Page 33 - MSAM-1-3

Materials Science in Additive Manufacturing Photocatalytic PA6/TiO powder for LPBF
2

A B

Figure 3. (A) The cooling curve of the reaction kettle held at 125℃ for 1 h immediately after precipitation and (B) its characteristic temperature fluctuation.
The dissolved concentration of PA6 is 50 g/L.

A B

Figure 4. (A) The morphology and (B) particle size distribution of PA6 powders precipitated after holding at 125℃ for 1 h. The dissolved concentration
of PA6 is 50 g/L.

(Figure 4B) shows that most powders were distributed in Table 1. Changes in powder size at different holding
the particle size range of 20–90 μm and showed a normal temperatures
distribution peak at 49.3 μm.
Parameters Holding temperature
According to the crystallization precipitation 120°C 122.5°C 125°C 127.5°C 130°C
temperature and the steady-state temperature, different
holding temperatures were taken to study their effects D (10)/μm 28.8 29.8 36.2 33.1 25.0
v
on the powder morphology and particle size distribution D (50)/μm 49.5 45.3 49.3 48.6 40.2
v
(Figures 5 and 6). The changes in powder size at different D (90)/μm 78.3 68.4 66.7 70.7 63.8
v
holding temperatures are shown in Table 1. According to D[3, 2]/μm 41.6 43.1 48.0 46.5 37.6
Figure 5, there were distinctly different morphological
features of powders precipitated above and below growth was irregular. Most of the powders showed
the precipitation temperature. When the holding solid structures, and there was no aggregation of small
temperature was low at 120°C, there were many small particles. When the holding temperature was higher
particles among the powders. The large particles also than the precipitation temperature at 127.5°C, some
had an obvious cracking phenomenon, and there were
opening pores inside. The particle size showed a bimodal powders showed a fish-scale surface, which promotes the
normal distribution, and the small particle powder was formation of internal lapped pores. This is not conducive
[24]
aggregated at 10 μm (Figure 6). This is mainly because to powder spreading and density improvement . When
the particles have already nucleated at 120°C but have the temperature reached 130°C, the excessively high
not grown up. The temperature holding at this time temperature promotes the generation of new secondary
increased the quantity of small-sized powders. The nucleated particles with the feature of fish-scale surface.
powders precipitated at 122.5°C showed the morphology From the perspective of particle size, too high or too low
transformation of flakes and long strips, and the powder holding temperature can produce small-sized particles.

Volume 1 Issue 3 (2022) 4 https://doi.org/10.18063/msam.v1i3.14