Comparison of SBF and DMEM in terms of electrochemical properties of common metallic biomaterials

Corrosion behavior is an important parameter for metallic biomaterials used in the body environment. To mimic bodily fluids, simulated body fluid (SBF) has been used extensively. Even though many studies focus on corrosion inside SBF, SBF has a very time consuming and delicate preparation procedure and contains no essential and organic components for the cell environment, which may affect corrosion kinetics. We aimed to investigate whether corrosion behavior or kinetics change in different solutions, SBF and Dulbecco's modified Eagle medium (DMEM). For this purpose, five commonly used metallic biomaterials, AISI 316 stainless steel, CoCrMo alloy, CP-Ti, Ti6Al4V, and Ti6Al7Nb were subjected to open circuit measurements, cyclic polarization, and electrochemical impedance spectroscopy. Quantitative analyses were performed and surface topography was investigated via scanning electron microscope and a roughness tester. We observed that the materials exhibited similar behaviors in SBF and DMEM but the corrosion kinetics were somewhat different and the results obtained from DMEM were time dependent.     

Electrochemical characterisation of biomedical alloys for surgical implants in simulated body fluids

The aim of this research is to compare the electrochemical behaviour of two biomedical alloys, AISI 316L and CoCrMo in simulated body fluids. This comparison is focused on the influence of solution chemistry and immersion time on the passive behaviour using electrochemical techniques, potentiodynamic curves, potentiostatic tests and electrochemical impedance spectroscopy (EIS).Influence of albumin, used as model protein, on both biomaterials depends on the nature of the alloy. It decreases the corrosion resistance of AISI 316L while increases the corrosion resistance of CoCrMo. Although it is known that it adsorbs on both alloys, properties of the passive layer modifies the effect of albumin. On the contrary, precipitation of phosphate ions could explain the highest resistance values in the phosphate solutions on both cases.The study shows that the electrochemical behaviour of CoCrMo shows higher transfer resistance and lower capacitance which means thicker and more protective passive films than AISI 316L. However, differences between both alloys disappear with time depending on the solution chemistry.     

EIS study of porous NiTi biomedical alloy in simulated body fluid

The electrochemical impedance spectroscopy was used for monitoring the formation of surface film on a fixtured sintering porous NiTi biomedical alloy in simulated body fluid (SBF) media during 12 days. Effect of NiTi sintering time on the formation of surface film in SBF was investigated. The formed surface film was calcium phosphate hydrate (CPH) with a pillar particulate structure which was developed to a spongy network with increasing the sintering time. Using such electrochemical techniques, it was shown that NiTi samples obtained after 3 h sintering at 950 °C, have higher tendency for the formation of a stable CPH film during the test.     

In Vitro Bioactivity of Surface-Modified β-Ti Alloy for Biomedical Applications

Ti-15Mo (β-Ti) alloy was subjected to chemical followed by thermal treatment for the enhancement of in vitro bioactivity and corrosion resistance. The surface-modified specimens were characterized using scanning electron microscopy (SEM) and energy dispersive x-ray analysis (EDAX). The results indicated the formation of nanoporous layer and flake-like structure developed during chemical and subsequent thermal treatments. The in vitro bioactivity of the surface-treated β-Ti alloy was evaluated by immersing in simulated body fluid (SBF) solution. The formation of apatite particles was confirmed using Fourier transform-infrared spectroscopy, SEM, and EDAX analyses. Moreover, the electrochemical behavior of surface-modified specimens in SBF solution was evaluated using potentiodynamic polarization and electrochemical impedance spectroscopy. The results revealed that the surface-modified specimens exhibited higher potential value and lower current density when compared to untreated specimen. The EIS studies showed the formation of new layer, indicating the growth of apatite-like particles.     

锻造CoCrMo合金关节材料的滑动摩擦腐蚀行为

采用UMT-2多功能摩擦磨损试验机和电化学工作站(CHI614E)摩擦腐蚀试验平台,考察了医用CoCrMo合金在生理盐水润滑条件下的摩擦腐蚀行为,利用扫描电镜观察了CoCrMo合金在摩擦腐蚀之后的形貌特征。结果表明,随着载荷的增大,CoCrMo合金摩擦腐蚀后的腐蚀电位降低,腐蚀电流增大。摩擦腐蚀的摩擦因数均大于纯摩擦因数,且随载荷的增加而减小。摩擦腐蚀的磨损破坏比纯摩擦严重,磨损机理主要表现为犁沟磨损和剪切塑变造成的局部剥落。     

载波处理对AZ91D镁合金耐蚀性能的影响 Ⅰ-载波处理对AZ91D镁合金腐蚀行为的影响

对AZ91D镁合金进行载波钝化,利用正交试验确定载波钝化工艺的最佳工艺参数。使用扫描电子显微镜(SEM)观察载波钝化后的AZ91D镁合金表面形貌;采用极化曲线、电化学阻抗谱(EIS)、扫描电化学显微镜(SECM)、Mott-Schottky曲线等电化学方法研究了载波钝化对合金耐蚀性能的影响。结果表明:载波钝化后,AZ91D镁合金表面生成了一层非常致密的膜,其耐蚀性能显著提高。     

Oxidation resistance of boronized CoCrMo alloy

Boronizing of CoCrMo alloy has been performed by means of a powder-pack method using commercial LSB powders at 850, 900 and 950 °C for 8 h, respectively. In this study, the boronized CoCrMo alloy before and after oxidation tests were characterized using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The distribution of alloy elements of boronized samples from surface to interior was determined using energy-dispersive X-ray spectroscopy (EDS). XRD study showed the boride layer formed at 950 °C/8 h consisted of the phases Co₂B and CrB. Depending on boronizing temperature, the thickness of boride layer ranged from 2 to 11 μm. Cyclic oxidation behavior of the boride layer has been investigated at an oxidation temperature of 950 °C with a total exposure time up to 50 h in air. The test results indicated that the boronized CoCrMo alloy had superior oxidation resistance compared to unboronized sample.     

NaOH浓度对NiTi形状记忆合金表面类骨磷灰石形成的影响

研究了不同浓度NaOH对NiTi形状记忆合金在模拟体液(SBF)中诱导磷灰石沉积的影响，用XRD，ESEM，FTIR及XPS等分析了碱处理前后试样表面的结构、形貌、基团和组元化合价的变化，结果表明，经1mol／L NaOH溶液处理的NiTi合金因为钛酸钠的生成而具有较高的生物活性，在SBF中浸泡3d后自然沉积含CO3^2-的类骨磷灰石，而且原子吸收光谱分析其在Hank’S溶液中的镍离子溶出量最少，随着碱处理浓度的提，NiTi合金表面除钛酸钠外，还有镍酸钠生成，使磷灰石形核的孕育期加长，在Hank’S溶液中的镍离子溶出量也明显增加。     

Effect of hydroxyapatite‐titanium‐MWCNTs composite coating fabricated by electrophoretic deposition on corrosion and cellular behavior of NiTi alloy

In this study, the hydroxyapatite (HA)‐titanium (Ti, 20 wt.%) multiwalled carbon nanotubes (MWCNTs, 1 wt.%) composite coating was applied on the NiTi alloy by using the electrophoretic deposition (EPD) technique. The morphologies and the phase structures of the coatings were investigated by the FESEM and XRD analysis, respectively. The corrosion behaviors of the coated NiTi samples were investigated using the polarization and electrochemical impedance spectroscopy tests in a simulated body fluid (SBF). The amounts of the released Ni ions from the coated NiTi were studied in the SBF. The results of the electrochemical tests revealed the corrosion resistance of the NiTi coated with HA was further improved by the addition of the Ti and MWCNTs to the HA coating. The current density and corrosion resistance of the NiTi alloy changed from 2.52 μA.cm^?2 and 24.13 kΩ to 0.91 nA.cm^?2 and 5.92 MΩ after coated with the HA‐Ti‐MWCNTs composite coating. Also, the number of nickel ions released from the surface of the NiTi alloy to the SBF medium suppressed from 11.8 to 0.08 μgr.L^?1, after coating with HA‐Ti‐MWCNTs. Also, the cellular proliferation in the culture medium consisting of the NiTi alloy coated with the HA‐Ti‐MWCNTs improved significantly (compared with that of the NiTi alloy) as shown no toxicity in the cell culture medium.     

Microstructure and surface mechanical properties of electrodeposited Ni coating on Al 2014 alloy

The surface of Al 2014 was modified by electrochemical deposition of Ni with an aim to improve the surface mechanical properties of the alloy. The deposition was performed at various values of DC current, potential and time using standard Watt's bath. The samples were heat treated to improve the adhesion and hardness of Ni coatings. Material characterization was performed using scanning electron microscopy coupled with energy dispersive X-ray spectroscopy, atomic force microscopy and X-ray diffraction. Microhardness, nanohardness, microscratch and coefficient of friction measurements were undertaken to determine the surface mechanical properties of the electrodeposited Ni coating. Experimental results indicate that electrochemical deposition combined with heat treatment can be used to improve the surface properties of Al alloys.     

Effect of Applied Stresses on the Microstructure and Dissolution Behavior of Plasma Sprayed Wollastonite Coatings

Wollastonite coatings were deposited on the U-shape titanium alloy coupons by atmospheric plasma spraying.The effect of applied stresses on the microstructure and dissolution behavior of wollastonite coatings was investigated.The microstructure and composition of coatings were examined by scanning electron microscope(SEM)and electron diffraction spectroscopy(EDS).In addition,the dissolution behavior of coatings was evaluated by immersion in simulated body fluid(SBF).More apatite is observed on the surface of coatings under a tensile stress and a stress-free condition after immersion in the SBF solution,whereas almost no apatite can be found for the coatings under a compressive stress.The dissolution rate of coatings characterized by the pH changes and the ion concentration of Ca,Si and P in the SBF solution is lower under the compressive stress than those under a tensile stress or a stress-free condition.It can be concluded from the experimental results that the compressive stress inhibits the dissolution of wollastonite coatings and the formation of apatite,whereas a tensile stress enhances the two processes.     

On the Electrodeposition of Ca-P Coatings on Nitinol Alloy: A Comparison Between Different Surface Modification Methods

In this study, a combination of surface modification process and the electrochemical deposition of Ca-P coatings was used for the modification of the Nitinol shape memory alloy. DSC, SEM, GIB-XRD, FT-Raman, XPS, and FTIR measurements were performed for the characterization of the samples. Results indicated that chemical etching and boiling of the samples in distilled water formed TiO film on the surface. After the chemical modification, subsequent aging of the sample, at 470 °C for 30 min, converted the oxide film to a stable structure of titanium dioxide. In that case, the treated substrate indicated a superelastic behavior. At the same electrochemical condition, the treated substrate revealed more stable and uniform Ca-P coatings in comparison with the abraded Nitinol substrate. This difference was attributed to the presence of hydroxyl groups on the titanium dioxide surface. Also, after soaking the sample in SBF, the needle-like coating on the treated substrate was completely covered with the hydroxyapatite phase which shows a good bioactivity of the coating.     

Corrosion of biomaterials: anodic treatment and evaluation of 316L stainless steel in simulated body fluid

The influence of electropolishing at different conditions on the electrochemical behaviour of 316L stainless steel (316L SS) in simulated body fluid (SBF) was investigated. Accordingly, 316L SS samples were electropolished in several electropolishing baths of H₃PO₄ and H₂SO₄ at 2–6 applied volts and 50–110°C for different time intervals. The corrosion behaviour then was studied by means of potentiodynamic polarisation technique and electrochemical impedance spectroscopy in SBF at 37°C. The surface morphology was also investigated by scanning electron microscopy. The results proved that the treated samples had better corrosion resistance than nonpolished one. The highest corrosion resistance was observed for the treated sample at 5?V and 90°C in 10:90 ratio of acidic electrolyte (H₃PO₄:H₂SO₄) for 15?min. Moreover, the corrosion resistances of anodically treated samples were found to be dependent greatly on applied volt, bath temperature, polishing time and phosphoric to sulphuric acids ratio.     

Influence of molybdate species on the tartaric acid/sulphuric acid anodic films grown on AA2024 T3 aerospace alloy

AA2024 T3 alloy specimens have been anodised in tartaric acid/sulphuric media and tartaric acid/sulphuric media containing sodium molybdate; molybdate species were added to the anodising bath to enhance further the protection provided by the porous anodic film developed over the macroscopic alloy surface. Morphological characterisation of the anodic films formed in both electrolytes was undertaken using scanning electron and transmission electron microscopies; the chemical compositions of the films were determined by Rutherford backscattering spectroscopy that was complemented by elemental depth profiling using rf-glow discharge optical emission spectrometry. The electrochemical behaviour was evaluated using potentiodynamic polarisations and electrochemical impedance spectroscopy; the corrosion performance was examined after salt spray testing. The porous anodic film morphology was little influenced by the addition of molybdate salt, although thinner films were generated in its presence. Chemical composition of the anodic film was roughly similar; however, addition of sodium molybdate in the anodizing bath resulted in residues of molybdate species in the porous skeleton and improved corrosion resistance measured by electrochemical techniques that was confirmed by salt spray testing.     

Influence of Nd on Microstructure and Bio-corrosion Rsistance of Mg-Zn-Mn-Ca Alloy

将0.4%(质量分数,下同)的Nd添加到Mg-6Zn-1Mn-0.5Ca合金中,以研究稀土元素Nd对合金显微组织和耐生物腐蚀性能的影响。采用金相(OM)、带能谱的扫描电镜(SEM+EDS)以及XRD等手段分析了合金的微观组织。采用静态浸泡、析氢和电化学极化等手段研究了合金在模拟体液(SBF)中的耐腐蚀性能。结果表明,随着Nd的添加,合金的显微组织得到了明显的细化。在Mg-6Zn-1Mn-0.5Ca-0.4Nd合金中形成了2种第二相的机械混合物Ca2Mg6Zn3+Mg41Nd5。在SBF中浸泡7d以后,较多的此种混合物仍残留于含Nd合金的表面,而在不含Nd的合金中,只有极少量的颗粒状Ca2Mg6Zn3残留在其表面。故Nd的添加显著提高了Mg-6Zn-1Mn-0.5Ca合金的耐生物腐蚀性能。     

等离子喷涂TiO2-CaF2复合涂层的结构及体外生物矿化能力

目的等离子喷涂TiO_2涂层是生物惰性材料,不能与骨组织很好地结合,制备TiO_2-CaF_2复合涂层以提高氧化钛涂层的体外生物矿化能力。方法利用等离子喷涂技术在医用Ti合金表面制备TiO_2-CaF_2复合涂层。采用X射线衍射仪(XRD)、扫描电子显微镜(SEM)和拉曼光谱仪(Raman)对复合涂层的微观结构进行表征,利用接触角仪、三维轮廓仪和电化学工作站考察复合涂层的接触角、表面粗糙度和耐腐蚀性能。采用模拟体液(SBF)浸泡实验考察复合涂层的体外矿化能力。结果 TiO_2和TiO_2-20%CaF_2涂层主要由金红石型TiO_2构成,其中含有少量的锐钛矿型TiO_2成分。20%CaF_2的掺杂会促进金红石型TiO_2的形成。CaF_2的加入可改变TiO_2涂层的表面形貌,表面粗糙度Ra从4.96μm降低至0.94μm,亲水性也得到增强。TiO_2-CaF_2复合涂层在SBF中的耐腐蚀性能也较TiO_2涂层有所提高。经SBF浸泡28 d后,TiO_2-CaF_2复合涂层表面可沉积类骨磷灰石,显示了较好的体外矿化能力,而TiO_2涂层则无此能力。结论 CaF_2的掺杂可使TiO_2涂层的表面粗糙度下降,亲水性增强,耐腐蚀性增强。体外矿化实验结果表明,TiO_2-CaF_2复合涂层表面可沉积类骨磷灰石,显示了较好的生物活性。     

Damage Behavior of SnAgCu Solder under Thermal Cycling

电子封装焊点的热循环失效是焊点材料损伤逐步发展的结果,本工作旨在对SnAgCu钎料的热循环损伤失效行为进行研究.以连续损伤力学理论为基础,提出了一种适用于热循环条件下SnAgCu钎料蠕变-疲劳交互作用的损伤模型.据此,设计了热力循环实验和热循环实验用以标定损伤模型相关参量.自行设计了双金属剪切加载装置并结合温度循环实验,对SnAgCu钎料的热力耦合损伤行为进行了深入研究.以电阻变化率作为损伤变量,并在热循环的不同周次测量试样的损伤值从而验证损伤模型.结果表明:所提出的幂函数形式的损伤模型能较好的描述SnAgCu钎料的热循环损伤演变.最后,对热循环条件下SnAgCu钎料试样的微观组织演变进行了SEM分析,从而揭示其损伤演变机理.     

天然海水微生物对5083铝合金初期腐蚀行为的影响

利用荧光电子显微镜,扫描电镜及能谱表面分析技术和开路电位,电化学阻抗谱,动电位极化电化学技术研究了在天然海水中浸泡初期,天然海水微生物对5083铝合金腐蚀行为的影响.结果表明,在天然海水中,铝合金表面形成良好的生物膜.电化学结果表明,在天然海水中铝合金腐蚀电位负移,点蚀电位正移,电荷转移电阻增大,说明短期浸泡时,天然海水生物膜的形成可以抑制其腐蚀,尤其对点蚀具有明显的抑制作用.在无菌海水中,随时间的增长,铝合金的腐蚀也受到一定程度的抑制,原因是锈蚀产物的形成对铝合金具有一定的保护作用.     

Corrosion protection of AZ31 magnesium alloy by silane film of partly hydrolysed BTESPT

Abstract

The corrosion protective behaviour of bis-[triethoxysilylpropyl]tetrasulphide (BTESPT) silane film formed by partly hydrolysed BTESPT on AZ31 Mg alloy was investigated. Fourier transform infrared spectroscopy (FTIR) was used for structural characterisation of the silane film. Scanning electron microscope (SEM) and energy dispersive X-ray (EDS) analysis were used for observation of surface morphology and elements analysis of the film. The corrosion behaviours of bare and the silane treated AZ31 Mg alloy in 3·5 wt-%NaCl solution were studied using electrochemical polarisation test, electrochemical impedance spectroscopy (EIS) and immersion test. The results demonstrate that bare AZ31 Mg alloy endures severe corrosion even in NaCl water solution at pH 12, although the corrosion is lighter than that in neutral and acidic NaCl water solution, and that the BTESPT silane film can improve the corrosion protection performances of AZ31 Mg alloy and a lower corrosion rate correlated with higher pH.     

Mg-4.0Zn-2.0Sr-0.4Ca合金复合涂层的耐腐蚀性能

通过环保型阳极氧化工艺及聚合沉积技术在生物材料Mg-4.0Zn-2.0Sr-0.4Ca合金表面逐层制备阳极氧化膜、SiO₂溶胶凝胶、聚多巴胺(PDA)和壳聚糖(CS)复合涂层。采用扫描电镜(SEM)、X射线衍射仪(XRD)观察涂层形貌并确定相组成,采用电化学测试、SBF浸泡试验比较涂层对合金耐蚀性能的影响。结果表明,制备的复合涂层致密完整无缺陷。在SBF溶液中,复合涂层随腐蚀时间的延长逐渐产生裂纹并破碎,产生较小的腐蚀坑,腐蚀在一定程度上被控制在表面,而无涂层Mg-4.0Zn-2.0Sr-0.4Ca合金在SBF溶液中的腐蚀以点蚀和局部腐蚀为主,且腐蚀程度随腐蚀时间的延长而加剧。复合涂层在SBF溶液中的腐蚀电流密度、腐蚀电位和平均腐蚀速率分别为5.7039 μA/cm²、-1.4203 V(vs SCE)和0.163 g/(m²·h),均优于无涂层镁合金,且平均腐蚀速率降幅达50%以上,说明制备的复合涂层可显著提高Mg-4.0Zn-2.0Sr-0.4Ca合金的耐腐蚀性能。