Timeline for Why don't metals bond when touched together?
Current License: CC BY-SA 3.0
21 events
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| Mar 3, 2018 at 19:42 | history | edited | pentane | CC BY-SA 3.0 |
defined mu
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| Feb 28, 2018 at 11:03 | comment | added | jinawee | @pentane Coefficient of friction. | |
| Feb 26, 2018 at 5:49 | comment | added | pentane | What is the $\mu$ he's referencing? | |
| S Oct 18, 2014 at 12:11 | history | suggested | user1686 | CC BY-SA 3.0 |
Added missing μ
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| Oct 18, 2014 at 10:30 | review | Suggested edits | |||
| S Oct 18, 2014 at 12:11 | |||||
| Nov 22, 2013 at 18:03 | review | Suggested edits | |||
| Nov 22, 2013 at 18:16 | |||||
| Nov 21, 2013 at 10:28 | comment | added | yo' | @Kaz Which is not an issue if you perform it in vaccum ;) | |
| Nov 19, 2013 at 22:37 | history | edited | jinawee | CC BY-SA 3.0 |
added 1794 characters in body
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| Nov 19, 2013 at 22:12 | comment | added | Kaz | @deed02392 Note that large flat objects pressed together are also hard to separate simply due to atmospheric pressure. The space between them is a void, and air has to rush in when you separate them. Early in the separation, the crevice through which air can get in is small. | |
| Nov 19, 2013 at 22:09 | comment | added | Kaz | @jcw An electric current can break through the oxidation layers. This is called fritting. Though not an instance of welding, it explains why high voltage electrical contacts don't have to be maintained much. Even a pretty tarnished appliance plug, for instance, will work fine. But, say, small-signal connectors (e.g. audio) will not perform well if they are not clean and polished. (It's good for high voltage connectors to be in good condition too, so that fritting doesn't have to be relied on so much. A high initial contact resistance that has to be broken down could briefly generate heat.) | |
| S Nov 19, 2013 at 21:14 | history | suggested | CommunityBot | CC BY-SA 3.0 |
Fixed some typos.
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| Nov 19, 2013 at 21:12 | review | Suggested edits | |||
| S Nov 19, 2013 at 21:14 | |||||
| Nov 19, 2013 at 20:21 | comment | added | deed02392 | I have witnessed this, with extremely precise height-gauge blocks which had an incredibly flat finish. Holding them together for 30 seconds or so made them tough to separate. Quite amazing to see. My lecturer referred to it as 'cold-welding'. | |
| Nov 19, 2013 at 19:08 | comment | added | jcw | So in basic physics terms, the electrons can pass through the oxide layer, but don't have any effect on the ions on either side while they are passing though, correct? | |
| Nov 19, 2013 at 19:04 | comment | added | jinawee | @jcw As a curiosity, electrons can only pass the oxide layer by tunnel effect. | |
| Nov 19, 2013 at 18:57 | comment | added | Carl Witthoft | @jcw - free electrons can't form a bond. electrons which are in an orbital create a bond by essentially "time-sharing" orbitals owned by neighboring nuclei. | |
| Nov 19, 2013 at 18:51 | comment | added | jcw | @ChrisWhite - so clearly some electrons are crossing between the two metals. What stops these few from bonding the two sides together? | |
| Nov 19, 2013 at 18:50 | history | edited | jinawee | CC BY-SA 3.0 |
added 22 characters in body
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| Nov 19, 2013 at 18:46 | comment | added | user10851 | @jcw A current just means there is a bulk motion of the electron cloud - there are no more or fewer electrons to bond things, and they probably aren't spending any more time than usual bridging the interface. | |
| Nov 19, 2013 at 18:41 | comment | added | jcw | But what if a current were passed through the two metals? Would this not make the electrons move through them, thereby creating a bond? | |
| Nov 19, 2013 at 18:36 | history | answered | jinawee | CC BY-SA 3.0 |