Sessile liquid drops have a higher vapor pressure than planar liquid surfaces, as quantified by Kelvin's equation. In classical derivations of Young's equation, this fact is often not taken into account. For an open system, a sessile liquid drop is never in thermodynamic equilibrium and will eventually evaporate. Practically, for macroscopic drops the time of evaporation is so long that nonequilibrium effects are negligible. For microscopic drops evaporation cannot be neglected. When a liquid is confined to a closed system, real equilibrium can be established. Experiments on the evaporation of water drops confirm the calculations.

On the derivation of young's equation for sessile drops : Nonequilibrium effects due to evaporation

https://hal.univ-lorraine.fr/hal-01570408/document

Dynamics and temperature of droplets impacting onto a heated wall

The particle formation process for microparticles of cellulose acetate butyrate dried from an acetone solution was investigated experimentally and theoretically. A monodisperse droplet chain was used to produce solution microdroplets in a size range of 55–70 μm with solution concentrations of 0.37 and 10 mg/mL. As the droplets dried in a laminar air flow with a temperature of 30, 40, or 55 °C, the particle formation process was recorded by two independent optical methods. Dried particles in a size range of 10–30 μm were collected for morphology analysis, showing hollow, elongated particles whose structure was dependent on the drying gas temperature and initial solution concentration. The setup allowed comprehensive measurements of the particle formation process to be made, including the period after initial shell formation. The early particle formation process for this system was controlled by the diffusion of cellulose acetate butyrate in the liquid phase, whereas later stages of the process were dominat...

Analysis of the Particle Formation Process of Structured Microparticles.

The gas synthesis of nanoparticles has gained major interest by different industries and research groups for the development of new materials and their subsequent implementation in numerous devices...

Synthesis of Metal Oxide Nanoparticles in Flame Sprays: Review on Process Technology, Modeling, and Diagnostics

Flame spray pyrolysis is an established technique for synthesizing nanoparticles in the gas phase through aerosol combustion of precursor/solvent droplets. The combustion characteristics of isolated micron-sized precursor/solvent droplets are investigated experimentally. Pure solvent droplets burn uniformly and classically quasisteady, whereas precursor/solvent droplets manifest disruptive combustion behavior. The fast onset of droplet disruption, which occurs only for solutions with dissolved metal precursors, is not due to solid-particle precipitation within the droplet. Instead, the mechanism of disruptive droplet burning is similar to that of slurry droplets, consisting of three main steps: (1) diffusion-controlled burning of the high-volatile solvent, (2) viscous-shell formation due to decomposition of the low-volatile metal precursor, and (3) subsequent disruption due to heterogeneous nucleation. The time sequence of the three steps depends on the concentration and decomposition characteristics of the metal precursor, shortening with increased concentration and higher incremental decomposition temperature. © 2013 American Institute of Chemical Engineers AIChE J, 59: 4553–4566, 2013

Disruptive burning of precursor/solvent droplets in flame‐spray synthesis of nanoparticles

Using a piezoceramic tube and a continuous glass capillary, droplets in a diameter range between 10 μm and 100 μm can be generated. This corresponds to a volume of up to 0.6 pl. The velocity of the generated droplets depends on droplet size but is constant for each diameter. The liquid can be dosed as single droplet, as an accumulation of droplets or as a chain of droplets in a frequency range between 1 Hz up to 3 kHz. The lifetime of the droplets depends on droplet size and the chemical and physical properties of the dispersed liquid. In addition, for water droplets the humidity of the air near the droplet trajectory influences the lifetime of the droplets.

Piezoelectric Droplet Generator for the Calibration of Particle-Sizing Instruments

The further development of a droplet generator which functions without the use of pressure (drop-on-demand system) for the production of monodisperse droplets of variable diameter opens up new fields of application.

Hartmut Ulmke

Papers

Piezoelectric Droplet Generator for the Calibration of Particle-Sizing Instruments

Piezoelectric Single Nozzle Droplet Generator for Production of Monodisperse Droplets of Variable Diameter

Piezoelektrischer Tropfengenerator zur Kalibrierung von Partikelzählern

zur Kalibrierung von Partikelzahlern