Questions tagged [metals]

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1answer
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Increasing the melting point of metal

I need to know how one can increase the melting point of a metals like steel, tungsten or ... about 500 degrees and without destroying its shape?
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0answers
15 views

Reflectance and transmittance equations for metal thin film

The Fresnel's equations no long work when the thickness of the metal thin film is thinner than skin depth. For example, the reflectance of a metal thin film is always the same according to fresnel's ...
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1answer
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Is the specular reflection on a polished gold sphere white or gold in colour?

My understanding is that all specular reflection is due to Fresnel reflection at the interface which is a broadband effect. A classic example might be a white reflection on a polished ball (e.g. ...
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1answer
89 views

How do knife blades become dull?

Knives are normally used to cut softer objects. So the edge of the knifes blade is harder than the substance it cuts through. A blades geometry is more complex, but let's simplify it to the blade ...
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1answer
27 views

Radiation emitted from a real melted piece of steel [1800C] VS emissivity

In a lot of questions I read that a good approximation of the radiation emitted from a hot piece of steel is the black body radiation. Than I search for the value of the emissivity of molted metal ...
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1answer
3k views

How can electric fields be used to detect cracks in metals? [closed]

My physics teacher brought this up in a lecture and I am not exactly sure what he is saying.
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3answers
135 views

How to show that the electrons responsible for a current have an energy within $k_BT$ of the Fermi energy?

It is commonly written in textbooks that in metals the electrons responsible for an electric current are the ones that have an energy about $E_F$ and a few $k_BT$ around that energy. See for example ...
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2answers
59 views

Are there any crystallographic effects we can see in the reflection of visible light from metal surfaces?

I started thinking about this in a discussion in comments. One can start by thinking of the reflection of visible light by most metals as similar to the reflection of radio waves in that it's an ...
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3answers
56 views

Band theory and molten metals

In solid state physics, features of crystals are explained by using the concept of energy bands, the existence of which is shown to be a result of the periodic order of the atoms in a crystal. When ...
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2answers
83 views

Hydrogen: Whether it's a metal or non-metal

I know hydrogen is a non metal, but when I just study about some introductory elementary band theory I find the band structure of hydrogen has a half filled valence band just like alkali metals, and ...
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1answer
57 views

Faraday cages and what constitutes the minimum number of atoms to build an optical mirror

I recently asked this question: What is the minimum number of metal atoms necessary to make a mirror? However it seems I did not make myself clear enough about what I was looking for, even though the ...
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0answers
17 views

What is a disordered alloy?

I would like some clarification on what is meant by a "disordered alloy." Is this a description of the crystal structure? Is it the same as describing the alloy as amorphous, without a set uniform ...
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0answers
20 views

How to calculate energy of conduction band - fermi energy (Ec-Ef) - semiconductor

I am learning shottky diodes and i want to work out the built in potential barrier using: $$V_{bi} = \phi_m - [E_c - E_f] $$ now i come across 2 equations when working out Ec-Ef. the first: $$E_c -...
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3answers
66 views

Why electricity does not seem to alter metal mirrors reflection? [closed]

If individual electrons absorb and reflect photons, and if those electrons happen to be on a conduction band which is most probable as the outer electrons have a greater probability of intercepting ...
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0answers
21 views

Can we change the spin of electron by applying electric field from ↑ to ↓ configuration?

I read in this forum a similary question with magnetic field. But is it possibile change the alignment of the spin with a electric field (DC or pulsant current) in a layer of metal? Probably the ...
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1answer
97 views

QM explanation (electrons and lattice structure) why aluminum does not get hot in an oven?

I have read this question: Why can I touch aluminum foil in the oven and not get burned? But the answers therein only explain on a classical level why aluminum foil being a very good conductor and ...
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0answers
34 views

Is the electrical permittivity of perfect conductor infinite or negative or both? What about a good conductor, is its permittivity large negative?

I have read that metals are very good conductors and thus their electrical permittivity is infinite. But I have also read that the permittivity of metals is negative. So is a perfect metal (conductor)...
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2answers
132 views

What opposes a smooth motion of a rubber eraser on a glass surface?

A metal block smoothly moves on a glass surface. But a rubber eraser doesn't move very smoothly on a glass surface. In each of the cases, the surfaces are smooth at the macroscopic scale. If the ...
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1answer
41 views

Voids in steel? [closed]

I have found black areas in the the surface of some steel. Are these voids from the original manufacure or are they created by corrosion? This one is approx 1mm x 0.5mm.
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1answer
29 views

Help with deriving simple heat equation [closed]

$$j^{q}=\frac{1}{2} n v[\varepsilon(T[x-v \tau])-\varepsilon(T[x+v \tau])]$$ To this: $$j^{q}=n v^{2} \tau \frac{d \varepsilon}{d T}\left(-\frac{d T}{d x}\right)$$ At first I was thinking of using ...
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0answers
30 views

Drude model electronic drift momentum rigorously derived

Specifically I'm referring to the equation below which I took from wikipedia. The derivation of this equation based on the Drude model seems to somewhat standard as all the resources I've looked at ...
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1answer
32 views

Why are experimentally obtained specific heat values for different metals higher than the theoretical values?

I have just performed an experimental measurement of the specific heat of various metals by introducing an electrically heated probe and measuring mass and temperature difference with respect to the ...
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1answer
69 views

What are physical obstacles for rare earth metal synthesis in nuclear reactors in industrial scale? [closed]

Diminishing availability of rare earth metals prohibits expansion of traditional and quantum computing and low temperature technologies. So - my question is about artificial synthesis of rare earth ...
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1answer
28 views

How to determine whether an alloy is single or multi phase

I would like to know what methods would be suitable to determine if an alloy of 2 elements is a single phase or two phase alloy.
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11answers
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Are there physical properties that can be used to differentiate stainless steel from copper in a home environment? [closed]

So the backstory is that I purchased a reusable drinking straw that is copper coloured, but is advertised to be stainless steel. That got me thinking about whether I could be sure it was one or the ...
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0answers
46 views

What is the difference between metallicity and semimetallicity?

I am looking for a definition of semimetallicity from an experimental point of view ( $\rho(T)$, carrier density, mean free path, scattering time, etc.) and from a theoretical point of view. Can ...
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0answers
100 views

InterAtomic Distance between atoms of a molten metal

I was figuring out and researching on interatomic/internuclear distance of metals (particularly Aluminium), but then I started wondering on the difference between magnitudes of interatomic distances ...
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0answers
25 views

Vertical vs. lateral malleability of copper plate in fine art etching [closed]

The malleability of copper has, in part, contributed to the viability of copper plate etching in fine art through the ages, by offering the ability to “erase” or flatten inadvertently placed or too ...
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1answer
62 views

Is rust a good thermal insulator as opposed to bare steel or hardened clay?

I have no idea if this is the correct site to find an answer on this topic but considering it's a question of physical interactions I wanna give it a shot. I am in no way a physicist, just a hobbyist ...
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0answers
24 views

Inverse work function?

The work function is the "work necessary to get the electron out of the metal" [Millikan] and plays an important role in the photoelectric effect. I assume that the "work gained by absorbing an ...
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1answer
26 views

Polarization density inside perfect conductor placed in an external electric field

I've stumbled about the following problem that I do not understand: The polarization density P is defined such that its divergence gives the charge density due to bound (immobile) charges in a ...
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1answer
37 views

Does “charge density” account for all charges, or only negative charges, and do opposite charges cancel each other or add?

if I had 10 electrons and 8 protons in a meter cubed would the charge density be 2 or 10 or 18? I suspect 10, but I don't see why charge density only takes into account the negative charges. another ...
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2answers
87 views

How is the a Fermi surface different from a Fermi sphere?

How is a Fermi surface (a surface in reciprocal space separating the occupied electron states from unoccupied states at $T=0$) different from a Fermi sphere? Is Fermi sphere a special case of Fermi ...
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1answer
40 views

Carbide machining inserts are supposedly extremely brittle but they don't break when machining why?

So everywhere I read I hear that carbide inserts for metal machining are extremely brittle and they will break very easily if you say drop them. However, you put them in your tool holder and spin up ...
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1answer
48 views

What is the term for the light-sensitive metals in the photoelectric effect?

Can anyone please tell me the term used to refer to metals such as those used in photoelectric effect which can generate a current from light?
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3answers
84 views

Ray sun heating

I recently got a curious question about the sun rays. Is there a material that can absorbs most of them and turn it into pure heat? For example, we all know that dark material (black t-shirts) get ...
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2answers
123 views

Star Trek - Transparent Metals Possible?

Is the concept of transparent metals (like the transparent aluminum in Star Trek IV - Voyage Home) a real-life concept? Or is it far-fetched movie fiction? Thus my main question then is: could we ...
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0answers
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Can any element be a metal?

I was reading that hydrogen can become a metal in some cases, like in Jupiter, and the same for helium. Is this true for all non-metals?
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1answer
152 views

Why is the residual-resistance ratio (RRR) a measure of good crystalline quality?

I am currently revising a paper on a few parameters of metallic Al, and it indicates that a higher RRR is a measure of good crystalline quality. My question is why would this be the case, if having a ...
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1answer
79 views

Where is the data for work functions of simple metals?

I am looking for actual, published data on the work function of metals (Al, Au, Cu) that I can analyze by myself using Matlab. Google Scholar only offers published articles on the utilization of the ...
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1answer
230 views

Reason for gold being the most malleable and ductile of metals

I understand how fcc structure enables plastic deformation in metals, but why is gold, in particular, the most malleable and ductile of fcc metals? Is there something about the electronic structure ...
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1answer
67 views

Can I trap mosquitos with Coulomb's force? [closed]

Can I fill a metallic conductor with a very large positive charge, attach it with a insulator to a wall, put it near a window under the sun (visible light and UV in order to cause it to expell ...
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4answers
378 views

Why do metals have high optical reflectivity?

What's the reason behind metals' high optical reflectivity?
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0answers
51 views

Why does nickel permeability decreases past 250 KHz?

I found this graph of nickel magnetic permeability vs frequency,it start to drop at around 250 KHz.Why isnt the permeability constant at all frequencies? Can that frequency curve somehow be ...
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0answers
47 views

Why do both these molten metals round in a crucible?

In one of my classes this past semester, we did a casting lab. In this lab we used an induction furnace which uses a coil to generate heat within the material. One of the things that I noticed, was ...
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1answer
499 views

Even/odd number of electrons per primitive cell and conductivity

In this pdf it says Because the number of electron states in a Brillouin zone is twice the number of primitive cells in a Bravais lattice (the factor two comes from spin), the zone can be ...
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1answer
68 views

Why are powdered silver and powdered platinum black?

The quantum-mechanical (relativistic) explanations for the observed colours of copper, silver & gold don't appear to explain the black colours of powdered silver (& powdered platinum). Can ...
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1answer
73 views

Why do thermal hotspots in a metallic nanoparticle do not match it's optical hotspots?

I am a little bit confused here. When a metallic nanoparticle is impinged with light at its resonance, the electric field is greatly enhanced at the surface along the polarisation of the wave(suppose ...
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2answers
76 views

What is the significance of the time $\hbar/E_F$ where $E_F$ is the Fermi energy?

For free electrons in a metal, the Fermi energy $E_F$ (defined as the highest filled energy level at $T=0$). It represents a characteristic energy scale of the system as well as the energy of the ...
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2answers
182 views

Why the electric field inside a metal sphere carrying a charge Q is zero?

I was solving some problem regarding the polarization during this I came across an example 4.5 in Griffith's where it is written that the Electric field inside the metal sphere carrying a charge Q is ...