Scanning electron microscopy nucleation

Some limitations of optical microscopy were apparent in applying [247—249] the technique to supplement kinetic investigations of the low temperature decomposition of ammonium perchlorate (AP), a particularly extensively studied solid phase rate process [59]. The porous residue is opaque. Scanning electron microscopy showed that decomposition was initiated at active sites scattered across surfaces and reaction resulted in the formation of square holes on m-faces and rhombic holes on c-faces. These sites of nucleation were identified [211] as points of intersection of line dislocations with an external boundary face and the kinetic implications of the observed mode of nucleation and growth have been discussed [211]. 

The melt mixed 80/20 PS/iPP blend displays a set of exotherms, where the amount of the iPP component that was heterogeneously nucleated is substantially reduced as indicated by the decrease of the crystallization enthalpy in the temperature region where the iPP crystallizes in bulk, i.e., at 109-111 °C (exotherm labeled A). This effect is due to the confinement of iPP into a large number of droplets. If the number of droplets of iPP as a dispersed phase is greater than the number of heterogeneities present in the system, fractionated crystallization occurs. The number of droplets for this composition is known (by scanning electron microscopy observations) to be of the order of 1011 particles cm-3 and polarized optical microscopy (POM) experiments have shown that this iPP contains approximately 9 x 106 heterogeneities cm-3. In fact, it can be seen in Fig. 1 that the fractionated crystallization of the iPP compon-... 

The mechanisms of the crystal-building process of Cu on Fe and A1 substrates were studied employing transmission and scanning electron microscopy (1). These studies showed that a nucleation-coalescence growth mechanism (Section 7.10) holds for the Cu/Fe system and that a displacement deposition of Cu on Fe results in a continuous deposit. A different nucleation-growth model was observed for the Cu/Al system. Displacement deposition of Cu on A1 substrate starts with formation of isolated nuclei and clusters of Cu. This mechanism results in the development of dendritic structures. 

Figure 2.17. Scanning electron microscopy image of the nucleation and growth of a mesoporous silica him on mica. Reproduced with permission from [126].

This conclusion was only partly confirmed by scanning electron microscopy micrographs of RuC>4 stained surfaces taken at the crack tip of deformed specimens at 1ms-1, where the non-nucleated and /3-nucleated materials showed, respectively, a semi-brittle and semi-ductile fracture behavior. While some limited rubber cavitation was visible for both resins, crazes—and consequently matrix shearing—could not develop to a large extent whether in the PP or in the /1-PP matrix (although these structures were somewhat more pronounced in the latter case). Therefore, a question remains open was the rubber cavitation sufficient to boost the development of dissipative mechanisms in these resins ... 

Fig. 30 SEM/BSE (Scanning Electron Microscopy/Back Scattering Mode) images of microdeformation of both a non-nucleated and b -modified PP/EPR grades described in Sect. 5.4 tested at 1 m s 1 and room temperature...

Powder x-ray diffraction (Siemens D-500 diffractometer) and scanning electron microscopy (JEOL, JSM-840) methods were used for characterization of zeolite products. Infrared spectra (Perkin Elmer 783 infrared spectrophotometer) were used for investigation of nucleation gel. The amount of Si, Al, Na in zeolite products was analysed by conventional analytical method, i.e. gravimetric for Si, gravimetric and volumetric methods (titration by EDTA) for Al and flame photometric method for Na. The WL value in Table 1 was used to estimate the amount of water and organic species in an as-synthesized zeolite product. 

FROM ICE TO CO2 HYDRATES AND BACK - STUDY OF NUCLEATION AND INITIAL GROWTH USING SCANNING ELECTRON MICROSCOPY... 

Figure 9.30 (a) Evidences about the homogeneous nucleation mechanism in neat poly(methyl methacrylate) (PMMA) and (b) evidences about the heterogeneous nucleation mechanism in 90/10 PMMA/MAM blends. SEM, scanning electron microscopy RT, room temperature. 

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