Study On Preparation And Microstructure Of Sepiolite/Spinel Metal Oxide Composites

Spinel type metal oxide is a kind of inorganic functional material with stable structure and wide application.As a typical spinel oxide,cobalt aluminate?CoAl₂O₄?is often used in pigments and other fields because of its bright color and stable performance.However,CoAl₂O₄ prepared by the traditional methods has serious defects,including agglomeration,uneven particle size distribution and poor dispersion,which seriously affect its application in the field of liquid pigments and ink-jet printing.Sepiolite nanofibers with a number of inner nano tunnels have a large specific surface area,as well as have strong dispersion and thermal stability,which is propitious to be utilized as a composites carrier.The composite materials prepared by sepiolite nanofibers supported CoAl₂O₄ can not only broaden the application field of oxide,but also achieve the utilization of sepiolite mineral materials with high added value.In this work,sepiolite/CoAl₂O₄ composites were prepared by sol-gel dipping and microwave hydrothermal method,respectively.The composites were characterized and tested by thermogravimetric-differential thermal analyzer?TG-DTA?,X-ray diffraction?XRD?,scanning electron microscope?SEM?,transmission electron microscopy?TEM?,chromatic aberration analyzer,ultraviolet-visible spectrophotometer and so on.On the above basis,the microstructure and the properties of composites were regulated and optimized.Results showed that the optimal preparation conditions of CoAl₂O₄ obtained by sol-gel method were as follows:ethylene glycol as solvent,the ratio of 1:1 for chelate to total cation,the pH of 7 and the calcination temperature of 1000°C.The best technological conditions of compsites fabricated by dipping method were stirring for 6 hours and calcinating at 300°C.The optimum preparation conditions of composites prepared by microwave hydrothermal method were as follows:the pH of 13,the hydrothermal temperature of 240°C,the hydrothermal time of 4 h,mass ratio of 15:1 for metal salt to sepiolite,the precursor mass of 0.17%and 10.00%for sodium dodecylbenzenesulfonate and triethanolamine respectively.The composites could be prepared in one-step and rapidly by microwave hydrothermal method while maintaining the phase stability of the sepiolite,and the regulation of the microstructure and properties could be achieved by adding organic additives.The CoAl₂O₄uniformly loaded on the surface of sepiolite in the composites was a spherical particle with an average particle size of 70⁸0 nm.Moreover,the transmittance of suspension obtained from the sky-blue composites was 0.66%after 48 h.The composites fabricated by microwave hydrothermal method had the advantages of high phase integrity and strong controllability of microstructures,and the preparation process is simple,efficient and energy-saving,which has a good application prospect in the research field of mineral supported spinel type metal oxide composites.