Density, monodisperse particle

Eng used the galvanostatic deposition of monodisperse polystyrene particles onto a RCE from an acidic copper sulfate to test her theoretical predictions. The particle deposition was found to increase with current density. The increase was greatest at a rotation speed of 615 rpm, and lower at higher and lower rotation speeds. The effect of current density on particle deposition is predicted using her MEIPET boundary conditions but the effect of the rotation speed cannot be explained. 

This paper outlines the basic principles and theory of sedimentation field-flow fractionation (FFF) and shows how the method is used for various particle size measurements. For context, we compare sedimentation FFF with other fractionation methods using four criteria to judge effective particle characterization. The application of sedimentation FFF to monodisperse particle samples is then described, followed by a discussion of polydisperse populations and techniques for obtaining particle size distribution curves and particle densities. We then report on preliminary work with complex colloids which have particles of different chemical composition and density. It is shown, with the help of an example, that sedimentation FFF is sufficiently versatile to unscramble complex colloids, which should eventually provide not only particle size distributions, but simultaneous particle density distributions. 

A series of monodisperse PMMA latexes was synthesized and characterized with respect to refractive index, percent solids, and solution density. The particle size of each latex was analyzed by several different instrumental methods. The methods used include DCP, SFFF, HDC, Quasielastic Light Scattering (QELS), TEM, and turbidity. 

It is important to note that the fluid-solid drag coefficients discussed above are valid only for monodisperse particles (i.e. particles with equal diameters and material densities). Using direct numerical simulations (DNS) of the microscale equations for fluid-particle flows, several authors (Beetstra et al, 2007 Buhrer-Skinner et al, 2009 Holloway et al, 2010 Tenneti et al, 2010, 2012 Yin Sundaresan, 2009) have proposed improved drag coefficients to account for polydisperse particles. 

Particles can be monodisperse, or possess a certain distribution of sizes—wide, narrow, bimodal, and so on. Distribution can be irregular, typically a mix of particles of different sizes. This property of a particle mix largely depends on milling technology and classihcation (screening) of particles. A wide distribution or a bimodal distribution of particles of a mineral hller can be benehcial because it can provide a better packing density of particles in the matrix. Particle size distribution can affect viscosity of the hot melt. 

We consider a system of monodisperse particles of number density N which are oriented at random. The scattering intensity I(q) as function of q, the magnitude of the scattering vector is given by [1-5]... 

Consider now a representative single particle of volume V and density Pp in such a fluidized swarm of monodispersed particles. Macroscopically steady-state fluidization requires that downward gravitational force = upward buoyant force -I- upward drag, i.e.. 

The value of x is determined by the geometry of the system, primarily by the particle size (radius, r, for spherical particles) and by the packing density of particles described by porosity, H. The porosity is a dimensionless characteristic defined as the ratio of the volume of pores, Vp to the total volume of the porous structure, V, that is, n = Vp/V. The x = Xir, H) dependence can be estimated from data on the degree of dispersion of the particles and the porosity of samples by employing the specific models for disperse structures. Eor example, in the case of loose monodisperse structures with spherical particles connected into crossing chains with n particles per chain between the nodes (Figure 3.17), the X function for the case when the porosity H does not exceed 48% can be described as... 

As particle counter a special automatic system devised by Technicon Instr. Corp., USA, has been applied. The method described above allows the preparation of 0.5-5 pm relatively low density monodisperse... 

A new reducing agent (one of the natural plant pigments, quercetin, Qr) for the synthesis of Ag nanoparticles in reverse micelles was reported to generate highly stable and rather monodisperse particles [311]. It was reported that apart from its strong interaction with performed nanoparticles, Qr reduces silver ions from aqueous salt solutions, presumably through the formation of an intermediate complex where electron density is shifted towards the silver ion. 

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