含氢碳薄膜500℃退火前后摩擦学行为研究

The Results of Annealing Treatment of Hydrogenated Amorphous Carbon Film Is Affected by Its Intrinsic Structure

目的为含氢碳薄膜在甲醇发动机中应用提供新思路。方法首先利用BiP–PECVD方法在Si基底上制备了含氢碳薄膜,并在500℃于Ar气氛中进行1 h退火处理。通过纳米硬度、X射线光电子能谱、傅里叶转变红外光谱、激光共聚焦拉曼光谱、场发射扫描电镜、CSM摩擦试验机等,分别评价未退火和500℃退火含氢碳薄膜的结构、力学性能、表面形貌及在干燥空气和甲醇环境中的摩擦学性能。通过对比,研究甲醇的引入对500℃退火含氢碳薄膜摩擦学行为造成的影响。结果500℃退火会改变含氢碳薄膜中碳的杂化方式由sp3–C向sp2–C转变,促使薄膜石墨化,C==C/C—C的值明显增大(从0.67到0.99),硬度降低(从26.5 GPa到22.0 GPa),弹性模量几乎不变,H/E减小,耐磨性变差。在干燥空气中,与未退火碳薄膜相比,500℃退火含氢碳薄膜的摩擦因数降低(从0.031到0.024),磨损率增加了1.27倍,而相应摩擦对偶球的磨损降低(从4.22×10^(–6)mm^(3)到3.99×10^(–6)mm^(3))。而在甲醇环境下,500℃退火含氢碳薄膜的摩擦因数增高(从0.052到0.062),磨损率增加了15.11倍,相应摩擦对偶球的磨损也增高(从6.16×10^(–6)mm^(3)到13.9×10^(–6)mm^(3))。但是,未退火含氢碳薄膜在甲醇环境中的磨损率是干燥环境中的1/2.84,表现出降低趋势;500℃退火的含氢碳薄膜在甲醇环境中的磨损率是干燥环境中的4.14倍。结论含氢碳薄膜经过500℃退火会造成薄膜内部碳原子杂化方式转变,薄膜石墨化,这对干燥环境中薄膜的摩擦学性能有所提高,但并不利于其甲醇环境中的摩擦。

To provide novel way for the application of hydrogen-containing carbon(a-C:H)films in methanol engines.First,a-C:H film was prepared on Si substrate by BiP-PECVD method,and then annealed at 500℃in Ar atmosphere for 1 h.The unannealed and annealed a-C:H films were characterized through Nano-indenter,X-ray Photoelectron Spectroscopy(XPS),Fourier Transform Infrared spectroscopy(FTIR),Raman spectroscopy,Field Emission Scanning Electron microscopy(FESEM),CSM tribometer,etc.to obtain its structure,mechanical properties,surface morphology and tribological properties.The effect of annealing at 500℃on the tribological behavior of a-C:H film was comparatively studied in dry air and methanol environment.As a result,after annealed at 500℃,the carbon hybridization have been changed from sp3-C to sp2-C resulting in graphitization of the film and the value of C==C/C—C increasing from 0.67 to 0.99.The hardness decreased from 26.5 Gpa to 22.0 GPa and the elastic modulus was almost unchanged as well as the H/E decreases,which means the wear resistance becomes worse in dry air.Compared with the unannealed a-C:H film,in dry air,the friction coefficient of the a-C:H film annealed at 500℃decreased from 0.031 to 0.024,and the wear rate increased by 1.27 times.Meanwhile,the wear volume of both corresponding friction ball reduced from 4.22×10^(–6)mm^(3)to 3.99×10^(–6)mm^(3);In the methanol environment,the friction coefficient of the a-C:H film annealed at 500℃increased from 0.052 to 0.062),and the wear rate increased by 15.11 times.Meanwhile,the wear volume of the corresponding friction counter ball also increased from 6.16×10^(–6)mm^(3)to 13.9×10^(–6)mm^(3)However,the wear rate of unannealed a-C:H film in methanol environment was 1/2.84 of that in dry environment which shows a decreasing trend;the wear rate of a-C:H film annealed at 500℃in methanol environment was 4.14 times lower than that in dry environment.In a summary,under annealing temperature of 500℃,a-C:H film will result in graphitization,which is conducive to tribological properties in dry air but not in the methanol environment.