Study On Preparation Of Zirconium Silicate Film And Its Anti-alkali Corrosion And Antioxidant Properties

In this study,zirconium silicate（Zr Si O₄）films were successfully prepared on the monocrystalline silicon substrates and Si C substrates via using non hydrolytic sol-gel method combining dip coating process using zirconium n-propanol as zirconium source,tetraethyl orthosilicate as silicon source,lithium fluoride as mineralizer,n-propanol as solvent and anhydrous citric acid（ACA）as cosolvent.The effect of process parameters such as prepareation of sol,dip-coating,drying temperature and heat-treatment on the synthesis of Zr Si O₄ and the quality of Zr Si O₄film were investigated by differential thermal analysis and thermogravimetry（DTA-TG）,X-ray diffraction（XRD）,Fourier transform infrared spectromemter（FTIR）,Field emission scaning electron microscopy（FE-SEM）and Atomic force microscope（AFM）,respectively.Additionally,the alkali corrosion resistance of Zr Si O₄ films covered on the surface of monocrystalline silicon substrates,the thermal shock resistance and high temperature oxidation resistance of Zr Si O₄films covered on the Si C substrate were also investigated.The results showed that adding appropriate amount of ACA could effectively promote the dissolution of Li F and facilitated the full contact reaction between silicon source and zirconium source,which was contributed to the preparation of pure phase Zr Si O₄.When the molar ratio of ACA to zirconium n-propanol was 1.1,the concentration of the precursor was 0.1 mol/L and the aging time of sol was 24 h,the stable sol suitable for the coating could be obtained.Then,dip coating process on the single crystal silicon at 1 mm/s of lifting rate were proceeded and coating for one time.Finally,uniform and dense Zr Si O₄ films were obtained when the dry temperature was40℃for 2 hours and heat treatment at 1000℃for 1 hour（the heat rate from room temperature to 500℃was 1℃/min）The monocrystalline silicon coated with Zr Si O₄ film was soaked in 40%Na OH solution for 42 h at 40℃.Only a small pit corrosion was found on the film surface and the mass changed a little with the corrosion time.The mass loss of monocrystalline silicon coated with film was only0.17%.It showed that the Zr Si O₄ film had excellent alkali corrosion resistance.It was more difficult for coating on polycrystal Si C substrate compared to silicon wafer,because of Si C substrate has rough surface and many holes.The optimized preparation process of sol and dip-coating process were realized by orthogonal experiment and single factor experiment on the basis of the surface coating process of silicon wafer,and the fine Zr Si O₄ film could be prepared on the surface of Si C substrate via adding the surfactant of Tetra Butyl Ammonium Bromide（TBAB）and increasing the times of coating.The quality of the film could be improved effectively and crack-free Zr Si O₄ film with a thickness of about 500 nm could be obtained when the molar ratio of ACA to zirconium n-propanol was 1.1,the precursor concentration was 0.1 mol/L,aging time was 24 h,the coating times was 5 and the amount of TBAB was 7 wt.%.The Zr Si O₄ film had better thermal shock resistance when the Si C substrate uncoated of film occurd fracture carry on quenching from 1000℃to room temperature while Si C substrate coated of film occurd fracture in carry on quenching from 1200℃to room temperature.The weight increment of the average unit area of Si C with coated Zr Si O₄ film at 1450℃for 60 h was only 2.2283×10^-4 g/cm²,but that of the uncoated Zr Si O₄ film was 7.2357×10^-4g/cm²,indicating that the Zr Si O₄ film has excellent oxidation resistance at high temperature.