Particles, anisometric

Analog calorimetry Anionic polymerization Anisometric particles Anisometric properties Annealing... 

Diffusion and sedimentation measurements on dilute solutions of flexible chain molecules could be used to determine the molecular extension or the expansion factor a. However, the same information may be obtained with greater precision and with far less labor from viscosity measurements alone. For anisometric particles such as are common among proteins, on the other hand, sedimentation velocity measurements used in conjunction with the intrinsic viscosity may yield important information on the effective particle size and shape. ... 

Table 6.2 Theoretical multiplication factors for anisometric particles with an aspect ratio r 1. (Note For a disc-shaped particle the aspect ratio is the ratio of disc diameter disk thickness and for a rod-shaped particle it is the ratio of rod length rod diameter). (Source R. Bown, Physical and Chemical Aspects of the Use of Fillers in Paper , in Paper Chemistry , ed. J.C. Roberts, Blackie, Glasgow, 1992, pp. 162-196).

Birefringence induced by flow in liquids, solutions and dispersions of optically anisotropic, anisometric or deformable molecules or particles due to a non-random orientation of the molecules or particles. 

When concluding on the particle size and shape from images obtained by freeze fracture TEM, the fact that the particles are fractured randomly with respect to the localization of the fracture site within the particle and to orientation toward the fracture plane has to be taken into consideration. Most of the particle remains hidden from observation. Therefore, a sufficiently large number of particles have to be investigated to obtain a realistic impression. The determination of a particle size distribution will not be possible when the particles are of anisometric shape. 

There has been much interest in flow and flow orientation effects with polymer melts containing anisometric particles which may be plate-like or fibrous. Flow-induced orientation of short reinforcing fibres is an area of considerable commercial importance, which is beyond the scope of the review [30]. 

For anisometric particles (e.g., needle- or platelet-shaped particles) mathematical statistics may likewise be applied [1.10]. The two-dimensional logarithmic normal distribution of the length L and breadth B of the particles also allows the representation and calculation of the characteristic parameters and mean values. The eccentricity of the calculated standard deviation ellipse (Fig. 2) is a measure of the correlation between the length and breadth of the particle. By using more than two... 

Similar to zero-dimensional metal nanoparticles, most of the work on one-dimensional metal nanostructures focuses almost exclusively on gold nanorods. The high interest in anisometric gold nanoclusters arises from their unique optical and electronic properties that can be easily tuned through small changes in size, structure (e.g., the position, width, and intensity of the absorption band due to the longitudinal surface plasmon resonance is strongly influenced by the shell as well as the aspect ratio of the nanorods), shape (e.g., needle, round capped cylinder, or dog bone), and the inter-particle distance [157]. 

Finally, magnetic nanowires and other submicrometer-scale anisometric particles can also be manipulated and organized via controlled spatial variations in the alignment of nematic liquid crystals. Leheny and co-workers, for example, measured the elastic forces imposed on anisotropic Ni nanowires suspended in a nematic liquid crystal (here 5CB, Fig. 13a), and showed that by applying a magnetic field the nanowire reorients and distorts the director in the adjacent area [445, 446]. 

The sedimentation of isometric particles, such as cubes and octa-hedra, deviates only slightly from the Stokes equation. Significantly anisometric particles that can be approximated by ellipsoids of revolution are amenable to rigorous sizing by centrifugation if the axial ratios q are known. If the major semi-axis is a and the minor semi-axis is c, the sedimentation velocity dx/dt can be written as... 

Figure 7.25 Alignment of anisometric particles in the slip-cast layer is possible due to the capillary forces acting normal to the mold wall. Particles will tend to follow the mold contours.

In the treatment below suspensions with monodisperse spherical particles are considered unless specific reference is made to anisometric particles or particle size distributions. 

The results collected in this review are focused to demonstrate the advantages of electro-optics for investigation of the electrical properties of anisometric particles in dilute suspensions containing polyelectrolytes. Results on the structure of the adsorbed macromolecules and the stability of suspensions containing polyelectrolytes will also be discussed. 

When we apply an electric field to a suspension of anisometric colloid particles (or a solution of polyelectrolyte molecules), the particles tend to orient into the field direction, and this results in a macroscopic optical anisotropy effect. This effect may be expressed by the equation... 

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