多孔NiTi形状记忆合金中Ni的释放行为

多孔NiTi合金在生理盐水和模拟体液中的Ni释放速率远大于具有相同名义表面积的致密态NiTi合金.在恒定的静弯曲应变的作用下.多孔NiTi形状记忆合金Ni释放速率呈现增大的趋势.多孔NiTi合金在60℃的4 mol/L的NaOH溶液中浸泡24 h,然后在600℃进行1 h处理后,合金表面形成一层氧化膜,阻隔了浸液与基体的接触,明显降低多孔NiTi合金的Ni释放速率.     

AZ91D压铸镁合金激光局部重熔区气孔的形成机制

采用扫描电镜(SEM)、X光电子能谱分析仪(XPS)等分析手段,研究了NiTi合金表面绝缘膜的结构及成分,从而探讨非阀金属NiTi合金表面微弧氧化陶瓷膜层的形成机制.结果表明,NiTi合金微弧氧化过程中的电流密度-时间曲线与纯钛形状基本一致,也可分为3个阶段,但其最大的电流密度为后者的13倍;NiTi合金表面的绝缘膜主要是通过电化学沉积形成的Al2O3及少量的TiO2、Ni2O3和磷酸盐薄膜,这一绝缘膜就相当于阀金属的阳极氧化膜,为NiTi合金进行微弧氧化处理提供了前提条件;NiTi合金表面的陶瓷膜层主要来源于电解液中的铝酸根离子和少量的基体Ni和Ti(包括固态的和溶解于电解液中离子态的),经反复的放电、熔融、喷射、冷却、凝固,发生一系列的电化学、等离子体化学和热化学反应最终形成表面粗糙多孔陶瓷膜层.     

在Na_2SiO_3溶液中NiTi合金的微弧氧化

在硅酸钠溶液中对NiTi合金进行了微弧氧化处理。结果表明,NiTi合金在Na2SiO3溶液中,微弧氧化过程分为2个阶段,即缓慢电压增长区和电压跃升区。微弧氧化获得氧化物层为Ti的氧化物。微弧氧化后表面硬度比NiTi要高出2倍以上。在NiTi合金微弧氧化过程中,首先是NiTi合金中的Ni氧化以离子形式溶解进入溶液,而Ti保留在合金表面。然后NiTi合金表面的Ti层在阳极电压下氧化形成绝缘层。当表面绝缘层达到一定厚度后就发生起弧现象。     

NiTi合金表面电化学氧化制备Ti02膜

采用恒电流阳极氧化法在NiTi形状记忆合金(SMA)表面制备完整致密且耐腐蚀的Ti02膜。通过对NiTi SMA和纯Ti在稀HC1中的动电位阳极极化曲线的分析,得到了选择性脱Ni阳极氧化电流密度工艺参数。试验采用稀HC1体系,以该工艺参数进行阳极氧化处理5 min,在NiTi SMA表面制备出了完整致密的Ti02膜,并进行了其表面的SEM、XRD、XPS分析和NiTi SMA表面处理前后在模拟唾液fusayama中的对比腐蚀试验测试。结果表明：经阳极氧化处理的NiTi SMA表面形成了十几纳米厚的Tio2膜,且其耐蚀性有明显的提高。     

NiTi合金表面电化学氧化制备TiO2膜

采用恒电流阳极氧化法在NiTi形状记忆合金(SMA)表面制备完整致密且耐腐蚀的TiO2膜.通过对NiTi SMA和纯Ti在稀HCl中的动电位阳极极化曲线的分析,得到了选择性脱Ni阳极氧化电流密度工艺参数.试验采用稀HCl体系,以该工艺参数进行阳极氧化处理5min,在NiTi SMA表面制备出了完整致密的TiO2膜,并进行了其表面的SEM、XRD、XPS分析和NiTi SMA表面处理前后在模拟唾液fusayama中的对比腐蚀试验测试.结果表明:经阳极氧化处理的NiTi SMA表面形成了十几纳米厚的TiO2膜,且其耐蚀性有明显的提高.     

医用NiTi合金表面改性技术研究进展

近等原子比的NiTi合金以其独有的形状记忆效应和超弹性在医疗领域具有广泛的应用,但近年来研究表明,镍离子会使人体发生中毒反应,甚至致癌,这一因素制约了它在生物医用材料领域的使用。为了抑制镍离子的释放,通过对NiTi合金表面改性,制备一层氧化膜,可有效提高使用的安全性。文章全面阐述了近几年来NiTi合金表面改性的研究进展,提出了对多孔医用NiTi合金表面TiO2改性的发展前景。     

NiTi合金基TiN薄膜的血液相容性和耐腐蚀性研究

采用电弧离子镀法在NiTi形状记忆合金表面制备了TiN薄膜，利用X射线衍射、扫描电子显微镜和原子力显微镜研究了TiN薄膜的相组成及表面特性；在生物体外，研究比较了镀膜和未镀膜的NiTi合金的血液相容性和耐腐蚀性。结果表明：TiN薄膜提高了NiTi合金的血液相容性，并使Ni离子的释放率约降低了1个数量级，有效地提高了NiTi合金的耐腐蚀性。薄膜越厚性能提高的效果越显著。     

医用NiTi合金的表面改性研究进展

近等原子比的NiTi合金作为生物医用材料,以其优异的特性而在医学各科临床得到广泛应用.但由于Ni离子释放而引起的潜在毒性和无生物活性问题,抑制了NiTi合金在生物医用领域的进一步发展.对医用NiTi合金进行表面改性是解决上述问题的有效途径,并成为近年国内外研究的热点.本文全面阐述了近几年来国内外对医用NiTi合金的表面改性方法的研究进展,并对各种方法可能出现的问题进行了分析;提出了采用微弧氧化技术对NiTi合金表面改性的可行性.     

SP700 钛合金的热处理 / 阳极氧化工艺研究

目的采用电化学阳极氧化法,在SP700钛合金的表面制备多孔结构的氧化膜。方法利用Autolab PGSTAT30型电化学工作站,采用三电极体系,辅助阴极为石墨电极,参比电极为饱和甘汞电极,工作电极为试样,测定试样的动态极化曲线和阳极氧化I-t曲线。利用扫描电子显微镜观察阳极氧化表面多孔氧化膜的微观形貌,分析热处理工艺、阳极氧化电压、电解液成分等参数对SP700钛合金阳极氧化行为的影响规律。结果钛合金材料经固溶时效处理后,α相和β相的相对含量发生了变化,从而使氧离子对电化学反应界面的内应力发生变化,使得表层氧化膜更加平整,耐腐蚀性提高。F-是阳极氧化膜上纳米孔形成的必要条件,随着F-浓度的增加,阳极氧化膜表面纳米孔的密集程度增加,孔径减小,氧化膜厚度增加。在一定范围内,随着阳极氧化电压的增大,氧化膜增厚,但电压过高会破坏氧化膜的稳定性。结论用电化学阳极氧化法处理钛合金表面,得到了多孔结构的氧化膜,获得了理想的耐腐蚀性能。固溶时效处理后,钛合金的耐腐蚀性提高。     

不同硫酸浓度对2A12脉冲硬质阳极氧化工艺的影响

采用自制脉冲恒流电源,对硬质铝合金2A12在高、低硫酸浓度下的阳极氧化工艺进行研究。结果表明：2A12合金在低硫酸浓度中进行硬质阳极氧化,氧化膜的硬度和膜层厚度较在高浓度硫酸溶液中的高;无论是硫酸溶液浓度高低．硫酸溶液浓度、槽液温度、氧化电流密度等均影响2A12铝合金硬质阳极氧化膜的硬度和膜层厚度。     

铝及铝合金的阳极氧化研究综述

较为系统地介绍了铝及其铝合金的阳极气体工艺技术，对传统的阳极氧化方法进行了总结，探讨了铝阳极氧化多孔膜的性能及微观结构，以及作为功能材料铝阳极氧化膜广泛的应用，对铝阳极氧化技术最近所取得的应用上的进展进行了总结。     

In situ synthesis of nanostructured titania film on NiTi shape memory alloy by Fenton＇s oxidation method

Fenton＇s oxidation method was successfully used to synthesize an ideal titania film in situ on NiTi shape memory alloy（SMA） for medical applications. Characterized with scanning electron microscopy, X-ray photoelectron spectroscopy, X-ray diffractometry, inductively coupled plasma mass spectrometry and electrochemical tests, it is found that the titania film produced by Fenton＇s oxidation method on NiTi SMA is nanostructured and has a Ni-free zone near its top surface, which results in a notable improvement in corrosion resistance and a remarkable decrease in leaching of harmful Ni ions from NiTi SMA in simulated body fluids. The improvement of effectiveness to corrosion resistance and the reduction in Ni release of NiTi SMA by Fenton＇s oxidation method are comparable to those by oxygen plasma immersion ion implantation reported earlier.     

NiTi合金表面类金刚石膜的表面特征和腐蚀行为

采用等离子浸没离子注入和沉积（PIIID）法以C2H2为等离子源对NiTi合金进行表面改性。利用Raman光谱分析膜层结构。采用原子力显微镜和纳米压痕分析涂层前后NiTi的表面形貌和力学性能。利用电化学测试、扫描电镜和原子吸收光谱测试涂层前后基体的耐腐蚀性和Ni离子析出。结果表明：NiTi合金表面的膜层是类金刚石（DLC）；经过PIIID处理后，基体表面的粗糙度降低；纳米硬度得到提高；耐腐蚀性能获得明显改善；Ni离子析出得到有效的抑制。     

Surface treatment of NiTi shape memory alloy by modified advanced oxidation process

A modified advanced oxidation process(AOP) utilizing a UV/electrochemically-generated peroxide system was used to fabricate titania films on chemically polished NiTi shape memory alloy(SMA). The microstructure and biomedical properties of the film were characterized by scanning electron microscopy(SEM), X-ray photoelectron spectroscopy(XPS), inductively-coupled plasma mass spectrometry(ICPMS), hemolysis analysis, and blood platelet adhesion test. It is found that the modified AOP has a high processing effectiveness and can result in the formation of a dense titania film with a Ni-free zone near its top surface. In comparison, Ni can still be detected on the outer NiTi surface by the conventional AOP using the UV/H2O2 system. The depth profiles of O, Ni, Ti show that the film possesses a smooth graded interface structure next to the NiTi substrate and this structure enhances the mechanical stability of titania film. The titania film can dramatically reduce toxic Ni ion release and also improve the hemolysis resistance and thromboresistance of biomedical NiTi SMA.     

A facile and cost-effective practical approach to develop clinical applications of NiTi: Fenton oxidation process

ABSTRACT

To date, numerous attempts have been made to modify the surface condition of NiTi shape memory alloy to fully benefit from its desirable characteristics, and develop its potential clinical applications. In this survey, the Fenton oxidation process as a newly presented technique for surface modification of NiTi, was employed to address two major priorities in biomedical applications of NiTi, i.e. corrosion improvement and suppression of Ni ion release. To meet these priorities, two important variables involved in the Fenton oxidation process, namely immersion time and electrolyte temperature, were controlled. Results suggested that the application of such an oxidation process may considerably improve the corrosion behaviour of NiTi. The Fenton oxidation process carried out at 65°C for 24?h yields the lowest corrosion current density, 74% lower than bare NiTi. Additionally, Ni ion releases from the surface of NiTi after Fenton's oxidation decreases by ～97%.     

Preparation and crystalline phase of a TiO2 porous film by anodic oxidation

Anatase titanium dioxide is an active photocatalyst, but it is difficult to immobilize on the substrate. A crystalline TiO2 porous film was prepared directly on the surface of pure titanium by anodic oxidation in this work. Constant voltage and constant current anodic oxidation were adopted with sulphuric acid used as the electrolyte, pure titanium as the anode and copper as the cathode. The morphology and structure of the porous film on the substrate were analyzed with the aid of Field Emission Scanning Electron Microscopy （FESEM） and X-ray Diffraction （XRD）. The effects of the parameters of anodic oxidation （such as voltage, the concentration of sulphuric acid, anodization time and current density） on the aperture and the crystalline phase of the TiO2 porous film were systematically investigated. The results indicate that the increase of current density facilitates the augment of the aperture and the generation of anatase and mille. In addition, the forming mechanism of anatase and mille TiO2 porous films was discussed.     

颗粒尺寸对微波烧结多孔NiTi合金的显微结构及力学性能的影响

以不同颗粒尺寸的Ni/Ti粉末为原料,采用微波烧结技术制备了多孔NiTi合金,并系统考察了颗粒尺寸对多孔NiTi合金的显微结构和力学性能的影响。结果表明,随着颗粒尺寸的减小,多孔NiTi合金中的Ti2Ni和Ni3Ti第二相减少而单质Ni相消失。同时,多孔NiTi合金的孔隙形貌由带尖角的不规则形状向近球形转变。此外,多孔NiTi合金的孔隙率和孔径随着颗粒尺寸的增大而增大,而洛氏硬度、抗压强度和抗弯强度均下降。因此,减小颗粒尺寸有利于获得理想的显微结构(纯净的物相和均匀的孔隙结构)和提高微波烧结多孔NiTi合金的力学性能。