The effect of high temperature on the release of heavy metals from AgCdO and AgSnO/sub 2/ contacts

An experiment was undertaken to study the release of heavy metals from AgCdO and AgSnO/sub 2/ contacts when they were subjected to high temperatures similar to those that would occur in a fire. Samples of AgCdO ( approximately=15 wt.% CdO) and AgSnO/sub 2/ ( approximately=15 wt.% SnO/sub 2/) were placed in a furnace and heated for 1 h at temperatures ranging from 800 degrees C to 1240 degrees C. Cadmium was released from the AgCdO contact samples, but even at the highest temperature (1240 degrees C), only 8% of the original Cd was lost from the contact. In the case of AgSnO/sub 2/ no Sn was released, but a very small amount of Ag was captured from the heated contacts. The characteristics of fully developed fires were identified and the expected range of gas temperatures produced by these fires was estimated. The major conclusion of this study was that unless these contact materials were directly exposed to hot flames for long periods of time, very little heavy metal would be released into the environment during a fire.<
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