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Barium-Calcium Ferrite Disc Magnet: 0.09 mol BaCO3 and 0.01 mol CaCO3 (Went, Philips 1956, Ex. 19)
Charlie

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Charlie

28. October 2026DE
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Barium-Calcium Ferrite Disc Magnet: 0.09 mol BaCO3 and 0.01 mol CaCO3 (Went, Philips 1956, Ex. 19)

A ceramic magnet with a tenth of the barium replaced by calcium: 0.09 mol barium carbonate and 0.01 mol calcium carbonate to 0.6 mol iron oxide, made as in Example 18: milled, presintered at 1000 °C, milled again, formed and passed through a 1330 °C furnace in 10 minutes. Went's rod held 1,705 gauss with a coercive force of 1,110 oersted. Source: J. J. Went, G. W. van Oosterhout and E. W. Gorter (Philips), US 2,762,777 (1956), Example 19. 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

Weigh barium carbonate, chalk and iron oxide

Weigh 17.76 g barium carbonate (0.09 mol), 1.001 g calcium carbonate (0.01 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)Barium Carbonate (Witherite)17.76 g
Calcium Carbonate - WhitingCalcium Carbonate - Whiting1.001 g
Ferric OxideFerric Oxide95.55 g

Tools needed:

Balance ScaleBalance Scale
Rubber GlovesRubber Gloves
P100 RespiratorP100 Respirator
2

Mill with alcohol 4 hours, dry at 150 °C

Grind with alcohol in a ball mill for 4 hours and dry in air at 150 °C.

Tools needed:

Iron Ball MillIron Ball Mill
Ethanol - Lab Grade, 95%Ethanol - Lab Grade, 95%
Drying OvenDrying Oven
3

Presinter in air at 1000 °C for 2 hours

Fire in air at 1000 °C for 2 hours.

Tools needed:

Muffle FurnaceMuffle Furnace
Crucible with Lid (Porcelain)Crucible with Lid (Porcelain)
Crucible TongsCrucible Tongs
Heat-Resistant GlovesHeat-Resistant Gloves
4

Mill again 4 hours, dry, form

Grind again with alcohol for 4 hours and dry. Example 19 extrudes a rod; ours: press discs at 1.5 tonnes per cm², as Example 18 moulds its rod.

Tools needed:

Iron Ball MillIron Ball Mill
Ethanol - Lab Grade, 95%Ethanol - Lab Grade, 95%
Drying OvenDrying Oven
Hydraulic PressHydraulic Press
Disc Pressing DieDisc Pressing Die
5

Pass through a 1330 °C zone in 10 minutes

Sinter at 1330 °C by passing the pieces through a 10 cm hot zone at 10 mm per minute: 10 minutes in the heat.

Tools needed:

Tube FurnaceTube Furnace
Heat-Resistant GlovesHeat-Resistant Gloves
6

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:

ElectromagnetElectromagnet
CompassCompass

Materials

3

Tools Required

15

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