Synthesis of polymeric precursors for refractory carbides and borides.
Hafnium Carbide and diboride are ceramics with ultra-high melting temperatures representing the upper end of refractory materials. Current standard syntheses of these ceramics form powders in an energy intensive carbo- (boro-) thermal reduction or coatings via vapor deposition, a time consuming process requiring high vacuum conditions. Under the support of the Office of Naval Research work is being done towards an alternative by thermally decomposing preceramic polymers, such as polycarbynes and "polyborynes".
Higher atomic weights and a polymer network rather than a chain structure eases the conversion from amorphous polymer to dense ceramic. For synthesis of polycarbynes, studies on Wurtz coupling of sp3 coordinated bromoform initiated with alkali metals have been published, but these reactions are extremely exothermic and potentially violent.
In an effort to reduce the hazards, the reaction set up was first modified to an electrochemical cell, and then to control the reaction rate with ultrasonic vibrations. The active metals used were alloys of sodium and potassium deposited in porous silica gel.
Work towards the "polyboryne" precursor will follow a similar reaction pathway to polycarbyne synthesis. Titanium will be used as a representative to hafnium as it is more stable for laboratory conditions.
Natalie Kirch, University of Idaho
Dr. Mark Roll, University of Idaho
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|Title Annotation:||56TH ANNUAL SYMPOSIUM OF THE IDAHO ACADEMY OF SCIENCE: THEME: ENERGY, MATERIALS, AND NANOTECHNOLOGY|
|Author:||Kirch, Natalie; Roll, Mark|
|Publication:||Journal of the Idaho Academy of Science|
|Article Type:||Brief article|
|Date:||Dec 1, 2014|
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