SGER: Direct Synthesis of L10 Phase FePt Nanoparticles Using Supercritical Fluids

University Of Rochester, Rochester NY

Investigators

Abstract

Abstract CTS-0417722 H. Yang, U of Rochester The recent development in the ultrahigh magnetic storage media has posed new challenges for the creation of nanomaterials with the design compositions and structures. Among the potential candidates, FePt nanoparticles have been considered as one of the most promising materials in longitudinal magnetic storage applications. Methods developed for the synthesis of quantum dots have recently been extended to this class of alloy. Monodisperse nanoparticles of disordered face-centered cubic (fcc) phase FePt alloys have been made using the so-called polyol process. The FePt nanoparticles however, need to be ordered face-centered tetragonal (fct, also known as L10) phase in order to have the high magnetic anisotropy and coercivity required for data storage applications. The transition temperatures from disordered fcc to ordered fct phase of FePt alloy beyond the reach of conventional solvents. The post-synthetic solid state treatment at the high temperature leads to the coalescence of FePt nanoparticles and makes them unsuitable for the applications. To explore the full potential of the materials, we propose to develop a direct synthesis of fct phase FePt nanoparticles at high reaction temperatures. Intellectual Merit Supercritical fluids maintain the liquid state under high temperature and pressure conditions. Such fluids have only one single phase and been used in the particle synthesis and process. In this proposal, the synthesis of L10 phase FePt nanoparticles in supercritical fluids at a temperature range (> 400 degrees C) that favors the formation of ordered fct phase will be explored. The specific objectives are as follows: 1) examine temperature dependent solubility of different precursors and capping ligands, particularly iron carbonyl, platinum acetylacetonate, octanol, oleic acid and oleylamine, in supercritical fluids; 2) map out the supercritical or near-supercritical conditions for the synthesis of temperature-dependent and fct phase-specific FePt nanoparticles; 3) study the structure-magnetic property relation of synthesized nanoparticles using transmission electron microscopy (TEM), atomic (and magnetic) force microcopy (AFM/MFM), superconducting quantum interference device (SQUID) magnetometer, powder X-ray diffraction (PXRD), energy disperse X-ray (EDX), and electron energy loss spectroscopy (EELS). Broader Impacts Motivated by developing new concepts pivotal to the advancement of advanced magnetic materials, we expect that the outcome of this research will directly impact on the microelectronic and data storage industries. The knowledge gained during this project will provide the fundamental understanding of nanoparticle formation at high temperatures under supercritical conditions and have broader impact in the design and synthesis of multi-component nanomaterials. Students trained through this project will master cutting-edge synthetic and characterization skills, and cultivate critical knowledge required for the future workforce in nanoscience and nanotechnology. This project will expand the research collaborations at the University of Rochester. The research outcome will be disseminated to students and the public through the incorporation of research results into the course curriculum, outreach programs with local high schools (currently with Pittsford Central High School, Career Intern Program), undergraduate research programs, and scholarly publications.