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Barium Ferrite Disc Magnet, Sintered at 1200 °C (Went, Philips 1956)
Charlie

Imeundwa na

Charlie

28. Oktoba 2026DE
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Barium Ferrite Disc Magnet, Sintered at 1200 °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 1200 °C, where his rod held 1,400 gauss with a coercive force of 3,100 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.
Juu
2 days

Maagizo

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.

Vifaa kwa hatua hii:

Kabonati ya bariamu (witherite)Kabonati ya bariamu (witherite)39.5 g
Oksidi ya feriOksidi ya feri191.7 g

Zana zinazohitajika:

Mizani ya mizani-mbiliMizani ya mizani-mbili
Glavu za mpiraGlavu za mpira
Kinga ya Kupumua ya P100Kinga ya Kupumua ya 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.

Zana zinazohitajika:

Kinu cha mipira ya chumaKinu cha mipira ya chuma
Etanoli ya maabara, 95 %Etanoli ya maabara, 95 %
Tanuri la kukaushiaTanuri la kukaushia
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.

Zana zinazohitajika:

Tanuri ya muffleTanuri ya muffle
Kikaango cha kuyeyushia chenye mfuniko (kaure)Kikaango cha kuyeyushia chenye mfuniko (kaure)
Koleo la kaure ya kuyeyushiaKoleo la kaure ya kuyeyushia
Glavu Zinazostahimili JotoGlavu Zinazostahimili Joto
4

Mill again for 4 hours

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

Zana zinazohitajika:

Kinu cha mipira ya chumaKinu cha mipira ya chuma
Etanoli ya maabara, 95 %Etanoli ya maabara, 95 %
Tanuri la kukaushiaTanuri la kukaushia
Kinga ya Kupumua ya P100Kinga ya Kupumua ya 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).

Zana zinazohitajika:

Mashine ya kubana ya haidrolikiMashine ya kubana ya haidroliki
Kalibu ya kubana diskiKalibu ya kubana diski
6

Sinter 4 hours at 1200 °C

Sinter the discs for 4 hours at 1200 °C in oxygen or in air. The patent's rod at 1200 °C: 1,400 gauss and 3,100 oersted.

Zana zinazohitajika:

Tanuri ya muffleTanuri ya muffle
Koleo la kaure ya kuyeyushiaKoleo la kaure ya kuyeyushia
Glavu Zinazostahimili JotoGlavu Zinazostahimili Joto
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.

Zana zinazohitajika:

Sumaku ya umemeSumaku ya umeme
DiraDira

Vifaa

2

Zana Zinazohitajika

14

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