Nanocomposites and nanomaterials

Origin of band contrast on TEM and HRTEM images of nanoparticles obtained by pulsed electrical discharge
Monastyrsky G.E.1
1 National Technical University of Ukraine “Igor Sikorsky Kyiv Polytechnic Institute”, 37, Prosp. Peremohy, Kyiv, 03056, Ukraine. 
E-mail: monastyrskygennady@gmail.com

Fig.1 Agglomerates of Ni-Al nanoparticles. Bright field TEM image with banded particle indicated by arrow

The peculiarities of TEM and HRTEN contrast of nanosized particles of shape memory B2 alloys Ti-Ni [1], Ni-Al [2], Cu-Al-Ni [2] are considered and discussed. Powders were obtained by electrical pulse discharge method (or spark erosion method) in liquid argon. During this process particles with sizes less than 100 nm form a nano-fraction by condensation from the vapor phase gathering usually in agglomerates. Some of this particles demonstrate the specific band contrast as shown on Fig.1.  

It was established that morphology of this banded contrast depends on the composition of alloy under consideration and to some extent on the particle size. In particular only in Ni-Al particles with the composition close to the composition of master alloy bands could be considered as twins associated with the martensitic transformation in nanosized particles. Bands in Ti-Ni, Cu-Al-Ni are rather structural twins. 

1.	Monastyrsky G.E. Nanoparticles formation mechanisms through the spark erosion of alloys in cryogenic liquids // Nanoscale Research Letters -2015.-10.-P. 503-511
2.	Monastyrsky G.E., Ochin P. Gilchuk A.V. at all The role of nano-sized fraction on spark plasma sintering the pre-alloyed spark-erosion powders // Journal of Nano- and Electronic Physics, -2012.-4:1.P.1007-1-7