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).

learn more… | top users | synonyms

1
vote
1answer
37 views

Why is metal stiffer at lower temperatures?

Each morning I cycle to school and lock my bike with a thick steel wire (about 8 mm thick). I noticed that it's much harder to change the shape of the wire in the morning when it's much colder than ...
4
votes
5answers
5k views

Graphene space elevator possible?

I just read this story on MIT working on industrial scale, km^2 sheet production of graphene. A quick check of Wikipedia on graphene and Wikipedia on space elevator tells me Measurements have ...
1
vote
3answers
217 views

Any scientific basis behind “crystal energy”? [closed]

I always hear people talking very loosely about the terms "vibration" and "energy" in relation to crystals. Is there any scientific basis in "crystal energy" or is it purely metaphysical ...
3
votes
5answers
53k views

Yield Strength versus Ultimate Strength

What is the qualitative difference between these two: As seen on the table Typical yield and ultimate strengths. I am trying to resolve the meaning of the phrase "contact yield stress" from C. ...
2
votes
2answers
308 views

Why is tearing paper irreversible?

Consider a piece of paper. If I pull on it in the right way it tears into two pieces. However, if I push those two pieces together, they do not spontaneously form a single piece. What happens at the ...
12
votes
3answers
3k views

Why are materials that are better at conducting electricity also proportionately better at conducting heat?

It seems like among the electrical conductors there's a relationship between the ability to conduct heat as well as electricity. Eg: Copper is better than aluminum at conducting both electricity and ...
2
votes
2answers
57 views

Quenching of binary alloy: Concentration equilibrium

I'm currently reading "Models for phase separation and their mathematics" by Paul C. Fife and there is a paragraph which I don't understand because I lack the necessary background in ...
-4
votes
1answer
77 views

Flattest possible surface? [closed]

a) What is the flattest surface possible of any material? b) What is the flattest surface material available to humans at the present time?
0
votes
3answers
76 views

Physical properties of niobium pentoxide ($\mathrm{Nb}_2\mathrm{O}_5$) for thermal simulation

I am looking all day long for heat capacity, thermal conduction, and expansion coefficient of niobium-pentoxide. I want to conduct a thermal (heat flow) analysis on this and need it as input data. Can ...
2
votes
1answer
93 views

How to make electrical connection to silicon wafer for testing?

I am trying to make an electrical connection to a silicon wafer using a wire (approx 32AWG). I find that conventional lead/tin (60/40, no flux) solder cannot adhere well to the silicon wafer, since ...
0
votes
0answers
34 views

Equilibrium and constitutive relation

The constitutive stress-strain relation, say $\sigma=Y\epsilon$ where $Y$ is the Young's modulus, gives you stresses. At equilibrium, force balancing (say, with respect to a internal pressure $p$) ...
0
votes
0answers
31 views

Stress profile of pressurized bent shell

Consider a pressurized cylindrical shell of radius $r$ and pressure $p$, which at equilibrium has a nonvanishing in-plane stress components $pr/2$ and $pr$. This result is generically found by ...
0
votes
0answers
34 views

Mooney-Rivlin coefficients sign

I'm doing a fitting of uniaxial compression data of a isotropic polymer using the Mooney-Rivlin model: $\sigma=\left( 2C_1 + \frac{2C_2}{\lambda} \right )\left( \lambda ^2- \frac{1}{\lambda } ...
0
votes
0answers
28 views

Lower Threshold optical beam limiter?

We would like to implement a very fast beam limiting, so far google search shows that the common threshold ranges is in 1J/cm^2 or more, this could take seconds to activate as our laser ranges from 1 ...
0
votes
2answers
132 views

Does hardening reduce the ductility of a metal?

Is hardening equivalent with reducing the ductility of a metal and improving the yield strength of it?
11
votes
1answer
493 views

Why does plastic turn white in the area of stress?

There is a phenomenon with plastic in which it changes color to white in areas where stress is applied. When I bend a plastic rod the area in the centre, it turns white or loses colour. Why does this ...
3
votes
2answers
119 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 ...
-7
votes
2answers
4k views

Can jet fuel melt steel beams? [closed]

Common sense suggests that steel beams should not yield under burning jet fuel without presence of other substances that produce very high temperatures when burning, such as thermite. So can jet fuel ...
0
votes
0answers
21 views

Flamant's use of mass and weight

I apologize for the stupid question, but I've consulted teachers and found their answers unsatisfactory. Professor E.Brune, in the XIX century, delivered a course on l'École des beaux-arts on ...
1
vote
1answer
335 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
votes
0answers
13 views

Role of Mn in Perovskites

Good Day everyone!i don't if its the right site to ask this, but by the way, right now i'm searching for possible research in magnetoresistance properties of perovskite. So far, i already know the ...
0
votes
1answer
168 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. ...
4
votes
1answer
134 views

Why can gold be drawn out finer than light?

The metal gold is extremely malleable. Gold is also ductile and one ounce can be drawn into 80 km (50 miles) of thin gold wire (5 microns diameter) to make electrical contacts and bonding wire. I ...
24
votes
2answers
917 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?
2
votes
1answer
64 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 ...
6
votes
4answers
4k 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?
7
votes
3answers
668 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 ...
1
vote
4answers
2k 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
votes
2answers
86 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?
1
vote
1answer
3k 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 ...
0
votes
0answers
25 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
votes
1answer
200 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 ...
0
votes
1answer
83 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
386 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
38 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 ...
1
vote
2answers
91 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
votes
2answers
10k 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: ...
1
vote
1answer
37 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 ...
1
vote
0answers
168 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 ...
1
vote
0answers
14 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 ...
1
vote
0answers
74 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
votes
2answers
306 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 ...
0
votes
0answers
22 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
544 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 ...
17
votes
5answers
2k views

Why is the surface of the Moon white?

Why is the surface of the Moon white? Rather, what makes the surface white?
0
votes
0answers
40 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
votes
2answers
1k 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
0answers
20 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?
10
votes
3answers
837 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
votes
1answer
104 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 ...