Palabora represents an interstratified vermiculite-biotite containing less than 50% vermiculite. The sodium-exchanged form was prepared by immersion in saturated brine at ambient conditions. The sodium content reached the equilibrium level within the first month of exposure. However, XRD spectra continued to evolve and sharpen over a six month period. The thermal-activated exfoliation was studied using thermo-mechanical analysis. The expansion of the neat "vermiculite" commenced at temperatures above 420 C. In some applications a lower exfoliation temperature is desirable, i.e. in the range 200 to 350°C. This study revealed that simple sodium exchange is effective towards this goal as it lowered the onset temperature by about 120 C. The linear expansion reached a maximum of about eight-fold at temperatures around 700 C and decreased again at higher temperatures.

Organo-bentonites containing quaternary ammonium surfactants were prepared using purified bentonite from the Boane deposit in Mozambique. The intercalation was effected by intimate mixing of the surfactants into a concentrated dispersion of soda ash activated bentonite. TG indicated organic contents that exceeded CEC expectations by up to 21 mass %. XRD results were consistent with: (i) paraffin-type extended chain intercalation at tilt angles of 27 º to 33 º; and (ii) interdigitated monolayer intercalation of the C14 single alkyl chain surfactant and bilayer intercalation of the C16 double alkyl chains and its 1:1 mixture with the single chain surfactant. However, FTIR analysis revealed disordered alkyl chain conformations. White oil dispersions containing 10 mass % organo-bentonite (inorganic basis) featured high viscosities. They showed strong shear thinning behaviour confirming the ability of the montmorillonite particles to exfoliate.

Abstract:The binary Mn + Sb 2 O 3 pyrotechnic composition was investigated for mining detonator time delay applications. EKVI thermodynamic modelling predicted two maxima in the adiabatic reaction temperature. The local maximum, at a manganese fuel content of ca. 36 wt-%, corresponds to a pure thermite-type redox reaction: 3Mn + Sb 2 O 3  3MnO + 2Sb. The overall maximum in the adiabatic reaction temperature (ca. 1640 K), at the fuel-rich composition of 49 wt-% Mn, is consistent with the reaction 5Mn + Sb 2 O 3  3MnO + 2MnSb, i.e. a combination of the standard thermite with an additional exothermic intermetallic reaction. XRD analysis of combustion residues confirmed the formation of MnSb and Mn 2 Sb for fuel-rich compositions. Burn rates were measured using delay elements assembled into commercial detonators. The d 50 particle sizes were 23.4 and 0.92 m for the Mn fuel and Sb 2 O 3 oxidant powders respectively. The delay elements comprised rolled lead tubes with a length of 44 mm and an outer diameter of 6.4 mm. The rolling action compacted the pyrotechnic compositions to 74  2 % theoretical maximum density. The burning rate increased linearly from 4.2 to 9.4 mm s 1 over the composition range 25 -50 wt-% Mn.

The crystal structure of a copper antimonite (CuSb 2 O 4 ) was determined from X-ray powder diffraction data. The structure was solved by simulated annealing (SA) in direct space using the

Three rectorite samples from the Beatrix Gold Mine, South Africa were characterized. Scanning electron microscopy revealed a layered morphology. High resolution transmission microscopy