403 23
as the inclusions, for subsequent analysis. All of this infor-
mation would be lost if these particles were simply over-
scanned. While the XSI collected with a single silicon drift
detector (SDD)-EDS inevitably shows the shadowing cre-
ated by specimen geometry, such shadowing can be greatly
diminished by collecting the XSI with an array of SDD-EDS
detectors placed symmetrically around the specimen, as
shown in. Fig. 23.29.23.6.4 Particle Geometry Factors
Influencing Quantitative Analysis
of Particles
There are two principal “particle geometry” effects: the “par-
ticle mass effect” and the “particle absorption effect” (Small
et al. 1978 , 1979 ).“Particle Mass Effect”
The penetration of beam electrons through the side and bot-
tom of a particle reduces the X-ray production compared to
a flat bulk target, creating the so called “particle mass effect.”. Figure 23.30 shows the intensity of Fe K-L2,3 produced as a
function of sphere diameter for spherical particles of NIST
SRM (K411), the composition of which is listed in
. Table 23.3, as calculated with the Monte Carlo simulation
. Fig. 23.28 Beam placement strategies for particle analysis: static
point beam placed at particle center, overscanning with a scan field
that brackets the particle (yellow box), overscanning within the particle
(green box)
TotalTotalComparison of mapping with a single SDD-EDS and an array of SDD-EDS50 μmNiNi TiTi. Fig. 23.29 Comparison of X-ray spectrum imaging with a single EDS and with an array of four EDS detectors; note reduction in shadowing
23.6 · Particle Analysis