Magnetic Assembly Of Palygorskite,Construction Of Magnetically Oriented Sol System And Its Optical Properties

Based on the structure,morphology and properties of natural clay minerals,functional materials with certain characteristics can be obtained,such as montmorillonite,palygorskite,sepiolite and kaolinite inorganic liquid crystal.However,due to the driving forces of the liquid crystal phase formation are gravity and the force between particles,the formation process of liquid crystal is slow,the relaxation time is too long and it is not adjustable,so it is difficult to be applied in practice.If the natural nano-minerals with specific structure and morphology can be coated with magnetic particles to have the characteristics of magnetic orientation,the controllable inorganic liquid crystal materials and mineral functional materials with special optical properties will be obtainedIn this paper,one-dimensional nanocomposites palygorskite@Fe₃O₄（Pal@Fe₃O₄）was prepared by chemical co-precipitation method with palygorskite（Pal）and ferric salt as raw materials.The effects of inorganic modifiers’type and amount on the structure and surface properties of Pal and the effects on the structure,morphology and properties of Pal@Fe₃O₄one-dimensional nanocomposites were studied.The mechanism of Pal surface activation via different modifiers and the mechanism of Fe₃O₄assembly on the surface of Pal were discussed.The method and process conditions for preparing Pal@Fe₃O₄one-dimensional nanocomposites using inorganic modified Pal were studied.The influence and law of the type,molecular weight and amount of dispersant on the stability and dispersibility of Pal@Fe₃O₄one-dimensional colloidal were studied and the Pal@Fe₃O₄magnetically oriented material was constructed.Based on the above works,the influence of dispersant types,the intensity and direction of the magnetic field,and the content of magnetic particles on the magnetic properties,liquid crystal and optical properties of the Pal@Fe₃O₄magnetically oriented material were studied.The results show that acid modification or hydrogen peroxide modification help Fe₃O₄nanoparticles grow more evenly on the surface of palygorskite,while acid+base synergistic modification will reduce the loading rate of Fe₃O₄on palygorskite surface,especially the Fe₃O₄nanoparticles growing on the surface of 2.0 mol/L HCl modified palygorskite are the most uniform,and the modification mechanism and the Fe₃O₄growing mechanism are explained by the electric double layer theory.The process conditions of the co-precipitation method（the amount and dropping order of alkali,the reaction time,the type of iron salt,etc.）were improved,and palygorskite@Fe₃O₄nanocomposites with uniform magnetic coating was prepared.The magnetic nanocomposites has superparamagnetism at room temperature,and can make a rapid and reversible response to an external magnetic field in a short time to form an orientation structure.The palygorskite@Fe₃O₄nanocomposites can form a stable sol system in three different dispersing media inorganic electrolyte（HCl,Li Cl and KCl）,organic small molecule（glycerol）,organic polymer（polyvinyl alcohol-1788）at an appropriate amount.Under an external magnetic field,the above five sol systems all show the properties of magnetically controlled liquid crystal phase and colloidal photonic crystal with Bragg diffraction,and the influence law is obtained:the direction between the magnetic field and incident light determines whether the Bragg diffraction can be generated,magnetic field intensity determines the range and brightness of the Bragg diffraction,and the content of magnetic particles determines the color of the Bragg diffraction light.The palygorskite@Fe₃O₄magnetic orientation material obtained in this study has potential application prospects in the fields of new optical materials,liquid crystal display devices,anti-counterfeiting materials,and photonic switch materials.