Guided Slow Continuous Suspension Film Flow for Mass Production of Submicrometer Spherical Particles by Pulsed Laser Melting in Liquid

Abstract

Pulsed laser melting in liquid (PLML) is a technique to fabricate submicrometer crystalline spherical particles of various materials by laser irradiation of suspended raw particles with random shapes. To fully exploit the unique features of PLML-fabricated particles (crystalline and spherical) in practice, a mass-production PLML technique is required. To this end, the present study develops a new slit nozzle that guides the suspension film flow into a non-droplet continuous stream with a low flow rate. These two incompatible flow properties (continuity and slowness) are difficult to be realized for a liquid jet to free space. The suspension film flow was irradiated with a typical laboratory scale-flash lamp pumping laser at 30 Hz pulse frequency. Only a single flow passage of the slit nozzle with a few laser pulse irradiation transformed 95% of the raw particles into spherical particles. This spheroidizing ratio exceeded those of low-rate drip flow and high-rate cylindrical laminar flow directly jetted into free space through a Pasteur pipette nozzle. Extrapolating the data obtained from a 20-ml suspension, the average production rate was determined as 195 mg h−1. The high spheroidizing ratio and yield through the slit nozzle is attributable to the uniquely slow but continuous liquid film flow. The structure of the slit nozzle also prevents particles from adhering to the slit wall during continuous laser irradiation. Thus, the suspension film flow through the newly developed slit nozzle can potentially scale up the PLML technique to mass production.

Spherical Particle Formation Mechanism in Pulsed Laser Melting in Liquid under Controlled-Pulse-Number Irradiation using a Slit Nozzle Flow System

“…Details of the slit nozzle are available elsewhere. 28 Raw cuboidal iron(II, III) oxide powder with a 200 nm side length (Hitachi Maxell, Ltd.) was suspended at a concentration of 0.1 g L −1 in either deionized water, a 30 wt % aqueous solution of glycerol, or a 60 wt % aqueous solution of glycerol. The suspension was fed at a volume flow rate of 1.1 mL s −1 into the slit nozzle via an injection needle connected to a cylinder operated using a precision liquid feeder (Furue Science, JP-S).…”

Laser Fragmentation Synthesis of Colloidal Bismuth Ferrite Particles

“…The fluid interface would have to be flat and perpendicular towards the laser beam to omit this effect entirely. In pulsed laser melting of colloidal boron particles, Ishikawa and Koshizaki found a higher sphericity factor for particles melted in a guided flow compared to particles melted in a circular liquid jet [20]. The guided flow was realised by injecting a liquid jet into the 1-mm wide slit between two quartz plates.…”

Generation of Size-Controlled Crystalline CeO2 Particles by Pulsed Laser Irradiation in Water

“…It is obvious that the process could be upgraded by confirming controlled irradiation of an even more regular mixed suspension or of one flowing at an adequate rate. The latter option was already demonstrated through the use of a purpose-designed reactors that allowed continuous liquid handling or single passage of a suspension film flowed via a slit nozzle at various flow rates . Nevertheless, we preferred overcoming this issue by irradiating relatively large portions of the suspension while employing routine mixing.…”

“…The latter option was already demonstrated through the use of a purpose-designed reactors that allowed continuous liquid handling 47 or single passage of a suspension film flowed via a slit nozzle at various flow rates. 48 Nevertheless, we preferred overcoming this issue by irradiating relatively large portions of the suspension while employing routine mixing.…”