Abstract
We continue here our previous work where SD powders were significantly strengthened by irradiation with electrons of lower energy under smaller dose. Previous results were obtained from the crushing strength analysis, no XRD was applied. In present work, powders of synthetic diamond with low strengthwere sorted on sets with different grain size. As established, the sets had various crushing strengths and morphology. They were irradiated with high energy electrons (6.5 MeV, D = 2 × 1019 and D = 6 × 1019 cm?2, Tirr = 450 K) and analyzed using XRD (CuKα) before and after irradiation. Nonlinear dependences a(Θ) = f{R(Θ), where a(Θ) is lattice constant and R(Θ) is Raily function, and the discovered extra-splits (additional to α1-α2-doublets on CuKα) of basic peaks in XRD patterns from the SD sets, testified that crystal lattice of diamond in sets was variously distorted, like of cBN doped with rare earth elements. As established, the first irradiation led to decreasing distortions, the more significantly the higher initial strength of the set. The second irradiation produced softening and increasing distortions of crystal lattice of diamond, the more effectively the less initial strength of diamond. XRD allows indirectly to presort synthetic diamond off the material with critically low relative mechanical strength as well as evaluate resistance of diamond crystal lattice against heavy irradiation and other external impacts.
Highlights
Diamond as super hard material is widely used in industrial applications
XRD patterns from all synthetic diamond (SD) sets were represented by (111), (220), (311), (331) basic peaks related to diamond
It is known that for a perfect crystal lattice, dependence of a (= Θ) f {R (Θ)} is linear, where a (Θ) is a lattice constant and R (Θ) is Raily function, both calculated for each peak of XRD pattern from a perfect crystal lattice
Summary
Diamond as super hard material is widely used in industrial applications. As wide band gap semiconductor (Eg = 5.5 eV) diamond in natural (ND) and synthetic (SD) forms is used in electronic devices. (2015) XRD Evaluation of Relative Mechanical Strength and Irradiation Resistance of Synthetic Diamond. Due to defects and impurities, characteristics (e.g., thermal conductivity, mechanical strength, radiative resistance and other macro-properties) of synthetic diamond (SD) and cBN are lower than that expected. As shown in [3], ferromagnetic impurities can be introduced into SD powders of low strength in larger concentration than nitrogen, and the non-uniform distribution of the impurities in crystal lattice of SD results in variation of mechanical strength of the material. We refer to [8], where authors by use of precise diffractometry, investigated (440) reflections in XRD pattern from different faces of pure single crystal of synthetic diamond. In XRD patterns from the distorted cubic crystal lattice appear extra-splits of basic peaks of cubic structure. On the basis of the representation, we try to make judgment about relative strength of irradiated SD powders and even about strength of SD of any morphological form in coming work
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