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Strontium Ferrite Disc Magnet: 0.7 mol SrCO3 to 3.2 mol Iron Oxide, 1280 °C (Went, Philips 1956, Ex. 12)
A strontium ferrite: 0.7 mol strontium carbonate to 3.2 mol iron oxide, milled, bound and formed as in Example 4, and passed through a 1280 °C furnace in 10 minutes. Went's rod held 1,955 gauss with a coercive force of 2,900 oersted.
Source: J. J. Went, G. W. van Oosterhout and E. W. Gorter (Philips), US 2,762,777 (1956), Example 12. 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 103.3 g strontium carbonate (0.7 mol) and 503.0 g ferric oxide (3.2 mol).
Materials for this step:
Strontium Carbonate103.3 g
Ferric Oxide503 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 1280 °C zone in 10 minutes
Pass through a 1280 °C zone in 10 minutes
Sinter in air at 1280 °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- 103.3 gPlaceholder
- 503 gPlaceholder
Tools Required
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