Surfactants, carbon black particles

A wellbore fluid has been developed that has a nonaqueous continuous liquid phase that exhibits an electrical conductivity increased by a factor of 10 to 10 compared with conventional invert emulsion. 0.2% to 10% by volume of carbon black particles and emulsifying surfactants are used as additives. Information from electrical logging tools, including measurement while drilling and logging while drilling, can be obtained [1563]. 

Preparation of aqueous carbon black dispersion Carbon black particles are dispersed in water with appropriate surfactant to form a dispersion. 

Table IV. Eifect of Surfactants on Size of Monarch Carbon Black Particles...

In view of such applications, the adsorption of a grafted (rake-type) polymeric siloxane surfactant containing 48% PDMS, 39% PEO, and 13% PPO on carbon black particles dispersed in mixtures of water with polar organic solvents has been investigated [58]. The adsorption was foimd to obey the Langmuir isotherm below the critical micelle concentration and a sharp increase in the adsorbed amount was observed at higher surfactant concentrations. DLS and SANS data indicate that the structure of the adsorbed layer is similar to that of micelles. 

Fig. VI.4. Adhesive interaction diagram for carbon black particles on steel surface (I) no adhesion (II) reversible adhesion, or unstable state (III) irreversible adhesion, or stable state Hq is the thickness of the adsorbed surfactant layer 5 is the degree of surface coverage A//tr=12.5.

A major problem in the treatment of nonaqueous systems is the removal of eolloidal particles to produce acceptable liquid products (e.g., fuel oil). Such a situation is encountered in hydrocarbon production from tar sands and oil shale. The particles (such as oxides, silicates, and clay mineral) suspended in the hydrocarbon hquids originate from a rock matrix. Particle separation problems occur in the solvent extraction of bitumen with nonaqueous media such as toluene. Electrostatic forces (bonding forces) play a predominant role in the physical state of these nonaqueous systems. In many instances, by addition of antisolvents, and selecting the proper temperature and agitation, these systems can be altered to improve solid separation. Separation of carbon black particles suspended in tetralin using Aerosol OT as a surfactant and by filtration through a bed of sand (deep-bed filtration) is another example of liquid-solids separation in nonaqueous systems. 

The typical MPL materials start as an emulsion of carbon black particles mixed with fluoropolymers in aqueous solution. The miscibility and partial surface area coverage are controlled by adding surfactants and light alcohols to the mixture. The resulting slurry consists of up to 20 wt% solids, and it can be apphed to the GDL substrate by spraying, screen-printing, and manual deposition. 

In addition to ionic surfactants, nonionic surfactant molecules can also adsorb onto the particle surfaces to impart satisfactory stabihty to colloidal dispersions [20, 21]. Some very old examples include India ink and carbon black particles dispersed in the continuous aqueous phase containing a natural gum. This kind of colloidal stabilization mechanism (termed steric stabilization) was first illustrated experimentally by M. Faraday [31, 32]. Some representative polymeric materials (protective colloids) that are effective in preparing steri-cally stabilized aqueous colloidal dispersions are summarized in Table 2.7 [21]. A portion of an effective protective colloid must be hydrophobic enough to show a strong tendency to adsorb onto the hydrophobic particle surface. Furthermore, the adsorbed macromolecules must form a relatively thick hydrophilic layer surrounding the particle, which serves as a steric barrier to prevent the colloidal particles from flocculation. 

Carbon black may serve as a low-cost additive for controlling the gas migration in cement slurries [303]. It is intended as a suitable substitute for polymer latex and silica fume and has been tested in field applications [304,1256]. The concentration of carbon black varies from 2 to 20 parts, based on the weight of the dry cement [1220]. The particle size varies from 10 to 200 nm. A surfactant is necessary for dispersion, for example, formaldehyde-condensed naphthalene sulfonate or sulfonated cumarone or indene resins. 

Nano-sized PtRu catalysts supported on carbon have been synthesized from inverse micro emulsions and emulsions using H2PtClg (0.025 M)/RuCl3 (0.025 M)/NaOH (0.025 M) as the aqueous phase, cyclohexane as the oil phase, and NP-5 or NP-9) as the surfactant, in the presence of carbon black suspended in a mixture of cyclohexane and NP-5-I-NP-9 [164]. The titration of 10% HCHO aqueous solution into the inverse micro emulsions and emulsions resulted in the formation of PtRu/C catalysts with average particle sizes of about 5 nm and 20 nm respectively. The RuPt particles were identified by X-ray diffraction. X-ray photoelectron, and BET techniques. All of the catalysts prepared show characteristic diffraction peaks pertaining to the Pt fee structure. XPS analysis... 

Of course, surface charge development has been well documented in the carbon black literature [36, where particle coagulation is the key issue. Thus, for example. Kratohvil and Matijevic [56] measured electrophoretic mobilities and concluded (without alluding to the work of Frampton and Gortner) that [c]arbon particles carry a positive charge at lower pH values." They also studied the pH dependence of the adsorption of a nonionic and an anionic surfactant as well as of electrolytes with counterions of varying charges. 

Carbon black Surfactant level Particle size (nm)... 

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