Preparation Of Al₂O₃-nSiO₂Powders With Water Glass By Co-Precipitation

According to the amorphous Al2O3-nSiO2(n=1,2) phase structure of natural aluminum silicate minerals material, a detailed study of the preparation method of high purity and amorphous Al2O3-nSiO2(n=1,2,4) powder material has been carried out. The powder product was synthesized by the process of forming a chemical precipitate, which is called Sol-coagulation method. The basic process is:At first,the water glass solution and aluminium nitrate solution was make-up;At second,silica sol and boehmite sol were prepared by method of hydrolysis;The third,the two sols were mixed and turn into precipitate,It’d be completely precipitated while conditioning the solution pH value to a sufficient number of suitable;At last,the sediment was separated from the mixed solution,wasded,dryed, grinded,and calcinated.To examine the effect of preparation conditions on properties of Al2O3-nSiO2(n=1,2,4) powder, such as particle size, particle size distribution, gelation activity.ect.the pH value, concentration, and dispergation temperature were studied.In order to improve the powder’s gelation activity (this is mainly related to the powder’s particle size and particle size distribution), drying methods, mixed methods, surfactants were studied in the preparation.With a modulus of1.0-1.2liquid sodium silicate,or85%of concentrated phosphoric acid mixed with the powder to prepare geological polymer materials, hardening the material and test the corresponding mechanical strength (compressive strength),which is called cementing material reactivity. The powder product was characterized by Nano-particle size analyzer, Inductively coupled plasma atomic emission spectroscopy, X-ray diffraction analysis (XRD), Fourier transform infrared spectroscopy (FT-IR), Scanning electron microscopy&Energy dispersive spectrometer (SEM-EDS),etc. It was shown that the powder has the amorphous micro-structure;the morphology of powder product is piece&bedded; the distribution of powder particle size is uniform,particle diameter of300-500nm; The ratio of powder between Silicon and aluminum atomic is accord with ratio of the original material;The appropriate preparation condition for Al2O3-nSiO2powder material was obtained as follow:6.5≤pH≤8.5,Molar concentration of aluminum nitrate and sodium metasilicate is about0.5-1.0mol/L,dispergation temperature is about90-95℃and80-95℃; It was shown that Al2O3-nSiO2powder product can be made into geopolymer gelation materials, compressive strength of which is about5-10Mpa (acid activation) or10-22MPa (alkali activation)...