Synergistic Effect of Plasma and Laser Processes in Liquid for Alloyed-Nanoparticle Synthesis

Abstract

Cu-Ag alloy nanoparticles (NPs) have been synthesized from micropowders of pure Cu and Ag using consecutively two non-equilibrium processes based on plasma and lasers in liquids. Plasma process reduces the size of initial micrometric powders down to nanometric size at which the laser fluence is sufficient to melt them, making alloying possible. Measurements at macroscopic (solution absorption), microscopic (scattering of individual NPs) and nanoscopic (electron microscopy) scales confirm alloying of NPs and homogenization in size and composition. This has noticeable effect on the final colloidal solution that absorbs yellow-orange light (550-600 nm) after laser treatment. The possibility to quench the as-formed liquid alloy leads to phase compositions that are not compliant with the phase diagram. With a synthesis rate of 360 mg/h, this process opens up interesting perspectives for non-equilibrium nanometallurgy of functional NPs.

Limited Elemental Mixing in Nanoparticles Generated by Ultrashort Pulse Laser Ablation of AgCu Bilayer Thin Films in a Liquid Environment: Atomistic Modeling and Experiments

“…The AgCu system is another example of an eutectic system with a very limited mutual solubility in the solid state, which presents a scientifically interesting and practically important case study for the nanoparticle synthesis. To our knowledge, there have only been a few studies dedicated to the generation of AgCu bimetallic nanoparticles by PLAL. − The results of a detailed investigation of AgCu nanoparticles produced by nanosecond PLAL in an aqueous solution of 0.02 M poly­(vinylpyrrolidone) as a capping agent are reported in ref . The bulk alloy targets used in these experiments have different compositions and eutectic microstructure featuring submicrometer thickness of the copper- and silver-rich layers.…”

“…In addition to the direct synthesis of bimetallic nanoparticles by PLAL of two-component targets with different degrees of phase separation, other techniques have been explored for generation of AgCu nanoparticles. These include nanosecond ablation of Cu targets into a colloidal solution of Ag nanoparticles, yielding core–shell morphologies with a Ag core and a Cu shell, as well as a combination of plasma treatment of Cu and Ag micropowder suspension in ethanol with nanosecond laser irradiation, leading to the formation of well-alloyed nanoparticles …”

“…These include nanosecond ablation of Cu targets into a colloidal solution of Ag nanoparticles, yielding core−shell morphologies with a Ag core and a Cu shell, 34 micropowder suspension in ethanol with nanosecond laser irradiation, leading to the formation of well-alloyed nanoparticles. 36 Theoretical and computational studies of PLAL have been focused on analysis of the general effects of the liquid environment on the ablation dynamics 39−42 and the mechanisms of the nanoparticle formation. 43−48 In particular, largescale atomistic simulations of ultrashort PLAL 40,45,46 have revealed two distinct mechanisms of the nanoparticle formation in PLAL, the rapid nucleation and growth of small nanoparticles in the metal−liquid mixing region and the generation of larger droplets through the breakup of a transient hot metal layer formed at the interface of the liquid environment, yielding nanoparticles of two different size ranges at the early stage of the ablation process.…”

Evidence of alloy formation in CoNi nanoparticles synthesized by nanosecond‐pulsed discharges in liquid nitrogen

“…[ 33 ] This also means that departure from equilibrium is probably very limited in the present process, thus there is the need for laser irradiation/melting to reach nonequilibrium conditions that are conducive to alloy formation. [ 19 ]…”

“…In such cases, a second step, based on laser irradiation of plasma‐produced nanoparticles, is necessary to form alloys. [ 19 ]…”