The study of how the properties of matter arise from its structure at all scales and of how processing can be used to modify those properties (often in pursuit of a specific application).

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1answer
34 views

Does Hooke's Law apply for microscopic amounts of compression?

I would like to set up a simple laser interferometer to measure the compression of a material experiencing forces around $8 \times 10^{-4}$ N. But I need to find the spring constant to calculate the ...
4
votes
1answer
432 views

Semiconductor problem: how much Boron is required to establish a certain amount of charge carrier density

The problem description is as follows: Boron is used to dope 1 kg of germanium (Ge). How much boron (B) is required to establish a charge carrier density of 3.091 x 10^17 / cm^3. One mole of ...
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4answers
3k views

Why does a spring lose its energy when compressed for a long time?

Why does a spring lose a part of its energy when compressed for a long period of time? Is it because the material gets bent?
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2answers
855 views

Why is tape so hard to rip when it is not broken, but so easy once there is the tiniest cut in it?

Question says it all. Ripping a piece of tape along the width is tough, stretches the tape, messes it up, etc, but if you put the tiniest nick at the top, it rips without any problems. Why is that?
7
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3answers
418 views

Why does foam dull knives?

I have recently taken up prop making and just started my first foam-built costume from a video game. These kinds of costume armour builds are often built out of the various foam floor mats you can buy ...
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4answers
1k views

Why does diamond have lower tensile strength than Iron?

Let me first give you the tensile strength of both substance: Diamond: 16000 MPa Steel : 2617 MPa As you guys should know, tensile strength is how much a ...
0
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2answers
60 views

Differences between elastic moduli

Is it true that in materials like aluminum and copper, the correct order of elastic moduli, in terms of value are: Bulk < Young's < shear modulii If this is correct, why is this the case?
0
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1answer
888 views

Ohmic and non-ohmic conductors

What sort of materials are ohmic and what sort of materials are non-ohmic? I have tried looking around on the internet and have not found any clear way to differentiate between ohmic and non-ohmic ...
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2answers
91 views

Software for analysing SEM or TEM images

I am looking for a software to analyse SEM and TEM images of some PLD experiments because I want to characterize the samples, like calculate the concentration of nanoparticles, size, and do some ...
5
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1answer
214 views

Force problem related to adhesive and bonding

I have two PCBs (printed circuit board), and they are glued by adhesives, as show in the pictures. And the location of the adhesives are indicated on the picture (please notice that NO adhesive is ...
0
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0answers
10 views

Material Resistance - Temperature increase in two merged bars

Context: Material Resistance, Temperature increases and affects axial forces The structure consists of an aluminum bar (AB) size L, which is surrounded by a copper wrap (CD), merged to the ...
0
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1answer
43 views

What does temperature coefficient of resistance depend on?

I tried looking up on Google if there was an expression for the temperature coefficient of resistance(TCR) of a material in terms of other fundamental factors, but couldn't find any. Specifically I am ...
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0answers
57 views

Quantitative understanding of excess heat capacity in ferroics

I'm looking to understand what an excess heat capacity in a ferroelectric (FE) can correspond to qualitatively. Typically one starts with a Landau expansion of the free energy if you want to study the ...
0
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1answer
25 views

Drilling a hole into a bone and measuring the force required to break it

I'm currently planning an experiment (high school biology) where I will drill a hole into a bone, then load weights onto it until it breaks. I will be repeating this with holes of different diameters. ...
2
votes
2answers
302 views

What are the specific electronic properties that make an atom ferromagnetic versus simply paramagnetic?

As I understand it, paramagnetism is similar in its short-term effect to ferromagnetism (spins of the electrons line up with the magnetic field, etc.), though apparently the effect is weaker. What is ...
0
votes
1answer
20 views

How can a phosphorous ion dope silicon when it is already ionized?

In ion implantation dopant ions are directly bombarded into the semiconductor (silicon for example)? But if say P ions (P+) were implanted then it does not have an extra electron to donate into the ...
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2answers
44 views

Can we measure speed of light in a non-transparent material

As I think even photons are absorbed by a non-transparent material, they aren't absorbed exactly at the same time. Light does propagate though a (sufficiently thin) opaque material. So can we measure ...
0
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2answers
6k views

Calculation of the maximum load to the bar

Looking for a way of calculating the maximum weight (W) to the rod with the given length (L) where the rod did not break and that only bend for (b) mm. Need only approximative solution (read: ...
0
votes
1answer
51 views

Is there surface tension between a solid and a liquid?

The molecules of a solid are so tightly bound together that they are fixed in position unlike in a liquid or gas where they may move freely. In that case it seems like the surface tension between the ...
1
vote
1answer
205 views

What factors cause the velocity saturation to occur at different electric fields for different materials?

In semiconductors the velocity of carriers gets saturated after a certain value of electric field. In silicon it occurs at around $10^4 kV/cm$ and in GaAs at some other value. What factors are ...
1
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1answer
30 views

Material that changes transparency when lased from side?

I am into photonics research, and have been searching about this topic in vain, but almost nothing from Google shows up. So i turned here for some light. Do you guys know any material that changes ...
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0answers
25 views

What is blocking the magnetic field of this neodymium magnet?

I opened up my hard drive and pulled out (among other things) the top and bottom braces for the reading arm. Each bracket contains a really powerful neodymium affixed to its underside. When the ...
1
vote
1answer
197 views

Work functions of ceramics/insulators

Is anyone aware of or know of a good source or means of estimating the work function of a ceramic material? Typically, work functions are given for pure elemental metals, rather than for compounds, ...
0
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1answer
202 views

Malleability in metals

I am trying to understand malleability in metal as a result of the micro structure. I am focusing on the metals of antiquity (in order of decreased malleability): Gold, Silver, Copper, and Iron. While ...
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0answers
40 views

The physics of running shoe cost and use [closed]

Two facts are relevant to the personal economics of running shoes: Running shoes vary greatly in cost (in my area, by $130 or more) Runners replace shoes that have been used a certain number of ...
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0answers
9 views

What is the best material for a flat heated surface

I am facing an application where I need to find a plate material that is very flat ( < 400microns per m flatness) And can resist temperature up to 200C while being lightweight and resiste thermal ...
0
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0answers
32 views

What is the strongest material transparent to alpha radiation?

Is there a material which is transparent to alpha radiation while being able to hold up under atmospheric pressure on one side and ultra high vacuum on the other? Put simply, what material is thin ...
3
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2answers
200 views

Degree of anisotropy of crystal tensors

Does there exist a scalar that can describe how anisotropic the elasticity of a crystal is? What about other tensors such as the permittivity or susceptibility? I found a Wikipedia article that was ...
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0answers
12 views

How can I estimate the density of non-ideal vapor mixtures

I am trying to estimate the density of a non-ideal gas mixture and can't seem to find any resources for how to go about this. For some gas pairs like ammonia-water there are empirical correlations ...
2
votes
1answer
377 views

What limits the maximum sustainable surface charge density of a sphere in space?

Suppose I charge a sphere and leave it in vacuum for 10 years. After that time, I want its surface charge density to be in the order of 10^5C/m^2. Would that be possible? Would it depend on the ...
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5answers
1k views

Why is the surface of the Moon white?

Why is the surface of the Moon white? Rather, what makes the surface white?
0
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0answers
30 views

Does an iron rich substance stay magnetised?

I am doing research (i.e. playing around) with a dry magnet and a material that has about 10% contained iron. The balance of the material is non-magnetic (i.e. silica and non-magnetic metals). It is ...
0
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2answers
884 views

Stress due to the mismatch of thermal expansion coefficients of two different attached materials

I'm simulating the thermo-electro-mechanical behavior of a copper wire which is surrounded by silicon dioxide. In other words, the wire segments is under mechanical and thermal loads and at the same ...
0
votes
1answer
80 views

Why do we have Indirect bandgap semiconductor?

If the energy of an electron is proportional to square of the momentum k, how come we have a Indirect Bandgap material in which the minimum of the energy in conduction band is not at k not zero. P.S. ...
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0answers
12 views

Why does carbon help with electron transfer in a dye sensitized solar cell?

what property of carbon(soot) makes it easier for electron transfer within a dye sensitized solar cell?
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3answers
766 views

Can a building get taller at night?

UberFacts recently tweeted "Office buildings are taller at night—a 1,300-foot-tall skyscraper shrinks about 1.5 millimeters under the weight of 50,000 occupants." Is what they are saying valid? It ...
0
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1answer
73 views

Could a Jumbo Jet aircraft fly on paper wings?

My dad was an airline pilot and, during his training, his instructor told him that, in absolutely ideal conditions, (in practice obviously impossible) that the actual material composing the wing ...
7
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3answers
2k views

Is there a Tungsten alloy more dense than gold?

This thought came from researching a previous question. In the spirit of our get-rich-quick scheming I looked up element densities and prices near gold. Element (g/cm^3) (dollars/kg) Uranium ...
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0answers
22 views

Why don't HCP metals have a brittle-to-ductile temperature transition?

I thought it had to do with the amount of slip systems...because BCC doesn't have as many slip planes, it cracks at low temperatures, while FCC has enough slip planes that it is not dependent upon ...
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0answers
25 views

Heat Retention of Wine

This may seem odd and lengthy but I am going to attempt to consolidate my thoughts as much as possible. I'm sorry in advance for the length of my post and if this is confusing. I am currently ...
3
votes
1answer
39 views

How does stress change through a bar that sharply increases in diameter?

I am looking to analyse the stress through the following bar: The bar is of circular cross section, homogeneous in material, that is of a certain diameter on one half, and a large diameter on the ...
0
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2answers
49 views

materials that can render Bluetooth useless

i'm currently preparing some experiments about using Bluetooth in real life. And to make the data more vary, i need some materials that can really giving side effects to Bluetooth functionality. i've ...
0
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2answers
22 views

Ozone elimination

I have a potential problem with airflow through a high voltage capacitively coupled RF discharge (in a tube) producing ozone. How can I remove ozone from the airflow? The use of liquids is not ...
0
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0answers
35 views

Exponential tower

I wanted to derive the formula for the equal strength exponential tower (more or less the compressive equivalent of a vertical Catenary) I was hoping I could get some validation on the reasoning, or ...
3
votes
2answers
97 views

With a machete, why is a diagonal cut more effective than a right angle one?

When cutting back some thick growth in the garden a question that always nagged me. Why is cutting diagonally seemingly more effective than cutting at right angles? Part of the answer is obviously to ...
0
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1answer
23 views

Dimensional scaling of structural stiffness

Consider a beam of some material with Young modulus $E$, the axial stiffness of the beam is given by the expression $$k = \frac{A E}{L}$$ where $A$ is cross-sectional area of the beam, and L is the ...
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0answers
46 views

Does Silver posses a color or Is it colorless reflection? [duplicate]

Why is silver said to have a color whereas water is not? Water is colorless because is allows penetration of light and doesn't reflect a colored wavelength, whereas Silver reflects light from its ...
3
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0answers
38 views

Physical cause of Negative Permittivity

What is the physical cause behind a material having a negative real part of its dielectric function? Given the complex permittivity, $\epsilon(\omega)=\epsilon(\omega)'+i\epsilon(\omega)''$, the Drude ...
0
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0answers
16 views

is there any element or material that ionized when pressure is applied to it?

I want to know if there is any material, that produce free electrons and ions when it undergoes to high pressure.
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1answer
5k views

Calculation of number density from material density

Material density is given by $ \rho =m/V$, where $m$ is mass and $V$ is volume. Again number density given by $n=N/V$, where $N$ is the total number of particle. How can I calculate number density $n$ ...