Transmission electron microscopy silicates

The nano-scale structures in polymer layered-silicate nano-composites can be thoroughly characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). XRD is used to identify intercalated structures. XRD allows quantification of changes in layer spacing and the most commonly used to probe the nano-composite structure and... 

In the matrix of PLA/ polycaprilactone (PCL)/OMMT nano-composites, the silicate layers of the organoclay were intercalated and randomly distributed (Zhenyang et at, 2007). The PLA/PCL blend significantly improved the tensile and other mechanical properties by addition of OMMT. Thermal stability of PLA/PCL blends was also explicitly improved when the OMMT content is less than 5%wt. Preparation of PLA/thermoplastic starch/MMT nano-composites have been investigated and the products have been characterized using X-Ray diffraction, transmission electron microscopy and tensile measurements. The results show improvement in the tensile and modulus, and reduction in fracture toughness (Arroyo et ah, 2010). 

The picture of cement microstructure that now emerges is of particles of partially degraded glass embedded in a matrix of calcium and aluminium polyalkenoates and sheathed in a layer of siliceous gel probably formed just outside the particle boundary. This structure (shown in Figure 5.17) was first proposed by Wilson Prosser (1982, 1984) and has since been confirmed by recent electron microscopic studies by Swift Dogan (1990) and Hatton Brook (1992). The latter used transmission electron microscopy with high resolution to confirm this model without ambiguity. 

Powdered, particulate MCM-41 molecular sieves (Si/Al = 37) with varied pore diameters (1.80, 2.18, 2.54 and 3.04 nm) were synthesized following the conventional procedure using sodium silicate, sodium aluminate and C TMAB (n = 12, 14, 16 and 18) as the source materials for Si, A1 and quaternary ammonium surfactants, respectively [13]. Each sample was subjected to calcination in air at 560 °C for 6 h to remove the organic templates. The structure of the synthesized material was confirmed by powder X-ray diffraction (XRD) and by scanning/transmission electron microscopy. Their average pore sizes were deduced from the adsorption curve of the N2 adsorption-desorption isotherm obtained at 77 K by means of the BJH method (Table 1). 

Electron microscopy, with its high spatial resolution, plays an important role in the physical characterization of these catalysts. Scanning electron microscopy (SEM) is used to characterize the molecular sieve particle sizes and morphologies as a function of preparation conditions. Transmission electron microscopy (TEM) is used to follow the changes in the microstructure of the iron silicates caused by different growth conditions and subsequent thermal and hydrothermal treatments. 

Transmission electron microscopy of ion-thinned sections provides data at higher resolution than can be obtained with polished sections. Rodger and Groves (R24) described regions which had probably formed in situ from the ferrite phase, and which consisted of C-S-H, a hydrotalcite-type phase and a poorly crystalline phase containing iron that could have been the precursor of a hydrogarnet. The particles of this last constituent were almost spherical and some 200 nm in diameter. The same investigation also showed that much of the product formed in situ from alite or belite was essentially pure calcium silicate hydrate. 

Dehydration/rehydration process of Tobermorite-like Calcium Silicates Hydrates (CSH) was investigated by means of High Resolution Transmission Electronic Microscopy (HRTEM) and X-Ray diffraction using a new in-situ temperature and pressure controlled experimental cell. The following points summarise the results obtained in our investigations ... 

Figs 4a and 4b illustrate the Transmission electron microscopy images of the composite silicate-carbon materials. These figures display the hexagonal pore symmetry and a uniform pore diameter of about 3.5 nm. The corresponding Energy Dispersive Spectroscopy (EDS) of the silicate-carbon microanalysis indicates an overall composition of 61 wt. % C, 23 wt. % of O and 16 wt. % Si. 

---