Adsorption on Single-Walled Carbon Nanohorns
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Transcript of Adsorption on Single-Walled Carbon Nanohorns
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Adsorption on Single-Walled Carbon NanohornsAdam Scrivener
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What are carbon nanohorns?● Nanostructures made from graphene sheets,
forming a dahlia-like structure.● Surface area is much
greater than graphene, which makes nanohorns a promising material for gas adsorption.
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What is adsorption?● Adsorption is the adhesion of atoms or
molecules from a gas, liquid, or dissolved solid to a surface.
● Caused by van der Waals force between an adsorbate (gas molecules/atoms) and an adsorbent (Carbon atoms).
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Applications of adsorption● Gas storage: gas particles can be stored at very high density using
nanohorns, due to the adsorption process and high surface area per volume ratio.
● Gas separation: Several materials, including carbon nanohorns, can be used as a filter in factories to reduce greenhouse gas emissions such as methane and CO2.
● Gas sensing: The ability to monitor how much gas is in a system is invaluable, and carbon-based materials such as carbon nanohorns are perfect for this because of their large specific surface areas.
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The van der Waals force● The van der Waals force is the sum of the
attractive forces between molecules other than those due to covalent bonds or electrostatic interactions involving ions.
● There are no covalent bonds or ions involved in the systems which we deal with, so the electrostatic forces can be disregarded.
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The Lennard-Jones potential● Approximates the interactions between the Carbon
atoms in the nanohorns and the gaseous adsorbate● Incorporates the attractive portion of the van der
Waals force and the repulsive forces caused by overlapping electron orbitals.
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Monte Carlo Simulations● An efficient method of observing the equilibrium properties of the
nanohorn/gas system.● Simulations can be combined with experiments to make it easier to
interpret the results● Using simulations, we can explore parameters that are not possible
in a real-world experiment. E.G., we can set any temperature or pressure that we want, or add impurities to the adsorbent easily.
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The Grand Canonical Monte Carlo Algorithm1. Start with an arbitrary configuration of particles.
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The Grand Canonical Monte Carlo Algorithm1. Start with an arbitrary configuration of particles.2. Randomly choose whether to:
a. Move a particle from the vapor into the system in a random location.
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The Grand Canonical Monte Carlo Algorithm1. Start with an arbitrary configuration of particles.2. Randomly choose whether to:
a. Move a particle from the vapor into the system in a random location.
b. Move a random particle from the system into the vapor.
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The Grand Canonical Monte Carlo Algorithm1. Start with an arbitrary configuration of particles.2. Randomly choose whether to:
a. Move a particle from the vapor into the system in a random location.
b. Move a random particle from the system into the vapor.c. Choose a random particle already in the system and move
it in a random direction within some fixed distance ∆.
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∆
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The Grand Canonical Monte Carlo Algorithm1. Start with an arbitrary configuration of particles.2. Randomly choose whether to:
a. Move a particle from the vapor into the system in a random location.
b. Move a random particle from the system into the vapor.c. Choose a random particle already in the system and move it in
a random direction within some fixed distance ∆. 3. Repeat until the system is in equilibrium.
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(After many iterations)
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Energy of Krypton-nanohorn system
40K 60K 77.4K
Egg EggEgg
EgsEgs
Egs
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Krypton Adsorption - Pressure vs. Temperature
40K 60K 77.4K
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Atoms inside
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Krypton Adsorption - Pressure vs. Temperature
40K 60K 77.4K
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Atoms insideand in between
nanohorns
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Krypton Adsorption - Pressure vs. Temperature
40K 60K 77.4K
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Atoms inside and on surface of nanohorns
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Future plans● Simulate Neon instead of Krypton ● Use Neon data to compare to already observed data
from real-world experiments.● This will further affirm that our simulations accurately
represent the equilibrium state of the nanohorn adsorption systems.
● We plan to simulate CO2 as well, and, similarly to Neon, compare to data from real-world experiments.