Ni-Fe,Ni-Co铁磁合金纳米粒子的软化学法制备与相变研究

Ni-Fe and Ni-Co alloy nanoparticles have been focused among researchers because of their excellent magnetic and microwave-absorption properties.In general, the key issue of the preparation of alloy nanoparticles (ANP) is the formation of chemical bond between two metallic elements. Thermal-decomposition and reduction methods are often used to fabricate ANP where heating treatment above 873 K is often required in order to enhance diffusion of atoms and formation of metallic bond. However, heating at high temperature often induces grain growth, which restrict the use of ANP.In this project,based on principle of coordination chemistry, chemical bond is formed between two metallic elements via coordination ligand. Then the coordination ligand decomposes during heating treatment and the remianing part is mainly metallic elements. Since chemical bond is fomed before heating treatment, low diffusion rate and hence low temperature such as 673 K is suitable for the preparation of ANP. The key problem of the preparation of Ni-Fe, Ni-Co alloy nanoparticles will be solved based on the research work in this project. Moreover, the universality of this method in preparation ANP will be explored and the mechanism of the formation of ANP will be revealed. Based on the principles of thermal, m?ssbauer and magnetic analysis, the order-disorder phase transition and Curie transition of Ni-Fe ANP will be studied, and the key issue of the determiantion of order-disorder phase transition temperature will be solved, the scale effect of order-disorder phase transition temperature and Curie temperature will be clarifed. Our project will provide theoretical basis and technical support for preparation and characterization of Ni-Fe and Ni-Co alloy nanoparticles.

Ni-Fe,Ni-Co合金纳米粒子由于具有优异的磁学及微波吸收性能而为研究者所广泛关注。形成合金纳米粒子（alloy naoparticles, ANP）的关键在于两种金属原子形成化学键。常用的热分解/还原方法需在约873 K热处理使原子扩散形成化学键，但高温则会造成晶粒生长。本项目基于配位化学原理，将金属盐通过配位体形成化学键，在还原性/惰性气氛下使配位体热分解，由于金属元素已经形成化学键，在约673 K下扩散可形成ANP。本项目将解决Ni-Fe, Ni-Co纳米粒子的制备难题，探索该方法在金属纳米粒子制备领域的普适性，揭示该方法制备纳米粒子的机理。基于差热分析、穆斯堡尔谱分析等原理，研究Ni-Fe纳米粒子的有序无序相变及居里转变，解决确定Ni-Fe纳米粒子的有序无序相变温度的难题，揭示该相变温度与居里温度的尺度效应。本项目将为纳米合金粒子的制备与表征提供理论基础与技术支撑。

本项目以Ni-Fe,Ni-Co 合金纳米粒子的软化学法制备为基础。首先采用溶胶凝胶法制备Ni-Fe, Ni-Co纳米合金粒子（alloy naoparticles, ANP），解决Ni-Fe, Ni-Co纳米合金粒子的制备难题。在实验过程中，基于配位化学原理，将金属盐通过配位体形成化学键，在还原性/惰性气氛下使配位体热分解，由于金属元素已经形成化学键，在约 673 K 下扩散可形成 ANP。在此基础上，探索该方法在金属纳米粒子制备领域的普适性，揭示该方法制备纳米粒子的机理。采用不同的配位体、不同的金属盐、不同的溶剂均能制备Ni-Fe, Ni-Co纳米合金粒子。进而研究发现，该方法也能用于制备Ag, Pt, Pd, Ni, Cu, Ni-Pd, Ni-Pt, Cu-Pt等不同成分的金属纳米粒子，从而表明该方法具有普适性。基于质谱、红外光谱、差热分析研究形成纳米材料的机理，研究表明，在煅烧过程中出现的还原性气体如甲烷、氢气对性能金属纳米粒子具有决定性作用。最后，采用穆斯堡尔谱和振动样品磁强计，研究 Ni-Fe 纳米粒子的有序无序相变及居里转变，实验结果表明 Ni-Fe 纳米粒子的有序无序相变温度与居里温度具有强烈的尺度效应。本项目目前已发表8篇SCI研究论文，申请专利10项。本项目将为纳米合金粒子的制备与表征提供理论基础与技术支撑。