Promotion of running-in process by UV irradiation to CN_x coating and improvement of proof property of pressure

认为氮化碳（CN_x）涂层在氮气中与氮化硅球发生滑动的超低摩擦现象发生在CN_x的最表层变为石墨结构时。假设紫外线（UV）在射线功率超过C-N单键能时可以破坏C-N单键，并假设紫外线在N2气体中照射可以使CN_x涂层的最上层无摩擦石墨化。制备了波长分别为254、312和365 nm的紫外辐射CN_x涂层，并在N2和环境空气中进行了摩擦测试，比较了紫外辐射前后CN_x涂层的摩擦性能。在N2或环境空气中进行摩擦试验时，所有试样均未出现超低摩擦系数，但经过几个摩擦循环后，紫外线照射后的涂层均出现了超低摩擦现象，且所有紫外线照射后的涂层的磨合期均短于沉积态CN_x。沉积CN_x初始几个摩擦循环的平均值约为0.04，而在312 nm紫外光照射下CN_x的平均摩擦系数为0.01或更低。这些结果表明紫外可以破坏C-N单键，这些断裂的键被重构成石墨层。

The superlow friction phenomena of CN_x (Carbon Nitride) coating slid against Si3N4 ball in N2 gas was suggested to be taken place when the topmost surface of CN_x changed to graphitic structure. It was assumed that ultraviolet ray (UV) could break C-N single bond when the ray power exceeded C-N single bonding energy, and we hypothesized that UV irradiation could make the CN_x coating topmost surface graphitic without friction in N2 gas. We carried out preparing the CN_x coating irradiated UV as 254, 312, and 365 nm wave length, then these specimens were friction tested in N2 gas or ambient air to compare frictional property of with and without UV irradiation. All specimens did not show superlow friction coefficient at the initial of friction tests in N2 or ambient air, however, the coatings which were UV irradiated showed superlow friction phenomena after several friction cycles and all UV irradiated specimens showed shorter running-in period than as-deposited CN_x. The average of initial several friction cycles of as-deposited CN_x showed approximately 0.04, on the other hand, in the case of 312 nm UV irradiated CN_x showed 0.01 or lower average friction coefficient. These results indicated that UV could break the C-N single bond, these broke bonds were restructured to graphitic layer.