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Barium-Calcium Ferrite Disc Magnet: Part of the Barium Replaced by Calcium (Went, Philips 1956, Ex. 21)
A ceramic magnet in which part of the barium is replaced by calcium: 0.06 mol barium carbonate and 0.04 mol calcium carbonate to 0.6 mol iron oxide, milled, fired in oxygen, milled again, pressed and passed quickly through a hot furnace. Went's rod held 1,660 gauss with a coercive force of 1,210 oersted.
Source: J. J. Went, G. W. van Oosterhout and E. W. Gorter (Philips), US 2,762,777 (1956), Example 21. 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
1
Weigh barium carbonate, chalk and iron oxide
Weigh barium carbonate, chalk and iron oxide
Weigh 11.84 g barium carbonate (0.06 mol), 4.004 g calcium carbonate (0.04 mol) and 99.55 g ferric oxide (0.6 mol). Barium carbonate is poisonous if swallowed: gloves and a dust respirator.
Materials for this step:
Barium Carbonate (Witherite)11.84 g
Calcium Carbonate - Whiting4.004 g
Ferric Oxide99.55 gTools needed:
Balance Scale
Rubber Gloves
P100 Respirator2
2
Mill with alcohol 4 hours and dry
Mill with alcohol 4 hours and dry
Grind the mixture with alcohol in a ball mill for 4 hours, then dry it.
Tools needed:
Iron Ball Mill
Ethanol - Lab Grade, 95%
Drying Oven3
3
Presinter in oxygen at 1000 °C for 2 hours
Presinter in oxygen at 1000 °C for 2 hours
Fire the dry powder in oxygen at 1000 °C for 2 hours (ours: a tube furnace fed from an oxygen cylinder).
Tools needed:
Tube Furnace
Oxygen
Pressure Gas Cylinder
Heat-Resistant Gloves4
4
Mill again 4 hours, dry, press at 1.5 t/cm²
Mill again 4 hours, dry, press at 1.5 t/cm²
Grind with alcohol in the ball mill for 4 hours, dry, and press at 1.5 tonnes per cm² (ours: discs instead of rods).
Tools needed:
Iron Ball MillEthanol - Lab Grade, 95%Drying Oven
Hydraulic Press
Disc Pressing Die5
5
Pass through a 1200 °C zone in 10 minutes
Pass through a 1200 °C zone in 10 minutes
Sinter at 1200 °C by passing the pieces through a 10 cm hot zone at 10 mm per minute, which is 10 minutes in the heat.
Tools needed:
Tube FurnaceHeat-Resistant Gloves6
6
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.
Tools needed:
Electromagnet
CompassMaterials
3- 11.84 gPlaceholder
- 4.004 gPlaceholder
- 99.55 gPlaceholder
Tools Required
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