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
Scientists from the MSU studied new liquid-crystalline photochrom
21.08.2017 | Lomonosov Moscow State University
Silk could improve sensitivity, flexibility of wearable body sensors
21.08.2017 | American Chemical Society
Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.
As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...
Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.
Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...
For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.
While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...
An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.
The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...
A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.
Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...
16.08.2017 | Event News
04.08.2017 | Event News
26.07.2017 | Event News
21.08.2017 | Medical Engineering
21.08.2017 | Materials Sciences
21.08.2017 | Life Sciences