Sol-gel preparation of hard transparent coatings containing nano-quartz for hardening polycarbonate substrate.

In the present work, various metal alkoxides such as tetraethoxysilane, zirconium(IV) propoxide, aluminum tri(sec-butoxide), and trimethyl borate (TMB) were used to successfully prepare homogenous transparent sols at room conditions. GPTMS was used add more flexibility. The metal alkoxides sols were prepared individually and then mixed together. Then the final sol was applied on polycarbonate (PC) substrate by dip-coating method. The thin film was completely transparent and adhesive to the PC substrate. The final obtained mixture sol was characterized by XRD, TEM, HR-TEM, and ATR-FTIR methods. The thin film coated on the PC substrate was examined by XPS, FE-SEM, elemental mapping EDS, UV/Vis spectroscopy, and nano-indentation/nano-scratch methods. XRD patterns showed some sharp peaks that suggested the formation of crystal structures attributed to quartz, dumortierite, kaolinite and zircon. As well as, there was a broad weak peak for amorphous silica. TEM micrographs showed nanoparticles of the size about 5 nm. HR-TEM micrographs proved the formation of the nano-quartz under ambient condition without any surfactant. FE-SEM micrographs proved that the thin film was smooth and crack-free. XPS patterns proved the formation of silica and zircon in the thin films regarding binding energies. Hardness and elastic modulus indicated an improvement.