Colloid specific surface

A colloid specific surface area of the colloid, in a colloid/rock system... 

This area, comparable to colloidal specific surface areas, is critical in the understanding of interfacial bonding and ensuing mechanical properties. Lipatov et used SAXS methods to determine the same quantities on polyurethane IPN s. The results are summarized in Table... 

Silica sols are often called colloidal silicas, although other amorphous forms also exhibit colloidal properties owing to high surface areas. Sols are stable dispersions of amorphous siUca particles in a Hquid, almost always water. Commercial products contain siUca particles having diameters of about 3—100 nm, specific surface areas of 50—270 m /g, and siUca contents of 15—50 wt %. These contain small (<1 wt%) amounts of stabilizers, most commonly sodium ions. The discrete particles are prevented from aggregating by mutually repulsive negative charges. 

In order to deposit gold on the supports with high dispersion as nanoparticles (NPs) and clusters, there are at least nine techniques which can be classified into five categories well mixed precursors, specific surface interaction, mixing gold colloids [18], physical deposition [19,20], and direct reduction [21]. The former two categories are schematically presented in Figure 3. 

The colloid can be recovered in the form of a powder with a specific surface of more than 100 m /g and can be redissolved in alcohol or water (pH > 7) 208,209)... 

One of the most obvious properties of a disperse system is the vast interfacial area that exists between the dispersed phase and the dispersion medium [48-50]. When considering the surface and interfacial properties of the dispersed particles, two factors must be taken into account the first relates to an increase in the surface free energy as the particle size is reduced and the specific surface increased the second deals with the presence of an electrical charge on the particle surface. This section covers the basic theoretical concepts related to interfacial phenomena and the characteristics of colloids that are fundamental to an understanding of the behavior of any disperse systems having larger dispersed phases. 

Microbial activity can also be stimulated by mineral colloids through their ability to sorb metabolites that would otherwise have an adverse effect on microbial growth (Filip et al. 1972 Filip and Hattori 1984) This may be due to the toxicity of metabolites, and their feed back repression and, encouraging competitors. Predictably, montmorillonite (CEC —100 cmol kg-1 and specific surface of 800 m g 1) is more effective than kaolinite and finely ground quarts. Other substances, such as antibiotics and pesticides that are toxic to some microorganisms, can also be adsorbed by the surfaces of mineral colloids (Theng and Orchard 1995 Dec et al. 2002). 

Particles of a size of less than 2 turn are of particular interest in Process Engineering because of their large specific surface and colloidal properties, as discussed in Section 5.2. The diffusive velocities of such particles are significant in comparison with their settling velocities. Provided that the particles scatter light, dynamic light scattering techniques, such as photon correlation spectroscopy (PCS), may be used to provide information about particle diffusion. 

Amorphous Silica The term amorphous silica refers to aggregate of smaU particles with high specific surface area. They lack crystal structure and do not form a sharp x-ray diffraction pattern. They are known in several forms such as colloidal silica, precipitated silica, silica gels, and fumed sdica. The surface of such amorphous silica may contain silanol (SiOH) groups or can be anhydrous. 

Schweikert s theory differs radically from the conventional thermohydrodynamic Chapman-Jouguet theory in that it provides for a continuous transition from burning to deton. In Section I entitled "Introduction , the author criticizes the validity of the C-J theory for condensed expls. In Section II the burning rate constants of a colloidal propint are related to fundamental parameters such.as specific surface vol of the powd, the most probable molecular vel, and the collision efficiency c. Schweikert arrives in Section III at the conclusion that burning deton differ primarily in the magnitude of c i.e. c l in a deton and is a much. smaller value in a burning process A surprisingly simple relation is derived in Section IV for the upper boundary of the deton vel Dm of a condensed expl ... 

The polydivinybenzene colloids prepared by the aerosol technique were carbonized to yield uniform porous spheres of carbon of relative high specific surface areas (69). 

The paradoxical situation just described means that it is entirely possible for a science or an engineering student to have completed a course in physical chemistry and still not have any clear idea of what colloid and surface science are about. A book like this one is therefore in the curious position of being simultaneously advanced and introductory. Our discussions are often advanced in the sense of building on topics from physical chemistry. At the same time, we have to describe the phenomena under consideration pretty much from scratch since they are largely unfamiliar. In keeping with this, this chapter is concerned primarily with a broad description of the scope of colloid and surface science and the kinds of variables with which they deal. In subsequent chapters different specific phenomena are developed in detail. 

Life sciences provide a fascinating array of examples in which colloid and surface science plays a vital (pun intended ) role in maintaining and promoting supramolecular structures and processes that sustain life. A specific example is the phospholipid bilayers that form the walls of biological cells and separate the interior of the cells from the rest of the environment (see Fig. 1.2 see also Chapter 8, Section 11). These bilayers arise from self-assembly of component molecules, each of which consists of a hydrophilic head group... 

A second kind of polymer, a colloidal aqueous dispersion, was reported by Renfrew (1950) who used bis- (/ -carboxypropionyl) peroxide as the polymerization initiator, and later described in more detail by Lontz and Happoldt. The specific surface of dispersion polymer is on the order of 12 m2/g, and the equivalent surface average diameter for dense spheres is about 0.2 fi. This is a good check with the observed size seen in the electron micrograph of Fig. lb and indicates that the primary dispersion particles have little, if any, porous structure. 

Colloids and interfaces are intimately related. This is a direct consequence of their enormous specific surface area. More precisely their interface-to-volume relation is so large, that their behavior is completely determined by surface properties. Gravity is negligible in the... 

Colloidal particles are formed from a homogeneous medium by the clustering of smaller units to form "embryos" of various sizes. In the case of polymers in solution the aggregates may be of repeat units of the same or different molecules. The specific surface area of such embryos is very great, and its creation requires the expenditure of an amount of energy equal to the area, A, times the interfacial free energy, y ... 

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