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Barium Ferrite Disc Magnet, Sintered at 1300 °C (Went, Philips 1956)
Charlie

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Charlie

28. Ukwakira 2026DE
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Barium Ferrite Disc Magnet, Sintered at 1300 °C (Went, Philips 1956)

The dark grey ceramic magnet on fridges and in loudspeakers is barium ferrite. It is made from two cheap powders: one part barium carbonate to six of iron oxide, milled, fired, milled again, pressed and sintered. No cobalt or nickel is needed. This is Example 34 of the Philips patent. This iteration sinters at 1300 °C, where his rod held 1,850 gauss with a coercive force of 1,780 oersted. Source: J. J. Went, G. W. van Oosterhout and E. W. Gorter (Philips), US 2,762,777 (1956). They pressed rods; the claim covers "a body of a desired shape", and the disc size is ours. The patent does not say how to magnetise it; our way is stated. Picture: ferrite magnets, Omegatron, Wikimedia Commons, CC BY-SA 3.0.
Hejuru
2 days

Amabwiriza

1

Weigh one part barium carbonate to six of iron oxide

Weigh 39.5 g of barium carbonate (0.2 mol) and 191.7 g of ferric oxide, Fe2O3 (1.2 mol). Barium carbonate is poisonous if swallowed: ours, gloves and a dust respirator.

Ibikoresho by'iyi ntambwe:

Karubonate ya bariyumu (witerite)Karubonate ya bariyumu (witerite)39.5 g
Oxide ya feriOxide ya feri191.7 g

Ibikoresho bikenewe:

Umunzani w'ibiroUmunzani w'ibiro
Uturindantoki tw'ikawusuUturindantoki tw'ikawusu
Agapfukamunwa ka P100Agapfukamunwa ka P100
2

Mill with ethanol for 4 hours

Grind the mixture with ethanol in an iron ball mill for 4 hours. Let the ethanol evaporate, then dry the powder in a drying oven.

Ibikoresho bikenewe:

Urusyo rw'imipira y'icyumaUrusyo rw'imipira y'icyuma
Etanoli - urwego rw'ubushakashatsi, 95 %Etanoli - urwego rw'ubushakashatsi, 95 %
Ifuru yo kumishahoIfuru yo kumishaho
3

Presinter at 1000 °C for 4 hours

Fire the dry powder in air at 1000 °C for 4 hours (ours: in a lidded porcelain crucible in a muffle furnace). Let it cool.

Ibikoresho bikenewe:

Ifuru ya muffleIfuru ya muffle
Ikirundo cyo gushongeramo gifite igifuniko (porukorene)Ikirundo cyo gushongeramo gifite igifuniko (porukorene)
Amakoro y'Icyombo GishongeshaAmakoro y'Icyombo Gishongesha
Uturindantoki twihanganira ubushyuheUturindantoki twihanganira ubushyuhe
4

Mill again for 4 hours

Grind the presintered product with ethanol in the ball mill for another 4 hours. Let the ethanol evaporate.

Ibikoresho bikenewe:

Urusyo rw'imipira y'icyumaUrusyo rw'imipira y'icyuma
Etanoli - urwego rw'ubushakashatsi, 95 %Etanoli - urwego rw'ubushakashatsi, 95 %
Ifuru yo kumishahoIfuru yo kumishaho
Agapfukamunwa ka P100Agapfukamunwa ka P100
5

Press discs at 1.5 tons per cm²

Press the powder at 1.5 tons/cm². The patent pressed rods; we press discs. Ours: a die 20 mm across, so about 4.7 tonnes on the punch (our arithmetic: 1.5 × 3.14 cm²).

Ibikoresho bikenewe:

Imashini ikanda ikoresha amaziImashini ikanda ikoresha amazi
Ifumbiro ryo gukanda disikiIfumbiro ryo gukanda disiki
6

Sinter 4 hours at 1300 °C

Sinter the discs for 4 hours at 1300 °C in oxygen or in air. The patent's rod at 1300 °C: 1,850 gauss and 1,780 oersted.

Ibikoresho bikenewe:

Ifuru ya muffleIfuru ya muffle
Amakoro y'Icyombo GishongeshaAmakoro y'Icyombo Gishongesha
Uturindantoki twihanganira ubushyuheUturindantoki twihanganira ubushyuhe
7

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.

Ibikoresho bikenewe:

Iroha ry'amashanyaraziIroha ry'amashanyarazi
IkirangamurongoIkirangamurongo

Ibikoresho

2

Ibikoresho bikenewe

14

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