supercritical fluid

Examples of supercritical fluid in the following topics:

• Supercritical Fluids

  • In general terms, supercritical fluids have properties between those of a gas and a liquid.
  • Table 2 shows density, diffusivity, and viscosity for typical liquids, gases, and supercritical fluids.
  • One of the most important properties of supercritical fluids is their ability to act as solvents.
  • Solubility in a supercritical fluid tends to increase with the density of the fluid (at constant temperature).
  • Supercritical fluids have properties between those of a gas and a liquid.

• Three States of Matter

  • A liquid is a fluid that conforms to the shape of its container but that retains a nearly constant volume independent of pressure.
  • A supercritical fluid (SCF) is a gas whose temperature and pressure are greater than the critical temperature and critical pressure.
  • A supercritical fluid has the physical properties of a gas, but its high density lends it the properties of a solvent in some cases.
  • For example, supercritical carbon dioxide is used to extract caffeine in the manufacturing of decaffeinated coffee.

• Interpreting Phase Diagrams

  • At this point and beyond it, the substance being evaluated exists as a "supercritical fluid".

• The Structure and Properties of Water

  • Water also exists in a rare fourth state called supercritical fluid, which occurs only in extremely uninhabitable conditions.
  • When water achieves a specific critical temperature and a specific critical pressure (647 K and 22.064 MPa), the liquid and gas phases merge into one homogeneous fluid phase that shares properties of both gas and liquid.

• Nuclear Reactors

  • When the reactor's neutron production exceeds losses, characterized by increasing power level, it is considered "supercritical."
  • The mere fact that an assembly is supercritical does not guarantee that it contains any free neutrons at all.
  • At least one neutron is required to "strike" a chain reaction, and if the spontaneous fission rate is sufficiently low, it may take a long time before a chance neutron encounter starts a chain reaction—even if the reactor is supercritical.

• Viscosity

  • When fluids flow smoothly through a tube or pipe, the motion can be thought of as consisting of layers, or lamina.
  • The term $\eta$ is called the viscosity, and it is a measure of a fluid's resistance to flow.
  • A rheometer is used for fluids that cannot be defined by a single value of viscosity.
  • When a fluid is less viscous, it flows more easily.
  • Velocity of a fluid's layers, or lamina, during smooth flow.

• The Atomic Bomb

  • In fission weapons, a mass of fissile material, either enriched uranium or plutonium, is assembled into a supercritical mass—the amount of material needed to start an exponentially growing nuclear chain reaction.

• Periodic Trends in Metallic Properties

  • In effect, the electropositive nature of the metallic atoms allows their valence electrons to exist as a mobile fluid.
  • Because each ion is surrounded by the electron fluid in all directions, the bonding has no directional properties; this accounts for the high malleability and ductility of metals.

• Capillary Action

  • Adhesion forces between the fluid and the solid inner wall pull the liquid column up until there is a sufficient mass of liquid for gravitational forces to counteract these forces.
  • The meniscus curve on a column of fluid in a capillary tube
  • The curvature of the surface at the top of a column of fluid in a narrow tube is caused by the relative strength of the forces responsible for the surface tension of the fluid (cohesive forces) and the adhesive forces to the walls of the container.

• Medical Solutions: Colligative Properties

  • Cell membranes are permeable to water, so the osmolality of the extracellular fluid (ECF) is approximately equal to that of the intracellular fluid (ICF).