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-1
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0answers
23 views

How many atoms in the particle (AuNP) [closed]

Let's say I have to determine number of atoms of gold in ball-shaped nanoparticle with diameter of 75 nm. I need general method of solving such problems more than specific answer for only this ...
0
votes
0answers
54 views

Thermal fluctuations in metals

My professor said that the $k_BT$ displacement in the energy levels of the band electrons is due to the space-thermal displacement of the potential of the ion host. I think that this displacement is ...
0
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1answer
37 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. ...
0
votes
1answer
27 views

A question about residual stress

Shot peening is a process of inducing residual compressive stress on the surface layer of metal parts. When shooting particles are colliding on the surface of metal there is a compressive stress. My ...
0
votes
0answers
27 views

Mixed-Alloy materials

Short version: Is it a physical problem (crystal structure/grains/redox/etc.) or just a logistics problem (keeping the solutes from homogenizing, molten/solid/temperature related problems) that keeps ...
-1
votes
1answer
27 views

Does it take a lot of energy to heat metals up?

Why does it take a lot of energy to heat metals? And to do it quicker it requires much more energy? What about the use of lasers would that be an efficient process that is quicker and requires less?
0
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0answers
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 ...
1
vote
1answer
45 views

How does the color of fine dispersed metal particles change between silver and black?

Small dispersed particles of metals are often black, while a solid object of the same material would be some shade of silver. The most notable example is the use of metallic silver as the black color ...
3
votes
2answers
1k views

Why does magnet attract iron but not other metals?

While searching, i found this page: http://timesofindia.indiatimes.com/home/stoi/Why-does-a-magnet-attract-iron/articleshow/4298171.cms but it does not have full explanation. So Please tell full ...
2
votes
1answer
25 views

plasma pressure initial condition

The authors in the paper below did a simulation of plasma plume evolution from a laser heated metal target. They used compressible transport equations and ideal gas EOS for Ar. I am having difficulty ...
0
votes
0answers
20 views

How to increase grain size in iron

Cut, polished and etched iron meteorites have grain size about 1000 times greater than air quenched iron. The reason for the large grain size is the very slow cooling of the core of a planet or ...
0
votes
0answers
37 views

Which metal will be on the surface after solidification?

I know that there are some metals that just "like" to be on a surface, so if I make an alloy of such metal and some other metal, the first one will be on the surface after solidification of initially ...
5
votes
2answers
274 views

Could airport security possibly distinguish gold and silver coins from other coins?

People usually don't carry pure gold and silver coins in their wallets. If I put some in my wallet, would it be likely that airport security would detect some anomaly with my wallet as compared to ...
1
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0answers
26 views

Any liquid metallic alloys which are safe to handle with bare hands?

http://en.wikipedia.org/wiki/Liquid_metal describes some alloys which are liquid at room temperature containing gallium, and sodium-potassium. We are advised not to handle them, and mercury, with ...
2
votes
0answers
41 views

Force constant of metals - Kohn anomaly

In Introduction to Solid State Physics (Kittel), it assumed the force constant between plane $s$ and $s+p$ $C_p=A\frac{\sin pk_0a}{pa}$ in metals to represent a Kohn anomaly. It says such a form is ...
6
votes
2answers
363 views

Can molten metal be suspended in air?

I wondered if magnets could be used to hold a drop of molten liquid metal in air (not for any particular reason just because it could be done), but was disappointed when a quick Google search showed ...
28
votes
1answer
3k views

Was Titanic's captain's decision correct?

I just saw a documentary on Titanic. Someone in that documentary told Captain Smith "Shall we close the water tight doors, sir?" and the Captain replied "No, let it be open. Let the water ...
0
votes
1answer
42 views

What makes different metals conduct better?

If a metal is a Fermi sea, what makes different metals better conductors? Clearly, one valance electron dominates. All things being equal, I would have assumed that the bigger atoms, with more ...
4
votes
4answers
175 views

If you suddenly move a piece of metal, will that disturb the free electron density?

If we have a hollow pipe sitting at rest filled with gas and we moved the pipe suddenly along its length to the right, then the gas density will be momentarily higher near the rear of the pipe and ...
0
votes
1answer
3k views

Dielectric Constant or Permittivity of Metals

I'm wondering what the dielectric constant or permittivity of metals is --particularly copper. Do metals have an infinite permittivity?
0
votes
2answers
104 views

Material breaking underneath its breaking point (due to repeated load)

I'm trying to recall some fact that I learned in my college materials science class, where we learned concepts like stress vs. strain. I remember that materials like metal have a breaking point, and ...
0
votes
0answers
42 views

Eddy Currents in Metal Implants

Related: Why is stainless steel a poor conductor of electricity? I recently had a metal implant, and I'm psyching myself out- should I be considered at all with eddy currents in the implant? I feel ...
1
vote
1answer
3k views

Why is stainless steel a poor conductor of electricity?

I recently had a metal plate put in my shoulder and was wondering why stainless steel isn't a good conductor (At least I hope it isn't). Does the alloy just lack free electrons? Why is that?
1
vote
0answers
107 views

How did gunsmiths create revolver cylinders in 1850's without the use of electrical drill? [closed]

How did gunsmiths create revolver cylinders holes in 1850's without the use of electrical drill? Which referces/ books specialize providing knowledge in similar molding method?
0
votes
1answer
20 views

The common major difference in thermal conducting properties between a random rock sample and metal?

what are some common major differences in thermal conducting properties between a random rock sample(non-metal) and metal?
0
votes
1answer
109 views

is this heat calculation equation correct?

If I have a line of copper wire (lets say $\textrm{1 meter}$ long, $\textrm{1 mm}$ thick) and one end is a flattened disk of copper about the size of a quarter, and I apply a lot of heat to it (I'm ...
0
votes
1answer
121 views

What happens when molten metal cools within a strong magnetic field?

What happens when molten metal cools within a strong magnetic field? I don't know what more say, don't remember anything relevant to this in my uni text books.
2
votes
0answers
88 views

Bubbling metal vapor through liquid Helium?

When a metal cools from its liquid state, part of the nucleation happens from pre-existing clusters (a group of unit cells of the crystal lattice) already present in the liquid. In the case of a ...
0
votes
0answers
90 views

Hysteresis loop of soft iron for different field strengths?

When calculating the work done to magnetize a material, what is the usefulness of coercivity in that calculation? If the material $Hc = 0.5\: \mathrm{A/m}$ or $Hc = 9 \times 10^5\: \mathrm{A/m}$? I ...
1
vote
0answers
46 views

Why do (most) metals cause problems in a microwave oven? Which metals (if any) don't? [duplicate]

Most of us have seen microwave ovens with metal racks or shelves, which challenges the common notion that you can't (safely) put metal in a microwave oven. What's going on here? Is it a matter of ...
169
votes
11answers
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 ...
0
votes
0answers
52 views

Finding proportions of metal microstructures from eutectic diagrams

So I have an equilibrium phase diagram of steel and I am asked to 'Calculate the proportion of pearlite in the microstructure of 0.4 wt% C steel just below the eutectoid temperature (727 °C).' I have ...
0
votes
1answer
127 views

Semiclassical description of EM waves reflection from metallic surfaces

Imagine an EM wave impinging on a metal. Fresnel's formulas tell us that no wave can propagate through the metal, or that the transmitted field is an evascent wave with some penetration depth ...
7
votes
2answers
356 views

Why does Platinum evaporate if left long enough?

I have been reading into research relating to the redefining the 1 kg weight as the current Platinum-Iridium is becoming smaller. In this article, here, it mentions that the original metal weight ...
1
vote
0answers
61 views

Maximise magnetic force at one point while minimizing at another

Is it possible to have a magnet that attracts one object strongly, but not another object behind that first object? Given an (electro-) magnet M above two thin parallel steel sheets P1 and P2 in the ...
3
votes
1answer
686 views

Why do most metals appear silver in color with gold being an exception from a scattering and EM viewpoint?

Related: Why are most metals gray/silver? After reading Johannes’ impressive answer to Ali Abbasinasab question of why do most metals appear silver in color with the exception of gold (and copper), ...
3
votes
1answer
1k views

What causes stress concentration (aka stress risers/raisers) at corners?

I've read a few explanations about why stress concentration occurs at sharp corners but I don't find the explanations intuitive. Can anyone explain it perhaps using an analogy such as atoms "holding ...
37
votes
5answers
5k views

Why are most metals gray/silver?

Why do most metals (iron, tin, aluminum, lead, zinc, tungsten, nickel, etc.) appear silver or gray in color? (What atomic characteristics determine the color?) What makes copper and gold have ...
8
votes
1answer
224 views

Why aren't superconductors shiny? [duplicate]

Superconductors are really good at conducting electricity. Should they not reflect light very well too?
2
votes
0answers
82 views

Is this a correct description of bonding in a metal?

I am reading the paper "Twenty five years of Finnis-Sinclair potentials" by Graeme Ackland, Adrian Sutton, and Vasek Vitek, Philosophical Magazine 2009, 89, 3111-3116. It is a review-type article ...
2
votes
2answers
347 views

How would a change in ambient temp affect a radiator?

I'm curious if you have a radiator or say a block of metal (lets say it's copper since it has the highest thermal conductivity) and on one side is a processor producing heat. At idle the processor ...
6
votes
1answer
151 views

Reflectivity of a glowing-hot metal surface

When a polished piece of metal (or steel in particular) is heated to incandescence, how do its reflective properties change? Given a mirror-like surface, would the object temporarily cease to act ...
2
votes
1answer
173 views

Why do cold metal plate make less noise?

I have a metal gate in my home so I have noticed that when it is a hot day and if I hit it it makes a lot of noise but when there is a rainy day and the weather and the gate re cold and if I hit the ...
1
vote
2answers
269 views

Does Earth produce metallic elements in its core?

Does Earth produce metallic elements in its core?
2
votes
1answer
927 views

How long does it take a warm object to cool in air?

This is a work-related question. A warm steel torus of a given diameter & thickness is left in a room held at a controlled temperature, how long does it take to reach equilibrium? Assume the air ...
20
votes
3answers
5k views

Is there a compound denser than the densest element?

I'm musing about how to give students an intuitive feeling about density by letting them lift a same sized volume of different materials, e.g. 1 liter of water, a 10x10x10 cm cube of iron, lead etc. ...
3
votes
1answer
63 views

Resources in space, and their distribution

I'm making a video game in which the economics of an interstellar civilization is important. What I'm wondering is, how are resources in space distributed? Since everything ultimately comes from ...
3
votes
2answers
310 views

X-ray diffraction from Metals

Is X-ray crystallography is possible for metals? Or not due to absorption?
3
votes
4answers
1k views

How does positive charge spread out in conductors?

I know that when there are excess positive charges in a conductor, for example, a metal sphere, the positive charges will spread out over its surface. However, I am confused about how this excess ...
11
votes
1answer
887 views

Resistance between two points in an infinite metal sphere/cube

Let's imagine that we have a tridimensional metal object of infinite size, and decide to calculate the resistance between two arbitrary points. How would we go about doing this? I have thought of two ...