[About the Foresight Institute]|
[Index of Foresight Conferences]
|[Index of Abstracts]|
University of Nevada
This is an abstract for a talk to be given at the Fifth Foresight Conference on Molecular Nanotechnology.
Theoretical studies of molecular nanotechnology (MNT) have focused on tetrahedral carbon ("diamondoid") frameworks as an ultimate goal. It seems natural to wonder, though, whether silicon, carbon's second row homolog in the periodic table, could form a reasonable basis for MNT, especially given the importance of Si in semiconductor technology. Although Si itself is unpromising--the Si-Si bond is not nearly so stable as is C-C, and Si shows minimal tendency to form the double and delocalized bonds so typical of C--silicates, compounds of Si and O, indeed show promise for MNT, because of:
This structural variety only in part accounts for the diversity of silicates, however, as other atoms can substitute for Si. In natural systems, Al substitution is ubiquitous; one class of alumino-tectosilicates, the feldspars,are the most common compounds in Earth's crust. Other alumino-tectosilicates,the zeolites, have great technological importance as "molecular sieves" and catalysts, due to their molecular-sized internal voids. Finally, other tetrahedral substitutions (e.g., B, Ga, P, transition metals) vastly increase the potential structures for MNT.
Siloxanes ("silicones"), "hybrids" of silicates and organic compounds that consist of siloxy (Si-O-Si) chains with H or organic side-groups attached to Si, show how silicate-based structures could be integrated with C-based structures. Cubosiloxane, H8Si8O12, the siloxy analog of cubane, C8H8, in which each C-C bond is replaced by an Si-O-Si bond, shows their diversity; moreover, cubosiloxane is both considerably easier to synthesize and more stable than cubane.
Though silicate raw materials are literally everywhere, conventional mining waste seems especially attractive. Despite their ubiquity, silicates are usually unattractive as ore minerals due to the energy required to break the Si-O bond. However, most ores consist largely of silicate minerals in which the valued non-silicate ore minerals constitute only a minor fraction. Such ore rock must be crushed and ground merely to separate out the ore minerals; hence, not only is the energy needed to break the rock up mechanically been largely wasted, but the very finely comminuted waste from such mineral dressing operations (the "tailings") presents a serious disposal problem. Such material should furnish an excellent feedstock for silicate-based MNT, however, especially as it is relatively reactive due to its comminution.
Last, silicate-based MNT has major potential applications in space
development, as many extraterrestrial bodies (e.g., the Moon) are dominated by
silicates but have scant carbon. Indeed, the surface material of the Moon,
which largely consists of silicate minerals comminuted by eons of meteorite
impact, would also be an excellent feedstock to a silicate MNT.
Stephen L. Gillett, Dept. Geol. Sciences, Mackay School of Mines, University of Nevada, Reno, NV 89557, ph:702-784-4760, fax: 702-784-1833, email: email@example.com
| Index of Abstracts | Conference Home Page | Index of Foresight Institute Conferences |
| About the Foresight Institute | Foresight Institute Home Page |
Foresight materials on the Web are ©1986-1997 Foresight Institute. All rights reserved.
Last updated 16August97. The URL of this document is: http://www.foresight.org/Conferences/MNT05/Abstracts/Gillabst.html
Send requests for information about Foresight Institute activities and membership to firstname.lastname@example.org.
Send comments and questions about material on this web site and reports of errors to email@example.com.