Particle diameter distributions

Fig. 4 Profiles of particle diameter distribution for Mg/Al-COs LDHs with different ratios prepared using (a) the new method using rapid mixing and nucleation in a colloid mill followed by a separate aging step and (b) conventional coprecipitation at constant pH. The new method affords materials with a much narrower range of diameter. Reprinted with permission from [20], Copyright ACS Journal Archives...

In exposures of humans to artificially generated aerosols, where the information is to be relevant to ambient aerosols, several factors are important the particle diameter distribution must be fairly constant and fall within size ranges typical for the given compound in the ambient air, the chemical composition of the aerosol must be stable and predictable, and the electric charge distribution of the aerosol must simulate that of normal atmospheric aerosols. 

Figure 1.2 Particle diameter distribution for a polydispersed colloidal dispersion expressed (a) in histogram form, and (b) as a cumulative distribution...

Fig. 3.5 Particle diameter distribution of monomolecular particles obtained from various molecular weight polystyrenes. (From ref. [53])...

Figure 3.5 shows the particle diameter distributions for the particles corresponding to the observation by transmission electron microscopy. From these results a clear molecular weight dependence of diameter distribution can be observed. 

Fig. 7.7 Scanning transmission electron microscopy (STEM) images of supported gold catalysts, along with particle diameter distributions, double-logarithmic plots showing how particle volume (proportional to intensity) depends on particle size, and geometric distributions of truncated octahedrons with certain edge lengths and thickness, as indicated in Figure 7.8. (Adapted from [18]).

Figure 2.1a shows a line chart of the midpoints of the data. Although the particle diameter distribution is plainly shown, it is possible to alter the shape of the distribution by changing the interval size. 

AN4 plus laser scattering particle meter (Coulter) was used to measure the sol particle diameter distribution at a 90 angle to the light beam. The material structure and chemistry were characterized by X-ray diffraction (XRD, Rigaku D/MAX-RB), atomic force microscopy (AFM, Nanoscope III), transmission electron microscopy (TEM, JEM2010) and N2 physi-adsorption (Omnisorp-lOOCX). 

Preparation of semithin sections (up to a few micrometers thick) by ultramicrotomy, and investigation of these sections in a 1000-kV, high-voltage electron microscope (HVEM) to reveal larger particles more precisely and, thus, the true particle-diameter distribution. 

In the past, several ABS grades were produced with a broad or bimodal particle-diameter distribution. Particles of different sizes can contribute to crazing in different ways. Figure 7 shows such a material and clearly reveals the greater capability of the largest particles to initiate crazes. Beside these large particles, the smaller ones show only a small effect on craze initiation. 

The result of the diameter-dependent modulus is an increased stress concentration and increased tendency to craze initiation with increasing particle diameter. This result is demonstrated in the micrograph of an ABS polymer in Figure 7, which shows the preferred craze formation at the largest rubber particles. Therefore, toughened materials with a broad particle-diameter distribution or a bimodal diameter distribution often show preferred craze initiation at the largest particles, which has the disadvantage of reduced effectiveness (23). The maximum formation of crazes appears in a material with rubber particles of optimum diameter, Dopt and a small diameter distribution. 

Figure 1 shows that the particle diameter distribution is narrower at the first peak (R = 1.5%) than at the second peak after agglomeration. The distribution width is 1.0689 at the first peak and 1.1998 at the second peak (Figs. 2-5). 

The emulsion samples were diluted with 2.0 percent NaCl electrolyte before measurement. These data were reported in particle diameter distribution by volume and population. 

After completion of each polymerization step, a sample of reartion mixture was analyzed. Diameters and diameter distributions of microspheres after the first polymerization step were equal to Dn = 3.97pm and D v/Dn=1.09. The second step yielded particles with Dn = 5.44pm and Dw/Dn = 1.13. The third monomer addition allowed to obtain particles with Dn = 6.36 pm and D /Dn = 1.20. Hius, the broadening of particle diameter distribution after each monomer addition is evident, but it is not very large. 

Fig. 2 Particle diameter distribution of i-PS single-chain crystals...

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