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Study on the Process and Properties of Perovskite Type Ceramic Coatings Prepared by Sol-Gel Method

Author: YangXiaoJie
Tutor: LiShengLi
School: Shandong University
Course: Materials Science
Keywords: Coating The composite sol - gel process Perovskite Densification
CLC: TG174.453
Type: Master's thesis
Year: 2007
Downloads: 218
Quote: 1
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Abstract

The purpose of this study is to develop a low cost, low preparation temperature, the shape of the substrate (such as large area and a complicated shape, etc.) require a small coating process. Two of the methods (composite sol - gel and sol - gel method) in the preparation of perovskite-type ceramic coating various substrates, and thermal gravimetric analysis (TG), differential scanning calorimetry (DSC), X -ray diffraction analysis (XRD), scanning electron microscopy (SEM) and other means of system of the coating preparation process and Organizations Also, hardness of the coating system on the type of process, the bonding strength and the electrical properties were studied. The results show that: the composite sol - gel method on sintered alumina substrate prepared La _0.8 Sr _0.2 the MnO ₃ coating is entirely feasible the. Optimized coating process: La _0.8 Sr _0.2 MnO ₃ powder mixed in the same component sol was stable slurry; alumina substrate with acetone and alcohol ultrasound coated sample after cleaning the substrate to be coated is immersed in the slurry by the Czochralski method, the pulling speed 1cm · min ^{-1 ; 5min, and then dried in a 120 ° C oven pre-burn for 10 minutes at 600 ℃. Repeat the above impregnation, dried, calcined process until a certain coating thickness. The remaining organic matter decomposition and finally calcined at 800 ℃ for 1 h, the perovskite phase crystallization completely. Cooling in the furnace La _0.8 Sr _0.2 the MnO ₃ sol sealing densification specific process for coating sol impregnation, dry 600 ° C pre-burn for 10 minutes, and then by calcination at 800 ℃ for 1h. XRD, SEM characterization results proved that the coating prepared on alumina matrix composite sol - gel process by La _0.8 the Sr _0.2 the MnO ₃ single-phase. Add powder significantly improved the surface quality of the coating to eliminate the cracks in the coating layer was made of pure sol. With the powder added to the increase in the amount and number of impregnation, coating thickness; powder 0.6g, surface and cross-section of the coating is continuous and smooth. In addition, with the powder added to the amount and number of impregnation increased the coating resistance decreases; increased with the Sr-doped La _1-x SrxMnO ₃ resistance decreases when x = 0.3 up to the minimum. Sol - gel process in the carbon steel substrate preparation the La _1-x the Ca _x the CrO ₃ coating optimization process: pretreatment after the carbon steel substrate (steel 20G) immersed in the precursor solution for a certain time, to the speed of 1cm · min ^{-1 remove sufficiently dried by 80 ° C, the calcined first 400 ° C 10min, repeat dipping, Finally, 800 ° C calcined 1h placed in a box furnace. The characterization results of XRD, SEM, etc. Reference, 20G steel surface coating by the ceramic layer and the oxide layer is composed of two parts, the ceramic layer is composed of La (0.7) Ca _{, CrO _{, 0.3}} single-phase composition, of a thickness of 12.5 ~ 25μm; oxide layer having a thickness of 25 to 50μm. The presence of the oxide layer affects the bonding strength between the coating and the substrate. Coating pores and increased roughness increases with the concentration of the precursor solution, the deterioration of uniformity, defects increased. Coating porosity increased significantly with the increase in pH value, the tissue was loose. With a dipping frequency and increase the holes in the coating continue to be filled, the porosity is greatly reduced, more compact and uniform coating; addition, a corresponding increase in coating thickness and bonding strength of the increase in the number of impregnation, but the frequency and immersed too will reduce production efficiency . The precursor solution concentration of 0.3mol · L ^{-1 impregnating the frequency is 6, a dense and uniform coating can be obtained.}}}

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