Nanocrystalline materials show a higher strain-rate sensitivity in contrast to the conventional coarse-grained materials and a different grain size dependency. To explain these phenomenon, a finite element model is constructed that considers both grain interior and grain boundary deformation of nanocrystalline materials. The model consist of several crystalline cores with different orientations...

The mechanical strengths of nano-scale individual crystal or nanopolycrystalline metals, and other dimensionally-related materials are increased by an order of magnitude or more as compared to those values measured at conventional crystal or polycrystal grain dimensions. An explanation for the result is attributed to the constraint provided at the surface of the crystals or, more importantly, a...

To better understand the mechanical response of ultrananocrystalline diamond (UNCD) and its grain boundary mechanism, a numerical study is performed of the specimen size and rate effects on the mechanical properties of single crystal diamond and UNCD films under uniaxial and shear loading paths, respectively. To compare with the UNCD films, single crystal diamond blocks of various sizes under t...

A novel method is presented for growth of polycrystalline silicon films on amorphous substrates at temperatures of 540-575 “C. Grain nucleation and grain growth are performed in two steps, using Si nanocrystals as nuclei (“sceds’“,L The nanocrystal seeds are produced by excimer laser photolysis of disilane in a room temperature flow cell. Film (grain) growth occurs epitaxially on the seeds in a...

nano-sized batio3 powders with particular nb concentrations were prepared by rotary- hydrothermal (rh) method. hydrothermal method was used at 180 °c for 5 hours with new ti pressure and the teflon vessel was rotated at a speed of 160 rpm during the hydrothermal reaction. new hydrothermal method was used instead of previous solid state reaction for the system batio3±nb2o3 in high temperature to...

Lead-free bismuth sodium titanate zirconate (Bi0.5Na0.5Ti1-xZrxO3 where x = 0.20, 0.35, 0.40, 0.45, 0.60, and 0.80 mole fraction) [BNTZ] ceramics were successfully prepared using the conventional mixed-oxide method. The samples were sintered for 2 h at temperatures lower than 1,000°C. The density of the BNTZ samples was at least 95% of the theoretical values. The scanning electron microscopy mi...

The ability to produce large, continuous and defect free films of graphene is presently a major challenge for multiple applications. Even though the scalability of graphene films is closely associated to a manifest polycrystalline character, only a few numbers of experiments have explored so far the electronic structure down to single graphene grains. Here we report a high resolution angle and ...