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Supercritical carbon dioxide sometimes intercalates into buttons, and, when the SCD is depressurized, the buttons pop, or break apart. Detergents that are soluble in carbon dioxide improve the solvating power of the solvent. [20] CO 2-based dry cleaning equipment uses liquid CO 2, not supercritical CO 2, to avoid damage to the buttons.
According to textbook knowledge, it is possible to transform a liquid continuously into a gas, without undergoing a phase transition, by heating and compressing strongly enough to go around the critical point. However, different criteria still allow to distinguish liquid-like and more gas-like states of a supercritical fluid. These criteria ...
Supercritical carbon dioxide is used in the production of silica, carbon and metal based aerogels. For example, silicon dioxide gel is formed and then exposed to s CO 2. When the CO 2 goes supercritical, all surface tension is removed, allowing the liquid to leave the aerogel and produce nanometer sized pores. [34]
The properties of the supercritical fluid can be altered by varying the pressure and temperature, allowing selective extraction. For example, volatile oils can be extracted from a plant with low pressures (100 bar), whereas liquid extraction would also remove lipids.
Supercritical fluids combine useful properties of gas and liquid phases, as it can behave like both a gas and a liquid in various aspects. A supercritical fluid provides a gas-like characteristic when it fills a container and it takes the shape of the container. The motion and kinetics of the molecules are quite similar to gas molecules.
One example is the liquid–vapor critical point, the end point of the pressure–temperature curve that designates conditions under which a liquid and its vapor can coexist. At higher temperatures, the gas comes into a supercritical phase, and so cannot be liquefied by pressure alone.
Supercritical drying, a process used to remove liquid in a precisely controlled way, similar to freeze drying; Supercritical fluid, a substance at a temperature and pressure above its thermodynamic critical point: Supercritical carbon dioxide:
Liquid CO 2 washing, like supercritical fluid CO 2 washing, relies on the high solvent power of CO 2, [4]: 275 but at lower temperatures and pressures, the latter making it simpler to implement. Because liquid CO 2 does not have the solvent power of the supercritical fluid, agitation and surfactants may be added to improve the effectiveness of ...