Difference between revisions of "20.109(F07): Phage by design, pt2"
From Course Wiki
MAXINE JONAS (Talk | contribs) m (23 revisions: Transfer 20.109(F07) to HostGator) |
|||
(One intermediate revision by one user not shown) | |||
Line 1: | Line 1: | ||
{{Template:20.109(F07)}} | {{Template:20.109(F07)}} | ||
==Introduction== | ==Introduction== | ||
− | Electrodeposition is a commonly used technique in which current is applied to layer one material, usually a metal, onto another.[[Image:200px-1937-Wheat-Penny-Front-Back.jpg|thumb|left|Wikipedia's image of an all-copper penny from 1937]] Modern pennies may be the most pervasive example of electrodeposition though older ones tucked away in piggy banks are not. Pennies used to be made of pure or nearly pure copper, but in 1982 when the price of copper increased and an all-copper penny had more than a | + | Electrodeposition is a commonly used technique in which current is applied to layer one material, usually a metal, onto another.[[Image:200px-1937-Wheat-Penny-Front-Back.jpg|thumb|left|Wikipedia's image of an all-copper penny from 1937]] Modern pennies may be the most pervasive example of electrodeposition though older ones tucked away in piggy banks are not. Pennies used to be made of pure or nearly pure copper, but in 1982 when the price of copper increased and an all-copper penny had more than a penny s worth of copper in it, a new kind of cent coin was minted. Post-1982 pennies are made with an inexpensive metal (zinc) that is covered with a thin copper-coat. [[Image:EarFlaresWithCondors giltcopper.jpg|thumb|right|Pair of earflares with condors from Loma Negra, Pirua Valley, 2nd-3rd century, The Metropolitan Museum of Art photo credit:web.site@metmuseum.org.]]The coating is applied using the positive terminal of a power supply to oxidize the material on the anode (a lump of copper in the case of pennies), allowing it to react with anions in solution. At the cathode, the material gets reduced (i.e. gains electrons), regains its zero valence state and is deposited on the cathode surface (i.e. zinc if we re still talking pennies). The electrolytes solution that carries the anode material to the cathode is often made from very nasty chemicals like cyanides since these are great conductors and prevent corrosion of the anode. An active search for |