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Phase Diagrams. Reading Phase Diagrams. Describing Phase Diagrams. Phase Boundary (boundary between phases) Triple Point (when three phases co-exist) Critical Point (where the properties of two phases become indistinguishable from each other) Fusion/Melting (s l)
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Describing Phase Diagrams Phase Boundary (boundary between phases) Triple Point (when three phases co-exist) Critical Point (where the properties of two phases become indistinguishable from each other) Fusion/Melting (s l) Evaporation (l g) Condensation (g l) Sublimation (s g) Desublimation (g s) and Freezing( l s)
Phase Diagram of H2O Supercritical phase Critical point
Supercritical Water Beyond the critical point in the liquid-vapor space, water is supercritical existing as small but liquid-like hydrogen-bonded clusters dispersed within a gas-like phase
Supercritical Water The properties of supercritical water are very different from ambient water. For example, supercritical water is a poor solvent for electrolytes; however, it is such an excellent solvent for non-polar molecules, due to its low dielectric constant and poor hydrogen bonding, that many organic substances are completely miscible.
Supercritical Systems Supercritical carbon dioxide is used to extract molecules from plants for pharmaceuticals. Supercritical water is used to remove toxic waste from contaminated soil. And some believe supercritical fluids could be used to extract magnesium from rocks on Mars to make rocket fuel.
Phase Diagram of UF6Name the name of the process in the boxes UF6
Crystallography crystalline (non-amorphous) Powder (amorphous)
Single crystal diffractometry Video recorder N2(liq or gas) injector CCD Detector
Bragg’s Law nl = 2d sinq (1) l =1.54Å (of X-ray) Rays striking atoms in the second layer travel a distance equal to BC +CB' farther than rays striking atoms in the first layer. If this distance is a whole number of wavelengths, the reflected rays are in-phase and interfere constructively. Knowing the angle q then makes it possible to calculate the distance d between the layers.
Crystal Packing Crystals are three dimensional ordered structures than can be described as a repetition of identical unit cells. The unit cell is made up of the smallest possible volume that when repeated, is representative of the entire crystal. Unit Cell
The dimensions of a unit cell can be described with 3 edge lengths (a,b,c) and 3 angles (alpha, beta, gamma).
YBa2Cu3O7+x Superconductivity is the tendency of a material to conduct electricity without any resistance . Meissner Effect
1X10-9 m = 1 E-9 m= 1 nm = 10 Å = 1000 pm NaCl Calculate density in g/cm3
Calculate the cell edge length in pm of the unit cell of Cu, which crystallizes in Face Center Cube lattice and has a density of 8.96g/cm3