You can’t saw without producing sawdust – and that can be expensive if, for example, the “dust” comes from wafer manufacturing in the photovoltaic and semiconductor industries, where relatively high kerf loss has been accepted as an unavoidable, if highly regrettable, fact of life.
New ultra-thin saw wire for cutting silicon wafers: diamond on top of carbon nanotubes.
© Fraunhofer IWM
But now scientists from the Fraunhofer Institute for Mechanics of Materials IWM in Freiburg together with colleagues from the Australian Commonwealth Scientific and Industrial Research Organisation CSIRO have developed a saw wire that is set to effect dramatic reductions in kerf loss: in place of diamond-impregnated steel wires, the researchers use ultra-thin and extremely stable threads made of carbon nanotubes coated with diamond.
The potential of coated carbon nanotubes has long been understood: possible applications include its use as a hard and tough composite material or as a component of highly sensitive sensors and thermoelectric generators. However, the new material is extremely difficult to synthesize. Diamonds only grow under extreme conditions – at temperatures of around 900 degrees Celsius in an atmosphere containing hydrocarbons. Growing diamonds on nanotubes is a tricky proposition, because carbon tends to form graphite. In order to catalyse the formation of the diamond phase, it’s necessary to use reactive hydrogen to prohibit the deposition of graphite. However, this process also damages the carbon nanotubes.
But the IWM scientist Manuel Mee found a solution for protecting the fine carbon nanotubes, which grow like forests on a substrate: “During our first experiments, fused silica from the reaction chamber accidentally came into contact with the coating plasma. It settled on the substrate and protected it against the aggressive hydrogen.” And to his surprise, diamonds actually grew on this layer. “What followed was careful, painstaking work,” points out Mee. “We had to study the silicon oxide layer, which was deposited in an undefined manner, and find a method of controlling the deposition and optimizing the process.” Tests with a transmission electron microscope at CSIRO’s lab in Australia revealed that the nanotubes actually survived under their protective layer.
A German-Australian success story
How exactly to proceed from there was the question that now faced the scientists. If they found a way to coat with diamond the nanothreads that the CSIRO specialists make from nanotubes, these diamond-coated nanothreads could be used to manufacture ultra-thin saws capable of cutting through silicon wafers for instance. The Australian team at CSIRO is one of the principal global experts with the know-how to manufacture yarns from carbon nanotubes.
The manufacturing process requires special carbon nanotube “forests”, which can be extracted as an ultra-thin “felt” and twisted into a very thin yarn ten to twenty micrometers in diameter. In principle, this diamond-coated yarn is the ideal material on which to base a new generation of saws, which could be used in the solar industry for example. As Mee explains: “The new saw wires held out the promise of being far superior to traditional steel wires. Because of their high tensile strength, they can be manufactured much thinner than steel wires – and that means significantly less kerf loss.”
In the meantime, the physicist has managed to implement his idea. A joint patent application by Fraunhofer and CSIRO has already been filed for the method and corresponding products. Mee and his colleagues are currently carrying out sawing tests. “To be able to show our partners in industry the potential the technology holds,” says Mee, “we have to demonstrate how it can help solar companies to save material when processing wafers.”
Manuel Mee | Fraunhofer Research News
Atomic structure of ultrasound material not what anyone expected
21.02.2018 | North Carolina State University
Hidden talents: Converting heat into electricity with pencil and paper
20.02.2018 | Helmholtz-Zentrum Berlin für Materialien und Energie
For the first time, a team of researchers at the Max-Planck Institute (MPI) for Polymer Research in Mainz, Germany, has succeeded in making an integrated circuit (IC) from just a monolayer of a semiconducting polymer via a bottom-up, self-assembly approach.
In the self-assembly process, the semiconducting polymer arranges itself into an ordered monolayer in a transistor. The transistors are binary switches used...
Breakthrough provides a new concept of the design of molecular motors, sensors and electricity generators at nanoscale
Researchers from the Institute of Organic Chemistry and Biochemistry of the CAS (IOCB Prague), Institute of Physics of the CAS (IP CAS) and Palacký University...
For photographers and scientists, lenses are lifesavers. They reflect and refract light, making possible the imaging systems that drive discovery through the microscope and preserve history through cameras.
But today's glass-based lenses are bulky and resist miniaturization. Next-generation technologies, such as ultrathin cameras or tiny microscopes, require...
Scientists from the University of Zurich have succeeded for the first time in tracking individual stem cells and their neuronal progeny over months within the intact adult brain. This study sheds light on how new neurons are produced throughout life.
The generation of new nerve cells was once thought to taper off at the end of embryonic development. However, recent research has shown that the adult brain...
Theoretical physicists propose to use negative interference to control heat flow in quantum devices. Study published in Physical Review Letters
Quantum computer parts are sensitive and need to be cooled to very low temperatures. Their tiny size makes them particularly susceptible to a temperature...
15.02.2018 | Event News
13.02.2018 | Event News
12.02.2018 | Event News
21.02.2018 | Life Sciences
21.02.2018 | Life Sciences
21.02.2018 | Materials Sciences