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Barium Ferrite Disc Magnet from Natural Magnetite, Presintered at 900 °C (Went, Philips 1956, Ex. 36, Procedure 1)
A barium ferrite magnet made from natural magnetite instead of ferric oxide: barium carbonate and magnetite ground 18 hours, presintered 3 hours at 900 °C, ground again 18 hours, pressed and sintered 2 hours at 1200 °C. Went's rod held 1,450 gauss with a coercive force of 2,425 oersted.
Source: J. J. Went, G. W. van Oosterhout and E. W. Gorter (Philips), US 2,762,777 (1956), Example 36. They sintered rods; discs and the magnetising are ours. Picture: ferrite magnets, Omegatron, Wikimedia Commons, CC BY-SA 3.0.
高级
2 days
说明
1
1
Weigh barium carbonate and magnetite
Weigh barium carbonate and magnetite
Weigh 9.9 g barium carbonate (0.05 mol) and 46.9 g natural magnetite, Fe3O4 (0.20 mol). Barium carbonate is poisonous if swallowed: gloves and a dust respirator.
此步骤所需材料：
碳酸钡（毒重石）9.9 克
磁铁矿46.9 克所需工具：
等臂天平
橡胶手套
P100 防毒面具2
2
Grind 18 hours in a ball mill
Grind 18 hours in a ball mill
Grind the mixture in a ball mill for 18 hours. The patent does not say whether wet or dry.
所需工具：
铁球磨机P100 防毒面具3
3
Presinter at 900 °C for 3 hours
Presinter at 900 °C for 3 hours
Fire the ground mixture at 900 °C for three hours and let it cool.
所需工具：
马弗炉
带盖坩埚（瓷质）
坩埚钳
耐热手套4
4
Grind 18 hours in a ball mill
Grind 18 hours in a ball mill
Grind it again in a ball mill for 18 hours. The patent does not say whether wet or dry.
所需工具：
铁球磨机P100 防毒面具5
5
Press at 1.5 t/cm²
Press at 1.5 t/cm²
Press at 1.5 tonnes per cm² (ours: discs instead of a rod).
所需工具：
液压机
圆片压模6
6
Sinter at 1200 °C for 2 hours
Sinter at 1200 °C for 2 hours
Sinter at 1200 °C for 2 hours. The patent gives no atmosphere for this example. Went's rod: 1,450 gauss, 2,425 oersted.
所需工具：
马弗炉坩埚钳耐热手套7
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.
所需工具：
电磁铁
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