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Barium-Calcium Ferrite Disc Magnet: 20 % Calcium, 5 Minutes at 1290 °C (Went, Philips 1956, Ex. 20)
A ceramic magnet with a fifth of the barium replaced by calcium: 0.08 mol barium carbonate, 0.02 mol calcium carbonate and 0.6 mol iron oxide, made as in Example 18 but sintered at 1290 °C for only 5 minutes. Went's rod held 1,615 gauss with a coercive force of 1,550 oersted.
Source: J. J. Went, G. W. van Oosterhout and E. W. Gorter (Philips), US 2,762,777 (1956), Example 20. They sintered rods; discs and the magnetising are ours. Picture: ferrite magnets, Omegatron, Wikimedia Commons, CC BY-SA 3.0.
Advanced
2 days
Instructions
1
1
Weigh barium carbonate, chalk and iron oxide
Weigh barium carbonate, chalk and iron oxide
Weigh 15.79 g barium carbonate (0.08 mol), 2.002 g calcium carbonate (0.02 mol) and 95.55 g ferric oxide (0.6 mol). Barium carbonate is poisonous if swallowed: gloves and a dust respirator.
Materials for this step:
Barium Carbonate (Witherite)15.79 g
Calcium Carbonate - Whiting2.002 g
Ferric Oxide95.55 gTools needed:
Balance Scale
Rubber Gloves
P100 Respirator2
2
Mill, presinter and mill as in Example 18
Mill, presinter and mill as in Example 18
As in Example 18: grind with alcohol 4 hours, dry at 150 °C, fire in air at 1000 °C for 2 hours, grind again 4 hours and dry.
Tools needed:
Iron Ball Mill
Ethanol - Lab Grade, 95%
Drying Oven
Muffle Furnace
Crucible with Lid (Porcelain)
Crucible Tongs3
3
Press at 1.5 t/cm²
Press at 1.5 t/cm²
Press at 1.5 tonnes per cm², as in Example 18 (ours: discs instead of rods).
Tools needed:
Hydraulic Press
Disc Pressing Die4
4
Pass through a 1290 °C zone in 5 minutes
Pass through a 1290 °C zone in 5 minutes
Sinter in air at 1290 °C by passing the pieces through a 10 cm hot zone at 20 mm per minute: 5 minutes in the heat.
Tools needed:
Tube Furnace
Heat-Resistant Gloves5
5
Magnetise the discs
Magnetise the discs
The patent gives no magnetising method. Ours: lay a disc with its faces against the poles of a strong electromagnet, switch the current on, then off. Find which face is north with a compass.
Tools needed:
Electromagnet
CompassMaterials
3- 15.79 gPlaceholder
- 2.002 gPlaceholder
- 95.55 gPlaceholder
Tools Required
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