MolaKule
Staff member
Lubricant Films and Diffusion
used by Permission of Molecule
This piece discusses the dimensions of atoms and molecules with respect to the diffusion of molecules through metals.
We will begin by examining some real numbers for selected atoms and molecules:
An iron crystal structure is a Body-Centered Cubic (BCC) structure. This means there are 9 iron atoms in a BCC structure, with one at each of the eight corners and one in the center.
The atomic radius of an iron atom is 126 pico-meters (126 x 10-^12 meters) or 126 micromicro meters.
The length of each side of the cubic cell in an iron BCC structure (from crystal geometry theory) is A = 4R/sqrt(3), where R = atomic radius of the iron atom.
So the distance between each adjacent atom is S = A – 2r = 4 X 10^-11 meters, or 40 picometers, or approximately 1/3 the RADIUS of each iron atom.
For a linear alkane molecule of 20 atoms, the molecule is 20 X 1.5 X 10^-10 meters (or 20 X 1.5 Angstroms) long = 3 X 10^-9 meters or 3 nanometers long. Add to this molecule other large molecules such as VII polymer molecules, dispersant molecules, and other additive molecules, and the total lubricant molecule is more than 10 X 10^-9 meters or 10 nanaometers in size.
Now ask yourself this question: How does one send a 10 nanometer molecule through an opening that is 40 picometers?
To put it another way, how does one deposit a molecule that is 4,000 times larger than the interstitial space between the iron atoms?
Or, how does one get a large molecule through an iron cubic cell opening that is 4,000 times smaller than the dimension of the lubricant molecule?
Diffusion:
Diffusion is the process whereby a higher source concentration of atoms or molecules spreads out or disperses through a host medium. Diffusion is likened unto a ball carrier in which he moves through the defensive line. His reason for running through the defensive line is to reach his goal. His energy is provided by bio-molecular energy.
For example, a concentration of perfume molecules from a perfume bottle (source), will disperse throughout the surrounding air (host medium) nearby where we can smell them.
But atoms or molecules need a reason or goal to disperse or to be “coaxed” through a host medium. Some of these reasons are heat energy, pressure, differences in concentration between one side of a membrane and the other side, and a large enough space through which they can travel.
If the host side does not have enough space through which the source atoms or molecules may travel, they will be trapped. If the bottle of perfume is contained properly, the perfume molecules cannot get through the glass or cap.
Why, because the glass and cap crystal structures are too closely packed to allow the perfume molecules to escape.
Likewise, what physical reason is there for a large molecule to attempt to get through and subsequently disperse through a closely packed crystal structure of iron, steel or aluminum?
Well, we certainly have heat, pressure, and a concentration of molecules, but the important item we don’t have is space.
References:
1. Diffusion in Solids, M.E. Glicksman, John Wiley and Son, 2000
2. Internal Combustion Engine Fundamentals, J.B. Heywood, McGraw-Hill, 1988.
3. Introduction to Nuclear Engineering, Lamarsh and Baratta, Prentice Hall, 2001.
Internet Websites:
http://books.google.com/books?id=h6X0NM7...ies&f=false
http://gtresearchnews.gatech.edu/newsrelease/LUBE.html
http://www.machinerylubrication.com/Read/477/molecular-spectroscopy-lubrication
http://www.abbeyclock.com/aoiltwo.html
used by Permission of Molecule
This piece discusses the dimensions of atoms and molecules with respect to the diffusion of molecules through metals.
We will begin by examining some real numbers for selected atoms and molecules:
An iron crystal structure is a Body-Centered Cubic (BCC) structure. This means there are 9 iron atoms in a BCC structure, with one at each of the eight corners and one in the center.
The atomic radius of an iron atom is 126 pico-meters (126 x 10-^12 meters) or 126 micromicro meters.
The length of each side of the cubic cell in an iron BCC structure (from crystal geometry theory) is A = 4R/sqrt(3), where R = atomic radius of the iron atom.
So the distance between each adjacent atom is S = A – 2r = 4 X 10^-11 meters, or 40 picometers, or approximately 1/3 the RADIUS of each iron atom.
For a linear alkane molecule of 20 atoms, the molecule is 20 X 1.5 X 10^-10 meters (or 20 X 1.5 Angstroms) long = 3 X 10^-9 meters or 3 nanometers long. Add to this molecule other large molecules such as VII polymer molecules, dispersant molecules, and other additive molecules, and the total lubricant molecule is more than 10 X 10^-9 meters or 10 nanaometers in size.
Now ask yourself this question: How does one send a 10 nanometer molecule through an opening that is 40 picometers?
To put it another way, how does one deposit a molecule that is 4,000 times larger than the interstitial space between the iron atoms?
Or, how does one get a large molecule through an iron cubic cell opening that is 4,000 times smaller than the dimension of the lubricant molecule?
Diffusion:
Diffusion is the process whereby a higher source concentration of atoms or molecules spreads out or disperses through a host medium. Diffusion is likened unto a ball carrier in which he moves through the defensive line. His reason for running through the defensive line is to reach his goal. His energy is provided by bio-molecular energy.
For example, a concentration of perfume molecules from a perfume bottle (source), will disperse throughout the surrounding air (host medium) nearby where we can smell them.
But atoms or molecules need a reason or goal to disperse or to be “coaxed” through a host medium. Some of these reasons are heat energy, pressure, differences in concentration between one side of a membrane and the other side, and a large enough space through which they can travel.
If the host side does not have enough space through which the source atoms or molecules may travel, they will be trapped. If the bottle of perfume is contained properly, the perfume molecules cannot get through the glass or cap.
Why, because the glass and cap crystal structures are too closely packed to allow the perfume molecules to escape.
Likewise, what physical reason is there for a large molecule to attempt to get through and subsequently disperse through a closely packed crystal structure of iron, steel or aluminum?
Well, we certainly have heat, pressure, and a concentration of molecules, but the important item we don’t have is space.
References:
1. Diffusion in Solids, M.E. Glicksman, John Wiley and Son, 2000
2. Internal Combustion Engine Fundamentals, J.B. Heywood, McGraw-Hill, 1988.
3. Introduction to Nuclear Engineering, Lamarsh and Baratta, Prentice Hall, 2001.
Internet Websites:
http://books.google.com/books?id=h6X0NM7...ies&f=false
http://gtresearchnews.gatech.edu/newsrelease/LUBE.html
http://www.machinerylubrication.com/Read/477/molecular-spectroscopy-lubrication
http://www.abbeyclock.com/aoiltwo.html
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