Heat-treated blacks

It is advisable to test a small portion of the filtrate for platinum by acidifying with hydrochloric acid and adding a few drops of stannous chloride solution a yellow or brown colour develops according to the quantity of platinum pVesent. The yellow colour is soluble in ether, thus rendering the t t more sensitive. If platinum is found, treat the filtrate with excess of formaldehyde and sodium iQrdroxide solution and heat,- platinum black septarates on standing and may be filtered and worked up with other platinum residues (see Method 3). 

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. 

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. 

Figure 7.26 Solubility of sodium caseinate (SC) before and after glycosyl-ation with dextran (Dex) (Mw = 250 kDa or 500 kDa) (white column) pH = 7 (grey column) pH = 4.0 (black column) pH = 4.5. The labels freeze-dried and conjugate relate to the non-treated and heat-treated samples, respectively. Reproduced from Fechner et al. (2007) with permission.

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... 

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. 

Figure 3 compares the exchange current densities on the initial nanodispersed diamond (4), modified nanodispersed diamond (after heat - treated treatment)(5), acetylene black AD-100 (1) and on the known catalysts tungsten (2) and vanadium (3) carbides. The specific surfaces of all samples of the powders were about 140 rrr/g. The exchange current density on modified diamond nanopowders is higher than that on tungsten or vanadium carbides by a factor of 1.6. 

Cold-seal stellite bombs and high oxygen pressures were used as described previously (6, 7, 8, 9, 10). An ordinary pot furnace was used for heat treatments carried out in air. As starting materials, purified palladium black (Fisher Scientific Co.) was mixed intimately with the other oxides or hydroxides [PbO, Sr(OH)2 8H20, CaO, CdO, Mg(OH)2]. The mixtures generally were inserted into gold foils and heat treated under various conditions of temperature and oxygen pressure. The runs were quenched and the products examined by x-ray diffraction. 

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.

For Vulcan XC-72R, the specific corrosion rates (Areal m 2) at 1.0 V and 180 °C in H3PO4 were essentially independent ofheat-treatment temperature however, since the Tafel slopes decrease with increasing heat-treatment temperature, heat treatment affords increased life at the fuel-cell calhode operating potential (0.7 V). Little difference in either the Tafel slope or specific corrosion rate at 1.0 V was observed between as-received and heat-treated samples of Shawinigan acetylene black. 

---