Unit – II D

Solid Solutions:

Solid Solutions (Alloys):

  • A solid solution of two or more metals or metal or metals with one or more non-metal is called an alloy.
  • Primarily there are two types of solid solutions

    Substitutional:

    Solute atoms occupy the regular lattice sites of the parent metal (solvent). Substitutional solid solutions can be random (Cu-Ni) or ordered (Cu-Au).

    Interstitial:

    Solute atoms occupy the interstitial positions (Steel – C solute atoms in Fe) .



Examples of Alloys:

Duralumin:

  • Composition: Aluminum, copper, manganese, magnesium.
  • Uses: aircraft, boats, railroad cars, and machinery because of its high strength and resistance to corrosion

Aluminium bronze:

  • Composition: Aluminum, copper, manganese
  • Uses: heavy duty sleeve bearings, and machine tool ways. Aluminum bronze castings have exceptional corrosion resistance, high strength, toughness and wear resistance and good casting and welding characteristics.

Hardened Lead:

  • Composition:10 to 20 % antimony
  • Uses: bearings, bullets and shrapnel

Stainless Steel:

  • Composition: Iron, chromium, nickel
  • Uses: Cutlery, surgical instruments, utensils

Spiegeleisen:

  • Composition: Iron and 5 to 20 % manganese
  • Uses: Very hard hence used for making rails, safes and heavy machinery.

Ferromanganeous:

  • Composition: Iron and 70 to 80 % manganese
  • Uses: Very hard hence used for making rails, safes and heavy machinery.

Manganin:

  • Composition: I84 % Cu, 12 % Mn, 4% Ni
  • Uses: electrical measurement instrument due to zero temperature coefficient of resistance.

Amalgams:

  • Alloys of mercury with other metals are called amalgams.
  • This property of mercury is used for extraction of metals like silver and gold from their ores. These metals are further recovered by distillation of mercury.


Problems:

  1. What is the concentration of dissolved oxygen at 25 °C at 1-atmosphere pressure if the partial pressure of oxygen is 0.22 atm? The henry’s law constant for oxygen is 1.3 × 10-5 mol dm-3 atm-1.
  2. The solubility of nitrogen gas at 1 atm pressure at 25 °C is 6.8 × 10-4 mol dm-3. Calculate the solubility of N2 gas from the atmosphere at 25 °C if the atmospheric pressure is 1 atmosphere and partial pressure of N2 gas at this temperature and pressure is 0.78 atm.

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