Yingjie HUA
,
Xin LIU
,
Changgong MENG
,
Dazhi YANG
材料科学技术（英文）
The discrete-variational method within the framework of density functional theory was used to investigate the process of O2 adsorption occurring on the surface of NiTi alloy. The calculated results showed that O2 exhibits the adsorption state of Odelta2 (0.36
关键词:
NiTi
,
null
,
null
Jingxiao LIU
,
Jihua CHEN
,
Dazhi YANG
,
Weiqiang WANG
,
Yinong WANG
,
Yingji CAI
材料科学技术（英文）
The biocompatibility of implants is determined by their corrosion resistance and surface characteristics. In this study, the surface composition, morphology and microstructure of TiO2/Ta2O5 films synthesized by ion beam enhanced deposition on NiTi alloy were studied. The scratch test results indicate that the interface adhesive strength of TiO2/Ta2O5 film increases with the increasing Ta content. The electrochemical corrosion measurement shows that the TiO2-36%Ta2O5 film is optimal for improving corrosion resistance of NiTi alloy.
关键词:
Wei WU
,
Xinjie LIU
,
Huimin HAN
,
Dazhi YANG
材料科学技术（英文）
A modified electrolyte (CH3COOH-HClO4-A-B) for electropolishing (EP) of NiTi was presented for improving the corrosion resistance and biocompatibility of the alloy. Using the proposed parameters, a homogeneous and uniform surface was obtained. Atomic force microscopy (AFM) revealed that the surface roughness (Ra) for EP sample (23.21 nm) was close to mechanical polishing (MP) sample (19.36 nm). Analysis by X-ray photoelectron spectroscopy (XPS) showed that Ti/Ni ratio increased from 3.1 for MP sample to 27.6 for EP sample. Measurements using potentiodynamic polarization in Hanks0 solution showed that no pitting occurred for EP sample even though the applied potential increased up to 1500 mV (vs SCE), while the MP sample was broken down at 650 mV. The present study indicates that electropolishing NiTi with this modified electrolyte contributes to the improved biocompatibility of NiTi.
关键词:
NiTi
,
null
,
null
,
null
,
null
Yanjun ZHENG
,
Lishan CU
,
IYan LI
,
Dazhi YANG
材料科学技术（英文）
The reverse martensitic transformation of TiNi shape memory alloy fibers embedded in a pure aluminum matrix was studied in this paper. Results showed that the phase composition of the TiNi alloy fibers prior to prestraining at the room temperature had a significant influence on the differential scanning calorimetry (DSC) results of the composites. By a comparison to the high temperature X-ray diffraction (XRD) results, it was confirmed that the martensite was divided into two groups: the self-accommodating martensite (SAM) and the preferentially oriented martensite (POM). The evolving process of the separation of martensite was discussed.
关键词:
Shape memory alloy
,
null
,
null
,
null
Xiaopeng LIU
,
Wei JIN
,
Mingzhou CAO
,
Dazhi YANG
,
Feixia CHEN
材料科学技术（英文）
Compared with the undeformed TiNi film, the martensite-austenite transformation (M-A) of the deformed one is elevated to a higher temperature on the first heating, but it nearly returns back to the original temperature on the second heating. An incomplete M-A transformation of the deformed TiNi film on the first heating divides the total martensite population into the self-accommodating martensite M2 and the oriented martensite M1. Thus, two transformations corresponding to M1-A and M2-A transition occur on the second heating. However, the forward transformation is not affected by the incomplete thermal cycle.
关键词:
TiNi film
,
null
,
null
,
null
Jingxiao LIU
,
Fei SHI
,
Dazhi YANG
材料科学技术（英文）
In order to improve the corrosion resistance and biocompatibility of NiTi surgical alloy, TiO2 and TiO2-SiO2 thin films were prepared by sol-gel method. The surface characteristics of the film, which include surface composition, microstructure and surface morphology, were studied by X-ray diffraction (XRD), atomic force microscopy (AFM) and X-ray photoelectron spectra (XPS), respectively. A scratching test was used to assess the interface adhesive strength between the film and substrate. The corrosion resistances of NiTi alloy coated with oxide films were studied by anodic polarization curves measurement in biological solution. Additionally, a preliminary study of the in vitro bioactivity of the films was conducted. The results indicated that TiO2 and TiO2-SiO2 (Ti/Si=4:1) films have higher electrochemical corrosion resistance and can be used as protective layers on NiTi alloy. In addition, TiO2-SiO2 composite films have better bioactivity than TiO2 film.
关键词:
TiO2
,
null
,
null
,
null
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null
