Metal & Alloys

Metal & Alloys

1. Metals and Alloys

   • Alloy Examples
     • Mixtures containing one or more metal elements.
     • Brass (copper and zinc) used in musical instruments, coins and door knockers.
     • Amalgam (mercury) used for tooth fillings.
     • Solder (lead and tin) used to join electrical wires through soldering.
   • Alloy Properties
     • Can differ extremely from the elements that they are made from.
     • i.e. steel doesn't corrode anywhere near as much as iron.
   • Smart Alloys
     • Nitinol = family of nickel/titanium alloys.
       • Have shape memory, remember their original shape, even after being bent and twisted.
     • Increased the number of uses for alloys, get spectacle frames that return to their shape after being bent.
   • Copper
     • Extracted by heating its ore with carbon, but it isn't very pure.
     • Purified by copper electrolysis.
       • Needs to be purer to be used in electrical conductors, as the purer it is, the better it conducts.
   • Copper Electrolysis
     • Splitting up with electricity, splitting the impure copper from the pure copper.
     • Anode - impure copper.
     • Cathode - pure copper.
     • Copper (II) sulphate solution as the electrolyte, contains Cu2+ ions.
     • Anode loses mass, copper dissolves: Cu -> Cu2+ + 2e-.
     • Cathode gains mass, copper is deposisted: Cu2+ + 2e- -> Cu
     • Reduction as the cathode, electrons gained.
     • Oxidation at the anode, electrons lost.
     • Electrical supply acts like electron pump, pulls electrons of copper ions at the anode so they are now Cu2+ ions, offers electrons at cathode to Cu2+ ions.
       • Impurities dropped to the bottom, near the anode, as sludge.
     • Electrolyte: conducts electricity, usually free ions dissolved in water.
   • Pos/Neg Copper Purification
     • Cheaper to recycle copper than to mine and extract more.
     • Uses only 15% of energy needed to mine/extract the same amount.
     • Hard to convince people it's worth the effort, it takes time and energy to sort out copper from other materials.