scholarly journals LaMer's 1950 model of particle formation: a review and critical analysis of its classical nucleation and fluctuation theory basis, of competing models and mechanisms for phase-changes and particle formation, and then of its application to silver halide, semiconductor, metal, and metal-oxide nanoparticles

2021 ◽  
Author(s):  
Christopher B. Whitehead ◽  
Saim Özkar ◽  
Richard G. Finke
Keyword(s):  
Reaction Mechanisms ◽  
Silver Halide ◽  
Metal Oxide Nanoparticles ◽  
Particle Formation ◽  
Phase Changes ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Wide Range ◽  
Competing Models ◽  
Chemical Reaction Mechanisms

Are classical nucleation theory and the 1950 LaMer model of particle formation supported for a wide range of particle formations, or do competing models in the form of chemical reaction mechanisms have better experimental support? Read on to find out.

scholarly journals An approximation for homogeneous freezing temperature of water droplets

2015 ◽  
Vol 15 (21) ◽  
pp. 31867-31889
Author(s):  
K.-T. O ◽  
R. Wood
Keyword(s):  
Experimental Studies ◽  
Freezing Temperature ◽  
Ice Nucleation ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Water Droplets ◽  
Wide Range ◽  
The Mean ◽  
Freezing Temperatures ◽  
Homogeneous Freezing

Abstract. In this work, based on the well-known formulae of classical nucleation theory (CNT), the temperature TNc = 1 at which the mean number of critical embryos inside a droplet is unity is derived and proposed as a new approximation for homogeneous freezing temperature of water droplets. Without consideration of time dependence and stochastic nature of the ice nucleation process, the approximation TNc = 1 is able to reproduce the dependence of homogeneous freezing temperature on drop size and water activity of aqueous drops observed in a wide range of experimental studies. We use the TNc = 1 approximation to argue that the distribution of homogeneous freezing temperatures observed in the experiments may largely be explained by the spread in the size distribution of droplets used in the particular experiment. It thus appears that this approximation is useful for predicting homogeneous freezing temperatures of water droplets in the atmosphere.

Analytical Investigation on the Homogeneous Nucleation in a Mono-Component and Bi-Component Droplet

2019 ◽  
Author(s):  
Xi Xi ◽  
Hong Liu ◽  
Chang Cai ◽  
Ming Jia ◽  
Weilong Zhang
Keyword(s):  
Nucleation Rate ◽  
Homogeneous Nucleation ◽  
Ambient Pressure ◽  
Analytical Investigation ◽  
Bubble Nucleation ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Liquid Temperature ◽  
Wide Range ◽  
Good Agreement

Abstract The work attempts to analyze the performance of homogeneous nucleation by using the non-equilibrium thermodynamics theory and the classical nucleation theory. A nucleation rate graph was constructed under a wide range of operating temperature conditions. The results indicate that the superheat limit temperature (SLT) estimated by the modified homogeneous nucleation sub-model is in good agreement with the experimental results. The nucleation rate increases exponentially with the liquid temperature rise when the liquid temperature exceeds the SLT under atmospheric pressure. The superheated temperature needed to trigger the bubble nucleation decreases with the elevated ambient pressure.

scholarly journals Parameterizing the competition between homogeneous and heterogeneous freezing in ice cloud formation – polydisperse ice nuclei

2009 ◽  
Vol 9 (16) ◽  
pp. 5933-5948 ◽  
Author(s):  
D. Barahona ◽  
A. Nenes
Keyword(s):  
Number Concentration ◽  
Nucleation Theory ◽  
Cloud Formation ◽  
Classical Nucleation Theory ◽  
Average Error ◽  
Ice Crystal ◽  
Ice Cloud ◽  
Ice Nuclei ◽  
Wide Range ◽  
Model Equations

Abstract. This study presents a comprehensive ice cloud formation parameterization that computes the ice crystal number, size distribution, and maximum supersaturation from precursor aerosol and ice nuclei. The parameterization provides an analytical solution of the cloud parcel model equations and accounts for the competition effects between homogeneous and heterogeneous freezing, and, between heterogeneous freezing in different modes. The diversity of heterogeneous nuclei is described through a nucleation spectrum function which is allowed to follow any form (i.e., derived from classical nucleation theory or from observations). The parameterization reproduces the predictions of a detailed numerical parcel model over a wide range of conditions, and several expressions for the nucleation spectrum. The average error in ice crystal number concentration was −2.0±8.5% for conditions of pure heterogeneous freezing, and, 4.7±21% when both homogeneous and heterogeneous freezing were active. The formulation presented is fast and free from requirements of numerical integration.

Macro-Micro Modeling Analysis of Melting and Re-Solidification of Thin Si Films by Excimer Laser Annealing

2008 ◽  
Vol 594 ◽  
pp. 306-311
Author(s):  
Long Sun Chao ◽  
Chien Hung Chang
Keyword(s):  
Grain Size ◽  
Excimer Laser ◽  
Laser Annealing ◽  
Transfer Problem ◽  
Phase Changes ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Micro Model ◽  
Excimer Laser Annealing ◽  
Si Films

In this work, an macro-micro model has been developed for the melting and resolidification of thin Si films induced by excimer-laser annealing. The macro-micro model, considering the formation of microstructures: nucleation and growth, can obtain the better results than macro-models. Except temperature distributions, the macro-micro models can offer more information about solidification process, such as undercooling, grain size, grain density etc. These data could help to predict the physical properties of materials. In this study, the finite difference method is utilized to solve the heat transfer problem. The specific heat/enthalpy method and the source term scheme are employed to handle the absorbed and released latent heat. The algorithm that allows for nucleation is based on classical nucleation theory. Accordingly, the model enables the prediction of grain size, as well as the calculation of other critical responses of the a-Si film, such as undercooling. From the computational results, it can be found that when the laser fluence is higher, the cooling rate after laser irradiation is lower, the maximum undercooling is smaller and the grain size is larger or the grain density is lower. The average grain sizes, obtained from the simulation results of the proposed model, agree fairly well with those from the experimental data reported in the literature. It can also be found that the reflectivity of the surface gives a good way to observe the phase changes and the melting duration.

scholarly journals Parameterizing the competition between homogeneous and heterogeneous freezing in ice cloud formation – polydisperse ice nuclei

2009 ◽  
Vol 9 (3) ◽  
pp. 10957-11004 ◽  
Author(s):  
D. Barahona ◽  
A. Nenes
Keyword(s):  
Size Distribution ◽  
Nucleation Theory ◽  
Cloud Formation ◽  
Classical Nucleation Theory ◽  
Average Error ◽  
Ice Crystal ◽  
Ice Cloud ◽  
Ice Nuclei ◽  
Wide Range ◽  
Model Equations

Abstract. This study presents a comprehensive ice cloud formation parameterization that computes the ice crystal number, size distribution, and maximum supersaturation from precursor aerosol and ice nuclei with any size distribution and chemical composition. The parameterization provides an analytical solution of the cloud parcel model equations and accounts for the competition effects between homogeneous and heterogeneous freezing, and, between heterogeneous freezing in different modes. The diversity of heterogeneous nuclei is described through a nucleation spectrum function which is allowed to follow any form (i.e., derived from classical nucleation theory or from empirical observations). The parameterization reproduced the predictions of a detailed numerical parcel model over a wide range of conditions, and several expressions for the nucleation spectrum. The average error in ice crystal number concentration was −2.0±8.5% for conditions of pure heterogeneous freezing, and, 4.7±21% when both homogeneous and heterogeneous freezing were active. Apart from its rigor, excellent performance and versatility, the formulation is extremely fast and free from requirements of numerical integration.

Classical Nucleation Theory and Its Application to Condensing Steam Flow Calculations

2005 ◽  
Vol 219 (12) ◽  
pp. 1315-1333 ◽  
Author(s):  
F Bakhtar ◽  
J B Young ◽  
A J White ◽  
D A Simpson
Keyword(s):  
Predictive Accuracy ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Droplet Radius ◽  
Droplet Growth ◽  
Wide Range ◽  
Recent Developments ◽  
Judicious Choice ◽  
The Many ◽  
Low Pressures

The paper discusses the classical theory of the homogeneous nucleation of water droplets from supersaturated vapour and its application in predicting condensation in steam nozzles. The first part consists of a review of classical nucleation theory, focusing on the many modifications made to the original Becker-Döring theory and providing some new insights into recent developments. It is concluded that the predictive accuracy required for engineering calculations is not yet attainable with a theory derived from first principles. The areas that require most attention relate to the properties of small molecular clusters and the energy transfer processes in the non-isothermal theory. Experiments in converging-diverging nozzles provide the best means for validation at the very high nucleation rates of interest, but measurements of pressure distribution and the Sauter mean droplet radius are insufficient to provide independent checks on the separate theories of nucleation and droplet growth. Nevertheless, a judicious choice for the nucleation rate equation, in combination with a standard droplet growth model and a suitable equation of state for steam, can provide accurate predictions over a wide range of conditions. The exception is at very low pressures where there is evidence that the droplet growth rate in the nucleation zone is underestimated.

scholarly journals Ice nucleation by water-soluble macromolecules

2015 ◽  
Vol 15 (8) ◽  
pp. 4077-4091 ◽  
Author(s):  
B. G. Pummer ◽  
C. Budke ◽  
S. Augustin-Bauditz ◽  
D. Niedermeier ◽  
L. Felgitsch ◽  
...  
Keyword(s):  
Theoretical Calculations ◽  
Pure Water ◽  
Global Radiation ◽  
Ice Nucleation ◽  
Water Soluble ◽  
Nucleation Theory ◽  
Radiation Budget ◽  
Classical Nucleation Theory ◽  
Chemical Structures ◽  
Wide Range

Abstract. Cloud glaciation is critically important for the global radiation budget (albedo) and for initiation of precipitation. But the freezing of pure water droplets requires cooling to temperatures as low as 235 K. Freezing at higher temperatures requires the presence of an ice nucleator, which serves as a template for arranging water molecules in an ice-like manner. It is often assumed that these ice nucleators have to be insoluble particles. We point out that also free macromolecules which are dissolved in water can efficiently induce ice nucleation: the size of such ice nucleating macromolecules (INMs) is in the range of nanometers, corresponding to the size of the critical ice embryo. As the latter is temperature-dependent, we see a correlation between the size of INMs and the ice nucleation temperature as predicted by classical nucleation theory. Different types of INMs have been found in a wide range of biological species and comprise a variety of chemical structures including proteins, saccharides, and lipids. Our investigation of the fungal species Acremonium implicatum, Isaria farinosa, and Mortierella alpina shows that their ice nucleation activity is caused by proteinaceous water-soluble INMs. We combine these new results and literature data on INMs from fungi, bacteria, and pollen with theoretical calculations to develop a chemical interpretation of ice nucleation and water-soluble INMs. This has atmospheric implications since many of these INMs can be released by fragmentation of the carrier cell and subsequently may be distributed independently. Up to now, this process has not been accounted for in atmospheric models.

Sign in / Sign up

Export Citation Format

Share Document