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Nanocrystalline diamond has been synthesized on a mirror-polished Si(001) substrate by means of direct ion beam deposition. Low-energy (80–200 eV) hydrocarbon and hydrogen ions, generated in a Kaufman ion source, were used to bombard the substrates. The bombarded samples were characterized by high-resolution transmission electron microscopy and Raman spectroscopy. Nanocrystalline diamond particles of random orientation were observed in a matrix of amorphous carbon film on the Si(001) substrate. The size of the nanocrystalline diamond particles varied in the range of 50–300 Å. The mechanism of ion-induced formation of nanocrystalline diamond is discussed.

Transmission electron microscopy analysis of the oriented diamond growth on nickel substrates Diamond films grown by hot filament chemical vapor deposition from a solid carbon source Textured diamond films have been grown on silicon ͑111͒ substrate by using hot filament chemical vapor deposition. A graphite plate immersed in hydrogen was used as the carbon source rather than the conventional gaseous methane source. During the nucleation period, a negative bias relative to the filaments was applied to the substrate. An epitaxial ␤-SiC layer was deposited during the bias treatment. Textured diamond film was subsequently grown on the ␤-SiC layer from the mixture of hydrogen and hydrocarbon species etched from the graphite.

The cause of the accelerated corrosion of zirconium alloys by hydrides is studied by investigating the corrosion of three section planes of Zr-2.5Nb tubes with different texture: the longitudinal normal section (LS) plane, the transverse normal section (TS) plane, and the radial normal section (RS) plane. Corrosion tests were conducted on those section planes taken from the unhydrided and prehydrided Zr-2.5Nb tubes with up to 450 ppm H in water at 350°C or in steam at 400°C. For Zr-2.5Nb tube with a strong circumferential texture, the deleterious effect of hydrides on enhanced corrosion was most striking on the LS specimen, while beneficial and little hydride effect on the corrosion was observed on the TS and RS specimens, respectively. However, for Zr-2.5Nb tube with a comparatively radial texture, the deleterious effect of hydrides on enhanced corrosion was observed on all the three section planes. The lattice broadening and the interplanar spacing in the zirconium matrix were measured by using X-rays on those section planes taken from Zr-2.5Nb tubes with a circumferential texture before and after charging with hydrogen. The precipitation of hydrides in the Zr-2.5Nb tube subjected the LS plane to residual tensile stress, expanding the zirconium lattice in the LS, and the TS plane to compressive stress, contracting it in the TS. Based on these results, the corrosion acceleration by hydrides is discussed by correlating the change in the zirconium lattice distance or lattice distortion including residual stress and the corrosion on each plane before and after charging with hydrogen. This finding leads us to the conclusion that the major controlling factor to the corrosion of zirconium alloys is the lattice coherency between the metal and the oxide.