Heat treated carbon blacks

Recently, it was reported that high-rate performance of Li-Mn02 cells could be improved through application of a partially graphitized carbon black such as PUREBLACK Carbon in the cathode formulation [19]. Here, a petroleum oil-derived synthetic carbon is heat treated at temperatures in excess of 2000°C to graphitize the outside of each particle, while the core of particles remaining amorphous. 

Nitrogen is usually present in minor amounts, but sulfur can be present in high concentrations, >1%, depending on the precursor that is used to manufacture the carbonaceous material. Besides sulfur that is bonded to carbon, other forms such as elemental sulfur, inorganic sulfate, and organosulfur compounds may be present. The carbon-sulfur surface compounds on carbon blacks are relatively stable, but they desorb as H2S when carbon is heat-treated in H2 between 500 and 1000°C. 

In Fig. 11 we show the Raman speetrum of earbo-naeeous soot eontaining l-2 nm diameter, singlewall nanotubes produeed from Co/Ni-eatalyzed carbon plasma[28). These samples were prepared at MER, Inc. The sharp line components in the spectrum are quite similar to that from the Co-catalyzed carbons. Sharp, first-order peaks at 1568 cm and 1594 cm , and second-order peaks at -2680 cm" and -3180 cm are observed, and identified with single-wall nanotubes. Superimposed on this spectrum is the contribution from disordered sp carbon. A narrowed, disorder-induced D-band and an increased intensity in the second-order features of this sample indicate that these impurity carbons have been partially graphitized (i.e., compare the spectrum of carbon black prepared at 850°C, Fig. Id, to that which has been heat treated at 2820°C, Fig. Ic). 

Figure 2. High-resolution transmission electron micrograps of carbon black (Sterling R, Cabot Corp.) (a) as-received (b) heat-treated at 2700 °C. Scale marker 10 nm.

Lalande G, Cote R, Tamizhmani G, Guay D, Dodelet JP. 1995. Physical, chemical and electrochemical characterization of heat-treated tetracarboxylic cobalt phthalocyanine adsorbed on carbon black as electrocatalyst for oxygen reduction in polymer electrolyte fuel cells. Electrochim Acta 40 2635-2646. 

A second possibility is that the metal center remains intact, but the macrocycle ligands react with each other. In macrocycles treated in the absence of a support there is evidence that polymerization of the macrocycles occurs.76,111 Likewise, in the presence of a carbon black support, such polymerization could occur during pyrolysis and could possibly affect activity and stability for similar reasons to the ones mentioned in the previous paragraph.76,92 However, for a treatment above 400 °C (which produces a more active material) the macrocycle polymer is thought to decompose.92 Another possibility is that the heat treatment helps disperse the macrocycles on the support surface and leads to strong chemisorption rather than physisorption.110... 

Spheron 6 carbon black, Sphoron 6, manufactured by Cabot Corp., Boston, Mass. Spheron C carbon black, Spheron C, manufactured by Cabot Corp., Boston, Mass. H.T. heat-treated unilcr nitrogen at 1200". 

Reaction of carbon with sulfur dioxide was observed by Fischer and Prauschke (131). In my laboratory it was recently found that sulfur is bound by heat-treated carbon blacks and by graphitized carbon black on treatment with hydrogen sulfide, carbon disulfide, or sulfur dioxide at low temperatures, even at room temperature. The sulfur content cannot be eliminated by outgassing at 100° or by prolonged extraction with various solvents. 

Several people in the 18th and 19th centuries attempted to produce a pure form of zinc oxide for medical purposes. They were unaware that their samples contained cadmium, which at that time was an unknown element. In 1817 Friedrich Strohmeyer (1776—1835), a German chemist, analyzed a zinc compound (calamine) he believed contained zinc oxide (ZnO). However, what he really found was zinc carbonate (ZnCO ), which, though at first unknown to him, contained some cadmium. Strohmeyer then treated his sample with acids until all the zinc was dissolved and thus removed. He then heated the residue with carbon black, resulting in a small ingot of soft, bluish-white metal that proved to be a new element—cadmium. Strohmeyer is given credit for the discovery of cadmium. 

While most published efforts aim toward maximum production of Di, one set of workers prepared a catalyst which selectively makes Tri. Workers from Wacker prepared a mixture containing SiCE powder (75 parts), Fe (75 parts), carbon black (60 parts) and Cu (18 parts) which was pelletized with H2O, dried at 220 °C and heated at 1100°C for 17 h62. The resulting solid was treated with MeCl at 200-350 °C under Ar to give a mixture containing MeSiCl3 80%, Me2SiCl2 5% and SiCl4 15 mol%. 

The second lithium primary cell is the Li-Mn02 [18]. For use in lithium cells, the high purity EMD must be heat treated at 350°C-375°C to activate and modify the crystal structure, as well as remove any water. Carbon black is used as a conductive diluent in the cathode. The cell electrolyte is propylene carbonate and 1,2-dimethoxyethane with LiAsF6. The cell reaction is... 

The carbon blacks consisted of Spheron 6 and Sterling FT (fine thermal) black, both non-heat-treated and 2700° C. heat-treated (obtained from the Godfrey L. Cabot Co., Boston, Mass.). Published surface areas for the four carbon blacks are 114, 84.1, 15.5, and 12.5 sq. meters per gram, respectively (31). The silica sand was supplied by the New Jersey Silica Sand Co., Millville, N. J., with the manufacturer s designation of No. 325 flour. Screen analysis by the supplier showed a considerable range in particle size about 60% was retained on a 90-mesh screen and 90% on a 200-mesh screen. Finally, a sample of asbestos was tested (obtained from the Canadian Johns-Manville Co., Port Credit, Toronto, with the designation 7R). Zettlemoyer (31) has studied this material. 

Figure 10. B.E.T. Surface areas of heat treated Vulcan XC-72R and Shawinigan acetylene black carbons.

The present review discusses the results of the H NMR spectroscopy for a wide range of carbonaceous materials (heat-treated and nongraphitizable activated carbons, carbon blacks, exfoliated and oxidized graphites, porous and amorphous carbonized silicas). This technique made it possible to determine the spectral characteristics of organic molecules with diverse chemical properties, as well as of water molecules adsorbed on the surface. These characteristics are compared with the structural properties of the materials under consideration. The calculations done for the majority of the subjects of inquiry gave the values of their free surface energies in an aqueous medium as well as the characteristics of bound water layers of various types. 

M is a commercial carbon black (Monarch 700. Cabot) treated in HNO, (M-HNOi) or first heat-treated at 2.S00°C in inert atmosphere and then soaked in HNO, (M-2500-HNO,) CPG is a comniercial activated carbon (CPG, Calgon Carbon Corp.),... 

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