A facile one-step gel process for precipitation of multifractal NaCl crystals and morphology evolution from sodium silicate gel

In the colloidal-salt system of sodium silicate and sodium chloride, threefold and fourfold symmetric dendrites and diffusion-limited aggregation (DLA) of sodium chloride crystals have been synthesized by a simple one-step gelation process without changing the solution composition. The morphology variation is realized by changing the sol pretreatment and gelation process's heating mode. And the gelation degree of sodium silicate and the anisotropy of crystal growth is the morphology formation mechanism. Fourfold symmetric dendrites are related to preferential growth in the 〈1 1 0〉 direction, while threefold symmetric dendrites are due to preferential orientation changes from 〈1 1 1〉 to 〈1 0 0〉 and then to 〈1 1 1〉. EDS composition analysis showed that the high gelling degree is more accessible to precipitate regular fractal dendrites with preferred orientation.