Preparation Of Magnetically Conductive Nano-sized Macroscopic Assemblies By Oriented Freezing Method

In recent years,the research and development of nanomaterials have aroused a great interest in scientific research field and enterprises.With the advent of a series of functional nanomaterials,their applications have been widely used in various fields.However,single nanostructure cannot meet the current requirements.It is a research hotspot that assembling nanomaterials into three-dimensional macroscopic structure,which could further realize the practical potentials of these functional nanomaterials.In this dissertation,we summary the development of three dimensionally macrostructural materials and their preparation methods in recent years,and we employ freeze casting technology to achieve two advanced macroscopic materials with both well conductivity and magnetic response.This dissertation mainly includes two contents:(1)A series of graphene/ iron oxide@silica nanoparticles composite aerogels were designed and prepared.(2)A series of flexible and magnetic conductors with good electrical conductivity were prepared using one-dimensional silver nanowires and iron oxide@silica nanoparticles by a freeze casting technique.First of all,we developed a low-cost,pro-environmental and convenient oriented freezing method to realize the preparation of highly ordered three-dimensional macroscopic assembly of graphene nanosheets and iron oxide@silica nanoparticles.With EDA served as the action of inducer,graphite oxide nanosheets were mixed with magnetic iron oxide nanoparticles,and graphene/iron oxide hydrogel was obtained by hydrothermal reduction.By adjusting the ratio of graphite oxide nanosheets to magnetic nanoparticles,we can achieve different requirements.As a result,our composite assembles possess ultra-high elasticity good heating effect and well magnetic response.In addition,the resistance change is sensitive during the compression process.Furthermore,in order to achieve conductive and magnetic macroscopic assembles of metallic nanomaterials,we combined silver nanowires prepared by polyol method with magnetic iron oxide nanoparticles.Three-dimensional macroscopic assembles of silver nanowires/nanoparticles with excellent electrical conductivity and magnetic properties were prepared using the freezing technology.Then,PDMS was infused into these composite aerogels of the silver nanowires and iron oxide nanoparticles to prepare the elastic conductors with excellent electrical conductivity without affecting the original structure of the material.According to the results,our elastic conductors possess better conductivity and more obvious advantages than other two-dimensional or three-dimensional elastic conductors.In the whole work,we not only retained the original shape memory characteristics of the material,but also endowed the material with unique properties.