Surface Area and Properties of Carbon Black

Abstract

The surface areas of a number of commercial carbon blacks have been determined by the low-temperature adsorption isotherm technique. Thermal decomposition and other nonimpingement type blacks possess areas of 15 to 64 M 2 per gram. Channel blacks commonly employed as reinforcing agents in rubber have areas around 100 M' per gram. Ink and color blacks range from 100 to nearly 1000 M per gram. The color values of these carbons increase with surface area. The relation of iodine and diphenylguanidine adsorption to surface area has also been studied. Iodine adsorption is a direct function of surface area and, with the NE of the outstanding characteristics of carbon blacks is the large surface they possess by virtue of their ex-0 tremely small particle size. In the past many attempts have been made to measure this surface in an effort to correlate it with the properties carbon black is capable of imparting to various media in which it is dispersed. Various methods of direct microscopic observations have been most widely employed (IO, Id, 16, 26). While these direct methods are reliable for particles having diameters larger than 1000 A,, we have found that they are not reliable for particles with diameters smaller than 500 A.Since the majority of the carbon blacks of commercial importance fall within this range, it must be concluded that surface areas calculated from diameters obtained by these methods are of doubtful significance. The electron microscope (5) is an exception to the above general criticism of direct optical methods. Recent investigations (2) with this instrument have been remarkably successful. In addition to electron microscopy, other methods have been recently described for determining not only particle size and distribution, but also the direct determination of total surface area. The present paper deals with our attempts to apply certain of these methods to a variety of commercial carbon blacks.Hauser and his co-workers (16, 17) used the supercentrifuge to determine particle size distribution in a variety of finely divided substances. We have applied their method to a standard channel black dispersed in a rubber cement. Fortyfive parts of black by weight were milled with 100 parts of rubber. This stock was then dissolved in xylene to give a final concentration of about 2 X gram of black per cc. of suspension. After centrifuging and analysis, a distribution curve was obtained with maxima in the region 300-400 A. in fair agreement with the published electron microscopic value (8). Unfortunately the rubber in which the black was dispersed also fractionated along the sides of the centrifuge liner. This made it necessary to analyze each interval sample for rubber. Consequently several weeks were required to evaluate IL single black. Because of these difficulties it did not exception of certain high-volatile blacks, may be used as a direct measure of total surface. The adsorption of diphenylguanidine depends much more strongly on the volatile content of the black rather than its total surface. While rubber...

Surface available to nitrogen on bone black and other carbonaceous adsorbents

“…This has been compared by Emmett and De Witt [7] with their value obtained from a determination of the surface area by adsorption of nitrogen at 77° K. Excellent agreement was obtained: the particular carbon-black particles yielded a value of 280 A from electron-microscope data as compared with 310 A obtained from the nitrogen adsorption. Even more striking confirmation was found by Smith, Thornhill, and Bray [8], who compared the results for two samples of carbon black. Their acetylene-black sample showed a surface of 64 m 2 Jg by adsorption of nitrogen, or an average particle diameter of 533 A ; the electron microscope value was 510 A.…”

Erratum: High Performance Hydrogen/Bromine Redox Flow Battery for Grid-Scale Energy Storage [J. Electrochem. Soc., 159, A1806 (2012)]

“…Carbon blacks have specific surface areas ranging up to nearly 1000 m 2 /g. 29 Thus a 2000 cm 2 carbon surface area per cm 2 geometric should be easily achievable; a CL carbon loading of only 2 mg/cm 2 with a specific surface area of only 100 m 2 /g would meet this requirement. Finally, it should also be noted that although Pt is used on the hydrogen electrode, it has been shown in hydrogen fuel cells that the fast kinetics allow for a much smaller amount to be used (∼0.05 mg/cm 2 ) than what is used in this study with negligible effect on performance up to 2 A/cm 2 .…”

Adsorption of Iodine and Bromine by Carbon Black

“…Although the adsorption of iodine from aqueous solution had been used for comparing blacks for many years (6,15,17), no systematic work known to the authors had been attempted until 1946 when Kendall (13) showed that the problem was more complex than previous workers had assumed.…”