Sonochemical preparation and characterization of nanosized amorphous Co-Ni alloy powders

Kurikka V.P.M. Shafi, Aharon Gedanken, Ruslan Prozorov

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Abstract

Nanosized amorphous alloy powders of Co20Ni80 and Co50Ni50 have been prepared by sonochemical decomposition of solutions of volatile organic precursors, Co(NO)(CO)3 and Ni(CO)4 in decalin, under an argon pressure of 100 to 150 kPa, at 273 K. The amorphous nature of these particles was confirmed by various techniques, such as SEM, TEM, SAED, and XRD. A transmission electron micrograph of the heated Co20Ni80 sample showed near uniform particles with sizes less than 10 nm. Magnetic measurements indicated that the as-prepared amorphous CoNi alloy particles were superparamagnetic. The observed magnetization, measured up to a field of 15 kG, of the annealed Co20Ni80 sample (54 emu g-1) was significantly lower than that for the reported multidomain bulk particles (75 emu g-1), reflecting the ultrafine nature of our sample. Thermogravimetric measurements of Co20Ni80 with a permanent magnet yielded a glass transition temperature of 338°C for the amorphous form, and a Curie temperature of 565°C for the crystallized form. The differential scanning calorimetry showed crystallization temperatures of 400°C for Co20Ni80 and 365°C for Co50Ni50 amorphous samples.

Original languageEnglish
Pages (from-to)769-773
Number of pages5
JournalJournal of Materials Chemistry
Volume8
Issue number3
DOIs
StatePublished - 1998

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