Carbon black, surface area

Figure 6.37 Viscosity as a function of (a) shear rate or (b) shear stress of a polystyrene melt My, = 214,000) filled with carbon black (surface area =124 m /g) at various volume fractions 0 at 170°C. (From Lobe and White 1979, reprinted with permission from the Society of Plastics Engineers.)...

ASTM D 3037-93. Carbon black - surface area by nitrogen adsorption. 

Even if they are usually called primary particles, spheres that constitute aggregate are partially fused together and never exist by themselves. Anyway, their size is of great importance because it defines the actual surface of interaction between carbon black and elastomeric phase the lower the size of primary particles, the higher the interface extension. Primary particle size distribution has been estimated by TEM image analysis, but carbon black surface area is usually more efficiently obtained by adsorption methods (see later section on surface area). 

Because bound rubber measures elastomer adsorption onto filler surface, it is highly dependent on filler loading, specific surface, and strucfure, which are parameters that can be measured independently (Meissner, 1974). However, at given loading and carbon black surface area and structure, it has been demonstrated that bound rubber is also dependent on carbon black surface energy (Wolff et ah, 1993). 

Carbon Black Surface Area Bound Rubber (%)... 

Carbon black Surface area ( m lg) Approximate diameter of primary Diameter of particle size (nm) aggregate (nm) Size of agglomerate... 

Carbon black Surface area, m /g Temperature, Residence time, s Maximum velocity, m/s... 

Given that the cathodes were identical in all three lots of cells, the large variation in first cycle coulombic efficiency can be explained by comparing the total surface area of the anodes. In Chap. 1, Table 1.7 it was noted that MCMB 6-28 has a surface area of 4 m g In Sect. 1.4, the surface area of carbon black was stated to be >50 m g For this experiment, the carbon black surface area was about 60 m g . Therefore, Lot 2 had 5.3 % less anode surface area than Lot 1. Lot 3 had 21 % less surface area than Lot 1. The importance of total surface area of anode becomes clear when it is noted that SEI formation is mostly a surface reaction between anode and electrolyte. Variations in the first cycle coulombic efficiency are so important because the inefficiency during formation is irreversible. 

Often the amount of carbon black (CB) in a sample can be determined by switching the gas in the TGA from nitrogen to air or oxygen at 500 0 to 550 C such that CB converts to CO2. The carbon-black surface area can be approximated from the temperature of its decomposition, often taken as T15 or T20, the temperature at which 15% or 20% of combustion is complete [see Mauer (1981) Sircar (1997) and Rg. 3.20]. This CB analysis assumes all polymeric material has been volatilized prior to the introduction of oxygen. Beware of polymers that can form a char, such as those that contain aromatic structures, for they can cause erroneous CB determinations unless the pyrolysis of their... 

Increases in carbon black structure give increases in the value of the first-order rate constant k, but increases in carbon black surface area give decreases in the values of the first-order rate constant k. 

Test Methods for Carbon-Black-Surface Area by Nitrogen Adsorption. (Discontinued 1999). 

FIGURE 33.2 Dispersive component of carbon black surface energy as a function of its surface area. 

Fig. 4 shows two STM images of the surface structure of a carbon black. The sample exhibits a specific surface area, determined by N2 adsorption at 77 K, of 15.3 m g, which is almost coincident with its geometric area (16.9 m g ). Therefore, this is a nonporous carbon and its STM images should be expected to differ from those of the ACFs. As a matter of fact, this is what can be observed in Fig. 4. First, it is noted that the carbon black does not display any mesoporosity (Fig. 4a) such as that of the AFCs (Fig. 2). Second, at the micropore scale the carbon black porosity is also very poorly developed (Fig. 4b) in comparison with the pore development of ACFs (e.g.. Fig. 3a). In the former case (Fig. 4b), altough some trenches are also present, they are very shallow and, consequently, are simple topographic variations of a smooth surface and cannot be considered as pores penetrating deeply into the material as in Fig. 3a. Also, pores of the type shown in Fig. 3b for the ACFs were not normally seen on the carbon black surface. Hence, all these observations agree with the lack of adsorption capabilities of this material.

The adsorption of ionic surfactants onto hydrophobic polar surfaces resembles that for carbon black [24,25]. For example, Saleeb and Kitchener [24] found a similar limiting area for cetyltrimethyl ammonium bromide on Graphon and polystyrene ( 0.4nm ). As with carbon black, the area per molecule depended on the nature and amount of the added electrolyte. This can be accounted for in terms of the reduction in head group repulsion and/or counterion binging. 

Porous carbons constitnte a fascinating kind of material. Different types with distinctive physical forms and properties (i.e., activated carbons, high-surface-area graphites, carbon blacks, activated carbon cloths and fibers, nanofibers, nanotubes, etc.) find a wide range of indnstrial applications in adsorption and catalysis processes. The main properties of these materials that make them very useful as catalyst supports, as well as some of their applications, have been described. The use of carbon as a catalyst support relies primarily on the relative inertness of its surface, which facilitates the interaction between active phases or between active phases and promoters, thus enhancing the catalytic behavior. This makes porous carbons an excellent choice as catalyst support in a great number of reactions. 

Compared to morphology, filler chemistry has been only slightly studied, partly because of the difficulty of such characterizations and more probably because since the 1970s reinforcement is broadly considered as a physical interaction between elastomer and filler. So carbon black chemical characterizations mainly date from the 1960s, and few new technical methods have been applied to carbon black surface characterization since then. The situation is somewhat different for silicas, because silica reinforcement is the consequence of a chemical reaction of silane with silica surface. Few studies have been published in the elastomer reinforcement area, probably because silica surface was already well characterized for other applications. 

Chem. Descrip. Furnace carbon black, surface oxidized (treated) grade CAS 1333-86-4 EINECS/ELINCS 215-609-9 Uses Colorant, filler for premium offset inks, specialty coatings Properties Beads, powd. 21 nm mean particle size sp.gr. 1.80 surf, area 122 m7g oil absorp. 66 (beads, powd.) 2.7% volatiles Raven 1500 [Columbian Chems.]... 

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