Synthesis and corrosion study of zirconia-coated carbonyl iron particles

• Published in: Journal of colloid and interface science 2010-02, Vol.342 (1), p.49-56
• Main Authors: Shen, Rui, Shafrir, Shai N., Miao, Chunlin, Wang, Mimi, Lambropoulos, John C., Jacobs, Stephen D., Yang, Hong
• Format: Article
• Language: English
• Subjects: Carbonyl iron; Carbonyls; Chemistry; Coated particles; Coating; Colloidal gels. Colloidal sols; Colloidal state and disperse state; Corrosion; Corrosion tests; Exact sciences and technology; General and physical chemistry; Iron; Magnetic particle; Roughness; Sol–gel; Surface physical chemistry; Zirconia; Zirconium dioxide
• ISSN: 0021-9797; 1095-7103
• DOI: 10.1016/j.jcis.2009.09.033

Coatings of faceted zirconia nanocrystals are synthesized on carbonyl iron (CI) magnetic particles using a sol–gel approach. The zirconia-coated CI particles show much improved air oxidation and acid corrosion resistances. This paper describes the surface modification of micrometer-sized magnetic carbonyl iron particles (CI) with zirconia from zirconium(IV) butoxide using a sol–gel method. Zirconia shells with various thicknesses and different grain sizes and shapes are coated on the surface of CI particles by changing the reaction conditions, such as the amounts of zirconia sol, nitric acid, and CI particles. A silica adhesive layer made from 3-aminopropyl trimethoxysilane (APTMS) can be introduced first onto the surface of CI particles in order to adjust both the size and the shape of zirconia crystals, and thus the roughness of the coating. The microanalyses on these coated particles are studied by field-emission scanning electron microscopy (FE-SEM) and X-ray-diffraction (XRD). Accelerated acid corrosion and air oxidation tests indicate that the coating process dramatically improved oxidation and acid corrosion resistances, which are critical issues in various applications of CI magnetic particles.