Tag Info

New answers tagged

13

Ice, as in the ice you see in cold weather, is most certainly a crystal. In fact ice has at least 11 different crystal forms depending on the temperature and pressure. The form we see on a cold day is ice 1h. A glass, i.e. an amorphous solid, is a material that has no long range order and shows a glass transition rather than a distinct melting point. It is ...


29

A crystalline substance doesn't necessarily have to be a single crystal to be deemed as such. An amorphous solid such as glass doesn't exhibit a crystalline structure even at very high levels of magnification. Glassy substances have a glass transition phase that is lower than the melting temperature. The melting point of ice formed under ordinary ...


0

In the free-electron approximation, the electron energy is indeed $\frac{(\hbar k)^2}{2m}$ with a minimum at $k=0$. However, in a real material the electron is not free, and feels a background potential due to the distribution of the other charges, which modifies the $E(k)$ relationship. In a material with low symmetry, I presume this can also shift the ...


1

A sharp knife is still several molecules thick on the edge; dull blades are even wider. So when you attempt to cut material, it needs to be ripped apart. As explained in other answers, the material either fractures along faults in the lattice, or you separate molecules (as when you cut bread). The only materials where you might split chemical bonds are ...


0

I guess you mean "silicone-like", not "silicon-like". Recently, I was looking for a similar material (Need an intermediate resistivity part/material ), but eventually obtained doped silicon rods. You have several options, depending on the required geometry and properties of the part. For example, there are so-called "intrinsically conducting polymers" ...


2

The space elevator probably deserves an entire series of questions (and I am sure there have been plenty of posts), but if we stick to this particular version, there are a couple of problems with it. First of all, a space elevator needs a counterweight in an orbit that is higher than the areostationary orbit (the Martian equivalent of Earth's geostationary ...


0

You could try PEBBLES which is freeware AFAIK


0

you could have a larger amount of the softer material so by the end of the cutting you have zero soft material left.


2

It depends on your definition of "cutting". Hardness of a material relates to its yield strength - the stress it can sustain without plastic deformation. Push a "soft" material with a sharpened point into a "harder" material, and the tip will go blunt because the soft material deforms. This is why diamond powder is often used to coat grinding wheels etc - ...


3

Firstly, I suspect that oxidation will throw a spanner into any such plan. For metals like aluminum, which have a very high affinity for oxygen, a "virgin" surface will begin to tarnish almost immediately. The second problem is that metals have microstructure. Neighboring crystals in a polycrystalline aggregate such as a metal piece have to satisfy certain ...


6

One can cut a any material by using a (slightly) softer abrasive material and a soft tool that can press the abrasive against the cutting surface. The tool will simply abrade much faster than the object that is being cut and it will take lots of abrasive and time, but that's OK. This kind of abrasive cutting/grinding is quite common.


4

The light rays are crisscrossing in front of you now! $_1$ Do you consider it as soft? It depends on your definition. Your softy light is used to cut hardest materials by using the process called laser cutting. The focused laser beam directed at the material, which then either melts, burns, vaporizes away, or is blown away by a jet of gas.$_2$ ...


1

I believe that it depends on the method of cutting, and on the energy of the material used for cutting. Sure, air can cut steel. If it is heated to several thousand degrees in an arc welder. However, air at the same temperature as the steel is not likely to cut the steel. I believe the method you are asking about is the classic material removal method. ...


1

I believe a fast-rotating blade can cut a harder material.


5

Yes, is possible. For example, you can see this, water can cut steel.


1

There's a nitinol wire that stiffens when warm and softens when cool. It's been used in various patented heat engine applications. see this reference http://www.imagesco.com/articles/nitinol/09.html



Top 50 recent answers are included