熔盐法合成无机纳米材料

In the preparation of inorganic nanomaterials, media can avoid the agglomeration of materials. When the water and organic solvents are not suitable as media for some reactions, molten salt can be used as a medium at high temperature.This project aims to design new molten salt reactions for the preparation of compounds with high melting point, such as carbide, nitride, boride, some kinds of carbon materials and silicon metal alloy materials, etc. Notably, in some cases, the instable solvents or absence of a medium leads to the low yiels of the main products or metastable phases in many chemical reaction, and the introduction of the molten salt may be an alternative way to solve these problems. It is worth to study the phases, size and shape of the final products when introducing of the molten salt media in the previous reported reactions. In addition, it is also important to research the control synthesis in the different molten salt systems by control of reaction temperatures, pressures and other reaction conditions. This project is based on our previous research in molten salt synthesis and the recent work regarding the low temperature molten salt method of reduction SiCl4 and SiO2 to prepare silicon nanomaterials, which have been published in Angew. Chem. Int. Ed., and Energy, Environ. Sci. respectly.

在无机纳米材料制备过程中，介质有助于避免材料团聚。当水和有机溶剂不宜作为介质时，熔盐在高温反应时可以作为介质。本项目旨在设计新的熔盐反应体系制备高熔点的碳化物、硼化物、氮化物，各种碳材料以及硅金属合金材料等。值得注意的是，熔盐的引入可以解决许多化学反应由于介质不稳定或反应时没有明确的介质，导致主要产物和介稳相产率较低的问题；熔盐介质的引入对于化学反应产物的物相、尺寸、形状的控制是一个值得研究的新方向。对熔盐体系的选择，反应时的温度、压力等的调控均需要研究。申请人在熔盐法合成方面有长期的研究基础，最近又成功的发展低温熔盐法还原SiCl4和SiO2制备硅纳米材料，分别发表在Angew. Chem. Int. Ed.和Energy Environ. Sci.上。

熔盐合成采用熔融无机盐作为介质，是传统液相合成（水热合成和溶剂热合成）的重要补充途径。根据盐的性质，操作温度范围从低于100 oC到超过1000 oC，从而可以获得广泛的无机晶体材料。通过熔盐热合成，可以实现对材料形貌，物相的调控，优化得到具有优异电化学，光学性能的无机功能材料。基于此，本项目发展了熔盐热法合成多种无机纳米材料，实现对材料形貌的可控调节，并探究化学反应机理，研究其在二次电池等领域的应用。1）发展不同的熔盐体系制备硅基，碳基，磷基纳米材料，如熔盐体系中利用化学剥离法制备二维Si纳米片；调控熔盐体系制备多级结构的空心Ge微球以及介孔Ge纳米颗粒；通过熔融盐辅助方法制备了（002）取向的碳纳米纤维；2）通过对反应过程的研究，探究形貌形成过程及反应机理；低温熔盐金属热还原方法合成红磷或磷化物，共价盐PCl5和AlCl3在低熔点50℃形成了由PCl4+和AlCl4-组成的复合盐PCl5·AlCl3，促进了反应进行；熔盐氯化锌体系中，经过固液固过程形成花束状的锗酸锌纳米团簇；3）通过电化学性能测试，研究材料在二次电池领域的应用。熔盐体系制备的均匀分散Sb纳米颗粒用于钾离子电池负极材料展现长循环稳定性。此外，发展了熔盐体系中新的化学反应硅热还原制备一系列硅基复合材料，表现出优异的电化学性能。