Nanocomposites and nanomaterials

Electronic structure and surface morphology of nanoscale crystal structures of iron-based complex alloys
Karbivskyy V.L., Kurgan N.A., Karbovska L.I., Romansky A.A., Zaika V.V.
G.V. Kurdymov Institute for Metal Physics of the NAS of Ukraine,
03680, blvd. Vernadsky, 36, Kiev, Ukraine 
E-mail: karb@imp.kiev.ua  

In this work, the XPS and STM methods were used to study the electronic structure and morphology of two BMGs iron-based alloys (Fe55Ni8Co6Mo4Cr2V1Al2P9C6B5Si2 (HB-4) and Fe61.37Cr3.78Co6.84V0.82Mo1.06Nb0.85B19.87C1.99Si2.57 (NHRP-6)).
 It was established that the near-surface layers are characterized by a significant fraction of oxygen at  depth up to 150 nm. The presence of iron carbide and borides, as well as low amounts of oxygen was detected in the volume of the tape. Since the Fe-Me interatomic distance (Me = Ni, Co, Mo, Al, Si) is greater than the Fe-B distance and close to the Fe-Fe distance, diffusion leads to Me atoms taking the place of iron atoms when forming the crystal structure. It may be one of the possible mechanisms of surface segregation.

Fig. 1. STM image of NHRP-6 alloy.

Examination of the surface morphology revealed atomic ordering along the current lines (Fig. 1). We also saw clustering areas with  sized from  3 to 5 nm. Nanostructuring occurs as a result of growth of crystallization centers frozen in the amorphous matrix during rapid quenching..