Just found this and the one on effusivity. Thank you so much. It's often difficult to explain to people what you intend the end result to be without using the human senses as examples and you've helped me do that
8:35 “In the area of aerospace and electronics reliability the rule of thumb is that for every 10 degrees increase in operating temperature you have a 50% reduction in reliability.”
Can someone help me out here. I don't major in physics. However, does this mean that the thermal conductivity of a material (poor or good conductors) is also dependent on their structural formation?
Yes, that's also what dr. Is trying to convey in the video. It greatly depends on molecular arrangement. Diamond for example, is an excellent conductor of heat because of its highly orderly arrangement of molecules.
The m in the units of W/m·K refers to the thickness but surely the area of transmission is a component too. Is it to be assumed that we are measuring the heat flow in a unit area. If this were so, shouldn't the units be W/m·K/sq.m
I do have one question. There are a few materials now that have a high thermal conductivity along (example) their x,y axis but it is a huge difference along the z axis. How can you explain that to people.
Great question Paul. Anisotropy in thermal conductivity can have a number of different causes: It can be an inherent property of the crystal structure of a pure crystalline material (such as in graphite, sapphire, or boron nitride sheets). Sometimes, it can be a result of the manufacturing of an amorphous or semi-crystalline material (many polymers, for example, exhibit anisotropy in thermal conductivity when they have been extruded due to the extrusion’s orientation of the polymer chains). And sometimes it has to do with the orientation of high-conductivity components of a mixture or composite system (for example, often filled polymer composites have high-conductivity fillers with large aspect ratios - such as carbon nanotubes - which conduct heat very efficiency along their length but can’t pass heat as well through the polymer matrix). In the case of crystalline materials, the difference is due to the difference in phonon transmission efficiency along the different axes of the material. In the case of non-crystalline long-chain materials, like polymers, it’s to do with chain organization: heat transmits more efficiently along a chain than between chains - and therefore if the polymer chains exhibit some degree of organization, the thermal conductivity will be higher in the direction that the chains tend to be oriented towards. In the case of composites, it is due to more efficient heat-transfer along the filler materials than through the matrix. Hope that helps!
This is a very interesting and very clear explanation, we know that Ti and Al are metal but TiO2 and Al2O3 are oxide-based materials, what is the microstructure looks like and how these two materials transfer the heat? Thanks, Dr. Jack
This video talks the difference between crystalline solids and plastics. However, the case of metal is different with other solids because of free electrons, which also plays an important role in thermal transport, in particular at high temperature. That is why thermal conductivity of metal is higher than other solids, such as diamond?
I love this explanation, it is just perfect! Simple to understand, thank you so much!!!
Very clear and precise. Exactly what I needed for school. Thank you so much!
This was absolutely brilliant!
Just found this and the one on effusivity. Thank you so much. It's often difficult to explain to people what you intend the end result to be without using the human senses as examples and you've helped me do that
this was really really good and helpfull, thanks alot :)
Thank you so much for a clear and concise presentation. Very thankful.
8:35 “In the area of aerospace and electronics reliability the rule of thumb is that for every 10 degrees increase in operating temperature you have a 50% reduction in reliability.”
Thanks for your very good explanation of thermal conductivity and how molecular structure plays a big role.
Excellent explanation, easy to follow. Thank you!!
Very informative.....keep doing the good work
Can someone help me out here. I don't major in physics. However, does this mean that the thermal conductivity of a material (poor or good conductors) is also dependent on their structural formation?
Yes, that's also what dr. Is trying to convey in the video. It greatly depends on molecular arrangement. Diamond for example, is an excellent conductor of heat because of its highly orderly arrangement of molecules.
The m in the units of W/m·K refers to the thickness but surely the area of transmission is a component too. Is it to be assumed that we are measuring the heat flow in a unit area. If this were so, shouldn't the units be W/m·K/sq.m
I do have one question. There are a few materials now that have a high thermal conductivity along (example) their x,y axis but it is a huge difference along the z axis. How can you explain that to people.
Great question Paul. Anisotropy in thermal conductivity can have a number of different causes: It can be an inherent property of the crystal structure of a pure crystalline material (such as in graphite, sapphire, or boron nitride sheets). Sometimes, it can be a result of the manufacturing of an amorphous or semi-crystalline material (many polymers, for example, exhibit anisotropy in thermal conductivity when they have been extruded due to the extrusion’s orientation of the polymer chains). And sometimes it has to do with the orientation of high-conductivity components of a mixture or composite system (for example, often filled polymer composites have high-conductivity fillers with large aspect ratios - such as carbon nanotubes - which conduct heat very efficiency along their length but can’t pass heat as well through the polymer matrix).
In the case of crystalline materials, the difference is due to the difference in phonon transmission efficiency along the different axes of the material. In the case of non-crystalline long-chain materials, like polymers, it’s to do with chain organization: heat transmits more efficiently along a chain than between chains - and therefore if the polymer chains exhibit some degree of organization, the thermal conductivity will be higher in the direction that the chains tend to be oriented towards. In the case of composites, it is due to more efficient heat-transfer along the filler materials than through the matrix.
Hope that helps!
Thank you, i was searching for that and you delivered clear and understandable answer
Dr. Josefowicz does a great job explaining it.
This is a very interesting and very clear explanation, we know that Ti and Al are metal but TiO2 and Al2O3 are oxide-based materials, what is the microstructure looks like and how these two materials transfer the heat? Thanks, Dr. Jack
I like this presentation. It's informative and helpful. Thanks.
It looks like he is standing on a stage and the white board is far i cant unsee that
This video talks the difference between crystalline solids and plastics. However, the case of metal is different with other solids because of free electrons, which also plays an important role in thermal transport, in particular at high temperature. That is why thermal conductivity of metal is higher than other solids, such as diamond?
Ye na u r right but in general thermal conductivity of crystalline material is higher than that of amorphous solid.
This was great. And now the question: why do atoms start vibrating with heat?
very interesting and helpful, thanks. Isn’t diamond the best thermal conductor
Really good explanation!
Yes, nice job.
why is it that if we heat a coil it reduces electricity?
Thank you so much sir :)
3:36 If the metal is shiny the emissivity will be very low and so will not absorb much radiation at all - at least it shouldn't.
Thank u sir.its helpful
So in plastic heat has promlems to go from up -> down, but in metal it goes easily from left -> right. Thumb up if I got this right.
You're amazing
I'm happy to see that Gustavo Fring left a life of crime behind and is now teaching material science.
You needed to edit the audio using a filter
woah I didnt know John Malkovich was a scientist
Hi
Isn't this the dude from Breaking bad?