Agglomerates, electron microscopy

Particle Formation, Electron microscopy and optical microscopy are the diagnostic tools most often used to study particle formation and growth in precipitation polymerizations (7 8). However, in typical polymerizations of this type, the particle formation is normally completed in a few seconds or tens of seconds after the start of the reaction (9 ), and the physical processes which are involved are difficult to measure in a real time manner. As a result, the actual particle formation mechanism is open to a variety of interpretations and the results could fit more than one theoretical model. Barrett and Thomas (10) have presented an excellent review of the four physical processes involved in the particle formation oligomer growth in the diluent oligomer precipitation to form particle nuclei capture of oligomers by particle nuclei, and coalescence or agglomeration of primary particles. 

Transmission electron microscopy for [Pd/l]coii reveals the presence of small spherical but in some cases agglomerated particles of ca. 4 nm mean size, and wide angle X-ray scattering analyses evidence the fee structure of bulk palladium [44] (Figure 1). 

The 11 nm-sized Ti02 were crystallized using either hydrothermal or thermal methods from 100 nm, amorphous gel spheres. The Ti02 crystal and agglomerate sizes were determined by X-ray diffraction (Philip 1080) and transmission electron microscopy (JEOL JEM 2010), respectively. The surface area and chemistry of the nanostructured Ti02 were analyzed by nitrogen physisorption (Coulter SA 3100) and Fourier transform infrared spectroscopy (FTIR, Perkin-Elmer GX 2000). Metal catalyst was deposited by incipient... 

The sfabilify of Pf particles during the 1.2 V hold has also been investigated. At 1.2 V and 80°C in 1 M H2SO4, up to 35% of the ECA was lost after 24 h. Transmission electron microscopy analysis of the tested catalysts found a growth in the Pt particle size distribution, suggesting that small Pt particles (-2 nm) are particularly susceptible to dissolution/agglomeration xmder steady-state voltage holds at 1.2 V. 

Particle morphology Scanning electron microscopy Fibre, agglomerated... 

Figure 20 demonstrates by transmission electron microscopy the distribution of platinum microcrystals on (transparent) graphitized soot. Soot particles form agglomerates that measure around 0.1 /u-m in diameter. 

As already mentioned, electron microscopy (both transmission and scanning) has been used to characterize the precipitated particles. The information obtained in this way includes (i) the nature of the precipitated phase (particulate or non-particulate), (ii) the average particle size, if particulate, (iii) the distribution of particle sizes, (iv) the degree to which the particles are well defined, and (v) the degree of agglomeration of the particles.18... 

The particles synthesized were observed to agglomerate, probably due to effects induced by the electron microscopy analysis. 

Descriptors of size, agglomeration state, shape, porosity, and surface could be obtained from images taken by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and atomic force microscopy (AFM) [46]. 

Figure 3. Electron microscopy images of the graphite (a) and nickel (b) explosion products in the toluene a) agglomeration of nanotubes, b) separated multy-walled nanotube.

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