Control of morphology in synthesizing mesoporous silica

Abstract

Mesoporous silica can be synthesized by either the alkaline route or the acidic route, both using surfactants as templates. Morphological transformations of mesoporous silica can produce various hierarchical orders. Different morphologies are produced under different synthetic conditions. In the alkaline route, the surfactant/silicate liquid crystal system undergoes phase transformation to form vesicles and further transforms to the hexagonal phase. The results are tubule-within-tubule and hollow pillar-within-sphere structures depending on cosurfactant/surfactant composition. Using nitric acid in the acidic route, one can obtain hierarchical ropes or gyroids depending on stirring conditions. Ammonia hydrothermal treatment can induce further morphological transformation to nanotubes of mesoporous silica.

Preparation of CaCO3 and CaO Replicas Retaining the Hierarchical Structure of SpruceWood

“…For similar purposes, nano-and mesoporous materials are utilized as well. Some well documented examples include mesoporous silica (e. g. MCM-41), prepared with quaternary ammonium surfactants ("quats") as templating agents [2,3], or nanoporous silica aerogels which are fabricated via sol-gel processess utilizing alkoxysilane precursors [4,5]. Among those materials, aerogels stand out because of their unsurpassed heat insulating properties which derive from their nanoporosity and the Knudsen effect [6].…”

Structural and Morphological Control of Cationic Surfactant‐Templated Mesoporous Silica

“…The particles of MMS made in acidic conditions tend generally to be bigger than MMS particles made in alkaline conditions. 11,12 This is due to the slower nucleation rate (cf. Figure 1) in acidic conditions.…”

“…[13][14][15] In a specially designed alkaline synthesis of MCM-41, the initial pH of sodium silicate solution is fairly high (pH ) [11][12]. This leads to highly charged anionic silicate species in solution and a lower rate of condensation.…”

Effect of synthesis time and treatment on porosity of mesoporous silica materials

“…MPS materials with hexagonal, cubic, or lamellar structures were invented by scienti sts at Mobil Corporation in 1992 (Inagaki et a l. 1996;Zhao et al 1998). These matcrial s have ordered cages or chan nels and they possess high surface areas with pore di ameters rangi ng from 1.5 to 10 nm Mou and Li n 2()(H) . MPS materials are normally in powder form when synthesized .…”