Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
7851898 | Carbon | 2015 | 33 Pages |
Abstract
This paper reports rapid, continuous and carbon-nanotube free synthesis of carbon encapsulated magnetic nanoparticles by thermal-plasma expansion technique, which combines the typical advantages of high-temperature plasma assisted synthesis method with efficient particle-size control. Core nanocrystals were encapsulated with few layers of graphitized carbon, which could provide protection against both oxidation and intense chemical treatment. The average iron/iron-carbide nanoparticle diameter (7.7, 9 and 10 nm) and the width of the size distribution increased with pressure in the sample collection chamber, as a result of the decreasing quenching rate of the plasma jet. This also resulted in the smaller particles remaining frozen predominantly in the high-temperature γ-Fe phases, part of which was oxidized subsequently and eliminated preferentially during the purification process. All samples could be correlated with smooth variation of magnetic properties; saturation magnetization, remnant magnetization and coercive-field enhancing with increasing chamber pressure or average particle size. The low pressure synthesized sample with smallest average particle size approached super-paramagnetic behavior (saturation magnetization = 51.8 emu/g, ratio of remnant to saturation magnetization = 4.9 and coercive field = 52 Oe), which may be ideal for biomedical applications. High-pressure samples on the other hand have a higher saturation magnetization (76.3 emu/g) and coercive fields (123 Oe).
Related Topics
Physical Sciences and Engineering
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Energy (General)
Authors
N. Aomoa, Trinayan Sarmah, U.P. Deshpande, V. Sathe, A. Banerjee, T. Shripathi, V.R. Reddy, N.P. Lalla, A. Gupta, Rajeev Gupta, Divesh N. Srivastava, R.K. Bordoloi, S. Sarma, A. Srinivasan, M. Kakati,