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Metal Oxide Varistor: Pure Zinc Oxide at 1150 °C, Bismuth Oxide Paste Fired at 800 °C (Masuyama 1972, Ex. 4)
A varistor made the other way round: a disc of pure zinc oxide, sintered, with bismuth oxide fired into its faces from a paste instead of mixed in. Sintered at 1150 °C and fired with the paste at 800 °C, the disc measured a C-value of 170 at 1 mA and a nonlinearity exponent n of 7.8. Masuyama found that firing on the bismuth oxide paste raises n a great deal over mixing it in.
Source: T. Masuyama, M. Matsuoka and T. Nishi (Matsushita), US 3,663,458 (1972), Example 4. Unknown: what the silver paint is, and how strong the epoxy solution of the paste is. The spraying is ours, after US Army Corps of Engineers EM 1110-2-3401 (1999). The 10 g batch is our arithmetic. Picture: the patent's drawing.
Ilọsíwájú
2 days
Ìlànà
1
1
Press pure zinc oxide at 340 kg/cm²
Press pure zinc oxide at 340 kg/cm²
Press zinc oxide powder at 340 kg/cm². Example 4 gives no disc size; ours: discs 13 mm across and 2.5 mm thick in the mould of Example 1.
Àwọn ohun èlò fún ìgbésẹ̀ yìí:
Lulú Sínkì Ọ́ksídì1 as requiredÀwọn irinṣẹ́ tí a nílò:
Òǹwọ̀n ìdọ́gba
Ẹ̀rọ ìtẹ̀ háídírọ́líìkì
Mọ́ọ̀dù títẹ díìsì
Kálípà Fáníà2
2
Sinter 1 hour at 1150 °C and cool
Sinter 1 hour at 1150 °C and cool
Heat the pressed disc for 1 hour at 1150 °C, then let it cool to room temperature.
Àwọn irinṣẹ́ tí a nílò:
Ààrò muffle3
3
Lap both faces
Lap both faces
Lap both faces with silicon carbide abrasive. Example 4 gives no thickness.
Àwọn irinṣẹ́ tí a nílò:
Kálípà Fáníà4
4
Coat with bismuth oxide paste and fire at 800 °C
Coat with bismuth oxide paste and fire at 800 °C
Coat both lapped faces with a paste of 50 % by weight bismuth oxide in a solution of epoxy resin in butyl alcohol, and fire it in air at 800 °C for 30 minutes. The bismuth oxide diffuses into the zinc oxide. Not given: how much paste, or the strength of the epoxy solution.
Àwọn ohun èlò fún ìgbésẹ̀ yìí:
Bismuth oxide1 as requiredÀwọn irinṣẹ́ tí a nílò:
Resini epoxy
n-Butanol
Ààrò muffle5
5
Spray aluminium electrodes and attach leads
Spray aluminium electrodes and attach leads
Spray a metallised film of aluminium on both faces. Attach a lead wire to each with conductive silver paint, as in Example 1. Ours, after US Army Corps of Engineers EM 1110-2-3401 (1999): wire-arc spray the aluminium from two 3.2 mm wires melted by an 18-40 V DC arc and atomised by compressed air, 15-20 cm from the disc and never at less than 45°, in at least two coats at right angles of 50-75 µm each. Unknown: the paint.
Àwọn ohun èlò fún ìgbésẹ̀ yìí:
Ìṣù aluminiọ̀mù1 as 3.2 mm spray wire
Kùn fàdákà tí ń gba iná mànàmáná1 as required
Okùn Bàbà2 ẹyọÀwọn irinṣẹ́ tí a nílò:
Kálípà Fáníà
Ìbọn ìfọ́nká iná-ọ̀run wáyà
Ohun ìtẹ̀ afẹ́fẹ́ ti iléeṣẹ́Àwọn ohun-èlò
5- 1 as requiredÀyè
- 1 as requiredÀyè
- 1 as 3.2 mm spray wireÀyè
- 1 as requiredÀyè
- 2 ẹyọÀyè
Àwọn irinṣẹ́ tó nílò
10- Àyè
- Àyè
- Àyè
- Àyè
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