Oxidation of Fe-7Cr-12Ni-(0-6)Al-(0-7)Si alloys

A series of Fe-7Cr-12Ni-(0-6)Al-(0-7)Si alloys was oxidized at test temperatures between 800° and 1000 °C. The master alloy, Fe-7Cr-12Ni, had no oxidation resistance at temperatures above 800 °C. Aluminum additions to the master alloy produced a protective A1₂O₃ layer over the substrate metal which prevented rapid oxidation and allowed time for a Cr₂O₃ layer to develop underneath. Silicon addition to the master alloy produced an SiO₂ oxide sublayer at the metal-oxide interface which, when formed, provided an effective barrier to oxidation. A combination of 1.5-pct-Al and 2.0-pct-Si additions provided the best oxidation protection.     

Letter: Gravigard (copper 7) IUCD

In response to a reported incidence of 18 pregnancies in 311 insertions the author tells of experience of 48 insertions of the Gravigard with an absence of pregnancies, expulsions, and only 2 removals for excessive bleeding. There are always a number of variable factors involved in such insertions. The continuation rate of 52.1% for this device compares favorably with insertion of the Dalkon shield performed by the same individual. In inserting the IUD a uterine sound is passed and the length of the cervical canal measured. The device is then inserted and the uterine sound passed again in order to check the p lacement of the device.