Mesoporous silica has attracted much attention in recent years, because of its potential for advanced applications in catalysis, separation technologies, electronic engineering, and manufacturing of optical devices. [1,2] The highly nanoporous structures with good thermochemical stability are suitable for the synthesis of new materials such as nanoparticles, wires and networks of platinum and carbon within the pore system. [3,4] In the case of the carbon synthesis, the fabrication technique has been fully developed so that ordered mesoporous carbons exhibiting Bragg X-ray diffraction (XRD) lines similar to those of the MCM-41-type mesoporous silica can be obtained after the complete removal of the silica template.Recently, an electron crystallographic analysis method based on transmission electron microscopy (TEM) has been developed to solve 3D structures of mesoporous silica crystals.[5] The structural solution provided direct information on detailed structures inside the mesoporous crystals such as pore diameter, shape and connectivity. But, the detailed structures at the crystal surfaces, such as the manner of channel openings at external surface and the accessibility to internal pores, were not clarified. Scanning electron microscopy (SEM) has advantages over TEM for the determination of the surface structures. SEM is a relatively simple experiment and requires minimum sample preparation, and solid information on surface structures can be obtained from "nonprojected" images in three dimensions because of the long focal depth of the objective lens.[6] However, because of "charging problems" common for insulators and low resolution, ordinary SEM has been unsuitable for accurate determination of the detailed surface structures of the mesoporous materials.Herein, we report that we can visualize directly the detailed surface structures of the SBA-15 mesoporous silica and its CMK-5 carbon replica, by using high resolution SEM and scanning transition electron microscopy (STEM) without metal coating. The high-resolution 3D SEM images clearly show the presence of interconnections between the hexagonally packed mesoporous channels, as suggested in previous works based on TEM imaging of the Pt replica. [4,7] Interestingly, the images show that the surfaces perpendicular to the direction of the channels (c direction) are intricately composed of tubes with closed ends, open ends, and channels that are curled back to the inside of the particles. Furthermore, we can distinguish two types of pores in the CMK-5 carbon, that is, the tubelike pores formed by carbon tubes and pores formed by removal of the silica wall.The SBA-15 silica and CMK-5 carbon samples observed in the SEM investigation were obtained by following procedures described elsewhere.[3a] Typical synthesis conditions and properties obtained from N 2 adsorption-desorption measurement are given in Table 1. Figure 1 shows SEM images and STEM image of the calcined SBA-15 silica sample. The silica particles in the SEM image exhibit hexagonal cylinderlike morphologies...
Mesoporous silica has attracted much attention in recent years, because of its potential for advanced applications in catalysis, separation technologies, electronic engineering, and manufacturing of optical devices. [1,2] The highly nanoporous structures with good thermochemical stability are suitable for the synthesis of new materials such as nanoparticles, wires and networks of platinum and carbon within the pore system. [3,4] In the case of the carbon synthesis, the fabrication technique has been fully developed so that ordered mesoporous carbons exhibiting Bragg X-ray diffraction (XRD) lines similar to those of the MCM-41-type mesoporous silica can be obtained after the complete removal of the silica template.Recently, an electron crystallographic analysis method based on transmission electron microscopy (TEM) has been developed to solve 3D structures of mesoporous silica crystals.[5] The structural solution provided direct information on detailed structures inside the mesoporous crystals such as pore diameter, shape and connectivity. But, the detailed structures at the crystal surfaces, such as the manner of channel openings at external surface and the accessibility to internal pores, were not clarified. Scanning electron microscopy (SEM) has advantages over TEM for the determination of the surface structures. SEM is a relatively simple experiment and requires minimum sample preparation, and solid information on surface structures can be obtained from "nonprojected" images in three dimensions because of the long focal depth of the objective lens.[6] However, because of "charging problems" common for insulators and low resolution, ordinary SEM has been unsuitable for accurate determination of the detailed surface structures of the mesoporous materials.Herein, we report that we can visualize directly the detailed surface structures of the SBA-15 mesoporous silica and its CMK-5 carbon replica, by using high resolution SEM and scanning transition electron microscopy (STEM) without metal coating. The high-resolution 3D SEM images clearly show the presence of interconnections between the hexagonally packed mesoporous channels, as suggested in previous works based on TEM imaging of the Pt replica. [4,7] Interestingly, the images show that the surfaces perpendicular to the direction of the channels (c direction) are intricately composed of tubes with closed ends, open ends, and channels that are curled back to the inside of the particles. Furthermore, we can distinguish two types of pores in the CMK-5 carbon, that is, the tubelike pores formed by carbon tubes and pores formed by removal of the silica wall.The SBA-15 silica and CMK-5 carbon samples observed in the SEM investigation were obtained by following procedures described elsewhere.[3a] Typical synthesis conditions and properties obtained from N 2 adsorption-desorption measurement are given in Table 1. Figure 1 shows SEM images and STEM image of the calcined SBA-15 silica sample. The silica particles in the SEM image exhibit hexagonal cylinderlike morphologies...
Monodispersed particles of the mesocaged material AMS‐8 have been prepared by using nonionic polymeric cosurfactants to control the particle size. These particles are faceted, porous, and show surface structural characteristics that are typical of cubic AMS‐8 (see picture), as well as an increased adsorption capacity as a result of the formation of intraparticle spaces.
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