Browsing by Author "Thabethe, T.T."

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    Crystal structure changes and weight kinetics of silicon-hexaboride under gamma irradiation dose
    (Results in Physics, 2018) Mirzayeva, M.N.; Jabarova, S.H.; Asgerova, E.B.; Mehdiyeva, R.N.; Thabethe, T.T.; Biira, S.; Tiep, N.V.
    The silicide hexaboride (B6Si) was irradiated with 60Co at room temperature to study the structural changes and weight kinetics. The B6Si samples were irradiated using a gamma source with a dose rate (D) of 0.27 Gy/s. At adsorption dose range of 9.7, 48.5, 97, 145.5 and 194 kGy. The samples were analysed using X-ray diffraction (XRD) and Energy dispersive spectroscopy (EDS) to study the microstructural and composition changes. The XRD results showed the crystalline structure for the sample before and after irradiation (with gamma irradiation dose 9.7, 48.5 and 97 kGy). Amorphization of the sample began at the gamma irradiation dose of 145.5 kGy. Increase in gamma irradiation dose had an inverse effect on the activation energy and had a directly proportional effect on the lattice volume.
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    Investigating the structural changes induced by SHI on W–SiC samples
    (Vacuum, 2020) Thabethe, T.T.; Ntsoane, T.P.; Biira, S.; Njoroge, E.G.; Hlatshwayo, T.T.; Skuratov, V. A.; Malherbe, J.B.
    The structural modification of tungsten-SiC samples irradiated with Xe26þ swift heavy ions (SHIs) was investigated. Tungsten (W) thin films were deposited on 6H–SiC using e-beam. After deposition, the W–SiC samples were irradiated by 167 MeV Xe26þ ions to fluences of 1012 cm􀀀 2, 1013 cm􀀀 2 and 1014 cm􀀀 2 at room temperature. The sample composition, phase identification, residual stress component and surface morphology were investigated with Rutherford backscattering spectrometry (RBS), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results indicated that the as-deposited samples were composed of W and SiC, with no reaction between them. The samples irradiated to a fluence of 1012 cm􀀀 2 showed that a reaction between W and SiC took place resulting in the formation of WSi2 and WC phases. The samples irradiated to fluences of 1013 and 1014 cm􀀀 2 showed further reactions between W and SiC with WSi2 and WC being the only phases formed. The SiC substrate had bi-axial compressive stress which did not excess 700 MPa after irradiating to the highest fluence. The W layer deposited on SiC was flat and homogeneous after deposition. A textured surface with identifiable grains was observed after the SHI irradiations.
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    Investigating the thermal stability of the chemical vapour deposited zirconium carbide layers
    (Journal of Alloys and Compounds, 2020) Biira, Saphina; Thabethe, T.T.; Hlatshwayo, T.T.; Bissett, H.; Ntsoane, T.; Malherbe, J.B.
    The effect of thermal treatment on zirconium carbide (ZrC) layers deposited by chemical vapour deposition process was investigated using X-ray diffraction (XRD), Raman spectroscopy, nanoindention and scanning electron microscopy (SEM). The ZrC layers deposited at 1400 C (composed of 96% ZrC and 4% C) were annealed at 1500, 1600, 1700 and 1800 C for 2 h under high vacuum of 2.6 10 7 mbar. After annealing, the lattice constant and the average crystallite sizes were found to increase whereas the lattice strain and dislocation density decreased. The preferred orientation of the as-deposited layers was (220); it changed to (200) when annealed at 1500 C and 1600 C. At annealing temperature of 1700 C and 1800 C, the preferred orientation was (220) just like for the as-deposited ZrC layers. From Raman spectroscopy analysis, the ID/IG ratio reduced from 0.694 to 0.414 with annealing temperature indicating an improvement in crystallinity level and a decrease in the defects in the carbon material in the ZrC layers. The hardness of the layers was found to decrease slightly with annealing temperature from 26.4 ± 0.6 GPa to 21.3 ± 0.5 GPa. Some voids initially present in the as-deposited ZrC layers closed up and particles increased in size with annealing temperature.
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    Irradiation effects of swift heavy ions on palladium films deposited on 6H-SiC substrate
    (Nuclear Inst. and Methods in Physics Research B, 2019) Thabethe, T.T.; Nstoane, T.; Biira, S.; Njoroge, E.G.; Hlatshwayo, T.T.; Skuratovd, V.A.
    The irradiation effect of swift heavy ions on palladium (Pd) films deposited on 6H-SiC was investigated. The samples were irradiated by Xe26+ ions with the energy of 167 MeV at fluences of 1×1013 cm−2 and 3×1014 cm−2 at room temperature. Phase identification, residual stress and surface morphology were investigated with X-ray diffraction (XRD) and scanning electron microscopy (SEM). The XRD results showed that the as-deposited sample was composed of Pd and SiC with no evidence of a reaction between Pd and SiC. No reaction was observed for the lower irradiation fluence, only an increase in the Pd peak intensities was observed indicating improvement in the crystallinity of the material. A reaction between Pd and SiC forming PdSi and Pd2Si was observed after irradiation at a fluence of 3×1014 cm−2. The stress measurements indicated that the films were having tensile and biaxial stress not exceeding 200 MPa. A decrease in stress values was observed with an increase in irradiation fluence. The surface morphology of the as-deposited was flat and composed of small granules. There was an increase in granule sizes due to irradiation at 1×1013 cm−2. Irradiating at 3×1014 cm−2 caused grain agglomeration and clustering.