The attractive method for the production of ND in liquid, in liquid-solid interface,or solids using carbon powders is Pulsed laser ablation. Thus, ND were obtained by suspending carbon powders (crystalline flake graphite, microcrystalline graphite or carbon black with particle size less than 10 µm) in a circulating liquid medium (water, alcohols, ketones, ethers, and their solutions or mixtures), bombarding the carbon powders by laser, and further purifying the product to obtain the diamond nanopowders41. This can be seen that only microcrystalline graphite transformed into diamond (cubic diamond about 5 nm) by laser into three carbon materials. This can also express that microcrystalline graphite was more superior than carbon black and crystalline flake graphite when the laser power density was 106 W/cm2. A theoretical kinetic approach was proposed to explain the nucleation and growth of nanocrystals with respect to the capillary effect of the nanometer-sized curvature of crystalline nuclei for example the ND synthesis by pulsed-laser ablating a graphite target in H2O.
The authors estimate the nucleation time, growth velocity, and the grown size of NDs from the proposed kinetic model42. Pulsed-laser irradiation of amorphous carbon films in a liquid phase at room temperature and ambient pressure led to a phase transformation from amorphous carbon to ND (4–7 nm). On the basis of the obtained results, it was finalized that laser irradiation in liquid actually opens a route toward self-assembly of surface into micro and nano structures, i.
e., functional nanostructures formation. The diamond-like carbon films with the highest sp3carbon bonding content were obtained at laser fluences of 850 to 1000 mJ/cm2 by irradiation of the polycarbyne polymer films, coated on silicon substrates, with a pulsed Nd:yttrium-aluminum-garnet laser (?= 532 nm) in argon gas atmosphere.46 Quartz substrates were used as supports in similar experiments (?= 1064 nm, ?= 20 ns, q = 4.9·108 W/cm 2) under vacuum (p = 2.
6·10?3 Pa).The effect of low power laser radiation on volume and surface microinclusions of graphite-like carbon during the CVD diamond film fabrication were studied. The simulation calculations showed that laser irradiation accelerates the processes of graphite and non-diamond phase etching43.