Talk:Amorphous solid

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Flowing[edit]

Should there be a mention of the urban legend that glass flows?

"Do Cathedral Glasses Flow?", Am. J. Phys. v66, pp 392-396, May, 1998

http://www.glassnotes.com/WindowPanes.html

http://www.phschool.com/_news/articles/property_glass.html

http://www.maths.adelaide.edu.au/people/ystokes/windows.html

There is one in the glass page, but I'll make mention of it in this article.--Polyparadigm 02:00, 16 Feb 2005 (UTC)
It's not an urban legend. Glass actually does flow, or rather, at least some types do; I've personally witnessed the effects. The house I grew up in was completed in 1932, and by the time I left there in 1999, the two remaining panes in the entire house that were original were easy to identify, because they were nearly 4 times as thick at their bottom edge than their tops, with a smooth taper from top to bottom, and some slight rippling, very similar in appearance to super-high-speed photos of flowing water. On the other hand, on vacation, I once visited the home of one of the USA founding fathers (I think it was Jefferson), and noted that some panes there, supposedly original, and thus far older than 1932, showed no macroscopically perceptible signs of flowing; I have speculated that the glass from that site was probably so-called "lead crystal", both due to the context in which it was made, and because it exhibited that material's distictive appearance. The same property of lead crystal that leads to its distictive ring ("Since the potash ions are bound more tightly in a lead-silica matrix than in a soda-lime glass", quoted from the wikipedia "lead glass" article), would also be reasonably expected to cause it to flow significantly more slowly. 67.162.34.172 (talk) 02:03, 19 December 2009 (UTC)
Glass is a solid. It is not a fluid. It does not flow, not even on geological timescales. There is absolutely no scientific evidence whatsoever that will back up your claims. The myth is the result of old methods of forming glass where one end of a pane was often thicker than the other. It makes sense to install the window pane with the thicker end at the bottom. Indeed there are cases where window panes were installed with the thicker end at the top! Polyamorph (talk) 10:24, 19 December 2009 (UTC)
From our glass article (which is fully referenced):

In glass factories, molten glass was poured onto a large cooling table and allowed to spread. The resulting glass is thicker at the location of the pour, located at the center of the large sheet. These sheets were cut into smaller window panes with nonuniform thickness. Modern glass intended for windows is produced as float glass and is very uniform in thickness.

Several other points exemplify the misconception of the "cathedral glass" theory:

  • Writing in the American Journal of Physics, physicist Edgar D. Zanotto states "...the predicted relaxation time for GeO2 at room temperature is 1032 years. Hence, the relaxation period (characteristic flow time) of cathedral glasses would be even longer."(1032 years is many times longer than the estimated age of the Universe.)
  • If medieval glass has flowed perceptibly, then ancient Roman and Egyptian objects should have flowed proportionately more — but this is not observed. Similarly, prehistoric obsidian blades should have lost their edge; this is not observed either (although obsidian may have a different viscosity from window glass).
  • If glass flows at a rate that allows changes to be seen with the naked eye after centuries, then the effect should be noticeable in antique telescopes. Any slight deformation in the antique telescopic lenses would lead to a dramatic decrease in optical performance, a phenomenon that is not observed.
  • There are many examples of centuries-old glass shelving which has not bent, even though it is under much higher stress from gravitational loads than vertical window glass.

Polyamorph (talk) 10:33, 19 December 2009 (UTC)

It is not just about thicker ends of the pane mounted at the bottom, the panes in the house I grew up in were perceptibly molded to the contours of the wood they were mounted in. Obsidian blades, cathedral panes, and telescope lenses are all made of specialized types of glass, and none of them are even particularly close to being the same type as was commonly used in residential windows in the 1920s. Siting 3 examples of cases where something didn't happen proves only that it doesn't happen in those particular cases, not that it can never happen in any case. I don't doubt that there are types of glass that either flow so slowly as to require geological timeframes to be significant, or even that don't flow at all at moderate temperatures, but that's not all glass. 67.162.34.172 (talk) 04:38, 16 May 2010 (UTC)

You are mistaken and I am still waiting for someone to provide a citation that proves that any form of glass flows. This is not the first of this kind of discussion and not once has anyone been able to cite a verifiable and accurate source that proves the claim that glass flows. That is because it is scientifically incorrect. Glass is a solid and is hence just as rigid as any crystalline material. Polyamorph (talk) 08:28, 16 May 2010 (UTC)

Ice[edit]

ice is a hydrogen bonded molecular crystalline solid Ice is an amorphous soli Acegikmo1 14:41, 17 Sep 2004 (UTC)

I've removed it, along with other substances that I'm fairly sure aren't amorphous solids, from the article. Acegikmo1 00:13, 17 Oct 2004 (UTC)
Ice does have several amorphous phases Polyamorph (talk) 19:20, 15 December 2007 (UTC)
See Amorphous ice. As with many crystalline materials which have distinct polymorphic structures, they may indeed also have several distinct polyamorphic structures. Polyamorph (talk) 08:55, 21 February 2009 (UTC)

Glass: substance or another word for amorphous solid[edit]

The article is a little confusing because it contains several inconsistent definitions of the word glass. In the first half of the article it refers to a liquid that is cooled below the [glass transition temperature]], but in the second half it refers to common glass this page sucks!!!!!!!!!

Some liquids have a glass transition temperature that is higher than the melting point. This means that you can create a glass without supercooling the liquids. Therefore the following sentence is wrong

Tg cannot be greater than the melting temperature. Above the melting temperature, the substance is an isotropic liquid with a viscosity well below that of a glass. ---Dan Miller —Preceding unsigned comment added by 67.188.147.13 (talk) 22:08, 2 December 2007 (UTC)

"Glass is often referred to as a 'super-cooled' liquid.". glass is called a super cooled liquid because of its ability to flow in heating.It is also called a pseudo-solid However it is correct to write that "Some substances can only be cooled below the glass transition temperature if they are supercooled."

One line says that glass is an amorphous ceramic. Is this correct? I have never heard this before and can find no corroboration in the Glass article. Garbagemania (talk) 02:43, 30 January 2009 (UTC)

Sometimes glasses are referred to as an amorphous ceramic but in this case I would tend to agree with you that this is just confusing. This entire article needs re-writing anyway, it seems to focus on glassy materials when these are extensively dealt with in the glass article. Although glasses are certainly amorphous solids and deserve a mention, I think this article should be dealing with materials manufactured using, for example, vapour deposition, splat quenching or sol-gel methods, to name but a few. Polyamorph (talk) 09:33, 30 January 2009 (UTC)

The definition[edit]

amorphous solid is a solid in which there is no long-range order of the positions of the atoms. (Solids in which there is long-range atomic order are called crystalline solids.)

Should we write "an amorphous solid is a solid in which the position of the atoms is in short-range order without long-range order"? Roscoe x 13:31, 16 Nov 2004 (UTC)

amorphous solids are solids having short range order.

No, the key concept here is the fact that amorphous solids lack long range translational periodicity, they will have a high degree of short range order by virtue of atomic bonding characteristics, and may even exhibit ordering on intermediate length scales. I agree that the article is poorly written though and should be re-worded to make the concept clearer. Polyamorph (talk) 09:28, 30 January 2009 (UTC)
We can also add the fact that an amorphous solid is pretty much the intermediate stage between a crystalline solid and a liquid. Majopius (talk) 01:03, 23 April 2009 (UTC)
Except that it isn't an intermediate stage, cooling a liquid below its melting temperature will typically lead to a crystalline solid there is no intermediate amorphous stage. The structure of an amorphous solid is, however, analagous to that of a liquid which is what I think you were referring to. Polyamorph (talk) 08:58, 23 April 2009 (UTC)

Eutectic system[edit]

You should be linking here to the explanation on the eutectic reaction. Metallic glasses are most easily formed when working with compositions as close as possible to deep eutectic systems. —Preceding unsigned comment added by 178.198.133.52 (talk) 21:22, 12 October 2010 (UTC)