Nonaqueous colloid

Gast A P, Flail C K and Russel W B 1983 Polymer-induced phase separations in nonaqueous colloidal suspensions J. Colloid Interface Sol. 96 251 -67... 

A.P. Gast, C.K. Hall, and W.B. Russel Polymer-Induced Phase Separations in Nonaqueous Colloidal Suspensions. J. Colloid Interface Sci. 96, 251 (1983). 

Polymerizations that are carried out in nonaqueous continuous phases instead of water are termed dispersion polymerizations regardless of whether the product consists of filterable particles or of a nonaqueous colloidal system. 

The phase behavior of nonaqueous colloidal suspensions containing nonadsorbing polymer was investigated by Gast et al. [3] on the basis of statistical mechanics. In their theory, a second-order perturbation approach was used to calculate the free energy. Rao and Ruckenstein [4,5] examined the phase behavior of systems involving steric, depletion, and van der Waals interactions. 

The scope of this volume is broad, with topics ranging from surface physics and chemistry to aqueous and nonaqueous colloid science. The subject matter chosen illustrates both the breadth and depth of scientific knowledge needed to advance these important technologies, and emphasizes the common scientific threads which run through these apparently differing subjects. 

This paper is intended to review characterization methods of nonaqueous colloids, their physical properties and technological applications. 

The description of a colloid should include particle size, mobility, charge and their distributions, charge/mass ratio, electrical conductivity of the media, concentration and mobility of ionic species, the extent of a double layer, particle-particle and particle-substrate interaction forces and complete interfacial analysis. The application of classical characterization methods to nonaqueous colloids is limited and, for this reason, the techniques best suited to these systems will be reviewed. Characteristic results obtained with nonaqueous dispersions will be summarized. Physical aspects, such as space charge effects and electrohydrodynamics, will receive special attention while the relationships between chemical and physical properties will not be addressed. An application of nonaqueous colloids, the electrophoretic development of latent images, will also be discussed. 

Figure 1. Schematic of low (left) and intermediate (right) conductivity nonaqueous colloids. Key 0, positively charged particles counterions +, positive excess ions and —, negative excess ions.

As with many technological advances, however, the development of stable, nonaqueous colloidal dispersions posed theoretical problems including the mechanism... 

Leo S, Tallon C, Franks GV (2014) Aqueous and nonaqueous colloidal processing of difficult-to-densify ceramics suspension rheology and particle packing. J Am Ceram Soc 97 3807-3817... 

Electrochemical methods are in general free from the difficulties associated with the current industry testing methods and present an opportunity for a relatively quick, simple, and inexpensive approach, free of temperature limitations and sample preparation issues. Electrochemistry has been previously employed to inspect lubricant condition over the life of engine oils [6, 7]. For example, electrochemical impedance spectroscopy (EIS) has been used for characterization of both engine oils [8] and nonaqueous colloidal dispersions [9]. 

Sodium borohydride is quite a strong reducing agent and therefore it has been often used for the reduction of metal salts to produce small metal particles in solution. Klabunde and co-workers performed a large amount of work on the synthesis of magnetic particles based on iron and cobalt " using borohydride reduction. For these metals however, some complications can arise if the stoichiometry is not carefully adjusted, since otherwise one can easily end up with the corresponding metal borides. Borohydride has also been applied for the reduction of noble metals, both in aqueous and in non-aqueous solution. We restrict ourselves in this section to reactions in aqueous media, while borohydride production of nonaqueous colloids is discussed in Section 2.2.1. 

The AC impedance technique is compatible with both conventional and microfabrication technologies, allowing production of rugged devices for applications in the harsh, highly resistive, chemically complex, and often aggressive media of industrial lubricants and colloids [25]. EIS presents an opportunity to resolve complicated nonaqueous colloidal system both spatially and chemically, and can be applied to monitoring lubricant s degradation process. 

EIS characterization of electrorheological fluids (ERF) represents an interesting subsegment of dielectric analysis of nonaqueous colloidal systems. Analogous to soot-contaminated lubricants (Chapter 10), ERFs can be described as... 

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