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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115 views

Tensorial version of Hooke's law

It is well known that $${\boldsymbol F} = k {\boldsymbol x}$$ for isotropic media. Also, according to Wikipedia $$F_k = k_{jk} x_j$$ for some elastic tensor $k_{jk}$. I'm a bit confused as to how ...
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212 views

Why does the overhand knot jam but the figure-8 knot doesn't?

After tensioning a rope with an overhand knot in it, it is often very hard if not impossible to untie it; a figure-8 knot, on the other hand, still releases easily. Why is that so? Most "knot and ...
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79 views

Wall stress of a hexagonal pressure vessel

Problem: I want to calculate the stress in the walls of a hexagonal pressure vessel but I can't manage to get coherent results. For long vessels, cylinders are supposed to have the lowest hoop stress ...
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1k views

Inflating a balloon (expansion resistance)

I am doing a quick calculation on how to calculate the pressure needed to inflate a perfectly spherical balloon to a certain volume, however I have difficulties with the fact that the balloon (rubber) ...
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59 views

What makes Obsidian edges sharper than other glass?

Obsidian is a volcanic glass with a reputation for being extremely sharp. Some surgeons use obsidian scalpels rather than high-quality steel surgical scalpels. At the same time, glass blades are used ...
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94 views

A physicists perspective on a material science/engineering problem

I am looking into some research that involves engineering and material science. As a physicists I wondered what other physicists would think of this problem and how they would approach it. Much of the ...
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32 views

Aerosol size distribution

When the size distribution of particles in an aerosol is obtained, there is always a bimodal distribution. The small peak accounts for the particles that are in sub-nanometer size range and the larger ...
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93 views

Where does one find pair-correlation functions for various materials?

What is the canonical source for finding pair-correlation functions for atoms in various materials? I am interested in both numeric computations and experimental measurements (like might be obtained ...
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156 views

Why Does Germanium Spontaneously Extrude Long Screw Dislocations?

Pure germanium is known to spontaneously extrude very long screw dislocations. They are one of the primary reasons for the failure of older diodes and transistors made from germanium; depending ...
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90 views

Does graphene actually remain strong for macroworld engineering?

I heard that people envision strong structural materials made out of graphene, but I heard it may weaken when being stack in layers. Is graphene viable for macroworld structural engineering or is it ...
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21 views

Effects of cutting carbon nanotube buckypaper

Carbon nanotube buckypaper is a film/paper made from a mesh of carbon nanotube fibers, where each fiber is a bundle of a couple hundred nanotubes. This paper is flexible and tough like normal paper, ...
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18 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 ...
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29 views

Carbon fibre laser beam dump material?

A few years ago I came across a material used as a high power laser beam dump. It was made from carbon fibre which looked like a mat made of high density bristles ie all the fibres on the top of the ...
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26 views

Does the surface of austenitic steels have an especially “dynamic” phase somewhere between 100 and 200 Celsius?

There is lots of kitchen lore about pans. One popular concept are the "pores" of a steel pan surface, which are the reason why food sticks to the pan when it's not heated properly. I don't know much ...
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97 views

Reasons to consider the coefficient of restitution velocity independent - conditions when this does apply

In high-school mathematics textbooks a bouncing ball is often considered as an example of an exponential decay. One can easily derive this if one assumes that the coefficient of restitution is ...
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103 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 ...
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191 views

How can I determine the type of magnet used in a DC motor?

I repair electrical motors in a workshop and sometimes I must repair permanent magnet DC motors and other motors that use permanent magnets. I need to specify type of permanent magnet (Ferrite or ...
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38 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 ...
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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 ...
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12 views

Is there any relation between single crystal elastic constants and plastic deformation?

The elastic constants are the tensor coefficient in Hook's Law. Which are valued only in elastic region.But, we are using elastic constants to find the hardness.The hardness is the measure of the ...
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48 views

Finding the strains from a 0, 90 rosette - Mohr's circle

I have used a strain rosette with two gauges at 0 and 90 degrees to find strain on a beam under force and an trying to plot Mohr's circle for the problem. As the gauges are at right angles finding the ...
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45 views

Applying Statistical Mechanics to Formulate Corrosion (Rusting)

I wanted to try and take my current knowledge of statistical mechanics (first quarter undergraduate course completed, beginning researcher in far from equilibrium statistical mechanics, basic ...
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52 views

What is the yield strength of a bar of different cross sections?

Will the yield strength of the combination will be same as that of the rod of uniform cross section?
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83 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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112 views

Is there a derivation of all possible Bravais lattices in 2D and 3D?

Do any of you know a (possibly elegant) derivation of all possible Bravais Lattice and the Crystallographic Group of Lattices in 2 and 3 dimensions? Group theory /abstract nonsense approaches are ...
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51 views

Twisted Nematic liquid crystal: extent of degradation due to DC drive?

It is commonly accepted wisdom that a Twisted Nematic LCD must always be driven using AC instead of DC, because DC will supposedly denature the LC. I have two questions: Does this effect only happen ...
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52 views

AWG chart for Tungsten

This is the American Wire Gauge (AWG) chart page for Copper that I found from Google: http://en.wikipedia.org/wiki/American_wire_gauge Is there a similar table for Tungsten/Wolfram available? Has ...
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301 views

Why is my ballpoint pen spatially temperamental?

I'm trying to write with a ball-point ink pen on a plastic[1] sandwich bag. When I try to write on some parts of the bag, no ink transfers to the bag: I can continue trying for quite a while in vain. ...
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346 views

Electrical machines: electrical and mechanical properties of steels and cast iron

I would like to know a good source of information for the common metals (steels and cast iron). Information that I need are basically the mass density and the electrical conductivity or resistivity. ...
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14 views

How can I tell apart the composition of my soft ferrites

I have an assorted bunch of soft ferrites. I need to know which ones are MnZn and which ones are NiZn, so I can sort them for usage at different frequencies.
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25 views

Magneto Optical Kerr Effects

I have a few questions on MOKE setup. Firstly, why is calibration of the coils necessary? Is it to get a relationship between the voltage and the Magnetic field? Secondly, why do we have to normalise ...
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22 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, ...
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19 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. ...
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15 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 ...
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15 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 ...
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33 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 - ...
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37 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 ...
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27 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 ...
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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 ...
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22 views

ZnO nanorods synthesis

Could someone please let me know the steps to be used for sol-gel method synthesis of ZnO nanorod arrays using PVA as solvent and Zn acetate as precursor? I need vertical and uniformly aligned NR ...
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33 views

Activation energy as a function of defects

Electrical conductivity has a form of Arrhenius equation. It is assumed that activation energy decreases with defect density in the insulating state and becomes zero in the conducting state. Can one ...
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26 views

absorption and reflection of sound on molecular level

Can someone explain the reflection and absorption of sound on the molecular level? What really is reflection? Why porous and soft material absorbs sound? What's the definition of soft in terms of ...
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38 views

Steel and aluminum fatigue limit

Is it true that steel has a fatigue limit? Is it true that past a certain number of stress strain cycles, steel will last indefinitely if its ultimate strength after the specified number of stress ...
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152 views

Find the maximum allowable bending moment

A rolled steel universal I-section beam with a serial size of $406\times178$ has a mass of $60$kg/m. What is the maximum safe allowable bending moment this beam can sustain,given that the maximum ...
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28 views

coherent grain growth

What is the driving force for growth of coherent precipitates in the matrix? The driving force for growth of incoherent precipitates in the matrix is concentration slope between tiny and large ...
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38 views

Martensitic transformation in ceramics

What is the specification of Martensite (displacive) transformation in ceramics comparing to yhe one in metals? I just know about Martensite transformation in metals. For example, these ...
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14 views

What curved, transparent media exists for full-motion holograms?

Looking to project light either on, or through, but not from, a transparent medium. So I'm thinking of half a hollow sphere with a surface thickness of 1/10th the radius of sphere. A clear curved ...
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37 views

Material Evaporation in Low Pressure Condition

Are there any references for the determination of evaporation temperature of materials under low pressure condition? Specifically, I need to evaporate InP under low pressure at around 1.0 Torr which ...
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35 views

Like viscoelastic polymers, why there are not storage and loss moduli for cast iron?

Viscoelastic polymers have different paths upon loading and unloading, so there is energy dissipation, so they have storage and loss moduli. Plastic behavior is also shown by cast iron: loading and ...
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20 views

What's responsible for dull or sharp sounds in a struck sintered rods?

I've sintered a number of rods from powdered oxide materials, and some of them ring clearly after being struck (not as clear as, say, a metal tube, but clear enough to hear a definite pitch), while ...