316L 不锈钢 TIG 焊接接头在 H2 S 溶液中的钝化性能

目的研究316L不锈钢TIG焊接接头各区域在不同浓度H2S溶液中的钝化及耐蚀性能差异。方法在H_2S质量浓度为0.05,0.1,0.2,0.4,0.8 g/L的H2S溶液中,通过极化曲线、恒电位阶跃、阳极极化、交流阻抗等方法,分别研究316L奥氏体不锈钢TIG焊接接头的母材区和焊缝区的钝化性及耐蚀性能。结果随着H_2S浓度的增加,焊接接头母材区和焊缝区的钝化性能都所有降低,电化学活性都明显升高,且腐蚀电位逐渐降低,腐蚀电流密度有所增加。交流阻抗拟合结果显示,母材区和焊缝区的抗腐蚀性能指标(R1+R2)随着H_2S浓度的升高而降低。此外,在相同浓度的H_2S溶液中,焊缝区的腐蚀电位、钝化性能、阻抗都比母材区低,而电化学活性、腐蚀电流密度都比母材区高。同时,随着H2S浓度的升高,焊缝区与母材区的钝化性能、耐腐蚀性差距逐渐变大。结论随着H_2S溶液浓度的增加,316L不锈钢TIG焊接接头母材区和焊缝区的钝化性能逐渐降低,耐蚀性下降,且二者耐蚀性的差距逐渐加大。在相同浓度的H_2S溶液中,母材区的耐蚀性比焊缝区好。     

Superfine Sr2CeO4 powder with blue-emission prepared by microemulsion method

Powder samples of Sr₂CeO₄ were prepared by microemulsion-heating method. Field emission scanning electron microscopy (FE-SEM) images showed that the sample fired at 850 °C for 4 h was spherical with an average diameter of 70∼80 nm while the samples which sintered at 900 °C for 4 h and 1000 °C for 4 h were shuttle-like shape and spherical respectively both with sizes less than 1 μm. X-ray diffraction (XRD) patterns disclosed that the superfine Sr₂CeO₄ exhibited an orthorhombic crystal structure. Room-temperature photoluminescence (PL) analysis indicated that there were three excitation peaks located at around 260, 280, and 350 nm, and all the Sr₂CeO₄ samples showed intensely blue emission at 470 nm. Compared with Sr₂CeO₄ samples prepared with other methods, the Sr₂CeO₄ phosphor fabricated with this method had a controllable shape with smaller size, lower calcination temperature, and shorter calcinations time.     

AZ91D镁合金表面不同树脂体系富镁涂层的保护性能

采用划叉浸泡实验,电化学交流阻抗(electrochemical impedance spectroscopy,EIS),开路电位(open circuit potential,OCP)及动电位扫描研究了不同类型的环氧树脂对于AZ91D镁合金的表面的富镁涂层的保护性能的影响。结果表明环氧618-593构成的富镁涂层防护性能较差;环氧6101-TY650制备的富镁涂层可明显改善涂层对破损处镁合金基体的保护作用,但涂层本身长期防护性能较差;环氧618-T31构成的富镁涂层对AZ91D镁合金的防护作用较强,适宜制备镁合金表面的富镁涂层。3种环氧涂料中加入镁粉颗粒制备的富镁涂层均可对缺陷处裸露的AZ91D镁合金基体提供保护,从而延长漆膜的破坏时间。涂层中的镁粉颗粒被激活后,为镁合金的基体提供了一定程度的阴极保护作用,减缓了镁合金基体的腐蚀。