添加Y(NO_3)_3电解液体系MAO陶瓷层组织和隔热性能研究

Study of Microstructure and Heat Insulation Properties of PEO Ceramic Coatings Formed in Electrolyte with Y(NO_3)_3

为研究电解液中Y（NO3）3对微弧氧化陶瓷层组织、生长速率及隔热性能的影响,通过微弧氧化技术在锆盐体系和锆钇盐体系电解液中于Al-Si合金表面制备ZrO2-Al2O3陶瓷层和Y2O3-ZrO2-Al2O3陶瓷层.采用环境扫描电子显微镜和X射线衍射仪分别对陶瓷层进行了表面、截面形貌分析,以及物相组成分析.利用涡流测厚仪测量不同反应时间段的膜厚,分析两种体系陶瓷层生长速率.通过自制隔热测试装置对两种不同体系陶瓷层进行了隔热性能测试.结果表明:ZrO2-Al2O3陶瓷层表面由胞状熔融物烧结而成,粗糙度较大,并分布着孔径较大的放电通道,膜厚约20μm;而Y2O3-ZrO2-Al2O3陶瓷层表面由细小颗粒组成,粗糙度较小,且陶瓷层更加致密,厚度增大到28μm.两种体系陶瓷层均形成了ZrO2及Al2O3相,在约20°30°范围之间出现明显的'馒头包'现象,说明陶瓷层中均含有非晶成分;但锆钇盐体系陶瓷层中形成了钇部分稳定锆的固溶体（Y2O3和Y0.15Zr0.85O1.93）,且Y2O3-ZrO2-Al2O3陶瓷层的衍射峰'馒头包'现象更为严重,非晶成分含量更高,说明电解液中Y（NO3）3的加入提高了反应温度.Y2O3-ZrO2-Al2O3陶瓷层生长速度大于ZrO2-Al2O3陶瓷层,主要表现为向外生长厚度明显增大.ZrO2-Al2O3陶瓷层与Y2O3-ZrO2-Al2O3陶瓷层的隔热温度分别为45.9℃和53.4℃,说明后者具有更优的隔热效果.

Effects of Y (NO3 )3 in electrolyte on the microstructure,growth rate and heat insulation properties of PEO ceramic coatings were investigated by preparing ZrO2-Al2 O3 ceramic coating and Y2 O3-ZrO2-Al2 O3 ceramic coating on Al-Si alloys through plasma electrolytic oxidation(PEO)technique in zirconium salt solution and zirconium yttrium salt solution,respectively.The surface and cross-section morphologies and the phase composition of the coatings were characterized by environmental scanning electron microscope(ESEM)and X-ray diffraction(XRD).The thicknesses in different stages of reaction were measured by eddy current thickness meter to study the growth rate of the coatings formed in the two different solution systems.Last,the heat insulation properties were tested through self-made heat insulation testing device.The result indicated:The surface of the ZrO2-Al2 O3 ceramic coating was composed of cystiform sintered melts,and was rather coarse with many discharge channels of large diameter scattered on it evenly.Its thickness was about 20 μm.However,the surface of the Y2 O3-ZrO2-Al2 O3 ceramic coating was smooth and dense,which was consisted of fine particles.And the thickness of it increased to around 28 μm.Both of the two kinds of ceramic coatings included phases of ZrO2 and Al2 O3 ,and the diffraction peaks appeared the phenomenon of “steamed bun peak”in 2θ range of about 20°~ 30°,which indicated apparently a certain proportion of amorphous components.Moreover,solid solution of yttrium partially stabilized zirconium(Y2 O3 and Y0.15 Zr0.85 O1 .93 )also was found in the coating treated in zirconium yttrium salt solution.The Y2 O3-ZrO2-Al2 O3 ceramic coating displayed heavier "steamed bun peak" phenomenon,meant higher content of amorphous components in it,also suggested that the addition of Y(NO3 )3 in the electrolyte improved the reaction temperature.The result of growth rate and mode showed that the Y2 O3-ZrO2-Al2 O3 ceramic coating growed faster than ZrO2-Al2 O3 ceramic coating,mainly due to the obviously increased thickness of the outward growth.Finally,the heat insulation property test concluded that the heat insulation temperature of ZrO2-Al2 O3 ceramic coating and Y2 O3-ZrO2-Al2 O3 ceramic coating was 45.9 ℃ and 53.4 ℃,respectively,which illustrated the latter one had a better heat insulation effect.