Inventors create covetics, the first known stable nano carbon-metal material in existence
March 2013 - High-end jewelry makers can find inspiration in anything, from the fluidity of a water droplet to the intricacies of ornate architecture or the play of color during a Southwestern sunset. Metals also are critical in the creative process, but any experienced artisan knows using precious elements to turn inspiration into workable designs can be troublesome. Difficulties with silver and gold, for example, can include surface porosity, inability to hold fine detail, softness, tarnish and brittleness. In a ground-breaking development, two engineers have created a new material with the ability to solve these problems and change the playing field for forward-thinking designers while redefining color, luster and surface finish.
Carbon meets precious metal
Under the name Zovoz, Waverly, Ohio-based Third Millennium Materials LLC has unveiled silver covetic, one of the rarest materials on earth. Invented by Jason Shugart and Roger Scherer, Ph.D., silver covetic was birthed in a furnace environment where high temperatures (up to 2,500 degrees Fahrenheit) are stoked to fuel an electrochemical carbon reaction that bonds high concentrations of sp² and sp³ carbon to molten silver metal and other alloys. According to Chemistry.about.com, carbon is made on the insides of stars, is the chemical building block for all living things and appears in diamonds. “Our world essentially is a carbon world,” says Shugart.
Metallurgists have been attempting to incorporate carbon into metals for more than 100 years. These efforts have been limited to ferrous metals like steel and iron. “It’s never been possible to integrate carbon with precious metals,” Shugart says. “In recent years, carbon nanotube manufacturers have produced carbon mixtures in some metals. However, when tested, these mixtures separate under remelt. Silver covetic is the only known stable, nano carbon-metal material in existence. It demonstrates the first true bonding of these elements because carbon has reacted with metal to become a permanent new material that does not separate when remelted.” He adds because covetics are carbon compounds that use different metals, potential users will have to gain an understanding of carbon and its effect on the properties and behavior of the material.
Out of the fire
Third Millennium Materials was awarded U.S. patent 8,349,759 on January 8, 2013, for the metal-carbon composition and the invention of silver covetic. The company owns the intellectual property for 15 elements that have been converted to covetics, including gold, copper and iron.
Shugart says early work focused on copper before the pair turned their attention to silver. “We had a Kerr electric jewelry furnace with a homemade carbon feeding system at the time,” he says. “We chose silver because we wanted to work with the purest material possible. We couldn’t find copper with a purity rating higher than 0.999 so we opted for silver with a purity rating of 0.99999.”
Shugart purchased the silver from Ohio Precious Metals LLC, Jackson, Ohio. The silver was first added to the crucible and heated well above its melting temperature. A unique agitation method formed a vortex to which powdered, activated carbon was introduced while the melt was subjected to an electric current before being poured into a holding vessel to cool. After cooling, the single phase silver-carbon composition was remelted in the crucible to demonstrate that no phase separation occurred. Testing also showed that the silver-carbon composition resisted tarnishing, provided improved fracture toughness and revealed an ultrafine molecular structure. “We knew immediately that we had something,” says Shugart.
“The properties of covetics are dominated by the superior properties of the carbon structures created during the chemical reaction,” says Harry Couch, chief technology officer for Third Millennium Materials. “Silver covetic responds to physical and mechanical loadings that are superior to either polymers or metals.”
Third Millennium Materials chose to target high-end jewelry makers and artists for its first commercial effort because of the advantages silver covetic can provide. Business Insider recently reported that silver has surpassed gold as the “trendiest metal to wear.” And while designers have gotten creative with the white metal, it is prone to tarnishing and lacks the capability to hold fine detail. The prongs used to set gemstones in both silver and gold must be checked annually to ensure they remain secure. Surface porosity plagues designers that want to achieve a high-polish finish in cast silver pieces. These pieces often require secondary operations such as grinding, polishing and hammering to remove the tiny pores which over time can turn black and appear as spots on the jewelry.
“Imagine never having to worry about losing a gemstone from a setting or having a piece of jewelry tarnish,” says Shugart. “Silver covetic has demonstrated its ability to pick up minute details, something that previously was impossible to achieve. Silver covetic is easily work hardened for areas like prongs that require creep resistance and durability. These features and the material’s improved castability open the door to new design possibilities for jewelry makers.”
Calling high-end jewelry designers>
Although covetics offer superior properties when compared to base metals or polymers, the new material presently defies classification. Until recently, it confounded universities, national laboratories and the military. The organizations could neither qualify nor quantify the presence of carbon in covetics. It wasn’t until 2007 that a Chicago-based materials testing laboratory confirmed the presence of carbon using transmission electron microscopy.
“So the question then became, ‘What form of carbon is it?’” says Shugart. “Further testing by the University of Maryland showed that the carbon in our silver covetic is made up of fullerenes (nanotubes and others), nano ribbons and amorphous carbon, and that all of these carbon forms are bonded together in a network and fused to metal. Work with the University of Illinois at Urbana-Champaign helped us better understand silver covetic. We’re currently searching for an analytical technique that can identify the bonds between the carbon nano structures in the covetic.” Shugart adds that TEM is not a standard test for the jewelry industry, making it challenging for refiners and manufacturers to understand covetics. “In 2012 a refiner and manufacturer of precious metals considered the jewelry industry’s gold standard, tested a silver covetic with greater than 6 weight percent carbon and reported its purity at 0.999 with no detection of the presence of carbon,” he says, “but they did confirm its performance characteristics.”
Silver covetic also lends itself to direct metal laser sintering, an emerging additive technology used in rapid prototyping. The process can build fine layers at any level of complexity required and provides the ability to fabricate parts by laser sintering or using a laser’s heat to melt powder into solids.The technology is attractive to manufacturers but also is capturing some interest in the jewelry industry. “One of the proven capabilities of silver covetic is it easily transforms into micro powder which permits additive manufacturing of very precise pieces,” says Couch. “Jewelry designers will be able to go directly from design to finished configuration.”
Although traditional silver and goldsmiths don’t have to adapt to additive technology to use silver covetic, jewelry makers who want to use direct metal laser sintering can gain advantages that include eliminating the casting step and the inherent loss of material and definition that often occurs with traditional lost wax methods or the shrinkage associated with setting uniquely-shaped gemstones. “Combining covetics with DMLS gives designers a powerful tool,” says Shugart. “Covetics improve a designer’s control over shrinkage while DMLS offers the capability to produce net-shape parts with 20 micron details.”
The science of silver covetic is game-changing, but the chance to work with a new, rare material that offers unique performance characteristics is already attracting the attention of some high-end custom jewelry designers. “Learning to work with the material will take some training,” says Shugart. “We’re planning to work with a select group of jewelry designers that want to invest the time in understanding how to work with silver covetics,” he says. “Simply put, we are interested in designers who want to work in new ways with a very rare, new material that offers problem-solving advantages. We also plan to create exclusive products using silver covetic with DMLS.” MM