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KEJURUTERAAN TERBALIK
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TEKNOLOGI
BOLEH PAKAI
Barium Ferrite Disc Magnet: Barium Carbonate and Iron Oxide Sintered (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. Fired 4 hours at 1100 °C, its rod held 1,375 gauss with a coercive force of 3,350 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.
Lanjutan
2 days
Arahan
1
1
Weigh one part barium carbonate to six of iron oxide
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.
Bahan untuk langkah ini:
Barium karbonat (witherit)39.5 g
Ferik Oksida191.7 gAlatan diperlukan:
Neraca dua piring
Sarung tangan getah
Alat Pernafasan P1002
2
Mill with ethanol for 4 hours
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.
Alatan diperlukan:
Kilang Bebola Besi
Etanol mutu makmal, 95 %
Ketuhar pengeringan3
3
Presinter at 1000 °C for 4 hours
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.
Alatan diperlukan:
Relau Muffle
Mangkuk pijar bertutup (porselin)
Penyepit Mangkuk Pijar
Sarung Tangan Tahan Haba4
4
Mill again for 4 hours
Mill again for 4 hours
Grind the presintered product with ethanol in the ball mill for another 4 hours. Let the ethanol evaporate.
Alatan diperlukan:
Kilang Bebola BesiEtanol mutu makmal, 95 %Ketuhar pengeringanAlat Pernafasan P1005
5
Press discs at 1.5 tons per cm²
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).
Alatan diperlukan:
Mesin tekan hidraulik
Acuan tekan cakera6
6
Sinter for 4 hours
Sinter for 4 hours
Sinter the discs for 4 hours in oxygen or in air. The patent's results: at 1100 °C, 1,375 gauss and 3,350 oersted; at 1200 °C, 1,400 and 3,100; at 1300 °C, 1,850 and 1,780. Hotter gives a stronger but less stubborn magnet.
Alatan diperlukan:
Relau MufflePenyepit Mangkuk PijarSarung Tangan Tahan Haba7
7
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.
Alatan diperlukan:
Elektromagnet
KompasBahan
2- Pemegang Tempat
- 191.7 gPemegang Tempat
Alatan Diperlukan
14- Pemegang Tempat
- Pemegang Tempat
- Pemegang Tempat
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- Pemegang Tempat
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- Pemegang Tempat
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