LAUSR

The dynamics of nanoparticle growth in pulsed anodic arc discharge has been studied in time-resolved mode. To this end, a fast moving probe was employed to extract the material generated in a pulsed arc plasma held between two graphite electrodes. The probe motion was synchronized with the pulse phase and the exposure time to the plasma was set to 10 ms. The graphite anode was eroded in a helium atmosphere (300 Torr) by an arc plasma pulsed at 1 Hz with a 10% duty cycle and showing 250 A of peak current. The structure and morphology of the probe depositions were characterized by Raman spectroscopy, scanning electron microscopy, and focused ion beam. A maximal deposition rate of 260 μm/s was measured 5 mm away from the arc core during the active 0.1 s of the pulse. Such a rate yields a growth flux of 1.3 × 1021 cm−2 s−1, rich in carbon nanostructures (graphene platelets, nanotubes) with a characteristic aggregate size within 1–10 μm. The deposition during the inactive 0.9 s of the pulse was several orders of magnitude slower and consisted of amorphous carbon traces. Moreover, the nanoparticle distribution along the collecting probe is correlated with the pulse phase, thereby providing information on particle transport. Pulsed nanosynthesis can be modeled as a periodical growth process, where the volume and propagation velocity of the growth region can be adjusted through modulation of the pulse signal waveform. The proposed model constitutes a suitable framework to investigate the pulsed arc synthesis of nanomaterials with tailored physical and chemical properties.