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Strontium Ferrite Disc Magnet: Presintered at 1100 °C, 0.2 mol SrCO3 to 1.1 mol Iron Oxide (Went, Philips 1956, Ex. 7)
A strontium ferrite: 0.2 mol strontium carbonate to 1.1 mol iron oxide, dried, milled, presintered 3.5 hours at 1100 °C, bound, formed and passed through a 1280 °C furnace in 10 minutes. Went's rod held 2,155 gauss with a coercive force of 2,500 oersted.
Source: J. J. Went, G. W. van Oosterhout and E. W. Gorter (Philips), US 2,762,777 (1956), Example 7. 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 29.5 g strontium carbonate (0.2 mol) and 176.1 g ferric oxide (1.1 mol).
Materials for this step:
Strontium Carbonate29.5 g
Ferric Oxide176.1 gTools needed:
Balance Scale
P100 Respirator2
2
Dry at 200 °C, mill with alcohol 4 hours
Dry at 200 °C, mill with alcohol 4 hours
Dry the mixture at 200 °C, then grind it with alcohol in a ball mill for 4 hours and dry it.
Tools needed:
Drying Oven
Iron Ball Mill
Ethanol - Lab Grade, 95%3
3
Presinter in air at 1100 °C for 3.5 hours
Presinter in air at 1100 °C for 3.5 hours
Fire the powder in air at 1100 °C for about 3.5 hours.
Tools needed:
Muffle Furnace
Crucible with Lid (Porcelain)
Crucible Tongs
Heat-Resistant Gloves4
4
Add a binder and form, dry overnight
Add a binder and form, dry overnight
Add a binder as in Example 1 (polyvinyl alcohol or nitrocellulose). The patent extrudes rods; ours: press discs at 1.5 tonnes per cm². Dry overnight.
Tools needed:
Polyvinyl Alcohol Powder
Hydraulic Press
Disc Pressing DieDrying Oven5
5
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 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
2- 29.5 gPlaceholder
- 176.1 gPlaceholder
Tools Required
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