Fundamentals of Materials Science and Engineering: An Integrated Approach, 3e

GTBL042-15 GTBL042-Callister-v2 August 29, 2007 8:52

622 • Chapter 15 / Composites

Figure 15.4 Photomicrograph of a WC–Co

cemented carbide. Light areas are the cobalt

matrix; dark regions, the particles of

tungsten carbide. 100×. (Courtesy of

Carboloy Systems Department, General

Electric Company.)

of 15 to 30 vol% of carbon black. For the carbon black to provide significant rein-

forcement, the particle size must be extremely small, with diameters between 20 and

50 nm; also, the particles must be evenly distributed throughout the rubber and must

form a strong adhesive bond with the rubber matrix. Particle reinforcement using

other materials (e.g., silica) is much less effective because this special interaction

between the rubber molecules and particle surfaces does not exist. Figure 15.5 is an

electron micrograph of a carbon black-reinforced rubber.

Concrete

concrete Concreteis a common large-particle composite in which both matrix and dispersed

phases are ceramic materials. Since the terms “concrete” and “cement” are some-

times incorrectly interchanged, perhaps it is appropriate to make a distinction

Figure 15.5 Electron micrograph showing

the spherical reinforcing carbon black

particles in a synthetic rubber tire tread

compound. The areas resembling water

marks are tiny air pockets in the rubber.

80,000×. (Courtesy of Goodyear Tire &

Rubber Company.)