Evaluation of electrochemical properties of antibacterial ZnO layers deposited to 316LVM steel using atomic layer deposition

The presence of a biofilm can lead to the disappearance of the surrounding bone tissue and, as a result, disturb the osseointegration process. Unfortunately, both in the case of instability of the implant and long-term bacterial infections, there is often a need for reoperation as well as replacement of the implant, which in turn is associated with huge costs, but most of all discomfort for the patient associated with long-term hospitalization. In order to limit this unfavorable process, the physicochemical properties of the surface layer of implants are indicated. Therefore, the paper proposes applying a layer with antibacterial effect on the surface of 316LVM steel used in bone surgery. As part of the work, the ZnO layer was applied using the atomic layer deposition method with different parameters of the application process (different number of cycles at constant temperature). In the first stage, pitting corrosion resistance tests were carried out using the potentiodynamic method and studies using electrochemical impedance spectroscopy. The surface morphology tests using a scanning electron microscope were also complemented. Obtained results may form the basis for the development of more detailed criteria for the assessment of the final quality of medical devices used in the skeletal system.     

Research on corrosion performance of 6061 aluminum alloy in salt spray environment

Salt spray corrosion test was carried out on 6061 aluminum alloy, and quasi-static tensile test at room temperature was carried out on the sample with universal testing machine. The effect of salt spray corrosion on the mechanical properties of 6061 aluminum alloy was studied by scanning electron microscope (SEM), energy dispersive spectrometer (EDS) and electrochemistry. The corrosion rate of 6061 aluminum alloy was quantitatively characterized by different corrosion parameters. It was found that local corrosion of 6061 aluminum alloy occurred in salt spray environment, mainly pitting corrosion and intergranular corrosion. With the increase of corrosion time, the polarization resistance of 6061 aluminum alloy decreases, and the corrosion rate significantly increases. The average corrosion rate and the maximum corrosion rate of 6061 aluminum alloy were characterized by corrosion weight loss and corrosion pit depth. And they can be transformed into each other. The mechanical properties of 6061 aluminum alloy were mainly affected by the depth of corrosion pit. With the increase of corrosion time, the tensile strength and fracture strain decreased, resulting in poor plasticity of the sample. At the same time, the change of elongation of 6061 aluminum alloy can be accurately predicted by the depth of corrosion pit.     

Design of best performing hexagonal shaped Ag@CoS/rGO nanocomposite electrode material for electrochemical supercapacitor application

The mixed metal/metal sulphide (Ag@CoS) with reduced graphene oxide (rGO) nanocomposite (Ag@CoS/rGO) was synthesized for the possible electrode in supercapacitors. Ag@CoS was successfully deposited on the rGO nanosheets by hydrothermal method, implying the growth of 2D Ag and CoS-based hexagonal-like structure on the rGO framework. The synthesized nanocomposite was subjected to structural, morphological and electrochemical studies. The XRD results show that the prepared nanocomposite material exhibits a combination of hexagonal and cubic phase due to the presence of CoS and Ag phases together. The band appearing at nearly 470.33 cm⁻¹ in FTIR spectra can be ascribed to the absorption of S–S bond in the Ag@CoS/rGO nanocomposite. The clear hexagonal structure was analysed by SEM and TEM with the grain sizes ranging from nanometer to micrometer. The electrode material exhibits excellent cyclic stability with a specific capacitance of 1580 F/g at a current density of 0.5 A/g without any loss of capacitive retention even after 1000 cycles. Based on the electrochemical performance, it can be inferred that the prepared novel nanocomposite material is very suitable for using as an electrode for electrochemical supercapacitor applications.     

Characterization of superficial modification of ferrous rusted substrates subjected to dechlorination-electrochemical process

Preservation of archaeological artefacts after their removal from saline media is a difficult task due to the chloride content of the oxide layers which are unstable in atmospheric conditions, especially if the relative humidity exceeds 85%. For this reason, removal of chlorides from rust layers is one of the priorities of conservationists or restorers of historical artefacts. However, removal of chloride ions is not an easy procedure because of the many considerations involved in the process. In this research, artificially pre-rusted iron samples and an actual historical cannonball were subject to a dechlorination process in a potassium hydroxide solution to measure constant chloride release in a bulk solution. After the chloride removal process, a commercial protective layer was applied to the rust for stabilization purposes. It was calculated that the kinetics of the dechlorination process is driven by diffusion behaviour following Fick’s second law. When this diffusion process prevails, the dechlorination extraction affects the integrity of rust layers as is demonstrated with scanning electron microscopy and X-ray diffraction analyses. It was proven that the chloride removal procedure causes the studied iron layers to stiffen, provoking superficial modification and, in some cases, fractures of the rust. By means of electrochemical impedance spectroscopy it was calculated that the magnitude of the positive effect of the dechlorinated samples depends on the protective features of the rust. Therefore, this research reveals that an efficient chloride removal procedure depends on the electrochemical properties of the dechlorination process and the initial morphology of the iron rust.     

Effects of Al content on the corrosion properties of Mg–4Y–xAl alloys

The corrosion performances of Mg–4Y–xAl (x = 1, 2, 3, and 4 wt%) alloys in the 3.5% NaCl electrolyte solution are investigated by electrochemical tests, weight loss measurement and corrosion morphology observation. The results indicate that corrosion modes for the alloys are localized corrosion and the filiform type of attack. With Al concentration increasing from 1 to 4 wt%, the corrosion rate of Mg–4Y–xAl alloys decreases firstly and then increases, and WA42 alloy shows the best corrosion resistance. The addition of Al element to Mg–4Y alloys leads to the formation of Al₂Y and Al₁₁Y₃ intermetallic compounds and reduces the proportion of Mg₂₄Y₅ phase. Corrosion resistance of the Mg–4Y–xAl alloys mainly depends on the size and distribution of the second phases. Besides, the addition of excessive Al can greatly consumes the Y element in the matrix, thus leading to a less protective film on the alloys. The effect of the relative Volta potential changes between the second phases and α-Mg on corrosion resistance of Mg–4Y–xAl alloys is insignificant. The main corrosion products of the Mg–4Y–xAl alloys are Mg(OH)₂, Mg₃(OH)₅Cl·4H₂O, Mg_0.72Al_0.28(CO₃)_0.15(OH)_1.98(H₂O)_0.48, and Mg₄Al₂(OH)₁₂CO₃·3H₂O.     

微观组织对2A14铝合金轮毂力学性能和腐蚀性能的影响

通过电子背散射衍射(EBSD)、场发射扫描电子显微镜(SEM)、透射电子显微镜(TEM)、室温拉伸、浸泡腐蚀、电化学极化等测试分析方法，研究了2A14铝合金轮毂内部不同区域上微观组织的差异及其对力学性能和腐蚀性能的影响。结果表明，2A14铝合金轮毂的芯部和1/4层的晶粒尺寸分别是113和54 μm，再结晶分数分别是16%和36%。1/4层的合金相和时效析出相的含量都大于芯部，其中两种时效析出相(θ’和Q相)的数量密度均为芯部的2倍左右。芯部具有较大的晶粒尺寸和较少的时效析出相，因此具有较低的力学性能。同时，芯部相对于1/4层具有较少的合金相和较大的晶界相间距，因而芯部的电化学腐蚀和晶间腐蚀倾向均低于1/4层。     

波前传感器电铸镍层应力实时检测精度评估

目的 搭建电铸应力实时检测平台，评估其测量精度，并探明电化学沉积过程中镍层平均内应力的变化规律。方法 采用横向剪切波前传感器搭建电铸应力实时检测平台，通过测量在铸层应力作用下电铸基底弯曲的曲率半径，利用Stoney公式计算铸层平均应力。采用参考球面反射镜评估横向剪切波前传感器曲率半径的测量精度，并在0.5 A/dm2电流密度下进行电铸应力实时检测实验，对铸层平均应力测量极限进行评估，同时对检测误差进行分析。结果 横向波前传感器曲率半径测量精度为99.22%，在0.5 A/dm2电流密度下，所搭建的铸层应力实时检测平台可测量的最小厚度为5.1 μm，由曲率测量波动带来的应力检测误差为1.3 MPa。实验测得铸层平均应力随铸层厚度的增加而变大，当铸层厚度达到30 μm左右，铸层平均应力趋于稳定，应力大小为79.7 MPa。同时发现，当铸层厚度小于30 μm时，沿电铸基底长度方向的铸层平均应力明显大于宽度方向铸层平均应力，随铸层厚度的增加，两个方向的应力大小趋于等值。结论 采用横向剪切波前传感器搭建的电铸应力检测平台，能有效对铸层应力进行高精度的实时测量，为精密电铸过程中应力变化规律的研究提供了检测技术基础。     

飞机蒙皮材料在醋酸钾型除冰液中腐蚀行为研究

目的 评价醋酸钾型除冰液能否用于飞机除冰以及对飞机蒙皮材料腐蚀性的影响。方法 采用AutoLab电化学工作站对飞机蒙皮材料在不同浓度缓蚀剂、无缓蚀剂醋酸钾型除冰液中的干湿交替腐蚀电化学行为进行分析，通过扫描电镜观察其腐蚀前后表面形貌及涂层/基体金属界面形貌。结果 无缺陷飞机蒙皮涂层在除冰液中的阻抗模值高达2.78×1010 Ω?cm2，而缺陷涂层的阻抗模值只有1.72×107 Ω?cm2，说明缺陷破坏了涂层的完整性，降低了涂层的阻抗模值，明显加速了飞机蒙皮材料的腐蚀。带缺陷飞机蒙皮试样经除冰液腐蚀不同周期后的低频区Rct存在较大变化，试样在高浓度无缓蚀剂除冰液中的Rct始终低于在低浓度溶液中的Rct；试验初期，试样在高浓度除冰液中的Rct较大，说明此时缓蚀剂浓度较高，缓蚀作用明显；但随着腐蚀周期的延长，Rct逐渐减小，说明缓蚀剂逐渐失效，高浓度除冰液的腐蚀性逐渐增强并高于低浓度除冰液。腐蚀实验后，飞机蒙皮涂层表面和涂层/基体金属界面处存在一定的腐蚀产物；人造缺陷破坏了涂层的完整性，降低了涂层的结合力，甚至产生局部剥离，造成除冰液浸入，在划痕处发生了较严重的膜下腐蚀。结论 醋酸钾型除冰液对飞机蒙皮材料存在一定的腐蚀性，尤其是当涂层存在缺陷时，腐蚀较为严重。     

Preparation and characterization of polyvinylchloride membrane embedded with Cu nanoparticles for electrochemical oxidation in direct methanol fuel cell

Copper nanoparticles were prepared by the chemical reduction method. These copper particles were embedded into the polyvinylchloride (PVC) matrix as support and used as an electrode (PVC/Cu) for the oxidation of methanol fuel for improving the current response. The PVC/Cu electrodes were characterized by thermal gravimetric analysis (TGA) for thermal stability of the electrode, X-ray diffraction (XRD) for identification of copper nanoparticles in the electrode, Fourier transform infrared spectroscopy (FTIR) to identify the interaction between PVC and Cu and scan electron microscopy (SEM) with EDAX for the morphology of the electrode. The electrocatalytic activity of the electrode was characterized by the cyclic voltammetry, linear sweep voltammetry, and chronoamperometry techniques. An increase in the electrode activity was observed with the increase of copper quantity from 0.18 g (PVC/Cu-0.18 g) to 0.24 g (PVC/Cu-0.24 g) and the maximum was found at 0.24 g of copper in the electrode. Also, it was observed that the electrode achieved the maximum catalytic current in 0.5 mol/L CH₃OH + 1 mol/L NaOH solution. FTIR identified that water molecules, C—H group, copper nanoparticle and its oxide were available in the electrode. SEM images with EDAX showed that copper particles were properly embedded in the polyvinylchloride matrix.