Corrosion behaviour of welded low-carbon steel in the Arctic marine environment

Arctic offshore sites have high potential for the exploration of energy resources; thus, data concerning the behaviour of structural materials in the Arctic environment are required. Here, we report the corrosive characteristics of welded low-carbon steels under simulated Arctic low-temperature conditions. The corrosion tendencies in the submerged and splash zones of offshore structures were investigated by immersion tests, salt spray tests (SST), and cyclic corrosion tests (CCT). The effects of decreasing seawater temperature on the corrosion were identified, and the differences in corrosion between the base metal (BM) and weld metal (WM) were analysed. In particular, the BM showed higher corrosion than the WM, indicating that the parent metal (PM) is corroded more than the fusion zone (FZ) in weld joints under severe corrosion conditions. Thus, we have identified the importance and influence of the thermal expansion of materials on corrosion under Arctic conditions.

The parent metal have shown higher corrosion than the weld zone under severe Arctic corrosion conditions.     

Synthesis of poly(ionic liquid) for trifunctional epoxy resin with simultaneously enhancing the toughness,thermal and dielectric performances

Poly(ionic liquid) (PIL), integrating the characteristics of both polymers and ionic liquid, is synthesized and employed to modify diglycidyl-4,5-epoxy-cyclohexane-1,2-dicarboxylate (TDE-85). With the addition of PIL, the fracture toughness, and thermal and dielectric performances of TDE-85 were discovered to be simultaneously improved, meanwhile the tensile modulus and strength is increased. Upon an optimal loading of 3 wt% PIL, the critical stress intensity factor (K_IC), tensile modulus and strength are raised by 92.9%, 13.3% and 10.7%, respectively. Multi-toughening mechanisms due to spherical domains of PIL formed in TDE-85 during curing are responsible for the improved toughness. Moreover, the dielectric and thermal properties of TDE-85 are also enhanced by adding PIL. With the optimal addition of 5 wt% PIL, the dielectric constant of the composites is enhanced by 62.5%, the glass transition temperature is increased by 16.58 °C and the residual weight of carbon is increased by 59%.

This work will provide a strategy to obtain epoxy with relatively high toughness, thermal and dielectric properties.     

Estimation of the tensile modulus of polymer carbon nanotube nanocomposites containing filler networks and interphase regions by development of the Kolarik model

In this paper, the Kolarik model for the tensile modulus of co-continuous blends based on cross-orthogonal skeleton structures is simplified and developed for polymer/carbon nanotube (CNT) nanocomposites assuming continuous CNT networks in the polymer matrix and the reinforcing and percolating efficiencies of the interphase. For this purpose, the Ouali model for the modulus of nanocomposites above the percolation threshold is linked with the Kolarik model and the interphase percolation is considered with the excluded volume of the nanoparticles. In addition, the simplified Kolarik model is developed with the interphase as a new phase surrounding the nanofiller. A good agreement between the experimental data and the predictions is observed in the samples containing interphases and filler networks, while the developed model cannot estimate the modulus in the absence of interphases and network structures. The developed model demonstrates the effects of all the parameters on the modulus. The interphase parameters more significantly affect the modulus compared to the concentration and modulus of the filler, demonstrating the importance of the interphase properties.

The Kolarik model for the tensile modulus of co-continuous blends is developed for polymer/carbon nanotube (CNT) nanocomposites assuming continuous CNT networks and the reinforcing and percolating efficiencies of the interphase.     

Polyoxymethylene/silica/polylactic acid-grafted polyethylene glycol nanocomposites: structure,morphology, and mechanical properties and ozone and UV durability

Polyoxymethylene (POM) is a semicrystalline thermoplastic that displays high tensile strength, thermal stability, and chemical durability. However, its widespread application is limited by its low elongation at break and thermal durability. In the present study, nanosilica (NS) and polylactic acid-grafted polyethylene glycol (PELA) were used as enhancement additives to improve the performance of POM homopolymer. Specifically, the POM/PELA/NS nanocomposites with a fixed NS content and varying PELA contents were prepared by a melt mixing method. The influence of the additives on the processability, and dynamic thermo-mechanical and tensile properties of the nanocomposites was evaluated by comparing the torque, mixing energy at melt state, storage modulus, shear stress, loss modulus, tan δ, tensile strength, elongation at break and thermal degradation of the nanocomposites. The results showed that the combined addition of NS and PELA enhanced the thermal stability, tensile strength, elongation at break and chemical stability of the POM/PELA/NS nanocomposites owing to the good compatibility between PELA and the POM matrix. Furthermore, the morphology, and UV and ozone durability of POM and the nanocomposites were assessed and discussed.

The combined addition of nanosilica (NS) and polylactic acid-grafted polyethylene glycol (PELA) enhanced some properties of polyoxymethylene (POM).     

Silicon surface patterning via galvanic microcontact imprinting lithography

Surface patterning without requiring expensive facilities and complex procedures is a major scientific and technological challenge. We report a simple surface patterning strategy on a silicon wafer surface. This strategy, termed galvanic microcontact imprinting lithography (GMIL), is based on the spontaneous galvanic oxidation of silicon due to the electrically coupled silicon/gold mold with lithographically defined patterns. The galvanic induced silicon oxide pattern can be selectively removed in dilute HF solution or serve as a robust etchant resist in alkaline solution, enabling the formation of regular silicon microstructures on the silicon surface, affording an accessible, simple and cheap surface patterning method with no requirement of expensive and sophisticated instrumentation and facilities. These results may open exciting prospects for next-generation low-cost lithographic techniques.

The “ancient” galvanic effect opens up the possibility of silicon surface patterning in ordinary laboratories without expensive and sophisticated facilities.     

Flexible and wearable strain sensor based on electrospun carbon sponge/polydimethylsiloxane composite for human motion detection

Flexible and wearable strain sensors have attracted considerable attention due to their potential applications in human motion detection. In this work, the as-fabricated strain sensor was obtained by encapsulation of electrospun carbon sponge (CS) with polydimethylsiloxane (PDMS). The formation mechanism of the self-assembled sponge has been explored. Meanwhile, the piezoresistive properties and the strain sensing mechanism of the CS/PDMS sensor were investigated. The results showed that the as-fabricated CS/PDMS sensor had high piezoresistive sensibility with a maximum gauge factor up to 130.49, superior stability and fast response to various cyclic loading with a tensile strain from 0% up to 40% and a tensile speed range of 2–18 mm min⁻¹. Finally, all the superior performances endow the sensor with abilities to precisely detect pronunciation, human palm motion, wrist joint motion, elbow joint motion, and finger motion in real-time. These results indicate that the strain sensor based on the CS/PDMS could have promising applications in flexible and wearable devices for human motion detection.

Electrospun carbon sponge was used to measure tensile strains with a high gauge factor.     

Effect of chromium on the corrosion behaviour of low Cr-bearing alloy steel under an extremely high flow rate

The effect of chromium on the corrosion behavior of low Cr-bearing alloy steel in a wet gas pipeline with a high flow rate was studied using a rotating cylinder electrode (RCE) and self-built wet gas flow loop device. The results show that the addition of chromium in the steel can increase the flow accelerated corrosion (FAC) resistance of steel effectively. It was hard for pure FeCO₃ to deposit onto the carbon steel surface to form an intact corrosion film when the flow rate or wall shear stress was high. However, a mixture of Cr(OH)₃ and FeCO₃ can still be deposited onto the 3Cr steel surface and form an intact and protective corrosion film even under conditions with a 212 Pa wall shear stress in the wet gas pipeline.

The effect of chromium on the corrosion behavior of low Cr-bearing alloy steel in a wet gas pipeline with a high flow rate was studied using a rotating cylinder electrode (RCE) and self-built wet gas flow loop device.     

Application of nanomaterials in the treatment of rheumatoid arthritis

Rheumatoid Arthritis (RA) is a chronic autoimmune disease, which mainly causes inflammation of the synovial joints and destruction of cartilage and bone tissue. At present, a variety of clinical drugs have been applied in the treatment of rheumatoid arthritis. With the development of nanotechnology, more and more nano-drugs have been applied in the treatment of rheumatoid arthritis due to the unique physical and chemical properties of nanomaterials. Treatment of RA with nanomaterials can improve bioavailability and selectively target damaged joint tissue. In this review, we summarized the progress of the application of nanomaterials in the treatment of rheumatoid arthritis and also proposed challenges faced by nanomaterials in the treatment of rheumatoid arthritis.

Rheumatoid Arthritis (RA) is a chronic autoimmune disease, which mainly causes inflammation of the synovial joints and destruction of cartilage and bone tissue.     

Infrared induced repeatable self-healing and removability of mechanically enhanced graphene–epoxy flexible materials

A repeatable self-healing epoxy composite mechanically enhanced by graphene nanosheets (GNS) was prepared from an epoxy monomer with Diels–Alder (DA) bonds, octanediol glycidyl ether (OGE) and polyether amine (D230). The GNS/epoxy composites, with a maximum tensile modulus of 14.52 ± 0.45 MPa and elongation at break more than 100%, could be healed several times under Infrared (IR) light with the healing efficiency as high as 90% through the molecule chain mobility and the rebonding of reversible DA bonds between furan and maleimide. Also, they displayed excellent recyclable ability by transforming into a soluble polymer, which offers a wide range of possibilities to produce epoxy flexible materials with healing and removable abilities.

The GNS/epoxy composites, with tensile modulus of 14.52 ± 0.45 MPa and elongation at break more than 100%, could be healed several times under infrared light with the healing efficiency as high as 90% and displayed excellent recyclable ability.     

Enhanced control of plasmonic properties of silver–gold hollow nanoparticles via a reduction-assisted galvanic replacement approach

Hollow noble metal nanoparticles are of growing interest due to their localized surface plasmon resonance (LSPR) tunability. A popular synthetic approach is galvanic replacement which can be coupled with a co-reducer. Here, we describe the control over morphology, and therefore over plasmonic properties including energy, bandwidth, extinction and scattering intensity, offered by co-reduction galvanic replacement. This study indicates that whereas the variation of atomic stoichiometry using the co-reduction method described in this work offers a rather modest tuning range of LSPR energy when compared to traditional galvanic replacement, it nevertheless has a profound effect on shell thickness, which imparts a degree of control over scattering intensity and sensitivity to changes in the dielectric constant of the surrounding environment. Therefore, in this context particle size and gold content become two design parameters that can be used to independently tune LSPR energy and intensity.

A co-reduction assisted method for the synthesis of Ag–Au hollow nanoparticles with enhanced control over plasmon wavelength and scattering intensity.     

Facile preparation of epoxy based elastomers with tunable Tgs and mechanical properties

In this work, a secondary amine-capped polyaspartic ester (PAE-D230) was synthesized using diethyl maleate and amine-terminated polyether (D230) via Michael addition reaction. By modulating the molar ratio of preliminary amine containing D230 and secondary amine-capped PAE-D230 during the curing process with epoxy precursor E44, we obtained epoxy shape memory polymers with tunable T_gs(−12–20 °C), controllable mechanical properties with tensile stress from 0.8 to 14.1 MPa, tensile modulus from 0.7 to 872.0 MPa, and elongation at break from 45.2 to 195.1%. The influence of the composition of curing components on the thermal properties, thermomechanical, mechanical properties, shape memory effect were systematically studied by DSC, TGA, DMA, tensile-stress measurements.

By modulating the molar ratio of preliminary amine containing D230 and secondary amine capped PAE-D230 during the curing process with epoxy precursor E44, We obtained epoxy shape memory polymers with tunable T_gs and controllable mechanical properties.     

Nanoindentation and deformation behaviors of silicon covered with amorphous SiO2: a molecular dynamic study

A fundamental understanding of the mechanical properties and deformation behaviors of surface modified silicon during chemical mechanical polishing (CMP) processes is difficult to obtain at the nanometer scale. In this research, MD simulations of monocrystalline silicon covered with an amorphous SiO₂ film with different thickness are implemented by nanoindentation, and it is found that both the indentation modulus and hardness increase with the growing indentation depth owning to the strongly silicon substrate effect. At the same indentation depth, the indentation modulus decreases shapely with the increase of film thickness because of less substrate influence, while the hardness agrees well with the trend of modulus at shallow depth but mismatches at larger indentation depth. The observed SiO₂ film deformation consists of densification and thinning along indentation direction and extension in the deformed area due to the rotation and deformation of massive SiO₄ tetrahedra. The SiO₂ film plays an important role in the onset and development of silicon phase transformation. The thinner the SiO₂ film is, the earlier the silicon phase transformation takes place. So the numbers of phase transformation atoms increase with the decrease of SiO₂ film thickness at the same indentation depth. It is suggested that the thicker film should be better during CMP process for higher material removal rate and less defects within silicon substrate.

Force–indentation depth curves and cross-section snapshots of phase transformation evolution of silicon under various film thickness (H).     

Correlation between electrochemical properties and stress corrosion cracking of super 13Cr under an HTHP CO2 environment

The susceptibility of super 13Cr steel to stress corrosion cracking (SCC) was assessed through slow strain rate testing in simulated formation water saturated with CO₂ under a high-temperature and high-pressure (HTHP) environment. The evolution, morphology, and chemistry of fracture and corrosion products on the steel surface were evaluated using in situ electrochemical methods and surface analysis. Results indicate that the occurrence of pitting corrosion increases SCC susceptibility. At 150 °C, the degradation of a surface film induces pitting corrosion because of an increase in anodic processes. The presence of Cl⁻ causes film porosity, and CO₂ reduces the Cr(OH)₃/FeCO₃ ratio in the inner film, which further promotes Cl⁻-induced porosity.

The degradation of a surface film induces pitting corrosion, which further increases SCC susceptibility.     

Strain engineering of optical activity in phosphorene

Optical activity is one of the most fascinating fields in current physics. The strong anisotropic feature in monolayer phosphorene leads to the emergence of non-trivial optoelectronic physics. This paper is devoted to a detailed analysis of strain effects on the optical activity of phosphorene ranging from low-optical-field to high-optical-field. To do so, a numerical study of the two-band tight-binding model is accomplished using the Harrison rule and the linear response theory. Although the transparency of phosphorene confirms at all frequencies independent of the strain modulus and direction, on average, from low- to high-optical-field limit, the polarization of the reflected wave at critical strains becomes circular and the ellipse axis tends to a rotation of 180°. It is found that the maximum absorption takes place at high-energy transitions, which quantitatively depends strongly on the strain modulus and direction. Furthermore, a detailed investigation of compressive and tensile strains results in the dominant contribution of the in-plane compressive and out-of-plane tensile strains to the reflected/transmitted light for low- and intermediate-optical-field ranges, whilst both contribute for the high-optical-field limit. However, overall, in-plane compressive and out-of-plane tensile strains come in to play a role in the absorption spectra. Thereby, the quality of the determined reflection, transmission and absorption waves depends on the regarded regime of the optical field, strain modulus, and strain orientation. These findings if sufficient can be performed and/or tuned experimentally, and a vast number of phosphorene-based optoelectronic devices can be achieved.

This paper is devoted to a detailed analysis of strain effects on the optical activity of phosphorene ranging from low-optical-field to high-optical-field.     

4-(Pyridin-4-yl)thiazol-2-amine as an efficient non-toxic inhibitor for mild steel in hydrochloric acid solutions

A novel eco-friendly corrosion inhibitor, namely, 4-(pyridin-4-yl)thiazol-2-amine (PTA), was synthesized and evaluated as a corrosion inhibitor for mild steel in 1 M HCl solution. Its inhibition effect against mild steel corrosion was investigated via weight loss methods, electrochemical measurements, and surface analyses. The experimental results showed that PTA is an effective corrosion inhibitor for mild steel in an acid medium, and the maximum inhibition efficiency reached 96.06% at 0.2 mM concentration. Polarization studies showed that PTA acted as a mixed inhibitor. The sorption behavior on the steel surface complies with the Langmuir adsorption isotherm, exhibiting both physisorption and chemisorption. The constitution and characteristic of the protective layer on the steel surface were verified using scanning electron microscopy (SEM)/energy-dispersive X-ray spectroscopy (EDX) and UV-Vis spectroscopy. Quantum chemistry calculations were used to study the relationship between the inhibition efficiency and molecular structure of the inhibitor.

The corrosion inhibition performance and mechanism of 4-(pyridin-4-yl)thiazol-2-amine toward mild steel in hydrochloric acid were studied for the first time.     

General corrosion during metal-assisted etching of n-type silicon using different metal catalysts of silver,gold, and platinum

Metal-assisted etching is a promising technique for microfabrication of semiconductors. In this method, porous silicon (Si) can be produced with a very simple procedure, and various nanostructures can be designed by changing the catalyst patterns. The kind of metal catalysts is one of the key factors to control the porous structure. In this work, we performed the etching of n-type Si (100) in a hydrofluoric acid solution containing hydrogen peroxide in the dark using silver, gold, and platinum particles electrolessly deposited at a constant coverage, and demonstrated the difference in the porous structures obtained for the different kind of metal catalysts. By comparing the mass loss of substrates with the depth of pores formed under the metal particles, we found that general corrosion occurred on the top-surface of the Si substrate around the metal particles even under the dark condition. The general corrosion depended on the metal species and it was explained by the formation and dissolution of a mesoporous layer. The kind of metal catalysts influences the dissolution of the Si surface not only under the metal catalysts but also between them.

The first report on general corrosion during metal-assisted etching of silicon.     

Investigation on the mechanical properties and fracture phenomenon of silicon doped graphene by molecular dynamics simulation

Silicon doping is an effective way to modulate the bandgap of graphene that might open the door for graphene to the semiconductor industries. However, the mechanical properties of silicon doped graphene (SiG) also plays an important role to realize its full potential application in the electronics industry. Electronic and optical properties of silicon doped graphene are well studied, but, our understanding of mechanical and fracture properties of the doped structure is still in its infancy. In this study, molecular dynamics (MD) simulations are conducted to investigate the tensile properties of SiG by varying the concentration of silicon. It is found that as the concentration of silicon increases, both fracture stress and strain of graphene reduces substantially. Our MD results also suggest that only 5% of silicon doping can reduce the Young''s modulus of graphene by ∼15.5% along the armchair direction and ∼13.5% along the zigzag direction. Tensile properties of silicon doped graphene have been compared with boron and nitrogen doped graphene. The effect of temperature, defects and crack length on the stress–strain behavior of SiG has also been investigated. Temperature studies reveal that SiG is less sensitive to temperature compared to free stranding graphene, additionally, increasing temperature causes deterioration of both fracture stress and strain of SiG. Both defects and cracks reduce the fracture stress and fracture strain of SiG remarkably, but the sensitivity to defects and cracks for SiG is larger compared to graphene. Fracture toughness of pre-cracked SiG has been investigated and results from MD simulations are compared with Griffith''s theory. It has been found that for nano-cracks, SiG with larger crack length deviates more from Griffith''s criterion and the degree of deviation is larger compared to graphene. Fracture phenomenon of pre-cracked SiG and the effect of strain rate on the tensile properties of SiG have been reported as well. These results will aid the design of SiG based semiconducting nanodevices.

Variations of fracture stress and Young’s modulus of graphene with the concentration of silicon doping.     

Plasticity control of poly(vinyl alcohol)–graphene oxide nanocomposites

Composite films containing poly(vinyl alcohol) filled with different amounts of graphene oxide (2 and 4 wt%) were prepared by the solution casting technique, and the mechanical properties of the resulting materials were modified with different amounts of glycerol as a plasticizer. Two series of pure poly(vinyl alcohol) and graphene oxide-loaded films with fixed amounts of water were used for modification with glycerol, since water can also serve as a plasticizer for poly(vinyl alcohol). The morphology and physical properties of the plasticized and non-plasticized composites were studied; tensile tests were performed to investigate and compare their mechanical properties. Glycerol addition does not affect the excellent compatibility of the filler with the polymer matrix and uniform distribution of graphene oxide in poly(vinyl alcohol). For poly(vinyl alcohol)/graphene oxide films an increase of the Young''s modulus and yield stress was found with an increase of the filler content; the Young''s modulus for poly(vinyl alcohol) filled with 4 wt% of graphene oxide is almost two times higher than that of the pure polymer. Simultaneously, a sharp decrease of the elongation at break from 80% for pure PVA to about 5% for the PVA/GO composite with 4 wt% of GO is observed, and the film''s brittleness dramatically increases. It was shown that the addition of glycerol to the composite films leads both to the Young''s modulus decrease and tensile energy at break increase; here the Young''s modulus decreases by 18 times after addition of 20 wt% of glycerol to the poly(vinyl alcohol) film filled with 4 wt% of graphene oxide. Thus, the use of plasticizer results in a significant increase of the ductile properties of graphene oxide filled poly(vinyl alcohol) composite films, and the higher the water content in the composite film, the more drastic the increase of the ductile properties observed.

The plasticity of poly(vinyl alcohol)–graphene oxide nanocomposites was significantly improved and the failure mechanism changed from brittle to ductile failure.     

Correlation between the corrosion rate and electrochemical noise energy of copper in chloride electrolyte

An electrochemical noise technique has been applied to describe the corrosion process of copper. The results show that the sampling frequency clearly changes both the energy distribution plot and the power spectral density spectra, which should be taken into consideration strictly and logically before an electrochemical noise test. The corrosion energy, (E_c), deduced using the fast wavelet transform method showed a similar variation trend with corrosion rate. Hence, the proposed parameter E_c represents the corrosion rate or severity.

Sampling frequency clearly changes EDP and PSD spectra and EN corrosion energy shows a similar variation trend with corrosion rate.     

Polyaniline/chitosan as a corrosion inhibitor for mild steel in acidic medium

The inhibition performance of polyaniline (PANI)/chitosan (CTS) on metal corrosion in 0.5 M HCl was studied using electrochemical measurements, quantum chemical calculations and morphological observations. Potentiodynamic polarization measurements show that PANI/CTS acts essentially as a mixed-type inhibitor. The inhibition efficiency increases and corrosion rates decrease with increasing concentrations of PANI/CTS. The relationship between experimental inhibition efficiency and quantum chemical calculations that were developed to describe the corrosion inhibition process are discussed.

One-pot synthesis route for PANI/CTS preparation. The inhibition performance of PANI/CTS on metal corrosion in 0.5 M HCl was studied using electrochemical measurements and quantum chemical calculations.