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Barium-Strontium Ferrite Disc Magnet: 0.5 mol BaCO3, 0.5 mol SrCO3, 1260 °C (Went, Philips 1956, Ex. 28)
A ceramic magnet with both barium and strontium: 0.5 mol barium carbonate and 0.5 mol strontium carbonate to 3 mol iron oxide, milled 15 hours, pressed and passed through a 1260 °C furnace in 20 minutes. Went's rod held 1,665 gauss with a coercive force of 3,235 oersted.
Source: J. J. Went, G. W. van Oosterhout and E. W. Gorter (Philips), US 2,762,777 (1956), Example 28. 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 the carbonates and iron oxide
Weigh the carbonates and iron oxide
Weigh 99.2 g barium carbonate (0.5 mol), 73.8 g strontium carbonate (0.5 mol), 483.3 g ferric oxide (3 mol). Barium carbonate is poisonous if swallowed: gloves and a dust respirator.
Materials for this step:
Barium Carbonate (Witherite)99.2 g
Strontium Carbonate73.8 g
Ferric Oxide483.3 gTools needed:
Balance Scale
Rubber Gloves
P100 Respirator2
2
Mill with alcohol 15 hours, dry
Mill with alcohol 15 hours, dry
Grind the mixture with alcohol in a ball mill for 15 hours, then dry it.
Tools needed:
Iron Ball Mill
Ethanol - Lab Grade, 95%
Drying Oven3
3
Press the powder
Press the powder
Example 28 moulds a rod without giving the pressure. Ours: press discs at 1.5 tonnes per cm², the pressure of the patent's other examples.
Tools needed:
Hydraulic Press
Disc Pressing Die4
4
Pass through a 1260 °C zone in 20 minutes
Pass through a 1260 °C zone in 20 minutes
Sinter at 1260 °C by passing the pieces through a 10 cm hot zone at 5 mm per minute: 20 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- Placeholder
- 73.8 gPlaceholder
- 483.3 gPlaceholder
Tools Required
12- Placeholder
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