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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Melting and Boiling Points of Odd Materials

In Chemistry, I was taught that there are three main states of matter: solid, liquid, and gas, and that heat and pressure determine that state. For some substances, the line is blurry between them. ...
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1answer
67 views

Is it possible that a battery goes flat faster in a cold environment?

I own an old iPod Classic with original lithium-ion polymer battery and I use it primarily while running. Recently I discovered that when a temperature outside is low, usually below 5 C degrees, the ...
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1answer
125 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 ...
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1answer
257 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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1answer
40 views

Where will a board break when weight is added to the end?

If you have a board, say a standard 2x4 of finite length, where one end is fixed in a cement wall and the other end is free, and you begin adding weight to the free end until it breaks, where will the ...
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333 views

How does water carve rock?

How does water carve rock? And more generally, how does a soft material carve a hard material? Obviously it happens, but is it a continual process (every drop of soft water carries away a minute ...
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7 views

Determining porosity in metals

I am in need of a book (preferably) or other reference material which would help technicians determine whether porosity exists in the fracture face of a tensile test bar for a variety of different ...
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1answer
47 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 ...
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1answer
39 views

Is there a textile like material that can act as a spring? [closed]

Imagine some sort of textile (as in very light, not metallic) that is tightly rolled up, can be easily unrolled by applying some force (i.e pulling it) but when released will eventually return to it's ...
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2answers
38 views

What keeps objects made of the same plastic apart?

I have two objects here which are made of the same plastic. When I hold them together, they remain separate objects: I can pull them apart with no resistance. How does each atom/molecule “know” which ...
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1answer
155 views

Why does finely cut paper curl?

When paper is cut to a small width, it curls up like this. Why does this happen?
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2answers
81 views

Not-so-hot black shirt

As it is getting warmer here by the minute I was asking myself: Are there materials, that are black (in th visible range) but reflect (most) invisible light? Furthermore, I asked myself what ...
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3answers
33 views

Does Mohs scale of mineral hardness always hold?

According to Wikipedia's article on the Mohs scale of mineral hardness, materials / minerals with a higher rating cannot be "visibly" scratched by materials with a lower rating. It goes on to admit ...
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2answers
58 views

Materials with directional friction property?

At the macroscopic level a simple metal file or rasp creates a large amount of friction in one direction and a much smaller amount in the opposit direction. Shark skin displays the same properties due ...
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58 views

Is Sapphire crystal flexible?

It is widely rumoured that the next iPhone's screen cover will be a sheet of synthetic Sapphire crystal. A video purporting to show a leaked part has emerged. The chap in the video (Marques Brownlee) ...
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1answer
92 views

Why is powdered sugar less dense than granulated sugar?

The density of powdered sugar is about 20% lower than that of granulated sugar. There is small composition difference between the two - about 3% cornstarch and 0.5% water in powdered sugar, but that's ...
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1answer
56 views

Why can't a dislocation terminate in the bulk?

We are told that they can only terminate on surfaces, grain boundaries or other dislocations but we are not told why they can't terminate inside the crystal.
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2answers
65 views

Can zinc nitride be used as light emitting material?

I cannot manage to find any journal papers about the applicability of zinc nitride as active layer of an light emitting diode (LED). But certain papers got mention that zinc nitride with a direct ...
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2answers
51 views

What temperature will create amorphous TiSi?

At what temperature will create amorphous TiSi? I think it's around 500 Celsius but I'm not sure.
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574 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 ...
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1answer
22 views

simple pores make ceramic opaque

I want to know how a ceramic transparency is mostly affected by the pores, grain boundary, second phases etc. present inside of it, but the major contribution is due to the pores. Let's consider the ...
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0answers
26 views

VO2 is a 3D^1 compount. What does this mean?

I'm reading a paper about VO2 and it says that it is a 3D*1* compound. What does this mean? I know of 3D*1* in the context of electron configuration of an atom, however V would be 3D*3*.
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1answer
50 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?
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3answers
119 views

What can justify the decrease of the electrical conductivity with the increase of light intensity?

I have currently been working with a sample that "appears to" decrease its resistance when I cover it and protect it from light. Basically it presents the opposite behaviour of a photoresistor. What ...
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3answers
86 views

Which is stronger, wire rope or chain?

Assume they are the same material with the same weight, which is stronger?
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1answer
56 views

What keeps objects made of gold apart? [duplicate]

I was told the following basic facts: Objects made of the same metal don’t fuse in the atmosphere because they form an oxide layer. They do fuse in space. Gold doesn’t oxidize. Yet, gold nuggets ...
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1answer
41 views

Does the Night Mode of the screen display (LCD) save more energy?

In some cases, we can enable the Night Mode (reversing the bright and dark color of the display; such as White Text, Black Background) for the screen display. LCD(Liquid-crystal display) seems to be ...
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1answer
221 views

What is tricritical point?

Critical point is the transition temperature of a second order phase transition. But what does tricritical point mean? WIki says that a tricritical point is a point in the phase diagram of a system at ...
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1answer
120 views

Material implementations of the holographic principle

I'm afraid this question is a little too open-ended, but bear with me while I find a better formulation. carbon allotropes (like fullerenes and graphene) are regular patterned. Conduction bands of ...
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1answer
25 views

Glass Hardness and Pressure

How is glass hardness defined? I understand that ordinary kitchen knives cannot scratch most toughened glass, such as the ones found on cell phones. However (I once tried) - with enough pressure, one ...
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1answer
21 views

Why defects moderate (reduce) electric field?

I am running a simulation with drift-diffusion equation, Poisson equation and Fourier heat equation with a metal/insulator/metal structure. In my simulation, initially electric field is at the top of ...
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3answers
133 views

What makes materials hard and strong?

This is something I have wondered for a long time. Why are some materials like steel, diamond, and even light materials like graphene stronger than others? Is it due to the strength of the ...
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2answers
129 views

Can Aluminium be softened

I have an aluminium baking plate that I did put in a very hot oven and now it is soft, so I can bend it or almost roll it up. Why?
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1answer
45 views

Reducing Friction between 2 abs plastic bodies [closed]

Here at the company we've been working on a new product, and it will more than a few times a day and with a considerable force, slide on a plastic surface, being itself, another plastic body, roughly ...
16
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3answers
4k views

Why can't a piece of paper (of non-zero thickness) be folded more than $N$ times?

Updated: In order to fold anything in half, it must be $\pi$ times longer than its thickness, and that depending on how something is folded, the amount its length decreases with each fold differs. ...
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12answers
35k views

Why don't metals bond when touched together?

It is my understanding that metals are a crystal lattice of ions, held together by delocalized electrons, which move freely through the lattice (and conduct electricity, heat, etc.). If two pieces ...
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2answers
103 views

Are there materials that get softer with temperature decrease?

Could be there material that begins melting/softening when it's temperature is lowered? I would say no, but I've seen enough physics to know that not always life is so easy. Moreover I think I've ...
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1answer
44 views

How does tempered glass work?

I've read that tempered glass work by heating and then rapidly cooling the glass so that the outer layer 'freezes' (stops expanding/contracting) but the core contracts further as it cools. I'm told ...
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1answer
137 views

Ashcroft Mermin Solid State Eq. 22.15

I recently read a paper on Specific heat of a Classical Crystal: Dulong-Petit law. In Eq. 22.15, I don't understand why the ionic displacement $\mathbf{u}$ and ...
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5answers
22k 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. ...
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0answers
39 views

Is there quantitative theory of cutting with edge or blade

I wonder if there is some simple theory of what determine efficiency ( speed, energy end force required ) of cutting by edge ( blade , knife, sword ) At least something phenomenological like in ...
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4answers
2k 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?
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2answers
57 views

What makes a material a good lens for CO2 lasers?

I read on Wikipedia that zinc selenide and germanium make good lenses for $\mathrm{CO}_2$ lasers. My question is, Why?
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1answer
1k views

Equation describing magnetic hysteresis

So when you're looking at B-H curves for ferromagnetic substances, you often see these magnetic hysteresis curves, which occur, I gather, largely because of domain formation which has some reversible ...
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1answer
3k views

Why does paper become translucent when smeared with oil but not (so much) with water?

When I smear oil onto a scrap of paper and rub it in, the paper becomes quite translucent; but when I attempt the same with water it doesn't as much. Why?
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1answer
69 views

What are the relative permeability and electrical conductivity of GaAs?

I am doing some simulations in COMSOL with the material GaAs. The COMSOL built-in models require me to input the relative permeability and electrical conductivity of GaAs. I have tried hard to search ...
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2answers
183 views

A few questions about the Fermi Level/Energy

My first question is, how is the Fermi Energy for a material actually determined? I know this derivation, but it seems to say that the Fermi Energy is just based on the electron density (and maybe ...
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3answers
543 views

Graphene +1 extra carbon bond

I'm not a physicist just a curious mind, so please go easy! I was just watching a BBC Horizon Documentary that featured a piece on the recently discovered material Graphene. One of the facts ...
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1answer
177 views

Limits of Poisson's ratio in isotropic solid

For an isotropic solid, Poisson's ratio can be expressed in terms of stiffness constants as: $$\sigma = \frac{c_{11} - 2c_{44}}{2c_{11} - 2c_{44}}$$ Alternatively we may express Poisson's ratio in ...
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3answers
392 views

What properties would the ideal material for spacecraft construction possess?

Assuming we develop the capability to send a robot to study Gliese 518, or any of the Earth-like planets discovered in the neighbourhood; the spacecraft would need to travel through the Solar System ...