多孔NiTi记忆合金化学氧化和热氧化表面改性的对比研究

研究了多孔NiTi记忆合金在H2O2＋HCl溶液中的低温化学氧化过程和500℃的高温热氧化过程。通过对比分析2种表面氧化处理后合金表面氧化膜的形貌、Ni/Ti比及膜层生长动力学曲线,探讨了多孔NiTi合金表面和孔内氧化膜的生长特点。结果表明,利用2种表面氧化技术在合金表面和孔内获得的氧化膜Ni含量均明显低于基体,且合金孔内氧化膜Ni含量低于表面氧化膜;多孔NiTi合金孔内的氧化对于与氧亲和力弱的Ni而言更加困难,孔内氧化膜的生长速率低于表面氧化膜的生长速率。     

多孔NiTi合金的化学氧化处理表面改性研究

在H2O2+HCl溶液中对多孔NiTi合金进行了化学氧化处理表面改性。利用EPMA、SEM、原子吸收光谱对合金表面氧化膜的组成、形貌及化学氧化处理前后的Ni离子释出进行了研究。结果表明,经过H2O2+HCl溶液化学氧化表面处理后合金表面Ni含量显著降低,在生理盐水中的Ni释放速率明显下降;H2O2+HCl溶液浓度和氧化时间均对合金表面氧化膜的生长有较大影响。     

医用镍钛合金表面多层薄膜的制备及摩擦磨损和耐腐蚀性能

采用阳极氧化技术和射频磁控溅射技术在NiTi合金表面分别制备了TiO2薄膜以及Ti/TiN/TiO2多层薄膜。借助扫描电子显微镜(SEM)、X射线衍射仪(XRD)、摩擦磨损试验仪及电化学工作站等仪器对薄膜的形貌、结构、摩擦磨损性能及耐腐蚀性能进行了研究。结果表明,NiTi合金经表面处理后,其摩擦磨损性能和耐腐蚀性能均得以不同程度的改善,其中阳极氧化和磁控溅射复合处理的NiTi合金的耐磨性和耐蚀性具有最佳的配合。     

TiNi-Pd形状记忆合金的高温氧化

使用X射线衍射仪、扫描电镜和电子探针微区分析仪等设备研究了TiNi，TiNiPd以及TiNiPd(Ce)三种TiNi-Pd形状记忆合金的高温氧化问题。合金在氧化之后产生多层的氧化膜，其最外层都是由金红石(TiO2)组成。二元合金TiNi的氧化膜呈现明显的两层，而TiNiPd合金的氧化膜则为四层。加稀土的TiNiPd(Ce)合金的氧化膜呈现出多层的结构，可分为五层。提出TiNiO3和Ti4Pd2O在氧化过程中充当了离子交换的媒介。试验显示，氧化后TiNi合金中钛的成分损失不大；而TiNiPd和TiNiPd(Ce)合金氧化后，钛的成分减少很多，显微硬度从合金表面到内部呈线性降低。     

离子束合成TiO2薄膜对医用NiTi合金表面的改性

采用离子束增强沉积法制备TiO2薄膜,对医用NiTi合金进行表面改性处理。系统研究了薄膜的表面组成、结构、形貌及耐蚀性、亲水性等与血液相容性相关的表面性质。NiTi合金表面沉积TiO2薄膜后,抗模拟体液的腐蚀性提高,凝血时间延长。为进一步提高TiO2薄膜的抗凝血性,对TiO2薄膜的进一步表面改性－表面结合肝素分子进行了初步尝试,结果表明,薄膜表面组成发生变化,表面亲水性进一步提高。     

纯钛微弧氧化膜的性能评价

采用微弧氧化-碱热处理复合的方法,在纯钛表面制备出较大表面积且成分单一的TiO2陶瓷膜,并在模拟体液中对膜层的生物活性予以评价。结果表明,纯钛微弧氧化膜层主要由锐钛矿型的TiO2构成,其表面孔径均匀,孔隙率达到12%;经碱热处理后,与模拟体液和去离子水的润湿角实验证明膜层具有较好的亲水性;碱热处理后的膜层置于模拟体液中培养14d后,膜层表面被生长出的类骨磷灰石完全覆盖,证明其具有良好的生物活性,且生长出的缺钙型磷灰石与人体自然骨成分相似。     

医用NiTi形状记忆合金表面氧化改性研究进展

氧化是NiTi形状记忆合金表面改性的重要手段,常用的氧化工艺包括热氧化、微弧氧化、阳极氧化和化学氧化。虽然四种工艺都依靠合金自身的Ti元素在合金表面原位生成以晶态或非晶态TiO2为主的氧化膜,但四种氧化工艺的原理及所制备的膜层形貌、结构等均不相同。本文评述了四种表面改性工艺的优势和缺陷,并对NiTi合金表面改性的发展方向进行了展望。     

TC4钛合金表面TiO_2-PTFE复合膜层的制备

采用特殊的化学及物理处理方法,在钛合金表面制备TiO2-PTFE复合膜层,该润滑膜由硬质阳极氧化膜与低摩擦系数的聚四氟乙烯(PTFE)结合而成,具有较好的自润滑特性。研究了TiO2-PTFE复合膜层的组织形貌、物相组成以及元素组分,讨论了阳极氧化处理工艺和涂覆时间对PTFE涂覆量的影响。结果表明,TC4钛合金阳极氧化后形成了由锐钛相和金红石相双相晶型组成的纳米级TiO2多孔膜,涂覆PTFE后,表面及膜孔处被PTFE聚合体所覆盖。TC4钛合金样品经过不同电压和不同氧化时间处理后,PTFE涂覆量趋于稳定。随着涂覆时间的延长,PTFE涂覆量逐渐增加,在最初5～20min内,涂覆量增加较快,超过20min后涂覆量增加缓慢。     

载银微弧氧化TiO2膜光催化杀菌研究

以磷酸钠为电解液,采用微弧氧化技术在钛网上直接制备TiO2膜,利用硝酸银光沉积法对该膜表面进行修饰,考察TiO2膜光催化杀灭空气中细菌的能力.利用XRD,SEM,EDX对微弧氧化膜晶型、表面形貌和成分进行观察分析.研究结果表明:微弧氧化TiO2膜主要由锐钛矿TiO2组成,随电解时间增长,锐钛矿TiO2增多,TiO2膜光催化杀菌效果明显好于单独紫外光的杀菌效果;光沉积银修饰可以改变微弧氧化TiO2膜的表面成分,改善膜的光催化性能.光沉积银微弧氧化TiO2膜和微弧氧化TiO2膜以及单独紫外光30 min的杀菌效率分别为95.2%,68.5%和36.1%.     

氧化时间对钛合金钻杆微弧氧化膜层结构和性能的影响

采用脉冲直流微弧氧化方法在钛合金钻杆表面制备了不同氧化时间下的TiO_2陶瓷膜层,用扫描电镜、X射线衍射仪、显微硬度计、球盘摩擦试验机及电化学工作站等分析了膜层的形貌、结构、组成以及膜层的硬度、摩擦磨损性能和耐蚀性。结果表明,随着氧化时间的延长,膜层的厚度增加,但膜层的硬度、耐磨性和耐腐蚀性先增加后降低。经不同氧化时间处理后,膜层的相结构主要由金红石型TiO_2和锐钛矿型TiO_2组成,此外还含有少量的Al2TiO5晶体和SiO_2非晶态。微观形貌分析表明,随着氧化时间延长,膜层表面粗糙度延长。在本实验条件下,当氧化时间为40min时,微弧氧化膜层的综合性能较好。     

Surface structure and biomedical properties of chemically polished and electropolished NiTi shape memory alloys

The surface structure and biomedical properties of NiTi shape memory alloy (SMA) samples after undergoing electropolishing and chemical polishing are determined and compared employing scanning electron microscopy, X-ray photoelectron spectroscopy, inductively-coupled plasma mass spectrometry, hemolysis analysis, blood platelet adhesion test, and MTT test. The results indicate that after chemical polishing, there is still a high Ni concentration on the surface of the NiTi SMA. On the other hand, electropolishing can form a thin surface titanium oxide film (about 10 nm thickness) with depleted Ni. In addition to the TiO₂ phase, some titanium suboxides (TiO and Ti₂O₃) are found in the surface film. Compared to chemical polishing, electropolishing can more effectively mitigate out-diffusion of Ni ions and the wettability, blood compatibility, and thromboresistance are also better. However, no difference on the cytocompatibility can be observed from samples that have been chemically polished or electropolished.     

Characterization of Sol-gel-derived TiO2 and TiO2-SiO2 Films for Biomedical Applications

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 resistance 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.     

TiNi合金表面轧制氧化膜激光清洗工艺研究

目的针对焊前去除TiNi合金表面致密氧化膜过程中,传统方法会造成环境污染的问题,运用激光清洗这一绿色清洗方法去除TiNi形状记忆合金表面轧制氧化膜,并对其清洗工艺进行研究。方法运用OM和XRD等分析测试手段对激光清洗后TiNi合金表面进行测试,研究激光清洗工艺对TiNi合金表面氧化膜及其组织的影响。结果激光清洗参数对激光清洗效率影响较大,扫描次数对TiNi合金激光清洗效率具有饱和性;激光清洗过后的TiNi合金表面仍存在一定含量的TiO,TiO_2,Ti_3O_5等氧化物。结论激光清洗可得到表面明亮且均匀的TiNi合金,但不能完全清除TiNi合金表面氧化膜。     

The effect of oxide thickness on osteoblast attachment and survival on NiTi alloy

NiTi alloy is used in various medical applications and the surface titanium oxide layer produced naturally or enhanced artificially has been thought to offer a protecting film against allergic and toxic effects of nickel (Ni). In this study, we investigated the effect of different oxide layer thicknesses on the survival and attachment of osteoblastic cells (ROS-17/2.8). AFM, X-ray diffraction and electrical resistance measurements were used to analyze the surface properties of oxidized NiTi samples and the effect of oxidation on material properties. The results clearly showed that straight correlation between oxide thickness and cellular well-being cannot be maid. However, the different thicknesses of oxide layer on NiTi had surprising impacts on cellular responses and also to the properties of the metal alloy.     

Nitinol surface roughness modulates in vitro cell response: a comparison between fibroblasts and osteoblasts

The purpose of the present in vitro study was to examine the biocompatibility of a nickel–titanium (NiTi) shape memory alloy. Human gingival fibroblastic and rat embryo osteoblastic cells were cultured on NiTi discs. The discs were prepared with two surface roughnesses. Cell response to these surfaces was compared for the two types of cells. The comparison was based on an analysis of the cell morphology, adhesion and proliferation rates. Fibronectin labeling by immunofluorescence staining was also performed. For osteoblastic cells, alkaline phosphatase assay was conducted as a function of NiTi surface roughness and for different durations.     

Fabrication and characterization of NiTi shape memory alloy synthesized by Ni electroless plating of titanium powder

In this work NiTi shape memory alloy was fabricated from mixed elemental powders, Ni plated titanium powder and Ni heated/plated titanium powder by Ar-sintering. Electroless plating process was utilized to fabricate Ni plated titanium powder. For this purpose titanium powder was plated in an electroless Ni bath for 225?min and hydrazine hydrate was used as a reductant to deposit pure nickel on the titanium particles. Ni plated titanium powder was heat treated under an argon atmosphere at 1000?°C to prepare Ni heated/plated titanium powder. Finally, the three sample powders were pressed by CIP followed by sintering at 980?°C for 8?h to manufacture NiTi shape memory alloy. The prepared powders, as well as sintered samples, were characterized by scanning electronic microscopy (SEM), energy dispersive spectrometer analysis (EDS), X-ray fluorescence (XRF), X-ray diffraction (XRD) and differential scanning calorimetric (DSC). The results indicated the presence of NiTi phase and also non-transformable phases (NiTi₂ and Ni₃Ti) in the heated/plated Ti powder and sintered samples. NiTi compound was dominated phase in the heated/plated sintered sample. All three sintered samples, as well as heated/plated powder, showed one-step phase transformation (B2???B19′).     

Surface modification of NiTi alloy and human platelet activation under static and flow conditions

The effect of surface nickel species on NiTi alloy thrombogeneity was investigated by assessment of platelet activation and whether oxidative modification of the alloy would affect platelet response. Tests were conducted under static conditions and arterial levels of shear stress. Heat treatment of the alloy at 600 °C significantly reduced surface nickel species. Under both static and flow conditions platelet activation on the heat-treated alloy was comparable to that on pure titanium and was significantly lower than that on polished NiTi. This study demonstrates that the risk of thrombotic complications associated with NiTi in vivo can be reduced through heat modification of the alloy surface to reduce surface nickel.     

Effects of microstructural mechanisms on the localized oxidation behavior of NiTi shape memory alloys in simulated body fluid

Localized oxidation and corrosion behavior of a nickel–titanium (NiTi) shape memory alloy (SMA) was investigated via static immersion experiments in a simulated body fluid solution. Detailed electron microscopy examinations on the sample surfaces revealed preferential formation of local oxide particles around dislocation networks, which constitute high-energy zones. Moreover, various intermediate phases were detected in addition to the parent NiTi phase around dislocation networks. These are also areas with enhanced diffusion, which promotes Ni release. These findings emphasize the significant role of fine microstructural features, such as dislocation networks, on the oxidation and Ni release, and thus, the biocompatibility of the NiTi SMAs.     

Characterization of TiO2/Ta2O5 Films Synthesized by Ion Beam on NiTi Alloy for Biomedical Applications

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.