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3.5.7 Application in Materials Science

The important of trace analysis in characterizing high
technology materials like semiconductors and ceram-
ics is becoming appreciated. Electrical properties of
metals, semiconductors and insulators and the me-
chanical and thermal properties of graphite and ceram-
ics are affected by many trace, impurities, electronics
excapsulants, catalutic substarates, crucibles, medical
implants and laboratory ware need to be freeof con-
taminants that may compromise their use. Materials of
current interest include carbon, aluminum,silicon, ger-
manium,alumina,silica,zirconia,silicon nitride, silicon car-
bide and carbon and silicon based polymers.

Some of these materials are extremely difficult to
dissolve, limiting the appplicationf of analytical techn-
qiues that rely on the sample being in solution. Some
that are excellent insulators are difficult to study with
electron or ion bombardment methods because of sub-
stare changing. The NDT nature of NAA is of advan-
tege in the analysis of these materials. With no chem-
istry needed before irradiation, there is less concern
with contamination than with most chemical methods.
Mostly of these materials are made of elements which
do not activate strongly with thermal neutrons or pro-
duce only short live activity, so trace analysis can often
be performed down to very low concentrations. For ex-
ample the analysis of pure rhodium metal is easy since
the rhodium produced on irradiation decay quickly to

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