Colloidal suspension of solid particles

The first phase in the process is the formation of the sol . A sol is a colloidal suspension of solid particles in a liquid. Colloids are solid particles with diameters of 1-100 nm. After a certain period, the colloidal particles and condensed silica species link to form a gel - an interconnected, rigid network with pores of submicrometer dimensions and polymeric chains whose average length is greater than one micrometer. After the sol-gel transition, the solvent phase is removed from the interconnected pore network. If removed by conventional drying such as evaporation, so-called xerogels are obtained, if removed via supercritical evacuation, the product is an aerogel . 

Clearly, colloidal particles lie on the border-line between coarse particles, which obey the ordinary sedimentation laws, and atoms and molecules, which do not it is therefore not surprising tnat colloidal particles behave as they do. Although we shall be concerned mainly with suspensions of solid particles in water, it should be realized that colloidal suspensions of solid particles in liquids other than water can be produced. 

A further advantage of PMMA relies on its availability. Uniformly sized PMMA spheres are prepared by polymerization of methyl methacrylate (MMA) in water. The product of the polymerization then takes the form of a colloidal suspension of solid particles that are so small that they tend not to settle. By centrifugation, the PMMA particles are forced to settle and pack into a solid, often called a colloidal crystal. In such colloidal crystals, the PMMA spheres are arranged in a close-packed fashion in the same manner as the silica spheres that make up natural opal [178]. Therefore, these materials can be referred to as synthetic opals. Several textbooks cover selective aspects of the physicochemical properties of PMMA [181,182]. 

The method consists of preparation of a sol (colloidal suspension of solid particles with size in the 1-1000 nm range, dispersed in a liquid), its gelation, and removal of the entrapped solvent molecules. Dispersion of a hydroxide M(OH) is not a suitable method to prepare a sol, as the particles do not disperse sufficiently and precipitation occurs formation of the hydroxide in situ by increasing the pH of a solution of the metal cation is not valid. Usually the sol is formed by... 

It is widely believed that On a clear day you can see forever, as proclaimed in the 1965 Broadway musical of the same name. While an admittedly beautiful thought, we all know that this concept is only figurative. Aside from Earth s curvature and Rayleigh scattering by air molecules, aerosols—colloidal suspensions of solid or liquid particles in a gas—limit our vision. 

Narrowing of NMR lines has been observed in colloidal suspensions of ultrafine particles, presumably by Brownian motion. A suggestion related to this principle is to take small solid particles into a liquid medium and induce sufficient reorientational motion of these particles to produce narrowing (Satoh and Kimura 1990). Ultrasound induces translational motion and collisions of the particles produce rotation. This sonically induced narrowing has been observed for Al in aluminium sulphate, with the advantage that no spinning sidebands were observed (Homer et al. 1991). The experiment depends on the frequency and the power of the ultrasound and the liquid medium. Although the first reports of this approach appeared in 1989 there have been few developments in this field. 

A number of colloids are familiar to us. An aerosol consists of liquid droplets or solid particles dispersed in a gas. Examples are fog and smoke. Mayonnaise, which is made by breaking oil into small droplets in water, is an example of emulsion, which consists of liquid droplets dispersed in another liquid. Milk of magnesia is an example of sol, a suspension of solid particles in a liquid. 

An important technique is that in which it is the precursor of the final colloidal particle that is reduced to a colloidal size. Thus a liquid reactant may be emulsified and then caused to react to form a colloidal dispersion of solid particles whose particle size distribution is related to that of the emulsion precursor. The commonest application of this method is in suspension polymerisation, in which an emulsion of monomer droplets, stabilised by a surfactant, is polymerised by adding an initiator which is soluble in the monomer. Polymerisation occurs within the monomer droplet, leading to the formation of a polymer latex. 

Emulsions and suspensions of solid particles are common examples of colloidal systems that are not in the equilibrium state. As the systems destabilize and approach the equilibrium state, several processes will be involved. Typically, flocculation, sedimentation, and coalescence, etc., take place simultaneously at more or less well-defined rates, continuously changing the properties of the system. 

The stability of an emulsion, once formed, towards electrolytes added to the system shows close resemblance to that of sols or suspensions of solid particles. In this respect emulsions may be compared with normal lyophobic colloids. Accordingly... 

Abstract. The stability of suspensions/emulsions is under consideration. Traditionally consideration of colloidal systems is based on inclusion only Van-der-Waals (or dispersion) and electrostatic components, which is refereed to as DLVO (Derjaguin-Landau-Verwey-Overbeek) theory. It is shown that not only DLVO components but also other types of the inter-particle forces may play an important role in the stability and colloidal systems. Those contributions are due to hydrodynamic interactions, hydration and hydrophobic forces, steric and depletion forced, oscillatory structural forces. The hydrodynamic and colloidal interactions between drops and bubbles emulsions and foams are even more complex (as compared to that of suspensions of solid particles) due to the fluidity and deformability of those colloidal objects. The latter two features and thin film formation between the colliding particles have a great impact on the hydrodynamic interactions, the magnitude of the disjoining pressure and on the dynamic and thermodynamic stability of such colloidal systems. 

Colloids are suspensions of solid particles that are so small that a large proportion of the atoms in the particles are part of the surface layer and not of the interior. Ultrafine particles can be said to have more surface than bulk atoms. Colloid chemistry is surface chemistry. ... 

In the laboratory you may form mists or aerosols when a bottle of chemical is opened, when the contents of an open bottle are shaken, when chemicals are poured into other vessels, or when a chemical is spilled and hits a solid surface. Fumes are a colloidal suspension of solid or liquid particles. Grinding a metal can generate fiimes when the metal gets hot enough to vaporize but then quickly cools and recondenses to a solid in the form of tiny small particles. Fuming sulfuric acid and fuming nitric acid produce clouds of these acids over the surfaces of the liquids. Dusts are solid particles suspended... 

Suspensions of colloidal particles exhibit different properties that are dependent on various parameters. One of these properties is that the suspension of solid particles will exhibit varying degree of stability. It is thus interesting to determine how these systems are stabilized as regards the various forces interacting between the particles. 

Definition Aerosols are snspensions of solid or liquid particles in a gas. Dust, smoke, mists, fog, haze, and smog are various forms of common aerosols. Colloids are suspensions of solid particles in a liquid. Colloidal particles are typically in the range of nanometers to few microns. The rheological properties of colloidal suspensions are strongly affected by the donble-layer forces. Emulsions are suspensions of droplets of liquids in another immiscible liquid. 

In the framework of the classical colloid-chemical concept, filled polymer can be considered as a suspension of solid particles, 1, separated by the interlayers of continuous polymeric phase, 2 (thickness, 8). The energy of interaction between any two particles of a solid phase is expressed as... 

AEROSOL A colloidal suspension of liquid or solid particles dispersed in gas. 

If the volume of solid particles is conserved during agglomeration, the volume fraction of colloidal particles, the volume of colloids per unit volume of suspension, <>, can be expressed as... 

Colloid chemistry investigates substance mixtures. These substance mixtures can be heterogenous, such as emulsions (in which tiny droplets of one liquid are dispersed in another), suspensions (consisting of a fine dispersion of solid particles in a liquid volume phase), and aerosols (in which liquid droplets are dispersed in the gas phase). However, there are also homogenous mixtures in which the solute is present in larger, supermolecular aggregates. These homogenous mixtures include micellar solutions and liquid crystalline... 

A sol is a colloidal suspension of particles in a liquid for the materials being discussed here, these particles will typically be 1 to 100 nm in diameter. A gel is a semi-rigid solid in which the solvent is contained in a framework of material which is either colloidal (essentially a concentrated sol) or polymeric. 

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