强磁场诱导FePt一维纳米材料的可控制备、生长机制及结构有序调控

L10-FePt one dimensional (1D) nanomaterials with excellent magnetic and catalytic performances have attracted a deal of attention because of their promising applications. However, L10-FePt 1D nanomaterials have been not applied because current wet chemical method performs a poor repeatability and controllability and it is difficult to obtain FePt 1D nanomaterials with L10 structure. In order to solve the problems, we are proposing a novel idea to prepare L10-FePt single crystal 1D nanomaterials. In this proposal, high magnetic field is introduced into wet chemical method. The high magnetic field can induce anisotropy growth of the nanomaterials and facilitate FePt ordering transition from fcc to L10 structure. Therefore, L10-FePt 1D nanomaterials with controllable size and morphology are expected to directly synthesize by using this method. In this work, the growth process of the 1D nanomaterials will be experimentally investigated by analyzing the nanomaterials sampled at different reaction conditions, and simulation works about influences of high magnetic field on anisotropy growth will be processed by using molecular dynamics simulation. A general growth mechanism of the FePt single crystal 1D magnetic nanomaterials should be defined. The influence of magnetic field on ordering transition will be investigated. First principle calculation will be employed to reveal influence of high magnetic field on structural order. L10-FePt single crystal 1D nanomaterials will be prepared by using this method. Magnetic and catalysis performances of the nanomaterials with different structural orders and morphology will also be discussed to understand the relationship between structural order and functional performance. FePt 1D nanomaterials with a designable structural order and optimal functional performance will be achieved by tuning magnetic fields. This proposal is expected to provide the urgent experimental and theoretical foundation for preparation technology and application of FePt 1D nanomaterials.

L10有序结构的FePt一维纳米材料在磁性、催化领域展现出优异特性，具有广阔应用前景。但现有湿化学制备FePt一维纳米材料可控性差，且无法获得L10结构，严重限制了其发展和应用。本申请提出将强磁场与湿化学法相结合的新思路，利用强磁场诱导各向异性生长和促进结构有序化的作用，实现FePt一维纳米材料的可控制备及结构有序调控。项目通过在线取样技术分析强磁场下反应各阶段的样品尺寸、形貌和结构，借助理论计算模拟强磁场诱导粒子各向异性生长情况，在实验和模拟基础上，揭示强磁场下FePt单晶一维纳米材料的生长机制，实现FePt一维纳米材料的严格可控制备；研究强磁场促进FePt有序化机理，明晰强磁场与有序度的关系，直接合成L10-FePt一维纳米材料；掌握有序度对磁性和催化性能的影响，实现磁场对FePt有序度和功能特性的调控。项目实施对FePt一维纳米材料的可控制备具有重要理论意义，将有力推动其应用化进程。

项目执行期间取得了较丰富的有价值成果，实现了研究目标，达到并超额完成了预期成果。首先研究磁场下FePt晶核、团簇的取向连接和一维生长行为，揭示了强磁场的磁极化作用对FePt纳米粒子取向生长的影响，强磁场可促进各向异性生长，获得一维FePt纳米材料。通过强磁场降低了FePt有序转变温度，通过固相烧结法制备了超细高矫顽力L10-FePt纳米粒子。通过第一性原理计算和实验相结合的方法分析了掺杂元素对有序化温度的影响，明确了元素掺杂诱导FePt有序转变的本质因素和掺杂元素选择策略。通过取样技术分析了反应各阶段的晶体尺寸、形貌和结构，揭示了FePt纳米材料有序转变机理，研究了合成工艺与有序度和磁性能之间的拟合关系。利用Pb元素掺杂将有序转变温度降至200℃以下，从而利用表面活性剂实现了低温可控异性生长，成功制备出了L10-FePt一维纳米线，完成了项目目标，其有序度s达到0.80，矫顽力Hc达到7.0 kOe以上。这些成果对L10-FePt纳米材料的形貌可控制备、结构调控和功能特性优化具有重要的理论指导意义。