Mehmet Burak KAYNAR, Ahmet TOPRAK, Şadan ÖZCAN

Islak öğütme yöntemi ile metalik demir ve kobalttan hazırlanmış CoFe2O4 nanoyapılarda doyum manyetizasyonunun yapıya bağlı değişimi

Nano-kristal kobalt-ferrit örnekler ıslak mekanik öğütme/tavlama yöntemi ile metalik demir ve kobalt kullanılarak hazırlanmıştır. 750 C de tavlanan örnekler, 12 saate kadar kuru öğütme yapılarak, öğütme süresinin yapısal ve manyetik özelliklere etkisi irdelenmiştir. Örneklerin ortalama kristalit büyüklükleri x-ışını toz difraksiyon desenlerinden Rietveld analiz programı (MaudLab) yardımıyla hesaplanmıştır. Sonuçlar tavlanmış örnekte kristalite büyüklüğünün 60 nm olduğunu ve 12 saat kuru öğütmeyle birlikte 12 nm’ye kadar düştüğünü göstermektedir. Ancak örneklerin geçirmeli elektron mikroskobu (TEM) görüntülerinde birleşmeler olmuş nano-kristalitler gözlenmiştir. Rietveld analizleri ayrıca kuru öğütme sırasında oluşan kristal kusurları nedeniyle örneklerdeki mikro-gerilmenin 12 saat kuru öğütmeyle berber 2 x 10-4‘den 1.4 x 10-3’e çıktığı hesaplanmıştır. Co+2 iyonları için elektron bağlanma enerjileri x-ışını foto-elektron tayf-ölçümü (XPS) ile belirlenerek, inversiyon katsayıları belirlenmiş ve hacim başına düşen manyetik momentleri hesaplanmıştır. Hesaplanan hacim başına düşen manyetik momentleri öğütme ile birlikte 4.87 µB’dan 6.17 µB’a artarken, oda sıcaklığı titreşimli örnek manyetometresi (VSM) ölçümleri öğütme süresi arttıkça doyum manyetizasyonunun 125 emu g-1’dan 57 emu g-1’e düştüğünü göstermiştir.

Anahtar Kelimeler:

Kobalt-ferrit, ıslak öğütme; manyetik özellikler; nanokristalit

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