Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!mips!dimacs.rutgers.edu!aramis.rutgers.edu!athos.rutgers.edu!nanotech From: erich@eecs.cs.pdx.edu (Erich Stefan Boleyn) Newsgroups: sci.nanotech Subject: Re: Diamonds? Keywords: diamonds, bones Message-ID: Date: 10 Apr 91 01:53:28 GMT Sender: nanotech@athos.rutgers.edu Lines: 89 Approved: nanotech@aramis.rutgers.edu neufeld@aurora.physics.utoronto.ca (Christopher Neufeld) writes: ...[deleted]... >lengths to make diamond is that it doesn't matter how much energy you >inject into graphite, it's not going to change to diamond until diamond >is the stable allotrope. > Looking at a phase diagram of carbon, one can see that around 13500 >atmospheres diamond is the preferred phase at absolute zero. At >increasing temperatures the diamond/graphite transition region rises in >pressure, reaching 70000 atmospheres around 1400 Celcius, and at about >215000 atmospheres and 3900 Celcius the graphite/diamond transition >curve hits the solid/liquid transition line, which is pretty close to >vertical (constant temperature) all the way down to the triple point at >about 130 atmospheres. Note that this means that the ideal conditions >for forming diamond are high pressure and LOW temperature. The hotter >you make it, the harder you have to squeeze it to make diamond the >stable allotrope. ...[references deleted]... >the stable allotrope in the conditions under which you made it. If you >have an efficient system which exposes all the graphite to the same >conditions for a reasonable period of time, you should have essentially >complete conversion to diamond. Hmmm... I am definitely out of my knowledge depth here... (nice references though ;-) I know about the vapor deposition methods to a point, but the conditions always have had to be very controlled. My comments in an earlier posting were partially referring to possible requirements in a non-pristine environment, but I got sloppy. The idea is to make these work in a chemically rich (or at least non-void) environment, where energy could be sapped off by nearby molecules, charges altered in a somewhat unpredictable pattern, etc. Any operation that takes a decent amount of energy, and/or needs a very specific event to take place, and where thermodynamic or chemical noise is a problem will of course cause a lot of interference, or at least a much higher probability of failed reactions. Anyway, These deposition methods are still energy expensive. Even supposing that you have high amounts of energy available that would not damage your nanotech machinery (energy high enough to establish the carbon- carbon pi sigma bonds are also high enough to pose possible danger to the strutural integrity of your device ?), that is still a lot of energy to direct locally. Specific atom deposition has been done with slightly modified scanning tunneling microscopes, but you have a large structure to feed the energy in, if you need it (I am not too familiar with what has actually been done, but I think they only placed the atoms onto the surface bonded by bulk bonds (Van der Waals, polar, etc.), not molecular). How would the energy feed be done for a nanomachine? Chemically? It would have to provide a good punch, so to speak... current biological-chemical reactions don't tend to be too high-energy... (this is where I don't know what the comparative energy levels would be, I'll check up on it). > The point of all this is that diamond would make a pretty good bone >material. It isn't going to transform spontaneously into graphite inside >a person's legs. I don't think there is much in the way of biological >impediments to the evolution of diamond bones. When you ask why >creatures haven't evolved diamond bones you might as well ask why they >haven't evolved bulletproof skins, asbestos fur, or for that matter, >warp drive. It just wasn't in the evolutionary dice. Moving around molecule subunits is easier than moving atoms, and calcium has always been abundant as a free ion in cells, not to mention being used by many other things. One of the main problems would be to work with raw carbon, and how to isolate that from the rest of the body. Making bones is a sloppy operation. I agree that it could be done, but think that it would involve some more radical changes than are hinted at, no system in the body exists even in semi-isolation. Erich "I haven't lost my mind; I know exactly where it is." / -- Erich Stefan Boleyn -- \ --=> *Mad Genius wanna-be* <=-- { Honorary Grad. Student (Math) }--> Internet E-mail: \ Portland State University / Phone #: (503) 289-4635 [I think it's a bit premature to speculate about diamond fabrication inside a body just now! It does seem that diamond fabrication is a reasonable thing to expect a molecular assembler to do, but the most I think we can deduce from this is that it is not UNreasonable to design an assembler with diamond parts (the "matrix" or frame of a mechanical nanocomputer, for example...). BTW, I've personally seen a 6-inch synthetic diamond wafer made for use as a substrate in advanced electronics. By the time diamond is made by nanotechnology, it won't be that uncommon as an engineering material. --JoSH]