Modification of the surface properties of carbon fibers via the catalytic growth of carbon nanofibers
- PDF / 3,254,818 Bytes
- 9 Pages / 588 x 796 pts Page_size
- 71 Downloads / 224 Views
The surface of commercial pitch and PAN-based carbon fibers has been modified by coating the structures with catalytically formed carbon nanofibers. Reaction conditions have been established that enable one to achieve optimum coverage by the secondary nanostructures without inducing any degradation in the mechanical properties of the parent fibers. Using this approach it is possible to produce a dramatic increase in the surface area of the fibrous structure from a nominal value of about 1.0 m 2 /g (untreated condition) up to between 250 and 300 m 2 /g (complete nanofiber coverage). This process results in a significant enhancement in the adhesion properties at the interface between the fiber and matrix components in a composite material. Mechanical tests performed on single uncoated and coated T300 carbon fibers demonstrated that it was possible to obtain an improvement of over 4.75 times in the interfacial shear strength of the fibers following deposition of a critical amount of nanofibers.
I. INTRODUCTION While high performance carbon fibers have met with a certain degree of commercial success as reinforcement agents in composite materials (CFRC's), these structures suffer from a number of shortcomings including inadequate interlaminar shear properties that contribute to delamination.1 Several approaches have been used in an attempt to enhance the interfacial properties between the carbon fibers and the matrix, including various oxidation procedures,2"8 vapor deposition of pyrolytic carbon and certain metal carbides,9"12 electrolytic etching,13'14 exposure to selected plasma environments,15"17 and, the notion of producing branched structures.1819 Although these treatments do improve the interfacial bonding in carbon composites, in many cases they can induce severe damage to the fiber surface, which ultimately leads to a weakening of the structure. A more attractive solution to the problem was first presented by Milewski and co-workers,20"22 who used the concept of "whiskerization" to grow a uniform coating of silicon carbide whiskers onto the surfaces of carbon fibers via a chemical vapor deposition technique at about 1400 °C. These workers claimed that following this process they were able to increase the interlaminar shear strength of a carbon composite by over 4 times. There are, however, major drawbacks to the use of silicon carbide in such an application. The material is very abrasive, much more dense, and has a different coefficient of thermal expansion than carbon. Moreover,
a) Author
to whom all correspondence should be addressed. J. Mater. Res., Vol. 10, No. 3, Mar 1995
http://journals.cambridge.org
Downloaded: 28 Jun 2014
very high temperatures are required to produce silicon carbide in a whisker form. In a previous paper23 we demonstrated the feasibility of growing carbon nanofibers from the surfaces of carbon fibers at relatively low temperatures. This process involves the participation of a metal catalyst, which is dispersed onto the parent fiber in the form of a soluble salt. Following careful
Data Loading...
