电流密度对MgO-ZnO陶瓷薄膜结构和热控性能的影响

doi:10.15541/jim20170057

摘要/Abstract

摘要：

在Zn(H₂PO₄)₂电解液中, 利用微弧氧化技术在AZ31镁合金表面原位生长MgO-ZnO热控陶瓷薄膜, 研究了电流密度对薄膜结构组成、结合强度和热控性能的影响, 以及紫外辐照作用下薄膜太阳吸收率的变化规律。结果表明：薄膜主要由MgO、ZnO和非晶态物质组成, 随着电流密度增大, 微孔数量逐渐减少而粗糙度逐步增大, 其厚度、结合强度和发射率先增大后减小, 而太阳吸收率则先减小后增大。电流密度9 A/dm²时所得薄膜的结合强度达到最大12.6 MPa, 且热控性能最佳, 其发射率为0.872, 太阳吸收率为0.363; 且随着紫外辐照时间延长, 此薄膜太阳吸收率先升高而后趋于平缓。研究结果为制备良好结合强度和抗紫外辐照能力的低吸收高发射热控薄膜提供技术支持。

关键词: 微弧氧化, 热控薄膜, ZnO, 紫外辐照

Abstract:

MgO-ZnO thermal control coatings were prepared on AZ31 magnesium alloy using micro-arc oxidation (MAO) in the electrolyte containing Zn(H₂PO₄)₂. The influence of current density on the microstructure, composition, adhesive strength, and thermal control performances of MAO coatings were investigated, and the variation of solar absorptance (α_s) was examined at different ultraviolet irradiation time. The results show that the MAO coating is composed of MgO, ZnO and a few amorphous phases. With an increase of current density, the number of pores gradually decreases while the roughness increases. As the thickness, adhesion and emittance (ε) firstly increase and then decrease, the changing tendency of α_s shows the opposite. When the current density is set at 9 A/dm², the MAO coating exhibits a stronger adhesive strength of 12.6 MPa, a higher ε of 0.872 and a lower α_s of 0.363. Moreover, the ultraviolet irradiation test reveals that the α_s increases followed by leveling off with increasing irradiation time. This process provides a technical support for fabricating thermal control coating with excellent adhesion, low α_s/ε ratio, and good anti-ultraviolet irradiation.

Key words: micro-arc oxidation, thermal control coating, ZnO, ultraviolet irradiation

中图分类号:

TQ174

李航, 卢松涛, 秦伟, 吴晓宏. 电流密度对MgO-ZnO陶瓷薄膜结构和热控性能的影响[J]. 无机材料学报, 2017, 32(12): 1292-1298.

LI Hang, LU Song-Tao, QIN Wei, WU Xiao-Hong. Current Density on Microstructure and Thermal Control Performances of MgO-ZnO Ceramic Coatings[J]. Journal of Inorganic Materials, 2017, 32(12): 1292-1298.

图/表 10

图1 不同电流密度下制备薄膜的表面SEM照片

Fig. 1 SEM images of coatings obtained at different current densities^(a) 3 A/dm2; (b) 6 A/dm2; (c) 9 A/dm2; (d) 12 A/dm2

图2 不同电流密度下所得薄膜的截面SEM照片

Fig. 2 Section images of coatings obtained at different current densities^(a) 3 A/dm2; (b) 6 A/dm2; (c) 9 A/dm2; (d) 12 A/dm2

图3 不同电流密度下制备薄膜的XRD图谱

Fig. 3 XRD patterns of coatings prepared at different current densities

图4 在电流密度9 A/dm2下所得薄膜的XPS图谱

Fig. 4 XPS spectra of coatings prepared at 9 A/dm2(a) Survey scan; (b) Zn2p; (c) O1s

图5 在电流密度9 A/dm2下所得薄膜的TEM分析结果

Fig. 5 TEM analysis of MAO coatings prepared at 9 A/dm2(a) TEM image; (b) Electron diffraction pattern

图6 电流密度对薄膜粗糙度的影响

Fig. 6 Effect of current density on the roughness of coatings

图7 电流密度对薄膜结合强度的影响

Fig. 7 Effect of current density on adhesion strength of coatings

图8 电流密度对薄膜发射率的影响

Fig. 8 Effect of current density on the emissivity of the coating

图9 不同电流密度下薄膜的漫反射光谱曲线

Fig. 9 Diffuse reflectance spectra of coatings prepared under different current densities

图10 紫外辐照前后薄膜的漫反射光谱曲线

Fig. 10 Diffuse reflectance spectra of the coatings before and after ultraviolet irradiation

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