Allotropes (an Ell Donsaii story #8) by Laurence Dahners Page B

appeared to be making. Off to the side of the layer was diagrammed a molecule that had boxed sixes at the nodes. Not chicken wire hexagons though. Instead of three lines emanating from each carbon like in graphene, each carbon had four lines tetrahedrally emanating from it. Emma gasped, “Is that diamond?”
    They heard the voice of Allan, Ell’s AI speak. “I’ve been monitoring. That isn’t quite diamond’s structure. It’s lonsdaleite. They look very similar.”
    Ell’s voice appeared in their conversation as she said, “Allan told me something was happening. Is this some kind of fabrication machine?”
    “We think so. Why would it be making lonsda… whatever?”
    “Well the first layer it lays down would be the outside eventually. So probably they want a hard outer coating.”
    “If they want it hard and can make a tetrahedral carbon, why not diamond? It would be a lot harder.”
    “Actually no,” Allan said. “Pure lonsdaleite should theoretically be about 15 on the Mohs hardness scale while diamond is only 10. Unfortunately, all the lonsdaleite we’ve found or created so far on earth has a lot of impurities and flaws that weaken it.”
    “What?!” Shan said. “I thought the top end of the Mohs hardness scale was set at 10 based on the fact that diamond was the hardest material?”
    “It was when the scale was established.”
    “Holy crap!” Shan whispered.
    Querlak’s disk now showed a different structural layer. This layer had a diagram beside it showing layers of the chickenwire pattern of graphene. Querlak pointed to it and said in pidgin English, “like graphe ne… but layers bonded… we say…” At this point Querlak uttered one of the tones that served the sigmas for words.
    Allan said, “That tone has many of the same harmonics that their tone for graphene does but a few tones from their word for diamond. I suggest we call it graphend.”
    Shan said, “That looks just like graphene to me?”
    Emma said musingly, “No, look. Some of the hexagon corners have a tetrahedral diamond type bond to the carbons in the graphene layer above or below them. That would keep the graphene layers from sliding past one another. It wouldn’t have quite the same tensile strength that graphene does but, because the layers won’t slide past one another, a thick stack of them would resist bending. You could use it for structures that need bending strength, not just tensile strength.” She looked around at the building, “Maybe the walls of this building and of the machines are made of it?”
    Querlak’s disk indicated a different material being laid down like a trough in the ongoing layer deposition. With time, the trough became a pipe designated with more tetrahedral molecules. The material inside the little pipe that was being formed was designated with the hexagonal pattern of graphene. Shan asked, “Is that more lonsdaleite?”
    “No, the tubular structure is diamond,” Allan said.
    “Why diamond in the middle of this machine?”
    “Diamond’s an insulator and properly oriented graphene’s an excellent conductor,” Ell said musingly.
    “ Oh my God!” Shan said wonderingly. “They’re laying down, layer by layer, a machine that has an incredibly hard lonsdaleite outer shell to protect it. Then a layer of graphend, similar to the strongest stuff we know of, made a little weaker in the process of giving it some bending strength. And then, instead of installing wiring inside of cavities in the machine, it has diamond insulator built right around graphene conductors!?”
    “It’s a single element 3D printer! Most of our 3D printers only build things out of one or a few materials, mostly plastics that aren’t all that strong and really can only be used as models. When we need different material properties, we use completely separate machines to print parts from each different material and then have to assemble them. This thing only uses one material, carbon, but it’s using the different