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Barium-Calcium Ferrite Disc Magnet: Equal Barium and Calcium, Sintered at 1280 °C (Went, Philips 1956, Ex. 22)
A ceramic magnet with equal parts barium and calcium: 0.3 mol barium carbonate, 0.3 mol calcium carbonate and 3.1 mol iron oxide, milled 15 hours, pressed and passed through a 1280 °C furnace in 10 minutes, with no presintering. Went's rod held 1,595 gauss with a coercive force of 1,890 oersted.
Source: J. J. Went, G. W. van Oosterhout and E. W. Gorter (Philips), US 2,762,777 (1956), Example 22. 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 59.5 g barium carbonate (0.3 mol), 30.2 g calcium carbonate (0.3 mol) and 500.0 g ferric oxide (3.1 mol). Barium carbonate is poisonous if swallowed: gloves and a dust respirator.
Materials for this step:
Barium Carbonate (Witherite)59.5 g
Calcium Carbonate - Whiting30.2 g
Ferric Oxide500 gTools needed:
Balance Scale
Rubber Gloves
P100 Respirator2
2
Mill with alcohol 15 hours, dry, press
Mill with alcohol 15 hours, dry, press
Grind with alcohol in a ball mill for 15 hours, dry, and press at 1.5 tonnes per cm² (ours: discs instead of rods). No presintering.
Tools needed:
Iron Ball Mill
Ethanol - Lab Grade, 95%
Drying Oven
Hydraulic Press
Disc Pressing Die3
3
Pass through a 1280 °C zone in 10 minutes
Pass through a 1280 °C zone in 10 minutes
Sinter at 1280 °C by passing the pieces through a 10 cm hot zone at 10 mm per minute: 10 minutes in the heat.
Tools needed:
Tube Furnace
Heat-Resistant Gloves4
4
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
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- 500 gPlaceholder
Tools Required
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