• A Jafari

      Articles written in Bulletin of Materials Science

    • Effect of SiO$^{2-}_{3}$/OH on plasma electrolytic oxidation of Ti–5Mo–4V–3Al

      M Asadi Mehdi Attarchi M Vahidifar A Jafari

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      Plasma electrolyte oxidation (PEO) was utilized to produce thick films on titanium and Ti–5Mo–4V–3Al alloys by immersing them in various solutions of Na2SiO3 and KOH with different concentrations to investigate the effect of SiO$^{2-}_{3}$/OH relations on the morphology and formed phases by utilizing SEM and XRD. Corrosion resistance is evaluated by open circuit potential (OCP) variation of samples in NaCl 3.5% and potentiodynamic polarization. The results show that the unstable film is formed by using more aggressive PEO electrolyte. By increasing this ratio, pore size varied from fine to coarse and the rate of corrosion decreased and OCP became more positive. The best protective film was formed in SiO$^{2-}_{3}$/OH ratio of 1.

    • The effects of growth time on the quality of graphene synthesized by LPCVD

      A Jafari R Alipour M Ghoranneviss

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      The graphene has several unique characteristics and many applications in all fields. Some of these characteristics are the quantum Hall effect at room temperature, the ambipolar field effect, the optical properties, the high electron mobility and the best electronic properties. The ability of fabricating large-area monolayer graphene is hindering its application. In this paper the effects of growth time on the quality of graphene synthesized by lowpressure chemical vapour deposition (LPCVD) has been investigated. Large-areamonolayer graphene is synthesized on polycrystalline Cu foil (∼1 cm2) by controlled experiment LPCVD at different growth times (30, 60, 120 and 150s). The synthesized graphene was characterized using Raman spectroscopy and scanning electron microscopy (SEM). The Raman spectrum showed a 𝐼G/𝐼2D ∼0.2 ratio which indicates that all samples are single-layer graphene and the SEM images demonstrate that the domain size increases when the growth time increases. The growth mechanism of LPCVD of graphene on Cu and the mechanisms governing the Raman scattering process in the films are also discussed. The control over the grain size of synthesized graphene by adjusting the growth time (achieved in this work), provides useful insights for understanding the growth mechanism of LPCVD of graphene and for optimization of the growth process to further improve the quality of graphene. Finally, with analyses of all investigations we found that the quality and the large-area of monolayer graphene improved by increasing the growth time and it is very important consequence for all those who do research on graphene.

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