多孔NiTi记忆合金化学氧化和热氧化表面改性的对比研究

A comparative study on surface modification of porous NiTi alloys by chemical oxidation and thermal oxidation

研究了多孔NiTi记忆合金在H2O2+HCl溶液中的低温化学氧化过程和500℃的高温热氧化过程。通过对比分析2种表面氧化处理后合金表面氧化膜的形貌、Ni/Ti比及膜层生长动力学曲线,探讨了多孔NiTi合金表面和孔内氧化膜的生长特点。结果表明,利用2种表面氧化技术在合金表面和孔内获得的氧化膜Ni含量均明显低于基体,且合金孔内氧化膜Ni含量低于表面氧化膜;多孔NiTi合金孔内的氧化对于与氧亲和力弱的Ni而言更加困难,孔内氧化膜的生长速率低于表面氧化膜的生长速率。

Two surface oxidation methods,i.e.,low temperature chemical oxidation in H2O2＋HCl solution and thermal oxidation at 500℃ were used to treat porous NiTi alloy for surface modification.The morphology,Ni/Ti atomic ratio and growth kinetics of the oxide films formed on porous NiTi alloy through two oxidation techniques were compared and analyzed.The characteristics of the oxidations on the surface and inside the pores of porous NiTi alloy were discussed.The results show that the two oxidation techniques bring about the formation of the oxide films depleted in Ni.The Ni content on the pore wall is lower than that on the surface of porous NiTi alloy,which indicates that the conditions inside the pores inhibit the oxidation of Ni due to the low oxygen affinity.The growth rate of the oxide film inside the pore is lower than that of the oxide film on the outmost surface of porous NiTi alloy.