Surface Analysis Measurements Research Articles

The Zn2+ Destabilized Surface Film and Accelerated Corrosion of Magnesium

The effect of Zn2+ ions on the corrosion of pure magnesium (Mg) in NaCl solutions was systematically investigated by means of hydrogen evolution, weight loss, surface analysis, polarization curve and solution pH measurements. It was found that the presence of Zn2+ ions in the solution could significantly accelerate the dissolution of Mg. A new mechanism of surface film destabilization was proposed for the detrimental effect of Zn2+ on Mg corrosion, aiming to provide insight into the corrosion behavior of Zn-containing Mg alloys and the galvanic corrosion of Mg alloys coupled by Zn alloys.

Ce addition enhances the microbially induced corrosion resistance of Cu-bearing 2205 duplex stainless steel in presence of sulfate reducing bacteria

Influences of Ce additions (0.08, 0.18 and 0.30 wt.%) on microbiologically influenced corrosion of Cu-bearing 2205 duplex stainless steel (DSS) were investigated through surface analysis and electrochemical measurements during 14-day exposure to a strain of corrosive sulfate reducing bacterium, Desulfovibrio desulfuricans. Results demonstrate the addition of Ce over 0.18 wt.% effectively inhibited the formation of SRB biofilm on surface of 2205-Cu-Ce DSS, and decreased the corrosion tendency to a great degree, indicating that Ce addition over a critical value can significantly enhance antibacterial effect of Cu-bearing 2205 DSS against SRB induced corrosion.

Effect of thermo‐oxidative aging on surface characteristics of benzoxazine and epoxy copolymer

AbstractThe copolymer of bisphenol A‐based benzoxazine and cycloaliphatic epoxy resin possesses greater processability and glass‐transition temperature compared to that of benzoxazine homopolymer, making it suitable for high‐temperature aerospace applications. The aim of this work is to investigate the behavior of the copolymers under thermos‐oxidative aging conditions using the surface characterization techniques. The benzoxazine homopolymer and copolymer samples were thermally aged in an air‐circulating oven under controlled temperatures of 180 and 200°C for various periods of time up to 24 weeks. The thermo‐oxidative‐induced weight change and surface cracking were monitored for samples during the aging period. As an alternative method to characterize thermal aging, static contact angle, and contact angle hysteresis of samples were measured over time. Moreover, droplet impact tests using deionized water were performed on stationary and moving samples to investigate the effects of aging time and temperature on impact dynamics of droplets. In addition, FTIR analysis was performed to evaluate the chemical changes on the surface of samples. The results indicated the extent of degradation of aged samples increased with increasing the aging time and temperature. In addition, the copolymer of cycloaliphatic epoxy and benzoxazine showed a greater amount of thermos‐oxidative degradation than the one for benzoxazine homopolymer. More importantly, the results obtained from the surface analysis measurements (e.g., contact angle) followed a similar trend to the one obtained from the traditional aging experiments (e.g., weight change). This showed the former nondestructive and simple method can be used to monitor thermal aging of materials in service.

Ruthenium(IV) Complexes as Potential Inhibitors of Bacterial Biofilm Formation.

With increasing antimicrobial resistance there is an urgent need for new strategies to control harmful biofilms. In this study, we have investigated the possibility of utilizing ruthenium(IV) complexes (H3O)2(HL1)2[RuCl6]·2Cl·2EtOH (1) and [RuCl4(CH3CN)2](L32)·H2O (2) (where L1-2-hydroxymethylbenzimadazole, L32-1,4-dihydroquinoxaline-2,3-dione) as effective inhibitors for biofilms formation. The biological activities of the compounds were explored using E. coli, S. aureus, P. aeruginosa PAO1, and P. aeruginosa LES B58. The new chloride ruthenium complexes were characterized by single-crystal X-ray diffraction analysis, Hirshfeld surface analysis, FT-IR, UV-Vis, magnetic and electrochemical (CV, DPV) measurements, and solution conductivity. In the obtained complexes, the ruthenium(IV) ions possess an octahedral environment. The intermolecular classical and rare weak hydrogen bonds, and π···π stacking interactions significantly contribute to structure stabilization, leading to the formation of a supramolecular assembly. The microbiological tests have shown complex 1 exhibited a slightly higher anti-biofilm activity than that of compound 2. Interestingly, electrochemical studies have allowed us to determine the relationship between the oxidizing properties of complexes and their biological activity. Probably the mechanism of action of 1 and 2 is associated with generating a cellular response similar to oxidative stress in bacterial cells.

Pickling behavior of 2205 duplex stainless steel hot-rolled strips in mixed solutions of HNO3-HF

The pickling behaviour of 2205 DSS hot-rolled strips after annealing and sand blasting was studied in the mixed solutions of HNO3-HF using weight loss rate, surface analysis, corrosion potential, and electrochemical impedance spectroscopy measurements. The pickling rate decreased as the concentration of HNO3 increased in the mixed solutions of x HNO3 + 25 g l−1 HF (x = 40 ∼ 200 g l−1) at 50 °C due to passivation. The passivating effect of HNO3 became weak as its concentration was less than 80 g l−1. The pickling rate increased noticeably when the concentration of HF in the mixed solutions of 120 g l−1 HNO3 + y HF (y = 5 ∼ 80 g l−1) at 50 °C was increased. The dissolution of the metal under the oxide scale may have changed from the passive state to the active state as the HF concentration was higher than 25 g l−1. The pickling dissolution accelerated noticeably as the temperature rose from 40 to 60 °C. With the optimised pickling process, 2205 DSS hot-rolled strips can be pickled industrially with good efficiency and surface topography.

Investigation of the failure mechanism of the TG-201 inhibitor: Promoting the synergistic effect of HP-13Cr stainless steel during the well completion

TG-201 inhibitor could minimize corrosion of HP-13Cr SS in the process of live acid. Moreover, it accelerated the probability of serious corrosion of SS during the well completion. The failure mechanism of TG-201 inhibitor was investigated using surface analysis and electrochemical measurements. TG201 inhibitor contains amounts of Cu2+, which would acquire the electrons prior to H+ to form Cu film. The failure mechanism was due to the synergistic effect attributed to the Cu film. Cu film promoted the formation of the occluded cell and the changes of fluid state evoked by the increase in interfacial roughness during the well completion.

Characterization of the passive film formed on the reinforcement surface in alkali activated fly ash: Surface analysis and electrochemical evaluation

Due to different ion types and concentration in pore solution, the passive film on the steel surface possesses different characteristics in alkali-activated fly ash (AAFA). In this study, the passive film formed in simulated AAFA pore solution was investigated by surface analysis and electrochemical measurements. The passive film possessed bilayer structure with FeOOH-rich outer layer and FeO-rich inner layer in simulated AAFA pore solution. Further, a firmly adsorbed zeolite-like layer (200 nm) formed on the steel surface. The formation of more protective passive film and adsorbed layer resulted in higher corrosion resistance of the reinforcement in simulated AAFS pore solution.

Surface analysis and pumping speed measurements of oxygen-free palladium/titanium nonevaporable getter after heating at 100–450 °C

A novel nonevaporable getter (NEG) consisting of an oxygen-free thin film of Ti covered with a thin film of Pd (oxygen-free Pd/Ti) with an activation temperature of 133 °C has recently been developed [T. Miyazawa et al., J. Vac. Sci. Technol. A 36, 051601 (2018)]. When activated by baking at 150 °C, an NEG pump using oxygen-free Pd/Ti evacuates H2 and CO efficiently at room temperature, and its pumping speeds for H2 and CO do not decrease even after repeated cycles of activation and exposure to the air [T. Kikuchi et al., AIP Conf. Proc. 2054, 060046 (2019)]. However, oxygen-free Pd/Ti does not evacuate other major residual gases, such as H2O or CO2. To expand the range of applications of the NEG, the authors analyzed the surface chemical composition of the oxygen-free Pd/Ti by synchrotron-radiation x-ray photoelectron spectroscopy after heating at various temperatures in the range of 100–450 °C for 10 min. The authors found that Ti segregated to the surface after heating at 300 °C for 10 min. In addition, the pumping speeds for H2 and CO of a vacuum vessel coated with oxygen-free Pd/Ti were measured after baking at various temperatures in the range of 150–400 °C for 12 h. These results suggested that Ti segregates to the Pd surface after baking at 250 °C for 12 h. Therefore, after heating above 250–300 °C, oxygen-free Pd/Ti can be used as an NEG pump for vacuum systems where active residual gases other than H2 and CO must be pumped.A novel nonevaporable getter (NEG) consisting of an oxygen-free thin film of Ti covered with a thin film of Pd (oxygen-free Pd/Ti) with an activation temperature of 133 °C has recently been developed [T. Miyazawa et al., J. Vac. Sci. Technol. A 36, 051601 (2018)]. When activated by baking at 150 °C, an NEG pump using oxygen-free Pd/Ti evacuates H2 and CO efficiently at room temperature, and its pumping speeds for H2 and CO do not decrease even after repeated cycles of activation and exposure to the air [T. Kikuchi et al., AIP Conf. Proc. 2054, 060046 (2019)]. However, oxygen-free Pd/Ti does not evacuate other major residual gases, such as H2O or CO2. To expand the range of applications of the NEG, the authors analyzed the surface chemical composition of the oxygen-free Pd/Ti by synchrotron-radiation x-ray photoelectron spectroscopy after heating at various temperatures in the range of 100–450 °C for 10 min. The authors found that Ti segregated to the surface after heating at 300 °C for 10 min. In addition...

Synthesis of a New Chloro Antimony Complex with Pyridinium Derivative: Crystal Structure, Hirshfeld Surface Analysis, Vibrational, and Optical Properties

The new organic–inorganic hybrid material (C6H7N2S)2[SbCl4]Cl was synthesized by slow evaporation method and characterized by single-crystal X-ray diffraction, infrared absorption, Hirshfeld surface analysis, optical absorption and photoluminescence measurements. The Centro symmetric compound crystallizes in the triclinic system of space group {text{P}}bar{1} with two formula units cell (Z = 2).The crystal structure is composed of a discrete [SbCl4]− anion and two isolated chloride Cl− anions which carried the same negative charge to balance the total charge of this compound surrounded by the 4 pyridiniumethioamide cations. Organic and inorganic parts which are linked by means of hydrogen bonding contacts N–H···Cl with N···Cl length are varied in the range of 3.221–3.456 Å to form a Zero-dimensional network. The infrared study performed at room temperature charge in the 4000–400 cm−1 frequency regions confirms the existence of the organic cation [C6H7N2S]+ and that of the [SbCl4]− anion. The Photoluminescence spectrum exhibits a broad and strong band of luminescence located at 1.95 eV (635 nm), which can be even observed with the naked eye at room temperature and is due to exaction emission. The various intermolecular interactions of the two independent cations and six chloride atoms were examined via Hirshfeld surface analysis.

Crystal structure, thermal studies, vibrational properties, atomic Hirshfeld surface, and electrical and dielectric studies of [C9H14N]3BiCl6 single crystal

The present research under study makes in attention the synthesis of a new organic inorganic hybrid material of formula [C9H14N]3BiCl6 by slow evaporation at room temperature. It is characterized by the following techniques: X-ray diffraction (XRD), IR absorption, Raman scattering, UV–Vis spectrum, Hirschfield surface analysis, thermal analysis, AC conductivity and dielectric measurements. The studied compound belongs to the centrosymmetric Pī space group of the triclinic system. The crystal structure is built up of one octahedral anion [BiCl6]3- and three monoprotonated cations [C9H14N]+. They give between them alternating anionic layers and cationic ones. The DSC revealed a phase transition at the temperature 380 K and the decomposition of the compound at 400 k. Raman and infrared spectra were recorded in the 50–400 and 400-4000 cm−1 frequency regions respectively. The optical properties were investigated by optical absorption and show three bands at 211, 266 and 321 nm. Hirshfeld surface analysis of close intermolecular interactions in this compound enables the identification and the examination of molecular shapes. The AC electrical conductivity and the dielectric relaxation properties of the [C9H14N]3BiCl6 material have been carefully studied by means of impedance spectroscopy measurements over 200 Hz–5 MHz frequencies and 330–400 K temperatures ranges. Nyquist plots (-Z″ versus Z′) results is well explained by an equivalent circuit which is modeled by a combination of a parallel Rp//CPE. Besides, the Arrhenius law is followed by temperature dependence of the electrical conductivity in the different phases and the Jonscher's universal dynamic law is also followed by the frequency dependence of σ (ω). Moreover, it is clear that the activation energy responsible for relaxation has been depicted and shown to be close to the DC conductivity. Finally, the modulus plots can be characterized by the non-experiential decay function ∅(t)=exp(−tτσ)β.

Microbiologically Influenced Corrosion of Carbon Steel Beneath a Deposit in CO2-Saturated Formation Water Containing Desulfotomaculum nigrificans.

The corrosion mechanism of carbon steel under deposit in the presence of sulfate reducing bacterium (SRB) Desulfotomaculum nigrificans was studied using surface analysis, weight loss and electrochemical measurements. Results showed that both the general corrosion and localized corrosion were considerably promoted by SRB under deposit. The corrosion rate of steel in the presence of SRB was approximately 6 times of that for the control according to the weight loss measurements. The maximum corrosion pit depth in the presence of SRB was approximately 7.7 times of that of the control. Both the anodic and cathodic reactions were significantly accelerated by SRB. A galvanic effect in the presence of SRB due to the heterogeneous biofilm led to serious localized corrosion.

Carbon steel corrosion controlled by vegetable polyol phosphate, in medium containing chloride and glyoxal: influence of phosphate content and CO2

Glyoxal is a potential sequestrant of H2S in the pre-salt exploration. However, the mixture containing packer fluid and glyoxal is corrosive. The addition of an eco-friendly polyol phosphate acts as corrosion inhibitor of the AISI 1020 in this environment. The objective of the present work was to study the influence of phosphate content in the inhibitor formulation, as well as its action in packer fluid and glyoxal solution in the presence of dissolved CO2, by means of surface analysis and electrochemical measurements. The results demonstrated that the inhibition efficiency increases as the phosphate content increases. In the beginning of the tests, the polarization resistance increases from 2.2 kΩ cm2 (2.5 % phosphate) to 11.2 kΩ cm2 (10 % phosphate). In CO2 – containing medium, 500 ppm dosage of polyol phosphate increases the polarization resistance (from 0.35 kΩ cm2 to 5.9 kΩ cm2) and decreases both the capacitance (from 111.5 μF cm-2 to 10.2 μF cm-2) and the corrosion current (in 67%). Polyol phosphate is effective as corrosion inhibitor in the presence of CO2 due to its adsorption on the metal surface or on the film of the previously formed oxide.

“PdO vs. PtO”—The Influence of PGM Oxide Promotion of Co3O4 Spinel on Direct NO Decomposition Activity

Direct decomposition of NO into N2 and O2 (2NO→N2 + O2) is recognized as the “ideal” reaction for NOx removal because it needs no reductant. It was reported that the spinel Co3O4 is one of the most active single-element oxide catalysts for NO decomposition at higher reaction temperatures, however, activity remains low below 650 °C. The present study aims to investigate new promoters for Co3O4, specifically PdO vs. PtO. Interestingly, the PdO promoter effect on Co3O4 was much greater than the PtO effect, yielding a 4 times higher activity for direct NO decomposition at 650 °C. Also, Co3O4 catalysts with the PdO promoter exhibit higher selectivity to N2 compared to PtO/Co3O4 catalysts. Several characterization measurements, including X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), H2-temperature programmed reduction (H2-TPR), and in situ FT-IR, were performed to understand the effect of PdO vs. PtO on the properties of Co3O4. Structural and surface analysis measurements show that impregnation of PdO on Co3O4 leads to a greater ease of reduction of the catalysts and an increased thermal stability of surface adsorbed NOx species, which contribute to promotion of direct NO decomposition activity. In contrast, rather than remaining solely as a surface species, PtO enters the Co3O4 structure, and it promotes neither redox properties nor NO adsorption properties of Co3O4, resulting in a diminished promotional effect compared to PdO.

Efficient removal of lead ions from water by magnetic nanosorbents based on manganese ferrite nanoparticles capped with thin layers of modified biopolymers

In this study we report findings on the elaboration of magnetic nanosorbents based on manganese ferrite nanoparticles (MNPs) capped with carboxymethylated biopolymers (starch or cellulose) for water remediation purposes. The functionalization was optimized through the analysis of pH-dependent speciation profiles of MNPs/biopolymers, and samples were characterized using X ray powder diffraction, atomic force microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, nitrogen adsorption–desorption surface analysis and magnetization measurements. Nanosorbents have all been shown to remove Pb (II) efficiently from aqueous solution (∼100%, after 30 min of contact) in spite of the presence of very tiny layers of biopolymers (the maximal amount of organic layer adsorbed on the MNP surface was only about 4.0% in mass and biopolymer coating thickness was estimated < 1 nm). This low biopolymer content was sufficient to increase the affinity of nanosorbents for Pb (II), preserving high magnetization of material (∼65 emu/g). Equilibrium adsorption isotherms for Pb (II) adsorption on biopolymer-modified MNPs indicated that more heterogeneous surfaces were formed after capping MNPs with biopolymers, corroborating the hypothesis that upon surface functionalization, affinity for Pb (II) adsorption by the magnetic adsorbents was enhanced. Adsorption was more effective at pH = 5.5, and the contact time required to reach equilibrium was relatively short (∼30 min), following a pseudo-second-order model, with adsorption capacities of (34 to 46 mg g−1), calculated from Sips model. Regeneration studies revealed that the nanosorbents can be recovered for reuse, indicating their use as a powerful tool for Pb (II) removal from contaminated water.

Improving the Cut Surface Quality by Optimizing Parameters in the Fibre Laser Cutting Process

One of the main problems with laser cutting equipment is related to the wrong setting of cutting parameters. The mismatching of these parameters leads to a loss of cut surface quality, which is hardly re-established. This loss of quality is usually related to a burr problem. Thus, this study is aimed to improve and optimize this process using a fibre laser equipment. Three important laser cutting parameters were studied in order to investigate their importance in the cut surface quality: radiation power, cutting speed and gas pressure. The different values were performed cutting a stainless steel AISI 316L and a cold rolled steel St12. Metallographic and cut surface analysis, burr and roughness measurements were carried out, supported by a Scanning Electron Microscopy and profilometry. Through the Taguchi statistical analysis model, it is possible to indicate the best set of laser cutting parameters. It was verified that the values recommended by the equipment manufacturer can be optimized, being possible to use less radiation power in the laser beam with greater speed of cut, providing a better cut surface quality, improving and optimizing the entire process.

Corrosion behavior of X80 pipeline steel in the presence of Brevibacterium halotolerans in Beijing soil

In this study, the corrosion behavior of X80 pipeline steel in the presence of Brevibacterium halotolerans (B. halotolerans) was investigated by surface analysis and electrochemical measurements. Results show that B. halotolerans can attach to the surface of X80 steel, and the entire surface is covered with B. halotolerans. The corrosion products induced by B. halotolerans were FeOOH, Fe2O3 and FeSO4. X80 steel corrosion was accelerated in the presence of B. halotolerans and was susceptible to pitting corrosion. The formation of pitting corrosion could be due that the B. halotolerans oxidization of elemental iron in X80 steel to either obtain electrons from the reduction of nitrate in the underlying biofilm or in the damaged corrosion product film.

The inhibition behavior of a water-soluble silane for reinforcing steel in 3.5% NaCl saturated Ca(OH)2 solution

The inhibition performance of a water-soluble silane on reinforcing steel in saturated Ca(OH)2 solution contaminated by Cl− was investigated and compared with commonly organic inhibitor N,N-dimethylethanolamine (DMEA) using electrochemical techniques and surface analysis measurements. The results indicate that the lower concentration of APTS has better inhibition efficiency than DMEA, the largest inhibition efficiency are 70.1% and 97.4% for DMEA and APTS after 72 h immersion. DMEA promotes the interfacial layer by formation of CaCO3 deposited on steel surface, while APTS changes the character of steel surface by adsorption and effectively inhibits the pitting corrosion.

Control of ferromagnetic properties of Ni80Fe20 thin films by voltage-induced oxidation

We demonstrate large voltage-induced changes of magnetic properties in thin films of Ni80Fe20 (permalloy) when gated using an ionic liquid medium [1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIMTFSI)]. The coercivity and magnetic moment of 5 nm thick permalloy films could be reduced by 75% and 35%, respectively, by using applied voltages. These changes were partially restored by reversing the potential polarity. Electrochemical, time-course magnetometry and surface analysis measurements suggest that the voltage-induced changes are due to changes in the oxidation state at the surface of the film, causing a thinning of the permalloy layer. The control of soft magnetic properties with low voltages may be of use in tuneable devices.

Nano-machining, surface analysis and emittance measurements of a copper photocathode at SPARC_LAB

R&D activity on Cu photocathodes is under development at the SPARC_LAB test facility to fully characterize each stage of the photocathode “life” and to have a complete overview of the photoemission properties in high brightness photo-injectors. The nano(n)-machining process presented here consists in diamond milling, and blowing with dry nitrogen. This procedure reduces the roughness of the cathode surface and prevents surface contamination introduced by other techniques, such as polishing with diamond paste or the machining with oil. Both high roughness and surface contamination cause an increase of intrinsic emittance and consequently a reduction of the overall electron beam brightness. To quantify these effects, we have characterized the photocathode surface in terms of roughness measurement, and morphology and chemical composition analysis by means of Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), and Atomic Force Microscopy (AFM) techniques. The effects of n-machining on the electron beam quality have been also investigated through emittance measurements before and after the surface processing technique. Finally, we present preliminary emittance studies of yttrium thin film on Cu photocathodes.

P-type conduction in two-dimensional MoS2 via oxygen incorporation

The effects of oxygen incorporation on the electronic transport properties of two-dimensional (2D) MoS2 have been studied via temperature dependent and gate voltage dependent transport measurements of physical vapor deposited 2D MoS2. Gated micro-van der Pauw cross devices were fabricated from the MoS2 film for transport measurements. Field-effect measurements indicate that incorporated oxygen acts as a p-type dopant for MoS2. The combination of X-ray photoemission spectroscopy surface analysis and Raman measurements of the film indicates that acceptor states resulting from MoSxO3-x inclusions in the MoS2 film are the origin of the p-type doping. Temperature dependent van der Pauw conductivity measurements indicate an acceptor energy of 214 meV above the valence band edge for the acceptor state.