Carbon glass-like

Fig. 5.28 Structure of glass-like carbon. (According to G. M. Jenkins and K. 

With respect to point 1, it has appeared that in oxidative detection, carbon is the best choice in nearly all cases. Therefore glassy carbon (an amorphous glass-like carbon) is the standard working electrode material in most cells for HPLC-EC. 

Other Papers.—Various iron species prepared by the vacuum pyrrolysis of acetyl-ferrocene-furfural resins at 400°C have been studied by Mossbauer spectroscopy. These consist of an amorphous glass-like carbon matrix containing free iron atoms, Fe+ ions, iron clusters, superparamagnetic iron, and ferromagnetic iron.333 The effect of pressure of up to 50kbar on the absorption spectra of five iron(m), two iron(n) and one mixed valence compound has been studied. In six of the compounds, but not in basic ferric acetate or soluble Prussian Blue, the observed pressure-induced bands were assigned to d-d transitions of converted iron(n) for the ferric compounds and to spin-forbidden d-d bands for the ferrous compounds. The charge-transfer band from iron(n) to iron(m) in soluble Prussian Blue showed a blue shift at pressures up to 7.2 kbar.334... 

In contrast to gas-phase carbonization, most thermosetting resins, such as phenol-formaldehyde and furfuryl alcohol, and also cellulose can be converted to carbon materials by solid-phase carbonization. When the carbonization of most of these precursors proceeds rapidly, the resultant carbon materials become porous. If the carbonization is performed so slowly that the resultant carbonaceous solids can shrink completely, the so-called glass-like carbons are produced, which contain a large number of closed pores. 

FIGURE 2.19 Progressive change from ultramicropores through supermicropores to mesopores during air activation of glass-like carbon spheres. 

Glass-like carbons (glassy carbons) are produced by the pyrolysis of different precursors, such as phenol-formaldehyde resin, poly(furfuryl alcohol), cellulose, etc., through an exact control of the heating process [88,89], They are characterized by an amorphous structure and also by... 

FIGURE 2.21 Changes in weight, volume, BET surface area, and water vapor adsorption during the carbonization of poly(furfuryl alcohol) to form glass-like carbon. (Courtesy of Dr. S. Yamada, Tokai Carbon Co. Ltd., Shizuoka, Japan. With permission.)... 

FIGURE 2.39 (a) 002 lattice fringe image of sugar coke and (b) nanotexture model for glass-like carbon. 

The above CVs (Figs. 24 and 25) display well-formed reduction peaks independent of the blank solution and the type of active carbon materials. The combined shape of the cathodic peaks indicates that surface species participate in electrochemical processes in different local environments, or with various structures but convergent peak potentials. The effect of anodic polarization is more readily observed in a basic environment than in an acid solution. Similarly, a positive shift of cathodic peak potential with a decrease in anodic sweep potential limit takes place. Similar results were obtained for studies of electrochemical oxidation of graphite [17] and glass-like carbon [222] electrodes. There was considerable enlargement of both anodic and cathodic peaks after anodic polarization in 20% sulfuric acid (Fig. 26) [17]. 

The cathodic production of carbyne was explored more extensively. Nishihara et al. [35-38] have carbonized hexachlorobuta-l,3-diene on Pt or glass-like carbon electrode in acetonitrile medium. Kijima et al. [39-41] have found that the product contained also considerable proportion of sp-bonded carbon atoms in addition to sp carbon ... 

The last three chapters summarize unique structural and chemical features of a variety of glasses. They also provide an overview of the important aspects of the glass systems. Chapters 12 and 13 discuss respectively oxide and chalcogenide glasses particularly in view of their chemistry, structure and a number of special phenomena associated with them. In chapter 14, synthesis, structure and properties of halide, oxyhalide, oxynitride and metallic glasses are discussed. Some aspects of glass-like carbon have also been presented. 

Figure 14.12 Two structural models of glass-like carbon heated to high temperature (a) network of ribbon stacking model (After Jenkins and Kawamura, 1971) (b) alternate model. (After, Shiraishi, 1984 ).

Based on the above properties, glass-like carbon has found applications as heating elements, as containers for chemical reactions and as containers for molten metals. They are also used as separators and electrodes in phosphoric acid fuel cells (Ovshinsky, 2000). 

The importance of adsorption for different carbon materials and, conversely, the contribution of each type of carbon to the field of adsorption is very different. This reflects the ivide variability in properties of solid carbons [1, 2], which makes their surface properties important in very different fields and for different reasons. Thus, graphite, due to its relatively simple structure, has often been used as a model material to simulate the adsorption of different molecules on its surface, or to carry out adsorption measurements on a well-controlled surface. Likewise, carbon blacks, particularly those thermally treated ( graphi-tized ), have often been used as reference nonporous adsorbents, as they only exhibit an external surface. The absence of open porosity and high chemical inertia are attributes that make glass-like carbon a material ffequendy used in... 

Figure 2,17 Jenkins-Kawamura ribbon model for glass-like carbon. (Reproduced from Ref. [85] with permission from the Royal Society.)...

Early models used to describe the structure of ACs included the Franklin model itself (Fig. 2.5), and a ribbon-hke structure [89] somewhat similar to the Jenkins and Kawamura model for glass-like carbon (Fig. 2.17). Interestingly, these models were based on results obtained with polyvinylidene chloride (PVDC) (or Saran) char, a typical nongraphitizable material (unlike the well-known graphitizability of polyvinyl chloride [PVC] char). Various arguments have been used to criticize these and other models based on the occurrence of sp carbon besides sp carbon in nongraphitizable materials [10, 75]. 

Yoshida, A., Kaburagi, Y., and Hishiyama, Y. (1991). Microtexture and magnetoresistance of glass-like carbons. Carbon, 29, 1107-11. 

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