In most cases, the formation of agglomerates is not intended, and consequently
many research investigations have been undertaken towards synthesizing individualized particles using this process. One typical – and successful – approach was
reported by Wang et al. [12], who used an atypical YAG laser with a wavelength of
1064 nm and a laser pulse width of 0.3–20 ms. A wire of pure iron was used as
precursor. The particle size of the product obtained (see Figure 4.18) was in the
range 5–50 nm, with only a minor proportion of material in the size range
50–90 nm.
The detailed size distribution spectrum (see Figure 4.19) shows a nonsymmetric
particle size distribution typical of a random process of particle formation and may
Figure 4.18 c-Fe 2 O 3 powder produced by a highly progressed laser ablation process. The starting
material was metallic iron [12]. This product, with individual particles in the size range of 5–90 nm,
contrasts with the product shown in Figure 4.17. (Reproduced with permission by Elsevier).
0
20
40
60
80
100
particle diameter [nm]
0
0.05
0.1
0.15
0.2
0.25
class
frequency
Figure 4.19 Particle size distribution of the c-Fe 2 O 3 powder product shown in Figure 4.18. The
nonsymmetric particle size distribution is typical of synthesis methods based on purely random
processes [12].
4.4 Laser Ablation Process j63