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Ferrite Toroid Core: Copper-Zinc Ferrite Sintered at 1200 °C, Presintered Three Times at 900 °C (Snoek 1948, Ex. I)
A soft ferrite ring core for coils and transformers: copper, zinc and iron oxides with a little brownstone, presintered three times at 900 °C, pressed into a ring and sintered at 1200 °C in oxygen. Snoek's ring had an initial permeability of 1,000.
Source: J. L. Snoek, US 2,452,530 (Philips, 1948), Example I and its table. Unknown: the 'violet' iron oxide, linked to an unknown head. Picture: the patent's Fig. 4, the ring core.
Advanced
2 days
Instructions
1
1
Weigh 20 : 30 : 50 mol % and 1 % brownstone
Weigh 20 : 30 : 50 mol % and 1 % brownstone
Mix 20 mol % pure copper oxide, 30 mol % pure zinc oxide and 50 mol % pure violet iron oxide, and add 1 % by weight of brownstone (manganese dioxide). Ours, by weight: 13.24 g copper oxide, 20.32 g zinc oxide and 66.44 g iron oxide per 100 g, plus 1 g brownstone. Unknown: what makes the iron oxide 'violet'; Snoek does not say.
Materials for this step:
Copper Oxide13.24 g
Zinc Oxide Powder20.32 g
Violet Iron Oxide66.44 g
Manganese Dioxide (Pyrolusite)1 gTools needed:
Balance Scale
Dust Mask2
2
Grind half an hour in an iron ball mill
Grind half an hour in an iron ball mill
Grind the mixture for half an hour in a mill with iron balls.
Tools needed:
Iron Ball MillDust Mask3
3
Presinter at 900 °C for 2 hours in oxygen
Presinter at 900 °C for 2 hours in oxygen
Heat the ground powder to 900 °C for 2 hours in oxygen and let it cool.
Tools needed:
Tube Furnace
Oxygen
Pressure Gas Cylinder
Pyrometer
Crucible with Lid (Porcelain)
Heat-Resistant Gloves4
4
Grind and presinter at 900 °C again (2 of 3)
Grind and presinter at 900 °C again (2 of 3)
Grind the powder, then heat it once more to 900 °C in oxygen. Snoek gives no times for the repeats.
Tools needed:
Iron Ball MillTube FurnaceOxygenPressure Gas CylinderCrucible with Lid (Porcelain)Heat-Resistant GlovesDust Mask5
5
Grind and presinter at 900 °C again (3 of 3)
Grind and presinter at 900 °C again (3 of 3)
Grind the powder, then heat it once more to 900 °C in oxygen. Snoek gives no times for the repeats.
Tools needed:
Iron Ball MillTube FurnaceOxygenPressure Gas CylinderCrucible with Lid (Porcelain)Heat-Resistant GlovesDust Mask6
6
Grind 2 hours with iron balls
Grind 2 hours with iron balls
Grind it for 2 hours in a disintegrator with iron balls.
Tools needed:
Iron Ball MillDust Mask7
7
Press a ring at 4 tons per cm²
Press a ring at 4 tons per cm²
Press the powder at 4 tons per square centimetre into a ring 3 cm across with a 4 × 4 mm cross-section.
Tools needed:
Hydraulic Press
Ring Pressing DieDust Mask8
8
Sinter at 1200 °C in oxygen, cool 5–10 °C a minute
Sinter at 1200 °C in oxygen, cool 5–10 °C a minute
Sinter the ring at 1200 °C in a current of oxygen. Example I heats for 1 hour and cools in the oxygen at 5 to 10 °C per minute. Snoek's ring had an initial permeability of 1,000, measured at room temperature at 2 kHz.
Tools needed:
Tube FurnaceOxygenPressure Gas CylinderPyrometer
Crucible TongsHeat-Resistant GlovesMaterials
4- 13.24 gPlaceholder
- 20.32 gPlaceholder
- 66.44 gPlaceholder
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Tools Required
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