Wormhole-like pore structure

Fig. 1 reports the XRD patterns of materials obtained at 60°C for different treatment durations. At this tenperature, onfy one peak located at 13.0, 11.6 and 16.4 nm for heating times of 2 (Fig.lb), 3 (Fig.lc) and 11 days (Fig.ld) respectively, is detected. The presence of only one reflection line indicates that the compounds belong to the MSU or DWM femily. The structure of these moleeular sieves consists of regularly sized wormhole-like channels. The single broad peak arises from the average pore-to-pore separation in the disordered... 

The TEM picture of one of our typical san jles reported in Fig. 2 confirms the wormhole-like structure of our materials and its adherence to MSU (or DWM) family. If the heating temperature is increased to 80 or 100°C (dififractograms are not reported), no peak is detected any more after 2 days of hydrothermal treatment. This results from the fact that, as will be discussed further, the pore size distributions are very likely to broaden and to become more or less inhomogeneous for the higher tenqjeratures. The regular size of the channels could then be partly lost. It should be noted that for the sample which has not been subjected to a hydrothermal treatment, one reflection located at 7.5 nm (Fig. la) is present on the XRD pattern. So, when tetramethoxysilane is added to the prepared micellar solution and pH is adjusted, the condensation and polymerization... 

An interesting study is that of Stebe ct al., which described the phase behavior of C8Fi7C2H4(OC2H4) OH/methanol/water systems [59]. Well-ordered liquid crystals can be obtained up to a concentration of methanol in the solution around 8 wt%. If the methanol content in the mixture is further increased, the pore ordering is lost and the recovered materials adopt a wormhole-like structure. 

Recently, a selective etching method has been developed as a simple and effective strategy to fabricate hollow mesoporous silica particles. Fang et al. reported the formation of hollow mesoporous sihca spheres with either a wormhole-like or an oriented pore structure by treatment of sohd silica spheres in a sodium... 

---