Life is a Journey, not a destination.
There is no surface tension in a supercritical fluid, as there is no liquid / gas phase boundary. By changing the pressure and temperature of the fluid, the properties can be “tuned” to be more liquid or more gas like. One of the most important properties is the solubility of material in the fluid. Solubility in a supe rcritical fluid tends to increase with density of the fluid. Since density increases with pressure, then solubility also tends to increase with pressure. The relationship with temperature is a little more complicated. At constant density, solubility will increase with temperature. However, close to the critical point, the density can drop sharply with a slight increase in temperature. Therefore, close to the critical temperature, solubility often drops with increasing temperature, then rises again.
1. Enhancement of CNTs purification and dispersion using supercritical fluids
Industrial applications of CNTs are strongly dependent upon homogeneous dispersion in organic or aqueous solvents. Although various dispersion techniques has been developed, critical balance between conductivity and transparency for transparent electrodes has not been achieved yet.
Especially Single walled carbon nanotube (SWCNT) having excellent physical and chemical properties has wide-ranged applications including transparent conducting films. Dispersion of SWCNT, especially debundling, is crucial for fabricating commercial products which need to get better transparency by reducing a percolation threshold.
In this study, we use supercritical fluids (SCFs) for enhancing purification and debundling, where SCF is expected to attenuate van der Waals interaction between individual tubes. Near-IR and Raman spectra will be presented for proving debundling. Additionally it will be presented that impurities originated from residual catalysts.
2. Purification of organic nanomaterials by supercritical fluids treatments
We build a effective purification process of organic nanomaterials using supercritical fluids systems. These technology can replace conventional processes having low yields due to thermal modification, especially for sublimation processes. Specifically we applied supercritical fluids along with organic solvents to the organic nanomaterials and developed purification processes including a re-crystallization in supercritical fluids. In these simple processes residual impurities in the materials can selectively be extracted without chemical damages on them.