• PDF / 220,802 Bytes
• 3 Pages / 612 x 792 pts (letter) Page_size
• 97 Downloads / 250 Views

DOWNLOAD

REPORT

---

MATERIALS RESEARCH

Welcome

Comments

Help

RAPID COMMUNICATIONS The purpose of this Rapid Communications section is to provide accelerated publication of important new results in the fields regularly covered by Journal of Materials Research. Rapid Communications cannot exceed four printed pages in length, including space allowed for title, figures, tables, references, and an abstract limited to about 100 words.

Magnetophoretic deposition of nanocomposites Joseph L. Katza) Department of Chemical Engineering and Department of Materials Science and Engineering, The Johns Hopkins University, Baltimore, Maryland 21218

Yangchuan Xing Department of Chemical Engineering, The Johns Hopkins University, Baltimore, Maryland 21218

R.C. Cammarata Department of Materials Science and Engineering, The Johns Hopkins University, Baltimore, Maryland 21218 (Received 2 August 1999; accepted 4 October 1999)

This communication reports the novel idea of using a magnetic field gradient to hold magnetic nanoparticles at desired densities in a fixed location (e.g., on an electrode surface), while metal atoms are deposited electrochemically in the interstices between them. Using it, nanocomposites consisting of ␥–Fe2O3 nanoparticles (with a mean size of about 40 nm) in a copper metal matrix were reproducibly fabricated, with particle volume fractions ranging from 0.2% to 50%. These nanocomposites, ceramic magnetic particles in a conductive metal matrix, are expected to have unusual or enhanced mechanical, electrical, and magnetic properties.

Nanostructured materials display a wide variety of unusual, and often enhanced, physical properties.1– 4 One example is a nanoparticulate composite composed of a matrix in which are embedded nanoparticles. Various deposition techniques have been used to produce such nanocomposites. For example, physical vapor deposition often is used to fabricate ceramic films in which metal particles are dispersed.5–7 Electrochemical deposition has been employed to produce metal films with embedded ceramic particles.8–11 In this electrochemical deposition technique, ceramic nanoparticles are suspended in the electrolyte and a few become embedded in the growing metal film during deposition. However, the concentration of particles embedded typically is less than 5 vol% (although there is one report of a film with 18% volume fraction).9 Furthermore, control of the particle volume fraction is poor. A schematic diagram of this magnetophoretic process is shown in Fig. 1. Mechanical stirring of the electrolyte solution causes shear forces at the electrode surface in addition to maintaining the dispersion of particles in the host medium. By adjusting the magnitude of the field gradient and by adjusting the stirring speed, the volume

a)

Address all correspondence to this author. e-mail: [email protected] J. Mater. Res., Vol. 14, No. 12, Dec 1999

http://journals.cambridge.org

Downloaded: 08 Feb 2015

fraction of nanoparticles embedded in the matrix material can be varied and very sensitively controlled. The experimental setup