Preparation and electrochemical corrosion behavior of bulk nanocrystalline ingot iron in HCl acid solution

Bulk nanocrystalline ingot iron (BNII) was produced by the severe rolling technique. The corrosion behaviors of BNII and as-received conventional polycrystalline ingot iron (CPII) in 1 M HCl solution were investigated by potentiodynamic polarization tests, electrochemical impedance spectroscopy measurement, and immersion tests at room temperature. For BNII, the anodic dissolution process is inhibited, but the cathodic process is enhanced. The corrosion current and average corrosion rate of BNII are 0.479 and 0.391 those of CPII, respectively. The resistance of the charge transfer of BNII is about 1.59 times higher than that of CPII. These results indicate that the corrosion resistance of BNII is improved in comparison with CPII.     

Corrosion and corrosion inhibition characteristics of bulk nanocrystalline ingot iron in sulphuric acid

The corrosion and corrosion inhibition of bulk nanocrystalline ingot iron (BNII) fabricated from conventional polycrystalline ingot iron (CPII) by severe rolling was studied in 0.5 M H₂SO₄ solution using electrochemical impedance spectroscopy and potentiodynamic polarization techniques. The results indicate that BNII was more susceptible to corrosion in the acidic environment essentially because of an increase in the kinetics of the anodic reaction. An amino acid cysteine (cys) was employed as a corrosion inhibitor at concentrations of 0.001 and 0.005 M. Tests in inhibited solutions revealed that cys reduced the corrosion rates of both metal specimens by different mechanisms. For CPII cys inhibited the cathodic reaction but had a stimulating effect on the anodic process at low concentration and a trivial effect at higher concentration. For BNII, cys inhibited both the cathodic and the anodic reactions, although the former effect was more pronounced. Iodide ions improved the inhibitive effect of cys without altering the inhibition mechanism.     

Electromagnetic Characteristics and Corrosion Resistance of New Magnetosoft Materials Based on Capsulated Iron Powders

A new method of depositing an insulating multifunctional oxide coating on metal particles was developed. Such coatings increase corrosion resistance and insulate metal particles from each other. On base of capsulated by oxide coating water-atomized iron powder ASC100.29, new composite soft magnetic materials were synthesized, which are able of replacing electrical steel in devices. Structural, electromagnetic properties and corrosion characte-ristics of the obtained composites were studied. It was found that the synthesized composite materials have low electromagnetic losses, high values of magnetic induction(up to 2.1 T) and good corrosion resistance. The results demonstrate that the use of such materials in power supplies, chokes, transformers, stators and rotors of electric machines and other products ensures their stable operation under various conditions.     

Fe基非晶和纳米晶合金晶化及电化学腐蚀行为

应用单辊甩带法制备非晶态Fe78Si13B9和Fe73.5Si13.5B9Nb3Cu1薄带,并以非晶晶化退火法制备出纳米晶Fe73.5Si13.5B9Nb3Cu1薄带.利用X射线衍射(XRD)仪和示差扫描量热计(DSC)对该非晶薄带的非晶特性及其晶化过程进行了研究.并用电化学极化曲线的方法和电化学阻抗技术研究了非晶态Fe78Si13B9和纳米晶Fe73.5Si13.5B9Nb3Cu1合金在1mol/LNaOH溶液里的电化学腐蚀行为,用SEM对极化测试后的试样形貌进行了观察;同时还研究了不同的热处理温度对材料结构及在1mol/LNaOH溶液里耐腐蚀性能的影响.结果表明,该非晶薄带的晶化过程分为两步;纳米晶比非晶合金的耐腐蚀性要好;且随着热处理温度的升高,非晶和纳米晶的耐腐蚀性能都得到提高.     

Inhibitor effect of sodium benzoate on the corrosion behavior of nanocrystalline pure iron metal in near-neutral aqueous solutions

Nanocrystalline iron coating was produced on carbon steel surface by pulse electrodeposition using citric acid bath. The grain size of a nanocrystalline surface was analyzed by X-ray diffractometry and scanning electron microscopy. The electrochemical behavior of nanocrystalline iron coating in the presence of sodium benzoate was evaluated in 30 mg l^-1 NaCl + 70 mg l^-1 Na₂SO₄ aqueous solution using potentiodynamic polarization curves and electrochemical impedance spectroscopy. The results were compared with that of the coarse-grained iron surface. The thermodynamic properties of the inhibitor adsorption were also determined. The results indicated that corrosion inhibition of sodium benzoate in near-neutral aqueous solution was increased as the grain size of iron was decreased from micro- to nanocrystalline surface. This was reported in terms of excess free energy of nanocrystalline surface.     

纳米晶体材料研究进展

综述了目前纳米晶体材料合成、结构、性质和应用的研究和发展现状。通过惰性气体凝结、机械合金、等离子体技术和其他许多方法可以制得纳米晶体材料。尽管早期的研究者认为纳米晶体材料的晶粒边界结构不同于常规材料, 但目前有关纳米晶体材料结构的研究表明其具有与常规晶体材料相同的晶粒边界结构。纳米晶体材料所具有的诸如扩散和烧结、力学、陶瓷和金属间化合物的延展性、电学、热膨胀、光学、磁学、催化和腐蚀行为等性质优于常规多晶材料, 这些性质具有巨大的潜在应用价值。     

硫酸盐体系三价铬沉积机理及镀层表征

在新研发的硫酸盐三价铬镀厚铬的镀液体系中, 运用线性扫描伏安法(LSV)和循环伏安法(CV)对三价铬在铜电极表面的电沉积过程进行研究, 并运用X射线荧光测厚仪、扫描电子显微镜(SEM)、X射线能量色散谱(EDS)、X射线衍射仪(XRD)、显微硬度计和Tafel曲线表征铬镀层厚度、形貌、组成、结构、显微硬度及在3.5wt% NaCl溶液中的耐蚀性. 结果表明, 在该体系中三价铬的沉积过程分两步进行(Cr³⁺ + e →Cr²⁺ , Cr²⁺ + 2e → Cr), 第一步得到1个电子, 受电化学过程和扩散过程共同控制, 第二步得到2个电子, 为扩散控制下的不可逆过程; 该镀层为瘤状纳米晶结构, 镀层中含有少量的铁元素(1.10 wt%), 显微硬度达到789.2 Hv, 镀层在3.5wt% NaCl溶液中的腐蚀电位(E_corr)为-0.29 V, 腐蚀电流密度(j_corr)为9.26×10^-5 A·dm^-2.     

Electrodeposition, Structure and Corrosion Resistance of Nanocrystalline Ni-W Alloy

Ni—W alloy was electrodeposited from the electrolyte solution containing sodium tungstate, nickel sulfate and ammonium citrate. The electrodeposition, heat treatment, structure, surface morphology and corrosion resistance in w=0.03 NaCl solution, of Ni-W alloys were studied by means of DSC, XRD, SEM and electrochemical techniques. The results showed that the obtained Ni-W alloy electrodeposit with W weight content (Ww=0.471) was presented in more typical nanocrystaUine, After heat treatment at 400 ℃ for 1 h, the phase structure of the deposits was not obviously changed whereas the agglomerate for the reunion of tiny grains on deposit surface caused the granule in a more smooth morphology, the microhardness was slightly increased and the corrosion resistance was enhanced.     

Preparation and properties of mechanically alloyed and electrochemically etched porous Ti–6Al–4V

Formation of porous Ti–6Al–4V nanostructure biomaterial was described. The alloy was prepared by mechanical alloying followed by pressing, sintering and subsequent anodic electrochemical etching in 1 M H₃PO₄ + 2% HF electrolyte at 10 V for 30 min. Mechanically alloyed Ti–6Al–4V has nanostructure with grain size of about 35 nm and large grain boundaries volume fraction, which essentially improve etching process. The electrolyte penetrates sintered compacts through the grain boundaries, resulting in effective material removing and pores formation. The pore diameter reaches up to 60 μm, which is very attractive for strong bonding with bone. The anodization of the microcrystalline alloy ingot results in selective etching, revealing of the two-phase structure with relatively flat surface. The corrosion properties were investigated in Ringer’s solution. Mechanically alloyed samples shows worse corrosion resistance than the bulk microcrystalline alloy ingot, but electrochemical etching results in improving corrosion resistance.     

Regularities of the formation of iron(III) nanocrystalline particles during the oxidation of iron(II) compounds in a neutral medium

The regularities of the formation of iron(III) oxide hydroxides as nanocrystalline particles via oxidation of iron(II) compounds in a near-neutral pH region were studied by potentiometric titration, electron microscopy, chemical analysis, and X-ray diffraction. The oxidation process comprises two steps. The first step produces Fe(II)-Fe(III) hydroxo salts having a “green rust” structure in the form of nanocrystalline particles shaped as hexagons. The second step produces anisotropic nanocrystalline particles of iron(III) oxide hydroxides via the dissolution-oxidation-precipitation mechanism and via solid-phase oxidation. The oxidation of chlorine-containing suspensions helps the formation of single-phase nanocrystalline lepidocrocite, while oxidation in the presence of sulfate ions yields nanocrystalline goethite.     

丝束电极研究裂纹对混凝土中钢筋腐蚀的影响

应用丝束电极技术测量浸在10%NaC l溶液中的混凝土内铁丝束的自腐蚀电位和极化电阻分布,研究裂纹对混凝土中铁丝腐蚀的影响和乙醇胺的缓蚀作用.结果表明,裂纹加速了水、氧和氯离子向两侧混凝土中扩散,增加了铁丝腐蚀的不均匀性.乙醇胺扩散到混凝土中,吸附在铁丝表面,基本不改变铁丝的自腐蚀电位,但显著降低了铁丝腐蚀速率,有效抑制了裂纹引起的不均匀腐蚀.     

Electrochemical corrosion behavior of nanocrystalline zinc coatings in 3.5% NaCl solutions

The corrosion behavior of electrodeposited nanocrystalline (NC) zinc coatings with an average grain size of 43 nm was investigated in 3.5% NaCl solutions in comparison with conventional polycrystalline (PC) zinc coatings by using electrochemical measurement and surface analysis techniques. Both polarization curve and electrochemical impedance spectroscopy (EIS) results indicate that NC and PC coatings are in active state at the corrosion potentials, and NC coatings have much higher corrosion resistance than PC ones. The corrosion products on both coating surfaces are mainly composed of ZnO and Zn₅(OH)₈Cl₂·H₂O, but the corrosion products can form a relatively more protective layer on NC coating surfaces than on PC coatings. The EIS characteristics and corrosion processes of PC and NC zinc coatings during 330 h of immersion were discussed in detail.     

非晶态Ni-W/ZrO2复合镀层的制备、热处理及腐蚀行为

在镍钨合金电解液中, 通过搅拌使二氧化锆固体微粒悬浮, 电沉积制备Ni-W/ZrO2复合镀层. 研究结果表明, 二氧化锆粒子影响复合镀层的电沉积、表面形貌、结构、热处理过程和抗腐蚀性能; 与Ni-W合金的电沉积过程相比, 复合镀层中的W含量和电流效率均降低; 在400 ℃处理1 h后, 嵌入Ni-W本体中的ZrO2粒子脱落, W向镀层表面富集. 扫描电子显微镜(SEM)结果显示, 复合镀层呈现团粒状形态, 无裂纹. 差示扫描量热(DSC)分析结合X射线(XRD)衍射实验指出, Ni-W/ZrO2复合镀层为非晶态结构. 复合镀层的显微硬度较纳米晶Ni-W合金的高; 热处理后, 复合镀层的显微硬度和在3%氯化钠溶液中的抗腐蚀行为显著增强.     

Mechanical and corrosion behavior of amorphous and crystalline electroless Ni–W–P coatings

Two types of electroless Ni–W–P coatings: nanocrystalline with low P and amorphous with higher P content are investigated. Scanning probe microscopy is applied to study their morphology. Textured nanocrystalline coatings consist of coarse pyramids built of nanometer thick lamellas. The surface morphology of amorphous coatings is much finer and uniform. Nanohardness of all coatings depends on W content. Microhardness is increasing during the heat treatment up to 350 °C due to nickel phosphide precipitation affected by tungsten also. The wear resistance of nanocrystalline Ni–W–P coatings is much higher than that of amorphous in spite of the similar tungsten content in both. Lower corrosion resistance of amorphous Ni–W–P coatings is found by weight loss method during long-term immersion in 5 % NaCl. Electrochemical tests by potentiodynamic polarization curves in two model corrosion media—solutions of 0.5 M H₂SO₄ and 5 % NaCl—are performed. The corrosion of bi-layered Ni–W–P/Ni–P and Ni–W–P/Ni–Cu–P deposits on mild steel is also investigated. The results prove that an electroless Ni–W–P coating on mild steel extremely improves its mechanical and corrosion behavior. It is demonstrated that in addition to deposit’s structure and composition, the distribution and chemical state of alloy ingredients are also responsible for its properties.     

Surface analytical investigation of the electrochemical and corrosion behaviour of nanocrystalline FeAl8

From the higher fraction of grain boundaries in nanocrystalline substances a different corrosion behaviour in comparison to the conventional polycrystalline material can be expected, which may be utilised for the development of new corrosion resistant alloys. Therefore, the oxidation behaviour of these two different crystallisation states of FeAl8 was compared by means of electrochemical and surface analytical experiments. The oxide films formed after electrochemical passivation were investigated by Auger Electron Spectroscopy. The application of inelastic peak shape analysis by the method of Tougaard showed, that for both materials the oxide layer may be described by a model of a (below the contamination) buried layer with a thickness of only a few nanometers depending on the preparation conditions. Factor Analysis was applied for the evaluation of the differentiated low energy Auger electron spectra (20–100 eV) as a function of depth profiling sputtering time. For both, the nanocrystalline and the polycrystalline material, the inner part of the oxide layer was enriched in Al, whereas the very outer part (surface region) was enriched in Fe. No differences concerning the sputtering time for removal of the oxide layers were found for the two alloys.     

A novel method for preparing aluminum diffusion coating by nanocrystalline plasma electrolysis

A crack-free Al diffusion coating has been developed to improve different properties of commercially pure titanium. It was produced by a method called pulsed bipolar nanocrystalline plasma electrolytic saturation (PBNPES). Morphology and elemental distribution through this layer has been studied with XRD, SEM and EDX. This layer improves the corrosion resistance of bare substrate.     

激光熔凝处理对纯铁渗稀土层组织与耐蚀性能的影响

通过SEM观察,X射线光电子能谱分析,电化学阻抗谱测定和阳极极化曲线的测试,探讨激光熔凝处理对纯铁渗稀土层组织与耐蚀性能的影响,结果表明,在一定条件下,激光熔凝处理可进一步提高纯铁渗稀土层组织的致密性与均匀性,显著提高稀土渗层的耐蚀性。     

Surface modification of iron particles with bis(3-oxa-2-chloroperfluorobutyl)disulfide

Gas-liquid chromatography has been employed to study bis(3-oxa-2-chloroperfluorobutyl)disulfide (S60Cl) adsorption from solutions in perfluoromethylcyclohexane, perfluorodimethylcyclohexane, perfluorodecalin, anisole, toluene, and butyl acetate on the surfaces of two iron particle samples, namely, carbonyl iron and iron produced by electric-arc recondensation. It has been shown that the pattern of adsorption isotherms is characteristic of monolayer adsorption. Parameters of S60Cl adsorption have been calculated using the linear form of the Langmuir equation. The structure of adsorption layers that provide iron particles with aggregation stability and corrosion resistance in various dispersion media has been discussed.     

Antibacterial Optimization of Highly Deformed Titanium Alloys for Spinal Implants

The goal of the work was to develop materials dedicated to spine surgery that minimized the potential for infection originating from the transfer of bacteria during long surgeries. The bacteria form biofilms, causing implant loosening, pain and finally, a risk of paralysis for patients. Our strategy focused both on improvement of antibacterial properties against bacteria adhesion and on wear and corrosion resistance of tools for spine surgery. Further, a ~35% decrease in implant and tool dimensions was expected by introducing ultrahigh-strength titanium alloys for less-invasive surgeries. The tested materials, in the form of thin, multi-layered coatings, showed nanocrystalline microstructures. Performed direct-cytotoxicity studies (including lactate dehydrogenase activity measurement) showed that there was a low probability of adverse effects on surrounding SAOS-2 (Homo sapiens bone osteosarcoma) cells. The microbiological studies (e.g., ISO 22196 contact tests) showed that implanting Ag nanoparticles into Ti/Ti_xN coatings inhibited the growth of E. coli and S. aureus cells and reduced their adhesion to the material surface. These findings suggest that Ag-nanoparticles present in implant coatings may potentially minimize infection risk and lower inherent stress.