Preparation And Application Properties Of Alumina Film

Alumina film has the advantages of high mechanical strength,low thermal conductivity and good chemical stability,which makes it have a broad application prospect in electronics,thermal barrier and anticorrosion fields.However,the existing preparation methods such as atomic layer deposition,magnetron sputtering and anodic oxidation have some defects,such as expensive equipment and harsh preparation conditions.Therefore,this study intends to replace the existing method with spin-coating calcination method to prepare alumina film in line with the application requirements as the goal.Alumina powder is prepared by non-hydrolyzed and hydrolyzed sol-gel method,and the effect of preparation method on the phase transition path and powder morphology of the precursor gel to alumina powder is explored in this study;On this basis,alumina film or coating is prepared on the surface of LLZO ceramic sheet and stainless steel plate by rotary coating-calcination method.The optimum preparation process and its influence on the ionic conductivity of LLZO ceramic sheet and anti-corrosion performance of alumina coating are investigated.The details are as follows:(1)Alumina powders are prepared by non-hydrolyzed and hydrolyzed sol-gel method.The phase transition paths and morphology of the precursor gel to the alumina powder in two methods are studied from three different angles,such as sol-gel process,calcination process and powder morphology.The results show that the precursor gel first occurs the nucleophilic substitution reaction and forms the Al-O-C bond,and then occurs the polycondensation reaction and forms the Al-O-Al bond during the sol-gel stage of non-hydrolyzed sol-gel method.At the calcination stage,the crystal evolution path from precursor gel to alumina powder is as follows:Ethylene glycol aluminum?amorphous(600?)??-Al₂O₃(800?)?coexistence of?-Al₂O₃,?-Al₂O₃ and?-Al₂O₃(1000?)??-Al₂O₃(1200?).The morphology changes from irregular block(600?)?flake(800?)?flake melting to irregular particles(1000?and 1200?).In contrast,the precursor gel first occurs the hydrolysis reaction and forms the Al-O-H bond,and then occurs the polycondensation reaction and forms the Al-O-Al bond during the sol-gel stage of hydrolyzed sol-gel method.The calcination temperature of?-Al₂O₃ phase is 600?,which is obviously lower than that of non-hydrolyzed sol-gel method.And when the temperature is below 1000?,the samples are irregular block;When the temperature rises to 1200?,fibrous structures with a length of2.47?m and a diameter of 316 nm appear on the massive solid surface.(2)The precursor sol is prepared by hydrolyzed sol gel method,and then the alumina film is prepared by spin coating calcining method.The preparation process is studied in two aspects:the former drive film and the alumina film.The results show that the surface of the precursor film with a loading rate greater than 1.50%is still smooth and flat without obvious cracks after the addition of glycerol;When the rotating speed is higher than 120 kr/min,the loading rate of precursor film tends to be stable;The film surface is flat without obvious cracks;the loss rate is basically zero and the stability is good after 15 days.When the calcination temperature is 200?,amorphous alumina can be prepared.When the loading rate is 1.50%,the surface of amorphous alumina film is uniform and compact without crack.The cross section is tightly bonded with LLZO ceramic sheet,and the thickness reaches 13.59?m.The ionic conductivity reaches the maximum,which is 3.29×10^-4 S·cm^-1?(3)Continue to prepare alumina coating by rotary coating-calcination method,and study its anticorrosion performance from three aspects of load rate,calcination temperature and soaking time.The results show that the loading rate of the precursor coating is proportional to the number of spin coating in a certain range,and when the loading rate increases to 0.205%,the surface of the alumina coating sample is not uniform and there are many stacking phenomena.In addition,the loading rate and calcination temperature have little effect on the surface properties of alumina coating samples.By comparing the anti-corrosion performance of alumina coating samples prepared under different loading rates and calcination temperatures,it can be seen that the anti-corrosion performance of alumina coating samples is the best when the loading rate is 0.155%and the calcination temperature is 300?.After soaking for 20 days,the anti-corrosion performance decreased,but it was still higher than that of the non-soaked empty steel plate.