TY - JOUR
T1 - Sonochemical preparation and characterization of nanosized amorphous Co-Ni alloy powders
AU - Shafi, Kurikka V.P.M.
AU - Gedanken, Aharon
AU - Prozorov, Ruslan
PY - 1998
Y1 - 1998
N2 - 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.
AB - 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.
UR - http://www.scopus.com/inward/record.url?scp=27844441929&partnerID=8YFLogxK
U2 - 10.1039/a706871i
DO - 10.1039/a706871i
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AN - SCOPUS:27844441929
SN - 0959-9428
VL - 8
SP - 769
EP - 773
JO - Journal of Materials Chemistry
JF - Journal of Materials Chemistry
IS - 3
ER -