heating (Drits et al, 1998).…”

“…Although lattice strain clearly affects KI values (,~rkai et aL, 1996;Wan" and Nieto, 1998;Drits et aL, 1998), its role is difficult to assess accurately in peak broadening analysis, because many authors interchange small variations of a single d value within one layer type with interstratification and CSD thickness (e.g., ,~rkal et al, 1996;Jiang et aL, 1997). According to Eberl et al (1998a), the 10-,~ peak is not significantly affected by strain. We believe that lattice strain is not sufficiently understood to be considered here.…”

Hydrothermal speleogenesis in carbonates and metasomatic silicites induced by subvolcanic intrusions: a case study from the Štiavnické vrchy Mountains, Slovakia

“…The illite mineral association, contained in the light yellow-green friable rock on cave walls, is a typical product of hydrothermal alteration of rocks. The thickness of coherent diffracting domains without expanding interlayers indicates temperature of hydrothermal fluids close to 300°C (see Eberl et al, 1998;Šucha, 2000). The origin of quartz crystals and illite mineral association has been connected with the hydrothermal origin of adjacent large epithermal vein system (before the formation of the cave).…”

Influence of Soluble Feed Proteins and Clay Additive Charge Density on Aflatoxin Binding in Ingested Feeds

“…Free expansion of smectites in water is almost unlimited. Completely dispersed smectite particles consist of single unit cells with no c-axis direction repeat distance (Eberl et al, 1998). Interlayer expansion of air-dried (32% relative humidity) samples of Na-smectite and Ca-smectite is illustrated in Figure 1 with characteristic basal spacings after McEwan & Wilson (1984).…”