New Replica Method for Powders of Active Materials

Abstract

There is descrived an improved method of surface replica suitable for observation of active pulverous materials, which are unstable in the atmosphere.
The process is as follows; (1) SiO is obliquely evaporated onto the specimen from two evaporating sources placed at the symetric positions for the center of the specimen in a high vacuum. (2) The specimen is exposed slowly to the atmosphere. (3) SiO evaporated specimen is molded with plastics applying rather light pressure without deep entrance of plastics into the powder. (4) Specimen are dissolved away chemically. (5) Disconnected SiO films which is fixed on the smooth surface of plastics are reinforced with thin film of evaporated carbon. These composite replica films are treated as usual.
This method is successfully applied to the study of the thermal decomposition, of oxide coated cathodes, and the crystal growth during the heat treatment is observed.
The resolution of this reprica is estimated to about 200Å or better from the measurement of a minimum separation of striations. Critical conditions for this method are briefly discussed.