制备条件对钛基IrO2+Ta2O5涂层阳极性能的影响

研究了基体喷砂处理，涂制母液溶剂体系，添加剂等制备技术对热分解法制备钛基IrO2 Ta2O5阳极组织结构，性能的影响，结果表明，基体经喷砂处理后与氧化物涂层间的结合力加大，其阳极寿命明显提高，采用有机溶剂制备的涂层表现出典型的裂纹形貌，且晶粒细化，增大了阳极的电化学活性表面，从而提高了阳极的析氧电催化活性，加入适量添加剂可以改善涂层的致密度，能够有效地抑制活性组元的溶解，并阻止电解液在涂层中的渗透，延长了阳极的使用寿命，实验表明，添加剂含量为0．7％时改善效果最为明显。     

酸蚀刻剂对钛基体及其IrO2-PbO2涂层表面形貌及电化学性能的影响研究

采用热分解法制备Ti/IrO₂-PbO₂阳极,深入研究硫酸、硝酸、盐酸、草酸、盐酸/草酸蚀刻顺序对Ti/IrO₂-PbO₂阳极性能的影响规律,借助场发射扫描电子显微镜、X射线衍射、循环伏安法、线性扫描伏安法、电化学交流阻抗谱、加速寿命试验等考察钛基体及氧化物涂层的形貌、结构及电化学行为。结果表明：钛基体在双酸中的腐蚀效果优于单酸,获得更致密更均匀的表面结构。双酸腐蚀使钛表面拥有完整的TiH_x晶型,有助于提高涂层负载量,增强活性层与基体的结合力。改变双酸蚀刻顺序对阳极电化学性能有一定的影响。草酸/盐酸蚀刻剂处理Ti/IrO₂-PbO₂阳极具有最佳的电催化活性与最长的加速寿命。     

不同酸处理对钛基体性能的影响

本研究在保持酸度和温度一致的条件下分别用草酸、硫酸及盐酸对TA2钛基体进行刻蚀处理,研究不同种类酸处理对钛基体及后续电极性能的影响。研究表明:钛基体在草酸和硫酸中的质量损失率要大于在盐酸中的损失率。金相及SEM观察表明:草酸对钛基体刻蚀效果最好,刻痕细致均匀。强化寿命测试结果显示:经草酸处理后的Sn-Sb氧化物涂层钛基电极强化寿命最长。循环伏安测试结果表明:3种酸刻蚀过后的Sn-Sb氧化物涂层电极的析氧电位基本相同,表明酸刻蚀对于该电极的析氧电位影响不大。     

RuTiSnMn/Ti阳极的电化学性能

热分解制备了RuTiSnMn／Ti阳极，在4mA／cm^2的电流密度下进行了恒电流试验。通过循环伏安法和交流阻抗谱研究了阳极在35g／LNaCl溶液、20g／LNaOH溶液和模拟孔隙液中的电化学行为．利用EsEM对阳极失效前后的微观形貌进行了观察,结果表明：阳极具有优良的耐析氯、氧反应能力；钛基体逐渐形成TiO2的钝化膜使阳极的氧化物膜电阻增大，活性组元的消耗使法拉第电荷传递电阻增加，这两者最终导致阳极失效。     

NaCl浓度对金属氧化物阳极电化学性能与失效影响研究

采用热分解法在钛基体上制备钌铱锡金属氧化物阳极。通过循环伏安测试、电流效率测试、极化曲线测试以及析氯电位测试等电化学测试手段,考察盐浓度对钌铱锡金属氧化物阳极电化学性能的影响;采用强化电解寿命测试考察盐浓度对金属氧化物阳极寿命的影响规律;通过电镜与能谱测试,分析盐浓度对失效行为影响。实验结果表明,NaCl的浓度升高时,钌铱锡金属氧化物强化电解寿命长,析氯阻力变小,析氯电位减小,钌铱锡金属氧化物阳极的选择性大。另外,随着NaCl浓度的升高,钌铱锡金属氧化物阳极的电流效率会随之增大。     

涂覆厚度对Ru-Ir-Ti氧化物阳极涂层电化学性能的影响

通过热分解法制备了不同涂覆层数的Ru-Ir-Ti氧化物阳极涂层。采用物理分析和电化学测试技术研究了不同涂覆层数氧化物阳极涂层的表面形貌、结构和电化学性能。结果表明,Ru-Ir-Ti氧化物阳极涂层涂覆30层(15.55μm)时,涂层与钛基体结合牢固,具有较好的电催化选择性。此时,析氧电位达到1.52V,析氯电位为1.02V,电流效率高达94.5%,伏安电量达到35mC/cm2,强化电解寿命长达525h。当涂覆层数达到40层(22.6μm)后,涂层呈疏松结构,表面粗糙,裂缝变得宽而深,涂层出现脱落,附着力下降。     

Ti基IrO_2+Ta_2O_5涂层阳极的析氧电催化活性

通过极化曲线与电化学阻抗谱测试研究了Ｔｉ基ＩｒＯ２＋Ｔａ２Ｏ５阳极的析氧电催化活性．结果表明, ＩｒＯ２含量为７０％（摩尔分数）时,混合氧化物阳极表面具有最高的析氧活性．这缘于该成分含量阳极中活性组元ＩｒＯ２的真实表面浓度达到最大;而且,由于表面析出晶粒的最细化,在析氧电位下受析出氧气的冲击,该成分阳极表面的活性点数目得到最大程度的提高．由此提出决定氧化物阳极析氧电催化活性的热力学及动力学判据．     

析氯析氧组合涂层钛阳极的研究

采用溶胶-凝胶法,制各具有三明治结构的钛阳极,即在钛基材上先被覆Ti70%-Ru30%(摩尔分数,下同)氧化物底层,然后被覆Ir70%-Ta30%中间层,最后被覆Ti70%-Ru30%氧化物表层.通过XRD、电极电位、极化曲线、循环伏安、强化电解寿命等试验方法研究具有三明治结构的钛阳极的物理性能和电化学性能.结果表明,三明治结构阳极涂层主要组成物相为(Ti,Ru)O2金红石相固溶体、IrO2金红石相和非晶态的氧化钽,三明治结构的钛阳极具有优越的析氯和析氧的电催化活性,在析氯和析氧环境中能更好地保持电位稳定性,在高电流密度和高酸度下,有更强的耐蚀性,是较好的析氯析氧合一的钛阳极.     

含TiN中间层IrO2-Ta2O5涂层钛阳极的电催化性能

采用钛片在氮气中700 ℃退火的方法,在钛片表面原位生成TiN薄膜,并以此为基体采用热分解法制备IrO2-Ta2O5涂层钛阳极.研究含TiN中间层IrO2-Ta2O5涂层钛阳极及传统IrO2-Ta2O5涂层钛阳极的开路电位、析氧行为、循环伏安和电化学阻抗等性能.结果表明:含TiN中间层IrO2-Ta2O5涂层钛阳极具有非连续状裂纹结构,且表面生长出大量IrO2纳米晶体,其电催化析氧性能优于传统IrO2-Ta2O5涂层钛阳极的电催化析氧性能;涂层烧结温度越低,电化学性能越好;当烧结温度低于500 ℃时,TiN中间层可以显著延长IrO2-Ta2O5涂层钛阳极的工作寿命.     

溶胶凝胶法制备Ru-Ir-Sn-Ti阳极涂层及其电化学性能研究

采用溶胶凝胶法制备Ru-Ir-Sn-Ti阳极涂层,对涂层进行析氯电位、析氧电位、极化曲线、循环伏安曲线、电化学交流阻抗等电化学测试以及强化电解寿命测试,并与热分解法制备的阳极涂层进行对比。结果表明:与热分解法制备的阳极涂层相比,溶胶凝胶法制备的Ru-Ir-Sn-Ti阳极涂层具有较低的析氯电位、较高的析氧电位、良好的电催化活性和较长的强化电解寿命。     

镁合金化学镀中预处理氟化镁膜的特征与作用

对镁合金的表面前处理工艺进行研究,探讨氟化镁在化学镀层中的存在形式及作用。结果表明：酸浸使镁合金表面形成一层氧化物膜;活化过程生成的氟化镁不具备反应活性,对镁合金基体有保护作用,使之免于受镀液的过度腐蚀;对化学镀层断口进行SEM元素分布分析显示氟化镁层集中存在于镁合金基体与Ni-P镀层之间;但过度活化会导致化学镀层孔隙率升高,以3.5%NaCl溶液为介质的动电位极化测试表明,过度活化会导致化学镀层耐蚀性下降。     

高能离子刻蚀前处理对AlTiSiN涂层切削性能的影响

目的提高AlTiSiN涂层与刀具基材的结合强度,降低涂层表面的粗糙度,减少切削过程中涂层的剥落,改善涂层刀具的切削寿命。方法采用离子源增强的多弧离子镀设备刻蚀清理基体材料,并制备AlTiSiN涂层。利用X射线衍射仪(XRD)、扫描电镜(SEM)、粗糙度仪、划痕仪和铣削实验探讨涂层沉积前不同Ar离子刻蚀清洗工艺对AlTiSiN涂层结构、膜基结合力和涂层表面形貌的的影响,探究不同刻蚀清洗工艺对涂层刀具切削机理和切削性能的影响。结果 AlTiSiN涂层的相结构主要由(Al,Ti)N固溶体相组成,涂层沿着基体呈现柱状生长。随着高能Ar离子刻蚀电流由40 A增加至100 A,涂层的表面粗糙度降低,Ra值由140 nm降至69 nm,Sq值由226 nm降至117 nm;涂层与基体之间的结合强度增加,Lc2由41 N增加至52 N;切削加工DC53模具钢结果显示,当清洗电流增加至100 A,涂层的剥落几率降低,涂层刀具的切削寿命增加,由11 m增加至23 m。结论高能离子刻蚀前处理过程可有效增加涂层与基体之间的结合强度,降低涂层表面粗糙度,进而提高涂层刀具的切削寿命。刻蚀清洗所用电流强度越大,清洗效果越好,刀具涂层切削性能提高越明显。     

钛合金表面GO/纳米ZnO复合涂层的制备及性能

为了有效解决生物医用钛合金长期植入人体后,易发生细菌感染和面临有害金属离子释放的问题,采用水热反应和涂覆方法,分别在聚多巴胺(PDA)预处理的Ti6Al4V合金表面制备了氧化石墨烯涂层(GP/T)和氧化石墨烯/纳米氧化锌复合涂层(GZP/T)。系统分析了2种涂层的物相结构、微观形貌及其在林格氏液中的耐腐蚀性能和在大肠杆菌环境中的抗菌性能。结果表明:聚多巴胺发挥“双面胶”桥接作用,有效增强了涂层与基底间的化学键合;GP/T涂层抗菌率随着GO浓度增大而增大;GZP/T纳米复合涂层相较Ti6Al4V基材具有优异的耐蚀性,该复合涂层中ZnO起主要抗菌作用。     

Effect of high temperature oxide scale on steel surface for electroless nickel plating process and characterization of coatings

An attempt has been made for an electroless nickel plating process on two steel substrates (with and without a high temperature oxide scale at the top surface) to identify the role of a high temperature iron oxide scale on coating kinetics. This study investigated if an iron oxide scale on the steel surface acts as a catalyst and promotes faster metal deposition. Coatings were characterized by scanning electron microscopy (SEM), glow discharge oxy emission spectroscopy (GDOES), and X-ray diffraction (XRD) and an iron oxide scale was characterized by Raman spectroscopy. Chemical composition and structure of both the coatings are the same but the coating obtained on a steel substrate having a high temperature oxide scale at the top is two times thicker. The electrochemical performances of both the coated steel substrates were evaluated by Tafel and electrochemical impedance (EIS) tests in an aggressive chloride environment. The coating obtained on a steel substrate containing a high temperature oxide scale at the top exhibits better resistance against chloride attack and charge transfer than the coating obtained on the steel substrate without a high temperature oxide scale at the top. This can be attributed to the highest thickness of this coating, which has the same chemical composition of the other coating, expected to give better resistance against chloride attack and charge transfer.     

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.     

Formation of adherent polypyrrole coatings on Ti and Ti–6Al–4V alloy

Highly adherent polypyrrole coatings were electrodeposited at etched Ti and Ti–6Al–4V from 0.2 M oxalic acid and 0.2 M pyrrole at a constant applied potential of 0.8 V versus SCE. The substrates were etched in an alkaline peroxide solution at ambient temperature for a 10 min period prior to the electropolymerization reactions. Chemical etching of the substrate gave rise to an increase in the hydrophilicity of the surface, the formation of a micro-etched surface and the formation of a semiconducting titanium oxide film. There was a considerable increase in the density of nucleation sites for polypyrrole growth at the micro-etched surface. Growth of the polypyrrole proceeded slowly from a high number of nucleation sites at the etched surface to give rise to a highly adherent polypyrrole coating. Adhesion of the polypyrrole coating was attributed to micro-etching of the substrate and the conductivity of the oxide film generated during the chemical etching process.     

Novel anti-corrosion nano-sized vanadia-based thin films prepared by sol–gel method for aluminum alloys

Chromate conversion coatings have been widely applied for the corrosion protection of aluminum alloys. However, the waste containing Cr6+ has many limitations due to the environmental consideration and health hazards. Vanadates are among the proposed alternatives to chromating. Series of specimens were prepared under the following conditions: (a) as polished, (b) directly treated with vanadia, (c) etched, (d) oxide thickened, and (e) etching followed by oxide thickening. After surface preparation, the specimens were dipped in vanadia solution prepared via sol gel method. Electrochemical impedance spectroscopy (EIS) and polarization measurements have been used to evaluate the coating performance in 3.5% NaCl. The optimum conditions under which vanadia treatments can provide good corrosion protection to the aluminum substrate were determined. The surface morphologies of the treated samples were investigated using SEM and EDS. Optical microscope was also used to investigate the occurrence of pitting corrosion. The surface preparation prior to vanadia treatment was found to have a marked effect on the corrosion protection of AA6061 T6. Generally, vanadia treatments improve the corrosion resistance due to formation of highly protective vanadium oxides. According to the EIS and polarization measurements, a combination between etching and oxide thickening prior to vanadia treatment plays an important role on the corrosion protection mechanism.     

HA coating on titanium with nanotubular anodized TiO2 intermediate layer via electrochemical deposition

Hydroxyapatite（HA） coating has been prepared on titanium substrate through an electrochemical deposition approach. In order to improve the bonding strength between HA coating and Ti substrate, a well oriented and uniform titanium oxide nanotube array on the surface of titanium substrate was applied by means of anodic oxidation pre-treatment. Then the calcium hydrogen phosphate（CaHPO4·2H2O, DCPD） coating, as the precursor of hydroxyapatite coating, was electrodeposited on the anodized Ti. At the initial stage of electro-deposition, the DCPD crystals, in nanometer precipitates, are anchored in and between the tubes. With increasing the deposition time, the nanometer DCPD crystals are connected together to form a continuous coating on titanium oxide nanotube array. Finally, the DCPD coating is converted into hydroxyapatite one simply by being immersed in alkaline solution.     

酸刻蚀处理对IrO2-Ta2O5/Ti阳极寿命的影响

通过改变腐蚀方法,研究了使用H₂C₂O₄和H₂SO₄进行钛基体表面刻蚀对金属氧化物钛阳极电化学性能和表面形貌的影响。采用扫描电子显微镜、X射线衍射仪和光电子能谱等测试方法对样品进行了结构分析。然后利用电化学工作站测试了样品的电催化活性,利用加速寿命测试研究了样品的电化学稳定性。结果表明,通过H₂C₂O₄和H₂SO₄分步腐蚀可以获得更加均匀致密的表面形貌和更好的催化稳定性。在此基础上,进一步研究了预处理对钛阳极寿命的影响原因。IrO₂-Ta₂O₅/Ti阳极的催化活性和稳定性与酸刻蚀处理的先后顺序及表面结构密切相关,并建立了预处理方法与阳极性能之间的关系。分步腐蚀使钛表面具有合适的粗糙度,因而提升了涂层附着力。在热分解过程中,经分步腐蚀形成的氢化钛在不改变表面形貌的情况下转变为金红石结构的氧化钛,有利于电子输运,从而增强涂层附着力并延长加速寿命。