Morphology agglomerates

Figure 39.4 shows the effect of urea addition on the morphology and nanoparticle formation of YAH (hexagonal YAIO3, an intermediate phase of YAG). The urea-nitrate ratio, in which the nitrate represents the precursor solution, was varied from 0 to 30. Figure 39.4a shows that most of the particles prepared from a precursor without a urea addition were in the submicron size (400-700 pm) with a small amount of nano-sized particles. When 1 M of urea (urea-nitrate ration is 10) was added, the quantity of nanoparticles increased while the size of larger particles was reduced. Well-dispersed nanoparticles, with an average size of 20 nm, were produced from the addition of 2 M urea in the nitrate precursor, as shown in Fig. 39.4c. The addition of more than 2 M of urea produced nanoparticles with an agglomerated morphology, as shown in Fig. 39.4d (urea addition of 3 M). These results show that the addition of 2 M urea into 0.1 M nitrate precursor is an effective way to produce...

In this section, we discuss theoretical and computational studies that provide insights into structural correlations and dynamical behavior of species in CLs. Structural complexity is an inherent trait of CLs. Advanced fabrication aims to improve Pt utilization by enhancing the interfacial area of Pt with water in pores and with Nafion ionomer [12, 94—95], A practical way to achieve this is by mixing ionomer with dispersed Pt/C catalysts in the ink suspension prior to deposition to form a CL. The solubility of the ionomer depends upon the choice of a dispersion medium. This influences the microstructure and pore size distribution of the CL [95]. Self-organization of ionomer and carbon/Pt in the colloidal ink leads to the formation of phase-segregated agglomerated morphologies. 

A PSD of the form given in Equation 8.24 can capture the main characteristics of the random phase-segregated, agglomerated morphology. Experimental data [139-141] have also suggested such log-normal pore size distributions in the mesoporous region. Typical pore size distributions obtained with this parameterization are depicted in Figure 8.9. 

Donnet and Voet [38] state that the DBP number is somewhat dependent upon the mechanical treatment of the carbon black during pelletisation. An increase in work done leads to an increase in pellet density and a reduction in DBP number. The variation in DBP number is partially related to a variation in the agglomerate morphology. 

Nucleation of particles in a very short time foUowed by growth without supersaturation yields monodispersed coUoidal oxide particles that resist agglomeration (9,10). A large range of coUoidal powders having controUed size and morphologies have been produced using these concepts (3,14). 

Characterization. The proper characterization of coUoids depends on the purposes for which the information is sought because the total description would be an enormous task (27). The foUowiag physical traits are among those to be considered size, shape, and morphology of the primary particles surface area number and size distribution of pores degree of crystallinity and polycrystaUinity defect concentration nature of internal and surface stresses and state of agglomeration (27). Chemical and phase composition are needed for complete characterization, including data on the purity of the bulk phase and the nature and quaHty of adsorbed surface films or impurities. 

The results of the mechanical properties can be explained on the basis of morphology. The scanning electron micrographs (SEM) of fractured samples of biocomposites at 40 phr loading are shown in figure. 3. It can be seen that all the bionanofillers are well dispersed into polymer matrix without much agglomeration. This is due to the better compatibility between the modified polysaccharides nanoparticles and the NR matrix (Fig. 4A and B). While in case of unmodified polysaccharides nanoparticles the reduction in size compensates for the hydrophilic nature (Fig. 3C and D). In case of CB composites (Fig. 3E) relatively coarse, two-phase morphology is seen. 

FIGURE 19.1 Morphology of nano-filler in rubbery matrix Nano-particles are aggregated, and the aggregates also associate to give filler agglomerate in rubber. (From Kohjiya, S., Kato, A., Suda, T., Shimanuki, J., and Ikeda, Y., Polymer, Al, 3298, 2006. With permission.)... 

The morphology of the agglomerates has been problematic, although some forms of network-like structures have been assumed on the basis of percolation behavior of conductivity and some mechanical properties, e.g., the Payne effect. These network stmctures are assumed to be determining the electrical and mechanical properties of the carbon-black-filled vulcanizates. In tire industries also, it plays an important role for the macroscopic properties of soft nano-composites, e.g., tear. 

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