C. H. Chen, S. K. Wu, National Taiwan University, Taipei, Taiwan; M. R. Yang, Tatung University, Taipei, Taiwan
SiC:H organic-like thin films are deposited on Ti50Ni50 shape memory alloy by DC-pulsed plasma enhanced chemical vapor deposition (PECVD) in the gas mixture of Hexamethyldisilazane (HMDSN) and Ar at room temperature. The deposition rate of the plasma-polymerized HMDSN (PPHMDSN) thin film is fast and the PPHMDSN thin films not only enhance the corrosion resistance but make the corrosion current density decay four orders. The surface morphology of the films is very smooth and uniform and the root mean square of surface roughness is in the range between 2 and 4 nm. The organic-like thin films containing peroxides or free radicals can be grafted with polymer which can improve the biocompatibility of TiNi shape memory alloys.
Summary: SiC:H organic-like thin films are deposited on TiNi shape memory alloys (SMAs) by DC-pulsed plasma enhanced chemical vapor deposition (PECVD) of HMDSN and Ar gas mixtures at room temperature. The deposition rate of the plasma-polymerized HMDSN (PPHMDSN) thin films is fast and the root mean square of surface roughness is in the range between 2 and 4 nm. The PPHMDSN thin films not only enhance the corrosion resistance but make the corrosion current density decay four orders. Based on the micro-FTIR spectra, the Si-C and C-H bonds of the original HMDSN monomer are broke and new Si-H and C=O bonds are formed. The free radicals react with each other and form silane and methane gas which will diffuse out. After deposition of PPHMDSN thin films, the water contact angle will raise from 42° to 87° because the PPHMDSN film consists of more non-polar groups as methyl and methylene. The surface becomes more hydrophobic, leading to the increase of relative wet friction coefficient (0.2539). The organic-like thin films containing peroxides or free radicals can be grafted with polymer to improve the biocompatibility of TiNi shape memory alloys.
