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A series of diamond crystals doped with hydrogen is successfully synthesized using LiH as the hydrogen source in a catalyst-carbon system at a pressure of 6.0 GPa and temperature ranging from 1255 °C to 1350 °C. It is shown that the high temperature plays a key role in the incorporation of hydrogen atoms during diamond crystallization. Fourier transform infrared micro-spectroscopy reveals that most of the hydrogen atoms in the synthesized diamond are incorporated into the crystal structure as sp3 -CH2-symmetric (2850 cm−1) and sp3 CH2-antisymmetric vibrations (2920 cm−1). The intensities of these peaks increase gradually with an increase in the content of the hydrogen source in the catalyst. The incorporation of hydrogen impurity leads to a significant shift towards higher frequencies of the Raman peak from 1332.06 cm−1 to 1333.05 cm−1 and gives rise to some compressive stress in the diamond crystal lattice. Furthermore, hydrogen to carbon bonds are evident in the annealed diamond, indicating that the bonds that remain throughout the annealing process and the vibration frequencies centred at 2850 and 2920 cm−1 have no observable shift. Therefore, we suggest that the sp3 C-H bond is rather stable in diamond crystals.

To extend the kind of diamond and solve the low life of diamond tools because of the insufficiency of holding force, the strip-shape diamond with more than 2.5 in length-diameter ratio and 0.81.0 mm in length is synthesized by optimizing FeNi based catalyst composition and using the technology in the China-type cubic anvil high pressure apparatus. Because of the unique morphology, the threshing phenomenon appearing in the using of diamond tools is controlled effectively. Furthermore, we find that the growth rate of strip-shape diamond is much faster than that of the conventional diamond. Strip-shape diamond morphology and catalyst composition around the growing diamond crystal are characterized by SEM and EDS. The results indicate that the facets of diamond crystal are elongated along {100} and {111} faces and catalyst compositions around the growing diamond crystal become segregated. On this basis, we illustrate the growth mechanism of strip-shape diamond.