Study On The Factors Of Color Of Rare Earth Polishing Powder

With the rapid increasing demand for LCD TV and computer,high level devices such as LCD and optics lens have had a growing demand for the high-performance rare earth polishing powder.Ceria based rare earth polishing powder is the most widely used polishing powder.It has good crystal form,small and uniform particle size,less dosage and long service life,high qualified rate of polishing a workpiece,easy cleaning and many other advantages.The appearance of rare earth polishing powder is crucial to the sale of product.Especially the color problems led to sales decline of domestic rare earth polishing powder manufacturers,so this subject has an important practical significance.The paper provided a method to prepare rare earth polishing powder by NH4HCO3 precipitation.Rare earth carbonate precursor was formed by precipitation reaction,using rare earth carbonate as raw materials and a mixed solution of NH4HCO3 and ammonia as precipitant.After aging,washing,drying,calcining process,high-performance rare earth polishing powder was prepared.Factors that influence the performance of rare earth polishing powder were studied by a large number of single factor experiments.Micro-morphology,powder particle size,Zeta potential and specific surface area of rare-earth polishing powder were characterized by XRD,TGA,SEM,laser particle size analyzer,Zeta potential instrument.The optimum experimental conditions of preparing rare earth polishing powder that meet the polishing requirements were found.Factors that influence the color of rare earth polishing powder,such as impurities of polishing powder,calcination temperature,calcination atmosphere,were studied by single factor experiments.Chemical composition of raw materials and products was analyzed by ICP,EDS,and the effect of chemical composition on color was studied.This subject proposed a method determining the color of polishing powder by the whiteness colorimeter,and gave the chroma values of polishing powder through a comparative study with foreign products.The experimental results showed,(1)Micro-morphology of cerium based polishing powder obtained under the optimum experimental conditions was a polyhedral sphere,D50 was 0.8-1.2?m,specific surface area was 3-5m2/g,and Zeta potential was±40-±60mV,(2)Impurities that had great influence on the color of white polishing powder were Ca,Mg,Zn,Mn,P,and impurities that may exist in white polishing powder of some plant were Ca,Mg,Mn,P,(3)The optimum conditions of calcination for white polishing powder were 850-950? 3h,and the optimum conditions of calcination for red polishing powder were 920-940?,4h,(4)The extraction agent made a great impact on the color of product,which need to be controlled under 0.25%(V/T),and the extraction residue had a great influence on the color of product under 0.25%(V/T),(5)Calcination atmosphere had little effect on the color of white polishing powder,it had great effect on the color of red polishing powder,(6)Suitable additives could effectively improve the color of product.The conclusion makes it possible to introduce color parameter factors into polishing powder quality assessment in the future.