Nanomaterials are being synthesized of TiO2 nanotubes and quantums dots for applications in photovoltaics, thermal absorbers, self-cleaning coatings and bone cements. Supercritical fluids such as scCO2 offer an exciting new method for self-assembly and crystallizing metal alkoxides to produce a new and improved range of materials. Due to the zero-surface tension of scCO2, it provides the ability to wet and penetrate the pores of nanomaterials for enhanced mass-transfer and kinetics to produce a new generation of nanofibers, nanowires, nanotubes, and defined nanoaerogel structures. These materials are studied by crystallography, TEM, AFM and other advanced techniques. As well, homo and copolymerizations can be carried out in scCO2 by various polymerization techniques including, free-radical, living, and metal catalyzed polymerizations. These are important to generate next-generation nanocomposites where a one-pot reaction can produce low-cost adanced polymers. Kinetic modeling of these systems is performed to understand the effect of scCO2 on chain-growth, the molecular weight distribution, and linking of the nanomaterials to the polymer matrix. In order to develop predictive quantitative descriptions of these systems, a detailed physical understanding of the role of CO2 in the process, such as polymer swelling, diffusion, mass-uptake and monomer partitioning is required; in addition to understanding the phase-equilibria behaviour.
Due to the ever-increasing energy needs of society, a new class of low-cost solar cells is required to produce electricity in so-called photovoltaic (PV) devices. We are developing a new class of low cost PV devices based on nano TiO2 and quantum dots. Quantum dots have been shown to produce multiple excitons per photon, which provides the potential for a new generation of high performance materials. As our manufacturing process is made in a reactor with low cost ingredients, scale-up issues are being explored. As well, solar absorbing materials are being studied using conductive plastics, for a new generation of nanocoatings that convert sunlight directly into heat for hot water and floor-heating.
A new generation of nano catalysts are being explored based on the low cost elements, Nickel and Cobalt. These materials are being studied in collaboration with Inco Ltd., the worlds largest producer of Nickel and Cobalt. Metal aerogel catalysts, based on low cost and high surface area ceramics, are being synthesized in our labs and characterized using techniques such as electron microscopy, and temperature programmed reduction (TPR). The catalysts are being tested for several applications including gasification, fuel cell electrolysis, and hydrogenation. A novel chemical vapor deposition (CVD) technique is being studied for depositing nickel.
Advanced polyurethane polymer coatings are being prepared by using scCO2. These coatings have both nanoTiO2 and nano SiO2 to provide self-cleaning and self-healing properties. Surface properties of these polymers are being studied to understand the basic physico-chemical properties that enable these properties and how they can be controlled from the molecular level.
The techniques that can achieve self-assembly of nanomterials utilizing scCO2 include the rapid expansion of supercritical solutions (RESS), and gas antisolvent crystallization (GAS & SAS). These techniques have the ability to produce ultra-fine particles with extremely narrow size distributions. These ultrafine particles are gaining importance in a wide range of fields from ceramics precursors to controlled release drugs. A continuous crystallization supercritical apparatus has been set-up for several projects such as: