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

摘要CTS-0417722 H。罗切斯特大学的Yang，U最近在磁性存储介质方面的发展为创造具有设计成分和结构的纳米材料提出了新的挑战。 在潜在的候选者中，FePt纳米颗粒被认为是纵向磁存储应用中最有前途的材料之一。 用于合成量子点的方法最近已经扩展到这类合金。 无序面心立方（fcc）相FePt合金的单分散纳米粒子已使用所谓的多元醇过程。 然而，FePt纳米颗粒需要是有序的面心四方晶系（fct，也称为L10）相，以便具有数据存储应用所需的高磁各向异性和磁性。 FePt合金从无序fcc相到有序fct相的转变温度超过了常规溶剂的范围。 合成后的高温固相处理导致FePt纳米颗粒的聚结，使其不适合应用。 为了探索材料的全部潜力，我们建议开发在高反应温度下直接合成fct相FePt纳米颗粒。 超临界流体在高温和高压条件下保持液态。 这样的流体只有一个单相，并且被用于颗粒合成和过程中。 在该提议中，将探索在超临界流体中在有利于形成有序fct相的温度范围（400 ℃）下合成L10相FePt纳米颗粒。 具体目标如下：1）考察不同前体和封端配体，特别是羰基铁、乙酰丙酮铂、辛醇、油酸和油胺在超临界流体中的温度依赖性溶解度：2）绘制出合成温度依赖性和fct相特异性FePt纳米颗粒的超临界或近超临界条件; 3）利用透射电子显微镜（TEM）、原子吸收光谱（AFM）、透射电子显微镜（TEM）、透射电子显微镜（TEM）和透射电子显微镜（AFM）研究了合成纳米颗粒的结构与磁性的关系。（和磁）力显微镜（AFM/MFM），超导量子干涉仪（SQUID）磁力计，粉末X射线衍射（PXRD），能量色散X射线（EDX）和电子能量损失谱（EELS）。 通过开发对先进磁性材料的发展至关重要的新概念，我们预计这项研究的结果将直接影响微电子和数据存储行业。 在该项目中获得的知识将提供对超临界条件下高温下纳米颗粒形成的基本理解，并对多组分纳米材料的设计和合成产生更广泛的影响。 通过该项目培训的学生将掌握尖端的合成和表征技能，并培养纳米科学和纳米技术未来劳动力所需的关键知识。 该项目将扩大罗切斯特大学的研究合作。 研究成果将通过将研究成果纳入课程，与当地高中（目前与皮茨福德中央高中，职业实习计划），本科研究计划和学术出版物的推广计划传播给学生和公众。

AbstractCTS-0417722H. Yang, U of RochesterThe 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.