STUDIES ON SYNTHESIS AND PROPERTIES OF AL UMINUM-MAGNESIUM HYDROXIDE POSITIVE SOL

A positive sol of aluminium magnesium hydroxide was synthesized by non -steady coprecipitation. The synthesis mechanism, shape, chemical comp osition, electrical property and thermal stability of colloidal partic les were studied by X-ray diffraction, transmission electron microscop e, chemical analysis, spectroanalysis and measuring of electrophoretic mobilities. The colloidal particles are tiny platelets with an averag e diameter of about 30 nm, and may aggregate with ''oxygen-bridge'' in water medium. In the process of synthesis, the peptization is the tra nsformation process from amorphous to crystalline. The chemical compos itions of particles are dependent od the composition of raw material. When the ratios; of Mg/Al in raw material are 1 : 2, 1 : 1 and 2 : 1, the chemical formulas of colloidal particles are Mg0.27Al(OH)(3.07)Cl- 0.47. 0.86H(2)O,Mg0.43Al(OH)(3.72)Cl-0.14.(0.5)H2O, Mg0.96Al(OH)(4.50) Cl-0.42. 1.45H(2)O, respectively. The electrophoretic mobilities and thermal stability of the colloidal particles increase with increasing the content of magnesium in chemical composition of the particles.