CHARACTERIZATION OF UNTREATED AND ALKYLAMMONIUM ION-EXCHANGED ILLITE SMECTITE BY HIGH-RESOLUTION TRANSMISSION ELECTRON-MICROSCOPY/

High resolution transmission electron microscopy (HRTEM) have been per formed on dispersed portions of one R > 1 and two R3 illite/smectite ( I/S) samples from Silurian K-bentonites. R > 1 sample was studied by H RTEM before and after alkylammonium ion treatment and R3 samples were studied only after alkylammonium ion treatment. The HRTEM images of th e chemically untreated R > 1 sample were predominated by lattice fring e contrast with 20-40 Angstrom periods, interpreted to represent vario us ordered VS units. HRTEM images of the three alkylammonium-treated s amples displayed very small, dispersed particles composed of illite pa ckets separated by alkylammonium expanded interlayers. In the R > 1 sa mple, illite packets were mostly 20 Angstrom to 40 Angstrom thick wher eas in R3 samples they were predominantly over 40 A. Although a good d egree of dispersion of the bulk samples was achieved, dispersed partic les recorded on images were thicker than the fundamental particles pos tulated by Nadeau and coworkers. Alkylammonium ion-expanded interlayer thicknesses point out a trend toward a higher charge in the expandabl e interlayers (i.e., illite particle surfaces) with increasing illite content from the R > 1 sample to the R3 samples. In the R3 samples, th e interlayer charge is sufficiently high to be vermiculitic.