Carbon shape categories

Figure 18.2 Rendering of shape categories for carbon black aggregates. Compare to data in Table 18.2. (After Ref [8], reprinted with permission from Marcel Dekker, Inc.).

Carbon black DBPA (cm /IOOg) Weight % of each shape category 12 3 4 ... 

Industrial carbon adsorbents are complex products difficult to classify on the basis of their behaviour, surface characteristics, properties or utility. However, they are usually categorised according to their particle shapes and size into powdered, granulated, spherical, pelletised or fibrous (in the form of felt or cloth) activated carbons. These categories can be further sub-divided according to their various properties, e.g. porous structural or surface chemical structural characteristics. 

Natural diamonds are divided into three categories. First are the carbonate or black diamonds. These are the hardest and most expensive diamonds. They are used primarily as gage reinforcement at the shockpoint. Second are the West African diamonds. These are used in abrasive formations and usually are of gemstone quality. About 80% of the West African diamonds are pointed in shape and, therefore, 20% are the desirable spherical shape. Third are the Congo or coated diamonds. These are the most common category. Over 98% of these diamonds are spherical by nature. They are extremely effective in soft... 

The soccer ball shaped framework of Cgg was confirmed for the first time by the X-ray crystal structure of 13 [52]. The bridging of the OSO4 unit occurs in the characteristic 1,2-mode to a [6,6] double bond of the fullerene core. The 17 sets of carbons in the C2v-symmetric 13 were assigned using the 2D NMR INADEQUATE technique on the basis of their connectivities [53]. In these experiments C-enriched material was used. The coupling constants fall into three categories, 48, 54—57 and 65-71 Hz. These values can be attributed to the three types of C-C bonds present in 13, namely C(sp )-C(sp ), the longer [5,6], and the shorter [6,6] bonds, respectively [53]. 

The porous structure of ceramic supports and membranes can be first described using the lUPAC classification on porous materials. Thus, macroporous ceramic membranes (pore diameter >50 nm) deposited on ceramic, carbon, or metallic porous supports are used for cross-flow microfiltration. These membranes are obtained by two successive ceramic processing techniques extrusion of ceramic pastes to produce cylindrical-shaped macroporous supports and slip-casting of ceramic powder slurries to obtain the supported microfiltration layer [2]. For ultrafiltration membranes, an additional mesoporous ceramic layer (2 nm<pore diameter <50 nm) is deposited, most often by the solgel process [11]. Ceramic nanofilters are produced in the same way by depositing a very thin microporous membrane (pore diameter <2 nm) on the ultrafiltration layer [4]. Two categories of micropores are distinguished the supermicropores >0.7 nm and the ultramicropores <0.7 nm. 

A key factor in the development of adsorption technology for the fluid separation has been the availability of appropriate adsorbents. The most frequently used categories include crystalline materials like zeolites, and amorphous materials like activated carbons, silica and alumina gels, polymeric sorbents, and ion-exchange resins. These materials exhibit a large spectrum of pore structures (networks of micro- and mesopores of different shapes and sizes) and surface chemistry (degrees of polarity), which provide a large choice of core adsorptive properties (equilibria, kinetics, and heat) to be utilized in... 

Cast irons contain much higher carbon and silicon levels than steels, theoretically higher than 1.8 wt.% but typically 3 to 5 wt.% Fe and 1 to 3 wt.% Si. These comprise another category of ferrous materials that are intended to be cast from the liquid state to the final desired shape. Various types of cast irons are widely used in industry, especially for valves, pumps, pipes, filters, and certain mechanical parts. Cast iron can be considered a ternary Fe-Si-C alloy. The carbon concentration is between 1.7 and 4.5%, most of which is present in insoluble form (e.g., graphite flakes or nodules). Such material is, however, normally called unalloyed cast iron and exists in four main types ... 

CWEs comprise a film of polyvinylchloride (PVC) or other suitable polymer matrix containing a dissolved electroactive species, coated on a conductive material (generally a metal or carbon). CWEs usually take the form of a wire of diameter from 1 mm to micrometers (e.g., the point of a needle), but small ball-shaped or plane active surfaces also fall into this category. 

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