METAL TAPES USING ULTRA FINE POWDER PREPARED BY GAS EVAPORATION METHOD

In the last decade, investigations of ultrafine powders prepared by the gas evaporation method have been carried out in Japan. Metals were evaporated in inert gases such as Xe or He or Ar. Ultra fine particles of 50 to 2000 A in diameter were precipitated like soot. The basic magnetic charctersties have already been reported in previous papers. The coercive force of ferromagnetic fine powders can be controlled by changing the constituents of the alloy up to 2500 Oe. Resistance heating, plasma jet, induction heating or LASER have been examined as evaporation heat sources. Viedo and Audio tapes were tested in Fuji Photo Film Co., Ltd. One of the typical tapes gave 12.8 dB higher output level at 5 MHz and 10.0 dB better C/N at 4.5 MHz compared with commercially available highest quality tape. Reduction of the saturation magnetization of the tape is 0% after being kept in the condition that 60°c, 90% R.H. for one week. Still frame is more than 30 minutes. © 1979 IEEE