Preparation Of Nano Spherical Cerium Oxide By Ultrasonic And Microwave Synergistic Liquid Phase Homogeneous Precipitation Method

Yttrium oxide（Y₂O₃）has excellent physical and chemical properties,and shows unique advantages in corrosion resistance,heat resistance,magnetic properties and dielectric constant.In addition to its original properties,nano de yttrium oxide has the unique characteristics of nanomaterial,which makes it unparalleled with conventional yttrium oxide materials.After the spheroidization of nano Y₂O₃,it will have higher specific surface area,surface energy,better fluidity and dispersivity,and improve the properties of light,electricity,magnetism and force.So it is widely used in optical materials,ceramics and alloy materials.At present,there are many techniques for preparing nano-spherical yttrium oxide,but the technology of using the synergistic effect of ultrasonic and microwave to prepare yttrium oxide is very few.Therefore,in this thesis,the spherical yttrium oxide was prepared by the simultaneous precipitation of ultrasonic and microwave in the liquid phase.By investigating the influence of various factors on the morphology and particle size of yttrium oxide,the optimum process conditions and reaction mechanism were obtained.The main work and main achievements are as follows:（1）Yttrium oxide precursor was prepared by simultaneous precipitation of ultrasonic and microwave in liquid phase.The effects of heating method,precipitator,Y³⁺concentration,urea concentration,reaction time,reaction temperature,ultrasonic mode,ultrasonic power,microwave power,pH value and aging time on the morphology and particle size of yttrium oxide precursor were investigated.The experimental results show that:When urea is used as precipitating agent,without the addition of surface modifier or dispersant,ultrasonic and microwave synergy will be beneficial to the preparation of spherical particles with uniform and dispersed size.In this mode,under the control of the initial concentration of Y³⁺of 0.05 mol·L^-1,CO（NH₂）₂ concentration of 2.5 mol·L^-1,the reaction time is 1 h,the reaction temperature is90℃,ultrasonic power 700 W,microwave power 500 W,ultrasonic mode of 1:2,without aging,the nanometer spherical multi crystal can be obtained and diameter in yttrium oxide precursor is about 94.05 nm.Meanwhile,through the analysis of TG-DTA and FT-IR,it is determined that the precursor is a basic yttrium carbonate containing 1 crystalline water:Y（OH）CO₃·H₂O,and its decomposition temperature is 768℃.（2）Calcining of yttrium oxide precursor by electric furnace heating,the influence of calcining temperature and holding time on the morphology and particle size of Y₂O₃.The experimental results show that,under the conditions of calcining temperature of 800℃and heat preservation time of 2 h,the morphology of the calcined Y₂O₃ is the best and the dispersion is better.The calcined Y₂O₃ inherited the morphology of the precursor,and obtained an average particle size of about 68.67 nm,uniform particle size and good dispersibility of second-order nano-spherical Y₂O₃.It is shown that the oxide morphology is"hereditary"in a certain temperature range.The XRD phase analysis of products shows that when calcination temperature is higher than 500℃,the XRD curve of calcined products is consistent with the standard card（NO.01-092-0927）,which is cubic crystal Y₂O₃.