Properties of nickel-zinc ferrites produced by shock hot working

Abstract

It is shown that 1000 NN nickel-zinc ferrite blanks produced by the process proposed, consisting of SHW and annealing, are characterized by high density (γ=5.26 Mg/m3) and a high level of magnetic characteristics (μi of up to 1850·10−6 H/m, Bm=0.27–0.32 T, and HC=8–16 A/m). The optimum parameters of the production process proposed, ensuring the best combination of the key magnetic and structural characteristics in 1000 NN ferrites, are a hot-working temperature of 1150–1200°C, an annealing temperature of 1200°C, and an annealing time of 5–10 h. The cause of a fall in density and of a deterioration in magnetic characteristics (μi and Bm) brought about by raising the temperature and increasing the duration of annealing are examined. The hypothesis is advanced that such changes in properties are due to a secondary pore formation process, which is linked with steady gas evolution accompanying the decomposition of some components of the ferrites.