Lab turns hazardouswaste into diamond

by Peter Kauffner

Researchers at the University’s Plasma Technologies Lab have yet to turn lead into gold, but they have used high temperature gas to turn methane and hazardous chemicals into diamond and other products with industrial applications.
When gases are heated to more than 20,000 degrees Fahrenheit, electrons are stripped of their atomic nuclei, creating ions. The ions form plasma, which scientists sometimes call the fourth state of matter. The other three states are solid, liquid and gas.
“The plasmas that we are working on are very high-temperature gases,” said Joachim Heberlein, a professor of mechanical engineering and co-director of the lab. “They are not plasmas as they appear in blood.”
The lab uses arcs of electricity to heat a gas, such as argon or hydrogen, until it becomes a plasma. The plasma is then propelled into the chamber of a torch, combined with a metal or ceramic powder and then sprayed at supersonic speeds out of the torch nozzle at the material to be coated.
“Plasma allows you to melt high-temperature materials at a very rapid rate,” Heberlein said. “Therefore, you get a relatively thick coating in a very short time period.”
Eighty percent of the parts in jet engines are currently coated using plasma sprays, said Heberlein.
Ford and General Motors have both expressed interest in a technique developed at the lab which allows cast iron to be sprayed on aluminum.
The automakers hope to use the technique to coat the inside of cylinder heads, which would allow engine blocks to be made of aluminum. Aluminum is much lighter than cast iron, the material engine blocks are currently made from.
“The weight of the engine block is a very important factor in the fuel efficiency of a car,” Heberlein said.
But the lab has some trouble applying a coating with a consistency adequate for the automotive industry.
“There are problems with the particles heating inconsistently,” Heberlein said. “When you have heat instability, it is difficult to get a uniform coating every time.”
Mechanical engineering professor Emil Pfender, the lab’s other co-director, is experimenting with various nozzle designs to see if heat stability can be improved.
Pfender and Heberlein have also developed a reactor that can convert polychlorinated biphenyls into a film-like coating of diamond.
PCBs are a hazardous waste produced by the electric power industry. But the reactor is currently too expensive for commercial use.
“NSP currently has a license to incinerate PCBs,” Pfender said. “As long as they have that, they have no incentive to look at alternatives.”
To avoid the special precautions required for handling PCBs, the researchers generally use methane, the major component of natural gas. Each diamond is so small that it would take 60 billion to weigh one carat.
“We have shown that we can put diamonds on dental drills,” Heberlein said. “That would mean that these drills would last at least 10 times longer than a normal drill.”
The lab also has looked into the idea of depositing diamond film on geological drill bits to increase their hardness and life span. Such larger industrial applications will require an advance in plasma reactor technology.
“One would have to design a relatively large plasma reactor to coat a larger curved area,” Heberlein said.
Not only does the lab use the wastes from the generation of electricity but scientists there might just revolutionize how power is produced.
A solid oxide fuel cell developed at the lab may one day replace the steam turbines now used to generate electricity.
“Now, electricity is generated by heating steam or gases and these gases are used to drive a turbine, which in turn drives a generator,” Heberlein said. “Each step in the process reduces efficiency.”
In a fuel cell, chemical energy is used to produce electricity directly, by dividing positively charged ions from negatively charged electrons. This allows fuel cells to achieve an energy efficiency of 60 to 65 percent, compared to 40 percent for current turbines.
“You have hydrogen and oxygen and then you recombine them (to form water) at a low temperature without going through the combustion process,” Heberlein said.
Manufacturing expenses are currently too high to justify the commercial use of such fuel cells. Heberlein hopes that the coating techniques developed at the lab will lower those costs.
Joel Blum, a mechanical engineering research assistant, is using a plasma spray nozzle of a different design to create tiny particles of ceramic.
The particles are about 10 nanometers in diameter. By comparison, an atom is about 0.1 nanometers in diameter. The particles are pressed together, creating a material with unique properties.
“You can actually coat something with ceramic and because the particles are so small they will tend to give a little more and you can actually bend a piece of ceramic,” Blum said.
This means that materials coated with nanosized-particle ceramic are far more resilient than those coated with ceramic tiles, such as the ones currently used on the space shuttle.
“Someone will make money from this idea,” said Heberlein. “(Blum) should start (his) own company and market it. I am too old for that.”