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

0
votes
2answers
773 views

How to calculate the coefficient of restitution for 2 bodies?

I have 2 rigid bodies (from different materials) in a collision. As you know I should have the coefficient of restitution value to get the velocities after collision. What is the information/values ...
2
votes
2answers
189 views

How does a fabric containing 10% stretch material make it stretchy?

Why should adding a small amount of a stretchy material make an otherwise non-stretchy fabric stretch? Shouldn't the non-stretch fibres still constrain the maximum stretch of the fabric?
2
votes
0answers
12 views

What is the volume magnetization of Fe3O4 (magnetite) monodomains at room temperature?

Magnetite is great stuff for making ferrofluids and has a huge amount of literature. Yet I can't seem to find an answer to the simple question in the title. The magnetization of various bulk ...
1
vote
1answer
79 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
17 views

Why do some materials have a negative coefficient of thermal expansion in all directions?

Those materials are especially ceramic-glasses. I've found some studies about how does it happens in one dimension (for example a nanocrystalline has a silica helix that works like twisting spring, ...
5
votes
1answer
58 views

Why does aluminium-on-glass mirror work without distortion?

I have read an article about glass (zerodur) with low thermal expansion coefficient. It is mentioned that large casts of such glass are covered with reflective layer of Aluminium and used as mirrors ...
3
votes
2answers
31 views

Air bubbles in Ice and cause for their shape?

I was looking at the ice formed in my refrigerator and found out there were a lot of air bubbles inside it. The shape of the air pockets seemed strange to me. There were many small spherical ones ...
0
votes
0answers
18 views

Spring limitation

Is there any limitation in acceleration and frequency of a spring. Please, imagine a horizontal spring with an object of mass $m$ attached in the free side and the friction is neglected. ...
0
votes
2answers
14 views

How can you see the difference between a melamine plate and a plate with a melamine coating?

How can you see the difference between a melamine plate and a plate with a melamine coating?
3
votes
1answer
412 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 ...
2
votes
1answer
34 views

Why does sunlight cause colors to fade?

If you leave something outside, its colors seem to inevitably fade or bleach due to exposure. Is this due to UV absorption? What sort of mechanism causes this - is it that man-made dyes deform on a ...
1
vote
1answer
138 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
1answer
121 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 ...
1
vote
1answer
161 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 ...
0
votes
2answers
46 views

Does metal sublimate?

I know that solid water (ice) sublimes ("evaporates" straight from solid to dissolved gas) in air. On the other hand, some metal objects seem to last forever (e.g. gold, stainless steel and other ...
0
votes
0answers
14 views

Reflectance spectrum and Real Refractive Index Relation

I have taken in the laboratory mesurment of the Reflectance spectrum of a material and via mathematica calculated the phase for Kramers-Kronig Relations,and finnaly i calculated from it the real part ...
0
votes
1answer
25 views

Mechanical properties and nanocoatings

How do you model the changes in the mechanical properties of materials coated in with nano-materials? If I coat abs plastic with amorphous diamond how does that change the sheer, tensile and other ...
0
votes
1answer
27 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 ...
2
votes
2answers
102 views

How absorption coefficient determines which material is used to make solar cells?

Does the knowledge of the material absorption coefficients aids engineers in determining which material to use in their solar cell designs? If yes, how?
0
votes
1answer
26 views

Why does adding thorium to a TIG welding electrode improve the arc?

Why does adding thorium to a TIG welding electrode improve the arc? What are the physics behind this and other tungsten alloys used for improving TIG electrodes?
1
vote
0answers
34 views

How does force transmit through a solid block?

If you take a solid block, say, a cube of side length $l$ with density $\rho$, you place it upon a solid floor, and you apply an external pressure of $p(x,y)$ on the upper face ($x$ and $y$ define a ...
6
votes
3answers
2k 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?
12
votes
3answers
428 views

What are the rules for breaking a glass with your voice?

So, this morning I woke up and remembered something I discussed about with one of my friends: Can human voice really break a wine glass? So I looked it up and after checking many websites and ...
16
votes
4answers
968 views

Does extreme cold make **everything** extremely brittle?

First of all, I'm genuinely sorry if this question isn't "serious" enough for this forum! A common cliche in movies and tv is that a very tough object (eg the villain) is frozen, and then hit with ...
4
votes
2answers
47 views

First-principles derivation of cutting force

I know that the amount of force required to separate a material from itself is linked to the surface energy of that material. However, looking at just the surface energy laughably underestimates the ...
2
votes
1answer
76 views

How much weight would I need to put on the end of a tube to break it?

Say I have a tube with a circular cross-section made from some material (for an example, I'd like to use acrylic). I support it horizontally from one end and hang a weight from the other end. How ...
1
vote
1answer
15 views

What is the physical process behind wool shrinking when dried?

Wool is a fibrous material, but other fibrous materials do not suffer the same problem. Let us set the scene; a woollen jumper shrinking when put in the washing machine, then the dryer. This involves ...
4
votes
1answer
39 views

Why does the refractive index not mirror the Lorentzian peak shape of the absorption index?

In the characterization of materials, there are many methods used: One of them is infrared spectroscopy. In a lab we saw the indices of refraction and absorption of a certain (semiconductor) solid ...
0
votes
1answer
44 views

Tension and compression in bicycle wheel spokes - what holds the wheel in place?

I assume that most of the weight of the bicycle is taken by spokes in tension, but there must also be a contribution from spokes in compression. Any idea of percentages?
-2
votes
1answer
26 views

how much weight can you put on a bike tire? [closed]

How much weight can you put on a bike tire? What does it depend on?
0
votes
0answers
17 views

Spectral reflectance identification of types of iron rust [migrated]

According to the Wikipedia page about rust, there are red and green types of rust that occur on iron. Red rust is the reaction with oxygen and water and the green with chlorine (in oxygen poor ...
5
votes
1answer
170 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 ...
1
vote
1answer
57 views

Why is elastic modulus greater than shear modulus?

I was looking at data for elastic modulus $E$ and shear modulus $G$, and found that $G$ is always lower than $E$. So I'm wondering what are the underlying principles that may be the cause of this. ...
0
votes
0answers
14 views

Is there a list of (the solid state version of) electron affinities?

I'm doing some energy band diagram analysis for a few scenarios, and I need the Electron affinity as defined in solid state physics for a few materials. Note that this is different than the one taught ...
1
vote
0answers
22 views

What will my diamond fibre shirt look like?

So, during an idle moment when I mused that our experimental setup would be a lot less hassle if it was made from a 1kg single crystal of diamond, this thought occurred to me... Since single crystal ...
1
vote
1answer
118 views

Grain boundary sliding in creep

To prevent grain boundary sliding so that creep is less likely to occur, usually engineers would design components of larger grains or have columnar grain structure to prevent grain-boundary sliding. ...
2
votes
1answer
69 views

A reliable aluminium battery that charges in a minute. What's the catch?

This article Ultra-fast charging aluminum battery offers safe alternative to conventional batteries, phys.org. reports on the finding by a Stanford group of an aluminium-ion battery that can ...
7
votes
5answers
4k views

Why will clay, when heated to high temperatures, harden and become waterproof?

I have a question Why will clay, when heated to high temperatures, harden and become waterproof?
4
votes
1answer
72 views

How can one reasonably theoretically model polycrystalline materials?

Many techniques are taught in advanced solid state courses but they are almost all derived for perfectly crystalline materials. For example, band structure really only appears theoretically when you ...
4
votes
2answers
3k views

what is difference between homogeneous vs isotropic material?

When we say a material is isotropic? When properties such as density, Young's modulus etc. are same in all directions. If these properties are direction dependent, then we can say that the material is ...
0
votes
0answers
29 views

Help with a couple of materials science questions

My first post on this forum is asking for some assistance in answering some questions. I was hoping as well as being given an answer, you could offer a little explanation so that I can understand - ...
0
votes
1answer
35 views

Why is a substrate needed in growing GaN?

Is the substrate a layer on which GaN crystal grows on? Is there a way to grow free-standing GaN? Would the resultant crystal be full of defects?
4
votes
2answers
77 views

Could a long carbon nanotube be broken by hand?

Assuming we could get a single nanotube a metre long, would it be possible to break it by hand or would it slice through just about everything including flesh and bone? Could we even grip it, or would ...
0
votes
1answer
10 views

What to measure for cylinder stiffness/compressibility?

I have 2 cylinders made from different polymers. Both cylinders are made to 'accept' the same volume of water. When I fill cylinder 1 it is subjectively stiff while cylinder 2 is subjectively floppy. ...
0
votes
0answers
35 views

In which direction along a GaN (wurtzite) crystal are only Ga atoms being observed?

So, if you have an electron microscope image of a GaN crystal, and that it shows only white dots which represent Ga atoms. No nitrogen atoms are seen in the image. Along which direction is this ...
0
votes
0answers
25 views

Directions in the Elastic/Stiffness Constant Tensor

I am working on a report for an experiment I did concerning the Elastic constant tensor. This has 36 terms for tensile and shear stresses. I don't understand what the off diagonal elements are! C11 is ...
0
votes
0answers
9 views

UV and gas permable material?

Are there any material that pass uv (365nm) and gas (air) through? In addition to that question, are there any that will pass through uv and things won't stick to them? I'm thinking about building a ...
1
vote
1answer
52 views

Is this crystal defect an example of dislocation or a vacancy

It looks to me that a regular hexagonal pattern formed by the Ga atoms is interrupted in the middle of the crystal. Is this a void (or vacancy...), dislocation or another type of defect? Plus what ...
2
votes
1answer
65 views

The Egg Smashing Tournament

My cousins and I have a annual egg breaking tournament. First, each of us gets a hard boiled egg. Then, in a bracket tournament style, a pair of us face off in an egg breaking round: one person holds ...
0
votes
1answer
791 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 ...