Carbon black, graphitized surface area

Figure 2.29 Multibed adsorption/desorption tube Carbotrap 300 (Supelco). Carbotrap, Carbotrap C graphitized carbon black, GCB, surface area about 12m /g. Carbosieve S-lll carbon molecular sieve, surface area about SOOm /g and pore size 15-40 A.

Nonmetal electrodes are most often fabricated by pressing or rolling of the solid in the form of fine powder. For mechanical integrity of the electrodes, binders are added to the active mass. For higher electronic conductivity of the electrode and a better current distribution, conducting fillers are added (carbon black, graphite, metal powders). Electrodes of this type are porous and have a relatively high specific surface area. The porosity facilitates access of dissolved reactants (H+ or OH ions and others) to the inner electrode layers. 

Measurement of adsorption phenomena by chemical means require adsorbents that have a relatively high surface area, preferably in excess of 20-50 m /g, to provide sufficient sensitivity. Such carbons are, e.g., activated carbons, carbon blacks, graphite wear dust, and carbon nanotubes. Physical measurements, such as by X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), electron energy loss spectroscopy (EELS), Fourier transform infrared (FTIR), and special Raman spectroscopies, can be done with materials of much lower surface area. 

Small amounts of inorganic fillers such as fumed silica, high surface area alumina, bentonites, glass spheres and ceramics are mixed with polyols such as propylene glycol to increase viscosity for printed electrodes. Proposed printed electrodes are carbon black, graphite, metallic or plated metaUic particles. 

With the exclusion of carbon black, graphite, acetylene black and vapor-grown carbon fibers as carbon conductive additives, multiwalled carbon nanotubes (MWCNTs) are also used as a carbon conductive additive. MWCNTs have many merits over amorphous acetylene black, such as high conductivity, small specific surface area and tubular shape. Thess et al. [138] report that electronic conductivity of MWCNTs thin film is about (l-4)xl0 S cm along the nanotube axis and 5-25 S cm perpendicular to the axis, respectively. 

Specific surface area of carbon blacks before and after graphitization, determined by electron microscopy (A,) end by nitrogen adsorption (A ]t... 

Molecular area, a (Ar) of argon at 77 K on graphitized carbon blacks (Argon BET plots constructed with p (liquid) surface areas determined by BET-nitrogen, with a (Na)... 

Acetylene black is very pure with a carbon content of 99.7%. It has a surface area of about 65 m /g, an average particle diameter of 40 nm, and a very high but rather weak stmcture with a DBPA value of 250 mL/100 g. It is the most crystalline or graphitic of the commercial blacks. These unique features result in high electrical and thermal conductivity, low moisture absorption, and high Hquid absorption. 

Carbon blacks are synthetic materials which essentially contain carbon as the main element. The structure of carbon black is similar to graphite (hexagonal rings of carbon forming large sheets), but its structure is tridimensional and less ordered. The layers of carbon blacks are parallel to each other but not arranged in order, usually forming concentric inner layers (turbostratic structure). Some typical properties are density 1.7-1.9 g/cm pH of water suspension 2-8 primary particle size 14-250 nm oil absorption 50-300 g/100 g specific surface area 7-560 m /g. 

Starting aaterial for their preparation and subsequent activation. Graphitized carbon blacks have low surface areas, usually less than 100 K /g and typically 5-30 u /g. They have a low capacity for low molecular weight analytes but have been used successfully for the isolation of heavier nonpolar analytes that might be difficult to recover from more active forms of carbon [169,170]. The most common form of carbon used for trace enrichment is granular activated carbon, generally prepared by tbe low temperature... 

Various forms of carbon are used to sample those analytes whose breakthrough volume is too low on Tenax for sufficient preconcentration [8,395-399]. Charcoal, graphitized carbon blacks, and ceurbosieves with wface areas from 5 to 900 w /g are commercially availablJ Bhe high surface area sorbents are used... 

Carbon comes in many forms and surfaces areas. Graphite can have surface area below 1 m2/g, while high surface area carbon blacks approach 2000 m2/g. If Pt adsorbs onto carbon at the same surface density, the Pt loading (Pt, wt%) will then be a function of the carbon surface area. Assuming that CPA can be adsorbed onto carbon at 1.6 mmol/m2, and PTA at 0.84 mmol/m2 at the respective SEA conditions, plot Pt (wt%) vs. surface area of carbon. 

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