Showing papers by "Chandran Sudakar published in 2003"
TL;DR: In this article, the hexaferrites of different compositions from the ternary phase diagram were prepared by a wet chemical process of gel-to-crystallite conversion and showed defect-free, regular, coherent growth of structural blocks.
97 citations
TL;DR: In this article, the effect of anions such as Cl −, SO 4 2−, and HPO 4 2 − on phase stability of FeOOH (α or γ) during precipitation is investigated.
77 citations
TL;DR: In this paper, it was shown that metal nanoparticles precipitate coherently as thin flakes along the a-b planes of the derivative magnetoplumbite lattice of the hexaferrites above the characteristic reduction temperature, $T_R$ >375 °C in the atmosphere.
Abstract: Nanocomposites are realized by chemical reduction whereby the conducting magnetic particles of Fe–Co alloy are generated within the insulating ferrimagnetic $BaCo_2Fe_{16}O_{27}$ or $Ba_2Co_2Fe_{12}O_{22}$ hexaferrite matrix. Transmission electron microscopy revealed that metal nanoparticles precipitate coherently as thin flakes along the a–b planes of the derivative magnetoplumbite lattice of the hexaferrites above the characteristic reduction temperature, $T_R$ >375 °C in $H_2$ atmosphere. The coercivity increases with $T_R$ in the early stages of the solid-state precipitation and then decreases with the formation of larger fractions of Fe–Co alloy; a converse trend is noticed for magnetization. The complex permittivity increases with reduction to ~50 in the broad frequency range of 4–18 GHz. The complex permeability is also enhanced with the content of Fe–Co nanoparticles. It is proposed that the spin reorientation at the Fe–Co/hexaferrite interface gives rise to broadband response, rendering these composite particles useful as electromagnetic microwave absorbers.
34 citations
TL;DR: In this article, the growth of acicular hydrogoethite particle proceeds by the oxidation of Fe(OH) 2 · x H 2 O to an intermediate phase through the nucleation within the amorphous ferric oxy-hydroxide [FeO x (OH) 3−2 x · y h 2 O] and growth of α-FeOOH·(H 2 O) x acicular particles with the aid of morphology controlling agents, as evidenced from X-ray diffraction and transmission electron microscope (TEM) studies.
15 citations