电化学沉积法制备镁基Ca-P生物陶瓷涂层的研究

利用电化学沉积法在AZ31镁合金表面制备了Ca-P基生物涂层,使用扫描电子显微镜观察了经不同沉积时间处理后的涂层形貌,采用X射线衍射和能谱分析了涂层的结构和成分,通过电化学测试技术研究了在Hank’s仿生溶液中AZ31镁合金及其Ca-P涂层的腐蚀行为。结果表明,镁合金表面在Ca(NO3)2和NH4H2PO4电解液中电化学沉积形成Ca-P涂层由DCPD(CaHPO4·2H2O)片状晶体组成。且涂层形貌随时间发生变化。AZ31镁合金表面的钙磷涂层提高了镁合金的自腐蚀电位,显著地减小了镁合金的腐蚀电流密度。这表明经钙磷涂层处理的AZ31镁合金耐蚀性能得到明显的提高。钙磷涂层的形貌和结晶程度影响AZ31镁合金的耐蚀性。     

阳极氧化对镁合金在仿生溶液中降解性能影响的研究

利用电化学测试技术和浸泡试验研究了几种电压下的阳极氧化工艺对镁合金在Hank’s仿生溶液中降解性能的影响,同时对Hank’s溶液浸泡前后的氧化膜的形貌和成分进行了比较分析,以探讨氧化膜在仿生溶液中的降解行为。研究表明,随阳极氧化电压增大,阳极氧化膜表面的孔隙增大,电压升至110V时,试样表面烧蚀,阳极氧化膜疏松,平整度较差。阳极氧化提高了镁合金的耐蚀性,100V下的阳极氧化试样具有最大的涂层电阻,90V下阳极氧化试样具有最大电荷转移电阻和极化电阻。阳极氧化处理后的试样在Hank’s仿生溶液中可延缓镁合金降解1周左右,随后析氢速率有所增高。其中110V电压下生成的阳极氧化试样自腐蚀电位降低,浸泡1周后的析氢量明显高于其它试样。浸泡过程中,随着阳极氧化层的溶解,Hank’s溶液中的磷酸根和钙离子沉积在氧化层表面形成磷酸钙盐,其产物进入氧化膜的小孔内,形成无孔表面。     

AZ31镁合金的生物降解行为研究

研究了AZ31镁合金作为生物医用材料的体内外生物降解行为.初步分析了其作为可降解生物医用材料的可行性.体外浸泡实验结果表明,AZ31镁合金的降解行为与其所处环境有关,在Hank's溶液中的降解速度较在0.9%NaCl溶液中低;经过热处理后的AZ31镁合金较铸态和锻态降低了点蚀发生倾向,降解速度更慢.体内植入实验结果表明,AZ31镁合金与动物不同组织接触,其降解速度不同,在骨髓腔内的降解速度更快.植入5周时,镁合金已发生降解,20周降解更为明显.降解过程中镁合金表面有Ca-P物质沉积,表面具有优异的生物活性,其降解产物主要通过尿液进行排泄.在表面制备Ca-P涂层可降低镁合金的降解速度.AZ31镁合金是一种具有良好应用前景的新型生物可降解医用植入材料.     

高锰酸盐转化处理对医用AZ31B镁合金体外耐蚀性能的影响

现有的医用镁及镁合金在植入人体后耐蚀性能较差。采用高锰酸盐在医用AZ31B镁合金表面制备氧化锰转化膜,并采用SEM、XRD、电化学测试及浸泡试验研究其性能,对膜的形貌、组分、电化学性能和耐体液腐蚀性能进行了探讨。结果表明:氧化锰转化膜均匀分布在AZ31B镁合金表面,无规则分布有微裂纹,膜厚约52~165μm;转化膜的主要成分包括MgO,MnO,MnO2,Mn2O3和Mn3O4;转化膜能够有效改善AZ31B镁合金的体外耐蚀性能。     

模拟体液中的尿酸对AZ31B镁合金腐蚀行为的影响

过去,探讨高尿酸浓度体液中AZ31B镁合金腐蚀状况的研究不多。采用开路电位、交流阻抗谱和失重法等研究了AZ31B镁合金在不同尿酸浓度的模拟体液中的腐蚀行为。结果表明:在模拟体液中尿酸会加快镁合金的腐蚀,但是尿酸加入量与腐蚀速度不是简单的线性关系,尿酸浓度较小时其对腐蚀速率影响较大,当尿酸浓度超过104μmol/L后,镁合金的腐蚀速率不再显著增大;镁合金的失重速率随着浸泡时间的延长而减小,经8~12 d的浸泡后,镁合金的腐蚀过程基本达到稳定状态。     

生物医用AZ31B镁合金表面氧化锰转化涂层制备及性能研究

采用转化处理的方式,在AZ31B镁合金表面成功制备一层氧化锰转化涂层,以提高合金表面耐蚀性能。SEM研究表明,氧化锰转化涂层均匀分布在AZ31B镁合金表面,涂层中无规分布着微裂纹,涂层厚度为10~12μm。XRD研究表明,氧化锰转化涂层的主要成分包括MgO、MnO和Mn2O3。电化学和腐蚀浸泡实验结果表明,氧化锰转化涂层能够有效改善AZ31B镁合金的体外耐蚀性能。     

镁合金在NaCl溶液中的腐蚀电化学行为

为了提高镁合金材料的耐蚀性能,用电化学方法对比研究了AZ31,AZ61和AZ91镁合金在3.5%NaCl溶液中的电化学行为及缓蚀剂亚硝酸钠(NaNO2)对AZ61腐蚀电化学行为的影响。结果表明:3种镁合金的腐蚀速度大小依次为AZ31>AZ61>AZ91,其中AZ31的活化性能最高;NaNO2能抑制AZ61的析氢腐蚀速度,腐蚀表面较均匀,腐蚀电流密度J corr降低,腐蚀电位E corr发生正移;NaNO2属于阳极型缓蚀剂,其含量为2.0%时,对AZ61的缓蚀率高达85.1%。     

微波辅助法制备镁合金的植酸镁/羟基磷灰石复合涂层及其耐蚀性能

采用微波辅助法在AZ31镁合金表面制备了植酸镁/羟基磷灰石(PA/HA)复合涂层。利用FESEM、EDS、XRD和电化学性能测试等方法表征涂层的表面形貌、物相组成以及耐蚀性能,探究了植酸溶液的pH值对PA/HA复合涂层形貌及耐蚀性能的影响,并通过浸泡实验研究了镁合金及PA/HA复合涂层在模拟体液(SBF)中的降解矿化行为。结果表明:在植酸预处理中,植酸溶液的pH=5.0时制备得到的PA/HA复合涂层表面均匀、无裂纹,与镁合金基底的界面结合良好;并且在此pH值下PA/HA复合涂层包覆镁合金样品的交流阻抗最大,自腐蚀电流密度最小,说明其耐蚀性最好。在SBF中,PA/HA复合涂层能够快速诱导磷灰石的生成,并显著提高镁合金基底的耐蚀性能。     

工艺参数对镁合金植酸转化膜的影响

传统铬酸盐化学转化处理能提高镁合金的耐腐蚀性能,但因处理液有剧毒而受到限制.采用环保型金属处理剂植酸对AZ31B镁合金进行化学转化处理,通过正交试验初步确定了工艺参数(植酸浓度、处理液pH值、处理时间、处理温度)对植酸转化膜耐蚀性影响的主次顺序,并优化了工艺参数.采用扫描电子显微镜(SEM)、电子能谱仪(EDS)、光学金相显微镜对植酸转化膜腐蚀前后的形貌、成分和厚度进行了分析;通过电化学测试技术和化学浸泡法测试了其耐蚀性能.结果表明:与传统的铬酸盐和磷酸盐体系相比,经植酸处理后,AZ31B镁合金在3.5%NaCl溶液中的腐蚀电位分别提高了0.06 V和0.09 V,且在相同的电位下,阳极电流密度最小,电化学性能得到显著改善,腐蚀速度降低.     

Zn含量对生物医用镁合金耐Hank’s模拟体液腐蚀的影响

为了探讨Zn含量对Mg-Zn-Ca镁合金腐蚀性能的影响,采用熔融浇注法制备了Zn含量分别为4%,6%和8%的Mg-Zn-Ca镁合金,在37℃恒温下,以Hank’s模拟体液为腐蚀介质,研究了其腐蚀、电化学行为。结果表明:在Hank’s模拟体液中,4%Zn的镁合金腐蚀速率最小,自腐蚀电位最高;3种镁合金中,4%Zn的容抗弧最大,即耐腐蚀性能最佳。     

Electrochemical noise analysis on the pit corrosion susceptibility of biodegradable AZ31 magnesium alloy in four types of simulated body solutions

Magnesium alloys have been investigated as biodegradable implant materials since the last century. Non-uniform degradation caused by local corrosion limits their application, and no appropriate technology has been used in the research. In this study, electrochemical noise has been used to study the pit corrosion on magnesium alloy AZ31 in four types of simulated body solutions, and the data have been analyzed using wavelet analysis and stochastic theory. Combining these with the conventional polarization curves, mass loss tests and scanning electron microscopy, the electrochemical noise results implied that AZ31 alloy in normal saline has the fastest corrosion rate, a high pit initiation rate, and maximum pit growth probability. In Hanks’ balanced salt solution and phosphate-buffered saline, AZ31 alloy has a high pit initiation rate and larger pit growth probability, while in simulated body fluid, AZ31 alloy has the slowest corrosion rate, lowest pit initiation rate and smallest pit growth probability.     

Fabrication and Characterization of Ca-Mg-P Containing Coating on Pure Magnesium

A biodegradable Ca-P coating mainly consisting of β-tricalcium phosphate(β-TCP) was fabricated on pure magnesium via the chemical deposition in a simulated Hank s solution.The method significantly accelerated the coating formation on magnesium.Moreover,the morphology,phase/chemical composition,the coating formation mechanism as well as degradation behavior in phosphate buffered saline(PBS) solution were investigated.Scanning electron microscopy(SEM) images showed that the coating had three layers and X-ray diffraction(XRD) patterns showed that the coating mainly contained Ca3(PO4)2 and(Ca,Mg)3(PO4)2.Electrochemical test showed that the corrosion current density(Icorr) of the coated Mg was decreased by about one order of magnitude as compared to that of pure magnesium.The immersion test indicated that the coating could obviously reduce the degradation rate.     

Electrochemical behaviour of Ti–25Nb–3Mo–3Zr–2Sn biomedical alloy in different simulated physiological environments

The electrochemical corrosion behaviour of biomedical Ti–25Nb–3Mo–3Zr-2Sn (TLM) alloy was investigated in various simulated body fluids at 37±0·5°C utilising potentiodynamic polarisation and current–time curves. The Ti–6Al–4V (TC4) alloy was also investigated to make a comparison. The different simulated body fluids comprised of 0·9%NaCl saline, Hank’s and Ringer’s solution were employed. The effect of heat treatment on the electrochemical behaviour of the TLM alloy was also considered. It was discovered that all the test specimens were passivated once immersed into the simulated body fluids. It was also found that the TLM alloy has poorer corrosion resistance in Hank’s solution, due to the chemical composition of the Hank’s. After different heat treated, the TLM alloy had different phases and microstructure, and the corrosion behaviour of the TLM alloy was different. In this study, after the heat treatment of 760°C/1 h/AC+550°C/6 h/AC, the TLM alloy had better corrosion resistance. Owing to the corrosion resistance of the TLM alloy was influenced by numerous factors, such as microstructure and the chemical composition of electrolyte, the corrosion behaviour of the TLM alloy is complex. By comparing with the corrosion behaviour of the TC4 alloy, the TLM alloy has poorer corrosion resistant than the TC4 alloy under the same conditions. But the current–time curves of the TLM alloy were more stable than these of the TC4 alloy with further experiments, because of the more passivation film on the surface of the TLM alloy.     

Hank′s溶液中注碳Ti6Al4V合金缝隙试样的电化学行为

为探索碳离子注入Ti-6Al-4V合金在人工模拟体液Hank's溶液中的性能,采用电化学方法、扫描电子显微镜和X射线衍射对其缝隙试样在人工模拟体液Hank's溶液中的电化学行为进行了研究.结果表明:碳离子注入后,Ti-6Al-4V合金缝隙试样的腐蚀电位升高、电荷转移电阻增大,阳极极极化电流密度降低,改善了电化学性能;碳离子注入后,Ti-6Al-4V合金表面形成主要由TiC组成的无序层膜,该膜层阻滞了合金元素的溶解,提高了合金的耐缝隙腐蚀性能.     

Galvanisches Verzinken von Magnesiumlegierungen

Zinc‐Plating of Magnesium Alloys Magnesium alloys are highly susceptible to corrosion that limits their application when exposure to corrosive service conditions is needed. One of the ways to prevent corrosion is to coat the magnesium‐based substrate to avoid a contact with an aggressive environment. Results concerning corrosion behaviour of wrought AZ31 magnesium alloy with electrolytic zinc coatings deposited from different electrolyte solutions are described. Evaluation of corrosion processes in chlorides containing solutions was performed by electrochemical measurements. It was found that thick and dense electrolytic zinc coatings formed on AZ31 significantly improve the corrosion behaviour of magnesium alloy after one hour immersion of zinc coated magnesium alloys in corrosive media. Further increase of immersion time leads to relatively fast decrease of corrosion properties. Electrolytic zinc coatings obtained in consecutive alkaline / acidic process demonstrate an improvement of corrosion resistance of coated AZ31. The time to coating degradation strongly increases.     

Preliminary study of biodegradation of AZ31B magnesium alloy

Magnesium alloys are potential to be developed as a new type of biodegradable implant material by use of their active corrosion behavior. Both in vitro and in vivo biodegradation properties of an AZ31B magnesium alloy were investigated in this work. The results showed that AZ31B alloy has a proper degradation rate and much lower hydrogen release in Hank’s solution, with a degradation rate of about 0.3 mm/year and hydrogen release below 0.15 mL/cm². The animal implantation test showed that the AZ31B alloy could slowly biodegrade in femur of the rabbit and form calcium phosphate around the alloy sample, with the Ca/P ratio close to the natural bone.     

New insights into the effect of Tris-HCl and Tris on corrosion of magnesium alloy in presence of bicarbonate,sulfate,hydrogen phosphate and dihydrogen phosphate ions

In vitro degradation is an important approach to screening appropriate biomedical magnesium(Mg) alloys at low cost. However, corrosion products deposited on Mg alloys exert a critical impact on corrosion resistance. There are no acceptable criteria on the evaluation on degradation rate of Mg alloys. Understanding the degradation behavior of Mg alloys in presence of Tris buffer is necessary. An investigation was made to compare the influence of Tris-HCl and Tris on the corrosion behavior of Mg alloy AZ31 in the presence of various anions of simulated body fluids via hydrogen evolution, p H value and electrochemical tests.The results demonstrated that the Tris-HCl buffer resulted in general corrosion due to the inhibition of the formation of corrosion products and thus increased the corrosion rate of the AZ31 alloy. Whereas Tris gave rise to pitting corrosion or general corrosion due to the fact that the hydrolysis of the amino-group of Tris led to an increase in solution p H value, and promoted the formation of corrosion products and thus a significant reduction in corrosion rate. In addition, the corrosion mechanisms in the presence of Tris-HCl and Tris were proposed. Tris-HCl as a buffer prevented the formation of precipitates of HCO_3~-, SO_4~(2-),HPO_4~(2-) and H_2PO_4~- ions during the corrosion of the AZ31 alloy due to its lower buffering p H value(x.x).Thus, both the hydrogen evolution rate and corrosion current density of the alloy were approximately one order of magnitude higher in presence of Tris-HCl than Tris and Tris-free saline solutions.     

Fluoride Conversion Coating on Biodegradable AZ31B Magnesium Alloy

A fluoride conversion coating was successfully prepared on AZ31B magnesium alloy by chemical reaction in hydrofluoric acid. Morphologies, composition, bonding strength, corrosion properties, in vitro cytotoxicity and antibacterial properties of the coating were investigated, respectively. The scanning electron microscopy observations revealed a dense coating with some irregular pores. The thin-film X-ray diffraction analysis indicated that the coating was mainly composed of MgO and MgF2. The electrochemical impedance spectroscopy results showed that the fluoride conversion coating significantly improved the corrosion resistance of AZ31B. The hydroxyapatite formed on the surface of the fluoride coated AZ31 B after being immersed in the simulated blood plasma indicated the good bioactivity of the material. The in vitro cytotoxicity test showed that the fluoride coated AZ31B alloy was not toxic to BMMSCs （human bone marrow-derived mesenchymal stem cells）. It was also found that the fluoride coated AZ31 B alloy had antibacterial capability.     

Formation by reactive magnetron sputtering of TiN coating on Ti-implanted magnesium alloy

Reactive magnetron sputtering method was used to deposit TiN coating on Ti-implanted magnesium alloy. FESEM, GIXRD and AES were used to investigate this surface system's micro-morphology, crystalline structure and chemical composition, respectively. It showed that TiN coating took on a compact surface morphology and existed as a columnar crystalline structure. The results of the electrochemical test and immersion test showed that the corrosion resistance of AZ31 was greatly improved in 3.5 wt.% NaCl solution by this kind of surface treatment technique. It was mainly due to the combined effect of the dense TiN coating, the Ti-implanted layer and the good adhesion between coating and substrate.