銅超微粉の真空焼結における脱ガスと緻密化との関係

抄録

Sintering characteristics and structure changes were examined for the oxidized (slow oxidation treated) Cu and fresh (not slow oxidation treated) Cu ultrafine powders.
Shrinkage of the compacts was observed at temperatures of 400-500 K, and it was considered to be the result of rearrangement of ultrafine powders accompanied by the extreme desorption of H₂O and CO₂ gases. The specific surface areas of the oxidized powders increased and took the maximum value at apploximately 420 K, which was also considered by the gas desorption.
Expansion of the compacts was obsereved for the oxidized powders at temperatures of 473-673 K, while densification occurred for the fresh ultrafine powders at temperatures above 573 K. These different characteristics were explained by the difference in amount of the produced Cu₂O.
Grain growth of the oxidized ultrafine powders was not observed at temperatures below 673 K, while large grain growth was observed at 623 K for the fresh powders. These results showed that the oxide phase depressed the grain growth of ultrafine powders.
The desorption occurred significantly at temperatures above 400 K especially for the oxidized powders. The desorbed gases were mainly carbon dioxide and water. The oxidation reaction was considered to be due to the adsorbed oxygen and water.