Roles of polyacrylate dispersant in the synthesis of well-dispersed BaSO4 nanoparticles by simple precipitation

Well-dispersed BaSO_4 nanoparticles were synthesized in the presence of sodium polyacrylate(PAAS) by a simple precipitation method,with BaCl_2 and(NH_4)_2SO_4 as reactants.The different roles performed by PAAS in the synthesis of BaSO_4 nanoparticles were investigated using X-ray diffractometry,Fourier transform infrared spectroscopy,and transmission electron microscopy.The results indicate that the assynthesized BaSO_4 nanoparticles were spheres with an average diameter of 30 nm and that their surfaces were affected by the PAAS.Under a typical procedure employed,PAAS reacted with BaCl_2 to yield an intermediate,serving as a control releasing agent and separating the nucleation and crystal growth processes of the BaSO_4 nuclei.During formation of the BaSO_4 nanospheres,the intermediate slowly dissolved and released barium and polyacrylate ions,inhibiting the growth and aggregation of newly formed BaSO_4seeds and resulting in particles of narrow diameter distribution and improved dispersibility.Moreover,these polyacrylate ions further modified the surfaces of the BaSO_4 nanoparticles.