Several synthetic approaches have been used to obtain nano-sized monoclinic WO₃ (m-WO₃) powders. All of these methods begin with a standard preparative method where H₂WO₄ is first generated by passing a Na₂WO₄ solution through a cation-exchange resin. It is shown that high surface area particles are produced by dripping the H₂WO₄ exiting from the ion-exchange column into a solution containing oxalate and acetate exchange ligands or alternatively, into a water-in-oil (w/o) based emulsion. In comparison to commercial WO₃ powders, the surface area of the m-WO₃ powders were higher by factors of 10 and 20 times when prepared in the presence of acetate/oxalate chelating agents and w/o emulsions, respectively. The much higher surface areas enable infrared spectroscopic identification of surface sites along with detection and monitoring of gaseous reactions and adsorbed species on the surface of this metal oxide. This is demonstrated with the adsorption of a nerve agent simulant, dimethyl methyl phosphonate. In general, little is known about the reactions of gaseous molecules on m-WO₃ surfaces and the fabrication of high surface area m-WO₃ particles will aid in gaining an understanding of the chemical processes occurring in WO₃ based sensors.

A novel method to obtain a high conversion of Ca(OH)₂ powder to CaCO₃ is reported. The method uses supercritical CO₂ containing water that is passed over the dry Ca(OH)₂ powder. Conversions greater than 98% are obtained. The dominant crystal structure is calcite. The process has the advantages of the conventional solution based process in terms of high conversion and the advantages of a gas–solid based process in that dry, non-agglomerated particles are obtained by simple venting of the solvent.

The photodecomposition of dimethyl methylphosphonate (DMMP) and trimethyl phosphate (TMP) adsorbed on monoclinic WO3 powders when irradiated by ultraviolet