Development of novel ceramic coatings with plasma electrolytic oxidation technique

本研究的目的是通过等离子体电解氧化(PEO)技术开发新型陶瓷涂层。具有磷灰石形成能力和光催化活性的新型氧化钛薄膜的研制为了提高骨与钛合金作为生物材料的结合强度，我们对体内形成高磷灰石形成能力的氧化钛薄膜提出了挑战。研究发现，选择乙酸铵作为PEO的电解液，可以促进二氧化钛的结晶。从而获得较高的磷灰石形成能力。我还发现由二氧化钛组成的聚氧化乙烯薄膜具有较高的光催化活性，这意味着该材料可以很容易地利用紫外光进行灭菌。磷灰石的形成能力是由于吸附在锐钛矿晶面上的羟基芳香基团将Ca~(2+)吸引到带负电荷的…表面所致(2)具有良好隔热性能的多孔氧化锆膜的研制作为喷气发动机涡轮叶片的镍基单晶高温合金，为了提高耐热性，通常在其表面涂覆氧化锆膜。我挑战用PEO在SA上形成一层陶瓷涂层。在制备氧化锆涂层之前，先用聚氧化乙烯(PEO)在镀铝SA表面形成抗氧化的氧化铝涂层。以K_2[Zr(CO_3)_2(OH)_2]为电解液，采用PEO方法在SA表面成功地制备了ZrO_2涂层。含氮化硅颗粒氧化膜的制备我尝试在钛表面用PEO法制备含氮化硅颗粒的氧化膜，电解液中分散有氮化硅颗粒。我发现控制氮化硅含量的关键参数是每个循环的高压持续时间。持续时间的增加可能会由于火花放电而引起强烈的局部对流，通过火花放电，氮化硅颗粒被结合到薄膜中。较少

The aim of this study is to develop novel ceramic coating through the plasma electrolytic oxidation(PEO) technique. The results obtained in the study period are as follows;(1) Development of novel titanium oxide film with the apatite-forming ability as well as photocatalytic activityTo improve the bonding strength between bone and titanium alloy widely used as a biomaterial, we challenged to the formation of titanium oxide film which has high apatite-forming ability in vivo. I found that the crystallization of titanium oxide was promoted when ammonium acetate was chosen as an electrolyte of PEO. Then high apatite-forming ability can be consequently obtained. I also found that the PEO film consisted of titanium oxide had relatively high photocatalytic activity, which means that the material can be sterilized easily by using UV light. The apatite-forming ability is attributed to OH aromatic group absorbed on anatase(101) surface, which attracts Ca^<2+> to the negatively charged surface o … More f anatase.(2) Development of porous zirconia film with excellent heat shieldingNi-based single crystal superalloy(SA), which is utilized as a turbine blade of a jet engine, is usually coated with ZrO_2 in order to improve heat resistance. I challenged to form a ceramic coating on SA with PEO. Before making ZrO_2 coating, anti-oxidation Al_2O_3 coating was formed by using PEO on aluminum plated SA. The ZrO_2 coating on SA was successfully obtained by PEO with K_2[ Zr(CO_3)_2(OH)_2] as an electrolyte. In terms of adhesion strength and heat shielding, the coating showed high performance equivalent to the conventional thermal barrier coating.(3) Fabrication of oxide film containing silicon nitride particlesI tried to make oxide film containing silicon nitride particles on titanium by PEO with an electrolyte dispersed with silicon nitride particles. I found that the key parameter to control the content of silicon nitride is the duration of high voltage per cycle. The increase in the duration may cause vigorous local convection due to the spark discharge, by which silicon nitride particles are incorporated in the film. Less