Fractal evolution of aluminosilicate sol and resulting effects on the synthesis of clinoptilolite via small angle X-ray scattering investigation

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Nanosol precursors with different hydrothermal treatment time were obtained at 150 °C, which was used as structure promoter (SP) to synthesis the clinoptilolites (CPs). The effected mechanism of the SP on the self-organization stage, the nucleation and growth of CP was investigated by XRD, SEM, SAXS, DLS, Uv-Raman, FT-IR and 29Si-NMR. During the self-organization stage of the SP with shorter pre-crystallization time (less than 100 h), its fractal structure underwent a process from densification (surface fractal) to looseness (mass fractal), and then to densification (surface fractal) accompanying with increased particle size and enhanced crystallinity of CP, which effectively promoted the formation of crystal nuclei, acting as structure directing agent. While the crystal growth of resultant CP in the SP pre-crystallized for longer time (144 h) could shorten the induction period, but had little impact on the growth period, serving as “seed”. However, overmuch resulted in that a large amount of heterophase (phillipsite) coexisted with CP.