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Strontium Ferrite Disc Magnet: 1 mol SrCO3 to 3 mol Iron Oxide, 1220 °C (Went, Philips 1956, Ex. 10)
A strontium ferrite: 1 mol strontium carbonate to 3 mol iron oxide, milled, bound and formed as in Example 4, and passed through a 1220 °C furnace in 10 minutes. Went's rod held 1,790 gauss with a coercive force of 3,260 oersted.
Source: J. J. Went, G. W. van Oosterhout and E. W. Gorter (Philips), US 2,762,777 (1956), Example 10. 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 strontium carbonate and iron oxide
Weigh strontium carbonate and iron oxide
Weigh 147.6 g strontium carbonate (1 mol) and 484.1 g ferric oxide (3 mol).
Materials for this step:
Strontium Carbonate147.6 g
Ferric Oxide484.1 gTools needed:
Balance Scale
P100 Respirator2
2
Mill with alcohol 15.5 hours, dry and sieve
Mill with alcohol 15.5 hours, dry and sieve
As in Example 4: grind the mixture with alcohol in a ball mill for 15.5 hours, then dry it and sieve it.
Tools needed:
Iron Ball Mill
Ethanol - Lab Grade, 95%
Drying Oven
Sieve3
3
Knead with a binder and form
Knead with a binder and form
Mix 300 g of the powder with a binder such as polyvinyl alcohol (Went names it or nitrocellulose) into a kneadable mass. The patent extrudes rods about 3 mm across; ours: press discs at 1.5 tonnes per cm², as in its other examples. Dry them in air for about 24 hours.
Tools needed:
Polyvinyl Alcohol Powder
Hydraulic Press
Disc Pressing DieDrying Oven4
4
Pass through a 1220 °C zone in 10 minutes
Pass through a 1220 °C zone in 10 minutes
Sinter in air at 1220 °C by passing the pieces through a 10 cm hot zone at 10 mm per minute: 10 minutes in the heat.
Tools needed:
Tube Furnace
Heat-Resistant Gloves5
5
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
2- 147.6 gPlaceholder
- 484.1 gPlaceholder
Tools Required
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