Influence of pulse frequency on synthesis of nano and submicrometer spherical particles by pulsed laser melting in liquid

Abstract

Submicrometer spherical particles (SMSPs) are reported to be fabricated by pulsed laser irradiation with a frequency of 10 or 30 Hz onto raw nanoparticles dispersed in liquid. Here, the effect of the pulse frequency on particles obtained by laser irradiation onto the suspension in a vessel, especially at higher pulse frequencies up to 800 Hz, is investigated. At 200 Hz or lower, SMSPs of similar size can be fabricated, as at 10 or 30 Hz, by the same number of pulses. This indicates that the time required for particle fabrication can be greatly reduced and production efficiency can be improved using a high-frequency laser. In contrast, at 400 Hz or above, nanospherical particles (NSPs) are formed in addition to SMSPs, and the mass fraction of SMSPs is drastically decreased. This result suggests that consecutive laser pulse irradiation induces heat accumulation in particles and suspensions, resulting in a temperature increase and partial evaporation of the particles at 400 Hz or above. From the temperature increase of the suspension, the local temperature of the liquid surrounding the particles is believed to be increased by heat dissipation from the heated particles. Calculations suggest that an increase in the local liquid temperature would cause further heating of the particles.

Early appearance of crystalline nanoparticles in pulsed laser ablation in liquids dynamics

“…[1][2][3] In many cases the use in applications is in reach, in particular in view of recent success in upscaling the process in ablation 4 or post-synthesis fragmentation. 5 While the general phenomena during the process are similar for many materials, as well as for different liquids, the morphology of the particles may vary significantly from case to case. The particle size distribution is of central concern, as many applications, such as in catalysis, require very small particles below 10 nm for an optimal efficiency in relation to the utilized amount of material.…”

Determining the Composite Structure of Au-Fe-Based Submicrometre Spherical Particles Fabricated by Pulsed-Laser Melting in Liquid

“…In PLML, the temperature surpasses the melting point of the particles in several hundreds of nanoseconds or shorter, with heating and cooling rates of 10 11 K s −1 and 10 10 K s −1 , respectively [ 24 ]. Since pulsed lasers with repetition rate of 10–100 Hz are generally used for PLML, these rapid heating and quenching cycles are repeated many times, with an interval of 10–100 ms for cooling process [ 25 ]. Liquid phase surrounding particles acts as a heat dissipation barrier after temporal vaporization and a cooling medium for quenching.…”

Preparation of binder‐free spherical submicron‐sized platinum particles using laser melting in liquids

“…Figure 9 presents simulated temporal change of particle temperature due to one-pulse irradiation of 10-nm platinum particles (close in size to original nanoparticles) and 150-nm platinum particles (close in size to PtSMPs obtained with laser fluence of 80 mJ/cm 2 ). Simulation details are omitted here, but energy received from laser light and energy dissipated to the environment were calculated at regular time intervals 11,[16][17][18] ; this approach already proved successful to explain experimental dependence of SMP temperature on laser pulse-width dependence, 16,18 on pulse frequency, 17 and particle diameter. 11 In Figure 9, 10-nm particles show lower maximum attainable temperature and shorter high-temperature retention time as compared to 150-nm particles; this is because smaller particles have narrower absorption cross section to receive laser energy, while on the other hand, increased specific surface area promotes heat diffusion.…”