Silica gels crystal growth

Probably the most widely used methods of reactant preparation are by crystallization, or by precipitation fi-om solution. Sometimes use can be made of a silica-gel crystal growth technique [2], especially when the compound formed is a sparingly-soluble precipitate from aqueous solution. 

Kurien, K. V. Ittyachen, M. A. (1979). Growth kinetics and habit modification of barium molybdate single crystals in silica gel.. Cryst. Growth. 47., 5-6., (November-December 1979) 743-745, ISSN 0022-0248. 

It has long been observed that very beautiful crystals sometimes develop in gels. Wonderfully fine crystals of sugar frequently grow in ordinary fruit jellies. Many splendid mineral crystals are embedded in silica and appear to have developed while the silica was in the state of a gel. For this geological aspect of the subject, consult the papers of Cornu in the first five volumes of Kolloid-Zeitschrift. The experiments on crystal growth require some time for the proper development of the crystals, but the technique of the method is very simple and easily acquired. 

McCauley J.W. and Roy R. (1974) Controlled nucleation and crystal growth of various CaCC>3 phases by the silica gel technique. Amer. Mineral. 59, 947-963. 

Zeolite ZSM-23 can be readily synthesized with pyrrolidine as organic template and fumed silica as silica source. Pyrrolidine seems to intervene in the nucleation and crystal growth process, in the latter case most probably as pore-filling agent. By proper optimization of the gel composition and the synthesis conditions, ZSM-23 can be synthesized in less than one day. The synthesis of ZSM-23 has some... 

The main types of SiOj used in indu.siry are high-purity a-quanz, vimeous silica, silica gel. fumed silica and diaiomaceous eanh. The most important application of quartz is as a piezoelectric material (p. 58) it is used in crystal oscillators and filters for frequency control and modulation, and in electromechanical devices such as transducers and pickups tens of millions of such devices are made each year. There is insufficient natural quartz of adequate purity so it must be synthesized by hydrothermal growth of a s crystal using dilute aqueous NaOH and vitreous SiOy at 4(I0°C and... 

Zeolite beta was synthesized with different silicon sources. The dissolution of the silicon sources and the reaction temperature obviously determined the crystallization rate of the zeolite. Silica sol reacted rapidly at 110, 140, and 170°C, while fumed silica and TEOS only reacted readily at 170°C. The aluminum content in the reaction gel determined the termination of the crystal growth, after all aluminum was consumed, the crystal growth stopped. The acidic properties of the obtained materials were very similar, but a significant influence of the silicon source on the particle size of the resulting zeolite was observed. 

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