水热处理对AZ31镁合金微弧氧化陶瓷层组织结构及耐蚀性的影响

采用两种不同成分的溶液对AZ31镁合金微弧氧化(MAO)陶瓷层进行125℃+18 h的水热处理,研究了水热溶液成分对微弧氧化陶瓷层组织结构及耐蚀性能的影响,探讨了水热成膜及膜层腐蚀机理。研究结果表明：水热处理过程中微弧氧化陶瓷层表面的MgO部分溶解,释放出的Mg²⁺与碱性水热溶液中的OH^-结合形成Mg(OH)₂纳米片沉淀在陶瓷层表面及孔洞内;而在含有Al³⁺和Co²⁺的溶液处理过程中,溶液中的Al³⁺和Co²⁺取代沉淀在MgO表面及孔洞内的Mg(OH)₂中部分Mg²⁺的位置形成双金属氢氧化物(LDH)纳米片,将微弧氧化陶瓷层表面的孔洞及裂纹缺陷闭合。润湿性与电化学测试结果表明,亲水性的Mg(OH)₂/MAO复合膜层因Mg(OH)₂对MAO陶瓷层的封孔效应能在一定程度上提高MAO陶瓷层的耐蚀性,而疏水性的LDH/MAO复合膜层因封孔效应和LDH离子交换能力能显著提高MAO陶瓷层的耐蚀性。     

TiO2-PTFE对6063铝合金微弧氧化膜层的影响

为了探究TiO₂和聚四氟乙烯(PTFE)对6063铝合金微弧氧化膜层的影响,在Na₂SiO₃基础电解液中添加TiO₂和PTFE固体纳米微粒,采用微弧氧化技术(MAO)在6063铝合金上制备了微弧氧化复合膜层。利用扫描电子显微镜(SEM)、X射线衍射(XRD)、摩擦磨损试验机以及电化学工作站研究了微弧氧化陶瓷膜层的形貌、相组成、元素分布以及耐磨性和耐蚀性。结果表明：加入4 g/L TiO₂和10 mg/L PTFE制成复合添加剂制备的复合膜层其表面孔径尺寸明显降低,膜层厚度增加,结构致密;摩擦系数由0.9降到0.5,耐磨性最好;电化学试验测得复合膜层的自腐蚀电位最大,为-0.18 V;自腐蚀电流密度最小,为1.09×10^-8 A/cm²。     

封闭对铝合金微弧氧化膜在酸性溶液中耐蚀性的影响

为了提高7A85铝合金的耐蚀性, 采用单极性正脉冲微弧氧化(MAO)技术在其表面制备了陶瓷膜层, 并采用稀土铈盐、铬酸盐和SiO₂溶胶对MAO膜进行封闭处理。采用扫描电子显微镜(SEM)、X射线衍射仪和电化学工作站研究了封闭处理对膜层表面形貌、结构和在酸性NaCl溶液中腐蚀行为的影响。实验发现, MAO膜在酸性NaCl溶液中不能有效地保护铝合金基体。稀土铈盐和铬酸盐封闭处理通过沉积水合氢氧化物封闭孔隙, 可以提高MAO膜的耐蚀性。但在酸性溶液中, 封孔物质会和H⁺发生反应而溶解, 故经封闭的MAO试样也会发生腐蚀失效。SiO₂溶胶封闭处理后MAO膜表面覆盖一层凝胶, 使膜层成为完整的致密层, 可以保护铝合金基体在酸性NaCl溶液中免受腐蚀。     

MgCl2对锌在干湿交替环境中腐蚀行为的影响

使用腐蚀失重、X射线衍射(XRD)、扫描电子显微镜与能谱(SEM-EDS)等手段研究了干湿交替环境中MgCl₂对锌腐蚀行为的影响。结果表明,MgCl₂对锌的腐蚀有显著的抑制作用;在沉积NaCl条件下锌表面的腐蚀产物为Zn₅(OH)₈Cl₂·H₂O、Zn₄CO₃(OH)₆·H₂O和Zn(OH)₂,而在沉积MgCl₂条件下锌表面的腐蚀产物只有Zn₅(OH)₈Cl₂·H₂O。在干湿交替环境中MgCl₂对锌腐蚀行为的影响主要是Mg²⁺与氧还原反应产生的OH^-结合使阴极区的pH值降低造成的。     

镁合金表面含ZrO2微弧氧化复合膜层的研究进展

镁合金耐蚀性差,极大限制了其在易腐蚀环境中的应用。微弧氧化能够在镁合金表面制备一层类陶瓷氧化膜,能有效提高其耐蚀性。受微弧氧化成膜机理的影响,膜层中往往存在大量孔洞和裂纹;并且通常氧化膜主要由MgO组成,在潮湿或酸性环境中会吸水或溶解,导致膜层的耐蚀性不理想。将具有优良化学稳定性和高硬度的ZrO₂引入镁合金微弧氧化膜中,获得主要由ZrO₂构成或含ZrO₂的氧化膜,同时减少膜层中缺陷,能够提高其对镁合金基体的保护效果。从镁合金微弧氧化电解液、电参数、两步微弧氧化工艺及与其他表面处理技术相结合的4个方面概述了含ZrO₂微弧氧化复合膜层的制备工艺、成膜机制及耐蚀性等方面研究的进展,同时分析了各自存在的问题及不足。未来有必要优化制备含ZrO₂微弧氧化膜的电解液的组成,以保证其稳定性和有效性,并明确使用过程中电解液各成分的消耗和补充规律。进一步研究两步微弧氧化工艺,获得对镁合金基体有更好保护作用的复合膜层。探索将微弧氧化与其他表面处理技术相结合,综合利用2种技术及膜层的优点。根据ZrO<...     

基于碳纤维的新型自支撑电极制备方法

借鉴自支撑电极的制备原理,利用电化学沉积结合(NH₄)₂S₂O₈和NaOH沉积液进行表面处理等手段制备了基于碳纤维表面Cu(OH)₂纳米结构的自支撑电极,分析测试了碳纤维表面的微观形貌、表面元素组成及其分布和表面物质的晶型以及利用水热反应在其表面附着电化学物质MnO₂后的电化学性能。结果发现,当(NH₄)₂S₂O₈的浓度为0.43 g/L、NaOH浓度为30.48 g/L、处理时间为12 min时,由SEM观察发现碳纤维表面的Cu(OH)₂纳米纤维的直径、长度、数量都较适宜;XPS、XRD和EDS的测试结果,沉积液处理后碳纤维表面部分单质铜转化为Cu(OH)₂,此结构非常有利于电化学物质的负载而由此构成开放、具有核壳结构的高性能电极材料;恒电流充放电(GCD)测试结果表明此电极材料具有极快的充放电速度。因此本文首次成功地在碳纤维表面的铜层表面原位生长出Cu(OH)₂纳米纤维,为未来以超级电容器为代表的能源设备的性能提升和商业化应用开拓了一种新的电极制备方法。      

镁合金表面微弧氧化-SiO2复合膜层的微观结构和耐蚀性

采用有机醇盐水解法制备SiO2溶胶,用浸溃-提拉制膜技术在AZ31B镁合金微弧氧化陶瓷层表面制备SiO2膜层,研究了镁合金表面微弧氧化-SiO2复合膜层的微观结构和耐蚀性.结果表明:SiO2溶胶进入微弧氧化陶瓷层表面的微孔并形成了SiO2膜层;由微弧氧化陶瓷层和SiO2膜层组成的复合膜层的腐蚀电位比单一陶瓷层明显提高,...     

碱式碳酸镁焙烧法制备多孔氧化镁晶体

【目的】实现多孔MgO晶体的可控制备。【方法】以菱镁矿为镁源,采用水化碳化-低温水溶液法,热解Mg(HCO₃)₂溶液合成平均直径为10.0μm、平均长度为50.0μm的多孔棒状碱式碳酸镁(4MgCO₃·Mg(OH)₂·4H₂O);通过焙烧法制备多孔MgO晶体,分别探讨焙烧温度、时间对前驱体4MgCO₃·Mg(OH)₂·4H₂O分解率、 MgO物相组成和形貌的影响,探究4MgCO₃·Mg(OH)₂·4H₂O热分解机制。【结果】在焙烧温度为700℃、时间为3.0 h时,制得平均直径为20.0μm、平均长度为50.0μm、比表面积为76.12 m²/g的介孔棒状MgO晶体;在4MgCO₃·Mg(OH)₂·4H₂O分解过程中,随着温度升高,结晶水失去,—OH的分离和C—...     

Mg-Al-Zn合金激光焊接头的耐蚀性研究

分别采用激光焊和激光填丝焊2种方法对4 mm厚的Mg-Al-Zn合金进行焊接，并对镁合金接头的腐蚀机理进行了探讨。采用极化曲线测量、电化学阻抗谱测试、SEM观察和EDS分析等方法，对获得的激光焊接头(LBW)和激光填丝焊接头(LBW-F)在3.5%NaCl溶液中的腐蚀行为进行研究，并与母材(BM)的耐蚀性进行对比，结果表明，腐蚀产物主要由Mg(OH)₂和碳酸盐组成，3种试样的耐蚀性由高至低为：LBW接头>LBW-F接头>BM母材。     

电化学法制备Co(OH)2/Cu(OH)2异质结电极及其作为析氧电催化剂的研究

贵金属IrO₂和RuO₂被广泛认为是优异的析氧(OER)催化剂，但是高成本限制其应用与发展，故开发高效的非贵金属OER催化剂具有重大的实际意义和应用前景。采用简便的电化学法制备了一种三维异质结电极Co(OH)₂/Cu(OH)₂作为优良的OER催化剂。Co(OH)₂/Cu(OH)₂由于其三维异质结构，使其具有较大的比表面积和充足的活性位点，同时调节了表面Co的电子结构进而提高OER活性，表现出优良的催化性能。在1mol/L KOH溶液中，Co(OH)₂/Cu(OH)₂能在270mV的低过电位下达到10mA/cm²,并且能保持在100mA/cm²的大电流密度下较长时间进行OER反应，是一种优良的OER催化剂。     

Biocorrosion resistance of coated magnesium alloy by microarc oxidation in electrolyte containing zirconium and calcium salts

The key to use magnesium alloys as suitable biodegradable implants is how to adjust their degradation rates. We report a strategy to prepare biocompatible ceramic coating with improved biocorrosion resistance property on AZ91D alloy by microarc oxidation （MAO） in a silicate-K2ZrF6 solution with and without Ca（H2PO4）2 additives. The microstructure and biocorrosion of coatings were characterized by XRD and SEM, as well as electrochemical and immersion tests in simulated body fluid （SBF）. The results show that the coatings are mainly composed of MgO, Mg2SiO4, m-ZrO2 phases, further Ca containing compounds involve the coating by Ca（H2PO4）2 addition in the silicate-K2ZrF6 solution. The corrosion resistance of coated AZ91D alloy is significantly improved compared with the bare one. After immersing in SBF for 28 d, the Si-Zr5-CaO coating indicates a best corrosion resistance performance.     

Al（OH）3和Cl一对稀土铝热浸镀层腐蚀行为的影响

以自制热浸镀稀土铝为研究对象,采用失重法、极化曲线、SEM和电化学阻抗测试研究了淡水中存在的A1（OH）3对镀层腐蚀行为的影响;同时,通过极化曲线考察了饱和A1（oH）3溶液中C1一浓度对镀层腐蚀的影响。结果表明：A1（OH）3能够抑制镀层破损钝化膜的修复,促进阳极活化,诱导镀层点蚀反应的发生,使腐蚀加剧;随Cl一浓度...     

Corrosion resistance of Ca-P coating induced by layer-by-layer assembled polyvinylpyrrolidone/DNA multilayer on magnesium AZ31 alloy

A hydrothermal deposition method was utilized to fabricate Ca-P composite coating induced by the layer-by-layer (LbL) assembled polyvinylpyrrolidone/deoxyribonucleic acid (PVP/DNA)₂₀ multilayer on AZ31 alloy. The surface morphology and compositions were characterized by SEM, EDS, FTIR and XRD. Besides, the corrosion resistance and degradation behavior of the coating were tested via electrochemical polarization, impedance spectroscopy and immersion measurements. Results show that the main components of Ca-P coatings are hydroxyapatite, Ca₃(PO₄)₂ and Mg₃(PO₄)₂·nH₂O. The LbL-assembled DNA and PVP promote the adsorption of Ca-P deposits on the sample surface, and structures and functional groups of the polyelectrolyte in the outermost layer are the primary influencing factor for the induction of the Ca-P coating. Carboxyl groups have the best biomineralization effect among all related functional groups. The enhanced corrosion resistance and adhesion highlight a promising use of (PVP/DNA)₂₀-induced Ca-P coatings in the field of biomedical magnesium alloys.     

Corrosion and drug release properties of EN-plating/PLGA composite coating on MAO film

The electroless nickel plating/poly(dl-lactide-co-glycolide) composite coating (EN-plating/PLGA composite coating) was fabricated on the surface of the micro-arc oxidation (MAO) film of the magnesium alloy AZ81 to double control the corrosion and drug release in the hanks' solution. The EN-plating was fabricated on the MAO coating to improve the corrosion resistance by overlaying most pores and micro-cracks on the surface of the MAO film. Meanwhile, a double layered organic poly(dl-lactide-co-glycolide)/paclitaxel (PLGA/PTX) drug releasing coating with a top layered PLGA drug controlled releasing coating on EN plating was prepared to control the drug release rate by adjusting the different lactide: glycolide (LA:GA) ratio of PLGA. Scanning electron microscopy (SEM) and the X-ray powder diffraction (XRD) were used to analyze the morphology and the composition of the EN-plating. The corrosion behavior of the magnesium alloy substrate and the status of the drug in the PLGA matrix were respectively evaluated by Potentiodynamic polarization and Differential scanning calorimetry (DSC). The drug release was determined by ultraviolet–visible (UV–visible) spectrophotometer. EN-plating coating which was composed of compact cauliflower nodules was uniform in size and defect free with no pores or cracks. EN-plating could seal the microcracks and microholes on the outer layer of the MAO coating effectively. The corrosion resistance was improved by preventing the corrosive ions from diffusing to the magnesium alloy substrate. The drug release rate of PTX exhibited a nearly linear sustained-release profile with no significant burst releases.     

镁合金超疏水环氧复合涂层的制备与性能EI北大核心CSCD

传统的超疏水表面的制备过程比较复杂,机械稳定性差,这严重制约了超疏水表面的实际应用。采用“黏合剂+纳米粒子”的方法,在镁合金表面制备一种无氟、持久稳定的超疏水环氧复合涂层。接触角测试结果表明,复合涂层的接触角最高可达160.2°,且在3.5%(质量分数)NaCl溶液中浸泡30天后,接触角仍然高达103°;EIS结果表明,在5个加速老化循环周期后,复合涂层的|Z|_(0.01 Hz)仍高于10^(9)Ω·cm^(2),展现出优异的耐盐雾性能和耐蚀性能;摩擦磨损实验结果显示,在19.6 N的载荷下机械摩擦8 h后,复合涂层的|Z|_(0.01 Hz)高达1.84×10^(9)Ω·cm^(2)。通过“空气垫”的屏障作用,复合涂层能够为镁合金提供高效且持久的腐蚀防护,“黏合剂+纳米粒子”策略为超疏水涂层的制备提供了新的思路。     

电解液组分对TiCP/Ti6Al4V复合材料微弧氧化膜耐蚀性及耐磨性影响

采用微弧氧化技术在 TiC_P/Ti6Al4V 复合材料表面制备陶瓷膜。在NaAlO₂和NaH₂PO₂两种溶液体系中通过添加不同添加剂 NaOH、C₁₀H₁₂CaNa₂N₂O₈·4H₂O和Na₂SiO₃, 研究电解液组分对陶瓷膜组织、耐蚀性和耐磨性的影响。结果表明: 在NaH₂PO₂电解液体系中生成的膜层由金红石型和锐钛矿型TiO₂相组成, 而在NaAlO₂体系中除了生成TiO₂外, 还生成了Al₂TiO₅和γ-Al₂O₃。添加NaOH可以加快微弧氧化反应速率, 添加NaAlO₂和Na₂SiO₃有利于提高膜层的硬度, NaH₂PO₂溶液体系中形成的膜层厚度是NaAlO₂溶液体系的2~3倍。 在NaAlO₂和NaH₂PO₂电解液体系中生成的膜层, 其耐腐蚀性能排序均为: Na₂SiO₃>C₁₀H₁₂CaNa₂N₂O₈·4H₂O>NaOH。在NaAlO₂电解液体系中生成的膜层的耐磨性能排序为: Na₂SiO₃>NaOH>C₁₀H₁₂CaNa₂N₂O₈·4H₂O, 而在NaH₂PO₂电解液体系中生成的膜层的耐磨性能排序为: Na₂SiO₃>C₁₀H₁₂CaNa₂N₂O₈·4H₂O>NaOH。TiC_P/Ti6Al4V复合材料经过微弧氧化处理后, 耐磨性和耐蚀性均优于基体, 在NaH₂PO₂+Na₂SiO₃电解液中生成的微弧氧化膜的耐蚀性最好, 耐磨性也较好, 其腐蚀电流密度较钛基复合材料基体降低约2个数量级, 因此综合性能最好。     

Corrosion resistance of in-situ growth of nano-sized Mg(OH)2 on micro-arc oxidized magnesium alloy AZ31—Influence of EDTA

One of the major obstacles for the clinical use of biodegradable magnesium (Mg)-based materials is their high corrosion rate. Micro-arc oxidation (MAO) coatings on Mg alloys provide mild corrosion protection owing to their porous structure. Hence, in this study a dense Mg(OH)₂ film was fabricated on MAO-coated Mg alloy AZ31 in an alkaline electrolyte containing ethylenediamine tetraacetic acid disodium (EDTA-2Na) to reinforce the protection. Surface morphology, chemical composition and growth process of the MAO/Mg(OH)₂ hybrid coating were examined using field-emission scanning electron microscopy, energy dispersive X-ray spectrometer, X-ray diffraction, X-ray photoelectron spectroscopy and Fourier transform infrared spectrophotometer. Corrosion resistance of the coatings was evaluated via potentiodynamic polarization curves and hydrogen evolution tests. Results manifested that the Mg(OH)₂ coating possesses a porous nano-sized structure and completely seals the micro-pores and micro-cracks of the MAO coating. The intermetallic compound of AlMn phase in the substrate plays a key role in the growth of Mg(OH)₂ film. The current density of Mg(OH)₂-MAO composite coating decreases three orders of magnitude in comparison with that of bare substrate, indicating excellent corrosion resistance. The Mg(OH)₂-MAO composite coating is beneficial to the formation of calcium phosphate corrosion products on the surface of Mg alloy AZ31, demonstrating a great promise for orthopaedic applications.