# Tag Info

## New answers tagged material-science

3

No, wings are designed to carry the maximum load with a minimum of weight. This results in their being flexible; to make them perfectly rigid would dramatically increase their weight and thereby reduce the payload of the aircraft. Aerodynamic flutter resulting from wing or control surface flexibility is then managed in a way consistent with minimizing the ...

0

The hydrogen bonds in cellulose is what gives paper its strength. When you try to tear a dry paper you have to apply a comparatively larger force to break these bonds. The breakage of the fine interlocked fibres in paper produces the sound. When the paper becomes wet, water gets absorbed into the paper. The high dielectric constant of water (80.4) decreases ...

0

This is just because of the damping in the molecules of paper. Generally, if you take a rope and wave it like a transverse wave, you would perfectly notice that after sometime, it stops. Why? Just because of damping. In the same way, when you wet a paper, damping is increased to very high number. Thats why it suppresses the vibrations caused due to tearing ...

1

following further why's ... Why or how does water dampens the vibrations ? – A Student 4ever https://wonderopolis.org/wonder/why-does-paper-rip-easier-when-wet#:~:text=These%20fibers%20are%20stiffened%20and,up%20of%20hydrogen%20and%20oxygen. From the above website... Tearing newspaper isn't too difficult, since it's relatively thin. If you've ever torn ...

4

I have a couple of thoughts on this question, and though I admit they are speculations, I hope they are educated ones! Paper is an interesting material. As to what exactly paper is, Wikipedia tells us that: Paper is a thin sheet material produced by mechanically and/or chemically processing cellulose fibres derived from wood, rags, grasses or other ...

2

Sound can't travel through vacuum. Why? Because sound is caused by vibrations in physical existence. Sound on its own doesn't have physical existence, it is caused by something that has physical existence. That is why sound can't propagate through vacuum. Dry paper has more vibrations and wet paper has negligible vibrations and that is why dry paper makes ...

1

Most magnetic materials in reality have some amount of magneto-crystalline anisotropy. This arises from spin-orbit coupling. This magneto-crystalline anisotropy dictates the 'easy', 'intermediate' and 'hard' axes in a magnet - For example, if your material has an 'easy' axis in-plane, this means that the lowest energy state is for a configuration in which ...

2

One of the advantages of the sintering process is avoiding macro segregations. The common foundry process can result in differences in chemical compositions between core and shell for example, due to differences in the rate of cooling along the solidification. It is particularly critical for high alloyed materials. In the sintering process, the components ...

5

Here is how it works. At temperatures above about 1/3 to 1/2 the melt temperature (in degrees absolute), solid state diffusion in metals is kinetically enabled. Metal atoms in their crystalline lattice networks start hopping between adjacent positions and if some positions are under more compressive stresses than others, there will be a net migration of ...

0

Let me first point out that Fermi level and Fermi energy are not the same thing (e.g., see here). What we are discussing here is mainly Fermi level (=chemical potential in the Fermi-Diract distribution), but the definition given in the OP is that of the Fermi energy: the highest energy occupied by an electron at zero temperature. They coincide in metals at ...

-1

The material has defined density of the states of given energy $\rho(E)$. Then it can be proven that the number of the electrons of given energy follows the distbibution $$n(E) = \rho(E) \frac{1}{1+e^{(E-E_F)/kT}}$$ with some (for now, unknown) parameter $E_F$. As the total number of electrons $N$ is also defined by the material, we have an equation  N = ...

1

That is SmFe$_{12}$ in which 20 % of the iron was replaced by cobalt.

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The generic plot above has some experimental verification at https://www.youtube.com/watch?v=fwh-i0WB_bQ. A pity they didn't measure radius of balloon, but if we assume constant rate of expansion, the shape of the graph plotted against time should be similar. Indeed, it clearly shows the initial maximum pressure, which is shown above to be caused by the ...

2

Finding "how it works" pages turns out to be rather difficult indeed. Here is one explanation from a college physics dept Q&A page. "Surface-to-surface adhesion" is just a fancy name for things sticking together, so it doesn't tell you much beyond what you were asking. The main mechanism is probably vanderWaals forces between the ...

0

In brief, every crystalline compound is characterized by a structure where the different lattice planes have different stoichiometric compositions and are separated by characteristic lengths. Taking into account the reflection conditions of the considered space group, a diffraction pattern is a collection of peaks whose positions are determined by the ...

1

The equal number of free electrons and holes is a general property of intrinsic semiconductors. It does not matter whether kind of material you consider. However, the same volumetric density does not imply the same electron/hole current. They might have different mobilities according to each particular material.

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For topography scanning purposes, especially for an undergrad experiment the pre-requisites are the robustness and stability in ambient conditions. Both PtIr and W make hard, and, with quite some practice, sharp tips which are ideal for STM. Moreover, W tips, when chemically etched are the go-to in most STM labs [1]. [1] https://pubs.acs.org/doi/10.1021/...

3

It says that mechanical strain is zero. The author considers mechanical strain and thermal strain separately. The mechanical one is zero if there is no external force. He never say that the thermal strain, due to thermal expansion, is zero. Edit According to the article: Thermal strain is due to the change in temperature of the bar. Mechanical strain is ...

3

Thermal strain is strain that develops when a material is heated or cooled. So the strain should not be zero. In addition to the site you provided, thermal strain for a non-constrained object is not zero as long as the coefficient of thermal expansion is not zero, per the following: http://emweb.unl.edu/NEGAHBAN/Em325/05-Thermal-strain/Thermal%20strain.htm ...

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