High-yield fabrication and properties of 1.4 nm nanodiamonds with narrow size distribution

Detonation nanodiamonds (DNDs) with a typical size of 5 nm have attracted broad interest in science and technology. Further size reduction of DNDs would bring these nanoparticles to the molecular-size level and open new prospects for research and applications in various fields, ranging from quantum physics to biomedicine. Here we show a controllable size reduction of the DND mean size down to 1.4 nm without significant particle loss and with additional disintegration of DND core agglutinates by air annealing, leading to a significantly narrowed size distribution (±0.7 nm). This process is scalable to large quantities. Such molecular-sized DNDs keep their diamond structure and characteristic DND features as shown by Raman spectroscopy, infrared spectroscopy, STEM and EELS. The size of 1 nm is identified as a limit, below which the DNDs become amorphous

Mechanical properties and microstructure evolution during deformation of ultrafine grained zirconium at low temperatures

Mechanical properties of ultrafine grained (UFG) zirconium (grain size 200 nm), produced by a combination of extrusion, wire drawing and specific annealing, were studied at temperatures 4.2 - 300K in uniaxial compression and compared with coarse grained (CG) Zr. In parallel, investigations by X-ray diffraction (texture) and transmission electron microscopy were undertaken in order to reveal the evolution of the microstructure with increasing strain. Volume fractions of twins have been determined for UFG and CG Zr. It has been found that the activity of twinning is smaller in UFG Zr in comparison with CG Zr at ambient and lower temperatures, but the contrary is true for very low temperatures (4.2K), where twinning increases with decreasing grain size. The influence of twinning on mechanical properties of UFG Zr has been discussed, too