Diamond can turn flexible when made into ultra-fine needles
Diamond is considered to be the hardest natural material but it can turn flexible when grown in extremely thin, needle-like shape.
Researchers from The Massachusetts Institute of Technology (MIT) demonstrated that diamond needles – about a thousand times thinner than a hair strand – can be bent and stretched up to nine percent without breaking. The needles can return to their original state once the pressure is removed.
Diamond are usually found in bulk form and can stretch only below one percent. If we try to bend them beyond this limit, they may break. But researchers have found that diamond needles can be deformed by exerting pressure. Before that, they were mostly able to compress diamonds.
“We developed a unique nanomechanical approach to precisely control and quantify the ultra large elastic strain distributed in the nanodiamond samples.” Co-author Yang Lu from Chinese University of Hong Kong said.
Researchers used a diamond probe to put pressure on the sides of the diamond nano-needles, which were grown through a special process called chemical vapor deposition and measured how much each needle could bend. Using a scanning electron microscope, researchers recorded the whole process in real time. They also ran hundreds of computer simulations to understand and explain how the diamond needles underwent large elastic strains.
“Our results were so surprising that we had to run the experiments again under different conditions just to confirm them. We also performed detailed computer simulations of the actual specimens and bending experiments to measure and determine the maximum tensile stress and strain that the diamond nano-needles could withstand before breaking,” said Prof Subra Suresh, from NTU Singapore.
“This work also demonstrates that what is usually not possible at the macroscopic and microscopic scales can occur at the nano-scale where the entire specimen consists of only dozens or hundreds of atoms, and where the surface to volume ratio is large.”
