Preparation Of Stabilized Aluminum Titanate Film And Mullite-Aluminum Titanate Composite Film Via Non-Hydrolytic Sol-gel Route

The stabilized aluminum titanate(Al2TiO5)film was coated on the silicon carbide substrate via nonhydrolytic sol-gel method(NHSG),using anhydrous aluminum chloride and titanium tetrachloride as precursors,ethanol as oxygen donor,ethanol iron as the stabilizer,and dimethyl mixed dibasic acid(DBE)with the characteristic of environmental protection and high boiling point as solvent.The effects of the kinds and dosage,adding timing of solvent and aging time on stabilized aluminum titanate sol have firstly been studied by means of DTA-TG,XRD,SEM,viscometer and so on.Furthermore,the phase transformation of stabilized aluminum titanate xerogel powder during heat treatment was analyzed.Meanwhile,the effect of the kinds and dosage of stabilizers,the kinds of oxygen donor,and coating environment on the stabilization of aluminum titanate film,and the influence of the coating process parameters on film quality have been investigated.Moreover,antierosion performance of stabilized Al2Ti05 film to aluminum melt has also been researched.Based on the above research,mullite was introduced for doping-modification stabilization to aluminum titanate film in an innovative way,and mullite-aluminum titanate composite film has been further prepared by nonhydrolytic sol-gel method.The influences of the introducing ways of mullite,adding amounts of mullite and calcining temperature of mullite xerogel with different introducing ways on the synthesis effect of mullite-aluminum titanate composite film have been explored by means of DTA-TG,XRD,SEM,FE-SEM,FT-IR and so on.The results indicate that DBE is the optimal solvent for the stabilized aluminum titanate film prepared by NHSG.The appropriate adding timing for DBE should be before refluxing and its optimal quantity is to control Al2TiO5 molar concentration of 1.333mol/L.Meanwhile,coating at temperature of 110? and 20-110min aging time of the sol can form stabilized aluminum titanate sol which is suitable for coating.The 1:1 volume ratio of ethyl acetate and DBE mixed solvent is good for the synthesis of aluminum titanate,but the film surface exists a very small amount of crack.Ethanol,n-propyl alcohol and n-butyl alcohol are fit for preparing the stabilized aluminum titanate film as oxygen donor.The alkoxides and organic acid salts of magnesium and iron can produce heterogeneous polymerization with halogenated metal alkoxides from reaction of precursors to form heterogeneous bond M-O-M'(M being Al or Ti,and M' being magnesium or iron),which makes magnesium,iron ions enter and stabilize the aluminum titanate lattice.Using ethanol iron as stabilizer,Al2TiO5 is stable without decomposition in the range of 800-1280?,but with the temperature increasing,aluminum titanate has better synthesis effect.And with fixing the doping content of ethanol iron to 10mol%,aluminum titanate film don't decompose even at 1100? for 80h.The stabilized aluminum titanate film can be prepared in a nitrogen atmosphere at room temperature.The optimum coating process parameters are as follows:the precursor concentration of 0.3 mol/L,the dipping time for lmin,coating for 4 times,the vertical sliding velocity for 3.75mm/s.The stabilized aluminum titanate films have a good performance of corrosion resistance to aluminum melt at 1100?.Well-developed mullite crystallization can be obtained by NHSQ using ethanol as oxygen donor with optimal quantity of 0.146L/1molTEOS,as well as the heat treatment temperature for 950?.When mullite-aluminum titanate composite films are prepared via NHSG;mullite can't be prepared when the mullite sol and stabilized aluminum titanate sol mix before or after refluxing.But mullite crystallization is produced via mixture of mullite xerogel powder and the stabilized aluminum titanate sol,due to the fixation of Al-O-Si heterogeneous bond by low temperature calcination of mullite xerogel powder.The obtained mullite-aluminum titanate composite film is very dense and defect-free.Moreover,mullite particles are embedded in the aluminum titanate film.And aluminum titanate can't decompose after heat treatment at 1100? for 20h.It shows that the film obtains good thermal stability.