Vyacheslav Romanov

Molecular Dynamics Simulations of Turbostratic Dry and Hydrated Montmorillonite with Intercalated Carbon Dioxide

Molecular dynamics simulations using classical force fields were carried out to study energetic and structural properties of rotationally disordered clay mineral-water-CO2 systems at pressure and temperature relevant to geological carbon storage. The simulations show that turbostratic stacking of hydrated Na- and Ca-montmorillonite and hydrated montmorillonite with intercalated carbon dioxide is an energetically demanding process accompanied by an increase in the interlayer spacing. On the other hand, rotational disordering of dry or nearly dry smectite systems can be energetically favorable. The distributions of interlayer species are calculated as a function of the rotational angle between adjacent clay layers.

Natural Materials for Carbon Capture

Naturally occurring clay minerals provide a distinctive material for carbon capture and carbon dioxide sequestration. Swelling clay minerals, such as the smectite variety, possess an aluminosilicate structure that is controlled by low-charge layers that readily expand to accommodate water molecules and, potentially, carbon dioxide. Recent experimental studies have demonstrated the efficacy of intercalating carbon dioxide in the interlayer of layered clays but little is known about the molecular mechanisms of the process and the extent of carbon capture as a function of clay charge and structure. A series of molecular dynamics simulations and vibrational analyses have been completed to assess the molecular interactions associated with incorporation of CO2 in the interlayer of montmorillonite clay and to help validate the models with experimental observation.

Applications of pulsed laser ablation for enhanced gold nanofluids

We report the exploration for enhanced gold nanofluids by using the laser ablation technique of which pulsed laser ablates energetic clusters from the bulk target immersed into liquid environment. By employing pulsed laser ablation, the behavior of optical absorption band was investigated on spherical Au nanoparticles that approach to the extremely small size of 1 nm, and rod-shaped Au nanoparticles were synthesized by controlling the aggregation behavior of energetic clusters in fluids. It was found that a nominal change in particle size induces a significant change in absorption band energy in the size range. In addition, the attempt to control the growth kinetics of particles has made remarkable progress on the synthesis of environmentally friendly gold nanorods. Experimental evidences show that the laser ablation synthesis can be widely used as a potential method for advanced gold nanofluids.

Experimental Studies: Clay Swelling

The best-known characteristic of clay is a dramatic change in its morphological and geomechanical properties: from hard, dense, and brittle upon drying or firing to soft, pliable, and swelling upon exposure to water. Chemical properties of the 1:1 and 2:1 clay minerals are significantly different, which is mainly related to the bonds between individual layers. The interlayer environment is determined by the chemical nature of clay layers, the layer charge, interlayer cations, and water molecules forming hydration shells around the cations and H-bonding with clay surfaces. Mechanisms of water sorption and cluster organization are electrochemical in nature and fundamental to the swelling process. Some researchers also observed irreversible CO2-induced swelling with smectite in 1–2 W hydration state, but the others reported only shrinking attributed to drying effects of high-pressure CO2, for the cation-exchanged smectite with partly filled second hydration layer. The current interpretation of swelling phenomena evolves rapidly, following advances in experimental techniques and Monte Carlo and MD simulations of the structured fluid behavior. MD simulations show that the interlayer molecules do not organize themselves in a strictly tilted or strictly parallel to the surface configuration, which may result in fairly steep but gradual rather than stepwise increase in the basal spacing as the interlayer is filled with the solvent molecules. The magnitude of swelling hysteresis varies with the hydration energy of the interlayer cations and is generally more pronounced for vermiculite than montmorillonite.

CO2 Interaction with coals of different mineral and moisture content

To improve our understanding of the role of moisture and mineral matter with respect to CO2 sequestration in unmineable coal semns, we investigated sorption and swelling behavior of several Eastern and Western US coal samples, pmiicularly, cuttings from San Juan Basin (Fruitland) site of the Southwest Regional Pminership and crushed-coal samples of the Central Appalachian Basin (Russell County, VA) coal seam received from the SECARB pminership. The CO2 55°C sorption isotherm measurements have been completed for moist (as received) and dried samples representing the well probes. The results are summarized versus mineral matter and moisture content.