Whisker-Like Goethite Nanoparticles Containing Cobalt Synthesized in a Wet Process

Abstract

Acicular α-FeOOH particles are formed through aging of ferric oxyhydroxide colloidal solution formed by the neutralization of FeCl 3 aqueous solution by NaOH. The effects of cobalt ion addition in the sol-gel-sol process on the formation rate and morphology of α-FeOOH nanoparticles have been investigated. The magnetic properties of metal nanoparticles prepared from the obtained particles have also been examined. The dependence of reaction rate constants in the formation of α-FeOOH in the wet process and the crystallite size of (110) on Co content in α-FeOOH has been made clear. Both the rate constant and crystallite size decrease with increasing Co content in α-FeOOH particles. The negative zeta-potential of the formed α-FeOOH particles increases slowly with increasing pH of the electrolytic solution. The negative zeta-potential of α-FeOOH particles containing Co is larger than that of α-FeOOH particles without Co in the range of pH6-pH12. The relationship between the morphology of the formed α-FeOOH particles and the cobalt content in α-FeOOH particles has been investigated. The length of major axis increases and the length of minor axis decreases with increasing Co content, and the aspect ratio increases remarkably. It is likely that Fe(OH) − 4 complex ion precipitates preferentially on the c plane, and the particles grow remarkably in the direction of c axis. The interplanar spacing of the α-FeOOH decreases with increasing Co content. The formed α-FeOOH grows abnormally like whisker in the direction of major axis: c axis in the case of significantly much Co content: 27 at%, and also the whisker like nanoparticles are observed to grow with curving. The magnetic metal nanoparticles produced have excellent dispersivity and high aspect ratio. The metal nanoparticles have magnetic properties enough for the magnetic recording media.

Production Conditions of Acicular Magnetic Metal Nanoparticles for Magnetic Recording

“…Acicular -FeOOH particles were synthesized by aging a colloidal amorphous ferric oxyhydroxide solution which was prepared by neutralizing a FeCl 3 aqueous solution and a NaOH solution [15][16][17][18][19][20][21] at a predetermined temperature, and a sample was made by surface-treating the particles in the following manner, using the acicular -FeOOH particles.…”

Structure and reactivity of synthetic Co-substituted goethites

“…Different aspects of Co-substituted goethite obtained in alkaline media have been studied by other authors (Cornell and Giovanoli 1989;Gerth 1990;Cornell 1991;Gasser et al 1996;Iwasaki and Yamamura 2002). Recent studies of Co-goethites obtained from aerial oxidation of both Fe 2+ and Co 2+ solutions were carried out by Pozas et al (2002Pozas et al ( , 2004.…”

“…Among the foreign cations, Co is attractive because of its significance for plant and animal nutrition (Alloway 1990). Besides, Co-substituted goethite has been used as precursor for the production of Co-Fe metallic particles (Iwasaki and Yamamura 2002;Nuñez et al 2003).…”

Effect of cobalt isomorphic substitution on the properties of goethite and the adsorption of lead

“…The introduction of manganese increased the surface roughness of goethite and improved the adsorption capacity of goethite for uranium (Zhang et al, 2020). Cobalt has been used to substitute goethite to prepare magnetic particle precursors (Iwasaki and Yamamura, 2002), and obtained a faster dissolution rate (Alvarez et al, 2008). However, current research on cobalt isomorphic substitution goethite has focused on the changes in crystal structure after the substitution, with little attention paid to the impact of substitution on the adsorption performance and mechanisms of heavy metals (Cornell et al, 1996;Gasser et al, 1996).…”