Half a croissant, on a plate, with a sign in front of it saying '50c'
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Reversible Pencil-Knife

Graphite at one end, pencil at the other
 
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A pure graphite pencil which has a diamond blade at the other end. This is made by taking a hexagonal column of graphite and applying extreme pressure and heat to half of it along a transverse axis, squashing it and converting it to diamond. This enables one end to be used as a very durable, sharp blade and the other as a writing implement. Alternatively, the blade can be used as a pen by drawing blood and writing with it. It needs to be held with some kind of spongy protective holder when written or drawn with.

I have a question. If the pressure in forming such a device is applied as a gradient, are there intermediate graphite/carbon allotropes and if so, what are they like?

Obviously you'd throw it away when you ran out of graphite.

nineteenthly, Jan 08 2017

https://www.newscie...s-hardest-material/ [hippo, Jan 09 2017]

[link]






       If you break it in half you can sharpen the pencil.
whatrock, Jan 08 2017
  

       Hardness and durability are different things.
Voice, Jan 08 2017
  

       I don't think there is a smooth transition. The heat/pressure will make a fracture gap.   

       Maybe if the intervening Carbon continuum was all different C containing molecules, just like the Metamorphosis print, then you could get something that stuck to graphite and transition to something that stuck to/into diamond. All solidified with pressure and heat.   

       Also thanks I will look into the canadian programme Continuum.
wjt, Jan 09 2017
  

       Is there a reason why there can't be bits of graphite embedded in diamond or vice versa? What happens with black diamonds?
nineteenthly, Jan 09 2017
  

       Diamond would make a fairly crappy knife blade. It's way too brittle (as well as not being heat-resistant, etc.)
hippo, Jan 09 2017
  

       Wurtzite boron nitride, of course (see link)
hippo, Jan 09 2017
  
      
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