新型磁场驱动物相转变材料：氢氧化钴基纳米结构及其相转变机理研究

The phase transformation originates from the rearrangement of martensite variant or the transition from the martensite to the parent phase in the magnetic field for the traditional magnetic field driven phase transformation materials.In these recent years, the interaction between magnetic field and the reactants' electron spins has been found to relax the corresponding chemical bonds, change the reactin route, and hence lead to the changes of the product's phase and microstructure. However, the underlying mechanism is still unclear. In this project, with the aim of cobalt hydroxide-based nanoparticles, we are going to change the hydrated cobalt ions' direction and postion, clarify the relation between hydrated cobalt ions' configuration and the intensity of magnetic field, understand fully the infulences of the interaction between magnetic field and the hydrated ions' spins on the particles product's phase and microstructure and develope a technique that the application of magnetic field can manipulate the particles product's phase via the interaction between the magnetic field and hydrated cobalt ions spin. Based on the coupling modes between magnetic field and different hydrated ions spins, a set of resource materials is expected to be obtained which can be manipulated by the application of magnetic field. The interaction between magnetic field and different hydrated ions spin is controled to manipulate the nanoparticles product's phase and microstructure via the change of the magnetic field intensity and make clear the relation between the nanoparticles product's phase and microstructure and the parameters of the applied magnetic field intensity, the duration of the application and so on. Our research will enrich the theoretical system of the interaction between magnetic field and matters, and provide a new tool for the manipulation of the phase, microstructure and even performance of nanoparticles.

传统磁驱动相变材料源自马氏体变体在磁场作用下发生重排或磁场诱发马氏体相向母相发生转变。近年来，人们发现磁场与反应物电子自旋间的相互作用，可导致相应的化学键松弛、改变化学反应路线，从而导致产物物相和微结构发生变化。其物理机制仍不清楚。本项目以氢氧化钴基纳米粒子为研究对象，利用磁场与水合钴离子自旋间的相互作用，改变水合离子配位方向和位置，揭示其配位构型与磁场强度和方向间的关系，弄清磁场与水合离子间相互作用对粒子物相和微结构的影响，获得一种磁场调控产物粒子物相的技术。基于磁场与不同水合离子自旋的耦合方式，获得一批适合磁场诱导调控粒子物相的源材料。通过改变磁场强度，控制与水合离子间的自旋相互作用，实现粒子物相和微结构的人工调控，并揭示粒子物相和微结构与外加磁场强度、作用时间等参数间的关系。本项目可以丰富磁场与物质相互作用的理论体系，为纳米粒子物相、微结构和性能的调控提供一种新的调控手段。

以Co(OH)2作为研究对象，当外加磁场达到一定程度，吉布斯自由能不可忽视，成为相变的驱动力，可以诱导β-Co(OH)2向α-Co(OH)2转变。在0、0.2T磁场下合成的样品表现出顺磁行为。但磁场到达2T时，样品完全转变成了α-Co(OH)2并且表现出铁磁性。相对于β-Co(OH)2，α-Co(OH)2拥有更加优异的电化学性能，其在电流密度为1 A/g时，比电容高达885 F/g，经过1500次充放电循环后仍能保持91％的数值。为获得高性能的储能器件，我们还制备了Co3S4 纳米片。结合理论计算，纳米片费米能级电子态密度促进了快速电子转移路径，为催化反应提供了高的活性位点。此外，我们通过光催化活性对其它过渡金属氧化物的氧化还原能力进行了研究。以SBA-15介孔分子筛、石墨烯、TiO2为基础，探究了它们与金属氧化物复合物的性能。SBA-15的吸附能力与NiO/ZnO层状复合材料，ZnO–CuO纳米粒子和SnO2纳米粒子的光催化性能结合可以有效分解有机污染物。为实现探测和降解双功能，我们研究了石墨烯和它们的复合材料的拉曼信号增强作用。累计发表SCI论文22篇，授权发明专利2项。