Homogeneous Nucleation of Smoke Particles and Its Relationship with Cosmic Dust Particles

Kimura, Yuki; Tsukamoto, Katsuo

doi:10.1007/978-3-319-45669-0_17

Cited by 3 publications

(3 citation statements)

References 31 publications

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“…Hot vapors of Ti, C, and TiC were generated by resistive heating of appropriate sources containing the corresponding bulk material under argon (Ar) as a buffer gas introduced into the nucleation chamber to decrease the mean free path, thereby permitting a reduction in the size of the nucleation chamber to a laboratory scale [ (30); see also Materials and Methods). The nanometer-sized particles that formed through nucleation in the cooling gas mimicked grain formation in the gas ejecta of evolved stars (22,23,30). The entire process involving nucleation and formation of the resulting particles was observed in situ using a double-wavelength Mach-Zehnder-type laser interferometer (Fig.…”

Section: Resultsmentioning

confidence: 99%

“…Under microgravity, both the temperature field and the concentration field of the evaporated gas are arranged concentrically around the evaporation source, and nucleation occurs under uniform conditions. This provides several advantages for the purposes of research (22,30,32). First, like the physical treatment of systems with identical Reynolds numbers in fluid mechanics, the formation process of cosmic dust can be realistically simulated if the cooling time scale, τ T , and the collision frequency, υ, are similar (Table 1) (33,34).…”

Section: Advantages Of Microgravity Experimentsmentioning

confidence: 99%

“…First, like the physical treatment of systems with identical Reynolds numbers in fluid mechanics, the formation process of cosmic dust can be realistically simulated if the cooling time scale, τ T , and the collision frequency, υ, are similar (Table 1) (33,34). In our microgravity experiment, control of the mean free path permitted a simulation of the nucleation process of cosmic grains in the gas outflow from supernovae and AGB stars (30). As a result, we were able to measure the sticking probability and surface tension at temperatures similar to the formation temperature of circumstellar grains.…”

Section: Advantages Of Microgravity Experimentsmentioning

confidence: 99%

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Nucleation experiments on a titanium-carbon system imply nonclassical formation of presolar grains

et al. 2023

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Just as the shapes of snowflakes provide us with information on the temperature and humidity of the upper atmosphere, the characteristics of presolar grains in meteorites place limits on their formation environment in a stellar outflow. However, even in the case of well-characterized presolar grains consisting of a titanium carbide core and a graphitic carbon mantle, it is not possible to delimit their formation environment. Here, we have demonstrated the formation of core-mantle grains in gravitational and microgravity environments and have found that core-mantle grains are formed by a nonclassical nucleation pathway involving the three steps: (i) primary nucleation of carbon at a substantially high supersaturation, (ii) heterogeneous condensation of titanium carbide on the carbon, and (iii) fusion of nuclei. We argue that the characteristics of not only core-mantle grains but also other presolar and solar grains might be accurately explained by considering a nonclassical nucleation pathway.

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Section: Resultsmentioning

confidence: 99%

Section: Advantages Of Microgravity Experimentsmentioning

confidence: 99%

Section: Advantages Of Microgravity Experimentsmentioning

confidence: 99%

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Nucleation experiments on a titanium-carbon system imply nonclassical formation of presolar grains

et al. 2023

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Direct observation of the moment of nucleation from a solution by TEM

Kimura

2021

Microscopy

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Recent discoveries of various nucleation processes make understanding the initial processes of crystallization, where atoms and molecules come together to form a crystal nucleus, difficult. Herein, transmission electron microscopy is used to directly visualize the moment of nucleation from a solution and to show that the singular phenomena of nanoparticles are critical to understanding nucleation. Our work revealed that nanoparticles undergo precipitation and dissolution even in undersaturated and equilibrium conditions, that crystal polymorphs formed at different frequencies compete, that molecules follow various nucleation pathways in the same solution, and that the hydration layer plays a critical role in crystallization. The observations visually support the common belief that dehydration is the greatest barrier to crystallization in an aqueous solution. These results are expected to contribute to the development of a unified nucleation model.

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Inefficient Growth of SiOx Grains: Implications for Circumstellar Outflows

Kimura¹,

Tanaka²,

Inatomi³

et al. 2022

ApJL

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To explain observations of abundant circumstellar dust and high stellar wind velocity, most models simply postulate the efficient nucleation and growth of silicate dust particles. Here, we report measurement of the SiO–(SiOx)n grain sticking coefficient in a microgravity sounding rocket experiment, indicating very inefficient (0.005–0.016) grain formation from the vapor. Application of this measurement to radiative-driven winds in oxygen-rich asymptotic giant branch stars indicates that the initial grain condensate population should consist of very tiny dust particles in very large numbers. Aggregation of this dust population will produce low-dimension fractal aggregates that should couple well to the stellar radiation field and efficiently drive stellar mass loss.

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Homogeneous Nucleation of Smoke Particles and Its Relationship with Cosmic Dust Particles

Cited by 3 publications

References 31 publications

Nucleation experiments on a titanium-carbon system imply nonclassical formation of presolar grains

Nucleation experiments on a titanium-carbon system imply nonclassical formation of presolar grains

Direct observation of the moment of nucleation from a solution by TEM

Inefficient Growth of SiOx Grains: Implications for Circumstellar Outflows

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