Alpha alumina synthesis by laser treatment of bi-phasic nanowires

Al/Al ₂ O ₃ bi-phasic nanowires (Al-core/Al ₂ O ₃ shell) are prepared by chemical vapor deposition (CVD) using single source precursor (SSP) approach. Such bi-phasic nanostructures were heat-treated using an argon laser operating at visible wavelengths. Al core seems to act as an active binder, which might decrease the inhomogeneous heating and thermal gradients. Nanoindentation method is used to estimate the hardness of the laser treated surfaces. Hardness values and pop-in behaviour in loading-curve indicate a formation of α-Al ₂ O ₃ with very low defect density. It is believed that Al/Al ₂ O ₃ bi-phasic layers exhibit a dynamic change by transforming into alumina after the laser irradiation and this leads to alteration of the optical absorption especially in the visible wavelength region. Following the full transformation to alumina, the surface reflects back the laser light which hinders inhomogeneous and excessive heating. In this context, laser treatment of Al/Al ₂ O ₃ bi-phasic nanowires provides a controlled sintering process which can open up various applications in different fields.