Development of novel ceramic coatings with plasma electrolytic oxidation technique

本研究的目的是利用等离子体电解氧化（PEO）技术制备新型陶瓷涂层。研究期间得到的结果如下：(1)具有磷灰石形成能力和光催化活性的新型氧化钛膜的开发为了提高骨与生物材料钛合金之间的结合强度，我们对具有高磷灰石形成能力的氧化钛膜在体内的形成提出了挑战。我发现选用乙酸铵作为PEO的电解液可以促进氧化钛的结晶。从而获得较高的磷灰石形成能力。我还发现由氧化钛组成的PEO膜具有较高的光催化活性，这意味着该材料可以很容易地使用紫外线进行灭菌。形成磷灰石的能力是由于羟基芳香基团吸附在锐钛矿（101）表面，吸引Ca^<2+>到带负电荷的锐钛矿表面。(2)具有优良热屏蔽性能的多孔氧化锆膜的研制。喷气发动机涡轮叶片用ni基单晶高温合金（SA）为提高其耐热性，通常在表面涂覆ZrO_2。我挑战用PEO在SA上形成陶瓷涂层。在制备ZrO_2涂层之前，先在镀铝的SA表面用PEO形成抗氧化Al_2O_3涂层。以K_2[Zr(CO_3)_2(OH)_2]为电解液，采用PEO法制备了ZrO_2涂层。在粘接强度和热屏蔽性能方面，涂层表现出与传统热障涂层相当的优异性能。(3)含氮化硅颗粒氧化膜的制备我尝试用分散有氮化硅颗粒的电解液，用PEO在钛上制备含氮化硅颗粒氧化膜。我发现控制氮化硅含量的关键参数是每个周期的高电压持续时间。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，从而使氮化硅颗粒融入薄膜中。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