Driven by functionality and purity demand for applications of inorganic nanoparticle colloids in optics, biology, and energy, their surface chemistry has become a topic of intensive research interest. Consequently, ligand-free colloids are ideal reference materials for evaluating the effects of surface adsorbates from the initial state for application-oriented nanointegration purposes. After two decades of development, laser synthesis and processing of colloids (LSPC) has emerged as a convenient and scalable technique for the synthesis of ligand-free nanomaterials in sealed environments. In addition to the high-purity surface of LSPC-generated nanoparticles, other strengths of LSPC include its high throughput, convenience for preparing alloys or series of doped nanomaterials, and its continuous operation mode, suitable for downstream processing. Unscreened surface charge of LSPC-synthesized colloids is the key to achieving colloidal stability and high affinity to biomolecules as well as support materials,...

Laser Synthesis and Processing of Colloids: Fundamentals and Applications

This review highlights various aspects of current palladium membrane research and serves as a comprehensive bibliography covering palladium membrane preparation methods and applications. There are many promising uses for palladium membranes, although widespread use of the available technologies is constrained primarily by the high cost of palladium, lack of durability due to hydrogen embrittlement, and susceptibility to fouling. Various researchers in the field are tackling these problems and fabricating thinner palladium alloy composite membranes that better withstand contaminantion and thermal cycling. What has been accomplished to address these issues and the directions presently being explored are discussed.

Innovations in palladium membrane research

https://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1275&context=mechengfacpub

Review of Electrochemical and Electrodischarge Machining

https://cyberleninka.org/article/n/1487470.pdf

External field-assisted laser ablation in liquid: An efficient strategy for nanocrystal synthesis and nanostructure assembly

The synthesis of chemically clean and environmentally friendly nanoparticles through pulsed laser ablation in liquids has shown a number of advantages over conventional chemical synthesis methods and has evolved into a thriving research field attracting laboratory and industrial applications. The fundamental understanding of processes leading to the nanoparticle generation, however, still remains elusive. In particular, the origin of bimodal nanoparticle size distributions in femto- and picosecond laser ablation in liquids, where small nanoparticles (several nanometers) with narrow size distribution are commonly observed to coexist with larger (tens to hundreds of nanometers) ones, has not been explained so far. In this paper, joint computational and experimental efforts are applied to understand the mechanisms of nanoparticle formation in picosecond laser ablation in liquids and to explain the bimodal nanoparticle size distributions. The results of a large-scale atomistic simulation reveal the critical role of the dynamic interaction between the ablation plume and the liquid environment, leading to the generation of large nanoparticles through a sequence of hydrodynamic instabilities at the plume-liquid interface and a concurrent nucleation and growth of small nanoparticles in an expanding metal-liquid mixing region. The computational predictions are supported by a series of stroboscopic videography experiments showing the emergence of small satellite bubbles surrounding the main cavitation bubble generated in single pulse experiments. Carefully timed double pulse irradiation triggers expansion of secondary cavitation bubbles indicating, in accord with the simulation results, the presence of localized sites of laser energy deposition (possibly large nanoparticles) injected into the liquid at the early stage of the bubble formation.

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Two mechanisms of nanoparticle generation in picosecond laser ablation in liquids: the origin of the bimodal size distribution

Bubble dynamics in metal nanoparticle formation by laser ablation in liquid studied through high-speed laser stroboscopic videography

Stress enhancement in laser-induced shock process by plasma-confining effect of liquid overlay was demonstrated visually and its dependence on liquid layer thickness was studied. Time-resolved photoelasticity imaging technique in bright-field mode was used to observe the stress wave in solid phase and the shock wave, plasma, and cavitation bubble in the liquid phase simultaneously. From the photoelastic images, intensity of the laser-induced stress wave (LSW) inside a solid was evaluated semi-quantitatively. We prove that LSW is weaker with thinner liquid layer. To achieve the same effect with bulk liquid, the liquid film needs to be thicker than a threshold value.

Laser-induced shock process in under-liquid regime studied by time-resolved photoelasticity imaging technique

A 56-year-old man complained of headache and the analgesia of the four extremities. Laboratory data presented signs of inflammation, but no other abnormality such as renal or respiratory dysfunction. Two months after the appearance of the primary symptoms, he developed cerebral infarction of the bilateral corona radiata. The patient did not have any of the risk factors for cerebrovascular disease. He was diagnosed with anti-neutrophil cytoplasmic autoantibody (ANCA)-associated vasculitis (AAV) because the systemic examinations revealed only that he tested positive for anti-neutrophil cytoplasmic autoantibody (ANCA). Moreover, the biopsy of the sural nerve displayed microscopic polyangitis (MPA). Despite undergoing steroid pulse therapy, the patient died from the fatal cerebral hemorrhage. The clinical course of AAV is rapid progressive. In cases of atypical cerebrovascular disease, the possibility of ANCA should be investigated.

Short communication ANCA-associated vasculitis (AAV) causing bilateral cerebral infarction and subsequent intracerebral hemorrhage without renal and respiratory dysfunction

The effects of an absorptive coating on the dynamics of underwater laser-induced shock process have been observed from the end of laser pulse to hundreds of microseconds after irradiation by time-resolved imaging techniques. A laser pulse of 13 ns at 1,064 nm was focused by a 40-mm focal length lens onto the surface of epoxy-resin blocks immersed in water to induce the shock process in the confining regime. A custom-designed time-resolved photoelasticity imaging technique and a high-speed laser stroboscopic videography technique in photoelasticity mode were used to analyze the evolution of shock waves in the water phase, the strength of stress waves in the solid phase, the oscillation of cavitation bubbles, and the generation of bubble-collapse-induced shock waves. We showed that black paint coating enhances the strength of laser-induced stress wave inside the solid, drives faster shock waves traveling in the water phase, and produces higher-energy cavitation bubbles. We propose that even at power densities of 1 GW/cm2 and above, an absorptive coating can intensify the shock process by enhancing the absorption of laser energy by plasma.

Effects of an absorptive coating on the dynamics of underwater laser-induced shock process

We compared the expansion characteristics of the plasma plumes and shock waves generated in laser-induced shock process between the two ablation regimes: in air and under water. The observation was made from the initial moment when the laser pulse hit the target until 1.5 μs. The shock processes were driven by focusing a single laser pulse (1064 nm, FWHM = 13 ns) onto the surface of epoxy-resin blocks using a 40-mm focal length lens. The estimated laser intensity at the target plane is approximate to 9 × 10 9 W cm - 2 . We used the fast-imaging technique to observe the expansion of the plasma plume and a custom-designed time-resolved photoelasticity imaging technique to observe the propagation of shock waves with the time resolution of nanoseconds. We found that at the same intensity of the laser beam, the plasma expansion during the laser pulse follows different mechanisms: the plasma plume that grows in air follows a radiation-wave model while a detonation-wave model can explain the expansion of the plasma plume induced in water. The ideal blast wave theory can be used to predict the decay of the shock wave in air but is not appropriate to describe the decay of the shock wave induced under water.

Yoshiro Ito

Papers

Bubble dynamics in metal nanoparticle formation by laser ablation in liquid studied through high-speed laser stroboscopic videography

Laser-induced shock process in under-liquid regime studied by time-resolved photoelasticity imaging technique

Short communication ANCA-associated vasculitis (AAV) causing bilateral cerebral infarction and subsequent intracerebral hemorrhage without renal and respiratory dysfunction

Effects of an absorptive coating on the dynamics of underwater laser-induced shock process

Comparative study of the expansion dynamics of laser-driven plasma and shock wave in in-air and underwater ablation regimes