Page 47 - Engineered Interfaces in Fiber Reinforced Composites

30 Engineered interfaces in fiber reinforced composites

Atomic Mass Units (amu)

Fig. 2.14. A typical spectrum of a carbon fiber obtained from SIMS. After Denison et ai. (1988a, b).

techniques by several years. There are two important features that make SIMS of
particular value (Castle and Watts, 1988):
(i) Hydrogen can be detected in the spectrum, a capability which is not possible in
the other methods.
(ii) Isotopes can be distinguished and thus the source of the material on the fiber
surface can be discovered by using tracers. Therefore, it is possible to distinguish
the oxygen derived from the atmosphere or matrix material from the oxygen
incorporated during an oxidative treatment of carbon fibers.

2.3.7. Ion scattering spectroscopy

In ISS, a sample is bombarded with gas ions such as helium or neon at a fixed
incident angle, as shown in Fig. 2.15, to obtain information about the atoms present
in the top layer of the surface. The high sensitivity of ISS permits detection of
elements at the ppm level. The ISS spectrum normally consists of a single peak of
scattered ion intensity at an energy loss that is characteristic of the mass of the
surface atom. Information regarding chemical bonding at the interface region can be
generated from the yield pattern of scattered ions as a function of the primary ion
energy.
The combined ISSjSIMS is an extremely useful surface analytical technique that
can provide several types of data from the same surface. Both ISS and SIMS employ
ion beams, and thereby both methods can utilize the same ion source for the surface
probe, as schematically shown in Fig. 2.16. Addition of a specially designed ion lens
and quadruple mass spectrometer can make the whole system much more efficient.
The value of information obtained from the combination of these two systems is