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Barium Ferrite Disc Magnet from Natural Magnetite, Ground Half an Hour Only (Went, Philips 1956, Ex. 36, Procedure 3)
A barium ferrite magnet from barium carbonate and natural magnetite, ground for half an hour only, pressed straight away and sintered 4 hours at 1200 °C. Went's rod held 1,345 gauss with a coercive force of 1,215 oersted.
Source: J. J. Went, G. W. van Oosterhout and E. W. Gorter (Philips), US 2,762,777 (1956), Example 36. 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 and magnetite
Weigh barium carbonate and magnetite
Weigh 9.9 g barium carbonate (0.05 mol) and 46.9 g natural magnetite, Fe3O4 (0.20 mol). Barium carbonate is poisonous if swallowed: gloves and a dust respirator.
Materials for this step:
Barium Carbonate (Witherite)9.9 g
Magnetite46.9 gTools needed:
Balance Scale
Rubber Gloves
P100 Respirator2
2
Grind half an hour in a ball mill
Grind half an hour in a ball mill
Grind the mixture in a ball mill for half an hour. The patent does not say whether wet or dry.
Tools needed:
Iron Ball MillP100 Respirator3
3
Press at 1.5 t/cm²
Press at 1.5 t/cm²
Press at 1.5 tonnes per cm² (ours: discs instead of a rod).
Tools needed:
Hydraulic Press
Disc Pressing Die4
4
Sinter at 1200 °C for 4 hours
Sinter at 1200 °C for 4 hours
Sinter at 1200 °C for 4 hours. The patent gives no atmosphere for this example. Went's rod: 1,345 gauss, 1,215 oersted.
Tools needed:
Muffle Furnace
Crucible Tongs
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
CompassTools Required
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